Barrel and Tunnel Etch Processes for Plasma Irradiated Photoresists

Abstract

A comprehensive experimental study of the response of barrel etching characteristics under the individual influence of several components of the process recipe has been made for unradiated as well as reactive plasma irradiated photoresist patterns. A maximum is observed in the strip rate of the two resists both as a function of etch pressure and the flowrate of O₂ in the overall chemistry. However, the strip rate is found to increase linearly and exponentially with RF power and process temperature respectively. Catalytic influence observed in the strip process with introduction of halocarbons for a controlled period has been discussed.

To alleviate the possibility of damage to underlayer from non-ionic radiations, a perforated conducting etch tunnel has been designed and introduced into the barrel. Only long life time ions are found to enter the etch tunnel thereby reducing the absolute value and process parameter coefficient of strip rates. In-situ optical coding of peripheral rings, formation of non-stripping polymers and comparison of radiation damage in tunnel versus barrel etch modes are discussed.

Indexing terms:

• Barrel etching
• Plasma irradiated photoresists
• Optical coding
• Plasma etching