Influences of Measurement Conditions on Etching Rate of GaAs/AlAs Superlattice in Auger Electron Spectroscopy Sputter Depth Profiling

抄録

  Influences of measurement conditions such as the base pressure of the analysis chamber, the acquisition time of Auger electron spectroscopy (AES) and the sputtering time in one period, on AES sputter depth profiling of a GaAs/AlAs superlattice reference material were investigated by irradiating 750 eV Ar⁺ ions at the incident angle of 50°. The results revealed that the ratio of the etching rate of AlAs to that of GaAs is strongly influenced by the base pressure of the analysis chamber. When the base pressure is ～2×10^-9 Torr, the ratio of the etching rate is almost constant at ～0.9 and not affected by measurement conditions. In contrast, when the base pressure is ～8×10^-9 Torr, the ratio of the etching rate is strongly affected by measurement conditions. The shorter the sputtering time in one period is, the smaller the ratio of the etching rate is. The longer acquisition time of AES is also considered to introduce the difference in the ratio of the etching rate. The influences on the etching rate caused by the measurement conditions might be attributed to the oxygen adsorption on the AlAs surface. In addition, in spite of the strong dependence of the ratio of the etching rate on the measurement condition at the base pressure of ～8×10^-9 Torr, the depth resolution does not depend on the measurement condition. The present results strongly suggest that careful attention for the optimization of the measurement condition of sputter depth profiling using the GaAs/AlAs superlattice reference material is required since the etching rate is an important factor to quantitatively understand the depth scale of depth profiles.