Temperature compensated RRAM circuit

• US 20040179414A1
• Filed: 03/10/2003
• Published: 09/16/2004
• Est. Priority Date: 03/10/2003
• Status: Active Grant

• Current Assignee: Xenogenic Development Limited Liability Company (Intellectual Ventures LLC)
• Original Assignee: Sharp Laboratories of America Incorporated (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Hsu, Sheng Teng
• Granted Patent: US 6,868,025 B2
• Time in Patent Office: Days
• US Class Current: 365/211
• CPC Class Codes: G11C 11/5678 using amorphous/crystalline phase transition storage elements
• CPC Class Codes: G11C 11/5685 using storage elements comprising metal oxide memory material, e.g. perovskites
• CPC Class Codes: G11C 13/0004 comprising amorphous/crystalline phase transition cells
• CPC Class Codes: G11C 13/0007 comprising metal oxide memory material, e.g. perovskites
• CPC Class Codes: G11C 13/004 Reading or sensing circuits or methods
• CPC Class Codes: G11C 2013/0054 Read is performed on a reference element, e.g. cell, and the reference sensed value is used to compare the sensed value of the selected cell
• CPC Class Codes: G11C 2213/31 Material having complex metal oxide, e.g. perovskite structure
• CPC Class Codes: G11C 2213/72 Array wherein the access device being a diode
• CPC Class Codes: G11C 2213/79 Array wherein the access device being a transistor
• CPC Class Codes: G11C 7/04 with means for avoiding disturbances due to temperature effects
• CPC Class Codes: G11C 7/062 Differential amplifiers of non-latching type, e.g. comparators, long-tailed pairs
• CPC Class Codes: G11C 7/067 Single-ended amplifiers
• CPC Class Codes: G11C 7/14 Dummy cell management; Sense reference voltage generators

Abstract

A temperature compensated RRAM sensing circuit to improve the RRAM readability against temperature variations is disclosed. The circuit comprises a temperature dependent element to control the response of a temperature compensated circuit to generate a temperature dependent signal to compensate for the temperature variations of the resistance states of the memory resistors. The temperature dependent element can control the sensing signal supplied to the memory resistor so that the resistance states of the memory resistor are compensated against temperature variations. The temperature dependent element can control the reference signal supplied to the comparison circuit so that the output signal provided by the comparison circuit is compensated against temperature variations. The temperature dependent element is preferably made of the same material and process as the memory resistors.

Claims

1. A temperature compensated RRAM sensing circuit to improve the readability against temperature variations, the circuit comprising

a) a temperature dependent memory resistor array;

b) a temperature dependent element;

c) a temperature compensated control circuit in communication with the temperature dependent element and to provide at least one temperature dependent output signal to the temperature dependent memory resistor to compensate for the temperature variation of the resistance of the memory resistor.

2. A circuit as in claim 1, wherein the temperature dependent output signal developed by the temperature compensated control circuit is a temperature dependent current source, the temperature dependency of the current source being in the opposite direction as the temperature dependency of the memory resistor so that the voltage across the memory resistor is compensated against temperature variations.

3. A circuit as in claim 1, wherein the temperature dependent output signal developed by the temperature compensated control circuit is a temperature dependent voltage source, the temperature dependency of the voltage source being in the same direction as the temperature dependency of the memory resistor so that the current across the memory resistor is compensated against temperature variations.

4. A circuit as in claim 1, further comprising a sense amplifier, the sense amplifier comprising an inverter.

5. A circuit as in claim 1, further comprising a sense amplifier, the sense amplifier comprising a comparison circuit.

6. A circuit as in claim 1, wherein the temperature dependent element is fabricated from the same material and process as the memory resistor.

7. A circuit as in claim 6, wherein the temperature dependent element is programmed to the lowest resistance state.

8. A circuit as in claim 1, wherein the temperature compensated control circuit is a current load nMOS circuit.

9. A circuit as in claim 1, wherein the temperature compensated control circuit is a current source pMOS circuit.

10. A circuit as in claim 1, wherein the memory resistor array is a 1R1D cross point memory array.

11. A circuit as in claim 1, wherein the memory resistor array is a 1R1T random access memory array.

12. A circuit as in claim 1, further comprising a diode connecting to the temperature dependent element.

13. A circuit as in claim 1, wherein the memory resistor array stores two-bit resistance states.

14. A circuit as in claim 1, wherein the memory resistor array stores multi-bit resistance states.

15. A circuit as in claim 14, further comprising a multi-bit sensing circuit.

16. A method to sense a resistance state of a selected memory resistor in an RRAM device to improve the readability against temperature variation, the method comprising the steps of:

a) providing a temperature compensated control circuit comprising a temperature dependent element;

b) developing at least one temperature dependent sensing signal by the temperature compensated control circuit;

c) applying the at least one temperature dependent sensing signal to the memory resistor to compensate for the temperature variation of the resistance of the memory resistor; and

d) sensing the compensated state of the memory resistor.

17. A method as in claim 16, wherein the temperature dependent sensing signal is a current source and the compensated state of the memory resistor is the voltage across the memory resistor.

18. A method as in claim 16, wherein the temperature dependent sensing signal is a voltage source and the compensated state of the memory resistor is the current through the memory resistor.

19. A method as in claim 16, wherein the temperature dependent element is fabricated from the same material and process as the memory resistor.

20. A temperature compensated RRAM sensing circuit to improve the readability against temperature variation, the circuit comprising

a) a temperature dependent memory resistor array;

b) a temperature dependent element;

c) a temperature compensated reference circuit in communication with the temperature dependent element and to provide at least one temperature dependent reference signal; and

d) a comparison circuit in communication with the memory resistor array and the temperature compensated reference circuit,

the comparison circuit adapted to

compare at least one sense signal developed by at least one memory resistor

with at least one reference signal developed by the temperature compensated control circuit

and to provide at least one output signal in response to the comparison.

21. A circuit as in claim 20, wherein the temperature dependent reference signal developed by the temperature compensated reference circuit is a temperature dependent current source, the temperature dependency of the current source being in the same direction as the temperature dependency of the resistance state of the memory resistor so that the output signal provided by the comparison circuit is compensated against temperature variations.

22. A circuit as in claim 20, wherein the temperature dependent reference signal developed by the temperature compensated reference circuit is a temperature dependent voltage source, the temperature dependency of the voltage source being in the same direction as the temperature dependency of the resistance state of the memory resistor so that the output signal provided by the comparison circuit is compensated against temperature variations.

23. A circuit as in claim 20, wherein the temperature dependent element is fabricated from the same material and process as the memory resistor.

24. A circuit as in claim 20, wherein the sense signal and the at least one reference signal are voltages.

25. A circuit as in claim 20, wherein the sense signal and the at least one reference signal are currents.

26. A circuit as in claim 20, wherein the output signal is indicative of the resistance state of the memory resistor.

27. A method to sense a resistance state of a selected temperature dependent memory resistor in an RRAM device to improve the readability against temperature variation, the method comprising the steps of:

a) providing a temperature compensated reference signal circuit comprising a temperature dependent element;

b) developing a sense signal by applying a sensing signal to the memory resistor;

c) developing at least one temperature dependent reference signal by the temperature compensated reference signal circuit;

d) comparing the sense signal with the at least one reference signal; and

e) providing an output signal in response to the comparing step.

28. A method as in claim 27, wherein the sensing signal is a current source and the sense signal and the at least one reference signal are voltages.

29. A method as in claim 27, wherein the sensing signal is a voltage source and the sense signal and the at least one reference signal are currents.

30. A method as in claim 27, wherein the temperature dependent element is fabricated from the same material and process as the memory resistor.