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Summary: Precise Release and Insulation Technology for Vertical Hall
Sensors and Trench-Defined MEMS
R. Sunier*, P. Monajemi+, F. Ayazi+, T. Vancura*, H. Baltes*, O. Brand+
*Physical Electronics Laboratory, ETH Zurich 8093 zurich, Switzerland, sunier@iqe.phys.ethz.ch
+School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta GA 30332, USA
Abstract
Vertical Hall sensors have been fabricated using a new
process combining deep-RIE silicon trench etching and
anisotropic TMAH silicon wet etching to precisely define the
sensor's active area. The demonstrated release of the bottom
of the devices with a wet etching step results in a well-
defined and uniformly doped active area. The trench-defined
vertical Hall sensors show a very high current related
sensitivity of up to 1000 V/AT, a non-linearity of 0.06
%FSO, and a residual offset (after spinning current offset
reduction) of about 0.5 mT. A method for etching the poly-
silicon inside the trenches using XeF2 without additional
mask is demonstrated on an SOI wafer. While the
technology is demonstrated for vertical Hall sensors, it is
also well suited for the fabrication and release of trench-
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