Ferroelectric devices including a layer having two or more stable configurations

Patent metadata

Field	Value
Publication number	US-9536975-B2
Application number	US-201514745457-A
Country	US
Kind code	B2
Filing date	Jun 21, 2015
Priority date	Sep 29, 2009
Publication date	Jan 3, 2017
Grant date	Jan 3, 2017

Abstract

Ferroelectric semiconductor devices are provided by including a ferroelectric layer in the device that is made of a material that is not ferroelectric in bulk. Such layers can be disposed at interfaces to promote ferroelectric switching in a semiconductor device. Switching of conduction in the semiconductor is effected by the polarization of a mechanically bi-stable material. This material is not ferroelectric in bulk but can be considered to be when the thickness is sufficiently reduced down to a few atomic layers. Devices including such ferroelectric layers are suitable for various applications, such as transistors and memory cells (both volatile and non-volatile).

First claim

The invention claimed is:

1. A method of ferroelectric switching, the method comprising:
providing a semiconductor substrate;
providing a ferroelectric layer of a material disposed on or above said substrate;
wherein said ferroelectric layer has at least two stable configurations having different electrical polarizations;
switching said ferroelectric layer between said stable configurations with an applied electric field;
wherein said material does not exhibit bulk ferroelectricity; and
wherein said ferroelectric layer is a single layer of lattice unit cells.

2. The method of claim 1 , wherein said substrate comprises silicon or germanium.

3. The method of claim 1 , wherein said material has a composition MX 2 .

4. The method of claim 3 , wherein said composition MX 2 has M selected from the group consisting of Zr, Hf, Ce, Ca, Pt, Pd, Rh, Ir, Ti, Fe, Ni, Co and V, and has X selected from the group consisting of O, F, S, As and P.

5. The method of claim 4 , wherein said ferroelectric layer comprises a material selected from the group consisting of: zirconium oxide, hafnium oxide, calcium fluoride, cerium oxide and mixtures thereof.

6. The method of claim 1 , wherein said ferroelectric layer is disposed on said substrate and wherein an insulator is disposed on a surface of said ferroelectric layer opposite said substrate.

7. The method of claim 6 , wherein said insulator comprises a material selected from the group consisting of lead titanate, barium titanate, strontium titanate, and alloys or mixtures thereof.

8. The method of claim 7 , wherein said insulator comprises strontium titanate.

9. The method of claim 6 , wherein said insulator comprises a material that does not exhibit bulk ferroelectricity, but is ferroelectric when substantially matched in size and symmetry to said substrate.

10. The method of claim 6 , wherein said insulator comprises a material that is not ferroelectric.

11. The method of claim 6 , wherein said insulator is amorphous.

12. The method of claim 1 , wherein an insulating layer stack is disposed on said substrate, wherein said ferroelectric layer is one of the layers of said insulating layer stack.

Assignees

• Univ Yale

Inventors

• Kolpak Alexie M
• Walker Fred J
• Reiner James W
• Ahn Charles H
• Ismail-Beigi Sohrab

Classifications

• H10D30/701

  IGFETs having ferroelectric gate insulators, e.g. ferroelectric FETs · CPC title

• H10B51/00 Primary

  Ferroelectric RAM [FeRAM] devices comprising ferroelectric memory transistors · CPC title

• H10D64/033

  comprising ferroelectric layers · CPC title

• H10D64/689 Primary

  having ferroelectric layers · CPC title

• H01L21/28291

  Electricity · mapped topic