High-temperature Implantation Research Articles

On diffusion of radiation defects during low and high temperature implantation near phase transitions

Since the last decade, radiation defects in solids during surface modification by ion beams have been extensively investigated. In this paper, defect diffusion coefficients for a variety of implantation energies and temperatures have been calculated on the basis of a modified model [V.A. Starostin, Phys. Chem. Mater. Treat. 5 (1999) 104–105] by Beloshitsky [P.A. Aleksandrov et al., Rad. Eff. 88 (1986) 249–255] with an emphasis given to relevant experiments [K.D. Demakov and V.A. Starostin, Tech. Phys. 46(4) (2001) 490–491]. For combinations of hydrogen in silicon (0.6 keV, 40 K), deuterium in diamond-like carbon (27 keV, 293 K) and arsenic in silicon (40 keV, 1123 K) this resulted in the equal value of the defect diffusion coefficient. A similar value is obtained for thermal diffusion of lead in zirconium. The advanced model enables quantitative estimates of self-diffusion coefficients as well as both defects and lattice vacancy profiles to be obtained.

Simulation of Coupled Diffusion of Impurity Atoms and Point Defects under Nonequilibrium Conditions in Local Domain

A two-dimensional model of doping of the active regions in semiconductor devices by means of ion implantation and thermal annealing is stated and analyzed. Radiation enhanced diffusion of impurity atoms during high temperature implantation of hydrogen ions is also considered. An economic finite difference method for solving the obtained system of diffusion equations is developed and numerical computations of the diffusion processes are carried out.

Masking Process for High-Energy and High-Temperature Ion Implantation

Masking Process for High-Energy and High-Temperature Ion Implantation

Transmission electron microscopy study of Ge implanted into SiC

Hexagonal 6H– and 4H–SiC wafers were implanted with (1−1.5) × 1016 cm−2 germanium ions at room temperature and at 700 °C with subsequent annealing between 1000 and 1600 °C. Structural changes in the SiC matrix were studied in detail by means of transmission electron microscopy (TEM). After implantation at room temperature the hexagonal SiC matrix becomes amorphous and, after annealing, recrystallizes into cubic SiC. The latter process was accompanied by the creation of voids and cracks. In case of high-temperature (700 °C) implantation, where amorphization was avoided, no polytype change in as-implanted and annealed SiC wafers was observed. In annealed samples nanocrystalline precipitates with high Ge content were observed in high-resolution TEM images.

Role of implantation temperature on residual damagein ion-implanted 6H-SiC

The optical and structural properties of ion-implanted 6H-SiC singlecrystals were investigated for samples implanted with 370 keV 28Si ionsto doses ranging from 5×1013 to 1×1016 cm-2 and atirradiation temperatures ranging from 20 to 600 °C. Rutherfordbackscattering spectrometry channelling (RBS/C) showed that the dynamicrecovery of the induced-damage layer increases with irradiation temperature.The final disorder determined from RBS/C as a function of implantationtemperature was modelled in terms of a thermally activated process whichyielded an activation energy of 0.08 eV. Defect distributions are found toshift to greater depths with increasing implantation temperature and dose.Some defects are even found farther than the accessible range of the implantedions. RBS/C data on high-temperature implantations also suggests that defectcomplexes are created at high doses in addition to the point defects that arestill stable at high temperature. A decrease in Raman intensity of implantedsamples relative to that of crystalline samples was observed and correlatedwith an increase in optical absorption near the wavelength of the laser pump(514.5 nm).

A Study of Temperature Effect on Ta+N Ion-Implanted Hardalloy

Hard alloy were implanted with a dual-ion of nitrogen and tantalum at temperature of 100 °C and 400 °C at a dose of 8×1017 ions cm-2. Auger electron spectroscopy (AES) was used to determine the nitrogen and tantalum concentration profiles. Microhardness measurements were performed to evaluate the improvements in surface property. The thickness of implanted layers increased by about an order of magnitude when the temperature was elevated from 100 °C to 400 °C. A higher surface hardness was also obtained in the higher temperature implantation. Scanning electron microscopy (SEM) image showed distinct microstructural changes, and x-ray diffraction (XRD) analysis showed the presence of nitrides of tantalum and tungsten on the surface implanted.

Atomistic modeling of the effects of dose and implant temperature on dopant diffusion and amorphization in Si

We discuss atomistic simulations of ion implantation and annealing of Si over a wide range of ion dose and substrate temperatures. The DADOS Monte Carlo model has been extended to include the formation of amorphous regions, and this allows simulations of dopant diffusion at high doses. As the dose of ions increases, the amorphous regions formed by cascades eventually overlap, and a continuous amorphous layer is formed. In that case, most of the excess interstitials generated by the implantation are swept to the surface as the amorphous layer regrows, and do not diffuse in the crystalline region. This process reduces the amount of transient enhanced diffusion (TED) during annealing. This model also reproduces the dynamic annealing during high temperature implants. In this case, the local amorphous regions regrow as the implant proceeds, without the formation of a continuous amorphous layer. For sufficiently high temperatures, each cascade is annealed out independently; interstitials and vacancies can escape from the cascade and thus increase dopant diffusion.

Mid-infrared (3.5 μm) electroluminescence from heavily Fe 2+ ion-implanted semi-insulating InP

Abstract We report the observation of efficient mid-infrared electroluminescence associated with internal transitions of Fe2+ deep levels in overcompensated n-type InP:Fe, ion implanted with Fe doses in the range 10 13 –10 15 cm −2 . Unprecedented high active Fe2+ densities up to ∼10 18 cm −3 are obtained with a combination of high temperature implantation and annealing procedure. The characteristic spectrum of Fe2+, dominated by a set of sharp lines corresponding to the symmetry allowed d-shell transitions, can be observed up to 30 K. A broader emission is detectable up to 200 K. The estimated conversion efficiency of electrical into mid-infrared optical power is ∼5×10−5, a factor of ∼50 larger than previously reported value in MOCVD-grown planar electroluminescent devices.

Diamond Pressure and Temperature Sensors for High-Pressure High-Temperature Applications

A high-pressure high-temperature diamond based sensor has been developed for the use in diamond anvil cells. The electronic structure of the sensor is that of p-i-p unipolar diode with boron doped p-type regions separated by an i-region containing compensated boron acceptors. The sensor has been fabricated by high-temperature high-energy boron ion implantation followed by high-energy carbon ion irradiation on the working surface of an anvil made of type IIa natural diamond. The performance of the sensor has been tested at pressures up to 70 kbar and temperatures up to 800 C. The sensor has a resolution of 5 bar for pressure and of 0.01 °C for temperature.

Ion beam synthesis of buried SiC layers in silicon: Basic physical processes

For the ion beam synthesis (IBS) of buried stoichiometric epitaxial layers of 3C–SiC in silicon, a complicated structure in the as-implanted state has been identified as a favourable starting structure prior to annealing. It consists of a nearly rectangular depth distribution of equally sized, oriented 3C–SiC nanocrystals sandwiched between two amorphous zones. The basic physical processes leading to such a distribution of amorphous and crystalline phases during high-dose, high-temperature carbon implantation into silicon are reviewed in this article. In particular, the precipitation of carbon in a self-organized lattice of amorphous inclusions, the formation of stable 3C–SiC nuclei via precursors, beam-induced nucleation of SiC in amorphous Si:C, the different growth of crystalline SiC precipitates in crystalline and amorphous silicon and the ballistic destruction of SiC nanoclusters by the continued bombardment with energetic ions – resulting in a carbon-induced amorphization at elevated temperatures – are described.

Optical and structural properties of 6H–SiC implanted with silicon as a function of implantation dose and temperature

Optical and structural properties of ion-implanted 6H–SiC single crystals were investigated for samples implanted with 370 keV 28 Si ions to doses ranging from 5×10 13 to 1×10 16 cm −2 and at irradiation temperatures ranging from 20°C to 600°C. Rutherford backscattering spectrometry channeling (RBS/C) showed that dynamic recovery of the induced-damage layer increases with temperature. The final disorder determined from RBS/C as a function of implantation temperature was modeled in terms of a thermally activated process which yielded an activation energy of 0.08 eV. RBS/C data on high temperature implantations also suggest that defect complexes are created at high doses in addition to point defects still stable at high temperature. A decrease in Raman intensity of implanted samples relative to that of crystalline samples was observed and correlated with an increase in optical absorption near the wavelength of the laser pump (514.5 nm).

Planar p-n Diodes Fabricated by MeV-Energy and High-Temperature Selective Implantation of Aluminum to 4H-SiC

Planar p-n Diodes Fabricated by MeV-Energy and High-Temperature Selective Implantation of Aluminum to 4H-SiC

Atomistic Modeling of Amorphization in Silicon

ABSTRACTWe discuss atomistic simulations of ion implantation and annealing of Si over a wide range of ion dose and substrate temperatures. The DADOS Monte Carlo model has been extended to include the formation of amorphous regions, and this allows simulations of dopant diffusion at high doses. As the dose of ions increases, a continuous amorphous layer may be formed. In that case, most of the excess interstitials generated by the implantation may be swept to the surface as the amorphous layer regrows, instead of diffusing through the crystalline region. This process reduces the amount of transient enhanced diffusion during annealing. This model also reproduces the dynamic annealing during high temperature implants.

Mechanical strain and damage in Si implanted with O and N ions at elevated temperatures: Evidence of ion beam induced annealing

The accumulation of damage and the development of mechanical strain in crystalline Si (c-Si) by O and N ion implantation to doses up to 4×1017 cm−2 at elevated temperatures have been studied using Rutherford backscattering spectrometry and high resolution x-ray diffraction. The implantation of O or N ions at high temperatures produces two distinct layers in the implanted c-Si: (i) a practically damage-free layer extending from the surface up to ≃ half of the depth of the mean projected range (Rp) and presenting negative strain (of contraction); and (ii) a heavily damaged layer located around and ahead of the Rp with no significant strain. Both the damage distribution and the magnitude of the strain were found to be dependent on the ion species implanted. We proposed that besides the spatial separation of Frenkel pair defects due to the mechanics of the collision processes and the intensive dynamic annealing, an ion beam induced annealing process also participate in the formation of the near-surface damage-free layer during high temperature implantation of c-Si.

Reverse-annealing phenomenon during the high-temperature implantation of Ar+ into GaN

AbstractA systematic investigation of the damage accumulation in GaN films induced by 150keV Ar ions as a function of implantation temperature and dose rate has been conducted. The depth distribution of the disorder in the Ga sublattice has been measured by RBS/channeling spectrometry with a glancing angle detector geometry to provide enhanced depth resolution. Two disordered regions were identified in the damage depth distribution: a near-surface peak and a bulk damage peak. These regions exhibit different behavior as a function of implantation temperature. The height of the near-surface peak, as expected, decreased with implantation temperature approaching the magnitude of the unimplanted sample. The displaced atomic density in the bulk damage peak also followed this tendency and decreased in the temperature range from room temperature to 500°C. The implantation at higher temperatures resulted in an increase in the amount of damage, reaching a maximum at about 700°C and displayed a characteristic “reverse annealing” behavior. Further increase of the implantation temperature to 1000oC reduced the disorder. The influence of the dose rate and implantation temperature on the radiation damage accumulation is discussed.

Activation of aluminum implanted at high doses in 4H–SiC

We report an investigation of the electrical activation of aluminum implanted at high dose in 4H–SiC. We show that at reasonably high temperature implantation and annealing conditions, one activates about 37.5% of the implanted species. Of course, the final (concentration-dependent) activation ratio differs slightly from this average value but varies only between 0.5 and 0.25 when the targeted concentration increases from 3.33×1018 to 1021 cm−3. Provided a standard mobility can be maintained, this results in fairly low sheet resistance. The best (lowest) value obtained in this work is 15 mΩ cm at 700 K (95 mΩ cm at room temperature) for a 190-nm-thick layer implanted with 1021 atoms cm−3. In MESA-etched p–n junctions with a 100 μm diameter, this resulted in a typical on-resistance of 1.5 mΩ cm2, mainly limited by the substrate and n− epitaxial 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.

He-induced cavity formation in silicon upon high-temperature implantation

40 keV He + ions were implanted into (1 0 0) oriented Si single crystals to a fluence of 9 × 10 15 cm −2 at room-temperature or 350°C. The implantations were performed at both, random or 〈0 0 1〉 Si channel directions. The implantation damage and the in situ annealing effects during the He implantations were investigated by transmission electron microscopy (TEM), Rutherford backscattering/channeling spectrometry (RBS/C) and elastic recoil detection analysis (ERDA). Significant differences in the microstructure evolution between the 350°C and the room-temperature implanted and subsequently annealed at 350°C samples were observed. The results are discussed in terms of a distinct He bubble nucleation process.

High-Fluence Implantation of Erbium into Silicon-Germanium Alloys: Structural and Thermal Properties

AbstractHigh-quality crystalline Si1-xGex (x=0.10 and 0.25) alloys were implanted with 70 keV Er+ ions at temperatures of 350°C and 550°C to a fluence of 1015 cm−2. In-situ Rutherford backscattering/channeling (RBS) analysis supplemented with transmission electron microscopy (TEM) showed that as-implanted alloys were in form of ternary solid solutions with a peak Er concentration of 1 at.% without any trace of Er-Si or Er-Ge precipitation.In the samples implanted at 350°C Er atoms were found to be distributed randomly in the amorphous host matrix. Post-implantation annealing at different temperatures up to 600° showed that the solid phase epitaxial regrowth of the damaged layers strongly depends on both the Ge concentration in the alloys and the temperature of annealing. Along with the recrystallization of the damaged matrix, annealing was observed to induce simultaneous removal of nearly all the implanted Er as the recrystallization front progresses towards the surface.In contrast, high temperature implantation at 550°C led to spontaneous recovery of the alloy crystallinity and incorporation of considerable fraction of implanted Er atoms on regular tetrahedral interstitial sites in the host lattice.

Improvement of Oxidation-Resistance of γ-TiAl Alloy by High Temperature Nb and Al Ion Implantation

The Nb and Al ion implantation on a γ-TiAl based alloy of Ti-48Al-1.3Fe-1.1V-0.3B (at%) at different implantation temperatures of room temperature, 973 and 1173K were performed respectively, with the same dose of 3.0 × 10 21 ions/m 2 and the acceleration voltage of 50 kV. The influence of implantation temperature upon the element distribution in the modification layer and the isothermal oxidation behavior of Ti-48Al-1.3Fe-1.1V-0.3B (at%) at 1173 K for 349.2 ks in air were investigated. It is found that the thickness of the modification layer is significantly increased when the implantation temperature increased to 1173 K in the case of Nb implantation. As Al implantation temperature is raised, Al 2 O 3 is formed and the concentration of Al and Ti in the modification layer is strongly changed. The oxidation resistance of Nb and Al implanted alloys is enhanced as the implantation temperature increased and especially 1173 K Nb implanted alloy shows the best result. The improvement of the oxidation resistance of Nb implanted alloy is attributed to the outward diffusion of Al resulting in the formation of Al 2 O 3 in the oxidation scale and this chemical effect of Nb doping can be further enhanced by high temperature implantation. The formation of Al 2 O 3 in the modification layer during the process of high temperature Al implantation is the main reason for the lower mass gain of high temperature Al implanted alloy. In addition, the reduction of the lattice defect and the stability enhancement of the doping element stayed in modification layer of high temperature implanted alloy are also responsible for the improvement of the oxidation resistance.