掺杂剂对重掺n型直拉硅片的氧化诱生层错生长的影响
Effects of dopants on the growth of oxidation-induced stacking faults in heavily dop ed n-typ e Czo chralski silicon
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摘要: 对比研究了电阻率几乎相同的重掺锑和重掺磷直拉硅片的氧化诱生层错(OSF)的生长,以揭示掺杂剂对重掺n型直拉硅片的OSF生长的影响。研究表明:在相同的热氧化条件下,重掺锑直拉硅片的OSF的长度大于重掺磷硅片的。基于密度泛函理论的第一性原理计算结果表明:与磷原子相比,锑原子是更有效的空位俘获中心,从而抑制空位与自间隙硅原子的复合。因此,在经历相同的热氧化时,氧化产生的自间隙硅原子与空位复合后所剩余的数量在重掺锑硅片中的更多,从而导致OSF更长。Abstract: Through comparative investigation on the growth of oxidation-induced stacking faults (OSFs) in heavily antimony (Sb)-doped and phosphorus (P)-doped Czochralski (Cz) silicon wafers with almost the same resistivity, effects of dopants on the growth of OSF in heavily doped n-type Cz silicon are studied experimentally. Moreover, the influences of Sb and P atoms on the recombination of self-interstitials and vacancies are also explored on the basis of the first-principles calculations. It is shown experimentally that all the OSF lengths are almost identical regardless of the type and density of OSF nucleation centers, such as copper precipitates and mechanical scratches etc.. However, 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. Essentially, the OSFs are formed by the aggregation of silicon self-interstitials released at the Si/SiO2interface during the oxidation. Therefore, a longer OSF implies that a higher quantity of silicon self-interstitials remains after the recombination of vacancies and silicon self-interstitials in the heavily Sb-doped Cz silicon wafer. The first-principles calculations based on density functional theory (DFT) indicate that Sb atoms combine with vacancies more readily than P atoms. This is actually due to the fact that Sb has a much larger atomic size than P. In other words, as compared with P atoms, the Sb atoms are the more e?cient vacancy-trapping centers, thus retarding the recombination of vacancies and silicon self-interstitials. Consequently, the silicon self-interstitials remain after recombination with the vacancies that are much more in heavily Sb-doped Cz silicon wafer than in heavily P-doped counterpart when undergoing the same oxidation. In turn, the OSFs in heavily Sb-doped silicon wafers are relatively longer.
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