ZEP resist process for high-accuracy photomask with a dry-etching capability

For the improvement of CD accuracy in reticles, we have optimized the ZEP resist development process using a dipping system with regard to the sensitivity, the contrast and the process stability. Each developer has the same performance with respect to the sensitivity and the contrast for ZEP810S under optimized development time. ZED-2EK has been chosen as the suitable developer for dipping system, because it is single- component developer. EB dose has been optimized as 8 or 9 (mu) C/cm 2 using ZED-2EK. ZEP810S resist process has been optimized, and CD uniformity of 0.024 micrometers on 3(sigma) , which is almost equal to the CD measurements error, has been obtained using this resist process. 64M- DRAM reticles have been fabricated successfully by using this resist process. The resist process has a potential such that 256M-DRAM fabrication with +/- 0.05 micrometers accuracy can be achieved by the uniformity improvement in EB exposure and etching.