Abrading – Abrading process – Utilizing fluent abradant
Utility Patent
1998-12-14
2001-01-02
Eley, Timothy V. (Department: 3723)
Abrading
Abrading process
Utilizing fluent abradant
C451S056000, C451S060000, C451S072000, C451S091000, C451S099000, C451S102000, C451S910000
Utility Patent
active
06168502
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates generally to a method and apparatus for polishing semiconductor devices and in particular to a method and apparatus used in chemical mechanical polish processing for polishing wafers. Still more particularly, the present invention relates to a method and apparatus for conditioning a polishing pad used in chemical mechanical polishing processing.
2. Description of the Related Art
As circuit dimensions shrink, the need for fine-line lithography becomes more critical and the requirements for planarizing topography becomes very severe. Major U.S. semiconductor companies are actively pursuing Chemical-Mechanical Polishing (CMP) as the planarization technique used in the sub-half micron and below generation of chips. CMP is used for planarizing bare silicon wafers, interlevel dielectrics, metals, and other materials. CMP machines, such as the one shown in
FIG. 1
, use orbital, circular, lapping, and linear motions. The wafer
116
is held on a rotating carrier
118
while the face of the wafer
116
being polished is pressed against a resilient polishing pad
114
attached to a rotating platen disk
112
. A slurry is used to chemically attack and lubricate the wafer surface to make the surface more easily removed by mechanical abrasion. Pad conditioning is done by mechanical abrasion of the pads
114
in order to ‘renew’ the surface. During the polishing process, particles removed from the surface of the wafer
116
become embedded in the pores of the polishing pad
114
and must be removed. Current techniques use a conditioning head
122
, also called a “grid”, with abrasive diamond studs to mechanically abrade the pad
114
and remove particles to condition the polishing pad. Conditioning arm
124
positions conditioning head
122
over polishing pad
114
.
The term “condition” defines the state of the polishing pad surface. The ideal surface of the polishing pad is free of embedded slurry particles and residual polished material. To provide a polishing surface, the condition is two fold. First, the mechanical action of the grid will clean the polishing pad of removed polished materials and old slurry particles embedded into the pad. Second, the abrasive surface of the grid will roughen the polishing pad and expose new pad surface for acceptance of slurry. These actions are used to provide a conditioned polishing pad. The repeated abrasive action of the conditioning will eventually erode enough material from the polishing pad to require replacement of the pad. The pad erosion from the conditioning can have an impact on the uniformity of the wafer. Also, if the slurry has a low pH, the acidic properties will erode metal grids and diamonds dislodged from the grid can cause severe scratching on the polished surface.
Therefore, it would be advantageous to have an improved method and apparatus to reduce the erosion of the polishing pad, enhance control of wafer nonuniformity, and allow the use of low pH solutions.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus for conditioning a polishing pad in which slurry is directed under pressure at the polishing pad. Additionally, energy (i.e., ultrasonic energy) may be added to the slurry as it is directed towards the polishing pad, wherein embedded material in the polishing pad is removed or dislodged.
The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description.
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Allman Derryl D. J.
Gregory John W.
Eley Timothy V.
LSI Logic Corporation
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