Semiconductor embedded layer technology including permeable base

Abstract

A layer of material such as the metal base of a transistor is embedded in single crystal. A layer of the material with small, uniformly dimensioned and uniformly spaced openings is formed on a single crystal substrate, and the single crystal is grown from the exposed portions of the substrate over the layer of material. For best results, the layer of material to be embedded is deposited relative to the crystal orientation to provide a much greater rate of crystal growth laterally across the layer than away from the crystal substrate. The method is particularly useful in fabricating a permeable base transistor having slits formed in the metal base layer. An integrated circuit can be fabricated by forming a pattern of conductive material on a single crystal, that pattern having continuous regions which inhibit further crystal growth and narrow regions or regions having openings therein which permit lateral crystal growth across those regions. In that way, the conductive pattern is selectively embedded with the continuous regions left exposed after crystal growth. Connections can be made between the exposed regions and a pattern on the new crystal layer. This method has particular usefulness in fabricating multi-level integrated circuits.