単結晶シリコン超精密切削面の微視的構造

Abstract

Diamond-turned single-crystal silicon surfaces and formed chips were studied by transmission electron microscope (TEM) method. The crystallographic structure of ductile-regime turned surfaces consisted of amorphous material forming a thin surface layer with underlying dislocations generated by the {111} <110> slip systems. Continuous chips were also converted into amorphous material by turning. As depth of cut increased, microcracks were partially formed through the accumulation of excessive dislocations, and consequently brittle fractures occurred. Under these conditions, no continuous chips were obtained. The chips were fragmented and polycrystalline, and contained many crystal defects. At a greater depth of cut, where the material removal mechanism was governed by brittle fracture, the turned surfaces were covered with microcracks, and few dislocations were observed in the damaged layer. Even though the continuous chips had been obtained using a diamond tool with a sharp cutting edge, their structure remained that of single crystal. TEM observations revealed that amorphization and {111} <110> slip deformation are essential in realizing ductile-regime turning of single-crystal silicon.