LiTaO3晶片CMP过程工艺参数研究

采用不同抛光条件抛光LiTaO3晶片,通过测量其加工表面粗糙度和材料去除率,探讨了化学机械抛光去除机理,分析了抛光垫材料和状态、抛光压力、抛光盘转速等因素对LiTaO3晶片抛光表面质量和材料去除率的影响规律,并获得了LiTaO3晶片CMP加工的有效工艺参数.实验表明,为获得LiTaO3晶片超精密表面,可采用沥青和平绒布抛光垫进行粗抛和精抛,然后采用旧无纺布(抛光垫)进行终抛,获得较大工件去除率和较光滑表面,得到良好的综合抛光效果.在修正环型超精密抛光机上,理想的LiTaO3工艺参数为:抛光压力为7.25 kPa,抛光盘转速为60rpm.     

超精密加工机床的模块化设计

分析了模块化设计的优点和超精密加工机床设计的现状 ,提出了超精密加工机床模块化设计的设想 ,并利用了模块化超精密组件设计了几种典型的超精密机床。     

精密与超精密磨削的发展现状

阐述了精密磨削与超精密磨削的机制,介绍了近年来精密与精密磨床的发展概况以及精密与超精密磨削技术的研究现状。在分析了精密磨削与超精密磨削的发展趋势基础上提出了研究应关注的几个热点问题,如超精密磨削的基本理论和工艺研究、研制高精度的驱动导向机构、ELID镜面磨削技术的攻关以及适用于超精密加工的新型材料。     

脆性材料磨粒加工的纳米尺度去除机理

以共价键或离子键结合的脆性单晶、多晶和光学玻璃是能源、通信、交通和医疗领域新兴微电子和光电器件的核心材料。为满足高性能器件的制造需求,脆性材料通常需要经过磨削、研磨、抛光等超精密磨粒加工,获得具有原子级光滑的表面、近无损伤的亚表面和微米甚至纳米级的加工精度。优化磨粒加工工艺不仅可以有效地提高加工效率,降低制造成本,还能够延长脆性材料元器件的服役寿命,但开发高效率、低损伤超精密磨粒加工技术需深入理解脆性材料纳米尺度的去除机理。本文基于划擦力学原理,揭示脆性材料纳米尺度磨粒加工去除的本质,阐明磨粒加工过程中脆性材料脆性–塑性转变去除的基本原理,概述单磨粒纳米划擦脆性材料的形变和去除机制,以及磨粒加工过程中脆性材料的去除机理及材料微观结构对其局部变形及后续去除的影响规律,提出实现脆性材料高效延性加工的控制策略,有助于推动脆性材料超精密磨粒加工技术的进一步发展。      

金属材料超快激光制孔研究进展

超快激光作为一种先进加工手段，因具有高柔性、高峰值功率密度、热影响小等特点可满足任意材料的精密加工，在航空航天、电子信息、新能源等领域的金属材料精密制孔中具有显著优势，故针对金属材料的超快激光冲击制孔、铣削制孔、螺旋制孔、环切制孔以及复合工艺制孔等工艺进行综述，总结了各制孔工艺的优势和面临的挑战。     

单晶SiC基片的化学机械抛光技术研究进展

单晶SiC因其优异的物理化学性质而成为重要的外延衬底材料，广泛应用于卫星通信、集成电路和消费电子等领域。衬底外延生长需要单晶SiC具有较低的加工表面损伤和残余应力的超光滑平坦表面，其表面质量决定了后续的外延层质量并最终影响器件的性能。化学机械抛光(CMP)是目前实现单晶SiC基片超精密加工的一种常用且有效方法。我们综述了单晶SiC基片化学机械抛光加工的研究现状，根据加工原理进行归类并分析了各种类别的优缺点及运用局限，指出了其在化学机械抛光领域的发展前景。      

超声振动辅助研磨单晶碳化硅晶片工艺研究

针对传统研磨方法加工单晶碳化硅晶片存在的材料去除率低、磨料易团聚等问题,本文提出超声振动辅助研磨方法,并探究不同工艺参数（转速、磨料质量分数、抛光压力、磨料粒径）对单晶碳化硅晶片研磨效率和表面质量的影响规律。试验结果和理论分析表明:超声振动有效提高了单晶碳化硅晶片研磨的材料去除率;在研磨盘转速为50 r/min,磨料质量分数为2.5%,压力为0.015 MPa,磨料粒径为0.5 μm时超声振动对材料去除率的提升效果最明显,分别提升23.4%,33.8%,72.3%,184.2%。同时,通过对研磨过程中表面粗糙度的追踪检测,能确定不同粒径磨料超声振动辅助研磨的最佳时间。      

超精密机床

本文详细介绍了超精密加工的特点和各种方法,以及超精密机床的设计特点和对各部件的设计要求,可供超精密加工设计、工艺人员参考.     

超精密晶圆减薄砂轮及减薄磨削装备研究进展

在芯片制程的后道阶段,通过超精密晶圆减薄工艺可以有效减小芯片封装体积,导通电阻,改善芯片的热扩散效率,提高其电气性能、力学性能。目前的主流工艺通过超细粒度金刚石砂轮和高稳定性超精密减薄设备对晶圆进行减薄,可实现大尺寸晶圆的高精度、高效率、高稳定性无损伤表面加工。重点综述了目前超精密晶圆减薄砂轮的研究进展,在磨料方面综述了机械磨削用硬磨料和化学机械磨削用软磨料的研究现状,包括泡沫化金刚石、金刚石团聚磨料、表面微刃金刚石的制备方法及磨削性能,同时归纳总结了软磨料砂轮的化学机械磨削机理及材料去除模型。在结合剂研究方面,综述了金属、树脂和陶瓷3种结合剂的优缺点,以及在晶圆减薄砂轮上的应用,重点综述了目前在改善陶瓷结合剂的本征力学强度及与金刚石之间的界面润湿性方面的研究进展。在晶圆减薄超细粒度金刚石砂轮制备方面,由于微纳金刚石的表面能较大,采用传统工艺制备砂轮会导致磨料发生团聚,影响加工质量。在此基础上,总结论述了溶胶–凝胶法、高分子网络凝胶法、电泳沉积法、凝胶注模法、结构化砂轮等新型工艺方法在超细粒度砂轮制备方面的应用研究,同时还综述了目前不同的晶圆减薄工艺及超精密减薄设备的研究进展,并指出未来半导体加工工具及装备的发展方向。     

砷化镓衬底加工技术研究及其新发展

第二代半导体砷化镓(GaAs)材料是衬底外延生长和器件制备的基础材料,其晶片表面要求超光滑、无表面/亚表面损伤和低的残余应力等,且其表面平坦化质量决定了后续外延层的质量,并最终影响相关器件的性能。通过归纳分析砷化镓单晶材料的本征特性及其切割、磨边、研磨、抛光等技术的研究进展,对砷化镓超光滑平坦化加工技术未来的研究方向进行展望。      

Grinding induced subsurface cracks in silicon wafers

Silicon wafers are used for production of most microchips. Various processes are needed to transfer a silicon crystal ingot into wafers. To ensure high surface quality, the damage layer generated by each of the machining processes (such as lapping and grinding) has to be removed by its subsequent processes. Therefore it is essential to assess the subsurface damage for each machining process. This paper presents the observation of subsurface cracks in silicon wafers machined by surface grinding process. Based on cross-sectional microscopy methods, several crack configurations are identified. Samples taken from different locations on the wafers are examined to investigate the effects of sample location on crack depth. The effects of grinding parameters such as feedrate and wheel rotational speed on the depth of subsurface crack have been studied by a set of factorial design experiments. Furthermore, the relation between the depth of subsurface crack and the wheel grit size is experimentally determined.     

Slicing,cleaning and kerf analysis of germanium wafers machined by wire electrical discharge machining

This paper investigates the slicing of germanium wafers from single crystal, gallium-doped ingots using wire electrical discharge machining. Wafers with a thickness of 350 μm and a diameter of 66 mm were cut using 75 and 100 μm molybdenum wire. Wafer characteristics resulting from the process such as the surface profile and texture are analyzed using a surface profiler and scanning electron microscopy. Detailed experimental investigation of the kerf measurement was performed to demonstrate minimization of material wastage during the slicing process using WEDM in combination with thin wire diameters. A series of timed etches using two different chemical etchants were performed on the machined surfaces to measure the thickness of the recast layer. Cleaning of germanium wafers along with its quality after slicing is demonstrated by using Raman spectroscopy.     

Surface damage in wire-cut silicon wafers

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Abrasive electrochemical multi-wire slicing of solar silicon ingots into wafers

To meet the growing demands of the global photovoltaic (PV) industry, preparing large scale and ultra-thin solar wafers becomes one of the key issues. This paper presents the preparatory investigations of slicing solar silicon ingot into wafers by an abrasive electrochemical method based on a multi-wire saw system. The anodic passivation on silicon can be controlled by applying an anodic potential during the mechanical slicing process, which improves the surface integrity and material removal rate remarkably. This new hybrid machining method has no influence on subsequent cleaning of wafers and preparing the solar cells, and the average photoelectric transformation efficiency is >17.5%.     

晶体取向对蓝宝石晶片抛光加工的影响研究

目的 对比分析不同晶向蓝宝石晶圆抛光结果,优化加工参数,探究晶体取向对抛光结果的影响规律.方法 选取A、C面蓝宝石晶片(50.8 mm)为研究对象,采用控制变量法,分别以加工载荷(9.87、14.81、19.75 kPa)和抛光盘转速(20、40、60、80 r/min)为变量,以表面粗糙度Ra和材料去除率MRR为评价指标,对两种晶体取向的蓝宝石晶片进行抛光加工试验,借助3D表面轮廓仪与扫描电子显微镜SEM,对加工前后蓝宝石晶片的表面形貌进行对比,并根据试验结果优化加工参数.结果 A、C面蓝宝石晶片的表面粗糙度与材料去除率,随时间均表现出先快速下降,然后逐渐变缓,最后趋于稳定的趋势.当选取转速60 r/min、载荷14.81 kPa的参数组合时,两种晶片获得目标最小粗糙度和最大材料去除率,最终得到A面Ra=24.874 nm,MRR=3.715 nm/min,C面Ra=2.763 nm,MRR=7.647 nm/min,C面材料去除率为A面的2.1～2.5倍.结论 蓝宝石晶体取向作用对材料加工结果存在显著影响,在相同的加工条件下,相较于A面蓝宝石,C面蓝宝石更容易获得纳米级的表面质量和更高的材料去除率,即C面更易加工.     

Fine grinding of silicon wafers

Silicon wafers are used for the production of most microchips. Various processes are needed to transfer a silicon crystal ingot into wafers. As one of such processes, surface grinding of silicon wafers has attracted attention among various investigators and a limited number of articles can be found in the literature. However, no published articles are available regarding fine grinding of silicon wafers. In this paper, the uniqueness and the special requirements of the silicon wafer fine grinding process are introduced first. Then some experimental results on the fine grinding of silicon wafers are presented and discussed. Tests on different grinding wheels demonstrate the importance of choosing the correct wheel and an illustration of the proper selection of process parameters is included. Also discussed are the effects of the nozzle position and the flow rate of the grinding coolant.     

单晶硅材料电火花加工试验研究

针对单晶硅材料的特点，研究单晶硅的电火花加工工艺对促进电火花加工技术在微机电系统中的应用有重要的意义。对单晶硅材料进行电火花加工工艺试验研究的结果表明，在一定的条件下，电火花加工工艺可成为单晶硅材料的一种较有效的加工方法。     

High efficiency slicing of low resistance silicon ingot by wire electrolytic-spark hybrid machining

As the semiconductor industry requires the cutting of silicon ingots into wafers, the slicing of large, ultra thin wafers is one of the main technologies to prevent wastage. Recently, apart from conventional inner diameter (ID) blade and multi-wire saw methods, wire electrical discharge machining (WEDM), which has no cutting force, has been introduced to this area and low resistance silicon may be sliced by WEDM. In this paper, a novel approach, based on wire electrolytic-spark slicing strategy using hybrid oil/aqueous electrolyte, combining electric discharge and anodic etching into a single process, is investigated experimentally. Some improvements, such as a new wire winding system, hybrid electrolyte and high efficiency pulse generator, have been adopted in a kind of high speed (HS)-WEDM machine. Experiments have been conducted to evaluate the machining rate, surface quality and wafer thickness of low resistance (0.5–3 Ω cm) mono-crystalline silicon. It has been demonstrated that with properly selected electrical parameters and electrolyte, a maximum machining rate of 600 mm²/min can be obtained and with a wafer thickness less than 120 μm. Furthermore, in comparison with WEDM, heat affected zone and harmful metal residues are considerably diminished, which provides significant theoretical and experimental support for future applications.     

Theoretical analysis on the effects of crystal anisotropy on wiresawing process and application to wafer slicing

Most of the crystals sliced using wiresaw are anisotropic to an extent. The effect of crystal anisotropy on the process of slicing using wiresaw is studied and presented in this paper. A method is proposed to determine the direction of approach (DOA) which will give a better surface finish and reduce deviation from the desired surface normal by maintaining symmetry in material removal rates on the two sides of the wire. The effect of cleavage anisotropy on wiresaw slicing is also studied. If the DOA is perpendicular to a cleavage direction, then the longitudinal direction of the wire aligns with the cleavage direction which increases the tendency of wafer breakage, resulting in lower yield of the wafers. This can be easily avoided by choosing an appropriate DOA. Theoretical analysis is carried out using the proposed methods for slicing silicon wafers. Recommendations are made for three most commonly sliced orientations of silicon: (100), (110) and (111). DOA can be any direction for (100) and (110) wafers from the symmetry point of view but preferred DOAs do exist for these wafers from cleavage point of view. For (111) crystal there are exactly six DOAs with symmetry. However, these six DOAs do not lie in the preferred zones suggested by cleavage criterion. It is suggested that in such situations the symmetry criterion should be given precedence over the cleavage criterion during wiresawing process, as the semiconductor industry has strict tolerances in place for surface normal deviation and flatness.     

热丝化学气相沉积法制备优质微米亚微米级单晶金刚石的研究

利用热丝化学气相沉积法（HFCVD）,在硅片衬底上进行微米级（〉1μm）及亚微米级（〈1μm）单晶金刚石的沉积研究。微米级金刚石是以高温高压法（HPHT）制备的1μm金刚石颗粒为籽晶,通过甩胶布晶的方法,在衬底上均匀分布晶种,并通过合理控制沉积工艺参数,在衬底上形成晶形完好的单晶金刚石。在沉积2 h后,可消除原HPHT籽晶缺陷,沉积6 h后,生长出晶形良好的立方八面体金刚石颗粒（约4μm）;对于亚微米级单晶金刚石,是直接在衬底上进行合成,通过调控沉积参数（如衬底预处理方法,偏流大小,沉积时间）对单晶金刚石的分布密度和颗粒度进行控制,经过2 h的沉积,最终获得了0.7μm的二十面体单晶金刚石。