双次曝光积分效应实现杂质浓度分布均匀化

Integration effects of twice irradiations on homogenizing distribution of one-dimentional impurity concentration

激光诱导扩散中,当入射激光光强为高斯分布甚至均匀分布时,微小扩散区的温度分布不均匀。由于扩散系数是温度的函数,必将导致扩散后杂质浓度分布的均匀性较差,无法制作出高性能的p-n结。提出采用多次激光诱导扩散的积分效应来实现杂质浓度分布的均匀化整形。对于InP衬底的CO2激光诱导Zn扩散,利用温度闭环测控系统测得的基片表面热斑温度场分布,分析计算了两次激光诱导扩散重叠区域的浓度分布积分效应。在此基础上模拟计算出,用双次曝光积分效应做杂质浓度分布的均匀化整形时,基片上两次激光照射位置的最佳间隔为20μm。这为改进激光诱导扩散工艺,用多次曝光实现面均匀的杂质浓度分布奠定了理论基础。

The temperature distribution in the small diffusion region induced by laser is nonuniform, and the distribution of impurity concentration is nonuniform too. It was proposed to homogenize the distribution of impurity concentration through integration effects of multi laser induced diffusions. In laser induced selective Zn diffusion in lnP, a computer controlled system was used to measure and control the temperature of the small exposed region. The distribution of impurity concentration in the overlapped region of twice irradiations was calculated according to the temperature distribution in the heated region. When the distance between the two adjacent laser irradiation position was 20 tim, the homogenization of one dimension by digital simulation was perfeet. This work is fundamental for improving the techniques of multi laser induced diffusions to achieve two-dimensional impurity concentration uniformity theoretically.