A systematic study of RIE for silicon tips

How to control the profile of silicon tip is desirable in many applications. Although there are many parameters that influence the final tip profile, dry etching conditions for producing controllable shapes of silicon tips have been systematically investigated in this work. The study demonstrates that the addition of O2 gas could change the profile of the etched silicon tips; at the same time, the chamber pressure also has significant influence on the aspect ratio of the tips. Comparing the ratio of lateral etch rate to vertical etch rate with the cross section of a conical tip, one method could be concluded for controllable shapes of tips’ fabrication, including tip size, height and apex radius. Based on this method, the tips with a half cone angle of about 20° and a tip height of 12μm have been realized. The diameter of the tips is less than 70nm by one etching step, without the use of oxidation sharpening.