Kevin Matthew Durocher

Experimental Study of a Novel Silicon Carbide MEMS Ignition Device

This paper presents a robust, low power MEMS igniter built using low pressure chemical vapor deposited (LPCVD) polycrystalline Silicon Carbide films. The MEMS igniter design is based on a 5 mum thick, low stress membrane composed of doped and undoped SiC layers making up the resistive heaters and passivation layer respectively. Experimental tests using an optical pyrometer to measure temperature indicate that this igniter can achieve temperatures beyond 1400degC, with less than 10 W power input, and a time response of less than 0.1 sec. Reliability tests were performed to characterize the igniter behavior as a function of time and determine the lifetime of the devices. Lifetime of the igniter at temperatures greater than 1300degC was limited due to the growth of unstable crystobalite oxide layers resulting in membrane fracture. Reliability significantly improved when operation of the igniter was limited to temperatures below 1 100degC.

Harsh-Environment Solid-State Gamma Detector for Down-hole Gas and Oil Exploration

The goal of this program was to develop a revolutionary solid-state gamma-ray detector suitable for use in down-hole gas and oil exploration. This advanced detector would employ wide-bandgap semiconductor technology to extend the gamma sensors temperature capability up to 200 C as well as extended reliability, which significantly exceeds current designs based on photomultiplier tubes. In Phase II, project tasks were focused on optimization of the final APD design, growing and characterizing the full scintillator crystals of the selected composition, arranging the APD device packaging, developing the needed optical coupling between scintillator and APD, and characterizing the combined elements as a full detector system preparing for commercialization. What follows is a summary report from the second 18-month phase of this program.

Multi-Layer Photopolymer Micromachining

This paper presents a novel method to create and integrate micro-machined devices and high aspect-ratio (height-to-width ratio) microstructures in which the microstructures are built up using multiple layers of photopolymer film and/or viscous solution. Very high aspect-ratio 2-and 3-dimensional (2-D and 3-D) microstructures were constructed by stacking photo-imageable polymer films. Such films may be dry films applied by lamination or solution layers applied by bar coating, or doctor blade coating. Photolithography is used in both cases to define the microstructure. This additive process of thin-film micromachining facilitates high aspect-ratio microstructure fabrication. We have demonstrated structures of up to 12-layers comprising 2-D arrays of deep trenches (180 μm deep and 25 μm wide) and a 2-layer SU-8 micro-trench array with an aspect ratio up to 36 on glass substrates. Miniaturized structures of interconnected reservoirs as small as 50 μm × 50 μm × 15 μm (∼38 pico liter storage capacity) are also being fabricated, along with a novel 5-layer microfluidic channel array and a vacuum-infiltration process for fluid manipulation. This method has the potential to create functional large-area micro-devices at low-cost and with increased device flexibility, durability, prototyping speed, and reduced process complexity for applications in optoelectronics, integrated detectors, and bio-devices. The novel multi-layer photopolymer dry film and solution process also allows microstructures in micro-electro-mechanical systems (MEMS) to be built with ease and provides the functionality of MEMS integration with electronic devices and integrated circuits (ICs).

Harsh-Environment Packaging for Downhole Gas and Oil Exploration

This research into new packaging materials and methods for elevated temperatures and harsh environment electronics focused on gaining a basic understanding of current state-of-the-art in electronics packaging used in industry today, formulating the thermal-mechanical models of the material interactions and developing test structures to confirm these models. Discussions were initiated with the major General Electric (GE) businesses that currently sell into markets requiring high temperature electronics and packaging. They related the major modes of failure they encounter routinely and the hurdles needed to be overcome in order to improve the temperature specifications of these products. We consulted with our GE business partners about the reliability specifications and investigated specifications and guidelines that from IPC and the SAE body that is currently developing guidelines for electronics package reliability. Following this, a risk analysis was conducted for the program to identify the critical risks which need to be mitigated in order to demonstrate a flex-based packaging approach under these conditions. This process identified metal/polyimide adhesion, via reliability for flex substrates and high temperature interconnect as important technical areas for reliability improvement.

Adhesive Tiecoat/Polyimide Interactions in High Temperature Flex Packaging

The high temperature reliability of flex-based Cu/tiecoat/polyimide structures was evaluated through finite element simulation and experimental approach. This study is part of an effort to characterize and optimize polyimide flex as a substrate material for electronics packages rated to greater than 204°C. The peel strength of several common adhesion metals (Ti, Cr, Ni, Cu) on Kapton E was quantified at room temperature and after high temperature storage in inert and highly oxidizing environments. These results were used in tandem with thermal-mechanical simulations to characterize the behavior of several tiecoat materials. Experimental results showed diminished peel strengths of both the Ti and Cr after a 100-hour 250°C heat treatment in air. However when annealed in an inert N2 environment at 250°C for 100 hours, Cr, Ni, and Ti retained their as-sputtered peel strength. Ni and Cu exhibited lower mechanical stresses in the simulation; however, their relatively low reactivity limits their adhesion strength at the interface in oxidizing environments. To further understand the origin of the thermal-mechanical stress, the effect of mismatched CTE was compared to mismatched elastic modulus. Both properties were found to contribute to stress generation; however elastic modulus mismatches had a much greater influence on the overall magnitude of the stress. Through experimentation and FEA analysis this study aims to develop a flexed-based high temperature packaging solution and to shed light onto high temperature tiecoat/polyimide interactions.Copyright

Integration of 50-GHz traveling-wave amplifier and polymer Mach-Zehnder device using flexible substrate technology

We present the results for a 50GHz drive amplifier for use with a Mach-Zehnder modulator. The MMIC device is packaged using a flexible substrate technology to obtain compact size and broadband performance. The packaged device exhibits well-matched transmission lines on the input and output, and large gain and bandwidth. The MMIC performance is directly related to performance of the drain bias circuit.

50-GHz drive amplifier for integration with polymer Mach-Zehnder device

We present the results for a 50GHz drive amplifier for use with a Mach-Zehnder modulator. The MMIC device is packaged using a flexible substrate technology to obtain compact size and broadband performance. The packaged device exhibits well-matched transmission lines on the input and output, and large gain and bandwidth. The MMIC performance is directly related to performance of the drain bias circuit.