Haiyun Wang

The Marangoni convection and the oxygen concentration in Czochralski-grown silicon

Abstract The Marangoni convection on the silicon melt surface in Czochralski method was investigated. The results showed that Marangoni convection is related strongly to oxygen in silicon. Introducing a magnetic field by NdFeB permanent magnet into the melt, when B → → B → 0 ( B → 0 is the critical value), all the macro-convections were restrained in the melt and the Marangoni convection on the free surface emerges and becomes dominant. The oxygen concentration in silicon can be controlled freely by the Marangoni convection.

Investigation of oxygen precipitation and intrinsic gettering in heavily Sb-doped silicon

The behavior of oxygen precipitation in heavily doped silicon was investigated. The experimental results showed that the behavior of oxygen precipitation in heavily doped silicon is not only related to initial oxygen concentration, but also is affected by dopant species. The growth of oxygen precipitation was not affected by dopant type. Dopant species only influenced the nucleation of oxygen precipitation, and the time of precipitate nucleus formation is shorter in P+ samples than in N+ samples. The morphology of oxygen precipitation is independent of dopant type and only depends on the heat-treatment cycles. Considering the hanging bond on the interface of Si-SiOx at precipitates embryo and amending the free energy item, an expression of nucleation critical radius associated with dopant species was derived, and the dependent relationship of oxygen precipitation behavior in heavily doped silicon and dopant species was explained by this model. Moreover, an effective intrinsic gettering cycle with suitable width of denuded zone in heavily Sb-doped silicon samples was obtained in order to reduce or eliminate the metallic impurities and unwanted defects in the surface of substrate and device active regions.

Growth of semiconductor crystals under the equivalent micro-gravity

In this paper, the theory analysis and experiments on the semiconductor silicon crystal growth under the equivalent micro-gravity, which induced by a permanent magnetic field, were investigated. The experimental results show that the crystal growth in the equivalent micro-gravity is similar to that in the space. The homogeneity of doping and the oxygen concentration in CZSi by using the permanent magnetic field, can be improved, because of restriction of the convection compared with the crystal growth in the conventional CZ method. Diffusion kinetics are dominated during movement of mass in melt under the equivalent micro-gravity, different from that in the conventional CZ method.

Growth of Si-GaAs crystal under the equivalent micro-gravity

When growth of GaAs by method of MLEC and the magnetic intensity is the critical value B/sub 0/, all macro-convections in melt were completely controlled and the transport of mass only depends on diffusion. In this case, Growth of GaAs is under the equivalent micro-gravity. The effective segregation coefficients of impurities trend to one. The homogeneity and micro zone homogeneity of crystals were greatly improved.

Study on the deep energy levels in neutron-irradiated Czochralski-grown silicon

Czochralski-grown crystal silicon (CZSi) was doped by neutron transmutation. The deep energy levels after heat treatment of neutron transmutation doped Czochralski-grown silicon (NTDCZSi) were investigated by photo-induced transient spectroscopy (PITS) and deep level transient spectroscopy (DLTS). The interstitial oxygen concentration and substitutional carbon concentration were measured by Fourier transfer infrared spectrometry (FTIR). The experimental results showed that there are seven deep levels in the band gap of silicon caused by neutron irradiation. The defect centers corresponding to these deep levels were also deduced. The formation and decomposition of these defects during annealing were discussed.