Crystallinity of thin silicon films deposited at low temperatures: Combined effect of biasing and structuring the substrate

The improvement of crystallinity of thin silicon films by (i) controlling the ion flux to the substrate and (ii) structuring the substrate surface is demonstrated. Films were deposited by electron-cyclotron resonance chemical-vapor deposition (ECR CVD) at 600 K on grooved substrates that were located on a dc-biased susceptor. The degree of crystallinity as determined by Raman spectroscopy and electron microscopy improved with increasing susceptor bias V-S. which is explained in terms of the local heating of the film surface during initial growth. For V-S = 15 V a pronounced increase of grain size was observed by X-ray diffraction that is accompanied by a texture inversion from (110)- to (111)-preferred orientation. The effect is discussed in terms of an ion-assisted reaction step on the surface of the growing film.