Temperature Ion Implantation Research Articles

Development of a continuously variable energy radio frequency quadrupole accelerator for SiC power semiconductor device fabrication

High energy ion implantation is an important process for controlling deep junction conductivity of SiC semiconductor devices. An radio frequency quadraupole (RFQ) accelerator can accelerate high current ions, but the conventional RFQ accelerator is unable to accelerate various ions with different energies. In order to form the box profile with a low number of defects, a high current MeV ion implanter was constructed using a newly designed continuously variable energy RFQ accelerator and high temperature ion implantation chamber. Results of the experiment showed that the resonance frequency varied from 11.7 to 29.3 MHz, so the output beam energy could be changed over a range of about 6.3 times. The results also showed a higher Q-value of over 5000 compared with that of a conventional machine of 1500. Beam acceleration tests were performed using Al ions, and beams were accelerated from 20 to 750 keV using an radio frequency power of 15 kW. The ions were implanted into 4H-SiC, and the projected ranged was 0.76 μm measured by secondary ion mass spectroscopy.

High Fe solubility in InP by high temperature ion implantation

High temperature (>200°C) Fe implantation in InP has been proved to be a suitable method to obtain high substitutional Fe concentrations ([ Fe 2+]>10 18 cm −3) , without substantial defect generation and Fe precipitation. Electrical (current–voltage), deep level (photo-induced current transient spectroscopy) and optical (photoluminescence) measurements have been used to assess the behaviour of the activated Fe fraction, which is compared with the total Fe concentration evaluated by secondary ion mass spectrometry. Our results show no detrimental effects on the electrical (and optical) Fe related properties for Fe peak concentrations as high as 2×10 19 cm −3 , in spite of a large inactive Fe fraction. A strong correlation between Fe activation and background n-doping concentration has been put in evidence.

Implantation parameters affecting aluminum nano-particle formation in alumina

The formation of nano-dimensional metallic Al precipitates in alumina due to the reduction of the host matrix as a result of ambient temperature ion implantation of Y ions is examined. The formation and growth of Al precipitates are dependent on both the Y ion dose and the energy available to the matrix, as reported here. Reducing the ion dose from 5 × 1016 to 2.5 × 1016 ions/cm2 results in smaller precipitates; 10.7 ± 1.8 nm to 9.0 nm ± 1.2 nm, respectively, for incident ion energies of 150 keV, based upon particle size measurements obtained using energy filtered transmission electron microscopy. Below a fluence of 2.5 × 1016, particle formation is not detected. The energy available to the matrix was varied; first, by controlling the incident ion energy (varied between 60 and 150 keV) while holding the substrate at ambient temperature, and second, by controlling the substrate temperature (varied between 44 and 873 K) while holding the incident ion energy constant at 150 keV. Experiments conducted with incident ion energies of 110 keV or higher produce crystalline Al precipitates; whereas implantations at 100 keV produce amorphous Al particles and implantations at 60 keV produce no detectable precipitates. The implantations carried out as a function of temperature produce successively smaller precipitates with decreasing temperature to 77 K (6.7 ± 1.0 nm), below which no precipitates are detected. An Arrhenius activation energy for the formation of the aluminum precipitates of 1.7 kJ/mole has been calculated using the volume of precipitates formed as a function of inverse temperature. This low activation energy suggests that radiation enhanced diffusion (RED) is responsible for particle growth during these implantations.

Nitrogen plasma immersion ion implantation and silicon sputter deposition combined with methane implantation as an in-line process for improving corrosion and wear performance of stainless steels

Plasma immersion ion implantation has been used to combine ion implantation with thermally enhanced diffusion and thus bridge the gap between low temperature ion implantation and plasma diffusion treatment at elevated temperature. Particularly stainless steels were of interest, because they often show a poor tribological behaviour, which can be improved when they are hardened by incorporating nitrogen and forming a hardened surface zone. Using this technique one has to be careful with the temperature because the corrosion performance may easily degrade. The present paper describes a combination of nitrogen PIII treatment of stainless steel at intermediate temperature with depositing a thin silicon carbide film on top of the nitrided zone in an on-line sputtering/PIII process with a methane plasma. The resulting multilayer/gradient layer system of a thin amorphous SiC film on a several micrometer thick nitrided zone of the steel shows a greatly improved performance both with respect to corrosion and wear in comparison to the untreated steel and the nitrided steel without a carbide top layer.

The post-annealing temperature dependences of electrical properties and surface morphologies for arsenic ion-implanted 4H-SiC at high temperature

High-temperature ion implantation of arsenic (As +) into the 4H-silicon carbide (SiC) substrates with high dose of 7×10 15 cm −2 has been investigated as an effective doping method of n-type dopant for SiC power electron devices fabrication. Regardless of the ion implantation temperature, the sheet resistances ( R s) decrease below 1600°C post-annealing and increase above 1700°C as the post-annealing temperature increases. The low R s value (213 Ω/□) is achieved in the sample implanted at 500°C and annealed at 1600°C, an order of magnitude smaller than that implanted at room temperature (RT). Atomic force microscopy (AFM) images reveal that the surface roughness of ion-implanted SiC increases with the increase of post-annealing temperature. Secondary ion mass spectroscopy (SIMS) results show that As + dopant depth profiles of the sample implanted at 500°C do not change before and after the post-annealing. On the other hand, for the sample implanted at RT, the As + concentration in the ion-implanted layer decreases due to the outer-diffusion. These results indicate that high-temperature ion implantation is an effective method to prevent the outer-diffusion of As + dopants during high-temperature post-annealing. It is considered that these post-annealing temperature dependences are caused by the evaporation of SiC surface layer.

Influence of tin ion implantation on the damage and annealing kinetics of sapphire

In order to study the amorphization of sapphire during room temperature ion implantation and the recrystallization of ion-implantation-induced amorphization, sapphire single crystals were implanted with tin (180 keV) at room temperature to fluences from 5×1015 to 1×1017 Sn/cm2. The calculated damage energy at the amorphous/crystalline interface varied from 85 eV/atom (1016 Sn/cm2) to 1.4 eV/atom (4×1016 Sn/cm2). The concentration of Sn at the interface was less than 2 at%. Samples implanted with 4×1016 Sn/cm2 were annealed for 1 hour in oxidizing or reducing atmospheres at a temperature of 700°C, 900°C, 960°C or 1100°C. Regrowth at temperatures below 960°C followed the sequence: amorphous →γ-Al2O3; γ-Al2O3→α-Al2O3. Essentially all (97%) implanted tin was lost during the 1100°C anneal in Ar–4% H2, whereas all Sn was retained in the sample annealed in the oxidizing atmosphere.

Characterization of n-type layer by S+ ion implantation in 4H-SiC

ABSTRACTWe investigated the optical, electrical and structural properties of the layer which was implanted with sulfur ion(S+) in 4H-SiC. By using the high temperature ion implantation technique more less residual defects were observed compared with the room temperature ion implantation by Rutherford backscattering spectrometry and channeling(RBS-channeling). After annealing at 1700°C there was no significant difference between the implanted sample and virgin sample in crystallinity within the detection limit of RBS-channeling. From the result of low temperature photoluminescence(LTPL) we could see the photoluminescences, so-called D1 and D2center, originating in the defects formed by ion implantation and post-annealing(∼1700°C) processes and confirmed that their intensities decreased with the increasing of the total dose of S+. The result of Hall effect measurement suggested that the conduction type of S+-implanted layer is n-type and their activation energies were 275meV and 410meV by the fitting of neutrality equation assuming the two activation energies for the hexagonal and cubic lattice sites in 4H-SiC.

Transient enhanced diffusion of aluminum in SiC during high temperature ion implantation

6H–SiC wafers were implanted at room temperature (RT) and at 1700 °C high temperature (HT) with 50 keVAl+ ions to doses from 1.4×1014 to 1.4×1016 cm−2. Compared to samples implanted at RT, the samples implanted at high temperature display considerable aluminum redistribution. The diffusion of Al is shown to be a transient effect with different decay times in the near-surface region and in the bulk. Investigation of the crystalline structure indicated that in the near-surface region dislocation loops grow in size and Al precipitates are formed as the dose of Al implanted at HT is increased. Changes in the structure of the implanted layer may have a strong effect on the redistribution of Al. The observed redistribution can be explained by a dissociative diffusion mechanism during the high-temperature implantation.

Transmission electron microscopy investigation of the crystal-amorphous-polycrystal transition in silicon during bismuth room temperature ion implantation

Transmission electron microscopy and related diffraction techniques are applied to characterize the structural modifications induced in a (1 0 0) silicon substrate by a bismuth ion implantation at room temperature. Calculations were performed to provide a theoretical support to the observations. It is shown that a 50 keV−10 μA cm −2 Bi + implantation successively induces: a complete silicon substrate amorphization — a clustering phenomenon inside the amorphous layer — an amorphous to polycrystal (a-p) transition. Combining the experimental measurements of the extension of the amorphous layer for increasing doses with concepts arising from the “critical damage energy density” model leads to a value of about 5 eV at. −1 for the crystal to amorphous transition to occur. Then, the clusters band formation at the center of the amorphous layer is attributed, by use of the calculated ion concentration profile, to the formation of Bi precipitates around the concentration peak. The calculated substrate temperature increase suggests that the Bi precipitates finally melt inside the amorphous silicon. These liquid Bi precipitates finally induce the a-p transition as a result of silicon crystallites nucleation at the droplets' sides and bismuth crystallites formation during the implanted sample cooling.

High current-density broad-beam boron ion implantation

Characteristics of iron discs implanted with boron using a high current-density broad-beam system with a rapid processing capability are examined. The effects of ion implantation temperature (150–900 °C), energy (7–50 keV) and current density (200–1000 μA cm −2) on the microstructures and thicknesses of layers implanted with B are examined using Auger electron spectroscopy, X-ray diffraction and conversion electron Mössbauer spectroscopy. Boron condensation on a surface is observed during implantation unless the combination of energy and temperature are sufficiently great to prevent it. The microstructures observed when conditions enable B penetration are amorphous, Fe 3B and Fe 2B. It is argued that the relative balance between the rate of B implantation into and temperature-controlled diffusion out of the ballistic layer determine the microstructure which forms. Preliminary wear tests show a layer containing Fe 2B in an α-Fe matrix which was formed at the highest temperature investigated (900 °C) yields the most wear-resistant surface.

The radiation stimulated diffusion role in high dose, low energy, high temperature ion implantation

A low energy, high dose and temperature ion implantation modeling method is presented. The diffusion equations for impurity and non-equilibrium vacancies are solved taking into account the source functions for impurity atoms and vacancies and the recession of surface due to sputtering. The source functions as well as the sputtering yields and the surface moving velocity are determined from atom collision cascades calculations with the Monte Carlo code CASNEW at dose increments. It is shown for Al + implanted into α-Fe at E 0 = 0.5−2 keV and D = 10 15−10 18 cm −2, that radiation-stimulated diffusion (RSD) is significant in temperature range of 100°C < t < 700°C. At t = 400°C, a penetration depth up to 0.3−0.4 μm is obtained at D = 10 18 cm −2.

Ellipsometric investigation of damage distribution in low energy boron implantation of silicon

As the scaling of silicon devices to 100 nm channel length requires the formation of ultra-shallow (< 60 nm) junctions, high depth resolution analytical techniques become necessary for the characterization of the dopant and damage distributions. In situ single wavelength Ellipsometric Etch Depth Profiling (EEDP) and non-destructive Variable Angle of incidence Spectroscopic Ellipsometry (VASE) have been used to obtain accurate and quantitative information on the depth profiles of radiation damage produced by low energy, room temperature ion implantation of B + into Si. Implantation energy ranged from 250 eV to 10 keV and the dose was in the range 5 × 10 14 B + cm −2 to 5 × 10 15 B + cm −2. EEDP has been applied to damage depth profiling of low energy implanted silicon for the first time. The range and shape of the damage distributions obtained from optical model calculations are in good agreement with TRIM calculations for the energy range investigated. However, for the 10 keV implant, EEDP results unambiguously show the presence of a 6 nm thick amorphous silicon layer at the surface which is not predicted by TRIM. In the case of the 250 eV implant the presence of an amorphous Si surface layer can not be inferred from VASE data analysis although the existence of a 1 nm thick amorphous Si surface layer is indicated by EEDP.

Optical activation of ion implanted and annealed GaN

Ion implantation and the associated annealing was investigated using luminescence and absorption measurements to demonstrate the efficacy of implantation for introducing various classes of dopants into GaN. A wide range of implantation and annealing studies were performed with several dopant species (Zn, Nd, Er, Ar). Room temperature ion implantation was performed on MOCVD grown GaN samples at energies between 200 and 400 keV with doses ranging from 1 × 1013 to 1 × 1015 cm−2. Conventional furnace annealing in flowing NH3 or N2 resulted in good recovery of implantation damage at an annealing temperature of 1000°C for 90 min. However, surface degradation became evident for annealing in an NH3 environment at temperatures above 1000°C. Low temperature photoluminescence showed that the optical activation of the Zn, and the rare earth elements, Er and Nd, was optimum in the NH3 annealing environment at 1000°C.

Behavior Of The Potential N-Type Dopants P And As In Diamondafter Low Dose Ion Implantation

AbstractWe have studied the lattice sites of P and As impurities in natural IIa diamond after room temperature ion implantation at very low doses of 1011 P/cm2 and ≤ 1013 As/cm2 and subsequent annealing. We implanted radioactive 33P and 73Se/73As probe atoms and used the sensitive emission channeling technique to determine the impurity lattice sites. In this technique the channeling effects of emitted decay electrons are measured for different crystal axes. By comparison with calculated electron emission distributions the fractions of emitter atoms on different lattice sites can be quantitatively determined. After annealing of the implanted samples above 900°C we find high substitutional fractions of 70 ± 10 % for 33P and 55 ± 5 % for 73As.

Effect of target temperature during nitrogen ion implantation on electrochemical properties of ion-implanted glassy carbon

Abstract The electrochemical properties of glassy carbon (GC) modified by nitrogen ion implantation (a fluence of 1 × 10 16 ions cm − 2 ) at various target temperatures were studied by conventional electrochemical methods. The structure of ion-implanted surface layers of carbon materials has already been investigated by Raman spectroscopy, which has revealed that the implantations at high and low target temperatures produce a graphitic and an amorphous structure respectively. GC implanted at high temperatures (150, 300 and 400°C) showed electrochemical properties resembling those of non-implanted GC as a result of its graphitic structure. In contrast, GC implanted at low temperatures (− 70 and 30°C) forms an electrode surface with an electrochemically inert nature and a low double-layer capacity, which is due to the formation of an amorphous surface layer. A structure of this type is commonly formed by ion implantation into diamond, highly ordered pyrolytic graphite and GC, which has high electrical resistivity and high wear resistance. It was found that the target temperature during ion implantation has a strong effect on the structure and properties of carbon materials. The electrochemically inert and highly wear-resistive carbon formed by low temperature ion implantation will be useful as a superior stable carbon material.

Investigation of irradiation-induced nucleation processes in silicon and germanium

Studies of the initial stages of nucleation of silicon and germanium have yielded insights that point the way to achievement of engineering control over crystal size evolution at the nanometer scale. In addition to their importance in understanding fundamental issues in nucleation, these studies are relevant to efforts to (i) control the size distributions of silicon and germanium “quantum dots𠇍, which will in turn enable control of the optical properties of these materials, (ii) and control the kinetics of crystallization of amorphous silicon and germanium films on amorphous insulating substrates so as to, e.g., produce crystalline grains of essentially arbitrary size.Ge quantum dot nanocrystals with average sizes between 2 nm and 9 nm were formed by room temperature ion implantation into SiO2, followed by precipitation during thermal anneals at temperatures between 30°C and 1200°C[1]. Surprisingly, it was found that Ge nanocrystal nucleation occurs at room temperature as shown in Fig. 1, and that subsequent microstructural evolution occurred via coarsening of the initial distribution.

Atomic Scale Simulations of Arsenic Ion Implantation and Annealing in Silicon

AbstractWe present results of multiple-time-scale simulations of 5, 10 and 15 keV low temperature ion implantation of arsenic on silicon (100), followed by high temperature anneals. The simulations start with a molecular dynamics (MD) calculation of the primary state of damage after l0ps. The results are then coupled to a kinetic Monte Carlo (MC) simulation of bulk defect diffusion and clustering. Dose accumulation is achieved considering that at low temperatures the damage produced in the lattice is stable. After the desired dose is accumulated, the system is annealed at 800 °C for several seconds. The results provide information on the evolution for the damage microstructure over macroscopic length and time scales and affords direct comparison to experimental results. We discuss the database of inputs to the MC model and how it affects the diffusion process.

Correlation of Size and Photoluminescence for Ge Nanocrystals in SiO2 Matrices

ABSTRACTSynthesis and size-dependent photoluminescence has been performed for Ge nanocrystals in SiO2 matrices with average diameters between 2 nm and 9 nm, formed by room temperature ion implantation into SiO2 followed by precipitation during vacuum thermal anneals. Nanocrystal size distributions obtained from electron microscopy data were used in conjunction with a quantum-confined exciton recombination model[l] to generate calculated photoluminescence spectra, which were compared with experimental spectra.

Inhomogeneous magnesium hydride synthesized by low temperature ion implantation: weak localization effect

Metastable MgHx hydride was prepared by H ion implantation into Mg films at 5 K. The resistivity and magnetoresistance temperature dependence reveal weak localization effects due to atomic disorder. At low hydrogen concentrations, x ≤0.3, the conductivity varies as σ∼log (T), typical of two-dimensional weak localization behaviour. The resistivity is also very sensitive to the sample inhomogeneity, due to H diffusion, which can be modelled by introducing a temperature-dependent geometrical percolating factor G. At higher H concentrations, 0.7 ≤x ≤3, after annealing at 20 K, 50 K and 110 K, the samples also exhibit weak localization but with three-dimensional behaviour i.e. a $\sigma \sim \sqrt{T}$. Our analysis is consistent with the existence of an inhomogeneous system formed by a mixture of two phases with contrasted conduction properties, one of which is a well-behaved metal, while the other displays the localization properties. The results lead us to identify the former phase to a non percolating superconducting phase at low temperature.

High temperature nitrogen implantation of Ti-6Al-4V II: Tribological properties

A high temperature ion implantation method employing a high current density beam ( e.g. 500 μA cm -2) of nitrogen ions, was used to modify the near-surface microstructure of Ti-6Al-4V to improve its tribological performance. A systematic study was performed with nitrogen implantations at temperatures from 400 to over 1000 °C, and doses in the range (0.1−1.0) × 10 18 N + 2− N + cm −2. Tribological properties ( e.g. coefficients of friction) were evaluated in ambient air as a function of applied load, under both unlubricated and perfluoroether fluid lubricated conditions. Metallographic examinations were performed to characterize wear damage. The lowest unlubricated coefficient of friction and greatest wear resistance were observed for the 1000 °C implantation treatment. These tribological properties were correlated with the distribution of the implanted nitrogen and resultant microstructure (as described in Part I of this paper series).