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Title: Development of an integrated bake/chill system for microlithography
Authors: WANG LAN
Keywords: wafer bake/chill, microlithography, temperature uniformity
Issue Date: 27-Apr-2009
Citation: WANG LAN (2009-04-27). Development of an integrated bake/chill system for microlithography. ScholarBank@NUS Repository.
Abstract: The increase in complexity of integrated circuits (IC), coupled with the decreasing size of individual circuit elements, is placing more stringent demands on the fabrication process. In particular, the variation in the critical dimension (CD) which is the size of the smallest feature in the design, has to be carefully controlled during the lithography process as tolerances become smaller. In particular, the primary contributor to CD variance is the post exposure bake (PEB) temperature uniformity. This thesis presents an innovative apparatus for wafer baking/chilling using a stream of temperature controlled airflow. This apparatus takes the form of a baking chamber on which the wafer is placed. A stream of hot air is passed through the chamber below the wafer. Heat is transferred from the hot air to the wafer from the bottom surface of the wafer. If the chamber has a uniform cross section, heat will be lost along the direction of flow and eventually the far-end of the wafer will be cooler. As a result, temperature uniformity across the wafer will be very poor. In our innovation, we have designed a profiled chamber through which the hot air flows. The idea is to control the speed of the air flow through the channel which in turn improves the coefficient of heat transfer between the hot air and the wafer. This helps tremendously in achieving temperature uniformity of the wafer. Numerical analysis and simulation results are used to support our design. We show how the gradient of the tapered channel affects temperature uniformity and we are able to deduce the optimal gradient under simulation conditions.
Appears in Collections:Ph.D Theses (Open)

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