Abrading – Abrading process – Utilizing fluent abradant
Reexamination Certificate
2000-01-18
2001-08-28
Eley, Timothy V. (Department: 3723)
Abrading
Abrading process
Utilizing fluent abradant
C451S059000, C451S113000
Reexamination Certificate
active
06280295
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an apparatus and method to polish a wafer using abrasive flow machining (AFM), and in particular to a polishing apparatus and method with high efficiency and stability.
DESCRIPTION OF THE RELATED ART
Planarization is a very important technology in wafer processing. Currently, chemical mechanical polishing (CMP) is a common manner to planarize the wafer. However, CMP technology has a lot of disadvantages, as enumerated below:
(1) a lot of water is needed,
(2) a lot of chemical treatment using slurry is required,
(3) short life time of every consumable part of the polishing apparatus,
(4) short PM time,
(5) dishing and other errors,
(6) a lot of vibration and noise is produced,
(7) the processed wafer is easily scratched;
(8) the quality of the polishing pad is unstable;
(9) precise control is required,
(10) the pre-polish topography will affect the result of the polish,
(11) the polishing apparatus is easily corroded,
(12) the supply tube and the discharge pipe of the slurry is easily clogged, and
(13) chemical evaporation results in pollution.
SUMMARY OF THE INVENTION
In view of the above problem, an object of the invention is to provide an apparatus and method to polish a wafer using abrasive flow machining. Under a high-pressure condition, the wafer is polished by abrasive media with high viscosity in order to planarize the wafer. Therefore, the polishing efficiency is higher, and the attained roughness is lower than by the conventional method. In addition, the selectivity of this method is lower.
To attain the above object, the polishing apparatus comprises a table, a carrier, an abrasive media supply device, a pressing device and an abrasive media-removing device. The table is used for supporting the wafer disposed thereon. The carrier is disposed on the table in an detachable manner. The abrasive media supply device, communicating with the carrier, is used for supplying abrasive media to a space defined by the carrier and the table. The pressing device, communicating with the carrier, is used for applying pressure to the abrasive media inside the space. The abrasive media-removing device, communicating with the carrier, is used for supplying high-pressure air to the space to remove the abrasive media.
Furthermore, the abrasive media supply device consists of a first tube, a first valve and a pump. The first tube is communicated with the carrier at one end. The first valve is attached to the first tube. The pump is communicated with the other end of the first tube.
Furthermore, the pressing device consists of a rod and a first cylinder. The rod is located inside the carrier partly and in contact with the abrasive media at one end. The first cylinder is connected with the other end of the rod.
Furthermore, the abrasive media-removing device consists of a channel, a check valve, a second tube, a second valve and an air source. The channel is located inside the rod. The check valve is attached to one end, in contact with the abrasive media inside the carrier, of the channel. The second tube is communicated with the other end of the channel. The second valve is attached to the second tube. The air source is communicated with the other end of the second tube.
Furthermore, the apparatus further comprises a robot, a lift pin, a second cylinder, a release hole and a cooling path. The robot is used for transferring the wafer. The lift pin is moveably disposed inside the table. The second cylinder, connected with the carrier, is used for moving the carrier. The release hole is disposed on the carrier. The cooling path is disposed inside the table.
The method of the invention comprises the steps of: (a) providing the polishing apparatus; (b) transferring the wafer on the lift pin by means of the robot; (c) positioning the wafer on the table by lowering the lift pin; (d) positioning the carrier on the table by means of the second cylinder to form the space between the carrier and the table; (e) supplying the abrasive media to the space through the first tube and the first valve by means of the pump; (f) shutting off the first valve when the abrasive media inside the space reaches a predetermined amount; (g) applying pressure to the abrasive media inside the space by moving the first cylinder to polish the wafer and discharge the abrasive media through the release hole; (h) supplying the high-pressure air from the air source through the second tube, the second valve, the channel and the check valve to the space to remove the abrasive media through the release hole; (i) after separating the carrier from the table by means of the second cylinder, separating the wafer from the table by raising the lift pin; and (j) removing the wafer from the table by means of the robot.
Furthermore, the size of the abrasive media is from 800 to 0.5 &mgr;m. The temperature during the polishing is from 25 to 80° C. The abrasive media is aluminum oxide, silica, silicon carbide or diamond. The pressure applied to the abrasive media is from 100 to 3000 psi. The discharge rate through the release hole is from 7 to 250 L/min.
REFERENCES:
patent: 5040336 (1991-08-01), Ahern
patent: 5125191 (1992-06-01), Rhoades
patent: 5582540 (1996-12-01), Su et al.
patent: 5746646 (1998-05-01), Shibano
Darby & Darby
Eley Timothy V.
Nguyen Dung Van
ProMOS Technologies Inc.
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