Deformation Control of Metal/Nitride Microbridges

Motohisa TAGUCHI  Kaoru KAWATA  Tsukasa MATSUURA  Kazuhiko TSUTSUMI  

IEICE TRANSACTIONS on Electronics   Vol.E80-C   No.2   pp.221-225
Publication Date: 1997/02/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Micromachine Technology)
Category: Actuator
deformation,  microbridge,  Pt/SiNx film,  residual stress,  flow sensor,  

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It is necessery to investigate the buckling mechanism in order to obtaining good performance from various sensors composed of resistors and microbridges or membranes. Especially for flow sensors, a convex formed bridge has an advantage over a flat or concave bridge with respect to heat transfer coefficient. We have fabricated various shapes of bridges and have prepared SiNx sputtered films as the support films of microbridges and Pt sputtered or evaporated films as resistors. We have achieved deformation control for both the longitudinal axis and transverse axis of Pt/SiNx double layered microbridges by appropriate selection of the total residual stress of Pt/SiNx structures and of the stress gradient between the Pt film and SiNx film. The deformation direction of the longitudinal axis of bridges for the beam bridge (Type ) are all the same as that of cantilevers and may be predicted via the stress gradient between the Pt and SiNx filmes of the bridges. The deflection of the transverse axis of the table bridge supported by four beams (Type ) changes linearly with the total stress of the Pt/SiNx structure and the deformation changes for the transverse axis are the same as that of completely free films as predicted from the stress gradient between the Pt film and the SiNx film. The interesting result is that the deformation direction for the longitudinal axis of Type is opposite to that of Type with the same film structure. We discuss the reason for this opposition via differences in the progress of the anisotropic etching. We consider that this result will expand the range of manufacturable shapes and film structures of microbridges.