Hitachi and Renesas develop MOS phase conversion memory cells
Guangdong Huate Gas Co., Ltd , https://www.huatehfc.com
The prototype unit is fabricated in a 130 nm CMOS process. The structure uses a MOS transistor and a phase conversion film that is amorphous* (high impedance) or crystalline (low impedance) in thermal response. Programming of the two states is achieved by a 180 nm diameter tungsten lower electrode contact (BEC). In a read operation, the stored digital (1 or 0) information is determined by the difference in current flow in the film.
In order to achieve breakthrough power consumption, Hitachi and Renesas researchers have developed an original low-current phase-conversion film with low-voltage programming capability. They used a controlled bismuth-tellurium-tellurium (GeSbTe) oxygen doping material to grow the film. Oxygen doping limits the impedance of the phase-converting film to an optimum level while suppressing excessive current flow during programming. Furthermore, the implementation of the cell can reduce the gate width of the MOS transistors forming these cells, as well as the number of output MOS transistors, thereby helping to reduce the size of the memory cells and drive circuits.
Details of the breakthrough low-power MOS phase-shift memory cell technology were disclosed in a technical paper presented at the International Electronics Conference in Washington, DC, on December 5, 2005.