Shea-Mode Grinding of Silicon Crystal and Damage Analysis

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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.