The nitrogen effect on enhancement of oxygen precipitation in Czochralski-grown silicon wafers has been investigated by means of a preferential chemical etching technique and secondary ion mass spectroscopy. The precipitate enhancement is evident in an oxygen out-diffused region in which oxygen precipitation does not normally occur. Incorporation of the nitrogen atoms in substitutional sites to generate very stable microdefects in Czochralski-grown silicon crystals can explain the nitrogen effect on oxygen precipitation.

The outdiffusion behavior of oxygen and carbon in heat-treated Czochralski (CZ) silicon has been investigated by secondary ion mass spectroscopy. The results show that oxygen diffusion is greatly retarded by oxygen precipitation and strongly support a vacancy-dominant diffusion mechanism for oxygen in silicon. In carbon-doped CZ silicon, the diffusion of both oxygen and carbon is greatly enhanced at 750 °C, but is significantly retarded at 1000 °C. In conjunction with the infrared absorption data, the enhanced diffusion has been attributed to the formation of fast-diffusing O-C complexes, while the retarded diffusion of carbon has been tentatively attributed to the formation of slow-diffusing complexes, such as Si-O-C.

A secondary-ion mass spectrometry analysis of the coimplantation of nitrogen, carbon, and oxygen into float-zone silicon followed by rapid thermal annealing for 10 s at different temperatures is used to study the anomalous diffusion behavior of nitrogen in silicon. The results may be only partially explained by a model of paired nitrogen atom diffusion. The complexity of the diffusion of nitrogen in ion-implanted samples, with and without coimplants, and the expectation that the nitrogen after annealing may be in many different forms, suggest that studies which use nitrogen implantation for basic understanding of nitrogen-related defects may be misleading.

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