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PIEZOELECTRIC BEHAVIOUR OF SPUTTERED ALUMINIUM NITRIDE THIN FILM FOR HIGH FREQUENCY ULTRASONIC SENSORS

AIP Conference Proceedings 2011年第1期1335卷 1663-1670页

作者： T. Herzog S. Walter H. Bartzsch M. Gittner D. Gloess H. Heuer aFraunhofer Institute for Non‐Destructive Testing IZFP Dresden Branch Maria‐Reiche‐Strasse 2 01109 Dresden Germany bFraunhofer Institute for Electron Beam and Plasma Technology FEP Dresden Winterbergstraße 28 01277 Dresden Germany

Many new materials and processes require non destructive evaluation in higher resolutions by phased array ultrasonic techniques in a frequency range up to 250 MHz. This paper presents aluminium nitride, a promising material for the use as a piezoelectric sensor material in the considered frequency range, which contains the potential for high frequency phased array application in the future. This work represents the fundamental development of piezoelectric aluminium nitride films with a thickness of up to 10 μm. We have investigated and optimized the deposition process of the aluminium nitride thin film layers regarding their piezoelectric behavior. Therefore a specific test setup and a measuring station were created to determine the piezoelectric charge constant (d33) and the electro acoustic behavior of the sensor. Single element transducers were deposited on silicon substrates with aluminium electrodes for top and bottom, using different parameters for the magnetron sputter process, like pressure and bias voltage. Afterwards acoustical measurements up to 500 MHz in pulse echo mode have been carried out and the electrical and electromechanical properties were qualified. In two different parameter sets for the sputtering process excellent piezoelectric charge constant of about 8.0 pC/N maximum were obtained.

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Time And Temperature Dependent Micromechanical Properties Of Solder Joints For 3D‐Package Integration

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AIP Conference Proceedings 2010年第1期1300卷 176-185页

作者： Mike Roellig Karsten Meier Rene Metasch aFraunhofer Institute for Non‐Destructive Testing Dresden branch (IZFP‐D) bDresden University of Technology Electronics Packaging Laboratory IAVT

The recent development of 3D‐integrated electronic packages is characterized by the need to increase the diversity of functions and to miniaturize. Currently many 3D‐integration concepts are being developed and all of them demand new materials, new designs and new processing technologies. The combination of simulation and experimental investigation becomes increasingly accepted since simulations help to shorten the R&D cycle time and reduce costs. Numerical calculations like the Finite‐Element‐Method are strong tools to calculate stress conditions in electronic packages resulting from thermal strains due to the manufacturing process and environmental loads. It is essential for the application of numerical calculations that the material data is accurate and describes sufficiently the physical behaviour. The developed machine allows the measurement of time and temperature dependent micromechanical properties of solder joints. Solder joints, which are used to mechanically and electrically connect different packages, are physically measured as they leave the process. This allows accounting for process influences, which may change material properties. Additionally, joint sizes and metallurgical interactions between solder and under bump metallization can be respected by this particular measurement. The measurement allows the determination of material properties within a temperature range of 20° C–200° C. Further, the time dependent creep deformation can be measured within a strain‐rate range of 10−31/s−10−81/s. Solder alloys based on Sn‐Ag/Sn‐Ag‐Cu with additionally impurities and joint sizes down to O/ 200 μm were investigated. To finish the material characterization process the material model coefficient were extracted by FEM‐Simulation to increase the accuracy of data.

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EXPERIMENTAL‐BASED DISCUSSION FOR THE SEPARATION OF RESIDUAL STRESSES AND COLD WORK IN SHOT PEENED IN718 USING HIGH FREQUENCY EDDY CURRENT SPECTROSCOPY

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AIP Conference Proceedings 2010年第1期1211卷 1349-1356页

作者： S. Hillmann H. Heuer A. Robbert H.‐U. Baron J. Bamberg N. Meyendorf aFraunhofer Institute for Non‐Destructive Testing Dresden branch of IZFP Maria‐Reiche‐Str. 2 01109 Dresden Germany bMTU Aero Engines GmbH Dachauer Str. 665 80995 Munich Germany

Typical aero engine alloys, such as IN718, can be surface‐treated by shot peening to induce near‐surface compressive strains. To calculate the remaining operation time for those critical aero engine components, a quantitative nondestructive determination of near‐surface strain gradients has to be developed. We have demonstrated in the past, that it is possible to obtain a characteristic depth profile (surface and sub‐surface) of the electrical conductivity of shot peened specimen by using high‐frequency eddy current techniques. The measured conductivity profile is resulting from residual stresses, cold work, surface roughness, and the microstructure of the material. The objective is to measure residual stresses (separately from other material properties) in such components after a defined life time. It can be assumed, that surface roughness and microstructure remain unchanged in IN718 materials over their lifetime, but cold work and residual stresses can change independently. Consequently, there is a need to clearly separate the information from both material properties of received eddy current conductivity signals in order to obtain specific information related to residual stresses. This paper presents results acquired from different experiments, conducted to separate both effects by using the eddy current technique on shot peened IN718 materials. We present different physical approaches and illustrate the experiments to solve them. In addition, we will demonstrate that there is a need to use additional techniques, for example ultrasonic time‐of‐flight measurements, to separate the effects of residual stresses from compound (mixed) signals obtained on cold work samples.

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Conical Dark‐Field Analysis For Small Grain Characterization In Narrow Cu Interconnect Structures: Potential And Challenges

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AIP Conference Proceedings 2010年第1期1300卷 39-46页

作者： René Hübner Hans‐Jürgen Engelmann Ehrenfried Zschech aFraunhofer Institute for Non‐Destructive Testing IZFP Dresden Branch Maria‐Reiche‐Strasse 2 01109 Dresden Germany bGLOBALFOUNDRIES Dresden Module One LLC & Co. KG Wilschdorfer Landstrasse 101 01109 Dresden Germany

Conical dark‐field (CDF) analysis in the transmission electron microscope is introduced as a suitable method for characterizing small Cu grains in advanced interconnect structures. With a proven spatial resolution in the <5 nm range, the CDF technique is not only applied for monitoring the microstructure of Cu interconnect lines during process development and control, but also for Cu grain orientation determination in conjunction with electromigration and stress‐migration experiments to study the influence of Cu microstructure on reliability‐limiting degradation processes. To obtain accurate orientation information with high lateral resolution, several challenges associated with data acquisition and subsequent data analysis have to be accomplished. Besides a well‐aligned microscope and stable measuring conditions, a suitable choice of the evaluation parameters and appropriate handling of diffraction pattern superposition are crucial for reliable Cu orientation determination.

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NEAR‐SURFACE RESIDUAL STRESS‐PROFILING WITH HIGH FREQUENCY EDDY CURRENT CONDUCTIVITY MEASUREMENT

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AIP Conference Proceedings 2009年第1期1096卷 1349-1355页

作者： S. Hillmann H. Heuer H.‐U. Baron J. Bamberg A. Yashan N. Meyendorf aFraunhofer Institute for Non‐Destructive Testing Dresden branch of IZFP Maria‐Reiche‐Str. 2 01109 Dresden Germany bMTU Aero Engines GmbH Dachauer Str. 665 80995 Munich Germany cFraunhofer Institute for Non‐Destructive Testing IZFP Campus E3 1 66123 Saarbruecken Germany

The lifetime of aero engine components can be extended by applying an additional strain to the material. Typical aero engine‐alloys like Nickel‐Base superalloys or Titanium alloys can be surface‐treated by use of shot peening to induce the compressive strain near the surface. However, in order to use the additional life for critical aero engine components, a quantitative determination of strain gradients near the surface has to be carried out periodically. We propose to measure the depth‐profile of residual stresses non‐destructively by use of high frequency eddy current techniques. This paper presents results obtained with an experimental set‐up based on a high precision impedance analyzer. Test samples prepared from IN718 by shot peening of different intensities can be easily distinguished. By sweeping the frequency from 100 kHz up to 100 MHz a depth profile for the electrical conductivity from 50 μm to 500 μm can be obtained. The measured conductivity profile is a resultant from residual stresses, cold work, surface roughness and the texture of the material. In addition, first results for strain profiling obtained with industry applicable NDE instrument will be presented.

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