Patent ID: 6146977
Filing Date: 2000-11-14
Classification: H01L

Abstract:
A method of manufacturing a semiconductor integrated circuit, comprising the steps of:providing a substrate of one conductivity type with a field oxide embedded partially within said substrate and extending partially above said substrate, said field oxide having a central region which is thicker than a peripheral region designated as a bird's beak and wherein said bird's beak is formed such that it tapers in thickness from a thickest portion immediately adjacent to said central region of said field oxide to a thinnest portion at a point on the surface of said substrate;directing ions of an impurity onto only said central region of said field oxide by using a relatively high first implantation energy, said first implantation energy being sufficient to pass said ions through said central region and into said semiconductor substrate beneath said central region, said impurity being of a conductivity type which is the same as said one conductivity type; anddirecting ions of said impurity by using a relatively low second implantation energy, lower than said first implantation energy, onto only said field oxide, said second implantation energy being sufficient to pass said ions through said bird's beak and into said semiconductor substrate beneath said bird's beak but said second implantation energy not being sufficient to pass said ions through said central region;wherein, upon applying ions of said impurity by using said first and second implantation energies, a channel stopper layer is formed in contact with an entire lower surface of said field oxide including said central region and said bird's beak.