Memory cells

Patent metadata

Field	Value
Publication number	US-9305929-B1
Application number	US-201514623749-A
Country	US
Kind code	B1
Filing date	Feb 17, 2015
Priority date	Feb 17, 2015
Publication date	Apr 5, 2016
Grant date	Apr 5, 2016

Abstract

A memory cell includes a select device and a capacitor electrically coupled in series with the select device. The capacitor includes two conductive capacitor electrodes having ferroelectric material there-between. The capacitor has an intrinsic current leakage path from one of the capacitor electrodes to the other through the ferroelectric material. There is a parallel current leakage path from the one capacitor electrode to the other. The parallel current leakage path is circuit-parallel the intrinsic path and of lower total resistance than the intrinsic path. Other aspects are disclosed.

First claim

The invention claimed is:

1. A memory cell, comprising:
a select device;
a capacitor electrically coupled in series with the select device, the capacitor comprising two conductive capacitor electrodes having ferroelectric material there-between, the capacitor comprising an intrinsic current leakage path from one of the capacitor electrodes to the other through the ferroelectric material; and
a parallel current leakage path from the one capacitor electrode to the other, the parallel current leakage path being circuit-parallel the intrinsic path and of lower total resistance than the intrinsic path, the parallel current leakage path not being directly against the ferroelectric material.

2. The memory cell of claim 1 wherein, in operation, the select device exhibits currents leakage when the memory cell is idle, the parallel current leakage path being configured so that current there-through when the memory cell is idle is greater than or equal to said current leakage of the select device when the memory cell is idle.

3. The memory cell of claim 2 wherein the parallel current leakage path is configured so that current there-through when the memory cell is idle is no more than one nanoampere.

4. The memory cell of claim 1 wherein the parallel current leakage path has a dominant band gap of 0.4 eV to 5.0 eV and that is less than dominant band gap of the ferroelectric material.

5. The memory cell of claim 1 wherein, in operation, any voltage differential across the capacitor when idle is such that any electric field in the ferroelectric material is at least 20 times lower than the intrinsic coercive field of the ferroelectric material.

6. The memory cell of claim 1 wherein the parallel current leakage path comprises a non-linear resistor between the two capacitor electrodes exhibiting higher resistance at higher voltages than at lower voltages.

7. The memory cell of claim 1 wherein the parallel current leakage path has minimum length greater than minimum thickness of the ferroelectric material between the two capacitor electrodes.

8. The memory cell of claim 7 wherein the minimum length of the parallel current leakage path is at least twice the minimum thickness of the ferroelectric material.

9. The memory cell of claim 7 wherein the minimum length of the parallel current leakage path is within 30% within 130% of the minimum thickness of the ferroelectric material.

10. The memory cell of claim 7 wherein the dominant band gap of the ferroelectric material is equal to or less than that of the parallel current leakage path.

11. The memory cell of claim 1 wherein the parallel current leakage path has minimum length within 95% to 105% of minimum thickness of the ferroelectric material between the two capacitor electrodes.

12. A memory cell, comprising:
a select device;
a capacitor electrically coupled in series with the select device, the capacitor comprising two conductive capacitor electrodes having ferroelectric material there-between, the capacitor comprising an intrinsic current leakage path from one of the capacitor electrodes to the other through the ferroelectric material; and
a parallel current leakage path from the one capacitor electrode to the other, the parallel current leakage path being circuit-parallel the intrinsic path, the parallel current leakage path having a dominant band gap of 0.4 eV to 5.0 eV, the parallel current leakage path not being directly against the ferroelectric material.

13. The memory cell of claim 12 wherein the dominant band gap of the parallel current leakage path is less than dominant band gap of the ferroelectric material.

14. The memory cell of claim 12 wherein the parallel current leakage path predominantly comprises one or more of amorphous silicon, polycrystalline silicon, and germanium.

15. The memory cell of claim 12 wherein the parallel current leakage path predominantly comprises one or more chalcogenides.

16. The memory cell of claim 12 wherein the parallel current leakage path predominantly comprises one or more of silicon-rich silicon nitride, silicon-rich silicon oxide, and intrinsically dielectric material doped with conductivity increasing dopants.

17. The memory cell of claim 12 wherein the parallel current leakage path where between the two capacitor electrodes is homogenous.

18. The memory cell of claim 12 wherein the parallel current leakage path where between the two capacitor electrodes is non-homogenous.

19. A memory cell, comprising:
a select device;
a capacitor electrically coupled in series with the select device, the capacitor comprising:
a first conductive capacitor electrode having a base and laterally-spaced walls extending there-from;
a second conductive capacitor electrode laterally between the walls of the first capacitor electrode; and
ferroelectric material laterally between the walls of the first capacitor electrode and laterally between the second capacitor electrode and the first capacitor electrode, the capacitor comprising an intrinsic current leakage path from one of the first and second capacitor electrodes to the other through the ferroelectric material; and

a parallel current leakage path between the second capacitor electrode and a surface of the base of the first capacitor electrode, the parallel current leakage path being circuit-parallel the intrinsic path and of lower total resistance than the intrinsic path.

20. The memory cell of claim 19 wherein the parallel current leakage path where between the second capacitor electrode and the surface of the base of the first capacitor electrode is within and through material having a dominant band gap of 0.4 eV to 5.0 eV, the material having dominant band gap of 0.4 eV to 5.0 eV being directly against the surface of the base of the first capacitor electrode.

21. The memory cell of claim 20 wherein the ferroelectric material comprises laterally-spaced walls having side surfaces, the material having dominant band gap of 0.4 eV to 5.0 eV being directly against the side surfaces of the laterally-spaced walls of the ferroelectric material.

22. The memory cell of claim 19 wherein the parallel current leakage path where between the second capacitor electrode and the surface of the base of the first capacitor electrode is within and through material having a dominant band gap of 0.4 eV to 5.0 eV, the material having dominant band gap of 0.4 eV to 5.0 eV not being directly against lateral side surfaces of the laterally-spaced walls of the first capacitor electrode.

23. The memory cell of claim 19 wherein,
the ferroelectric material has a base and laterally-spaced walls extending there-from; and
the parallel current leakage path where between the second capacitor electrode and the surface of the base of the first capacitor electrode is within and through material having a dominant band gap of 0.4 eV to 5.0 eV, the material having dominant band gap of 0.4 eV to 5.0 eV extending through the base of the ferroelectric material.

24. The memory cell of claim 23 wherein the material having dominant band gap of 0.4 eV to 5.0 eV is not directly against lateral side surfaces of the laterally-spaced walls of the ferroelectric material.

25. A memory cell, comprising:
a select device;
a capacitor electrically coupled in series with the select device, the capacitor comprising:
a first conductive capacitor electrode having laterally-spaced walls;
a second conductive capacitor electrode latera

Assignees

• Micron Technology Inc

Inventors

• Karda Kamal M
• Tao Qian
• Ramaswamy Durai Vishak Nirmal
• Liu Haitao
• Prall Kirk D
• Chavan Ashonita A

Classifications

• H01G4/008 Primary

  Selection of materials · CPC title

• H01G4/40

  Structural combinations of fixed capacitors with other electric elements, the structure mainly consisting of a capacitor, e.g. RC combinations · CPC title

• H01G4/08

  Inorganic dielectrics · CPC title

• H01G4/33

  Thin- or thick-film capacitors {(thin- or thick-film circuits; capacitors without a potential-jump or surface barrier specially adapted for integrated circuits, details thereof, multistep manufacturing processes therefor)} · CPC title

• H10D1/696

  comprising multiple layers, e.g. comprising a barrier layer and a metal layer (barrier layers to prevent diffusion of hydrogen or oxygen in perovskite based capacitors H10D1/688) · CPC title