Sub-0.1 μm nitride hard mask open process without precuring the ArF photoresist

Abstract

A nitride hard mask open process with an ArF photoresist (PR) has been achieved in a dual-frequency capacitively coupled plasma-type reactor to pattern 200 nm high and 90 nm wide nitride lines. It was found that the most serious problems of the hard mask open process with ArF PR are striation and wiggling of the PR. Striation is a serious side roughness of nitride lines that results from the deformation of the top portion of the PR during dry etching. This striation is aggravated by the high ion energy and the low selectivity of the nitride to the PR. Wiggling of the PR is defined as the collapse of the PR resulting from slimming of the ArF PR and deposition of a fluorocarbon polymer during dry etching. The wiggling of the PR is strongly dependent on the conditions of the dry etching, such as chamber pressure, chiller temperature, gas chemistry, and total etch time, all of which determine the temperature of the top surface of the ArF PR during dry etching. With the help of plasma diagnostics and an understanding of the mechanism of the striation and wiggling of the ArF PR, nitride lines of 90 nm width and height of 200 nm are successfully patterned without any precuring of the ArF PR.