Ruixin Fan

Oxygen precipitation in nitrogen-doped Czochralski silicon

Abstract Oxygen precipitation in nitrogen-doped Czochralski (NCZ) silicon has been investigated by one-step and two-step annealing. It was found that nitrogen in NCZ silicon enhanced oxygen precipitation at lower temperatures (

Formation of pnp bipolar structure by thermal donors in nitrogen-containing p-type Czochralski silicon wafers

The carrier concentration profile in boron-doped p-type nitrogen-containing Czochralski silicon wafer subjected to a one-step high-temperature (1150 °C) annealing followed by a prolonged 450 °C annealing has been investigated by spreading resistance profile. It is found that the carrier concentration profile is characteristic of a pnp bipolar structure, while, that in the control wafer of p-type conventional Czochralki silicon subjected to the identical thermal treatment is just characteristic of a p-n junction. Moreover, it is suggested that only one-step annealing at high temperatures is an efficient method for intrinsic gettering of a nitrogen-containing Czochralski silicon wafer due to the outdiffusion of oxygen and nitrogen in the near-surface region and the nitrogen-enhanced oxygen precipitation in the bulk region.

Oxygen-related centers in multicrystalline silicon

Abstract Oxygen and oxygen-related centers in cast multicrystalline silicon (mc-Si) have been investigated. The concentration profile and the map of oxygen in mc-Si revealed that oxygen with higher concentration occurred at the bottom area and at the edge area of mc-Si ingots. The oxygen concentration and its profile were partly dependent on the cooling progress. It was found that the thermal donors related to oxygen were generated in the area of higher oxygen concentration. The concentration of thermal donors can reach to 1×1014/cm3. Meanwhile, as-grown oxygen precipitates were observed at the bottom of mc-Si.

Enhanced oxygen out-diffusion in silicon crystal doped with germanium

Out-diffusion of oxygen during high temperature annealing has been investigated in Czochralski silicon with germanium doping through the spreading resistance profile and secondary ion mass spectrometry techniques. It has been suggested that oxygen out-diffusion in silicon could be enhanced by germanium doping when annealed at 1050 °C−1200 °C. Such enhancement effect increases with the annealing temperature applied to materials as well as increases with the germanium concentration introduced in silicon. It is proposed that the enhanced oxygen out-diffusion may be due to the fast diffusion channel for the interstitial oxygen atoms, which is induced by the substituted germanium atoms in silicon.

Infrared absorption of nitrogen–oxygen complex in silicon

Abstract The infrared optical absorption of nitrogen–oxygen complex in Czochralski (CZ) silicon measured by a Fourier Transmission Infrared Spectroscope (FTIR) has been studied. The CZ silicon samples grown in N–O complex were annealed in the temperature range of 450–1150°C for 10, 20 and 30 min. It was found that the variation of the optical lines measured in the middle infrared range and that in the far infrared range had the same tendency during annealing. The relations of the absorption lines in the middle and far infrared range were built. It is considered that the absorption lines in both infrared ranges come from same defects in silicon.

EFFECT OF IRON ON OXYGEN PRECIPITATION IN NITROGEN-DOPED CZOCHRALSKI SILICON

The effect of iron on oxygen precipitation in nitrogen-doped Czochralski (NCZ) silicon was investigated by Fourier transform infrared spectroscopy at room temperature or at liquid helium temperature. The experiments revealed that the oxygen precipitation could be enhanced by the contamination of iron in common Czochralski (CZ) silicon, or by the doping of nitrogen in NCZ silicon. In NCZ silicon, iron did not affect the precipitation of oxygen during annealing at high temperatures. After preannealing at 750 °C, the oxygen precipitation in NCZ silicon was suppressed due to the addition of iron. It is concluded that the generated iron nitride, which is related to an optical absorption line at 669 cm−1, emits self-interstitial silicon atoms to impede the nucleation of oxygen precipitates at low temperatures.

Bipolar Structure in Thermally Treated Czochralski Silicon Wafer

The carrier concentration profiles in p-type Czochralski (CZ) silicon (Si) wafers respectively subjected to one-step high temperature and three-step high-low-high annealing followed by a prolonged 450°C annealing have been investigated by spreading resistance profile (SRP). It is found that the carrier concentration profile in the p-type CZ Si wafer subjected to three-step annealing is characteristic of a PNP bipolar structure, while, that in the wafer subjected to one-step annealing is just characteristic of a PN junction. It is suggested that the formation of the PNP bipolar structure is due to the denuded zone formation and bulk oxygen precipitation.

Room-Temperature Near-Infrared Electroluminescence from Boron-Diffused Silicon Pn-Junction Diodes

Silicon pn junction diodes with different doping concentrations were prepared by boron diffusion into Czochralski (CZ) n-type silicon substrate. Their room-temperature near-infrared electroluminescence (EL) was measured. In the EL spectra of the heavily boron doped diode, a luminescence peak at ~1.6 m (0.78 eV ) was observed besides the band-to-band line (~1.1eV) under the condition of high current injection, while in that of the lightly boron doped diode only the band-to-band line was observed. The intensity of peak at 0.78 eV increases exponentially with current injection with no observable saturation at room temperature. Furthermore, no dislocations were found in the cross-sectional transmission electron microscopy image, and no dislocation-related luminescence was observed in the low-temperature photoluminescence spectra. We deduce the 0.78 eV emission originates from the irradiative recombination in the strain region of diodes caused by the diffusion of large number of boron atoms into silicon crystal lattice.