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150 ㎜ GaAs 웨이퍼의 플라즈마 식각에서 식각 깊이의 균일도에 대한 가스 흐름의 최적화 연구
정필구(Philgu Jung),임완태(Wantae Lim),조관식(Guansik Cho),전민현(Minhyun Jeon),임재영(Jaeyoung Lim),이제원(Jewon Lee),조국산(Kuksan Jo) 한국진공학회(ASCT) 2002 Applied Science and Convergence Technology Vol.11 No.2
대면적 GaAs 웨이퍼의 플라즈마 식각 공정에서 식각 깊이의 좋은 균일도를 얻기 위해 반응기 내의 가스 흐름을 조절하는 진보된 기술을 실험하였다. 유한차분수치법(Finite Difference Numerical Method)은 GaAs 웨이퍼의 건식 식각을 위한 반응기 안의 가스 흐름의 분포를 시뮬레이션하기에 유용한 방법이다. 이 방법을 이용해 시뮬레이션된 자료와 실제의 것이 상당히 일치한다는 것이 BCl₃/N₂/SF_6/He ICP 플라즈마의 실험 결과로 확인되었다. 대면적 GaAs 웨이퍼의 플라즈마 식각 공정 중에서 포커스 링(focus ring)의 최적화된 위치가 가스 흐름과 식각 균일성을 동시에 향상시키는 것을 이해했다. 반응기와 전극(electrode)의 크기가 변하지 않는 상황에서 샘플을 고정시키는 클램프 배치의 최적화를 통해 100 ㎜(4 inch) GaAs 웨이퍼에서 가스 흐름의 균일성을± 1.5 %, 150 ㎜(6 inch) 웨이퍼에서는 ± 3 % 이하로 유지시킬 수 있는 것을 시뮬레이션결과에서 확인할 수 있다. 시뮬레이션된 가스 흐름의 균일도 자료와 실제 식각 깊이 분포실험 데이터의 비교로 대면적 GaAs 웨이퍼에서 건식 식각의 뛰어난 균일성을 얻기 위해서는 반응기 내의 가스흐름분포의 조절이 매우 중요함을 확인하였다. We developed engineering methods to control gas flow in a plasma reactor in order to achieve good etch depth uniformity for large area GaAs etching. Finite difference numerical method was found quite useful for simulation of gas flow distribution in the reactor for dry etching of GaAs. The experimental results in BCl₃/N₂/SF_6/He ICP plasmas confirmed that the simulated data fitted very well with real data. It is noticed that a focus ring could help improve both gas flow and etch uniformity for 150 ㎜ diameter GaAs plasma etch processing. The simulation results showed that optimization of clamp configuration could decrease gas flow uniformity as low as ± 1.5 % on an 100 ㎜(4 inch) GaAs wafer and ± 3 % for a 150 ㎜(6 inch) wafer with the fixed reactor and electrode, respectively. Comparison between simulated gas flow uniformity and real etch depth distribution data concluded that control of gas flow distribution in the chamber would be significantly important in order or achieve excellent dry etch uniformity of large area GaAs wafers.
Leem, Young-Chul,Kim, Na-Yeong,Lim, Wantae,Kim, Sung-Tae,Park, Seong-Ju The Royal Society of Chemistry 2014 Nanoscale Vol.6 No.17
<P>Light-emitting diodes (LEDs) play an important role as a formidable contender for next-generation lighting sources and rapidly replace conventional lighting sources. In this report, the growth of high density inclined ZnO nanorods (NRs) on the N-face n-GaN surface for high efficiency vertical light-emitting diodes (VLEDs) is demonstrated based on oxygen plasma pretreatment and hydrothermal growth. Surface modification by oxygen plasma pretreatment efficiently produces GaOxnanoparticles on the N-face n-GaN surface and they play an important role in the hydrothermal growth of dense and inclined ZnO NRs. The optical output power of ZnO NR VLEDs following oxygen plasma pretreatment is strongly enhanced by a factor of 3.25 at an injection current of 350 mA, compared to that of planar VLEDs. The large enhancement of optical power is attributed to the dense ZnO NR layer which efficiently reduces the total internal reflection and enhances the waveguide effect in ZnO NRs.</P>
Hong, Sang-Hyun,Cho, Chu-Young,Lee, Sang-Jun,Yim, Sang-Youp,Lim, Wantae,Kim, Sung-Tae,Park, Seong-Ju Optical Society of America 2013 Optics express Vol.21 No.3
<P>We demonstrate localized surface plasmon (LSP)-enhanced near-ultraviolet light-emitting diodes (NUV-LEDs) using silver (Ag) and platinum (Pt) nanoparticles (NPs). The optical output power of NUV-LEDs with metal NPs is higher by 20.1% for NUV-LEDs with Ag NPs and 57.9% for NUV-LEDs with Pt NPs at 20 mA than that of NUV-LEDs without metal NPs. The time-resolved photoluminescence (TR-PL) spectra shows that the decay times of NUV-LEDs with Ag and Pt NPs are faster than that of NUV-LEDs without metal NPs. The TR-PL and absorbance spectra of metal NPs indicate that the spontaneous emission rate is increased by resonance coupling between excitons in the multiple quantum wells and LSPs in the metal NPs. (C) 2013 Optical Society of America</P>
고밀도 평판형 유도결합 BCl<sub>3</sub>/SF<sub>6</sub> 플라즈마를 이용한 GaAs/AlGaAs와 InGaP 반도체의 선택적 식각에 관한 연구
유승열,류현우,임완태,이제원,조관식,전민현,송한정,이봉주,고종수,고정상,Yoo Seungryul,Ryu Hyunwoo,Lim Wantae,Lee Jewon,Cho Guan Sik,Jeon Minhyon,Song Hanjung,Lee BongJu,Ko Jong Soo,Go Jeung Sang,Pearton S. J. 한국재료학회 2005 한국재료학회지 Vol.15 No.3
We investigated selective dry etching of GaAs over AlGaAs and InGaP in high density planar inductively coupled $BCl_3/SF_6$ plasmas. The process parameters were ICP source power (0-500 W), RE chuck power (0-30W) and gas composition $(60-100\%\;BCl_3\;in\;BCl_3/SF_6)$. The process results were characterized in terms of etch rate, selectivities of GaAs over AlGaAs and InGaP, surface morphology, surface roughness and residues after etching. $BCl_3/SF_6$ selective etching of GaAs showed quite good results in this study. Selectivities of GaAs $(GaAs:AlGaAs\~36:1,\;GaAs:InGaP\~45:1)$ were superior at $18BCl_3/2SF_6$, 20 W RF chuck power, 300 W ICP source power and 7.5 mTorr. Addition of $(5-15\%)SF_6\;to\;BCl_3$ produced relatively high selectivities of GaAs over AlGaAs and InGaP during etching due to decrease of etch rates of AlGaAs and InGaP (boiling points of etch products: $AlF_3\~1300^{\circ}C,\;InF_3>1200^{\circ}C$ at atmosphere) at the condition. SEM and AFM data showed slightly sloped sidewall and somewhat rough surface$(RMS\~9nm)$. XPS study on the surface of processed GaAs proved a very clean surface after dry etching. It shows that planar inductively coupled $BCl_3/SF_6$ plasmas could be a good candidate for selective dry etching of GaAs over AlGaAs and InGaP.
Hydrogen sensing characteristics of non-polar a-plane GaN Schottky diodes
Yu-Lin Wang,F. Ren,S.J. Pearton,Kwang Hyeon Baik,Sung-Min Hwang,Yong Gon Seo,장수환,Wantae Lim 한국물리학회 2010 Current Applied Physics Vol.10 No.4
Pd and Pt Schottky diodes on non-polar a-plane (11–20) GaN layers show large increases in both forward and reverse bias current upon exposure to 4% H2 in N2. The barrier height reduction due to hydrogen exposure is 0.11 eV for Pd/GaN and 0.14 eV for Pt/GaN, with long recovery times (>25 min) at room temperature. The sensitivity to hydrogen is significantly greater than for diodes on conventional c-plane (Gapolar)GaN, but less than for c-plane (N-polar) material. The diode characteristics remain rectifying after exposure to hydrogen, unlike the case of N-polar GaN where Ohmic behavior is observed.