Title :
Pass transistor designs using pocket implant to improve manufacturability for 256 Mbit DRAM and beyond
Author :
Chatterjee, A. ; Liu, J. ; Aur, S. ; Mozumder, P.K. ; Rodder, M. ; Chen, I.-C.
Author_Institution :
Semicond. Process & Device Center, Texas Instrum. Inc., Dallas, TX, USA
Abstract :
Pass transistor designs for scaled 256 Mbit DRAM are studied in this paper. It is shown, for the first time, that a L/sub g/=0.25 /spl mu/m and t/sub ox/=85 /spl Aring/ transistor utilizing a pocket implant together with a light V/sub TN/ implant (pocket-with-V/sub TN/) can satisfy the stringent requirements of subthreshold leakage, diode leakage, V/sub T/ during charging, and a tolerance for L/sub g/ variation of 0.08 /spl mu/m for manufacturability. The success of the pocket-implant device in meeting the above design spec is due to the reduced V/sub T/ roll-off at shorter L/sub g/ and reduced body effect at longer L/sub g/ compared to those of a conventional device. An optimum range of substrate bias is determined to be -1.5 to -2 V. It is also shown that the pocket implant does not degrade the gate oxide integrity nor channel hot-electron reliability.<>
Keywords :
DRAM chips; hot carriers; integrated circuit design; integrated circuit reliability; ion implantation; leakage currents; -1.5 to -2 V; 0.25 micron; 256 Mbit; body effect; channel hot-electron reliability; diode leakage; dynamic RAM; gate oxide integrity; manufacturability improvement; pass transistor designs; pocket implant; scaled DRAM; substrate bias; subthreshold leakage; Auditory implants; Degradation; Instruments; Manufacturing; Random access memory; Semiconductor device manufacture; Semiconductor diodes; Substrates; Subthreshold current; Thickness control;
Conference_Titel :
Electron Devices Meeting, 1994. IEDM '94. Technical Digest., International
Conference_Location :
San Francisco, CA, USA
Print_ISBN :
0-7803-2111-1
DOI :
10.1109/IEDM.1994.383457
