Temporization of a scanning ion gun for the in-depth measurement of the erosion rate compatible with SIMS data acquisition: a recursive method

摘要

In-depth high resolution erosion rate measurement is very important when looking for the best results in Profiling thin, gradual atomic concentration films with SIMS, AES, or other techniques of surface analysis based on sputtering. We have developed an improved procedure to obtain the erosion rate, following the classic method using sputtered crater wall profile derivatives, fully compatible with SIMS data acquisition, adapted to digital raster scan primary ion beams, and independent of the nature of the materials to be studied. As derivatives introduce much noise and the measurement of changing slopes by conventional mechanical profilometers often carries several systematic errors, we pattern the crater shape to minimize these problems. With the proper timing, we reduce the sputtered area step-by-step, so that the final crater has straight-line walls when the analyzed material is homogeneous. In the case of heterogeneous materials, we sputtered a series of craters, each made using the time calculated from the erosion rate obtained from the previous one, such that the profiles of the walls of each new crater took the aspect of straight lines. This iterative method ended when a crater looked like one made on a homogeneous material using the first temporization. So, we check the quality of the achieved erosion rate in a self-consistent way. # 1997 Elsevier Science Ltd. All rights reserved