制绒Si片清洗工艺的研究

研究对比了不同清洗工艺对制绒Si片性能的影响,采用原子力显微镜和少子寿命测试仪测试经不同化学清洗工艺处理之后的Si片表面微粗糙度和少子寿命。研究发现,使用浓硫酸、双氧水混合液和稀释的氢氟酸溶液清洗Si片能够有效改善Si片表面的质量,Si片表面的微粗糙度由原先的5.96μm降低到4.45μm;采用等离子体增强化学气相沉积法在清洗之后的Si片上生长本征氢化非晶Si层,对Si片进行表面钝化,钝化之后的Si片少子寿命可达107.88μs。测试结果还表明,采用此种清洗方法处理的Si片少子寿命稳定性有很大提高。     

碳化硅晶片表面质量差异影响因素研究

分析了金刚石线锯多线切割150 mm SiC晶片的表面形貌及质量,通过测试SiC片Si面和C面的表面粗糙度(Ra),发现C面Ra值约为Si面的2倍。在切割过程中晶片向Si面弯曲,使锯丝侧向磨粒对Si面磨削修整作用更强,从而使晶片Si面更加光滑。此外,通过显微截面法测试了SiC晶片两面的损伤层深度。结果表明,Si面损伤层深度约为7.89 μm,明显低于C面的13.8 μm,显微镜下观察到截面边缘更加平整。该方法进一步证明了多线切割时晶片向Si面弯曲,使锯丝侧向磨粒对Si面的磨削效果更强,从而造成SiC晶片两面表面形貌和质量存在差异。     

化学机械抛光产生的碲镉汞材料亚表面损伤层的研究

针对化学机械抛光工艺对碲镉汞材料所产生的亚表面损伤层进行了研究。利用椭圆偏振光谱方法对经过腐蚀剥层的碲镉汞材料表面进行了光学表征,认为化学机械抛光工艺造成的亚表面损伤层的深度大概为抛光工艺中所使用研磨颗粒直径的15~20倍。通过少子寿命表征和光导器件性能的对比测试,认为将该亚表面损伤层完全去除后,材料的少子寿命和器件的光电性能会得到明显的提高。     

晶体硅太阳电池的双层结构钝化膜研究

针对目前基于p型硅片制备的单结太阳电池进一步提高表面钝化膜生产效率,利用氮化硅(SiNx)薄膜良好的钝化效果与价格低廉的二氧化钛(TiO2)膜,降低SiNx镀膜厚度减薄对少子寿命的影响。在单晶硅片表面先用PECVD法沉积SiNx薄膜,然后用热喷涂沉积TiO2薄膜。对比测试了热喷涂沉积TiO2薄膜前后电池的性能,结果表明在SiNx膜上增加TiO2膜层后少子寿命明显提高,这可能是TiO2膜结构内存在固定正电荷所致。这种双层结构封装后的太阳电池显示出了较好的光学与电学性能,对进一步改进太阳电池性能具有重要参考价值。     

InSb晶片的机械加工损伤层研究

结合X射线衍射技术以及逐层化学 腐蚀剥离损伤层的方法,定量分析了InSb晶体 由于切割、研磨、抛光等工艺所引入的损伤层的深度,并探讨了 损伤层结构及引入因素。研究结果表明,切割加工是引入InSb晶 片表面损伤层的主要工序,其表面损伤层的深度达 到16 μm左右;双面研磨的InSb晶片表面的损伤层深度约 为12 μm;经机械化学抛光加工后的InSb晶片表面的损伤层深 度明显减小,约为2 μm。     

太阳电池用Si片切割过程中浆料作用研究

Si片生产技术及工艺的进步使得太阳电池用Si片的切片厚度不断降低,而超薄的太阳电池用Si片必须通过多线切割机进行切割.基于Si片切割过程中砂浆性能对Si片表面质量、Si片成片率和切割线寿命的影响,分析了多线切割机中切削液的性能,并采用不同工艺参数多次进行试验,总结出了砂浆对太阳电池用Si片切割状态的影响因素.通过分析,得出了改善砂浆性能来提高多线切割机切片性能并获得更高的Si晶片表面质量的方法.     

Si片磨削中砂轮粒径对Si片损伤层的影响

在直径300 mm Si片制备中,利用双面磨削技术能为后续加工提供高精度的表面,但Si片损伤层厚度较大.通过扫描电子显微镜和透射电子显微镜对Si片表面及截面进行观察,得到了经不同粒径的砂轮磨削后的Si片的表面及截面形貌、Si片的表面及亚表面损伤层的厚度并进行了分析比较.结果表明,用粒度更小的3000#砂轮磨削,能够有效地降低Si片表面及亚表面损伤层的厚度,为优化300 mm单晶Si片双面磨削工艺、提高Si片表面磨削质量提供了清晰、量化的实验理论依据.     

液相外延碲镉汞薄膜的表面损伤研究

HgCdTe薄膜表面损伤层厚度测试对其加工工艺及其重要。本文采用白光干涉仪对HgCdTe薄膜表面粗糙度测试,并与损伤层厚度对比,研究发现粗糙度值达到稳定值后,上一步工艺引入的表面损伤已经完全去除,表面的损伤为抛光工艺引入的损伤。这一方法,既能方便快捷地确定损伤层是否完全去除,又未对测试样品产生破坏。     

Si片多线切割技术与设备的发展现状与趋势

介绍了Si片的多线切割宏观切割机理与微观切割机理,指出控制钢线张力减少钢线震动是切割工艺的重要指标。讨论了切割过程主要影响因素,钢线的外包Cu会造成Si片表面金属残留,钢线磨损影响Si片厚度,砂浆喷嘴和线网角度在形成水平薄膜层时能够获得好的表面质量。分析了钢线带动砂浆进行切割的核心工艺,给出了Si片切割工艺理论切片量的计算方法。并简要概括了目前多线切割技术及设备的国内外发展形势和未来发展趋势,指出未来多线切割技术将朝着提高加工精度与加工效率、降低成本、改良切割用钢线这几个方向迈进。     

硅片的化学减薄

硅衬底的质量直接影响外延层质量和器件的性能.一般要求外延前的衬底具备:(1)无或极少量机械损伤;(2)小的弯曲度;(3)高度平整光洁的抛光表面,且抛光表面的损伤应力尽量小.这三者是相互制约的.众所周知,晶体经切割、研磨之后会引入大量的机械损伤.据报道,损伤层的厚度在50μ以上,其中多晶层为2～3μ,裂纹层20μ,弹性畸变层为30μ左右.其中弹性畸变是由应力引起的,较深.单用抛光方法去除50μ以上的损伤层,需要6小时,难以达到良好的平整度,也是不经济的.化学减薄既能除去衬底原有的表面损     

Experiment study on electroplated diamond wire saw slicing single-crystal silicon

This paper conducted the slicing experiments of single-crystal silicon using a reciprocating electroplated diamond wire saw. The machined wafer topography and wire wear were observed by using scanning electron microscope (SEM). The influences of process parameters and cutting fluids on single-crystal silicon wafer surface roughness (SR), subsurface micro-crack damage (SSD) depth, total thickness variation (TTV) and warp were investigated. The bonded interface sectioning technique was used to examine the cut wafers SSD depth. Study results show that a higher wire speed and lower ingot feed speed can produce lower wafer SR and SSD; the lower warp of wafer needs lower wire speed and ingot feed speed; and low wafer TTV can be obtained by an appropriate matching relationship between wire speed and ingot feed speed. The synthetic cutting fluid has a better total effect to improve the wafer quality. The pulled-out of diamond abrasives is the main wear form of wire, which indicates that more research on improving the abrasives retaining strength on wire surface should be investigated in fixed-abrasive wire manufacturing process, in order to improve the wire life and wire saw machining process.     

Characterization of polycrystalline silicon wafers for solar cells sliced with novel fixed‐abrasive wire

For slicing crystalline silicon ingots, we have developed a novel fixed‐abrasive wire where diamond grit is fixed onto a bare wire by resin bonding. The properties of the wafers sliced using a multi‐wire saw with the fixed‐abrasive wire have been investigated. When compared with the wafers sliced with the loose‐abrasive wire, the slicing speed is improved by approximately 2.5‐fold and the thicknesses of saw‐damage layers are reduced by more than a factor of two. Polycrystalline silicon solar cells have been fabricated for the first time utilizing the wafers sliced with the fixed‐abrasive wire, and the cells with the saw‐damage etching depth of 7 µm have shown photovoltaic properties comparable to those prepared using the wafers sliced with the loose‐abrasive wire and subsequently etched to remove the damage layers up to 15 µm. It has been clarified that wafer slicing using the fixed‐abrasive wire is promising as a next‐generation slicing technique for fabrication of solar cells, particularly thin silicon cells where the wafer thicknesses approach or become less than 150 µm. Copyright © 2010 John Wiley & Sons, Ltd.     

金刚石多线切割设备在SiC晶片加工中的应用

介绍了金刚石多线切割设备的原理,并采用直径为250μm的金刚石线进行切割工艺实验。使用不同的工艺参数,比较了不同工艺参数对晶片TTV(整体厚度偏差)的影响,给出了实验比较结果,通过改变工艺参数可以使各切割片的TTV控制在25μm之内。     

Subsurface crack damage in silicon wafers induced by resin bonded diamond wire sawing

In order to optimize the process of wire sawing, this work studied the subsurface crack damage in silicon wafers induced by resin bonded diamond wire sawing using theoretical and experimental methods. A novel mathematical relationship between subsurface crack damage depth and processing parameters was established according to the indentation fracture mechanics. Sawing experiment using resin bonded diamond wire saw was performed on a wire saw machine. The validity of the proposed model was conducted by comparing with the experimental results. At last, the influences of processing parameters on subsurface damage depth were discussed. Results indicate that the median cracks are mainly oblique cracks which generate the subsurface crack damage. On the diamond wire saw cross section, the abrasives with the position angle 78° between abrasive position and vertical direction generate the largest subsurface damage depth. Furthermore, abrasives, generating the subsurface damage, tend away from the bottom of diamond wire with the increase of wire speed or decreases with the increase of feed rate. However, the wire speed and feed rate have opposite effects on the subsurface crack damage depth. In addition, the subsurface crack damage depth is unchanged when the ratio of feed rate and wire speed does not change.     

Prediction of sawing force for single-crystal silicon carbide with fixed abrasive diamond wire saw

Fixed abrasive diamond wire saw has been used to cut hard-and-brittle materials into wafers, such as silicon carbide. The force of a single abrasive determines the cutting depth, and affects material removal mode and crack propagation length. Therefore, the sawing force is a key factor that affects the surface/subsurface quality of wafers. In this paper, a numerical sawing force predicting method considering wire saw parameters was proposed with the combination of both ductile removal and brittle fracture removal for each single abrasive. A new calculation method of single abrasive cutting force considering frictional force component and new material removal way considering the effect of lateral crack were adopted. Then the influences of process parameters and wire parameters on sawing force were analyzed. Finally, mathematical sawing force formulas described by both process parameters and wire saw parameters were obtained using the new sawing force prediction method. The validity of this prediction method and sawing force formulas was verified through experiments in the literature under the same process parameters and wire saw parameters.     

SiC单晶生长及其晶片加工技术的进展

回顾了SiC单晶的发展历史，总结了目前的发展状况，同时介绍了SiC单晶生长所需要的温场和生长工艺，最后介绍了SiC单晶的加工技术. 通过模拟计算与具体实验相结合的方法，调整坩埚在系统中的位置及优化坩埚设计可以得到理想温场. 近平微凸的温场有利于晶体小面的扩展，进而有利于减少缺陷提高晶体的质量. 由于SiC硬度非常高，对单晶后续的加工造成很多困难，包括切割和磨抛. 研究发现利用金刚石线锯切割大尺寸SiC晶体，可以得到低翘曲度、低表面粗糙度的晶片；采用化学机械抛光法，可以有效地去除SiC表面的划痕和研磨引入的加工变质层，加工后的SiC晶片粗糙度可小于1nm.     

SiC单晶生长及其晶片加工技术的进展

回顾了SiC单晶的发展历史,总结了目前的发展状况,同时介绍了SiC单晶生长所需要的温场和生长工艺,最后介绍了SiC单晶的加工技术.通过模拟计算与具体实验相结合的方法,调整坩埚在系统中的位置及优化坩埚设计可以得到理想温场.近平微凸的温场有利于晶体小面的扩展,进而有利于减少缺陷提高晶体的质量.由于SiC硬度非常高,对单晶后续的加工造成很多困难,包括切割和磨抛.研究发现利用金刚石线锯切割大尺寸SiC晶体,可以得到低翘曲度、低表面粗糙度的晶片;采用化学机械抛光法,可以有效地去除SiC表面的划痕和研磨引入的加工变质层,加工后的SiC晶片粗糙度可小于1nm.     

固结磨料研磨硫化锌的亚表面损伤预测分析

研磨抛光后产生的工件亚表面损伤是评价工艺优劣及确定加工余量的主要参考,因此对亚表面损伤准确的预测有助于提高加工效率。采用离散元法对典型的软脆材料硫化锌固结磨料研磨过程中产生的亚表面损伤进行模拟,预测不同粒径金刚石加工工件后的亚表面微裂纹层深度。利用角度抛光法将工件抛光出一个斜面,作为亚表面损伤观测平面,通过盐酸的腐蚀使亚表面微裂纹显现,在金相显微镜下寻找微裂纹消失的终点位置并转换成亚表面微裂纹层深度,对仿真结果进行实验验证。结果表明:粒径为5、15、25、30 μm的磨粒造成的亚表面微裂纹层深度预测值分别为2.28、3.62、5.93、7.82 μm,角度抛光法实测值分别为2.02、3.98、6.27、8.27 μm。以上结果表明磨粒粒径对硫化锌亚表面损伤情况有很大的影响,随着磨粒粒径的增大,亚表面微裂纹深度增加,微裂纹数量增多。离散元法预测值与实测值偏差范围处在5%~15%之间,利用离散元法能有较为准确的预测软脆材料硫化锌加工后的亚表面损伤情况,为其研抛工艺的制定提供参考。     

金刚线切割多晶硅片表面酸制绒效果研究

为了探索金刚线切割多晶硅片的表面制绒新技术,采用常规酸制绒、添加剂酸制绒和酸蒸气制绒三种方法对金刚线切割多晶硅片表面进行制绒处理,并用扫描电镜和光谱仪分析了三种制绒方法处理后多晶硅片的表面形貌和反射率比变化。结果表明,酸蒸气制绒能够更加有效地去除线锯切割产生的平行纹,降低表面反射率。通过调节蒸气源蒸发的温度,可以有效改善多晶硅的表面形貌,大幅降低入射光在多晶硅表面的反射率,300~1100nm波长范围内多晶硅样品的最低平均反射率达11.6%,有望用于制作高效多晶硅太阳电池。