Title :
A thermally isolated microstructure suitable for gas sensing applications
Author :
Huff, M.A. ; Senturia, S.D. ; Howe, R.T.
Author_Institution :
Dept. of Electr. Eng. & Comput. Sci., MIT, Cambridge, MA, USA
Abstract :
A thermally isolated microstructure for use in metal-oxide gas sensing applications was fabricated and tested. Using the techniques of bulk micromachining, a thin silicon membrane 5 mu m thick was fabricated and then used as a structural support during subsequent device processing. The mechanical stability of the thin silicon membrane was found to be dependent on the compressive surface-oxide thickness which induced membrane buckling. A study of the buckling criteria was examined in detail by performing etch-back experiments on a series of sequentially sized membranes and observing the transition for buckling. A linear relationship between oxide thickness and membrane edge length squared was found. The device is fabricated over the membrane on the wafer surface and consists of a sandwich of LPCVD Si/sub 3/N/sub 4/, LPCVD poly-Si and LPCVD Si/sub 3/N/sub 4/. After device fabrication, the support membranes is etched away leaving the device completely isolated from the substrate. The measured values of power consumption and thermal time constant are compared with a simple model.<>
Keywords :
CVD coatings; chemical variables measurement; electric sensing devices; elemental semiconductors; semiconductor-insulator-semiconductor structures; silicon; silicon compounds; 5 micron; Si/sub 3/N/sub 4/-Si-Si/sub 3/N/sub 4/; buckling criteria; bulk micromachining; etch-back experiments; gas sensing; low pressure CVD; mechanical stability; membrane buckling; model; power consumption; sequentially sized membranes; support membranes; thermal time constant; thermally isolated microstructure; thin Si membrane; Biomembranes; Etching; Fabrication; Micromachining; Microstructure; Power measurement; Silicon; Stability; Testing; Time measurement;
Conference_Titel :
Solid-State Sensor and Actuator Workshop, 1988. Technical Digest., IEEE
Conference_Location :
Hilton Head Island, SC, USA
DOI :
10.1109/SOLSEN.1988.26430
