Manufacture Of Silicon Carbide Research Articles

Coating-assisted picosecond laser ablation for microstructure fabrication of SiC ceramics.

Silicon carbide (SiC) ceramics have emerged as critical materials in the production of high-precision components. Ultrafast laser processing is deemed the optimal technique for micro-nano manufacturing of SiC. However, the permanent deposition layer induced by laser ablation can critically impact the precision of the component. In this work, a coating-assisted picosecond laser ablation (CAPLA) method was proposed, in which sacrificial photoresist coating was utilized to improve surface quality without efficiency loss. The coating serves to prevent the uncooled plasma from contacting with the substrate, thereby preventing the formation of a permanent deposition layer. By comparing the CAPLA method with laser direct ablation, the influence of laser parameters and photoresist coating characteristics on the deposition layer was investigated systematically. A processed surface devoid of deposition layers can be achieved by CAPLA with low pulse energy and a high number of scans. The uniformity is critical to ensure the transmission of the laser beam, and a larger thickness can improve the processing efficiency by increasing the limit of pulse energy capacity. Pin arrays and vacuum grooves for SiC ceramic vacuum chucks were fabricated to demonstrate the superiority of the CAPLA method. These results suggest that this method can be a novel and promising approach for high-precision component manufacturing.

Multiscale Simulations of Plasma Etching in Silicon Carbide Structures

Manufacturing of Silicon Carbide (SiC) based devices will soon require the accuracy and control typical of the advanced Si based nanoelectronics. As a consequence, the processes development will surely benefit of technology computer aided design (TCAD) tools dedicated to the current and future SiC process technologies. Plasma etching is one of the most critical and difficult process for optimization procedures in the micro/nanofabrication area, since the resultant 2D (e.g. in trenches) or 3D (e.g in holes) profiling is the consequence of the complex interactions between plasma and materials in the device structures. In this contribution we present a simulation tool dedicated to the etching simulation of SiC structures based on the sequential combination of a plasma scale global model and feature scale Kinetic Monte Carlo simulations. As an example of the approach validation procedure the simulations are compared with the characterization analysis of particular real process results.

New thick silicon carbide detectors: Response to 14 MeV neutrons and comparison with single-crystal diamonds

Abstract In this work we present the response of a new large volume 4H Silicon Carbide (SiC) detector to 14 MeV neutrons. The device has an active thickness of 100 μ m (obtained by epitaxial growing) and an active area of 25 mm2. Tests were conducted at the ENEA-Frascati Neutron Generator facility by using 14.1 MeV neutrons. The SiC detector performance was compared to that of Single-Crystal Diamond (SCD) detectors. The SiC response function was successfully measured and revealed a very complex structure due to the presence in the detector of both Silicon and Carbon atoms. Nevertheless, the flexibility in the SiC manufacturing and the new achievements in terms of relatively large areas (up 1x1 cm2) and a wide range of thicknesses makes them an interesting alternative to diamond detectors in environments where limited space and high neutron fluxes are an issue, i.e. modern neutron cameras or in-vessel tokamak measurements for the new generation fusion machines such as ITER. The absence of instabilities during neutron irradiation and the capability to withstand high neutron fluences and to follow the neutron yield suggest a straightforward use of these detectors as a neutron diagnostics.

Incoming and Inline Defectivity Control Solutions for Silicon Carbide Manufacturing

Si l icon car b ide (Si C ) man u f act u ring is transitioning from 4 inch wafers to 6 inch wafers for production line devices. The main obstacle for SiC manufacturing high yield is defect control. Defectiveness inline control is well established for silicon power device. However, there are two main challenges related to SiC technology. The first challenge is incoming 4H-SiC substrates defectivity and epi layer crystallographic defects. The second challenge is inline defect detection at process steps such as implantation and annealing activation [,]. Defect detection and classification are difficult with current defect inspection tools because of substrate transparency at visible light, color variation, roughness, and wafers’ high warpage. In addition, SiC device integration has been requesting specific optimization. In this paper, collaboration studies have been done to develop solutions to these challenges. Yield correlation analyses have validated the process control flow set to address these two major challenges and to enable the fast ramp of the 6” production line of SiC devices.

SiCの焼結性に及ぼす粒度分布の影響

Silicon carbide (SiC) has drawn a significance attention in recent decades for its excellent properties such as high oxidation resistance, high hardness and low density. However, an important drawback for SiC manufacturing is its poor sinterability due to its highly covalent nature of bonding. This work investigates the effect of dispersion in particle size distribution (PSD) on the sinterability of SiC ceramics. In the present work, two types of SiC powders, consisting powders of sizes 0.3 μm and 2.5 μm, were subjected to mechanical milling in order to produce various patterns of particle size distributions. Subsequently, milled powders were sintered by spark plasma sintering. This sintering technology is used on account of its rapid heating and short time sintering. This work also suggests the usage of coefficient of variation, Cv as an appropriate parameter to indicate the dispersion level in PSD range investigated.

Silicon Carbide Ceramic Turning Process Design and Parameter Analysis

This article mainly aims at the problem of silicon carbide ceramic mechanical turning difficult processing,by adopting the method of the numerical control turning processing.Design a special fixtures and a NC machining process to accomplish the manufacture of silicon carbide plate.And through the single factor analysis method to process parameters were analyzed.

Determination of Silicon Content in SiC Ceramics Precursor by Modified Titration

Polycarbosilane (PCS), an important precursor for manufacture of silicon carbide (SiC) ceramics, was prepared and analyzed to determine its chemical composition. The major elements of silicon (Si) and carbon (C) in Si-C backbones and side chains in PCS represent more than 80% with minor elements of oxygen and hydrogen being less than 20%. In this work, a conventional potassium silicofluoride volumetric method was explored and modified for establishing a standard routine procedure to evaluate Si content in PCS. The optimal conditions were investigated using an orthogonal designed four-factor-three-level normal experimental scheme. The suitable parameters and standard procedure to analyze Si in PCS were obtained.

Study of Silicon Carbide Ceramics

AbstractThe TRISO fuel that is intended to be used for the generation IV nuclear reactor design consists of a fuel kernel of Uranium Oxide (UOx) coated in several layers of materials with different functions. One consideration for some of these layers is Silicon Carbide (SiC) [1]. The design, manufacture and fabrication of SiC are done at the Center for Irradiation of Materials (CIM). This light weight material can maintain dimensional and chemical stability in adverse environments and very high temperatures. The characterization of the elemental makeup of the SiC material used is done using X-ray photoelectron spectroscopy (XPS). Nano-indentation is used to determine the hardness, stiffness and Young's Modulus of the material. Raman Spectroscopy is used to characterize the chemical bonding for different sample preparation temperatures.

Pulmonary impairment in workers exposed to silicon carbide.

Two hundred and sixty seven workers employed in the manufacture of silicon carbide (SiC) were examined to determine the effects of exposure to contaminants (SiC, quartz, and SO2) in the workplace on pulmonary function. No exposure concentrations exceeded the current permissible limits. Ten subjects (3.7%) showed rounded opacities (profusion greater than or equal to 1/0). Two subjects employed only in the final stages of the production process and not exposed to crystalline silica showed opacities (profusion q1/0 and q2/1) on x ray film suggesting a role of SiC in the genesis of interstitial lung disease. Chest abnormalities on x ray film were correlated with cumulative exposure to dust and pulmonary function was affected by cumulative dust exposure, profusion of opacities, and smoking. It is concluded that the current standards do not provide adequate protection against pneumoconiosis and chronic pulmonary disease in this industry.

Pulmonary effects of exposures in silicon carbide manufacturing.

Chest x rays, smoking histories, and pulmonary function tests were obtained for 171 men employed in the manufacturing of silicon carbide. A lifetime exposure to respirable particulates (organic and inorganic fractions) and sulphur dioxide was estimated for each worker. Chest x ray abnormalities were related to respirable particulates (round opacities) and to age and smoking (linear opacities). Pulmonary function was affected by respirable particulates (FVC) and by sulphur dioxide and smoking (FEV1). Pleural thickening was related to age. No exposures exceeded the relevant standards; we therefore conclude that the current standards do not provide protection against injurious pulmonary effects, at least in this industry.

炭化ケイ素製造に関する諸問題

炭化ケイ素製造に関する諸問題