Application and evaluation of direct-write electron beam for ASICs

The application of direct-write electron-beam (DW-EB) technology to 1.3-μm fine geometry and high-density 24 K-gate CMOS VLSI is investigated. Particular attention is paid to EB radiation damage of MOS devices and the effectiveness of DW-EB for CMOS application-specific integrated circuit (ASIC) VLSIs. To increase throughput for direct-writing and maintain good resolution, a high-sensitivity EB resist and appropriate proximity-effect correction method are adopted. EB radiation damage cannot be observed when low-electron beam dosage is applied to thin 25-μm oxide lightly doped drain (LDD) structure devices, thus making DW-EB applicable for fabricating CMOS VLSIs. Good electrical characteristics, high reliability and good yield can also be obtained. The advantages of DW-EB for quick turnaround time and more efficient debugging capability by forming different VLSIs on the same wafer are discussed