Carbon Film Oxidation‐Undercut Kinetics

Abstract

A process is presented for fabricating micromechanical structures or freestanding shapes such as sheets of polysilicon. A sacrificial layer of carbon is deposited on a substrate, followed by a top layer of a second material. After oxidation of the carbon, the top layer is left free. The kinetics of the diffusion-limited oxidation process are modeled and compared to experimental data for the undercut of large (17 • 8.6 cm) sheets of polysilicon.

Chemical Vapor Deposition in a Partitioned Box Reactor

“…Furnace induced temperature error, measured by suddenly shutting off the furnace, was less than 20~ and was compensated by calibrating the pyrometer during test runs with thermocouples embedded in the boxes. Thus box temperature could be controlled to within 10~ After silicon deposition, the boxes were unloaded and the partitions were loaded in stacks into semiconductor oxidation furnaces at 1000~ There, the carbon layers were oxidized, freeing the silicon sheets (2). The polysilicon sheets were zone melted with CO2 lasers to increase grain size, and then used as feedstock in a solar cell process.…”

“…Using the ion milling method, there is a redeposition layer problem (2). When the angle of the cross-sectional shape of the photoresist pattern is large, the redeposition layer grows on the sidewall of the photoresist pattern.…”

“…Experimental results will be presented on the deposition at atmospheric pressure of high purity films of carbon and silicon. These films were used as feedstock in a solar cell process (2,3). Highly uniform films of Si3N4, SiO2, and SiC were also grown successfully in this reactor.…”

Oxidation of Carbon/Carbon through Coating Cracks

“…As discussed, these equations have been solved analytically by several authors (6)(7)(8)(9)(10)(11)(12). The first step is to derive an expression for x f /L .…”

Countercurrent Gaseous Diffusion Model of Oxidation Through a Porous Coating

“…Additionally, for carbon film undercut oxidation kinetics used for describing the fabrication of micromechanical structures 5 , it was shown that the present model should provide a better description of the low temperature kinetics. The possible use of the counter-current gaseous diffusion model was also described for CVI.…”