Finfet crosspoint flash memory
A flash memory device in a dual fin single floating gate configuration is provided. Semiconductor fins are formed on a stack of a back gate conductor layer and a back gate dielectric layer. Pairs of semiconductor fins are formed in an array environment such that shallow trench isolation structures can be formed along the lengthwise direction of the semiconductor fins within the array. After formation of tunneling dielectrics on the sidewalls of the semiconductor fins, a floating gate electrode is formed between each pair of proximally located semiconductor fins by deposition of a conformal conductive material layer and an isotropic etch. A control gate dielectric and a control gate electrode are formed by deposition and patterning of a dielectric layer and a conductive material layer.
1. A semiconductor structure comprising:
a pair of semiconductor fins located on a substrate;
a tunneling gate dielectric located on proximal sidewalls of said pair of semiconductor fins;
a floating gate electrode located between said pair of semiconductor fins and contacting said tunneling gate dielectric, wherein said floating gate electrode fills an entire space between said pair of semiconductor fins;
a control gate dielectric contacting distal sidewalls of said pair of semiconductor fins and a top surface of said floating gate electrode;
a control gate electrode overlying said control gate dielectric;
a back gate dielectric located in said substrate and contacting bottom surfaces of said pair of semiconductor fins; and
a back gate electrode located in said substrate and underlying said back gate dielectric,
wherein said tunneling gate dielectric is in contact with portions of a top surface and sidewalls of said back gate dielectric and a top surface of said back gate electrode.
2. The semiconductor structure of claim 1 , wherein said tunneling gate dielectric is in contact with a bottom surface of said floating gate electrode.
3. The semiconductor structure of claim 1 , further comprising a shallow trench isolation structure comprising a dielectric material and embedded in said substrate and laterally extending along a lengthwise direction of said pair of semiconductor fins.
4. The semiconductor structure of claim 3 , wherein a sidewall of said back gate dielectric and a sidewall of said back gate electrode contact a sidewall of said shallow trench isolation structure.
5. The semiconductor structure of claim 1 , wherein an entirety of said pair of semiconductor fins and an entirety of said floating gate electrode are located within an area defined by a periphery of said back gate electrode.
6. The semiconductor structure of claim 1 , wherein sidewalls of said floating gate dielectric that do not contact said pair of semiconductor fins are vertically coincident with sidewalls of said control gate dielectric.
7. The semiconductor structure of claim 1 , wherein each of said pair of semiconductor fins comprises:
a body region underlying said control gate electrode;
a source region including a portion that does not underlie said control gate electrode; and
a drain region including a portion that does not underlie said control gate electrode and laterally spaced from said source region by said body region.
8. The semiconductor structure of claim 1 , wherein said tunneling gate dielectric contiguously extends along proximal sidewalls of said pair of semiconductor fins, said back gate dielectric and said back gate electrode.
9. The semiconductor structure of claim 1 , wherein said back gate electrode is located over a handle substrate layer and comprises a doped semiconductor material having a conductivity type opposite a conductivity type of said handle substrate layer.
10. The semiconductor structure of claim 1 , further comprising a fin cap structure atop each semiconductor fin in said pair of semiconductor fins.
11. The semiconductor structure of claim 10 , wherein said control gate dielectric contacts sidewalls and a top surface of said fin cap.
12. The semiconductor structure of claim 1 , wherein a top surface of said floating gate electrode is coplanar with top surfaces of said pair of semiconductor fins.
13. A semiconductor structure comprising:
a pair of semiconductor fins located on a substrate;
a tunneling gate dielectric located on proximal sidewalls of said pair of semiconductor fins;
a floating gate electrode located between said pair of semiconductor fins and contacting said tunneling gate dielectric, wherein said floating fate electrode fills an entire space between said pair of semiconductor fins;
a control gate dielectric contacting distal sidewalls of said pair of semiconductor fins and a top surface of said floating gate electrode;
a control gate electrode overlying said control gate dielectric;
a fin cap structure atop each semiconductor fin in said pair of semiconductor fins, wherein said control gate dielectric contacts sidewalls and a top surface of said fin cap; and
a back gate dielectric located in said substrate and contacting bottom surfaces of said pair of semiconductor fins; and
a back gate electrode located in said substrate and underlying said back gate dielectric.
14. The semiconductor structure of claim 13 , wherein said tunneling gate dielectric is in contact with a bottom surface of said floating gate electrode.
15. The semiconductor structure of claim 13 , further comprising a shallow trench isolation structure comprising a dielectric material and embedded in said substrate and laterally extending along a lengthwise direction of said pair of semiconductor fins.
16. The semiconductor structure of claim 15 , wherein a sidewall of said back gate dielectric and a sidewall of said back gate electrode contact a sidewall of said shallow trench isolation structure.
17. The semiconductor structure of claim 13 , wherein an entirety of said pair of semiconductor fins and an entirety of said floating gate electrode are located within an area defined by a periphery of said back gate electrode.
18. The semiconductor structure of claim 13 , wherein sidewalls of said floating gate dielectric that do not contact said pair of semiconductor fins are vertically coincident with sidewalls of said control gate dielectric.
19. The semiconductor structure of claim 13 , wherein each of said pair of semiconductor fins comprises:
a body region underlying said control gate electrode;
a source region including a portion that does not underlie said control gate electrode; and
a drain region including a portion that does not underlie said control gate electrode and laterally spaced from said source region by said body region.