Abrading – Precision device or process - or with condition responsive... – Controlling temperature
Reexamination Certificate
2000-01-25
2001-05-08
Banks, Derris H. (Department: 3723)
Abrading
Precision device or process - or with condition responsive...
Controlling temperature
C451S053000
Reexamination Certificate
active
06227939
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to chemical mechanical polishing (CMP) of semiconductor dies.
BACKGROUND OF THE INVENTION
FIG. 1
is a cross-sectional view of a representative MOSFET transistor
10
before CMP. The transistor includes a gate region (G) and dopant wells
13
that form a source region (S) and a drain region (D). Electrical connection to the S,G and D regions is typically achieved through vias
16
-
18
which are made of a conductive material
19
, typically tungsten (W) or the like. While the present invention is particularly well suited for treatment of tungsten or like material, it should be realized that the teachings of the present invention are applicable to other conductive materials including but not limited to copper, nickel, silver, gold and other metallic and non-metallic conductive materials.
FIG. 1
represents an in progress stage of transistor fabrication. After deposition of conductive material to fill the via openings, conductive material above the vias is removed to provide appropriate signal isolation. The conductive material is typically removed with a combination of a chemical etchant and mechanical abrasion or polishing.
FIG. 2
illustrates a typical CMP arrangement
21
that includes one or more wafer carriers
20
(three are shown) and a platen
22
provided thereunder for abrasive polishing. A slurry that contains a chemical etchant and abrasive grains is preferably provided on the top surface
23
of the platen. Each carrier
20
holds a wafer
5
and the wafers are brought into contact with the rotating platen (which rotates in the direction of arrow A). The carriers also preferably rotate. The rotating platen machines away the conductive material that has been weakened by the etchant.
While this technique removes conductive material, the amount of conductive material removed from each wafer or from different regions of the same wafer may differ by a significant amount. Stated in other words, prior art polishing processes tend to produce inconsistently or unevenly polished wafers. In prior art assessments, these inconsistencies were often attributed to misalignment of the carriers and the platen and the resultant misdistribution of polishing forces. The below discussed present invention, however, teaches that inconsistently polished wafers are a result of more than polishing force mis-distribution.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a method for producing more consistently polished wafers.
It is another object of the present invention to provide a wafer carrier that delivers uniform heat to a wafer during CMP to thereby achieve more uniform polishing.
It is another object of the present invention to provide a wafer undergoing CMP with insulation against undesired heat sinks or sources.
It is also an object of the present invention to provide wafers that are so polished.
These and related objects of the present invention are achieved by use of a temperature controlled chemical mechanical polishing method and apparatus as described herein.
In one embodiment, the present invention includes a wafer carrier that regulates wafer temperature and thus delivers more uniform heat to a wafer. More uniform heat leads to more uniform CMP and hence greater polish consistency within a wafer and from wafer to wafer.
In another embodiment, the present invention includes either as an alteration to or in addition to temperature regulation of the carrier and wafer, the provision of sufficient insulation between a wafer and the carrier to substantially insulate the wafer from heat sinks or sources provided by the carrier.
The present invention also includes methods of treating a wafer with more uniform heat during CMP and wafers produced by these processes.
The attainment of the foregoing and related advantages and features of the invention should be more readily apparent to those skilled in the art, after review of the following more detailed description of the invention taken together with the drawings.
REFERENCES:
patent: 5036630 (1991-08-01), Kaanta et al.
patent: 5605488 (1997-02-01), Ohashi et al.
patent: 5873769 (1999-02-01), Chiou et al.
patent: 5882244 (1999-03-01), Hiyama et al.
patent: 6000997 (1999-12-01), Kao et al.
patent: 6007408 (1999-12-01), Sandhu
patent: 6077151 (2000-06-01), Black et al.
Agilent Technologie,s Inc.
Banks Derris H.
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