Abrading – Abrading process – Glass or stone abrading
Reexamination Certificate
2000-08-11
2003-05-13
Rachuba, M. (Department: 3723)
Abrading
Abrading process
Glass or stone abrading
C451S056000, C451S285000, C451S444000, C451S450000
Reexamination Certificate
active
06561877
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an apparatus and a method for retaining moisture on a polishing pad in chemical mechanical polishing during machine idling and more particularly, relates to an apparatus and a method for retaining moisture on a polishing pad in chemical mechanical polishing during machine idling by covering the polishing pad with a circular disc equipped with a moisture retention means and a fastening means.
BACKGROUND OF THE INVENTION
Apparatus for polishing thin, flat semi-conductor wafers is well known in the art such apparatus normally includes a polishing head which carries a membrane for engaging and forcing a semi-conductor wafer against a wetted polishing surface, such as a polishing pad. Either the pad, or the polishing head is rotated and oscillates the wafer over the polishing surface. The polishing head is forced downwardly onto the polishing surface by a pressurized air system or, similar arrangement. The downward force pressing the polishing head against the polishing surface can be adjusted as desired. The polishing head is typically mounted on an elongated pivoting carrier arm, which can move the pressure head between several operative positions. In one operative position, the carrier arm positions a wafer mounted on the pressure head in contact with the polishing pad. In order to remove the wafer from contact with the polishing surface, the carrier arm is first pivoted upwardly to lift the pressure head and wafer from the polishing surface. The carrier arm is then pivoted laterally to move the pressure head and wafer carried by the pressure head to an auxiliary wafer processing station. The auxiliary processing station may include, for example, a station for cleaning the wafer and/or polishing head; a wafer unload station; or, a wafer load station.
More recently, chemical-mechanical polishing (CMP) apparatus has been employed in combination with a pneumatically actuated polishing head. A CMP apparatus is used primarily for polishing the front face or device side of a semiconductor wafer during the fabrication of semiconductor devises on the wafer. A wafer is “planarized” or smoothed one or more times during a fabrication process in order for the top surface of the wafer to be as flat as possible. A wafer is polished by being placed on a carrier and pressed face down onto a polishing pad covered with a slurry of colloidal silica or alumina in de-ionized water.
A perspective view of a typical CMP apparatus is shown in FIG.
1
A. The CMP apparatus
10
consists of a controlled mini-environment
12
and a control panel section
14
. In the controlled mini-environment
12
, typically four spindles
16
,
18
,
20
, and
22
are provided (the fourth spindle
22
is not shown in
FIG. 1A
) which are mounted on a cross-head
24
. On the bottom of each spindle, for instance, under the spindle
16
, a polishing head
26
is mounted and rotated by a motor (not shown). A substrate such as a wafer is mounted on the polishing head
26
with the surface to be polished mounted in a face-down position (not shown). During a polishing operation, the polishing head
26
is moved longitudinally along the spindle
16
in a linear motion across the surface of a polishing pad
28
. As shown in
FIG. 1A
, the polishing pad
28
is mounted on a polishing disc
30
rotated by a motor (not shown) in a direction opposite to the rotational direction of the polishing head
26
.
Also shown in
FIG. 1A
is a conditioner arm
32
which is equipped with a rotating conditioner disc
34
. The conditioner arm
32
pivots on its base
36
for conditioning the polishing pad
38
for the in-situ conditioning of the pad during polishing. While three stations each equipped with a polishing pad
28
,
38
and
40
are shown, the fourth station is a head clean load/unload (HCLU) station utilized for the loading and unloading of wafers into and out of the polishing head. After a wafer is mounted into a polishing head in the fourth head cleaning load/unload station, the cross head
24
rotates 90° clockwise to move the wafer just loaded into a polishing position, i.e. over the polishing pad
28
. Simultaneously, a polished wafer mounted on spindle
20
is moved into the head clean load/unload station for unloading.
A cross-sectional view of a polishing station
42
is shown in
FIGS. 1B and 1C
. As shown in
FIG. 1B
, a rotating polishing head
26
which holds a wafer
44
is pressed onto an oppositely rotating polishing pad
28
mounted on a polishing disc
30
by adhesive means. The polishing pad
28
is pressed against the wafer surface
46
at a predetermined pressure. During polishing, a slurry
48
is dispensed in droplets onto the surface of the polishing pad
28
to effectuate the chemical mechanical removal of materials from the wafer surface
46
.
An enlarged cross-sectional representation of the polishing action which results from a combination of chemical and mechanical effects is shown in FIG.
1
C. The CMP method can be used to provide a planner surface on dielectric layers, on deep and shallow trenches that are filled with polysilicon or oxide, and on various metal films. A possible mechanism for the CMP process involves the formation of a chemically altered layer at the surface of the material being polished. The layer is mechanically removed from the underlying bulk material. An outer layer is than regrown on the surface while the process is repeated again. For instance, in metal polishing, a metal oxide layer can be formed and removed repeatedly.
Referring now to
FIG. 2A
, wherein a simplified plane view of the CMP apparatus
10
is shown. In the apparatus
10
, a polishing chamber
52
houses a cross member
54
equipped with four spindles
16
~
22
(shown in ghost lines) . The spindles
16
~
22
are normally connected to a polishing head
26
through a rotatable shaft (not shown).
A plane view of the CMP apparatus
10
is shown in
FIG. 2B
illustrating three polishing pads
92
,
94
,
96
and a conditioner arm
82
. Polishing pads
92
,
94
and
96
are also shown without the polishing heads in place. It should be noted that for each of the polishing pad positions, i.e. for each of
92
,
94
and
96
, a conditioner arm
82
is utilized for the in-situ conditioning of the respective polishing pads.
A slurry composition is a material that easily dries and accumulates after contacting dry air. When slurry is left on the surface of the process equipment, i.e. on the surface of the polishing pads while the machine is idling during maintenance, it will dry and accumulate to become a source of particle contamination for the wafers that are processed in the polishing chamber. Solid particles easily form on the polishing pad to cause macro-scratch on the wafer surface. Slurry particles may also become sources of particle contamination for the wafer surface and for the chamber environment. It is therefore highly desirable that particle contaminants resulting from dry slurry to be avoided or eliminated.
It is therefore an object of the present invention to provide an apparatus for retaining moisture on a polishing pad in chemical mechanical polishing during machine idling that can be utilized to eliminate the drawbacks or shortcomings of the conventional chemical mechanical polishing apparatus.
It is another object of the present invention to provide an apparatus for retaining moisture on a polishing pad in chemical mechanical polishing during machine idling which is constructed of a circular disc having a protruded top portion.
It is a further object of the present invention to provide an apparatus for retaining moisture on a polishing pad in chemical mechanical polishing during machine idling which is constructed of a circular disc made of a substantially transparent material for covering the polishing pad.
It is another further object of the present invention to provide an apparatus for retaining moisture on a polishing pad in chemical mechanical polishing during machine idling which is constructed of a substantially transparent circular disc h
Cheng Chung-I
Lin Chung-Yang
Lo Young-Wang
Shen Yu-Sheng
Rachuba M.
Taiwan Semiconductor Manufacturing Co. Ltd.
Tung & Associates
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