Phase-change random access memory and programming method
A programming method for a phase-change random access memory (PRAM) may be provided. The programming method may include determining an amorphous state of a chalcogenide material using programming pulses to form programming areas having threshold voltages corresponding to logic high and logic low, and/or controlling a trailing edge of programming pulses during programming to control a quenching speed of the chalcogenide material so as to adjust a threshold voltage of the chalcogenide material. Accordingly, programming pulses corresponding to logic low or logic high may have uniform magnitudes regardless of a corresponding logic level. Accordingly, reliability of a PRAM device may be improved.
1. A programming method for a phase-change random access memory (PRAM), comprising:
determining an amorphous state of a chalcogenide material using programming pulses to form programming areas having threshold voltages corresponding to logic high and logic low; and
controlling a trailing edge of the programming pulses to control a quenching speed of the chalcogenide material so as to adjust a threshold voltage of the chalcogenide material.
2. The programming method of claim 1 , wherein controlling the trailing edge of programming pulses is temporary.
3. The programming method of claim 1 , wherein the programming pulses have a melting portion and a quenching portion.
4. The programming method of claim 3 , wherein the quenching portion is varied using program information to control the quenching of the chalcogenide material melted during the melting portion.
5. The programming method of claim 3 , wherein a magnitude of the melting portion has no variation between programming pulses.
6. The programming method of claim 1 , wherein a duration of the trailing edge of the programming pulses corresponding to the logic high is longer than a duration of the trailing edge of the programming pulses corresponding to the logic low.
7. The programming method of claim 4 , wherein a duration of the quenching portion corresponding to the logic high is longer than a duration of the quenching portion corresponding to the logic low.
8. The programming method of claim 1 , wherein a duration of the trailing edge of the programming pulses corresponding to the logic low is 20 ns or less, and a duration of the trailing edge of the programming pulses corresponding to the logic high is 20 ns or more.
9. The programming method of claim 4 , wherein a duration of the quenching portion corresponding to the logic low is 20 ns or less, and a duration of the quenching portion corresponding to the logic high is 20 ns or more.
10. The programming method of claim 6 , wherein a duration of the trailing edge of the programming pulses corresponding to the logic low is 20 ns or less, and a duration of the trailing edge of the programming pulses corresponding to the logic high is 20 ns or more.
11. The programming method of claim 7 , wherein a duration of the quenching portion corresponding to the logic low is 20 ns or less, and a duration of the quenching portion corresponding to the logic high is 20 ns or more.
12. The programming method of claim 1 , further comprising:
applying a reading pulse to the programming area having a lower threshold voltage so that a current flows the programming area having the lower threshold voltage.
13. The programming method of claim 1 , further comprising:
applying a reading pulse to the programming area having the higher threshold voltage so that no current flows in the programming area having the higher threshold voltage.