Method of fabricating an MOS memory array having electrically-programmable and electrically-erasable storage devices incorporated therein

Abstract

Abstract A method for fabricating an MOS memory array is disclosed, wherein the method includes steps for constructing electrically-programmable and electrically-erasable memory cells (2, 198, 200) in combination with assorted peripheral devices (202, 204, 206) on a semiconductor substrate (8, 71). Tunneling regions (20, 78) are formed in the substrate (8, 71) and thin tunnel dielectrics (22, 84) comprised of silicon dioxide/oxynitride material are grown over the tunneling regions (20, 78) to facilitate transport of charge carriers between the tunneling regions (20, 78) and subsequently-fashioned floating gate structures (14R, 14L, 156) in the memory cells (2, 198, 200). A first layer of doped polycrystalline silicon is then deposited over the substrate and etched to define large polysilicon areas. An oxide layer is grown over the large polysilicon areas in a manner such that out-diffusion of the impurity present in the large polysilicon areas is prevented. Thereafter, a second layer of doped polycrystalline silicon is deposited over the substrate and etched together with the large polysilicon areas to define the memory cell floating gate structures (14 R, 14L, 156) as well as various memory cell program and control gates (16R, 16L, 40R, 40L, 128, 132) and peripheral device control gates (136, 138). Source and drain regions (34, 36, 58, 60, 64, 66, 168-179) for the memory cells (2, 198, 200) and the peripheral devices (202, 204, 206) are established by implanting an impurity in the semiconductor substrate (8, 71), using the memory cell program and control gates (16R, 16L, 40R, 40L, 128, 132) and the peripheral device control gates (136, 138) for alignment. Protective coverings of refill oxide (188) and VapOx (190) are formed over the substrate to complete the fabrication process.

Inventors

• 👤 Te-Long Chiu

Bibliographic Details