Transducer having a resonating silicon beam and method for forming same

DETAILED DESCRIPTION The invention provides apparatus including a force transducer having a resonating beam that is formed in a silicon wafer and which apparatus is of relatively simple and inexpensive construction.
As used herein, the term beam should be interpreted broadly to include microstructures such as tuning forks, H-beams, cross beams, interleaved combs, and spiral springs, etc.
The invention also provides a method having relatively few manufacturing steps for forming apparatus including a force transducer having a resonating beam formed in a silicon wafer.
In one form, the method includes the steps of implanting in a substrate a layer of either n-type or the p-type dopant; depositing a doped epitaxial layer on the upper surface of the substrate (wherein the dopant in the epitaxial layer is the opposite from that type of dopant in the substrate, i.
e.
, if the substrate has therein a p-type dopant, then the epitaxial layer includes an n-type dopant and vice versa); implanting a pair of spaced sinkers through the epitaxial layer and into electrical connection with the epitaxial layer, each of the sinkers including either the n-type or p-type dopant; anodizing the substrate to form porous silicon from the sinkers and the underlying doped substrate layer; oxidizing the porous silicon to form silicon dioxide; and etching the silicon dioxide to form the cavity and beam.
It is an advantage of the invention to provide a method of forming a single crystal resonating beam within a cavity, which beam facilitates the placement of electronic circuitry directly on the beam.
Other features and advantages of the invention will become apparent to those skilled in the art upon review of the following detailed description, claims, and drawings.