Thinning of 2-Inch SiC Wafer by Plasma Chemical Vaporization Machining Using Cylindrical Rotary Electrode

2011 ◽  
Vol 679-680 ◽  
pp. 481-484 ◽  
Author(s):  
Yasuhisa Sano ◽  
Takehiro Kato ◽  
Kohei Aida ◽  
Kazuya Yamamura ◽  
Hidekazu Mimura ◽  
...  
Keyword(s):  
Removal Rate ◽  
Atmospheric Pressure Plasma ◽  
High Hardness ◽  
Scanning Speed ◽  
Plasma Chemical ◽  
Power Transistors ◽  
Device Processing ◽  
High Removal Rate ◽  
Mechanical Machining ◽  
Sic Wafer

To reduce the on-resistance in vertical power transistors, backside thinning is required after device processing. However, it is difficult to thin a SiC wafer with a high removal rate by conventional mechanical machining because its high hardness and brittleness cause cracking and chipping during thinning. In this study, we attempted to thin a 2-inch 4H-SiC wafer by plasma chemical vaporization machining (PCVM), which is plasma etching using atmospheric-pressure plasma. By controlling the scanning speed of the table and optimizing the oxygen percentage in the CF4+O2+He mixture gas, a maximum removal rate of 0.56 μm/min was obtained over the entire wafer. Furthermore, the surface roughness was improved after thinning. Therefore, PCVM can be used as an effective method for thinning SiC wafers.

Plasma Chemical Vaporization Machining of Silicon Carbide Wafer Using Flat-Bar Electrode with Multiple Gas Nozzles

2012 ◽  
Vol 497 ◽  
pp. 160-164 ◽  
Author(s):  
Yasuhisa Sano ◽  
Kohei Aida ◽  
Hiroaki Nishikawa ◽  
Kazuya Yamamura ◽  
Satoshi Matsuyama ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Removal Rate ◽  
Atmospheric Pressure Plasma ◽  
High Hardness ◽  
Plasma Chemical ◽  
Power Transistors ◽  
Device Processing ◽  
High Removal Rate ◽  
Mechanical Machining ◽  
Sic Wafer

Silicon carbide (SiC) power devices have received much attention in recent years because they enable the fabrication of devices with a low power consumption. To reduce the on-resistance in vertical power transistors, backside thinning is required after device processing. However, it is difficult to thin a SiC wafer with a high removal rate by conventional mechanical machining because its high hardness and brittleness cause cracking and chipping during thinning. We have attempted to thin a SiC wafer by plasma chemical vaporization machining (PCVM), which is plasma etching using atmospheric-pressure plasma. In this paper, we describe a machining property using a newly developed flat-bar electrode with multiple gas nozzles for thinning a SiC wafer.

Thinning of a Two-Inch Silicon Carbide Wafer by Plasma Chemical Vaporization Machining Using a Slit Electrode

2014 ◽  
Vol 778-780 ◽  
pp. 750-753 ◽  
Author(s):  
Yuu Okada ◽  
Hiroaki Nishikawa ◽  
Yasuhisa Sano ◽  
Kazuya Yamamura ◽  
Kazuto Yamauchi
Keyword(s):  
Silicon Carbide ◽  
Removal Rate ◽  
Atmospheric Pressure Plasma ◽  
High Hardness ◽  
Power Devices ◽  
Plasma Chemical ◽  
Power Transistors ◽  
Device Processing ◽  
High Removal Rate ◽  
Sic Wafer

In recent years, silicon (Si) has been mainly used in power devices, but the limit of its performance is being reached. Therefore, silicon carbide (SiC) power devices have been attracting attention because they enable the fabrication of devices with low power consumption. To reduce the on-resistance in vertical power transistors, backside thinning is required after device processing. However, it is difficult to thin a SiC wafer with a high removal rate by conventional mechanical processing because its high hardness and brittleness cause cracking and chipping during thinning. Therefore, we have attempted to thin a SiC wafer using plasma chemical vaporization machining (PCVM), which is plasma etching using atmospheric-pressure plasma. In this study, we describe a machining property using a newly developed slit electrode that is composed of two parts and has a slit that allows for a new gas to pass.

Thinning of SiC Wafer by Plasma Chemical Vaporization Machining

2010 ◽  
Vol 645-648 ◽  
pp. 857-860 ◽  
Author(s):  
Yasuhisa Sano ◽  
Takehiro Kato ◽  
Tsutomu Hori ◽  
Kazuya Yamamura ◽  
Hidekazu Mimura ◽  
...  
Keyword(s):  
Plasma Etching ◽  
Atmospheric Pressure ◽  
Atmospheric Pressure Plasma ◽  
High Hardness ◽  
High Yield ◽  
Plasma Chemical ◽  
Power Transistors ◽  
Device Processing ◽  
Mechanical Machining ◽  
Sic Wafer

In order to reduce the on-resistance in vertical power transistors, backside thinning is required after device processing. However, it is difficult to thin an SiC wafer with a high yield rate by conventional mechanical machining because its high hardness and brittleness cause cracking and chipping during thinning. In this study, a small rectangular SiC sample was thinned by plasma chemical vaporization machining (PCVM), which is plasma etching using atmospheric-pressure plasma. As a result, the sample was successfully thinned to 40 m without any cracking or chipping. Furthermore, the surface roughness was improved after thinning, and the edge of the wafer became rounded automatically. Therefore, PCVM can be used as an effective method for thinning SiC wafers.

Beveling of Silicon Carbide Wafer by Plasma Chemical Vaporization Machining

2008 ◽  
Vol 600-603 ◽  
pp. 843-846 ◽  
Author(s):  
Takehiro Kato ◽  
Yasuhisa Sano ◽  
Hideyuki Hara ◽  
Hidekazu Mimura ◽  
Kazuya Yamamura ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Atmospheric Pressure ◽  
Removal Rate ◽  
Atmospheric Pressure Plasma ◽  
High Hardness ◽  
Wafer Surface ◽  
Plasma Chemical ◽  
Pressure Plasma ◽  
Surface Polishing ◽  
High Removal Rate

Beveling is essential for preventing the chipping of the edge of a wafer during surface polishing and other processes. Plasma chemical vaporization machining (PCVM) is an atmospheric-pressure plasma etching process. It has a high removal rate equivalent to those of conventional machining methods such as grinding and lapping, which are used for high-hardness materials such as silicon carbide, due to the generation of high-density radicals in atmospheric-pressure plasma. Furthermore, PCVM does not damage the wafer surface because it is a purely chemical process; therefore, it is considered that PCVM can be used as an effective method of beveling the edge of SiC wafers. In this paper, we report the investigation of the beveling of SiC wafers by PCVM.

Dicing of SiC Wafer by Atmospheric-Pressure Plasma Etching Process with Slit Mask for Plasma Confinement

2014 ◽  
Vol 778-780 ◽  
pp. 759-762 ◽  
Author(s):  
Yasuhisa Sano ◽  
Hiroaki Nishikawa ◽  
Yuu Okada ◽  
Kazuya Yamamura ◽  
Satoshi Matsuyama ◽  
...  
Keyword(s):  
Plasma Etching ◽  
Atmospheric Pressure ◽  
Removal Rate ◽  
Atmospheric Pressure Plasma ◽  
Etching Process ◽  
Plasma Confinement ◽  
Plasma Etching Process ◽  
Pressure Plasma ◽  
High Removal Rate ◽  
Sic Wafer

Silicon carbide (SiC) is a promising semiconductor material for high-temperature, high-frequency, high-power, and energy-saving applications. However, because of the hardness and chemical stability of SiC, few conventional machining methods can handle this material efficiently. A plasma chemical vaporization machining (PCVM) technique is an atmospheric-pressure plasma etching process. We previously proposed a novel style of PCVM dicing using slit apertures for plasma confinement, which in principle can achieve both a high removal rate and small kerf loss, and demonstration experiments were performed using a silicon wafer as a sample. In this research, some basic experiments were performed using 4H-SiC wafer as a sample, and a maximum removal rate of approximately 10 μm/min and a narrowest groove width of 25 μm were achieved. We also found that argon can be used for plasma generation instead of expensive helium gas.

Polishing Characteristics of 4H-SiC Si-Face and C-Face by Plasma Chemical Vaporization Machining

2007 ◽  
Vol 556-557 ◽  
pp. 757-760
Author(s):  
Yasuhisa Sano ◽  
Masayo Watanabe ◽  
Kazuya Yamamura ◽  
Kazuto Yamauchi ◽  
Takeshi Ishida ◽  
...  
Keyword(s):  
Atmospheric Pressure ◽  
Etch Rate ◽  
Removal Rate ◽  
Atmospheric Pressure Plasma ◽  
Plasma Chemical ◽  
Machined Surface ◽  
Pressure Plasma ◽  
High Etch Rate ◽  
High Removal Rate ◽  
Conventional Machining

Silicon carbide (SiC) is a promising semiconductor material for power devices. However, it is so hard and so chemically stable that there is no efficient method of machining it without causing damage to the machined surface. Plasma chemical vaporization machining (PCVM) is plasma etching in atmospheric-pressure plasma. PCVM has a high removal rate equivalent to those of conventional machining methods such as grinding and lapping, because the radical density in atmospheric-pressure plasma is much higher than that in normal low-pressure plasma. In this paper, the polishing characteristics of SiC by PCVM are described. As a result of machining, the surface roughnesses of both Si- and C-faces were improved under a relatively low-etch-rate (100-200 nm/min) condition. The C-face was also improved under a relatively high-etch-rate (approximately 10 μm/min) condition, and a very smooth surface (below 2 nm peak-to-valley in a 500-nm-square area) was achieved.

Temperature Dependence of Plasma Chemical Vaporization Machining of Silicon and Silicon Carbide

2008 ◽  
Vol 600-603 ◽  
pp. 847-850 ◽  
Author(s):  
Yasuhisa Sano ◽  
Masayo Watanabe ◽  
Takehiro Kato ◽  
Kazuya Yamamura ◽  
Hidekazu Mimura ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Temperature Dependence ◽  
Atmospheric Pressure ◽  
Removal Rate ◽  
Atmospheric Pressure Plasma ◽  
Plasma Chemical ◽  
Machined Surface ◽  
Pressure Plasma ◽  
Temperature Dependences ◽  
High Removal Rate

Silicon carbide (SiC) is a promising semiconductor material for power devices. However, it is extremely hard and chemically stable; thus there is no efficient method of machining it without causing damage to the machined surface. Plasma chemical vaporization machining (PCVM) is plasma etching in atmospheric-pressure plasma. PCVM has a high removal rate because the radical density in atmospheric-pressure plasma is much higher than that in conventional low-pressure plasma. Although it was found that the machining characteristic of SiC by PCVM had stronger rf power dependence than that of Si, it has not been clear whether it is radical density dependence or temperature dependence. In this paper, the temperature dependences of the PCVM of Si and SiC are examined using pipe electrode apparatus. As a result, it is found that the removal rate of SiC has a much stronger temperature dependence than that of Si and that the surface roughness of the SiC Si face becomes worse as the etching temperature increases whereas that of the C face does not increase at etching temperatures of up to 360°C.

Cause of Etch Pits during the High Speed Plasma Etching of Silicon Carbide and an Approach to Reduce their Size

2020 ◽  
Vol 1004 ◽  
pp. 161-166
Author(s):  
Yuma Nakanishi ◽  
Risa Mukai ◽  
Satoshi Matsuyama ◽  
Kazuto Yamauchi ◽  
Yasuhisa Sano
Keyword(s):  
Silicon Carbide ◽  
High Pressure ◽  
Plasma Etching ◽  
High Speed ◽  
Removal Rate ◽  
Etch Pits ◽  
Power Transistors ◽  
Pressure Plasma ◽  
Device Processing ◽  
High Removal Rate

To reduce the on-resistance in vertical power transistors, backside thinning is required after device processing. However, it is difficult to thin silicon carbide (SiC) wafers with a high removal rate by conventional mechanical processing because their hardness and brittleness cause cracks and chips during thinning. Therefore, the authors have attempted to thin SiC wafers using plasma chemical vaporization machining (PCVM), which is plasma etching using high-pressure plasma. PCVM has a high removal rate because of the high radical density in the high-pressure plasma, and it does not form a damaged layer on the processed surface because of the low ion energy. The authors have already achieved a very high removal rate of 15.6 μm/min by PCVM. However, many etch pits were generated on the wafer during PCVM in these high-speed machining conditions. Therefore, this study, using molten potassium hydroxide (KOH) etching, investigated the cause of such etch pits and found that they may stem from threading screw dislocation in the wafers. In addition, this research considered a process for reducing an etch pit size and succeeded in doing so by controlling wafer temperature.

Material Removal Rate Control in Open-Air Type Plasma Chemical Vaporization Machining by Pulse Width Modulation of Applied Power

2014 ◽  
Vol 625 ◽  
pp. 593-596
Author(s):  
Yoshiki Takeda ◽  
Yuki Hata ◽  
Katsuyoshi Endo ◽  
Kazuya Yamamura
Keyword(s):  
Material Removal Rate ◽  
Pulse Width ◽  
Material Removal ◽  
Pulse Width Modulation ◽  
Removal Rate ◽  
Scanning Speed ◽  
Control Mode ◽  
Pwm Control ◽  
Rf Power ◽  
Plasma Chemical

Plasma chemical vaporization machining (PCVM) is an ultraprecise figuring technique for optical components without introducing the subsurface damage. In our previous study, the material removal volume was controlled by changing the scanning speed of the worktable. However, because of inertia of the worktable, a discrepancy between the theoretical scanning speed and the actual scanning speed will occur if the spatial change rate of speed is rapid. Therefore, we proposed the application of the pulse width modulation (PWM) control and the amplitude modulation (AM) control of the applied RF power to control the material removal rate (MRR). Experimental results showed that the relationship between the MRR and the average RF power had high linearity, the control range of the PWM control mode was from 0.19 x 10-2 mm3/min to 3.90 x 10-2 mm3/min (from 5% to 100%), which was much wider than that of the AM control mode.

Effect of Substrate Heating in Thickness Correction of Quartz Crystal Wafer by Plasma Chemical Vaporization Machining

2010 ◽  
Vol 447-448 ◽  
pp. 218-222 ◽  
Author(s):  
Masaki Ueda ◽  
Masafumi Shibahara ◽  
Nobuyuki Zettsu ◽  
Kazuya Yamamura
Keyword(s):  
Quartz Crystal ◽  
Removal Rate ◽  
Thickness Distribution ◽  
Atmospheric Pressure Plasma ◽  
Scanning Speed ◽  
Quartz Resonator ◽  
Clock Frequency ◽  
Telecommunication System ◽  
Crystal Wafer ◽  
Thickness Correction

Quartz resonator is a very important device to generate a clock frequency for information and telecommunication system. Improvement of the productivity of the quartz resonator is always required because huge amounts of resonator are demanded to install to various electronic devices. Resonance frequency of the quartz resonator is determined by the thickness of the quartz crystal wafer. Therefore it is essential to uniform the thickness distribution of the quartz crystal wafer with nanometric level. We propose the improvement process of the thickness distribution of the quartz crystal wafer by numerically controlled correction using atmospheric pressure plasma which is noncontact and chemical removal technique. We have already succeeded in obtaining a thickness uniformity of 33.1nm within 2 min in the thickness correction of an AT-cut quartz crystal wafer with an area of 24 mm × 24 mm. However, increase of removal rate and improvement of correction accuracy are required for industrial manufacturing. Heating effects of the quartz crystal wafer in the removal rate and the correction accuracy were investigated. The heating of the substrate and compensate of the scanning speed of the worktable in accordance with the variation of the surface temperature enabled an increase of 50% in removal rate and 10-nanometric-level accuracy in correction of the thickness distribution of the quartz crystal wafer.

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