重掺硼对直拉单晶硅片上压痕位错运动的影响

Effect of Heavy Boron-doping on Motion of Indentation Dislocations on Silicon Wafers

对比研究了轻掺硼(1.5×10^(16)cm^(-3))和重掺硼(1.2×10^(20)cm^(-3))直拉硅片上维氏压痕周围的残余应力分布及压痕位错在900℃滑移的情况。研究表明:重掺硼直拉硅片上压痕周围的残余应力及应力场区域显著小于轻掺硼硅片的。在900℃热处理时,轻掺硼硅片上的压痕位错发生显著的滑移,而重掺硼硅片上的压痕位错几乎不发生滑移。一方面,重掺硼降低了单晶硅的压痕断裂韧性,使侧向裂纹尺寸增大而释放更多的应力,从而使压痕的残余应力变小;另一方面,重掺硼对位错具有明显的钉扎作用,使位错的滑移需要更大的应力驱动。可以认为正是上述两方面的效应使得重掺硼硅片的压痕位错几乎不发生滑移。

We have comparatively investigated the residual stress distribution around Vicker indentation and the dislocation gliding at 900℃for lightly boron（B）-doped（1.5×10^（16）cm^（-3））and heavily B-doped（1.2×10^（20）cm^（-3））Czochralski silicon wafers.It is found that the residual stress and the strained area in the heavily Bdoped silicon wafer is much smaller than those in the lightly B-doped counterpart.During the anneal at 900℃,the indentation dislocations on the lightly B-doped silicon wafer glide significantly,while those on the heavily B-doped counterpart hardly glide.On one hand,the heavy B-doping into silicon reduces the indentation fracture toughness,which leads to larger lateral cracks thus liberating more stresses around the indentation.On the other hand,the heavy B-doping exerts remarkable pinning effect on dislocations,necessitating larger stress to drive the dislocation gliding.It is believed that the aforementioned two effects of heavy B-doping make the indentation dislocations to hardly glide.