One time programmable EPROM fabrication in STI CMOS technology
AssigneeTexas Instruments Incorporated
InventorXiaoju Wu
Life of this patent
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Abstract
The formation of a one time programmable (OTP) transistor based electrically programmable read only memory (EPROM) cell (100) is disclosed. The cell (100) includes multiple concentric rings (108, 110) out of which gate structures are formed. An inner transistor based cell (130) formed from the inner ring (108) is shielded from isolation material (106) by one or more outer rings (110). The lack of overlap between the inner transistor and any isolation material promotes enhanced charge/data retention by mitigating high electric fields that may develop at such overlap regions (30, 32).
Claims20
A one time programmable (OTP) transistor based electrically programmable read only memory (EPROM) cell, comprising:
- an inner ring of semiconductor material formed upon an active area of a semiconductor substrate, an inner transistor of the memory cell at least partially formed out of the inner ring of semiconductor material;
- an outer ring comprising semiconductor material formed upon the active area of the semiconductor substrate, wherein a word line for the memory cell which surrounds the inner ring on at least three sides and an outer transistor of the memory cell are at least partially formed out of the outer ring;
- and
- a region of isolation material that electrically isolates the active area from one or more other active areas of a memory array, where the outer ring surrounds the inner ring of semiconductor material such that there is no overlap between the isolation material and the inner ring of semiconductor material.
A method of forming a one time programmable (OTP) transistor based electrically programmable read only memory (EPROM) cell, comprising:
- forming an inner ring of semiconductor material upon an active area of a semiconductor substrate, an inner transistor of the memory cell being at least partially formed out of the inner ring of semiconductor material;
- and
- forming an outer ring of semiconductor material upon the active area of the semiconductor substrate, with a wordline for the memory cell which surrounds the inner ring on at least three sides and an outer transistor of the memory cell being at least partially formed out of the outer ring of semiconductor material,
- where the active area is electrically isolated from one or more other active areas of a memory array formed in the semiconductor substrate by a region of isolation material, the outer ring of semiconductor material being formed such that it surrounds the inner ring of semiconductor material so that there is no overlap between the isolation material and the inner ring of semiconductor material.
A method of forming a one time programmable (OTP) transistor based electrically programmable read only memory (EPROM) cell, comprising:
- forming a doped well within an active area of a semiconductor substrate, where the active area is electrically isolated from one or more other active areas of a memory array by a region of isolation material;
- forming a thin layer of gate dielectric material over the active area;
- forming a layer of gate electrode material over the thin layer of gate dielectric material;
- patterning the layer of gate electrode material and the thin layer of gate dielectric material to establish an inner ring and an outer ring, where the inner ring defines a gate structure for an inner transistor and the outer ring defines a gate structure for an outer transistor;
- forming a first doped region of the substrate inside the inner ring;
- forming a second doped region of the substrate between the inner and outer rings;
- forming a third doped region of the substrate between the outer ring and the isolation material, where the inner transistor is at least partially formed out of the first and second doped regions, and the outer transistor is at least partially formed out of the second and third doped regions;
- forming a first contact within the first doped region to enable the first doped region to be contacted;
- and
- forming a third contact within the third doped region to enable the third doped region to be contacted.
Dependencies are inferred from the claim text.