U.S. patent application number 09/091004 was filed with the patent office on 2001-07-12 for hf-plasma coating chamber or pecvd coating chamber, its use and method of plating cds using the chamber.
This patent application is currently assigned to UNAXIS BALZERS AG. Invention is credited to WEICHART, JUERGEN.
Application Number | 20010007245 09/091004 |
Document ID | / |
Family ID | 4256821 |
Filed Date | 2001-07-12 |
United States Patent
Application |
20010007245 |
Kind Code |
A1 |
WEICHART, JUERGEN |
July 12, 2001 |
HF-PLASMA COATING CHAMBER OR PECVD COATING CHAMBER, ITS USE AND
METHOD OF PLATING CDS USING THE CHAMBER
Abstract
A HF plasma treatment chamber is provided for at least one
dielectric substrate. A HF generator for the plasma discharge, a
coupling-in arrangement connected with the generating for supplying
HF energy into the chamber, and at least one substrate receiving
device defining a receiving surface for the substrate comprise the
chamber. The generator is operatively connected with the chamber by
way of a dielectric layer. The chamber is a coating chamber and,
for the coating of a metallic surface of at least one dielectric
substrate and/or the coating of at least one dielectric substrate
with a metallic layer. The receiving device as well as the HF
connection to the generator are arranged such that the HF discharge
current circuit is connected with the chamber by way of the
dielectric substrate as the capacitive coupling-in element.
Inventors: |
WEICHART, JUERGEN; (BALZERS,
LI) |
Correspondence
Address: |
EVENSON MCKEOWN EDWARDS & LENAHAN
1200 G STREET N W SUITE 700
WASHINGTON
DC
20005
|
Assignee: |
UNAXIS BALZERS AG
|
Family ID: |
4256821 |
Appl. No.: |
09/091004 |
Filed: |
November 13, 1998 |
PCT Filed: |
November 27, 1996 |
PCT NO: |
PCT/CH96/00420 |
Current U.S.
Class: |
118/723MW ;
427/255.28; 427/569; 427/575 |
Current CPC
Class: |
H01J 37/32091 20130101;
H01J 37/32238 20130101 |
Class at
Publication: |
118/723.0MW ;
427/569; 427/575; 427/255.28 |
International
Class: |
C23C 016/505; C23C
016/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 8, 1995 |
CH |
3477/95 |
Claims
1. HF plasma treatment chamber for at least one dielectric
substrate 1, having a HF generator 19 for the plasma discharge as
well as a coupling-in arrangement connected therewith for HF energy
into the chamber 20 as well as at least one substrate receiving
device 9 defining a receiving surface for the substrate 1,
characterized in that the receiving device 9 as well as the HF
connection to the generator 9 are arranged such that the HF
discharge circuit includes the substrate 1 as a capacitive
coupling-in element.
2. PECVD coating chamber for at least two plane substrates having a
generator 19 for the plasma discharge as well as a coupling-in
arrangement, connected therewith, for the discharge energy into the
chamber 20 as well as having at least two substrate receiving
devices 9 defining one receiving surface 11 respectively for one of
the substrates 1, and having a gas inlet 13 as well as a gas
pump-out 7 arrangement on the chamber, characterized in that the
receiving surfaces 11 are situated opposite one another and
defining, essentially in a closing manner, mutually opposite
process space boundary surfaces, in that A.ltoreq.10 mm applies to
the distance A of these surfaces.
3. Treatment chamber according to the characteristics of claim 1
having substrate receiving devices according to claim 2.
4. Chamber according to one of claims 1 or 3, characterized in that
the HF generator 19 is a microwave generator, and the substrate
forms the coupling-in window.
5. Chamber according to one of claims 1, 3 or 4, characterized in
that coupling-in arrangement has a metallic electrode surface 21
which is arranged in the area of the receiving surface 11 and is
essentially plane-parallel thereto, which electrode surface 21 is
exposed toward the chamber interior 20 or is dielectrically
closed.
6. Chamber according to one of claims 1 to 5, characterized in that
the receiving device 9 or the receiving devices 9 is/are formed for
circular-disk-shaped substrates 1, a gas inlet arrangement 13 leads
into the peripheral area of the respective receiving-device-defined
receiving surface 11, preferably in a distributed manner, and a gas
pump-out arrangement 7 leads centrally with respect to the
receiving surfaces 11 into the chamber.
7. Chamber according to one of claims 2 to 6, characterized in that
the coupling-in arrangement comprises an electrode 17 which is
arranged on a chamber wall section 15, 17 spacing the receiving
surfaces 11, preferably as a surrounding ring electrode 15.
8. Chamber according to one of claims 1, 3 to 7, characterized in
that it is constructed as a PECVD chamber and, for this purpose,
has a gas inlet arrangement 13 as well as a gas pump-out
arrangement 7.
9. Use of the chamber according to one of claims 1 to 8 for the
treatment of substrates with a basic plastic body.
10. Use according to claim 9 for the protective coating of a
metal-coated substrate surface, preferably of an optical storage
disk, preferably on a CD.
11. Process for the protective coating of metallically coated
storage disks in the continuous operation, characterized in that a
vacuum coating process is used for this purpose.
12. Process according to claim 11, characterized in that a PECVD
process is used.
13. Process according to one of claims 11 or 12, characterized in
that a HF plasma is generated for the coating an the HF energy for
this purpose is coupled into the process space by way of the
substrate.
Description
[0001] The present invention is based on problems and requirements
which have arisen during the manufacturing of CDs. However, in
principle, the resulting solutions can be used for other
applications. For this reason, the present description will first
specifically start out from the requirements and problems during
the manufacturing of CDs and solutions according to the invention
will be described in order to then, in a generalizing manner,
indicate how the found principles can be used in general.
[0002] In the manufacture of CDs, it has been accepted to treat the
individual plastic substrates at very short cycle times per
processing step, specifically in the second range. In this case,
the vacuum sputtering technique has been accepted for applying the
reflecting metal layer. The subsequent lacquering with a protective
lacquer takes place in a wet coating process.
[0003] In particular, the subsequent fast hardening of the lacquers
under ultraviolet light presents a problem for the reliability of
the CD manufacture.
[0004] The above-mentioned lacquering also has no relationship to
the vacuum coating technique which is normally used for metal
coating.
[0005] So that the very short metal coating cycle times are not
canceled out by much longer wet lacquer coating process cycle
times, high technical expenditures are required for the lacquering
process.
[0006] It is an object of the present invention to provide a vacuum
treatment chamber which permits the implementing of the
above-mentioned protective layers in a vacuum process of a type
related to the sputtering technique with the required short cycle
times.
[0007] Methods are definitely known from the vacuum coating
technology for depositing non-conductive layers, such as corrosion
protection layers. However, normally significantly longer coating
times must be accepted than the above-mentioned required few
seconds.
[0008] If, as, for example, in the case of known so-called plasma
enhanced chemical vapor deposition (PECVD) processes with microwave
plasma discharges in the interior of the plasma discharge, coating
rates of approximately 40 nm/sec are possible, the plasma densities
required for this purpose are so high that the resulting
temperature stresses do not permit a coating on plastic substrates.
For maintaining the plastic-compatible temperatures (for example,
of PMMA or polycarbonate), the substrate would have to be moved out
so far from the range of the highest plasma density because, as the
result of the coating rate which is lower there, the required short
cycle times could not be maintained.
[0009] Also, according to experiences, coatings which are deposited
at a high rate in the marginal range of microwave discharges,
frequently have a loose construction and are therefore unsuitable
for a use as corrosion blocking layers.
[0010] Summarizing, it may therefore be stated that the combined
meeting of the short cycle times in the second range with the
required coating thickness and the limiting of the
temperature-caused stress as well as the maintaining of a
sufficient layer quality so far has not been considered possible by
using vacuum coating methods.
[0011] Of a less basic nature, also known high-frequency CVD
processes have the disadvantage that not only the substrate but
also HF coupling-in arrangements are coated, whether, in the case
of microwave plasmas, these are dielectric coupling-in windows or,
at lower frequencies, metallic coupling-in electrodes. The cleaning
with the exchange of the mentioned parts or by a plasma-chemical in
situ cleaning is not compatible with the requirement of short cycle
times to be maintained over long time periods.
[0012] It is therefore another object of the present invention to
develop a system and a method for a fast and economical depositing
of layers from the gas phase, in which case a low loss of coating
material and a high homogeneity are required.
[0013] In the case of a high-frequency plasma treatment chamber
according to the preamble of claim 1 which, with a view to the CD
production problems, is then constructed as a coating chamber and
in this case, is also designed particularly for a PECVD process,
the above-mentioned problems are solved according to the
characterizing part of claim 1; that is, in that the high-frequency
discharge current circuit includes the substrate as a capacitative
coupling-in element.
[0014] While, in the case of the specific application to
metal-coated, specifically plastic substrates, as in the production
of CDs, the substrate cannot be used as a microwave coupling-in
window, according to a general aspect of the present invention of
claim 1, the microwave coupling-in by the dielectric substrate is
definitely possible if the carried-out coating is also
dielectric.
[0015] According to the invention, a metal-coated dielectric
substrate basically also takes over an electrode function with
respect to high-frequency plasmas in the lower frequency range.
[0016] It is the basic recognition according to claim 1 that, as a
result, the required high-frequency output can be kept low which
solves the problem of the temperature-caused stress. However, such
high coating rates are simultaneously achieved that the required
effective protective layers can be deposited within extremely short
coating times, of even one second.
[0017] In addition, it was found that the thus deposited protective
layers, that is, deposited in a high-frequency PECVD coating
process by means of the chamber according to claim 1, while the
layer thickness is comparable, are even harder than conventional
lacquer layers. Furthermore, the layer depositing takes place
virtually only on the substrate surface to be coated which acts as
the high-frequency coupling-in surface.
[0018] More specifically on a PECVD coating chamber according to
the preamble of claim 2, the above-mentioned problems can be
eliminated, first independently of the suggestion of claim 1, by
its construction according to the characterizing part of claim 2.
The construction first has the object of minimizing the coating of
process chamber walls, other than the substrates to be coated.
However, when this solution is considered by itself, it has the
disadvantage that the coating rate on process chamber walls which
are not covered by the substrate remains high so that, in a longer
operation without any cleaning, problems occur as the result of the
chipping-off of layers. On the other hand, also in the case of this
chamber, high coating rates are achieved at the required low stress
temperatures.
[0019] A chamber which is optimized in every respect is obtained by
the simultaneous implementation of the coupling-in technique
according to claim 1 on the chamber with the minimal volume
according to claim 2.
[0020] Therefore, a protective coating process for storage disks,
particularly optical storage disks, such as CDs, according to the
invention is also provided according to claim 11 which, in the
continuous manufacturing operation is designed as a vacuum coating
process and is therefore of the same type as the fast sputtering
process normally provided for metal coating. According to claim 12,
a high-frequency PECVD process is preferably used in the case of
which the high-frequency plasma discharge energy is coupled into
the process space by way of the substrate.
[0021] In the following, preferred embodiments of the invention
will be explained by means of figures. On this basis, additional
embodiments of the invention are shown by means of additional
figures, moving away from the specific CD or storage disk
production and following the principles of the invention.
[0022] Particularly preferred embodiments are specified in claims 3
to 8 with respect to the treatment chamber according to the
invention, while its preferred uses are indicated in claims 9 and
10.
[0023] FIG. 1 is a schematic cross-sectional view of a coating
chamber according to the invention designed specifically for the
protective coating of CDs with PECVD;
[0024] FIG. 2 is a view of another coating chamber according to the
invention designed specifically for the HF-PECVD protective coating
of CDs;
[0025] FIG. 3 is a schematic view, based on the coating chamber
according to FIG. 2, of the HF coupling-in technique according to
the invention for the treatment of non-metal-coated dielectric
substrates in the microwave plasma;
[0026] FIG. 4 is a schematic representation analogous to FIG. 3 of
the coupling-in technique used in the case of the chamber according
to FIG. 2 on a substrate without a metal coating;
[0027] FIG. 5 is a representation analogous to FIGS. 3 and 4 of
another coupling-in technique according to the invention;
[0028] FIG. 6 is a schematic view of a HF-PECVD coating chamber
according to the invention which, in combination, has the
characteristics according to the invention of the chamber according
to FIG. 1 and of the chamber according to FIG. 2.
[0029] According to FIG. 1, as a first example, specifically for
the protective coating of circular-disk-shaped substrates 1 with a
center opening, specifically particularly storage disks,
particularly optical storage disks, such as CDs, with a metal
coating, for example, an aluminum coating 3, the chamber according
to the invention has an extremely flat construction around the
central axis C, in the special case, the construction of a flat
cylinder. The plane chamber walls 5, which are situated opposite
one another with respect to the central axis C, essentially have
the same construction and centrally each carry pump-out pieces 7,
also a receiving device 9 for the periphery of the substrates 1 to
be coated. Because the chamber is constructed according to the
invention which is not only shown when receiving the substrates 1
to be coated, the substrates 1 are indicated by broken lines.
[0030] The receiving devices 9 each define receiving surfaces 11
for the substrates 1 to be received. The pump pieces 7 are designed
such that they project through the provided substrate enter
openings and are optionally also used for holding or positioning
the substrates together with the receiving devices 9.
[0031] The chamber walls 5 are spaced such that the receiving
surfaces 11 for the substrates 1 have a distance A which must be at
least so large that uncontrollable hollow-space discharges between
the plates are avoided, and therefore measures at least 10 mm. On
the other hand, the depositing on the cylinder jacket surfaces
should be as low as possible, so that the distance A should be
smaller than the plate radius.
[0032] Peripherally with respect to the receiving devices 9, gas
feed lines 13 lead, preferably in a distributed manner, into the
area of both walls 5 and are connected with a reactive gas tank
(not shown). Pump units (not shown) are connected to the pump-out
piece 7.
[0033] The spacing of the walls 5 is ensured by insulation parts
15, between these, preferably in a surrounding manner, a metallic
electrode 17 is embedded. The latter is connected to a generator 19
for maintaining the plasma discharge in the process space 20, as
well as preferably both walls 5.
[0034] According to the intended coating process, the generator 19
may be constructed as a d.c. generator or as an a.c. generator or
emit a superimposing of the d.c.+a.c. signal or emit a pulsating
signal.
[0035] As also clearly illustrated in FIG. 1, along the substrates
which in this case are to be coated with PECVD, a homogeneous,
radially inwardly directed flow is obtained of reactive gas first
admitted in an unconsumed manner, toward the pumping-out of
remaining reactive gas and of gaseous, not deposited reaction
products.
[0036] By means of a chamber illustrated schematically in FIG. 1, a
protective coating was implemented on Al-coated polycarbonate CD
substrates maintaining the following quantities:
[0037] Distance to the substrate surfaces to be coated: 50 mm
1 Reactive gases: a) Monomer Hexamethyldisiloxane Flow: 80 sccm b)
O.sub.2: Flow: 40 sccm Total pressure: 42 Pa Generator frequency:
100 kHz Generator output: 250 W on load Process time: 15 sec
[0038] Results:
[0039] The layer thickness measured on a measuring circle with a
radius of 20 mm on the CD amounted to 430 nm; measured on a
measuring circle of a radius of 55 mm, to 436 nm.
[0040] This corresponds to a depositing or coating rate of 29
nm/sec.
[0041] If it is taken into account that layer thicknesses of
approximately 140 nm already are sufficient, it is demonstrated
that by means of the chamber according to the invention according
to FIG. 1, the required coating can be carried out within
approximately 5 seconds.
[0042] The CD substrate made of polycarbonate showed no thermal
impairment.
[0043] It is a disadvantage of the chamber illustrated in FIG. 1
that the preferably ring-shaped electrode 17 is also coated. The
coating rate on the electrode 17 determined in the above-mentioned
example was approximately three times as high as on the substrate.
During a longer operation without any cleaning, problems may
therefore occur as a result of layers splitting off from the
electrode which could contaminate the substrate coating and/or
disturb the plasma discharge.
[0044] These problems are solved on the second preferred chamber
according to the invention of FIG. 2.
[0045] This figure shows the chamber according to the invention,
again specifically for the protective coating of
circular-arc-shaped dielectric substrates, particularly of storage
disks, with plastic substrates, in this case, again particularly
for CDs. The substrate 1 with the metal coating 3, again because it
is not part of the chamber according to the invention, being
indicated by a broken line, is situated on the receiving surface 11
of the receiving device 9, which is provided for receiving the
substrate 1, along the peripheral area of the chamber. The pump-out
connection 7 is constructed such that it projects through the
center opening of the inserted substrate 1. The reactive gas inlets
13 lead, preferably in a distributed manner, into the area of the
receiving device 9 on the periphery, in which case, in the
embodiment illustrated here, in contrast to that according to FIG.
1, a separate gas inlet 13a for the reactive gas O.sub.2 with a
separate pump-out piece 7a is provided which, however, is not
absolutely necessary.
[0046] The high-frequency coupling-in from the generator 19, which
in this case must be a high-frequency generator, operating into the
microwave range, is connected with a coupling electrode 21 which is
exposed on the receiving surface 11 for the substrate 1 and is
embedded preferably in a ring shape, into an insulation carrier 22.
As illustrated the other metallic chamber parts are connected to a
reference potential, particularly the mass potential. In this case,
the connection piece 7 as well as the flange 13a are electrically
insulated from the chamber wall or constructed as insulators (not
shown); the chamber wall being connected to the reference
potential.
[0047] Because the material of the substrate is dielectric, that
is, in this special case, it consists of plastic, particularly of
PMMA or polycarbonate, the electrode 21, one the one hand, the
plastic body, on the other hand, and the metal coating 3 act as a
coupling capacitor by means of which the high-frequency energy is
coupled into the reaction space 20. The chamber according to FIG.
2, which represents a preferred embodiment of the invention, was
operated as follows:
2 Reactive gases: a) Monomer: 100 sccm 1,3
divinyl-1,1,3,3-tetramethyl disiloxane b) Oxygen: Flow: 100 sccm
Total pressure: 60 Pa Generator frequency: 13.56 MHz Generator
output on load 450 W (reflection approximately 5%) Process time: 1
sec
[0048] As the result, a layer was deposited which had a thickness
of 140 nm, which corresponds to a coating rate of 140 nm/sec.
[0049] Particularly, in the case of a preliminary coating with a
metallic layer of Al, it is recommended to precede the
above-mentioned protective PECVD coating by a short oxygen
treatment of approximately 0.2 seconds. Even layer thicknesses of
more than 7 .mu.m can be applied adhesively in this manner to CD
substrates in a pulsating operating mode. In the continuous
operating mode, the process time for CDs is limited for thermal
reasons to 10 to 20 seconds. This is understandable if it is
assumed that, if only a fraction of 100 W is coupled into a CD with
a mass of 16 g for 15 seconds, its temperature would increase by
80.degree..
[0050] Because, as illustrated in FIG. 2, the metal layer 3 or its
surface acts as an equipotential surface, the uniformity of the
coating thickness distribution is very good, for example, with
deviations of no more than 4% from the mean value. The depositing
rate on reactor parts not to be coated was measured at a distance
of 1 cm from the CD surface to be coated at no more than {fraction
(1/30)}of the CD coating rate.
[0051] The following process quantity ranges are recommended
particularly for the coating of optical storage disks, such as
CDs:
3 Base pressure: <8 Pa, which can be reached even by means of a
two-stage vane-type rotary pump within a very short time. Pump
cross-section: Corresponding to the center opening of the storage
disk as well as, according to FIG. 2, optionally by additional pump
lines above the substrate to be coated. Process pressure: 30 to 100
Pa, preferably approximately 60 Pa. Monomer: Preferably a siloxane
compound, such as such as hexamethyl disiloxane or
divinyltetramethyl disiloxane, preferably supplied to the
circumference of the substrate to be coated. Additional reactive
Preferably oxygen, not necessarily supplied gas: to the
circumference of the substrate to be coated. Plasma operating 1 to
500 MHz, for reasons of availability, frequency: preferably 13.56
MHz. Output: 200 to 1,000 W RF. Process time: 1 to 15 sec.
Preferably, a preliminary plasma treatment takes place in pure
oxygen during a process time of 0.1 to 1 sec.
[0052] The coating process carried out by means of the chambers
according to the invention takes place at a relatively high
pressure and is not residual-air-sensitive; that is, as mentioned
above, a two-stage vane-type rotary pump is sufficient for the
pumping out.
[0053] The required high-frequency output is low, for example, 600
W, which permits corresponding savings, among others, with respect
to providing generators. Effective corrosion protection layers can
be produced within very short process cycle times of 1 sec. While
the layer thickness is comparable, the layers are harder than
wet-applied lacquer layers. The depositing takes place, as desired,
virtually only on the substrate.
[0054] The chambers according to FIG. 1 as well as according to
FIG. 2 can easily be constructed for an automatic handling.
[0055] Particularly the approach according to FIG. 2 with the
high-frequency coupling-in by the substrate can be used for many
other high-frequency plasma treatment processes, as, for example,
for reactive etching processes of the substrate; further, for
example, for depositing dielectric intermediate layers or
metal-organic compounds as metallic layers on dielectric
substrates.
[0056] In comparison with the known protective lacquering
techniques, particularly for CDs, a higher reliability and a higher
layer hardness are obtained. This results in a lower consumption of
coating material and in less stress to the environment.
[0057] As a person skilled in the art will immediately recognize,
basically different possibilities are obtained by means of the HF
coupling-in technique, as explained specifically for the CD
application by means of FIG. 2.
[0058] According to FIG. 3, by means of the dielectric substrate 1,
if not metal-coated, microwave energy can be coupled into the
process space 20, where the substrate 1 is coated or etched in a
non-conductive manner.
[0059] According to FIG. 4, a substrate 1, which is not
metallically precoated, can be treated in that, by way of the
electrode 21, the high-frequency energy of the generator 19 is
coupled into the process space 20 and the latter therefore acts as
a capacitance counterelectrode with respect to the electrode
21.
[0060] In this case, it should be stressed that, as illustrated
specifically in FIG. 5, in the case of the chamber according to
FIG. 2 as well as according to FIG. 4, the electrode 21 must not be
exposed with respect to the process space 20 in order to contact
the substrate 1 directly. It may also be covered
dielectrically.
[0061] Naturally, the coupling-in process according to the
invention can also be carried out if, as in the case of the CD, the
surface to be coated and/or the back side of the substrate is
metal-coated. Here, the dielectric carrier of he substrates takes
over the function of a coupling capacitor in a HF discharge. The
resulting self-bias voltage on the metal layer has an advantageous
effect on the increase of the coating rate and its uniformity by
the forming of an equipotential surface.
[0062] With respect to the dimensioning of the electrode surfaces
of the electrodes 21 as well as of the dielectrics situated between
the latter and the process space 20, and their thicknesses as well
as the used operating frequencies, the person skilled in the art
knows the corresponding regularities. In order to achieve
particularly the coupling-in in the metal layer on the CD, the
electrode surface and its projection should not be larger than the
surface of the metal layer.
[0063] FIG. 6 illustrates another preferred embodiment of a chamber
according to the invention, which is easily obtained without any
further explanation from viewing FIGS. 1 and 2.
[0064] On the chamber according to FIG. 1, the coupling-in
principle by way of the substrate 1 according to FIG. 2 is used.
With a view to FIG. 1, the electrode 17 is therefore eliminated
which, on the embodiment of FIG. 1, is excessively-disturbance
coated.
[0065] Naturally, on the chamber according to FIG. 6, both provided
coupling-in electrodes 21 are preferably operated by the same
high-frequency operator if a symmetrical discharge is to be
achieved, as in the predominant number of cases--as illustrated by
broken lines at 19a. Concerning the potential application of a
chamber housing (not shown here), of the flanges 13a as well as of
the connection pieces 7, the statements made concerning FIG. 2
apply.
* * * * *