纳米级超精密磨削IC硅片的金刚石砂轮材料研究

发布时间：2018-03-27 18:06

  本文选题：金刚石砂轮　切入点：IC硅片　出处：《上海大学》2016年博士论文

【摘要】：IC芯片是电子计算机、智能手机和平板电脑等智能终端设备所用微处理器的核心部件。目前,全球90%以上的IC芯片均采用硅片作为衬底材料,可以说IC芯片硅片衬底材料减薄磨削的技术水平,直接关系到未来一个国家微处理器的发展水平。目前制造IC芯片的主流技术为采用精密金刚石砂轮的自旋转磨削工艺,该技术对砂轮的自锐性要求极高,磨削后的硅片表面须达到纳米级表面粗糙度(Ra)和微米级亚表面损伤层厚度(SSD)。当前国产砂轮普遍自锐性低,磨削出的衬底硅片存在硅片表面Ra和SSD过大的问题,容易导致硅片碎裂而造成巨大经济损失。特别是制备高端IC芯片时需使用直径大于Ф200 mm的硅片衬底材料,而发达国家将磨削大直径硅片的精密金刚石砂轮作为战略物质限制对中国出口,对其材料组分、配方及制作工艺严格保密,因此急需针对该金刚石砂轮的材料及其制备工艺开展系统研究。针对磨削大尺寸硅片衬底用精密金刚石砂轮自锐性低、磨削出的衬底硅片存在表面Ra和SSD过大的问题,通过研究树脂砂轮和陶瓷砂轮的造孔机理,采用在砂轮中引入大量气孔,弱化粘结剂与磨料结合力的方法,开发制备大气孔率砂轮试样的混料、成型、烧结和修整的新工艺,制备出新型陶瓷粘结剂和树脂粘结剂。采用TG-DSC、FTIR、SEM和EDS等方法,观察试样形貌并对比分析试样力学强度等数据,探索砂轮材料含量对试样力学强度的影响规律,开展砂轮材料性能优选工作。研究材料组分及含量对砂轮磨削性能的影响,开展硅片磨削机理研究并进行砂轮试样的工业化应用试验。硅片加工分为粗磨和精磨两道工序,分别采用锋利耐用的陶瓷金刚石砂轮和抛光性能好的树脂金刚石砂轮。陶瓷砂轮使用研制的Na2O-Al2O3-Si O2-B2O3多元陶瓷粘结剂,其烧结温度685℃,该温度下其流动性为140~150%,膨胀系数为4.46×10-6m/K,接近金刚石的膨胀系数4.40×10-6 m/K。树脂砂轮使用研制的BMI树脂粉,粒径为10~40μm,密度1.33 g/cm3,吸水性在0.2%~0.3%,TG曲线显示该树脂的5%热失重温度为348.9℃。开发包括聚合物粉在陶瓷砂轮粘结剂桥造孔和陶瓷粘结剂湿法球磨等工艺,在陶瓷砂轮料中加入6%体积百分数的聚合物粉末,在最高温度685℃烧结后在陶瓷粘结桥上生成较多5~8μm的气孔。通过添加聚合物成孔弱化陶瓷粘结剂与磨料的把持力,使磨钝的金刚石磨粒自行脱落,提高砂轮自锐性。添加聚合物粉的陶瓷粘结剂砂轮的毛坯采用热压工艺成型,热压温度为215℃,压力10 MPa。设计陶瓷粘结剂配方并经多次玻化破碎,采用自制行星式球磨机和开发的湿法球磨工艺将陶瓷粘结剂研磨成粒径小于2μm的粉末。采用最大粒径为90μm到2μm的8种金刚石制作陶瓷和树脂砂轮,开展磨削硅片试验。试验结果表明:8种金刚石制作陶瓷和树脂砂轮磨削出的硅片表面粗糙度Ra可从378 nm至1.91 nm,硅片SSD可从16.5μm至0.92μm,砂轮MMR可从35μm/s至0.3μm/s。多晶金刚石的磨削效果较单晶金刚石的更好,在磨削工件Ra、磨削电流、MMR和SSD等方面均有优势。同粒径条件下,陶瓷砂轮较树脂砂轮的MMR高20%,SSD高20%,磨削电流低5%,但Ra高近100%。造孔剂的成孔机理分为占位后去除成孔和气体发泡成孔等。结果表明:发气型造孔剂制作的砂轮试样磨削效果较好。添加造孔剂后,金刚石砂轮磨削时不需强制修锐,砂轮的自锐性明显改善。硅片SSD由3.5μm减至0.92μm,硅片表面Ra从6.72 nm减至1.91 nm。当加工磨削余量为20μm的Ф200 mm硅片时,砂轮寿命为25000片。多晶金刚石磨料的粗糙表面可增加其与粘结剂的嵌合力,减少磨料脱落造成的磨削划伤。多气孔结构可减小砂轮与硅片工件的接触面积并降低二者之间摩擦力,固体润滑剂可减小树脂粘结剂与硅片的摩擦系数并降低磨削功率。采用硅屑EDS和SEM等测试方法,通过对比硅屑与硅片表面磨痕宽度及即将脱落的颗粒直径,确定2μm的颗粒为硅屑颗粒。通过分析磨削液中存在的颗粒状磨屑和拉丝状磨屑,提出在磨削过程中硅片材料存在脆性崩裂和塑性变形两种去除机制的机理。经工业化应用验证表明,采用在砂轮中引入大量气孔,弱化粘结剂与磨料结合力的方法,制备出的砂轮持续锋利磨削,可控制磨削时砂轮对硅片的挤压力,多气孔砂轮的自锐性提高,硅片表面达到纳米级硅片表面粗糙度和微米级硅片亚表面损伤层要求,砂轮试样磨削硅片无碎裂现象,满足IC芯片衬底硅片的磨削要求。
[Abstract]:IC chip is the core component of the electronic computer, microprocessor for intelligent mobile phone and tablet computer and other intelligent terminal equipment. At present, more than 90% of global IC chip using silicon as the substrate material, can be said that the technical level of thinning grinding IC chip silicon substrate materials, directly related to the future development of a national mainstream microprocessor. The current IC chip manufacturing technology for the self rotating grinding process using diamond grinding wheel, the grinding technology on self sharpening of the requirements that a silicon wafer surface after grinding to achieve nanometer surface roughness (Ra) and micron surface damage layer thickness (SSD). The current domestic general self sharpening grinding wheel is low. The silicon substrate is grinding out the existence of Ra and SSD on silicon wafer surface is too large, easily lead to wafer fragmentation caused enormous economic losses. Especially the preparation of high-end IC chip for use with diameter greater than 200 Silicon substrate materials of mm, while the developed countries will be diamond grinding wheel with large diameter silicon wafer grinding as a strategic material restrictions on the export of China, its material composition, formulation and production process strictly confidential, so there is an urgent need for the material of diamond grinding wheel and its preparation technology development system research. For the large size silicon substrate by precision grinding self sharpening diamond grinding wheel, grinding out the surface of the silicon substrate is Ra and SSD. The pore forming mechanism of resin grinding wheel and ceramic grinding wheel, with the introduction of a large number of pores in the grinding wheel, the weakening of the bonding agent and method of abrasive binding force, the development of material preparation, mixing air hole ratio of wheel specimen the forming, sintering and dressing, preparation of new ceramic binder and resin binder. By using TG-DSC, FTIR, SEM and EDS, to observe the surface morphology and the comparative analysis of mechanical strength Data, explore the influence of wheel material content on mechanical strength and work performance of wheel material optimization. The influences of composition and content of materials on the grinding performance of grinding wheel, industrial application test sample and study the grinding mechanism of silicon wafer processing and grinding. The two process for coarse grinding, using resin ceramic diamond grinding wheel and diamond grinding wheel polishing performance sharp and durable good. Na2O-Al2O3-Si O2-B2O3 multiple ceramic binder ceramic grinding wheel used developed, the sintering temperature is 685 degrees centigrade, the temperature of the flow is 140~150%, expansion coefficient is 4.46 * 10-6m/K, BMI resin powder expansion coefficient is close to 4.40 * 10-6 m/K. diamond resin grinding wheel used for the particle size of 10~40, m, density of 1.33 g/cm3, water absorption in 0.2%~0.3%, TG curve shows 5% heat loss temperature of the resin is 348.9 DEG. Development including polymerization Powder pore in ceramic grinding wheel binder bridge and ceramic binder by wet milling process, the polymer powder with 6% volume fraction in ceramic grinding wheel material, the maximum temperature of 685 DEG C after sintering in ceramic bonding bridge 5~8 m generated more pores. By adding polymer into hole weak ceramic binder and abrasive holding force so, blunt diamond abrasive wheel off on their own, improve self sharpening. The polymer powder ceramic binder wheel blank by hot pressing molding, hot pressing temperature is 215 DEG C, the pressure of 10 MPa. design of ceramic binder and has broken glass, by wet milling process of self-made planetary mill and the development of the ceramic binder a particle size less than 2 mu m powder. The maximum particle diameter of 90 mu m to 8 mu m 2 Diamond making ceramic and resin grinding wheel, grinding out wafer test. The test results show :8绉嶉噾鍒氱煶鍒朵綔闄剁摲鍜屾爲鑴傜爞杞�纾ㄥ墛鍑虹殑纭呯墖琛ㄩ潰绮楃硻搴�Ra鍙�浠�378 nm鑷，

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