Abrading – Abrading process – With tool treating or forming
Reexamination Certificate
2001-07-18
2004-01-27
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
With tool treating or forming
C451S072000, C451S443000, C451S444000
Reexamination Certificate
active
06682405
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chemical mechanical polishing apparatus that is used for manufacturing semiconductor devices. In particular, the present invention relates to a polishing adjustment of a polishing pad using a dresser.
2. Description of Related Art
FIGS. 9A-9D
show drawings for explaining the prior art. A state in which a polishing pad
102
is dressed is shown. As shown in
FIG. 9A
, a dresser
103
is placed on a polishing pad
102
that is adhered onto a surface plate
101
. When a pressure is applied to the dresser
103
, the surface of the polishing pad
102
is ground by a diamond particle surface
103
A formed on the peripheral surface zone of the dresser
103
. As a result, the surface of the polishing pad
102
is polished as shown in FIG.
9
A. In general, an abrasive material or pure water is supplied to the polishing pad during a dressing process.
Polishing is carried out in a planarization process during manufacturing of a semiconductor device or the like. During such polishing, however, the abrasive material and/or polishing dust sticks to the surface of the polishing pad
102
, which eventually causes the polishing process to become unstable. For this reason, in order to maintain stable polishing, the polishing pad
102
needs to be dressed and polished by the dresser
103
.
However, the above-described prior art has the following problem. As shown in
FIGS. 9B and 9C
, the grind amount of the portion of the polishing pad
102
at distance Rt from the center of rotation of the surface plate
101
is proportional to the contact length L of the diamond particle surface
103
A, with the polishing pad
102
at distance Rt from the center of the surface plate
101
. By a simple calculation, the length L is given by
L
=2
·Rt
·(Cos
−1
((
Rt
2
+Rx
2
−R
1
2
)/(2
·Rt·Rx
))−Cos
−1
((
Rt
2
+Rx
2
−R
2
2
)/(2
·Rt·Rx))
(1)
Here, as shown in
FIGS. 9B and 9C
,
Rx: the distance between the center of the dresser
103
and the center of the surface plate
101
;
R
1
: the outside radius of the diamond particle surface
103
A; and
R
2
: the inside radius of the diamond particle surface
103
A.
FIG. 11
shows the dependency of the contact length L of the diamond particle surface
103
A with the surface of the polishing pad
102
at distance Rt from the center of the surface plate
101
when, for example, Rx=17 cm, R
1
=16 cm, and R
2
=15.5 cm. The graph shows that the length L varies over a wide range within the polishing pad. Since the grind amount of the polishing pad
102
is proportional to the length L, the grind amount of the polishing pad
102
varies over a wide range. As a result, the surface of the polishing pad
102
cannot be made flat as needed. The minimum grind amount required to achieve a satisfactory state of polishing is pre-determined. Therefore, even at a location where the value of L is the smallest, the required minimum grind amount must be secured. On the other hand, at a location where the value of L is large, the polishing pad is over-ground.
As discussed above, the value of L grows very large in a region near the periphery of the surface plate (at points 29 cm from the center of the surface plate) and in a region near the center of the surface plate (at points 1.5 cm from the center of the surface plate). Therefore, in these regions, the polishing pad is ground by a large amount. The problem that the polishing pad is ground by a large amount in a region near the periphery of the surface plate can be solved by increasing the diameter of the dresser
103
.
FIG. 12
shows the dependency of L on the distance Rt from the center of the surface plate
101
in case the diameter of the dresser
103
has been increased to Rx=20 cm, R
1
=19 cm, and R
2
=18.5 cm. In this case, as seen from
FIG. 12
, the value of L is 1.47 cm at the point where Rt=29 cm, which is shorter by 2.1 cm than the value of L at the point where Rt=29 cm in the case shown in FIG.
11
. However, in the interior of the admissible range, the value of L achieves a maximum of 2.44 cm at the point where Rt=1.5 cm, which is not significantly smaller than the maximum value of L achieved at Rt=1.5 cm in the case shown in
FIG. 11
, resulting in practically no improvement at all.
Thus, in the case the grind amount of the polishing pad varies over a wide range depending on the distance Rt from the center of the surface plate
101
, the life span of the polishing pad is seriously shortened. A polishing pad is dressed and ground after it has been used to polish a prescribed number of semiconductor wafers.
FIG. 10
is a schematic cross sectional view of the grind surface
102
A of the polishing pad
102
attached onto the polishing surface plate
101
. In
FIG. 10
, the region
102
A
1
where the grind amount is the largest (position 1.5 cm from the center of the surface plate), the region
102
A
2
where the grind amount is the smallest (position 6.9 cm from the center of the surface plate), and the region
102
A
3
which is the outer limit of the admissible polishing range (position 29.0 cm from the center of the surface plate) are indicated with arrows.
As mentioned before, in order to carry out stable polishing, the polishing pad must be ground at least by a minimum necessary amount. The region
102
A
2
, where the grind amount is the smallest (position 1.5 cm from the center of the surface plate), must also be ground at least by the same minimum necessary amount, which is 0.67 &mgr;m per wafer in this case. However, in the region
102
A
1
, where the grind amount is the largest (position 1.5 cm from the center of the surface plate), 1.67 &mgr;m per wafer is ground. The life span of the polishing pad
102
is determined by the amount ground by the dressing. Therefore, if the polishing pad
102
is dressed by an excessive amount, even the surface of the polishing surface plate
101
can be ground. When this happens, the surface of the polishing surface plate
101
is damaged, and the polishing surface plate
101
needs to be replaced.
As explained above, the polishing pad
102
is ground by a large amount in the interior of the admissible polishing range even though other parts of the polishing pad
102
remain sufficiently thick within the admissible polishing range. Therefore, the polishing pad
102
, which is relatively expensive among the required items for manufacturing semiconductors, needs to be replaced at an early stage. This means that the semiconductor manufacturing cost is significantly increased. Moreover, it normally takes 1 to 1.5 hours to replace a polishing pad, during which time the CMP apparatus cannot manufacture any semiconductor devices, resulting in a low operation rate. As the life span of the polishing pad
102
becomes shorter, the polishing pad
102
must be replaced more frequently, which leads to a low operation rate of the apparatus.
SUMMARY OF THE INVENTION
The present invention aims to solve the above-described problems. Therefore, it is an object of the present invention to provide a polishing apparatus having a dresser equipped with a polishing pad and an inclined polishing particle surface for adjusting polishing. It is also an object of the present invention to provide a polishing apparatus having a dresser equipped with a polishing pad and a polishing particle surface for adjusting polishing such that a pressure for adjusting a polishing can be applied onto the polishing particle surface. This object is achieved by combinations as will be described. Further advantageous and exemplary combinations of the present invention are also described.
REFERENCES:
patent: 5287663 (1994-02-01), Pierce et al.
patent: 5605499 (1997-02-01), Sugiyama et al.
patent: 5626509 (1997-05-01), Hayashi
patent: 6077155 (2000-06-01), Hayakawa et al.
patent: 6159075 (2000-12-01), Zhang
patent: 6169931 (2001-01-01), Runnels
patent: 6220936 (2001-04-01), Quek
patent: 6302772 (2001-10-01), Hosoki et
Grant Alvin J
Hail III Joseph J.
Oki Electric Industry Co. Ltd.
Volentine & Francos, PLLC
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