Ultrathin Wafer Pre-Assembly and Assembly Process Technologies: A Review

Ultrathin silicon wafer technology is reviewed in terms of the semiconductor applications, critical challenges, and wafer pre-assembly and assembly process technologies and their underlying mechanisms. Mechanical backgrinding has been the standard process for wafer thinning in the semiconductor industry owing to its low cost and productivity. As the thickness requirement of wafers is reduced to below 100 μm, many challenges are being faced due to wafer/die bow, mechanical strength, wafer handling, total thickness variation (TTV), dicing, and packaging assembly. Various ultrathin wafer processing and assembly technologies have been developed to address these challenges. These include wafer carrier systems to handle ultrathin wafers; backgrinding subsurface damage and surface roughness reduction, and post-grinding treatment to increase wafer/die strength; improved wafer carrier flatness and backgrinding auto-TTV control to improve TTV; wafer dicing technologies to reduce die sidewall damage to increase die strength; and assembly methods for die pick-up, die transfer, die attachment, and wire bonding. Where applicable, current process issues and limitations, and future work needed are highlighted.     

基片与不同方位多形态缺陷粒子的复合光散射特性分析

结合光学表面无损检测工艺实际情况,给出基片与镶嵌及掩埋的球体/回转椭球体缺陷粒子的散射特性分析。针对基片与缺陷粒子的半空间问题,结合时域有限差分方法使用广义完全匹配吸收层(GPML),结合三波技术引入激励源,给出了相应的连接边界条件,并将互易性定理应用到近远场外推中,使过程简化。数值计算给出了镶嵌及掩埋的球体/回转椭球体缺陷粒子的散射场的角分布。结果显示:镶嵌比掩埋的缺陷粒子受粒子尺寸的影响更明显。在大散射角下,缺陷粒子的位置因素带来的贡献较大。粒子分别掩埋或镶嵌于基片时,在-10°、30°、70°附近的球体粒子和回转椭球体粒子的微分散射截面(DSCS)差别较大。在基片无损检测工程中可以通过对特定角度散射场的测量定标诊断出缺陷的方位和形态。     

基片与多形态缺陷粒子的复合光散射

为了给基片无损检测工程提供强有力的理论基础,提出三种形态的缺陷粒子散射模型。针对基片与缺陷粒子的半空间问题,吸收边界使用了广义完全匹配吸收层,结合三波技术引入激励源给出相应的连接边界条件并将互易性定理应用到近远场外推中使过程简化。数值计算给出了镶嵌于基片中的多种几何体Cu和SiO2缺陷粒子的散射场的角分布及p偏振和s偏振下镶嵌Cu球体粒子的电场分布。结果显示：角分布和场分布跟粒子形态关系密切。椭球体散射场的震荡明显比柱体场震荡激烈。在s偏振下电场强度分布差值极小,不利于通过分析场值分布特点反演缺陷特征值。因此建议工程上使用p偏振光对基片进行无损检测。     

面向水下应用的电容式微机械超声换能器*

电容式微机械超声换能器具有宽频带和易于制造二维阵列等优势,已经成为一种重要的新型超声换能器。该文针对图像声呐系统对新型超声换能器的迫切需求,提出了一种电容式微机械超声换能器结构和参数,并利用硅微加工技术制备出了该换能器,最后对其主要性能参数进行了测试和分析。测试结果表明该换能器具有发射和接收超声波的功能,中心工作频率为1.965 MHz,6 dB相对带宽达到109.4%,在1 MHz、2 MHz和3 MHz频率时的接收灵敏度分别为-218.29 d B、-219.39 dB和-218.11 dB。该文研制的电容式微机械超声换能器显示出了优秀的宽频带特性,且工作频率和接收灵敏度性能均基本满足了高频图像声呐系统的需求。     

Slip damage of silicon wafers subjected to continuous infrared laser irradiation

Laser irradiation can cause damage to solids, such as slipping, cracking, melting, and ablation. Silicon crystals are brittle, so slipping is a serious problem because it can easily result in fracture. This study investigates the amount of continuous near-infrared (NIR) laser irradiance that induces slip damage in a single-crystal silicon wafer. For this purpose we developed a simulation model based on heat transfer and thermo-elastic analyses. To verify the simulation model, silicon wafer specimens were irradiated by a fiber laser beam (of wavelength 1065 nm), and the surface morphology after laser beam irradiation was inspected using optical microscopy (OM). The irradiation time was fixed at 10 s, and nine different irradiances from 180 W/cm² to 380 W/cm² were tested in steps of 25 W/cm². No slip surface was found after exposure to the irradiances up to 230 W/cm², but straight slips in the <110> direction appeared at the irradiances of 255 W/cm² and above. These experimental findings agreed well with the simulation.     

Cyclic voltammetry study of silver seed layers on p-silicon (100) substrates

The anodic stripping behavior of the Ag seed layers on a p-silicon (100) wafer was studied by cyclic voltammetry (CV). The seed layers were prepared by immersing the silicon wafer in a solution of 0.005 M AgNO₃+0.06 M HF at room temperature. Then the layer adhered wafers were used as the work electrodes. The oxidation energy of the Ag monolayer based on the Si-Ag combination was observed and the oxidation energy of the Ag multilayer based on the Ag-Ag combination was also found.     

Immobilized enzyme studies in a microscale bioreactor

Novel microreactors with immobilized enzymes were fabricated using both silicon and polymer-based microfabrication techniques. The effectiveness of these reactors was examined along with their behavior over time. Urease enzyme was successfully incorporated into microchannels of a polymeric matrix of polydimethylsiloxane and through layer-bylayer self-assembly techniques onto silicon. The fabricated microchannels had cross-sectional dimensions ranging from tens to hundreds of micrometers in width and height. The experimental results for continuous-flow microreactors are reported for the conversion of urea to ammonia by urease enzyme. Urea conversions of > 90% were observed.     

旋转圆盘空蚀试验中的硅材料破坏过程研究

利用自制旋转圆盘空蚀试验装置,以流动自来水为介质,对磨片、化抛片、抛光片和刻蚀片等4种硅片进行连续8 h试验以及对磨片进行连续14 h跟踪观察试验,研究硅材料的微观破坏过程,并利用扫描电子显微镜、触针式表面形貌仪和原子力显微镜对其表面微观形貌进行分析.结果表明:经连续8 h空蚀试验后,磨片原始表面的片状层基本消失,表面破坏程度最严重,化抛片次之,其表面尖锐的边缘发生了钝化,抛光片和刻蚀片的表面变化不大;化抛片的表面粗糙度Ra值由227.79 nm降至173.31 nm,抛光片的Ra值由0.483 nm增加至3.455 nm,磨片在14 h试验后其Ra值由0.3304 μm降至0.1965 μm;一定尺度的表面微观形貌对硅材料产生显著影响.     

Fracture mechanics analysis on Smart-Cut technology. Part 1： Effects of stiffening wafer and defect interaction

In the present paper, continuum fracture mechanics is used to analyze the Smart-Cut process, a recently established ion cut technology which enables highly efficient fabrication of various silicon-on-insulator （SOI） wafers of high uniformity in thickness. Using integral transform and Cauchy singular integral equation methods, the mode-I and mode-II stress intensity factors, energy release rate, and crack opening displacements are derived in order to examine several important fracture mechanisms involved in the Smart-Cut process. The effects of defect interaction and stiffening wafer on defect growth are investigated. The numerical results indi- cate that a stiffener/handle wafer can effectively prevent the donor wafer from blistering and exfoliation, but it slows down the defect growth by decreasing the magnitudes of SIF＇s. Defect interaction also plays an important role in the splitting process of SOI wafers, but its contribution depends strongly on the size, interval and internal pressure of defects. Finally, an analytical formula is derived to estimate the implantation dose required for splitting a SOI wafer.     

船用制动器摩擦片的寿命用可靠性分析

对某船用２ＺＦ－１２０Ｂ齿轮箱制动器摩擦片磨损数据进行回归分析，并讨论可靠度及耐磨寿命预测推算的原理和方法。该方法可推广应用于其他磨损件。