AVS 49th International Symposium
    Microelectromechanical Systems (MEMS) Thursday Sessions
       Session MM-ThA

Paper MM-ThA7
Thick and Thermally Isolated Si Microheaters for Preconcentrators

Thursday, November 7, 2002, 4:00 pm, Room C-210

Session: Fabrication, Integration, and Packaging Techniques for MEMS
Presenter: W.-C. Tian, The University of Michigan
Authors: W.-C. Tian, The University of Michigan
S.W. Pang, The University of Michigan
Correspondent: Click to Email
Thick, thermally isolated microheaters in Si are fabricated using high aspect ratio etching technology. These thick microheaters with large surface area provide large adsorbent capacity needed for high sensitivity preconcentrators in a micro gas chromatography system (@micro@GC). Microheaters in this work are different from previous work which consisted of mostly thin poly-Si or metal microheaters (<2 µm) on top of the dielectric membranes. Instead, thick microheaters (>500 µm) surrounded by air gaps are generated to provide large surface area and good thermal isolation, which are important for high sensitivity, low power preconcentrator in a @micron@GC system. A 520 µm thick Si microheater with good thermal isolation has been made and its backside is anodically bonded to a pyrex glass substrate. To provide good thermal isolation, a 500 µm wide air gap around the microheater, thin poly-Si interconnects on top of dielectric membrane, and air gap isolation from the bottom glass substrate are used. Microheaters with 500 µm air gap can be heated up 50% faster to a temperature of 270 @super o@C compared to those with 100 µm air gap, while the power consumption is 25% less and there is a larger temperature difference between the microheater and the bonding area. Operating the microheater in vacuum results in lower power consumption. At 250 @super o@C, 38% less power is needed at 1.2 Torr compared to atmosphere pressure. Power consumption is further reduced by minimizing the contact area with the heater support substrate. Up to 33% power reduction has been demonstrated by placing heaters on thin membrane or etching trenches in supporting substrate. This is the first demonstration of using thick Si microheaters with air gap isolation for @micron@GC system. These thick, thermally isolated Si microheaters can provide good power efficiency, large adsorbent capacity, and high mechanical strength as preconcentrators.