Single Crystal Ingots Research Articles

Ultrasonic-assisted stripping of single-crystal SiC after laser modification

Laser stripping technology is an advanced processing method with high efficiency and low material loss, which can greatly reduce material loss in the production process of single-crystal SiC wafer, but the single-crystal SiC ingot still have a certain bonding force after laser modification. Ultrasonic vibration can reduce the bonding force and thus strip single-crystal SiC wafer. In order to investigate the effect of ultrasonic vibration on the reduction of the bonding force of single-crystal SiC internal modification layer, through the ultrasonic-assisted stripping of single-crystal SiC orthogonal experiment, the ultrasonic vibration parameters of ultrasonic frequency, vibration time and ultrasonic power of the three indexes of the reduction of the bonding force was analyzed. The results show that the bonding force of the modified layer decreased by 25 %–60 % after ultrasonic vibration. Variance analysis of the experiment results showed that the main factors influencing the bond strength reduction were vibration time and ultrasonic power in turn. When the vibration time is longer and the ultrasonic power is higher, the stripping force decreases more, and the stripping force of single-crystal SiC wafers decreases up to 60 % under the condition of vibration time of 5min and ultrasonic power of 700 W. Through analysis of the single-crystal SiC cross-section, distinct cleavage steps and cleavage channels are evident. The laser-modified region exhibits defect such as nano-pores, micro-cracks, and nano-particles.After the single-crystal SiC laser modification process was upgraded, the distance between the ultrasonic tool head and the single-crystal SiC was 1.5 mm can directly strip off the single-crystal SiC wafer. And eventually stripped 6-inch single-crystal sic wafers. Therefore, ultrasonic vibration can increase the internal defects in the single-crystal SiC modified layer, causing crack expansion to occur and ultimately stripping the single-crystal SiC wafer.

Impurities related micro-defects in GaSb crystal grown by LEC method

The epitaxial growth of devices based on gallium antimonide (GaSb) is negatively impacted by defects related to impurities in the crystal. Liquid encapsulated czochralski (LEC) technology was used to grow 2-inch Te-doped GaSb (100) single crystal ingots, which were then processed into polished wafers in order to investigate the origins and consequences of defects related to impurities. Polished GaSb wafers were found to have surface micro-defects. Energy dispersive x-ray spectroscopy (EDAX) and scanning electron microscopy (SEM) measurements indicate that the micro-defects are associated with carbon and oxygen impurities. Glow discharge mass spectrometry (GDMS) is used to identify the origins of carbon and oxygen impurities. Based on the findings, an optimization process was developed to enhance the crystal quality, and a micro-defect-free GaSb single crystal was produced.

3D technology of growing single-crystal ingots in the form of hollow tungsten cylinders

3D technology of growing single-crystal ingots in the form of hollow tungsten cylinders

Development of Single Crystal CsPbBr3 Radiation Detectors from Low-Cost Solution Synthesized Material

The all-inorganic perovskite CsPbBr3 is a strong candidate for room-temperature, semiconducting radiation detecting applications. With a high stopping power, a large bandgap, and a high mobility-lifetime (μτ) product for both holes and electrons, CsPbBr3 contains all the desirable properties of a room temperature radiation detector. Unfortunately, the production of detector-grade single crystal samples requires high quality starting materials, which must be further processed to achieve the desired purity for semiconducting operation. We have developed a modified zone refining method combining the continuous purification of ternary CsPbBr3 and the subsequent crystal growth step. Taking advantage of this technique, low-cost polycrystalline CsPbBr3 synthesized via solution chemistry processes can be directly used in the production of high-purity, detector-grade crystals. Semi-cylindrical CsPbBr3 single crystal ingots up to 120 mm in length and 22 mm in diameter were obtained. The final product exhibited good chemical stoichiometry and high trace metal purity (2.34 ppm across 73 elements). Detector devices fabricated from the crystal wafers displayed resistivities > 2.0 × 108 Ω·cm and high photocurrent responses. The radiation detectors were able to produce spectroscopy responses to 241Am α-particle. The hole mobility-lifetime (μτH) product of the detectors was determined to be in the range of 1.45 × 10−3 cm2/V.

Insights into dendrite growth and phase transition during Cs2LiLaBr6 crystal growth

The lanthanum crystal Cs2LiLaBr6 (CLLB) has excellent scintillation properties for gamma/neutron discrimination. The initial melt with hyper-peritectic ratios (55 < LiBr/mol.% < 61) was found beneficial for CLLB crystal growth. The hyper-peritectic melt would pass though the peritectic point. However, the detailed process was still unknown. Herein, the dendrite growth and peritectic reaction were discovered near the peritectic point in CLLB single crystal ingots for the first time. The mechanism of dendrite growth was analyzed. The Cs2LaBr5-LiBr phase diagram was modified according to these results. The understanding of phase transition and dendrite evolution can guide crystal growth of CLLB and other similar elpasolite crystals.

β-Ga2O3 bulk single crystals grown by a casting method

A novel casting method was developed to grow β-Ga2O3 bulk single crystals without using a seed crystal. After separation from the crucible and processing, 2-inch diameter single crystal β-Ga2O3 ingots with (100) plane could be obtained and no large imperfection were observed. The 10 × 10 mm2 β-Ga2O3 single crystals samples with different crystal orientation have good crystal quality with full width at half maximum less than 50″, surface roughness less than 0.5 nm and defect density at the magnitude of 104 cm−2. On the basis of the experimental phenomena, a numerical simulation model was proposed to explain the crystal growth process in the casting method.

Recent Progress on Single-Crystal Growth and Epitaxial Growth of 4H Silicon Carbide

The review article describes the recent progress on SiC single-crystal and epitaxial growth technology. SiC is a third-generation semiconducting material with wide bandgap and high electrical breakdown field. Thanks to its excellent properties, it becomes an advantageous material in the field of high-temperature and high-power electronic device applications. Power devices fabricated of SiC are able to be operated at higher power density and higher switching frequency. This review focus on the growth, doping control and defect control of SiC single-crystal ingot and epilayer. The process of PVT, CVD, defect control, doping control and some recent applications of SiC are described. Various types of defects are described, including Micropipes, Dislocations, Stacking Faults etc. The wafering and polishing technology are also described.

Single-Crystal Quality Detection and Evaluation Algorithms Applied to Roller Mill Orientation Instrument

The roller mill orientation instrument (RMOI) integrates the processing and the orientation of single-crystal bars. This type of equipment realizes the integration of two processes: grinding of the single-crystal ingot and orientation of the single-crystal bar. This integration enhances production efficiency and the precision of the orientation. However, this type of approach has two significant constraints: 1) there is no quality detection algorithm for the plane of the crystal bar; it is, therefore, currently necessary to randomly find a crystal plane for orientation, which means that there is no guarantee of the quality of the plane after cutting and 2) there is a lack of evaluation methods to determine the overall quality of the crystal bar. This affects the production process and the requirements for the quality of the crystal bar and further affects the popularization and application of the equipment. Here, to overcome these constraints, we first propose a deep learning 1-D convolutional neural network (1-D-CNN) algorithm to perform feature extraction and supervised classification based on the rocking curve of the single crystal. In sharp contrast to the shallow learning method support vector machine (SVM), SVM feature extraction is insufficient, and the accuracy is low. The average accuracy of 1-D-CNN is 92.00%. This realizes the quality requirements for the successful detection of the crystal plane. Next, using the obtained quality detection results of each crystal plane, a hybrid algorithm combining improved Canopy (ICanopy) and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> -means algorithms is presented, which improved the average accuracy by 10% compared with the traditional Canopy- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> -means algorithm, and the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> -nearest neighbor ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> NN) algorithm is further utilized. Finally, an ICanopy- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${K}$ </tex-math></inline-formula> -means- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> NN algorithm is formed, which realizes the overall quality evaluation of the crystal bar under various situations, and the average accuracy increases by 3.33%–90%. The effectiveness of the proposed algorithms is demonstrated by the analysis of results obtained from practical data.

Optimal Magnetic Graphite Heater Design for Impurity Control in Single-Crystal Si Grower Using Crystal Growth Simulation

In this paper, we report a successfully modified single-crystal Si growth furnace for impurity control. Four types of arbitrary magnetic heater (AMGH) systems with 3, 4, 5, and poly parts were designed in a coil shape and analyzed using crystal growth simulation. The concentration of oxygen impurities in single-crystal Si ingots was compared among the designed AMGHs and a normal graphite heater (NGH). The designed AMGHs were confirmed to be able to control turbulence and convection in a molten state, which created a vortex that influenced the oxygen direction near the melt–crystal interface. It was confirmed that replacing NGH with AMGHs resulted in a reduction in the average oxygen concentration at the Si melt–crystal interface by approximately 4.8%.

Oxidation related particles on GaSb (1 0 0) substrate surfaces

Oxidation layer and particles on polished and epi-ready cleaned surface of GaSb (100) wafers have been investigated and analyzed by surface scanner KLA candela, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) measurements, respectively. From a large quantity of statistical results, most of the particles are related with the oxides of gallium and antimony. GaSb wafers from upper position of a single crystal ingot exhibits a high surface reactivity with the characteristics of being oxidized easily and more particles left on the surface. After the standard wafer clean process, more particles are detected on the wafer surface from this ingot region, implying a correlation between native gallium antisite acceptor concentration (electrical compensation) and particle adhesion by a combination of SEM, XPS and PL results. The key role of the oxide layer composition, Ga-rich property and the defect states in producing oxidation and particle adhesion behavior has been discussed.

Growth of nickel single crystals with a diameter of 8 in. using the Czochralski method

We grew large single crystals of metal nickel with a maximum diameter of 8 in. using the Czochralski (CZ) method. Characteristics of the metal material, namely, the seed elongation and intense cooling radiation at high temperatures during crystal growth, are the main challenges when growing ingots with large diameters. These problems were resolved by optimizing the parameters related to crystal growth, such as reduction of crucible and ingot rotation speed, and adjustment of shoulder formation angle of ingot shape. The produced ingots were confirmed to be single crystals by the Laue back-reflection method. Wafers were cut from single crystal ingots using a multi-wire saw with diamond abrasive grains. A smooth, mirror-like surface was obtained on the wafers by using an ordinary mechanical polishing method. The full width at half maximum values of the X-ray rocking curve of the metal nickel crystal surface significantly depends on the surface treatment method. It was found that ordinary mechanical mirror polishing introduces strain on the surface and non-uniformity of the crystal orientation.

Conceptual Design of Experimental Facility for Large-Diameter NTD-Si at the IRT-T Reactor

The IRT-T reactor has been conducting research in the field of irradiation of ingots of single-crystal semiconductor materials since 1987. The article describes the existing silicon doping facility. The results of studies on the possibility of creating an additional irradiation channel for neutron-transmutation doping of silicon are presented. It is shown that the use of a graphite reflector and a thermal neutron filter based on boron makes it possible to achieve non-uniformity of irradiation up to 5 %. The principal possibility of irradiating single-crystal silicon ingots with a diameter of up to 203 mm and a length of up to 500 mm is shown. The questions of optimizing the configuration of the core and the regime of reactors operation for increasing the neutron flux in the irradiation channels are discussed. In addition, applying the facility to produce base materials for neutron dosimeter in neutron capture therapy studies is proposed.

Enhancing the Thermoelectric Performance of Mg2Sn Single Crystals via Point Defect Engineering and Sb Doping.

Mg2Sn is a potential thermoelectric (TE) material that exhibits environmental compatibility. In this study, we fabricated Sb-doped Mg2Sn (Mg2Sn1-xSbx) single-crystal ingots and demonstrated the enhancement of TE performance via point defect engineering and Sb doping. The Mg2Sn1-xSbx single-crystal ingots exhibited considerably enhanced electrical conductivity because of the donor-doping effect in addition to high carrier mobility. Moreover, the Mg2Sn1-xSbx single-crystal ingots contained Mg vacancy (VMg) as a point defect. The introduced VMg and doped Sb atoms formed nanostructures, both acting as phonon-scattering centers. Consequently, lower lattice thermal conductivity was achieved for the Mg2Sn1-xSbx single-crystal ingots compared with polycrystalline counterparts. Owing to the significant enhancement in the electrical conductivity and the reduction in the lattice thermal conductivity, the maximum power factor of 5.1(4) × 10-3 W/(K2 m) and the maximum dimensionless figure of merit of 0.72(5) were achieved for the Mg2Sn0.99Sb0.01 single-crystal ingot, which are higher than those of single-phase Mg2Sn1-xSb polycrystals.

Gray-box modeling of 300 mm diameter Czochralski single-crystal Si production process

More than 95% of 300 mm diameter single-crystal silicon ingots, the raw material for semiconductors, are produced by the Czochralski process. The demand for improving yield, throughput, and control performance has been increasing. The present study developed a gray-box model that can predict controlled variables from manipulated variables with higher accuracy than the conventional first-principle model (Zheng et al., 2018), aiming at realizing model predictive control of the Czochralski process. The proposed gray-box model used a statistical model to predict the temperature gradient of the crystal at the solid–liquid interface Gcry, which was constant in the first-principle model. The crystal length and the melt temperature are used as the input variables to predict Gcry. The prediction accuracy of the proposed gray-box model was compared with that of the first-principle model using real process data obtained during the production of four silicon ingots. The results demonstrated that the proposed model reduced the root mean square errors of the crystal radius, the crystal growth rate, and the heater temperature by 94.1%, 62.7%, and 70.6% on average, respectively.

Effect of a Nickel Impurity on the Galvanomagnetic Properties and Electronic Structure of PbTe

The phase and elemental composition and galvanomagnetic properties of the Pb1 – yNiyTe alloys at temperatures of 4.2 K < T < 300 K in magnetic fields of B < 7 T are investigated upon a variation in the nickel-impurity concentration along a single-crystal ingot synthesized by the Bridgman–Stockbarger technique. The solubility of nickel is shown to be no more than 0.35 mol %. The anomalous temperature dependences of the Hall coefficient and temperature and field dependences of the magnetoresistance are established. The results obtained are explained under the assumption of the formation of an inversion layer with n-type conductivity on the sample surface and the existence of several competing conductivity mechanisms in the samples. A model of the Pb1 – yNiyTe electronic structure is proposed that suggests Fermi-level pinning within the Ni impurity band located at the edge of the valence band and moving deeper into it with increasing temperature.

Optimization of awj process using fuzzy taguchi method for improving surface characteristics of silicon wafer

This study investigates the slicing capabilities and surface characteristics of Silicon wafer by optimizing the operation parameters of the Abrasive water jet machining process. Slicing carried out on single crystal pure silicon ingot in AWJM by using an abrasive particle of size 80 mesh. To optimize the AWJ operation parameters L9 Taguchi orthogonal array is used and compare the superficial feature like surface roughness, topography, and slicing rate using different input parameters like SOD, water jet pressure, and flow rate of abrasives. To know the significant slicing parameter, which impact in the surface finish of silicon wafer by ANOVA analysis and the empirical model of the slicing process is find by using a regression model, Further Fuzzy logic analysis used to predict the abrasive water jet machining process parameters with Mamdani fuzzy rules and Triangular membership function. SEM analysis is portrayed by the surface morphology of different mesh size machined on pure Si wafer.

Modern Techniques for Automated Acquiring and Processing Data of Diffraction Electron Microscopy for Nano-Materials and Single-Crystals

Progress in modern science and technology is impossible without the use of new materials, which include nanoparticles and single crystals. Existing approaches in the field of computer vision are difficult to apply to the processing of diffraction patterns, which contain information about the parameters of the fine structure of nanostructured and single-crystal materials. The aim of the work was to develop modern computer-aided techniques that, interacting with the software of the electron microscope, automatically receive and process the information contained in electron diffraction patterns. Replacing the diffraction pattern obtained by a transmission electron microscope with a three-dimensional relief makes it possible to reduce the problem to the solution of the optimization problem. This approach allows not only automating the process of scientific research, but also significantly reduces the time for obtaining the result and increases its accuracy. The application of the proposed approach is demonstrated in measuring the misorientation angles of large single-crystal tungsten ingots, which are obtained by the plasma-induction growing technology.

Facile Strategy for Facet Competition Management to Improve the Performance of Perovskite Single-Crystal X-ray Detectors.

Methylammonium lead tribromide perovskite single crystals have been demonstrated to be good candidates as sensitive X-ray detectors in direct detection mode in recent years. However, its X-ray detection performance based on the orientation of different facets is still not clear. Here, we developed a facile strategy to chemically expose the [110] facet of single crystals from low-cost solution processes by tailoring the nonstoichiometry of feeding ions to selectively suppress the growth of the [100] facet. In contrast to physically cutting and sawing single-crystal ingots, this avoids damage to the fragile single crystals as well as orientation errors, more suitable for the naturally soft lattice. Compared to the [100] facet, the exposed [110] facet of perovskite single crystals exhibits a smaller trap density and excellent charge carrier transportation properties, leading to an improved sensitivity of 3928.3 μC/Gyair/cm2 to 120 keV hard X-rays, which potentially outperforms the currently dominating CsI scintillator of a commercial digital radiography (DR) medical imager for a routine health check.

Growth of Single-Crystal Cd0.9Zn0.1Te Ingots Using Pressure Controlled Bridgman Method

We report growth of single-crystal Cd0.9Zn0.1Te ingots while using the pressure-controlled Bridgman method. The Cd pressure was controlled during growth to suppress its evaporation from the melt and reduce the size of Te inclusions in the as-grown crystals. The accelerated crucible rotation technique (ACRT) was used to suppress constitutional supercooling. The fast accelerating and slow decelerating rotation speeds were optimized. Two-inch Cd0.9Zn0.1Te single-crystal ingots without grain boundaries or twins were grown reproducibly. Glow discharge mass spectrometry results indicate the effective segregation coefficients of Zn and In dopants are 1.24 and 0.18, respectively. The full width half maximum (FWHM) of X-ray rocking curve was approximately 22.5 ″, and the IR transmittance was approximately 61%, indicating high crystallinity. The mean size of the Te inclusions was approximately 13.4 μm. Single-crystal wafers were cut into 5 × 5 × 2 mm3 slices and then used to fabricate gamma ray detectors. The energy resolution and peak-to-valley ratio maps were constructed while using 59.5 keV gamma ray measurements, which proved the high uniformity of detection performance.

Control of the Thermoelectric Properties of Mg2Sn Single Crystals via Point-Defect Engineering

Mg2Sn is a potential thermoelectric (TE) material that can directly convert waste heat into electricity. In this study, Mg2Sn single-crystal ingots are prepared by melting under an Ar atmosphere. The prepared ingots contain Mg vacancies (VMg) as point defects, which results in the formation of two regions: an Mg2Sn single-crystal region without VMg (denoted as the single-crystal region) and a region containing VMg (denoted as the VMg region). The VMg region is embedded in the matrix of the single-crystal region. The interface between the VMg region and the single-crystal region is semi-coherent, which does not prevent electron carrier conduction but does increase phonon scattering. Furthermore, electron carrier concentration depends on the fraction of VMg, reflecting the acceptor characteristics of VMg. The maximum figure of merit zTmax of 1.4(1) × 10−2 is realised for the Mg2Sn single-crystal ingot by introducing VMg. These results demonstrate that the TE properties of Mg2Sn can be optimised via point-defect engineering.