Sharp needle tip formation based on triangular pyramidal structure

A Si triangular pyramidal structure was proposed to produce a sharp needle tip for MEMS applications. It has the advantage that it can always become sharp because the vertex of a triangular pyramid becomes a point and is not affected by fabrication errors. The triangular etching mask in which three planes dominate the etched shape was designed based on an eight-sided pyramid formation. Finally, a Si triangular pyramidal needle was fabricated by photolithography and anisotropic TMAH (25.0 wt.%, 70°C) wet etching. The height of the needle was 0.1 mm. It is clear that the vertex of the triangular pyramid successfully became a point because of its shape. A sharp needle tip with a radius of less than 1.0 μm was obtained.