Tin Doping of Silicon for Controlling Oxygen Precipitation and Radiation Hardness

Abstract

This paper reviews the impact of doping silicon with substitutional tin impurities on the formation of intrinsic and extrinsic lattice defects. The two major topics covered are ͑i͒ the effect on the diffusivity and aggregation/precipitation of interstitial oxygen in Czochralski ͑CZ͒ silicon and ͑ii͒ the formation of stable radiation defects in irradiated Sn-doped material. As demonstrated, the compressive stress associated with incorporating a large Sn atom on a lattice site is the basic feature governing the interactions with point defects. Consequently, Sn acts as a selective vacancy trap, while, in contrast, not affecting interstitial reactions. This leads to a reduced formation of oxygen thermal donors in n-type Si and lowers the concentration of vacancy-oxygen and divacancy centers in irradiated material. Enhanced oxygen precipitation has been noted around 750°C in p-type CZ silicon. Furthermore, specific Sn-related radiation defects are introduced, which question the use of doping with tin as a technique for substrate hardening.

Effect of tin doping on oxygen- and carbon-related defects in Czochralski silicon

“…The present results verify previous reports that Sn doping in Si is an important tool in studying radiation defects and their properties. 50 …”

“…This is in agreement with previous reports. 50 The final VO concentration of the VO defect in the Sn H sample is smaller than that in the Sn L sample. Two possible reasons could account for this observation.…”

“…Notably, photoluminescence (PL) studies have shown a reduction of the carbon-related defects C i O i and C i C s in 61-MeV proton-irradiated Fz-Si. 50,55 It is well known that Sn atoms interact with C i atoms to form SnC i complexes, and certain IR bands at 873.5, 1025, and 6875 cm À1 have been correlated with this center. 7 We note that the defect anneals out just above room temperature.…”

Vacancy-oxygen defects in silicon: the impact of isovalent doping

“…In this sense, the formation of thermal donors, oxygen aggregation and precipitation processes in Si are substantially affected [18,[109][110][111][112][113][114] by the presence of isovalent dopants.…”

Tin doping effect on crystallization of amorphous silicon obtained by vapor deposition in vacuum

“…Since Sn does not create energy levels in Si band gap (E g ), tin doping does not affect electrical, optical and recombination properties of Si crystals. At the same time, Sn atoms available in Si significantly slow down the degradation of these characteristics caused by heating [4][5][6] and radiation [6][7][8]. The first reports about crystallization of Si a  films doped by Sn from the gaseous phase in the process of film formation were made in [9].…”