Low-pressure thermogravimetric analysis for finding sublimation temperatures for organic precursors in atomic/molecular layer deposition

Abstract

Atomic/molecular layer deposition (ALD/MLD) is strongly emerging as the state-of-the-art gas-phase fabrication technique for novel functional inorganic-organic thin-film materials. In the actual ALD/MLD process development, selecting the proper sublimation temperatures for the inorganic and organic precursors is an important task. In particular, the latter ones tend to require higher sublimation temperatures. In this work, we systematically investigate a representative set of most common ALD/MLD organic precursors using low-pressure (4 mbar) thermogravimetric (TG) analysis. The onset temperature (TG(onset)) where the weight loss starts is found to well foretell us the optimal precursor source temperature (T-MLD) for ALD/MLD; typically, the T(MLD)value used in a practical ALD/MLD experiment is lower by approximately 14% than the TG(onset)value. Moreover, we discuss the possibility to utilize the melting point of the compound as a starting point if such vacuum TG measurements are not available.