Method for fabricating an ultra-shallow junction with low resistance using a screen oxide formed by poly re-oxidation in a nitrogen containing atmosphere

A method for fabricating ultra-shallow, low resistance junctions, comprising of the steps of:

• a. providing a substrate having a gate structure thereon;
• said substrate having an exposed undoped area adjacent to said gate structure;
• b. forming a nitrogen containing screen oxide layer on said undoped area of said substrate;
• said nitrogen containing screen oxide layer being formed by poly re-oxidation in an oxygen atmosphere followed by a post re-oxidation rapid thermal anneal in a nitrogen containing atmosphere;
• wherein said nitrogen containing screen oxide layer has a thickness of between about 20 Å and 70 Å and said screen oxide layer comprises between about 2 at. % and 7 at. % nitrogen at the interface with said substrate;
• c. implanting impurity ions into said substrate, in said undoped area, through said nitrogen containing screen oxide layer to form lightly doped source and drain regions;
• whereby said nitrogen containing screen oxide layer prevents gate oxide degradation;
• and
• d. performing a post-implant anneal on said lightly doped source and drain regions using a rapid thermal anneal in a nitrogen containing atmosphere;
• whereby said nitrogen containing screen oxide layer prevents surface dopant loss, and said nitrogen in said nitrogen containing screen oxide layer acts as a diffusion barrier at the oxide/silicon interface reducing oxygen enhanced diffusion.

A method for fabricating ultra-shallow, low resistance junctions, comprising of the steps of:

• a. providing a substrate having a gate structure thereon;
• said substrate having an exposed undoped area adjacent to said gate structure;
• b. forming a nitrogen containing screen oxide layer on said undoped area of said substrate;
• said nitrogen containing screen oxide layer being formed by poly re-oxidation using a rapid thermal process in a nitrogen containing atmosphere;
• wherein said nitrogen containing screen oxide layer has a thickness of between about 20 Å and 70 Å and said screen oxide layer comprises between about 2 at. % and 7 at. % nitrogen at the interface with said substrate;
• c. implanting impurity ions into said substrate, in said undoped area, through said nitrogen containing screen oxide layer to form lightly doped source and drain regions;
• whereby said nitrogen containing screen oxide layer prevents gate oxide degradation;
• and
• d. performing a post-implant anneal on said lightly doped source and drain regions using a rapid thermal anneal in a nitrogen containing atmosphere;
• whereby said nitrogen containing screen oxide layer prevents surface dopant loss and said nitrogen in said nitrogen containing screen oxide layer acts as a diffusion barrier at the oxide/silicon interface reducing oxygen enhanced diffusion.