The effects of ion bombardment sputtering and atomic transport related roughening and smoothing on depth profiling resolution

A theoretical analysis is presented on the effects of the competing processes of random atomic removal by sputtering and atomic transport on the depth resolution delta z/z obtained in sputter depth profiling. If is shown that these processes can give rise to a steady state roughening, or even a smoothing of initially rough surfaces. However, if correlated processes such as surface curvature dependent sputtering yield occur, this can lead to exponentially increasing roughening. The analysis reveals the importance of experimental parameters such as ion flux and sputtering yield and substrate temperature and sample and probe beam dimensions and suggests how these may be varied to optimize depth resolution.