Method for forming a nitridized interface on a semiconductor substrate

A method for forming localized field oxide during fabrication of MOS semiconductor devices on a substrate having a silicon dioxide pad layer present on an upper surface of said substrate and a polysilicon buffer layer disposed on an upper surface of said silicon dioxide pad layer, comprising:

• forming a fluorine-doped nitridized surface on an upper surface of said polysilicon buffer layer;
• wherein an interface is defined between said fluorine-doped nitridized surface and said upper surface of said polysilicon buffer layer;
• forming an undoped nitridized surface on said fluorine-doped nitridized surface, said undoped nitridized surface and said fluorine-doped nitridized surface together forming a silicon nitride layer;
• defining at least one active region pattern on said silicon nitride layer;
• removing said silicon nitride and said polysilicon buffer layers in an area outside said active region pattern;
• and
• forming a field oxide region in the area where said silicon nitride layer and polysilicon buffer layers have been removed.

A method for forming localized field oxide during fabrication of MOS semiconductor devices on a silicon substrate, comprising:

• forming a pad layer of silicon dioxide on said silicon substrate;
• forming a buffer layer of polysilicon on said silicon dioxide pad layer, said pad layer of silicon dioxide being disposed between said buffer layer of polysilicon and said silicon substrate;
• forming a fluorine-doped nitridized surface on an upper surface of said polysilicon buffer layer;
• wherein an interface is defined between said fluorine-doped nitridized surface and said upper surface of said polysilicon buffer layer;
• forming an undoped nitridized surface on said fluorine-doped nitridized surface, said undoped nitridized surface and said fluorine-doped nitridized surface together forming a silicon nitride layer;
• defining at least one active region pattern on said silicon nitride layer;
• removing said silicon nitride layer and said polysilicon buffer layer in the area outside said active region pattern;
• and
• forming a field oxide region on said silicon substrate in the area where said silicon nitride layer and polysilicon buffer layers have been removed.