An air-flow based wafer bake system for improved temperature uniformity

This paper presents an innovative apparatus for wafer baking/chilling using a stream of temperature controlled air-flow. 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 tapered 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.