Design, Fabrication, Processing, and Testing of Micro-Electro-Mechanical Chemical Sensors
Abstract
Chemical microsensors are a new field integrating chemical thin film technology with solid-state fabrication techniques to make devices capable of detecting chemicals in the environment. This thesis evaluated commercially available fabrication processes and numerous sensor designs for working chemical sensors. The commercial processes used were MUMPS for surface micromachined devices and MOSIS for bulk micromachined devices. Overall, eight fabrication runs and 29 different designs were made. Of these designs, two were shown to work effectively. Other designs failed due to fabrication problems and design errors that caused release problems. One design that worked was a surface micromachined chemoresistor with interdigitated gold sensing fingers and a polysilicon heater. The other design was a bulk micromachined suspended bridge structure with bimorphic action drivers at each end. Thin films were also investigated to determine which would have the most affinity to specific chemicals and therefore provide measurable responses. Once selected, a technique was developed to apply the thin film in such a way as not to damage the devices. Several thin films were identified for application, but only two polymers, poly(isobutylene) and poly(vinyl tetrachloride), were successfully applied and tested. Because the sensing devices were released micro-electro-mechanical structures, they were extremely susceptible to forces and could be damaged easily. This thesis showed that released MEMS devices could be subjected to a complete photolithographic process including spin-coating, baking, exposure, and development without damage. A hybrid mask process was developed that used photoresist to expose sensing areas for thin film deposition, bond pads for packaging, and a physical mask to cover regions and bond pads during the actual film application.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1995
- Accession Number
- ADA310075
Entities
People
- Brian S. Freeman
Organizations
- Air Force Institute of Technology