Dry Etching of GaAs/AlGaAs와 GaAs/InGap in Inductively Coupled High Density Plasma System for Fabrication of Heterojunction Bipolar Transistors : 이종접합트렌지스터 (HBT) 제조를 위한 고밀도유도결합플라즈마(ICP)를 이용한 GaAs/AlGaAs와 GaAs/InGap 구조의 건식식각
Graduate School, Inje Uiv.
Department of Broadband Communications and Information
트렌지스터 GaAs/InGap 플라즈마 Dry Etching GaAs/AlGaAs Fabrication Heterojunction Bipolar Transistors 고밀도 High Density Plasma System;
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For fabrication of GaAs-based HBTs, characteristic effects of InGaP/GaAs, AlGaAs/GaAs structures during a planar coil inductively coupled plasma (PICP) dry-etching process were simulated and investigated. Based on the data, we could determine the effects of plasma parameters including gas composition, process pressure, inductively coupled plasma (ICP) and radiofrequency (RF) source power on GaAs-based Ⅲ-Ⅴ compound semiconductors (GaAs, AlGaAs and InGaP). Plasma gas flow uniformities in several types of reactor were simulated with using a finite difference numerical method. The simulated data were compared to obtain good gas flow distribution for 100 mm (4 in.), 150 mm (6 in.) and 200 mm (8 in.) diameter GaAs wafers. According to the results, it showed that introduction of an optimized clamp and focus ring in a different geometrical type of plasma reactor had powerful effects on gas flow distribution on the wafer. It was confirmed that advanced design of gas flow distribution in a reactor was very important to have excellent depth uniformity for a large area GaAs wafer during plasma etching. Effects of plasma parameters (ICP source power, RF chuck power, process pressure and plasma gas composition) to the plasma intensity were investigated with an optical emission spectrometry (OES) on PICP plasmas. According to the OES results, it was indicated that the plasma emission intensity depended on both of ion density and ion energy in PICP discharges with variable ranges of ICP power, RIE power and chamber pressure. The gas mixture was fixed at 15BCl_(3)/5N_(2) during the OES experiment. All of Ar, CH_(4), N_(2), BCl_(3) and H_(2) plasma emission pecks were investigated in the PICP reactor. Metal (Aluminum and Nickel) patterning processes for etch mask were studied using a thermal evaporation, PR processes (i.e. PR deposition, W exposure and development) and wet processes (HNO_(3) and KOH etching). The optimized wet etching solutions of each metal film were characterized. A1 was patterned in a KOH-based solution (10 H20 : 1 KOH, 8 H20 : 1 KOH, 6 H_(2)0 : 1 KOH with 10-20 sec.). Ni was done in HNO(_3)-based condition (1 H20 : 1 HNO_(3) within 10 see.). Dry etching of Ⅲ-V compound semiconductors (GaAs, AlGaAs, InGaP and InGaAs) in BCl_(3)/N_(2) by a planar coil inductively coupled plasma (PICP) was studied. Detailed results were discussed for the BCl_(3)/N_(2) ratio, process chamber pressure, ICP ( f = 13.56 MHz) and RF ( f = 13.56 MHz) power effects on etch rates of samples. In the case of InGaP, AlGaAs and InGaAs, they had slightly lower etch rate than those of GaAs.