Method for Making Epitaxial Silicon Crystals with Uniform Doping Levels.
DEPARTMENT OF THE ARMY WASHINGTON DC
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A crystal substrate of 111 silicon is doped by being exposed to a liquid metal solvent. The substrate is carried in a cavity in a refractory boat, and the solvent is carried in a perforation of a cover for the boat. The boat is heated to a certain temperature in a non-oxidizing atmosphere and is moved to place the substrate cavity under the cover perforation whereby the solvent and substrate come in contact. The temperature is raised and held to allow the desired substrate-solvent solution to form, then is reduced and held to allow supersaturation and eventually precipitation of the doped substrate. The boat is next moved to remove the cavity from beneath the perforation, is allowed to cool to room ambient, and is removed from the non-oxidizing atmosphere. The doped substrate is then cleaned as desired to remove any attached solvent. Author