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In fabrication of next-generation photomask for devices under 100 nm, more precise control of critical dimension (CD) is required. Each process for the photomask fabrication must be developed corresponding to each requirement of CD accuracy. The same applies to post-exposure baking (PEB) and post-coat baking (PCB), and so more precise control of reaction amount in baking is required. Multiple zone-controlled type of hot plate to improve uniformity of temperature has been enthusiastically developed Generally, conventional hot plates don't directly control the temperature of resist film because its measurement means, for example, thermo-couples or resistance bulb are embedded near the surface of hot plate, and so cannot accurately control resist temperature. We think next-generation baking technology should involve direct measurement and control of the actual temperature of films. Furthermore, serious problems arose in that heat history in PEB was different in each pattern area, such as mask center or edge, and large overshooting of temperature was caused in photomask baking because heat capacity of quartz is very large and heat transfer speed of quartz is very slow. To solve this problem, it is necessary to control resist temperature directly by means of a quick response. It is difficult to satisfy this requirement with conventional bakers of the hot plate type or with such bakers to which a minor improvement has been made to achieve the quick response. To realize the quick response, the four following concepts are needed. (i) Quick response of heat source for resist film (ii) Direct measuring of temperature of resist film (iii) Shortening interval of feedback (iv) Improvement of repeatability ofmeasuring temperature We have studied a candidate next-generation baking technology for photomask fabrication, namely a novel baking system consisting of halogen lamps and non-contact type thermometers. We call this novel baking system "Lamp Heater System". In this paper, the heating performance is reported.
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