Boron Penetration and Hot-Carrier Effects in Surface-Channel PMOSFETs with p^+ Poly-Si Gates
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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 BF_2- implanted gates cause larger boron penetration than those with Boron-implanted gates. However, 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, BF_2 and Boron. PMOSFETs with BF_2-implanted gates have about 100 times longer lifetime than those with Boron-implanted gates. The main reason for the longer lifetime of BF_2-doped PMOSFETs is the incorporation of fluorine in the gate oxide of the PMOSFET with the BF_2-implanted gate, resulting in the smaller electron trapping in the gate oxide. The maximum allowed supply voltage, based on the hot-carrier reliability, is higher than |-4| V for sub-half micron PMOSFETs with BF_2- or Boron-implanted poly Si gates.
- IEICE transactions on electronics
IEICE transactions on electronics 78(3), 255-260, 1995-03-20
The Institute of Electronics, Information and Communication Engineers