Anisotropic wet etching silicon tips of small opening angle in KOH solution with the additions of I2/KI

Etching silicon tips in potassium hydroxide (KOH) solution has the advantages of simplicity, easy to handle, low-cost and homogeneous etching rate of the (1 0 0) crystal plane. But the opening angle of silicon tips etched in pure KOH solution or KOH solution saturated with isopropyl alcohol (IPA) addition is usually greater than 40° before sharpening, which is not suitable for probing samples with steep trenches and inclined side walls. This paper presents a novel method of etching silicon tips of small opening angle employing anisotropic wet etching in KOH solution with the addition of I2/KI. The silicon tips show a geometry similar to ‘rocket tip’ which can only be fabricated by dry etching before and fit for probing samples with deep trenches and inclined side walls.