A process technology for IC compatible micromechanical sensors using merged epitaxial lateral overgrowth of silicon
A novel technology for manufacturing thin silicon diaphragm structures is presented. Controllability of thin silicon diaphragm is one of the most important issues in fabricating silicon micromechanical sensors whose sensitivity depends on the diaphragm thickness. This can be accomplished by epitaxial lateral overgrowth (ELO) of single crystal silicon on a patterned layer of masking material, typically SiO$\sb2,$ combined with crystallographic etching of which etching rate depends on the crystal plane. With recent improvement of ELO material, good quality of 10$\mu$m thick, 200$\mu$m x 1000$\mu$m single crystal silicon was obtained with its thickness being precisely controlled by growth rate ($\le$1$\mu$m/min.). The junction leakage of the p-n junction diodes fabricated on merged ELO silicon indicated the material quality is comparable to the substrate silicon. Using this technology, a bridge-type piezoresistive accelerometer with four beams and one proof mass was fabricated successfully. Its sensitivity and resonant frequency were comparable to the accelerometers made by other methods. They were analyzed by comparing the experimental results to a simple analytical solution as well as ANSYS stress simulator using a finite element method. The experimental results showed a potential application of the new technology to silicon sensor fabrication but some further refinement is remaining. ^
Major Professor: Gerold W. Neudeck, Purdue University.
Engineering, Electronics and Electrical|Physics, Condensed Matter