• 대한기계학회논문집A
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• 제28권12호
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• pp.1937-1941
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• 2004

We present lateral actuated piezoelectric actuator using U-shaped PZT strip and lever structure for the RF switch application. In the previous study of RF switch, they used horizontal contact switch fabricated by thin film metals. However, thin film metals could not generate large contact force due to low stiffness. In this work, we suggest lateral contact switch which makes large contact force by increasing stiffness. In addition, we use PZT actuator for the high force actuation. Generally actuator using thin film PZT moves to the vertical direction due to the neutral axis shift. Therefore we need lateral motion generation mechanism based on the thin film PZT actuator. In order to increase lateral motion of thin film PZT actuator, we use U-shaped PZT actuator using residual stress control. Also, thin film PZT actuator can generate very small lateral motion of 120${\times}$10$^{-6}$ ${\mu}{\textrm}{m}$/V for d$_{31}$ mode, thus we suggest lever structure to increase stroke amplification. From the experimental study, fabricated PZT actuator shows maximum lateral displacement of 1 ${\mu}{\textrm}{m}$, and break down voltage of the thin film PZT actuator is above 16V.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2004년도 춘계학술대회
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• pp.252-257
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• 2004

Nanometer-sized structures are being applied to many devices including micro/nano electronics, optoelectronics, quantum devices, MEMS/NEMS, biosensors, etc. Especially, the thin film with submicron thickness is a basic structure for fabricating these devices, but its mechanical behaviors are not well understood. The mechanical properties of the thin film are different from those of the bulk structure and are difficult to measure because of its handling inconvenience. Several techniques have been applied to mechanical characterization of the thin film, such as nanoindentation test, micro/nano tensile test, strip bending test, etc. In this study, we focus on the strip bending test because of its high accuracy and moderate specimen preparation efforts, and measure Au thin film, which is a very popular material in micro/nano electronic devices. Au film is deposited on Si substrate by evaporation process, of which thickness is 100nm. Using the strip bending test, we obtain elastic modulus, yield and ultimate tensile strength, and residual stress of Au thin film.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2013년도 춘계학술대회 논문집
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• pp.454-459
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• 2013

For the purpose of rapid development and superior design quality assurance, sophisticated finite element model for SOM(Spatial Optical Modulator) piezo actuator of MOEMS device has been developed and evaluated for the accuracy of dynamics and residual stress analysis. Parametric finite element model is constructed using ANSYS APDL language to increase the design and analysis performance. Geometric dimensions, mechanical material properties for each thin film layer are input parameters of FE model and residual stresses in all thin film layers are simulated by thermal expansion method with psedu process temperature. $6^{th}$ mask design samples are manufactured and $1^{st}$ natural frequency and 10V PZT driving displacement are measured with LDV. The results of experiment are compared with those of the simulation and validate the good agreement in $1^{st}$ natural frequency within 5% error. But large error over 30% occurred in 10V PZT driving displacement because of insufficient PZT constant $d_{31}$ measurement technology.

• 전기화학회지
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• 제9권4호
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• pp.141-150
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• 2006

도금용액 내 텅스텐 이온 농도, 전류밀도, 도금용액 pH의 변화가 CoW 박막/후막의 화학조성, 전류효율, 잔류응력, 표면형상, 미세결정 구조, 결정립 크기에 미치는 영향을 조사하기 위하여, citrate 도금용액으로부터 전기도금공정에 의해 나노결정립 CoW 박막/후막 합금을 제조하였다. CoW 박막/후막에서 전기도금된 텅스텐 함량은 도금용액내의 텅스텐 이온 농도, 전류밀도, pH를 증가시킴에 따라 증가하였다. CoW 박막/후막에서 잔류응력은 도금용액내의 텅스텐 이온 농도와 pH를 증가시킴에 따라 감소함을 관찰하였다. CoW 박막/후막은 0.02M로부터 0.08M 범위의 텅스텐 이온 농도에서 hcp Co [(100), (002)]와 hop $Co_3W$ [(002), (201)] 혼합된 상들을 나타내었다. 그러나 0.1 M로부터 0.2M 범위의 텅스텐 이온 농도에서는 비정질에 가까운 상들을 나타내었다. 5, 10, 25, $100mA{\cdot}cm^{-2}$의 전류밀도에서 CoW 박막/후막은 hop Co (002)와 hcp $Co_3W$ [(200), (002), (201)] 상들로 구성되어 있다 그러나 50과 $75mA{\cdot}cm^{-2}$의 전류밀도에서는 비정질에 가까운 상들을 나타내었다. 8.7의 도금용액 pH에서 CoW 박막/후막은 hcp Co (002)와 hcp $Co_3W$ [(200), (002), (201)]상들을 나타내었다. 그러나 8.7 이하위 도금용액 pH 에서는 비정질에 가까운 상을 나타내었다. CoW 박막/후막의 최적 전기도금조건은 0.08M의 텅스텐 이온농도, $10mA{\cdot}cm^{-2}$ 전류밀도, 8.7의 도금용액 pH로 관찰되었다.

• 마이크로전자및패키징학회지
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• 제8권3호
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• pp.19-24
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• 2001

반도체 패키지에 사용되는 주요 재료인 리드프레임은 반도체 제품의 소형화, 박형화, 고집적 화에 대응하기 위해서 리드 및 피치의 미세화가 요구되며 제조 과정에서 발생되는 버(burr)의 제거와 잔류응력 제거에 대한 노력이 필요하다. 본 논문은 리드프레임의 제작 시 스탬핑 공정 중에 발생하는 버와 잔류응력을 제거하기 위해 전해연마를 적용하였다. 전해연마를 적용한 리드프레임은 표면의 버 등이 제거되었으며, 잔류음력은 실험에 사용된 전해액의 종류에 따라 차이가 있으나, 과염소산계의 경우에는 잔류응력을 23%제거하여 리드프레임의 신뢰성을 높일 수 있었다.

• The Korean Journal of Ceramics
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• 제6권4호
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• pp.385-389
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• 2000

Residual stresses in epitaxial films were measured by X-ray diffraction method. Lattice strains of the (hkl) planes measured along particular Ψ-angles were converted to the in-plane stress according to the equation of stress-strain tensor conversion. Residual tensile stresses were observed in epitaxial PbTiO$_3$ films deposited on (100) SrTiO$_3$ substrate. Tensile stresses approximately 0.9 GPa were measured in Pb-rich films, while it increased to approximately 2.0 GPa with the decreasing of Pb content in the case of Pb-poor films, which ascribed to the formation of lead and oxygen vacancies (expressed as x in Pb$_1-x$TiO$_3-x$).

• JSTS:Journal of Semiconductor Technology and Science
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• 제5권1호
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• pp.38-44
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• 2005

Pyrolyzed polyimide is explored in terms of MEMS material. This paper describes chemical, electrical, mechanical properties of pyrolyzed polyimide (PIX-1400) thin film as MEMS material. When polyimide thin film was pyrolyzed at $800^{\circ}C$ for 60 minutes in $N_{2}$ ambient, the residual ratio of pyrolyzed film thickness measured with a surface profiler is about 49 %, and the resistivity is about $2.17{\times}10^{-2}\;{Omega}cm$. From the result of the load-deflection test, the estimated Young's modulus and initial average stress of pyrolyzed polyimide are 67 GPa and 30 MPa, respectively. As one demonstration of MEMS structures of pyrolyzed polyimide, the fabrication method of the microbridge structure is proposed for a micro heater and a resonator.

• 한국세라믹학회지
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• 제33권9호
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• pp.969-976
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• 1996

RuO2 thin films were deposited on SiO2(1000 $\AA$)/Si by hot-wall Metal Organic Chemical Vapor Depositon. The crystallinity of RuO2 thin films increased with increasing deposition temperature and the preferred orienta-tion of RuO2 films converted (200) plane to (101) plane with increasing film thicknesses. Such a change in preferred orientation was influenced on the crystallographic structure and the residual stress of RuO2 thin films. The resistivity of the 2700$\AA$-thick RuO2 thin films deposted at 30$0^{\circ}C$ was 52.7$\mu$$\Omega$-cm and they could be applicable to bottom electrodes of high dielectric materials. However the resistivity of RuO2 thin films increased with decreasing film thicknesses. The grain size and the resistivity of RuO2 thin films were densified with increasing the annealing temperature and showed the decrease of resistivity.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1996년도 춘계학술대회 논문집
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• pp.220-223
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• 1996

Mechanical properties of Plasma-Enhanced Chemical Vapor Deposited (PECVD) silicon nitride thin film was studied to determine the feasibility of the film as a passivation layer over the aluminum bonding areas of integrated circuit chips. Ultimate strain of the films in thicknesses of about 5 k${\AA}$ was measured using four-point bending method. The ultimate strain of these films was constant at about 0.2% regardless of residual stress. Intrinsic and residual stresses of these films were measured and compared with thermal shock and cycling test results. Comparison of the results showed that more tensile films were more susceptible to crack- induced failure.

• 공업화학
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• 제10권7호
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• pp.1014-1019
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• 1999

Dianhydride로서 1,2,4,5-benzenetetracarboxylic dianhydried(PMDA)와 2,2'-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride(6FDA)를, diamine으로서 1,4-phenylenediamine(PDA)을 사용하여 homopolyimides인 PMDA-PDA, 6FDA-PDA와 다른 당량비의 copolyimides를 각각의 ploy(amic acid)로부터 제조하였다. 이들 박막에 대하여, thin film stress analyzer(TFSA)를 이용하여 공중합체 폴리이미드 박막의 잔류 응력거동을 공정온도 ($25{\sim}400^{\circ}C$)하에서 전구체의 열적 이미드화에 따라 in-situ로 측정하였고, WAXD분석을 통해 모폴로지 변화를 알아보았다. 다른 단량비로 이루어진 공중합체 폴리이미드 박막의 잔류 응력 결과는 PMDA 분율이 증가함에 따라 잔류 응력이 큰 폭으로 감소하였고 순수 PMDA-PDA 폴리이미드에서는 압축모드로 5 MPa로 나타났다. 본 연구에서는 PMDA-PDA의 높은 $T_g$로 인한 공정상의 어려움과 6FDA-PDA의 상대적으로 높은 응력을 서로 보완해 기계적 물성이 좋은 저응력의 폴리이미드를 만들 수 있음을 보였다. 즉, random한 PMDA/6FDA-PDA 공중합체 폴리이미드 합성을 이용하여 사슬 내에 벌키한 di(trifluoromethyl)기와 같은 관절기로 인한 상대적으로 높은 응력을 보이는 6FDA-PDA 폴리이미드 사슬 내에 강직한 사슬 구조를 가진 PMDA-PDA 폴리이미드의 사슬 구조를 적당량 첨가함으로써 우수한 기계적 물성을 갖는 저응력 폴리이미드를 만들 수 있었다. 특히, PMDA/6FDA-PDA (0.9:0.1:1.0) 폴리이미드가 저유전 상수 층간 절연막으로서의 우수한 기계적 물성과 낮은 응력 수준을 보여주고 있다.