• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.102-102
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• 2008

Sapphire (${\alpha}-Al_2O_3$) has been used as the substrate of opto-electronic device because of characteristics of thermal stability, comparatively low cost, large diameter, optical transparency and chemical compatibility. However, there is difficulty in the etching and patterning due to the physical stability of sapphire and the selectivity with sapphire and mask materials [1,2]. Therefore, sapphire has been studied on the various fields and need to be studied, continuously. In this study, the etching properties of sapphire substrate were investigated with various $CH_4$/Ar gas combination, radio frequency (RF) power, DC-bias voltage and process pressure. The characteristics of the plasma were estimated for mechanism using optical emission spectroscopy (OES). The chemical compounds on the surface of sapphire substrate were investigated using energy dispersive X-ray (EDX). The chemical reaction on the surface of the etched sapphire substrate was observed by X-ray photoelectron spectroscopy (XPS). Scanning electron microscopy (SEM) was used to investigate the vertical and slope profiles.

• 한국세라믹학회지
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• 제41권7호
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• pp.493-496
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• 2004

The chemical etching of sapphire substrates was peformed to produce smooth surfaces on an atomic scale. The sapphire sur-face etched by using a $H_2$S $O_4$ solution showed a pit-free morphology and was yen smooth as much as $\sigma$$_{rms}$=0.13 nm, that etched by using a mixture of $H_2$S $O_4$ and $H_3$P $O_4$ contained large pits with $\sigma$$_{rms}$=0.34 nm. The $\sigma$$_{rms}$’s and the number of the pits increased with increasing etching temperature. The sapphire etched by using $H_2$S $O_4$ at 32$0^{\circ}C$ had the best surface. These results provide important information on the effects of etching treatment on the structural properties of sapphire for the growth of high-quality epilayers.ayers.

• 한국전기전자재료학회논문지
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• 제24권1호
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• pp.7-11
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• 2011

Sapphire substrate was patterned by a selective chemical wet etching technique, and GaN/InGaN structures were grown on this substrate by MOVPE (Metal Organic Vapor Phase Epitaxy). The surface of grown GaN on patterned sapphire substrate (PSS) has good morphology and uniformity. The patterned sapphire substrate LED showed better light output than conventional LED that improvement 50%. We think these results come from enhancement of internal quantum efficiency by decrease of threading dislocation and increase of light extraction efficiency. Also these LED showed more uniform emission distribution in angle than conventional LED.

• 대한화학회지
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• 제39권1호
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• pp.1-6
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• 1995

단결정 적층막을 제조하기 위해 사용되는 사파이어 기판에 대하여 황산과 인산의 혼합용액 화학적 에칭을 조사하였다. 여러가지 배향면의 사파이어에 대한 에칭정도는 황산과 인산의 3:1 조성과 $315{\pm}2^{\circ}C$에서 에칭시간에 의존하였다. 280~320$^{\circ}C$ 범위에서 30분간씩 산에칭시킨 후에 에칭속도(R)를 구하였고, log R에 대한 $1/T$ semilog plot로부터 활성화에너지$(E_a)$를 구하였으며, 그것은 $({\bar1}012) > (10{\bar1}0) > (11{\bar2}0) > (0001)$면 순서로 감소하였다. 한편 (0001), $({\bar1}012),\;(10{\bar1}0)$과 $(11{\bar2}0)$면의 표층 두께를 각각 64.6, 46.5, 16.2와 5.1 ${\mu}m$ 에칭시킨 후의 기판 표면을 SEM으로 관찰하였다.

• 한국재료학회지
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• 제10권11호
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• pp.784-788
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• 2000

The Vickers microhardness was measured on the basal (0001) plane of sapphire single crystals in the temperature range from 25$^{\circ}C$to 1000$^{\circ}C$. The substructure surrounding the indents was investigated using selective chemical polishing and etching, optical microscopy, and trasmission electron microscopy (TEM). At room temperature, cracks were predominant, and at intermediate temperatures (400$^{\circ}C$and 600$^{\circ}C$), extensive rhombohedral twinning was observed. On the other hand, at higher temperatures, prism plane slip bands on prism plane {1120}(원문참조) were dominant in the microstructure. TEM observations revealed that the dislocation substructure at the vicinity of the indents consisted of fairly straight dislocations lying in basal and/or prism planes and aligned along the <1100> and <1120> directions. The details of the glide dissociation of perfect <110> screw dislocations into three collinear 1/3<1100> partials on the prism plane and the Peierls potential for sapphire single crystals were discussed.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2008년도 추계학술대회 논문집 Vol.21
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• pp.363-363
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• 2008

The development of dry etching process for sapphire wafer with plasma has been key issues for the opto-electric devices. The challenges are increasing control and obtaining low plasma induced-damage because an unwanted scattering of radiation is caused by the spatial disorder of pattern and variation of surface roughness. The plasma-induced damages during plasma etching process can be classified as impurity contamination of residual etch products or bonding disruption in lattice due to charged particle bombardment. Therefor, fine pattern technology with low damaged etching process and high etch rate are urgently needed. Until now, there are a lot of reports on the etching of sapphire wafer with using $Cl_2$/Ar, $BCl_3$/Ar, HBr/Ar and so on [1]. However, the etch behavior of sapphire wafer have investigated with variation of only one parameter while other parameters are fixed. In this study, we investigated the effect of pressure and other parameters on the etch rate and the selectivity. We selected $BCl_3$ as an etch ant because $BCl_3$ plasmas are widely used in etching process of oxide materials. In plasma, the $BCl_3$ molecule can be dissociated into B radical, $B^+$ ion, Cl radical and $Cl^+$ ion. However, the $BCl_3$ molecule can be dissociated into B radical or $B^+$ ion easier than Cl radical or $Cl^+$ ion. First, we evaluated the etch behaviors of sapphire wafer in $BCl_3$/additive gases (Ar, $N_2,Cl_2$) gases. The behavior of etch rate of sapphire substrate was monitored as a function of additive gas ratio to $BCl_3$ based plasma, total flow rate, r.f. power, d.c. bias under different pressures of 5 mTorr, 10 mTorr, 20 mTorr and 30 mTorr. The etch rates of sapphire wafer, $SiO_2$ and PR were measured with using alpha step surface profiler. In order to understand the changes of radicals, volume density of Cl, B radical and BCl molecule were investigated with optical emission spectroscopy (OES). The chemical states of $Al_2O_3$ thin films were studied with energy dispersive X-ray (EDX) and depth profile anlysis of auger electron spectroscopy (AES). The enhancement of sapphire substrate can be explained by the reactive ion etching mechanism with the competition of the formation of volatile $AlCl_3$, $Al_2Cl_6$ or $BOCl_3$ and the sputter effect by energetic ions.

• JSTS:Journal of Semiconductor Technology and Science
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• 제6권3호
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• pp.199-205
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• 2006

Patterned sapphire substrates (PSS) were fabricated by a simple wet etching process with $SiO_2$ stripe masks and a mixed solution of $H_2SO_4$ and $H_3PO_4$. GaN layers were epitaxially grown on the PSS under the optimized 2-step growth condition of metalorganic vapor deposition. During the 1st growth step, GaN layers with triangular cross sections were grown on the selected area of the surface of the PSS, and in the 2nd growth step, the GaN layers were laterally grown and coalesced with neighboring GaN layers. The density of threading dislocations on the surface of the coalesced GaN layer was $2{\sim}4\;{\times}\;10^7\;cm^{-2}$ over the entire region. The epitaxial structure of near-UV light emitting diode (LED) was grown over the GaN layers on the PSS. The internal quantum efficiency and the extraction efficiency of the LED structure grown on the PSS were remarkably increased when compared to the conventional LED structure grown on the flat sapphire substrate. The reduction in TD density and the decrease in the number of times of total internal reflections of the light flux are mainly attributed due to high level of scattering on the PSS.

• 한국결정성장학회지
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• 제11권5호
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• pp.218-223
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• 2001

수평 Bridgman 방법으로 성장한 사파이어 인고트를 절단 연마한 후, 사파이어 결정기판의 표면을 우레탄 천 위에서 실리카 졸을 사용하여 폴리싱하였다. 표면의 결정성을 X-선 회절을 통하여 조사하였으며, 2중 결정회절에 의한 반치폭은 200~400 arcsec을 가지며, 결정 인고트의 절편화 또는 양면 연삭 연마에 따른 잔류응력에 의한 표면에서의 기계적인 스트레스에 의해 결정성이 손상되어진다. 화학-기계적인 폴리싱공정을 수행한 수에 표면처리로 $1,200^{\circ}C$로 4시간 열처리 및 산처리를 연속적으로 수행할 경우 결정성이 반치폭 8.3 arcsec까지 줄어들어 향상됨을 확인하였다.

• 한국재료학회:학술대회논문집
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• 한국재료학회 2009년도 춘계학술발표대회
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• pp.38.1-38.1
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• 2009

Plasma etching is an essential process for electronic device industries and the particulate contamination during plasma etching has been interested as a big issue for the yield of productivity. The oxynitride glasses have a merit to prevent particulate contamination due to their amorphous structure and plasma etching resistance. The YSiAlON oxynitride glasses with increasing nitrogen content were manufactured. Each oxynitride glasses were fluorine-plasma etched and their plasma etching rate and surface roughness were compared with reference materials such as sapphire, alumina and quartz. The reinforcement mechanism of plasma etching resistance of the YSiAlON glasses studied by depth profiling at plasma etched surface using electron spectroscopy for chemical analysis. The plasma etching rate decreased with nitrogen content and there was no selective etching at the plasma etched surface of the oxynitride glasses. The concentration of silicon was very low due to the generation of SiF4 very volatile byproduct and the concentration of aluminum and yttrium was relatively constant. The elimination of silicon atoms during plasma etching was reduced with increasing nitrogen content because the content of the nitrogen was constant. And besides, the concentration of oxygen was very low on the plasma etched surface. From the study, the plasma etching resistance of the glasses may be improved by the generation of nitrogen related structural groups and those are proved by chemical composition analysis at plasma etched surface of the YSiAlON oxynitride glasses.

• 한국결정성장학회지
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• 제11권3호
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• pp.106-111
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• 2001

The freestanding GaN substrates were grown by hydride vapor phase epitaxy (HVPE) on (0001) sapphire substrate and prepared by using laser induced lift-off. After a mechanical polishing on both Ga and N-surfaces of GaN films with 100$\mu\textrm{m}$ thick, their polarities have been investigated by using chemical etching in phosphoric acid solution, 3 dimensional surface profiler and Auger electron spectroscopy (AES). The composition of the GaN film measured by AES indicted that Ga and N terminated surfaces have the different N/Ga peak ratio of 0.74 and 0.97, respectively. Ga-face and N-face of GaN revealed quite different chemical properties: the polar surfaces corresponding to (0001) plane are resistant to a phosphoric acid etching whereas N-polar surfaces corresponding to(0001) are chemically active.