DEPENDENCE OF COPPER IMPURITY REMOVAL EFFICIENCY ON SUBSTRATES ETCHING RATE FOR VARIOUS SUBSTRATES IN HYDROFLUORIC SOLUTIONS

摘要

We have investigated the removal efficiency of copper impurities on various surface crystal structures. The study reveals that it depends on surface crystal structure. The copper impurities on phosphorus doped amorphous silicon (a-Si) are hardly removed by a hydrofluoric acid-hydrogen peroxide mixture (FPM) cleaning while are easily removed on single crystalline silicon (c-Si). A hydrofluoric acid-hydrogen peroxide mixture with non-ionic surfactant (FPMS) cleaning, however, can efficiently remove copper contaminants on both c-Si and a-Si surfaces. We suppose that both silicon etching by FPM solution and surface passivation by surfactant are essential to remove copper contaminants on a-Si surface. The etching rate difference of c-Si and a-Si surfaces has a relationship of interaction force between substrate and copper particles. This is attributed to the difference in crystalline structure between c-Si and a-Si.