US Patent 7660147 Programming method for phase change memory

A programming method for a phase change memory based on the phase transformations between amorphous and crystalline phases is disclosed. The programming method comprises a current pulse with step waveform providing a first crystallization current pulse to the phase change memory and providing a second crystallization current pulse to the phase change memory. The first crystallization current pulse has a first rising edge, a first falling edge and a first peak current held for a first hold time. The second crystallization current pulse has a second peak current. The second peak current follows the first falling edge and is held for a second hold time.