Chemistry: electrical and wave energy – Apparatus – Coating – forming or etching by sputtering
Reexamination Certificate
1997-05-14
2001-04-10
Nguyen, Nam (Department: 1753)
Chemistry: electrical and wave energy
Apparatus
Coating, forming or etching by sputtering
C118S728000, C156S345420
Reexamination Certificate
active
06214184
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to a pedestal for holding a substrate and more particularly, relates to an insulated pedestal for holding a substrate that includes a pedestal body and at least three spacers of insulating material situated on a top surface of the pedestal body for supporting and insulating a substrate on and from the pedestal body.
BACKGROUND OF THE INVENTION
Physical vapor deposition (PVD) is a frequently used processing technique in the manufacture of integrated circuit chips that involves the deposition of a metallic layer on the surface of a silicon wafer. The technique is also known as a sputtering process. For instance, in more recently developed advanced semiconductor manufacturing technology, the PVD technique is frequently used to deposit metallic layers of TiN as anti-reflective coating or barrier layers.
In a typical PVD process, an inert gas such as argon is first ionized in an electrical field producing a plasma of charged gas particles wherein the particles are attracted toward a negatively charged source (or target). The energy of these gas particles physically dislodges, or sputters off atoms of the metallic target material. Physical vapor deposition is a versatile technique in that many different materials can be deposited by using an RF or a DC power source.
In a typical PVD process chamber
10
, as shown in
FIG. 1
, major components include a stainless steel chamber
12
that is vacuum tight and is equipped with a cryopump
16
which has the capability of reducing the chamber pressure to 10
−6
Torr or lower, a pressure gauge
18
, a sputter source or target
20
, a power supply (not shown), a wafer holder
26
and a clamp ring
28
. The sputter source
20
and the wafer holder
26
are positioned facing each other. The target is a Ti disc when sputtering of TiN is desired. One of such PVD process chamber is the Endura® 5500 which is commercially supplied by Applied Materials, Inc. of Santa Clara, Calif.
The wafer holder
26
is normally a pedestal of a disc shape. In the top surface
34
of pedestal
26
, metal screws
36
are used as wafer support by holding a wafer at the tip
38
of screw
36
. This is shown in FIG.
2
and FIG.
2
A.
FIG. 2
is an enlarged, plane view of the pedestal
26
shown in FIG.
1
. The pedestal
26
is generally of a metal disc structure that has a pedestal body
42
mounted to a backing plate (not shown). The screw or pedestal pin
36
are generally of a 8-32 stainless steel screw mounted through a bottom surface
44
of the pedestal body
42
. The tip
38
of the screw
36
protrudes the top surface
46
of the pedestal body
42
by a distance of approximately 1 mm. The enlarged, cross-sectional view shown in
FIG. 2A
indicates a section of a wafer that is supported by tip
38
of the pedestal pin
36
. It is seen that the outer periphery of wafer
30
normally extends over the pedestal pin
36
by approximately 1 cm. The pedestal pins
36
, normally requires at least two on each pedestal body
42
for the secure supporting of a wafer
30
. The pedestal pin
36
allows a gap of approximately 1 mm to be maintained between the wafer
30
and the top surface
46
of the pedestal body
42
. Such distance between the wafer and the pedestal top surface is necessary so that a subsequently deposited film, i.e., a TiN layer will not glue the wafer to the pedestal surface. A thin TiN film is normally deposited on top of an aluminum-copper film layer as an anti-reflective coating.
In a typical PVD deposition process, as shown in
FIG. 1
, plasma cloud
16
is generated by a cascading ionization reaction in which electrons and ion pairs are formed. For instance, when an electron bumps into an argon atom, it forms an argon ion and another electron. The newly formed electron then collides with another argon atom such that a chain reaction or ionization reaction is started.
When electrons bombard the wafer surface
48
, it can be charged to a negative voltage higher than 30 volts. The charge distribution or the formation of an electric field is more severe at or near the location of wafer pins
36
. When the wafer pin
36
has a sharp tip
38
(or a rough tip surface), arcing can occur at one of the three wafer pin locations. During the occurrence of arcing, a large number of hot electrons are showered on top of the wafer surface which greatly heat up the area on the wafer that the electrons showered on and furthermore, causes damage to the same area on the metal film that has been deposited on top of the wafer. For instance, in the present case, the aluminum-copper film predeposited on the wafer surface can be greatly damaged to produce a roughened surface. The arcing damages the metal film severely to alter the appearance and the electrical properties of the metal film during the IC fabrication.
It is therefore an object of the present invention to provide a wafer holder that does not have the drawbacks or shortcomings of a conventional wafer holder device.
It is another object of the present invention to provide an insulated wafer pedestal that does not require electrically-conductive pedestal pins for supporting a wafer on the pedestal.
It is a further object of the present invention to provide an insulated wafer pedestal that is an electrically-non-conductive wafer support such that arcing on the wafer can be eliminated.
It is still another object of the present invention to provide a wafer pedestal that utilizes at least three spacers made of insulating material for supporting and insulating a wafer on and from a pedestal body.
It is yet another object of the present invention to provide an insulated wafer pedestal that has a pedestal body of essentially a metal disc and at least three spacers made of insulating material for supporting and insulating a wafer on and from the pedestal body.
It is another further object of the present invention to provide a wafer pedestal that has a pedestal body equipped with recessed areas such that at least three spacers of insulating material can be mounted in such recessed areas to provide support and insulation for a wafer positioned on the pedestal body.
It is still another further object of the present invention to provide an insulated wafer pedestal that has a pedestal body equipped with apertures therethrough and at least three spacers of insulating material mounted in said apertures for supporting and insulating a wafer on and from the pedestal body.
It is yet another further object of the present invention to provide a metal deposition chamber that has a wafer pedestal equipped with at least three spacers of insulating material mounted in a top surface of a pedestal body for supporting and insulating a wafer on and from the pedestal body.
SUMMARY OF THE INVENTION
In accordance with the present invention, a wafer pedestal for supporting a wafer that has a pedestal body and at least three ceramic spacers on top of the pedestal body for supporting a wafer is provided.
In a preferred embodiment, a pedestal for holding a substrate that has a pedestal body of essentially a metal disc, and at least three spacers of insulating material situated on a top surface of the pedestal body for supporting and insulating a substrate on and from the pedestal body is provided.
In another preferred embodiment, a wafer holder is provided which has a body portion made of an electrically conductive metal, and at least three spacers made of an electrically non-conductive material mounted to the body portion, each of the three spacers has a bottom portion adapted for intimately contacting the body portion, a top portion adapted for supporting a wafer, and a thickness sufficient to keep the wafer at a distance away from the body portion so as not to adhered the wafer to the body portion by a subsequently deposited film.
In yet another preferred embodiment, a metal deposition chamber is provided which includes a DC power supply for producing a plasma, a metal target for producing metal atoms, and a wafer pedestal that has a metallic pedestal body and at least thre
Chen Shun-Hsiang
Chien Tingray
Wang Shih-Ming
Cantelmo Gregg
Nguyen Nam
Taiwan Semiconductor Manufacturing Company Ltd
Tung & Associates
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