Abrading – Precision device or process - or with condition responsive... – Computer controlled
Reexamination Certificate
2000-11-22
2003-01-28
Morgan, Eileen P. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
Computer controlled
C451S290000, C451S041000
Reexamination Certificate
active
06511362
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a polishing apparatus and a polishing method.
2. Description of the Related Art
Along with higher integration and multiple layer interconnection of semiconductor devices, flattening of various inter-layer insulation films or other films has become important in the process of production of a semiconductor device.
A variety of means have been proposed as a flattening technology. In recent years, attention has been paid to chemical mechanical polishing (CMP) using the mirror-like polishing technology of silicon wafers. Methods of flattening utilizing this are being developed.
An example of a polishing apparatus using a CMP process as a background of the present invention will be described with reference to FIG.
1
.
A polishing apparatus
301
shown in
FIG. 1
has a main shaft spindle
303
for rotating a polishing tool
302
and a table
304
for holding a wafer W.
The table
304
is rotatably mounted on a slider
306
provided to be able to move in an X-axial direction along a rail
305
. It is driven to rotate by a rotation driving means constituted by for example a motor, a pulley, a belt, etc.
The main shaft spindle
303
is held to be movable in a Z-axial direction and is positioned at a target position in a Z-axial direction by a not illustrated drive mechanism.
In the polishing apparatus
301
having the above constitution, first, the wafer W is rotated at a predetermined speed. Slurry obtained by mixing a polishing abrasive such as silicon oxide into a liquid such as an aqueous solution of potassium hydroxide is fed as an abrasive from a not illustrated slurry feeder onto the wafer W.
Next, the polishing tool
302
is rotated at a predetermined speed, and the wafer W and the polishing tool
302
are positioned in the X-axial and Z-axial directions so that an outer circumferential edge of the polishing tool
302
overlaps and contacts the outer circumferential edge surface of the wafer W.
The polishing tool
302
is positioned in the Z-axial direction so as to obtain a predetermined depth of cut to the wafer W. Due to this, a predetermined polishing pressure is generated between the polishing tool
302
and the wafer W. In this state, the wafer W is moved in the X-axial direction with a predetermined speed pattern. The wafer W is polished while bringing the polishing tool
302
in contact with the wafer W, whereby the wafer W is flattened.
Summarizing the disadvantages, in the polishing apparatus
301
of the above configuration, the polishing surface
302
a
of the polishing tool
302
is parallel to the holding surface of the rotation table
304
, and the overlapping regions of the polishing surface
302
a
of the polishing tool
302
and a surface to be polished of the wafer W contact each other over their entire surfaces according to the relative movement of the polishing tool to the wafer W
302
in the X-axial direction. For this reason, the area of the effective working region of the polishing surface
302
a
of the polishing tool
302
to the surface to be polished of the wafer W becomes a region where the polishing surface
302
a
of the polishing tool
302
and the surface to be polished of the wafer W overlap. This area is relatively large and varies according to the relative movement of the polishing tool
302
in the X-axial direction.
When the area of the effective working region of the polishing surface
302
a
of the polishing tool
302
to the surface to be polished of the wafer W is large, the amount of polishing in the effective working region is apt to be uneven due to the irregularities of the surface to be polished of the wafer W. If the area of the effective working region varies, the amount of polishing per unit time, that is, the polishing rate, varies, so it is difficult to uniformly polish the surface to be polished of the wafer W. Further, when the polishing surface
302
a
of the polishing tool
302
and the surface to be polished of the wafer W are parallel, the slurry cannot easily penetrate between the polishing surface
302
a
of the polishing tool
302
and the surface to be polished of the wafer W, so the amount of polishing again sometimes does not become stable.
For this reason, in the related art, for example, as shown in
FIG. 2A
, the polishing was performed by inclining a axis K
1
of the polishing tool
302
toward the direction of advance of the polishing tool
302
by an inclination angle &agr;.
Here,
FIG. 3
is a view of the distribution of pressure generated between the polishing surface
302
a of the polishing tool
302
and the surface to be polished of the wafer W when the axis K
1
of the polishing tool
301
is inclined in the direction of advance of the movement of the polishing tool
302
. Note that
FIG. 3
shows the distribution of virtual pressure when polishing the surface to be polished of the wafer W by just rotating the polished tool
302
without rotating the wafer W.
As shown in
FIG. 3
, the distribution of the pressure generated between the polishing surface
302
a
of the polishing tool
302
and the surface to be polished of the wafer W becomes an approximately crescentic region PR. In this crescentic region PR, an area PH where the pressure is relatively high is generated inside and an area PL where the pressure existing around this is relatively low is generated. The area PH where the pressure is relatively high exhibits an approximately symmetric shape about the X-axis. This area PH becomes a region effectively acting upon the surface to be polished of the wafer W. The area PH is made sufficiently smaller than the overlapping area of the wafer W and the polishing surface
302
a
of the polishing tool
302
. Even if the polishing tool
302
moves relatively in the X-axial direction, the surface area of the area PH becomes approximately constant. For this reason, the amount of polishing in the effective working region can be made uniform, and the polishing rate can be made constant.
However, the polishing tool
302
is for example an elastic member made of for example a disk-shaped member and formed by polyurethane foam or other plastic. It is pressed against the surface of the wafer W by a polishing pressure F as shown in FIG.
3
. For this reason, the polishing tool
302
pressed against the wafer W resiliently deforms.
In addition, if the polishing surface
302
a
of the polishing tool
302
is inclined to the wafer W surface by the inclination angle &agr;, the polishing surface
302
a
of the polishing tool
302
deforms in a riding region
190
and a relief region
191
shown in
FIG. 3
as shown in for example
FIGS. 4A and 4B
when riding up on the wafer W. In the riding region
190
, as shown in
FIG. 4A
, the polishing surface
302
a
of the polishing tool
302
rides up on the surface of the wafer W from an outer circumferential edge EG of the wafer W, so the polishing surface
302
a
of the polishing tool
302
resiliently deforms and the polishing surface
302
a
immediately before the riding up on the surface of the wafer W located in the vicinity of the outer circumferential edge EG protrudes downward from the surface of the wafer W. In the relief region
191
, as shown in
FIG. 4B
, the polishing surface
302
a
of the polishing tool
302
passes the outer circumferential edge EG from the top of the surface of the wafer W and then separates from it, so the resiliently deformed polishing surface
302
a
of the polishing tool
302
separates from the outer circumferential edge EG of the wafer W and the deformation is restored while the stress is eased.
When the polishing surface
302
a
of the polishing tool
302
resiliently deforms, the portion of the polishing surface
302
a
protruding downward from the surface of the wafer W strongly contacts the outer circumferential edge EG of the wafer W, the majority of the working energy is consumed for the work of the protruding portion of the polishing surface
302
a
riding up on the outer circumferential edge EG of the wafer W, and, as shown in
FIG. 3
, da
Akaike Yoshifumi
Nagai Hiroyuki
Suzuki Takashi
Morgan Eileen P.
Rader & Fishman & Grauer, PLLC
Shakeri Hadi
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