Shea-Mode Grinding of Silicon Crystal and Damage Analysis

工程工具生产有许多小桩在单晶金刚石表面。立柱的尺寸、形状、密度可灵活设计。此外，还可以对柱的结晶取向进行对齐。利用KrF准分子激光（波长248nm），在2x2x1 mm的金刚石上，精确加工成间距20μm、5 × 5μm的正方形、10μm高的立柱。利用该工具对熔融石英进行了飞切实验。结果表明，在0.1μm的切削深度下，熔融二氧化硅可被加工成延性模式。在超声振动下的单晶Si飞切实验中，在0.2μm的切割深度下出现了延性模态表面。针对柱形的设计理念，提出了超声振动作用下柱形的谐波型设计和非谐波型设计。为了表征硅片亚表面抛光损伤，提出了表面电位、光导频率响应、电子束层析成像以及紫外/毫米波PCD和PPCA两种新方法。使用表面电位方法测量的镜面抛光压力与损伤特性与PPCA非常一致，其中在CMP过程中发现的损伤最小为65g/cm2。应用于ULSI的硅晶片的CMP损伤可以通过UV/毫米PCD方法检测到，也可以通过3次SC1清洗去除，并发现深度为21nm。

Engineered Tool is produced to have many small posts on a single crystal diamond surface. The post size, form, and density can be designed flexibly. In addition, it is possible to align crystallographic orientation of posts. The posts were precisely machined to be 20μm apart, 5 × 5μm square, and 10μm high on 2x2x1 mm diamond, using the KrF Excimer laser(wave length, 248nm). A fly-cut experiment of fused silica was performed using this Engineered Tool. As a result, it was found fused silica can be machined in ductile mode under 0.1μm depth of cut. And, in a fly-cut experiment of single-crystal Si with ultrasonic vibration, ductile mode surface was observed under 0.2μm depth of cut. Concerning to design concept of the post patterns, harmonic type design and non-harmonic type design were proposed for the use with ultrasonic vibration.In order to characterize the polishing damage in subsurface of silicon wafers, three new methods as a surface potential, a photoconductivity-frequency response, an electron beam tomography have been proposed in addition to two methods as an UV/millimeter-wave PCD and PPCA.The mirror polishing-pressure vs.damage characteristics measured using the surface potential method was in well agreement with one with PPCA, where the damage has been founded to be minimum at 65g/cm2 in the CMP process. The CMP damage in Si wafers in commercial use for ULSI was founded to be detected by UV/millimeter PCD method and also founded to be removed by 3 SC1 cleanings besides founded the depth to be 21nm.