超声波雾化施液技术抛光硅片的表层损伤研究

发布时间：2018-01-14 17:41

本文关键词：超声波雾化施液技术抛光硅片的表层损伤研究　出处：《江南大学》2015年硕士论文　论文类型：学位论文

【摘要】：随着当今时代半导体工业的不断发展,硅单晶材料已经成为了半导体器件和集成电路中极为重要的基础功能材料,同时对硅片的表面质量要求也在不断提高。化学机械抛光(CMP)是目前实现硅片表面平整化的主流技术之一,但是传统CMP中存在着抛光液大量浪费、材料去除不一致、磨粒分布不均等弊端。针对上述传统CMP中存在的弊端,提出了超声波雾化施液抛光方法,极大节省了抛光液的消耗量并进一步提高了硅片的表面质量。然而由于抛光工艺本身的原因仍会不可避免地对硅片表层造成损伤,影响晶片的使用性能。因此有必要对雾化施液技术抛光硬脆晶体的表层损伤展开研究,进一步完善基于表面精度和质量要求的评价手段和检测方法。对雾化施液抛光过程中硅片的表层损伤形式进行了检测和分析。利用扫描电子显微镜(SEM)、原子力显微镜(AFM)等仪器对硅片的表面质量进行了定量和定性分析,发现研磨硅片经雾化施液抛光后表面粗糙度小于10nm,表面无划痕和破碎现象。运用化学腐蚀法、显微拉曼光谱法分别对硅片亚表面的微裂纹、位错和残余应力等损伤进行了分析和表征,发现微裂纹损伤随表面到亚表面深度的增加而愈加严重;硅片边沿处的位错密度要小于其他区域,未出现位错排和小角度晶界等严重缺陷,增大雾化器的功率能有效降低位错蚀坑的密度;硅片经雾化施液抛光后表面会引入残余拉应力,残余应力沿硅片对角线方向呈对称分布,从中心至边沿处逐渐增大。采用差动蚀刻速率法测量了研磨硅片经雾化施液抛光后的亚表面损伤深度,并在相同工艺参数下和传统CMP进行了对比,结果表明:在雾化施液CMP系统下,特种抛光液加工的硅片亚表面损伤深度(0.83μm)小于市购的SSP-L型抛光液(0.99μm);和传统CMP相比较时材料去除率稍低,但加工出的硅片损伤深度更小。对雾化施液技术抛光硅片表层损伤的产生机理进行了分析,认为损伤层主要由水解层、缺陷层、残余应力层构成。以亚表面损伤深度、表面粗糙度、材料去除率为综合评价指标,建立正交试验矩阵分析模型进行了抛光工艺参数的优化。分析出工艺参数对综合评价指标的影响主次顺序为雾化器电压、抛光压力、抛光垫转速,得到了工艺参数的最优组合方案为雾化器电压50V、抛光垫转速60r/min、抛光压力8psi,此时硅片的材料去除率为166.487 nm/min、亚表面损伤深度为0.83μm、表面粗糙度为4.9nm。设计单因素试验研究了工艺参数对亚表面损伤深度的影响规律,结果表明:增大雾化器的电压可以有效降低硅片的损伤深度,而抛光垫转速和抛光压力分别存在一个最佳的参数使得损伤深度达到最小。
[Abstract]:With the development of semiconductor industry, silicon single crystal has become an important basic functional material in semiconductor devices and integrated circuits. Chemical and mechanical polishing (CMP) is one of the main technologies to realize the surface leveling of silicon wafers, but there is a lot of waste of polishing liquid in traditional CMP. The removal of materials is inconsistent and the distribution of abrasive particles is not equal. In view of the disadvantages of the traditional CMP mentioned above, the ultrasonic atomization polishing method is put forward. It greatly saves the consumption of polishing liquid and further improves the surface quality of silicon wafer. However, due to the polishing process itself, it will inevitably cause damage to the surface layer of silicon wafer. Therefore, it is necessary to study the surface damage of hard and brittle crystal polishing by atomization. The evaluation method and detection method based on surface precision and quality requirements were further improved. The surface damage forms of silicon wafer during atomization polishing were detected and analyzed. Scanning electron microscope (SEM) was used to detect and analyze the damage form of silicon wafer. The surface quality of the wafer was quantitatively and qualitatively analyzed by atomic force microscope (AFM) and other instruments. It was found that the surface roughness of the wafer was less than 10nm after atomized polishing. The microcracks, dislocations and residual stresses on the subsurface of silicon wafers were analyzed and characterized by chemical etching and Raman spectroscopy. It is found that the microcrack damage becomes more and more serious with the increase of the depth from the surface to the sub-surface. The dislocation density at the edge of the wafer is smaller than that in other regions and there are no serious defects such as dislocation row and small angle grain boundary. Increasing the power of the atomizer can effectively reduce the density of the dislocation etch pit. The residual tensile stress will be introduced into the surface of the wafer after atomization and the residual stress will be distributed symmetrically along the diagonal direction of the wafer. The subsurface damage depth of the polished silicon wafer was measured by differential etching rate method from the center to the edge, and compared with the traditional CMP under the same process parameters. The results showed that the damage depth of subsurface of silicon wafer processed by special polishing liquid was 0.83 渭 m in atomized liquid CMP system, and 0.99 渭 m of SSP-L type polishing liquid was less than that of SSP-L type polishing liquid purchased on the market. Compared with traditional CMP, the material removal rate is slightly lower, but the damage depth of silicon wafer is smaller. The mechanism of surface damage of silicon wafer polished by atomization is analyzed, and it is considered that the damage layer is mainly hydrolyzed layer. Defect layer, residual stress layer. The subsurface damage depth, surface roughness and material removal rate are taken as the comprehensive evaluation index. The orthogonal test matrix analysis model was established to optimize the polishing process parameters, and the influence of the process parameters on the comprehensive evaluation index was analyzed in the order of atomizer voltage, polishing pressure and polishing pad speed. The optimal combination of process parameters is as follows: atomizer voltage 50 V, polishing pad speed 60 r / min, polishing pressure 8 psi. At this time, the material removal rate of silicon wafer is 166.487 nm / min, and the depth of subsurface damage is 0.83 渭 m. The surface roughness is 4.9 nm. The influence of process parameters on the depth of subsurface damage is studied by single factor experiment. The results show that increasing the voltage of atomizer can effectively reduce the damage depth of silicon wafer. However, there is an optimum parameter of the rotation speed and polishing pressure of the polishing pad to minimize the damage depth.
【学位授予单位】：江南大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN304.12

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