Method to form ultra-shallow buried-channel MOSFETs

Claim 1

A method of forming buried channel MOSFETs in an integrated circuit comprising: providing a semiconductor substrate; providing field oxide isolation regions overlying said substrate isolating active device regions; cleaning the surface of said substrate in said active device regions; depositing a doped silicate glass layer overlying said field oxide regions and said substrate; etching said doped silicate glass to remove said doped silicate glass layer in all areas except where counter-doped junctions of said buried channel MOSFETs are planned; annealing said substrate and said doped silicate glass to diffuse ions from said doped silicate glass into said substrate and thereby forming said counter-doped junctions; etching away all of remaining said doped silicate glass; thereafter, cleaning said surface of said substrate in said active device regions; depositing a gate oxide layer overlying said field oxide regions and said substrate; depositing a doped polysilicon layer overlying said gate oxide; etching said doped polysilicon layer to form polysilicon gates of said MOSFETs overlying said counter-doped junctions; forming silicon dioxide spacers on the sidewalls of said polysilicon gates; depositing a silicon nitride layer overlying said polysilicon gates; etching said silicon nitride layer to form silicon nitride spacers on said silicon dioxide spacers; implanting ions into said substrate through exposed areas of said substrate adjacent to said nitride spacers and thereby forming source and drain regions of said MOSFETS; annealing said substrate to activate said implanted ions and to outwardly diffuse said ions from said source and drain regions into said substrate and thereby forming lightly doped regions adjacent to said source and drain regions and connecting said source and drain regions to said counter-doped junctions; depositing an interlevel dielectric overlying the surfaces of said MOSFETs and said field oxide isolation regions; etching an opening through said interlevel dielectric to one of said source and drain regions; depositing a metal layer overlying said interlevel dielectric and filling said opening; etching said metal layer to form metal connective traces; depositing a passivation layer overlying said metal connective traces and said interlevel dielectric; and completing said integrated circuit.

Claim 2

A method of forming buried channel MOSFETs in an integrated circuit comprising: providing a semiconductor substrate; providing field oxide isolation regions overlying said substrate isolating active device regions; cleaning the surface of said substrate in said active device regions; depositing a doped silicate glass layer overlying said field oxide regions and said substrate; etching said doped silicate glass to remove said doped silicate glass layer in all areas except where counter-doped junctions of said buried channel MOSFETs are planned; annealing said substrate and said doped silicate glass to diffuse ions from said doped silicate glass into said substrate and thereby forming said counter-doped junctions; etching away all of remaining said doped silicate glass; thereafter, cleaning said surface of said substrate in said active device regions; depositing a gate oxide layer overlying said field oxide regions and said substrate; depositing a doped polysilicon layer overlying said gate oxide; etching said doped polysilicon layer to form polysilicon gates of said MOSFETs overlying said counter-doped junctions; forming silicon dioxide spacers on the sidewalls of said polysilicon gates; depositing a silicon nitride layer overlying said polysilicon gates; etching said silicon nitride layer to form silicon nitride spacers on said silicon dioxide spacers; implanting ions into said substrate through exposed areas of said substrate adjacent to said nitride spacers and thereby forming source and drain regions of said MOSFETS; annealing said substrate to activate said implanted ions and to outwardly diffuse said ions from said source and drain regions into said substrate and thereby forming lightly doped regions adjacent to said source and drain regions and connecting said source and drain regions to said counter-doped junctions; depositing an interlevel dielectric overlying the surfaces of said MOSFETs and said field oxide isolation regions; etching an opening through said interlevel dielectric to one of said source and drain regions; depositing a metal layer overlying said interlevel dielectric and filling said opening; etching said metal layer to form metal connective traces; depositing a passivation layer overlying said metal connective traces and said interlevel dielectric; and completing said integrated circuit.

Claim 10

A method of forming buried P-channel MOSFETs in an integrated circuit comprising: providing an N-type doped semiconductor substrate; providing field oxide isolation regions overlying said substrate isolating active device regions; cleaning said surface of said substrate in said active device regions; depositing a P-type doped silicate glass layer overlying said field oxide regions and said substrate; etching said P-type doped silicate glass to remove said P-type doped silicate glass layer in all areas except where P-type counter-doped junctions of said buried P-channel MOSFETs are planned; annealing said substrate and said P-type doped silicate glass to diffuse ions from said P-type doped silicate glass into said substrate and thereby forming said P-type counter-doped junctions; etching away all of remaining said P-type doped silicate glass; thereafter, cleaning said surface of said substrate in said active device regions; depositing a gate oxide layer overlying said field oxide regions and said substrate; depositing an N-type doped polysilicon layer overlying said gate oxide; etching said polysilicon layer to form polysilicon gates of said MOSFETs overlying said P-type counter-doped junctions; forming silicon dioxide spacers on the sidewalls of said polysilicon gates; depositing a silicon nitride layer overlying said polysilicon gates; etching said silicon nitride layer to form silicon nitride spacers on said silicon dioxide spacers; implanting ions into said substrate through exposed areas of said substrate adjacent to said sidewall spacers and thereby forming P-type source and drain regions of said MOSFETS; annealing said substrate to activate said implanted ions and to outwardly diffuse said ions from said source and drain regions into said substrate and thereby forming lightly doped regions adjacent to said source and drain regions and connecting said P-type source and drain regions to said P-type counter-doped junctions; depositing an interlevel dielectric overlying the surface of said MOSFETs and said field oxide isolation regions; etching openings through said interlevel dielectric to said polysilicon gates and said source and drain regions; depositing a metal layer overlying said interlevel dielectric and filling said openings; etching said metal layer to form metal connective traces; depositing a passivation layer overlying said metal connective traces and said interlevel dielectric; and completing said integrated circuit.

Claim 11

A method of forming buried P-channel MOSFETs in an integrated circuit comprising: providing an N-type doped semiconductor substrate; providing field oxide isolation regions overlying said substrate isolating active device regions; cleaning said surface of said substrate in said active device regions; depositing a P-type doped silicate glass layer overlying said field oxide regions and said substrate; etching said P-type doped silicate glass to remove said P-type doped silicate glass layer in all areas except where P-type counter-doped junctions of said buried P-channel MOSFETs are planned; annealing said substrate and said P-type doped silicate glass to diffuse ions from said P-type doped silicate glass into said substrate and thereby forming said P-type counter-doped junctions; etching away all of remaining said P-type doped silicate glass; thereafter, cleaning said surface of said substrate in said active device regions; depositing a gate oxide layer overlying said field oxide regions and said substrate; depositing an N-type doped polysilicon layer overlying said gate oxide; etching said polysilicon layer to form polysilicon gates of said MOSFETs overlying said P-type counter-doped junctions; forming silicon dioxide spacers on the sidewalls of said polysilicon gates; depositing a silicon nitride layer overlying said polysilicon gates; etching said silicon nitride layer to form silicon nitride spacers on said silicon dioxide spacers; implanting ions into said substrate through exposed areas of said substrate adjacent to said sidewall spacers and thereby forming P-type source and drain regions of said MOSFETS; annealing said substrate to activate said implanted ions and to outwardly diffuse said ions from said source and drain regions into said substrate and thereby forming lightly doped regions adjacent to said source and drain regions and connecting said P-type source and drain regions to said P-type counter-doped junctions; depositing an interlevel dielectric overlying the surface of said MOSFETs and said field oxide isolation regions; etching openings through said interlevel dielectric to said polysilicon gates and said source and drain regions; depositing a metal layer overlying said interlevel dielectric and filling said openings; etching said metal layer to form metal connective traces; depositing a passivation layer overlying said metal connective traces and said interlevel dielectric; and completing said integrated circuit.

Claim 19

A method of fabricating a P-type doped junction in a substrate in the manufacture of an integrated circuit comprising: providing a semiconductor substrate; providing field oxide isolation regions overlying said substrate isolating active device regions; depositing a boron doped silicate glass layer overlying said field oxide regions and said substrate; etching said boron doped silicate glass to remove said boron doped silicate glass layer in all areas except where said P-type doped junctions are planned; annealing said substrate and said boron doped silicate glass to diffuse boron ions from said boron doped silicate glass into said substrate and thereby forming said P-type doped junctions; etching away all of remaining said boron doped silicate glass; thereafter, cleaning said surface of said substrate in said active device regions; depositing a gate oxide layer overlying said field oxide regions and said substrate; depositing an N-type doped polysilicon layer overlying said gate oxide; etching said polysilicon layer to form polysilicon gates overlying said P-type doped junctions; forming silicon dioxide spacers on the sidewalls of said polysilicon gates; depositing a silicon nitride layer overlying said polysilicon gates; etching said silicon nitride layer to form silicon nitride spacers on said silicon dioxide spacers; implanting ions into said substrate through exposed areas of said substrate adjacent to said sidewall spacers and thereby forming P-type source and drain regions; annealing said substrate to activate said implanted ions and to outwardly diffuse said ions from said source and drain regions into said substrate and thereby forming lightly doped regions adjacent to said source and drain regions and connecting said P-type source and drain regions to said P-type doped junctions; depositing an interlevel dielectric overlying said polysilicon gates and said field oxide isolation regions; etching openings through said interlevel dielectric to said polysilicon gates and said source and drain regions; depositing a metal layer overlying said interlevel dielectric and filling said openings; etching said metal layer to form metal connective traces; depositing a passivation layer overlying said metal connective traces and said interlevel dielectric; and completing said integrated circuit.

Claim 20

A method of fabricating a P-type doped junction in a substrate in the manufacture of an integrated circuit comprising: providing a semiconductor substrate; providing field oxide isolation regions overlying said substrate isolating active device regions; depositing a boron doped silicate glass layer overlying said field oxide regions and said substrate; etching said boron doped silicate glass to remove said boron doped silicate glass layer in all areas except where said P-type doped junctions are planned; annealing said substrate and said boron doped silicate glass to diffuse boron ions from said boron doped silicate glass into said substrate and thereby forming said P-type doped junctions; etching away all of remaining said boron doped silicate glass; thereafter, cleaning said surface of said substrate in said active device regions; depositing a gate oxide layer overlying said field oxide regions and said substrate; depositing an N-type doped polysilicon layer overlying said gate oxide; etching said polysilicon layer to form polysilicon gates overlying said P-type doped junctions; forming silicon dioxide spacers on the sidewalls of said polysilicon gates; depositing a silicon nitride layer overlying said polysilicon gates; etching said silicon nitride layer to form silicon nitride spacers on said silicon dioxide spacers; implanting ions into said substrate through exposed areas of said substrate adjacent to said sidewall spacers and thereby forming P-type source and drain regions; annealing said substrate to activate said implanted ions and to outwardly diffuse said ions from said source and drain regions into said substrate and thereby forming lightly doped regions adjacent to said source and drain regions and connecting said P-type source and drain regions to said P-type doped junctions; depositing an interlevel dielectric overlying said polysilicon gates and said field oxide isolation regions; etching openings through said interlevel dielectric to said polysilicon gates and said source and drain regions; depositing a metal layer overlying said interlevel dielectric and filling said openings; etching said metal layer to form metal connective traces; depositing a passivation layer overlying said metal connective traces and said interlevel dielectric; and completing said integrated circuit.