• 한국결정성장학회지
• /
• 제27권3호
• /
• pp.143-147
• /
• 2017

PVT법으로 성장된 AlN 단결정의 표면 특성 및 결정성을 신뢰성 있게 평가하기 위해 $KOH/H_2O_2$ 혼합액을 이용한 화학적 습식 에칭을 통하여 AlN 단결정의 결함을 분석하였고, 고온 어닐링 공정을 통해 단결정의 결정성 변화를 관찰하였다. $300^{\circ}C$ 이상의 고온에서 강 염기성의 etchant를 사용하는 기존 에칭 방법에서는 재료의 결정성에 따라 쉽게 over etching이 일어난다. Over etching이 일어날 경우 면적당 정확한 에치 핏의 개수를 알 수 없기 때문에 전위 밀도의 신뢰성이 매우 떨어진다. 따라서 이러한 단점을 보완하기 위해 KOH 수용액에 $H_2O_2$를 산화제로 사용하여 $100^{\circ}C$ 이하의 저온에서 에칭을 성공하였으며, 주사전자현미경(SEM, scanning electron microscope)을 통해 에치 핏을 관찰하여 최적 에칭 조건 및 전위 밀도를 확인할 수 있었다. 또한, 성장된 AlN 단결정에 고온 어닐링 공정을 적용한 후, DC-XRD(double crystal X-ray diffraction)를 이용하여 결정성을 평가한 결과, 고온 어닐링 공정 후 FWHM(full with at half maximum) 값이 급격히 감소되는 것을 확인하였으며 이에 대한 메커니즘을 분석하였다.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2012년도 제43회 하계 정기 학술대회 초록집
• /
• pp.319-320
• /
• 2012

Large aperture optical modulator called optical shutter is a key component to realize time-of-flight (TOF) based three dimensional (3D) imaging systems [1-2]. The transmission type electro-absorption modulator (EAM) is a prime candidate for 3D imaging systems due to its advantages such as small size, high modulation performance [3], and ease of forming two dimensional (2D) array over large area [4]. In order to use the EAM for 3D imaging systems, it is crucial to remove GaAs substrate over large area so as to obtain high uniformity modulation performance at 850 nm. In this study, we propose and experimentally demonstrate techniques for backside etching of GaAs substrate over a large area having high uniformity. Various methods such as lapping and polishing, dry etching for anisotropic etching, and wet etching ([20%] C6H8O7 : H2O2 = 5:1) for high selectivity backside etching [5] are employed. A high transmittance of 80% over the large aperture area ($5{\times}5mm^2$) can be obtained with good uniformity through optimized backside etching method. These results reveal that the proposed methods for backside etching can etch the substrate over a large area with high uniformity, and the EAM fabricated by using backside etching method is an excellent candidate as optical shutter for 3D imaging systems.

• 한국전기전자재료학회논문지
• /
• 제29권8호
• /
• pp.455-460
• /
• 2016

A textured front surface is required in high efficiency silicon solar cells to reduce reflectance and to improve light trapping. Wet etching with alkaline solution is usually applied for mono crystalline silicon solar cells. However, alkali texturing method is not appropriate for multi-crystalline silicon wafers due to grain boundary of random crystallographic orientation. Accordingly, acid texturing method is generally used for multi-crystalline silicon wafers to reduce the surface reflectance. To reduce reflectivity of multi-crystalline silicon wafers, double texturing method with combination of acid and reactive ion etching is an attractive technical solution. In this paper, we have studied to optimize RIE condition by different RF power condition (100, 150, 200, 250, 300 W).

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 하계학술대회 논문집
• /
• pp.644-647
• /
• 2001

Amorphous As-Ge-Se-S thin films have been studied with the aim of identifying optimum etching condition which can be used to produce holographic grating structure for use as diffractive optical elements. In this study, holographic gratings have been formed using He-Ne laser(632.8nm), and fabricated by the method of wet etching using NaOH etchant with various concentration(0.26N, 0.33N, 0.40N). The diffraction efficiency was obtained by +1st order intensity of the diffracted beam. The formed grating profiles were observed by atomic force microscope and showed that the expected grating profile could be achieved by controlling the etching time. Over-etching resulted in under-cutting of the grating lines. The highest 1st order diffraction efficiency for these gratings was about 5.05%.

• 반도체디스플레이기술학회지
• /
• 제8권1호
• /
• pp.1-5
• /
• 2009

Typically, single-wafer wet etching is done by dispensing chemical onto the front and back side of spin wafer. The wafer is fixed by a number of chuck pins, which obstruct the chemical flow and would result in the incomplete removal of the remaining film, which can become a source of contamination in the next process. In this paper, we introduce a novel design of wafer chuck, in which chuck pins are groupped into two and each group of pins fixes the substrate alternatively. Two groups of chuck pins fix the high-speed spin substrate with non contact method using a magnetic material. The actual process has been executed to observe the effectiveness of this new wafer chuck. It was found that the new wafer chuck performed better than the conventional wafer chuck for removing the remaining film from the bevel and edge side of substrate.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2016년도 제50회 동계 정기학술대회 초록집
• /
• pp.419-419
• /
• 2016

High efficiency silicon solar cell requires the textured front surface to reduce reflectance and to improve the light trapping. In case of mono-crystalline silicon solar cell, wet etching with alkaline solution is widespread. However, the alkali texturing methods are ineffective in case of multi-crystalline silicon wafer due to grain boundary of random crystallographic orientation. The acid texturing method is generally used in multi-crystalline silicon wafer to reduce the surface reflectance. However the acid textured solar cell gives low short-circuit current due to high reflectivity while it improves the open-circuit voltage. To reduce the reflectivity of multi-crystalline silicon wafer, double texturing method with combination of acid and reactive ion etching is an attractive technical solution. In this paper, we have studied to optimize RIE experimental condition with change of RF power (100W, 150W, 200W, 250W, 300W). During experiment, the gas ratio of SF6 and O2 was fixed as 30:10.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 1999년도 춘계학술대회 논문집
• /
• pp.497-500
• /
• 1999

This paper reports on the fabrication and characteristics of recessed gate GaN MESFETs fabricated using a photoelectrochemical wet etching method. The unique etching process utilizes photo-resistive mask and KOH based etchant. GaN MESFETs with successfully recessed gate structure was characterized in terms of dc and RF performance. The fabricated GaN MESFET exhibits a current saturation at $V_{DS}$ = 4 V and a pinch-off at $V_{GS}$ =-3V The peak drain current of the device is about 230mA/mm at 300 K and the value is remained almost same for 500K operation. The $f_{T}$ and $f_{max}$ from the device are 6.357Hz and 10.25 GHz, respectively.y.y.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 2004년도 추계학술대회 논문집 전기물성,응용부문
• /
• pp.268-270
• /
• 2004

This paper reports a novel masking method with various mask materials for wet etching of glass. Various mask materials such as Cr/Au, Ti/Au, Polyimide and thick SU-8 photoresist were investigated for borosilicate glass (Borofloat33) etching in concentrated hydrofluoric acid (48% HF). Polyimide and thick SU-8 photoresist are not suitable as masking material due to its poor adhesion to glass surfaces. Titanium has good adhesion is suitable as the first layer to make multi-protective layers. The best protection was obtained with a combination of Ti/Au, polyimide and Ti/Au as masking material with etch depth of $350{\mu}m$ achieved.

• 센서학회지
• /
• 제25권4호
• /
• pp.275-279
• /
• 2016

Chemical vapor deposited (CVD) polycrystalline graphene is widely used for various sensor application because of its extremely large surface-to-volume ratio. The electrical properties of CVD-graphene is significantly affected by the grain size and boundaries (GGBs), but evaluation of GGB of continuous monolayer graphene is difficult. Although several evaluation methods such as tunneling electron microscopy, confocal Raman, UV/ozone-oxidation are typically used, they still have issues in evaluation efficiency and accuracy. In this paper, we suggest an improved evaluation method for precise and simple GGB evaluation which is based on UV/ozone-oxidation and chemical etching process. Using this method, we could observe clear GGBs of CVD-graphene layers grown by different process conditions and statistically evaluate average grain sizes varying from $1.69{\sim}4.43{\mu}m$. This evaluation method can be used for analyzing the correlation between the electrical properties and grain size of CVD-graphene, which is essential for the development of graphene-based sensor devices.

• 한국레이저가공학회지
• /
• 제11권1호
• /
• pp.7-11
• /
• 2008

Decapsulation technology is useful to inspect EMC of package device and the etching technology enable to check inside of device by removing plastic molding. Chemical etching method is used widely to fabricate a lot of semiconductor. But the method has some disadvantage due to wet process. Proposed method in this paper shows the application possibility such as fast processing time, processing accuracy and dry process. These result was obtained by directly removing of packed EMC using UV laser.