U.S. patent application number 09/838039 was filed with the patent office on 2001-12-06 for dc plasma power supply for a sputter deposition.
Invention is credited to Lantsman, Alexander D..
Application Number | 20010047933 09/838039 |
Document ID | / |
Family ID | 26902242 |
Filed Date | 2001-12-06 |
United States Patent
Application |
20010047933 |
Kind Code |
A1 |
Lantsman, Alexander D. |
December 6, 2001 |
DC plasma power supply for a sputter deposition
Abstract
DC plasma power supply for a sputter deposition of material
layers on a substrate includes a plasma controller and a plasma
input for the settings of the output voltage and output current
providing plasma ignition and termination with no arcing and no
striking voltage. Pre-defined voltages are applied in the vacuum
state before sputtering and after sputtering until vacuum is
restored in a sputtering apparatus.
Inventors: |
Lantsman, Alexander D.;
(Neptune, NJ) |
Correspondence
Address: |
Alexander D. Lantsman
303 Sea Spray Lane
Neptune
NJ
07753
US
|
Family ID: |
26902242 |
Appl. No.: |
09/838039 |
Filed: |
April 20, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60207453 |
May 30, 2000 |
|
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Current U.S.
Class: |
204/192.13 ;
204/298.03; 204/298.08 |
Current CPC
Class: |
H01J 37/3444 20130101;
H01J 37/34 20130101; C23C 14/54 20130101 |
Class at
Publication: |
204/192.13 ;
204/298.03; 204/298.08 |
International
Class: |
C23C 014/54; C23C
014/34 |
Claims
We claim:
1. A DC plasma power supply to improve yield at a sputter
deposition of a material layer onto a substrate, to improve
electrical integrity of a (magnetron) sputtering apparatus and of
said power supply, and to reduce the AC and RF electromagnetic
interference and soft X-ray hazard, comprising: an AC-to-DC power
conversion module; a filter and monitors of the output current and
output voltage; a control module, regulating the mode of operation
and the output; a plasma controller to administer plasma ignition
and termination; whereby eliminating arcing at plasma ignition and
plasma termination and a need in a striking voltage to initiate a
plasma.
2. A DC plasma power supply of claim 1 wherein a plasma controller
is a stand-alone apparatus interfaced with a control module of said
power supply and with a sputtering apparatus.
3. A DC plasma power supply of claims 1, 2 wherein a plasma
controller has means of interface to a sputtering apparatus and/or
manual controls, including: a cycle input to define a beginning and
an end of a cycle of a sputter deposition, corresponding to
transition of a sputtering apparatus from the vacuum state before
introduction and back to the vacuum state after evacuation of the
process gas(es) respectively. a program input for a commanded value
at the output of said power supply; a plasma input for the minimal
settings of the output voltage and output current providing stable
plasma discharge at plasma ignition and termination.
4. A DC plasma power supply of claim 3 wherein a plasma controller
has means of interface with the inputs of a control module
administering the mode of operation and the output of said power
supply.
5. The method of operation a DC plasma power supply of claim 4
wherein a plasma controller: before and after a cycle of a sputter
deposition: defines the voltage mode; directs to a control module a
commanded value per a program input; during a cycle of a sputter
deposition: defines a safety margin as a value sufficient to
prevent the output voltage from decreasing at a sputtering
apparatus below the corresponding setting per a plasma input;
defines settings for the output voltage and output current at
plasma ignition and termination as the increased by safety margins
settings for the output voltage and output current per a plasma
input; defines a setting for the output power at plasma ignition
and termination as a product of the increased by safety margins
settings for the output voltage and output current per a plasma
input; provides at plasma ignition and termination the output
voltage equal to or greater than the increased by a safety margin
setting for the output voltage per a plasma input.
6. The method of operation a DC plasma power supply of claim 5
wherein a plasma controller during a cycle of a sputter deposition:
defines the voltage mode if a commanded value per a program input
is smaller than said defined setting for the output power; defines
the power mode if a commanded value per a program input is greater
than said defined setting for the output power; in the voltage mode
provides a control module with said defined setting for the output
voltage; in the power mode directs to a control module a commanded
value per a program input.
7. A DC plasma power supply of claims 4 and 6, wherein: a computing
unit calculates settings for the output power and output voltage at
plasma ignition and termination and provides them to a comparator
and to a discriminator respectively; a comparator defines the
voltage mode if a commanded value per a program input is smaller
than a calculated setting for the output power; a comparator
defines the power mode if a commanded value per a program input is
greater than a calculated setting for the output power; a
discriminator in the voltage mode directs to a control module a
calculated setting for the output voltage; a discriminator in the
power mode directs to a control module a commanded value per a
program input.
8. The method of operation a DC plasma power supply of claim 5,
wherein a plasma controller during a cycle of a sputter deposition:
defines the power mode; replaces a commanded value per a program
input with said defined setting for the output power if it is
greater than said commanded value; replaces a feedback signal from
a monitor of the output current with said defined setting for the
output current if it is greater than said feedback signal.
9. A DC plasma power supply of claims 4 and 8, wherein: a computing
unit calculates settings for the output power and output current at
plasma ignition and termination and provides them to a
discriminator and to a comparator respectively; a discriminator
directs to a control module the greater of a calculated setting for
the output power and a commanded value per a program input; if a
calculated setting for the output power is greater than a commanded
value per a program input; a comparator directs to a control module
a calculated setting for the output current; if said calculated
setting for the output power is smaller than a commanded value per
a program input; a comparator directs to a control module a
feedback signal from a current monitor of said power supply.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Provisional Patent Application No. 60/207,453 filed with US
PTO on May 30, 2000.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not applicable
REFERENCE TO A MICROFICHE APPENDIX
[0003] Not applicable
BACKGROUND OF THE INVENTION
[0004] Present invention relates generally to power supplies
technologies and specifically to the DC plasma supplies for a
sputter deposition of material layers on a substrate, and it was
originally disclosed in Provisional Patent Application No.
60/207,453 filed with US PTO on May 30, 2000.
[0005] DC plasma power supplies are used as sources of energy at a
sputter deposition in the apparatuses, typically of a magnetron
design, in the semiconductor industry.
[0006] DC plasma power supplies are manufactured by the companies
worldwide, including Advanced Energy Industries, Inc. of Fort
Collins, Colo., USA.
[0007] Major drawbacks of the DC plasma power supplies of the prior
art are intensive and repetitive arcing at plasma ignition and
plasma termination and a need in the striking voltage to initiate a
plasma in a sputtering apparatus of either magnetron or
non-magnetron design.
[0008] Cumulative negative effects of the arcing are severe damage
to substrates (wafers), caused by the induced particle
contamination and soft X-rays, deterioration of electrical
integrity of a sputtering apparatus and of a DC plasma power
supply, and induced electromagnetic interference.
[0009] Plasma at arcing represents a short circuit and a DC plasma
power supply generates at arcing the repetitive 0.1-10 microsecond
pulses (surges) of the output current typically exceeding 10-100
times the nominal output current at a sputter deposition and
reaching hundreds of amps. Repetition rate of these pulses may vary
from 0.1 to 10-50 kHz. The surges of the output current result in
micro-evaporation of the target material and in the particle
contamination of a substrate.
[0010] The spikes of the output voltage of 1.5-2.5 kV accompany the
surges of the current at arcing and these instabilities may last
from several to hundreds of milliseconds. Arcing in a sputtering
apparatus also results in release of the particles of different
origin otherwise suspended by stable plasma off the perimeter of a
substrate. At arcing these particles fall onto a substrate and
contaminate it, representing one of the major sources of the yield
losses at sputtering.
[0011] To initiate plasma a DC plasma power supply of the prior art
produces a striking voltage, also typically in a range of 1.5-2.5
kV, and a striking voltage itself promotes arcing in a sputtering
apparatus at plasma ignition.
[0012] Soft X-rays are generated at arcing by the spikes of the
output voltage exceeding or about 1 kV, including the striking
voltages, and they are detrimental to the dielectric layers on a
substrate and also represent an environmental hazard.
[0013] High voltage spikes also deteriorate electrical integrity
and reliability of a sputtering apparatus, specifically, of a
cathode assembly. High voltage spikes and surge currents at arcing
deteriorate electrical integrity and reliability of a DC plasma
power supply of the prior art. They are also a source of AC and RF
electrical interference for devices and instruments of a sputtering
apparatus and of the other electronic systems. Arcing at plasma
ignition and plasma termination tends to be supported by the energy
stored in the DC plasma power supplies of the prior art. This
phenomenon dictates use of the reactive components with the reduced
nominal value in the output filters of these power supplies. It
results in the less effective filtering and higher ripples of the
output voltage and output current during a sputter deposition.
These ripples themselves may promote various plasma instabilities
and arcing at sputtering.
[0014] The invented DC plasma power supply provides plasma ignition
and termination with no arcing regardless of the amount of energy
stored in the power supply itself, offering more margins for better
filtering and lower ripples at sputtering.
BRIEF SUMMARY OF THE INVENTION
[0015] A DC plasma power supply of the present invention corrects
the drawbacks of the prior art. Present invention is based on a
theory of the plasmas, teaching that a DC plasma discharge becomes
stable at the applied voltages greater than a specific voltage Vmin
(Handbook of plasma processing technology, S. M. Rossnagel et al
1990, Noyes Publications, pp. 47-58; Industrial plasma engineering,
J. R. Roth 1995, IOP Publishing, pp. 283-390; Handbook of sputter
deposition technology, K. Wasa et al 1992, Noyes Publications, pp.
97-122; U.S. Pat. No. 6,190,512 Soft plasma ignition in plasma
processing chambers).
[0016] Value of voltage Vmin depends on composition and pressure of
the process gas(es), design properties of a sputtering target and a
sputtering apparatus, and it can be measured prior to the
processing of a product substrate.
[0017] Results of these measurements are used in the invented DC
plasma power supply to define the settings for the arcing free
plasma ignition and termination.
[0018] The invented DC plasma power supply effectively eliminates
arcing, high voltage spikes, and soft X-ray radiation at plasma
ignition and at plasma termination during a sputter deposition, and
it does not require a striking voltage to initiate a plasma.
[0019] The invented DC plasma power supply reduces particle
contamination and damage to a substrate at a sputter deposition. It
also increases electrical integrity of a sputtering apparatus and
its own electrical integrity by limiting the output voltages and
output currents to the values required for sputtering. It also
reduces the AC and RF electrical interference and a soft X-ray
hazard.
[0020] These and other advantages of the invented DC plasma power
supply are achieved by means of preventing exposure of the process
gas(es) at sputtering to the output voltages lower than Vmin, by
means of dynamic control of the mode of operation, and by means of
controlled and gradual transitions from a gaseous state to a plasma
state and from a plasma state to a gaseous state in a sputtering
apparatus.
[0021] It is objective of the present invention to increase yield
at a sputter deposition by eliminating arcing in a sputtering
apparatus at plasma ignition and termination.
[0022] It is another objective of the present invention to increase
electrical integrity of a sputtering apparatus.
[0023] It is another objective of the present invention to increase
electrical integrity of a DC plasma power supply.
[0024] It is another objective of the present invention to reduce
the AC and RF electromagnetic interference and the soft X-ray
hazard caused by arcing at plasma ignition and termination.
[0025] It is another objective of the present invention to reduce
limitation to filtering of the ripples of the output voltage and
output current of a DC plasma power supply.
[0026] The invention is particularly useful in production by means
of a sputter deposition of the Very Large Scale Integration (VLSI)
devices in the semiconductor industry, optical and magneto-optical
media, ultra thin film magnetic heads for computer hard drives, and
in other related industries
[0027] The above and other objectives and advantages of the present
invention shall be made apparent from the accompanying drawings and
the description thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0028] The accompanied drawings, which are incorporated in and
constitute a part of this application, illustrate embodiments of
the invention and, together with a general description of the
invention given above, and with the detailed description of the
embodiments given below, serve to explain the principles of the
invention.
[0029] FIG. 1 is a schematic view of one embodiment the invented DC
plasma power supply.
[0030] FIG. 2 is a schematic view of another embodiment of power
supply 1 shown on FIG. 1.
[0031] FIG. 3 is a schematic view of embodiment of plasma
controller 9 of power supply 1 shown on FIGS. 1-2.
[0032] FIG. 4 is a typical timing diagram of embodiments shown on
FIGS. 1-3.
[0033] FIG. 5 is a schematic view of another embodiment the
invented DC plasma power supply.
[0034] FIG. 6 is a schematic view of another embodiment of power
supply 50 shown on FIG. 5.
[0035] FIG. 7 is a schematic view of embodiment of plasma
controller 51 of power supply 50 shown on FIGS. 5-6.
[0036] FIG. 8 is a typical timing diagram of embodiments shown on
FIGS. 5 -7.
[0037] FIG. 9 is a diagram illustrating method of measurement of
settings Vmin, Amin.
[0038] FIG. 10 is a schematic view of a DC plasma power supply of
the prior art.
[0039] FIG. 11 is a typical timing diagram of a DC plasma power
supply of the prior art.
FIGS. 1-11 share the same denotations for common functional
devices, inputs, outputs, signals, and time intervals.
DETAILED DESCRIPTION OF THE INVENTION
[0040] At a sputter deposition a DC plasma power supply typically
operates in the power mode, and between cycles of a sputter
deposition it operates in the voltage mode. A mode of operation is
a hardware configuration and/or a software algorithm used to
regulate the output of a power supply. In the power mode Pout=Vout
* Aout=Set Point, in the voltage mode Vout=Set Point, in the
current mode Aout=Set Point, and in the energy mode Eout=Pout *
(Process Time)=Set Point. Here Pout, Vout, Aout and Eout are the
output power, output voltage, output current and output energy
respectively, and "Set Point" corresponds to a commanded value at
the output of a DC plasma power supply. Typically, the power mode
provides the most consistent performance of the deposited films,
while the energy mode is used for the most delicate sputtering
processes. The voltage mode is commonly used for the sputtering
apparatus and personnel safety reasons between the cycles of
sputtering.
[0041] Further in the description of the present invention the
power and the energy modes of operation may be assumed
interchangeably, wherever the power mode is mentioned. Settings
Vmin can be measured with a test substrate in the same sputtering
apparatus filled with the gas(es) at pressure per the process
recipe prior to the processing of a product substrate, as
illustrated on FIG. 9. At these measurements a DC plasma power
supply, either invented or of the prior art, is set to the voltage
mode. During the test a commanded value Vp of the output voltage is
slowly increased from 0 (zero) to Vp(max), corresponding to a
stable plasma discharge in the sputtering apparatus, and further Vp
is slowly decreased back from Vp(max) to 0 (zero).
[0042] Minimal steady state output voltages Vmin(1), Vmin(2) and
output currents Amin(1), Amin(2) at the voltages Vp(1) and Vp(2)
respectively are measured during this test. Voltage Vp(1) relates
to the minimal commanded value of the output voltage at plasma
ignition corresponding to a stable plasma discharge after the
arcing state. Respectively, voltage Vp(2) relates to the minimal
commanded value of the output voltage at plasma termination
corresponding to a stable plasma discharge before the arcing state.
Voltage Vp(max) relates to a commanded value of the output voltage
greater than Vp(1) and Vp(2) but lower or about a typical value at
sputtering. Values V3, A3 and V4, A4 (not to scale) are a graphical
illustration of the repetitive peak output voltages and surge
currents during the arcing state at plasma ignition and
termination, respectively.
[0043] Settings Vmin are defined as the minimal output voltages
Vmin(1), Vmin(2) providing stable plasma discharges. The
corresponding values for the output current and the output power at
Vout=Vmin are Amin and Pmin=Vmin * Amin respectively. At the output
voltage equal to or greater than Vmin, voltage at a sputtering
target is stable. As indicated on FIG. 9, voltages Vmin(1) and
Vmin(2) may differ. Voltage Vmin(1) at plasma ignition is expected
to be higher than voltage Vmin(2) at plasma termination. Either
both values of Vmin(l) and Vmin(2) may be communicated to the
invented power supply, one for each of the corresponding
transitions specifically, or just the greater one of these
voltages. For simplicity of the description only, further in
disclosure of this invention and pictorially on FIG. 4 and FIG. 6,
voltage Vmin(1) as a greater of the voltages Vmin(1), Vmin(2) is
chosen as the single value for Vmin.
[0044] In embodiments of the invented power supply shown on FIGS.
1-3, 5-7 are used settings V1=Vmin+Vs, A1=Amin+As, P1=Pmin+Ps=V1 *
A1=(Vmin+Vs) * (Amin+As), where Vs, As, Ps are optional safety
margins. Typically, safety margins Vs, As and Ps are 10-100 times
smaller than Vmin, Amin, and Pmin, respectively.
[0045] The purpose of the safety margins is to assure that at
plasma ignition and termination the output voltage of the invented
DC plasma power supply of an individual physical design, or more
accurately voltage at the target assembly of a sputtering
apparatus, does not decrease below Vmin during the transitions of
the mode and of the output. In practical systems there is also a
small but finite voltage drop associated with losses in the wiring
between the power supply and a sputtering apparatus. This voltage
drop may be included in either Vmin or Vs. It is specifically small
at the arcing free plasma ignition and termination provided by the
invented power supply.
[0046] In disclosure of the present invention a voltage drop due to
the losses in the wiring is considered included in the margin Vs.
Accordingly, no distinction is further made between the output
voltage of the invented power supply and the voltage at the target
assembly of a sputtering apparatus.
[0047] Setting V1 is substantially smaller than the output voltage
at sputtering. Current Al at Vout=V1 is typically 10-100 times
smaller than a typical current at sputtering, and the same is true
for the output power P1. For practical purposes, at Vout=V1 a
sputter deposition has not started yet, but the process gas(es) is
pre-ignited and a weak but stable plasma is established in a
sputtering apparatus. Values of Vmin and Amin can be further
reduced by means of external sources of ionization, by increasing
temporarily pressure of the process gas(es) in a sputtering
apparatus ("pressure bursts") and by other means known to those
skilled in the art.
[0048] FIG. 1 illustrates DC plasma power supply 1 in accordance
with one embodiment of the present invention. AC power from an
external source is transmitted to power module 2 via AC input 12.
Module 2 converts AC power in the highly regulated DC power,
delivered through output filter 3, current monitor 4, and voltage
monitor 5 to output terminals 6, 7. Typically, power supply 1 has
the floating output terminals with negative terminal 6 connected to
a target assembly and positive terminal 7 connected to the chassis
of a sputtering apparatus.
[0049] A sputtering apparatus provides interfaces to program input
13, to plasma input 14, and to cycle input 15. Inputs 13-15 can be
implemented as analog, digital or manual means or can be
represented by a data interface like RS-232, etc. In description of
the present invention further arbitrarily assumed and presented
pictorially on FIGS. 4, 8 that inputs 13, 14 are analog inputs, and
input 15 is a digital input.
[0050] Commanded value of the output at terminals 6, 7 is
communicated via input 13. Input 14 is used for communicating the
settings Vmin, Amin. Via input 15 are communicated the beginning
and the end of a cycle of a sputter deposition, defined as
transition of a sputtering apparatus from the vacuum state before
introduction and back to the vacuum state after evacuation of the
process gas(es) respectively.
[0051] Typically, before and after a cycle of a sputter deposition
a sputtering apparatus via input 15 defines the voltage mode for
power supply 1 and via input 13 sets the output voltage Vout to 0
(zero).
[0052] Power supply 1 may also have other interfaces to a
computerized sputtering apparatus and/or manual controls, displays,
and other supplemental means.
[0053] Control module 8 administers the output and mode of
operation of power supply 1. Module 8 is connected to module 2 via
interface 18 (output "a"), to monitors 4 and 5 via interfaces 19
and 16 (inputs "b", "c"), and to plasma controller 9 via mode
interface 11 and output interface 17 (inputs "d", "e").
[0054] Module 8 administers the mode of operation of power supply 1
by responding to interface 11 and it sets the output at terminals 6
and 7 by responding to interface 17. Monitors 4 and 5 provide
module 8 with the output current feedback Afb and output voltage
feedback Vfb, respectively.
[0055] Transitions between the modes are executed with no output
voltage drop below Vmin. Plasma controller 9 is connected to inputs
13, 14 and 15 and via interfaces 11 and 17 to inputs "d" and "e" of
module 8, administering the mode of operation and the output. At
the beginning of the cycle of a sputter deposition controller 9
confirms the voltage mode and also switches control over the output
from input 13 to input 14.
[0056] During a cycle of a sputter deposition controller 9 defines
settings V1, P1 for the output voltage and output power at plasma
ignition and termination and provides dynamic control over a mode
of operation of power supply 1.
[0057] If a commanded value of the output power per input 13 is
lower than the setting P1, controller 9 via interface 11 and module
8 sets power supply 1 to the voltage mode, and via interface 17 and
module 8 sets the output voltage at terminals 6, 7 to V1.
[0058] If a commanded value of the output power per input 13 is
greater than the setting P1, controller 9 via interface 11 and
module 8 sets power supply 1 to the power mode and switches control
over the output of power supply 1 at terminals 6, 7 to input
13.
[0059] When a commanded value per input 13 is equal to P1 it
corresponds to a request of the same output voltage V1 and output
current Al as set up by controller 9. As a result, the described
transitions between the modes and of the output are performed with
no output voltage drop below Vmin as assured by the safety margins
of a sufficient value. During a cycle of a sputter deposition after
a sputtering apparatus is filled with the process gas(es), a
sputter deposition begins by communicating via input 13 a commanded
value of the output power at terminals 6, 7.
[0060] Until a sputtering apparatus is filled with the process
gas(es), a commanded value per input 13 is equal to 0 (zero) and
thus lower than setting P1.
[0061] Controller 9 holds power supply 1 in the voltage mode and
sets the output voltage at terminals 6, 7 to V1 starting from the
vacuum state until a sputtering apparatus is filled with the
process gas(es) and until a commanded value per input 13 starts
exceeding setting P1. As a result, process gas(es) during plasma
ignition is not exposed to voltages lower than Vmin.
[0062] As a commanded value per input 13 starts exceeding the
setting P1, controller 9 switches power supply 1 from the voltage
mode to the power mode and at the same time it switches control
over the output at terminals 6, 7 from input 14 to input 13.
Further the output power increases from P1 to a commanded level of
P2. The output voltage and output current at Pout=n are V2 and A2
respectively. Output power P2 may vary during sputtering, and later
it stays at a level higher than P1 till the end of a sputter
deposition.
[0063] At the end of a sputter deposition a commanded value per
input 13 decreases from P2 to 0 (zero). Accordingly, as it
decreases to the value of setting P1, controller 9 switches power
supply 1 back to the voltage mode and sets the output voltage at
terminals 6, 7 to V1. Voltage V1 stays applied until vacuum is
restored in a sputtering apparatus. As a result, process gas(es)
during plasma termination is not exposed to voltages lower than
Vmin.
[0064] At the end of the cycle of a sputter deposition controller 9
confirms the voltage mode and also switches control over the output
from input 14 back to input 13. Power supply 1 stays in the voltage
mode till the beginning of the next cycle of sputtering, while the
output voltage Vout is set to 0 (zero) per input 13.
[0065] If the output power temporarily decreases below setting P1
during a sputter deposition, power supply 1 will terminate and
re-ignite plasma with no arcing and no need in a striking voltage,
as described above.
[0066] In another embodiment of power supply 1 shown on FIG. 2,
controllers 9 is a stand-alone apparatus interfaced with a
sputtering apparatus and with DC plasma power supply 10 of the
prior art (FIG. 10). In other embodiments of power supply 1 the
elements and functions of controller 9 may be in part or fully
incorporated in the means of power supply 10 and of a sputtering
apparatus.
[0067] In embodiment shown on FIG. 3, controller 9 comprises
read-write memory 23, register 22, comparator 28, computing unit
21, and discriminator 24. Settings Vmin, Amin are communicated to
unit 21 via interface 14. Register 22 contains codes of the safety
margins Vs, As, and unit 21 calculates settings V1, A1, and P1. In
memory 23 are stored and available for retrieval setting Vmin, Amin
and the settings calculated by unit 21.
[0068] Comparator 28, unit 21, and discriminator 24 can be
implemented either by means of electronic hardware or as software
programs or as a combination of thereof.
[0069] Setting V1 is communicated via interface 25 to discriminator
24, and setting P1 is communicated via interface 26 to comparator
28. Comparator 28 via interface 11 and module 8 sets power supply 1
to the voltage mode if a commanded value per input 13 is lower than
setting P1, otherwise it sets power supply 1 to the power mode.
[0070] Input 15 and comparator 28 via interface 27 also controls
the state of discriminator 24:
[0071] before and after a cycle of a sputter deposition (input 15
is in the inactive state):
[0072] discriminator 24 connects input 13 to module 8 and
disconnects unit 21 from module 8; these commutations set power
supply 1 to the voltage mode and also set the output voltage to 0
(zero) per input 13;
[0073] during a cycle of a sputter deposition (input 15 is in the
active state):
[0074] in the voltage mode (a commanded value at input 13 is lower
than setting P1):
[0075] discriminator 24 connects unit 21 to module 8 and
disconnects input 13 from module 8; and these commutations set the
output voltage to V1 at plasma ignition and plasma termination;
[0076] in the power mode (a commanded value at input 13 is greater
than setting P1):
[0077] discriminator 24 connects input 13 to module 8 and
disconnects unit 21 from module 8; and these commutations set the
output power to a commanded value per input 13.
[0078] A typical timing diagram of a sputter deposition with power
supply 1 is shown on FIG. 4. On or prior to T1 settings Vmin, Amin
are communicated to controller 9 by a sputtering apparatus via
input 14, retrieved from memory 23 or entered manually in
controller 9.
[0079] At T<T1 before a cycle of sputtering begins a signal at
input 15 is in the inactive state, arbitrarily shown as a low
state. In response to input 15, controller 9 via interface 11 and
module 8 sets power supply 1 to the voltage mode. At the same time
controller 9 via interface 17 and module 8 sets the output voltage
at terminals 6, 7 to 0 (zero) as commanded per input 13 by a
sputtering apparatus between the cycles of deposition.
[0080] At T1 a sputtering apparatus starts a cycle of a sputter
deposition by setting the signal at input 15 to the active state,
arbitrarily shown as a high state. Controller 9 continues to hold
power supply 1 in the voltage mode but it switches control over the
output from input 13 to input 14 and sets the output voltage to V1
till a commanded value per input 13 is lower than P1.
[0081] At T2 process gas(es) starts filling a sputtering apparatus
in presence of the output voltage V1 applied to a sputtering
target.
[0082] At T3 pressure of the process gas(es) reaches the level per
a process recipe.
[0083] At T4 a commanded value of the output power at input 13
starts increasing from the initial value of 0 (zero) reaching P1 at
T5, and after T5 it exceeds the setting P1.
[0084] Accordingly, at T5 controller 9 via interface 11 and module
8 switches power supply 1 from the voltage mode to the power mode
and switches control over the output at terminals 6, 7 to input 13.
These transitions are executed with no output voltage drop below
Vmin, and it is beneficial, but not critical, if they take little
time.
[0085] By T6 the a commanded value of the output power per input 13
increases to P2 and further it stays at a level higher then P1 till
T7.
[0086] At T7 a sputtering apparatus sets a commanded value per
input 13 to 0 (zero), and power supply 1 starts gradual
transitioning of the output power from P2 to 0 (zero).
[0087] By T9 the output power decreases from P2 to P1, and after T9
it continues decreasing reaching Pout=0 at T11. Accordingly, at T9
controller 9 switches power supply 1 back to the voltage mode and
switches control over the output at terminals 6, 7 from input 13 to
input 14, thus setting the output voltage to V1. These transitions
are executed with no output voltage drop below Vmin, and it is
beneficial, but not critical, if they take little time. Voltage V1
stays until vacuum is restored in a sputtering apparatus.
[0088] At T10 evacuation of the process gas(es) starts, and by T11
vacuum is restored in a sputtering apparatus.
[0089] At T12 a sputtering apparatus sets signal at input 15 to the
inactive state and sets a commanded value per input 13 to 0 (zero).
Accordingly, at T12 controller 9 confirms the voltage mode for
power supply 1, sets the output voltage to 0 (zero), and a cycle of
a sputter deposition is completed.
[0090] Power supply 1 stays in the voltage mode from T9 to T5 of
the next cycle of sputtering.
[0091] Power supply 1 provides the free of arcing plasma ignition
and termination and it does not require a striking voltage to
initiate plasma in a sputtering apparatus.
[0092] Another embodiment of the present invention is shown on FIG.
5. In this embodiment DC plasma power supply 50 operates during
plasma ignition and termination in the power mode, but in a way
preventing exposure of the process gas(es) to the output voltages
lower than Vmin.
[0093] Plasma controller 51 is connected to inputs 13, 14 and 15,
to monitor 4 via interface 19, to inputs "e", "b", and "d" of
module 8 administering a commanded value at the terminals 6 and 7,
feedback Afb, and a mode of operation via interfaces 40, 41, and 42
respectively.
[0094] Before and after a cycle of sputter deposition a sputtering
apparatus sets a signal at input 15 to the inactive state. In
response, controller 51 via interface 42 and module 8 sets power
supply 50 to the voltage mode. At the same time controller 51
connects input 13 via interface 40 to module 8, setting the output
voltage to 0 (zero).
[0095] At the beginning of a cycle of sputtering a signal at input
15 is set to the active state by a sputtering apparatus. In
response, controller 51 via interface 42 and module 8 switches
power supply 50 from the voltage mode to the power mode while the
sputtering apparatus is still in the vacuum state. Active level of
a signal at input 15 also enables controller 51 to replace a signal
per input 13 and feedback Afb: a signal per input 13 is replaced
with the setting P1, and feedback Afb is replaced with the setting
Al. Settings P1, Al are transmitted to module 8 via interfaces 40
and 41 respectively.
[0096] It is beneficial, but not critical, if setting Al is
processed by module 8 faster than setting P1. In the power mode of
operation these commutations result in module 8 setting the output
voltage to P1/A1=V1, and it happens before introduction of the
process gas(es) while a sputtering apparatus is still in the vacuum
state. As a result, at plasma ignition there is no exposure of the
process gas(es) to the voltages lower than Vmin. These commutations
stay during a cycle of a sputter deposition till a commanded value
per input 13 is lower than setting P1.
[0097] After a sputtering apparatus is filled with the process
gas(es), a commanded value of the output power per input 13 starts
increasing. As it reaches a level exceeding the setting P1, control
over the output at terminals 6,7 is switched by controller 51 back
to input 13 and to monitor 4.
[0098] At the end of a sputter deposition a commanded value of the
output power per input 13 starts decreasing from P2 to 0 (zero).
Accordingly, as it decreases below setting P1, controller 51
replaces a signal per input 13 and feedback Afb with settings P1
and Al, respectively. In the power mode of operation these
commutations result in module 8 setting the output voltage to
P1/A1=V1, and it happens before evacuation of the process gas(es)
from a sputtering apparatus started.
[0099] Voltage V1 stays applied till vacuum is restored in a
sputtering apparatus at the end of the cycle of sputtering. As a
result, at plasma termination there is no exposure of the process
gas(es) to the voltages lower than Vmin.
[0100] At the end of the cycle of a sputter deposition a sputtering
apparatus sets a signal at input 15 to the inactive state. In
response, controller 51 via interface 42 and module 8 switches
power supply 50 back to the voltage mode and switches control over
the output at terminals 6,7 from input 14 to input 13 and monitor
4. Power supply 50 stays in the voltage mode till the beginning of
the next cycle of sputtering, with the output voltage Vout set to 0
(zero) per input 13.
[0101] When a commanded value per input 13 is equal to P1 it
corresponds to a request at the described commutations of the same
output voltage V1 and output current Al as set up by controller 51.
As a result, these commutations can be performed with no output
voltage drop below Vmin as assured by a safety margins of a
sufficient value.
[0102] If the output power temporarily decreases below setting P1
during a sputter deposition, power supply 50 will terminate and
re-ignite plasma with no arcing and no need in a striking voltage,
as described above.
[0103] In another embodiment of power supply 50 shown on FIG. 6,
controllers 51 is a stand-alone apparatus interfaced with a
sputtering apparatus and with DC plasma power supply 10 of the
prior art (FIG. 10). In the other embodiments of power supply 50
the elements and functions of controller 51 may be in part or fully
incorporated in the means of power supply 10 and of a sputtering
apparatus.
[0104] In embodiment shown on FIG. 7, controller 51 shares the same
functional devices with controller 9, but the algorithm of
operation is different.
[0105] In the voltage mode before and after a cycle of a sputter
deposition, corresponding to the inactive state of a signal at
input 15, discriminator 30:
[0106] disconnects unit 21 from module 8;
[0107] directs to module 8 a commanded value per input 13, thus
setting the output voltage to 0 (zero).
[0108] Power mode of operation during a cycle of a sputter
deposition relates to the active state of a signal at input 15.
[0109] While in the power mode if a signal per input 13 corresponds
to the output power lower than P1, discriminator 30:
[0110] disconnects input 13 from module 8 and connects via
interface 43 unit 21 to provide setting P1 to module 8;
[0111] configures comparator 31 to disconnect monitor 4 from module
8 and to connect via interface 45 unit 21 to provide setting Al to
module 8.
[0112] These commutations result in setting the output voltage to
V1 and in no exposure of the process gas(es) at plasma ignition and
termination to the output voltages lower then Vmin.
[0113] While in the power mode if signal per input 13 corresponds
to the output power higher than P1, discriminator 30:
[0114] disconnects unit 21 from module 8, and directs to module 8 a
commanded value per input 13;
[0115] configures comparator 31 to disconnect unit 21 from module 8
and to direct feedback Afb from monitor 4 to module 8.
[0116] These commutations result in switching control over the
output from input 14 to input 13 and monitor 4.
[0117] Typical timing diagram of a sputter deposition with power
supply 50 is shown on FIG. 8.
[0118] On or prior to T1 settings Vmin, Amin are communicated to
controller 51 via input 14, retrieved from memory 23, or manually
entered in controller 51.
[0119] Before a cycle of sputtering at T<T1 a signal at input 15
is in the inactive (arbitrarily, low) state. In response,
controller 51 via interface 42 and module 8 holds power supply 50
in the voltage mode while the output voltage is set to 0 (zero) per
input 13.
[0120] At T1 a sputtering apparatus starts a cycle of a sputter
deposition by setting a signal at input 15 to the active (high)
state. Accordingly, at T1 controller 51 via interface 42 and module
8 switches power supply 50 to the power mode and sets output
voltage to V1.
[0121] At T2 process gas(es) starts filling a sputtering apparatus
in presence of the voltage V1 applied to a sputtering target.
[0122] At T3 pressure of the process gas(es) reaches the level per
a process recipe.
[0123] At T4 a commanded value of the output power at input 13
starts increasing from the initial value of 0 (zero) reaching P1 at
T5, and after T5 it exceeds the setting P1.
[0124] Accordingly, at T5 controller 51 via interfaces 40, 41 and
module 8 switches control over the output at terminals 6, 7 from
input 14 to input 13 and monitor 4. These transitions are executed
with no output voltage drop below Vmin, and it is beneficial, but
not critical, if they take little time.
[0125] By T6 a commanded value of the output power per input 13
increases to P2 and further it stays at a level higher then P1 till
T7.
[0126] At T7 a sputtering apparatus sets a commanded value per
input 13 to 0 (zero), and power supply 50 starts gradual
transitioning of the output power from P2 to 0 (zero).
[0127] By T9 the output power decreases from P2 to P1, and after T9
it continues decreasing reaching Pout=0 at T11. Accordingly, at T9
controller 51 via interfaces 40, 41 and module 8 switches control
over the output at terminals 6, 7 from input 13 and monitor 4 back
to input 14 and sets the output voltage to V1. These transitions
are executed with no output voltage drop below Vmin, and it is
beneficial, but not critical, if they take little time.
[0128] At T10 evacuation of the process gas(es) starts, and by T11
vacuum is restored in a sputtering apparatus.
[0129] At T12 a sputtering apparatus sets a signal at input 15 to
the inactive state and sets a commanded value per input 13 to 0
(zero). Accordingly, at T12 controller 51 (via interface 42 and
module 8) switches power supply 50 to the voltage mode, sets the
output voltage to 0 (zero) as per input 13, and a cycle of a
sputter deposition is completed. Power supply 50 stays in the
voltage mode from T12 to T11 of the next cycle of sputtering.
[0130] Power supply 50 provides the free of arcing plasma ignition
and termination and it does not require a striking voltage to
initiate plasma in a sputtering apparatus.
[0131] The embodiments and timing diagrams of power supplies 1 and
50 may have many modifications, including but not limited to:
[0132] output power at a sputter deposition may stay constant from
T6 to T7 or vary per input 13;
[0133] output voltage Vout=V1 may be applied any time before T2 and
may be removed any time after T11;
[0134] setting Vmin, Amin, Pmin, Vs, As, Ps, V1, A1, P1 may be
directly communicated via input 14 to controllers 9, 51 and/or
stored in memory 23, thus eliminating a need in unit 21 and
register 22;
[0135] settings per input 14 may be saved in the data storage of
module 8, thus eliminating a need in memory 23;
[0136] dedicated inputs could be used to set the voltage mode at
T<T1 and T>T12, and to enable/disable controllers 9, 51 and
the output of power supplies 1, 50;
[0137] a cycle signal 15 may be interfaced directly with input "d"
of module 8 for administering a mode of operation of power supply
50;
[0138] gradual transitions of the output power from 0 (zero) to P2
and from P2 to 0 (zero) may take various time as administered by a
sputtering apparatus or by module 8 and/or by controllers 9, 51 to
assure realization of the described algorithms and the timing
diagrams shown on FIGS. 4, 6;
[0139] means to provide said gradual transitions in power supplies
1, 50 may include integrating circuits and/or other hardware and/or
software means known to those skilled in the art;
[0140] values of Pout, Vout, Aout during intervals from T2 to T6
and from T7 to T11 may be monitored/recorded for sputter deposition
control purposes;
[0141] controllers 9, 51 performing the described above algorithms
may have various designs readily available to those skilled in the
art;
[0142] settings V1 may differ for transitions at plasma ignition
and plasma termination, and if suppression of the arcing is desired
only for either one transition, for the unprotected transition
setting V1 could be set to 0 (zero);
[0143] However, these modifications do not effect the subject and
objectives of the present invention.
[0144] To illustrate further advantages of this invention, DC
plasma power supply 10 of the prior art and its typical timing
diagram are shown on FIG. 10 and FIG. 1 1 respectively. Before a
cycle of sputtering at T<T1 the inactive (arbitrarily, low)
state of a signal at input 15 sets power supply 10 to the voltage
mode, while the output voltage is set to 0 (zero) per input 13.
[0145] At T1 a sputtering apparatus starts a cycle of a sputter
deposition by setting a signal at input 15 to the active (high)
state. Accordingly, at T1 module 8 switches power supply 10 to the
power mode.
[0146] At T2 process gas(es) starts filling a sputtering apparatus
and by T3 pressure reaches the level per a process recipe.
[0147] At T4 a commanded value of the output power at input 13
starts increasing from the initial value of 0 (zero).
[0148] At T4, in response to a request of Pout greater than 0
(zero), power supply 10 produces a striking voltage, typically in a
range of 1.5-2.5 kV.
[0149] The arcing at a sputtering target starts at T4 and continues
until TX. Arcing at the plasma ignition is shown on FIG. 8 as bars
V3, A3 (not to scale). It may last from several to hundreds of
milliseconds.
[0150] At TX the output power stabilizes as it reaches the value of
Pmin=Vmin * Amin.
[0151] By T6 a commanded value of the output power per input 13
increases to P2 and further it stays at a level higher then P1 till
T7.
[0152] At T7 a sputtering apparatus sets a commanded value per
input 13 to 0 (zero), and power supply 10 starts transitioning of
the output power from P2 to 0 (zero).
[0153] By T8 a commanded value of the output power per input 13
decreases from P2 to Pmin, and after T8 it continues decreasing
reaching 0 (zero) at TY.
[0154] At T8 starts arcing somewhat similar to the observed from T4
to TX. Arcing at the plasma termination continues from T8 to TY and
it is shown on FIG. 8 as bars V4, A4 (not to scale).
[0155] At T10 evacuation of the process gas(es) starts, and by T11
vacuum is restored in a sputtering apparatus.
[0156] At T12 a sputtering apparatus sets a signal at input 15 to
the inactive state and sets a commanded value per input 13 to 0
(zero). Accordingly, module 8 switches power supply 10 to the
voltage mode, sets the output voltage to 0 (zero), and a cycle of a
sputter deposition is completed.
[0157] Power supply 10 stays in the voltage mode from T12 to T1 of
the next cycle of a sputtering. If the output power temporarily
decreases below Pmin during the interval from TX to TB, power
supply 10 will terminate and re-ignite plasma with the repetitive
arcing and with a striking voltage, as described above.
[0158] The embodiments and timing diagram of power supply 10 may
have modifications, including but not limited to:
[0159] output power at a sputter deposition may stay constant from
T6 to T7 or vary per input 13;
[0160] transitions of the output power from 0 (zero) to P2 and from
P2 to 0 (zero) may take various time as commanded per input 13 or
administered by module 8;
[0161] power supply 10 may have dedicated means for gradual
transitions from 0 (zero) to P2 and from P2 to 0 (zero);
[0162] the voltage mode may be switched to the power mode any time
before T6, and the power mode may be switched to the voltage mode
any time after T7;
[0163] dedicated inputs could be used to set the voltage mode at
T<T1 and T>T1 2 and to enable/disable the output of power
supplies 10.
[0164] However, these modifications do not eliminate the major
drawbacks of power supply 10--repetitive arcing at plasma ignition
and termination and a need in the striking voltage to initiate a
plasma.
[0165] A preferred embodiment of the present invention can be built
around the DC plasma power supplies of the prior art by means of
controller 9, input 14, and interfaces 11, 17 or by means of
controller 51, input 14, and interfaces 19, 40, 41, 42.
[0166] While the present invention has been illustrated by a
description of various embodiments and while these embodiments have
been described in considerable detail, it is not the intention of
the applicant to restrict or in any way limit the scope of the
appended claims to such detail. Additional advantages and
modifications will readily appear to those skilled in the art. The
invention in its broader aspects is therefore not limited to the
specific details, representative apparatus and method, and
illustrative example shown and described. Accordingly, departures
may be made from such details without departing from the spirit or
scope of applicant's general concept.
* * * * *