Original Publication Date: 1963-Jan-01
Included in the Prior Art Database: 2005-Mar-07
AbstractThe photoanodization process fabricates low cost, thin film circuitry comprising passive elements and conductive members. The entire circuit fabrication is essentially completed in a single operation.
The photoanodization process fabricates low cost, thin film circuitry comprising passive elements and conductive members. The entire circuit fabrication is essentially completed in a single operation.
One aspect of the technique of anodic oxidation that makes it useful in thin film technology is the fact that the thickness of oxide which is grown depends (to a first approximation) only on the anodizing voltage used and not on the length of time for which it is applied. This is because the oxide grows until it is just thick enough to withstand the applied voltage. Thus, if the electrical resistivity of the oxide were temporarily reduced, a thicker oxide would grow for the same applied voltage. One way of reducing the electrical resistivity of an insulator is to illuminate it with radiation of sufficiently short wavelength. This effect of light on the growth of an anodic oxide film is here termed Photoanodization.
In one form, the process employs the steps of evaporating or sputtering a layer of indium antimonide 20 of the order of 5000 angstroms thickness on a substrate material 22. Then, the deposited substrate is established as an anode 24 in an electrolysis process. Here, potassium hydroxide 26 is the electrolyte and a carbon cylinder functions as a cathode terminal 28. Variable voltage source 29 is connected between the anode and cathode. Then, all lighting is removed from the electrolysis system except that originating from light source 30. This is directed toward a negative pattern 32 of a circuit desired to be reproduced on the indium antimonide or valve metal. Next, voltage source 29 is energized for a preselected interval. At the end of the interval, source 29 is disconnected and the selective illumination of the indium anti...