Formation of high-conductivity NiSi2 layers on Si at zero-mismatch temperature by high-current Ni-ion implantation

2 and Si lattices at 380 °C, which was defined as zero-mismatch temperature. The implantation was conducted with a metal vapor vacuum arc (MEVVA) ion implanter at an extraction voltage of 45 kV. Based on a thermal conduction estimation, a temperature rise of 380 °C required the Ni-ion current density to be 35 μA/cm². For the Si(111) wafers, the high conducting NiSi₂ layers were indeed directly formed after Ni-ion implantation with this specific current density to a normal dose of 2×10¹⁷ ions/cm² and the resistivity was as low as 9 μΩ cm. For the Si(111) wafers pre-covered with a 10-nm Ni overlayer, the resistivity of the NiSi₂ layers obtained under the same conditions decreased down to about 6 μΩ cm. The superior electrical property of the NiSi₂ was thought to be related to its formation temperature, i.e. at a zero-mismatch temperature of 380 °C, which resulted in minimizing the stress and stress-induced defects involved in its formation as well as cooling process. Received: 27 April 1998 / Accepted: 26 October 1998     

Effects of Helium and Oxygen Common Implantation in Silicon Wafer

Defect engineering for SiO2 precipitation is investigated using He-ion implantation as the first stage of separation by implanted oxygen （SIMOX）. Cavities axe created in Si by implantation with helium ions. After thermal annealing at different temperatures, the sample is implanted with 120 keV 8.0 ×1016 cm 2 0 ions. The Q ion energy is chosen such that the peak of the concentration distribution is centred at the cavity band. For comparison, another sample is implanted with O ions alone. Cross-sectionM transmission electron microscopy （XTEM）, Fourier transform infrared absorbance spectrometry （FTIR） and atomic force microscopy （AFM） measurements are used to investigate the samples. The results show that a narrow nano-cavity layer is found to be excellent nucleation sites that effectively assisted SiO2 formation and released crystal lattice strain associated with silicon oxidation.     

Hydrogen implantation and diffusion in silicon and silicon dioxide

Depth profiles of hydrogen implanted into crystalline silicon in random direction at different fluences have been measured by the¹⁵N technique and by SIMS. Whereas hydrogen implanted at a fluence of 10¹⁵ ions/cm² shows some limited mobility, no such mobility is observed for higher implantation fluences. In these cases, ballistic computer codes describe the depth distributions well, within the ranges of both experimental and theoretical accuracy. Annealing up to 510 K does not change the hydrogen distributions.Furthermore, high-fluence hydrogen implantation into silicon dioxide has been examined. There is some indication for radiation-enhanced diffusion during the implantation process. Upon subsequent thermal annealing, the hydrogen is found to diffuse, probably via a trapping/detrapping mechanism associated with an OH/H₂ transformation of the hydrogen bonding.     

Doping mechanism of optical-damage-resistant ions in lithium niobate crystals

The doping mechanism of optical-damage-resistant ions (Mg²⁺, Zn²⁺, In³⁺, Sc³⁺, Hf⁴⁺, and Zr⁴⁺) in the lithium niobate crystallographic frame is quantitatively studied from the chemical bond viewpoint. Calculated results show that optical-damage-resistant ions have a strong interaction with the lithium niobate matrix, which is quantitatively evaluated by the deviation between normal and calculated valence states and the global instability index. All optical-damage-resistant ions first substitute Nb_Li and then Li ions, they change their dopant occupancies from Li to Nb sites at the same global instability index value 0.1055. On the basis of such a quantitative interaction, the doping mechanism of these ions is finally derived. Furthermore, a criterion in searching for new optical-damage-resistant ions is also proposed.     

Three-dimensional damage distributions of molecular ions implanted into silicon,as recorded by RBS/channeling combined with tomography

The depth distributions of damage of 1.4 MeV nitrogen molecular ions (N ₂ ⁺ ) implanted into Si crystals at doses slightly below the value for amorphization have been measured by means of standard RBS/channeling for different directions of impact. These damage distributions were fed into our modified tomographic program MO-TOR [1, 2], by which we could reconstruct the spatial distributions of nuclear energy transfer. These distributions are compared with the three-dimensional theoretical prediction of a modified TRIM code [3].It turns out that there exists a pronounced deviation from the purely ballistic damage distribution insofar as the reconstructed damage distribution is twice as broad in the lateral direction than predicted. This is essentially explained by deviations in flight geometry of molecular ions in comparison with single-atomic ones.     

Crystalline quality of 3C-SiC formed by high-fluence C-implanted Si

Carbon ions at 40 keV were implanted into (1 0 0) high-purity p-type silicon wafers at 400 °C to a fluence of 6.5 × 10¹⁷ ions/cm². Subsequent thermal annealing of the implanted samples was performed in a diffusion furnace at atmospheric pressure with inert nitrogen ambient at 1100 °C. Time-of-flight energy elastic recoil detection analysis (ToF-E ERDA) was used to investigate depth distributions of the implanted ions. Infrared transmittance (IR) and Raman scattering measurements were used to characterize the formation of SiC in the implanted Si substrate. X-ray diffraction analysis (XRD) was used to characterize the crystalline quality in the surface layer of the sample. The formation of 3C-SiC and its crystalline structure obtained from the above mentioned techniques was finally confirmed by transmission electron microscopy (TEM). The results show that 3C-SiC is directly formed during implantation, and that the subsequent high-temperature annealing enhances the quality of the poly-crystalline SiC.     

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.     

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     

Nitrogen implantation in GaAs1−xPx (x=0.4; 0.65)

Nitrogen ions were implanted in GaAs_1−xP_x (x=0.4; 0.65) at room temperature at various doses from 5×10¹² cm⁻² to 5×10¹⁵ cm⁻² and annealed at temperatures from 600°C up to 950°C using a sputtered SiO₂ encapsulation to investigate the possibility of creating isoelectronic traps by ion implantation. Photoluminescence and channeling measurements were performed to characterize implanted layers. The effects of damage induced by optically inactive neon ion implantation on photoluminescence spectrum were also investigated. By channeling measurements it was found that damage induced by nitrogen implantation is removed by annealing at 800°C. A nitrogen induced emission intensity comparable to the intensity of band gap emission for unimplanted material was observed for implanted GaAs_0.6P_0.4 after annealing at 850°C, while an enhancement of the emission intensity by a factor of 180 as compared with an unimplanted material was observed for implanted GaAs_0.35P_0.65 after annealing at 950°C. An anomalous diffusion of nitrogen atoms was found for implanted GaAs_0.6P_0.4 after annealing at and above 900°C.     

Preparation, structure, and properties of metal nanocomposites in lithium niobate

Crystals of lithium niobate LiNbO₃ are implanted with 60-keV Cu^? ions at different ion fluxes to a fluence of 2 × 10¹⁷ ions/cm². The structure and the linear and nonlinear optical properties of the implanted layers are investigated. The optical transmission and ion-induced photon spectra of the LiNbO₃ crystals are measured in the course of implantation. It is revealed that the implantation brings about the formation of complex nanocomposites consisting of metallic copper nanoparticles and nanodomains of the matrix. The distributions of nanoparticles and nanodomains in the implanted layers do not correlate with each other. It is shown that the variations in the linear and nonlinear optical absorption of the nanocomposites are predominantly determined by the changes in the chemical composition and the structure of the matrix.     

Carrier removal by implanted IONS in GaAs

Abstract

A model for calculation of the range distribution of energetic ions with taking into account the channeling effect is proposed. The measurement of the depth distributions of boron ions in silicon crystals implanted at 13.6 and 91 MeV revealed significant difference between the measured and the calculated range profiles when the channeling effects have not been included in the calculation. In spite of deminishing the critical angles of channeling with growing ion energy the probability of the capture of ions into the channeling regime is significant in case of high energy implantation even when the incident angles are 7–10° off the main crystallographic directions.     

The excitation mechanism of rare-earth ions in silicon nanocrystals

A detailed investigation on the excitation mechanisms of rare-earth (RE) ions introduced in Si nanocrystals (nc) is reported. Silicon nanocrystals were produced by high-dose 80-keV Si implantation in thermally grown SiO₂ followed by 1100 °C annealing for 1 h. Subsequently some of the samples were implanted by 300-keV Er, Yb, Nd, or Tm at doses in the range 2×10¹²–3×10¹⁵ /cm². The energy was chosen in such a way to locate the RE ions at the same depth where nanocrystals are. Finally an annealing at 900 °C for 5 min was performed in order to eliminate the implantation damage. These samples show intense room-temperature luminescence due to internal 4f shell transitions within the RE ions. For instance, luminescence at 1.54 μm and 0.98 μm is observed in Er-doped nc, at 0.98 μm in Yb-doped nc, at 0.92 μm in nc and two lines at 0.78 μm and 1.65 μm in Tm-doped nc. Furthermore, these signals are much more intense than those observed when RE ions are introduced in pure SiO₂ in the absence of nanocrystals, demonstrating the important role of nanocrystals in efficiently exciting the REs. It is shown that the intense nc-related luminescence at around 0.85 μm decreases with increasing RE concentration and the energy is preferentially transferred from excitons in the nc to the RE ions which, subsequently, emit radiatively. The exact mechanism of energy transfer has been studied in detail by excitation spectroscopy measurements and time-resolved photoluminescence. On the basis of the obtained results a plausible phenomenological model for the energy transfer mechanism emerges. The pumping laser generates excitons within the Si nanocrystals. Excitons confined in the nc can either give their energy to an intrinsic luminescent center emitting at around 0.85 μm nor pass this energy to the RE 4f shell, thus exciting the ion. The shape of the luminescence spectra suggests that excited rare-earth ions are not incorporated within the nanocrystals and the energy is transferred at a distance while they are embedded within SiO₂. Rare-earth excitation can quantitatively be described by an effective cross section σ_eff taking into account all the intermediate steps leading to excitation. We have directly measured σ_eff for Er in Si nc obtaining a value of ≈2×10⁻¹⁷ cm². This value is much higher than the cross section for excitation through direct photon absorption (8×10⁻²¹ cm²) demonstrating that this process is extremely efficient. Furthermore, the non-radiative decay processes typically limiting rare-earth luminescence in Si (namely back-transfer and Auger) are demonstrated to be absent in Si nc further improving the overall efficiency of the process. These data are reported and their implications. Received: 9 April 1999 / Accepted: 10 April 1999 / Published online: 2 June 1999     

Ion implantation inducing nanovoids characterized by TEM and STEM

The evolution of nanoparticles in sequentially ion-implanted Ag and Ag/Cu into silica glasses has been studied. The doses for implantation (×10¹⁶ ions/cm²) were 5Ag, 5Ag/5Cu and 5Ag/15Cu. Ag nanoclusters have been formed in the implanted 5Ag specimen. In the implanted 5Ag/5Cu specimen, some formed nanoclusters have brighter center features. With an increase of Cu ions dose, the nanoclusters with brighter center features become prevalent. The microstructural properties of the nanoparticles are characterized by transmission electron microscopy. Scanning transmission electron microscope high-angle annular dark field and high-resolution transmission electron microscopy are also utilized to study the formed nanoparticles. The results show that nanovoids have been induced into metal nanoparticles during the ion implanting process, not the core-shell nanoparticles as other workers believed. The nanovoids can be the aggregation of vacancies induced by irradiation.     

Characteristics of laser-produced Ge ion fluxes used for modification of semiconductor materials

This paper describes the laser generation of Ge ion fluxes and their application to the modification of semiconductor materials by ion implantation. The Ge ions were produced by ablating solid targets using the PALS high-power iodine laser system at the PALS Research Centre in Prague, operating at its third harmonic frequency (438 nm wavelength) and producing 0.4 ns pulses with energy up to 0.25 kJ (intensity≤10¹⁵ W/cm²). The goal of these investigations was optimisation of the implantation of low and medium energy laser-generated Ge ion fluxes and they were carried out as part of the project PALS000929. Recently, a new repetitive pulse laser system at IPPLM in Warsaw, with a wavelength of 1.06 μm, energy of ～0.8 J in a 3.5 ns-pulse, repetition rate of up to 10 Hz, and intensity on target of up to 10¹¹ W/cm², has also been employed to produce Ge ions by irradiating solid targets. The laser-generated ions were investigated with diagnostics based on the time-of-flight method: various ion collectors and an electrostatic ion-energy analyzer. The Ge ion fluxes were implanted into Si and SiO₂ substrates located at distances of 10–30 cm from the target. The SiO₂ films were prepared on single crystal Si substrates and were implanted with Ge ions with different properties. The properties of the Ge-implanted layers, in particular, the depth distributions of implanted Ge ions, were characterised using Rutherford backscattering and other material surface diagnostic methods.     

Interaction of high-power laser pulses with glasses containing implanted metallic nanoparticles

Sodium calcium silicate glasses with Ag⁺ implanted ions are studied. The ion implantation conditions are as follows: the energy is 60 keV, the dose is 7×10¹⁶ cm⁻², and the ion current density is 10 μA/cm². Ion implantation provides the formation of a composite layer that incorporates silver nanoparticles in the surface region of glass. The size distribution of nanoparticles over the depth in the composite layer is strongly nonuniform. The effect of a high-power pulsed excimer laser on the composite layer is investigated. It is found that, under laser irradiation, the size of silver nanoparticles in the implanted layer decreases but the size distribution of nanoparticles over the depth remains nonuniform, even though it becomes slightly narrower compared to that observed prior to irradiation. The experimental results are interpreted in terms of the effects of the melting of glass and metallic particles on a nanosecond scale. __________ Translated from Fizika Tverdogo Tela, Vol. 43, No. 11, 2001, pp. 2100–2106. Original Russian Text Copyright ? 2001 by Stepanov, Popok, Hole, Bukharaev.     

Peculiarities of heavy ion channeling

Abstract

Depth distributions of implanted Mg⁺- and Ca⁺-ions and the corresponding radiation damage were studied for different channeling orientations of silicon crystals. The shape of the implantation profiles is discussed by using simple models for dechanneling and energy loss processes. A correlation between dechanneling, damage production and depth distributions of the channeled ions could be observed. This correlation is seen by the maxima shifts in damage and implanted ion distributions between channel and random incidence.     

Optical properties of ZnO and Al2O3 implanted with silver ions

ZnO and Al₂O₃ samples implanted with 30-keV silver ions with fluences in the interval (0.25–1.00) × 10¹⁷ ions/cm² are studied by the method of optical photometry in the visible part of the spectrum. The optical transmission spectra of the implanted samples exhibit a selective band associated with surface plasmon resonance absorption of silver nanoparticles. The intensity of this band nonmonotonically depends on the implantation fluence. The silver ion depth distribution in the samples is calculated. It is shown that the non-monotonicity observed in experiments is due to an increase in the substrate sputtering ratio with increasing implantation fluence. It is found that vacuum thermal annealing of the implanted Al₂O₃ layers up to 700°C causes a considerable narrowing of the plasmon absorption bandwidth without a tangible change in its intensity. At higher annealing temperatures, the plasmon absorption band broadens and its intensity drops. Annealing of the ZnO films under such conditions causes their complete vaporization.     

Optical study of implantation damage recovery from Si-implanted GaN

Comprehensive and systematic optical activation studies of Si-implanted GaN grown on sapphire substrates have been made as a function of ion dose and anneal temperature. Silicon ions were implanted at 200 keV with doses ranging from 1×10¹³ to 5×10¹⁵ cm⁻² at room temperature. The samples were proximity cap annealed from 1250 to 1350 °C with a 500-Å-thick AlN cap in a nitrogen environment. The results of photoluminescence measurements made at 3 K show a very sharp neutral-donor-bound exciton peak along with a sharp donor-acceptor pair peak after annealing at 1350 °C for 20 s, indicating excellent implantation damage recovery. The results also indicate the AlN cap protected the implanted GaN layer very well during high temperature annealing without creating any significant anneal-induced damage. This observation is consistent with the electrical activation results for these samples.     

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     

Determination of migration of ion-implanted Ar and Zn in silica by backscattering spectrometry

It is well known that the refractive indices of lots of materials can be modified by ion implantation, which is important for waveguide fabrication. In this work the effect of Ar and Zn ion implantation on silica layers was investigated by Rutherford Backscattering Spectrometry (RBS) and Spectroscopic Ellipsometry (SE). Silica layers produced by chemical vapour deposition technique on single crystal silicon wafers were implanted by Ar and Zn ions with a fluence of 1–2?×10¹⁶ Ar/cm² and 2.5?×10¹⁶ Zn/cm², respectively. The refractive indices of the implanted silica layers before and after annealing at 300°C and 600°C were determined by SE. The migration of the implanted element was studied by real-time RBS up to 500°C. It was found that the implanted Ar escapes from the sample at 300°C. Although the refractive indices of the Ar-implanted silica layers were increased compared to the as-grown samples, after the annealing this increase in the refractive indices vanished. In case of the Zn-implanted silica layer both the distribution of the Zn and the change in the refractive indices were found to be stable. Zn implantation seems to be an ideal choice for producing waveguides.