• 대한전기학회:학술대회논문집
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• 대한전기학회 1994년도 하계학술대회 논문집 C
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• pp.1250-1253
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• 1994

(100), (110) and (111) Si wafers are etched by isotropic etching method, anisotropic etching method using KOH etchant and EPW etchant and combined two-step etching method to compare the results. Isotopic etching method is effective in fabrication of wedge-shaped tips, especially (110) Si. Anisotropic etching method of (100) Si using EPW etchant can fabricate sharp cone-shaped tips and isotropic etching after anisotropic etching of (100) Si can fabricate wedge-shaped tips.

• 전기화학회지
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• 제14권4호
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• pp.191-195
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• 2011

Wet chemical etching methods were utilized to conduct Si surface texturing, which could enhance photoelectrochemical hydrogen generation rate. Two different etching methods tested, which were anisotropic metal-catalyzed electroless etching and isotropic etching. The Si nano-texture that was fabricated by the anisotropic etching showed ~25% increase in photocurrent for H2 generation. The photocurrent enhancement was attributed to the reduced reflection loss at the nano-textured Si surface, which provided a layer of intermediate density between water and the Si substrate.

• 한국전기전자재료학회논문지
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• 제11권2호
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• pp.101-105
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• 1998

This paper describes anisotropic etching technology of highly doped polysilicon. The main etching gases are $Cl_2$ and $SiCl_4$ for reactive ion etching of polysilicon. The mixed $CHCl_3$ to main etching gas makes polymer on etching side wall, so it prevents side etching of polysilicon. The etch rate of polysilicon is increased with increasing RF power. But the etching rate is decreased as the flow rate of $CHCl_3$ is increased with fixed RF power. The etch selectivity of polysilicon and $SiO_2$ is about 12:1. And that of polysilicon and $Si_3N_4$ is about 19:1. In the main etching gas condition, the slope of polysilicon is same as that of photoresist. But in the mixed $CHCl_3$ condition, the slope of polysilicon is larger than that of photoresist. This represents that the polymer made on side wall by added $CHCl_3$ prevents side etching, so anisotropic etching can be possible by polymer.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 추계학술대회 논문집
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• pp.334-337
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• 1996

Si anisotropic etching is a key technology for micromachining. The main advantages of tetramethyl ammonium hydroxide (TMAH)-based solution are their full compatibility with IC process. In this work the anisotropic etching of single crystal Si in a TMAH (($CH_3$)$_4$NOH) based solution was studied. The influence of the addition of IPA to TMAH solution on their etching characteristics was also presented. The crystal planes bounding the etch front and their etch rates were determined as a function of temperature, crystal orientation, and etchant concentration. The etch rates of (100) oriented Si crystal planes decreased linearly with increasing the IPA concentration, The etched (100) planes were covered by Pyramidal-shaped hillocks below 15 wt.%, but very smooth surfaces were obtained above 20 wt.%. The addition of IPA to TMAH solution leads to smoother surfaces of sidewalls etched planes.

• E2M - 전기 전자와 첨단 소재
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• 제10권5호
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• pp.481-486
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• 1997

This paper describes the anisotropic etching characteristics of Si in acqueous TMAH/IPA solutions. The etch rates of (100) oriented Si crystal planes decrease with increasing TMAH concentration and IPA concentration. Etchant concentration and etch temperature have a large effect on hillock density. Hillock density strongly increase with lower TMAH concentration and higher etch temperature. The etched (100) planes are covered by pyramidal-shaped hillocks below TMAH 15 wt.%, but very smooth surface is obtained TMAH 25 wt.%. The addition of IPA to TMAH solution leads to smoother surfaces of sidewalls etched planes. Undercutting ratio of pure TMAH solution is much higher than KOH. But, addition of IPA to TMAh the underrcutting ratio reduces by a factor of 3∼4. Therefore, acqueous TMAH/IPA solution is able to use as anisotropic etchant of Si because of full compability with IC fabrication process.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 II
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• pp.1033-1036
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• 2003

In this paper, Si anisotropic etching characteristics of tetramethylammonium hydroxide (TMAH)/ ammonium persulfate (AP) solutions were investigated to realize the optimum structure of a diaphragm for the piezoresistive pressure sensor application. Due to its low toxicity and its high compatibility with the CMOS processing, TMAH was used as Si anisotropic etchants. The variations of Si etch rate on the etching temperature, TMAH concentration, and etching time were obtained. With increasing the etching temperature and decreasing TMAH concentrations, the Si etch rate is increased while a significant non-uniformity exists on the etched surface because of formation of hillocks on the <100> surface. With the addition of AP to TMAH solution, the Si etch rate is increased and an improvement in flatness on the etching front is observed. The Si etch rate is also maximized with increasing the number of addition of AP to TMAH solution per one hour. The Si square diaphragms of 20${\mu}{\textrm}{m}$ thickness and 100~400${\mu}{\textrm}{m}$ one-side length were fabricated successfully by applying optimum Si etching conditions of TMAH/AP solutions.

• 반도체디스플레이기술학회지
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• 제2권4호
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• pp.19-22
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• 2003

In this paper, Si anisotropic etching characteristics of tetramethylammonium hydroxide (TMAH)/ammonium persulfate (AP) solutions were investigated to realize the optimum structure of a diaphragm for the piezoresistive pressure sensor application. Due to its low toxicity and its high compatibility with the CMOS processing, TMAH was used as Si anisotropic etchants. The variations of Si etch rate on the etching temperature, TMAH concentration, and etching time were obtained. With increasing the etching temperature and decreasing TMAH concentrations, the Si etch rate is increased while a significant non-uniformity exists on the etched surface because of formation of hillocks on the <100> surface. With the addition of AP to TMAH solution, the Si etch rate is increased and an improvement in flatness on the etching front is observed. The Si etch rate is also maximized with increasing the number of addition of AP to TMAH solution per one hour. The Si square diaphragms of 20$\mu\textrm{m}$ thickness and 100-400 $\mu\textrm{m}$ one-side length were fabricated successfully by adding AP of (5/6)g to 800 ml TMAH solution every 10 minutes.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 C
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• pp.1974-1976
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• 1996

An electrostatically driven comb actuator with $525{\mu}m$ height was fabricated using (110) Si anisotropic etching in the Potassium Hydroxide(KOH) solution. The etch-rate and etch-rate ratio are strongly dependent on the weight % and temperature of KOH solution. We developed the optimal condition for the anisotropic etching on (110) wafer with varying these conditions. The force that the comb-drive actuator generates is inversely proportional to the distance of gap and proportional to the height of the comb electrodes. The electrodes must have the high aspect ratio. The (110) Si anisotropic etching is very useful to get a high aspect ratio structure.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1997년도 춘계학술대회 논문집
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• pp.23-26
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• 1997

This work presents the TMAH/IPA anisotropic etching characteristics with addition of Pyrazine. (100) Si etching rate of 0.747 ${\mu}{\textrm}{m}$/min at 8$0^{\circ}C$ was obtained using TMAH 25 wt.% / IPA 17 vol.% / pyrazine 0.1 g. The etching rate of (100) Si is increased about 52% compare to pure TMAH 25 wt.%. But etching rate of (100) Si is decreased with increasing Pyrazine additive. Activation energy of TMAH/IPA/pyrazine is much lower than TMAH and TMAH/IPA solutions. Addition of Pyrazine does not effect on surface flatness and decreases undercutting ratio about 20 %. Therefore, TMAH/IPA/pyrazine is an attractive anisotropic etchant because of alkaline-ion free.

• 전기화학회지
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• 제16권1호
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• pp.1-8
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• 2013

본 총설에서는 Si 비등방성 식각(anisotropic etching) 공정인 metal-assisted chemical etching(MAC etch 혹은 MACE) 분야 기본 원리, 중요 변수, 그리고 최근 연구 성과들을 정리하였다. 1990년에 최초로 Si 표면에 금속 촉매를 증착한 후 $H_2O_2$/HF 기반 식각을 진행하면 용액 중에서도 비등방성 식각을 통해 다양한 고종횡비(high aspect ratio) 나노구조를 형성할 수 있다는 것이 밝혀 졌다. 고가의 진공기반 장비가 필요한 건식 식각에 비해, 습식 식각을 통해서도 상대적으로 간편하고 경제적으로 종횡비가 큰 Si 마이크로/나노 구조를 만들 수 있게 되었다. 초기 연구들을 통해 MAC etch중 산화제가 촉매에 의해 환원되고, 촉매/Si 계면 근처의 Si 원자들이 선택적으로 식각/용해되어 수직 방향으로 촉매가 Si 기판을 파고 들어가며 비등방성 식각이 발생함이 밝혀졌다. MAC etch에 영향을 미치는 중요 변수로는 금속 촉매의 종류 및 모양, 식각액의 조성, Si기판의 도핑 농도이다. 또한 본 총설은 MAC etch에 의해 형성된 Si 나노 구조를 이용한 태양전지, 수소 연료, 리튬 이온 전지 등의 응용 분야를 다루었다.