Browsing by Author "Chiang, Chia-Wen"

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A Wafer-Level Three-Dimensional Integration Scheme With Cu TSVs Based on Microbump/Adhesive Hybrid Bonding for Three-Dimensional Memory Application
(2012-06-01)
Ko, Cheng-Ta
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Hsiao, Zhi-Cheng
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Chang, Yao-Jen
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Chen, Peng-Shu
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Hwang, Yu-Jiau
Thin wafer/chip stacking with vertical interconnect by a Cu through-silicon via (TSV) and a Cu/Sn microjoint is one of the candidates for 3-D integration. The insertion loss of the two-chip stack was evaluated with different TSV pitches, microbump diameters, and chip thicknesses to realize the signal transmission effects in high-speed digital signaling via TSV and microjoint interconnection. In addition, a wafer-level 3-D integration scheme with Cu TSVs based on Cu/Sn microbump and BCB adhesive hybrid bonding was demonstrated. Key technologies, including TSV interconnection, microbumping, hybrid bonding, wafer thinning, and backside RDL formation, were well developed and integrated to realize 3-D integration. This paper presents a complete study of the structure design, the process condition, and the electrical and reliability assessment of the wafer-level 3-D integration scheme. This 3-D integration scheme with excellent electrical performance and reliability provides a promising solution for 3-D memory application.
Effects of signal averaging, gradient encoding scheme, and spatial resolution on diffusion kurtosis imaging: An empirical study using 7T MRI
(2019-11-01)
Chiang, Chia-Wen
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Lin, Shih-Yen
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Cho, Kuan-Hung
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Wu, Kuo-Jen
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Wang, Yun
Background Although diffusion gradient directions and b-values have been optimized for diffusion kurtosis imaging (DKI), little is known about the effect of signal averaging on DKI reliability. Purpose To evaluate how signal averaging influences the reliability of DKI indices using two gradient encoding schemes with three spatial resolutions. Study Type Prospective. Animal Model Fifteen naive Sprague-Dawley rats. Field Strength/Sequence DKI was performed at 7T using two schemes (30 directions with three b-values [30d-3b] and six directions with 15 b-values [6d-15b]), three resolutions, and eight repetitions. Assessment DKI reliability was assessed using voxelwise relative error (sigma) and test-retest error of fractional anisotropy (FA), mean diffusivity (MD), and mean kurtosis (MK) within gray matter (GM) and white matter (WM). The number of excitations (NEX) was optimized by considering DKI reliability. The influence of the partial volume effect (PVE) was also assessed. Statistical Test One-way analysis of variance. Results The 30d-3b scheme, compared with the 6d-15b scheme, exhibited apparently smaller sigma(FA) and sigma(MK) (eg, at NEX 1, in GM, for three resolutions, sigma(FA): 19.9-38.2% vs. 34.2-61.4%, sigma(MK): 6.9-11.4% vs. 14.1-15.4%) and similar sigma(MD) (all differences between two schemes <1.6%). The optimal NEX was determined as 2 for enabling a reliable measurement of DKI-derived indices. The PVE at the lowest resolution apparently increased sigma(FA) for both schemes (19.9% for 30d-3b and 34.2% for 6d-15b) and sigma(MK) for the 6d-15b scheme (14.7%) in GM, and exerted lower effects on MK values for the 30d-3b scheme (P > 0.05). Data Conclusion A higher number of diffusion directions would benefit FA and MK estimation. A higher spatial resolution helps to reduce PVE. By using the 30d-3b scheme, MK is considered a robust index to reflect microstructural changes in GM and WM. We propose a systematic approach to determine the optimal DKI protocols for appropriate preclinical settings. Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;50:1593-1603.