Investigation On Microstructure Of Fpds In Large-Diameter CZ-Si And Behavior Of Fpds During Rta Process

In this paper, the microstructure of flow pattern defects (FPDs), one kind of grown-in micro-defects, in large-diameter as-grown CZ-Si single crystals was investigated. The microstructure of FPDs was analyzed and the evolution of FPDs during Secco etching procedure was also studied. Furthermore, the lightly B-doped and heavily Sb-doped CZ-Si wafers were treated by rapid thermal annealing (RTA) technique in Ar, H2, N2, N2/O2 (3%) respectively at high tempretures. The behavior of FPDs during RTA process and the effective RTA process to decrease the density of FPDs were discussed in detail.The experimental results showed that the outline of FPDs is parabola, and several steps exist in the inner part of FPDs. There are two kinds of voids on the tip of FPDs observed by atomic force microscope (AFM), one of which is single and the other is dual type. Two heaves are 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.After RTA treatment at 1100 C or even high tempretures, the density of FPDs decreased obviously and decreased successively with the annealling time increasing. The microstruture of the void on the tip of FPDs changed during RTA process, and the annihilation mechanism was discussed in this paper. The RTA treatment in H2 atmosphere was the most effective annealling process to decrease the density of FPDs, and RTA in Ar atmosphere takes second place.The FPDs in large-diameter heavily Sb-doped silicon wafers was investigated firstly. The density of FPDs in heavily Sb-doped silicon wafers was 10 times or so higher than that in lightly B-doped silicon wafers. After RTA treatment, the density of FPDs decreased too. The difference between them was that the FPDs in Sb-doped wafers was more easily eliminated than that in lightly B doped wafers due to the effects of the high concentration of Sb, which strongly effected the behivior of oxygen in silicon. The mechanism needs to be investigated later.