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Boron Penetration and Hot-Carrier Effects in Surface-Channel PMOSFETs with p+ Poly-Si Gates
Tohru MOGAMI Lars E. G. JOHANSSON Isami SAKAI Masao FUKUMA
IEICE TRANSACTIONS on Electronics
Publication Date: 1995/03/25
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Sub-1/4 Micron Device and Process Technologies)
hot-carrier effects, boron penetration, surface-channel PMOSFETs, gate current, BF2,
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Surface-channel PMOSFETs are suitable for use in the quarter micron CMOS devices. For surface-channel PMOSFETs with p+ poly-Si gates, boron penetration and hot-carrier effects were investigated. When the annealing temperature is higher and the gate oxide is thinner, a larger threshold voltage shift was observed for p+ poly-Si PMOSFETs, because of boron penetration. Furthermore, PMOSFETs with BF2-implanted gates cause larger boron penetration than those with Boron-implanted gates. Howerer, the PMOSFET lifetime, determined by hot-carrier reliability, does not depend on the degree of boron penetration. Instead, it depends on doping species, that is, BF2 and Boron. PMOSFETs with BF2-implanted gates have about 100 times longer lifetime than those with Boron-implanted gates. The main reason for the longer lifetime of BF2-doped PMOSFETs is the incorporation of fluorine in the gate oxide of the PMOSFET with the BF2-implanted gate, resulting in the smaller electron trapping in the gate oxide. The maximun allowed supply voltage,based on the hot-carrier reliability, is higher than4V for sub-half micron PMOSFETs with BF2- or Boron-implanted poly Si gates.