Contact formation with extremely low proximity effect by double patterning technology

Abstract

Contact hole within a NOR FLASH memory array is one of the most challenging features to print in the semiconductor manufacturing. It has been the key limiter of NOR FLASH memory scaling due to the difficulties involved in patterning the one-dimensional contact arrays and extremely stringent contact to gate overlay constraints. In this study, DPT (Double Patterning Technology) by ArF dry process was introduced for patterning NOR FLASH memory contact arrays. This approach has demonstrated a contact patterning with extremely low optical proximity effect for 50nm half-pitch with satisfied lithography process latitude and especially the circular contact shape can be maintained without compromise of NOR FLASH cell area. The novel hard mask scheme was the key enabler for this contact double patterning and this approach can be easily extended to ArF immersion lithography as a promising option for contact formation in leading-edge memory products.