A new and fast in-situ spectroscopic infrared absorption measurement technique

Abstract

Silicon oxide like films are deposited using an expanding thermal plasma (cascaded arc) in combination with HMDSO and oxygen as deposition precursors. These films are deposited at high rate (up to 200 nm/s). In general Fourier transform infrared (FTIR) reflection absorption spectroscopy is a useful tool for in situ analysis of the film deposition growth process [1,2]. However this technique is difficult to apply when the film deposition rate is reaching high values (10 to 100 nm/s). At this rate the time to deposit a monolayer of film material is approximately 3 to 30 ms, whereas the typical time to make a single scan by means of FTIR is 0.1 - 1.0 s, which is almost two orders of magnitude longer than the monolayer deposition time. This excludes FTIR spectroscopy as a means to study e.g. initial growth effects. Therefore to study the monolayer or submonolayer growth of films deposited at high deposition rates by means of infrared reflection absorption spectroscopy it is necessary to use another technique instead of FTIR. To improve the speed of the measuring technique an offer has to be made. FTIR spectroscopy normally measures a broadbanded spectrum (typical for infrared spectroscopy 500 to 7500 cm-1), therefore it is possible to investigate the behaviour of various absorption peaks at the same time. However to gain scanning speed, it is necessary to concentrate on one single absorption peak, i.e. reducing the spectral range