Patent ID: 6144076
Filing Date: 2000-11-07
Classification: H01L

Abstract:
An integrated circuit structure formed on a semiconductor substrate with enhanced protection against latchup in a CMOS region of said integrated circuit structure by provision of a buried P well in said CMOS region spaced within a particular vertical distance range below an N well and a first P well in said CMOS region, said CMOS region comprising;a) an N well in said substrate extending down from the surface of said substrate;b) a first P well extending down from said surface of said substrate adjacent said N well;c) a buried P well formed in said substrate [at least] beneath said N well and said first P well, wherein the depth of the peak dopant concentration in said buried P well is;(i) spaced from the peak dopant concentration of said N well a minimum distance of at least about 0.7 .mu.m which will not introduce an amount of P type dopant into the region of the substrate where the N well has been or will be formed sufficient to reduce the effective depth of said N well; and(ii) spaced a maximum distance from said peak dopant concentration of said N well not exceeding about 1.1 .mu.m, wherein the resistance path from said buried P well to said substrate surface will not be too high to provide enhanced latchup protection to one or more transistors formed in said CMOS region; andd) an isolation region extending down from said surface of said substrate and separating at least a portion of said N well from said first P well, wherein:i) the minimum depth of said isolation region substrate is at least equal to the depth of one or more source/drain regions formed in said N well and/or said first P well of said CMOS region to provide punch through protection for said source/drain regions; andii) the minimum width of said isolation region between said N well and said first P well, at said surface of said substrate, is further that width:1) sufficient to permit formation of said isolation region in said substrate to said minimum depth; and2) sufficient to permit formation of a P-N junction beneath said isolation region capable of functioning as a channel stop between said source/drain regions formed in said respective wells.