2.0-MeV Er+ implanted in silicon: depth distribution, damage profile and annealing behaviour

Si crystals were implanted with 2.0- MeV Er⁺ at the doses of 5×10¹² ions/cm², 1×10¹⁴ ions/cm², 5×10¹⁴ions/cm², 1×10¹⁵ ions/cm² and 2.5×10¹⁵ ions/cm². Conventional furnace thermal annealing was carried out in the temperature range from 600 °C to 1150 °C. The depth distribution of Er, associated damage profiles and annealing behavioar were investigated using the Rutherford backscattering spectrometry and channelling (RBS/C) technique. A proper convolution program was used to extract the distribution of Er from the experimental RBS spectrum. The obtained distribution parameters, projected range R_p, projected range straggling ΔR_p and skewness SK were compared with those of TRIM96 calculation.The experimental R_p and SK values agree well with the simulated values, while the experimental ΔR_p is larger than TRIM 96 simulated value by a factor of 18%. The damage profile of silicon crystal induced by 2.0-MeV Er⁺ at a dose of 1×10¹⁴ ions/cm² was extracted using the multiple-scattering dechannelling model based on Feldman’s method, which is in a good agreement with the TRIM96 calculation. For the samples with dose of 5×10¹⁴ ions/cm² and more, an abnormal annealing behavioar was found and a qualitative explaination has been given. Received: 11 October 1999 / Accepted: 28 March 2000 / Published online: 5 July 2000     

Doping and radiation damage profiles of P+ ions implanted in silicon along the [110] axis

Several doses of 200 KeV phosphorus ions have been implanted under channeling conditions along the [110] direction in silicon.

Range distribution has been determined for the three implant doses 10¹³, 10¹⁴, 10¹⁵ P⁺/cm² both with the electrical measurements and the neutron activation techniques.

The radiation damage distribution has been determined both with 290 KeV proton back-scattering analysis and with transmission electron microscopy (TEM) observations.

Good agreement has been found between electrical and neutron activation profiles in the samples where 100% of the implanted dose had been electrically activated by means of annealing.

Carrier concentration profiles, from samples implanted with 10¹⁵ P⁺/cm², determined after two different annealing temperatures (500°C and 700°C) have bcen compared with the radiation damage distribution and a correlation between damage and phosphorus electrical activation process seems to be possible.

Maximum damage peak, as determined by back-scattering analysis, shifts from ～0.4 μ depth in the lower dose(5 × 10¹⁴ P⁺/cm²), to ～0.22 pm depth in the higher implanted dose (4 × 10¹⁵ P⁺/cm²). Damage distribution of phosphorus ions random implanted in the same experimental conditions shows 3 peak at ～0.2 μn depth.

In accordance with the back-scattering analysis, T.E.M. observations on 10¹⁵P⁺/cm² implanted samples show the presence of amorphous regions at depth between 0.25 and 0.5 μm from the surface. In the most damaged layer ～0.3μm in depth, a surface density of ～10¹²/cm² amorphous regions 25-50 A diameter was observed.     

implantation of Bi into GaP. II. channeling studies

The channeling technique has been used to investigate the properties of Bi-implanted Gap. Measurements of the crystal disorder for 100 keV room temperature implants indicate a damage vs dose curve corresponding to ～13000 displacements/ion in the linear region and saturation at ～1.5 × 10¹³ Bi ions/cm². Annealing of the radiation damage has been observed and indicates two annealing steps at ～450°C for light damage and ～750°C for implants in the 1 × 10¹⁴/cm² range. Difficulties associated with the thermal decomposition of the implanted area have been overcome with the use of SiO _x coatings. The experimental details associated with the use of the SiO _x layer and with the use of a C¹² beam to obtain better depth and mass resolution in the backscattering spectrum are discussed. The lattice location measurements of the Bi impurity show ～50 per cent of the Bi atoms to be along the 〈110〉 string after a 900°C anneal for a 7.5 × 10¹³/cm² implant. In addition, the spectra show ～25 per cent of the Bi atoms have diffused to the surface. Correlations of these lattice location results with measurements of the photoluminescent intensity of the GaP (Bi) isoelectronic trap show an agreement in trend with anneal temperature but indicate a factor of ～10 more substitutional ions in the channeling measurement as compared to the photoluminescence results.     

Damage anneal of antimony/phosphorus double implants in silicon

A method is presented for avoiding the dislocation generation in (100) silicon implanted with phosphorus doses up to 5×10¹⁵ ions/cm² at 50 keV. The residual defects after the damage anneal are considerably reduced if the phosphorus implant is combined with a low dose, e.g. 1×10¹⁴ ions/cm², antimony implant which produces a deeper surface layer of amorphous silicon. It is essential that the phosphorus ions are implanted shallower than the antimony ions, and come to rest within the amorphous layer. Subsequent thermal annealing proceeds by a solid phase epitaxial regrowth mechanism.     

Influence of Cr<Superscript>+</Superscript> ion implantation and pulsed ion-beam annealing on the formation and optical properties of Si/CrSi<Subscript>2</Subscript>/Si(111) heterostructures

The effect of pulsed ion-beam annealing on the surface morphology, structure, and composition of single-crystal Si(111) wafers implanted by chromium ions with a dose varying from 6 × 10¹⁵ to 6 × 10¹⁶ cm⁻² and on subsequent growth of silicon is investigated for the first time. It is found that pulsed ion-beam annealing causes chromium atom redistribution in the surface layer of the silicon and precipitation of the polycrystalline chromium disilicide (CrSi₂) phase. It is shown that the ultrahigh-vacuum cleaning of the silicon wafers at 850°C upon implantation and pulsed ion-beam annealing provides an atomically clean surface with a developed relief. The growth of silicon by molecular beam epitaxy generates oriented 3D silicon islands, which coalesce at a layer thickness of 100 nm and an implantation dose of 10¹⁶ cm⁻². At higher implantation doses, the silicon layer grows polycrystalline. As follows from Raman scattering data and optical reflectance spectroscopy data, semiconducting CrSi₂ precipitates arise inside the silicon substrate, which diffuse toward its surface during growth.     

Characterization of silicon doped with sodium upon high-voltage implantation

The depth distribution profiles of sodium atoms in silicon upon high-voltage implantation (ion energy, 300 keV; implantation dose, 5 × 10¹⁴ and 3 × 10¹⁵ cm ^?2) are investigated before and after annealing at temperatures in the range T _ann = 300–900°C (t _ann = 30 min). Ion implantation is performed with the use of a high-resistivity p-Si (ρ= 3–5 kΩ cm) grown by floating-zone melting. After implantation, the depth distribution profiles are characterized by an intense tail attributed to the incorporation of sodium atoms into channels upon their scattering from displaced silicon atoms. At an implantation dose of 3 × 10¹⁵ ions/cm², which is higher than the amorphization threshold of silicon, a segregation peak is observed on the left slope of the diffusion profile in the vicinity of the maximum after annealing at a temperature T _ann = 600°C. At an implantation dose of 5 × 10¹⁴ ions/cm², which is insufficient for silicon amorphization, no similar peak is observed. Annealing at a temperature T _ann = 700°C leads to a shift of the profile toward the surface of the sample. Annealing performed at temperatures T _ann ≥ 800°C results in a considerable loss of sodium atoms due to their diffusion toward the surface of the sample and subsequent evaporation. After annealing, only a small number of implanted atoms that are located far from the region of the most severe damages remain electrically active. It is demonstrated that, owing to the larger distance between the diffusion source and the surface of the sample, the superficial density of electrically active atoms in the diffusion layer upon high-voltage implantation of sodium ions is almost one order of magnitude higher than the corresponding density observed upon low-voltage implantation (50–70 keV). In this case, the volume concentration of donors near the surface of the sample increases by a factor of 5–10. The measured values of the effective diffusion parameters of sodium at annealing temperatures in the range T _ann = 525–900°C are as follows: D ₀ = 0.018 cm²/s and E _a = 1.29 eV/kT. These parameters are almost identical to those previously obtained in the case of low-voltage implantation.     

Properties of ion implanted silicon,sulfur, and carbon in gallium arsenide

Work is described in which chromium-doped semi-insulating gallium arsenide has been successfully doped n-type with ion implanted silicon and sulfur, and p-type with ion implanted carbon. A dilute chemical etch has been employed in conjunction with differential Hall effect measurements to obtain accurate profiles of carrier concentration and mobility vs. depth in conductive implanted layers. This method has so far been applied to silicon-and sulfur-implanted layers in both Cr-doped semi-insulating GaAs and high purity vapor grown GaAs. In the case of sulfur implants, a strong diffusion enhancement has been observed during the annealing, presumably due to fast-diffusing, implantation-produced damage. Peak doping levels so far obtained are about 8 × 10¹⁷ electrons/cm³ for silicon implants and 2 × 10¹⁷ electrons/cm³ for sulfur implants. Mobility recovery has been observed to be complete except in regions near the surface which are heavily damaged by the implantation.     

The influence of argon ion bombardment on the electrical and optical properties of clean silicon surfaces

The effect of low energy noble gas ion bombardment on the electrical and optical properties of Si(211) surfaces has been investigated by surface conductivity and field effect measurements, ellipsometry and AES. With this combination of techniques, information is obtained concerning the electrical properties, the chemical composition and the damage of the surface layer. Upon ion bombardment in the energy range of 500–2000 eV, ellipsometry shows the formation of a damaged surface layer with optical properties close to those of an evaporated amorphous silicon film. In order to measure the conductivity changes as sensitive as possible, nearly intrinsic silicon crystals were used. For the clean, 5200 Ω cm Si(211) surface, bombarded only with a mass-analyzed argon ion beam, a small increase in conductivity is found to occur after a small ion dose (saturation after 5 × 10¹⁴ ions cm^?2 while after 5 × 10¹³ ions cm^?2 already half of the increase has occurred). The effect was found to be independent of ion energy between 500 and 2000 eV. As the field effect signal did not change after this treatment, it is concluded that the surface state density in the neighbourhood of the Fermi level shows a slight decrease.     

Blistering of rhenium irradiated with 21keV helium ions

This paper describes blistering of rhenium following 21 keV He⁺-ion irradiation at temperatures between 300 K and 1200 K. Blistering starts at 300 K at a dose of 3×10¹⁷ ions/cm². The most probable blister diameter varies from 4400 ? at 300 K to 10100 ? at 1200 K. The blister depth τ _bl , the blister diameter φ _bl and the blister heighth _bi show a distribution. From the observations one could derive the following relationships:h _bl = 0.35φ _bl ; τ _bl =3.43φ _bl ^2/3 . The erosion yieldE _y due to blistering is function of doseE _y =0.51 atoms/ion at 3×10¹⁷ ions/cm²,E _y =0.56 atoms/ion at 6×10¹⁷ ions/cm² andE _y =0.14 atoms/ion at 3×10¹⁸ ions/cm². The sputtering yieldS (21 keV) is estimated to be ∼0.1 atom/ion. The corresponding surface regression is 44? at 3×10¹⁷ ions/cm² and 1323 ? at 9×10¹⁸ ions/cm². Surface regression has therefore little influence on the observations at low doses. Work performed at the Mathematicals Science Department of S.C.K./C.E.N. at Mol (Belgium)     

Synthesis of silicon dioxide layers by high dose ion implantation

Single crystal <100> silicon was implanted with molecular oxygen with energies ranging from 80 to 240 keV in a non-channeling direction. Rutherford backscattering (RBS) analysis was used to obtain the oxygen/silicon atomic ratio depth profiles and the thickness of the buried oxide layer, for doses ranging from 10¹⁶ to 1. 5 × 10¹⁸ O₂+/cm². This work links the early low energy work and the more recent higher energy work, and generally excellent agreement has been obtained. The minimum energy for formation of buried silicon dioxide has been identified as 160 keV per oxygen molecule and corresponding oxygen dose of 6 × 10¹⁷ O₂+/cm₂.     

Depth resolved structural study of heavy ion induced phase formation in Si/Fe/Si trilayer

Intermixing in Si/Fe/Si trilayer induced by 120 MeV Au ions has been studied. X-ray fluorescence provides information about the depth distribution of Fe atoms, while Mössbauer spectroscopy and XAFS provide information about the changes in the local structure. In the as-deposited film Fe layer is amorphous in nature with a significant Si content in it. Irradiation to a fluence of 1 ×10¹³ ions/cm² results in formation of non-magnetic intermixed layer with its hyperfine parameter close to those of Fe_0.5Si with CsCl structure. XAFS measurements under X-ray standing wave condition provide depth resolved structural information.     

X-ray study of lateral strains in ion-implanted silicon

Lateral strains induced by 80 keV argon ion implants into silicon have been studied using X-ray interferometry and X-ray diffraction topography. The stressed state is described by the expansion of a thin surface layer, and it is shown, how it will affect the dilatational moiré patterns observed in the interferograms. The integrated stress acting in the damaged layer has been studied as a function of the bombardment dose. A maximum is reached at a dose of about 2×10¹⁴ ions/cm². The maximum local stress is of the order of 1×10⁹ dyn/cm².     

铒离子注入碳化硅的射程和退火行为研究

用300—500 keV能量的铒(Er)离子注入碳化硅(6H-SiC)晶体中,利用卢瑟福背散射技术研究了剂量为5×10¹⁵ cm^-2 的Er离子注入6H-SiC晶体的平均投影射程R_p和射程离散ΔR_p,将测出的实验值和TRIM软件得到的理论模拟值进行了比较,发现R_p的实验值与理论值符合较好,ΔR_p的实验值和理论值差别大一些 关键词： 离子注入 投影射程和射程离散 退火行为 卢瑟福背散射技术     

Design of an end station for a high current ion implantation system

Single crystal silicon has been implanted with nitrogen and phosphorus ions at MeV energies to fluences between 10¹⁶ and 1.6 × 10¹⁸ ions/cm₂. Infrared transmission and reflection spectra in the range of 1.25 to 40 μm were measured for as-implanted samples and after various annealing treatments. Interference fringes were observed in the IR spectra which are produced by the interference of light which has been multiply reflected between the front surface and the buried layers. By detailed theoretical analyses of the interference fringe structure, we obtained refractive index profiles, which, under suitable interpretation, provide accurate measurements and several quantities of interest. These quantities are the range and straggling of the implanted ions, the depth of disordered layers, and the width of the order-disorder transition. Mechanisms for the refractive index changes which have been identified include amorphization of the implanted silicon, bulk compositional change in the buried layer, localized vibrational mode dispersion, and free electron dispersion. Experimental results and theoretical predictions are presented, demonstrating each of these mechanisms.     

Effect of bombardment with iron ions on the evolution of helium,hydrogen, and deuterium blisters in silicon

The effect of bombardment with iron ions on the evolution of gas porosity in silicon single crystals has been studied. Gas porosity has been produced by implantation hydrogen, deuterium, and helium ions with energies of 17, 12.5, and 20 keV, respectively, in identical doses of 1 × 10¹⁷ cm^–2 at room temperature. For such energy of bombarding ions, the ion doping profiles have been formed at the same distance from the irradiated surface of the sample. Then, the samples have been bombarded with iron Fe¹⁰⁺ ions with energy of 150 keV in a dose of 5.9 × 10¹⁴ cm^–2. Then 30-min isochoric annealing has been carried out with an interval of 50°C in the temperature range of 250–900°C. The samples have been analyzed using optical and electron microscopes. An extremely strong synergetic effect of sequential bombardment of silicon single crystals with gas ions and iron ions at room temperature on the nucleation and growth of gas porosity during postradiation annealing has been observed. For example, it has been shown that the amorphous layer formed in silicon by additional bombardment with iron ions stimulates the evolution of helium blisters, slightly retards the evolution of hydrogen blisters, and completely suppresses the evolution of deuterium blisters. The results of experiments do not provide an adequate explanation of the reason for this difference; additional targeted experiments are required.     

Fourier Transform Mid-Infrared Photoacoustic Spectroscopy for Presymptomatic Detection of Powdery Mildew Infection in Rubus corchorifolius L.

A powdery mildew fungi-induced disease appearing on leaves of Rubus corchorifolius L. has been observed in China, which resulted in seriously influencing the yield and quality of the fruit, and a presymptomatic detection of powdery mildew infection is needed to guarantee the yield and quality through removing the fungi in an early stage. Depth-profiling Fourier transform mid-infrared photoacoustic spectroscopy was applied to characterize both the healthy leaves and powdery mildew-infected leaves of Rubus corchorifolius L. The profiled surface could be divided into out layer (depth of about 1.32 µm) and deep layer (depth of about 1.87 µm). There were numerous differences in the total spectral range (500–4000 cm^?1) between healthy leaves and infected leaves, especially the intensity of absorption bands of 2800–3000 cm^?1 (aliphatic C–H vibration) and 2250–2350 cm^?1 (CO₂) significantly decreased when the leaf was infected by powdery mildew. For the out layer the standard spectral variance between healthy leaf and infected leaf was 7.33 × 10², whereas it was 1.86 × 10⁴ for the deep layer; the standard spectral variance between out layer and deep layer for healthy leaf was 3.38 × 10³, whereas it was 1.84 × 10⁴ for infected leaf, which implied that both out layer and deep layer responded to powdery mildew infection. Combining spectral differences between healthy leaf and infected leaf and variances between out layer and deep layer, a presymptomatic detection of powdery mildew infection was successfully made, which provided an alternative option and noninvasive method for the fast diagnosis of powdery mildew infection on Rubus corchorifolius L.     

Plasma enhanced atomic layer deposition of gallium oxide on crystalline silicon: demonstration of surface passivation and negative interfacial charge

Herein we report on the passivation of crystalline silicon by gallium oxide (Ga₂O₃) using oxygen plasma as the oxidizing reactant in an atomic layer deposition (ALD) process. Excess carrier lifetimes of 2.1 ms have been measured on 1.75 Ω cm p‐type silicon, from which a surface recombination current density J₀ of 7 fA cm^–2 is extracted. From high frequency capacitance‐voltage (HF CV) measurements it is shown that, as in the case of Al₂O₃, the presence of a high negative charge density Q_tot/q of up to –6.2 × 10¹² cm^–2 is one factor contributing to the passivation of silicon by Ga₂O₃. Defect densities at midgap on the order of ～5 × 10¹¹ eV^–1 cm^–2 are extracted from the HF CV data on samples annealed at 300 °C for 30 minutes in a H₂/Ar ambient, representing an order of magnitude reduction in the defect density compared to pre‐anneal data. Passivation of a boron‐diffused p⁺ surface (96 Ω/□) is also demonstrated, resulting in a J₀ of 52 fA cm^–2. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Formation of cubic silicon carbide layers on silicon under the action of continuous and pulsed carbon ion beams

The structure and infrared absorption of cubic silicon carbide (β-SiC) layers produced by the continuous high-dose implantation of carbon ions (C⁺) into silicon (E=40 keV and D=5×10¹⁷ cm⁻²), followed by the processing of the implanted layers with a high-power nanosecond pulsed ion beam (C⁺, τ=50 ns, E=300 keV, and W=1.0–1.5 J/cm²), are investigated. Transmission electron microscopy and electron diffraction data indicate the formation of a coarse-grained polycrystalline β-SiC layer with grain sizes of up to 100 nm. A characteristic feature of such a layer is the dendritic surface morphology, which is explained by crystallization from the melt supercooled well below the melting point of β-SiC.     

The study of damage and optical properties in LiNbO3 implanted by MeV Er and He ions

Abstract

Two LiNbO₃ (X and Y cut) crystals from different companies were implanted by 3.0 MeV Er ions to a dose of 7.5 × 10¹⁴ ions/cm² and 3.5 × 10¹⁴ ions/cm² with different beam current densities, respectively. After annealing at 1060°C in air for 2 hours, one LiNbO₃ sample was implanted by 1.5 MeV He ions to a dose of 1.5 × 10¹⁶ ions/cm². The Rutherford backscattering/channeling and prism coupling method have been used to study the damage and optical properties in implanted LiNbO₃. The results show: (1) the damage in LiNbO₃ created by 3.0 MeV Er ions depends strongly on the beam current density; (2) after annealing at 1060°C in air for 2 hours, a good Er doped LiNbO₃ crystal was obtained; (3) there is waveguide formation possible in this Er-doped annealed LiNbO₃ after 1.5 MeV He ion implantation. It is suggested that annealing is needed to remove the damage created by MeV Er ions before the MeV He ion implantation takes place, to realize the waveguide laser for Er doped LiNbO₃.     

The Formation of Helium Bubbles in Silicon Surface Layers via Plasma Immersion Ion Implantation

The surface layers of single-crystal silicon Si(001) substrates subjected to plasma-immersion implantation with 2- and 5-keV helium ions to a dose of 5 × 10¹⁷ cm^–2 were probed via grazing incidence small-angle X-ray scattering and transmission electron microscopy. A surface layer formed by helium ions was found to possess a multilayer structure, wherein the upper layer is amorphous silicon, being on top of a sublayer with helium bubbles and a sublayer with a disturbed crystal structure. The in-depth electron density distribution, as well as the concentration and pore-size distribution, were established. The average pore sizes of bubbles at the above implantation energies are 4 nm and 8 nm, respectively.