Ferroelectric mechanical memory and method

Patent metadata

Field	Value
Publication number	US-9887205-B2
Application number	US-201615200816-A
Country	US
Kind code	B2
Filing date	Jul 1, 2016
Priority date	Mar 14, 2014
Publication date	Feb 6, 2018
Grant date	Feb 6, 2018

Abstract

A method of making a memory device comprising a base; a capacitor comprising a ferroelectric layer and at least two electrically conductive layers, the ferroelectric layer being located between the at least two electrically conductive layers; each of the at least two conductive layers being operatively connected to a current source; a cantilever attached to the base at first end and movable at a second end, the ferroelectric capacitor being mounted to the cantilever such that the second end of the cantilever moves a predetermined displacement upon application of a current to the ferroelectric layer which induces deformation of the ferroelectric layer thereby causing displacement of the cantilever which is operatively associated with a contact so that an electrical connection is enabled with the contact upon the predetermined displacement of the cantilever. The presence or absence of a connection forms two states of a memory cell.

First claim

What is claimed is:

1. A method of making a nonvolatile memory cell comprising;
forming a ferroelectric layer;
forming a ferroelectric capacitor by positioning the ferroelectric layer between conductive layers;
the conductive layers adapted to be connected to a voltage source;
securing one end of the ferroelectric capacitor while allowing the ferroelectric capacitor to flex into first and second positions; the ferroelectric capacitor flexing into the second position upon application of a voltage from the voltage source;
providing a first contact, the capacitor being in operative electrical connection with the first contact in the second position;
providing a sense amplifier operatively connected to the first contact to sense the opening and closing of the operative connection to the first contact such that during a read operation the sense amplifier is used to detect the amount of time the contact is in operative electrical connection with the voltage source;
the voltage source operative to apply a positive or negative voltage to the ferroelectric capacitor causing the ferroelectric layers to deform internally and resulting in different internal deformation of the ferroelectric material depending upon whether a positive or negative voltage is applied that is retained after the voltage is removed, and wherein the deformation can be used to store either a one or zero binary bit, and wherein a subsequent voltage across the ferroelectric capacitor operates to determine whether a one or zero has been stored based upon operative electrical contact between the first contact and the ferroelectric capacitor.

2. The method of claim 1 further comprising;
providing a base; wherein the ferroelectric capacitor forms part of a cantilever subassembly wherein a first portion of the cantilever subassembly is secured to the base and the second portion moves from the first position to the second position, the ferroelectric capacitor flexing in the second position to allow operative electrical connection to the first contact to provide a reading of memory.

3. A method of making a nonvolatile memory device comprising:
providing two electrically conductive layers adapted to be connected to a voltage source;
providing a first ferroelectric layer positioned between the two conductive layers; the ferroelectric layer comprising a fixed portion and a movable portion; the movable portion being displaced a predetermined distance from a first position to a second position upon application of a positive or negative voltage between the two conductive layers;
providing a first contact operatively connectable to one of the two conductive layers and to one of a voltage potential or ground;
providing a sense amplifier operatively connected to the first contact to sense the opening and closing of the operative connection to the first contact such that during a read operation the sense amplifier is used to detect the amount of time the contact is in operative electrical connection with the voltage source;
the application of one of a positive or negative voltage from the voltage source resulting in the first ferroelectric layer deforming internally and resulting in different internal deformation of the ferroelectric material when a positive voltage is applied than the internal deformation when a negative voltage is applied and the internal deformation is retained after the voltage is removed, and
causing movement of the movable portion from the first to the second position resulting in operative electrical connection between one of the two conductive layers and the contact; the ferroelectric layer being configured to retain a first state if a positive voltage is applied and a second state if a negative voltage is applied;
whereby the internal deformation is due to hysteretic dimensional changes and can be used to store either a one or zero binary bit that is retained when no voltage is applied, and wherein a subsequent voltage across the ferroelectric capacitor operates to determine whether a one or zero has been stored.

4. The method of claim 3 wherein the application of a positive charge from the voltage source causes a first state of deformation within the ferroelectric layer and the application of a negative charge causes a second state of deformation within the ferroelectric layer; and wherein a subsequent application of a voltage across the one of the two conductive layers and the contact operates to determine whether the ferroelectric layer is in the first or second states.

5. The method of claim 3 further comprising providing a second ferroelectric layer positioned between two second conductive layers; the second ferroelectric layer comprising a fixed portion and a movable portion; the movable portion being displaced a predetermined distance from a first position to a second position upon application of a positive or negative voltage between the two second conductive layers;
a second contact operatively connectable to one of the two conductive layers and to one of a voltage potential or ground; the application of one of a positive or negative voltage from the voltage source causing movement of the movable portion from the first to the second position resulting in operative electrical connection between one of the two second conductive layers and the second contact; the second ferroelectric layer being configured to retain a first state if a positive voltage is applied and a second state if a negative voltage is applied; whereupon the memory device has four possible states, the first and second states of the first ferroelectric layer and the first and second states of the second ferroelectric layer.

6. The method of claim 3 wherein the first and second ferroelectric layers comprises one or more of PbZr 0.52 Ti 0.48 O 3 , (1-x)PbMg 1/3 Nb 2 /3O 3 -(x)PbTiO 3 , BaTiO 3 , KNaNbO 3 , LiNbO 3 , LiTaO 3 , doped (Mg, Y, Ca, Si, Hf) ZrO 2 , undoped ZrO 2 , doped (Mg, Y, Ca, Si) HfO 2 ,undoped HfO 2 , SrBi 2 Ta2O 9 , SrBi 2 Ti 2 O 9 , Bi 4 Ti 3 O 12 , Pb 5 Ge 3 O 11 , lead meta-niobate, and polyvinylidene fluoride.

7. A method of making a nonvolatile memory device comprising:
providing a base;
providing two electrically conductive layers adapted to be connected to a voltage source;
providing a ferroelectric layer positioned between the two conductive layers; the ferroelectric layer comprising a fixed portion operatively connected to the base and a movable portion; the movable portion being displaced a predetermined distance from a first position to a second position upon application of a positive or negative voltage between the two conductive layers;
providing a first contact operatively connectable to one of the two conductive layers;
providing a sense amplifier operatively connected to the first contact to sense the opening and closing of the operative connection to the first contact such that during a read operation the sense amplifier is used to detect the amount of time the contact is in operative electrical connection with the voltage source;
the application of one of a positive or negative voltage from the voltage source causing movement of the movable portion from the first to the second position resulting in operative electrical connection between one of the two conductive layers and the contact; the ferroelectric layer being configured to retain a first state of deformation if a positive voltage is applied and a second state of deformation if a negative voltage is applied and the state of deformation is retained after the voltage is removed.

8. The method of claim 7 wherein the application of a positive charge from the voltage source causes a first state of deformation within the ferroelectric layer and the application of a negative charge causes a second state of deform

Assignees

• Us Army Res Lab
• Us Army

Inventors

• Fox Glen R
• Pulskamp Jeffrey S
• Polcawich Ronald G

Classifications

• H01L27/11507 Primary

  Electricity · mapped topic

• G11C11/50

  using actuation of electric contacts to store the information · CPC title

• G11C11/2273

  Reading or sensing circuits or methods · CPC title

• H01L43/12

  Electricity · mapped topic

• H01L43/08

  Electricity · mapped topic