Development of the Non-Contact Characterization Techniques of Minority Carrier Lifetime and Surface Recombination Conditions of Semiconductor Wafers

从理论上分析了小α-函数载流子注入脉冲的光导衰减法(WLT)和大的α-载流子注入脉冲的光导调制方法(SRMI和R-SRMI)，发现SRMI和R-SRMI比WLT方法更灵敏。此外，R-SRMI方法对tau_b不敏感，因为R-SRMT信号被定义为从BRMI(小α注入)中减去SRMI(大α注入)的值。R-SRMI与SRMT呈负相关，与S关系密切。R-SRMI对tau_b不敏感，非常适用于i)不同条件的硅片，特别是表面活性区域，ii)在LST工艺中具有tau_b和/或电阻率分布的晶片。激光-微波表征系统(WLT、SRMI和R-SRMI测量)相继被应用于晶片表面污染的检测、氧化及其干法刻蚀、离子注入和退火工艺、杂质扩散结形成、合金化工艺等。受污染的晶片表面的SRMI和/或R-SRMI的变化是WLT的两到三倍。利用激光-微波的SRMI和R-SRMI映射测量系统是在各种器件制造过程中表征硅片的方便、实用和有用的方法。

From the theoretical analysis of the photoconductivity decay method (WLT) with small alpha delta-function carrier injection pulse and photoconductivity modulation method (SRMI and R-SRMI) with large alpha carrier injection pulse, it is found that SRMI and R-SRMI are more sensitive than the WLT method. Furthermore, R-SRMI method is insensitive to tau_b, because the R-SRMT signal is defined as the value subtracted SRMI (large alpha injection) from the BRMI (small alpha injection). The R-SRMI has inverse relation to SRMT and is related to S_<eff> closely. The R-SRMI is insensitive to tau_b and is very suitable for i) different condition Si wafers, especially surface active region, ii) a wafer which has distribution of tau_b and/or resistivity in LST processes. SRMI and R-SRMI measurements can reduce the calculation time compared to the photoconductivity decay curves analysis (WLT ; tau_b and S_<eff>).The laser-microwave characterization systems (WLT, SRMI and R-SRMI measurement) are successively applied to several wafer processes, detection of surface contamination of the starting wafer, oxidation and its dry etching, ion implantation and annealing processes, junction formation by impurity diffusion, alloying processes etc. The change of the SRMI and/or R-SRMI at contaminated wafer surface are two to three times larger than those of WLT values. The SRMI and R-SRMI mapping measurement systems with laser-microwave are convenient, practical and useful ways for characterizing the Si wafer in various device fabrication processes.