Abrading – Abrading process – With tool treating or forming
Reexamination Certificate
2000-11-17
2003-10-21
Hail, III, Joseph J. (Department: 3723)
Abrading
Abrading process
With tool treating or forming
C451S443000, C451S444000, C451S287000
Reexamination Certificate
active
06634934
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to method of cleaning a polishing tool used for flattening a variety of films, such as inter-layer insulation films, metal films, and polysilicon films, formed on, for example, a semiconductor wafer by chemical mechanical polishing and a polishing method and polishing apparatus using such a polishing tool.
2. Description of the Related Art
Along with the higher integration and use of multi-layer interconnections of semiconductor devices, the flattening of a variety of films, such as inter-layer insulation film, metal film, and polysilicon film, has become important in the process of production of a semiconductor device. As a technique for the flattening, a variety of means have been proposed, but in recent years, the chemical mechanical polishing (CMP) process is attracting attention, and a polishing apparatus for flattening by utilizing this has been developed.
An example of a polishing apparatus using the conventional CMP process is shown in
FIG. 1. A
polishing apparatus
301
shown in
FIG. 1
has a main shaft spindle
303
for rotating a polishing tool
302
and a rotating table
304
for holding a wafer W. The table
304
is rotatably mounted on a slider
306
provided moveably in an X-axial direction along a rail
305
and rotated by a rotation driving means constituted by, for example, a motor, a pulley, and a belt. The main shaft spindle
303
is held moveably in a Z-axial direction and positioned at a target position in the Z-axial direction by a not illustrated drive mechanism.
In the polishing apparatus
301
having the above constitution, first, the wafer W is rotated at a predetermined speed, and a slurry is continuously fed as an abrasive from a slurry feeder (not illustrated) onto the wafer W. The slurry is obtained by mixing a very fine polishing abrasive, for example, silicon oxide, with a liquid such as an aqueous solution of potassium hydroxide. Next, the polishing tool
302
is rotated at a predetermined speed to position the wafer W and the polishing tool
302
in the X-axial and Z-axial directions so that the polishing tool
302
is located at a position where it contacts an outer circumferential portion of the wafer W. In this state, a surface of the wafer W and a polishing surface of the polishing tool
302
are in substantially a parallel state.
The polishing tool
302
is positioned in the Z-axial direction so as to obtain a predetermined depth of cut with respect to the wafer W. By this, a predetermined polishing pressure is generated between the polishing tool
302
and the wafer W. By movement of the wafer W in the X-axial direction with a predetermined speed pattern and by movement of the contact position between the polishing surface of the polishing tool
302
and the wafer W in this state, the entire surface of the wafer W is polished and the wafer W is flattened.
In the polishing apparatus
301
, at the time of discharge of the slurry onto the wafer W and the polishing of the wafer W, the slurry sometimes deposits on the polishing tool
302
and the periphery of its attachment portion and then adheres and solidifies. When the solidified slurry or the like drops from the polishing tool
302
during the polishing and enters into the space between a polished surface of the wafer W and the polishing surface of the polishing tool
302
, it acts as a giant abrasive. When polishing pressure is added to the polished surface of the wafer W through the polishing tool
302
and a polishing operation is carried out in this state, it will scratch the polished surface of the wafer W or cause particles to deposit on it. If more than a prescribed number of scratches or residual particles are generated on the polished surface of the wafer W after the polishing, the wafer W ends up becoming a defect.
Further, the polishing tool
302
of the polishing apparatus having the above constitution is formed by an independent foam member, for example, polyurethane foam. The polishing surface of the polishing tool
302
made of such a material is susceptible to a so-called clogged state where the reaction product generated at the time of polishing and the flaked off substance forming the polishing tool
302
enter into the foam member. When in the clogged state, stable polishing cannot be carried out, so it is necessary to dress the tool to remove the surface layer of the polishing surface of the polishing tool
302
in the clogged state to condition the polishing surface of the polishing tool
302
. The tool is dressed by shaving the polishing surface of the polishing tool
302
by a dresser with, for example, a diamond abrasive fixed thereto. When dressing the tool, part of the substance constituting the polishing tool
302
flaked from the polishing tool
302
and part of the substance constituting the dresser flaked from the dresser sometimes deposit on the polishing tool
302
. The deposited substances sometimes become a cause of scratching the wafer surface.
In order to prevent the scratching of the wafer surface mentioned above, conventionally, for example, pure water was discharged onto the polished surface of the wafer W before the polishing, the polishing tool
302
was moved downward in the Z-axial direction while rotating the same and brought into contact with the pure water layer resident on the wafer W, and the slurry and impurities deposited on the polishing tool
302
were thereby removed to a certain extent.
Further, for example, as shown in
FIG. 2
, a cleaning use spray nozzle
307
having discharge ports at several positions is disposed in the vicinity of the position just under the polishing tool
302
on the slider
306
moveable in the X-axial direction. The spray nozzle
307
is moved downward up to that vicinity of the polishing tool
302
while rotating immediately before the polishing operation or while standing by for the operation. By cleaning the surface of the polishing tool
302
by discharging pure water from the spray nozzle
307
at a point of time when the polishing tool
302
reaches a predetermined height, the slurry and the impurities deposited on the polishing tool
302
have been removed to a certain extent.
However, there are also cases where they deposit on the outer circumferential surface of the polishing tool
302
or the periphery of the attachment portion of the polishing tool
302
and adhere and solidify. It was difficult to sufficiently remove these solidified impurities by the methods mentioned above or the solidified slurry and impurities deposited on the polishing tool
302
were insufficiently removed in some cases.
Further, there is also a method of disposing a cleaning use brush directly contacting the polishing tool
302
to clean the polishing tool
302
, but there is the disadvantage that the solidified slurry and impurities remained inside or outside the cleaning use brush. These solidified slurry and impurities sometimes again are deposited on the polishing tool
302
at the time of the next cleaning and on. Further, if the cleaning use brush is brought into direct contact with the surface of the polishing tool
302
, it changes the shape of the polishing surface of the polishing tool
302
or the cleaning use brush gradually deteriorates. Further, it is advantageous for improving the polishing efficiency if an adequate amount of slurry is provided at the surface of the polishing tool
302
, but there is also the disadvantage that if the cleaning use brush is brought into direct contact with the surface of the polishing tool
302
to clean the same, even the useful slurry provided at the polishing tool
302
was scraped off.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a method for cleaning a polishing tool capable of reliably removing deposited solidified abrasive and impurities.
Another object of the present invention is to provide a polishing method capable of suppressing scratching of a polished object and capable of reducing residual particles on the polished surface of the polished object.
Hail III Joseph J.
Thomas David B.
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