微波数字复合基板金属化孔工艺方法

微波数字复合基板是将微波电路与数字电路集合在一起的新型复合多层基板,其体积的缩小实现了雷达天线系统的轻量化和小型化.在复合基板的制作过程中,金属化孔的可靠性是保证天线电性能指标的关键.主要介绍了微波数字复合基板中微盲孔孔金属化及提高金属化孔可靠性的工艺方法.     

半导体晶圆化学镍/金UBM工艺与设备

介绍了半导体晶圆化学镍金UBM的工艺流程及其自动控制生产线,包括设备材料的要求及设备内部结构。在200mm的半导体晶圆上成功制作5μm化学镍/金UBM和18μm化学镍金凸点。在光学显微镜、表面轮廓仪和SEM下检测了化学镍/金镀层的表面形貌。通过EDX分析化学镍/金UBM中的镍磷含量。3D自动光学检测了200mm晶圆上化学镍/金凸点的高度和共面性,讨论了镍/金凸点的剪切强度和失效模式,分析了生产中化学镍/金UBM的两种常见缺陷及成因。     

Design and Fabrication of Segmented GeTe/(Bi,Sb)2Te3 Thermoelectric Module with Enhanced Conversion Efficiency

GeTe and (Bi,Sb)₂Te₃ are two representative thermoelectric (TE) materials showing maximum performance at middle and low temperature, respectively. In order to achieve higher performance over the whole temperature range, their segmented one-leg TE modules are designed and fabricated by one-step spark plasma sintering (SPS). To search for contact and connect layers, the diffusion behavior of Fe, Ni, Cu, and Ti metal layers in GeTe is studied systematically. The results show that Ti with a similar linear expansivity (10.80 × 10⁻⁶ K⁻¹) to GeTe, has low contact resistance (3 µΩ cm²) and thin diffusion layer (0.4 µm), and thus is an effective metallization layer for GeTe. The geometric structure of the GeTe/(Bi,Sb)₂Te₃ segmented one-leg TE module and the ratio of GeTe to (Bi,Sb)₂Te₃ are determined by finite element simulation method. When the GeTe height ratio is 0.66, its theoretical maximum conversion efficiency (η_max) can reach 15.9% without considering the thermal radiation and thermal/electrical contact resistance. The fabricated GeTe/(Bi,Sb)₂Te₃ segmented one-leg TE module showed a η_max up to 9.5% with a power density ≈ 7.45 mW mm⁻², which are relatively high but lower than theoretical predictions, indicating that developing segmented TE modules is an effective approach to enhance TE conversion efficiency.     

Optimizing annealing steps for crystalline silicon solar cells with screen printed front side metallization and an oxide‐passivated rear surface with local contacts

Silicon solar cells that feature screen printed front contacts and a passivated rear surface with local contacts allow higher efficiencies compared to present industrial solar cells that exhibit a full area rear side metallization. If thermal oxidation is used for the rear surface passivation, the final annealing step in the processing sequence is crucial. On the one hand, this post‐metallization annealing (PMA) step is required for decreasing the surface recombination velocity (SRV) at the aluminum‐coated oxide‐passivated rear surface. On the other hand, PMA can negatively affect the screen printed front side metallization leading to a lower fill factor. This work separately analyzes the impact of PMA on both, the screen printed front metallization and the oxide‐passivated rear surface. Measuring dark and illuminated IV‐curves of standard industrial aluminum back surface field (Al‐BSF) silicon solar cells reveals the impact of PMA on the front metallization, while measuring the effective minority carrier lifetime of symmetric lifetime samples provides information about the rear side SRV. One‐dimensional simulations are used for predicting the cell performance according to the contributions from both, the front metallization and the rear oxide‐passivation for different PMA temperatures and durations. The simulation also includes recombination at the local rear contacts. An optimized PMA process is presented according to the simulations and is experimentally verified. The optimized process is applied to silicon solar cells with a screen printed front side metallization and an oxide‐passivated rear surface. Efficiencies up to 18.1% are achieved on 148.8 cm² Czochralski (Cz) silicon wafers. Copyright © 2009 John Wiley & Sons, Ltd.     

Pressure-induced metallization in the absence of a structural transition in the layered transition-metal dichalcogenide ZrSe2

First-principles calculations were carried out on the ZrSe₂ compound, which has been of interest owing to its technologically important physical properties. The structural, electronic and optical properties of this compound were investigated under pressure through the plane wave pseudopotential approach within the framework of density functional theory. A comparison between the computed crystal structure parameters and the corresponding experimental counterparts shows a very good agreement between them. Fitting the pressure–volume data using the third-order Birch–Murnaghan equation of state yielded a bulk modulus B₀ = 38.17 GPa and a pressure derivative of bulk modulus  = 8.2 for hexagonal ZrSe₂. The relationship between the band structure and pressure is revealed. We calculated the total density of state (TDOS) under different pressures and partial density of state (PDOS) from 0 to 10 GPa. According to our calculations, metallization of hexagonal ZrSe₂ is predicted to occur at around 10 GPa and pressure-induced band-gap engineering reveals the transformation of the indirect to direct band gap with increasing pressure. Furthermore, optical properties, such as the complex dielectric function, refractive index and reflectivity spectra of this compound, were studied for incident electromagnetic waves in an energy range up to 45 eV. The contributions to various transition peaks in the optical spectra are analyzed and discussed with the help of the energy-dependent imaginary part of the dielectric function.