Chemistry: electrical and wave energy – Processes and products – Coating – forming or etching by sputtering
Reexamination Certificate
2001-10-19
2003-11-25
McDonald, Rodney G. (Department: 1753)
Chemistry: electrical and wave energy
Processes and products
Coating, forming or etching by sputtering
C204S192120, C204S298110, C204S298150, C204S298230, C118S721000, C118S729000
Reexamination Certificate
active
06652716
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an apparatus and a method for operating a sputter chamber equipped with a cover ring and a wafer pedestal and more particularly, relates to an apparatus and a method for self-aligning a cover ring to a wafer pedestal in a sputter 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® 5500. 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 component 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
21
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
21
. A DC bias circuit
23
is connected to the clamping ring and thus applies a DC bias to the wafer (not shown). A perspective view of the clamp ring
30
and the chamber shield
34
is shown in FIG.
1
A. An enlarged, partial cross-sectional view of the clamp ring
30
and the chamber shield
34
is shown in FIG.
1
B. The hood
36
of the clamp ring
30
protects the tip
38
from being coated by the sputtered particles.
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
40
is normally maintained between the clamp ring
30
and the chamber shield
34
.
In a typical metal sputtering process where a Ti, W, TiW, Sn or other metal target 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.
In another typical metal sputtering chamber, instead of the clamp ring
30
shown in FIGS.
1
~
1
B, a cover ring
42
is used. The cover ring
42
, as shown in
FIG. 2C
, does not clamp onto the surface of wafer
44
. The cover ring
42
is equipped with alignment mark shields
46
which extend radially inwardly from an inner periphery
48
of the cover ring
42
. The function of the alignment mark shield
46
is to cover the alignment marks (not shown) located on the top surface of the wafer
44
and to prevent the deposition of metal particles thereon. In this configuration, when the wafer lifter
24
raises up with a wafer
44
mounted on top to meet the cover ring
42
, the cover ring
42
must be properly seated on the wafer pedestal
20
in order to provide proper shielding of the alignment marks. Such alignment cannot be ensured when the sputter chamber has been operated after a length of time and when the sputter chamber has been cleaned during a preventive maintenance procedure. When the cover ring
42
is not properly seated, or aligned with the wafer pedestal
20
, excess metal particle deposition between the cover ring
42
and the chamber shield
34
may cause arcing between the two components. Moreover, metal particles may further penetrate through gaps formed between the two components and deposit on the chamber bottom which may cause serious contamination problem.
It is therefore an object of the present invention to provide an apparatus for self-aligning a cover ring to a wafer pedestal in a sputter chamber 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-aligning a cover ring to a wafer pedestal in a sputter chamber such that the alignment marks are properly shielded during sputtering.
It is a further object of the present invention to provide an apparatus for self-aligning a cover ring to a wafer pedestal in a sputter chamber by providing at least two male alignment members on the outer periphery of the wafer pedestal.
It is another further object of the present invention to provide an apparatus for self-aligning a cover ring to a wafer pedestal in a sputter chamber by engaging at least two male alignment members on the wafer pedestal to at least two female alignment member on the cover ring.
It is still another object of the present invention to provide an apparatus for self-aligning a cover ring to a wafer pedestal in a sputter chamber by providing at least two protruding tabs on the wafer pedestal for engaging at least two recessed slots on the cover ring.
It is yet another object of the present invention to provide a method for self-aligning a cover ring to a wafer pedestal in a sputter chamber by engaging at least two male alignment members on the wafer pedestal to at least two female alignment members on the cover ring.
SUMMARY OF THE INVENTION
In accordance
Kao Chung-En
Lai Min-Te
McDonald Rodney G.
Taiwan Semiconductor Manufacturing Co. Ltd
Tung & Associates
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