Deposition control for reduction of 193nm photoresist degradation in dielectric etching

Abstract

The 193nm photoresist (ArF resist) degradation mechanism in dielectric etching was investigated by using an ultra-high-frequency electron-cyclotron-resonance plasma. This investigation focused on via-hole etching. It was found that the bottom-antireflection coating (BARC) etching condition is a critical factor in the reduction of striation and pitting after via-hole etching. X-ray photoelectron spectroscopy and scanning electron spectroscopy studies revealed that argon-less and low-incident-ion-energy conditions in BARC etching can keep the resist surface smooth and maintain a carbon-rich micromask-less state because decomposition of the C–H or OC–O bonds is suppressed. As a result, resist damage after via-hole etching is reduced remarkably. Furthermore, in the via-hole etching, it was also found that the characteristics of the fluorocarbon polymer, i.e., deposition rate and flourine-to-carbon ratio of the fluorocarbon polymer, stacked on the resist surface during etching strongly affect the ArF resist degradation. Low-sticking-coefficient radicals such as CF2 and a low amount of deposition thickness are suitable for damage-less etching. In regard to the formation of striations at the pattern corner, the sputtering effect was taken into consideration. As a result, in the case of via-hole etching, line-edge-roughness in the trench pattern was improved by about 50%, and a striation-less and pitting-less hole etched profile was obtained by using either an argon-and-xenon (20%) mixture as a dilution gas or a fluorocarbon gas at low flow rate under low gas pressure.