Abrading – Precision device or process - or with condition responsive... – Computer controlled
Patent
1995-07-25
1997-08-05
Rose, Robert A.
Abrading
Precision device or process - or with condition responsive...
Computer controlled
451 41, 451 21, B24B 4900, B24B 722
Patent
active
056536224
ABSTRACT:
A chemical mechanical polishing system for processing semiconductor wafers has a polishing arm and carrier assembly that press the topside surface of a semiconductor wafer against a motor driven, rotating polishing pad. Improved uniformity of material removal, as well as improved stability of material removal rate, is achieved through the use of a controller that applies a variable wafer backside pressure to the wafers being polished. More specifically, a control subsystem maintains a wafer count, corresponding to how many wafers have been polished by the polishing pad. The control subsystem regulates the backside pressure applied to each wafer in accordance with a predetermined function such that the backside pressure increases monotonically as the wafer count increases. In the preferred embodiment, the control system regulates the backside pressure in accordance with a linear function of the form: Backside Pressure=A+(B.times.Wafer Count). Whenever a new polishing pad is mounted, the wafer count value is reset to a predefined minimum wafer count value and the backside pressure for the next wafer to be polished is reset to a preset minimum backside pressure value.
REFERENCES:
patent: 3691697 (1972-09-01), Bender
patent: 3848365 (1974-11-01), Bovensiepen et al.
patent: 4712470 (1987-12-01), Schmitz
Drill Charles
Weling Milind G.
Rose Robert A.
VLSI Technology Inc.
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