Bit line charge accumulation sensing for resistive changing memory

• US 8,638,597 B2
• Filed: 05/21/2012
• Issued: 01/28/2014
• Est. Priority Date: 12/02/2008
• Status: Active Grant

• Current Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Original Assignee: Seagate Technology LLC (Seagate Technology Holdings Plc)
• Inventors: Jung, Chulmin, Lu, Yong, Kim, Kang Yong, Kim, Young Pil
• Primary Examiner(s): HIDALGO, FERNANDO N
• Application Number:
  US13/476,368
• Publication Number:
  US 20120230094A1
• Time in Patent Office: 617 Days
• Field of Search: 365/46, 365/55, 365/74, 365/97, 365/100, 365/131, 365/148, 365/158, 365/171, 365/173, 365/163
• US Class Current: 365/158
• CPC Class Codes: G11C 11/1673 Reading or sensing circuits or methods
• CPC Class Codes: G11C 7/02 with means for avoiding parasitic signals
• 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 7/14 Dummy cell management; Sense reference voltage generators

Abstract

A memory array includes a plurality of magneto-resistive changing memory cells. Each resistive changing memory cell is electrically between a source line and a bit line and a transistor electrically between the resistive changing memory cell and the bit line. The transistor has a gate electrically between a source region and a drain region and the source region being electrically between the r magneto-resistive changing memory cell and the gate. A word line is electrically coupled to the gate. A bit line charge accumulation sensing for magneto-resistive changing memory is also disclosed.

Claims

1. A memory array comprising:

a plurality of spin-transfer torque memory cells, each spin-transfer torque memory cells electrically between a source line and a bit line and a transistor electrically coupled to the spin-transfer torque memory cells and the bit line, the transistor having a gate electrically between a source region and a drain region and the source region being electrically between the spin-transfer torque memory cell and the gate, a word line is electrically coupled to the gate; and

a high resistance state resistive changing memory cell and a low resistance state resistive changing memory cell that provide an average voltage reference value when a read operation is applied across a selected spin-transfer torque memory cell along a same word line row connecting the transistor, the high resistance state resistive changing memory cell, and the low resistance state resistive changing memory cell.

2. The memory array according to claim 1, further comprising:

a plurality of high resistance state resistive changing memory cells, each high resistance state resistive changing memory cell is electrically coupled to a high resistance state transistor, and the high resistance state transistor is electrically coupled to a reference voltage word line; and

a plurality of low resistance state resistive changing memory cells, each low resistance state resistive changing memory cell is electrically connected to a low resistance state transistor, and the low resistance state transistor is electrically coupled to the reference voltage word line;

wherein one high resistance state resistive changing memory cell and one low resistance state resistive changing memory cell provide an average voltage reference value when a read operation is applied across a selected resistive changing memory cell along a same word line row connecting the transistor, the high resistance state transistor, and the low resistance state transistor.

3. The memory array according to claim 2, further comprising a sense amplifier that senses the read operation voltage and the average reference voltage.

4. The memory array according to claim 3, wherein the sense amplifier is electrically connected to a high resistance state bit line, a low resistance state bit line and a selected magneto-resistive changing memory cell bit line.

5. A memory array comprising:

a plurality of spin-transfer torque memory cells, each spin-transfer torque memory cell electrically between a source line and a bit line and a transistor electrically between the spin-transfer torque memory cell and the bit line;

a plurality of high resistance state spin-transfer torque memory cells, each high resistance state spin-transfer torque memory cell is electrically connected to a high resistance state transistor and the high resistance state transistor is electrically coupled to a reference voltage word line; and

a plurality of low resistance state spin-transfer torque memory cells, each low resistance state spin-transfer torque memory cell is electrically connected to a low resistance state transistor and the low resistance state transistor is electrically coupled to the reference voltage word line;

wherein one high resistance state spin-transfer torque memory cell and one low resistance state spin-transfer torque memory cell provide an average voltage reference value when a read operation is applied across a selected spin-transfer torque memory cell along a same word line row connecting the transistor, the high resistance state transistor, and the low resistance state transistor.

6. The memory array according to claim 5, further comprising a sense amplifier that senses the read operation voltage and the average reference voltage.

7. The memory array according to claim 6, wherein the sense amplifier is electrically connected to a high resistance state bit line, a low resistance state bit line and a selected spin-transfer torque memory cell bit line.

8. A method of sensing a data state of resistive changing memory, comprising steps of:

precharging a bit line to a predetermined voltage value;

discharging the bit line charge through a selected spin-transfer torque memory cell and reducing the bit line precharge voltage value to a bit line voltage value;

sensing the bit line voltage value to determine a data state of the spin-transfer torque memory cell by comparing the bit line voltage value to an average reference voltage value to determine a data state of the spin-transfer torque memory cell; and

precharging a high resistance state bit line and a low resistance state bit line to a predetermined reference charge level having a reference precharge voltage value, and discharging the reference charge level through a high resistance state spin-transfer torque memory cell and a low resistance state spin-transfer torque memory cell to obtain the average reference voltage value.

9. The method according to claim 8, wherein the sensing step further comprises comparing the bit line voltage value to the average reference voltage value to determine a data state of the spin-transfer torque memory cell.

10. The method according to claim 9, wherein the predetermined reference charge level is substantially the same as the predetermined bit line charge level.

11. The method according to claim 9, wherein the predetermined reference charge level is discharged at substantially the same time as the predetermined bit line charge level.

12. The method according to claim 11, wherein the predetermined reference charge level stops discharging at substantially the same time as the predetermined bit line charge level.