Integrated circuit with sensing unit and method for using the same

• US 9,395,410 B2
• Filed: 06/06/2011
• Issued: 07/19/2016
• Est. Priority Date: 06/06/2011
• Status: Active Grant

• Current Assignee: III Holdings 1, LLC (Intellectual Ventures LLC)
• Original Assignee: III Holdings 1, LLC (Intellectual Ventures LLC)
• Inventors: Mani, Krishnakumar
• Primary Examiner(s): Phan, Huy Q
• Assistant Examiner(s): RHODES-VIVOUR, TEMILADE S
• Application Number:
  US13/153,472
• Publication Number:
  US 20150355272A1
• Time in Patent Office: 1,870 Days
• Field of Search: 324/301, 324/207.21, 324/210, 324/212, 324/219, 324/239, 324/244, 324/246, 324/249, 324/252, 324/259, 324/260, 338/32.R
• US Class Current: 1/1
• CPC Class Codes: G01R 31/2884 using dedicated test connectors, test elements or test circuits on the IC under test G01R31/2855 takes precedence
• CPC Class Codes: G01R 31/3004 Current or voltage test
• CPC Class Codes: G11C 11/1673 Reading or sensing circuits or methods
• CPC Class Codes: G11C 11/1677 Verifying circuits or methods
• CPC Class Codes: G11C 29/50008 of impedance
• CPC Class Codes: G11C 29/52 Protection of memory contents; Detection of errors in memory contents
• CPC Class Codes: G11C 5/00 Details of stores covered by group G11C11/00
• CPC Class Codes: G11C 5/005 Circuit means for protection against loss of information of semiconductor storage devices
• CPC Class Codes: H01F 1/00 Magnets or magnetic bodies characterised by the magnetic materials therefor; Selection of materials for their magnetic properties
• CPC Class Codes: H01L 21/00 Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof

Abstract

Integrated circuit comprising a sensing unit that includes a sensing circuit, two conductors and a magnetic storage element. The sensing circuit monitors a voltage drop across the element when a current is passed between the conductors with the element in between. The voltage drop is pre-calibrated to indicate a change in conductivity in the element that is caused by an external magnetic field. Advantageously, this indication is usable particularly for assessing a possible data corruption in a magnetic memory circuit in the integrated circuit, due to stray and external magnetic fields. Methods of using the sensing unit are also proposed.

Claims

1. A circuit comprising:

a first conductor;

a second conductor;

a magnetic memory circuit including a magnetic storage element disposed between the said first and second conductors, wherein the magnetic storage element comprises a magnetic tunnel junction (MTJ) stack;

a sensing circuit configured to determine a change in conductivity of the magnetic storage element by monitoring a voltage drop across the magnetic storage element when a constant current is passed from the first conductor to the second conductor, thereby passing through the magnetic storage element; and

an indicator configured to indicate that the magnetic storage element is not reliable for use when the change in conductivity exceeds a pre-determined value.

2. The circuit of claim 1, wherein the indicator comprises at least one of an audio indicator or a visual indicator.

3. The circuit of claim 1, wherein the magnetic storage element is configured to not contain any stored data when the sensing circuit monitors the voltage drop across the magnetic storage element.

4. A method of using a circuit, the method comprising:

using a sensing unit in the circuit, wherein the sensing unit comprises a magnetic memory circuit including a magnetic storage element, two conductors, and a sensing circuit, and wherein the magnetic storage element comprises a magnetic tunnel junction (MTJ) stack;

determining, by the sensing circuit, a change in conductivity of the magnetic storage element by monitoring a voltage drop across the magnetic storage element when a constant current is passed from a first of the two conductors to a second of the two conductors, thereby passing through the magnetic storage element; and

indicating, by an indicator, that the magnetic storage element is not reliable for use when the change in conductivity exceeds a pre-determined value.

5. The method of claim 4, wherein the indicator comprises at least one of an audio indicator or a video indicator.

6. The method of claim 4, wherein the magnetic storage element does not contain any stored data when the sensing circuit monitors the voltage drop across the magnetic storage element.

7. A method of using a circuit, the method comprising:

using a plurality of sensing units in the circuit, wherein each of the plurality of sensing units comprises a magnetic memory circuit including a magnetic storage element, two conductors, and a sensing circuit, and wherein the magnetic storage element comprises a magnetic tunnel junction (MTJ) stack;

in each of the plurality of sensing units, determining, by the sensing circuit, a change in conductivity of the magnetic storage element by monitoring a voltage drop across the magnetic storage element by said sensing circuit when a constant current is passed from a first of the two conductors to a second of the two conductors, thereby passing through the magnetic storage element; and

indicating, by an indicator, that the plurality of magnetic storage elements is not reliable for use when the change in conductivity exceeds a pre-determined value.

8. The method of claim 7, further comprising:

operating the sensing units by a multiplexer that is disposed in the circuit.

9. The method of claim 7, wherein each of the plurality of magnetic storage elements has a different aspect ratio for indicating the change in conductivity with improved sensitivity when the change in conductivity in the magnetic storage element is caused by a magnetic field from a particular direction.

10. The method of claim 7, wherein a selected magnetic storage element is storing no data when a sensing unit is monitoring a voltage drop across the selected magnetic storage element.

11. A circuit comprising:

a first conductor;

a second conductor;

a magnetic memory circuit including a magnetic storage element comprising a magnetic tunnel junction (MTJ) stack including;

a fixed layer electrically connected to the first conductor;

a tunnel oxide layer above the fixed layer; and

a free layer above the tunnel oxide layer, wherein the second conductor is electrically connected to the free layer;

at least one constant current source configured to drive a constant current from the first conductor to the second conductor, thereby passing through the magnetic storage element;

sensing circuitry configured to measure the conductivity of the magnetic storage element while the constant current is driven from the first conductor to the second conductor; and

an indicator configured to indicate that the magnetic storage element is not reliable for use when a change in conductivity exceeds a pre-determined value.

12. A circuit comprising:

a plurality of first conductors;

a plurality of second conductors;

a plurality of magnetic memory circuits including a corresponding plurality of magnetic storage elements, wherein each of the plurality of magnetic storage elements includes a fixed layer electrically connected to one of the plurality of first conductors, and wherein each of the plurality of magnetic storage elements includes a free layer electrically connected to one of the plurality of second conductors, and wherein each of the plurality of magnetic storage elements comprises a magnetic tunnel junction (MTJ) stack;

a plurality of sensing circuitries corresponding to the plurality of magnetic storage elements;

wherein;

at least one constant current source is configured to drive constant currents from each of the first conductors to a respective one of each of the second conductors, thereby passing through a respective one of the plurality of magnetic storage elements; and

the plurality of sensing circuitries is configured to measure a change in conductivity in the plurality of magnetic storage elements if the constant currents are passed through the plurality of magnetic storage elements; and

an indicator configured to indicate that the plurality of magnetic storage elements is not reliable for use when the change in conductivity exceeds a pre-determined value.

13. The circuit of claim 12, wherein each of the plurality of magnetic storage elements comprises a different aspect ratio.