Rossen A. Yankov

Strong blue and violet photoluminescence and electroluminescence from germanium-implanted and silicon-implanted silicon-dioxide layers

The photoluminescence (PL) and electroluminescence (EL) properties of Ge-implanted SiO2 layers thermally grown on a Si substrate were investigated and compared to those of Si-implanted SiO2 films. The PL spectra from Ge-implanted SiO2 were recorded as a function of annealing temperature. It was found that the blue-violet PL from Ge-rich oxide layers reaches a maximum after annealing at 500 °C for 30 min, and is substantially more intense than the PL emission from Si-implanted oxides. The neutral oxygen vacancy is believed to be responsible for the observed luminescence. The EL spectrum from the Ge-implanted oxide after annealing at 1000 °C correlates very well with the PL one, and shows a linear dependence on the injected current. The EL emission was strong enough to be readily seen with the naked eye and the EL efficiency was assessed to be about 5×10−4.

Advanced Thermal Processing of Ultrashallow Implanted Junctions Using Flash Lamp Annealing

The use of flash lamp annealing for ultrashallow junction formation in silicon has been described. Low energy boron and arsenic implants have been heat-treated in this way using peak temperatures in the range of 1100 to 1300°C and effective anneal times of 20 and 3 ms. Secondary ion mass spectrometry and four-point probe measurements have been undertaken to determine the junction depth and the sheet resistance, respectively. Optimum processing conditions have been identified, under which one can obtain combinations of junction depth and sheet resistance values that meet the 90 nm technology node requirements and beyond.

OVERPRESSURIZED BUBBLES VERSUS VOIDS FORMED IN HELIUM IMPLANTED AND ANNEALED SILICON

The formation of helium induced cavities in silicon is studied as a function of implant energy (10 and 40 keV) and dose (1×1015, 1×1016, and 5×1016 cm−2). Specimens are analyzed after annealing (800 °C, 10 min) by transmission electron microscopy (TEM) and elastic recoil detection (ERD). Cavity nucleation and growth phenomena are discussed in terms of three different regimes depending on the implanted He content. For the low (1×1015 cm−2) and high (5×1016 cm−2) doses our results are consistent with the information in the literature. However, at the medium dose (1×1016 cm−2), contrary to the gas release calculations which predict the formation of empty cavities, ERD analysis shows that a measurable fraction of the implanted He is still present in the annealed samples. In this case TEM analyses reveal that the cavities are surrounded by a strong strain field contrast and dislocation loops are generated. The results obtained are discussed on the basis of an alternative nucleation and growth behavior that all...

Proximity gettering of transition metals in separation by implanted oxygen structures

The gettering behavior of Cu and Fe in ion beam synthesized silicon on insulator (SOI) material incorporating a buried oxide layer is investigated before and after the formation of deep gettering zones by either C or He implantation. Secondary ion mass spectroscopy (SIMS) analysis is employed to obtain information as to the C, O, Fe, and Cu depth distributions. It is shown that the proximity gettering approach using C and He renders the possibility of removing and stabilizing metal contaminants not only away from the near‐surface region, but also remote from the buried oxide/substrate interface to which they normally segregate in the absence of efficient implantation induced gettering sinks. C implants are found to have better gettering efficiency as they getter both Cu and Fe whereas He implants getter Cu only. In addition, the C implant dose needed to achieve one and the same gettering effect is an order of magnitude lower than the He dose.

Nucleation and growth of platelet bubble structures in He implanted silicon

He a ions were implanted into (1 0 0) Si at energies from 30 to 120 keV and fluences from 5 · 10 15 to 1 · 10 16 cm ˇ2 . After implantation, pieces of these samples were subjected to rapid thermal annealing for 600 s at temperatures ranging from 300∞C to 700∞C. The samples were analyzed by Transmission Electron Microscopy (TEM) and by Rutherford Backscattering and channeling spectrometry (RBS/C). The TEM observations were related to the RBS/C measurements and the results discussed in terms of a nucleation model to explain the formation of overpressurized bubbles in He implanted and annealed silicon. ” 1998 Published by Elsevier Science B.V.

Annealing effects in light-emitting Si nanostructures formed in SiO2 by ion implantation and transient preheating

A dose of 1.6 × 1017 cm−2 Si+ ions was implanted in 500-nm-thick SiO2 layers with subsequent transient annealing at different temperatures. After the highest temperatures light-emitting Si nanoclusters were found that were formed in SiO2. Then all the layers were subjected to isochronal (30 min) furnace anneals and their properties were controlled by room temperature photoluminescence (PL) and Raman spectroscopy. The PL intensity from Si nanocrystal-containing layers progressively decreased with an increase in the anneal temperature (Ta) up to 800–900°C, but rapidly arose again in the Ta range of 1000–1150°C. Raman scattering has shown that Si nanocrystals vanish at Ta ∼ 800°C and that the amorphous silicon signal reappears. When the initial transient annealing failed to form Si nanocrystals, the furnace heat treatment at Ta < 700°C gave rise in PL intensity followed by its drop at Ta ∼ 800–900°C and a strong increase at Ta ∼ 1000–1150°C. The disappearance of Si nanocrystals and PL is considered to result from low stability of the smallest crystallites quenched in SiO2 by transient processing. When Si nanocrystals were not induced by transient preheating, the increase in Ta supposedly led to percolation-like formation of Si inclusions, their transformation to amorphous Si phase nanoprecipitates and, finally, to Si nanocrystals. For all the samples the formation of nanocrystals at Ta = 1000–1150°C was provided by the increase in their stability due to diffusion-limited grain growth. The results obtained are considered to support the idea of quantum-confined origin of PL.

Enhancement of the intensity of the short-wavelength visible photoluminescence from silicon-implanted silicon-dioxide films caused by hydrostatic pressure during annealing

We have studied the influence of the hydrostatic pressure during annealing on the intensity of the visible photoluminescence (PL) from thermally grown SiO2 films irradiated with Si+ ions using double-energy implants at 100 and 200 keV and ion doses ranging from 1.2×1016 to 6.3×1016 cm−2. Postimplantation anneals have been carried out in an Ar ambient at temperatures Ta of 400 and 450 °C for 10 h at both atmospheric pressure and hydrostatic pressures of 0.1, 10, 12, and 15 kbar. It has been found that the intensity of the ultraviolet (∼360 nm), blue (∼460 nm), and red (∼600 nm) PL emission bands increases with raising hydrostatic pressure whereby the PL peaks retain their wavelength positions. The results obtained have been interpreted in terms of enhanced, pressure-mediated formation of ≡Si–Si≡ centers and small Si clusters within metastable regions of the ion-implanted SiO2.

Spatial distribution of defects in ion-implanted and annealed Si: The RP/2 effect

Abstract Gettering of metal impurities in ion-implanted Si occurs midway between the surface and the projected ion range, RP, after annealing at temperatures in the range of 700–1000°C and vanishes at higher temperatures. This phenomenon, called the RP/2 effect, seems to be a common feature of ion-implanted and annealed Si. The gettering ability of the damage at RP/2 is commensurate with or may exceed that of the damage at RP. The defects around RP/2 acting as gettering sites have not yet been identified by other analysis techniques. They are formed after ion implantation in the process of defect evolution during annealing and, probably, consist of small complexes of intrinsic defects (vacancies or/and self-interstitials).

DAMAGE IN SILICON CARBIDE INDUCED BY RUTHERFORD BACKSCATTERING ANALYSIS

Abstract Damage in silicon carbide generated by ion implantation or irradiation is usually analyzed by Rutherford backscattering spectroscopy in combination with channeling (RBS/C) of MeV He + ions, a technique which is considered to be largely non-destructive. In this paper we report on swelling of 6H–SiC induced by He + implantation at doses commensurate with, or lower than those commonly used for obtaining RBS/C spectra of desirable statistics. The swelling increases by about 40% if the He + ions are implanted in a non-channeling direction. The formation of high concentrations of deep-reaching (μm range) defects due to RBS/C is confirmed by slow positron implantation spectroscopy (SPIS) measurements. An optical damage depth-profile, with distinct optical properties corresponding to the regions of electronic and nuclear stopping, is obtained from a fit to polarized infrared reflection spectroscopy (PIRR) data and compared to TRIM calculation. Auger electron spectroscopy (AES) shows that the specific color of the implanted area is not due to the deposition of a thin surface film during He + implantation, and the swelling is not related to chemical reactions in the near-surface region. The formation of additional disorder from RBS/C may corrupt the respective data obtained subsequently by SPIS and PIRR. Therefore, RBS/C measurements should always be carried out last, i.e. following analytical techniques which are certainly non-destructive.

Blue and violet photoluminescence from high-dose Si+- and Ge+-implanted silicon dioxide layers

Abstract Strong blue (around 470 nm) and violet (around 395 nm) photoluminescence (PL) at room temperature (RT) was obtained from thermally-grown SiO 2 films on crystalline Si implanted with Si + and Ge + ions, respectively. Photoluminescence excitation (PLE) spectroscopy measurements indicate maximum PL at 248 nm (for Si + ) and 242 nm (for Ge + ). The blue PL intensity was investigated as a function of subsequent furnace and flash lamp annealing. The results obtained are interpreted in terms of the excess atoms introduced in the SiO 2 network.