Coating apparatus – Work holders – or handling devices
Reexamination Certificate
2001-10-12
2004-06-01
VerSteeg, Steven (Department: 1753)
Coating apparatus
Work holders, or handling devices
C204S298150, C427S445000, C248S363000, C269S016000, C269S053000, C269S055000, C269S904000
Reexamination Certificate
active
06743296
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an apparatus and a method for loading a wafer into a physical vapor deposition chamber and more particularly, relates to an apparatus and a method for self-centering a wafer onto a wafer pedestal situated in a physical vapor deposition chamber.
BACKGROUND OF THE INVENTION
Physical vapor deposition (PVD) or sputter deposition is a frequently used processing technique in the manufacturing of semiconductor devices that involves the deposition of a metallic layer on the surface of a semiconductor device. The physical vapor deposition technique is more frequently known as a sputtering technique. In more recently developed semiconductor fabrication processes, the sputtering technique is used to deposit metallic layers of tungsten or titanium tungsten as contact layers.
In a sputtering process, inert gas particles such as those of argon or nitrogen, are first ionized in an electric field to produce a gas plasma and then attracted toward a source or a target where the energy of the gas particles physically dislodges, i.e., sputters off, atoms of the metallic or other source material. The sputtering technique is very versatile in that various materials can be deposited utilizing not only RF but also DC power sources.
In a typical sputter chamber, the major components utilized include a stainless steel chamber that is vacuum-tight and is equipped with a helium leak detector, a pump that has the capacity to reduce the chamber pressure to at least 10
−6
torr or below, various pressure gauges, a sputter source or target, a RF or DC power supply, a wafer holder, a chamber shield and a clamp ring. The sputter source is normally mounted on the roof of the chamber such that it faces a wafer holder positioned in the center of the chamber facing each other. The sputter source utilized can be a W or TiW disc for a process in which W or TiW is sputtered. A typical sputter chamber is that supplied by the Applied Materials, Inc. of Santa Clara, Calif. under the trade name of ENDURA®. In some of the sputter chambers, the wafer holder is structured as a pedestal which includes an internal resistive heater.
One of the more important components in the sputter chamber is the clamp ring which serves two purposes during a sputter process. The first purpose is to clamp the wafer to the pedestal heater. The clamp ring holds the wafer in place on the pedestal when a positive gas pressure is applied between the heater and the pedestal such that heat can be efficiently conducted from the heater to the wafer. The second purpose served by the clamp ring is to allow a predetermined flow of argon to leak from under the wafer into the sputter chamber. The clamp ring is generally constructed in a circular shape with an oriented cut-out to match a wafer's flat contour. A hood is built into the clamp ring and is used for shadowing purpose to protect the lip of the clamp ring from being coated by the sputtered metal particles. The lip portion also allows the force of the clamp ring to be evenly distributed around the wafer.
A cross-sectional view of a typical sputter chamber
10
is shown in FIG.
1
. Sputter chamber
10
is constructed by a stainless steel chamber body
12
that is vacuum-tight, a sputter target
16
of W, TiW or Sn, a wafer holder
20
equipped with a heater
22
, a wafer lift mechanism
24
, a wafer port
28
, a pumping port
32
, a clamp ring
30
and a chamber shield
34
. A DC power supply
25
is connected to a target
16
and a conductive part of the chamber, such as the chamber wall
18
or chamber shield
34
, thereby establishing a voltage potential between the grounded chamber wall
18
and the target
16
. A DC bias circuit
23
is connected to the clamping ring and thus applies a DC bias to the wafer (not shown). The hood
36
of the clamp ring
30
protects the tip
38
from being coated by the sputtered particles. A perspective view of the same sputter chamber
10
is shown in FIG.
2
.
As shown in
FIG. 1
, the chamber shield
34
is another important component in the sputter chamber
10
. It forms a seal between the clamp ring
30
and the chamber body
12
such that sputtered particles from the sputter target
16
do not contaminate the chamber wall
18
during a sputtering process. It should be noted that, during the sputtering process, the wafer pedestal
20
is in a raised position with the tip portion
38
of the clamp ring
30
touching the heater
22
on the pedestal
20
. In order to achieve a tight seal from the chamber wall
18
, a small gap is normally maintained between the clamp ring
30
and the chamber shield
34
. In a typical metal sputtering process where a W, TiW, Sn or other metal is used in the sputter chamber, the emission of sputtered particles of the metals is shaped with a forward cosine distribution such that a more desirable deposition process in which metal particles are deposited uniformly at the center and the edge of the wafer can be achieved.
One of the processing difficulties incurred in a sputtering chamber is the placement of the wafer on the wafer pedestal. When a wafer is not positioned at a perfectly centered position on a wafer pedestal, i.e., the wafer position has shifted away from the center, subsequent metal deposition process produces a wafer that has thinner coating on one edge which will then lead to defocusing during photolithography resulting in defective dies being produced on the wafer edge. The defective dies result in a low yield of the physical vapor deposition process. It is therefore an important task during the fabrication process to center a wafer on a wafer pedestal properly before a deposition is to take place.
It is therefore an object of the present invention to provide an apparatus for self-centering a wafer on a wafer pedestal that does not have the drawbacks or shortcomings of the conventional apparatus.
It is another object of the present invention to provide an apparatus for self-centering a wafer on a wafer pedestal situated in a physical vapor deposition chamber that does not require any additional processing step.
It is a further object of the present invention to provide an apparatus for self-centering a wafer on a wafer pedestal in a sputtering chamber by using a modified wafer lifter equipped with at least four support fingers.
It is another further object of the present invention to provide a wafer lifter for self-centering a wafer on a pedestal by providing four support fingers on a lifter body that are each equipped with a slanted surface for contacting the wafer and for performing the self-centering function.
It is still another object of the present invention to provide a wafer lifter for self-centering a wafer on a pedestal situated in a physical vapor deposition chamber by utilizing a modified hoop equipped with improved support fingers.
It is yet another object of the present invention to provide a method for self-centering a wafer on a wafer pedestal by utilizing a modified wafer lifter equipped with improved wafer support fingers.
SUMMARY OF THE INVENTION
In accordance with the present invention, an apparatus and a method for self-centering a wafer on a wafer pedestal in a physical vapor deposition chamber are provided.
In a preferred embodiment, a wafer lifter for self-centering a wafer on a pedestal may be provided which includes a lifter body of annular shape that has a center cavity with a diameter that is larger than a diameter of the wafer pedestal; at least four support fingers emanating upwardly from the lifter body and are spaced-apart from each other; and a platform on a tip portion of each of the at least four support fingers defined by a surface slanted from a vertical plane of an outside surface of the support finger; the platform, when supporting a wafer thereon, leaves substantially no gap between the slanted surface and an outer periphery of the wafer.
In the wafer lifter for self-centering a wafer onto a wafer pedestal, the platform may be defined by a slanted shoulder portion of the support finger. A base of t
Taiwan Semiconductor Manufacturing Co. Ltd
Tung & Associates
VerSteeg Steven
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