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 t he 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 locate d on a dc-biased susceptor. The degree of crystallinity as determined by Ra man spectroscopy and electron microscopy improved with increasing susceptor bias V-S. which is explained in terms of the local heating of the film sur face during initial growth. For V-S = 15 V a pronounced increase of grain s ize was observed by X-ray diffraction that is accompanied by a texture inve rsion from (110)- to (111)-preferred orientation. The effect is discussed i n terms of an ion-assisted reaction step on the surface of the growing film .