This paper investigates the feasibility of using an electrostatic chuck (ESC) on a post exposure bake (PEB) plate in the
track to improve the critical dimension uniformity (CDU) for bowed wafers. Although it is more conventional to
consider vacuum chucking during PEB, electrostatic chucking offers some potential advantages, chief among which is
the fact that electrostatic chucking does not require any type of a seal between the wafer and the PEB plate whereas
vacuum chucking does. Such a seal requires contact and therefore has the potential to generate backside particles on the
wafer. Electrostatic chucking therefore has the potential for a cleaner overall process. Three different PEB plates were
tested in the course of this investigation, a non-chucking PEB plate (SRHP), a PEB plate equipped with a vacuum chuck
(VRHP), and a PEB plate equipped with an ESC (eBHP). It was found that CD uniformities were up to 84 percent lower
for bowed wafers that were chucked during PEB relative to wafers that were not chucked. In every case tested, wafers
processed through chucking PEB plates showed lower CDUs than wafers processed through the non-chucking plate.
CDU results were similar between vacuum chucked wafers and electrostatic chucked wafers. Based on the results
presented in this paper, it can be concluded that electrostatic chucking during PEB is a feasible method for controlling
CD uniformities on bowed wafers.
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