Thermal processing of photoresist are critical steps in the microlithography sequence. The post-expose bake steps for current DUV chemically-amplified resists is especially sensitive to temperature variations. Requirements call for temperature to be controlled to within 0.1 degree(s)C at temperature between 70 degree(s)C and 150 degree(s)C. The problem is complicated with increasing wafer size and decreasing feature size. Conventional thermal system, which utilizes single or dual zone heating, is no longer able to meet these stringent requirements. The reason is that the large thermal mass of conventional hot plates prevents rapid movements in substrate temperature to compensate for real-time errors during transients. The implementation of advanced control systems with conventional technology cannot overcome the inherent operating limitation. A spatially-programmable thermal processing module for the baking of 300 mm wafers has been developed.
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