Improved surface treatments for recycled (100) GaAs substrates in view of molecular-beam epitaxy growth: Auger electron spectroscopy, Raman, and secondary ion mass spectrometry analyses

摘要

The effects of chemical treatments on recycled (100) GaAs surfaces processed in microelectronic industry have been studied. The recycling process consists in establishing reproductive techniques of polishing and chemical cleaning of rejected processed wafers (with diameter of 100 mm) in order to obtain surfaces reusable to molecular-beam epitaxy (MBE). The recycling process is applied to any processed surface whatever the former technological applications and the doping type. Surfaces were first chemically treated in acid and basic solutions (HCl, diluted HF, and NH_4OH solutions). Then, thin layers of GaAs by MBE on them have been elaborated to study the chemical quality at the interface. Surfaces and epilayers have been analyzed using Raman and Auger electron spectroscopies (AES) to qualify the crystalline disorder as well as the chemical composition. Also, secondary ion mass spectrometry (SIMS) have been used to determine the level of contamination at the interface epilayer/substrate. A systematic comparison between the various treatments applied on the GaAs substrates has enabled us to obtain a high surface quality suitable for MBE. Specific results of AES and SIMS analyses clearly indicate that the diluted NH_4OH solutions remove the carbon contamination and, reduce the polishing residues content and the oxide thickness.