To resolve ultra-fine patterns of 0.13 mum or less, chucking accuracy must
be within +/-0.05 mum except 1 mm from the wafer edge. This paper describes
the contact distribution between the back surface of a wafer and a chuck s
urface measured after clamping and vacuum-pin-chuck flattening ability arou
nd the periphery of a processed wafer calculated with the finite element me
thod. It is shown that it is difficult to flatten the periphery of a proces
sed wafer. Conventional static-pressure seal chucks can only flatten wafers
whose bow amount is 260 mum or less for a concave 12" wafer, so a new chuc
k was designed to improve the flattening ability. The seal width is enlarge
d so that the seal reaches the wafer edge or beyond. As a result, the flatt
ening amount increases to 360 mum. To suppress process-induced bowing below
the above amount, a low-temperature process of 270 degreesC or less will b
e required. (C) 2001 Elsevier Science BY All rights reserved.