Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
2000-06-05
2003-03-04
McDonald, Rodney G. (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C204S192130, C118S728000, C118S663000, C118S665000, C118S666000, C118S668000, C118S669000, C118S671000, C118S675000, C156S345240, C156S345250, C156S345260, C156S345270, C156S345280
Reexamination Certificate
active
06527927
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a vacuum treatment system with at least one vacuum treatment chamber, wherein a first part of the system is connected with an electrical system reference potential—by convention ground potential; in the vacuum chamber a further part is provided to which is applied an electric potential varying by at least ±12 V from the system reference potential, and wherein at this further part at least one sensor and/or at least one adjusting element is disposed, further with an electronics unit which is operatively connected at the input and/output side with the sensor and/or adjusting element.
Such a prior known vacuum treatment system is depicted schematically in
FIG. 1
as an example with a path of plasma discharge and will be discussed in conjunction with this Figure. In the vacuum chamber
1
a plasma discharge path is provided in this example between electrodes
3
a
and
3
b
. The discharge path denoted by
3
is operated electrically by a supply unit
5
, with this being either DC, pulsed DC, with AC or with AC and superimposed DC, wherein the AC signal frequency can be in the Hz up to the high frequency, for example even in the microwave range.
For the purpose of explanation, in
FIG. 1
the electrical supply leads to the discharge path
3
from the chamber
1
are shown as being electrically insulated. Different ways exist of superimposing the system reference potential, by convention ground potential &phgr;
0
. This is schematically shown by the option selection switch
7
. It is conventional, for example, to put the housing
1
as well as one of the electrodes
3
a
,
3
b
at ground. In the vacuum chamber
1
a further part
9
is depicted, for example a substrate support, an instrument support, a further electrode etc., wherein this part
9
, shown separately for the purpose of the explanation, can also be one of the electrodes
3
a
,
3
b
. This part
9
is now not at potential &phgr;
0
. This is shown with the unit
4
according to an impedance and/or source equivalent circuit diagram.
SUMMARY OF THE INVENTION
The present invention builds on problems in connection with part
9
in the chamber
1
to which (part) the system reference potential &phgr;
0
is not applied. It is at any electrical potential &phgr;
9
varying decisively, i.e. by at least ±12 V, from &phgr;
0
, i.e. it is at DC potential, AC potential, at superimposed AC and DC potential, at a pulsed DC potential, wherein in terms of frequency the AC potential can be launched up into the high-frequency range or even into the microwave range. If, for example, part
9
is a substrate support, it can, if mounted electrically insulated, be operated with respect to &phgr;
0
, on self-bias potential of the discharge. If part
9
is one of the electrodes
3
a
,
3
b
in the case of plasma generation, it is at high HF potential with respect to &phgr;
0
.
As shown further in
FIG. 1
, it is frequently necessary to carry out measurements or adjusting intervention at said part
9
, not operated at system reference potential &phgr;
0
, as is schematically shown on unit
11
, by means of at least one sensor and/or at least one adjusting element. Adjusting signals or sensor output signals are transmitted from an electronics unit
13
to the unit
11
or received by the latter. As shown in
FIG. 1
, it is conventional to apply to such an electronics unit
13
the system reference potential &phgr;
0
. Such an electronics unit is often
a digital, programmable unit with storage means for the operating programs, therein preferably comprising
at least one programmable digital logic package and/or
a digital computing unit,
it preferably comprises a microprocessor and/or a microcomputer with associated storage means for operating programs.
The reason for the reference potential placement comprises that for example with HF operation of the discharge path, simple protective measures are possible, as shown schematically at
15
, for example by means of shielding also placed at &phgr;
0
. Furthermore, the signal communication between unit
13
and a unit
17
supervisory to it, such as for example a supervisory computer, is especially simple. The communication interface
19
comprises as reference potential the system reference potential &phgr;
0
which, as stated, is by convention ground potential. Under the assumption of the communication connection between unit
11
and unit
13
, which is schematically shown by
21
in
FIG. 1
, also, if appropriate, feed signals for unit
11
from an external feed device, the supplied voltages to unit
11
are reduced through suitable electronic means to the measuring or total adjusting range of by convention a few volts. For this purpose are used, for example, voltage dividers, as described in U.S. Pat. No. 5,270,637, and/or suitable rectifiers and filter elements, as shown in U.S. Pat. No. 5,144,231.
This prior known configuration entails problems:
Measuring and adjusting signals from respectively to the unit
11
must be isolated from often large “Common Mode” signals, namely from the signal, already mentioned, between part
9
, &phgr;
0
and &phgr;
9
. This entails expenditures in particular if part
9
is at HF potential, in particular high HF potential, or at a potential with high spectral components of higher frequencies, such as occur during pulse operation, interference spark formation, switch-on processes etc. But even if the part
9
were at an ideal DC potential with respect to &phgr;
0
, the problem remains that on unit
11
relatively small measuring or adjusting signals with respect to a large “Common Mode” signal must be processed which strongly limits the accuracy or resolution of said measuring or adjusting signals. If part
9
is operated for example at HF potential, for each individual measuring or control line from, respectively to, the unit
11
an HF filter must be provided—with, depending on the expenditure, restricted effect—as well as for each additional signal, such as for example for feed signals to unit
11
in order to ensure an optimal HF uncoupling with respect to the electronic unit
13
. This entails considerable expenditures. In addition, in particular measuring and control signal lines to unit
11
must be efficiently shielded, especially if the, by convention, high-ohmic and sensitive inputs of unit
13
are taken into consideration. In principle, expensive precautionary measures for protecting the electronics must be provided.
It is the task of the present invention to develop a vacuum treatment system of the discussed type such that a substantial simplification of the signal processing with the electronic unit
13
results, further a more accurate measurement signal evaluation or a more precise adjusting element variation and which is significantly more cost effective. This is attained thereby that the electronics unit, differing from the prior known technique described in conjunction with
FIG. 1
, is operated at a further reference potential which further reference potential is equal to the potential of the further part
9
.
The potential placement is especially highly effective with low expenditure where the operation of the vacuum treatment system leads to the occurrence of, to some extent stochastic, high-frequency signal components. A vacuum treatment system in which such processes occur frequently is in particular a system in which a discharge path is used.
In such a system said further part
9
forms preferably one of the discharge electrodes or is a part exposed to the discharge operated at a floating potential and thus, for example assumes the self-bias potential of the discharge or which is operated tied in potential.
In a further preferred embodiment, therein in particular in said system with discharge path, said at least one sensor is a temperature sensor, the adjusting element is a heating and/or cooling device, therein preferably a multizone heating or cooling device, wherein further, preferred in this case, the further part
9
is formed by a workpiece support. A
McDonald Rodney G.
Notaro & Michalos P.C.
Unaxis Balzers Aktiengesellschaft
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