Patent ID: 6723621
Filing Date: 2004-04-20
Classification: H01L

Abstract:
A method for forming an abrupt doping profile comprising the steps of:selecting a single crystal semiconductor substrate having a major upper surface, placing the substrate in a first chemical vapor deposition (CVD) reactor, first forming a first epitaxial layer of Ge having a thickness less than the critical thickness over said upper surface, said step of first forming includes epitaxially growing a first layer of Ge on the major upper surface of the substrate by flowing in-situ a germanium containing gas and a first dopant containing gas to incorporate a dopant having a concentration greater than 5Ã—1019 atoms/cc into said first layer of Ge, said dopant concentration changing by at least ten times in less than 80 angstroms of thickness thereby the layer of Ge has an abrupt doping profile, said thickness including all or a portion of said first epitaxial layer, said dopant selected from the group consisting of phosphorus and arsenic, and second forming a second epitaxial layer of a semiconductor material over said first epitaxial layer, wherein said first epitaxial layer of Ge accelerates the incorporation rate of said dopant into the first layer of Ge, wherein said step of second forming said second epitaxial layer includes the steps of removing said substrate from said first CVD reactor to a load lock having a controlled atmosphere to prevent oxidation of the upper surface of said first epitaxial layer, flowing a silicon containing gas into said first CVD reactor having heated surfaces to coat said heated surfaces with a third silicon containing layer to cover said heated surfaces that may contain phosphorus containing layers that may have formed during the formation of the first epitaxial layer, transferring said substrate into said first CVD reactor, and forming said second epitaxial layer on said upper surface of said first epitaxial layer.