Surface Contamination of GaAs during Photo-Etching

Surface contamination of GaAs due to resist film stripper “J–100” during the photo-etching process is investigated. It is found that the electron concentration near the surface decreases due to the heat treatment after soaking in J–100. The depth of contamination sometimes reaches about 100 µm. Contamination also occurs due to some organic solvents, although the degree of contamination is smaller than that due to J–100. Such contamination can be removed by etching the contaminated surface of GaAs lightly or soaking contaminated samples in a dilute solution of KCN before the heat treatment. Furthermore, the temperature and time dependence of the depth of the contamination are similar to those of the samples soaked in a dilute solution of CuSO 4 . It is concluded that contamination originates from Cu atoms contained in these solvents.