P. C. Zalm

Mechanisms of implant damage annealing and transient enhanced diffusion in Si

Interactions between self‐interstitials (I) and {113} interstitial defects during annealing of Si implant damage have been studied. At low damage levels diffusion is ultrafast, driven by I released direct from the ion collision cascade. At higher damage levels, free I are quenched by nucleation of {113} defects. We show that the transient enhanced diffusion seen in most previous studies arises from the subsequent dissolution of the {113} defects.

Studies on the mechanism of chemical sputtering of silicon by simultaneous exposure to Cl2 and low‐energy Ar+ ions

The sputtering yield of Si when bombarded with a flux φAr+ of low‐energy Ar+ ions may be enhanced a few times when the Si surface is exposed simultaneously to Cl2 fluxes φCl2 about one order of magnitude larger than φAr+. The mechanism of this synergistic etching has been studied, using mass spectroscopy and time‐of‐flight techniques, for a φAr+ of about 5×1014 Ar+ cm−2 s−1 at Ar+ ion energies (Ep) from 0.25 to 5 keV, Cl2 fluxes between 1015 and 5×1016 Cl2 cm−2 s−1 and T in the range 300–625 K. As has been shown previously [J. Vac. Sci. Technol. A 2, 487 (1984)] the main products of the synergistic reaction are atomic Si and Cl and molecular SiCl and SiCl2; the kinetic energy distributions of the molecular products consist of two parts, a Maxwell–Boltzmann and a collision cascade‐like distribution. The Maxwell–Boltzmann part decreases relative to the collision cascade‐like part when T and/or Ep are increased and/or φCl2 is decreased. At the same time the collision cascade‐like part shifts to higher kineti...

On the energy and angular distribution of sputtered polyatomic molecules

Abstract A model is presented for the kinetic energy and angular distribution of sputtered molecules. After developing the model explicitly for diatomic molecules, a generalization to polyatomic molecules is given. The formalism is related to an earlier model for sputtered clusters by Konnen, Tip and De Vries, Radiat. Eff. 26 (1975) 23. It is assumed that the individual atoms of a molecule are given an initial momentum according to linear collision cascade properties. If the molecule does not dissociate, it is treated as an entity and carried as such through a planar surface potential barrier. This approach makes the present model more applicable to sputtering of molecules (for which the intramolecular bond energies are generally much larger than the intermolecular energies) than the cluster model of Konnen, Tip and De Vries. The model shows a continuous transition from a fragmentation dominated behaviour at high kinetic energies to an atomic collision cascade-like behaviour at low kinetic energies of the sputtered molecules. Alternative theoretical approaches are discussed. The model is compared with experimental data. In the appendix a correction to the model of Konnen, Tip and De Vries is given.

Si ultrashallow p+n junctions using low‐energy boron implantation

Ultrashallow boron‐doped junctions in silicon have been investigated using secondary‐ion mass spectroscopy and four‐point probe technique. The junctions were obtained by implanting B+ ions into n‐type Si(100) at 200 eV to doses of 1.5×1014 and 6×1014 cm−2 and at substrate temperatures in the range 30–900 °C during B implantation. Both post‐implantation in situ annealing by electron bombardment heating and rapid thermal annealing in a separate system were employed. The results show that sub 20 nm p+n junctions are obtained without the need for further processes such as preamorphization and high‐temperature annealing.

On some factors limiting depth resolution during SIMS profiling

Abstract The claim that the systematics observed in high-energy ion-beam-mixing experiments applies equally well to broadening observed in low-energy sputter depth profiling studies is addressed. Taking the expression for energetic mixing derived by the Caltech group at face value, it is shown that under fairly general assumptions this can be cast into a more tractable analytical formula. Essentially the final result reads that the broadening at low impact energy E is proportional to E 1 2 cos ϑ for not too glancing angles of incidence (ϑ

An effective barrier against the interdiffusion of iron and zinc dopants in InP

The diffusion of iron and zinc in InP is studied with secondary‐ion mass spectrometry (SIMS). Intentionally doped metalorganic‐vapor‐phase‐epitaxy‐ (MOVPE‐) grown layers as well as ion‐implanted samples were investigated. In addition, resistivity measurements were performed on MOVPE‐grown, iron‐doped InP layers. The diffusion behavior of iron is strongly influenced by the presence of zinc and vice versa. In adjacent regions of iron and zinc‐doped layers of InP there is a dramatic interdiffusion of both dopants. The interdiffusion process can be described with a kick‐out mechanism in which iron interstitials kick out substitutional zinc. The diffusion of the iron interstitials is an extremely fast transport process in InP, but the concentration of iron interstitials remains below 5×1014 at cm−3. Due to this fast transport, the interdiffusion process proceeds even through barrier layers of (undoped) InP, while in the barrier layer itself the iron concentration remains below the SIMS detection limit (<5×1014...

Overlayer corrections in XPS

It appears that the same scaling law applies to the attenuation of bulk XPS signals by thin uniform overlayers on rough surfaces, on powdered samples or when using an electron spectrometer with a magnetic immersion lens (i.e. one that integrates the intensity over all ejection angles). A simple but accurate analytical approximation of the attenuation function for these cases will be provided. The existence of a ‘magic’ detection angle of ∽40–45°, where the possible effects of roughness, etc. can be ignored, follows logically from this analysis. First, however, it is argued that while thickness estimates of overlayers are generally rather unreliable due to a lack of knowledge of the necessary material parameters, the corrections applied to the bulk concentrations are usually fairly precise.

Proximity gettering of transition metals in silicon by ion implantation

We compare the gettering efficiency of C, O and He implantation into Cz-grown silicon. After the getter implantation, with a projected range of 1.2 μm, we introduce a controlled amount of either Fe or Cu through low-energy implantation. Subsequently, we study the distribution of the impurities for various annealing conditions by means of secondary ion mass spectroscopy. In contrast to the C and O implantations which already show gettering behaviour at relatively low doses, the He implantation requires a dose in excess of 6 × 1015 ions/cm2 before observable gettering occurs. When sufficiently high doses of He are implanted its gettering efficiency significantly exceeds that of comparable C and O implantations, i.e. implantations with the same projected ranges and doses, subjected to the sa me annealing treatment. The shape of the getter profile in the sample implanted with He is strongly influenced by the annealing treatment.

Characterization of epitaxial layers by the depth dependence of boron diffusivity

Differences in boron diffusivity have been used to characterize epitaxially grown silicon layers. After oxidation‐enhanced diffusion of boron spikes, a decrease in boron diffusivity with increasing depth is observed in epitaxial silicon layers grown by molecular beam epitaxy and fast gas switching vapor deposition, in contrast to layers grown by low‐temperature chemical vapor deposition. The reduced boron diffusivity is thought to be caused by an oversaturation of vacancy defects, acting as interstitial traps, suppressing the diffusion of boron.

Molecular contamination mitigation in EUVL by environmental control

Abstract EUVL tools operate under vacuum conditions to avoid absorption losses. Under these conditions, the MoSi multilayer mirrors are contaminated, resulting in reduced reflection and thus throughput. We report on experiments on MoSi mirrors exposed to EUV radiation from a synchrotron. To mimic the effects of EUV radiation we also exposed samples using an electron gun. The oxidation rate was found to be ∼0.016 nm/h per mW/mm 2 of EUV radiation under conditions expected for a high throughput EUVL system. This oxidation can to a large extent be suppressed by using smart gas blend strategies during exposure, e.g. using ethanol. A carbon growth rate of 0.25 nm/h was found for a hydrocarbon pressure of 10 −9 mbar Fomblin. We demonstrate that carbonisation can be suppressed by admitting oxygen during electron gun exposure.