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26 June 2003 Printing 95-nm DRAM full chip patterns in KrF lithography
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95nm KrF lithography has been developed for 512 Mb DRAM. KrF 0.80NA scanner was used to print 190nm pitch patterns and this means the process factor k1 is 0.306. Crosspole illumination was used to print critical layers, which has four poles on x and y-axis. To improve CD uniformity of critical layers we also used fogging effect corrected (FEC) reticles and thin photo resist process, which needs the hard mask etching process to overcome poor dry etch resistance. For 95nm DRAM cell patterns, we could get more than 8% exposure latitude (EL) and 0.3 μm depth of focus (DOF). With FEC masks and optimized resist process, CD uniformity of word line layer printed on wafer was less than 10nm. Overlay accuracy of critical layers is mostly less than 25nm. However at core and periphery area of DRAM the extreme off-axis illumination like crosspole brought poor process latitude in weak zone duties and therefore the hard optical proximity correction (OPC) work was required. In a real integration other novel technologies are used such as gap-filling for STI and ILD processes, Wsi gate, W bit line and SAC processes. This paper reported only lithographic performance for printing 95nm DRAM patterns. Consequently KrF lithography is still promising technology to print sub 100nm node DRAM.
© (2003) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Seok-Kyun Kim, Jin-Soo Kim, Tae-Jun Yoo, Keun-Kyu Kong, Hyoung-Soon Yun, Young-Deuk Kim, Hyoung-Ryeun Kim, Young-Sik Kim, and Hyeong-Soo Kim "Printing 95-nm DRAM full chip patterns in KrF lithography", Proc. SPIE 5040, Optical Microlithography XVI, (26 June 2003);

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