GB986403A - Method of forming p-n junctions - Google Patents

Abstract

<PICT:0986403/C6-C7/1> A method of forming a PN junction by epitaxial deposition comprises depositing on a semi-conductor substrate of one conductivity type a continuation layer of the same conductivity type semi-conductor and then depositing a layer of opposite conductivity type semi-conductor. In a first example a single crystal silicon substrate heavily doped with antimony is heated to 1250 DEG C. in a reactor and etched with hydrogen at a rate of 10 litres per minute for five to ten minutes. 1.5% by volume of silicon tetrachloride doped with 60 parts per 109 by volume of antimony pentachloride is added to the hydrogen stream for three minutes to deposit an N type continuation layer. The reactor is flushed with hydrogen and then 1.5% by volume of silicon tetrachloride doped with 100 parts per 106 by volume of boron tribromide is added to the hydrogen for half a minute to deposit a P type layer. In a second example the process of the first example is applied to a boron doped silicon substrate using the doping materials in reverse order, the growth times of the P tye continuation layer and the N type layer being three minutes and ten minutes respectively, a P type emitter being added by normal diffusion methods to form a transistor. In a third example an antimony doped germanium substrate is heated to 850 DEG C. and hydrogen etched using a flow rate of 3.5 litres per minute. 2% by volume of germanium tetrachloride doped with 0.27 parts per 106 antimony pentachloride is aded to the hydrogen flow to deposit an N aype continuation layer. The reactor is then flushed with hydrogen and the temperature increased to 880 DEG C. and the flow rate to 11.2 litres per minute. 0.6% by volume of germanium tetrachloride doped with 0.4% by volume boron trobromide is then added to the hydrogen stream to deposit a P type layer. An evaporator is described in which the semi-conducor and impurity solutions are vaporized and added to the hydrogen stream.