Abrading – Machine – Sandblast
Reexamination Certificate
1999-11-26
2001-08-28
Banks, Derris H. (Department: 3723)
Abrading
Machine
Sandblast
C451S088000
Reexamination Certificate
active
06280300
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a filter apparatus provided in a pipeline for conveying a fluid to remove solid impurities from the fluid. More particularly, the present invention relates to a filter apparatus suitable for use in a supply line for an abrasive liquid used in a chemical/mechanical polisher (CMP) for semiconductor substrates. The present invention also relates to a method of regenerating a filter unit.
With the rapid progress of the technology to fabricate high-integration semiconductor devices in recent years, circuit wiring patterns or interconnections have been becoming increasingly small and fine, and spaces between wiring patterns have also been decreasing. As the wiring spacing decreases, the depth of focus becomes shallower in circuit pattern formation by photolithography or the like. Accordingly, surfaces of semiconductor wafers on which circuit pattern images are to be formed by a stepper require a higher degree of surface flatness.
FIG. 15
shows a conventional polishing apparatus for making the surface of a semiconductor wafer flat. The apparatus has a polishing table
4
with a polishing cloth
2
, for example, bonded to the surface thereof to form a polishing surface. The apparatus further has a substrate holder
6
for holding a substrate W to be polished, e.g. a semiconductor wafer. With an abrasive liquid Q being supplied between the polishing surface and a surface of the substrate W that is to be polished from an abrasive liquid supply pipe
8
, the substrate W is pressed against the polishing surface with a predetermined pressure by the top ring
6
, and while doing so, the polishing surface and the substrate W are caused to slide relative to each other to perform polishing. Such a polishing apparatus performs mechanical polishing using an abrasive liquid as a polishing fluid, and in some cases, it also performs polishing accompanied by a chemical action using an alkaline or acidic polishing solution.
In an abrasive liquid supply system of such a polishing apparatus, abrasive grains may agglomerate to form particles in the pipeline. If supplied to the surface to be polished, such particles cause flaws, known as scratches, on the surface to be polished. Accordingly, it is conceivable to equip the pipeline with a filter apparatus for trapping particles larger than a predetermined size in the supplied fluid. In such a filter apparatus, as shown in
FIG. 16
, filter units fa and fb are connected to branched pipelines, which are branched off from the abrasive liquid supply pipeline, through respective joints (not shown), so that when a predetermined processing time has elapsed, the used filter unit fa or fb can be replaced without stopping the abrasive liquid supply line.
However, in a case where filter units are connected to the pipeline through joints as stated above, it is necessary to conduct an operation of detaching and reattaching bolts and nuts when the filter units are replaced. The efficiency of the operation is unfavorably low because the abrasive liquid scatters. Moreover, abrasive grains in the abrasive liquid remaining in the branched pipeline that is not used may agglomerate to form particles.
SUMMARY OF THE INVENTION
In view of the above-described circumstances, an object of the present invention is to provide a filter apparatus that enables a filter replacing operation to be carried out smoothly and reliably and that is also capable of reliably trapping solid particles contained in a fluid, e.g. an abrasive liquid, in a pipeline continuously without the need of a filter replacing operation, thereby allowing supply of a fluid of high quality and a stable operation free from clogging.
Another object of the present invention is to provide a regenerating method capable of efficiently removing abrasive grains deposited in a filter unit by passing a liquid through the filter unit and allowing a completely automated operation by repeating a filtering operation and a regenerating operation continuously without carrying out a filter replacing operation.
The present invention provides a filter apparatus provided in a fluid pipeline for conveying a treatment fluid. The filter apparatus includes a regenerating pipeline provided adjacently to the fluid pipeline to convey a regenerating liquid, and at least two filter units. The filter apparatus further includes a switching valve device for switching the filter units between the fluid pipeline and the regenerating pipeline.
Thus, the filter unit having trapped abrasive grains is moved to the position of the regenerating pipeline and subjected to a regenerating treatment at this position. Accordingly, a continuous filtering treatment can be performed without detaching the filter unit for replacement. Regarding the regenerating treatment, the number of filter units to be switched should be set by taking into consideration the period of time required for regeneration. The used filter unit may be replaced with a filter unit in a purified state, which has been cleaned in the regenerating pipeline.
The switching valve device may be one in which the filter units are mounted on a valving element so as to move together with the valving element as one unit. Such a structure allows the flow path arrangement of the switching valve device to be simplified to a considerable extent.
In the above-described filter apparatus, the treatment fluid may be an abrasive liquid, and the regenerating liquid may be a chemical liquid containing a component that redissolves deposited abrasive grains. In this case, the filter apparatus further includes an adjusting mechanism for adjusting at least one of the temperature and concentration of the regenerating liquid to a predetermined level. With this arrangement, the solidified abrasive grains are redissolved so as to be readily washed away. Accordingly, it is possible to speed the regeneration of the used filter unit. The predetermined temperature is preferably not lower than 40° C., more preferably not lower than 50° C. The device for controlling the temperature of the regenerating liquid may be provided in a regenerating liquid source. Alternatively, the device may be provided in the filter apparatus itself or in a pipeline between the regenerating liquid source and the filter apparatus.
The abrasive grains may be silica grains, and the regenerating liquid may be a liquid containing KOH. It was found that a liquid containing KOH has a superior ability to redissolve colloidal silica. It should be noted that the pH of the regenerating liquid is preferably not lower than 11.0.
In addition, the present invention provides a polishing apparatus including a polishing table and a holding device for pressing the surface of a substrate to be polished against the surface of the polishing table. The polishing apparatus further includes a driving device for causing the surface of the polishing table and the surface of the substrate to be polished to slide relative to each other, and an abrasive liquid supply system for supplying an abrasive liquid between the surface of the polishing table and the surface of the substrate to be polished. The above-described filter apparatus is provided in an abrasive liquid supply pipeline of the abrasive liquid supply system.
In addition, the present invention provides a method of regenerating a used filter unit which has been provided in a fluid pipeline for conveying a polishing solution containing abrasive grains and in which abrasive grains have been deposited. According to the regenerating method, a regenerating liquid containing a component that redissolves the abrasive grains deposited in the filter unit is adjusted to a predetermined temperature and/or a predetermined concentration, and the filter unit is soaked with the regenerating liquid. Thus, the solidified abrasive grains are redissolved so as to be readily washed away, and it is possible to speed the regeneration of the filter unit.
The above and other objects, features and advantages of the present invention will become more apparent from the following descr
Kawashima Kiyotaka
Komatsu Mitsunori
Tanikawa Mutsumi
Banks Derris H.
Ebara Corporation
Wenderoth , Lind & Ponack, L.L.P.
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