Residual stress tuning in UV- LIGA fabricated microstructures using deposition temperature and reverse pulse plating

Abstract

This paper utilizes pulse reverse plating to control the residual stress in electroplated Copper MEMS structures. The residual stress plays a significant role in many MEMS devices and control (not just minimization) over it is desirable. We have tuned the stress either compressive or tensile for different plating parameters, without utilizing any additives in the bath or annealing in the process. We demonstrate the use of this technique using a UV-LIGA fabricated microstrain gauge, that is also utilized to measure the stress. We show that the stress can be tuned from a value of 364 MPa to -194 MPa by varying the pulse plating parameters like ratio of forward/reverse time and temperature.