Title :
Using n-channel TFTs without LDD structures for high stabilities of 1.2-V high-density SRAMs
Author :
Liu, C.T. ; Diodato, P.W. ; Lee, K.H. ; Gong, H.I.
Author_Institution :
AT&T Bell Labs., Murray Hill, NJ, USA
Abstract :
In high-density SRAMs, cell-stability issues have limited the lower boundary of the operation voltage (VDD) for low-power applications. In 1990, p-channel thin-film-transistors (TFTs) were introduced to make 3.3-V operation possible. As VDD dropped to 2.0 V in 1991, however, p-TFTs could not solve the stability issues and cell β ratios as large as 4.4 had to be used, and 1.2-V operation was not possible in the analyses at all. In addition to stability issues, hot carrier aging and sodium-ions also limited the memory density through the limits of device dimensions. In this paper we have demonstrated that 1.2-V SRAM cells with high stabilities can be designed with n-channel TFTs and p-MOSFETs. The n-TFTs are also easier to fabricate and have superior characteristics than p-TFTs
Keywords :
MOS memory circuits; SRAM chips; circuit stability; integrated circuit noise; thin film transistors; 1.2 V; PMOSFET; cell stability; high stability cell; high-density SRAMs; hot carrier aging; low-power applications; memory density; n-channel TFTs; p-MOSFETs; static RAM cells; thin-film-transistors; Aging; Design optimization; FETs; Hot carriers; MOSFET circuits; Process design; Random access memory; Stability analysis; Thin film transistors; Voltage;
Conference_Titel :
Electron Devices Meeting, 1995. IEDM '95., International
Conference_Location :
Washington, DC
Print_ISBN :
0-7803-2700-4
DOI :
10.1109/IEDM.1995.499366
