Estimation of wafer warpage profile during thermal processing in microlithography

Wafer warpage is common in microelectronics processing. Warped wafers can affect device performance, reliability, and linewidth control in various processing steps. Early detection will minimize cost and processing time. We propose in this article an in situ approach for estimating wafer warpage profile during the thermal processing steps in the microlithography process. The average air gap between wafer and bake-plate at multiple locations of a multizone bake-plate can be estimated and a profile can be obtained by joining these points. Experimental results demonstrate the feasibility and repeatability of the approach. This is a major improvement over our previously developed approach, in which only the average warpage could be obtained. The proposed approach requires no extra processing steps and time, as compared to conventional off-line methods. (c) 2005 American Institute of Physics.