Applied Science and Convergence Technology 2009; 18(4): 288-295
Published online July 1, 2009
Copyright © The Korean Vacuum Society.
S. H. Lee , J. H. Park , H. S. Noh , K. H. Choi , H. J. Song , G. S. Cho , J. W. Lee
We report the etch characteristics of GaAs and AlGaAs in the diffusion pump-based capacitively coupled BCl₃ plasma. Process variables were chamber pressure (50~180 mTorr), CCP power (50~200 W) and BCl₃ gas flow rate (2.5~10 sccm). Surface profilometry was used for etch rate and surface roughness measurement after etching. Scanning electron microscopy was used to analyze the etched sidewall and surface morphology. Optical emission spectroscopy was used in order to characterize the emission peaks of the BCl₃ plasma during etching. We have achieved 0.25 ㎛/min of GaAs etch rate with only 5 sccm BCl₃ flow rate when the chamber pressure was in the range of 50~130 mTorr. The etch rates of AlGaAs were a little lower than those of GaAs at the conditions. However, the etch rates of GaAs and AlGaAs decreased significantly when the chamber pressure increased to 180 mTorr. GaAs and AlGaAs were not etched with 50 W CCP power. With 100~200 W CCP power, etch rates of the materials increased over 0.3 ㎛/min. It was found that the etch rates of GaAs and AlGaAs were not always proportional to the increase of CCP power. We also found the interesting result that AlGaAs did not etched at 2.5 sccm BCl₃ flow rate at 75 mTorr and 100 W CCP power even though it was etched fast like GaAs with more BCl₃ gas flow rates. By contrast, GaAs was etched at ~0.3 ㎛/min at the 2.5 sccm BCl₃ flow rate condition. A broad molecular peak was noticed in the range of 500~700 ㎚ wavelength during the BCl₃ plasma etching. SEM photos showed that 10 sccm BCl₃ plama produced more undercutting on GaAs sidewall than 5 sccm BCl₃ plasma.
Keywords: 플라즈마 식각,축전 결합형 플라즈마,GaAs,AlGaAs,확산펌프,BCl₃,Plasma etching,Capacitively coupled plasma,Diffusion pump