Improved manufacturability and characterization of a corrugated Parylene diaphragm pressure transducer

Abstract

Corrugated Parylene diaphragm based pressure transducers have been used in a wide range of MEMS devices. This paper presents a reusable silicon micromold based process to fabricate optically reflective, corrugated Parylene diaphragm s for fiber-optic-linked pressure sensing in an ultralow pressure range (98 Pa). The silicon micromolding process is combined with a novel chip-level tube bonding method to mount the diaphragms to the end of a tube before releasing them from the mold. This fabrication approach vastly improves the manufacturability of these pressure sensors over the previously used photoresist mold-based process. It provides greater flexibility in design and is shown to produce Parylene diaphragms with an accurate corrugation profile. Such a biomedical ultralow pressure sensor can be attached to a catheter tip and used in confined space for intra-cavity pressure measurements. Fabrication and testing results related to six different corrugated diaphragm designs have been presented here. These diaphragms are characterized in the operating pressure range (98 Pa) with a 5 Pa resolution using an optical profilometer and U-tube manometer setup. The sensor characterization results show that all three designs of 1.0 mm diameter diaphragms have good agreement with the predicted values that were obtained from finite element analysis. Deflections of up to 6 νm were measured in these diaphragms. Larger displacements of up to 19 νm were obtained in 1.5 mm diameter diaphragms. However, the characteristic curve obtained in these sensors differed significantly from the simulated results. Higher initial deflection due to stress release, localized buckling and lower stiffness of the SU-8 support ring are believed to be the reason behind such deviation from the design values. © 2006 IOP Publishing Ltd.