scholarly journals Study on Improving the Precise Machinability of Single Crystal SiC by an Ultrasonic-Assisted Hybrid Process

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7320
Author(s):  
Dong Shi ◽  
Tianchen Zhao ◽  
Tengfei Ma ◽  
Jinping Pan
Keyword(s):  
Single Crystal ◽  
High Efficiency ◽  
Surface Defects ◽  
Removal Rate ◽  
Oxide Semiconductor ◽  
Hybrid Process ◽  
Ultrasonic Assisted ◽  
Single Crystal Sic ◽  
Surface Damages ◽  
Sic Wafer

Silicon carbide (SiC) devices have become one of the key research directions in the field of power electronics. However, due to the limitation of the SiC wafer growth process and processing capacity, SiC devices, such as SiC MOSFET (Metal-oxide-semiconductor Field-effect Transistor), are facing the problems of high cost and unsatisfied performance. To improve the precise machinability of single-crystal SiC wafer, this paper proposed a new hybrid process. Firstly, we developed an ultrasonic vibration-assisted device, by which ultrasonic-assisted lapping and ultrasonic-assisted CMP (chemical mechanical polishing) for SiC wafer were fulfilled. Secondly, a novel three-step ultrasonic-assisted precise machining route was proposed. In the first step, ultrasonic lapping using a cast iron disc was conducted, which quickly removed large surface damages with a high MRR (material removal rate) of 10.93 μm/min. In the second step, ultrasonic lapping using a copper disc was conducted, which reduced the residual surface defects with a high MRR of 6.11 μm/min. In the third step, ultrasonic CMP using a polyurethane pad was conducted, which achieved a smooth and less damaged surface with an MRR of 1.44 μm/h. These results suggest that the ultrasonic-assisted hybrid process can improve the precise machinability of SiC, which will hopefully achieve high-efficiency and ultra-precision machining.

scholarly journals Investigation on the Material Removal and Surface Generation of a Single Crystal SiC Wafer by Ultrasonic Chemical Mechanical Polishing Combined with Ultrasonic Lapping

Materials ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2022 ◽  
Author(s):  
Yong Hu ◽  
Dong Shi ◽  
Ye Hu ◽  
Hongwei Zhao ◽  
Xingdong Sun
Keyword(s):  
Surface Roughness ◽  
Single Crystal ◽  
Material Removal Rate ◽  
Chemical Mechanical Polishing ◽  
Material Removal ◽  
Removal Rate ◽  
Surface Generation ◽  
Ultrasonic Assisted ◽  
Single Crystal Sic ◽  
Sic Wafer

A new method of ultrasonic chemical mechanical polishing (CMP) combined with ultrasonic lapping is introduced to improve the machining performance of carbide silicon (SiC). To fulfill the method, an ultrasonic assisted machining apparatus is designed and manufactured. Comparative experiments with and without ultrasonic assisted vibration are conducted. According to the experimental results, the material removal rate (MRR) and surface generation are investigated. The results show that both ultrasonic lapping and ultrasonic CMP can decrease the two-body abrasion and reduce the peak-to-valley (PV) value of surface roughness, the effect of ultrasonic in lapping can contribute to the higher MRR and better surface quality for the following CMP. The ultrasonic assisted vibration in CMP can promote the chemical reaction, increase the MRR and improve the surface quality. The combined ultrasonic CMP with ultrasonic lapping achieved the highest MRR of 1.057 μm/h and lowest PV value of 0.474 μm. Therefore this sequent ultrasonic assisted processing method can be used to improve the material removal rate and surface roughness for the single crystal SiC wafer.

Effect of Abrasives on the Lapping Performance of 6H-SiC Single Crystal Wafer

2013 ◽  
Vol 690-693 ◽  
pp. 2179-2184 ◽  
Author(s):  
Wei Li ◽  
Qiu Sheng Yan ◽  
Jia Bin Lu ◽  
Ji Sheng Pan
Keyword(s):  
Surface Roughness ◽  
Grain Size ◽  
Single Crystal ◽  
Material Removal Rate ◽  
Material Removal ◽  
High Efficiency ◽  
Removal Rate ◽  
Lower Surface ◽  
Crystal Wafer ◽  
Sic Wafer

In order to remove the cutting marks on the cutting surface of 6H-SiC single crystal wafer, experiments were conducted to investigate the effect of the abrasive characteristics (types, grain size, concentration and mixed abrasives) on the lapping performance of 6H-SiC single crystal wafer, then the removal mechanism of the abrasive grains in the lapping process was studied. Results indicate that the abrasives with larger grain size and higher hardness can result in a higher material removal rate while the abrasives with smaller grain size and lower hardness can achieve a lower surface roughness value. When the concentration of the abrasives is 7.69 wt%, a good lapping effect was obtained. Lower surface roughness value Ra can be obtained with a high material removal rate by using certain proportion mixed abrasives. Selecting appropriate abrasives can obtain a high surface quality of 6H-SiC wafer with a high efficiency.

scholarly journals A Review on Precision Polishing Technology of Single-Crystal SiC

Crystals ◽  
2022 ◽  
Vol 12 (1) ◽  
pp. 101
Author(s):  
Gaoling Ma ◽  
Shujuan Li ◽  
Feilong Liu ◽  
Chen Zhang ◽  
Zhen Jia ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Single Crystal ◽  
Chemical Mechanical Polishing ◽  
Surface Defects ◽  
Waste Treatment ◽  
Removal Rate ◽  
Research Direction ◽  
Mechanical Polishing ◽  
Neutral Salt ◽  
Single Crystal Sic

Single-crystal SiC is a typical third-generation semiconductor power-device material because of its excellent electronic and thermal properties. An ultrasmooth surface with atomic surface roughness that is scratch free and subsurface damage (SSD) free is indispensable before its application. As the last process to reduce the surface roughness and remove surface defects, precision polishing of single-crystal SiC is essential. In this paper, precision polishing technologies for 4H-SiC and 6H-SiC, which are the most commonly used polytypes of single-crystal SiC, such as chemical mechanical polishing (CMP), photocatalytic chemical mechanical polishing (PCMP), plasma-assisted polishing (PAP), electrochemical mechanical polishing (ECMP), and catalyst-referred etching (CARE), were reviewed and compared with emphasis on the experimental setup, polishing mechanism, material removal rate (MRR), and surface roughness. An atomically smooth surface without SSD can be obtained by CMP, PCMP, PAP, and CARE for single-crystal SiC. However, their MRRs are meager, and the waste treatment after CMP is difficult and expensive. Moreover, PAP’s operation is poor due to the complex polishing system, plasma generation, and irradiation devices. A high MRR can be achieved by ECMP. In addition, it is an environmentally friendly precision polishing process for single-crystal SiC since the neutral salt solution is generally used as the electrolyte in ECMP. However, the formation of the egglike protrusions at the oxide/SiC interface during anodic oxidation would lead to a bigger surface roughness after ECMP than that after PAP is processed. The HF solution used in CARE was toxic, and Pt was particularly expensive. Ultrasonic vibration-assisted single-crystal SiC polishing and electrolyte plasma polishing (EPP) were discussed; furthermore, the research direction of further improving the surface quality and MRR of single-crystal SiC was prospected.

Study on the Machining Parameters in Polishing Single-Crystal SiC Wafers with SG Films

2013 ◽  
Vol 589-590 ◽  
pp. 457-463 ◽  
Author(s):  
Zhi Du ◽  
Jing Lu ◽  
Cong Fu Fang ◽  
Hui Huang ◽  
Xi Peng Xu
Keyword(s):  
Surface Roughness ◽  
Single Crystal ◽  
Smooth Surface ◽  
Sol Gel ◽  
Machining Parameters ◽  
Processing Quality ◽  
Rotating Speed ◽  
Single Crystal Sic ◽  
Sic Wafer ◽  
Diamond Abrasive

In this paper, diamond abrasive SG films were prepared by means of sol-gel technology for polishing single-crystal SiC wafers. The effects of machining parameters on processing quality including pressure, rotating speed and polishing time were investigated, respectively. The results indicated that the surface roughness decreased with increasing polishing time. While for pressure and rotating speed, there were inflections existing. Polishing SiC wafer under optimized machining parameters, an ultra smooth surface with the roughness of 3.7 nm could be achieved using 40 μm diamond grits.

High-Efficiency Planarization of SiC Wafers by Water-CARE (Catalyst-Referred Etching) Employing Photoelectrochemical Oxidation

2019 ◽  
Vol 963 ◽  
pp. 525-529
Author(s):  
H. Kida ◽  
Daisetsu Toh ◽  
Pho V. Bui ◽  
Ai Isohashi ◽  
Ryosuke Ohnishi ◽  
...  
Keyword(s):  
High Efficiency ◽  
Catalyst Surface ◽  
Removal Rate ◽  
Contact Point ◽  
Care Process ◽  
Wafer Surface ◽  
Chemical Solution ◽  
Photoelectrochemical Oxidation ◽  
Sic Wafer ◽  
Atomically Flat

Catalyst-referred etching (CARE) is an abrasive-free and damage-free polishing method that involves applying a catalytic reaction at the contact point of the catalyst surface and workpiece in a chemical solution. An atomically flat silicon carbide (SiC) wafer surface can be obtained by the CARE process. Recently, it was found that water can be used as a chemical solution, even in the case of SiC polishing. However, its current removal rate of 4H-SiC (0001) 4°off-axis substrate is only 2 nm/h and is expected to increase. In this study, the use of photoelectrochemical oxidation in combination with the CARE process using water was investigated, successfully increasing the removal rate up to approximately 100 nm/h.

Detection and Analysis of Subsurface Cracks of Single Crystal SiC Wafers Based on Cross-Sectional Microscopy Method

2014 ◽  
Vol 1027 ◽  
pp. 240-245
Author(s):  
Qiu Sheng Yan ◽  
Sen Kai Chen ◽  
Ji Sheng Pan
Keyword(s):  
Sample Preparation ◽  
Single Crystal ◽  
Crack Detection ◽  
Preparation Method ◽  
Subsurface Crack ◽  
Cross Sectional ◽  
Preparation Methods ◽  
Subsurface Cracks ◽  
Single Crystal Sic ◽  
Sic Wafer

For subsurface crack detection of single crystal SiC wafer, this paper proposed a cross-sectional cleavage detection method and compared with traditional cross-sectional sample preparation method. The characteristics and detection results of two cross-sectional sample preparation methods were compared and the subsurface crack characteristics in SiC wafer grinding were researched. The results show that the configurations and depth of subsurface cracks measured by two cross-sectional sample preparation methods were similar. The cross-sectional cleavage sample preparation method is simpler and more rapid in subsurface crack detection. The subsurface crack system of single crystal SiC wafer grinding mainly includes lateral crack and median crack.

Research on Ultrasonic-Assisted Fixed-Abrasive Lapping Technology for Engineering Ceramics Cylindrical Part

2017 ◽  
Vol 5 (2) ◽  
Author(s):  
Feng Jiao ◽  
Bo Zhao
Keyword(s):  
Ultrasonic Vibration ◽  
Material Removal ◽  
High Efficiency ◽  
Removal Rate ◽  
Tangential Force ◽  
Cylindrical Part ◽  
Engineering Ceramics ◽  
Machining Quality ◽  
Ultrasonic Assisted ◽  
Fixed Abrasive

Lapping is a key processing step for precision parts, which directly affects machining quality, precision, and efficiency. Due to some drawbacks of free-abrasive lapping such as deep scratches on the lapped surface, lower lapping efficiency for lower lapping speed, severe waste of abrasive, high-processing cost, and so on, conventional fixed-abrasive lapping (CFL) technology was proposed and developed recently. Meanwhile, considering the unique advantages of the ultrasonic-assisted machining during the processing of those hard and brittle materials and the effect of ultrasonic vibration on the self-sharpening characteristic of abrasive pellet, a novel ultrasonic-assisted fixed-abrasive lapping (UAFL) technology is put forward and corresponding lapping device for engineering ceramics cylindrical part is developed in this paper. Meanwhile, UAFL mechanism and characteristics were studied theoretically and experimentally. Research results show that superimposed ultrasonic vibration changes the lapping movement characteristics and material removal mechanism to a certain extent, helping to heighten material removal rate, smoothen the waveform of tangential force, reduce the average tangential force, and improve surface machining quality. UAFL can be regarded as a high efficiency and precision processing technology for engineering ceramics cylindrical part.

scholarly journals Effects of Depth of Cutting on Damage Interferences during Double Scratching on Single Crystal SiC

Crystals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 519
Author(s):  
Duan Nian
Keyword(s):  
Single Crystal ◽  
Material Removal ◽  
Single Crystal Silicon ◽  
Crystal Silicon ◽  
Particle Hydrodynamics ◽  
Single Crystal Sic ◽  
Smoothed Particle ◽  
Planarization Process ◽  
Material Removal Mode ◽  
Sic Wafer

In this work, the damage interference during scratching of single crystal silicon carbide (SiC) by two cone-shaped diamond grits was experimentally investigated and numerically analyzed by coupling the finite element method (FEM) and smoothed particle hydrodynamics (SPH), to reveal the interference mechanisms during the micron-scale removal of SiC at variable Z-axis spacing along the depth of cutting (DOC) direction. The simulation results were well verified by the scratching experiments. The damage interference mechanism of SiC during double scratching at micron-scale was found to be closely related to the material removal modes, and can be basically divided into three stages at different DOCs: combined interference of plastic and brittle removal in the case of less than 5 µm, interference of cracks propagation when DOC was increased to 5 µm, and weakened interference stage during the fracture of SiC in the case of greater than 5 µm. Hence, DOC was found to play a determinant role in the damage interference of scratched SiC by influencing the material removal mode. When SiC was removed in a combined brittle-plastic mode, the damage interference occurred mainly along the DOC direction; when SiC was removed in a brittle manner, the interference was mainly along the width of cutting; and more importantly, once the fragment of SiC was initiated, the interference was weakened and the effect on the actual material removal depth also reduces. Results obtained in this work are believed to have essential implications for the optimization of SiC wafer planarization process that is becoming increasingly important for the fabrication of modern electronic devices.

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