Coating apparatus – Gas or vapor deposition – Work support
Reexamination Certificate
1998-08-27
2001-02-13
Meeks, Timothy (Department: 1775)
Coating apparatus
Gas or vapor deposition
Work support
C414S935000, C414S941000, C118S715000
Reexamination Certificate
active
06187103
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an apparatus and a method for transporting a semiconductor substrate and more particularly, relates to an apparatus and a method for transporting wafers wherein the apparatus is a quartz robot blade which has a top surface provided with at least partially a surface roughness sufficiently great to prevent a wafer positioned thereon from slipping off.
BACKGROUND OF THE INVENTION
In the fabrication processes for a semiconductor device, numerous processing steps must be carried out on a semi-conducting substrate before the device is fabricated. The numerous processes may be as many as several hundred processing steps. Each processing step is executed in a process chamber such as an etcher, a physical vapor deposition chamber (or a sputter), a chemical vapor deposition chamber, etc.
In the vast majority of the processing steps, a special environment of either a high vacuum, a low vacuum, a gas plasma or other chemical environment must be provided for the wafer. For instance, in a sputter chamber, a high vacuum environment must first be provided surrounding the wafer such that metal particles sputtered from a metal target can travel to and deposit on an exposed surface of the wafer. In other process chambers, such as in a plasma enhanced chemical vapor deposition chamber, a plasma cloud of a reactant gas or gases is formed over a wafer positioned in a chamber such that deposition of a chemical substance can occur on the wafer. During any processing step, the wafer must also be kept in an extremely clean environment without the danger of being contaminated. The processing of a wafer therefore must be conducted in a hermetically sealed environment that is completely isolated from the atmosphere. Numerous processing equipment has been designed for such purpose. One of such widely used equipment is marketed by the Applied Materials Corporation of Santa Clara, Calif., i.e., Centura® 5000 system.
In a Centura® 5000 wafer handling system, as shown in
FIG. 1
, the basic system
10
consists of two independent vacuum cassette loadlocks
12
and
14
, a capacity for one to four independent process chambers (two of such chambers
16
and
18
are shown in FIG.
1
), a capacity for two service chambers, including the cool-down chamber
22
, and a vacuum transfer chamber
20
which is isolated from vacuum cassette load locks
12
,
14
and process chambers
16
,
18
by slit valves
32
(shown in FIG.
3
). The modular design of the basic system
10
is such that up to three high-temperature silicon deposition chambers may be used as the process chambers. The basic system
10
can be used for fully automatic high-throughput processing of wafers by utilizing a magnetically coupled robot. The basic system
10
is further capable of transferring wafers maintained at a high temperature such as 700° C. The basic system
10
further allows cross-chamber pressure equalization and through-the-wall factory installation. The vacuum pumps for the process chambers
16
,
18
, the transfer chamber
20
and the cassette loadlocks
12
,
14
are mounted at a remote location to prevent mechanical vibration from affecting the operation of the system.
Each of the vacuum cassette loadlocks
12
,
14
and the process chambers
16
,
18
and the service chamber
22
are bolted to the vacuum transfer chamber
20
and are self-aligned for ease of expansion or modification. Each of the process chambers
16
,
18
is capable of processing a single wafer for achieving wafer-to-wafer repeatability and control. The temperatures in the process chambers
16
,
18
are further closed-loop controlled for accuracy.
A plane view of the basic system
10
of
FIG. 1
is shown in FIG.
2
. An enlarged, perspective view of the vacuum transfer chamber
20
is further shown in FIG.
3
. As shown in
FIG. 3
, the process chambers
16
,
18
communicate with the vacuum transfer chamber
20
by slit valves
32
. Similarly, the vacuum cassette loadlocks
12
,
14
and the service chamber
22
(such as the cool-down chamber) communicate with the vacuum transfer chamber
20
through slit valves
32
.
In the basic wafer processing system
10
shown in
FIGS. 1 and 2
, the handling of wafers between the various loadlock chambers
12
,
14
, the process chambers
16
,
18
and the cool-down chamber
22
must be carefully conducted to avoid damage to the wafers. To accomplish such purpose, the wafer is handled by a wafer transfer system
24
. The wafer transfer system
24
, as shown in
FIGS. 2
,
3
and
4
, consists mainly of a robotic handler which handles all wafer transfers by a single, planar, two-axis, random access, cassette-to-cassette motion. A magnetically coupled robot permits good vacuum integrity and service without interrupting chamber integrity. The major component of the wafer transfer system
24
is the quartz robot blade
28
, The high-purity quartz blade
28
permits high-temperature transfer at up to 700° C. without incurring contamination. A non-contact optical wafer centering process is also performed during the wafer transfer process. A constant flow of filtered inert gas such as nitrogen is used in the cassette loadlocks
12
,
14
and the vacuum transfer chamber
20
. An enlarged view of the wafer transfer system
24
including the quartz robot blade
28
is shown in
FIG. 4. A
frog-leg-type robot arm
34
is used to operate the quartz robot blade
28
.
A conventional quartz robot blade
28
is shown in both a cross-sectional view in FIG.
5
A and in a plane view in FIG.
5
B. The robot blade
28
can be fabricated of a high temperature ceramic material such as quartz. The blade is provided with mounting holes
36
for mounting to a blade mount
38
(shown in FIG.
4
). The quartz robot blade
28
normally has an elongated construction in a rectangular shape. The elongated body
40
consists of an aperture
42
provided for ventilation of the backside of a wafer (not shown), a recessed surface area
44
and three raised peripheral areas
46
,
48
and
50
. The first raised peripheral area
46
has a maximum diameter measured across the elongated body
40
of approximately 200 mm adapted for receiving an 8-inch wafer. The second raised peripheral area
48
acts as a cradle for holding an 8-inch wafer therein on top of the first raised peripheral area
46
.
Since the robot blade
28
is fabricated of a high temperature resistant ceramic material such as quartz which has a smooth surface, problem occurs when the blade is used for transporting a silicon wafer which also has a smooth surface. The positioning of a wafer on the blade
28
resulting in two smooth surfaces being positioned face-to-face and the wafer is frequently lost by slipping off the blade during transport. When a wafer falls off the blade
28
, the wafer may be either severely damaged or broken resulting in a total loss. A quartz robot blade that has a smooth top surface for engaging a wafer is therefore inadequate for transporting wafers.
It is therefore an object of the present invention to provide a wafer-transporting apparatus that does not have the drawbacks or shortcomings of the conventional wafer-transporting devices.
It is another object of the present invention to provide an apparatus for transporting semiconductor substrates which is constructed of a rectangular-shaped member that has a top surface with a surface roughness for engaging and holding a substrate thereon.
It is a further object of the present invention to provide an apparatus for transporting wafers which is equipped with a surface roughness in a top surface for engaging a wafer wherein the surface roughness is provided by a sand-blasting method.
It is another further object of the present invention to provide a wafer-transporting blade for transporting wafers into process chambers wherein the blade is fabricated of a quartz material.
It is still another object of the present invention to provide a wafer-transporting blade that is fabricated of a quartz material which has a top surface with a surface roughness for
Ding T. H.
Huang C. Y.
Meeks Timothy
Taiwan Semiconductor Manufacturing Company , Ltd.
Torres Norca L.
Tung & Associates
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