Effect of seed layer stress on the fabrication of monolithic MEMS microstructure

Abstract

This paper reported the effect of seed layer stress on the fabrication of monolithic polymer-metal MEMS microstructure and what is a better material for the seed layer. The monolithic microstructure is gaining more and more attentions in MEMS application, especially in three-dimensional microstructure and inkjet printhead. The polymer-metal MEMS microstructure can be fabricated by combining the lithography and electroforming technologies. It is an integrated technology by batch process at low cost. The metal seed layer with large stress will lead to cracks and failure during the process integration. Several metal materials and thicknesses were studied to find a better candidate as the seed layer for the monolithic MEMS microstructure. The relationship between the monolithic MEMS structure and seed layer selection is also discussed. The lower residual stress of seed layer will result in a better surface condition for the followed integration process. The pure Ti metal and two-layer Ti/Au composite are the better seed layer materials in this study for the followed electroforming process of the monolithic polymer-metal MEMS microstructure.

Fabrication of high-frequency moiré gratings for microscopic deformation measurement using focused ion beam milling

“…Micro-electro-mechanical systems (MEMS) is an active field in micro-manufacturing engineering, which has been growing rapidly in recent years for its wide applications in microfluids, communications, medicine, etc [1][2][3][4][5]. The performance and reliability of these devices strongly depend on the mechanical properties including residual stress in the micro-scale, which has drawn great attention from the researchers [6][7][8][9][10]. To accurately analyze the mechanical properties, the deformation under load (mechanical or thermal) has to be measured first.…”

Experimental-Numerical Comparison of the Cantilever MEMS Frequency Shift in presence of a Residual Stress Gradient

“…Although great improvements have been made in the reliability of these devices, significant gaps remain in the understanding of fundamental mechanical properties such as stress/strain relationships and the origin of residual stress within the thin-film metals used for the mechanical structure [1,2]. Residual stress/strain becomes a parameter of fundamental importance in micro-structure, surface micromachining and improving reliability of micro-devices [3-5].…”