Wet Etchant Diffusion through Photoresist during Gate Oxide Patterning

Abstract

Gate oxide patterning during integrated circuits manufacturing can be defined by a photolithography and wet etch sequence. Wet etching process can be at risk. Indeed, during this step, liquid molecules can penetrate through resist layer to reach and damage the underlying material. The key parameter to know is the maximum duration that a given resist can ensure an effective protection. This study shows in the first time how to evaluate etching molecules diffusion thanks to ATR-FTIR technology and a gravimetric approach. Then a two-steps diffusion model has been established. Finally, differences are observed between four different commercial resists.

Chemical Infiltration through Deep UV Photoresist

“…During this soft mask patterning, the gate oxide under the resist can be degraded by two different mechanisms: either a lateral wet etchant infiltration at the PR(Photo resist) / gate oxide interface [2], or a vertical diffusion of chemicals down to this same interface. Diffusion kinetics and characterization have already been proposed [3] [4]. A deeper understanding of the gate oxide degradation by HF based chemicals infiltration through the resist is hereby discussed.…”