Papers by Keyword: Machining Process

Abstract: We have developed a novel, material-lossless silicon carbide (SiC) wafer manufacturing process that eliminates the need for conventional grinding and polishing. Utilizing a thermal sublimation growth and etching technique called Dynamic AGE-ing^® (DA), we simultaneously performed thermal sublimation etching and growth on both the Si-face and C-face of single-crystal SiC wafers. This study investigated the impact of surface undulations—arising during DA planarization of as-sliced wafers with varying slicing qualities—on the densities of basal plane dislocations (BPDs) and in-grown stacking faults (IGSFs) in the epitaxial layers. Our findings demonstrate that larger pre-growth surface undulations correlate with higher BPD and IGSF densities in the DA-grown layers. By optimizing the initial wafer quality and DA process conditions, we achieved epitaxial layers with low defect densities (BPD density of 0.09 cm⁻² and IGSF density of 1.37 cm⁻²) without any material loss. This advancement offers a significant breakthrough in SiC device manufacturing, potentially reducing material costs and enhancing device performance by suppressing killer defects in the epitaxial layers.

Abstract: The development of non-destructive quantitative evaluation techniques for the in-plane depth distribution of sub-surface damage (SSD) layer induced by mechanical processing of chemical mechanical polishing (CMP) finished SiC wafers is essential to reduce the occurrence of crystal defects during epitaxial growth. Until now, no wafer inspection method has been able to nondestructively and quantitatively assess the in-plane depth distribution of the SSD. This study investigates the correlation between the scattered light intensity measured nondestructively by the Laser light scattering (LLS) method and the SSD depth estimated by destructive inspection using the Dynamic AGE-ing^® method, a sublimation-controlled etching and growth process, to develop a novel non-destructive SSD inspection method. As a result, it was found that there is an exponential relationship between the scattered light intensity by the LLS method on the bare wafer surface and the depth of the SSD layer that contributes to the formation of in-grown stacking faults (IGSF) during subsequent epitaxial growth. The results show that SiC wafer inspection using the novel LLS method, which introduces this relational equation, enables non-destructive and quantitative evaluation of SSD depth and in-plane distribution.

Abstract: In conventional machining of SiC wafers, material loss and sub-surface damage (SSD) of both the front and back surfaces are major issues. In this study, we focused on Dynamic AGE-ing^® (DA), which is a sublimation-controlled process, and applied it to the total wafering process without any mechanical contact of both the front and back surfaces to explore the possibilities to reach the CMP-equivalent quality. DA process enables material lossless planarization of SiC wafers by applying a temperature gradient to achieve simultaneous etching and growth at the same rate on one and the other surfaces, respectively. To drive the planarization function for a multi-wire saw finished as-sliced wafer, as an example, a high-temperature regime above 2000 °C under an Ar background pressure higher than 1 kPa to suppress etching and growth rates was employed as the first step in the DA treatment. In this step, an effective annealing function arises where sublimation and recrystallization occur simultaneously through a sub-surface region on both sides of the wafer. Due to the active interchange of the surface and subsurface layer, a self-organizing planarization effect occurs on a macroscopic scale on both surfaces with the removal of SSD. The conventional DA processes were employed for the following microscopic flatness control. As a result, the roughness of the 6-inch as-sliced wafer was reduced to 0.7 nm on the Si-face and 2.0 nm on the C-face while maintaining the wafer thickness. This is the first promising result exhibiting the potential of thermal contactless treatment for next-generation wafer manufacturing by improving quality and cost.

Abstract: The essential features and scale of sensor data was discussed to monitor the tool anomaly in the machining process from the pattern variation of large scale sensor data such as vibration and effective power. The cycle data, the time series sensor data collected with an acceleration or power sensor in one periodical machining of the given groove shape, had been measured periodically. In this study, the graphic pattern formed by overwriting the time series cycle data on a specific coordinate system was treated as the “big sensor data”. The big data from the effective power sensor can stably respond to the cutting power changes and showed a strong possibility as a detecting device for tool anomaly such as abrasive wear and chipping. While the big data from the acceleration sensor only responded to a big event like the chattering vibration. The number of cycle data needed to generate the big sensor data also affected on the detection sensitivity for tool anomaly. It had been required a family of time series sensor data enough to represent the cutting power change as a visual graphic pattern.

Abstract: In article has been presented machining process mathematical model of elastic-deformable shafts. It has been presented problem of optimal regulation of technological system in automated production systems too.

Abstract: The aim of this study is to realize a simple simulation tool, in order to predict the form defect of cylinder block bore liners in the moment of rough boring process. Geometrical defect prediction is critical for Process Engineering in order to optimize all machining sequences in the production line, to grantee the finale product, according to the norms defined by the Design Engineering. In revenge, Process Engineering can suggest a new product design according to geometrical defect predictions. Simulation can significantly reduce the time of Process-Product parameters adjustment (pre-project).In this study a simple static FEM model, based on the cylinder block geometry, is proposed to predict the form defect of the bore liners in the moment of process. The cutting tool is supposed as a rigid part in this model. The clamping condition and meshing information are applied on the part in the initial state. Calculation of cutting force components is performed through the Kienzle cutting law and applied on the bore liners by means of a Python script. The Python script runs the calculation automatically by means of ABQUS software. Another Python script is in charge of simulation results post-processing. The interface of this tool is an Excel sheet which allows us to inter the process parameters and automatically run the FEM calculation. Out-put excel file contains the form defect of each bore according to 3 levels of bore (top, middle and the bottom) and different angular position.The simulation results put forward that the clamping condition plays an import role in the bore distortion. Consequently, optimizing the clamping pressure and its localization is critical, before cutting parameters adjustment, in line boring process. Experimental validation is performed in parallel with the simulation. The first correlation between experimentation and simulation results shows that the first influent factor which disturbs the correlation is the initial form defect of rough part due to the casting process. Integration of casting form defect in the simulation is crucial and should be taken into account in the next studied.

Abstract: In recent years, researching the stability of the CNC machining process is a hotpot in CNC industry. Based on cDAQ and labVIEW, online monitoring system is presented, meanwhile, both software structure and hardware structure are introduced in detail. Researches show that vibration and pressure are the main factors for the quality of the flatness. By studying the relative vibration between the spindle and the platform in the Z axis direction, as well as the shifty pressure that tool works on the flatness of the workpiece, four experiments are designed in this paper under different technological conditions including free moving, Axial Depth of cut, speed and feed speed, which verify the reliability of the online monitoring system.

Abstract: In a multistage machining process, due to the variation accumulation and interaction between different machining stages, variation analysis and diagnosis for quality-related problems become complicated. In this paper, a fault analysis and prediction method is proposed for connecting engineering design with the activities of process variation sources modeling, dimensional variation analysis, and statistical estimate of variations source. Furthermore, a hypothesis testing method is introduced to determine whether each of potential process faults exists in terms of the statistical significance. At last, an experimental study is provided to illustrate the validity and the significance of the proposed methodology.

Abstract: In order to improve the efficiency of NC machining programming, and realize the rapid establishment of blank model or middle blank model, a geometrical modeling method of process driven by typical process model was put forward. This method is based on the typical process for the establishment of typical process model, to establish a mapping between modeling operation and machining process ontology, and format model mapping rules. In the process geometrical modeling of the high similarity parts, by calling the typical process model mapping rules, can generate process models automatically. A enterprise disc type parts typical process as an example is used to verify the proposed method.

Abstract: Ultrasonic machining is a non-conventional machining process. Ultrasonic machining offers an effective alternative for ultra precision machining of hard and brittle materials due to its unique characteristics. This paper did a comprehensive analysis on ultrasonic machining mechanism in theory. The experiment compared this ultrasonic machining process with the common machining process in surface quality is done and the experimental result show that the smooth high quality surface can be obtained under ultrasonic machining.