Phase Change Memory: Array Development and Sensing Circuits Using Delta-Sigma Modulation

Chalcogenide based non-volatile Phase Change Memory (PCM) circuits were designed to investigate new emerging non-volatile memory technologies. An overview of the operation of chalcogenide-based resistive PCM for circuit designers is presented. MOSIS fabrication service was used along with Idaho Microfabrication Lab at Boise State University to develop PCM chips. Experimental results show successful integration of two discreet processing services for developing chalcogenide based non-volatile memory circuits. Possible multi-state capabilities were observed during the testing of single memory bits. Four Delta Sigma Modulation (DSM) based sensing techniques for resistive memory are presented. The proposed sensing techniques have the advantage over traditional sensing circuits in being able to reliably and accurately distinguish resistance values separated by a small margin, easily within 10 kΩ for practical sense times. The experimental results show that resistances varying from 10 kΩ to 4.1 MΩ could be sensed reliably within an error percentage of 15%