A 7-Mask CMOS Process with Selective Oxide Deposition

This paper describes a new 7-mask CMOS process using liquid phase oxide deposition which has selectivity against photoresist. The process modules for self-aligned well and one mask LDD formation are developed. The features of the process are 1) short TAT: 7 masks to first metallization, 2) self-aligned twin retrograde wells with 40% reduction of the p⁺-n⁺ spacing compared to conventional wells, and 3) optimal LDD design using different sidewall spacer width for n- and p-channel MOSFET’s giving a 10% larger on-current for p-channel MOSFET’s compared to a conventional process.