Oxidation Induced Stacking Faults Of Heavily Doped Czochralski Silicon

Oxidation induced stacking faults (OSF) is one defect that may be generated in the oxidation of wafers. It can increase leakage current and decrease breakdown voltage, leading to the degradation or even failure of the device. So far the OSF of lightly doped Czochralski (CZ) silicon has been researched systematically, but the investigation of heavily doped CZ silicon is not comprehensive, especially the heavily n-doped CZ silicon. Compared to the heavily p-doped CZ silicon, OSF behavior of the heavily n-doped CZ silicon is more complicated. Therefore, it is very important to investigate the OSF of heavily n-doped CZ silicon for purpose of understanding OSF deeply. In this dissertation, the formation and growth of OSF for heavily n-doped CZ silicon have been studied, effects of the type of dopants, nucleation centers and annealing ambience on OSF have been discussed. The primary results are described as follows:1. The behavior of OSF for heavily doped CZ silicon wafers of different doping types and doping concentrations has been addressed. It is found that OSF can be generated in heavily n-doped CZ silicon wafers with modest resistivity; but when the resistivity decreases to certain value (as less than 5mΩ·cm), the formation of OSF can be supressed in the heavily n-doped CZ silicon wafers, even if introducing high-density nucleation centers.2. The OSF for heavily antimony (Sb)-doped and heavily phosphorus (P)-doped Cz silicon wafers with nucleation centers of various types and densities has been studied. It is shown that densities of OSF are affected by nucleation centers significantly, namely, nucleation centers of high density lead to high-density OSF. However, OSF lengths are almost identical regardless of the type and density of OSF nucleation centers.3. Through the comparative investigation on the growth and shrinkage of OSF in heavily Sb-doped and P-doped Cz silicon wafers, the effects of dopants on the dynamics of OSF in heavily doped n-type Cz silicon have been experimentally revealed. It is found that the OSF length of heavily Sb-doped Cz silicon wafer is larger than that of heavily P-doped Cz silicon wafer under the same oxidation condition. The first-principles calculations based on density functional theory (DFT) indicate that Sb atoms are the more efficient vacancy-trapping centers thus retarding the recombination of vacancies and self-interstitials as compared with P atoms. Consequently, the silicon self-interstitials remained after the recombination with the vacancies are much more in heavily Sb-doped Cz silicon wafer than in heavily P-doped counterpart when receiving the same oxidation. In turn, the OSF in heavily Sb-doped silicon wafer is relatively longer.4. The shrinkage of OSF is irrelevant to doping types. However, OSF shrinkage can be suppressed in nitrogen ambience. The reason of that is surface reconstruction is restrained by silicon nitride which is formed in the annealing process at high temperature, accordingly slowing down the emission of self-interstitials. The existence of oxide film can accelerate OSF shrinkage in inert atmosphere annealing, due to the back-diffussion of self-interstitials from Si surface to oxide; on the contrary, OSF shrinkage is suppressed in the nitrogen atmosphere annealing because of the obstruction of back-diffusion by nitrogen.