26 May 1995 Optical proximity correction using a transmittance-controlled mask (TCM)
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When small feature delineation is considered using existing exposure tools, special techniques might be needed such as phase shift mask, oblique illumination, top surface imaging, etc. When different types of patterns exist simultaneously or island patterns exist predominantly, optical proximity effect will become more important to be controlled. In this study, six different mask types were prepared and evaluated in view of a pattern fidelity and process latitude for 256 mega bit DRAM's storage node patterns. The masks used for this experiment were conventional transmission mask, serif patterned mask, square patterned Transmittance Controlled Mask (TCM), horizontally rectangular TCM, vertically rectangular TCM, and cross patterned TCM. The cross patterned TCM had three different transmittance on it and was evaluated also. In view of both pattern fidelity and process latitude, cross-TCM showed the best result. The vert-TCM also showed fairly good result. But the worst results always came from the conventional mask. From plane surface area point of view, once serif mask or TCMs are used, the areas always improved ranging from 120% to 145% at the best focus condition compared to the convention mask. There was not so much difference among three different transmittance in view of pattern fidelity and process latitude. As one of candidates for optical proximity correction, since small serif delineation on mask level is not easy for devices with small features such as 1 giga bit DRAM or beyond, TCM is more promising which has much bigger and easily writable gray area.
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Woo-Sung Han, Woo-Sung Han, Chang-Jin Sohn, Chang-Jin Sohn, Yongbeom Kim, Yongbeom Kim, Keeho Kim, Keeho Kim, Hoyoung Kang, Hoyoung Kang, Young-Bum Koh, Young-Bum Koh, Moon-Yong Lee, Moon-Yong Lee, "Optical proximity correction using a transmittance-controlled mask (TCM)", Proc. SPIE 2440, Optical/Laser Microlithography VIII, (26 May 1995); doi: 10.1117/12.209279; https://doi.org/10.1117/12.209279


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