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Hsiao T.-C.,Electronics and Optoelectronics Research Laboratories | Hsiao T.-C.,National Tsing Hua University | Wang P.-H.,National Tsing Hua University | Fan C.-T.,National Tsing Hua University | And 2 more authors.
Progress in Biomedical Optics and Imaging - Proceedings of SPIE | Year: 2011

Recently, photoacoustic imaging has been intensively studied for blood vessel imaging, and shown its capability of revealing vascular features suggestive of malignancy of breast cancer. In this study, we explore the feasibility of visualization of micro-calcifications using photoacoustic imaging. Breast micro-calcification is also known as one of the most important indicators for early breast cancer detection. The non-ionizing radiation and speckle free nature of photoacoustic imaging overcomes the drawbacks of current diagnostic tools - X-ray mammography and ultrasound imaging, respectively. We employed a 10-MHz photoacoustic imaging system to verify our idea. A sliced chicken breast phantom with granulated calcium hydroxyapatite (HA) - major chemical composition of the breast calcification associated with malignant breast cancers - embedded was imaged. With the near infared (NIR) laser excitation, it is shown that the distribution of ∼ 500 μm HAs can be clearly imaged. In addition, photoacoustic signals from HAs rivals those of blood given an optimal NIR wavelength. In summary, photoacoustic imaging shows its promise for breast micro-calcification detection. Moreover, fusion of the photoacoustic and ultrasound images can reveal the location and distribution of micro-calcifications within anatomical landmarks of the breast tissue, which is clinically useful for biopsy and diagnosis of breast cancer staging. © 2011 SPIE. Source

Lu S.-T.,National Tsing Hua University | Lu S.-T.,Electronics and Optoelectronics Research Laboratories | Chen W.-H.,National Tsing Hua University | Chen W.-H.,National Applied Research Laboratories
IEEE Transactions on Advanced Packaging | Year: 2010

The need for flexible interconnects in advanced applications in consumer electronic products is increasing rapidly. The reliability and flexibility of ultra-thin chip-on-flex (UTCOF) interconnects formed using anisotropic conductive adhesive (ACA) are thus investigated. Two films of ACA materials, namely ACA-P and ACA-F, are assembled at different bonding temperatures to study the effect of temperature on the adhesion at the substrate-adhesive and adhesive-chip interfaces using differential scanning calorimetry (DSC) and a 90° peeling test. The contact resistance of a daisy chain with 188 input/output (I/O) is measured to examine the quality of bonding through dummy test samples with an 80-μm pitch. The reliability of the fabricated UTCOF interconnects bonded via selected ACA joints is evaluated by performing an 85 °C/85% RH thermal humidity storage test (THST) for 1000 h, and their flexibility is evaluated in static bending and four-point bending tests. The interfaces between the ultra-thin silicon chip and the substrate of failed samples in the THST and four-point bending testing are then investigated by scanning electron microscopy (SEM), which is utilized to obtain cross-sectional images. Finite element analysis is also conducted to elucidate the failure mechanism of the UTCOF interconnects in the four-point bending test. The averaged maximum allowable deflections of the fabricated UTCOF interconnects with ACA-P and ACA-F materials are 26% and 168%, respectively, higher than those of the COF interconnects with a chip thickness of 670 μm. Moreover, the contact resistance remains stable, varying by less than 10%, in the static bending test with a bending radius of 30 mm. According to the results thus obtained, give the appropriate choice of an ACA material and the optimal curing conditions, the UTCOF interconnects with ACA joints reliably serve as flexible interconnects for use in consumer electronic products. © 2006 IEEE. Source

Chang P.-C.,National Tsing Hua University | Huang H.-W.,National Tsing Hua University | Chang C.-C.,National Tsing Hua University | Chang S.-C.,National Tsing Hua University | And 2 more authors.
Thin Solid Films | Year: 2013

We studied Ga19Sb81 film deposited on SiO x/Si(100) by RF co-sputtering using GaSb and Sb targets aiming for applications in multi-level phase-change memory. Crystallization temperature (Tx) is 228 °C-235 °C determined by electrical resistance versus temperature measurements at various heating rates. The dramatic resistance drop is attributed to increased carrier concentration based on Hall measurements. The films show p-type conduction behavior at all temperature regimes. The temperature for ten-year failure-time (T10y) and the activation energy of crystallization (Ea) is 156 °C and 4.2 eV, respectively, as deduced using Arrhenius plots from as-deposited films. The two-step drop in resistance is attributed to the two-step phase formation as depicted by X-ray diffractometry. Density changes before and after crystallization is 5.3% (Ge2Sb2Te5: 9.5%) as analyzed by the X-ray reflectivity method. Memory switching is carried out by using test cells with a via hole size of 600 nm. Set and reset processes can be achieved by using pulse widths of 20-100 ns. The cycling test showed performance at least 104 set-reset times. Furthermore, two stable set states are routinely achieved by controlling set voltages. The two states can be operated at least 102 cycles steadily with resistance ratios ~5 and ~22 times, respectively. The two set states arise from the formation of two phases (Sb then GaSb) during set operations. © 2013 Elsevier B.V. All rights reserved. Source

Chen T.T.,Electronics and Optoelectronics Research Laboratories | Wang C.P.,Electronics and Optoelectronics Research Laboratories | Fu H.K.,Electronics and Optoelectronics Research Laboratories | Chou P.T.,Electronics and Optoelectronics Research Laboratories | And 2 more authors.
Optics Express | Year: 2014

This study of the optoelectronic properties of blue light-emitting diodes under direct current stress. It is found that the electroluminescence intensity increases with duration of stress, and the efficiency droop curves illustrated that the peak-efficiency and the peak-efficiency-current increases and decreases, respectively. We hypothesize that these behaviors mainly result from the increased internal quantum efficiency. © 2014 Optical Society of America. Source

Wang C.-P.,Electronics and Optoelectronics Research Laboratories | Chen T.-T.,Electronics and Optoelectronics Research Laboratories | Fu H.-K.,Electronics and Optoelectronics Research Laboratories | Chang T.-L.,National Taiwan Normal University | And 2 more authors.
Microelectronics Reliability | Year: 2012

The purpose of this study is to investigate the thermal behavior at the die-attached interfaces of flip-chip GaN high-power light emitting diodes (LEDs) using a combination of theoretical and experimental analyses. The results indicate that contact thermal resistance increased dramatically at the die-attached interfaces with aging time and stress, degrading the luminous flux. The junction temperature and thermal uniformity of the flip-chip structure both strongly depend on the arrangement of gold bumps. Local hot spots effectively reduce light output under high electric and thermal stress, influencing the long-term performance of the LED device. The results were validated using finite element analysis and in experiments using an infrared and an emission microscope. A two-step thermal transient degradation mode was identified under various aging stresses. A simulation further optimized the bump configuration that was associated to yield a low junction temperature and high temperature uniformity of the LED chip. Accordingly, the results are helpful in enhancing the performance and reliability of high-power LEDs. © 2011 Elsevier Ltd. All rights reserved. Source

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