In-situ thin film growthretch measurement and control by laser light reflectance analysis

In this article, I report in-situ thin film growth and etching measurement and control with ultra high precision. A stack of thin film layers of AlAsrAl0.1Ga0.9As to form Bragg reflector for the surface emitting semi-conductor laser was grown by gas source molecular beam epitaxy on a rotating wafer and the growth process was monitored with inclined incident polarized He–Ne laser light reflectance measurement. The multiple thin film layers were preferred to increase the visibility of the oscillating intensity variation signal for feasibility experiments. The inferred growth rate from the reflectance analysis was found to be 0.15 nmrs which remained in agreement with set growth parameters. The laser light reflectance analysis method was also employed for in-situ control and measurement of thin film etching process. The inferred etching rate was found to be 0.75 nmrs by the chemical etchant H3PO4:H2O2:H2O::3:1:100. Calibrated optical reflectance signal for growth and etching process is proposed for measuring and control their respective thickness and depth with very high accuracy and precision. q1999 Elsevier Science B.V. All rights reserved