Coating apparatus – Gas or vapor deposition – With treating means
Reexamination Certificate
1998-12-02
2001-04-03
Mills, Gregory (Department: 1763)
Coating apparatus
Gas or vapor deposition
With treating means
C156S345420
Reexamination Certificate
active
06210483
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to a chemical vapor deposition (CVD) chamber. More particularly, the present invention relates to an improved susceptor used in a CVD chamber.
2. Background of the Related Art
CVD vacuum chambers are useful for depositing thin films on semiconductor substrates. Generally, a precursor gas is flown into a vacuum chamber through a gas distribution system and reacts with a heated substrate surface to deposit a thin film thereon. The deposition gas reaction also forms volatile by-product gases which are pumped away through a chamber exhaust system. Typically, a susceptor or substrate support member is provided to secure the substrate during the deposition process as well as to heat the substrate to the required processing temperature. Furthermore, a purge gas is flown towards the backside and/or edge of the substrate during processing to prevent deposition on the backside and the edge of the substrate which tends to flake off and contaminate the chamber. Exemplary CVD chambers are disclosed in U.S. Pat. Nos. 5,516,367 and 5,476,548, both of which are hereby incorporated by reference.
To increase manufacturing efficiency and device capabilities, the sizes of the devices formed on a substrate have decreased while the number of devices formed on a substrate has increased. Uniform CVD deposition across the surface of the substrate has become increasingly important to form uniform devices on substrates and to maximize the number of devices that can be formed on the substrate. Moreover, reduction of particle contaminates generated in the chamber has also become increasingly important to produce functional devices.
FIG. 1
a
is a partial cross sectional view of a substrate
14
supported on a susceptor having a purge gas channel
30
surrounding the edge of the substrate.
FIG. 1
b
is a partial top perspective view of the substrate
14
supported on the susceptor showing the purge gas channel
30
surrounding the edge of the substrate. As shown in
FIG. 1
a
, the substrate
14
is releaseably secured on the susceptor surface by a vacuum chuck having vacuum channels
20
which are connected to a vacuum pump (not shown), and the edge of the substrate is surrounded by a purge gas channel
30
. A purge gas feed line
22
, preferably disposed within the susceptor
10
, feeds a purge gas into the purge gas channel
30
surrounding the edge of the substrate
14
, thereby inhibiting the process gas from coming in contact with the substrate edge and depositing thereon. Preferably, a plurality of purge gas feed lines
22
supply purge gas into the purge gas channel
30
to achieve even distribution of the purge gas to the edge of the substrate.
Generally, the purge gas flows past the edge of the substrate
14
and outwardly away from the center of the substrate. However, because a substrate typically includes a notch
16
at the substrate edge as an identifying mark of the type and the orientation of the substrate, an excess amount of purge gas passes through the notch, diluting the processing gases adjacent to the notch and preventing formation of functional devices in the region adjacent to the notch.
FIG. 1
b
shows the effects of the purge gas, as indicated by the arrows, in the region adjacent to the notch. Typically, deposition in the region adjacent to the notch
16
is non-uniform because the excess purge gas coming through the notch creates an area of exclusion on the substrate. Thus, the region adjacent the notch
16
is wasted because of improper processing.
A similar purging effect in the region adjacent the notch occurs in a processing system where a purge guide is used for controlling the purge gas.
FIG. 2
a
is a partial cross sectional view of a purge guide
26
in combination with a substrate
14
disposed on a susceptor
10
in a processing position.
FIG. 2
b
is a partial top view of a purge guide and a substrate having a notch
16
, showing the effects of the purge gas in the region adjacent the notch. As shown in
FIG. 2
a
, the substrate
14
is supported by the susceptor
10
and releaseably secured on the susceptor surface by a vacuum chuck having vacuum channels
20
which are connected to a vacuum pump (not shown). When the susceptor
10
is moved to a processing position, the purge guide
26
rests on the susceptor
10
, preferably on a plurality of anti-sticking grooves
21
, and a shield portion
12
of the purge guide
26
extends over the edge of the substrate
14
. The shield portion
12
of the purge guide
26
maintains a fixed gap, typically between about 2 and about 10 mils, above the substrate
14
through which the purge gas flows as the gas continues into the processing area of the CVD chamber. It is important to maintain a consistent gap around the edge of the substrate
14
to control the purge gas distribution so that a uniform center to edge deposition on the substrate can be achieved.
A purge gas feed line
22
, preferably disposed within the susceptor
10
, feeds a purge gas into a purge gas opening
24
between the purge guide
26
and the susceptor
10
. The purge guide
26
then guides the flow of purge gas, as shown by the arrows, to the edge of the substrate
14
, thereby inhibiting the process gas from coming in contact with the substrate edge and depositing thereon. Preferably, the purge gas opening
24
completely surrounds the edge of the substrate, and a plurality of purge gas feed lines
22
supply purge gas into the purge gas opening
24
to achieve even distribution of the purge gas to the edge of the substrate.
However, an excess amount of purge gas passes through a notch
16
on the substrate, diluting the processing gas adjacent the notch and preventing formation of functional devices in the region adjacent the notch.
FIG. 2
b
shows the effects of the purge gas, as indicated by the arrows, in the region adjacent the notch. Typically, deposition in the region adjacent the notch
16
is non-uniform because the excess purge gas coming through the notch
16
creates an area of exclusion on the substrate. Thus, the region adjacent the notch
16
is wasted because of improper processing.
Therefore, there remains a need for an apparatus for supporting a substrate in a processing chamber which delivers a purge gas to the edge of the substrate and prevents excess purge gas from causing non-uniform and inconsistent deposition at the region adjacent the substrate notch.
SUMMARY OF THE INVENTION
The invention provides an apparatus for supporting a substrate in a processing chamber and excluding unwanted deposition at the edge of a substrate without adversely affecting deposition on the substrate in the region adjacent the substrate notch. In one aspect of the invention, a purge gas channel is provided in a susceptor and includes a notch portion disposed outwardly of the channel to direct gases at the location of a notch on a substrate away from the upper surface of the substrates. The notched portion enables delivery of purge gas to achieve the desired edge exclusion without detrimentally affecting the deposition on the region adjacent the notch on the substrate.
Another aspect of the present invention provides a purge guide with a notch formed therein which guides the purge gas away from the upper surface of the substrate adjacent the notch on the substrate to achieve the desired edge exclusion without detrimentally affecting the deposition on the region adjacent the notch on the substrate.
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patent: 5230741 (1993-07-01), van de Ven et al.
patent: 5231690 (1993-07-01), Soma et al.
patent: 5238499 (1993-08-01), van de Ven et al.
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patent: 5304248 (1994-04-01
Ghanayem Steve
Lai Ken
Tsai Ken
Yudovsky Joseph
Applied Materials Inc.
Hassanzadef P.
Mills Gregory
Thomason Moser & Patterson LLP
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