Atomic Layer Deposition of GeSb₂Te₄ Thin Films for Reliable Phase Change Memory With a High Dynamic Range

With the increase of memory cell density, the structure of phase change memory (PCM) has changed from two-dimensional to three-dimensional, the manufacturing process has become increasingly complex, and the cost of tape-out has risen sharply. In order to optimize device performance and improve yield, improving device reliability has become a primary focus of attention. A high dynamic range can significantly reduce the possibility of device failure or bit errors, thereby improving reliability. In this study, we utilized atomic layer deposition (ALD) to fabricate a crystalline GeSb2Te4 film using special precursor pulses. By inducing crystallization through crystal nucleation, the film was able to switch stably between high and low resistance states during device operation without experiencing any intermediate states that may lead to device failure or bit errors. Moreover, the Rhombohedral phase film (similar to 10(3) Omega) fabricated by ALD resulted in PCM cells with a higher dynamic range (similar to 1000X) compared to physical vapor deposition (PVD) (similar to 10X). The PCM cell's endurance under a dynamic range of 1000X was able to reach 106 cycles, with a low drift coefficient (0.00066) for the low resistance state. This work offers a new approach to improving the reliability of PCM.