Voltage-tunable magnetic devices for communication applications

Patent metadata

Field	Value
Publication number	US-9817088-B2
Application number	US-201615075088-A
Country	US
Kind code	B2
Filing date	Mar 18, 2016
Priority date	Mar 19, 2015
Publication date	Nov 14, 2017
Grant date	Nov 14, 2017

Abstract

Magnetic devices and methods for forming a magnetic device are disclosed. The magnetic device includes a MTJ element. The MTJ element has first and second MTJ terminals which include first and second electrodes. The free layer of the MTJ element includes a natural precessional frequency which undergoes Rabi oscillation in the presence of a radio frequency (RF) matching the natural precessional frequency. A strain induced magnetoelectric (SIM) unit contacts one of the electrodes proximate to the free layer of the MTJ element while a digital line is coupled to the SIM unit. A desired voltage is provided on the digital line to cause the SIM unit to produce a desired strain on the electrode proximate to the free layer to tune the precessional frequency of the free layer to a desired precessional frequency for detecting a desired RF by the magnetic device. The desired RF causes a change in current through the MTJ element due to Rabi oscillation.

First claim

What is claimed is:

1. A magnetic device comprising:
a magnetic tunnel junction (MTJ) element disposed between a first and a second electrode, wherein the MTJ element is directly coupled to a first major surface of the first and second electrodes, wherein the first and second electrodes define a first and a second MTJ terminal respectively, wherein the MTJ element comprises
a fixed layer and a free layer, wherein the free layer is disposed between the first electrode and the fixed layer
a tunnel barrier sandwiched between the fixed and free layers, and
wherein the free layer includes a predetermined precessional frequency, wherein the free layer undergoes Rabi oscillation in the presence of a first radio frequency (RF) signal matching the predetermined precessional frequency;

a strain induced magnetoelectric (SIM) unit coupled to the first MTJ terminal, wherein the SIM unit comprises a stress induced layer disposed within the first electrode of the MTJ element, wherein a partial thickness of the first electrode separates the stress induced layer from the MTJ element, wherein the first electrode covers a first major surface and sides of the stress induced layer, wherein a second major surface of the stress induced layer is substantially coplanar with a second major surface of the first electrode; and
a digital line directly coupled to the second major surface of the stress induced layer, wherein the digital line is biased to apply a voltage to the stress induced layer to induce a strain on the first electrode, wherein inducing the strain on the first electrode changes the precessional frequency of the free layer from the predetermined precessional frequency to a tuned precessional frequency, wherein the free layer undergoes Rabi oscillation in the presence of a second RF signal matching the tuned precessional frequency.

2. The device of claim 1 wherein a magnitude of the strain on the first electrode defines the tuned precessional frequency, wherein a change in the magnitude of the strain on the first electrode corresponds with a change to the tuned precessional frequency.

3. The device of claim 2 wherein the magnitude of the strain on the first electrode is defined by a magnitude of the voltage applied to the stress induced layer, wherein the tuned precessional frequency is adjustable by adjusting the magnitude of the voltage applied to the stress induced layer.

4. The device of claim 1 wherein the predetermined precessional frequency is a first desired precessional frequency and the tuned precessional frequency is a second desired precessional frequency, wherein the second RF signal comprises a different radio frequency from the first RF signal.

5. The device of claim 1 wherein a footprint of the stress induced layer is larger than a footprint of the free layer.

6. The device of claim 1 wherein the first electrode is a top electrode disposed over the MTJ element, wherein the second major surfaces of the stress induced layer and the first electrode are top surfaces, wherein the top surface of the stress induced layer is coplanar with the top surface of the first electrode.

7. The device of claim 1 wherein the stress induced layer comprises a piezo electric material or a ferroelectric material.

8. The device of claim 1 wherein the first electrode is a bottom electrode disposed below the MTJ element, wherein the second major surfaces of the stress induced layer and the first electrode are bottom surfaces, wherein the bottom surface of the stress induced layer is coplanar with the bottom surface of the first electrode.

9. The device of claim 1 wherein a width of the stress induced layer is larger than a width of the MTJ element and a width of the digital line.

10. A method of forming a magnetic device comprising:
providing a substrate defined with a device region;
forming a selector unit on the substrate, wherein forming the selector unit comprises forming a select transistor;
forming a lower back-end dielectric layer, wherein the lower back-end dielectric layer includes one or more interlevel dielectric (ILD) levels;
forming a bottom electrode on the lower back-end dielectric layer;
forming a MTJ element on the bottom electrode, wherein the MTJ element includes
a fixed layer
a tunnel barrier,
a free layer, the free layer is separated from the fixed layer by the tunnel barrier, and
wherein the free layer includes a predetermined precessional frequency, wherein the free layer undergoes Rabi oscillation in the presence of a first radio frequency (RF) signal matching the predetermined precessional frequency;

forming a top electrode layer over the MTJ element;
forming a stress induced layer, wherein the stress induced layer is disposed within one of the top or the bottom electrode which is proximate to the free layer of the MTJ element, wherein a partial thickness of the top or the bottom electrode separates the stress induced layer from the MTJ element, wherein the top or the bottom electrode covers a first major surface and sides of the stress induced layer, wherein a second major surface of the stress induced layer is substantially coplanar with a second major surface of the top or the bottom electrode;
forming a digital line directly coupled to the second major surface of the stress induced layer, wherein the digital line is biased to apply a voltage to the stress induced layer to induce a strain on the top or the bottom electrode, wherein inducing the strain on the top or the bottom electrode changes the precessional frequency of the free layer from the predetermined precessional frequency to a tuned precessional frequency, wherein the free layer undergoes Rabi oscillation in the presence of a second RF signal matching the tuned precessional frequency.

11. The method of claim 10 wherein:
the electrode proximate to the free layer comprises the bottom electrode;
the stressed induced layer is disposed within the bottom electrode below the MTJ element;
the digital line is disposed below the stress induced layer; and
the bottom electrode comprises an extended bottom electrode for accommodating the stress induced layer and coupling a pad interconnect for connecting to a first terminal of the select transistor.

12. The method of claim 11 wherein the stress induced layer comprises a piezo electric material or a ferroelectric material.

13. The method of claim 10 wherein the predetermined precessional frequency is a first desired precessional frequency and the tuned precessional frequency is a second desired precessional frequency, wherein the second RF signal comprises a different radio frequency from the first RF signal.

14. The method of claim 10 wherein:
the electrode proximate to the free layer comprises the top electrode;
the stressed induced layer is disposed within the top electrode over the MTJ element;
the digital line is disposed above the stress induced layer; and the top electrode comprises an extended top electrode for accommodating the stress induced layer, digital line and the BL.

15. The method of claim 14 wherein the stress induced layer comprises a piezoelectric material or a ferroelectric material.

16. The method of claim 10 wherein a footprint of the stress induced layer is larger than a footprint of the free layer.

Assignees

• Globalfoundries Sg Pte Ltd

Inventors

• Naik Vinayak Bharat
• Datta Deepanjan
• Kota Murali V R M

Classifications

• H01L43/12

  Electricity · mapped topic

• G01R33/098 Primary

  comprising tunnel junctions, e.g. tunnel magnetoresistance sensors · CPC title

• H01L43/08

  Electricity · mapped topic

• H01L43/10

  Electricity · mapped topic

• H01L27/22

  Electricity · mapped topic