Ncr Corporation

Werner A Metz, Jr

Gayle W Miller

Nicholas J Szluk

George J Collins

Maurice M Moll

George Maheras

Hubert O Hayworth

Paul A Sullivan

Michael J Drury

A simplified small geometry MOS process incorporates a tungsten shunt layer on the thin silicon gate electrode layer allowing reduction of the thickness of the silicon layer and the use of an implant through the layer to form precisely controlled shallow source/drain regions without channeling. Lightly doped extension of the source and drain regions are automatically formed by an LDD implant following an isotropic undercutting etch of the silicon. The process is readily adapted to optional guard band implants and other beneficial structures such as gate sidewall oxide spacers.

MOSFET process using implantation through silicon

A method for forming channel stops in the sidewalls of a trench isolation structure formed in a semiconductor substrate. In one form, anistrophically etched substrate trenches are conformally covered by doped glass, the doped glass is anisotropically etched to retain vertical, sidewall segments of doped glass, and the substrate is annealed to form shallow diffusions in the trench sidewalls. The depth of the sidewall diffusion is related to differences in the dopant segregation coefficients between the glass and substrate materials.

Method for forming channel stops in vertical semiconductor surfaces

A process for using selectively deposited tungsten in the making of ohmic contacts and contact/interconnect metallization patterns. In one form the process is employed to interconnect fully formed field effect devices using contacts through the dielectric layer. A thin layer of intrinsic polysilicon or amorphous silicon is conformally deposited, patterned and covered by selectively deposited tungsten, An anneal operation then forms self-aligned contacts or shunts, between the tungsten layer and the source/drain type diffusions exposed during the contact cut, by updiffusion through the thin intrinsic silicon, or by conversion of the thin intrinsic silicon to tungsten. Alternatively, contacts and shunts can be formed using polysilicon layers without regard to impurity type by making contact cuts through the dielectric to expose substrate regions, patterning a deposited polysilicon layer to cover only parts of such exposed regions, forming the field effect device source/drain regions, and then selectively depositing tungsten on all exposed surfaces of silicon. The tungsten thereby bridges the polysilicon layer to the adjacent, exposed substrate region and shunts all surface adjacent p-n junctions, including the polysilicon-to-substrate contact junction.

Use of selectively deposited tungsten for contact formation and shunting

An electrically programmable memory cell using selectively deposited tungsten on a sidewall to define a fuse region. Fabrication of the fuse structure involves only a single mask departure from standard MOSFET processing during which a selective isotropic etch of a silicon nitride sidewall structure facilitates the formation of a fuse structure comprised of a tungsten layer selectively deposited on exposed silicon and a source/drain diffusion separated by an oxide or selectively thinned oxide as the degenerating element. The actuation region of the fuse is proportional to the thickness of the selectively deposited tungsten layer.

Programmable read only memory using a tungsten fuse

A twin-well process is formed using a single mask and lift-off techniques. The single implant mask is formed and the first well implanted followed by the deposition of a low temperature CVD film and the application of lift-off techniques to remove the mask and the overlying CVD film. The remaining portions of the CVD film provide a second mask which is self-aligned with and is the complement of the original mask. A second implantation then forms the second well. Alternative approaches using a photoresist mask and a composite nitride-photoresist mask structure are disclosed.

Growing community of inventors

Fort Collins, CO, United States of America

Werner A Metz, Jr