Abrading – Machine – Sandblast
Reexamination Certificate
1999-08-25
2001-02-06
Gerrity, Stephen F. (Department: 3723)
Abrading
Machine
Sandblast
C451S036000, C451S060000, C451S088000, C451S099000, C451S446000, C451S447000, C210S107000, C210S096100, C210S416100, C210S739000
Reexamination Certificate
active
06183352
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a slurry recycling apparatus and method for a chemical-mechanical polishing technique (hereinafter referred to as a CMP technique).
2. Description of the Related Art
A CMP technique is employed for polishing semiconductor wafers and for obtaining planer surfaces thereof.
To polish an object (particularly, the semiconductor wafer, etc.) with the CMP technique, the object is pressed against a polishing pad, and the object and the polishing pad are rotated and moved relatively. A chemical solution, that is, slurry for polishing is supplied onto the polishing pad so as the object to be polished.
A by-product, and changes in a chemical composition and a pH of the slurry which are produced and caused during the polishing process entail a drawback that the object is not satisfactorily polished. Therefore, slurry which has optimum chemical properties such as concentration, pH, etc. needs to be supplied onto the polishing pad.
For the above-described reasons, new slurry is always supplied onto the polishing pad, resulting in consuming a large amount of slurry. However, slurry is expensive, therefore, various techniques have been proposed for recycling used slurry.
In the technique disclosed in Unexamined Japanese Patent Application No. H2-257627, the slurry is recycled by an apparatus having a structure shown in FIG.
5
.
As shown in
FIG. 5
, slurry used in a polisher
101
is collected into a tank
103
via a tube
102
. After silica contained in the used slurry is removed therefrom by a centrifugal separator
104
connected to the tank
103
, the slurry is supplied back to the tank
103
.
In order to recycle the used slurry, undiluted slurry having a high concentration is supplied into the tank
103
from an undiluted slurry tank
105
, whereas water, etc., is supplied from a solvent tank
106
into the tank
103
. An amount of undiluted slurry and water, etc., to be supplied is controlled based on a concentration of the slurry in the tank
103
. The concentration of the slurry in the tank
103
is measured by a ultrasonic propagation speed measuring device
107
. The slurry recycled within the tank
103
is supplied to the polisher
101
via a tube
109
by a pump
108
.
In the technique disclosed in Unexamined Japanese Utility Model Application KOKAI Publication No. H5-49257, the used slurry is collected into a recycled fluid storage tank. In this case, a flow rate and a concentration of the used slurry are measured. Based on this measured result, an amount of coolant (a surface-active agent, a rustproof agent, a fluid addition agent, etc.) is supplied into the recycled fluid storage tank. Hence, the used slurry is recycled in the recycled fluid storage tank, and the recycled slurry is supplied therefrom to a polisher.
In the technique disclosed in Japanese Patent Application No. H10-58314, the slurry is recycled by an apparatus having the structure shown in FIG.
6
.
A semiconductor wafer is placed with force on a polishing pad
201
and is made to rotate by a carrier
203
which is mounted with a shaft
202
. Slurry
204
is supplied onto the polishing pad
201
from a tube
205
and is applied to polish the semiconductor wafer so as to be caught by a catch ring
206
. The used slurry caught by the catch ring
206
is collected in a manifold
208
via a tube
207
. New slurry is supplied into the manifold
208
via a tube
209
, chemical components for recycling is supplied via a tube
210
and nonionic water is supplied via a tube
211
. The new slurry, chemical components and nonionic water are added to the used slurry in the manifold
208
so as the slurry to be recycled.
The recycled slurry heats up or cools down at a predetermined temperature by a heat switcher
212
. Afterward, the recycled slurry is measured and analyzed by sensors
213
to
215
. An amount of new slurry, chemical components and nonionic water to be supplied is controlled by the measured and analyzed results of the sensors
213
to
215
.
Further, the recycled slurry is filtered by a filter
216
and supplied onto the polishing pad
201
via the tube
205
.
In the technique disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H10-118899, the used slurry is concentrated by means of a ultrafiltration (UF) unit employing a ultrafilter. In such a case, a concentration of the concentrated slurry is measured, and if the concentration thereof is equal to or above a predetermined value, an alkali agent or an acid is added to the concentrated slurry. The used slurry which has been recycled in such a manner is once stored in a polishing agent bath and supplied to a polishing apparatus.
However, the above-described techniques entail problems described below.
According to the technique disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H2-257627, there is provided a single tank (tank
103
) for collecting the used slurry. Thus, while the used slurry is being recycled, more used slurry is continuously supplied into the tank
103
. That is, collection of the used slurry and adjusting (recycling) the concentration of the slurry are parallelly and continuously performed. Accordingly, the used slurry and the centrifuged slurry each having various concentrations exist within the tank
103
. This causes a drawback that adjusting the concentration of the slurry delays and the concentration thereof is hardly stable.
In addition to the above, the slurry is supplied to the polisher
101
from the tank
103
containing the used slurry together with the recycled slurry, that is, adjusting the concentration of the slurry (recycling the slurry) and supplying the slurry are parallelly and continuously performed. Hence, the slurry which has not been satisfactorily recycled may be supplied to the polisher
101
, therefore, the to-be-polished object is polished with a low degree of accuracy.
In the technique disclosed in Unexamined Japanese Utility Model Application KOKAI Publication No. H5-49257, the flow rate and the concentration of the slurry to be supplied into the recycled fluid storage tank are measured, however, the concentration of the slurry recycled in the recycled storage tank is not measured. As a result of this, the concentration of the recycled slurry is not recognized. That is, even if the concentration of the recycled slurry does not satisfy a predetermined value, the slurry concentration value is not detected. Therefore, the concentration of the slurry may become unstable.
In the technique disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H10-58314, each amount of new slurry, chemical components and nonionic water to be supplied into the manifold
208
is adjusted on the basis of the chemical properties and the concentration of the already-recycled slurry. However, the concentration of the slurry to be collected into the manifold
208
from the catch ring
206
is not constant, so that the concentration and the chemical properties of the to-be-recycled slurry are not stable. Accordingly, the to-be-polished object may not be preferably polished.
In the technique disclosed in Unexamined Japanese Patent Application KOKAI Publication No. H10-118899, the used slurry is concentrated by means of the ultrafiltration unit, thus, the alkali agent contained in the slurry is removed. Thus, the alkali agent needs to be added to the concentrated slurry, and it is required to arrange an apparatus for monitoring the addition amount, etc. This entails a problem that the structure of the recycling apparatus becomes comnplicated.
The recycled slurry is once collected in the polishing agent bath, and its concentration is not checked therein. The concentration of the slurry supplied to the polisher changes, without being detected. Therefore, the to-be-polished object may not preferably be polished.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a slurry recycling apparatus for a CMP technique capable of providing, to a polishing apparatus, slurry
Gerrity Stephen F.
McDonald Shantese
McGinn & Gibb, P.C.
NEC Corporation
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