Abrading – Precision device or process - or with condition responsive... – Computer controlled
Reexamination Certificate
1999-07-21
2001-06-05
Rachuba, M. (Department: 3724)
Abrading
Precision device or process - or with condition responsive...
Computer controlled
C451S008000, C451S024000, C451S041000, C451S288000
Reexamination Certificate
active
06241578
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to polishing apparatus for polishing a semiconductor wafer or other articles, and in particular, to a carrier device adapted for use in such polishing apparatus and designed to controllably carry an object with the object held in engagement with the polishing surface of a turntable during a polishing process.
FIG. 5
shows a typical semiconductor wafer polishing apparatus wherein a polishing process, commonly known as “chemical-mechanical planarization” (CMP), is carried out to finely polish a semiconductor wafer. The polishing apparatus generally includes a turntable
200
, a wafer carrier device
210
and a polishing surface dressing device
220
.
The turntable
200
is provided on its upper surface with a polishing pad made of polyurethane foam, artificial leather or the like or a fixed abrasive plate and is connected to a drive shaft
201
. The drive shaft is in turn connected to a motor (not shown) so that the turntable
200
is turned around its center axis. The wafer carrier device
210
includes a wafer carrier
211
in the shape of a disc and a motor
212
for ratating the wafer carrier
211
around its center axis through a transmission with a drive shaft
215
connected to the wafer carrier. The wafer carrier
211
is fluidly connected to a vacuum source (not shown) through a pipe
217
. The pipe is connected to the drive shaft to positively hold a semiconductor wafer against the bottom surface of the wafer carrier
211
by vacuum. The polishing surface dressing device
220
includes a dressing tool
221
and a motor
222
for rotating the dressing tool
221
around its center axis. The wafer carrier device
210
and the dressing device
220
are mounted on pivot shafts
231
and
241
, respectively, so that the wafer carrier
211
and the dressing tool
221
are brought into and out of engagement with the polishing pad of the turntable
200
. Further, the wafer carrier
211
and the dressing tool
221
are both moved in a vertical direction by actuators or air cylinders
252
and
272
.
During operation, the wafer carrier holds a semiconductor wafer on its bottom surface and brings it into engagement with the polishing pad on the rotating turntable
200
while being rotated around its center axis. After a desired numberof wafers are successively subjected to the polishing operation, the wafer carrier
211
is pivoted and brought out of engagement with the turntable and the dressing device
220
is pivoted to bring the dressing tool
221
into contact with the polishing pad on the turntable for conducting a dressing operation with respect to the polishing pad.
In such a polishing apparatus, there is a possibility that a crack may be created in a wafer which is being polished. If the polishing operation is continued in such a condition, the crack may become bigger so that the wafer carrier and/or the turntable may be eventually damaged. Further, a pressure controller may malfunction, whereby an inappropriate pressure such as an excessive pressure or insufficient pressure may be imposed on a wafer.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a carrier device with a control device for positively detecting such an anomalous situation in a polishing operation to make it posible to take a necessary action to cope with the anomalous situation.
In accordance with this invention, there is provided a carrier device adapted for use in a polishing apparatus with a turntable having a polishign surface. The carrier device comprises a carrier for carrying an article to be polished and a control device operatively associated with the carrier. The control device includes an actuator operable to cause the carrier to urge the article against the polishing surface of the turntable to polish the article, a sensor operatively associated with the actuator and operable to sense a pressure as applied to the article when the article is urged against the polishing surface of the turntable and a control unit operatively associated with the actuator and the sensor to monitor the pressure during a polishing operation. The control uhit is operable to control operation of the actuator in response to the pressure as monitored so as to keep the pressure at a target level and halt the polishing operation when the pressure deviated from a predetermined range over a predetermined period of the time.
Specifically, the carrier device further comprises a casing for supporting the carrier, the sensor being disposed between the casing and the acutator so as to sense the pressure as a reactive force developed when the actuator causes the carrier to urge the article against the polishing surface of the turntable.
The control unit may be adapted to halt the polishing operation after the current polishing operation for the article is completed if the pressure exceeds a first threshold pressure level over a predetermined period of time, and to immediately halt the polishing operation if the pressure exceeds a second threshold pressure level over a predetermined period of time, the second threshold pressure level being greater than the first threshold pressure level.
Further, The control unit includes a memory for storing the target value, the first threshold pressure level, and the second threshold presure level.
Furthermore, the control unit may be adapted to halt the polishing operation if the pressure drops below a first threshold pressure level and thereafter exceeds a second threshold presure level, the target level being less than the second threshold pressure level and greater than the first threshold pressure level.
The present invention further provides a method for controlling a carrier deice in a polishing apparatus which has a turntable having a polishing surface, the carrier device comprising a carrier for carrying an article to be polished and an actuator operable to cause the carrier to press the article against the polishing surface of the turn table. The method includes monitoring a pressure as applied to the article while the article is urged against the polishing surface of the turntable, regulating the actuator in response to the pressure as monitored so as to keep the pressure at a target level, and halting a polishing operation when the pressure deviates from the predetermined range over a predetermined period of time.
In another method, if the pressure exceeds a first threshold pressure level over a predetermined period of time, a polishing operation is halted after the current polishing operation for the article is completed, and if the pressure exceeds a second threshold pressure level greater than the first threshold pressure level over a predetermined period of time, the current polishing operation is immediately halted.
In another method, if the pressure drops below a first threshold pressure level and thereafter exceeds a second threshold pressure level greater than the first threshold level, a polishing operation is immediately halted.
The above and other features and advantages of the present invention will become apparent from the following description and the appended claims taken in conjunction with the accompaning drawings.
REFERENCES:
patent: 5498196 (1996-03-01), Karlsrud et al.
patent: 5868896 (1999-02-01), Robinson et al.
patent: 5908530 (1999-06-01), Hoshizaki et al.
patent: 5916009 (1999-06-01), Izumi et al.
patent: 63-295165 (1988-12-01), None
patent: 6-270054 (1994-09-01), None
patent: 10-58313 (1998-03-01), None
Takada Nobuyuki
Togawa Tetsuji
Ebara Corporation
Rachuba M.
Wenderoth , Lind & Ponack, L.L.P.
LandOfFree
Carrier device in polishing apparatus and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Carrier device in polishing apparatus and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Carrier device in polishing apparatus and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2439212