Roles of Surface Functional Groups on TiN and SiN Substrates in Resist Pattern Deformations

Abstract

Resist pattern deformations on a bottom anti-reflective layer (BARL) are a serious problem for deep UV lithography. To clarify the mechanism of these pattern deformations, we analyzed SiN and TiN substrates (candidates of BARL materials) by Auger electron spectroscopy (AES) and thermal desorption (TDS). We also applied N2 annealing and thermal oxidation to the substrates. To examine the reactivity of the substrates to the acid generated in the resist, the potential energy and partial charges of model compounds were calculated using the molecular orbital method. By comparing experimental and calculational results, it was found that the Si–OH group neighboring N atoms on SiN substrates was a stronger base than the Si–OH group neighboring O atoms. We also found that NHx groups can easily react with the acid. The oxidation of SiN, which eliminates NHx and N–Si–OH, prevented pattern deformation. In the case of TiN, on the other hand, oxidation was not effective because Ti–O–Ti can be decomposed by the acid.