Ion-implanted Region Research Articles

Comparison of single Shockley-type stacking fault expansion rates in 4H-SiC under ultraviolet illumination after hydrogen or fluorine ion implantation

The expansion of single Shockley-type stacking faults (1SSFs) was observed in 4H-SiC below the ion-implanted region of hydrogen or fluorine under ultraviolet illumination, and it was found that 1SSF expansion slowed, the expansion angle decreased, and the termination of 1SSF expansion became deeper as the dose of implanted ions was increased. A comparison of implanted ion species revealed that fluorine ion implantation more strongly suppresses 1SSF expansion under ultraviolet illumination than hydrogen ion implantation. The thermal stability of hydrogen and fluorine was also compared by using depth profiles of the implanted species concentrations before and after annealing. Fluorine was found to have superior thermal stability to that of hydrogen.

Cavity Mode-Matching InGaN Aperture-Emitting Device with a Nanoporous GaN Reflector via Ion Implantation

Cavity mode-matching InGaN resonant-cavity light-emitting diodes (RC-LEDs) with aperture size-dependent emission have been demonstrated through nitrogen ion (N+) implantation and electrochemical wet etching processes. The RC-LED structure consisted of 570 nm-depth ion-implanted regions and an embedded 17-pair nanoporous-GaN/n-GaN distributed Bragg reflector (DBR) outside the aperture, while there existed a full 20-pair DBR structure within the aperture regions. Shorter and mode-matching cavity lengths were fabricated, confirmed by transmission electron microscopy and angle-resolved photoluminescence spectra inside the aperture area without subjecting to the N+ implantation. By reducing the aperture sizes, higher current density and narrower far-field electroluminescence emission patterns were observed in the RC-LED with an aperture size of 40 μm-diameter. These results demonstrate that the cavity mode-matching RC-LEDs with optical/electrical confinements and controllable cavity length mismatch features can be applied in a wide range of optoelectronic-based device applications.

Physical mechanism of field modulation effects in ion implanted edge termination of vertical GaN Schottky barrier diodes

In this study, the physical properties of F ion-implanted GaN were thoroughly studied, and the related electric-field modulation mechanisms in ion-implanted edge termination were revealed. Transmission electron microscopy results indicate that the ion-implanted region maintains a single-crystal structure even with the implantation of high-energy F ions, indicating that the high resistivity of the edge termination region is not induced by amorphization. Alternately, ion implantation-induced deep levels could compensate the electrons and lead to a highly resistive layer. In addition to the bulk effect, the direct bombardment of high-energy F ions resulted in a rough and nitrogen-deficient surface, which was confirmed via atomic force microscopy (AFM) and X-ray photoelectron spectroscopy. The implanted surface with a large density of nitrogen vacancies can accommodate electrons, and it is more conductive than the bulk in the implanted region, which is validated via spreading resistance profiling and conductive AFM measurements. Under reverse bias, the implanted surface can spread the potential in the lateral direction, whereas the acceptor traps capture electrons acting as space charges, shifting the peak electric field into the bulk region in the vertical direction. As a result, the Schottky barrier diode terminated with high-energy F ion-implanted regions exhibits a breakdown voltage of over 1.2 kV.

Ion-beam synthesis of InSb nanocrystals at the Si/SiO2 interface

The formation of InSb nanocrystals at the bonding Si/SiO2 interface of silicon-on-insulator structure was obtained as a result of the In and Sb atom diffusion from the ion-implanted SiO2 and Si regions, respectively, toward the interface. After the annealing at 1000 °C, the Raman scattering peaks corresponding to the transverse and longitudinal optical phonon mode in the monocrystalline InSb matrix were obtained. As the annealing temperature grew to 1100 °C, the transverse optical phonon mode vanished and the longitudinal optical phonon mode dominated in the spectrum. This effect is explained by matching InSb and Si lattice constants under ion-beam synthesis conditions.

Proximity gettering design of silicon wafers using silicon hydride and hydrocarbon mixture molecular ion implantation technique

We developed a novel hybrid-molecular-ion-implantation technique for proximity gettering to reduce the carbon dose. In this molecular-ion-implantation technique, a molecular ion beam with a mixture of silicon hydride and hydrocarbon-molecular-ions is used. We found that 150 nm silicon {111} extrinsic Frank-type dislocation loops in the ion-implanted region are formed by this technique after epitaxial growth. Nickel and copper gettering test results showed that the ion-implanted region can getter Ni and Cu contaminants that diffused from the wafer surface at a carbon dose lower than those in hydrocarbon-molecular-ion-implanted wafers. We determined by energy dispersive x-ray (EDX) observation that end of range defects (EOR) act as gettering sites. We speculate two types of gettering induced by this technique: the relaxation-type gettering caused by EOR defects and the segregation-type gettering caused by the high concentration of carbon around EOR defects.

(Invited) Plasma Immersion Ion Implantation: Technology, Modelling, and Applications for Nanofabrication and 2D Materials

Plasma Immersion Ion Implantation (PIII) is an ion implantation technology in which the target to be implanted (i.e. a semiconductor wafer) is immersed in a plasma, and implanted with positive ions by the application of a high-voltage negative-bias pulse to the target. Because of the high plasma density achievable in modern plasma sources, large fluences can be implanted across large wafer areas, without beam scanning. PIII is well suited for a variety of nanofabrication applications. Because of its compatibility with ordinary silicon CMOS device processing, high fluence PIII is a versatile method for in situ fabrication of nanocrystals for integrated circuit applications. This talk will review the physics of energetic ions implanted into solid materials, and illustrate how post-implant thermal treatment can be used to form nanocrystals in the ion-implanted region. A number of potential applications of PIII as a materials synthesis technique will be discussed.

Effect of Sequential Helium and Nickel Ion Implantation on the Nano-Indentation Hardness of X750 Alloy

Abstract Sequential He+ and Ni+ implantations were performed to investigate their combined effect on the indentation hardness of heat-treated X750 alloy. The microstructure of the ion-implanted region was also characterized with transmission electron microscope (TEM). The X750 alloy displayed a pronounced softening with very low Ni+ implantation levels, ψ = 0.01–1.0 dpa, however it showed a clear increase in hardness when implanted with He+ up to CHe = 5000 appm. Samples subjected to sequential He+ and Ni+ implantations displayed hardness values between those presented by sole He+ or Ni+ implantation suggesting that the effects of ion-induced microstructural damage and helium accumulation on the hardness of this alloy can be considered as independent and additive over the range of conditions studied. This observation is in contradiction to previously reported TEM-based studies, which suggest that accumulated helium slows the dissolution/disordering of the γ′ hardening phase in this alloy. In our study, established theories were applied to assess the contribution of ion-induced defect clustering, γ′ precipitate disordering, and helium bubble accumulation to the hardness of the X750 alloy. It was observed that generation of ion-induced defect clusters and the formation of helium bubbles increased the indentation hardness slightly while the disordering of γ′ precipitates resulted in a dramatic decrease in the total hardness. Ni+ and He+ implantation also had different effects on the depth dependence of the indentation hardness indentation size effect (ISE). The ISE was pronounced in the samples subjected to only Ni+ implantation while it was almost absent in samples subjected to only He+ implantation.

Effects of arsenic implantation and rapid thermal annealing on ZnO nanorods for p-type doping

Ion implantation is a useful method of fabricating p-type zinc oxide (ZnO) nanorods; however, it typically causes structural defects in the substrate material. Rapid thermal annealing (RTA) is a well-known annealing process in the semiconductor industry used to restore lattice defects, and it has the advantage of a fast processing time. Herein, we report on the effects of arsenic (As) implantation and RTA on ZnO nanorods for p-type doping. As+ ions were implanted using a mid-current ion implanter. A long-duration RTA of over 10 min that was used to activate the implanted As+ ions and recover the destroyed ZnO lattice changed the morphology of the As+-ion-implanted regions. The structural recovery after RTA at over 750 °C for 1 min was significant. In the low-temperature photoluminescence spectra, a new acceptor-bound exciton emission (A°X) peak associated with the As acceptor was observed. When RTA was conducted at 950 °C, p-type behavior of the As-doped ZnO nanorods could be observed, and the hole concentration was determined to be 6.311 × 1016 cm−3. This result indicates that the implanted As+ ions were activated as p-type dopants for 1 min.

Corrosion Behavior and Mechanism of Carbon Ion-Implanted Magnesium Alloy

Carbon ion implantation was conducted on an AM60 magnesium alloy with fluences between 1 × 1016 and 6 × 1016 ions/cm2 and an energy of 35 keV. The microstructure and electrochemical properties of the samples were systematically characterized by X-ray photoelectron spectroscopy, X-ray diffraction, Raman scattering, scanning electron microscopy, transmission electron microscopy, and electrochemical methods. These studies reveal that a 250 nm-thick C-rich layer is formed on the surface and the Mg2C3 phase embeds in the ion-implanted region. The crystal structure of the Mg2C3 was constructed, and an electronic density map was calculated by density-functional theory calculation. The large peak in the density of states (DOS) shows two atomic p orbitals for Mg2C3. The main electron energy is concentrated between −50 and −40 eV, and the electron energy mainly comes from Mg (p) and Mg (s). The electrochemical experiments reveal that the Ecorr is −1.35 V and Icorr is 20.1 μA/cm2 for the sample implanted with the optimal fluence of 6 × 1016 ions/cm2. The sample from C ion implantation gives rise to better corrosion resistance.

Proximity gettering technique using CH3O multielement molecular ion implantation for the reduction of the white spot defect density in CMOS image sensor

We have characterized CH3O ion-implanted epitaxial wafers in device fabrication processes. We confirmed that the CH3O ion-implanted wafers can reduce the density of white spot defects in CMOS image sensors. Evaluation of the CH3O ion-implanted region before and after device fabrication processes which included heat treatment and ion implantation, showed that two types of defects, namely stacking faults and carbon-related defects, exist in the CH3O ion implantation region getter the metallic impurities during device fabrication processes. In particular, it was clarified that stacking fault defects existing in the CH3O ion-implanted region are powerful gettering sinks for oxygen. Thus, it was considered that two types of gettering sink formed by CH3O ion implantation contribute to the reduction in the density of white spot defects. We believe that these characteristics can contribute to the improvement of fabrication processes for advanced CMOS image sensors.

Effect of low-oxygen-concentration layer on iron gettering capability of carbon-cluster ion-implanted Si wafer for CMOS image sensors

The effect of oxygen (O) concentration on the Fe gettering capability in a carbon-cluster (C3H5) ion-implanted region was investigated by comparing a Czochralski (CZ)-grown silicon substrate and an epitaxial growth layer. A high Fe gettering efficiency in a carbon-cluster ion-implanted epitaxial growth layer, which has a low oxygen region, was observed by deep-level transient spectroscopy (DLTS) and secondary ion mass spectroscopy (SIMS). It was demonstrated that the amount of gettered Fe in the epitaxial growth layer is approximately two times higher than that in the CZ-grown silicon substrate. Furthermore, by measuring the cathodeluminescence, the number of intrinsic point defects induced by carbon-cluster ion implantation was found to differ between the CZ-grown silicon substrate and the epitaxial growth layer. It is suggested that Fe gettering by carbon-cluster ion implantation comes through point defect clusters, and that O in the carbon-cluster ion-implanted region affects the formation of gettering sinks for Fe.

Физические особенности формирования локальных субмикронных ионно-имплантированных областей

Физические особенности формирования локальных субмикронных ионно-имплантированных областей

Mapping of ion-implanted n-SiC schottky contacts using scanning internal photoemission microscopy

Nitrogen-ion-implantation damage on SiC has been clearly imaged using scanning internal photoemission microscopy (SIPM). Ni Schottky contacts were formed on selectively N-ion-implanted n-SiC surfaces at 80keV with an ion dose of 1×1015cm−2. A photocurrent, Y (photoyield; defined as photocurrent per incident photon), was detected by focusing and scanning a laser beam over the contacts. The N-ion-implanted regions were clearly imaged with Y measurements. Y was detected even where the implanted region is protruding out of the electrode in the unannealed sample. We also found significant increase of Y in the periphery of the ion-implanted region. We confirmed that SIPM is a powerful tool for mapping damages due to ion implantation.

(Invited) Anisotropic Strain Introduction into Si/Ge Hetero Structures

Ge is one of the most attractive materials toward ultra-low-power and high-performance complementary metal oxide semiconductor (CMOS) circuits owing to its higher hole mobility than Si and various III-V materials. Moreover, it is possible to enhance the mobility further by introducing strain into the channel. Especially an uniaxial strain is expected to provide the highest hole mobility [1,2]. So far, several approaches have been researched to create uniaxially strained SiGe and Ge channels. We have been developing the selective ion implantation technique to induce uniaxial strain into SiGe buffer layers [3,4]. In this method, a Si substrate is selectively subjected to the ion implantation and followed by the SiGe overgrowth. A subsequent post-growth-annealing promotes the strain relaxation of the SiGe selectively in the implanted region as the implantation-induced defects formed act as dislocation nucleation sources. And hence, with proper configurations of the selective implantation, the anisotropic strain can be induced in the SiGe in the unimplanted area since the neighboring relaxed SiGe films in the ion-implanted areas provide shear stress at the interfaces. In previous works, we succeeded in fabrication of uniaxially strained SiGe buffer layers with Ge concentrations below 30% [3,4], which can serve as proper templates for uniaxially strained Si/Ge heterostructures, such as uniaxially strained Si and Si1-xGex (x < 0.5) channels. For the formation of uniaxially strained Ge and Si1-xGex(x > 0.5) channels, however, SiGe buffers with higher Ge concentrations are required. In this study, therefore, we fabricate uniaxially strained SiGe buffer layers with high Ge concentrations with the selective ion implantation technique and overgrew uniaxially strained Ge layers on the SiGe buffers. The sample fabrication procedure is as follows (Fig.1). Ar+ ions were selectively implanted into the Ge substrate through the SiO2 mask window. Line widths of the ion-implanted and unimplanted regions were varied from 2 to 20 μm. A SiGe layer was pseudomorphically grown on the selectively ion-implanted Ge substrate with solid source molecular beam epitaxy. Subsequently, postgrowth annealing was carried out to promote the strain relaxation of the SiGe only in the implanted region. Finally a Ge layer with the thickness of 10 nm was pseudomorphically grown on the SiGe. Figure 2 shows a Raman mapping image for the sample with 3-μm-width stripe lines, where a Ge-Ge mode peak wavenumbers obtained from the top Ge layer were scanned. A clear contrast is observed corresponding to the large and small compressive strain of the Ge layer in the implanted and unimplanted regions, respectively. This demonstrates that the strain of the Ge is laterally controlled by the selective implantation. Since XRD measurements confirmed that the SiGe buffer layer has uniaxial strain, it can be said that the top Ge layer is also uniaxially strained. This uniaxially strained Ge layer can be transferred onto the insulator substrate via wafer bonding process, where the ion-implanted defective region can be removed. Finally defect-free uniaxially strained GOI substrate can be obtained, which is applicable to high mobility uniaxilly strained Ge channel MOSFETs. [1] Y. Sun, et al., J. Appl. Phys. 101, 104503 (2007). [2] T. Krishnamohan et al., IEDM Tech. Dig., 899 (2008). [3] K. Sawano et al., Appl.Phys.Express 1, 121401 (2008). [4] K. Sawano et al., J. of Crystal Growth 378, 251 (2013). Figure 1

Enhanced germanium precipitation and nanocrystal growth in the Ge+ ion-implanted SiO2 films during high-pressure annealing

Abstract The effect of pressure employed during subsequent annealing of the Ge + -ion implanted SiO 2 layers on the Ge nanocrystal formation was studied. Ge + ions implanted in the thin SiO 2 layers formed Gauss-like profiles with a Ge peak concentration varied from 1 to 12 at%. Subsequent annealing was carried out at temperature 600–1130 °C under pressures 1–1.2×10 4 bar. Strong effect of the pressure on the Ge atom distribution was obtained. High-temperature annealing under pressure within the range of 1–10 3 bar resulted in the out-diffusion of germanium from the SiO 2 layer to the Si substrate. As the pressure reached 1.2×10 4 bar, Ge migration to the Si/SiO 2 interface was prevented. At that, the Ge nanocrystal growth within the ion-implanted region of the SiO 2 film took place. The nanocrystal size was investigated as a function both of the Ge atom concentration and the annealing temperature. The obtained results show a diffusion-controlled nanocrystal growth mechanism. The high-pressure (1.2×10 4 bar) diffusion coefficient of germanium in silicon dioxide was estimated as a function of the temperature and expressed by D= 1.1×10 −10 exp ( −1.43 eV/kT) cm 2 /s.

Optimization of 4H-SiC UV Photodiode Performance Using Numerical Process and Device Simulation

A numerical model for the simulation of ultraviolet sensitive ion-implanted 4H-SiC photodiodes is established. To explain the measured wavelength dependence of the photoresponsivity of such photodiodes, conventional simulation model was modified twofold. First, new experimental data on the optical properties of 4H-SiC were included into the model. Second, the doping dependence of recombination lifetimes was recalibrated, resulting in a stronger recombination of charge carriers in the ion-implanted region near the SiC surface. After the calibration of the model using experimental data, the model was applied for the optimization of the photodiode performance. An improvement of photoresponsivity by about 30% can be achieved by optimizing the thickness of antireflective layer. An improvement by more than 70% can be achieved by lowering doping level to $1\cdot 10^{14}$ cm $^{\mathrm {-3}}$ in the epitaxial layer of 4H-SiC diodes.

4H-SiC n-Channel DMOS IGBTs on (0001) and (000-1) Oriented Lightly Doped Free-Standing Substrates

We experimentally demonstrate 4H-SiC n-channel, DMOS Insulated Gate Bipolar Transistors (IGBTs) on 180 µm thick lightly doped free-standing n- substrates with an ion-implanted collector region, and metal-oxide-semiconductor (MOS) gate on (0001) and (000-1) surfaces. The IGBTs show an on-state current of 20A/cm2 at a power dissipation of 300W/cm2. Threshold voltage of 7.5V and 10.5V was obtained on Si-face and C-face respectively. Both IGBTs show a small positive temperature coefficient of the forward voltage drop, which is useful for easy parallelization of devices.

4H-SiC n-Channel Insulated Gate Bipolar Transistors on (0001) and (000-1) Oriented Free-Standing n−Substrates

We experimentally demonstrate 4H-SiC n-channel, planar gate insulated gate bipolar transistors (IGBTs) on 180- $\mu \text{m}$ thick lightly doped free-standing n− substrates with ion-implanted collector regions, and metal–oxide–semiconductor gates on (0001) and (000-1) surfaces. The IGBTs show an ON-state current density of 20 A/cm2 at a power dissipation of 300 W/cm2. The threshold voltages are measured to be 7.5 V and 10.5 V on Si-face and C-face, respectively. Both IGBTs show a small positive temperature coefficient of the forward voltage drop, which is useful for easy parallelization of devices.

Annealing Temperature Dependence of Dislocation Extension and its Effect on Electrical Characteristic of 4H-SiC PIN Diode

In this study, we investigated the annealing temperature dependence of dislocation extension in an ion-implanted region of a 4H-silicon carbide (SiC) C-face epitaxial layer, revealing that a high temperature annealing led to dislocation formation. We also investigated the current-voltage (I-V) characteristics of a 4H-SiC PIN diode with and without these extended dislocations. We demonstrated that the forward biased I-V characteristics of samples with extended interfacial dislocations have a kink at lower current regions.

Splitting of spin-wave modes in thin films with arrays of periodic perturbations: theory and experiment

A joint theoretical–experimental study focusing on the description of the ferromagnetic resonance response of thin films in the presence of periodic perturbations introduced on the upper film surface is presented. From the viewpoint of theory, these perturbations may exist in the form of any kind of one- or two-dimensional rectangular defect arrays patterned onto one surface of the magnetic film. Indeed, the defects may be pits or bumps, or ion-implanted regions with a lower saturation magnetization. The complete set of response functions, given by the components of the frequency and wave-vector dependent dynamic magnetic susceptibility tensor of the film exposed to microwave excitation, are provided and are used to explain the experimental data. This allows us to obtain the response of the system due to microwave absorption, from which the zero wave-vector spin-wave modes in the field-frequency spectra, including their intensity, are calculated. Explicit calculations for periodic defects featuring the shape of stripes, dots and rectangles are given in detail, as well as experimental results for stripe-like defects prepared either by topographical depressions or by ion implantation of thin magnetic films. The excellent agreement of the theoretical and experimental results manifests the validity of the presented model.