Nitrogen And Germanium On The Mechanical Properties Of Czochralski Silicon

The development of ultra large-scale integrated (ULSI) circuit requires large diameter and defect free Czochralski (CZ) silicon wafers, which challenges the traditional crystal growth process and the 1C processing of silicon crystal. Especially nowadays, it is often the critical problems in ULSI devices fabrication that defects and dislocations generated in silicon caused by the increased crystal diameter. The enlarged wafer diameter that demanded silicon wafers suffered much higher thermal stress and gravitational stress as well as the seed bearing more weight. Therefore, it is desirable to investigate the mechanical property of silicon crystal and enhance its mechanical property.It is well known that impurities influence not only the formation of microdefects and the electronic property, but also the mechanical property. In recent years, the nitrogen (N) doped and germanium (Ge) doped CZ silicon crystals have been received intensive attention due to their novel properties. Hence, it is worth to investigate the effect of N and Ge on the mechanical property from both the practical and theoretic purposes.This paper was focused on the interaction between the impurities and dislocations by indentation. It was founded that the distance traveled of dislocations was related to the load, annealing temperature, and crystal orientation, but independent with the loading time. By this method, the effect of common impurity dopants in CZ silicon were investigated and summarized. Our experiments suggest that the N enhanced the mechanical property of silicon either in lightly or in heavily doped wafers. And it was interesting that an incubation of the dislocations slide in the HSb CZ silicon was founded. The incubation was attributed that dislocations needed more time to escape from the pinning of the large amount of impurity atoms or complexes.On the other hand, the effect of N and Ge on the mechanical property of silicon crystal had been done systemically. For Ge doped wafers, the dislocation pinningcould be observed only when Ge concentration was high than 1018cm"3. And the further experiment proved that the individual Ge atom hardly increased the fracture strength of silicon at room temperature. The enhancement of Ge on silicon was obtained mainly by the formation of complex or clusters with oxygen.In short, the better understanding on the mechanical property of silicon makes better use of the silicon material to ULSI industry. Also through the investigation on the N doped and Ge doped CZ silicon, it will greatly advance the development of our national intellectual property of the silicon material used for ULSI.