Patent ID: 6177315
Filing Date: 2001-01-23
Classification: H01L

Abstract:
A method of forming an EEPROM cell in a semiconductor material of a first conductivity type, the semiconductor material having a surface, the method comprising the steps of:forming a layer of isolation material on the semiconductor material, the layer of isolation material having a first thickness;forming a mask on the layer of isolation material that defines a first area on the surface of the semiconductor material;removing the layer of isolation material formed over the first area to form an exposed area on the surface of the semiconductor material;introducing a dopant of a second conductivity type through the first area to form a first region in the semiconductor material;forming a layer of tunnel oxide on the exposed area, the layer of tunnel oxide having a second thickness that is less than the first thickness;forming a first layer of polysilicon (poly-1) on the layer of isolation material and the layer of tunnel oxide;selectively etching the layer of poly-1 to form a poly-1 region on the surface of the layer of isolation material, the poly-1 region being formed over the first region;forming a layer of dielectric material on the poly-1 region;forming a second layer of polysilicon (poly-2) on the layer of dielectric material; andselectively removing the poly-2 layer, and underlying layers of dielectric material and the poly-1 layer to form a memory-transistor stacked-gate structure and an access-transistor stacked-gate structure, and to expose a first implant area on the layer of isolation material between the memory transistor stacked-gate structure and the access transistor stacked-gate structure, a second implant area on the layer of isolation material that is spaced apart from the first implant area and adjacent to the memory-transistor stacked-gate structure, and a third implant area on the layer of isolation material that is spaced apart from the first and second implant areas and adjacent to the access-transistor stacked-gate structure.