Patent GB-1159995-A (GB)
Title: Method and Apparatus for Epitaxial Deposition
IPC: C30B25/08
Filed: 1966-07-29
Abstract: 1,159,995. Epitaxial deposition of semiconductors. MONSANTO CO. 29 July, 1966 [29 July, 1965], No. 34119/66. Heading C1A. [Also in Divisions C7 and F4] A method of depositing an epitaxial coating of semi-conductor material on a semi-conductor member comprises introducing the semi-conductor member on a supportive structure into the second of two chambers, means being provided to provide operative communication between the two chambers and between the second chamber and the atmosphere when open and gas-tight seals therebetween when closed, introducing a purging gas inert with respect to the semi-conductor material into the second chamber for purging the semi-conductor member, passing the loaded support into the first chamber without contact with any foreign atmosphere and introducing thermally decomposable feed gases into the first chamber for causing an epitaxial coating material to be produced and deposited on the semi-conductor member. The semi-conductor element on its support may be introduced into the second chamber without contact with any foreign atmosphere via a third chamber operatively communicable therewith wherein it is treated with an inert purging gas, the third chamber when closed having gas-tight seals between it and the atmosphere and it and the second chamber. Following deposition, the supported semi-conductor may be withdrawn via the second and third chambers with purging at each stage. The apparatus may comprise a water-cooled deposition chamber 3 having bridge-type electric heating elements 17 held by electrode clamps 16 and gas inlets 12; a second chamber 31 separated from the first by hinged plate 50, having hooks 47 for holding elements 17, and gas inlets 45; a third chamber 58, separated from chamber 31 by a door 71 and from the atmosphere by door 64, having hooks 69 for holding elements 17, and gas inlets 77; and a hand glove 48 for moving the elements 17 from chamber to chamber. The semi-conductor members may be substrate wafers which are supported by pins in two rows on the legs of heating elements 17. The elements may be made of Si, SiC, graphite, Ta, Mo, Ti or graphite coated with SiC (e.g. by depositing Si from SiHCl 3  and heating to form SiC or by depositing SiC from SiHCl 3  and CHCl 3 ) or with alternate layers of Si and SiC. The legs may have reduced cross-sectional areas at their ends. In operation, heating elements with Si wafers are placed in the three chambers which are then sealed off and purged with N 2 . After then purging with H 2 , the elements in chamber 3 are heated to at least 1170 C. and H 2  and SiHCl are introduced with or without a dopant, e.g. PH 3 , AsH 3  or B 2 H 6 . After deposition, the chamber is purged and the elements in chambers 3 and 31 are interchanged and after closure of plate 50, the elements in chambers 31 and 58 are interchanged and finally the coated element in the third chamber is replaced by a fresh element. Reduced or increased pressure may be used. Reference is also made to the deposition of SiC, GaAs, InSb and GaP and the production of layers of different conductivity.