A liquid-based gravity-driven etching-stop technique and its application to wafer level cantilever thickness control of AFM probes**This paper was presented at the 18th IEEE MEMS conference, held in Miami, USA, 30 Jan.–3 Feb. 2005, and is an expansion of the abstract as printed in the Technical Digest of this meeting.

Abstract

This paper mainly describes a liquid-based gravity-driven etching-stop technique used for cantilever thickness control of atomic force microscope (AFM) probes on the wafer level. The technique makes use of the opposite etching trenches or the depth rulers to control the beam thickness of AFM probes at first. A pair of opposite trenches surrounds several AFM probes on both sides of the wafer to form probe chips. The trench depth on the cantilever front side is equal to the design thickness of the cantilevers. In the final step of the fabrication process for AFM probes, the backside of the wafer is etched by potassium hydroxide (KOH) solution to form the probe handles. The probe chips will be separated from the wafer simultaneously with the penetration of wafers at the trenches. The separated probe chips therefore fall into the diiodomethane (CH2I2) solution beneath the KOH etchant and the wet etching of the AFM probe stops automatically. The cantilever thickness of the AFM probe can then be wafer-level controlled by the proposed etching-stop technique of low processing cost and high product yield.