This project combines several high technology, albeit mature, techniques with the emerging field of silicon micromachining to investigate several aspects of the application of this novel field to the fabrication of surgical microtools. The designed common thread of these aspects is their relationship to a technology demonstrator, which is a surgical microtool with built-in safety control. Lack of such safety control is identified as a gap in the development of microtools, of particular importance in health sciences applications of micromachining. The demonstrator is structured as a double-V-groove silicon microbearing that accommodates a 100-250mum stainless steel shaft connected, initially, to a miniature dc macro-motor rotor. The microbearing is temperature sensing and the tool can be feedback controlled. Two silicon wafers with microlithographically defined etched V-grooves will be aligned face-to-face for the definition of a three dimensional microbearing. A solder bump self-alignment technique, borrowed from flip-chip microelectronic applications in optical interconnects, will be utilized for the microalignment. The V-grooves will be hardened by the deposition of thin-film silicon nitride (Si3N4) by LPCVD. The automatic safety control relies on a series of microlithographically defined heat sensing diodes integrated along the length of the V-groove. Mechanical considerations of deflection will be applied for the optimal determination of shaft dimensions and feasibility studies performed for different specs and parameters. Heat flow calculations with transient time specs and heat flow modeling of the Si3N4 thin film structure will be performed in order to determine the optimum Si3N4 thickness and the optimum positioning of the diode temperature sensors. Initial calculations performed as a feasibility study have indicated workable values. An appropriate V-groove and Si3N4 layer formation technology will be developed as will a solder reflow self-alignment technique.
