Flattening ability of a vacuum pin chuck around the periphery of a processed wafer

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.