Wafer bonding using microwave heating of parylene intermediate layers

Abstract

This paper describes a novel wafer bonding technique using microwave heating of parylene intermediate layers. The bonding is achieved by parylene deposition and thermal lamination using microwave heating. Variable frequency microwave heating provides uniform, selective and rapid heating for parylene intermediate layers. The advantages of this bonding technique include short bonding time, low bonding temperature, relatively high bonding strength, less void generation and low thermal stress. In addition, the intermediate layer material, parylene, is chemically stable and biocompatible. This bonding technique can be used for structured wafers also because parylene provides a conformal coating. Therefore, this is a very attractive bonding tool for many MEMS devices. The bonding strength and uniformity were evaluated using diverse tools. Fracture mechanisms and the effects of bonding parameters and an adhesion promoter were also investigated. The bonding with a structured wafer was also successfully demonstrated.

Formation of three-dimensional Parylene C structures via thermoforming

“…Also, these techniques may not be suitable to achieve structures with large aspect ratios, as the Parylene structure is limited by the photolithographic or mold fabrication processes employed. To address these limitations, some studies have focused on leveraging the thermoplastic nature of Parylene to form 3D structures using a hot embossing process [21], as well as a modified polymer bonding technique [22], for both die level [13,23] and wafer level bonding [22,24] to assemble Parylene structures via bonding of a top open structure and a bottom substrate layer. These processes successfully produced microchannel structures while eliminating the need for a sacrificial material.…”

Polymer Tube Embedded In-Plane Micropump: Design, Analysis and Fabrication

“…The bonding takes place by chain inter-diffusion between Parylene layers. This phenomenon was reported in [32,39]. The bonding was tested for shear and leakage and was found that it survived the tests.…”

“…Parylene microchannels were formed and analyzed as a free standing structure and as a wafer bonding material in [32,39]. Use of Parylene as a diaphragm material is shown in [37,40].…”

“…Deflections of the tube lead to the pump stroke within the chamber, thus causing pumping of fluid. The fabrication of Parylene microchannels is presented in [32,39]. Parylene microchannels of aspect ration 1:1…”

“…were successfully fabricated in [32,39], but the process was not suitable to fabricate microchannels with aspect ratio greater that 1:1. A new technique of chemical release of Parylene tube was reported by our group in [8].…”