Gettering of particles from an electro-negative plasma with insulating chuck
AssigneeInternational Business Machines Corporation
InventorsJohn H. Keller, Gregory Costrini
Life of this patent
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Abstract
Apparatus controls a wafer potential in a plasma system when the plasma is off to keep the wafer slightly negative at all times in order to reduce and eliminate the collection of charged particles on the wafer. The apparatus allows the wafer bias to be reduced to a small negative voltage and then holds that voltage. This greatly reduces the net positive flux to the wafer. A diode and a programmed power supply hold a minimum negative voltage on the back of the wafer electrode when the plasma density is decaying to zero.
Claims5
A method for use in a plasma processing system used in the manufacture of semiconductor circuits for preventing particulates from going to a semiconductor wafer mounted on a negative electrode after a plasma discharge is turned off, said wafer being separated from said negative electrode by an insulator, said method comprising the steps of:
- sensing a current flowing to the wafer from a plasma;
- and
- maintaining or driving the wafer negative when plasma density decays to zero.
Dependencies are inferred from the claim text.