Czochralski법에 의한 단결정 자동직경 제어시스템 개발;Nd:YAG 단결정 성장

배소익,이상호,김한태,Bae, So-Ik,Lee, Sang-Ho,Kim, Han-Tae 한국결정학회 1996 韓國結晶學會誌 Vol.7 No.1

Czochralski 인상장치에 로드 셀(load cell) 및 데이터 입출력 장치를 부착하고, computer에 의해 목표로 하는 크기의 단결정이 성장되도록 RF power가 자동 조정되는 프로그램을 개발하였다. 본 연구에서는 개발된 프로그램의 동작원리, 특성 및 구성 장치를 중심으로 기술하였으며, Nd:YAG산화물 단결정에 이 방법을 적용한 결과 ±5% 내에서 Nd:YAG 결정의 직경이 조절됨을 확인하였다. We developed an automatic diameter control system to control the diameter of single crystal for Czochralski growth. The system is composed of load cell, software program and data acquisition system connected to computer which controls RF power. This study describes the basic principle, characteristics and components of the system. The diameter of Nd:YAG crystal could be controlled within ±5% tolerance by this system.

수직경사응고(VGF)법에 의한 Si 도핑 GaAs 단결정 성장시 $B_{2}O_{3}$ 첨가에 따른 캐리어 농도 변화

배소익,한창운,Bae, So-Ik,Han, Chang-Woon 한국결정성장학회 2009 韓國結晶成長學會誌 Vol.19 No.2

PBN 도가니를 이용하여 Si이 도핑된 GaAs 단결정을 수직경사 응고법으로 성장시켰다. PBN 도가니에 산화막인 $B_{2}O_{3}$의 양을 $0{\sim}0.2wt%$ 범위에서 변화시키면서, 성장 후 캐리어 농도를 측정하였다. $B_{2}O_{3}$ 첨가량이 증가함에 따라, 초기 0.1 정도의 Si 도판트의 편석계수는 0.01 부근까지 급격히 감소하고, 동시에 캐리어 농도도 감소하는 것을 알 수 있었다. 이는 성장도중 도판트인 Si이 $B_{2}O_{3}$과 반응하며 도너인 Si 양을 감소시키며, 동시에 억셉터인 B 양을 증가시키기 때문으로 보인다. 한편 PBN 도가니 내면에 얇은 유리질의 $B_{2}O_{3}$층 형성이 용이한 고온 산화막 처리가 결함감소에 효과적임을 확인하였다. Si-doped GaAs single crystals were grown by vertical gradient freeze using PBN crucibles. The amount of oxide layer $B_{2}O_{3}$ in PBN crucible was changed($0{\sim}0.2wt%$) and measured the concentration of carriers. The segregation coefficients of Si in GaAs melt decreased rapidly from initial 0.1 to 0.01 as the amount of $B_{2}O_{3}$ increases. At the same time, concentration of carriers was shown to decrease. It is likely that the reaction between dopant Si and $B_{2}O_{3}$ in GaAs melt results in the reduction of Si dopants(donor) while increase in the amount of boron(acceptor). The thin layer of $B_{2}O_{3}$ glass in PBN crucible was proved to be a better way to reduce defect formation rather than the total amount of $B_{2}O_{3}$.

오존과 초음파를 이용한 실리콘 웨이퍼의 Post Sliced Cleaning

최은석,배소익,Choi, Eun-Suck,Bae, So-Ik 한국재료학회 2006 한국재료학회지 Vol.16 No.2

The effect of ozone and/or ultrasound treatments on the efficiency of slurry removal in post sliced cleaning (PSC) of silicon ingot was studied. Efficiency of slurry removal was evaluated as functions of time, temperature and surfactant with DOE (Design of Experiment) method. Residual slurries were observed on the wafer surface in case of cleaning by ozone or ultrasound separately. However, a clean wafer surface was appeared when cleaned with ozone and ultrasound simultaneously. It has found that cleaning time was the main effect among temperature, time and surfactant. Elevated temperature, addition of surfactant and high ozone concentration helped to accelerate efficient removal of slurry. The improvement of removal efficiency seems to be related to the formation of more active OH radicals. The highly cleaned surface was achieved at 10 wt% ozone, 1 min and 10 vol% surfactant with ultrasound. Application of ozone and ultrasound might be a useful method for PSC process in wafer cleaning.

융액인상법에 의한 Nd;YAG 단결정 성장시 온도구배의 변화에 따른 결함거동

김한태,배소익,이상호,정수진 한국세라믹학회 1997 한국세라믹학회지 Vol.34 No.10

In the Nd;YAG crystal growth by Czochralski method, the relationship between the core formation and the solid-liquid interface was observed by controlling the temperature gradient in the furnace. When the crystal was grown along<111> direction, defects and core area were reduced as the temperature gradient increased. The optimum temperature gradient was found to be higher than 4$0^{\circ}C$/cm. The Nd3+ concentration analysis by ICP-Mass showed that the segregation coefficient was about 20% higher in the core region than core-free region, where the segregation coefficients of core region and core-free region were 0.22 and 0.18, respectively.

세정액에 따른 실리콘 웨이퍼의 Cu 및 Fe 불순물 제거

김인정,배소익,Kim, In-Jung,Bae, So-Ik 한국재료학회 2006 한국재료학회지 Vol.16 No.2

The removal efficiency of Cu and Fe contaminants on the silicon wafer surface was examined to investigate the effect of cleaning solutions on the behavior of metallic impurities. Silicon wafers were intentionally contaminated with Cu and Fe solutions by spin coating and cleaned in different types of cleaning solutions based on $NH_4OH/H_2O_2/H_2O\;(SC1),\;H_2O_2/HCl/H_2O$ (SC2), and/or HCl/$H_2O$ (m-SC2) mixtures. The concentration of metallic contaminants on the silicon wafer surface before and after cleaning was analyzed by vapor phase decomposition/inductively coupled plasma-mass spectrometry (VPD/ICP-MS). Cu ions were effectively removed both in alkali (SC1) and in acid (SC2) based solutions. When $H_2O_2$ was not added to SC2 solution like m-SC2, the removal efficiency of Cu impurities was decreased drastically. The efficiency of Cu ions in SC1 was not changed by increasing cleaning temperature. Fe ions were soluble only in acid solution like SC2 or m-SC2 solution. The removal efficiencies of Fe ions in acid solutions were enhanced by increasing cleaning temperature. It is found that the behavior of metallic contaminants as Cu and Fe from silicon surfaces in cleaning solutions could be explained in terms of Pourbaix diagram.

연마 Recycling 시간에 따른 콜로이드 실리카 슬러리의 안정성 및 연마속도

최은석,배소익 한국세라믹학회 2007 한국세라믹학회지 Vol.44 No.2

The stability of slurry and removal rate during recycling of colloidal silica slurry was evaluated in silicon wafer polishing. The particle size distribution, pH, and zeta potential were measured to investigate the stability of colloidal silica. Large particles appeared as recycling time increased while average size of slurry did not change. Large particles were identified by EDS (energy dispersive spectrometer) as foreign substances from pad or abraded silicon flakes during polishing. As the recycling time increased, pH of slurry decreased and removal rate of silicon reduced but zeta potential decreased inversely. Hence, it could be mentioned that decrease of removal rate is related to consumption of OH− ions during recycling. Attention should be given to the control of pH of slurry during polishing.

질소 도핑된 P/P^- Epitaxial Silicon Wafer의 Slip 및 강도 평가

최은석,배소익,Choi Eun-Suck,Bae So-Ik 한국재료학회 2005 한국재료학회지 Vol.15 No.5

The relation between bulk microdefect (BMD) and mechanical strength of $P/P^-$ epitaxial silicon wafers (Epitaxial wafer) as a function of nitrogen concentrations was studied. After 2 step anneal$(800^{\circ}C/4hrs+1000^{\circ}C/16hrs)$, BMD was not observed in nitrogen undoped epitaxial silicon wafer while BMD existed and increased up to $3.83\times10^5\;ea/cm^2$ by addition of $1.04\times10^{14}\;atoms/cm^3$ nitrogen doping. The slip occurred for nitrogen undoped and low level nitrogen doped epitaxial wafers. However, there was no slip occurrence above $7.37\times10^{13}\;atoms/cm^3$ nitrogen doped epitaxial wafer. Mechanical strength was improved from 40 to 57 MPa as nitrogen concentrations were increased. Therefore, the nitrogen doping in silicon wafer plays an important role to improve BMD density, slip occurrence and mechanical strength of the epitaxial silicon wafers.

플라즈마기반 표면 Texturing 공정에 따른 다결정 실리콘 웨이퍼 표면물성과 태양전지 동작특성 연구

박광묵,정지희,배소익,최시영,이명복,Park, Kwang-Mook,Jung, Jee-Hee,Bae, So-Ik,Choi, Si-Young,Lee, Myoung-Bok 한국진공학회 2011 Applied Science and Convergence Technology Vol.20 No.3

다결정 실리콘 태양전지 표면의 광흡수율을 극대화시키기 위하여 플라즈마기반의 reactive ion etching (RIE) 공정을 적용하였으며 maskless 표면 texturing조건을 최적화하여 310~1,100 nm 파장대역의 평균 표면반사율을 $4{\pm}1%$ 내외로 감소시킬 수 있는 grass-like 한 블랙실리콘을 제조할 수 있었다. Saw damage를 가진 $15.6{\times}15.6\;cm^2$ bare 웨이퍼에서부터 중요 공정단계별로 처리된 시료들의 평균반사율, 표면형상, 소수운반자 수명 등의 위치분포를 측정하여 최종 제작된 태양전지의 광전변환효율과 외부양자효율 등과 비교 검토하여 고효율 다결정 실리콘 태양전지 양산에 필요한 표면 texturing 조건들을 연구하였다. 평균 반사율을 4% 이하로 감소시키는 texturing 공정조건에서 웨이퍼 중앙에서 가장자리로 갈 수록 표면구조의 깊이 2배 반치폭 3배의 불균일성이 발생하였으며 이에 따라 입사광자의 다중반사확률이 높아져 평균반사율이 1% 정도 낮아지는 것으로 밝혀졌다. 비반사막이 코팅된 시료에서 측정된 소수운반자수명분포도 중앙에서 가장자리로 갈수록 약 40% 이상 더 긴 수명을 갖는 것으로 밝혀져 표면구조의 크기에 따른 사이즈효과가 발생하는 것으로 판단된다. 제조된 태양전지의 위치에 따른 광전변환효율도 낮은 반사율과 더 긴 소수운반자수명을 갖는 가장자리에서 2% 가량 높은 광전변환효율을 보였으며, 380~1,100nm 파장대역의 외부양자효율 측정결과도 이를 뒷받침하고 있다. 균일한 에미터 층 형성 및 ARC 증착에 있어서 구조적으로 가장자리 부분의 구조가 유리한 것으로 예상되며, 동시에 표면 구조의 사이즈 효과 때문에 표면 재결합확률이 중앙보다 가장자리에서 더 감소되어 더 높은 광전변환효율을 보이는 것으로 해석된다. Reactive ion etching (RIE) technique for maskless surface texturing of mc-silicon solar wafers has been applied and succeed in fabricating a grass-like black-silicon with an average reflectance of $4{\pm}1%$ in a wavelength range of 300~1,200 nm. In order to investigate the optimized texturing conditions for mass production of high quantum efficiency solar cell Surface characteristics such as the spatial distribution of average reflectance, micrscopic surface morphology and minority carrier lifetime were monitored for samples from saw-damaged $15.6{\times}15.6\;cm^2$ bare wafer to key-processed wafers as well as the mc-Si solar cells. We observed that RIE textured wafers reveal lower average reflectance along from center to edges by 1% and referred the origin to the non-uniform surface structures with a depth of 2 times deeper and half-maximum width of 3 times. Samples with anti-reflection coating after forming emitter layer also revealed longer minority carrier lifetime by 40% for the edge compared to wafer center due to size effects. As results, mc-Si solar cells with RIE-textured surface also revealed higher efficiency by 2% and better external quantum efficiency by 15% for edge positions with higher height.

실리콘 웨이퍼 세정을 위한 오존의 거동에 관한 연구

이건호,김인정,배소익,Lee Gun-Ho,Kim In-Jung,Bae So-Ik 한국반도체디스플레이기술학회 2005 반도체디스플레이기술학회지 Vol.4 No.4

The behavior of ozone in $NH_4OH$ was investigated to evaluate the solution as a cleaning chemical of the silicon wafer. The solubility of ozone in DI(Deionized) water increased as the oxygen flow-rate decreased and ozone generator power increased. Ozone in DI water showed solubility of 100 ppm or higher at room temperature. Ozone concentration was stabilized at the range of ${\pm}2ppm$ by controlling oxygen flow rate and ozone generator power. On the contrary, the solubility of ozone in $NH_4OH$ was very low and strongly depended on the concentration of $NH_4OH$ and pH. The redox potential of ozone was saturated within 10 minutes in DI water and decreased rapidly with the addition of $NH_4OH$. The behavior of ozone in $NH_4OH$ is well explained by redox potential calculation.

Czochralski 방법에 의한 Nd : YAG 단결정의 육성 및 레이저 출력특성

이상호,김한태,배소익,정수진 한국광학회 1998 한국광학회지 Vol.9 No.3

고체 레이저매질로 가장 널리 쓰이는 Nd:YAG 단결정을 Czochralski 방법으로 육성하였다. 자체 제작한 Czochralski 결정 육성로 및 자동 결정 적경제어 장치를 써서 유효 직경 50mm, 길이 100mm의 Nd3+ 이온농도가 0.9at%이고 <111>방향의 단결정을 육성하였다. 단결정 육성시 융액의 수직방향에 대한 온도구배가 중용한 변수인 것이 확인되었으며, 결정 직경은 자동 제어가 가능하도록 컴퓨터 프로그램을 제작하였다. 육성된 단결정을 절단, 가공, 연마, 코팅 과정을 거쳐서 레이저 발진용 Nd:YAG막대를 제작하고 흡수 스펙트럼, 형과 스펙트럼 분석을 통하여 정확한 Nd:YAG의 레이저 발진특성을 확인하였다. 자체 가공된 레이저 막대로부터 발진된 CW 레이저의 최대 출력은 70W이었고, 발진문턱값과 효율은 각각 1.3kW, 1.64%이었다. Nd:YAG single crystal widely used as solid state laser was grown by Czochralski method. <111> single crystal with 0.9at% of $Nd^{3+}$ was grown from the Czochralski furnace with a automatic diameter control system. The vertical temperature gradient in the liquid was the major factor that influence the crystal quality, and the crystal diameter was controlled by the home made computer program. The crystal boule with $\phi$50mm$\times$ι100mm effective size was cut, polished, and antireflection coated. The optical evaluation such as absorption spectrum, fluorescence spectrum coincide with typical features of Nd:YAG single crystal. The laser rod was assembled into the CW laser generator with a Kr lamp. The maximum CW laser output was 70 W and the threshold power and efficiency was 1.3kW and 1.64% respectively.