Intergrated circuit for programming resistive memory cells
View Patent ↗Methods and devices for programming conductive bridging RAM (CBRAM) memory cells improve the cycle stability by ensuring that the memory cells are erased before being written to anew. Optionally, in the event of overwriting the memory cells, memory cells may be written to only when the writing operation would alter the cell content (i.e., the state of bit stored in the memory cell is being changed from a logical 0 to a logical 1 or vice versa).
1. An integrated circuit having resistive memory cells in which the memory cells are capable of being put into a low-resistance or on state corresponding to a first logic state by application of a write pulse having a specific polarity and into a high-resistance or off state corresponding to a second logic state by application of an erase pulse having an opposite polarity, comprising:
a circuit configured to compare a cell content read out from a resistive memory cell that is to be written to with data to be stored in the resistive memory cell, and to supply the erase pulse to the resistive memory cell, independent of the comparison by the circuit, in the event that the data to be stored corresponds to the second logic state, and to supply the write pulse for writing data corresponding to the first logic state in response to the comparison revealing that a logic value of the cell content read out differs from the data to be stored.
2. The integrated circuit of claim 1 , wherein the circuit comprises a NAND element suitable for carrying out a logic NAND operation with cell content read out and the data to be stored.
3. The integrated circuit of claim 1 , wherein the write pulse and the erase pulse are voltage pulses.
4. A method for programming CBRAM memory cells capable of being put into a low-resistance or on state corresponding to a first logic state by application of a write pulse having a specific polarity and into a high-resistance or off state corresponding to a second logic state by application of an erase pulse having an opposite polarity, the method comprising:
comparing a cell content read out from a memory cell that is to be written to with data to be stored in the memory cell; and
performing a memory cycle wherein the memory cell is supplied the erase pulse, independent of the comparison, in the event that the data to be stored corresponds to the second logic state, and wherein the memory cell is supplied the write pulse for writing data corresponding to the first logic state in response to the comparison revealing that the cell content differs from the data to be stored.
5. The method as claimed in claim 4 , wherein the write pulse and the erase pulse are current pulses.
6. The method as claimed in claim 4 , wherein the write pulse and the erase pulse are voltage pulses.
7. The method as claimed in claim 4 , wherein the duration of the erase pulse is substantially equal to the duration of the write pulse.
8. The method as claimed in claim 4 , wherein the duration of the erase pulse is longer than the duration of the write pulse.
9. The method as claimed in claim 4 , wherein an amplitude of the erase pulse is substantially equal to an amplitude of the write pulse.
10. The method as claimed in claim 4 , wherein an amplitude of the erase pulse is higher than an amplitude of the write pulse.
11. The integrated circuit of claim 1 , wherein the resistive memory cells comprise CBRAM memory cells.
12. The integrated circuit of claim 1 , wherein the write pulse and the erase pulse are current pulses.
13. The integrated circuit of claim 1 , wherein a duration of the erase pulse is substantially equal to a duration of the write pulse.
14. The integrated circuit of claim 1 , wherein a duration of the erase pulse is longer than a duration of the write pulse.
15. The integrated circuit of claim 1 , wherein an amplitude of the erase pulse is substantially equal to an amplitude of the write pulse.
16. The integrated circuit of claim 1 , wherein an amplitude of the erase pulse is higher than an amplitude of the write pulse.
17. An integrated circuit comprising:
a resistive memory cell configured to be programmed to a low-resistance state in response to a first pulse and to a high-resistance state in response to a second pulse; and
a circuit configured to compare a resistance state of the memory cell to a resistance state to be programmed to the memory cell, and to supply the second pulse to the memory cell independent of the comparison in response to the resistance state to be stored corresponding to the high-resistance state, and to supply the first pulse to the memory cell in response to the resistance state of the memory cell differing from the resistance state to be programmed to the memory cell.
18. The integrated circuit of claim 17 , wherein the first pulse has a polarity opposite the second pulse.
19. The integrated circuit of claim 17 , wherein the resistive memory cell comprises a CBRAM memory cell.
20. The integrated circuit of claim 17 , wherein an amplitude and duration of the first pulse is substantially equal to an amplitude and duration of the second pulse.