摘要 ：

In this study, the effects of processing parameters on the geometry of femtosecond laser fabricated microgrooves on 4H-SiC wafer were investigated. To achieve a fast, accurate and intelligent manufacturing process, response surface methodology (RSM) and artificial neural network (ANN) method were applied for modeling and predicting the geometric features of microgrooves. In addition, analysis of variance (ANOVA) was employed to determine the most significant input variables on the responses. The RSM result showed that the third-order polynomial model equation was in high accordance with the experi-ments. During the analysis, laser power, scanning speed, and scanning times were set as input variables, and the depth, width and surface roughness (Ra) were set as response/ output variables. Finally, the predictive capabilities of the RSM and ANN models were compared with each other in terms of coefficient of determine (R-2), root mean squared error (RMSE), and relatively error (RE). The results indicated that the ANN method have a higher accuracy compared to those of the RSM model. (C)& nbsp;2022 The Author(s). Published by Elsevier B.V.& nbsp;& nbsp;

关键词 ：

4H-SiC wafer Response surface methodology (RSM) Artificial neural network (ANN) Femtosecond laser Precision manufacturing

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摘要 ：

The third generation semiconductors, such as Silicon Carbide (SiC), are widely used in aerospace, automobile and other industries. It has a lot of characteristics such as wide band gap, high thermal conductivity and high bonding energy etc. Since its hardness is only less than that of diamond, it is difficult to be cut during semiconductor process. SiC semiconductor devices are still mainly in the research and development stage, but the process is basically similar to Si semiconductor production process. The cutting process is the first stage during semiconductor process, during which crystal ingot is cut into wafer. This process produces a large number of surface defects. If the defects are not removed, the defects will be copied to the epitaxial layer. Therefore, it is necessary to remove surface damage and defects before the epitaxial process to improve the surface quality. The result shows the optimal tool parameters are small negative rake angle (-30 degrees) and large clearance angle (15 degrees). The cutting force in second cutting process is less than the first cutting process and it enters the stable stage more quickly. Considering that the second cutting process contains a part of the amorphous structure, the required cutting force will become smaller which means the material easier to remove.

关键词 ：

interference effect tool shape Silicon Carbide (SiC)

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本文采用基于密度泛函理论的第一性原理计算,使用CASTEP软件建立了4H-SiC重掺杂模型,对通过激光辐照固态Al膜制备的p型重掺杂4H-SiC薄膜的晶体结构和电子结构进行了计算分析,研究获得不同浓度Al掺杂4H-SiC的能带结构和态密度.结果表明,随着Al原子掺杂浓度的增大,辐照样品禁带宽度随之减小,费米能级进入价带,体现出p型半导体的特征.结合二次离子质谱测试分析,得到Al掺杂浓度随辐照层深度的变化规律, Al掺杂浓度在30 nm范围内较为均匀,约为1×10~(20)cm~(–3).证明KrF准分子激光可以实现4H-SiC之Al原子重掺杂,随着深度的增加,激光能量密度逐渐降低, 4H-Si...

关键词 ：

4H-SiC Al掺杂 二次离子质谱分析 激光辐照 第一性原理计算

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采用KrF准分子激光辐照4H-SiC制备石墨烯层,从4H-SiC晶面取向对石墨烯生长质量影响的角度开展研究工作,分析激光能量密度、脉冲数及晶面取向对石墨烯质量的影响。当激光能量密度为1.06 J/cm~2,脉冲数为8000时,4H-SiC样品极性Si(0001)面和非极性■面上生长的石墨烯质量均达到最好。石墨烯与4H-SiC衬底极性Si(0001)面之间存在缓冲层,为石墨烯的生长提供了模板,得到的石墨烯更为有序,缺陷态更少;而非极性■面上生成的石墨烯与衬底之间未生成缓冲层,生长的石墨烯层较为无序,对激光参数的变化更为敏感。

关键词 ：

4H-SiC 晶面指数 材料 激光辐照 石墨烯

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We demonstrate the surface defect type, density and related electrical modification of graphene sheet generated by 193-nm ArF excimer laser irradiation on n-type 4H-SiC. The charge density difference and partial density of states (PDOS) carried out by density functional theory (DFT) calculations predict the graphene with lattice imperfection can induce virtual bound states at the vacancy sites and Fermi level shift compared to perfect graphene. The surface defects density of laser generated graphene is characterized by nanoscale electrical measurements using the conductive atomic force microscope (c-AFM). The corresponding current-voltage (I-V) curves show that the electronic charge transfers, thereby electrical conductivities of laser generated graphene, are influenced by the lattice defects. The defect densities are tunable by change laser fluence and pulse number. This research provides an understanding of the interfacial transport properties between laser generated graphene and 4H-SiC through a detailed analysis of surface defects. (C) 2020 The Authors. Published by Elsevier B.V.

关键词 ：

Graphene Interfacial transport Laser SiC Surface defect

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In this paper, enhancement of Aluminum doping profile in semi-insulating 4H-SiC by using Eximer laser in AlCl3 aqueous solution is focused. Several active parameters like number of shots, laser power and dopants solution density affect the doping mechanism. Laser doping with increase of AlCl3 solution concentration from 28 to 36 wt.% results in more efficient doping with merging features like better ohmic contact formation having ideal symmetry factor. Hall Effect measurement using Van der Pauw method show that laser produces a highly doped p-type layer with increasing carrier concentration from 10(12) /cm(2) to a maximum 10(15)/cm(2) by tuning parameter. Current-Voltage characteristics of modified region show the ohmic behavior with reduction in resistance. UV spectrometer absorption tangent line shifts from 375 nm to 401 nm indicating that Al impurity has been introduced in 4H-SiC.

关键词 ：

SiC AlCl3 solution Excimer Laser doping carrier concentration

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We used a 193-nm ArF excimer laser to produce a surface functional layer with a tunable Schottky barrier height (SBH) on the n-type 4H-SiC surface. The SBHs of the laser-modified layer/SiC contact ranged from 0.38 +/- 0.05 to 1.82 +/- 0.1 eV. We evaluated the I-V characteristics of Schottky barrier diodes (SBDs) and investigated their corresponding nanoscale current transport characteristics across the laser-modified layer/4H-SiC interface. We attributed changes of the interfacial transport properties between Au and SiC to the laser-induced formation of SiOx/Si compounds with oxygen vacancies in the nitrogen-doped (N-doped) defective graphitic structure. Density functional theory calculations suggested that defect oxide in the SiOx/Si decreased the Schottky barrier width and increased the direct electron tunneling current. Furthermore, the Fermi level of the laser-induced N-doped defective graphitic structure shifted towards the conduction band compared with that of pristine graphene, which was also beneficial for reducing the SBH. This study provides a novel understanding of the interfacial interactions of a laser-modified layer on SiC through nanoscale electrical analysis. These findings will be useful for further investigations of SiC-based nano-photoelectric devices.

关键词 ：

Excimer laser SiC Interface Schottky barrier height

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As the research on the 3rd generation semiconductor goes further, SiC wafer has gained popularity in the market, because its distinctive properties allows it to overcome the limitations of Si wafer, which enables SiC to contribute to the breakthrough in a number of areas. The one-dimensional polymorphism of SiC means that SiC with different polytypes share the same tetrahedral arrangement of Si and C atoms but differ in stacking sequences. In this study, molecular dynamics (MD) method is adopted to study the nano grinding process of 3C-SiC and 4H-SiC, and the performance parameters of the two during the grinding process will be discussed in order to explore the functional differences and give reference for the application of SiC in various scenarios. The result indicates that SiC grinding process is the plastic removal process of materials, and the crystal structure of surface atoms becomes amorphous structure after grinding process. Higher cutting speed can make the material more ductile and easier to be removed. It also leads to better work surface.

关键词 ：

MD SiC grinding

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采用等离子体增强化学气相沉积(PECVD)低温处理和高温快速退火的技术,研究了退火条件对SiO_2/4H-SiC界面态密度的影响。在n型4H-SiC外延片上高温干氧氧化50 nm厚的SiO_2层并经N_2原位退火,随后在PECVD炉中对样品进行350℃退火气氛为PH_3,N_2O,H_2和N_2的后退火处理,之后进行高温快速退火,最后制备Al电极4H-SiC MOS电容。I-V和C-V测试结果表明,各样品的氧化层击穿场强均大于9 MV/cm,PH_3处理可以降低界面有效负电荷和近界面氧化层陷阱电荷,但PH_3处理样品的界面态密度比N_2O处理的结果要高。经N_2O氛围PECVD后退火样品在距离...

关键词 ：

C-V测试 4H-SiC 界面态密度 MOS电容 等离子体增强化学气相沉积(PECVD)

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通过激光辐照固态Al膜,制备了一种p型重掺杂4H-SiC,分析了Al膜厚度、激光脉冲个数对掺杂结果的影响,验证了不同工艺参数对p型掺杂层表面电学性能的调控作用。结果表明,当Al膜厚度为120nm,脉冲个数为50时,掺杂试样的最大载流子浓度为6.613×10~(17) cm~(-3),最小体电阻率为17.36Ω·cm,掺杂浓度(粒子数浓度)可达6.6×10~(19) cm~(-3)。4H-SiC的Al掺杂改性机理为:在紫外激光作用下,Si—C键断裂,Al原子替代Si原子形成p型掺杂层。

关键词 ：

Al掺杂 准分子激光 半绝缘4H-SiC 薄膜

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