Analysis of Boron Penetration and Gate Depletion Using Dual-Gate PMOSFETs for High Performance G-Bit DRAM Design

Norikatsu TAKAURA  Ryo NAGAI  Hisao ASAKURA  Satoru YAMADA  Shin'ichiro KIMURA  

IEICE TRANSACTIONS on Electronics   Vol.E85-C   No.5   pp.1138-1145
Publication Date: 2002/05/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Microelectronic Test Structures)
boron penetration,  gate depletion,  dual-gate PMOSFETs,  Vth fluctuation,  G-bit DRAM,  

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We developed a method for analysis of boron penetration and gate depletion using N+ and P+ dual-gate PMOSFETs. An N+ gate PMOSFETs, which is immune to boron penetration and gate depletion, exhibited the threshold voltage shifts and fluctuation in P+ gate PMOSFETs fabricated using identical N- substrates. We showed the importance of Vth fluctuation analysis and found that the Vth fluctuation in N+ gate PMOSFETs was negligible, but, the Vth fluctuation in P+ gate PMOSFETs was significant, indicating that the Vth fluctuation in P+ gate PMOSFETs was dominated by boron penetration. It was also shown, for the first time, that boron penetration occurred with gate depletion, and gate depletion must be very strong to suppress boron penetration. The dual-gate PMOSFET method makes it possible to select high-performance G-bit DRAM fabrication processes that are robust against Vth fluctuation.