Effect of Oxygen on the Diffusion of Nitrogen Implanted in Silicon

Abstract

Nitrogen implants were performed in Si wafers of variable purity, i.e., epitaxial layers, float zone, and Czochralski silicon ͑CZ-Si͒. The diffusion behavior of nitrogen reported by Hockett in Appl. Phys. Lett., 54, 1793 ͑1989͒, where nitrogen diffuses for several micrometers at temperatures as low as 750°C and the profiles assume a ''double-peak'' structure, is peculiar of CZ-Si. In contrast, in pure epitaxial-Si, nitrogen is immobile at low temperature but, at a higher temperature ͑850°C͒, the broadening of the nitrogen profile never assumes the shape observed in CZ-Si. Our results suggest that oxygen determines the shape of the nitrogen diffusion profiles.Nitrogen is currently attracting a broad interest in the semiconductor industry due to the possibility it offers to improve thin oxide reliability, prevent dopant penetration, silicide stability, and to control grown-in defects during the Si ingot growth. 1-3 A full implementation of such an atomic impurity into wafer processing still requires a deeper knowledge of the interaction mechanism of nitrogen with dopants, with other impurities present in the silicon substrate ͑e.g., oxygen and carbon͒ and, more important, of its diffusion mechanism. In this respect several theoretical studies have been performed to explain the preferred locations of the nitrogen atoms in the silicon lattice and some possible diffusion paths. 4-6 Almost all the experiments are devoted to the investigation of thin-oxide properties and fabrication in the presence of nitrogen, but much less work has been done on the experimental determination of nitrogen diffusion behavior. 7-10 Moreover, under quasi-identical experimental conditions, some striking discrepancies can be found, for example, between the mobility that allows nitrogen to diffuse out of the sample through the surface, as recently reported by Adam et al., 10 and the partial immobility close to the surface, associated with long-range diffusion ͑for several micrometers͒ into the bulk, reported by Hockett. 9 In this paper we explore nitrogen diffusion by intentionally varying the impurity content of the silicon substrate in which nitrogen is implanted at medium energy. Our approach, not used so far in other experiments reported in the literature, allows one to learn more about the diffusion beahvior of nitrogen, through the establishment of the conditions under which nitrogen may diffuse easily at low temperatures for several micrometers or when the tendency for nitrogen to form complexes with impurities or itself prevails.In this work ͑100͒-oriented n-type crystalline Si wafers were used. In particular, epitaxially grown Si layers ͑Epi͒, Float zone ͑FZ͒, and Czochralski ͑CZ͒ grown wafers with resistivities of 5-15 ⍀ cm have been used. This allowed us to use samples with widely different concentrations of intrinsic contaminants, from the most pure Epi to the CZ material rich of C and O ͑i.e., ͓C͔ and ͓O͔ varied in the range ϳ10 15 to 10 18 /cm 3 ). These samples were implanted with N ions at an energy of 240 keV and fluences o...

Kinetics of Bulk Lifetime Degradation in Float‐Zone Silicon: Fast Activation and Annihilation of Grown‐In Defects and the Role of Hydrogen versus Light

“…In ref. [34], it was shown that the effusion of N sets in rather spontaneously between 800 and 900 °C, in accordance with the recovery of τ bulk (cf. Figure 3 and 4).…”

Ab InitioIdentification of the Nitrogen Diffusion Mechanism in Silicon

“…Profiles after ion implantation [18,19] are considerably more complex, and the possibility of a catalytic effect of oxygen on nitrogen diffusion was reported recently [20]. In the analysis of Adam et al…”

“…Profiles after ion implantation [18,19] are considerably more complex, and the possibility of a catalytic effect of oxygen on nitrogen diffusion was reported recently [20]. In the analysis of Adam et al [21], nitrogen dimers were not taken into consideration nor apparently needed to obtain an excellent description of the experimental profiles.…”

Ab initio assisted process modeling for Si-based nanoelectronic devices

“…Profiles after ion implantation [28,29] are considerably more complex and the possibility of a catalytic effect of oxygen on nitrogen diffusion has been reported recently [30]. In the analysis of Adam et al [31] nitrogen dimers were not taken into consideration nor apparently needed to obtain an excellent description of the experimental profiles.…”