Investigation On Micro-defects In Large-diameter CZSi Crystal Used For Sub-micro IC

As IC devices grow ever smaller in size, the grown-in defects in large-diameter CZSi crystal exert stronger effects on their performance. Especially, when the size of defect is the 1/3 of the CD, they will destroy the gate oxide integrality (GOI) of MOS device. For this reason, it has become very important to control the void defects. In this paper, the micro-structure and annealing behavior of void defect in large-diameter CZSi crystal have been systematically investigated by using AFM and RTA. All these research results will be very useful in the"defect engineering"of ULSI circuits.The micro-structure of FPDs in large-diameter CZSi crystals and the evolution of FPDs during Secco etching procedure has been investigated. It was found that the outline of FPDs is parabola, and several steps exist in the inner part of FPDs. single and dual type were observed by atomic force microscope (AFM). Two heaves were firstly found on the left and right sides of the void. Moreover, a parabola model was put forward to explain the evolution of FPDs in CZ-Si wafers during Secco etching procedure firstly.The effects of rapid thermal annealing on voids in lightly-doped CZSi crystals have been investigated. It was verified that the effective annihilation temperature of the void defects is higher than 1100°C, and the density of FPDs decreased obviously with the annealing time increasing. The annihilation mechanism was discussed in this paper. The annealing results indicated that the O₂ and H2 atmospheres are the most effective annealing atmosphere, and the density of FPDs near the wafer surface about 20μm depth can be decreased obviously in all annealing atmosphere.The effect of dopant on the density of void defects has been investigated and the it is the first time to study the FPDs in heavily Sb-doped CZSi crystal. It is found that the density of FPDs in heaviy Sb-doped CZSi decreased more obviously than that in lightly B-doped CZSi crystal.The magic denuded zone (MDZ) in CZ silicon wafers was investigated after pre-RTA and two-step annealing in different atmosphere. After annealing in Ar or N₂/O₂(9%) mixed atmosphere, low FPDs density, high oxygen precipitation density and wide denuded zone occurred in wafer. In the case of N₂/O₂ mixed atmosphere, the experiments results indicated that the FPDs density and oxygen precipitation density can be controlled through adjusting the proportion of N₂ and O₂ in N₂/O₂ mixed atmosphere.