Abstract
Silicon nitride thin films for the encapsulation of GaAs were prepared by plasma-enhanced CVD. The chemical and physical properties of these films, before and after conventional thermal annealing, were examined by ellipsometry, IR spectroscopy, AES and film etch rate measurement. It was apparent that the silicon nitride underwent molecular rearrangement during the anneal where hydrogen was lost and the film densified. From an examination of the characteristic bonded hydrogen absorption peaks in the IR spectra, we have established that this process began at 500°C and thereafter increased with anneal temperature. A commensurate decrease in film thickness and increase in refractive index and etch rate were observed to follow this trend. Other film samples were subjected to an incoherent radiation, ‘flash lamp’, anneal at temperatures up to 1000°C. Despite the much shorter duration of the flash anneal, these samples showed a film densification and hydrogen loss similar to those given a conventional anneal.
Published Version
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