Push-back junction isolation semiconductor structure and method

In the manufacture of an integrated circuit in a silicon semiconductor, a method of forming a junction isolated tub region, comprising the steps of:

• (a) providing a silicon substrate with first conductivity type impurity,
• (b) forming an epitaxial layer of second conductivity type of said substrate,
• (c) introducing a second conductivity type impurity in which is opposite to said first conductivity type impurity on a surface of said substrate, wherein said epitaxial layer is formed such that there is an impurity concentration gradient of the second conductivity type impurity that decreases toward the surface of the substrate, and
• forming a closed isolation region by introducing first conductivity type impurities through said epitaxial layer, wherein the first conductivity type impurity concentration of said isolation region decreases with distance toward the inside of said closed region, said isolation region surrounding a region of said epitaxial layer, thereby forming an electrical junction enclosing said isolated tub region therewith, and wherein said electrical junction is held back during formation of said isolation region due to the impurity concentration gradient.

In the manufacture of an integrated circuit in a silicon semiconductor, a method of forming a junction isolated tub region, comprising the steps of:

• (a) providing a silicon substrate with first conductivity type impurity,
• (b) forming an epitaxial layer of second conductivity type which is opposite to said first conductivity type impurity on a surface of said substrate,
• (c) introducing by implanting or diffusing a second conductivity type impurity layer on said epitaxial layer for increasing second conductivity type impurity concentration of the surface of said epitaxial layer, and
• (d) forming a closed isolation region by introducing first conductivity type impurities through said epitaxial layer wherein said conductivity type concentration of said impurities in said isolation region decreases with distance toward the inside of said closed region, said isolation region surrounding a region of said epitaxial layer, thereby forming an electrical junction enclosing said isolated tub region therewith, and wherein said electrical junction is held back during formation of said isolation region due to the higher second conductivity type impurity concentration of the surface of said epitaxial layer.