Appeal No. 2001-1512 10
Application No. 09/273,541
valve 17 is closed and the gas flow rate necessarily corresponds
to the leakage rate at the wafer-chuck interface.
Turning now to White, we find that the reference is directed
to a similar vacuum processing apparatus that includes an
electrostatic chuck and a cooling gas flowing in the gap between
the wafer and the chuck. However, as also indicated by Appellant
(brief, page 18), White introduces a constant flow of cooling gas
at the interface between the workpiece (wafer) and the platen
(chuck) having a controlled flow rate of approximately 0.25 sccm
(col. 5, lines 16-20). White’s constant flow rate of the cooling
gas is comparable to Tezuka’s desired flow rate which is
indicated by pressure gage 19. We further find that White
teaches that the tightness of contact between the wafer and the
chuck may be compromised if the wafer is separated from the chuck
due to incorrect placement of the wafer or the presence of
particles (generated from the process) landing on the chuck (col.
10, lines 20-44). White also indicates that such separation
decreases capacitance between the wafer and the electrode on the
chuck and causes the current flow to the electrodes of the
electrostatic chuck be reduced (id.). Therefore, White keeps the
cooling gas flow at a constant level without corresponding the
flow rate to the leakage rate from the gap between the wafer and
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