Abrading – Rigid tool – Rotary disk
Reexamination Certificate
2000-08-31
2002-07-16
Eley, Timothy V. (Department: 3723)
Abrading
Rigid tool
Rotary disk
C451S443000
Reexamination Certificate
active
06419574
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an abrasive tool with metal binder phase, containing electrodeposited abrasive tool or metal bonded abrasive tool, used for the conditioner for carrying out conditioning of the polishing pad. Which is used for the polishing of the surface of workpiece, for example, a semiconductor wafer with CMP equipment etc.
This specification based on the following Japanese Patent applications (Patent Application number No. 11-247676 (JP), No. 11-247677 (JP), No. 11-269298 (JP), No. 11-338734 (JP), No. 2000-29614 (JP), and the written contents of these concerned Japanese applications are taken in as a part of this specification.
2. Background Art
Conventionally, there is CMP equipment (Chemical-Mechanical Polishing machine) which chemically and mechanically polishes the surface of the semiconductor wafer (henceforth a wafer) cut down from the silicone ingot, and shown in
FIG. 32
as an example.
It is required that a mirror polish is carried out so that a wafer may serve as high precision and the zero defect surface in connection with microfabrication of devices. The mechanism of polish by CMP is based on the mechano-chemical polishing method, compounded with the mechanical element by particle silica etc. (free abrasive grain) and the etching element by alkali liquid, acid liquid, etc.
The polishing pad
4
, which was attached in the main axis
2
as shown in
FIG. 33
, and consists, for example, of hard urethane is formed on the disk shaped rotation table
3
at this CMP equipment
1
. And wafer carrier
5
, which can rotate on its axis, is laid out and attached, oppositely to this pad
4
, and also in a position eccentric from the main axis
2
of a pad
4
. This wafer carrier
5
is made into smaller disk form rather than the pad
4
, and holds a wafer
6
. And this wafer
6
is arranged between the wafer carrier
5
and the pad
4
, and a mirror polish is offered and carried out to polishing the surface by the side of a pad
4
.
Many fine foamed layers are prepared on the pad
4
, which polishes the wafer
6
and made of hard urethane etc., for the hold of slurry s. Thereby, polish of the wafer
6
is performed by slurry s held in these foamed layers. Then, the problem arises that the polish accuracy and polish efficiency of wafer
6
falls, because the flatness of the polishing surface of the pad
4
falls or clogging occurs by repeating polish of wafer
6
.
Therefore, conventionally, as shown in
FIG. 32
, the pad conditioner
8
is formed in the CMP equipment
1
and used for re-polish or re-grinding (conditioning) of the surface of a pad
4
.
An electrodeposited abrasive wheel
11
is attached to this pad conditioner
8
, attached through an arm
10
to the rotation axis
9
, which is formed in the exterior of the rotation table
3
. By making the arm
10
move around the rotation axis
9
, both-way rocking of the electrodeposited abrasive wheel
11
is carried out on the rotating pad
4
. Thus, the surface of pad
4
is ground, the flatness of the surface of pad
4
is recovered or maintained, and clogging is canceled. Or it can be ground by the wafer career
5
equipped with an electrodeposited abrasive wheel
11
.
As shown in FIGS.
33
(A) and (B), as for this electrodeposited abrasive wheel
11
, at the upper surface of this wheel, a plane and ring-like abrasive grain layer
13
is formed by fixed width on the disk-formed base metal
12
. As shown for example, in
FIG. 34
, this abrasive grain layer
13
is constituted of ultra abrasive grains
14
on the base metal
12
, such as a diamond and cBN, distributed and fixed by the electrodeposited metal phase
15
by electroplating etc. This electrodeposited metal phase
15
consists of nickel etc.
In addition, the concave groove
17
is formed in the surface of the abrasive grain layer
13
in the direction of diameter at intervals of predetermined, such as 45 degrees, then slurry s and ground wastes will be discharged outside through this concave groove
17
.
By the way, when pad
4
is ground using such an electrodeposited abrasive wheel
11
, the electrodeposited abrasive wheel
11
should be carried out both-way rocking on pad
4
, covering the distance equivalent to the radius of pad
4
at least. Nap raising of pad
4
is beaten and cut, while the ultra abrasive grains
14
, distributed on the abrasive grain layer
13
, carries out grinding. The ultra abrasive grains
14
are protruded from the surface of the abrasive grain layer
13
, which performs as grinding surface, only about ⅓ of the mean particle diameter of the ultra abrasive grains
14
in this case. Then, the whole surface of the abrasive-grain layers
13
contact directly to workpiece. For this reason, the abutment pressure disperses and becomes slippery, and nap raising could not be cut and pushed down. Then the fault arises that sharpness becomes worse and clogging becomes easy to occur.
Moreover, the other electrodeposited abrasive wheel is disclosed in the Japanese Patent Laid-Open No., 9-19868 for example.
This electrodeposited abrasive wheel gathers 2-10 ultra abrasive grains, and laid out these grains in the shape of islands. These islands-like ultra abrasive grains are distributed on the surface of the abrasive grain layer, which corresponds to a grinding surface, in order to prevent clogging at the time of grinding, and also to continue grinding for a long period of time. In such an electrodeposited abrasive wheel, masking on a base metal is provided, then island-like priming plating is formed at first. Then, temporary fixation against 2-10 ultra abrasive grains for one-layer is carried out by electroplating at this priming plating part. After that, electroplating of the whole base metal is carried out, and ultra abrasive grains are electrodeposited to an abrasive grain layer.
However, in such an electrodeposited abrasive wheel, ultra abrasive grains are electrodeposited and fixed on a flat base-metal surface. Therefore, the difference of the height between the electrodeposited-metal-phase surface of the abrasive grain layer, and the ultra abrasive grains protruded from this surface, is only less than about ½ of the mean particle diameter of ultra abrasive grains substantially.
Therefore, when this electrodeposited abrasive wheel is used as a pad conditioner. And if grinding work piece has a composition with much elasticity or flexibility as like the pad
4
of CMP equipment
1
, which consists of elastic nap raising 1.7 mm in thickness with foamed layer and an under laid cushion layer with a thickness of about 3.5 mm. The whole abrasive-grain-layer surface will make direct contact with grinding workpiece in this case, since the height difference is less than about ½ of the mean particle diameter of ultra abrasive grains. Then, the abutment pressure disperses from ultra abrasive grains and becomes slippery, and nap raising could not be cut and fallen down. Therefore, sharpness becomes worse, and the opening of a foamed layer is crushed, then discharge of ground wastes becomes insufficient. Consequently, there arises a fault that a pad
4
becomes easy to cause clogging.
Moreover, because the height difference (gap) between the ultra abrasive grains at the abrasive grain layer and the surface of the electrodeposited metal phase is small, the grinding liquid (for example, pure water) of pad
4
is flipped out.
Therefore, pad
4
becomes easy to dry and appears a fault that wet grinding becomes spoiled.
SUMMARY OF THE INVENTION
In the view of such circumstances mentioned above, the object of the present invention is to provide an abrasive tool with metal binder phase, such as an electrodeposited abrasive tool, having sufficient sharpness and good discharge performance to ground wastes.
Moreover, the other object of the present invention is to provide an abrasive tool, above-mentioned, which provides clean cut end of the opening of the foamed layer of polishing pad, does not occur clogging, and enables to hold slurry in foamed layer.
The other addition
Hata Hanako
Shimomae Naoki
Takahashi Tsutomu
Yamashita Tetsuji
Eley Timothy V.
Mitsubishi Materials Corporation
Nguyen Dung Van
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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