Annihilation of Stacking Faults in Silicon by Impurity Diffusion

Abstract

The stacking faults grown into silicon during thermal oxidation were shrunk by high temperature heat-treatment in a nitrogen atmosphere. The activation energy for fault shrinkage was 5.2 eV, and nearly equal to that of silicon self-diffusion, 5.13 eV. The shrinkage phenomenon is due to the removal of silicon atoms, which form the stacking faults of extrinsic type, by diffusion via vacancies. Therefore the shrinkage rate depends on the vacancy concentration" in silicon. The high concentration diffusion of boron, phosphorus, and arsenic in silicon generates the excess vacancies induced by donor doping, or by the stress due to solute lattice contraction of the impurity. The shrinkage of stacking faults by these excess vacancies was investigated. The faults shrank rapidly and disappeared for a short time in comparison with simple heat-treatment. The annihilation of stacking faults in silicon was also influenced by the coulomb interaction or the complex formation between the negatively charged vacancy and impurity.Thermal oxidation is one of the important processes in the manufacture of silicon planar transistors and other devices. Crystallographic defects such as stacking faults are often introduced in silicon in this oxidation process (1-5). When stacking faults lie across a p-n junction, excess reverse leakage currents in the junction are increased (6). Therefore, it is necessary to suppress stacking fault generation. If a crystal free from mechanical damage and grown-in defects, which act as the nucleation, is used, stacking faults are not generated. However, it is difficult to obtain such a crystal. Accordingly, the suppression of stacking fault generation and shrinkage of the faults by HC1 oxidation (7), or the preoxidation gettering of silicon wafers by misfit dislocations due to phosphorus diffusion (8), etc. have been carried out. Stacking faults also can be shrunk by high temperature heat-treatment (9).In this study, the shrinkage of stacking faults was investigated first. It was found that the shrinkage related intimately to the vacancy concentration in silicon. The vacancy concentration depends not only on treatment temperature, but also on impurity doping. And so the relation between the annihilation of stacking faults and the excess vacancies which were ~nduced during impurity diffusion into silicon was studied, and the mechanism of the annihilation is discussed. ExperimentalThe specimen wafers used in these experiments were 1-5 ~-cm (100) oriented dislocation-free silicon crystals grown by the Czochralski method. They were doped with phosphorus for n-type and boron for ptype. The surface was mechanically polished and the thickness was about 250 ~m. After appropriate treatments, they were etchd in a HF:HNO3 = 1:5 solution for 2 min to remove the surface mechanical damage. The oxidation of silicon was carried out at 1200~ in dry oxygen for 210 min. This thermal oxidation grew a stacking fault in the silicon crystal about 40 ~m long, provided that the fault size was defined as the fault length on the silic...

Correlation between the diffusion of borons atoms and the growth kinetics of oxidation-induced stacking faults

“…It should be remarked however that the results of Hashimoto et al [31] are obtained with a much higher boron concentration at the surface (4.3 x 1019-2.7 x 102° cm-3) than in our experiments. In the wafer with a boron concentration of 1 x 102° cm-3 they already observe slip dislocations.…”

“…Hashimoto et al [31] studied the influence of a boron diffusion on the growth kinetics of OSF's during a nitrogen anneal at 1100 °C. They observe no stacking faults within the diffused layer.…”

Modeling high-concentration phosphorus diffusion in crystalline silicon

“…Thermal phosphorus diffusion leads to substantial changes in the fault subsystem of the crystals. Indeed, it has been shown in [8] that the processes of thermal diffusion of phosphorus, boron, or arsenic are responsible for the accelerated reduction in interstitial stacking faults in the region of occurrence of the impurity atoms. At the same time, it has been shown experimentally in [6,9,10] that in high-concentration phosphorus diffusion, we have the supersaturation of the silicon volume with self-interstitials and the decrease in the concentration of vacancies, which produces a growth in the interstitial stacking faults beyond the region of high concentration of the impurity.…”

Annihilation Behavior of Planar Defects on Phosphorus-Doped Silicon at Low Temperatures

“…When P atoms were diffused into Si having SFs, and the P concentration exceeded the intrinsic carrier concentration, the SFs in the diffused layers were annihilated for a short time due to vacancy generation and Si self diffusion. 19 In other words, the annihilation was enhanced by the donorinduced vacancies. P-doped Si for interconnect has excessive P dopants due to low resistance.…”