【作者】 李猛；

【导师】 朱祥龙； 马赛；

【作者基本信息】 大连理工大学 ， 机械工程， 2025， 硕士

【摘要】 超精密磨削技术作为晶圆平整化与背面减薄的关键工艺,其加工精度直接影响着芯片三维堆叠封装效果和纳米级电路图形的光刻质量。随着IC芯片集成度的不断增大,晶圆表面需要具有高精度、高的表面和亚表面完整性,但是目前晶圆磨削后的表面普遍存在明显的波纹度误差,导致芯片封装的良率下降、热阻增加,降低芯片的电学性能。为了揭示晶圆磨削表面波纹度误差的形成原因,提高晶圆磨削后的表面质量,本文针对晶圆表面波纹度误差溯源和补偿开展深入研究,建立了磨削系统结构动力学与晶圆表面中频波纹度误差的映射模型,具体研究包含以下内容:(1)针对在晶圆磨削过程中缺乏对磨削系统结构进行有效动力学建模开展理论研究的问题。首先基于超精密磨床整机灵敏度分析结果,根据集中质量法建立了磨床砂轮与工件主轴系统的动力学方程,并且利用赫兹接触理论计算了磨削系统各结合面参数,分析了砂轮与工件主轴系统端部的动态响应与频率特性。最终通过锤击模态试验,利用模态稳态图对磨床整机模态参数进行识别,将试验模态结果与磨削端部动态响应频率进行对比,发现模态频率最大误差仅为12%,证明了建立的磨床整机动力学模型的正确性。(2)针对在晶圆磨削过程中,因砂轮轮齿表面磨粒的空间分布以及磨削端部振动对晶圆表面形成过程及形貌特征影响不明的问题。根据砂轮轮齿表面磨粒空间随机分布的特点,对砂轮轮齿表面形貌进行重构,建立了砂轮磨粒运动轨迹方程。并对晶圆表面材料去除产生的塑性测流、弹性回弹、以及脆性断裂等综合影响进行量化,提出基于磨削轨迹叠加的多磨粒磨削仿真算法,结合磨削端部振动特性的影响,建立了包含振动激励的晶圆磨削表面形成过程的仿真模型,最后根据砂轮磨削端部的振动特点,得到了磨削振动幅值与频率对晶圆表面形貌特征参数的影响规律。(3)针对当前在抑制晶圆磨削表面中频波纹度误差问题时,缺少有效手段来识别磨削系统关键振源结构并对其进行优化的问题。通过对晶圆表面开展磨削试验,提取了晶圆表面中频波段误差的特征频率,将实测晶圆表面形貌与引入磨削端部振动的仿真模型进行几何特征与频域特征的对比,发现其中实际测量的表面形貌与仿真模形的几何特征指标Sa和Sz的最大相对误差分别为5.4%和7.7%,磨削表面中频特征频率与端部的动态响应频率的最高的相干性在0.87以上,证明磨削端部的动态响应频率是晶圆表面中频波纹度误差的形成原因。最后通过频率溯源分析对振源结构进行优化,利用仿真分析的方法确定最优的优化结构。本文揭示了晶圆表面波纹度误差的形成机理,突破了因无法精准关联系统动力学与表面误差而导致难以有效控制波纹度的技术瓶颈,已在某IC制造企业的实际生产中发挥了关键的指导作用。为“中国芯”制造提供了技术支撑。更多还原

【Abstract】 Ultra-precision grinding technology,as a key process for wafer flattening and backside thinning,has a direct impact on the processing accuracy of the chip’s three-dimensional stacked packaging effect and the lithographic quality of nanoscale circuit graphics.With the increasing integration degree of IC chips,the wafer surface needs to have high precision and high surface and sub-surface integrity,but at present,the surface after wafer grinding generally has obvious corrugation degree error,which leads to the decrease of the yield of the chip package,the increase of the thermal resistance,and the decrease of the chip’s electrical performance.In order to reveal the reasons for the formation of corrugation error on the wafer grinding surface and improve the surface quality after wafer grinding,this paper carries out an in-depth study on the traceability and compensation of corrugation error on the wafer surface,and establishes a mapping model of the structural dynamics of the grinding system and the mid-frequency corrugation error on the wafer surface,and the specific study includes the following contents:(1)Aiming at the lack of theoretical research on effective kinetic modelling of the grinding system structure in the wafer grinding process.Firstly,based on the results of sensitivity analysis of the whole machine of the ultra-precision grinding machine,the kinetic equations of the grinding wheel and workpiece spindle system of the grinding machine are established according to the concentrated mass method,and the parameters of the bonding surfaces of the grinding system are calculated by using the Hertzian contact theory to analyse the dynamic response and frequency characteristics of the grinding wheel and the end of the workpiece spindle system.Finally,through the hammering modal test,the modal parameters of the grinding machine are identified by using the modal steady state diagram,and the test modal results are compared with the dynamic response frequency of the grinding end,and it is found that the maximal error of the modal frequency is only 12%,which proves the correctness of the established dynamics model of the grinding machine.(2)In the process of wafer grinding,the spatial distribution of abrasive grains on the surface of grinding wheel teeth and the vibration of the grinding end have no clear influence on the process of wafer surface formation and morphological features.According to the characteristics of the spatial random distribution of abrasive grains on the surface of grinding wheel teeth,the surface topography of grinding wheel teeth is reconstructed,and the trajectory equations of grinding wheel abrasive grains are established.And the plastic flow measurement,elastic rebound,and brittle fracture generated by the removal of wafer surface materials are quantified,and a multi-grain grinding simulation algorithm based on the superposition of grinding trajectories is proposed,combined with the influence of vibration characteristics of the grinding end,a simulation model of the formation process of wafer grinding surfaces containing vibration excitation is established,and finally,according to the vibration characteristics of the grinding end of the grinding wheel,the amplitude and frequency of grinding vibration are obtained.The influence of the amplitude and frequency of grinding vibration on the parameters of wafer surface topography.(3)To address the current lack of effective means to identify and optimise the key vibration source structure of the grinding system when suppressing the mid-frequency ripple degree error on the wafer grinding surface.By carrying out the grinding test on the wafer surface,the characteristic frequency of the intermediate frequency band error on the wafer surface is extracted,and the measured wafer surface shape is compared with the geometric features and frequency domain features of the simulation model that introduces the vibration of the grinding end,and it is found that the maximal relative errors of the geometric feature indexes Sa and Sz of the actual measured surface shape and the simulated mode shape are 5.4%and 7.7%,respectively,and the intermediate frequency of the grinding surface is 5.4%and 7.7%,and the characteristic frequency and dynamic vibration of the end section are 5.4%and 7.7%,respectively.The highest coherence between the characteristic frequency of the grinding surface and the dynamic response frequency of the end is above 0.87,which proves that the dynamic response frequency of the grinding end is the reason for the formation of the mid-frequency corrugation error of the wafer surface.Finally,the vibration source structure is optimised by frequency traceability analysis,and the optimal optimised structure is determined by simulation analysis.This paper reveals the formation mechanism of wafer surface corrugation error,breaks through the technical bottleneck due to the inability to accurately correlate the system dynamics with the surface error,resulting in the difficulty of effectively controlling the corrugation degree,and has played a key role in guiding the actual production of an IC manufacturing enterprise.It has played a key role in guiding the actual production of an IC manufacturing enterprise,and provided technical support for the manufacture of‘China’s core’.更多还原