Electrical and Structural Properties of Processed Silicon Surfaces

The results of a detailed study of the effects on the texture and recombination properties of the Si substrate surface of two different dry etching processes, the CHF3/Ar plasma etching of a gate oxide and the SiCl4 plasma etching of a polysilicon film, are reported.The processing needed to prepare the structures to be etched is an important source of damage. The plasma etching has two opposite effects. On one side it produces defects and enhances the roughening, on the other side it can reduce the process induced defects by etching away the first defective substrate layer or by passivating the electrically active defects. The final defect content is the results of the equilibrium between these two actions. The surface recombination velocity comes out as the parameter most sensitive to the induced damage. In evaluating the damage the surface roughening has to be considered: the recombination properties of the surface are in fact largely influenced by the surface morphology.