차세대 반도체 재료 SOI(Silicon On Insulator) Wafer

홍진균,이재춘 영남대학교 재료기술연구소 2000 재료기술연구 Vol.1 No.1

현대 마이크로 일렉트로닉스의 비약적인 발전은 그 기초 소재인 실리콘 웨이퍼의 획기적인 품질 향상을 요구하고 있으며, 이에 따라 실리콘 웨이퍼 제조업체는 새로운 개념의 차세대 웨이퍼 개발을 위한 활발한 연구개발 활동을 전개하고 있다. 차세대 실리콘 웨이퍼의 발전 방향은 크게 대구경화와 프로세스드 웨이퍼(proces sed wafer ) 개발로 요약할 수 있다. 실리콘 웨이퍼의 대구경화는 94년 세마테크 미팅합의에 의해 본격적으로 출발되었고 이미 각종 국제전시행사를 통해 여러 반도체 재료 업체에서 300mm실리콘 웨이퍼 샘플을 출시하고 있으며 이르면 2000년 초 양산에 돌입할 예정이다. 한발 더 나아가 일본 선진업체를 중심으로 한 SSI(Super Silicon Institute)에서는 400mm 실리콘 웨이퍼 개발을 위한 기초연구가 진행 중에 있다. 대구경 실리콘 웨이퍼가 기존의 개념과 기술의 연장성 상에 있다고 볼 때, 또다른 발전 방향인 프로세스드 웨이퍼 개발은 새로운 개념의 차세대 웨이퍼 도입이라 할 수 있으며 종류로는 에피텍셜 웨이퍼(epitaxial wafer ), 디퓨즈드 웨이퍼(diffused wafer ), SOI(silicon on insulator )웨이퍼 등이 있다. 여기에서는, 미래 정보화 시대의 멀티미디어 산업과 통신기기 산업의 대용량 기기에 필요한 저전력. 저전압 고속의 초고집적 메모리 제품을 만드는데 가장 적합한 SOI웨이퍼의 기술개발 현황에 대해 살펴 보고자 한다.

절삭공구의 현황과 제조기술 및 발전동향

이건우 영남대학교 재료기술연구소 2000 재료기술연구 Vol.1 No.1

1900년대초 F. W. T aylor와 M. White에 의해 고속도공구강이 개발되었고, 1926년에는 Krupp사에 의해 최초의 초경합금(Widia)이 상품화되었다. 이 두 가지의 절삭공구의 개발은 20세기 전반의 금속절삭 가공기술을 혁신적으로 진보시키는 밑거름이 되었다. 특히, 초경합금 절삭공구의 개발을 시작으로 T iCN-Ni계 서메트공구, Al₂O₃ 및 Si₃N₄계 세라믹공구, 코팅초경공구, PCD, CBN소결체공구^(1-3) ) 등이 개발되어 각각의 절삭공구는 자동차, 기계, 전기기기 등의 여러 산업분야에서 금속, 비금속의 절삭가공에 뛰어난 성능을 발휘함으로써 근대공업의 발전에 지대한 공헌을 해 왔다고 할 수 있다. 초경합금을 중심으로 한 이러한 절삭공구재료는 고경도, 고인성을 가짐으로써 내마모성이 뛰어날 뿐만 아니라 내결손성, 내열, 내식성이 우수하여 절삭공구를 비롯해 내마모, 내열, 내충격성 공구와 소재로 산업계 전반에서 현재까지 널리 사용되고 있으며 21세기에서도 이러한 용도상에서 재료의 큰 변화는 없으리라 예측된다. 여기서는 이러한 금속가공용 절삭공구의 주류를 이루는 초경합금(코팅초경합금)을 중심으로 서메트, 세라믹공구에 대해서 발전과정, 재종분류 및 특성, 제조기술 및 용도별 적용법 등을 살펴보고 최근의 각 절삭공구의 발전동향에 대해서도 언급하고자 한다.

Fe-C-Cr-Mo-V계 공구강의 미세조직과 건식 긁힘 마멸 거동 (마모재 : Al₂O₃)

백응률,최상호 영남대학교 재료기술연구소 2000 재료기술연구 Vol.1 No.1

High carbon- high chromium tool steels display a number of advantages in abr asive wear applications. They contain moderat e amounts of chromium that produces massive chromium- rich carbides in an austenitic matrix of sufficient hardenability to be transformed to martensit e with relatively simple heat treatment . In this study the role of vanadium- rich carbides with high hardness as well as chromium- rich carbides in improving abrasive wear resistance was investigat ed using a series of Fe- C- Cr -Mo- V system alloys with varying carbide volume fr action. The abr asive wear resistance of the alloys against Al₂O₃ harder than chromium- rich carbides but softer than vanadium- rich carbides was measured with a dry abrasive rubber wheel abr asion test. The abr asive wear resist ance was affected by a volume fraction and variety of carbide because of a differance of hardness between carbide and abrasive. As a result, The specimen with the most volume fraction of vanadium- rich carbide harder than Al2O3 had the mot excellent abrasive wear resistance.

M_(7)C₃형 크롬탄화물의 경도에 미치는 고용원소(V, Mo, Mn)의 영향

백응률,유국종,정재영,안상호 영남대학교 재료기술연구소 2000 재료기술연구 Vol.1 No.1

This study makes an investigation into the effect of dissolved alloy element (V,Mo,Mn) on hardness of the M_(7)C₃ type chromium carbide. Dis solved alloy element (V,Mo,Mn) content in M_(7)C₃ type chromium carbide was analyzed by EDS and micro- hardness of the M_(7)C₃ type chromium carbide was measured by micro- Vicker s hardness tester . Increasing to V, Mo content in specimen, result to increasing dissolved V, Mo content in M_(7)C₃ type chromium carbide. Also hardnes s of M_(7)C₃ type chromium carbide was increased. At this point , V added specimen was superior to Mo added specimen. According as Mn content in specimen increases , Mn cont ent in M_(7)C₃ type chromium carbide some increased but hardness in M_(7)C₃ type chromium carbide some decreased.

The Effect of Heating Conditions on the Characteristics of Hydroxyapatite Layer on Ti6Al4V Coated by Sol-Gel Process

You, Changkook,Oh, Sunho,Kim, Sukyoung 영남대학교 재료기술연구소 2000 재료기술연구 Vol.1 No.1

A transparent HA sol was prepared and coated on T i6Al4V substr ates by a spin- coating technique. T he crystallization of the HA coated on the metallic substrates could be done at relatively low firing temperatur es as low as 600 ℃. The characteristics of HA layer was dependent on the heating conditions such as firing temper ature, holding time, heating rat e and atmospher e. The cryst allinity of HA layer increased with increasing firing temperature up to 600 ℃ and longer heating time (10 hours ) at 600 ℃. T he surface morphology of the coated HA layer showed uniform and homogeneous microstructure with decreasing heating rate (about 2 ℃/min.) and incr easing firing time at 800 ℃. The heat - treatment at 800℃ over 4 hours in Ar atmospher e was found not to be effective with weakening of OH vibrational peak at 630 cm^(-1).

Relationship between Strength and Fracture Toughness in Ceramic Materials

Na, Sang Woong,Lee, Seung Whan,Jang, Joon Hyuk,Ryu, Jung Ho,Lee, Jaehyung 영남대학교 재료기술연구소 2000 재료기술연구 Vol.1 No.1

A fine- grained Mg- PSZ has been fabricated by adding SiC particles and by hot pressing. The average grain sizes of the Mg- PSZ added with carbide particles were as small as a few micrometers depending on the TiC content. The addition of TiC particles did not seem to affect the growth of tetragonal precipitates appreciably during annealing. With increasing TiC content , the bend strength increased while the fractur e toughness decreased. The bend strength and fractur e toughness of the fine- gr ained Mg- PSZ containing 5 vol% TiC were 1.0 GPa and 8.2 MPam respectively. For the Al2O3/ 30 vol% SiC particulate, the addition of SiC particles of 1 to 10 m improved the fracture toughness significantly. The fracture toughnes s of the composite cont aining 3 m SiC particles was 7.0 MPam at the cr ack length of 700 m. The high toughness and R- curve behaviors with these particulate composites are believed to be owing to mainly the crack bridging phenomena by the SiC particles. Larger SiC particles tended to give higher toughness and stronger R- curve behaviors but decreased the bend strength. Therefore, a compromise between the fr acture toughness and strength is necessary depending on the application for the design of fine- grained Mg- PSZ and the Al₂O₃/ SiC particulate composites.

Al₂O₃-TiO₂ 복합체의 기계적 및 열적 특성에 미치는 MgO의 첨가효과

박재성,이상욱,남효덕 영남대학교 재료기술연구소 2000 재료기술연구 Vol.1 No.1

Aluminum titanate(Al₂O₃TiO₂ ) was known to low thermal expansions over wide temperature ranges, but showed poor mechanical properties. The present studies have been concerned with the thermal and mechanical properties of aluminum titanate based on the ceramics containing MgO. The addition of MgO powder to Al₂O₃-TiO₂ inhibited the grain growth and this result can be increased sintering density and vickers hardnes s. The thermal expansion of Al₂TiO_(5) increased with the addition of MgO and also increased with temperature up to 1000℃, however, it decreased in the temperature range between 1000℃ and 1200℃ during heating. The test of thermal shock showed that the addition of 10 wt% MgO generated macrocrack of 25%.

중성자회절을 이용한 Nd₃Ba_(5)Co₄O_(15)상의 Rietveld 정산

송수호,이재열 영남대학교 재료기술연구소 2000 재료기술연구 Vol.1 No.1

The refined crystal structure of Nd₃Ba_(5)Co₄O_(15) by Rietveld analysis with X- ray diffraction data had been reported by us . But some parameters, such as oxygen thermal unisotropy had not refined due to accuracy of the electron scattering. In this study the crystal structure and magnetic properties of Nd₃Ba_(5)Co₄O_(15) have been investigated using Neutron diffraction powder data by means of Rietveld method. The starting model was based on the Nd₃Ba_(5)Co₄O_(15) structure. The crystal system was hexagonal, space group P6₃mc, a=11.6407(12), c= 6.8524(3). Final R values are : R_(wp)=0.171, R_(p) =0.153. This compound showed paramagnetic behavior in their magnetic susceptibility vs. temperature plots.

화학용액코팅법으로 제조한 Sr₂(Nb,Ta)₂O_(7) 박막의 결정화 및 강유전특성 연구

김창영,이희영 영남대학교 재료기술연구소 2000 재료기술연구 Vol.1 No.1

Recently, several research groups has started extensive research on Sr₂Nb₂O_(7) (SNO)- Sr₂Ta₂O_(7) (STO) binary solid solution. As it may be suitable for non- volatile memory devices such as ferroelectric gate field effect transistor . Ferroelectric Sr₂ (Nb1- xTax )₂O_(7) (SNT O) thin films were prepared by sol- gel process . Sol- gel derived stock solutions were spin- coated onto either Pt/ T i/ SiO₂/ Si(100) or Pt/T iO₂/ SiO₂/ Si(100) substrate. After multiple coating/ baking steps, dried films were annealed for crystallization and densification at 850℃ for 24hour s in flowing oxygen. Form IR and NMR analyses of stock solutions, it was revealed that acetic acid is most effective to stabilize solutions during solution preparation steps. From the study, it was found that the film remains ferroelectric regardless of x values, i.e. molra ratio between SNO and STO compounds. This is not in agreement with published single crystall data, where the cryst al with x values exceeding 0.88 is non- ferroelectric. This rather contradictory looking result may indicate the effect of residual stress in this films , which is often existent due to thermal expansion mismatch with underlying substrat e. Remanent polarization value, which si important for ferroelctric memory applications , was the highest when the x value of the film was 0.7. Leakage current and relative permittivity (εr ) values were typically about 10^(-8) ∼ 10^(-7)A/ ㎠, and 30 at 1MHz, respectively . Remanent polarization (2P_(r) ) and coercive field(E_(c) ) values of Sr₂ (Nb_(0.3)Ta_(0.7) )O_(7) film were 0.5 μC/ ㎠, and 17 kV/ ㎝, respectively, when ±3V triangular pulse was applied.

Laser Ablation 법에 의해 제조된 CuIn_(x)Ga_(1-x)Se₂ 박막의 특성

김민호,이상율,吉田明,김규호 영남대학교 재료기술연구소 2000 재료기술연구 Vol.1 No.1

The photovoltaic power system has received considerable attention as a petroleum- alternative energies to solve environmental problems in the worldwide scale. The energy gap of CuInSe₂ which attracts the considerable attention as absorber layer material of a thin film solar cell is 1.04eV, and it is smaller than 1.4∼1.5eV which is optimum range for the solar cell. In this study, CuInxGa_(1 - x) Se₂ thin film which added Ga to CuInSe₂ for the wide band gap was deposited by laser ablation method. And its composition , structure, optical- absorption coefficient and band gap were ex amined. Thin films equal to the composition of the targets were obtained, and lattice parameter of a and c axis linearly changed to 5.61∼5.76 and 11.09∼11.58Å respectively with the increase in x. The optical- absorption coefficient as all experimental range was over 2×10⁴cm^(- 1), and the band gap changed from 1.00 to 1.69eV with the decrease in the In content x.