Optical measurement of the rms roughness of ion-implanted surfaces

Abstract

Ion implantation and other ion-beam processing techniques sometimes roughen the surfaces to which they are applied. If undetected, such roughness can lead to erroneous interpretation of data gathered by RBS, AES, and other surface analysis techniques. Many surface profilometers and scanning electron microscopes lack sufficient resolution to detect fine-scale roughness that can complicate the data interpretation. We have constructed a simple optical instrument to measure the root-mean-square (rms) roughness, below ~ 100 nm, of ion-implanted surfaces. This instrument measures the total integrated scatter (TIS) of almost-normally incident laser light, which (under certain conditions) is simply related to the rms surface roughness. This paper describes the construction and calibration of the TIS instrument, and presents preliminary results on the roughness of Cr surfaces deposited under various vacuum conditions and implanted during deposition with energetic Cr ions.