Oxidation Sharpening Mechanism for Silicon Tip Formation

Abstract

A new silicon tip formation mechanism is proposed. A neck fracture stage precedes the formation of sharp silicon tip rather than a continuous oxidation of hyperbolic shaped silicon neck as was previously believed to be the case. Stress from the volume difference between silicon and silicon dioxide is the main reason for the silicon neck fracture. Micro-cracks form around the neck at high temperature due to stress from Si/ volume difference. This is followed by oxide growth into the cracks after crack formation and a sharp silicon tip is then formed by further oxidation. After the sharp silicon tip is formed, extensive over-oxidation would shorten and blunt the tips, but a short over-oxidation would only shorten the tip without altering the small tip radius.