【作者】 朱祥龙；

【导师】 康仁科；

【作者基本信息】 大连理工大学 ， 机械制造及其自动化， 2011， 博士

【摘要】 硅片的超精密磨削技术主要用于硅片制备中的硅片平整化和IC后道制程中的背面减薄。随着硅片直径的增大和厚度的减小,硅片超精密磨削技术及设备面临新的挑战：大的进给速度调速范围和高的进给稳定性,对磨床进给系统的结构特性和运动性能提出了较高要求；硅片在磨削中容易翘曲变形,磨削面型精度难以保证；硅片原始厚度的增大和芯片磨后厚度的减小趋势,使硅片表面磨削的材料去除量增大,提高加工效率成为一个亟待解决的问题；硅片减薄后,其表面质量和加工变形对磨削力的变化更加敏感,监控磨削力以提高成品率的问题亟待解决。面向大尺寸薄硅片的超精密磨削技术及设备的需求,针对表面质量和磨削效率这对突出矛盾问题,以提高硅片表面质量、面型精度和加工效率为目的,作者深入研究了精密进给、面型控制和磨削力监控等关键技术,设计开发了300mm硅片超精密磨床。主要研究内容和结论如下：(1)研究了基于控制力和工件旋转磨削原理的大尺寸硅片超精密磨削技术,提出了Ф300mm硅片全自动超精密磨床设计方案,该磨床采用双主轴三工位的布局结构,具有在线测量硅片厚度、在线测量磨削力等功能,可完成硅片的传输、定心、浸润、粗磨、精磨、清洗和干燥等工序,实现了硅片全自动磨削。(2)建立了硅片超精密磨床的三维虚拟样机,并对硅片磨床整机和各主要零部件进行了结构静力学分析及动力学有限元分析,完成了对各部分结构的优化设计及设计方案定型。建立了进给系统的刚柔耦合模型,分析了进给系统的运动学特性。创建了进给伺服系统的机电协同仿真模型,并推导了进给系统各环节的传递函数。对硅片磨床进给系统的位移、静态和动态等特性进行了实验验证研究。(3)针对双主轴三工位超精密硅片磨床的结构特点,研究了砂轮主轴与工件主轴相对夹角对磨削面型的影响规律,分别建立了粗磨单元和精磨单元的硅片磨削面型的数学模型；提出了双主轴三工位硅片磨床主轴倾角的调整方法,并研制了主轴倾角调整装置。通过吸盘修整和硅片磨削试验,验证了磨削面型的数学模型,实现了硅片面型精度的精确控制。(4)分析了磨削硅片过程中三向磨削力的特点,研制了基于石英晶体压电效应的三向磨削力在线测量系统,并实现了与硅片超精密磨床的集成。对所研制的三向磨削力在线测量系统进行了静态标定、动态性能测定以及在线标定,获得了三向磨削力在线测量系统的灵敏度、线性和重复性等静态及动态性能指标。以兼顾加工效率和表面质量为目标,提出了分阶段控制力磨削的工艺策略,并在所研制的硅片超精密磨床上通过控制力磨削硅片试验对上述工艺策略进行了验证。(5)与企业合作研制出国内首台0300mm硅片全自动超精密磨床,磨削后硅片的TTV值<4μm,#4800金刚石砂轮磨削后硅片的表面粗糙度值Ra<1.4nm,亚表面损伤层深度<0.25μm,实现了0300mm硅片的高效低损伤超精密磨削。更多还原

【Abstract】 During the process to turn silicon ingot into the integrated circuits (IC) chips, ultra-precision grinding is mainly used in planarization for planarization in silicon wafer preparation and back thinning in the backend of semiconductor manufacturing process. The ultra-precision grinding technology of the large size silicon wifer with ultra-smooth damage-free surface is facing many new challenges:first, the large size ground wafer is easy to warp so that it is difficult to achieve the high accuracy grinding surface shape. Second, the high machining efficiency is required because the material removal amount of the wafer with increasing of wafer diameter and decreasing of IC chip thicknes is increasing. Finally, as the wafer surface quality and processing efficiency is more sensitive to the grinding force, it is essential to monitor grinding force during grinding thinning wafer. Demand on ultra-precision grinding technology and equipment, aiming at improving wafer surface quality, the processing efficiency and precision, the key technologies of precision feeding, surface shape control and grinding force monitoring have been studied. Then the ultra-precision grinder for 300mm wafer is designed and developed.The main research contents and conclusions are as follows:(1)Based on the principle of the infeed grinding and control forces, the ultra-precision grinding technology for large-sized wafer was studied, and the ultra-precision automatic wafer grinder for silicon wafer with maximum diameter of 0300mm was developed. The layout structure of the wafer grinder, which has the characteristics of compact structure and high automation, etc., is constructed into one with double-spindle and triple-workstation. The wafer grinder has many functions including on-line measurement of the thickness and grinding force. All the process are performed automatically, such as wafer transmission, centering, soakage, rough grinding, fine grinding, cleaning and drying, etc.(2)The three-dimensional virtual prototyping of the ultra-precision wafer grinder is established, and then the static and dynamic analysis of the major components and grinding unit are carried out in order to perfect the design. The rigid-flexible coupling model of the infeed system is established, and kinematic characteristic of the infeed system is analyzed. The co-simulation with mechanical and electric model of the infeed system is established and the transfer function of the infeed system is derived. At last, the displacements, static and dynamic characteristics of the infeed system are verified by experiments.(3)According to the structural features of the ultra-precision grinder with double-spindle and triple-workstation, the influence law of the obliquity between wheel spindle and workpiece spindle on the grinding surface shape is studied, and then the mathematical model of the grinding surface shape for rough grinding unit and fine grinding unit are established. The adjustment method of the spindle obliquity for wafer grinder with double-spindle and triple-workstation is proposed, and the obliquity adjustment devices of the rough grinding spindle, fine grinding spindle are developed. At last, the model of the surface shape control is verified by self-grinding chuck and wafer grinding experiments.(4)The main grinding force Fc, Cut-in force Fp, Feeding force Ff in the process of the wafer grinding are analyzed. The piezoelectric quartz crystal-based dynamometer, integrated in 0300mm silicon ultra-precision grinder, is developed for measuring grinding force in three directions. The sensitivity, linearity, repeatability and other static and dynamic characteristics of the dynamometer are obtained by performing static calibration, dynamic performance measurement and on-line calibration. Aiming at processing efficiency and surface quality, an innovative process, which combines wheel feeds step by step and grinding based on force control, is put forward. At last, a series of the grinding experiments, which the grinding wheel feed rate is controlled by grinding force feedback, are conducted.(5)The ultra-precision automatic wafer grinder for silicon wafer with maximum diameter of 0300mm was developed, which is first in domestic. The results show that the total thickness variation of the ground wafer, the surface roughness of the wafer ground by #4800 grinding wheel and the thickness of the sub-surface damage layer are less than 4μm,1.4nm, 0.25μm, respectively. The ultra-precision grinding with high efficiency and low damage can be realized.更多还原