Improvement of Crystallinity by Substrate Nitridation in InN/sapphire

Kwon, Hyuk Joo,Lee, Yong Hyun,Saiki, Hisao,Miki, Osamu,Yamano, Hirofumi,Yoshida, Akira 경북대학교 센서기술연구소 1995 센서技術學術大會論文集 Vol.6 No.1

InN film on sapphire substrate was prepared by ME-MOVPE and its surface morphology was shown by atomic force microscopy. The effect of nitridation of sapphire substrate for a buffer layer between InN film and sapphire substrate was investigated. Nitridation of sapphire substrate before epitaxy of InN is very useful for preparing single crystalline on sapphire substrate.

Effect of Relative Surface Charge of Colloidal Silica and Sapphire on Removal Rate in Chemical Mechanical Polishing

Chuljin Park,김형재,Hanchul Cho,Taekyung Lee,김도연,Sangjik Lee,Hae-Do Jeong 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.6 No.2

Many studies have looked at the chemical mechanical polishing (CMP) process of sapphire substrates. However, the research on the processing mechanism of the sapphire substrate is insufficient compared with semiconductor CMP processing. This paper focuses on the effect of the slurry pH on the removal rate of sapphire substrate in CMP. When the pH of the slurry is changed, the possible factors that can influence removal rate of sapphire include the zeta potential, abrasive agglomeration, and hydration reaction layers. The colloidal silica slurry used in this study did not show aggregation at any pH value. However, the zeta potential between the abrasive and the substrate changed remarkably at acidic and basic pH. The attractive force between the abrasive and substrate in acidic conditions is higher than that in basic conditions due to the relative surface charge. A higher attractive force caused by opposite charges makes more of the abrasive participate in the polishing process, which increases the removal rate in acidic conditions. However, the removal rate in basic conditions is higher than that in acidic conditions despite the repulsive relative charges. The reason for the higher removal rate in basic conditions seems to be the easier formation of a hydration layer, which is caused by the higher concentration of [OH]− in basic conditions. If the hydration effect is negligible, then the removal rate strongly depends on the magnitude of relative surface charges, which can be defined by the product of the zeta potentials of the abrasives and the substrate. If the product of the potentials is large, the probability of contact between the abrasives and the substrate is increased. Thus, the removal rate is increased. However, if the hydration layer forms, it plays a dominant role in determining the removal rate.

반도체 발광 소자의 변형 제어를 위한 연구

이재철 사단법인 한국융합기술연구학회 2023 아시아태평양융합연구교류논문지 Vol.9 No.6

The nitride semiconductor light emitting device has a light emitting region covering ultraviolet, blue, and green regions. In addition, such a GaN-based semiconductor light emitting device does not have a lattice matched substrate, and it is difficult to grow a high-quality nitride semiconductor thin film due to a large difference in lattice constant and thermal expansion coefficient. For this reason, a sapphire substrate is generally used to grow a GaN semiconductor thin film. In this study, I devised a method for controlling deformation of a substrate by deposition other materials on the back side of a GaN layer when the GaN based semiconductor layer is grown on the sapphire substrate. The deformation of the substrate caused by the process temperature, thickness and thermal expansion coefficient was calculated using finite element method. Based on these analysis results, the relationship between process temperature and material variables and displacement is derived. The range of the thermal expansion coefficient according to the process temperature and the thickness of the control layer for defining the displacement of the sapphire substrate within an allowable displacement range is estimated using the derived relational equation. The results of the derived relational equation were compared with those obtained by finite element analysis. Compared with the maximum displacement, the error result was 8.72%. Through this, it is possible to define the physical properties and thickness of the displacement control layer using the proposed relational expression without complex analysis and calculation in molding a semiconductor light emitting device using a 6-inch substrate. 질화물 반도체 발광소자는 자외선, 청색, 및 녹색 영역을 포괄하는 발광 영역을 가진다. 그리고 이러한 GaN계 반도체 발광소자는 격자 정합이 되는 기판이 존재하지 않고, 격자 상수 및 열팽창 계수의 차이가 커서 양질의 질화물 반도체 박막 성장이 어렵기 때문에, 일반적으로 GaN 반도체 박막을 성장시키기 위해 사파이어 기판을 주로 사용하고 있다. 본 연구에서는 사파이어 기판 위에 GaN계 반도체층을 성장시킬 때 GaN층 이면에 다른 물질을 증착하여 기판의 변형을 제어하는 방법을 고안하였다. 유한요소법을 이용하여 기판 두께와 열팽창계수에 따른 기판의 변형을 계산하였다. 이러한 해석 결과를 바탕으로 공정온도와 재료 변수 및 변위 간의 관계를 도출하였다. 도출된 관계식을 이용하여 사파이어 기판의 변위를 허용 범위 안에 위치시키도록 하기 위한 제어 층의 공정온도와 두께에 따른 열팽창계수의 범위를 정의하였다. 유도된 관계식의 결과를 유한요소해석으로 얻은 결과와 비교하였다. 최대 변위와 비교하여 오차 결과는 8.72%였다. 이를 통해, 6인치 기판을 적용한 반도체 발광 소자의 성형에서 복잡한 해석과 제안된 관계식으로 변위 제어 층의 물성과 두께를 정의할 수 있게 된다.

사파이어 기판에 제작한 YBa₂Cu₃O_(7-δ) 박막의 특성연구

임해용,김인선,김동호,박종철,박용기 경북대학교 센서기술연구소 1998 센서技術學術大會論文集 Vol.9 No.1

C-axis oriented YBa_(2)Cu_(3)O_(7-δ) (YBCO) thin films on R-cut sapphire substrate were grown by pulsed laser deposition. CeO_(2) film was used as a buffer layer for YBCO deposition on R-cut sapphire substrate. Crystallinity of CeO_(2) buffer layer was researched by XRD. Surface morphology and superconducting properties of YBCO thin films were characterized by SEM and four probe method. Critical temperature of YBCO thin films was ≥89 K, and critical current density was 1.5 x10^(6) A/cm^(2) if at 77 K.

활성화 이온빔 처리된 Sapphire기판 위에 성장시킨 MOCVD-GaN 박막의 격자변형량 측정

김현정,김긍호,Kim, Hyun-Jung,Kim, Gyeung-Ho 한국현미경학회 2000 Applied microscopy Vol.30 No.4

사파이어 기판을 이용한 GaN 박막성장에서 완충층의 사용과 기판의 질화처리는 GaN 박막 내의 격자결함을 줄이는 가장 보편적인 방법이다. GaN박막의 초기 핵생성과 성장 거동을 향상시키기 위한 새로운 방법으로 사파이어 표면을 질소 활성화 이온빔으로 처리하는 방법이 시도되었다. 활성화 이온빔 처리의 결과 약 10nm두께의 비정질 $AlO_xN_y$ 층이 형성되었으며 GaN의 성장온도에서 부분적으로 결정화되어 계면 부위에 고립된 비정질 영역으로 존재하였다. 계면에 존재하는 비정질 층은 기판과 박막사이에서 발생하는 열응력을 효과적으로 감소시키는 역할이 가능하며 이를 확인하기 위하여 활성화 이온빔 처리에 의한 GaN박막 내의 격자변형량 차이를 비교하였다. GaN박막에서 얻어진 $[\bar{2}201]$ 정대축고차 Laue도형을 전산모사 도형과 비교하여 격자변형량을 측정하였다. 본 연구의 결과 활성화 이온빔 처리를 하지 않은 기판 위에 성장시킨 GaN박막의 격자변형량은 처리한 경우에 비해 6배 이상 높은 값을 가졌으며 따라서 활성화 이온빔 처리에 의해 GaN박막의 열응력은 크게 감소함을 확인하였다. Introduction of the buffer layer and the nitridation of a sapphire substrate were one of the most general methods employed for the reduction of lattice defects in GaN thin films Brown on sapphire by MOCVD. In an effort to improve the initial nucleation and growth condition of the GaN, reactive ion beam (RIB) of nitrogen treatment of the sapphire surface has been attempted. The 10 nm thick, amorphous $AlO_xN_y$ layer was formed by RIB and was partially crystallized alter the main growth of GaN at high temperature, leaving isolated amorphous regions at the interface. The beneficial effect of amorphous layer at interface in relieving the thermal stress between substrate and GaN film was examined by measuring the lattice strain value of the GaN film grown with and without the RIB treatment. Higher order Laue zone pattern (HOLZ) of $[\bar{2}201]$ zone axis was compared with simulated patterns and lattice strain was estimated It was confirmed that the great reduction of thermal strain was achieved by RIB process and the amount of thermal stress was 6 times higher in the GaN film grown by conventional method without the RIB treatment.

Growth and Evaluation of GaN Grown on Patterned Sapphire Substrates

Dong-Hun Kang,Eun-Su Jang,Heon Song,Dong-Wook Kim,Jin-Soo Kim,이인환,KANNAPPANSANTHAKUMAR,이철로 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.6

We report the microstructure and the optical properties of gallium nitride (GaN) epilayers grown on a lens-shaped patterned sapphire substrate (PSS) by using metalorganic chemical vapor deposition (MOCVD) for various growth times. The lens shaped pattern was used to reduce the threading dislocation density and to improve the optical emission efficiency. The scanning electron microscope (SEM) image shows a flat and smooth surface for the GaN grown on the PSS for 80 min, which could be achieved by lateral growth from the trench region. From the double crystal X-ray diffraction (DCXRD) spectra, the full width at half maximum (FWHM) value was found to decrease with increasing growth time. The FWHM of the sample grown for 80 min was 473.5 arc sec. This indicates that there is an improvement in the crystalline quality of the GaN grown on the PSS as the growth time increases. From the Raman spectra, the shift of the A1(LO) and E2high phonon mode frequencies towards a higher wavelnumber was observed for GaN grown on PSS as compared to GaN grown on an unpatterned sapphire substrate (UPSS). The high Raman peak intensity of the GaN epilayers using the patterned substrate with a low FWHM indicates that there is an improvement in the quality of the GaN compared to the layer grown on an unpatterned substrate. From the photoluminescence (PL) spectra, an increase in the band edge emission intensity and a decrease in the defect related yellow luminescence were observed for GaN on the PSS as the growth time increased. From the PL spectra, the FWHM was 82.2 meV at a peak position of 363.9 nm for the sample grown for 80 min. It is clearly seen that threading dislocations can be reduced by lateral growth, thereby improving the light emission efficiency by internal light reflection on the lens surface for the GaN grown on the PSS.

Characteristic of SiC Slurry in Ultra Precision Lapping of Sapphire Substrates

Tao Yin,ZhiDa Wang,Toshiro Doi,Syuhei Kurokawa,Zhe Tan,XiaoKang Ding,Huan Lin 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.6

A method is proposed in this paper to prepare a SiC slurry with SiC particles selected by an ultrasonic-assisted elutriation method to reduce substrate surface damage caused by abrasive particles during lapping. Sapphire substrate lapping experiments were carried out using the prepared SiC slurry, and the lapping performance of the slurry was analyzed. The experimental results show that the SiC particle size is a factor that directly affects the material removal rate and surface roughness Ra, of sapphire substrates. When a SiC slurry with a particle size of 630 nm was used, the material removal rate was 508 nm/h, and the surface roughness Ra was 1.9 nm; increasing the slurry concentration and the platen rotating speed can improve the material removal rate. In addition, the agglomeration of SiC particles in the slurry depends on the pH of the slurry. Efficient precision lapping of sapphire substrates can be achieved by selecting appropriately sized SiC particles and by adjusting the slurry pH to control the agglomeration and dispersion of SiC particlesto further reduce the scratches on the substrate surface during the lapping process.

미스트 화학기상증착법을 이용한 c면, a면, m면, r면 사파이어 기판 위의 산화갈륨 박막 성장 연구

성기려,조성호,김경호,신윤지,정성민,김태규,배시영 한국전기전자재료학회 2023 전기전자재료학회논문지 Vol.36 No.1

Gallium oxide (Ga2O3) thin films were grown on c-, a-, m-, r-plane sapphire substrates using a mist chemical vapor deposition system. Various growth temperature range of 400~600°C was applied for Ga2O3 thin film deposition. Then, several structural properties were characterized such as film thickness, crystal phase, lattice orientation, surface roughness, and optical bandgap. Under the certain growth temperature of 500℃, all grown Ga2O3 featured rhombohedral crystal structures and wellaligned preferred orientation to sapphire substrate. The films grown on c-and r-plane sapphire substrates, showed low surface roughness and large optical bandgap compared to those on a-and m-plane substrates. Therefore, various sapphire orientation can be potentially applicable for future Ga2O3-based electronics applications.

Comparison of AIN Nanowire-Like Structures Grown by using Mixed-Source Hydride Vapor Phase Epitaxy Method

김경화,이강석,안형수,양민,이삼녕,전인준,조채용,전헌수,김석환 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.3

Four AlN nanowire-like structures were simultaneously grown directly without a buffer layer on four substrates-sapphire, quartz, Si(111), and 6H-SiC-via a mixed-source hydride vapor phase epitaxy (HVPE) method using a mixed source (Al+Ga) containing a small quantity of Ga at 1150 °C for 2 h. Deposition was carried out using a simplified reactor designed in series without any separation between the source and the growth zones. AlN nanostructures with hexagonal crystal structures were grown successfully and directly on thin, pre-grown AlN nucleation areas on the quartz substrates. Furthermore, AlN nanostructures were grown on the sapphire substrate without a buffer layer and on pre-grown epilayers on the Si (111) and the 6H-SiC substrates, respectively. The characteristics of the AlN nanowire-like structures grown on the four substrates were investigated using energy-dispersive X-ray spectrometry and field-emission scanning electron microscopy.

미세 전극 패턴을 갖는 알루미나 정전척을 이용한 LED용 사파이어 기판 흡착 연구

김형주(Hyung-Ju Kim),신용건(Yong-Gun Shin),안호갑(Ho-Kap Ahn),김동원(Dong-Won Kim) 한국표면공학회 2011 한국표면공학회지 Vol.44 No.4

In this work, handling of sapphire substrate for LED by using an electrostatic chuck was studied. The electrostatic chuck consisted of alumina dielectric, which was doped with 1.2 wt% TiO₂. As the volume resistivity of alumina dielectric was decreased, the electrostatic force was increased by Johnsen-Rahbek effect. The narrower width and gap size of electrode led to the stronger electrostatic force. When alumina dielectric with 3.20×10¹¹Ωㆍ㎝ resistivity and 3 ㎜ width/1.5 ㎜ gap sized electrode was used, the strongest electrostatic force in this work was obtained, which value reached to ~14.46 gf/㎠ at 2.5 ㎸ for 4-inch sapphire substrate. This results show that alumina electrostatic chuck with low resistivity and fine electrode pattern is suitable for handling of sapphire substrate for LED.