Abrading – Machine – Rotary tool
Reexamination Certificate
2000-06-02
2001-07-31
Rose, Robert A. (Department: 3723)
Abrading
Machine
Rotary tool
C451S533000, C451S530000
Reexamination Certificate
active
06267654
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a chemical mechanical polishing machine. More particularly, the present invention relates to a pad backer for the polishing head of a chemical mechanical polishing machine.
2. Description of the Related Art
In semiconductor wafer fabrication, chemical mechanical polishing, is applied to planarize various material layers, including the dielectric layers and the metallization layers. The planarity of the wafers is critical for many reasons. For example, during wafer fabrication, a planar layer reduces the likelihood of the accidental coupling of active conductive devices between different metallization layers. Planar layers further provide a surface absent in height differences to facilitate the subsequent photolithography process.
Chemical mechanical polishing typically involves mounting a wafer on a holder, facing down, and rotating the wafer against a polishing pad mounted on a platen. The platen is usually rotating in an orbital state. Slurry containing a chemical that chemically interacts with the wafer surface layer and an abrasive that physically removes a portion of the surface layer is supplied between the wafer and the polishing pad.
The polishing pad is normally applied to the wafer under a polishing pressure to maintain a uniform level across the wafer. In order to maintain a uniform polishing pressure, the polishing pad is attached to a flexible platen or pad backer. An air bladder, which can be inflated, is disposed between a plumbing device and the pad backer and is arranged to essentially press against the bottom surface of the pad backer.
As shown in
FIG. 1
, the conventional pad backer
100
comprises scribe lines
102
in the x and the y directions on the pad backer
100
surface. The x-direction scribe lines and the y-direction scribe lines intersect to form a grid of square
104
. During a CMP process, a polishing air pressure is applied to the pad backer
100
. The pad backer
100
, in turns, presses against the polishing pad. After the CMP process, however, by-product patterns are shown to appear on the polishing pad.
FIG. 2
is a top view of the conventional pad backer having the by-product pattern on the polishing pad superimposed onto the pad backer. As shown in
FIG. 2
, the by-product patterns
202
occur in the center of each square
204
on the pad backer
200
. The by-product pattern
202
, however, is missing on the polishing pad in the vicinity at the cross-sections
206
of the scribe lines. The formation of the alternating by-product pattern
202
suggests a low usage probability of the polishing pad, which leads to an undesirable polishing result
SUMMARY OF THE INVENTION
Based on the foregoing, a pad backer for a polishing head of a chemical mechanical polishing machine is provided. The pad backer comprises a series of scribe lines in the x and the y directions on the pad backer surface. Additional scribe lines are formed at angles of about 45 degree and 135 degrees from the x-direction scribe lines.
The additional scribe lines increase the usage probability of the polishing pad. The formation of the by-product patterns on the polishing pad and undesirable polishing result are thereby obviated.
It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the invention as claimed.
REFERENCES:
patent: 5212910 (1993-05-01), Breivogel et al.
patent: 5664989 (1997-09-01), Nakata et al.
patent: 5876271 (1999-03-01), Oliver
patent: 5897424 (1999-04-01), Evans et al.
patent: 5899799 (1999-05-01), Tjaden et al.
patent: 0036066 (1990-02-01), None
Lai Chien-Hsin
Lin Huang-Yi
Shih Hui-Shen
Tseng Jung-Nan
Huang Jiawei
J. C. Patents
Rose Robert A.
United Microelectronics Corp.
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