1 March 1991 EBES4: mask/reticle writer for the 90's
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Abstract
The challenges of producing 16M, 64M and perhaps 256M DRAMS in the 90's, requires mask/reticles with better specs than that can be provided by present generation systems. Overlay error, pattern size uniformity (CD control), pattern placement error (stitching) and patterns linewidth (MFS) have to improve by at least a factor of two over existing systems. In addition, the time required to write these patterns has also become intolerable on present systems. A faster, higher resolution and more accurate system is needed and EBES4 meets all these requirements. From minimum feature size standpoint, EBES4 provides 1/8 (mu) writing spot and can write (MFS) from 1/8 (mu) to 1/2 (mu) , depending on resist sensitivity, with high accuracy. The three tiered deflection system optimizes both speed and accuracy, so that 500 MHz data rate can be achieved while not introducing writing error larger than 0.05 (mu) (3(sigma) ). EBES4's proprietary TFE cathode provides not only high current (250 na) so that 500 MHz rate can be achieved with 3 (mu) C/cm2 resist but also very long lifetime of 8,000 hours. The vector deflecting and raster fill-in strategy minimizes non-writing overhead time as in conventional put raster system. Attention has been paid to kinematically hold the mask and use temperature insensitive material for the metrology sub-system of EBES4. Overlay accuracy can be improved by a factor of two over MEBES3. Topics covered are DRAM Reticle Requirements, EBES4 system error budget, EBES4 Electron optics and beam stability. Stage and Meteorology design considerations are outlined. Writing strategy and Software requirements are discussed. Finally we discuss hidden pattern writing issues such as any angle pattern, corner radius etc.
© (1991) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
George C. K. Chen, George C. K. Chen, } "EBES4: mask/reticle writer for the 90's", Proc. SPIE 1496, 10th Annual Symp on Microlithography, (1 March 1991); doi: 10.1117/12.29748; https://doi.org/10.1117/12.29748
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