Won-Chul Moon

AFM fabrication of oxide patterns and immobilization of biomolecules on Si surface

A novel method of protein patterning based on anodic oxidation of Si surface by atomic force microscope (AFM) is presented. An oxide pattern is drawn on the Si surface by applying d.c. voltage between the Au-coated AFM tip and the Si substrate. The oxide patterns can be used as a template for patterning of biomolecules. Protocols for both positive and negative patterning of protein were established.

Nanotribology of Si oxide layers on Si by atomic force microscopy.

Atomic force microscopy (AFM) has been used for tribological studies of Si surfaces covered by oxide layers of various kinds: chemical oxides prepared by the SC1 (NH4OH/H2O2/H2O) and the SC2 (HCl/H2O2/H2O) treatments and a thermal oxide. In the case of the SC1 chemical oxide, the oxide layer was scratched and the underlying Si substrate was ploughed by the Si3N4 AFM tip. On the other hand, no wear of the sample was noted on the other surfaces: the AFM often produced elevated patterns in the shape of the scanned area, which were no longer visible after HF etching. By annealing the SC1-treated surface in N2 gas at above 200 degrees C for 30 min, the oxide layer could not be scratched any more. By soaking the thermal oxide in KOH, the oxide layer was then scratched. It is concluded that the presence of OH bases is the necessary condition for the nano-scratching of the oxide layers.

Enhanced Nano-Oxidation on a SC1-Treated Si Surface Using Atomic Force Microscopy.

We studied the effects of hydrophilicity of Si surfaces on nanometer-scale anodic oxidation with atomic force microscopy (AFM). We found that nano-oxidation is greatly enhanced on a SC1-treated Si (111) surface, which is hydrophilic, compared with that on a hydrophobic HF-treated surface: the average height (average width) of the oxide line was 4.8 nm (550 nm) for the former surface and 1.9 nm (340 nm) for the latter one, for a bias voltage of 18 V and a scan rate of 2.3 µm/s. The enhanced nano-oxidation was reverted when the SC1-treated Si surface was modified with chlorotrimethylsilane.

Nanotribology of Clean and Oxide-Covered Silicon Surfaces Using Atomic Force Microscopy.

Atomic force microscopy (AFM) has been used for tribological studies of silicon surfaces both with and without an oxide layer on the surface. Three different types of surfaces were prepared: a silicon surface with a chemical oxide made by the SC1 process, a silicon surface with a thermal oxide, and a H-terminated silicon surface without an oxide layer. Only in the case of the chemical oxide, scratching of the oxide and ploughing of the silicon by the Si3N4 AFM tip were observed. On the other hand, no wear of the sample was noted on the other surfaces. On these surfaces, the AFM often produced elevated patterns in the shape of the scanned area, which were no longer visible after HF etching. The difference between the tribological behavior of the chemical-oxide-covered surface and that of the other surfaces is discussed in relation to the presence of hydroxyl groups in the oxide layer.

Flip-chip Bonding Technology and Reliability of Electronic Packaging

IT (Information Technology) 산업의 급속한 발전과 새로운 서비스 요구로 인해, 최근 반도체는 무게와 크기 측면에서 기존 반도체에 비해 더욱 작고 가벼운 방향으 로 진화하고 있으며, 다양한 데이터의 처리 및 멀티미디 어 기능을 구현하기 위해 한 개의 패키지 내에 복수의 소자 또는 칩을 통합시키는 새로운 방식의 반도체 패키 징 기술의 수요가 증가되고 있다. 특히, 크기와 무게가 작은 패키지를 요구하는 휴대용 통신기기 및 멀티미디 어 기기 시장의 급격한 증가는 고집적의 새로운 반도체 패키지 기술의 수요가 비약적으로 증가될 것임을 보여 준다. 전자.정보통신 산업이 이렇게 발전함에 따라 카메라, 게임기, 전화, PDA (Personal Digital Assistants) 등과 같은 멀티미디어 시스템 전자 제품들이 휴대전화로 빠 르게 융합화 되고 있다 (Fig. 1참조). 이러한 전자 제품 의 진화에 따라 빠른 신호처리가 가능한 고성능 반도체 칩의 개발 및 칩과 칩 또는 칩과 다른 주변 장치들간의 상호 신호전달을 위한 전자패키징 (electronic packaging) 기술의 발전 또한 요구되고 있다. 특히, 전 자 및 반도체 패키징 분야에 있어서 재료, 부품, 기판 및 모듈 (module)의 고성능화 (high performance), 고집적 화 (high density integration), 다기능화 (multi functionality) 및 소형화 (miniaturization)에 대한 요구 가 점차 증대되고 있다. 기술적인 측면에서 90년대 중반 까지의 패키징은 칩의 물리적인 보호와 보드와 칩 간의 전기적 연결을 제공하는 것이 중요한 문제였으나, 최근 들어 칩의 고성능화뿐만 아니라 다기능화와 칩 성능의 최적화, 발열처리 문제 등에서 패키징의 역할이 더욱 중 요해지고 있다. 최종 시스템에서 패키지의 역할은 IC 칩들이 동작할 수 있도록 파워 (power)와 시그널 (signal)을 전달하며 다른 시스템과 전기적 연결이 가능 하도록 채널을 공급하여 인터패이싱 (interfacing)이 가 능하도록 하는 동시에, 전체 시스템을 물리적으로 보호 하여 신뢰성을 보장하는 역할을 수행한다. 최근 전자 제 품의 성능은 칩 자체보다는 패키징 구조에 의한 신호지 연에 의해 결정되고 있으며, 전체 신호지연의 약 50% 가량을 차지하고 있다. 따라서 패키징 기술 개발의 발전 이 점차 중요한 문제로 대두되고 있으며, 이를 개선하기 위해서 많은 연구들이 진행되고 있다. 본 고에서는 최신 마이크로 시스템 패키징 분야에서 주목받고 있는 플립칩 (Flip-chip) 본딩의 기술 및 종류, 접착제를 이용한 플립칩 본딩, 초음파를 이용한 플립칩 본딩, 플립칩 패키지의 일렉트로마이그레이션 (electromigration) 현 상, 3차원 실장 (3 Dimensional Packaging) 기술 및 금주석 (Au-Sn) 솔더를 이용한 패키징기술에 대해서 간 략히 소개하고자 한다.

Lift-off patterning of thin Au films on Si surfaces with atomic force microscopy

We studied a new lift-off process of thin Au film on silicon surfaces in nanometer-scale, combining anodic oxidation patterning with AFM, deposition of Au thin film on the patterned substrate and chemical etching processes of the Si oxide underneath the Au film. For Au films of thickness of 2-5 nm, the Au films on the Si oxide patterns were left unbroken and bent down to stick to Si surface after the removal of the oxide by the chemical etching. For an Au film of 1 nm in thickness, it was possible to lift-off the Au film on oxide patterns of the lines and dots in nanometer-scale using Si oxide as a sacrificial mask.

Patterned surface as a template for DNA-based nanotechnology

A novel method of DNA patterning on silicon surface based on atomic force microscopy (AFM) is presented. This method is based on the AFM anodic oxidation technique, which has the ability to make nano-level oxide patterns on the silicon surface. The oxide patterns drawn by the AFM anodic oxidation is used as a template for nano-patterning of biomolecules such as protein and DNA. We describe the protocols and preliminary results of experiments and discusses its applicability to DNA-based nanotechnology armed with DNA computation method.