193nm resist chemical modification induced by HBr cure plasma treatment: a TD-GC/MS outgassing study

In this paper, we propose to bring new insights of the resist chemical modifications induced by HBr plasma treatment by using thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) measurements and thermal analysis. In order to isolate effect of plasma ions and radicals of resist chemical modification induced by VUV plasma light, samples coated with a model 193nm resist (polymer only and full formulation) and exposed to a HBr plasma (directly or via a LiF window) are analysed. Our approach, based on TD-GC/MS technique, is an indirect method to monitor the outgassed by-products during different treatments. Thus the outgassing rate associated with sample exposed directly to HBr cure plasma is significantly lower that outgassing rate of the samples exposed under LiF window, suggesting plasma induced surface hardening. Moreover a short O2 plasma treatment seems enough to remove the surface layer. Quantitative and qualitative TD-GCMS analysis correlated with Thermo-Gravimetric Analysis (TGA) allow us to show that plasma H+ ions induce resist deprotection . In conclusion, using such methodology we propose a fine analysis of fundamental mechanisms involved in 193nm resist modification under HBr cure plasma treatment.