• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 2009년도 제38회 동계학술대회 초록집
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• pp.180-180
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• 2010

Thin film transistors (TFTs) based on oxide semiconductors have emerged as a promising technology, particularly for active-matrix TFT-based backplanes. Currently, an amorphous oxide semiconductor, such as InGaZnO, has been adopted as the channel layer due to its higher electron mobility. However, accurate and repeatable control of this complex material in mass production is not easy. Therefore, simpler polycrystalline materials, such as ZnO and $SnO_2$, remain possible candidates as the channel layer. Inparticular, ZnO-based TFTs have attracted considerable attention, because of their superior properties that include wide bandgap (3.37eV), transparency, and high field effect mobility when compared with conventional amorphous silicon and polycrystalline silicon TFTs. There are some technical challenges to overcome to achieve manufacturability of ZnO-based TFTs. One of the problems, the stability of ZnO-based TFTs, is as yet unsolved since ZnO-based TFTs usually contain defects in the ZnO channel layer and deep level defects in the channel/dielectric interface that cause problems in device operation. The quality of the interface between the channel and dielectric plays a crucial role in transistor performance, and several insulators have been reported that reduce the number of defects in the channel and the interfacial charge trap defects. Additionally, ZnO TFTs using a high quality interface fabricated by a two step atomic layer deposition (ALD) process showed improvement in device performance In this study, we report the fabrication of high performance ZnO TFTs with a $Si_3N_4$ gate insulator treated using plasma. The interface treatment using electron cyclotron resonance (ECR) $O_2$ plasma improves the interface quality by lowering the interface trap density. This process can be easily adapted for industrial applications because the device structure and fabrication process in this paper are compatible with those of a-Si TFTs.

• Applied Chemistry for Engineering
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• 제8권3호
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• pp.395-402
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• 1997

The $SiO_2$ films were prepared by ECR(electron cyclotron resonance) plasma diffusion method, Deal-Grove model and Wolters-Zegers-van Duynhoven model were used to estimate the oxidation rate which was correlated with surface morphology for different orientation of Si(100) and Si(111). It was seen the $SiO_2$ thickness increased linearly with initial oxidation time. But oxidation rate slightly decrease with oxidation time. It was also shown that the oxidation process was controlled by the diffusion of the reactive species through the oxide layer rather than by the reaction rate at the oxide interface. The similar time dependency has been observed for thermal and plasma oxidation of silicon. From D-G model and W-Z model, the oxidation rate of Si(111) was 1.13 times greater than Si(100) because Si(111) had higher diffusion and reaction rate, these models more closely fits the experimental data. The $SiO_2$ surface roughness was found to be uniform at experimental conditions without etching although oxidation rate was increased, and to be nonuniform due to etching at experimental condition with higher microwave power and closer substrate distance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 한국전기전자재료학회 2008년도 하계학술대회 논문집 Vol.9
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• pp.169-169
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• 2008

To keep pace with scaling trends of CMOS technologies, high-k metal oxides are to be introduced. Due to their high permittivity, high-k materials can achieve the required capacitance with stacks of higher physical thickness to reduce the leakage current through the scaled gate oxide, which make it become much more promising materials to instead of $SiO_2$. As further studying on high-k, an understanding of the relation between the etch characteristics of high-k dielectric materials and plasma properties is required for the low damaged removal process to match standard processing procedure. There are some reports on the dry etching of different high-k materials in ICP and ECR plasma with various plasma parameters, such as different gas combinations ($Cl_2$, $Cl_2/BCl_3$, $Cl_2$/Ar, $SF_6$/Ar, and $CH_4/H_2$/Ar etc). Understanding of the complex behavior of particles at surfaces requires detailed knowledge of both macroscopic and microscopic processes that take place; also certain processes depend critically on temperature and gas pressure. The choice of $BCl_3$ as the chemically active gas results from the fact that it is widely used for the etching o the materials covered by the native oxides due to the effective extraction of oxygen in the form of $BCl_xO_y$ compounds. In this study, the surface reactions and the etch rate of $Al_2O_3$ films in $BCl_3/Cl_2$/Ar plasma were investigated in an inductively coupled plasma(ICP) reactor in terms of the gas mixing ratio, RF power, DC bias and chamber pressure. The variations of relative volume densities for the particles were measured with optical emission spectroscopy (OES). The surface imagination was measured by AFM and SEM. The chemical states of film was investigated using X-ray photoelectron spectroscopy (XPS), which confirmed the existence of nonvolatile etch byproducts.

• Journal of the Korean Vacuum Society
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• 제7권3호
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• pp.267-267
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• 1998

The fluorine doped silicon oxide (SiOF) intermetal dielectric (IMD) films have been of interest due to their lower dielectric constant and compatibility with existing process tools. However instability issues related to bond and increasing dielectric constant to water absorption when the SiOF films was exposured to atmospheric ambient. Therefore, the purpose of this research is to study the effect of post oxygen plasma treatment on the resistance of moisture absorption and reliability of SiOF film. Improvement of moisture absorption resistance of SiOF film is due to the forming of thin SiO₂layer at the SiOF film surface. It is thought that the main effect of the improvement of moisture absorption resistance was densification of the top layer and reduction in the number of Si-F bonds that tend to associate with OH bonds. However, the dielectric constant was increased when plasma treatment time is above 5 min. In this study, therefore, it is thought that the proper plasma treatment time is 3 min when plasma treatment condition is 700 W of microwave power, 3 mTorr of process pressure and 300℃ of substrate temperature.

• Korean Journal of Materials Research
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• 제7권11호
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• pp.969-973
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• 1997

저유전율 층간절연물질인 불소첨가 SiO$_{2}$박막을 ECR(electron cyclotron resonance) Plasma chemical vapor deposition 법으로 성막하였다. SiOF박막의 증착은 SiF$_{4}$/O$_{2}$의 가스유량비를 변수로하여 0.2에서 1.6까지 변화시켜 증착하였고, 이때 마이크로파 전력은 700W, 기판온도는 30$0^{\circ}C$에서 행하였다. 증착된 SiOF박막의 흡습특성을 알아보기 위하여 Fourier transformed infrared spectroscopy(FTIR)을 이용하여 분석한 결과, 가스유량비 (SiF$_{4}$O$_{2}$)가 0.2 에서 1.6으로 증가하였을 때 Si-Ostretching피크의 위치는 1072$cm^{-1}$ /에서 1088$cm^{-1}$ /로 증가하였으며, Si-F$_{2}$피크는 가스유량비가 1.0이상에서 나타나기 시작하였다. 또한 가스유량비가 0.2에서 0.8까지 변화하여 증착한 시편은 Si-OH 피크가 관찰되지 않았지만 가스유량비가 1.0이상(11.8at.% F함유)의 시편의 경우 Si-OH 피크가 관찰되어 내흡습성이 저하되고 있음을 확인할 수 있었다.

• 한국초전도학회:학술대회논문집
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• 한국초전도학회 2000년도 High Temperature Superconductivity Vol.X
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• pp.179-183
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• 2000

For a ground plane in high-temperature superconducting ramp-edge junction devices, YBa$_2$Cu$_3$O$_{7-{\delta}}$/SrTiO$_3$/YBa$_2$Cu$_3$O$_{7-{\delta}}$ multilayer structures were fabricated using pulsed laser deposition and ECR ion milling. Various process parameters were adjusted to enhance the device characteristics. By etching the STO layer to form a tapered edge of about 15$^{\circ}$ and in-situ RF plasma treatment of bottom YBCO surface prior to deposition of top YBCO, the top-to-bottom YBCO showed T$_c$ of 75${\sim}$80 K and I$_c$ of about 40 mA through holes. It was found that the deposition of bottom YBCO at a reduced laser repetition rate of 1Hz increased the T$_c$ of top YBCO to 79.9 K. The resistivity of 570 layer was about 10$^6$ ${\Omega}$cm at 60 K, which ensures good electrical isolation between successive YBCO layers.

• Journal of the Microelectronics and Packaging Society
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• 제11권2호
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• pp.29-35
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• 2004

Hafnium-oxide gate dielectric films deposited by a metal organic chemical vapor deposition technique on a $N_2-plasma$ treated SiNx and a hydrogen-terminated Si substrate have been investigated. In the case of $HfO_2$ film deposited on a hydrogen-terminated Si substrate, suppressed crystallization with effective carbon impurity reduction was obtained at $450^{\circ}C$. X-ray photoelectron spectroscopy indicated that the interface layer was Hf-silicate rather than phase separated Hf-silicide and silicon oxide structure. Capacitance-voltage measurements show equivalent oxide thickness of about 2.6nm for a 5.0 nm $HfO_2/Si$ single layer capacitor and of about 2.7 nm for a 5.7 nm $HfO_2/SiNx/Si$ stack capacitor. TEM shows that the interface of the stack capacitor is stable up to $900^{\circ}C$ for 30 sec.

• Proceedings of the Materials Research Society of Korea Conference
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.54.2-54.2
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• 2010

최근까지는 주로 비정질 실리콘이 디스플레이의 채널층으로 상용화 되어왔다. 비정질 실리콘 기반의 박막 트랜지스터는 제작의 경제성 및 균일성을 가지고 있어서 널리 상용화되고 있다. 하지만 비정질 실리콘의 구조적인 문제인 낮은 전자 이동도(< $1\;cm^2/Vs$)로 인하여 디스플레이의 대면적화에 부적합하며, 광학적으로 불투명한 특성을 갖기 때문에 차세대 디스플레이의 응용에 불리한 점이 있다. 이런 문제점의 대안으로 현재 국내외 여러 연구 그룹에서 산화물 기반의 반도체를 박막 트랜지스터의 채널층으로 사용하려는 연구가 진행중이다. 산화물 기반의 반도체는 밴드갭이 넓어서 광학적으로 투명하고, 상온에서 증착이 가능하며, 비정질 실리콘에 비해 월등히 우수한 이동도를 가짐으로 디스플레이의 대면적화에 유리하다. 특히 Zinc Oxide의 경우, band gap이 3.4eV로써, transparent conductors, varistors, surface acoustic waves, gas sensors, piezoelectric transducers 그리고 UV detectors 등의 많은 응용에 쓰이고 있다. 또한, a-Si TFTs에 비해 ZnO-based TFTs의 경우 우수한 소자 성능과 신뢰성을 나타내며, 대면적 제조시 우수한 균일성 및 낮은 생산비용이 장점이다. 그러나 ZnO-baesd TFTs의 경우 일정한 bias 아래에서 threshold voltage가 이동하는 문제점이 displays의 소자로 적용하는데 매우 중요하고 문제점으로 여겨진다. 특히 gate insulator와 channel layer사이의 interface에서의 defect에 의한 charge trapping이 이러한 문제점들을 야기한다고 보고되어진다. 본 연구에서는 Zinc Oxide 기반의 박막 트랜지스터를 DC magnetron sputtering을 이용하여 상온에서 제작을 하였다. 또한, $Si_3N_4$ 기판 위에 electron cyclotron resonance (ECR) $O_2$ plasma 처리와 plasma-enhanced chemical vapor deposition (PECVD)를 통하여 $SiO_2$ 를 10nm 증착을 하여 interface의 개선을 시도하였다. 그리고 TFTs 소자의 출력 특성 및 전이 특성을 평가를 하였고, 소자의 field effect mobility의 값이 향상을 하였다. 또한 Temperature, Bias Temperature stability의 조건에서 안정성을 평가를 하였다. 이러한 interface treatment는 안정성의 향상을 시킴으로써 대면적 디스플레의 적용에 비정질 실리콘을 대체할 유력한 물질이라고 생각된다.

• Korean Journal of Materials Research
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• 제10권6호
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• pp.450-455
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• 2000

For further scaling down of the silicon devices, the application of low dielectric constant materials instead of silicon oxide has been considered to reduce power consumption, crosstalk, and interconnection delay. In this paper, the effect of $O_2/SF_6$ plasma chemistry on the etching characteristics of polyimide-one of the promising low-k interlayer dielectrics-has been studied. The etch rate of polyimide decreases with the addition of $SF_6$ gas due to formation of nonvolatile fluorine compounds inhibiting reaction between oxygen and hydrocarbon polymer, while applying substrate bias enhances etching process through physical attack. However, addition of small amount of $SF_6$ is desirable for etching topography. $SiO_2$ hard mask for polyimide etching is effective under $O_2$plasma etching(selectivity~30), while $O_2/SF_6$ chemistry degrades etching selectivity down to 4. Based on the above results, $1-2\mu\textrm{m}$ L&S PI2610 patterns were successfully etched.

• Proceedings of the Korean Vacuum Society Conference
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• 한국진공학회 1999년도 제17회 학술발표회 논문개요집
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• pp.249-249
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• 1999

GaN과 같은 III-nitride 반도체 관한 식각 기술의 연구는 blue-emitting laser diode(LD)를 위한 경면(mirror facet)의 형성뿐만아니라 새로운 display 용도의 light emitting diodes (LED), 고온에서 작동되는 광전소자 제조 등에도 그 중요성이 증대되고 있다. 최근에는 III-nitride 물질의 높은 식각속도와 미려하고 수직한 식각형상을 이루기 위하여 ECR(Electron Cyclotron Resonance)이나 ICP(Inductively Coupled Plasma)와 같은 고밀도 플라즈마 식각과 CAIBE(Chemically assisted ion beam etching)를 이용한 연구가 진행되고 있다. 현재 제조되어 지고 있는 LED 및 LD와 같은 광소자의 구조의 대부분은 p-GaN/AlGaN/InGaN(Q.W)/AlGaN/n-GaN 와 같은 여러 층의 형태로 이루어져 있다. 이중 InGaN는 광소자나 전자소자의 특성에 영향을 주는 가장 중요한 부분으로써 현재까지 보고된 식각연구는 undoped GaN에 대부분 집중되고 있고 이에 비해 소자 특성에 핵심을 이루는 InGaN의 식각특성에 관한 연구는 미흡한 상황이다. 본 연구에서는 고밀도 플라즈마원인 ICP 장비를 이용하여 InGaN를 식각하였고, 식각에는 Cl2/CH4, Cl2/Ar 플라즈마를 사용하였다. InGaN의 식각특성에 영향을 미치는 플라즈마의 특성을 관찰하기 위하여 quadrupole mass spectrometry(QMS)와 optical emission spectroscopy(PES)를 사용하였다. 기판 온도는 5$0^{\circ}C$, 공정 압력은 5,Torr에서 30mTorr로 변화시켰고 inductive power는 200~800watt, bias voltage는 0~-200voltage로 변화시켰으며 식각마스크로는 SiO2를 patterning 하여 사용하였다. n-GaN, p-GaN 층 이외에 광소자 제조시 필수적인 InGaN 층을 100% Cl2로 식각한 경우에 InGaN의 식각속도가 GaN에 비해 매우 낮은 식각속도를 보였다. Cl2 gas에 소량의 CH4나 Ar gas를 첨가하는 경우와 공정압력을 감소시키는 경우 식각속도는 증가하였고, Cl2/10%Ar 플라즈마에서 공정 압력을 감소시키는 경우 식각속도는 증가하였고, Cl2/10%CHF3 와 Cl2/10%Ar 플라즈마에서 공정압력을 15mTorr로 감소시키는 경우 InGaN과 GaNrks의 선택적인 식각이 가능하였다. InGaN의 식각속도는 Cl2/Ar 플라즈마의 이온에 의한 Cl2/CHF3(CH4) 플라즈마에서의 CHx radical 형성에 의하여 증가하는 것으로 사료되어 진다.