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轻掺杂多晶硅制作高值电阻已广泛用于VLSI中。本工作研究了离子注入的轻掺砷多晶硅在氢、氮和高真空气氛中的低温退火特性。研究发现,高温活化退火并除去覆盖的SiO_2层后的轻掺砷多晶硅,在低温下再次退火后其电导将增加2～4个数量级。对此提出了新的解释,认为在高温活化阶段,SiO_2层中的自由氧可能进入了晶界并形成载流子俘获态;当SiO_2被除去并在低温下退火时,这些氧将从晶界解吸而使轻掺杂多晶硅的电导显著增加。可据以解释轻掺杂多晶硅许多不同于重掺杂多晶硅的特性。由于晶界氧俘获态的变化强烈影响轻掺杂多晶硅的电学行为,因此对氧俘获态的研究和认识对轻掺杂多晶硅的广泛应用有重要意义。
Lightly doped polycrystalline silicon has been widely used in high-value VLSI resistors. This work investigated the low-temperature annealing properties of ion-implanted light-doped arsenic polysilicon in hydrogen, nitrogen and high-vacuum atmospheres. It is found that the lightly doped arsenic polycrystalline silicon annealed at high temperature and the SiO 2 layer removed can increase the conductance by 2 to 4 orders of magnitude after re-annealing at low temperature. A new explanation is put forward that at the high-temperature activation stage, the free oxygen in the SiO 2 layer may enter the grain boundary and form a carrier-trapping state. When SiO 2 is removed and annealed at a low temperature, the oxygen will migrate from the grain boundary Desorption led to a significant increase in the conductance of the lightly doped polysilicon. It is possible to explain many of the characteristics of lightly doped polysilicon that differ from heavily doped polysilicon. Since the change of the oxygen trapping state in the grain boundary strongly influences the electrical behavior of the lightly doped polycrystalline silicon, the research and understanding of the oxygen trapping state is of great significance for the wide application of lightly doped polycrystalline silicon.