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.     

锗单晶切割工艺研究

多线切割机是一种将晶棒切割成晶片的设备,近年来得到大规模使用,其切割原理为利用高速运动的切割钢线将砂浆带入切割区,砂浆中的坚硬颗粒（主要为SiC）与晶棒进行磨削,进而起到切割作用。根据锗材料的特殊性,通过改变工艺参数（主轴平均转速,砂浆流量,砂浆供给方式等）与硅材料成熟切割工艺进行对比实验,进而稳定锗材料的切割工艺。     

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.     

Prediction of the thickness for silicon wafers sawn by diamond wire saw

A higher yield and lower processing cost for the production of the silicon wafer can be realized by reducing the sliced thickness. However, a larger fracture probability is accompanied with the thinner silicon wafer, which limits the wafer thickness to be reduced. The contradiction between reducing wafer thickness and keeping a smaller fracture probability is an important problem for the industrial production of the silicon wafer. This paper investigates the influences of silicon wafer size and machining defects on the fracture probability in order to understand the essential relationship between damage information and fracture probability adequately. A theoretical model of the fracture probability for silicon wafer is proposed based on the probabilistic fracture mechanics to determine a proper thickness for wafers with different size. Furthermore, one method of predicting a proper thickness for silicon wafers sawn by diamond wire saw is developed. The thickness of 450-mm silicon wafer obtained by this proposed method is 920 µm, which is comparable with the value 925 µm specified by the International Technology Roadmap for Semiconductor. The comparison of these two values reveals the feasibility and correctness of this proposed method. The proposed model in this paper can be used to evaluate the fracture probability and predict a proper thickness for silicon wafers with different size, which is benefit to optimize the processing technology and decrease the breakage ratio for the wafer production.     

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。     

变速切割速度曲线对硅片翘曲度的影响

根据线切割机的工作原理,综合考虑了砂浆中磨料在磨削过程中的变化以及单晶直径的变化,确定了变速切割的工艺方法,同时考虑到125 mm单晶直径大、SIC磨削路线长、磨削发热量大,制定了包括线速度、耗线量、砂浆温度、砂浆流量以及各部分温度的工艺参数。通过该工艺参数进行了切割实验,验证了该工艺参数下切割的晶片可以满足要求。     

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.     

多线切割工艺中晶片翘曲度的控制

翘曲度是鉴别晶片几何参数好坏的重要指标之一.采用逐点扫描法对多线切割制备的晶片翘曲度分布进行了测量.通过对切割线张力、砂浆使用次数、切割速度等影响翘曲度的主要因素进行实验分析,阐述了产生的原因,并得出了翘曲度的分布规律.针对影响翘曲度的主要因素,根据其分布规律调整相应的切割工艺条件,可较好地控制晶片的翘曲度.虽是针对Si单晶加工中出现的实验情况进行分析,但该结论完全可用于Ge、GaAs等其他晶体的加工中.     

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.     

300-mm Low-${hbox {k}}$ Wafer Dicing Saw Development

With the further shrinking of IC dimensions, low- material has been widely used to replace the traditional SiO interlayer dielectric (ILD) in order to reduce the interconnect delay. The introduction of low- material into silicon imposed challenges on dicing saw process. ILD and metal layers peeling and its penetration into the sealing ring of the die during dicing saw are the most common defects. In this paper, the low- material structure and its impact on wafer dicing were elaborated. A practical dicing quality inspection matrix was developed to assess the cutting process variation. A 300-mm CMOS90-nm dual damascene low- wafer was chosen as a test vehicle to develop a robust low- dicing saw process. The critical factors (dicing blade, index speed, spindle speed, cut in depth, test pattern in the saw street, etc.) affecting cutting quality were studied and optimized. The selected C90 Dual damascene low- device passed package reliability tests with the optimized low- dicing saw recipe and process. The further improvement and solutions in eliminating the low- dicing saw peeling were also explored.     

多线切割加工中单晶硅片晶向影响关系研究

单晶硅片的晶向是大规模集成电路衬底材料的一个重要参数。硅片的晶向是根据单晶的生长晶向以一定的角度粘结固定到多线切割机的工作台上切割实现的。但是在实际粘结操作过程中,单晶棒易滑移导致角度产生偏差从而影响到加工后的硅片晶向超差而报废。为了明确粘结角度偏差对切割后硅片晶向的影响关系,在产生误差的情况下做出科学正确的判断,对粘结角度的计算原理进行了推导、得出了单晶棒X．ray定向仪的计算原理。在此基础上,对粘结产生的角度误差对晶向的影响关系进行了理论推导．得出了它们之间的明确影响关系的函数关系。此函数关系表明。粘结过程的角度误差对硅片晶向的影响是复杂的反三角函数关系,必须通过实际计算才能确定其大小。通过此函数关系,可以明确的确定单晶棒粘结的角度偏差对硅片晶向的影响。为科学的现场判断提供了理论依据,能有效的服务于生产实际,．     

多线切割工艺中切割线直径对翘曲度影响的研究

目前,在硅单晶锭切割领域多线切割机已得到广泛的应用。切割砂浆及切割线在切割中有着极其重要的作用,不同的使用条件会直接影响切割晶片的几何参数。主要讨论切割线直径的不同对切割出晶片几何参数的影响。     

多线切割工艺中切割速度对晶片翘曲度的影响

目前,半导体单晶材料的加工多采用多线切割机进行切割。切割工艺直接影响着切割过后晶片的参数。在这些参数中,翘曲度是鉴别晶片几何参数好坏的重要指标之一。影响翘曲度的因素很多,如切割速度、砂浆密度、晶片内部应力等,在切割工序中,通过调整多线切割的工艺条件,来控制和改善晶片的翘曲度。     

晶体Si片切割表面损伤及其对电学性能的影响

对比观察了不同工艺条件下金刚石线锯和砂浆线锯切割晶体Si片的表面微观形貌;分析了其切割机理及去除模式;对比分析了三种不同化学方法钝化Si片的效果和稳定性;采用逐层腐蚀去除Si片的损伤层,使用碘酒对其进行化学钝化,然后测试其少子寿命,分析Si片少子寿命随去除深度的变化趋势,根据Si片少子寿命达到最大值时的腐蚀深度,测试确定Si片的损伤层厚度。经实验测得,砂浆线锯切割Si片的损伤层厚度为10μm左右,金刚石线锯切割Si片的损伤层厚度为6μm左右。结果表明,相比于砂浆线锯切割Si片,金刚石线锯切割Si片造成的表面损伤层更浅,表面的机械损伤也更小。     

Mechanisms of wafer sawing and impact on wafer properties

Silicon wafer wire‐sawing experiments were realized with different sets of sawing parameters, and the thickness, roughness, and cracks depth of the wafers were measured. The results are discussed in relation to assumptions underlying the rolling–indenting model, which describes the process. It was also found that the silicon surface at the bottom of the sawing groove is different from the wafer surface, implying different sawing conditions in the two positions. Furthermore, the measured parameters were found to vary along the wire direction, between the entrance of the wire in the ingot and its exit. Based on these observations, some improvements for the wire‐sawing model are discussed. Copyright © 2010 John Wiley & Sons, Ltd.     

纳米CeO2磨料对硅晶片CMP的效果与机理研究

通过均相沉淀法制备了纳米CeO_2超细粉体,并配制成抛光液对硅片进行化学机械抛光(CMP),研究了纳米CeO_2磨料对硅片的抛光效果,通过建立的接触模型进一步地解释了纳米级磨料的化学机械抛光机理。实验结果分析表明:由于纳米磨料粒径小,切削深度小,材料是以塑性流动的方式去除。使用纳米CeO_2磨料最终在1μm的范围内达到了微观表面粗糙度Ra为0.103 nm的超光滑表面,而且表面的微观起伏更趋向于平缓。     

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。     

Effect of wire vibration on the materials loss in sapphire slicing with the fixed diamond wire

Sawn kerf, wafer profile error and wafer subsurface damage were systematically measured and were used to evaluate the materials loss for the sapphire slicing with the fixed diamond wire. The vibration of saw wire was also measured during the slicing process. The impact of each part on the materials loss was discussed. The effect of the wire vibration on the materials loss was explored. It was found that the sawn kerf loss and the wafer profile error loss were the main forms of the materials loss during the slicing process. Wire vibration has significant influence on sliced wafer morphology. Influence of slice parameters on the kerf loss is similar with the case on the vibration amplitude, which indicates that the wire vibration is the key factor to cause the kerf loss. Wire slicing model with the wire vibration is established to understand the influence of wire vibration on the materials loss.     

VB GaAs抛光片几何参数控制技术研究

在VB(垂直布里奇曼法)GaAs材料加工过程中,切割、研磨、化学腐蚀、抛光等工序对VB GaAs抛光片的几何参数有着不同程度的影响.通过试验对比,找出了影响不同几何参数指标的关键工艺,其中切割和化学腐蚀是控制VB GaAs晶片翘曲度的关键工艺,而抛光是控制VB GaAs总厚度变化和总指示读数的关键工艺.研究表明,通过调整切割速度、化学腐蚀速率和抛光速率等工艺参数,能够有效地控制VB GaAs抛光片的几何参数.     

镍包覆率对固结金刚石磨料研磨垫加工性能的影响

通过化学镀镍的方法,在金刚石磨粒表面包覆一层Ni-P 合金层;采用不同包覆率的金刚石磨料制备固结磨料研磨垫;通过SEM 观察分析金刚石的微观形貌;研究了磨料包覆率对研磨垫加工K9 玻璃过程中的摩擦系数和声发射信号的影响;采用马拉松式试验方法,比较了不同包覆率磨料的研磨垫加工K9 的材料去除速率及研磨后工件的表面粗糙度。结果表明:化学镀镍可以显著改变磨料的表面形貌;研磨过程中的摩擦系数、材料去除速率和工件表面粗糙度均随着包覆率的提高呈现出先增大后减小的趋势;包覆率50%时的金刚石磨料对工件的摩擦力和切入深度最大,研磨垫的磨粒保持与自修整性平衡,加工效率及其稳定性最高。