Corrosion selectivity and structural evolution in N doped Sb2Te thin films for lithography application

Te-based phase-change resist has lots of advantages such as high-resolution, broad spectral response, and simple preparation process, making it a promising candidate for lithography. Particularly, both positive and negative features can be simultaneously implemented in the resist. However, there are few reports on regulating atom concentration of the resist to realize both positive and negative features. This work has reported N doped Sb2Te thin films as both positive and negative resists by adjusting N concentration. The negative resist with the N concentration of lower than 21.7 at% possesses the corrosion selectivity of as high as 4.2 while the positive resist with the N concentration of higher than 24.7 at% has the maximum corrosion selectivity of 10.9. The mechanism of corrosion selectivity has been further investigated. Electrochemical analysis reveals that for the negative resist, the increased annealing temperature results in the gradual increment of charge-transfer resistance and thus the higher corrosion potential. For the positive resist, however, the increased annealing temperature leads to the gradual decreased charge-transfer resistance and thus the lower corrosion potential. Structural analysis indicates that the annealed state for the negative resist can form large amounts of Sb2Te or Sb phases containing Sb-Sb and Te-N bonds, which will restrain the corrosion of thin films whereas the formation of TeeTe bond in the as-deposited state will promote the corrosion of thin film. However, the annealed state for the positive resist can generate large amounts of Te phase consisting of Te-Te bonds, which is readily oxidized into TeO2 and further be dissolved whereas the as-deposited state comprising more Sb-N and Te-N bonds will retard the further corrosion of thin film. Results indicate that N doped Sb2Te thin film is a promising inorganic resist for lithography applications. (c) 2022 Elsevier B.V. All rights reserved.

Automated summary

This study reports N-doped Sb2Te thin films as a resist material with both positive and negative features by adjusting the N concentration. The negative resist film shows high corrosion selectivity, while the positive resist film exhibits the maximum corrosion selectivity. The mechanism behind the corrosion selectivity is investigated through electrochemical and structural analysis.