Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
2000-03-28
2003-06-03
VerSteeg, Steven H. (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S298030, C204S298230, C204S298280, C427S008000, C427S162000, C118S712000, C118S500000
Reexamination Certificate
active
06572738
ABSTRACT:
BACKGROUND OF THE INVENTION
This application claims the priority of Swiss application 964/99, filed in Switzerland on May. 25, 1999, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a vacuum treatment system having a vacuum treatment chamber, having elements for establishing a, treatment atmosphere in the chamber, and a sensor arrangement for detecting the treatment atmosphere momentarily existing in a treatment area in the chamber. The sensor arrangement ACTUAL value sensor of at least one of the elements is a regulating element of a control circuit for the treatment atmosphere, and having a workpiece carrier is moved in a driven manner through the, treatment area. The present invention also relates to processes for manufacturing workpieces in which the workpieces are moved in a treatment atmosphere guided by a control.
With respect to the vacuum treatment of workpieces, it is known to control the treatment atmosphere by one or several control systems concerning the maintaining of defined characteristics. This is particularly necessary if the processes taking place for the implementation of a desired treatment atmosphere in a vacuum treatment chamber are unstable per se in desired working points and can be stabilized only by way of a control. An example which is typical in this respect are reactive sputtering processes for coating substrates with non-conductive, thus typically oxidic layers, in the case of which a metallic DC-operated target, typically a magnetron arrangement is used in a reactive gas atmosphere. In addition to an inert working gas, such as argon, the reactive gas, such as oxygen or nitrogen, is fed to the treatment atmosphere. On the one hand, this leads to an intentional coating of the workpieces, for example, an oxide coating, but also to an interference coating of the metallic target. Without a working-point control, such a reactive sputtering process cannot be operated in a stable manner in the so-called transition mode or intramode. With respect to a detailed description of reactive sputtering processes in the above-mentioned transition mode, reference is made to U.S. Pat. No. 5,423,970, the disclosure of which is incorporated herein.
In such control systems, the control quantity (ACTUAL value measurement) is detected by measuring the plasma light emission, for example, in the case of a specific spectral line, by measuring the target voltage. A DESIRED value is defined for the measured control quantity and, corresponding to the control deviations, for example, the flow of reactive gas, in the above-indicated example, the oxygen flow (or, if it is not detected as a control quantity, the target voltage) is set as a regulating quantity in the control circuit. As a result, the operation, particularly a stabilization of the process in the desired working point, for example, in the above-mentioned transition mode, is achieved.
FIGS. 1
to
4
are schematic views of typical vacuum treatment systems of the latter type. They are systems of this type and workpiece manufacturing processes which can be implemented by vacuum treatment systems of this type and at which the problems to be described were recognized and solved according to the invention. The solutions according to the invention can, however, basically be used for systems and processes of the initially mentioned type in which the treatment process or the treatment atmosphere is controlled.
As illustrated by the arrow &ohgr;, substrates
1
are moved in a workpiece carrier drum
3
rotating in a treatment chamber past at least one sputtering source
5
. The sputtering source
5
with the metallic, thus electrically highly conductive target is, normally constructed as a magnetron source, DC-operated; often additionally with a chopper unit connected between a DC feeder generator and the sputtering source
5
, as described in detail in EP-A-0 564 789, also incorporated by reference herein. A chopper unit intermittently switches a current path situated above the sputtering source connections to be of high resistance and low resistance.
In
FIGS. 1
to
4
, the DC generator and the optionally provided chopper unit are each illustrated in the blocks
7
of the sputtering source feed. In addition to a working gas G
A
, such as argon, a reactive gas G
R
, such as oxygen O
2
, is admitted to the treatment atmosphere U of the vacuum chamber, the reactive gas G
R
particularly by way of gas flow regulating valves
10
.
Above the sputtering sources
5
, a reactive plasma
9
is formed in which the substrates and workpieces
1
moved through by the drum
3
above the sputtering surfaces are sputter-coated. Because not only the substrates
1
are coated with the electrically poorly conductive reaction products formed in the reactive plasma
9
but also the metallic sputtering surfaces of the sputtering sources
5
, the coating process described so far, particularly for achieving coating rates which are as high as possible, is unstable. For this reason, particularly in the case of these treatment processes and systems, the treatment process and, in this case, actually the treatment atmosphere acting upon the workpieces
1
, is stabilized in the treatment area BB with a control.
As a possible implementation embodiment of such a control circuit according to
FIG. 1
, a plasma emissions monitor
12
measures the intensities of at least one of the spectral line or lines characteristics of the light emission from the reactive plasma
9
. These intensities are fed as a measured control quantity X
a
to a controller
14
d
.
In
FIG. 2
, the target voltage on the sputtering source
5
is measured as the measured ACTUAL quantity X
b
of the control circuit by a voltage measuring device
16
and is fed to a controller
14
b
. With respect to the detection of the measured control quantity X,
FIGS. 1
,
3
and
2
,
4
correspond to one another. At the controllers
14
a
and
14
b
, for forming control differences, the respective measured control quantities X
a
and X
b
are compared with the preferably adjustable guide values W
a
and W
b
, which correspond to the measured control quantities.
In accordance with the formed control differences at the controllers
14
a
and
14
b
and their amplification on transmission paths (not illustrated separately) dimensioned with respect to the frequency response according to the rules of control engineering, regulating signals are generated at the output side of the respective controllers
14
a
,
14
b
. As seen in
FIGS. 1 and 2
, the regulating signals, correspondingly marked S
aa
and S
ba
, are guided to the flow control valves
10
for the reactive gas as regulating elements which are set such that the respectively measured control quantities X
a
and X
b
are led to the values defined by the guide quantities W
a
and W
b
and are held there.
As seen in
FIGS. 3 and 4
, the regulating signal generated on the output side of the controllers
14
a
and
14
b
, which is correspondingly marked S
ab
and S
bb
, is fed to the sputtering source feeds
7
which now themselves act as control regulating elements. This takes place either at their DC generators and/or at their optionally provided chopper units, where the chopper duty cycle is set.
The systems illustrated, for example, by
FIGS. 1
to
4
are therefore vacuum treatment systems with a vacuum chamber, having elements for establishing a treatment atmosphere (specifically particularly a sputtering source and reactive gas feeds), and a sensor arrangement for detecting the treatment atmosphere momentarily existing in the chamber, the plasma emissions monitors and voltage measuring devices described as examples. The sensor arrangements ACTUAL-value sensors of at least one of the mentioned elements form a regulating element of one control circuit respectively for the treatment atmosphere.
For depositing electrically poorly conducting or non-conductive layers by way of the release of one layer material component of electrically conductive targets, an approach described in U.S. Pat. No.
Unaxis Balzers Aktiengesellschaft
VerSteeg Steven H.
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