Use of anodic aluminum oxide in MOS structures

Aluminum oxide formed by a method of electrotytic anodization, which is compatible with the existing planar silicon technology, has been used to fabricate MOS-FET structures with and without an initial layer of thermally grown silicon dioxide on n-type substrates. Fully anodized aluminum directly evaporated on the silicon surface results in devices with a positive threshold voltage. The same structure when over-anodized yields negative threshold voltage devices. C-V and I-V characteristics are analyzed for a physical understanding of the device operation.