Implanted Si Substrate Research Articles

Formation of Fe-Co-Si Structure in Fe and Co Implanted Si Substrate

ABSTRACTTernary Fe-Co-Si B20 phase structure was formed by implanting Fe and Co ions consecutively into Si(100) substrate at 50 keV energy, each with a fluence of 1.0 × 1017 atoms/cm2 and post-thermal vacuum annealing at 500 oC for 60 minutes. An in-situ magnetic field was used to enhance the formation of the ternary phase in the Si substrate during the implantation process. The magnetic field of 0.05 T was applied perpendicular to the incoming ion beam direction and parallel to the substrate surface to form elongated clusters in the transverse direction of the sample. Prior to the implantation of ions, the implant ions depth profiles were simulated using a dynamic ion-solid interaction code (TRIDYN). The TRIDYN simulation predicted a saturation in the peak concentration of the Fe and Co ions at a fluence of 1.0 × 1017 atoms/cm2. XPS measurement at the peak concentration depth (40 nm) showed the presence of Fe (23 %) and Co (32 %) in the Si matrix. XRD characterization confirmed the presence of stable Fe-Co-Si B20 phase structure in the annealed samples implanted with the in-situ magnetic field.

Study on ion implantation conditions in fabricating compressively strained Si/relaxed Si1−xCx heterostructures using the defect control by ion implantation technique

The influence of ion implantation energies on compressively strained Si/relaxed Si1−xCx heterostructures formed on Ar ion implanted Si substrates was investigated. It was found that relaxation ratio can be enhanced over 100% at relatively low implantation energies, and compressive strain in the topmost Si layer is maximized at 45keV due to large lattice mismatch. Cross-sectional transmission electron microscope images revealed that defects are localized around the hetero-interface between the Si1−xCx layer and the Ar+-implanted Si substrate when the implantation energy is 45keV, which decreases the amount of defects in the topmost Si layer and the upper part of the Si1−xCx buffer layer.

Study of the electrical behavior in Intermediate Band-Si junctions

ABSTRACTIn this study we analyze the electrical behavior of a junction formed by an ultraheavily Ti implanted Si layer processed by a Pulsed Laser Melting (PLM) and the non implanted Si substrate. This electrical behavior exhibits an electrical decoupling effect in this bilayer that we have associated to an Intermediate Band (IB) formation in the Ti supersaturated Si layer. Time-of-flight secondary ion mass spectrometry (ToF-SIMS) measurements show a Ti depth profile with concentrations well above the theoretical limit required to the IB formation. Sheet resistance and Hall mobility measurements in the van der Pauw configuration of these bilayers exhibit a clear dependence with the different measurement currents introduced (1µA-1mA). We find that the electrical transport properties measured present an electrical decoupling effect in the bilayer as function of the temperature. The dependence of this effect with the injected current could be explained in terms of an additional current flow in the junction from the substrate to the IB layer and in terms of the voltage dependence in the junction with the measurement current.

Nanoparticle process formation in zinc implanted silicon with followed thermal annealing

Results of temperature treatment effect on near surface layer properties of Zn ion implanted Si substrate are presented. Radiation induced point defects and Zn in depth profile was studied by Rutherford back scattering (RBS) method with use of channeling technique. Topology of substrate surface was studied by atomic force microscopy (AFM) and scaning electron microscope (SEM). Phase composition of samples was test by x-ray diffraction in grazing geometry.

Ferromagnetic Behavior of Fe+ Implanted Si(100) Semiconductor

Fe ions have been implanted into Si (100) single crystals using ion implantation technique. The Fe ions have been accelerated to 45 keV with a dose of 5×1017 ion/cm2 at room temperature. The ions have been sent to the substrate’s surface at normal incidence. The temperature dependence of magnetization measurement was explored at the temperature range of 10–300 K. The implanted Si substrate was studied with Ferromagnetic Resonance (FMR) technique and Vibrating Sample Magnetometer (VSM). The FMR spectra were recorded by applying external magnetic field in different experimental geometries. FMR spectra were analyzed and the magnetic properties, which are the g-factor, effective magnetization and uniaxial anisotropy parameter, were estimated by simulation of the experimental data. The sample showed two-fold magnetic anisotropic symmetry. By fitting the Si-2p region obtained through XPS measurements it is observed that Fe and Fe compounds are present in the material.

Improvement of Thermal Stability of Ni-Silicide Using Vacuum Annealing on Boron Cluster Implanted Ultra Shallow Source/Drain for Nano-Scale CMOSFETs

In this paper, Ni silicide is formed on boron cluster (B 18 H 22 ) implanted source/drains for shallow junctions of nano-scale CMOSFETs and its thermal stability is improved, using vacuum annealing. Although Ni silicide on B 18 H 22 implanted Si substrate exhibited greater sheet resistance than on the BF2 implanted one, its thermal stability was greatly improved using vacuum annealing. Moreover, the boron depth profile, using vacuum post-silicidation annealing, showed a shallower junction than that using N₂ annealing.

Metrology for Implanted Si Substrate Loss Studies

A spectroscopic ellipsometry (SE) model was developed and implemented to study substrate loss in shallow implanted silicon (i-Si) substrates following a photoresist strip. The model is based on different optical properties of silicon dioxide and i-Si layers and silicon substrates and is used to characterize relevant layers, i-Si and , before and after plasma treatment. An increase in and a decrease in the i-Si layer were observed after plasma exposure. Changes in the i-Si layer are the result of two phenomena, oxidation and heating-induced regrowth of the i-Si layer, while changes in the thickness represent the direct measure of substrate loss due to oxidation. Transmission electron microscopy (TEM) and secondary-ion mass spectrometry (SIMS) analysis were performed to cross-check the validity and accuracy of the SE model. The TEM results confirm that the SE model can distinguish between a crystalline (c-Si) substrate and an i-Si layer regardless if the i-Si is damaged, crystalline, or amorphized. There is also good consistency between the SE and SIMS results. For the plasma processes studied in this work, minimal changes in layer thicknesses and substrate losses measured by SE agree very well with the measured SIMS dopant profiles.

The Formation of p-Type ZnO Films by Thermal Diffusion from the Low Energy, High Dose Phosphorus-Implanted Si Substrate

The p-type ZnO film is obtained out of thermal diffusion of phosphorus (P) atoms from the low energy, high dose implanted Si substrate through rapid thermal annealing (RTA). Many nonactivated P atoms exist on the surface of the shallow-implanted Si substrate and easily out-diffuse into the ZnO films at lower RTA temperatures. The concentration of the p-type ZnO reached . The p-ZnO/n-Si heterojunction was fabricated using the one-step RTA process. This method offers various choices of dopants with low energy, high dose implanting into silicon without considering the restriction of the substrate.

Metrology for Implanted Si Substrate and Dopant Loss Studies

Spectroscopic ellipsometry (SE) model was developed to study substrate loss of shallow implanted silicon substrate following photoresist strip. Model is based on different optical properties of silicon oxide (SiO2) and implanted silicon (i-Si) layers and silicon substrate, and is used to characterize relevant layers, i-Si and SiO2, before and after plasma treatment. The increase in SiO2 and decrease in i-Si layer was observed after plasma exposure. Changes in i-Si layer are the result of two phenomena, oxidation and heating induced re-growth of i-Si layer, while changes in SiO2 thickness represent direct measure of substrate loss due to oxidation. Good agreement between TEM and SE measurements confirms that SE model can distinguish between crystalline (c-Si) substrate and i-Si, regardless if i-Si is only damaged, d-Si (crystalline) or amorphized, a-Si after implantation. We have also found consistency in SIMS dopant profiles and substrate losses extracted from SE measurements for plasma processes studied.

Metrology for Implanted Si Substrate and Dopant Loss Studies

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Formation of SiC using low energy CO 2 ion implantation in silicon

Carbon dioxide ions with 29 keV energy were implanted into (4 0 0) high-purity p-type silicon wafers at nearly room temperature and doses in the range between 1 × 10 16 and 3 × 10 18 ions/cm 2. X-ray diffraction analysis (XRD) was used to characterize the formation of SiC in implanted Si substrate. The formation of SiC and its crystalline structure obtained from above mentioned technique. Topographical changes induced on silicon surface, grains and evaluation of them at different doses observed by atomic force microscopy (AFM). Infrared reflectance (IR) and Raman scattering measurements were used to reconfirm the formation of SiC in implanted Si substrate. The electrical properties of implanted samples measured by four point probe technique. The results show that implantation of carbon dioxide ions directly leads to formation of 15R-SiC. By increasing the implantation dose a significant changes were also observed on roughness and sheet resistivity properties.

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 × 10 17 ions/cm 2. 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.

Characterization of the crystalline quality of β-SiC formed by ion beam synthesis

The ion beam synthesis (IBS) technique is applied to form crystalline silicon carbide (SiC) for future optoelectronics applications. Carbon ions at 80 and 40keV were implanted into (100) high-purity p-type silicon wafers at room temperature and 400°C, respectively, to doses in excess of 1017ions/cm2. Subsequent thermal annealing of the implanted samples was performed in a vacuum furnace at temperatures of 800, 900 and 1000°C, respectively. Elastic recoil detection analysis was used to investigate depth distributions of the implanted ions and infrared transmittance (IR) measurement was used to characterize formation of SiC in the implanted Si substrate. Complementary to IR, Raman scattering measurements were also carried out. Levels of the residual damage distribution of the samples annealed at different temperatures were compared with that of the as-implanted one by Rutherford backscattering spectrometry (RBS) in the channeling mode. The results show that C-ion implantation at the elevated temperature, followed by high-temperature annealing, enhances the synthesis of crystalline SiC.

Nanogap Capacitors Used for Impedance Characterization of Living Cells

ABSTRACTNano-gap metal oxide semiconductor (MOS) capacitors were studied to evaluate their limitations in applications of dielectric spectroscopy in living cells. The purpose was to optimize the design of a transducer to avoid interfacial polarization at the electrodes. Silicon IC technology was selected for designing processes in which we could limit electric double layer impedance by precisely controlling dielectric thickness of the capacitors in the range of 17 to 150 nm. The working capacitance was defined by lateral oxide etching of capacitor structures of various configuration to ensure high perimeter to area ratio. Highly doped n+ polysilicon and n+ implanted Si substrate were acting as capacitor's electrodes. Restrictions known from CMOS circuits regarding oxide leakage current, which depends on geometry and increases with the gate area were taken into account. To allow for testing cells (yeasts), which have larger dimensions than nano structures it was necessary to include cell manipulation using dielectrophoresis (DEP). Entrapment of cells at the electrode perimeter preceded electrical measurements. Our focus in analyses was on the frequency dependence of impedance parameters.

Ion Beam Synthesis of Silicon Carbide

Formation and crystallization of a thin near-surface layer of silicon carbide on a silicon substrate, created by ion-beam synthesis (IBS), are discussed. 80 and 40 keV carbon ions were implanted into a (1 0 0) high-purity p-type silicon substrate at room temperature and 400 oC, respectively, using doses in excess of 1017 ions/cm2. Elastic recoil detection analysis (ERDA) technique, developed for routine atomic depth profiling at the Angstrom laboratory, Uppsala University, Sweden, was used to investigate the depth distributions of implanted-ions. Infrared transmittance measurement was used as an indication of SiC in the implanted Si substrate. For the samples implanted at high temperature, the results show the existence of a peak at 797 cm-1, indicating the presence of β-SiC, already directly formed during the implantation without postimplantation annealing. While for the samples implanted at room temperature, starting with the band of amorphous Si-C network, the crystalline SiC appears at the annealing temperature as low as 900 oC. In both cases, during further annealing in vacuum, the peak grows in height and narrows in width (according to the measured FWHM) with increasing annealing temperature, indicating a further growth of the SiC layer. However, for thermal annealing at 1000 oC in a vacuum furnace the SiC crystallization was not completed and crystal imperfection where still present. Complementary to IR, Raman scattering measurements were performed. Although no direct evidence of SiC vibrations were observed, the appearance and disappearance of both Si-Si and C-C related bands points out to the formation of silicon and carbon clusters in the implanted layer.

Elemental depth profiling of a-Si1−xGex:H films by elastic recoil detection analysis and secondary ion mass spectrometry

Abstract The hydrogen content in a-Si1−xGex:H thin films is an important factor deciding the density and the optical band gap. We measured the elemental depth profiles of hydrogen together with Si and Ge by elastic recoil detection analysis (ERDA) combined with Rutherford backscattering (RBS) using MeV He2+ ions. In order to determine the hydrogen depth profiles precisely, the energy- and angle-dependent recoil cross-sections were measured in advance for the standard sample of a CH3+-implanted Si substrate. The cross-sections obtained here are reproduced well by a simple expression based on the partial wave analysis assuming a square well potential (width: r0 = 2.67 × 10−13 cm, depth: V0 = −36.9 MeV) within 1%. For the a-Si1−xGex:H films whose elemental compositions were determined by ERDA/RBS, we measured the secondary ions yields of HCs2+, SiCs2+, H−, Si− and Ge− as a function of Ge concentration x. As a result, it is found that the useful yield ratios of HCs2+/SiCs2+, H−/Si− and Ge−/Si− are almost constant and thus the elemental depth profiles of the a-Si1−xGex:H films can be also determined by secondary ion mass spectrometry (SIMS) within 10% free from a matrix effect.

Formation of thin SiGe virtual substrates by ion implantation into Si substrates

Almost fully relaxed thin SiGe buffer layers are obtained by Ar ion implantation into Si substrates before SiGe molecular beam epitaxy (MBE) growth. The strain relaxation ratio of the 100 nm thick Si 0.65Ge 0.35 layer grown on ion implanted Si substrate is about 95%, while it is only 60% in the unimplanted case. Surface morphology of the buffer layer on the implanted Si is very different from that of the conventional buffer, suggesting that a new strain relaxation mechanism takes place in the SiGe film grown on the ion implanted Si.

Microstructural study of annealed Cr/Si system using cross-sectional TEM combined with nano-analysis

Among the various characterization methods generally used in the study of silicidation mechanisms, particularly interfaces structure, the cross-sectional transmission electron microscopy (XTEM) combined with nano-analysis were not much used. This work dealt with the study, by mean of this method, of interfacial atomic diffusion phenomena in thin Cr/Si system in dependence on heat treatment conditions. The chromium film of 850 Å thickness was electron gun deposited onto (111) oriented phosphorus implanted Si substrate. The XTEM observations of samples annealed at 475 °C during 60 and 120 min showed that the chromium was partially consumed in opposite to the case where the Si substrate was not implanted. The thickness of formed chromium silicide was practically the same for 60 and 120 min. Nano-analysis revealed the presence of Si atoms at the surface and Cr atoms into the substrate leading to the formation of a crystalline Cr–Si alloy. However, after 500 °C during 5 min the obtained results showed that no reaction occurred between Si and Cr and Si atoms were present in the Cr film. This indicated that Si diffused towards the surface before silicidation.

Effects of local facet and lattice damage on nucleation of diamond grown by microwave plasma chemical vapor deposition

Diamond deposition on an anisotropic etched Si and ion implanted Si surfaces have been examined here for the first time. Local facets on an anisotropic etched surface shows no nucleation of diamond. Synthetic diamond, in contrast, has been able to nucleate on an As+ or Si+ ion implanted Si substrate without diamond abrasive pretreatment. Selective deposition of diamond occurs only for low dose ion implantation, 100 keV 1014 cm−2, but not for high dose ion implantation, 100 KeV 1016 cm−2. Strain is proposed as the main reason for nucleation of diamond on the ion implanted Si substrates.

AC Photovoltaic Inspection of P-N Junctions having High Leakage Current

AbstractA focused photon beam chopped at 2 kHz scans p-n junctions in a p-type Si wafer and ac photovoltages are capacitively measured in order to inspect homogeneities of the junctions. It is found that the ac photovoltages are high not only in the junction areas but also in the field oxide regions around the junctions when the junctions are leaky. This indicates that dense positively charged traps exist at the interface between the heavily boron implanted Si substrate and the field oxide layer around the high leakage junction, and that the traps cause the increase in both the junction leakage current and the ac photovoltage.