AVS 47th International Symposium
    MEMS Wednesday Sessions
       Session MM-WeA

Invited Paper MM-WeA3
Application of Deep Silicon Etching and Wafer Bonding in the MicroManufacturing of Turbochargers and Micro Gas Turbine Engines

Wednesday, October 4, 2000, 2:40 pm, Room 309

Session: MEMS Processing
Presenter: A.A. Ayon, Massachusetts Institute of Technology
Authors: A.A. Ayon, Massachusetts Institute of Technology
J. Protz, Massachusetts Institute of Technology
R. Khanna, Massachusetts Institute of Technology
X. Zhang, Massachusetts Institute of Technology
A. Epstein, Massachusetts Institute of Technology
Correspondent: Click to Email
This paper describes the first successful micromanufacturing of MEMS turbochargers and micro gas turbine engines (MGTE), complete with an integrated compressor, turbine, and combustor. The realization of both devices involves the deep etching and fusion bonding of six single-crystal silicon wafers. The deep etching steps define turbomachinery and gas bearings, associated with the rotor, as well as fluidic interconnects and instrumentation access ports. A turbocharger includes a freely rotating rotor comprised of a turbine and a compressor mounted on the same shaft. It increases the power output of the engine to which it is attached by effectively acting as a pump to force more fuel into the engine. With this scheme, the turbine extracts power from the hot exhaust gas stream to drive the compressor that, in turn, raises the fluid density, and, hence, the mass flow rate to the engine. Turbochargers have applications to conventional and rocket engines, fuel cells, and microfluidic systems. A MGTE integrates a combustor with the turbocharger, making the device a complete, self-powered engine, for propulsion and electrical power generation applications. For the fabrication of the MGTE, the turbocharger geometry was modified to include a cooling jacket that linked the compressor and turbine and that also surrounded a combustion chamber. This introduced additional challenges for the microfabrication of three of the six required wafers, due to the extensive removal of the underlying silicon substrate and the concomitant fragility of the wafers involved. Fully operational, the demonstration MGTE is expected to have a rotor spinning at the rate of 1.2 million rpm, burn 16 g/hour of H2 fuel and produce 11 g of thrust. The present work is applicable to projects with intricate geometries requiring stacks of bonded wafers. We describe and discuss the etching and bonding challenges, as well as observations and results obtained in the microfabrication of these heat engines.