INFLUENCE OF RAPID THERMAL ANNEALING PROCESSES ON THE PROPERTIES OF SINX-H FILMS DEPOSITED BY THE ELECTRON-CYCLOTRON-RESONANCE METHOD

We have analyzed the effects of rapid thermal annealing on the composi tion and on the bonding and optical properties of amorphous hydrogenat ed silicon nitride (a-Si-x:H) thin films deposited at room temperature by the electron cyclotron resonance plasma method. Films with three d ifferent as-grown compositions have been studied, namely x = 0.97, 1.4 3 and 1.55, Annealing effects were related to film composition. In fil ms with the presence of both Si-H and N-H bonds (as-grown compositions x = 0.97 and 1.43), we found that a reorganization of bonds takes pla ce at temperatures less than or equal to 500 degrees C, where the well -known cross linking reaction Si-Si + N-H --> Si-H + Si-N occurs witho ut detectable release of hydrogen. In the same range of temperatures, an increase of the band gap was observed and attributed to Si-Si bond substitution for Si-H, but no changes in composition were detected. At higher temperatures (T greater than or equal to 600 degrees C), the o ptical gap decreases and both Si-H and N-H bonds are lost along with a release of hydrogen and nitrogen. For the films with an as-gown compo sition x = 1.55, we observe that the release of hydrogen only occurs a t temperatures above 900 degrees C, but it is not accompanied by any l oss of nitrogen. An increase of the optical gap until the release of h ydrogen begins and a decrease thereafter is observed. (C) 1998 Elsevie r Science B.V, All rights reserved.