U.S. patent application number 10/123247 was filed with the patent office on 2002-10-24 for method of manufacturing an object in a vacuum recipient.
This patent application is currently assigned to Unaxis Balzers Aktiengesellschaft. Invention is credited to Haag, Walter, Kugler, Eduard, Rudigier, Helmut, Signer, Hans, Wellerdieck, Klaus.
Application Number | 20020153242 10/123247 |
Document ID | / |
Family ID | 4198894 |
Filed Date | 2002-10-24 |
United States Patent
Application |
20020153242 |
Kind Code |
A1 |
Signer, Hans ; et
al. |
October 24, 2002 |
Method of manufacturing an object in a vacuum recipient
Abstract
A method of manufacturing an object in a vacuum treatment
apparatus having a vacuum recipient for containing an atmosphere,
includes the steps of supporting a substrate on a work piece
carrier arrangement in the recipient and treating the substrate to
manufacture the object in the vacuum recipient. The treating
process includes generating electrical charge carriers in the
atmosphere and in the recipient which are of the type that form
electrically insulating material and providing at least two
electroconductive surfaces in the recipient. Power, such as a DC
signal, is supplied to at least one of the electroconductive
surfaces so that at least one of the electroconductive surfaces
receives the electrically insulating material for covering at least
part of that electroconductive surface. This causes electrical
isolation of that electroconductive surface which leads to arcing
and damage to the object. A control signal is applied to the
electroconductive surfaces during repeating and alternating first
time spans and second time spans, for prevent arcing at the part of
the electroconductive surfaces which is, or is becoming
electrically isolated from the atmosphere by being covered by the
electrical charge carriers.
Inventors: |
Signer, Hans; (Oberschan,
CH) ; Kugler, Eduard; (Feldkirch Tisis, AT) ;
Wellerdieck, Klaus; (Buchs, CH) ; Rudigier,
Helmut; (Bad Ragaz, CH) ; Haag, Walter;
(Grabs, CH) |
Correspondence
Address: |
ANTONELLI TERRY STOUT AND KRAUS
SUITE 1800
1300 NORTH SEVENTEENTH STREET
ARLINGTON
VA
22209
|
Assignee: |
Unaxis Balzers
Aktiengesellschaft
|
Family ID: |
4198894 |
Appl. No.: |
10/123247 |
Filed: |
April 17, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10123247 |
Apr 17, 2002 |
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09724449 |
Nov 29, 2000 |
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09724449 |
Nov 29, 2000 |
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09314333 |
May 19, 1999 |
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6176979 |
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09314333 |
May 19, 1999 |
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08887091 |
Jul 2, 1997 |
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5948224 |
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08887091 |
Jul 2, 1997 |
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08641707 |
May 2, 1996 |
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08641707 |
May 2, 1996 |
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08300865 |
Sep 2, 1994 |
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08300865 |
Sep 2, 1994 |
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08020672 |
Feb 22, 1993 |
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Current U.S.
Class: |
204/192.12 ;
204/192.13; 204/298.03; 204/298.08 |
Current CPC
Class: |
H01J 37/32431 20130101;
C23C 14/32 20130101; H01J 2237/0206 20130101; C23C 14/54
20130101 |
Class at
Publication: |
204/192.12 ;
204/192.13; 204/298.08; 204/298.03 |
International
Class: |
C23C 014/32 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 24, 1992 |
CH |
948/92 |
Claims
We claim:
1. A method of enhanced thin film processing in a plasma system
comprising the steps of: a. supplying a target material within a
coating chamber; b. furnishing direct current power to said coating
chamber through a circuit having a first and second lead to create
a plasma through which current flows; c. causing deposition of a
thin film of coating material upon a substrate through action of
said plasma for a deposition period for thin film processing; and
d. timing to accomplish periodically clearing said system of an
uneven buildup of charged particles in the first place so that such
timing is set to eliminate the occurrence of arcs throughout said
deposition period for thin film processing.
2. A method of enhanced thin film processing in a plasma system as
described in claim 1, wherein said periodically clearing is
performed with a repetition rate of 50 kHz to 500 kHz.
3. A method of enhanced thin film processing in a plasma system as
described in claim 2, wherein said repetition rate is at least 90
kHz.
4. A method of enhanced thin film processing in a plasma system as
described in claim 2, wherein said repetition rate is at least 100
kHz.
5. A method of enhanced thin film processing in a plasma system as
described in claim 2, wherein said thin film processing is ion
plating.
6. A method of enhanced thin film processing in a plasma system as
described in claim 1, wherein said periodically clearing is
performed with a repetition rate of between 50 Hz and 1 MHz.
7. A method of enhanced thin film processing in a plasma system as
described in claim 6, wherein said repetition rate is between 5 kHz
and 100 kHz.
8. A method of enhanced thin film processing in a plasma system as
described in claim 6, wherein said repetition rate is between 10
kHz and 20 kHz.
9. A method of enhanced thin film processing in a plasma system as
described in claim 6, wherein said thin film processing is
sputtering.
10. A method of enhanced thin film processing in a plasma system as
described in claim 1 wherein said step of timing to accomplish
periodically clearing said system of an uneven buildup of charged
particles periodically causes the step of immediately stopping
current from flowing through said plasma.
11. A method of enhanced thin film processing in a plasma system as
described in claim 1 wherein said step of furnishing direct current
power to said coating chamber comprises the step of applying a
voltage to said coating chamber and wherein said step of timing to
accomplish periodically clearing said system of an uneven buildup
of charged particles periodically causes the step of applying a
reverse voltage to said coating chamber.
12. A method of enhanced thin film processing in a plasma system as
described in claim 11 wherein said reverse voltage is
substantial.
13. An enhanced DC plasma processing system comprising: a. a
coating chamber having an anode and a cathode; b. a material target
disposed to expose coating material within said chamber; c. a DC
power source wherein said DC power source has a direct current
power output and first and second leads which are connected across
a plasma to establish a circuit through which current flows; and d.
a timer which causes periodic clearing of said system of an uneven
buildup of charged particles in the first place, wherein the timer
is set to eliminate the occurrence of arcs throughout a deposition
period for thin film processing.
14. An enhanced DC plasma processing system as described in claim
13, wherein said timer courses said periodic clearing at a
repetition rate of 50 kHz to 500 kHz.
15. An enhanced DC plasma processing system as described in claim
14, wherein said timer causes said periodic clearing at a
repetition rate of at least 90 kHz.
16. An enhanced DC plasma processing system as described in claim
14, wherein said timer causes said periodic clearing at a
repetition rate of at least 100 kHz.
17. An enhanced DC plasma processing system as described in claim
14, wherein said plasma processing system is an ion plating
system.
18. An enhanced DC plasma processing system as described in claim
13, wherein said timer causes said periodic clearing at a
repetition rate of between 50 Hz and 1 MHz.
19. An enhanced DC plasma processing system as described in claim
18, wherein said timer causes said periodic clearing at a
repetition rate between 50 kHz and 100 kHz.
20. An enhanced DC plasma processing system as described in claim
18, wherein said timer causes said periodic clearing at a
repetition rate between 10 kHz and 20 kHz.
21. An enhanced DC plasma processing system as described in claim
18, wherein said plasma processing system is a sputtering
system.
22. An enhanced DC plasma processing system as described in claim
13 wherein said timer which causes periodic clearing of said system
of an uneven buildup of charged particles causes current flowing
through said plasma to immediately stop.
23. An enhanced DC plasma processing system as described in claim
13 wherein DC power source applies a voltage to said coating
chamber and wherein said timer which causes periodic clearing of
said system of an uneven buildup of charged particles comprises
reversing circuitry which applies a reverse voltage to said coating
chamber.
24. An enhanced DC plasma processing system as described in claim
23 wherein said reverse voltage is substantial.
25. A method of enhanced thin film processing in a plasma system
comprising the steps of: a. supplying a target material within a
coating chamber; b. furnishing direct current power to said coating
chamber through a circuit having a first and second lead to create
a plasma through which current flows; c. causing deposition of a
thin film of coating material upon a substrate through action of
said plasma for a deposition period for thin film processing; and
d. timing to accomplish periodically clearing said system of an
uneven buildup of charged particles in the first place so that such
timing is set to eliminate the occurrence of arcs throughout said
deposition period for thin film processing, wherein said step of
periodically clearing comprises the step of applying a reverse
voltage.
26. An enhanced DC plasma processing system comprising: a. a
coating chamber having an anode and a cathode; b. a material target
disposed to expose coating material within said chamber; c. a DC
power source wherein said DC power source has a direct current
power output and first and second leads which are connected across
a plasma to establish a circuit through which current flows; d. a
timer which causes periodic clearing of said system of an uneven
buildup of charged particles in the first place, wherein the timer
is set to eliminate the occurrence of arcs throughout a deposition
period for thin film processing; and e. reversing circuitry which
applies a reverse voltage to said coating chamber.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a divisional application of application Ser. No.
09/724,449, filed Nov. 29, 2000, which in turn is a divisional of
application Ser. No. 09/314,333, filed May 19, 1999, now U.S. Pat.
No. 6,176,979, which is a divisional application of application
Ser. No. 08/887,091, filed Jul. 2, 1997 and now U.S. Pat. No.
5,948,224, which was a continuation of application Ser No.
08/641,707, filed May 2, 1996 and is now abandoned, which itself
was a continuation of application Ser. No. 08/300,865, filed Sep.
2, 1994, and also now abandoned, which in turn was a continuation
of application Ser. No. 08/020,672, filed Feb. 22, 1993, and now
abandoned, which claimed priority from Swiss patent application
948/92, filed Mar. 24, 1992 and which is related to the present
application.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention is directed to a method of controlling
a treatment process for an object in a vacuum atmosphere containing
electrical chargecarriers and to a vacuum treatment apparatus. More
specifically, the invention is directed to such a method or
apparatus wherein at least two surfaces of electro-conductive
material are exposed to the vacuum atmosphere at least one thereof
being at least in part covered with material of lower
electro-conductivity than the material of said one surface to form
a resultant exposed surface.
[0004] The invention may be implemented for all physical vapor
deposition treating processes, reactive PVD-processes as well as to
all plasma-enhanced CVD-processes. It may also be implemented to
other treatment processes if the two surfaces with the covering are
exposed in such a process to a vacuum atmosphere with electrical
chargecarriers. Such treatment processes are especially reactive or
not reactive sputtering by which workpieces are sputter etched or
are sputter coated and are thereby biased on predetermined electric
potential or are connected to an electric reference potential or
are operated on a floating electrical potential.
[0005] The present invention is also especially directed to
ionplating treatment processes which are reactive or not reactive.
It may also be implemented to evaporation processes, e.g. to
electron beam evaporation processes, arc evaporation processes,
evaporation processes with heated crucibles, all such evaporation
processes being possibly part of ionplating processes. Thus, and as
repeated, the invention may be implemented to all vacuum treatment
processes whereat one of the electro-conductive surfaces is
entirely or in part covered with a lower electro-conductive
material. This may be caused by the specific treatment process
itself or may be due to such a covering at such a surface already
provided before the specific treatment process is started as, e.g.
if such a covering is a surface oxidation of a metallic part to be
exposed to the process.
[0006] 2. Description of Prior Art, General
[0007] It is known that always when electro-conductive surfaces are
at least in part covered by a lower electro-conductive material,
called an "isolating covering" throughout the following
description, and are exposed to the vacuum atmosphere containing
electrical chargecarriers, a problem may arise by the fact that the
isolating covering will become occupied with electrical
chargecarriers. This especially if electro-magnetical force fields
are applied to the vacuum atmosphere and/or inhomogeneous
distributions of chargecarriers in the atmosphere lead to
diffusion-forces in the vacuum atmosphere on such carriers. This
may also happen at thermical CVD-treatment processes if
chargecarriers are additionally used, e.g. for the activation of a
surface to be treated so, e.g. ion or electron bombardment. The
occupation by electrical chargecarriers leads to electrostatic
charging of the isolating covering like a capacitor up to a degree
where such electrostatic fields are established that an
uncontrolled discharge occurs, e.g. by break-through or
overflash.
[0008] Principally this problem was approached up to now in that
whenever such surfaces--forming a "oneport" or single port
set--were to be fed by electrical energy, as energy generators,
AC-generators were applied or a DC-signal generator and
additionally, simultaneously and continuously, an AC-signal
generator.
[0009] In spite of the fact that the problems of uncontrolled
discharges, as break-throughs and overflashings only occur
stochastically distributed in time and during very short time
intervals compared to the treatment process working time, one thus
remedied these problems by permanently applying during the entire
treatment process working time an AC-generator, be it an
impulse-generator, or a RF-generator, etc.
SUMMARY OF THE INVENTION
[0010] The present invention departs from the recognition that
disturbing phenomena only occur during relatively short time
intervals during the overall processing time so that the permanent
application of an AC-generator during the overall processing time
is in fact not justified if there are options to counteract and
avoid the disturbing phenomena by signal control techniques just at
the moments and as long as it is necessary to ensure a treatment
process to be accomplished, leading to a desired result.
[0011] This first object of the present invention is resolved by
providing a method of controlling a treatment process for an object
in a vacuum atmosphere containing electrical chargecarriers which
comprises the steps of:
[0012] providing at least two surfaces of electro-conductive
material, at least one thereof at least in part covered with
material of lower electro-conductivity than the material of said
one surface to form a resultant surface;
[0013] exposing said surfaces forming an electrical oneport with
said resultant surface to said vacuum atmosphere;
[0014] connecting an electrical DC-signal to said oneport;
[0015] controlling the occupation of said covering by electrical
chargecarriers by applying in time intervals a further electrical
signal to said oneport, said further electric signal being
different from said electrical DC-signal; and
[0016] applying said electrical DC-signal during said treatment
process considerably longer than said further electric signal.
[0017] By this method additionally to the DC-signal generators may
be applied to generate the further electric signal in a controlled
manner just at moments and just as long as considered necessary
i.e. during significantly shorter time intervals, then the
DC-signal for the treatment process is applied. This leads to the
fact that such additional signal generators may previously be
experienced by experiment.
[0018] According to the invention, the actual degree of occupation
of the isolating covering by chargecarriers may be monitored in
real time and dependent on the result of such monitoring, the
further electrical signal may selectively be applied.
[0019] Thus, and under this first aspect of the present invention
it is avoided that a "dangerous" occupation by electrical
chargecarriers occurs in spite of electrical DC-feed to the two
electro-conductive surfaces.
[0020] Departing from the above mentioned recognition the invention
has the second important object to counteract the electrostatic
effects of an occupation by electrical chargecarriers of the
isolating covering in the case that occupation is a desired result
of a treatment process as is especially the case for ionplating.
Thereby the electrostatic negative effect of such an occupation
shall be counteracted and the occupation of the isolating covering
with the material of the electrical chargecarriers shall be
maintained as the desired result of such a process.
[0021] In this way, problems of stochastic discharge shall be
resolved independent from whether electrical energy is externally
supplied to the two electro-conductive surfaces considered--the
oneport--or not.
[0022] This is resolved by a method of controlling a treatment
process for an object in a vacuum atmosphere containing electrical
chargecarriers which comprises the steps of:
[0023] providing at least two surfaces of electro-conductive
material at least one thereof at least in part covered with
material of lower electro-conductivity than the material of said
one surface to form a resultant surface;
[0024] exposing said surfaces forming an electrical oneport with
said resultant surface to said vacuum atmosphere;
[0025] repeatedly applying to said oneport in time intervals one of
with a predetermined and of with an adjustable repetition rate at
least one of a short-circuit and of a source of electrical charge
by means of a controlled discharge or charge exchange current path
bridging said oneport.
[0026] A most typical example in which inherently to the treatment
process an occupation by electrical chargecarriers is desired, is
ionplating mentioned above. In ionplating processes ions are
deposited from the vacuum atmosphere onto a workpiece surface so as
to build up a desired coating. Thereby these ions are driven to the
said workpiece surface by means of electric field applied to the
vacuum atmosphere. Due to this iondeposition which is inherent to
ionplating processes it was up to now not possible to grow coatings
of not or low electro-conductive material by such ionplating or to
deposit coating onto not or low-conductive surfaces of workpieces
be it of non or bad conductive material or of conductive material.
This because controlled influencing the electrostatic fields
resulting from the desired occupation of the isolating covering
with charge carriers, was not possible.
[0027] Thus, ionplating as an important process to which the
present invention is implemented is a process at which
[0028] a) by means of an externally applied one directional
electric field in the vacuum atmosphere ions are to be deposited on
the surface of a workpiece which necessitate external application
of a desired electrical potential to the workpiece.
[0029] b) the occupation of the said surface with electrical
chargecarriers is not to be counteracted because then the target of
ionplating would not be reached.
[0030] By combining the two methods mentioned above some treatment
processes and especially ionplating processes under the said
isolating covering condition become inventively possible.
[0031] This is realized by a method of controlling a treatment
process for an object in a vacuum atmosphere containing electrical
chargecarriers which comprises the steps of
[0032] providing at least two surfaces of electro-conductive
material at least one thereof at least in part covered with
material of lower electro-conductivity than the material of said
one surface to form a resultant surface
[0033] exposing said surfaces forming an electrical oneport with
said resultant surface to said vacuum atmosphere
[0034] connecting an electrical DC-signal to said electrical
oneport
[0035] controlling the occupation of said covering by electrical
chargecarriers by applying a further electrical signal to said
oneport said further electrical signal being different from said
electrical DC-signal
[0036] applying said electrical DC-signal during said treatment
process considerably longer than said further electric signal
and
[0037] applying in time intervals said further electrical signal by
applying repeatedly at least one of a short-circuit and of a source
of electrical charge to said oneport at least one of with a
predetermined and of with an adjustable repetition rate by means of
a controlled discharge or charge-exchange current path bridging
said oneport.
[0038] As was mentioned above isolating covering of the mentioned
kind may be coverings which have been formed independently from the
treatment process or as an undesired or desired effect during such
process. Such undesired effect may be caused by uncontrolled
reaction of contaminating gases in the vacuum atmosphere and
deposition of their reaction product onto surfaces which are
exposed to the vacuum atmosphere. An independently formed covering
may be a contamination layer on electro-conductive surfaces which
has been generated before the treatment process is started so e.g.
by surface oxidation of a metallic surface or by a previous
coating. The said isolating covering may as was stated also be
formed inherently to the treatment process so e.g. at coating
processes of not or low electro-conductive surfaces and/or when
coating surfaces with layers of not or low electro-conductive
materials whereby in latter case the isolating covering is grown by
the process.
[0039] For treatment processes at which process, inherently, bad or
low conductive materials are not concerned it is common to operate
oneports between two metallic surfaces in the vacuum atmosphere by
applying electrical DC-signal be it e.g. for generating a plasma
discharge between such surfaces or for biasing workpieces, screens,
electrodes etc. In spite of the fact that at such processes, as was
mentioned, bad or low electro-conductive materials are not
concerned it is known that e.g. on metallic surfaces previously
exposed to normal atmosphere a contamination layer is built up as
especially an oxidic layer. If such surfaces are then applied to
the mentioned processes their results, at the start of such a
process and as well known to the man skilled in the art,
stochastical discharge phenomena as discussed above which are
tolerated because the provision of an AC-signal generator just for
counteracting these initial phenomena would not be justified.
Nevertheless electrical sources and generators and other electronic
devices coupled to the process apparatus are significantly loaded
by such initial discharge phenomena be it electrically and/or
mechanically and/or thermically and must be accordingly
dimensioned, protected or frequently replaced.
[0040] It is just this problem which is resolved by the method
mentioned above under the first aspect of the present invention
without the necessity of providing expensive AC-generators.
[0041] Summarizing, the present invention thus proposes under its
first aspect to resolve the problem to become able to apply
DC-signal generators in cases in which up to now only combined DC-
and AC-generators were used respectively dimensioned for continuous
operation.
[0042] Under the second aspect the present invention resolves the
problem to become able to deposit onto isolating coverings
electrical chargecarriers and thereby to neutralize the electrical
charge thereof without significantly interfering with the
deposition of the material of the electrical chargecarriers.
COMPARISON OF THE INVENTION AND OF PRIOR ART
[0043] From the U.S. Pat. No. 4,692,230 a method is known by which
in a cathode sputtering process from magnetron sputter sources
electro-conductive as well as isolating target material are
intermittently sputtered. With the sputtered off material a
workpiece is coated. It is most relevant that in time-spans during
which electro-conductive target material is sputtered this is
performed by DC-sputtering. When the non-conductive target material
is sputtered this is performed by means of a continuous train of
monopolare impulses output from an AC-generator. These operating
modes are applied intermittently.
[0044] The U.S. Pat. No. 4,693,805 describes a process for sputter
coating departing from dielectric target objects or for reactive
sputter coating, for sputter etching etc., thus treatment processes
in which inherently not or badly electro-conductive materials are
involved and form isolating coverings.
[0045] So as to control the electrostatic charge occupation of such
isolating coverings at a target cathode- and anode-arrangement
there is installed an additional oneport formed between the said
target cathode and a third auxiliary electrode.
[0046] The two oneports, at which the target object forms a common
electrode, are electrically fed from respective DC-signal
generators via electronically controlled series resistant element
formed by transistors. They are fed intermittently with
specifically shaped signal-forms so that in the one cycles the
electric potential at the target object leads to its sputtering and
in the other cycles the occupation by electric chargecarriers at
the said target is removed by building up a removing electric field
at the auxiliary oneport.
[0047] Whereas the latter U.S.-patent removed the occupation by
electrical chargecarriers by means of an additional "suction
circuit" the DE-A-31 42 900 follows the approach to realize
intermittently with ionizing cycles neutralization cycles during
which built up chargecarrier occupations are electrically
neutralized.
[0048] For an ionplating treatment process the DE-A-31 42 900
provides a low voltage glow discharge between a glow cathode and an
anode. During ionizing cycles the glow plasma-discharge is
initiated and material evaporated from a crucible as substantially
electrically neutral material is ionized and is accelerated onto
the negatively biased workpiece. In the neutralizing cycles the
plasma-discharge and thus the generation of ions is interrupted and
the electrons generated at the glow cathode are used to neutralize
the electric charge formed by the ionsurface occupation of the
workpiece surfaces. By means of accordingly tailored circuits the
glow discharge plasma is operated by means of a triggered
circuit.
[0049] The EP-A-0 101 774 proposes a technique to avoid for a glow
plasma-discharge which is operated in the "abnormal" mode that it
transits into the arc discharge mode. With respect to definition of
these operating modes reference is made to the U.S. Pat. No.
3,625,848 FIG. 1. Thereby there is provided for the glow discharge
a current measurement and there is further provided a resistance
element so as to limit the discharge current as an arc is about to
occur. By this measure an already prevailing arc discharge between
the glow discharge electrode is extinguished.
[0050] The EP-A-0 062 550 proposes to operate a reactive treatment
process by a pulsed glow discharge. To become able to adjust the
work piece temperature by means of the temperature of a treatment
furnace independently from the plasma discharge there is generated
a "cold" plasma by lowering the electrical energy fed between
subsequent impulses to such an amount that the plasma discharge is
just not extinguished.
[0051] From the DE-A-33 22 341 it is further known to counteract
the danger that at a glow discharge which is operated at high
discharge voltage the discharge mode transits in an arc discharge
mode (see also EP-A-0 101 774) and that a disadvantage of a plasma
discharge operated by DC-current is that the pressure of the
treatment vacuum atmosphere and the temperature therein are
mutually dependent. The problem is resolved by intermittently
operating the glow discharge respectively with impulse spikes for
initiating the discharge and with subsequent time-spans of voltage
with a value which just suffices to maintain the glow discharge.
Thereby treatment processes are to be performed which are
customarily operated by DC-generated glow discharges.
[0052] The object of the U.S. Pat. No. 3,437,784 is again to
prevent a glow discharge to transit into the arc discharge mode
with local arc between the electrodes. This is reached by feeding
to the glow discharge oneport a two-way rectified signal of
mains-frequency whereby the amplitude of the half-waves is so
selected that during the one half-wave cycles the glow discharge is
initiated and in the other half-wave cycles it is switched off.
Thereby ions which are about to be generated in the discharge path
of an arc discharge about to occur may recombine. If the extent of
time-spans, according to the half-wave time-spans during which the
feeding signal is below a discharge generating level, do not
suffice for recombination, there is generated by means of a
mechanically operated synchronious rectifier formed by a series
switch arrangement separation of the feeding voltage from the glow
discharge oneport between subsequent glow discharge initiating
cycles.
[0053] The U.S. Pat. No. 4,863,549 describes an RF etching process
in which the glow discharge is RF-operated and the sputtering
ioncurrent on the workpiece is adjusted by a medium frequency
signal (90 to 450 kHz) whereby it is reached that the amplitude of
the medium frequency signal is not to be adjusted by applying an
impulse number modulation technique.
[0054] From the EP-A-0,432,090 a reactive ionplating process is
known at which a glow discharge is operated between a glow cathode
and a crucible with the material to be evaporated and wherein the
evaporated material is ionized.
[0055] A workpiece carrier is operated with a pulsating DC-voltage
with respect to electric reference potential be it anode or cathode
potential of the glow discharge. With the pulsating operation of
the oneport with the workpiece carrier apparently especially good
ceramic coatings at the workpieces are achieved.
[0056] The pulsating DC-voltage is generated as a modulatable
square impulse train by means of an impulse generator provided
therefor.
[0057] From the DE-PS-37 00 633 it is finally known to operate a
glow discharge or an arc discharge by means of DC-current square
impulses from an impulse voltage source. This to avoid undesired
thermical loading of the workpieces.
[0058] Looking back to the present invention:
[0059] By means of the inventive methods and especially due to the
resulting controllability of electrical chargecarrier occupation,
principally novel treatment processes become possible. Already
under its first aspect the present invention is not limited to
replacing well known electrical feeding by a simplified feeding.
Nevertheless already installed apparatus with DC-signal operation
may be easily amended, by providing a module which realises the
invention, to become able to operate treatment processes which
would not work or would hardly work without this additional module
with DC-signal operation. This e.g. due to initial disturbances by
oxidic layer on metal surfaces to be treated.
[0060] It is a further object of the present invention to realise
the inventive method as simply as possible.
[0061] This is reached by applying the further electric signal by
choppering the electric DC-signal. By selectively adjusting the
repetition rate and/or the duty cycle of choppering, which is
preferably realised by parallel choppering, the efficiency of the
treatment process may easily be optimized by applying just during
the time-spans necessary and just as often as necessary DC-signal
choppering. By coupling a signal with a broad frequency spectrum
during optimally short time intervals to the oneport the occurrence
of discharge phenomena is prevented thereby only lowering the
electric energy fed to the oneport during optimally short
time-spans during processing time. By further providing parallel
choppering an optimal combination of the invention under its two
aspects results namely under the first aspect "DC-signal generator
feeding" and "oneport-discharge".
[0062] As will be seen at the end of the present description sets
of features of the present invention and of combinations thereof
are summarized which are considered important.
BRIEF DESCRIPTION OF THE DRAWINGS
[0063] The present invention will be better understood and objects
other than those set forth above will become apparent when
consideration is given to the following detailed description and to
the summarizing list of important features thereof. Such
description makes reference to the annexed drawings wherein:
[0064] FIG. 1a and 1b show schematically functional block diagrams
of respectively known methods or apparatus for electrically feeding
a oneport formed between electro-conductive surfaces in a vacuum
treatment atmosphere provided with an isolating covering,
[0065] FIG. 2 shows by means of a schematic functional diagram the
principle approach according to the present invention and an
electric feed according to FIG. 1a or 1b under a first aspect of
the present invention,
[0066] FIG. 3 shows in a representation in analogy to that of FIG.
2 the present invention under its second aspect,
[0067] FIG. 4 show in a representation in analogy to that of the
FIGS. 1 to 3 the inventive method and apparatus preferably
combining the two aspects of the invention as shown in the FIGS. 2
and 3,
[0068] FIG. 5a to 5c show schematically and heuristically a oneport
in a vacuum treatment atmosphere comprising an isolating covering
of not or badly electro-conductive material for explaining the
charge deposition mechanism and to explain the electrical
neutralization thereof according to the present invention and to
further explain the equivalence circuit which is valid for such a
oneport at least in a first approximation,
[0069] FIG. 6 shows a functional blockdiagram of the inventive
method and of an inventive apparatus and of the two aspects of the
invention whereby respectively under I and II the two aspects of
the invention are denoted as combined according to the teaching of
FIG. 6,
[0070] FIG. 7a to 7c show schematically three examples of
inventively adjusting the discharge or charge exchange behaviour of
the oneport by external feed of electrical charge, the oneport
being represented by its equivalent circuit,
[0071] FIG. 8 shows a functional block/signal-flow-diagram of a
preferred embodiment of the inventive method and apparatus
according to which the discharge behaviour of the oneport is
monitored and the discharge time-span is automatically
optimized,
[0072] FIG. 9 shows schematically the influence of raising
thickness of a not or badly electro-conductive coating on the
electro-conductive surface of the inventively considered oneport on
the discharge time constant,
[0073] FIG. 10 shows a further embodiment of the invention
according to which the discharge behaviour of the oneport shown by
its equivalent network is monitored and compared with a rated
behaviour and discharge repetition rate and/or discharge time-span
is adjusted by negative feedback control technique and/or
electrical charge, fed to the oneport respectively,
[0074] FIG. 11 shows by means of a functional block/signal flow
diagram principally the inventive method and apparatus for
adjusting the occupation with electric chargecarriers on an
isolating covering which latter being formed on one of the two
electro-conductive surfaces of the inventively controlled
oneport,
[0075] FIG. 12a to 12c show a preferred embodiment of the inventive
method and apparatus for ionplating with (FIGS. 12b and 12c)
respectively the equivalent circuits which are valid for the
different operating cycles of the apparatus according to FIG.
12a,
[0076] FIG. 13 shows a preferred form of realization of the
technique and apparatus according to FIG. 12a
[0077] FIG. 14 schematically shows by means of a functional
block/signal-flow-diagram a further preferred embodiment of an
inventive method and apparatus according to FIGS. 12a or 13
respectively, by which the electrical charge deposition is
controlled during operating cycles of ionplating,
[0078] FIG. 15 shows by means of a schematic representation of an
apparatus according to the present invention a preferred feeding of
a plasma-discharge electrode and of an inventively operated
electro-conductive surface by electric potential,
[0079] FIG. 16 shows a further preferred embodiment of the present
invention for reactive sputtering under the inventive
implementation of a DC-signal generator,
[0080] FIG. 17 schematically shows by means of a functional
block/signal flow diagram a further preferred embodiment of the
inventive method and of an inventive apparatus according to which
the rate of occurrence and/or the kind of occurrence of spontaneous
discharge phenomena (breakthroughs, flashovers) in the vacuum
treatment chamber are monitored and as a function therefrom the
discharge and/or the adjustment of the desired electric charge
deposition is performed in a negative feedback control technique
according to one aspect of the present invention,
[0081] FIG. 18 by means of a schematic functional block/signal flow
diagram an inventive method and apparatus at which more than one
oneport are operated mutually staggered in time,
[0082] FIGS. 19, 19a to 19h show schematically a number of
embodiments of the present invention in different constellations to
show how broad the present invention may be implemented.
DETAILED DESCRIPTION OF THE INVENTION AND OF BEST MODES OF
REALIZATION
[0083] FIGS. 1a and 1b show prior art methods and accordingly prior
art apparatus.
[0084] In a vacuum recipient 3 a vacuum atmosphere is confined with
carriers of electrical charge q. Electroconductive surfaces 2a and
2b, and thereby the area of atmosphere between these surfaces, are
electrically operated so that an electric field becomes effective
between the two surfaces. Thereby at least one of the two surfaces
2a and/or 2b is at least in part covered with material being of low
electroconductivity which will be referred to during the following
description as an "isolating covering".
[0085] The isolating covering may thereby be a contamination
covering independent from a treatment process performed in the
recipient, as e.g.; an oxide layer on a metal surface, or may be a
coating which has before been applied to an electro-conductive
surface, which layer is made of material of low
electro-conductivity, i.e. of non-conductive or low conductive
material. Further, the isolation covering may be generated during a
treatment process performed in the recipient, by which a coating of
the not or low electro-conductive material is deposited. Such a
coating generated during the process considered may be the target
of such a process or may be a contamination layer which is
unwanted, but is anyway deposited during such process.
[0086] The two surfaces 2a, 2b and all structure and atmosphere in
recipient 3 bridging these surfaces are defined in the following
description and claims as a "oneport" or single port set.
[0087] The isolating covering is schematically shown with the
reference number 4. Except the case where the isolating covering 4
is a contamination layer, as e.g. the said oxidic layer on a
metallic surface, which e.g. was formed at normal atmosphere, such
a oneport between two input tabs to the surfaces 2a and 2b is in a
first embodiment customarily operated with an AC generator 6, i.e.
a generator which generates an at least substantially sinusoidal
output signal or, as schematically shown, which generates an output
impulse train, possibly with varying duty cycle.
[0088] For such conditions FIG. 1b shows a further known approach
by which the output signal of a continuous AC generator 6b is
superimposed as shown at 7 on the output signal of a DC signal
generator 6a. This approach is selected because by applying a
unipolar electrical field between the electroconductive surfaces 2a
and 2b an occupation layer of electrical chargecarriers will
deposit on the isolation covering. E.g., at a negatively biased
surface 2b positive electrical chargecarriers, ions, will deposit
and there will result, as will be further explained, a voltage
across the isolating covering 4. As soon as such voltage reaches
respective limit values according to the local conditions along
such isolating covering, local and spontaneous discharges occur,
generally called arcing here, be it across and through the
isolating covering, be it along its surface and on the
electroconductive surface 2b and/or to other neighbouring
accordingly electrically polarized parts within the recipient
3.
[0089] In FIG. 2, a first principle inventive approach is shown in
schematic form and, accordingly, an inventive apparatus. Here the
oneport formed between the surfaces 2a and 2b must be electrically
fed, this according to a desired operation for a desired treatment
process within recipient 3.
[0090] The surfaces 2a and 2b are inventively fed by a
DC-signal-generator 8. A further electrical signal is superimposed
to the output of the DC-signal generator 8 with a predetermined or
adjustable repetition-rate and/or during predetermined or
adjustable time-spans controlled by a timing-unit 10 and, as
schematically shown, by a switching unit S. The further electrical
signal, generated, as schematically shown, by a signal generator
unit 12, is applied to the oneport formed between the two surfaces
2a and 2b at predetermined or adjustable time moments and during
predetermined or adjustable time-spans then resulting in an
electrical composite signal which is different from the output
signal appearing at the output of DC signal generator 8.
[0091] The signal generator unit 12 may thereby be a signal
generator which is specifically tailored for this specific use.
Thus such signal generator may be tailored that, according to
repetition rate, at which its output signal is superimposed to the
output signal of generator 8, and according to the time-spans
during which such a signal remains superimposed, just the
specifically necessitated power is delivered to the oneport. As
will be shown later, the unit 12 is construed in a preferred
embodiment as a passive unit, by which the output signal of the DC
signal generator 8 is varied in time and in a controlled manner
before being applied to the oneport 2a, 2b.
[0092] In FIG. 3 there is shown in an analogue representation the
inventive approach and an according apparatus under the second
inventive aspect, namely that the oneport 2a, 2b must not
electrically be power-fed. This is e.g. the case when one of the
two surfaces is to be operated at a floating electrical potential
during a plasma discharge process. Inventively in this case, the
two surfaces 2a and 2b on at least one thereof the isolation
covering 4 is provided, are bridged by a controlled discharge
current path, as is shown in FIG. 3 with a discharge switching unit
14, which latter is controlled by a timing unit 16. At this unit 16
the repetition rate, i.e. the frequency at which the controlled
current path is controlled at least for short time-spans to become
low-ohmic, especially shortened, is predetermined or adjusted. The
extent of the time-spans during which the discharge current path
becomes low-ohmic and substantially short circuits the oneport is
adjusted or predetermined by the unit 16 too.
[0093] Neither the repetition rate nor the extent of time-spans
during which a discharge current is enabled from the oneport 2a, 2b
must necessarily be constant in time during a treatment process
considered in the vacuum atmosphere with the carriers of electrical
charge q. Both these values may be adjusted dependent from the
behaviour of the process and dependent from the kind of process
performed in recipient 3.
[0094] In FIG. 4 a preferred variant of the inventive method and of
an inventive apparatus is shown. Here, the two approaches which
were explained with the help of FIGS. 2 and 3, are combined. The
unit 14 bridges the oneport and is controlled by time unit 16.
Bridging the control switching-unit 14, there is provided the DC
signal generator 8.
[0095] As becomes evident and in a most advantageous manner, the
unit 14 is operated as well as a switching unit for closing the
controlled discharge current path and, additionally, operates as
the switching unit S of FIG. 2 by means of which the output signal
of the DC signal generator 8 is varied. Thus, the timing unit 16
simultaneously operates as the timing unit 10 and 16, according to
FIGS. 2 and 3, and further the unit 14 itself operates as unit S
and unit 12 of FIG. 2.
[0096] In this combined function, the control unit 14 will be
referred to by the reference 14.sub.S and the timing unit 16 will
be referred to by the reference number 160.
[0097] The principle, namely that by the present invention under
both of its aspects, but especially under the second one, shall now
be explained heuristically by means of FIGS. 5a to 5c.
[0098] In FIG. 5a there is schematically shown the vacuum recipient
3 and therein, in the vacuum atmosphere, electrical charge-carriers
q, which are e.g. and especially generated by a plasma discharge
PL. The two inventively operated surfaces 2a and 2b of
electroconductive material are shown and the isolating covering 4.
The surface O of the isolating covering 4 shall become occupied by
positive ions.
[0099] There is generated at the surface of the isolating covering
4 adjacent to the surface 2b a layer of electrical charge, which is
oppositely equal to the charge occupying surface O. Thereby, the
isolating covering 4 forms the dielectric of a capacitor C.sub.I
which is shown in the equivalent circuit of FIG. 5b. One plate of
this capacitor is formed by the surface 2b, the other plate by the
surface O which is disposed adjacent to the vacuum atmosphere,
which is due to the electrical chargecarriers q, electrically
conductive. The vacuum atmosphere between surface O and
electroconductive surface 2a may be considered in the equivalent
circuit by the impedance Z.sub.P, whereby, and at least as a first
approximation, this impedance may be further considered as ohmic.
This because the movable electrons in the vacuum atmosphere lead,
at least in first approximation, to proportionality of electric
field and displacement of chargecarriers.
[0100] Inventively, namely according to the second aspect of the
present invention according to FIG. 3, the oneport 2a, 2b is
intermittently and substantially shortened.
[0101] If electrical charge-carriers according to FIG. 5a have
deposited on surface O, then a voltage U.sub.CI is generated across
the capacitor C.sub.I as shown in FIG. 5b. If the oneport is
shortened by means of switching unit S.sub.1, according to the unit
14 of FIG. 3, then the Kirkoff-law must still prevail, the sum of
all voltages along the discharge current path and the oneport must
be zero. Thus, the situation as shown in FIG. 5c is rapidly
installed: When the switching unit S.sub.1 is closed, a voltage as
shown in FIGS. 5b and 5c in dashed lines is rapidly installed
across the impedance Z.sub.P. By this voltage rapidly movable
electrons are propelled towards the surface O. Thereby, adjacent to
the surface O, there is formed an electrical double layer without
substantial variation of the occupation of surface O by the
material of the ions, which double layer per se is electrically
neutral.
[0102] Thus, by closing the switching unit S.sub.1, the occupation
of surface O by electrical chargecarriers is electrically
neutralized, thereby without significantly disturbing the material
occupation by ion material, which ions are of significantly lower
movability than electrons.
[0103] Thereby, problems of occupation of the isolating covering by
electrical charge-carriers, as shown in FIG. 5a, which would lead
to problems as soon as the voltage U.sub.CI across isolating
covering 4 reaches break-through or spark-over values which would
lead to the said spontaneous arcing, are overcome.
[0104] Already here, it shall be emphasized that only by the
described approach it becomes possible to apply coatings of
material to surfaces which are not or badly electroconductive or on
bottom coatings of such material or to apply to electroconductive
surfaces not or low conducting coatings, all by electrostatic
fields. This besides of the resolution which was described to
remedy problems which occur by spontaneous arcing.
[0105] The time constant of the electrical discharge or charge
exchange-process which occurs when the switching unit S.sub.1 is
closed, is substantially given by the value of capacitance of the
capacitor C.sub.I and the "resistance" values in series thereto,
which are substantially given by the movability of the electrons
provided in the vacuum atmosphere, according to the impedance
Z.sub.P. This time constant may obviously be influenced by external
measures at the discharge current path as e.g. by providing
possibly adjustable resistances. If necessary, the discharge
current loop, consisting of the oneport and the discharge current
path, which provides in a first approximation for a first order
system, may be altered to a system of second order or higher order
by adding further impedance elements as e.g. inductivities.
[0106] In view of the present invention, it is further important to
recognize that the occupation of the capacitor C.sub.I with
electrical charge-carriers after a discharge process may be
influenced by applying an electrical charge source in the discharge
current path, generating a flow of electrical charge in the current
path.
[0107] Further, and especially in view of an ionplating process, it
is important to recognize that during time-spans in which the
switching unit S.sub.1 is open, one may influence the development
of electrical chargecarriers depositing on surface O in an open
loop control or even in a negative feedback control manner by
externally supplying electrical charge to the oneport as will be
explained.
[0108] Before proceeding with the description of further preferred
embodiments, the concept of the present invention under its
different aspects shall be further explained with the help of FIG.
6 taken into consideration the explanations which were given to
FIGS. 2 to 4.
[0109] In FIG. 6 the inventive method and the inventive apparatus
are shown under both aspects and in a preferred form of realization
in schematic form. The vacuum recipient 3, wherein in a preferred
mode of realization a plasma discharge PL is generated, may be
provided with an inlet 18 for a reactive gas or for a reactive gas
mixture. Between the electroconductive surfaces 2a and 2b, i.e.
bridging the oneport formed between these surfaces, in a first
preferred variant of the method and embodiment respectively of the
apparatus according to FIG. 4, the unit 14.sub.S is provided as a
chopper unit. Further, the output of the DC signal generator 8 is
bridged by the chopper unit 14.sub.S which, thus, acts as parallel
chopper unit. The chopper unit 14.sub.S is controlled by the time
control unit 160 which is preferably controllably adjustable.
[0110] The chopper unit 14.sub.S, preferably construed by
electronic switching elements, as with transistors, MOSFET's ,
TYRATRON's , TYRISTOR's , spark gaps, saturated core-inductors
etc., controls the discharge current path of the oneport.
[0111] As evident to the man skilled in the art, and as will be
specified later, measures may be taken to avoid shortening the
output of DC signal generator 8 when the switching unit S.sub.1 of
the chopper unit 14.sub.S is closed.
[0112] Under the first aspect and as framed under "I" in FIG. 6 in
dash lines, the invention comprises the simple combination of a DC
signal generator 8 and of a short circuiting chopper unit 14.sub.S
by which the oneport between the surfaces 2a and 2b at the vacuum
treatment apparatus are electrically operated. Thereby a customary
vacuum treatment apparatus provided with a DC signal generator may
be retrofitted in simple manner, namely by providing the chopper
unit 14.sub.S, so as to become able to perform vacuum treatments
which would not or hardly be possible by means of the mere DC
signal operation.
[0113] Under the second aspect "II", the present invention proposes
to exclusively provide a chopper unit 14.sub.S provided between two
surfaces which are not electrically power-fed by a generator. One
of which is e.g. disposed on a reference potential, as on ground
potential, the second customarily operated on floating potential,
whereby the electric potential of the latter electrode results from
the distribution of electric potentials in the vacuum atmosphere.
At such oneports, too, it may be of great advantage to reduce the
effect of electrical charge-carriers occupating the floating
electrode, which influence the floating potential of that
electrode. Thus, the inventive discharging with the help of the
chopper unit 14.sub.S is considered per se as an inventive part of
the present invention. This part of the present invention is shown
within dash-dotted lines at II.
[0114] In FIG. 7a provision of a source of electrical charge in the
inventive discharge current path according to FIG. 5 is shown. The
source of electrical charge becomes effective to the oneport 2a/2b
during time-spans in which the discharge current path is closed,
i.e. when the switching unit S.sub.1 is closed.
[0115] There is provided in the discharge current path, e.g. one
source 20 of electrical charge Q, which is realized e.g. by a
current impulse source. The source is triggered, as schematically
shown, and at least substantially in synchronism with closing of
the switching unit S.sub.1 by the timing unit 16 or 160
respectively, depending therefrom whether the configuration shown
in FIG. 7a is implemented in the manner shown in FIG. 3 or is
implemented in a combined configuration as principally shown in the
FIGS. 4 or 6.
[0116] By closing the switching unit S.sub.1 electrical charge of
predetermined polarity is fed to the capacitor C.sub.I and the
occupation of surface O with electrical charge according to FIG. 5a
is risen or lowered. Thereby especially the discharge-or charge
neutralization-process may be shortened, in that, and in the
extreme, the entire charge occupation prevailing at surface O, i.e.
at the capacitor C.sub.I is neutralized by the charge fed from
source 20 at the very beginning of the time-span during which
switching unit S.sub.1 is closed.
[0117] In FIG. 7b a first variant is shown for externally
influencing the charge of capacitor C.sub.I in a controlled manner.
When the switching unit S.sub.1 is open, a discrete capacitor
C.sub.D is loaded by a current source 22 in a desired polarity and
to a desired amount so as indicated, e.g., in FIG. 7b.
[0118] When the switching unit S.sub.1 is closed the resulting
discharge or charge exchange process is governed by the values of
capacitant at C.sub.I and C.sub.D and from the respective charging
conditions as initial conditions, as is clearly known to the man
skilled in the art.
[0119] If, in the time-spans in which S.sub.1 is opened, the charge
which is built up on C.sub.I is monitored, then it may be
neutralized by the charge source, formed according to FIG. 7b by
current source 22 and capacitor C.sub.D. In the one time-spans the
loading condition of the capacitor C.sub.I is monitored, in the
other time-spans this loading resulting from occupation of surface
O with electrical chargecarriers, especially positively charged
ions, is neutralized.
[0120] Possibly, the switching unit S.sub.1 may be omitted.
[0121] According to the preferred embodiment of FIG. 7c, there is
introduced into the discharge current path a voltage source U.sub.E
so that the discharge process is governed by the difference between
the voltage at capacitor C.sub.I and the voltage U.sub.E. Thus, by
adjusting the value and the polarity of the voltage U.sub.E,the
discharge or charge exchange process at capacitor C.sub.I may be
influenced. In a preferred mode the discharge process is thus
accelerated in that a predetermined remaining voltage at capacitor
C.sub.I is reached quicker compared with the case where the oneport
is just short-circuited.
[0122] An important advantage of the inventive discharge or charge
exchange process is that such discharging or charge exchanging may
be monitored by measuring. This is realized in a preferred way by a
current or a charge measurement at the discharge current path. As
an example, this shall be explained with the help of FIG. 8.
[0123] According to FIG. 8 the surface 2b of electroconductive
material of the oneport 2a, 2b is laid on electric reference
potential .PHI..sub.o. The oneport is further connected to the
switching unit S.sub.1 to the inverting input of a current or, as
shown, charge amplifier 24 of known construction. As further shown,
as an example, the differential amplifier provided is connected
with its positive input to the reference potential .PHI..sub.o.
When the switching unit S.sub.1 is shut or closed there appears at
the output of the measuring amplifier 24 the time integral of the
discharge current as schematically shown over the time axis t. As
shown at reference No. A the measuring result of the discharge or
charge exchange process may be further exploited for a variety of
objects which shall be later discussed.
[0124] The output signal of measuring amplifier 24 is preferably
led to a comparator unit 26 to which a threshold value W is fed
generated by a threshold-value generator 28. As soon as the output
signal of the amplifier 24 reaches the threshold value W selected,
which indicates that the discharge process has dropped to an
accordingly predetermined value, e.g. a bi-stable element 30 is
reset, which latter opens switching unit S.sub.1. The bi-stable
element 30 may thereby be set by the rising edge of the output
signal of time unit 16 or 160 which closes the switching unit
S.sub.1.
[0125] This results in the fact that the discharge time-span is
automatically adjusted to be only of that extent which is necessary
to reach a desired state of charge at capacitor C.sub.I. Thereby
only smallest possible time-spans are blocked from processing time,
the remaining time is still available, especially for process
energy feeding from the DC signal generator 8 in the configuration
according to FIG. 4.
[0126] As obvious to the man skilled in the art, the time constant
.tau. of the discharge process is significantly dependent from the
capacitance value of capacitor C.sub.I. Whenever the invention is
implemented for coating a workpiece with an isolating covering as
by reactive coating, the capacitance value of C.sub.I drops as
thickness of such a coating increases.
[0127] Thus, and as schematically shown in FIG. 9, by exploiting
the signal A of FIG. 8, the diminishing discharge time constant may
be exploited to get information about the increasing thickness d of
such coating which leads to information about the time-course of
coating growth.
[0128] In FIG. 10 a further embodiment is shown according to which
the actual discharge-characteristic is monitored, is then compared
with a rated characteristic and, according to the result of this
comparison and in the sense of negative feedback control, the
switching unit S.sub.1 is so operated so that the actual discharge
characteristic is negative feedback controlled to substantially
follow the rated characteristic. As schematically shown, this is
realized in that the discharge current I.sub.E is measured by a
current detector 32. A voltage value according to the current
measured is e.g. digitalized with the help of an analog to digital
converter 34. The digitalized measuring signal is stored in an
actual value storage unit 36. The content of the actual value
storage unit 36 is compared at a comparing unit 38 with a rated
discharge characteristic, which latter is stored in a rated value
storage unit 40.
[0129] An evaluation unit 42 evaluates differences .DELTA. between
the rated values and the actual values. The output of the unit 42
acts on one hand on source 44 of electrical charge which is
invertable with respect to its polarity, so as to affect the
respective charging state of the capacitor C.sub.I when the
switching unit S.sub.1 is opened and thus influencing the charge
occupation of surface O according to FIG. 5a. On the other hand,
the output signal of unit 42 is led to a control input of timing
unit 16 or 160 so as to enlarge or reduce the repetition rate of
triggered discharge processes and/or to vary the duty cycle of an
impulse train at the output of unit 16 or 160 controlling the
switching unit S.sub.1. The two possibilities to feedback the
output signal of unit 42 are schematically shown in FIG. 10 by the
throw-over switch N.
[0130] If by appropriate control of the charge source 44, the
actual discharge characteristics become vanishing, this means that
the occupation with electrical chargecarriers of surface O has been
neutralized by the action of charge source 44. This, too, may be
achieved by the negative feedback control 30, shown in FIG. 10.
[0131] Thereby, and as an example, the circuit may be operated
cyclicly as follows:
[0132] a) Opening of S.sub.1; source 44, drives electrical charge
on C.sub.I which charge results in chargecarriers from the vacuum
atmosphere depositing on surface O, e.g. namely positive ions.
[0133] b) Switching unit S.sub.1 remaining open: source 44 is
invertedly operated for short time, the charge occupying surface O
of positive ions is electrically neutralized by electrons.
[0134] c) Switch unit S.sub.1 is closed, the discharge current
I.sub.E is measured; depending on the remaining magnitude and
polarity of the measured discharge current neutralizing in repeated
step b is adjusted and/or the deposition of chargecarriers on
surface O controlled in step a) is adjusted in a negative feedback
control loop.
[0135] The effect of external application of a source of electrical
charge to the oneport as e.g. of source 44 in time-spans, during
which the switching unit S.sub.1 is open, will be further
explained. This especially in connection with ionplating of
workpieces as one important part of the present invention.
[0136] By influencing the state of electrostatical charge at
capacitor C.sub.I and/or on the repetition rate of discharge and/or
the extent of discharge time-spans, one may influence the
occupation of surface O with electrical chargecarriers in a
negative feedback controlled manner, so that, as long as the
capacitance value of capacitor C.sub.I remains substantially
constant in time, the discharge characteristic and thus the said
occupation with chargecarriers is maintained substantially on a
rated value. This even then, when the discharge time constant
varies with varying capacitance value of C.sub.I. In this case one
may evaluate the instantaneous value of that capacitance from the
discharge time constant and then from the value of that capacitance
thus found and by the initial value of the discharge process
conclude on the occupation of surface O by chargecarriers,
especially by ions.
[0137] According to FIG. 11, and departing from the representation
of FIG. 3 or from a combined configuration according to FIG. 4,
according to one important aspect of the present invention, in
time-spans in between subsequent discharge time-spans, the
occupation of the isolating covering 4, according to FIG. 5a, with
electrical chargecarriers may be adjusted in an open control loop
manner or in a negative feedback closed loop control manner.
[0138] Therefore, attention is again drawn to FIG. 5. If in FIG. 5
an electrical charge is enforced externally to the oneport
comprising the surfaces 2a and 2b then, clearly, capacitor C.sub.I
is charged. If, and according to current direction convention, in a
current i which accords with an electrical charge per time unit is
fed, this results in an increase of the charge occupation by
positive ions at the isolating covering 4. If the current direction
is inverted, this results in a decrease of occupation by electrical
charge, i.e. results in positive ions being removed from the
surface O and or electrons being drawn towards said surface.
Attention shall be drawn to the fact that it is customary that the
direction of current i is defined opposite to the direction of
electron current.
[0139] Thus, by external feeding a current or an electrical charge
to the oneport, the occupation with electrical chargecarriers of
the isolating covering may be controlled. This is of predominant
importance, especially for all those treatment processes in which
just by such an occupation with chargecarriers and with the
corresponding occupation with material, a coating shall be built up
which is especially the case in ion- plating process. There, ions
out of the vacuum atmosphere are controllably deposited on the
surface of a workpiece by means of electrostatic forces.
[0140] For this object, according to FIG. 11, when the switching
unit S.sub.1 is opened at the unit 14 or 14.sub.S according to the
FIGS. 3 or 4, by means of the timing unit 16 or 160, a flow of
electrical charge is generated through the oneport 2a, 2b, as is
shown in FIG. 11 schematically by the charge source 46 which is
enabled synchronously with switching unit S.sub.1.
[0141] Thereby, at the said treatment processes and especially at
an ionplating process, the deposition of a layer or coating on the
non or badly conductive surface of a workpiece or the deposition of
a layer or coating made of non or badly conductive material on
either conductive or not conductive surfaces of a workpiece may
controllably be influenced, be it controlled in open loop manner or
in negative feedback controlled manner.
[0142] In FIGS. 12a to 12c, schematically, a preferred variant of
this inventive method is shown and respectively of a preferred
apparatus. In the recipient 3, material is evaporated from a
crucible 52, e.g. by means of a plasma discharge. This may be done
by means of an arc discharge to crucible 52 or by electron beam
evaporation of material in the crucible 52 or, as shown, by means
of a glow discharge, especially by a low voltage glow discharge
generated between an electron emitter cathode, so e.g. a glow
filament cathode 50 and crucible 52. It is clear that material may
also be evaporated by heating the crucible or may be sputtered. It
is only of predominant importance that the material in the
atmosphere is ionized, whereby it is of less importance how the
source of that material is construed and by which process the
material is freed into the vacuum atmosphere. Further, such a
process may be operated in a reactive gas atmosphere, so that the
material freed in the vacuum atmosphere first reacts with a
reactive gas before depositing or such process may be
non-reactive.
[0143] Through the gas inlet 18 and according to the embodiment
shown, a working gas is inlet to the vacuum recipient 3, at least
comprising reactive gas, which reacts in the glow discharge with
the material evaporated from crucible 52. Ions are formed. As a
reaction product, non or badly electroconductive material deposits
in the form of positive ions, thus first forming an occupation of
electrical chargecarriers onto one or more than one workpieces 1,
which are deposited on one of the electroconductive surfaces, e.g.
surface 2a, which thus acts as a workpiece carrier surface. The
workpieces 1 thereby have either intrinsically an electroconductive
surface and are coated by the ionplating process with a coating of
non or badly conductive material or such workpieces intrinsically
have a surface of non or badly conductive material and are then
ionplated with a layer or coating of either non or badly conductive
material or of electroconductive material.
[0144] The method allows on one hand ionplating with non or badly
conductive coatings on all kinds of conductive or non conductive
surfaces or ionplating conductive coatings on non or badly
conductive surfaces at workpieces, said surfaces being formed
either by previously deposited coatings or by the intrinsic surface
of the workpiece. Such coating/workpiece systems could up to now
only be realized by ionplating to a very restricted amount. This
because the unipolar plating current necessary could not be
realized to a sufficient amount and during sufficient
time-spans.
[0145] Further, the workpieces 1 may be provided in the apparatus
according to FIG. 12 or in other configurations which will be
described later, with multi-coating systems too. Thereby especially
workpieces made of material of any electric conductivity may be
provided with a non or bad conductive first layer, especially as a
corrosion protective layer, then with a second layer of
electroconductive material, especially as a wear resistance layer,
or with a combination of such layers comprising more than the said
two layers.
[0146] For ionplating it is important that the material to be
deposited is, as was mentioned, ionized in the vacuum recipient.
This may be realized in different manners. Material evaporated by
electron beam may be ionized by means of a plasma discharge, as
e.g. by an arc discharge on the crucible. For arc evaporation or
glow discharge evaporation, ionization occurs by means of the
plasma discharge itself. Alternatively or additionally electrons or
ions may be fed into the vacuum recipient which improve or lead to
the desired ionization. Further, and as was mentioned before, other
than reactive processes may be performed if, e.g., the evaporated
material shall be deposited as it is freed into the process
atmosphere after ionization.
[0147] Further, instead of evaporation, the material may be
sputtered. If an electroconductive material is sputtered, a
sputtering source, as e.g. a magnetron source, may be provided
instead of crucible 52. If a non-conductive material shall be
sputtered, the sputtering source is preferably operated separately
by means of an RF plasma discharge. Thereby the crucible 52 is
replaced for implementing of the present invention by an
electroconductive surface, independent from the RF discharge as a
reference surface in the recipient (see e.g. FIG. 19f).
[0148] In every case the conductive surface 2a acting as a
workpiece carrier surface is to be connected to an electrical
potential so that for ionplating positive ions are accelerated
towards the workpieces 1 to form the said occupation by electrical
chargecarriers, the positive ions. The electric power which is
necessary to be applied at the oneport 2a/2b is significantly lower
compared to the electric power necessary for maintaining a plasma
discharge which is eventually to be generated in the crucible.
[0149] According to the embodiment of FIG. 11, the plating current
which is externally applied, accords with the ion and electron
propagation in between the electroconductive surfaces 2a and 2b. At
least one of the electroconductive surfaces 2a and 2b, preferably
that one 2a which acts as workpiece carrier surface according to
FIG. 12a, is connected to a discrete capacitor C.sub.D1. The
switching unit S.sub.1 closes the discharge current path to the
second electroconductive surface 2b. This second electroconductive
surface 2b is formed by the crucible in the case of evaporation or
by a sputter source in the case of sputtering a conductive or
semiconductive material. There is provided a current or electrical
charge source 46a (compare FIG. 11) which, when the switching unit
S.sub.1 is open, as shown in FIG. 12b, appears in series to the
discrete capacitor C.sub.D1, the capacitant C.sub.I and the
impedance Z.sub.P of the vacuum atmosphere between the two surfaces
2a and 2b. When the switching unit S.sub.1 is closed and as shown
in FIG. 12c, the current or electrical charge source 46a is
shortened via the closed discharge current path.
[0150] This apparatus operates as follows:
[0151] In time-spans of ionplating, i.e. in processing timespans,
during which a layer is deposited on the workpieces 1, the
switching unit S.sub.1 is opened. During these timespans an
electrical charge, e.g. in the form of a current impulse, is driven
through the series connection according to FIG. 12b by the source
46a which is e.g. realized according to FIG. 12b and 12c as a
current impulse source. The polarity of the electrical charge fed,
according to the time integral of current, is selected as shown.
Thus, both the discrete capacitor C.sub.D1 and the capacitor
C.sub.1 of the oneport are charged, whereby the electric field E
which is generated in the vacuum atmosphere between the surfaces
2a, 2b acts so as to drive positive ions towards the workpieces 1
as shown in FIG. 12b : There is deposited at the surface O of the
isolating covering on the workpiece, i.e. on its non or badly
conductive surface, an occupation of chargecarriers which accords
to the current i which was fed during such plating time
interval.
[0152] Thereby, it becomes evident that the amount of electrical
charge, which is externally fed by means of the source 46a, accords
at least approximately to the amount of electrical chargecarriers
(ions) which are deposited in these plating time intervals on the
workpieces 1. By varying the externally applied electrical charge
in the plating time interval, thus, the degree or amount of
electrical charge deposition and thus, the grow rate of coating is
varied. After or between such plating time intervals, the switching
unit S.sub.1 is closed as was described above.
[0153] The capacitant of the oneport which was described before, as
well as the discrete capacitance C.sub.D1, act initially, as is
well-known, as a short circuited element. When the switching unit
S.sub.1 is closed, the configuration as shown in FIG. 12c becomes
valid. The equivalent circuit elements which now appear in
parallel, namely especially capacitance C.sub.I and capacitor
C.sub.D1 are first still charged to equally directed voltages as
shown in FIG. 12c, so that the discharge process of the discrete
capacitor C.sub.D1, accelerates the discharge or charge exchange
process of capacitor C.sub.I. The time constant of the overall
discharge process is given by the series connection of the two
capacitive elements, so that by selection of the value of
capacitance C.sub.D1 significantly larger than the value of the
capacitance C.sub.I, the time behaviour of the discharge process
remains predominantly given by C.sub.I and the impedance
Z.sub.P.
[0154] The charge applied to capacitor C.sub.D1 is (FIG. 12b)
substantially equal to the charge applied to C.sub.I due to series
connection, so that the said discharge process, according to FIG.
12c, is in fact accelerated by which the voltages in the parallel
configuration of FIG. 12c are brought to equal value when the
transient discharge process is terminated.
[0155] It is evident that after transient discharge, the voltages
at C.sub.D1, and C.sub.I are, in the parallel structure, oppositely
directed and of equal values.
[0156] Because, and as was explained above, during the discharge
process substantially only the electrical charge of the occupation
ions is neutralized and not the occupation with the material
particles of the ions, there occurs during the discharge process no
significant variation of the ion particle layer which has already
been deposited and is now just electrically neutralized.
[0157] In FIG. 12a there is shown a further improvement of this
preferred embodiment, especially for ionplating. Thereby, and as
was already described, the discharge current is measured, the
respective measuring signal is possibly analog to digital converted
in the converter 34 and is stored as actual value in the actual
value storage 30. The content of the storage 30 acting as a data
buffer is compared at the comparing unit 38 with the rated value
stored in rated value storage 40. Thereby, significant values of
the respective actual and rated discharge characteristics are
compared.
[0158] The evaluation unit 42 evaluates the result of actual to
rated value comparison A, possibly under consideration of the
varying time constant as a function of varying values of the
capacitance C.sub.I due to coating thickness increase. In the sense
of negative feedback control, the output signal of unit 42 acts on
a control input of source 46a so that this source is controlled to
adjust the actual discharge characteristic or its significant
parameters to at least substantially become equal to the rated
discharge characteristic or its characteristic parameters. Thus, it
becomes possible to accurately control the growth of layer by
adjusting the occupation of the respective surfaces at the
workpieces 1, according to surface O of FIG. 5, during time
intervals of plating deposition and thereby, additionally, to avoid
the occurrence of dangerous voltages across the respective
isolating covering 4 according to FIG. 5 with respect to general
arcing, by neutralizing the electrical chargeplating deposited
during discharging time intervals.
[0159] In FIG. 13 a further improvement is shown, namely a very
simple form of realization of the technique, which was explained
for the embodiment of FIG. 12. Therefrom it will become evident
that now the invention is realized under its combined aspect which
was explained in connection with FIG. 4.
[0160] With respect to the treatment chamber in recipient 3 the
same conditions prevail which were described in connection with
FIG. 12. The main object is to realize in a most simple way source
46a of FIG. 12. This is done in that the output of the DC signal
generator 8, according to FIG. 4, acts via a choke L.sub.66 on the
network which was described in connection with FIG. 12a instead of
the source 46a.
[0161] The DC signal generator 8 is e.g. poled according to the
voltage U.sub.B of FIG. 13. When the switching unit S.sub.1 is
closed and first without considering unit 56, a current flows
through the choke L.sub.66 and over the closed switching unit
S.sub.1. The current which then flows is shown in FIG. 13 at
I.sub.1. As soon as the switching unit S.sub.1 is opened for
starting a plating time interval there is generated across the
choke L.sub.66 a high negative voltage impulse, as schematically
shown at U.sub.L66. This voltage-impulse drives through the series
connection Of C.sub.D1 and C.sub.I, as was explained in connection
with FIGS. 12b, the electric plating charge. After this transient
caused by U.sub.L66 the voltage U.sub.B lays commonly across the
capacitors C.sub.I and C.sub.D1. By the choke L.sub.66 the
transient plating process is accelerated in this plating time
interval. The operation remains qualitatively the same if the choke
L.sub.66 is omitted and the voltage U.sub.B is directly applied to
the series connection of the two capacitive elements C.sub.I and
C.sub.D1 when the switching unit S.sub.1 is opened.
[0162] Thereby, one must make sure that the DC signal generator 8
is capable to hold its output voltage to rapidly charge the
capacitive load which appears at its output.
[0163] When the choke L.sub.66 is provided, e.g. an electronically
variable resistance element may be provided in the discharge
current path, so e.g. a transistor stage 56, which is controlled
from the output of unit 42, according to FIG. 12a, and which varies
the current which flows through the choke L.sub.66 when the
switching unit S.sub.1 is closed. By varying this current the peak
value of the voltage impulse U.sub.L66 is varied and thus the time
behaviour in the transient plating time intervals. By varying the
resistance value at the stage 56 to be different in plating time
intervals and in discharge time intervals, the stage 56 can be made
of no influence during discharge time intervals, i.e. forming a
short circuit, or may be used in these time intervals, too, to
adjust the transient discharge characteristic. Thereby, the
switching unit S.sub.1 may evidently be combined with the
transistor stage 56, which latter then acts as controlled
resistance stage forming the switching unit.
[0164] It is further evident that it is absolutely possible to
preselect the resistance value of stage 56 without providing a
measurement of discharge current and negative feedback, as was
shown in FIG. 12a, and thus to adjust the stage 56 e.g. during
first adjusting experiments and then to operate the stage 56 just
synchronized with the timing unit 16, 160 of FIG. 12.
[0165] In a further alternative embodiment to that of FIG. 13, FIG.
14 shows a further preferred variant. Thereby, a highly efficient
and accurately controlled transfer of electrical charge is realized
in plating time intervals, i.e. a highly efficient control of
coating deposition in those time intervals. Thereby, to the
arrangement of FIG. 12a, there is superimposed to the output signal
of DC signal generator 8 a voltage signal as shown with source 58,
the output voltage of which having a predetermined or adjustable
course with respect to time, i.e. having a predetermined
characteristic of dU/dt.
[0166] This source 58 is triggered by the output signal of time
unit 16 or 160 at a trigger input T.sub.r in the plating time
intervals, i.e. when the switching unit S.sub.1 is open. As is
shown in FIG. 14 at the bottom, the source 58 may generate e.g. a
linear or a progressive output ramp or another output voltage curve
form with a predetermined characteristic of its time derivative
being triggered, according to a desired growth rate of an
ionplating deposited layer. Due to the time differentiating
characteristic of the series connection of the two capacitive
elements C.sub.I and C.sub.D1 there results from as dU/dt known the
corresponding current flow i.e. corresponding electric charge flow
per time unit. This time derivative dU/dt may also be applied for
source 44 in FIG. 10 as an adjusting value in the negative feedback
control loop.
[0167] As has already been discussed in connection with FIG. 13,
according to FIG. 14 a desired time course of the time derivative
may be preselected or may be adjusted within a negative feedback
control loop, e.g. by the output signal of a unit 42. Thereby in
plating time intervals a desired occupation by chargecarriers is
achieved which, as was mentioned, is monitored during the discharge
time interval to be readjusted in the said negative feedback
control sense. Adjusting the plating current is shown in FIG. 13 in
dash lines. Instead of providing an additional triggered voltage
source, the output voltage of the DC signal generator 8 is varied
in synchronism with the output signal of the timing unit 16 or 160
to provide for desired dU/dt.
[0168] The method explained with the help of the FIGS. 11 to 14, is
most advantageously combined with an ionplating treatment process.
Thereby, a novel ionplating method is created with the ability to
apply electroconductive coating on non-conductive surfaces or to
apply non-conductive coatings on conductive or non-conductive
surfaces.
[0169] The method as has been explained with the help of the FIGS.
12 to 14, for controlling the charge occupation of the surface O
according to FIG. 5 during plating time intervals is considered per
se as an invention which, obviously, may be most advantageously
combined with other features described.
[0170] At all embodiments of the inventive method or apparatus at
which, according to FIG. 4, the oneport 2a, 2b is fed from a DC
signal generator 8 via a chopper unit 14.sub.S or via a chopper
switching unit S.sub.1 and a plasma discharge PL is generated in
the vacuum recipient, as shown schematically in FIG. 15 between
plasma generating electrodes 60a and 60b, electrical instabilities
are avoided in that one of the electrodes loaded with plasma
discharge current, as e.g. electrode 60b, is connected to an
electric potential at the discharge current path. Preferably one of
the inventively provided two electroconductive surfaces of the
oneport is further used according to FIG. 15 as plasma generating
electrode. This is clearly shown by the connection 62 in FIG.
15.
[0171] In FIG. 16 a further preferred embodiment of the inventive
method and apparatus is shown. In the vacuum recipient 3 a glow
discharge is generated, e.g. between the wall of the recipient 3
and a target 64 of conductive or at least semiconductive material.
By means of a gas feed 18 a working gas with a reactive gas is
inlet in the recipient 3. Thus, FIG. 16 shows an apparatus for a
reactive cathode sputtering process. The target 64 may be a part of
a magnetron sputtering source. The workpieces are not shown in FIG.
16. They are either operated floatingly or are driven at a biasing
potential, e.g. as was shown at FIGS. 11 to 14 for ionplating.
[0172] The glow discharge in the embodiment of FIG. 16 is operated
principally according to FIG. 4. After the explanations which were
given, the embodiment of FIG. 16 must not be explained for the man
skilled in the art in details. Because the DC signal generator 8
for operating the glow discharge necessitates relatively high
output power, when the switching unit S.sub.1 is closed by the
timing unit 160, thus generated in phaseopposition thereto, a
series switching unit S.sub.2 is opened, so that the glow discharge
current may not flow through the switching unit S.sub.1. Especially
when the DC signal generator 8 has the output characteristic of a
DC current source, the switching unit S.sub.2 is preferably bridged
by a network, preferably by a resistance network, as is shown at R
in FIG. 16, but may also be bridged by an electronic control
network as by a transistor network.
[0173] Thereby, it is reached that, when switching unit S.sub.2 is
open, not too high voltages occur across the open switching unit
S.sub.2.
[0174] The measures which have been described before, so e.g.
provision of a possibly controlled voltage source U.sub.E according
to FIG. 7c to influence discharge process or the measures for
measuring the discharge process and accordingly influencing the
timing unit 160, as was described with the help of FIG. 8, will be
implemented preferably also in this embodiment. Especially the
features of FIG. 8 allow in the case of cathode sputtering, e.g.
according to FIG. 16, to optimize efficiency of the apparatus in
that the discharge timespans are optimally adapted and adjusted to
the shortest possible extent.
[0175] For the inventive ion plating according to the FIGS. 11 to
14, preferably the output signal of the DC signal generator 8 is
varied at a repetition rate according 50 kHz to 500 kHz, preferably
of at least 90 kHz, and especially preferably with at least 100 kHz
which results in operating the switching unit S.sub.1 at the said
frequency, i.e. the timing unit 16 or 160. The closing times of the
switching unit S.sub.1 are thereby preferably selected to be 50
nsec and 10 .mu.sec preferably between 0.5 82 sec and 2 .mu.sec or
between 2 .mu.sec and 10 .mu.sec, also in dependency from the above
mentioned repetition rate selected and from the intended treatment
process to perform, especially from the intended ionplating
process. If sputtering is performed, as was explained with the help
of FIG. 16 as one preferred embodiment, operating frequency of the
switching unit S.sub.1 according to repetition rate with which the
output signal of the DC signal generator 8 is varied is selected
preferably to be between 50 Hz and 1 MHz further preferably between
5 kHz and 100 kHz, thereby especially preferably between 10 kHz and
20 kHz (all limits included). Here too, the time interval, i.e. the
closing timespans during which the switching unit S.sub.1 remains
closed, are selected to be between 50 nsec and 10 .mu.sec,
preferably between 0.5 .mu.sec and 2 .mu.sec or between 2 .mu.sec
and 10 .mu.sec, dependent on the desired treating process and the
selected repetition rate respectively.
[0176] The inventive method which was described with the help of
FIG. 16 is especially suited for generating silicon oxide coatings,
i.e. coatings of Si.sub.xO.sub.y. The method is extremely suited to
be applied in connection with a sputtering cathode of a mixture of
indium oxide and tin oxide or of indium and tin, which material
being sputtered into an atmosphere containing oxygen to realize a
respective coating at the workpieces. The same apparatus may also
be used for sputtering instead of a target the surfaces of
workpieces, to perform sputter-etching, or to sputter-etch the
surface of a target, so as to remove e.g. a contamination layer as
e.g. an oxide layer or other undesired depositions.
[0177] The reactive cathode sputtering process, as it was described
in connection with FIG. 16, may be operated in the oxidic
(reactive) or in the transition mode, whereby, and with respect to
definition of these operating modes, it is referred to "reactive DC
high rate sputtering as a production method" ("Reaktives
DC-Hochratezerstauben als Produktionsverfahren") of S. Schiller et
al., speech to the International Conference on Metal Coating, San
Diego/Calif., March 1987, Surface and Coating Technology 33
(1987).
[0178] Thereby, it has been recognized that with the inventive
cathode sputtering method, the transition from the metallic to the
reactive mode is considerably less abrupt as is customarily
expected. This means that with the inventive method the
characteristic of the per se instable transition mode, the
so-called intra-mode, becomes flatter than it would be expected,
and that thus a process working point is significantly easier to
stabilize inventively in this intramode than with other methods by
means of negative feedback control.
[0179] In FIG. 17, a further preferred embodiment is shown which
has to be considered in connection with that of FIG. 16.
Nevertheless, the embodiment and method according to FIG. 17 may
also be implied in connection with ion plating or with other
treatment processes. Some further examples shall later be disclosed
with the help of FIG. 19. Without limiting, this further
improvement is shown in FIG. 17 on the basis of the cathode
sputtering method according to FIG. 16.
[0180] Instead of measuring the discharge current here and as an
example, there is provided a current detector 66 to monitor e.g.
the glow discharge current. With monitoring the current I.sub.S,
the occurrence of stochastical arcing, be it overflashing or
breakthroughs, is registered which arcing may be recognized by the
occurrence of current spikes superimposed on the discharge current
I.sub.S. Instead of monitoring the current, stochastic arcing can
also be monitored by an optical detector in the vacuum recipient.
The characteristic of the current monitored by detector 66 is
evaluated in an arc occurrence detection unit 68. The output signal
of the arc detection unit 68 is led to a comparator unit 70.
Therein it is monitored at which repetition frequency the said
stochastic arcing occurs and/or at which intensity which is
recovered by analysing the occurrence and the shape of the said
current spikes. The evaluated actual characteristic value, be it
intensity and/or rate of repetition, is compared in unit 70 with a
predetermined rated value for this characteristic value,
predetermined at unit 72. The output of unit 70 adjusts via a
controller 73 the inventive arrangement framed in broken lines in
block 74 of FIG. 17. Thereby, the occurrence of arcing is monitored
instead of monitoring the discharge current.
[0181] With the controller 73 the repetition rate and/or the extent
of timespans during which the switching unit S.sub.1 is closed, is
controlled via time control unit 16 or 160, this also for a oneport
which is not electrically actively fed, in contrary to the
embodiment of FIG. 17 for cathode sputtering, i.e. for a oneport
with no DC signal generator 8-feed.
[0182] If e.g. the occurrence frequency of stochastic arcing is too
high, the repetition rate of closing the switching unit S.sub.1 is
risen and/or the timespans during which the switching unit S.sub.1
closes the discharge current path are enlarged. By these features,
too, an optimal efficiency is reached, in that the discharge
timespans are generated only so often and so long as necessitated
by the actual arcing behaviour of the process.
[0183] Especially the repetition rate of installing the discharge
or charge exchange timespans is adapted to the actual growth of an
isolating covering. Thereby, automatically, the efficiency of the
processing plant and apparatus is optimized.
[0184] Measuring apparatus for detecting the said arcing
characteristic in plasma discharges and especially in glow
discharges are known.
[0185] The just described method of FIG. 17 is preferably applied
in combination with a cathode sputtering apparatus as was shown in
connection with FIG. 16.
[0186] In FIG. 18 a further most important embodiment of the
inventive method and apparatus is shown, which is especially
important for ion plating according to the FIGS. 11 to 14.
Nevertheless, the methods and principles shown here are not
exclusively applicable for ion plating. FIG. 18 shows,
nevertheless, and without being limiting, such improvement for ion
plating as was disclosed in connection with the FIGS. 11 to 14.
[0187] In FIG. 18 parts, which were already described in connection
with FIG. 12, are referred to with the same reference numbers. In
the vacuum recipient 3 there is performed in one of the
pre-described manners ionplating, e.g. with an evaporating crucible
52 which forms the one of the two electroconductive surfaces of the
inventively exploited oneport. A glow discharge or another plasma
discharge according to the description to FIG. 12 is here not
shown. Several workpiece carrier surfaces 2a.sub.1, 2a.sub.2,
2a.sub.3. . . , 2a.sub.n are provided on which workpieces 1 to be
ionplated are deposited. The respective pairs of inventively
operated electroconductive surfaces 2a.sub.x and 2b are
respectively and as only schematically shown here operated by an
inventive operating block B.sub.x, realized as was explained in
connection with the FIGS. 11 to 14.
[0188] If at such a configuration all switching units S.sub.1
schematically shown are simultaneously closed, then significant
energy is removed from the treating process and especially from the
plasma discharge if the process is operated with such plasma
discharge. This leads to instabilities in the process control.
[0189] Therefore, and according to FIG. 18, there is provided a
supervising time control unit 162 which controls e.g. via a time
staggering unit 71, realized e.g. by a shift register unit, each of
the units B.sub.1 to B.sub.n cyclicly and in a time staggered
manner. This is schematically shown on the time axis t by time
staggered control impulses to each of the units B.sub.x. If it is
desired to operate each of the oneports 2a.sub.x/2b separately and
separately in an optimized manner, then for each of these oneports
there is provided a time control unit 16 or 160, according to FIG.
12, and each of the oneports is operated according to the FIGS. 11
to 14, whereby a synchronization unit makes sure that via the
timing unit 16 or 160, as shown in FIG. 18, the oneports are
discharged staggered in time. It is evident that possibly more than
one workpiece carrier surface 2a.sub.x may be operated together so
as to form groups, which groups of surfaces 2a.sub.x are operated
in a time staggered manner.
[0190] Further, it must be emphasized that with the chopper unit 14
or 14.sub.S, which has been explained with the help of FIG. 6 and
the following figures, a large number of existing vacuum treatment
apparatus with DC signal generator feed may be retrofitted so that
with such retrofitted apparatus processes become realizable for
which, up to now, completely different apparatus and plants were to
be used, especially with different generators as was explained in
connection with FIG. 1.
[0191] Thus, with one and the same apparatus treatment processes
may be realized which, on one hand, necessitate DC operation and
which, on the other hand, could not be realized with DC operation
up to now but which apparatus can now be operated for such
treatments too by the mere fact that the present invention is
implemented
[0192] In FIG. 19 some possibilities of implementing the present
invention shall be further explained, without being complete and
without intent of limiting the invention, just so that the man
skilled in the art gets the clear idea, where and how the present
invention may be applied.
[0193] FIG. 19 departs from a workpiece 1 made of non or low
conductive material which, thus, forms itself the isolating
covering. In the vacuum recipient 3, a plasma discharge PL is
initiated in known manner. The workpiece 1 may be subjected to
etching or may be coated with a conductive or non-conductive layer,
be it by evaporation of electroconductive or non-conductive
material, reactive or non-reactive, or sputtering of conductive or
semi-conductive material, again reactive or non-reactive. The
inventive operational unit, as was described before, is
schematically shown with block 5. In FIG. 19a, departing from the
general representation of FIG. 19, a plasma discharge is shown
between plasma discharge electrodes 80a and 80b, which plasma
discharge is generated by a DC or AC current generator 82,
specially foreseen to feed the plasma discharge. The treating
process may be e.g. ionplating. The inventively operated
electroconductive surfaces 2a and 2b are operated independently
from the plasma discharge. If e.g. non or low conductive material
shall be sputtered, so as to afterwards be deposited in a reactive
or not reactive deposition process on the workpieces 1, one may see
that the generator 82 is preferably provided as an RF generator in
known manner.
[0194] According to FIG. 19b, the plasma discharge PL is sustained
by the field of an induction coil 84. With respect to operating the
inventively provided electroconductive surfaces 2a and 2b forming
the oneport, nothing changes with respect to FIG. 19a.
[0195] According to FIG. 19c, again a plasma discharge is
maintained between plasma discharge electrodes 80a and 80b, whereby
here one of the plasma discharge electrodes, so e.g. the electrode
80b, is used as one of the inventively operated conductive
surfaces, e.g. as surface 2a.
[0196] According to FIG. 19d, a workpiece 1 is e.g. etched in a
plasma discharge, whereby here the electrodes 80a, 80b respectively
form simultaneously the inventively operated conductive surfaces 2a
and 2b.
[0197] With the plasma discharge according to the FIGS. 19a, 19c, a
material disposed on one of the plasma discharge electrodes may be
sputtered to be directly deposited on a workpiece 1 or to be
deposited on such a workpiece after reaction with a working gas or
with parts of such a working gas within the recipient 3. Equally,
evaporated material may be ionized with the plasma discharge shown
to be deposited by ionplating on the workpieces, be it unreacted or
after reaction with a reactive gas led to the vacuum recipient 3.
Principally, how the material sources and its ionization are
realized in the vacuum recipient are of secondary importance for
the present invention. Of prime importance is that workpieces with
an isolating covering are treated in a vacuum atmosphere comprising
electrical charge-carriers.
[0198] One can apply arc evaporation, a so-called rod feed
technique, electron beam evaporation, thermical evaporation or
sputtering, all reactive or not reactive, and further plasma
enhanced chemical wafer deposition (PECVD).
[0199] According to FIG. 19e, a target 85 made of electroconductive
or at least semi-conductive material is sputtered in the plasma
discharge and the sputtered off material is deposited without or
with additional reaction with a reactive gas in recipient 3 as an
electroconductive or a not electroconductive or low
electroconductive layer on workpiece 1. In the first case, the
workpiece comprises a non or low conductive surface which may have
been realized by previous coating or which is inherent to the
workpiece material.
[0200] Both, the plasma discharge and the oneport, may be operated
between the conductive surfaces 2a and 2b.sub.1 as well as between
2a and 2b.sub.2 inventively. Principally and preferably, pairs of
electroconductive surfaces are inventively operated, whereon
deposition of non or low conductive material is to be considered or
at which such materials are provided.
[0201] According to FIG. 19f, in a RF plasma discharge non or low
conductive material of a target 87 is sputtered and is possibly
reacted with a reactive gas inlet through an inlet arrangement 18.
A layer of non or low conductive material is ionplated on
workpieces 1, whereby in this case the workpiece carrier electrode
is formed by one of the inventively operated electroconductive
surfaces, 2b, and the second electroconductive surface 2a is
provided separate from the plasma discharge.
[0202] According to FIG. 19g, there is operated a plasma discharge
between electrodes 80a and 80b, so e.g. a glow discharge, and there
is evaporated material from a crucible 89, an electroconductive
material, a not electroconductive material or a material of low
electroconductivity. In the plasma discharge the evaporated
material is ionized and deposited by ionplating on workpiece 1, so
as to form there a layer of respective material. Here too, a
reactive process may be operated, in that through the gas inlet 18
a reactive gas is fed to the process-atmosphere.
[0203] The glow discharge electrodes as well as the oneport between
the two electroconductive surfaces 2a and 2b are inventively
operated as schematically shown with the two blocks 5.
[0204] Finally, FIG. 19h shows an embodiment of the invention in
analogy to FIG. 19g, whereby here the plasma discharge is generated
for ionizing evaporated material by the field coupled into the
recipient 3 and generated by an induction coil 91.
[0205] The example shown and described may show to the man skilled
in the art to which an extent the present invention may be
applied.
Example for Inventive Cathode Sputtering
[0206]
1 1) apparatus BAS 450 of the firm Balzers AG, Balzers/FL Cathode
AK 510 of the firm Balzers AG magnet system MA 525 of the firm
Balzers AG target: S10-2403 silicon target (5 .times. 10 inches) DC
power supply: 10 kW distance between target and substrate: 70 mm
rotation-frequency of workpiece carrier: <0.5 Hz frequency
(repetition rate) 17 kHz of inventive discharge: timespan of
discharge .9 .mu.sec kind of discharge: short circuit sputtering
power: 2 kW gas pressures in the recipient: Ar: pAr = 8E-3 mbar
O.sub.2: pO2 = 2E-3 mbar DC voltage at the target: in the metallic
mode: -668 V in the working point between -340 V metallic mode and
oxidic mode: coating: SiO.sub.2 index of refraction SiO.sub.2 at
.lambda. = 633 nm: 1.47 extinction coefficient k of SiO.sub.2
<1E-5 at .lambda. = 633 nm: 2) apparatus BAK 760 of the firm
Balzers AG, Balzers/FL cathode: AK 525 of the firm Balzers AG
magnet system: MA 525 of the firm Balzers AG target: S10-3976
silicon target (5 .times. 25 inches) DC power supply: 10 kW
distance between target and substrate: 60 mm rotational frequency
of workpiece carrier: 0.5 Hz repetition frequency (repetition rate)
17 .mu.sec of inventively applied discharge: time-span of discharge
16 .mu.sec discharge conditions: short circuit sputtering power 2
kW gas pressures in the recipient: Ar: pAr = 8E-4 bar O2: pO2 =
2E-5 mbar DC voltage at the target -660 V in the metallic mode: in
the working point between -550 V metallic and oxidic mode:
deposited layer: 284 nm SiO2 energy yield DDR(SiO2) = 44.6 nm mm
2/Ws (DDR = deposited volume of coating per energy applied
therefor) index of refraction of the SiO2 1.47 at .lambda. = 633 nm
extinction coefficient k for the SiO2 <1E-5 at .lambda. = 633
nm
Examples for Inventive Ionplating
[0207] 1. Forming tools were coated in a reactive ionplating
process with an apparatus construed as schematically shown in FIG.
12a and according to the embodiments according to the FIGS. 15 and
18. Silicon was evaporated and the tools coated with a silicon
nitride coating. The forming tools thus coated with a corrosion
resistant layer were afterwards coated with a further hard material
coating to make the tools wear resistant.
[0208] Therefore, titanium-carbonitride was used for aluminum
flanching wheels as forming tools, titanium-nitride for injection
mould forms for polyvinylchloride and chromium-nitride coating for
metal pressure die casting tools.
[0209] Thereby, first, well-known prior art ionplating processes
were used.
[0210] Only with the implementation of the inventive method to form
an inventive ion plating apparatus, i.e. applying a DC voltage and
discharging at a predetermined repetition rate, problems were
resolved which resulted from the electrically isolated bottom layer
(isolating covering) and, especially, a sufficiently adhering
abrasion resistant coating could be deposited on the
silicon-nitride layer. Only the tools which had been treated by
inventive ionplating could be used in practice.
[0211] 2. It was attempted to coat turn-over cutting plates by
known physical vapor deposition procedures (PVD). Thereby,
simultaneously aluminum and chromium were evaporated from crucible.
Thereby it was recognized that coating layers are on one hand of
sufficient hardness, but that the abrasion resistance does not
suffice for applications with specially high demands with respect
to abrasion.
[0212] An analysis of the coating with the raster electron
microscope showed that the layers were not sufficiently
compact.
[0213] Therefore, the same coating was deposited by the inventive
ion plating method, whereby and as desired a significant increase
of the abrasion resistance was achieved at the turn-over cutting
plates.
[0214] For mass production according to the two examples given
above with more than two workpiece carriers, the apparatus was
construed as schematically shown in FIG. 18. It was recognized that
a minimal timespan of 10 nsec between discharge timespans applied
at the different workpiece carriers was necessary. The operation
became especially stable with such time intervals larger than 20
nsec between respective discharge timespans at the different
workpiece carriers.
[0215] With this method workpieces deposited on a large number of
workpiece carrier surfaces could be treated "quasi simultaneously"
by inventive ionplating. The apparatus used comprised twelve
different workpiece carriers. Thereby, when the turn-over cutting
plates were coated, their abrasion resistance became substantially
equal to the abrasion resistance of such turn-over cutting plates
which had been coated by prior art high temperature CVD
methods.
[0216] Generally spoken, workpieces which have been inventively ion
plated, have a higher ductility than workpieces which have been
treated by high temperature CVD methods. This because the inventive
ion plating leads to significant lower temperatures during the
treating process. The said high ductility which was achieved by the
inventively ionplated turn-over cutting plates, allows such cutting
plates to be used in uninterrupted cutting operation.
[0217] The following additional and substantial advantages of the
invention were recognized:
[0218] 1. For Cathode Sputtering
[0219] Besides the advantages which have been already mentioned,
that the efficiency of the inventive method and apparatus in the
sense of deposited coating volume per applied electrical energy is
risen compared with previously known methods, the transition from
the metallic mode in the reactive or oxidic mode becomes steadier
so that a process working point is easier to stabilize by negative
feedback control measures in the said transition mode.
[0220] 2. For Inventive Ionplating
[0221] Besides the advantages mentioned above the following
advantages were recognized, namely that the adherence of
inventively ion plated coatings is significantly improved, the
compactness of inventively deposited coatings is significantly
increased and thereby the abrasion resistance, the treatment
temperature of the workpieces to be treated may inventively be
significantly lowered as is known for ionplating. By the fact that
ionplating may now be applied due to its inventive improvement
there, where up to now it was customary to apply high temperature
CVD methods, the ductility of inventively treated workpieces may
significantly be increased compared with workpieces equally coated,
but by high temperature CVD.
[0222] Subsequently and in the form of a sequence of summarizing
statements, the most important features and feature combinations of
the invention are listed:
[0223] The invention considers:
[0224] I. A method for treating workpieces in a vacuum atmosphere
by which method an electrical signal is applied to at least two
electroconductive surfaces, which surfaces are exposed to a vacuum
treatment atmosphere and whereby at least one of said two surfaces
has a "isolating covering" of not or low conductive material which
at least in part covers said surface and whereby the vacuum
atmosphere comprises electrical chargecarriers and whereby further
the output signal of a DC signal generator is applied to the
oneport formed by said two electroconductive surfaces, and wherein
further, during the treatment, there is applied a further
electrical signal which is different from the output signal of said
generator to said oneport at a repetition rate and during timespans
of such extent as required by electric charges depositing in the
vacuum atmosphere and on said isolating covering and whereby,
further, during said treatment the output signal of the DC signal
generator is applied considerably longer than the further electric
signal is applied.
[0225] II. A method for workpiece treatment in a vacuum atmosphere
which comprises electrical chargecarriers and whereby at least two
electroconductive surfaces are interact with the vacuum atmosphere
and at least one thereof is covered at least in part by an
isolating covering of not or low conductive material, and whereby
the said electroconductive surfaces are at least for short time
intervals at predetermined or at adjustable repetition rate
shortened and/or are connected to a source of electrical charge via
a discharge or charge exchange current path.
[0226] III. A method following a method with the features of I and
II, whereby further short circuiting and/or applying a source of
electrical charge is performed in timespans during which said
further electrical signal is applied and whereby at least the
isolating covering surface according to (I) forms that one
according to (II).
[0227] IV. A method preferably realized according to the features
of I or III, whereby the further signal is generated by choppering
of the output signal of the generator.
[0228] V. A method preferably realized according to the features of
IV, whereby the further signal is generated by parallel choppering
of the output signal of the generator.
[0229] VI. A method preferably following one of the sets of
features I to V, at which the at least one workpiece
[0230] a) comprises a surface of not or low conductive material as
said isolating covering and/or
[0231] b) is coated with a layer of not or low conductive material
as said isolating covering by said treatment and the workpiece is
deposited on one of said electroconductive surfaces.
[0232] VII. A method preferably following the set of features
according to VI, whereby on a surface which is formed of not or low
conductive material as the said isolating covering, a layer of
conductive material is deposited by the treatment process.
[0233] VIII. A method wherein preferably the set of features of one
of the sets I to VII is applied and whereby the workpiece treatment
is an ionplating process.
[0234] IX. A method which preferably follows the features of one of
the sets I to VIII, whereby further
[0235] a) a conductive material, whereon the said isolating
covering is provided independent from the treatment process or is
applied during the treatment process, is evaporated or sputtered as
source material for the treatment process and/or
[0236] b) a not or low conductive material as a source material,
which forms the said isolating covering, is evaporated for the
treatment process and the material forms one of said surfaces or is
deposited on a conductive one of the said surfaces.
[0237] X. A method preferably following one of the sets defined in
I to IX, whereby the treatment process is a PVD treatment process
or a reactive PVD treatment process or a plasma enhanced CVD
treatment process.
[0238] XI. A method preferably following the features of one of the
sets I to X, whereby further a plasma is generated in the vacuum
atmosphere.
[0239] XII. A method preferably following the set of features
according to IX, whereby further the plasma is fed from one of the
said surfaces.
[0240] XIII. A method preferably following the set defined in XI,
whereby further one of the electrodes from which the plasma
discharge is fed, is deposited on the electric potential of one of
the said surfaces.
[0241] XIV. A method preferably following one of the sets II to
XIII, whereby further the discharge or charge exchange behaviour is
measured in the current path.
[0242] XV. A method preferably following the set defined in XIV,
whereby further the thickness of an isolating covering is retrieved
from the measured discharge or charge exchange behaviour.
[0243] XVI. A method preferably following the set of features as
defined in XIV, whereby the actual occupation of the isolating
covering by electrical chargecarriers is retrieved from the
measured discharge or charge exchange behaviour.
[0244] XVII. A method which preferably follows one of the sets of
features according to II to XVI, whereby the growth of an
occupation with electrical chargecarriers on the isolating covering
is measured.
[0245] XVIII. A method preferably following a set of features
according to XIV to XVII, whereby further the measured discharge or
charge exchange behaviour is compared with a rated behaviour and,
as a function of the result of this comparison, the covering with
electrical chargecarriers of the isolating covering is adjusted by
external feeding electrical charges and/or by adjusting the
repetition frequency of discharge or charge exchange cycles and/or
by adjusting the time extent provided for each discharge or charge
exchange step, so that the resultant measured actual discharge or
charge exchange characteristic substantially accords to the rated
behaviour.
[0246] XIX. A method preferably following the features of one of
the sets XIV to XVIII, whereby spontaneous break-throughs or
flash-overs, generally called "arcing", caused by occupation of
said isolating covering by electrical chargecarriers, is monitored
or watched and, according to their frequency of occurrence and/or
their kind of occurrence the occupation by electrical
chargecarriers is open loop adjusted or is negative feedback
controlled by varying an electrical charge externally input and/or
by varying the repetition rate of discharge or charge exchange
cycles and/or by adjusting the time extent of discharge or charge
exchange cycles, so that a desired behaviour with respect to the
said spontaneous arcing is reached.
[0247] XX. A method preferably following the features of one of the
sets XIV to XIX, whereby then, when the measured discharge or
charge exchange behaviour at least substantially accords with a
predetermined behaviour, the respective discharge or charge
exchange cycle is stopped.
[0248] XXI. A method preferably following a set of features
according to one of II to XX, whereby in timespans between
discharge or charge exchange cycles a growth of said occupation
with electrical chargecarriers is controlled by external input of
electrical charge onto that surface with the isolating covering,
thus being the surface carrying the electrical chargecarriers
deposited on said isolating covering.
[0249] XXII. A method preferably following the set of features
according to XXI, whereby further the growth of occupation with
electric chargecarriers is controlled as growth of a desired layer
on at least one workpiece during ionplating deposition of said
layer.
[0250] XXIII. A method which preferably follows one of the sets of
features according to I to XXII, whereby the workpiece surface
acting itself as isolating covering is not or low conductive and is
coated by ionplating and/or the workpiece surface is coated by
ionplating with a coating of not or low conductive material as an
isolating covering, and thereby a workpiece carrier surface is one
of said electroconductive surfaces, whereby a capacitive element is
connected in series to the said carrier surface in the discharge
current path, so that during time intervals of ionplating this
capacitance and the capacitance formed by the at least one
isolating covering at the workpiece appears connected in series and
during time intervals of discharge or charge exchange appear
connected in parallel, and that during plating time intervals this
series connection is electrically charged so that there occurs an
at least predominantly pre-set ion occupation on said
workpieces.
[0251] XXIV. A method which preferably follows the set of features
according to XXIII, whereby in time intervals of ionplating a
predetermined or adjustable electric charge is fed through the
series connection of the said two capacitors and that therewith the
occupation with electrical chargecarriers at the workpiece surface
is controlled.
[0252] XXV. A method which preferably follows the set of features
according to XXIV, whereby the said electrical charge is applied by
applying a voltage with predetermined time derivative to the said
series connection of the two capacitors.
[0253] XXVI. A method preferably following the set of features
according to XXIII to XXV, further comprising electrically charging
said series connection with inductively generated over-voltage.
[0254] XXVII. A method which preferably follows the set of features
as defined in one of XXIII to XXVI, whereby charging said series
connection in time intervals of ionplating occurs with a voltage
signal having a ramp-shaped time course and thus with an at least
substantially constant electrical current, and that thereby there
is realized a substantially constant rate of electric
chargecarriers deposition.
[0255] XXVIII. A method following preferably a set of features
according to one of I to XXVII, whereby further two or more than
two pairs of surfaces are provided and each pair or each group of
such pairs is provided with a DC signal generator and/or with a
discharge or charge exchange current path, each pair or groups is
operated mutually staggered in time.
[0256] XXIX. A method which preferably follows a set of features
according to one of I to XXVIII, whereby workpieces are provided on
at least two pairs or groups of said surfaces and are treated by
ionplating, and that further the pairs or groups of pairs are
subjected in time staggered manner to discharge cycles.
[0257] XXX. A method which preferably follows one of the sets of
features according to XXIII to XXIX, whereby the discharge
behaviour is measured, the measuring result is compared with a
rated behaviour and by varying charging the said series connection
during time intervals of ionplating as a function of the result of
said comparison, the occupation by ions of the workpiece and thus
the measured discharge behaviour is adjusted to substantially
become equal to the rated behaviour, thereby possibly considering
time-variations of the capacitor formed by said one surface,
thereon the isolating covering and thereon the occupation by
electrical chargecarriers, by considering variations of the
discharge time constant.
[0258] XXXI. A method which preferably follows a set of features
according to one of XXIII to XXX, whereby further the discharge
cycle is repeated with a repetition rate or frequency of between 50
kHz and 500 kHz (both included), preferably with at least 90 kHz
and even more preferably with at least 100 kHz.
[0259] XXXII. A method preferably following the set of features
according to one of the sets XXIII to XXXI, whereby on at least one
workpiece there is deposited at least one corrosion resistant
and/or at least one wear resistant coating by ionplating, so e.g. a
not or low conductive first layer as a corrosion resistant layer
and an electroconductive second layer as wear resistant layer or
further combinations of layers as a system of layers with two and
more than two layers.
[0260] XXXIII. A method which preferably follows the features
according to one of the sets I to XXI, whereby an electroconductive
material is sputtered by means of a plasma discharge in the vacuum
atmosphere, which plasma discharge is sustained between the
material to be sputtered and a counter-electrode, and whereby the
sputtered material is reacted in the vacuum atmosphere with an
inlet reactive gas to form a not or low conductive material
compound, and further a controlled discharge current path is
provided across the plasma discharge stage and that there is
provided across said discharge current path the DC signal generator
and an interrupting switch unit, both connected in series, whereby
the interrupting switch unit and the controlled discharge current
path are closed in phase opposition.
[0261] XXXIV. A method preferably following a set of features as
defined in XXXIII, whereby further, especially when the said DC
signal generator has an output characteristic substantially
according to a current source, the said interrupting switching unit
is bridged by an electronic circuit, preferably made of passive
elements, preferably made of resistances.
[0262] XXXV. A method which preferably follows a set of features as
defined in XXXIII or XXXIV, whereby further the reactive sputtering
process is operated in the oxidic or in the transition mode between
metallic and oxidic operation mode.
[0263] XXXVI. A method which preferably follows the features as
defined in one of the sets XXXIII to XXXV, whereby further silicon
is sputtered and is reacted with oxygen for depositing a silicon
oxide layer.
[0264] XXXVII. A method which preferably follows the features
according to one of the sets XXXIII to XXXVI, whereby dielectric or
low or semi-conductive layers are formed from material based on a
metal.
[0265] XXXVIII. A method which preferably follows the features as
defined in the sets I to XXI, XXXIII to XXXVII, whereby the further
electric signal is applied intermittently and with a repetition
rate according to a frequency of 50 Hz to 1 MHz (both limits
included), preferably of 5 kHz to 100 kHz (both limits included),
further preferred especially of 10 kHz to 20 kHz(both limits
included).
[0266] XXXIX. A method which preferably follows features according
to one of the sets I to XXXVIII whereby the said further electric
signal is intermittently applied during time spans with extents of
between 50 nsec and 10 .mu.sec (both limits included) preferably of
between 0.5 .mu.sec and 2 .mu.sec (both limits included) or of 2
.mu.sec and 10 .mu.sec (both limits included).
[0267] XL. A method for controlling the occupation with electrical
chargecarriers of a surface of an object which surface is formed by
a not or low conductive part of said object or by a not or low
conductive covering of said object, whereby said object is
deposited adjacent or on an electro-conductive surface and whereby
the surface of said object is exposed to a vacuum atmosphere with
electrical chargecarriers whereby a further electro-conductive
surface is provided exposed to said vacuum atmosphere and a
electrical charge is driven through said one electro-conductive
surface, the said object with said surface, a region of said vacuum
atmosphere and said further electro-conductive surface in a
controlled manner whereby preferably a plasma-discharge is
generated in said vacuum atmosphere.
[0268] XXXXI. A vacuum treatment apparatus with a vacuum recipient
(3) therein a carrier arrangement for workpieces at which apparatus
an electric signal generator is connected to at least (2a, 2b)
electro-conductive surfaces which interact with said atmosphere in
the vacuum recipient whereby the signal generator comprises a
DC-signal generator (8) and a unit (12, 14, 14.sub.S, S.sub.1) at
the output side of the DC-signal generator by which unit the output
signal of the generator (8) is controllably varied to generate an
electric signal applied to said two electro-conductive surfaces
(2a, 2b) whereby the said unit is so controlled or is so
controllable (16, 160) that with a predetermined or adjustable
repetition frequency and/or for predetermined or adjustable
time-spans the signal applied to the said two surfaces is different
from the output signal of the said DC-signal generator (8).
[0269] XXXXII. A vacuum treatment apparatus with a vacuum recipient
(3) and therein a carrier arrangement for workpieces further with
means for generating electrical chargecarriers in said recipient
whereby two electro-conductive surfaces (2a, 2b ) are in
interaction with the atmosphere in the recipient (3) and are
interconnected via a controllable discharge or charge exchange
current path (14, 14.sub.S, S.sub.1).
[0270] XXXXIII. A vacuum-treatment apparatus which preferably has
the feature of the sets XXXXI and XXXXII whereby further the
repetition rate and the control of said discharge or charge
exchange current path are synchronized and at least one of the
electro-conductive surfaces according to the apparatus as defined
in XXXXI is that of the apparatus defined in the features of
XXXXII.
[0271] XXXXIV. A vacuum-treatment apparatus which has preferably
the features as defined in one of the sets XXXXI to XXXXIII whereby
further the two electro-conductive surfaces (2a, 2b ) are
interconnected via a controlled short-circuiting unit (14.sub.S,
S.sub.1).
[0272] XXXXV. A vacuum-treatment apparatus which preferably has
features as defined f or the apparatus according to XXXXIV whereby
the short-circuiting switching unit (S.sub.1) acts as well as the
unit at the output side of said DC-signal generator (8) an d as a
control unit (14) in the discharge or charge exchange current
path.
[0273] XXXXVI. A vacuum apparatus which preferably has the features
of the apparatus according to one of the apparatus as defined in
XXXXI to XXXXV whereby further one of the electro-conductive
surfaces (29) forms a workpiece carrier surface of forms a surface
(52, 2b) for supporting a source-material which source-material is
used during a coating process at said apparatus of at least one
workpiece (1).
[0274] XXXXVII. A vacuum apparatus which preferably has the
features of an apparatus according to one of XXXXI to XXXXVI
whereby one of the electro-conductive surfaces (2a) forms a
workpiece carrier surface and the apparatus is a ionplating
apparatus.
[0275] IIL. A vacuum treatment apparatus which preferably has the
features of an apparatus as defined in one of the sets XXXXI to
XXXXVI whereby further a target object (64) is provided which is
sputtered and wherein one of said electro-conductive surfaces (2b)
is contacting said vacuum atmosphere via the said target object
(64).
[0276] IL. A vacuum treatment apparatus which has preferably the
feature of the apparatus according to IIL whereby the target object
is part of a magnetron arrangement.
[0277] L. A vacuum treatment apparatus which has preferably the
features of the apparatus according to one of the sets XXXI to IL
whereby means (52, 50, 3, 64) are provided to generate a
plasma-discharge (PL) in the recipient.
[0278] LI. A vacuum treatment apparatus which preferably has the
features of an apparatus as defined in one of the sets XXXI to L
whereby at least one electrode-pair is provided to generate a
plasma-discharge in the recipient and whereby preferably at least
one of these electrodes (64) forms one of the said
electro-conductive surfaces (2b).
[0279] IIL. A vacuum treatment apparatus which has preferably the
features of an apparatus as defined in one of the sets XXXXI to LI
whereby further at least three (2a.sub.1, 2a.sub.2, 2b) of the said
electro-conductive surfaces are provided and grouped at least in
pairs and at least one generator (8) according to set XXXXI and/or
a current path according to set XXXXII is provided to each group
and relatively, controlled by means of a time-control-unit (70)
staggered in time.
[0280] LIII. A vacuum treatment apparatus which has preferably the
features of an apparatus as defined by the features of set LII
whereby further more than two groups of electro-conductive surfaces
are controlled in mutually time staggered manner by the time
control unit.
[0281] LIV. A vacuum treatment apparatus which has preferably the
features of an apparatus as defined in one of the sets XXXXI to LII
whereby further a gasfeed arrangement (18) is provided in the
vacuum recipient which gasfeed arrangement is linked to a reactive
gas tank.
[0282] LV. A vacuum treatment apparatus which preferably has the
features of an apparatus as defined by the features of one of the
sets XXXXI to LIV whereby the apparatus is a PVD-apparatus or a
reactive PVD-apparatus or an apparatus for plasma-enhanced CVD or
an apparatus for thermical CVD with an arrangement for ionizing of
a gasious part of said vacuum atmosphere in the recipient.
[0283] LVI. A vacuum treatment apparatus which has preferably the
features of an apparatus defined by the features of one of the sets
XXXXI to LV whereby further a low voltage glow discharge-stage is
provided preferably with a glow electron-emitting cathode (50).
[0284] LVII. A vacuum treatment apparatus which has preferably the
features of an apparatus as defined by one of the sets of features
XXXXI to LVI whereby at least two electrodes (60a, 60b) are
provided for generating a plasma (PL) in the vacuum recipient (3)
and whereby at least one of these electrodes (60b) is connected to
the electrical potential of one of the said electro-conductive
surfaces (62).
[0285] LVIII. A vacuum treatment apparatus which preferably has the
features of an-apparatus as defined by one of the sets of features
XXXXI to LVII whereby the controlled discharge or charge exchange
current path is capacitive (C.sub.I, C.sub.D, C.sub.D1) when this
path is controllably closed.
[0286] LIX. A vacuum treatment apparatus which has preferably the
features of an apparatus as defined by one of the sets XXXXI to
LVIII whereby an electrical charge storage (C.sub.D, 20, C.sub.D1)
is provided in the discharge current path and/or a voltage source
(U.sub.E).
[0287] LX. A vacuum treatment apparatus which has preferably the
features of an apparatus as defined in one of the sets XXXXI to LIX
whereby further a measuring arrangement (24, 32, 66) is provided
along for measuring a signal representative for a current flowing
through said controlled discharge or charge exchange current
path.
[0288] LXI. A vacuum treatment apparatus which has preferably the
features according to an apparatus as defined in set LX whereby the
output signal of the measuring arrangement acts on an adjusting
means (30, 16, 160, 56, 73) for controlling said control-discharge
or charge-exchange current path.
[0289] LXII. A vacuum treatment apparatus which has preferably the
features of an apparatus as defined in one of the sets LX or LXI
whereby the output of the measuring arrangement acts on a threshold
sensitive unit (26) with preferably adjustable threshold value (W)
the output thereof being led to a control input (30, R) for said
control discharge or charge exchange current path.
[0290] LXIII. A vacuum treatment apparatus which has preferably the
features of an apparatus as defined by at least one of the sets LX
to LXII whereby further the output of the measuring arrangement
possibly via an analogue to digital converter (34) acts on an
actual value storage means (36) the output of which being led to
one input of a comparison unit (38) as well as the output of a
rated value storage means (40) and that the output of the
comparison unit (38) acts on a control input of said controlled
discharge or charge exchange current path.
[0291] LXIV. A vacuum treatment apparatus which has preferably the
features of an apparatus as defined according to one of the sets
XXXXI to LXIII whereby a controlled or controllable source of
electric charge (20, 22, 44, 58, C.sub.D1) is provided on an
electric path between the said two electro-conductive surfaces (2a,
2b) especially during time-spans in which the said controlled
discharge or charge-exchange current path is controllably
interrupted or controlled to become high-ohmic.
[0292] LXV. A vacuum treatment apparatus which preferably has a
feature of an apparatus as defined by one of the sets XXXXI to LXIV
whereby further a capacitive element (C.sub.D1) is connected to at
least one of the said electro-conductive surfaces (2a, 2b) in said
current path and further comprising means (46, 46a, 58) for
electrically charging the serial connection of said capacitive
element (D.sub.D1) with the oneport formed between said two
electro-conductive surfaces (2a, 2b) whereby said capacitive
element appears in electrical parallelism to said oneport when said
current path is controllably closed.
[0293] LXVI. A vacuum treatment apparatus which comprises
preferably the features of an apparatus as defined in one of the
sets of features XXXXI to LXV whereby a capacitive element
(C.sub.D1) is electrically connected to at least one of the
electro-conductive surfaces (2a) and that when the said current
flow path is controlled to be high-ohmic or interrupted the oneport
defined between the two electro-conductive surfaces (2a, 2b) is
connected in series with the said capacitive element and a
voltage'source (58) is as well in series thereto which source
generates an output signal controllably varying in time or
adjustably varying. in time (dU/dt) so that by the said serial
connection and as a function of the variation of said output signal
of said voltage source in time there flows through said serial
connection a controlled or adjustable current.
[0294] LXVII. A vacuum treatment apparatus preferably with the
features of an apparatus as defined in one of the sets, of features
LXV to LXVI whereby means are provided to charge said serial
circuit which comprise inductive means (L.sub.66).
[0295] LXVIII. A vacuum treatment apparatus preferably with the
features of an apparatus as defined in at least one of the sets of
features XXXXI to LXVI whereby the apparatus is an ionplating
apparatus and one of the said electro-conductive surfaces (2a)
forms the carrier for workpieces (1) and whereby via a capacitive
element (C.sub.D1) and a control switching unit (S.sub.1) a
discharge current path is formed between the said conductive
surfaces (2a, 2b) and the DC signal generator (8) is connected in
parallel to said switching unit (S.sub.1) and whereby preferably a
source of electric charge (58, D.sub.D1) acts in series to said
switching unit (S.sub.1) and said capacitive element (C.sub.D1) or
that a charge source comprises said capacitive element (C.sub.D1)
whereby operation of said source of electric charge is synchronized
with the operation of said switching unit (S.sub.1) so that when
said switching unit (S.sub.1) is open a predetermined or adjustable
charging current is generated to and from said electro-conductive
surfaces (2a, 2b).
[0296] LXIX. A vacuum treatment apparatus preferably comprising the
features of an apparatus as defined in the set of features LXVIII
whereby more than one, preferably more than two of the
electro-conductive surfaces (2a.sub.x) acting as workpiece carriers
are provided and wherein, respectively, a switching unit is
provided to each of said electro-conductive surfaces acting as
workpiece carriers to form, respectively, a discharge current path
and therein a capacitive element (C.sub.D1) and, preferably, a
source of electric charge (58, C.sub.D1) or a source of electric
charge is formed with said capacitive elements (C.sub.D1) whereby a
time control unit (162, 71) is provided which operates the
switching units (S.sub.1) in a mutually time staggered manner.
[0297] LXX. A vacuum treatment apparatus preferably construed with
the features of an apparatus as defined by one of the sets of
features XXXXI to LXIX whereby there is provided in the recipient a
sputtered target object (64) at which there is provided one of the
said electro-conductive surfaces (2b) whereby the two
electro-conductive surfaces (2a, 2b) are linked by a controlled
switching unit (S.sub.1) to form a control discharge current path
and further a DC-signal generator (8) is provided with a switching
unit (S.sub.2), in series to its output whereby the switching units
(S.sub.1, S.sub.2) are intermittently operated under the control of
a time control unit (160) in phase opposition.
[0298] LXXI. A vacuum treatment apparatus preferably construed with
the features of an apparatus as defined by the set of features LXX
whereby detection means are provided to detect arcing so e.g.
flash-overs and break-throughs within the recipient (3) and that
the output signal or said detection means acts on a first input of
a comparator unit (70), the output signal of a rated value
generating unit (72) being led to a second input of said comparison
unit, the output signal of said comparison unit (70) acting on an
adjusting unit and preferably on a control input of a time control
unit (16, 160) which latter adjusts the intermittent operation of
the switching unit (S.sub.1).
[0299] LXXII. A vacuum treatment apparatus preferably with the
features of an apparatus as defined in at least one of the sets of
features XXXXI to LXXI the apparatus being an apparatus for
producing optical layers on workpieces.
[0300] LXXIII. An apparatus preferably construed with features of
an apparatus as defined by the sets of features LXXII whereby the
apparatus comprises at least one sputtered target object (64).
[0301] LXXIV. A vacuum treatment apparatus which preferably
comprises the features of an apparatus as defined in one of the
sets of features XXXXI to LXXI the apparatus being an apparatus for
the production of hard material and/or wear-protective
coatings.
[0302] LXXV. A vacuum treatment apparatus which is preferably
construed with the features of an apparatus as defined by the set
of features LXXIV whereby the apparatus is an ionplating
apparatus.
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