铒离子注入6H-SiC的横向离散研究

利用离子注入掺杂技术设计、制作半导体集成器件时,了解离子注入半导体材料的射程分布、射程离散和横向离散规律等是很重要的.用400 keV能量的铒(Er)离子分别与样品表面法线方向成0°,45°和 60°倾角注入碳化硅(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400 keV Er离子注入6H-SiC晶体的横向离散.测出的实验值与TRIM98和SRIM 2006得到的理论模拟值进行了比较,发现实验值跟TRIM98和SRIM 关键词： 离子注入 6H-SiC 卢瑟福背散射技术 横向离散     

Three-dimensional range distribution of 400 KeV Nd ions implanted into Si

Abstract

The 400 keV Nd ions were implanted into Si at a variety of tilt angles from 7° to 75°. The range distributions were accurately measured by the TOF-SIMS (Time-of-Flight secondary ion mass spectrometry) method. The results show that the measured range profiles can be represented by Pearson I type distributions which are in the same category as predicted by TRIM (TRansport of Ions in Matter). The first four statistical moments of the Nd-depth distribution, namely range, longitudinal straggling, skewness, and kurtosis, were obtained from the fitted profiles, and compared with the corresponding TRIM calculated values. Results show that the experimentally obtained range profiles are obviously deeper and broader than TRIM'95 (version 95.2) predictions, but very good agreements were obtained between the measured values and TRIM'98 (version 98.10) calculation. The longitudinal and lateral range stragglings for normal incidence were deduced from the angular dependence of the measured range distributions. Based on the range distributions for different angle implantation, the three-dimensional range distribution was reconstructed, and the lateral range straggling was obtained from the three-dimensional distribution and compared with both the predicted TRIM values and the deduced value.     

Non linear volume expansion in helium implanted erbium metal films

Large dimensional expansion has been observed at room temperature in erbium metal films implanted at room temperature with high fluences of helium. The interferometrically measured film thickness increases linearly with fluence up to a critical dose of 3 × 10¹⁷ He+/cm² (E = 160 keV) and is superlinear at higher fluences. Annealing at 400°C causes a reduction of the induced expansion for fluences below the critical dose without apparent release of helium. Annealing of samples implanted to fluences greater than 3.5 × 10¹⁷ He⁺/cm² causes accentuated expansion which is accompanied by formation and rupture of bubbles at the film surface.     

Study of the lateral distribution of neodymium ions implanted in silicon

Due to the need to reduce electronic device sizes,it is very important to consider the depth and lateral distribution of ions implanted into a crystalline target.This paper reports that Nd ions with energies of 200 keV to 500 keV and dose of 5×10 15 ions/cm 2 are implanted into Si single crystals at room temperature under the angles of 0,30,and 45,respectively.The lateral spreads of 200 keV-500 keV Nd ions implanted in Si sample are measured by Rutherford backscattering technique.The results show that the measured values are in good agreement with those obtained from the prediction of SRIM2010 codes.     

Investigation of silicon doped by zinc ions with a large dose

The formation of nanoparticles in СZn-Si(100) implanted with ⁶⁴Zn⁺ ions using a dose of 5 × 10¹⁶ cm^–2 and an energy of 50 keV at room temperature with subsequent thermal processing in oxygen at temperatures ranging from 400 to 900°C is studied. The surface topology is investigated with scanning electron (in the secondary emission mode) and atomic force microscopes. The structure and composition of the near-surface silicon layer are examined using a high-resolution transmission electronic microscope fitted with a device for energy dispersive microanalysis. An amorphized near-surface Si layer up to 130 nm thick forms when zinc is implanted. Amorphous zinc nanoparticles with an average size of 4 nm are observed in this layer. A damaged silicon layer 50 nm thick also forms due to radiation defects. The metallic zinc phase is found in the sample after low-temperature annealing in the range of 400–600°C. When the annealing temperature is raised to 700°C, zinc oxide ZnO phase can form in the near-surface layer. The complex ZnO · Zn₂SiO₄ phase presumably emerges at temperatures of 800°C or higher, and zinc-containing nanoparticles with lateral sizes of 20–50 nm form on the sample’s surface.     

Ion implantation induced by Cu ablation at high laser fluence

High energy laser plasma-produced Cu ions have been implanted in silicon substrates placed at different distances and angles with respect to the normal to the surface of the ablated target. The implanted samples have been produced using the iodine high power Prague Asterix Laser System (PALS) using 438 nm wavelength irradiating in vacuum a Cu target. The high laser pulse energy (up to 230 J) and the short pulse duration (400 ps) produced a non-equilibrium plasma expanding mainly along the normal to the Cu target surface. Time-of-flight (TOF) technique was employed, through an electrostatic ion energy analyzer (IEA) placed along the target normal, in order to measure the ion energy, the ion charge state, the energy distribution and the charge state distribution. Ions had a Boltzmann energy distributions with an energy increasing with the charge state. At a laser fluence of the order of 6 × 10⁶ J/cm², the maximum ion energy was about 600 keV and the maximum charge state was about 27+.In order to investigate the implantation processes, Cu depth profiles have been performed with Rutherford backscattering spectrometry (RBS) of 1.5 MeV helium ions, Auger electron spectroscopy (AES) with 3 keV electron beam and 1 keV Ar sputtering ions in combination with scanning electron microscopy (SEM). Surface analysis results indicate that Cu ions are implanted within the first surface layers and that the ion penetration ranges are in agreement with the ion energy measured with IEA analysis.     

Selective X-ray generation by heavy ions (Part 2) measurement of the concentration distribution of ion-implanted antimony in silicon by the use of selective heavy ion X-ray excitation

This investigation demonstrates how the total, concentration distribution of antimony, previously implanted into silicon at 100 keV, may be elucidated without recourse to the usual radioactive isotope techniques. It uses the fact that 100 keV Kr⁺ ions can preferentially excite characteristic X-rays from antimony, even in the presence of a huge excess of silicon. The resultant high sensitivity for the detection of antimony in silicon is accompanied by the fact that the X-rays arise predominantly from less than one hundred Angstroms below the surface of the specimen. Thus bombardment by 100 keV Kr⁺ íons is used ín conjunction with an anodic stripping technique (which removes 169±20 Å at a time) to obtain the antimony distribution profile in silicon. Consideration is also given to the possibility of obtaining the implanted antimony range distribution by using 100 keV Kr⁺ ions to detect the antimony and simultaneously remove silicon by sputtering.     

Phase analysis in α-Fe after high-dose Si ion implantation by depth-selective conversion-electron Mössbauer spectroscopy (DCEMS)

Si⁺ ions of 50 keV in energy were implanted into α-Fe (95% ⁵⁷Fe) with a nominal dose of 5 × 10¹⁷ cm^?2 at 350°C. The depth distribution of the Fe-Si phases formed by ion implantation after annealing at 300 and 400°C for 1 h was studied quantitatively by depth-selective conversion-electron Mössbauer spectroscopy (DCEMS). Ordered Fe₃Si and ε-FeSi was observed.     

Ion mixed Co-Nb amorphous films

Multilayers of cobalt and niobium have been deposited in ultra high vacuum, using two E-beams onto both corning glass and silicon wafers substrates kept at 20°C. These films were then ion mixed using Xe ions at 200, 300 and 400 keV. The dose was 3 × 10¹⁵ ions cm^-2 in all cases. FMR and usual magnetization measurements were made to characterize the samples. Films mixed at 300 and 400 keV are homogeneous. FMR line width of 60 Oe and the simple spectra obtained lead us to conclude that these films are much more homogeneous than co-evaporated amorphous films of the same composition.     

The measurement of cone length and range in etched plastics

Abstract

Group V impurities implanted at 400 keV into silicon have been detected in substitutional lattice positions by EPR. Three samples of VFZ, p-type 1200–1500 ohm-cm silicon from the same ingot were implanted with As⁷⁵, Sb¹²¹, and Sb¹²³, respectively. The EPR spectrum of each implanted substitutional impurity was observed after annealing the lattice damage. Only the isotope implanted in each sample was seen. Since only those donors which are electrically active can be observed, this technique measures the electrically active fraction of the implanted species. Upon annealing to 970°C, most of the antimony was active whereas only about 1/5 of the arsenic was observed. Comparisons with backscattering results indicate that between 350 and 600°C, ～95 per cent of the implanted antimony is substitutional but ～0 per cent is electrically active. The increase in electrical activity at 600°C is due to the rise of the Fermi level to the donor level as the residual lattice damage anneals. The paramagnetic damage centers observed were those also seen in oxygen-implanted silicon, Si-P3 and Si-Pl, but the Si-P3 center was not as well resolved and grows upon annealing to 200°C.     

Some studies of BF2 and B+F implanted Silicon

Ion-implanted shallow junctions have been investigated using BE₂ (molecular ions) by the anodic oxidation method coupled with a four-point probe technique. BF₂ ions were implanted through screen oxide at doses of 3–5 × 10¹⁵ ions/cm² and energies of 25 and 45 keV which is equivalent to 5.6 keV and 10 keV of boron ions. The effect of energy, dose and annealing temperature on shallow junctions is presented in this paper. The shallow junctions in the range of 0.19 μm to 0.47 μm were fabricated.

The effect of fluorine on sheet resistivity of boron implanted silicon at various doses, treated with two-step and three-step annealing, is also presented for comparison in the paper.     

The electrical activity of phosphorus channelled into silicon

The electrical activity of phosphorus ions, implanted at energies between 40 and 400 keV along the 〈110〉 axis of silicon crystals, has been measured as a function of depth, following a 700°C anneal. The electrical activity, determined by differential electrical sheet conductivity measurements combined with anodic stripping, was found to be close to 100 per cent in both pulled and float-zoned material. In some cases it was possible to compare carrier concentration and impurity ion distributions within the same specimen, implanted with a mixed dose of P³¹ and Pa³².

By radioactive tracer techniques it has been shown that de-channelling of phosphorus ions is significantly greater in certain dislocation-free crystals than in other, dislocated silicon crystals. Scanning X-ray diffractometer measurements reveal considerably more lattice strain in the former. It is proposed that both effects may arise from vacancy clustering, together with associated decoration by impurity atoms, as a result of the absence of sinks provided by a few dislocations.

The degree of channelling of P³² in epitaxially-grown 〈111〉 silicon has been found to exceed that in high-quality bulk-grown crystals. The consequences of this observation, combined with the high electrical activity of channelled phosphorus, are considered briefly.     

Low energy boron and phosphorus implants in silicon (a) electrical sheet measurements

Silicon wafers were implanted in 〈111〉-direction with boron and phosphorus ions of 7 keV at room temperature. Doses between 10¹² and 10¹⁸ ions/cm² were applied. After successive annealing steps the electrical properties of the implanted layers have been determined by Hall effect and sheet resistivity measurements. The annealing characteristics of the implants depend on ion dose and species. Three annealing stages can be distinguished: (I) the temperature range below 500°C, (II) 500—700°C, (III) 700—900°C.

After annealing at 90°C the apparent electrical yield is proportional to dose for all implants and amounts to approx. 80 per cent for boron and 40 per cent for phosphorus.

Sheet resistivity vs. dose curves were derived for the annealing temperature of 400°C and used for the fabrication of position sensitive detectors. The position characteristics were found to be linear within ～1 per cent for resistive layers as long as 20 cm.     

Photoluminescence and structural defects in silicon layers implanted by iron ions

The photoluminescence spectra of silicon samples implanted by ⁵⁶Fe⁺ ions [energy, 170 keV; dose, 1×10¹⁶, (2–4)×10¹⁷ cm^?2] and annealed at temperatures of 800, 900, and 1000°C are measured. The structure of the samples at each stage of treatment is investigated using transmission electron microscopy (TEM). It is found that the phase formation and morphology of crystalline iron disilicide precipitates depend on the dose of iron ions and the annealing temperature. A comparison of the dependences of the intensity and spectral distribution of the photoluminescence on the measurement temperature, annealing temperature, and morphology of the FeSi₂ phase revealed the dislocation nature of photoluminescence.     

Lattice location and dopant behavior of group II and VI elements implanted in silicon

Outdiffusion, lattice location and electrical behavior of Zn, Cd, Hg and Se, Te implanted into silicon at 50 keV were investigated by backscattering and channeling effect of 1 MeV He⁺ ions and by Hall effect and sheet resistivity measurements. All the species exhibited outdiffusion with thermal processing. A significant fraction of Zn, Cd and Hg, when implanted into a substrate of 350°C, occupied regular interstitial lattice sites, while 50–60 per cent of the Se and Te atoms were on substitutional lattice sites. Selenium implanted at room temperature and mercury implanted into a substrate of 350°C exhibited depth dependent lattice location. The implanted layers showed n-type behavior: the maximum value of number of carriers/cm² was less than the number of implanted ions/cm² in all cases. The highest electrical activity was observed for Se corresponding to 25 per cent of the substitutional component.     

Electrical measurements of boron implanted silicon on sapphire and bulk silicon

Hall effect and sheet resistivity measurements have been performed on boron implantations in 1μm silicon layers on sapphire (SOS), and in bulk silicon. The doses used were 10¹⁴, 10¹⁵ and 10¹⁶ ions/cm², and implantation energies were 150 and 300 keV. The samples were annealed at temperatures between 300 and 800°C. As a rule the effective number of carriers in SOS was found to be about twice the number of carriers in bulk silicon. However, the mobility is lower in bulk silicon, resulting in a sheet resistivity almost the same in boron implanted SOS and bulk silicon.     

Electrical properties of Cd,Zn and S ion-implanted layers in GaAs

The electrical properties of cadmium, zinc, and sulfur ion-implanted layers in gallium arsenide have been measured by the van der Pauw-Hall technique. Ion implantation was performed with the substrates held at room temperature. The dependence of sheet resistivity, surface carrier concentration, and mobility on ion dose and on post-implantation anneal temperature was determined. In the case of 60 keV Cd⁺ ions implanted into n-type substrates, a measurable p-type layer resulted when samples were annealed for 10 minutes at a temperature in the range 600—900°C. After annealing at 300—900°C for 10 minutes, 100 per cent electrical activity of the Cd ions resulted for ion doses ≤ 10¹⁴/cm².

The properties of p-type layers produced by implantation of 85 keV Zn⁺ ions were similar to those of the 60 keV cadmium-implanted layers, in that no measurable p-type behavior was observed in samples annealed below a relatively high temperature. However, in samples implanted with 20 keV Zn⁺ ions a p-type layer was observed after annealing for 10 minutes at temperatures as low as 300°C.

Implantation of sulfur ions into p-type GaAs substrates at room temperature resulted in the formation of a high resistivity n-type layer, evcn before any annealing was performed. Annealing at temperatures up to 200°C or above 600°C lowered the resistivity of the layer, while annealing in the range 300—500°C eliminated the n-type layer.     

Ion beam shaping of embedded metal nanoparticles by Si+ ion irradiation

Fine Co and Pt nanoparticles are nucleated when a silica sample is implanted with 400 keV Co⁺ and 1370 keV Pt⁺ ions. At the implanted range, Co and Pt react to form small Co _x Pt_(1?x) nanoparticles during Si⁺ ion irradiation at 300 °C. Thermal annealing of the pre-implanted silica substrate at 1000 °C results in the formation of spherical nanoparticles of various sizes. When irradiated with Si⁺ ions at 300 °C, particles in the size range of 5–17 nm undergo rod-like shape transformation with an elongation in the direction of the incident ion beam, while those particles in the size range of 17–26 nm turn into elliptical shape. Moreover, it is suspected that very big nanoparticles (size >26 nm) decrease in size, while small nanoparticles (size <5 nm) do not undergo any transformation. During Si⁺ ion irradiation, the crystalline nature of the nanoparticles is preserved. The results are discussed in the light of the thermal spike model.     

Comparative study on low energy ion beam modification of thermoplastic polymers

ABSTRACT

Polycarbonate (PC) and polyethylene terephthalate (PET) thermoplastic polymer films were irradiated by low energy ion beams such as 100 keV Hydrogen (H⁺) ions and 350 keV Nitrogen (N⁺) ions at varied fluence from 1?×?10¹³ ions/cm² to 5?×?10¹⁴ ions/cm². The depth profile concentration of ions was calculated using Stopping and Range of Ions in Matter (SRIM) software code. Fourier Transform Infrared (FTIR) technique shows decrement in the intensity of peaks and disappearance of peaks mainly related to carbonyl stretching at 1770?cm^?1 and C–C stretching at 1500?cm^?1. Scanning electron microscopy (SEM) of irradiated polymers showed the formation of pores. X-ray diffraction (XRD) analysis has showed decrease in the intensity indicating the decrease in crystallinity after irradiation. Mechanical studies revealed that the molecular weight and microhardness decrease with increase in ion fluence due to increase in chain scission. The contact angle increased with increase in ion fluence indicating the hydrophobic nature of polymer after irradiation. Antibiofilm activity test of irradiated films shows resistance to Salmonella typhi (S. typhi) pathogen responsible for typhoid. The study shows that Nitrogen ion induces more damage compared to Hydrogen ions and PC films get more modified than PET films.     

Investigation of gallium arsenide single crystals with various crystallographic orientations, after implantation of silicon ions and pulsed photon annealing

The results of experimental investigations of gallium arsenide single crystals with the orientations (100), (311)A, (211)A, (111)A, and (221)A are presented. The crystals were doped with silicon ions on the Iolla-3M setup (ion energy 75 keV, ion beam density 1 μA/cm², implantation dose 1.2×10³ cm⁻²) at room temperature and annealed on the Impul’s-5 setup at 950°C. Raman scattering and low-temperature photoluminescence methods established that the highest electrical activity of the implanted silicon under identical implantation and annealing conditions obtains for (100) and (311)A gallium arsenide. In the process n-type layers are produced. Zh. Tekh. Fiz. 69, 78–82 (May 1999) Deceased.