Defect Engineering In Czochralski Silicon Used For Large-scale Integrated Circuits

The development of ultra large-scale integrated (ULSI) circuits requires large diameter and defect-free Czochralski (CZ) silicon wafers and therefore challenges the 'defect engineering' of silicon crystal, which includes three projects: firstly, the CZ silicon crystals cannot be grown by the traditional Dash necking when the diameter of crystal is above 300mm; secondly, with the decrease of oxygen content in the large diameter CZ silicon, it is difficult to form oxygen precipitation in the bulk and therefore reduce the ability of intrinsic gettering (IG); thirdly, the new void defects will reduce the gate oxide integrality (GOI) of MOS device. In this dissertation, it is systematically investigated that the effect of nitrogen and heavily-doped boron on the behavior of dislocation, oxygen precipitation and voids in CZ silicon, which develop the theory of defect engineering. Furthermore, it is the first time to control the microdefects in the CZ silicon by germanium doping. A series of innovated research results have been obtained as follows, which indicated that the novel properties of these doped silicon are quite promising to meet the increasingly stringent requirements arising from ULSI circuits.1) The effects of nitrogen, heavily-doped boron, and germanium on the dislocation generation during crystal growth of CZ silicon have been investigated. It was found that the thermal shock induced dislocations during the dipping process could be substantially suppressed using the nitrogen-doped or germanium-doped seeds, the same as the heavy boron-doped seeds. It is thus suggested that the seed crystals doped with nitrogen or germanium would be feasible for the dislocation-free growth of large diameter silicon crystals without using Dash-necking process, which resolve the problem that heavy boron-doped seed cannot be used for the crystal growth of n-type silicon. Nevertheless, the dislocations will occur in the silicon crystals grown with the annealed seed, in which dislocation loops have been introduced due to the annealing. This issue should be further fixed for the application of the above-mentioned seed crystals in the large diameter silicon crystal growth.2) The effects of nitrogen and heavily-doped boron on oxygen precipitation have been investigated. It was suggested that oxygen precipitation in NCZ silicon crystal growth was well distinguished into two characteristic temperature phases. It was found that, on one hand, nitrogen doping enhanced the formation of grown-in oxygen precipitates in larger sizes at high temperatures up to 1150 C via the complexes of N2V2O, thus leading to significant loss of vacancies prior to the generation of voidsduring NCZ silicon crystal growth; on the other hand, the nitrogen doping also enhanced the formation of grown-in oxygen precipitates in smaller sizes at low temperatures of 750 C and below via N2O complexes. Furthermore, it was found that oxygen precipitation in the mixed type (i.e coexistence of vacancy type and interstitial type defects) NCZ silicon crystal was in sharp contrast to that in the mixed type CZ silicon crystal, the reason for which is that, as mentioned above, the complexes of N2V2O and N2O respectively play critical roles in the enhancement of oxygen precipitation at high and low temperatures during the crystal growth respectively. Meanwhile, it is pointed out that the oxygen precipitation in HBCZ silicon can be enhanced below 1150 C, which was via the complexes of 8203 by the help of vacancies. These innovated results are benefic for us to further understand the oxygen precipitation in NCZ and HBCZ silicon.3) The effects of nitrogen and heavily-doped boron on voids in CZ silicon doped have been investigated. It was verified that these two impurities substantially suppressed the formation of voids in large sizes while significantly enhanced the formation of voids in small sizes. Such an effect was increasingly stronger with higher concentration of the doped impurities. Of importance was the voids in the CZ wafers contained these impurities could be...