Spin-On Glass as a Sacrificial Layer for Patterned Metallization of Compliant SU-8 Microstructures

Abstract

A new micromachining technique is described in this paper for polymer MEMS process. By using spin-on glass (SOG) as the underlying sacrificial layer, existing SU-8 micromachining processing has been enhanced to allow for metallization, patterning, as well as post-development hard baking of SU-8 structures. Chemical compatibility of the SOG sacrificial layer makes direct metallization and patterning on top of unreleased SU-8 structures possible. Detail fabrication process flow and fabricated structures are presented in this paper.

Polydimethylglutarimide (PMGI) as a sacrificial material for SU-8 surface-micromachining

“…When compared to the other sacrificial materials used for SU-8 surface micromachining [10,[26][27][28], the PMGI-SF series can provide equivalent or better performance as a sacrificial material. The POP processes are capable of fabricating all of the structures produced by these other sacrificial systems [10,[26][27][28], and more. The overall advantages to using PMGI as a sacrificial material are described as follows:…”

“…Many multi-layer micromachining processes have been developed for producing SU-8 structures, for both microfluidic devices [11][12][13][14][15][16][17][18][19] and mechanical devices [10,[20][21][22][23][24][25][26][27][28][29]. These all belong to one of four general categories: assembly/bonding, exposure dose, buried mask and sacrificial system processes.…”

“…The buried mask [24][25][26] processes require, very low baking temperatures or vacuum processing of the layers, to avoid reticulation of the masking material. Of the processes designed for micromechanics the sacrificial methods [10,[26][27][28] provide the best results.…”

“…Ma et al's process uses spin-on-glass as a thin sacrificial layer and patterns two metal layers on top a single SU-8 layer [28]. However, this process is limited in the thickness of the sacrificial layer to less than 1 µm, and it is only capable of producing single-layer structures.…”

Development of an SU-8 MEMS process with two metal electrodes using amorphous silicon as a sacrificial material

“…SU-8 has many applications in UV-LIGA, MEMS and microfluidics. It was used in MEMS as a structural layer [2,[12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], a packaging material [29] and a sacrificial layer [30,31]. It was also used in microfluidics as a mold for forming channels [32], and also as a structural material for forming microfluidic channels [33,34].…”