Integrating nonvolatile memory capability within SRAM devices

• US 7,944,734 B2
• Filed: 12/07/2009
• Issued: 05/17/2011
• Est. Priority Date: 03/12/2007
• Status: Active Grant

• Current Assignee: Marvell Asia Pte Limited (Marvell Technology Group Limited)
• Original Assignee: International Business Machines Corporation
• Inventors: Lamorey, Mark C. H.
• Primary Examiner(s): Nguyen; Tuan T
• Assistant Examiner(s): REIDLINGER, RONALD LANCE
• Application Number:
  US12/631,900
• Publication Number:
  US 20100080042A1
• Time in Patent Office: 526 Days
• Field of Search: 365/154, 365/156, 365/185.08, 365/158, 365/171, 365/173
• US Class Current: 365/154
• CPC Class Codes: G11C 11/16 using elements in which the storage effect is based on magnetic spin effect
• CPC Class Codes: G11C 14/0081 and the nonvolatile element is a magnetic RAM [MRAM] element or ferromagnetic cell

Abstract

A nonvolatile static random access memory (SRAM) device includes a pair of cross-coupled, complementary metal oxide semiconductor (CMOS) inverters configured as a storage cell for a bit of data and a pair of magnetic spin transfer devices coupled to opposing sides of the storage cell. The magnetic spin transfer devices are configured to retain the storage cell data therein following removal of power to the SRAM device, and are further configured to initialize the storage cell with the retained data upon application of power to the SRAM device.

Claims

1. A nonvolatile static random access memory (SRAM) device, comprising:

a pair of cross-coupled, complementary metal oxide semiconductor (CMOS) inverters configured as a storage cell for a bit of data;

a pair of magnetic spin transfer devices coupled to opposing sides of the storage cell;

wherein the magnetic spin transfer devices are configured to retain the storage cell data therein following removal of power to the SRAM device, and are further configured to initialize the storage cell with the retained data upon application of power to the SRAM device; and

a single port coupled to the SRAM cell, the single port comprising a pair of pass gates, the pair of magnetic spin transfer devices and a pair of bitlines;

wherein the pair of bitlines is configured for read and write operations of the SRAM cell during power on conditions, and wherein the pair of bitlines also serves as a programming node.

2. The device of claim 1, wherein the magnetic spin transfer devices are configured to retain storage cell data by programming of a low resistance state in one of the magnetic spin transfer devices and a high resistance state the other of the magnetic spin transfer devices.

3. The device of claim 2, wherein the magnetic spin transfer devices are programmed to the low and high resistance states by application of current therethrough.

4. The device of claim 3, wherein the low resistance state corresponds to current passed through either of the magnetic spin transfer devices in a first direction, and the high resistance state corresponds to current passed through either of the magnetic spin transfer devices in a second, opposite direction.

5. A method of integrating nonvolatile capability within a static random access memory (SRAM) device, the method comprising:

coupling a pair of magnetic spin transfer devices to opposing sides of an SRAM storage cell;

the SRAM storage cell further comprising a pair of cross-coupled, complementary metal oxide semiconductor (CMOS) inverters configured to store a bit of data therein;

wherein the magnetic spin transfer devices are configured to retain the storage cell data therein following removal of power to the SRAM device, and are further configured to initialize the storage cell with the retained data upon application of power to the SRAM device; and

coupling a single port to the SRAM cell, the single port comprising a pair of pass gates, the pair of magnetic spin transfer devices and a pair of bitlines;

wherein the pair of bitlines is configured for read and write operations of the SRAM cell during power on conditions, and wherein the pair of bitlines also serves as a programming node.

6. The method of claim 5, wherein the magnetic spin transfer devices are configured to retain storage cell data by programming of a low resistance state in one of the magnetic spin transfer devices and a high resistance state the other of the magnetic spin transfer devices.

7. The method of claim 6, wherein the magnetic spin transfer devices are programmed to the low and high resistance states by application of current therethrough.

8. The method of claim 7, wherein the low resistance state corresponds to current passed through either of the magnetic spin transfer devices in a first direction, and the high resistance state corresponds to current passed through either of the magnetic spin transfer devices in a second, opposite direction.