Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – With microwave gas energizing means
Reexamination Certificate
1999-11-30
2002-03-19
Utech, Benjamin L. (Department: 1765)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
With microwave gas energizing means
C438S690000, C438S691000, C438S692000, C438S693000, C438S753000, C438S754000
Reexamination Certificate
active
06358360
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a precision polishing method and a precision polishing apparatus for polishing a semiconductor substrate. More particularly, the present invention relates to a precision polishing method and a precision polishing apparatus for flattening or removing the wiring material film formed on an insulating film of a semiconductor element in the process of manufacturing a semiconductor integrated circuit.
2. Related Background Art
The trend in recent years of producing semiconductor integrated circuits that are increasingly down-sized and multilayered is accompanied by the need for improved flattening technologies. A major advancement is brought forth in the filed of flattening technologies by chemical mechanical polishing (CMP).
FIG. 7
of the accompanying the drawing schematically illustrates a known chemical mechanical polishing (CMP) apparatus. As shown, it comprises a substrate-holding part
202
for removably holding a substrate
201
that may be a wafer with the surface to be polished facing downward and a polishing table
205
placed vis-a-vis the substrate
201
held by the substrate-holding part
202
and carrying a large caliber polishing pad
204
having a diameter greater than that of the substrate
201
as the latter is bonded thereto. The apparatus further comprises a first drive means
211
for driving the substrate-holding part
202
to revolve, a pressuring means
212
for applying pressure to the substrate
201
so as to make the surface, to be polished, of the substrate
201
pressed against polishing pad
204
and a second drive means
213
for driving the polishing table
205
to revolve, a polishing agent supply means
215
being additionally provided in order to supply the polishing pad
204
with a polishing agent
207
.
With a polishing apparatus having a configuration as described above, the substrate
201
and the polishing pad
204
are driven to revolve respectively by the first drive means
211
and the second drive means
213
in the directions as indicated by the arrows in
FIG. 7
so as to make the surface, to be polished, of the substrate
201
held by the substrate-holding part
202
abut the upper surface of the polishing pad
204
on the polishing table
205
and the pressurizing means
212
apply pressure to the substrate
201
to a predetermined pressure level to polish the surface while the polishing agent supply means
215
is operated to drop the polishing agent
207
onto the polishing pad
204
. The polishing agent
207
is normally referred to as slurry that is a suspension prepared by mixing fine particles of silicon oxide, cerium oxide or alumina into an aqueous solution of potassium hydroxide or ammonium. Thus, the surface to be polished is flattened and smoothed by the combination of the chemical effect of the polishing agent and the physical effect of the polishing particles.
As described above, a polishing agent normally referred to as slurry that is a suspension prepared by mixing fine particles of silicon oxide, cerium oxide or alumina into an aqueous solution of potassium hydroxide or ammonium is used for CMP. Such a polishing agent is designed to be mainly used for polishing interlayer insulating films of semiconductor devices and hence can give rise to scratches on the metal surface when it is used for ductile metals such as copper (Cu) and aluminum (Al) and metal alloys containing them as principal ingredients as well as other problems including the problem of particles of the polishing agent buried into the metal surface. In the case of burying a tungsten (W) plug, where the plug has a small diameter between 0.5 and 1 &mgr;m while the surface of the insulating film on the surface to be polished is far greater than the exposed surface of the tungsten plug and both tungsten and the material of the insulating film are fragile, the dishing problem can be alleviated to a certain extent by using a polishing pad showing an appropriate degree of compressibility.
However, in the process of forming wires from a metal film, particularly in a dual damascene process mainly using copper, the ratio of the exposed surface area of the insulating film to the surface area of the wiring metal is closer to 1 than the above instance so that conventional CMP techniques encounter the problem of a remarkable dishing phenomenon appearing on the wiring metal along with the problem of producing a process-altered layer near the surface of the object to be polished because the surface to be polished is subjected to pressure of a level between 200 to 500 gr/cm
2
for the purpose of polishing.
SUMMARY OF THE INVENTION
In view of the unsolved problems of conventional techniques, it is therefore the object of the present invention to provide a precision polishing method and a precision polishing apparatus applicable to dual damascene processes involving the use of metal, highly ductile copper in particular, and adapted to be used with a chemical etching technique of utilizing a chemical effect for polishing a wiring metal film without producing any process-altered layer nor any scratches on the metal surface and without the risk of partly burying the polishing agent near the metal surface in order to flatten a smooth or remove the metal film.
In an aspect of the invention, the above object is achieved by providing a precision polishing method, comprising supplying an etching solution to the surface to be polished comprising the metal of a semiconductor device and flattening and removing said surface to be polished comprising said metal by utilizing a change of etching rate caused by the change of the temperature of the etching solution.
Preferably, with a precision polishing method according to the invention, a local temperature change is produced on the surface to be polished to cause said change of etching rate by locally applying heat to the semiconductor substrate having said surface to be polished or causing it to locally emit heat in order to produce a selective etching effect due to temperature difference, thereby flattening and removing said surface to be polished comprising said metal. Preferably, with a precision polishing method according to the invention, the temperature of the projecting areas of said metal in said surface to be polished is set higher than the temperature of the area other than said projecting areas of said metal in said surface to be polished and an abutting member is made to abut on said surface to be polished, thereby polishing and flattening said surface to be polished comprising the metal.
With a precision polishing method according to the invention, the projecting areas of the surface to be polished can be selectively caused to emit heat and raise the temperature thereof by making an abutting member abut on the surface to be polished with or without an etching solution interposed therebetween and driving the abutting member to move along and relative to the surface to be polished.
In another aspect of the present invention, there is provided a precision polishing apparatus adapted to polishing the surface to be polished comprising the metal of a semiconductor device by making the surface to be polished comprising the metal of a semiconductor device abut on a hard polishing pad under pressure of a predetermined level while supplying an etching solution to the surface to be polished and the abutment surface of said hard polishing pad and driving said surface to be polising to move relative to said polishing pad, thereby polishing said surface to be polished comprising the metal, said apparatus comprising at least either a means for locally raising the temperature of the projecting areas of said metal in said surface to be polished or a means for cooling the area other than said projecting areas of said metal in said surface to be polished so as to make the temperature of the projecting areas of said metal in said surface to be polished higher than the temperature of the area other than said projecting areas in said surface and utilize the change of
Brown Charlotte A.
Canon Kabushiki Kaisha
Fitzpatrick ,Cella, Harper & Scinto
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