Diffusion Of Ion Implanted Boron Research Articles

Aluminum and boron diffusion in 4H-SiC

ABSTRACTA brief survey is given of some recent result of boron diffusion in low doped n-type (intrinsic) and p-type 4H-SiC. Aluminum diffusion and solubility limit in 4H-SiC are also discussed. Ion implantation of boron has been performed in epitaxial material to form a diffusion source but also epitaxial 4H-SiC structures, with heavily boron or aluminum doped layers prepared by vapor phase epitaxy have been studied. Heat treatments have been made at temperatures ranging from 1100 to 2050°C for 5 minutes up to 64 h. Secondary ion mass spectrometry has been utilized for analysis. For boron diffusion in acceptor doped 4H-SiC, 4×1019 Al atoms/cm3, an activation energy of 5.3 eV has been determined and a strong dependence on Al content for the diffusion coefficient is revealed. Transient enhanced diffusion of ion-implanted boron in intrinsic 4H-SiC samples is discussed. Solubility limits of ∼1×1020 Al/cm3 (1700°C) and <1×1020 B/cm3 (1900°C) have been deduced.

The Effect of Oxygen on The Electrical Activation and Diffusion of Ion-Implanted Boron

ABSTRACTTransient enhanced diffusion (TED) and electrical activation (EA) of ion-implanted boron during rapid thermal annealing has been investigated using three types of boron doped p-type Si (100) substrates: (a) Cz 20 Ωcm, (b) 3 μm thick 20 Ωcm epitaxial Si layer (epi-layer) grown on a 20 Ωcm Cz substrate, and (c) 3 μm thick 20 Ωcm epi-layer grown on a 5 mΩcin Fz substrate. The level of oxygen is known to decrease from material type (a) to (c). The samples were implanted with 20 keV, 5×1013cm−2boron and subjected to rapid thermal annealing (RTA) at various temperatures and times. The EA and TED were studied using spreading resistance profiling (SRP) and secondary ion mass spectrometry (SIMS), respectively. Although the amount of TED is almost identical for the three substrates, the EA is found to be significantly higher in the epi-layers compared to Cz substrates. It is speculated that the trapping of vacancies by oxygen in the ion-damaged region leads to an increase in the interstitial supersaturation during annealing, which then results in enhanced boron clustering and reduced electrical activation in the peak of the implanted profile.

Formation of p+n junctions by Si++B+ implantation and laser annealing

The effects of rapid thermal annealing (RTA) and laser annealing (LA) on the activation and diffusion of ion-implanted boron in Si substrate have been investigated. The implant and anneal regimes, forming good shallow junctions, were presented. The Si+-preamorphized samples boron implanted with a high dosage showed largely enhanced diffusion in RTA processing. The LA process serves as an excellent scheme to effectively activate the dopant and suppress the anomalous diffusion because of its very high heating rate. A high-quality p+/n junction with a leakage current density lower than 2 nA/cm2 and a forward ideality factor of about 1.01 was formed by laser processing.

Transient enhanced diffusion of ion-implanted boron in Si during rapid thermal annealing

Transient enhanced diffusion of ion-implanted boron in Si during rapid thermal annealing

Diffusion and segregation of ion-implanted boron in silicon in dry oxygen ambients

The diffusion of ion-implanted boron in silicon has been studied in the temperature range 1050-1250\ifmmode^\circ\else\textdegree\fi{}C. The diffusion drive-ins were carried out in oxygen and in various oxygen-nitrogen mixtures. Computer calculations were made to solve the diffusion equation under oxidizing conditions and to yield values of sheet resistance, junction depth, etc., for given values of the diffusion coefficient and the coefficient of segregation of boron between silicon and silicon dioxide. By iteration, values of diffusion coefficient and segregation coefficient were found which yielded values closest to the experimental sheet resistance and junction depth. It was found that boron diffusion in (100) silicon was significantly enhanced if the oxygen content in the annealing ambient was more than 10%. During drive-in in oxygen as much as 2/3 of the initially implanted boron could be lost to the oxide. The temperature dependence of the segregation coefficient and of the diffusion coefficient could be described by $m=9.82\mathrm{exp}(\ensuremath{-}0.29 \frac{\mathrm{eV}}{\mathrm{kT}})$, $D=0.15\mathrm{exp}(\ensuremath{-}3.19\frac{\mathrm{eV}}{\mathrm{kT}})$ ${\mathrm{cm}}^{2}$/sec. These data have been discussed in light of the available data from previously reported investigations. A possible mechanism of diffusion in an oxidizing medium has been examined.