SURFACE ROUGHENING DURING PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION OF HYDROGENATED AMORPHOUS-SILICON ON CRYSTAL SILICON SUBSTRATES

The morphology of a series of thin films of hydrogenated amorphous sil icon (a-Si:H) grown by plasma-enhanced chemical-vapor deposition (PECV D) is studied using scanning tunneling microscopy. The substrates were atomically flat, oxide-free, single-crystal silicon. Films were grown in a PECVD chamber directly connected to a surface analysis chamber w ith no air exposure between growth and measurement. The homogeneous ro ughness of the films increases with film thickness. The quantification of this roughening is achieved by calculation of both rms roughness a nd lateral correlation lengths of the a-Si:H film surface from the hei ght difference correlation functions of the measured topographs. Homog eneous roughening occurs over the film surface due to the collective b ehavior of the flux of depositing radical species and their interactio ns with the growth surface.