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制作了离子注入MOS晶体管,测量了诸如阈值电压、有效迁移率等电学性质。发现在注入硼离子(~(11)B~+)的p型沟道的情况下,阈值电压V_T随注入剂量的变化呈线性关系。其变量△V_T完全由进入硅中的净剂量决定。另一方面,在注入硼离子的n型沟道的情况下,阈值电压变量△V_T随剂量呈亚线性变化,并且表现出对剂量分布的强烈依赖关系。剂量分布随注入能量和退火时间的改变而变化。根据最大表面耗尽层X_(dmax)随注入剂量的增加而迅速地减小这一事实,能够解释这些结果。把非均匀注入分布造成的阈值电压变化的计算值与观测结果进行了比较,两者相符甚好。注入硼离子的p型和n型沟道MOS晶体管的有效迁移率μ_(eff)也表现出对剂量的不同依赖关系。在低剂量范围内,注入硼离子的p型沟道MOSFET的有效迁移率几乎保持不变,但对于n型沟道,有效迁移率却随剂量的增加而单调下降。本文还给出了考虑到表面散射和杂质散射作用的定性解释和近似计算。
Ion-implanted MOS transistors were fabricated and electrical properties such as threshold voltage, effective mobility were measured. It is found that the threshold voltage V_T has a linear relationship with the change of implantation dose in the case of p-type channel implanted with boron ions (~ (11) B ~ +). Its variable ΔV_T is completely determined by the net dose into the silicon. On the other hand, in the case of an n-type channel implanted with boron ions, the threshold voltage variable ΔV_T varies sub-linearly with dose, and shows a strong dependence on the dose distribution. The dose distribution varies with the implantation energy and annealing time. These results can be explained by the fact that the maximum surface depletion layer X_ (dmax) decreases rapidly with increasing implantation dose. Comparing the calculated value of the threshold voltage change caused by the non-uniform injection distribution with the observed results, the two are in good agreement. The effective mobilities μ eff of p-type and n-type channel MOS transistors implanted with boron ions also exhibit different dependence on dose. In the low dose range, the effective mobility of p-channel MOSFETs implanted with boron ions remains almost unchanged, but for n-type channels, the effective mobility decreases monotonically with increasing dose. This paper also gives qualitative explanation and approximate calculation considering the effects of surface scattering and impurity scattering.