# Huge Temperature-Induced Increase in Chemical Resistance of Solution-Processed Amorphous Thin Films along the As3S7–MoS3 Tie-Line and Its Structural Explanation

## TL;DR

This paper shows that adding molybdenum to amorphous thin films significantly boosts their chemical resistance when heated, making them useful for lithography.

## Contribution

The study reveals a 4-orders-of-magnitude increase in chemical resistance of MoS3-doped films after thermal treatment.

## Key findings

- Etching rates of As3S7–MoS3 films decrease significantly after annealing above 160 °C.
- Molybdenum enhances thermal stability and chemical resistance of the films.
- The observed changes are explained through optical and thermal analysis.

## Abstract

Amorphous chalcogenide
thin films have been widely studied
for
use in lithography as a photoresist due to significant changes in
etching rates caused by photoinduced structural changes upon exposure
to light. Here, we report on the role of the transition metal molybdenum
contained in MoS3 on the significantly enhanced thermal
stability and chemical resistance of As3S7–MoS3 thin films deposited by a sol–gel method. We demonstrate
that the dependences of etching rates of As3S7–MoS3 thin films in a solution consisting of 1
vol % n-butylamine in dimethyl sulfoxide on the annealing
temperature exhibit two linear regimes with a sudden change of their
slopes at 160 °C. The first regime, below 160 °C, is characterized
by a significantly lower chemical resistance of As3S7–MoS3 thin films in comparison with As3S7 thin films, while the second regime manifests
a gradual decrease in etching rates by 4 orders of magnitude in a
range of annealing temperatures from 160 to 200 °C. We explain
both trends using optical properties, differential scanning calorimetry,
and attenuated total reflection results. We propose that the vast,
4-orders-of-magnitude difference in the etching rate between as-deposited
As3S7–MoS3 and annealed thin
films at 200 °C can be successfully applied as a resist layer
in wet lithography.