Fabricating Boron-Doped Silicon Membranes
Original Publication Date: 1988-Dec-01
Included in the Prior Art Database: 2005-Feb-15
A technique is described whereby the process for fabricating silicon membranes, as used in semiconductor X-ray mask lithography substrates, is simplified by combining diffusion and post-diffusion oxidation operations. In conventional processing of boron-doped silicon membranes for use as X-ray mask substrates, a boron diffusion operation in a high temperature furnace, followed by oxidation in steam in a separate furnace at a lower temperature is required to produce the appropriate boron distribution profile in the silicon substrate. This profile, in turn, determines the stress and thickness of the boron-doped membrane itself. The boron diffusion operation forms a boron-rich surface layer, the so-called B-Si phase, which must be removed by oxidation in order to produce quality membranes.