Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – Having insulated gate
Reexamination Certificate
1999-04-14
2001-01-23
Chaudhari, Chandra (Department: 2813)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
Having insulated gate
C438S296000, C438S430000
Reexamination Certificate
active
06177317
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is directed towards a method for manufacturing high density integrated circuit memory arrays. More particularly, the present invention is directed towards a method for manufacturing nonvolatile memory devices having reduced resistance diffusion regions.
2. Description of Related Art
Nonvolatile memory arrays typically use an implantation process to create diffusion regions with reduced resistance. The reduced resistance improves performance because the voltage drop is reduced, read current and read speed are enhanced, the threshold voltage distribution is tightened, and the program voltage on the drain side is reduced.
However, the implantation process is limited in how much the resistance can be reduced by both implant dose and depth. Because the implantation process is limited in implant dose, the diffusion regions are constrained to the kind of reduced resistances that can be achieved by doping a silicon substrate. Because the implantation process is limited in implant depth, only diffusion regions of limited thickness can be created. In addition, the implantation process requires a drying process, which increases the number of thermocycles and adversely affects device yield and performance.
What is needed is a method for manufacturing a nonvolatile memory device capable of producing diffusion regions with lower resistances than are possible with implantation processes. What is needed is a method for manufacturing a nonvolatile memory device capable of producing diffusion regions with greater thicknesses than are possible with implantation processes. What is needed is a method for manufacturing a nonvolatile memory device which can eliminate the need for an additional drying process required if an implantation process is used to create the diffusion regions.
SUMMARY OF THE INVENTION
The present invention is directed towards a method for manufacturing a nonvolatile memory device. The method comprises: providing a multilayer structure, the multilayer structure having a substrate, a tunnel oxide layer over the substrate, a polysilicon layer over the tunnel oxide layer, and an etch stop layer over the polysilicon layer; defining gates in the multilayer structure by using a photoresist mask layer to remove portions of the etch stop layer, polysilicon layer, and tunnel oxide layer to form openings in the multilayer structure; creating source/drain regions in the substrate by doping the substrate through the openings; forming sidewall spacers adjacent to the gates by forming a spacer layer in the openings and etching back the spacer layer, the sidewall spacers defining source regions, drain regions, and trench regions; forming trenches by removing portions of the substrate in the trench regions, the trenches extending deeper into the substrate than the source/drain regions; depositing a conductive material on sidewalls and bottoms of the trenches, forming diffusion regions by removing the conductive material from the bottoms of the regions, the diffusion regions being continuous with the source/drain regions; and filling the trenches with an insulating material.
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Chang Yun
Chen Huei Huarng
Huang Chin-Yi
Pan Samuel C.
Chaudhari Chandra
Haynes Mark A.
Haynes & Beffel LLP
Macronix International Co. Ltd.
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