Through an innovative microfabrication process, enclosed microstructures are created for "laboratory on a chip" applications, such as medical diagnostics. These microstructures include capillaries, tunnels, pipettes, reaction vessels, and cavities. Using only conventional lithographic techniques, curved as well as straight structures ranging in size down to 1 micron can be produced on a single-crystal silicon wafer.
Microstructures are produced through a single-mask process that patterns vias on the wafer surface. Etchants are introduced through the vias to the silicon, creating parallel subsurface tunnels. The duration of the etch determines if the tunnels will be joined to form a single larger tunnel, or remain separated by a thin membrane. After the tunnel structure is complete, a high-quality thermal oxide (SiO2) can be grown on the inside walls of the tunnel. This oxide is a glass that is chemically inert, mechanically strong, and an excellent insulator.
This invention has been implemented in the laboratory, using processes suitable for mass production in the semiconductor industry. The process allows for the creation of high-quality enclosed structures of a wide variety of shapes. In mass-production quantities, they could be produced very inexpensively.