Metal working – Barrier layer or semiconductor device making
Reexamination Certificate
1997-03-03
2001-02-06
Graybill, David E. (Department: 2814)
Metal working
Barrier layer or semiconductor device making
C250S398000, C118S725000, C118S728000
Reexamination Certificate
active
06183523
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the transfer of heat to and from generally flat articles in a vacuum or low pressure environment by means of a thin layer of gas.
BACKGROUND OF THE INVENTION
An article in a vacuum or low pressure environment is generally thermally isolated from its surroundings. Even if placed on or clamped to a support surface, only a limited number of microscopic points of actual thermal contact exist between the article and the support surface. In order to improve both the effectiveness and uniformity of thermal contact, it is known technique to introduce a thin layer of heat conveying gas between the article and the support surface.
This technique is frequently used in the deposition by sputtering or etching of thin films on silicon, ceramic or glass substrates. In these processes, it is sometimes desired to maintain a substrate at a low temperature in spite of heat generated by the sputter deposition or etching processes. In such cases, the thin layer of the heat conveying gas is used to transfer heat from the substrate to the support platform. The support platform is then cooled with suitable cooling means.
Alternatively, in sputtering processes, it is sometimes desired to maintain a substrate at a temperature higher than it would normally reach from the heat generated by the sputter deposition alone. In this case, the heat conveying gas film transfers heat from a support platform containing heating means to the substrate.
The same support platform may contain both cooling and heating means so that heat may be transferred either from or to a substrate as required.
The technique of thermally controlling a substrate by means of a heat conveying gas layer is disclosed in the following U.S. Pat. Nos.: 4,261,762, 4,457,359; 4,512,391; 4,542,298; 4,680,061; 4,743,570; 4,909,314 and 4,949,783.
A typical embodiment of this art is shown in FIG.
1
. which is a section view through substrate and support platform and in
FIG. 2
which is a plan view of the support platform surface.
A substrate
1
is placed on the engaging surface
2
of a support platform
3
which may contain cooling means
4
and heating means
5
. Flange
6
and seal
7
connect the apparatus to processing chamber wall
8
, providing for a vacuum or low pressure environment
9
around substrate
1
by sealing out an atmospheric environment
10
on the opposite side of plate
3
.
A heat conveying gas, such as argon or helium, is introduced through port
11
and is distributed by channel
12
. Port
13
is used to measure the pressure of the heat conveying gas, which may be adjusted to approximately 10 Torr in order to provide effective thermal transfer between substrate
1
and support platform
3
.
Holding means
14
, which may be a plurality of individual fingers or may be a continuous ring, retain substrate
1
against the force of the heat conveying gas pressure and maintain a close fit between substrate
1
and engaging surface
2
. Because some heat conveying gas may escape in direction
15
at the perimeter
16
of substrate
1
, thereby reducing gas pressure and thermal transfer, it is desirable that the gap between substrate
1
and engaging surface
2
is 0.003 or less.
In embodiments where heating means
5
are not used, a soft rubber seal may be placed near perimeter
16
to further reduce gas loss, but such seals are generally not used at elevated temperatures due to degradation of the seal material.
In order to maximize the area of thermal transfer between substrate
1
and support platform
3
, the outermost portion
17
of gas distribution channel
12
is generally configured to conform closely to perimeter
16
of substrate
1
, thus limiting the use of a particular support platform to substrates of a specific shape and size for which the support platform was constructed.
SUMMARY OF THE INVENTION
In some applications, it may be desired to process substrates of different sizes. Unfortunately, the prior art configuration requires that the support platform
3
be replaced with each substrate size change.
Therefore, it is an object of this invention to provide a gas thermal transfer support platform which accommodates substrates of more than one size or shape avoiding the need for replacing the support platform.
It is a further object of this invention to provide a gas thermal transfer support platform which accommodates a plurality of substrates at one time.
In accordance with principles of the present invention, these objects are achieved by a substrate support platform having a substrate engaging surface which defines a first channel for introducing and distributing a thermal transfer gas to a first region of the engaging surface, and a second channel, nonintersecting with the first channel, for introducing and distributing a thermal transfer gas to a second region of the engaging surface.
In specific embodiments, a gas delivery system is independently connected between a gas source and the first and second channels, for independently providing (via valved connections) a thermal transfer gas to the first and second channels, whereby gas delivery may be limited to one of the channels, or gas may be delivered to both of the channels in case a substrate is placed over either or both of the associated regions.
In addition, a pressure measuring device, for measuring a gas pressure, is independently coupled to each of the channels via measuring ports, permitting measurement and control of gas pressure from the gas source.
The second channel may be nested within the first channel, such that the first region encompasses the second region. In this embodiment, a smaller substrate can be placed over the second channel, and gas can be delivered to the second channel only, to effect thermal transfer between the support platform and the smaller substrate. Alternatively, a larger substrate can be placed over the first channel and second channel, and gas may be delivered to the first channel and the second channel to effect thermal transfer between the support platform and the larger substrate.
In an alternative embodiment, the first and second channels are not nested in this manner, so that the first and second regions are nonoverlapping. In this embodiment, substrates may be selectively placed on the first channel and/or the second channel, and gas delivered only to the channel(s) which have a substrate placed thereon.
In any of these embodiments, the channels may be circular, square, or any other shape, in any combination. The regions served by the channels may be of similar shapes and sizes or different shapes and sizes.
In further embodiments, third or further nonintersecting channels may be formed on the substrate support platform to provide additional regions to which gas may be provided to thermally control substrates.
In further aspects, the invention features a semiconductor processing chamber incorporating the novel wafer support surface, and methods of using the wafer support surface.
The benefits and advantages of the invention over the prior art apparatus and methods will become more readily apparent from the description of the drawings and detailed description which follow.
REFERENCES:
patent: 4261762 (1981-04-01), King
patent: 4457359 (1984-07-01), Holden
patent: 4512391 (1985-04-01), Harra
patent: 4542298 (1985-09-01), Holden
patent: 4680061 (1987-07-01), Lamont, Jr.
patent: 4705951 (1987-11-01), Layman et al.
patent: 4743570 (1988-05-01), Lamont, Jr.
patent: 4909314 (1990-03-01), Lamont, Jr.
patent: 4949783 (1990-08-01), Lakios et al.
patent: 5001423 (1991-03-01), Abrami et al.
patent: 5583737 (1996-12-01), Collins et al.
Hurwitt Anne
Hurwitt Steven
Reiss Ira
Graybill David E.
Hurwitt Anne
Tokyo Electron Limited
Wood Herron & Evans L.L.P.
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