14 June 1988 An E-Beam Direct Write Process For Half Micron DRAMS
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Direct write electron beam (EB) lithography is expected to write a very fine wafer pattern below half micron for the development of the comming generation ULSIs. But direct write EB lithography has two main peculiar problems for obtaining such a very fine resist pattern on an uneven topography of a processed wafer. One is a pattern dimension deviation from the designed value due to resist topography and proximity effects. The other problem is pattern registration deviation due to charge-up in the EB-resist. In order to investigate the proximity effect. we evaluated the deposited energy density profile by a double gaussian Exposure Intensity Distribution ( EID ) function. The theoretical and experimental results showed that in a 2.2 micron thick trilayer planerizing resist system. both 0.5 micron isolated line and isolated space were simultaneously resolved in half micron thick top layer resist. To compensate the charge-up problem, we treated the bottom-layer by a brand-new ion shower material modification process. A 40 KV proton shower irradiation decreased the resistance of the bottom layer. The charge of the electron beam was dissipated through the bottom layer resist. The resultant half micron rule 16 M-bit DRAM patterns were compared with the optically exposed tri-level resist patterns. The optically exposed patterns also had an optical proximity effect and half micron patterns were not resolved even adopting the contrast enhancement lithographic ( CEL ) technology. On the other hand, we successfully obtained 16M-bit DRAM patterns on the uneven topography of the processed wafer using EB direct write.
© (1988) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Noboru Nomura, Noboru Nomura, Kenji Kawakita, Kenji Kawakita, Toshihiko Sakashita, Toshihiko Sakashita, Kenji Harafuji, Kenji Harafuji, Toyoki Takemoto, Toyoki Takemoto, "An E-Beam Direct Write Process For Half Micron DRAMS", Proc. SPIE 0923, Electron-Beam, X-Ray, and Ion Beam Technology: Submicrometer Lithographies VII, (14 June 1988); doi: 10.1117/12.945662; https://doi.org/10.1117/12.945662

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