SiC晶片不同晶面的CMP抛光效果对比研究
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摘要
化学机械抛光(CMP)已被认为是目前实现Si C晶片全局平坦化和超光滑无损伤纳米级表面的最有效加工方法之一,然而Si C晶片的化学氧化反应受其表面极性的强烈影响,从而导致其不同晶面表面原子在CMP过程中的可氧化性以及氧化产物去除的难易程度存在差异。采用K2S2O8作为氧化剂、Al2O3纳米颗粒作为磨粒,对比研究了6H-SiC晶片Si面和C面的CMP抛光效果,并分析不同晶面对其CMP抛光效果的影响机理。结果表明,6H-SiC晶片Si面和C面的CMP抛光效果存在显著差异。6H-SiC晶片Si面的材料去除率在pH=6时达到最大值349 nm/h;相比之下,C面的材料去除率在pH=2时达到最大值1184 nm/h,抛光后的Si面和C面均比较光滑。氧化剂进攻C面上C原子的位阻明显小于其进攻Si面上的C原子的位阻,从而导致C面比Si面具有更高的反应活性和氧化速度。此外,C面上的氧化物比Si面上的氧化物更容易被去除,因此C面比Si面易于获得更高的材料去除率。
Chemical mechanical polishing(CMP) has been considered as the one of the most effective method to achieve global flatness and ultra-smooth surface of SiC wafers. However,the chemical oxidation reaction of Si C wafers is strongly influenced by its surface polarity,resulting in the difference in the oxidability of the surface atoms and the removable of the oxide products on the surface of the different crystal faces during the CMP process. In this study,the CMP polishing performance of the 6 H-SiC substrates surface between Si-face and C-face were compared using K2 S2 O8 and nano-alumina particles as the oxidant and abrasive particles respectively,and its influence mechanism of different crystals was also analyzed. The results indicate that the CMP polishing performance of the 6 H-SiC substrates on Si-face and C-face was significantly different. The maximum Material Removal Rate(MRR) of the Si-face of6 H-SiC substrates was 349 nm/h at pH of 6. In contrast,the material removal rate of C surface reaches the maximum value of 1184 nm/h at pH of 2,and the polished Si-face and C-face were both relatively smooth. The steric hindrance of the oxidant attacking C-atom on the surface of C-plane is significantlyless than that of C-atom on the surface of Si-plane,which leads to higher reactivity and oxidation rate on the surface of C-plane than on the surface of Si-plane. In addition,the oxide on C-face was easier to remove than that on Si-face. As a result,it was easier for C-face to obtain higher material removal rate than Si-face during 6 H-SiC CMP process.
Chemical mechanical polishing(CMP) has been considered as the one of the most effective method to achieve global flatness and ultra-smooth surface of SiC wafers. However,the chemical oxidation reaction of Si C wafers is strongly influenced by its surface polarity,resulting in the difference in the oxidability of the surface atoms and the removable of the oxide products on the surface of the different crystal faces during the CMP process. In this study,the CMP polishing performance of the 6 H-SiC substrates surface between Si-face and C-face were compared using K2 S2 O8 and nano-alumina particles as the oxidant and abrasive particles respectively,and its influence mechanism of different crystals was also analyzed. The results indicate that the CMP polishing performance of the 6 H-SiC substrates on Si-face and C-face was significantly different. The maximum Material Removal Rate(MRR) of the Si-face of6 H-SiC substrates was 349 nm/h at pH of 6. In contrast,the material removal rate of C surface reaches the maximum value of 1184 nm/h at pH of 2,and the polished Si-face and C-face were both relatively smooth. The steric hindrance of the oxidant attacking C-atom on the surface of C-plane is significantlyless than that of C-atom on the surface of Si-plane,which leads to higher reactivity and oxidation rate on the surface of C-plane than on the surface of Si-plane. In addition,the oxide on C-face was easier to remove than that on Si-face. As a result,it was easier for C-face to obtain higher material removal rate than Si-face during 6 H-SiC CMP process.
引文
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[2]彭同华,刘春俊,王波,等.宽禁带半导体碳化硅单晶生长和物性研究进展[J].人工晶体学报,2012,41(S1):234-241.
[3]刘桂玲,黄政仁,刘学建,等.碳化硅表面改性和光学镜面加工的研究现状[J].无机材料学报,2007,22(5):769-774.
[4] Zhou L,Audurier V,Pirouz P,et al. Chemomechanical polishing of silicon carbide[J]. Journal of the Electrochemical Society,1997,144(6):L161-L163.
[5] Neslen C L,Mitchel W C,Hengehold R L. Effects of process parameter variations on the removal rate in chemical mechanical polishing of 4HSiC[J]. Journal of electronic materials,2001,30(10):1271-1275.
[6] Lee H,Park B,Jeong S,et al. The effect of mixed abrasive slurry on CMP of 6H-SiC substrates[J]. Journal of Ceramic Processing Research,2009,10(3):378-381.
[7] Chen G M,Ni Z F,Xu L J,et al. Performance of colloidal silica and ceria based slurries on CMP of Si-face 6H-SiC substrates[J]. Applied Surface Science,2015,359:664-668.
[8] Zhou Y,Pan G S,Zou C L,et al. Chemical mechanical polishing(CMP)of Si C wafer using photo-catalyst incorporated pad[J]. ECS Journal of Solid State Science and Technology,2017,6(9):603-608.
[9] Wang C W,Kurokawa S,Doi T,et al. Surface morphology evolution induced by multiple femtosecond laser ablation on 4H-SiC substrate and its application to CMP[J]. ECS Journal of Solid State Science and Technology,2017,6(12):853-861.
[10] Wang C W,Kurokawa S,Doi T,et al. The Polishing Effect of Si C Substrates in Femtosecond Laser Irradiation Assisted Chemical Mechanical Polishing(CMP)[J]. ECS Journal of Solid State Science and Technology,2017,6(4):105-112.
[11] Zhu Z Z,Muratov V,Fischer T E. Tribochemical polishing of Silicon Carbide in Oxidant Solution[J]. Wear,1999,225-229(2):848-856.
[12] Hornetz B,Michel H J,Halbritter J. ARXPS studies of Si O2-SiC interfaces and oxidation of 6H Si C single crystal Si-(001)and C-(001)surfaces[J]. Journal of Materials Research,1994,9(12):3088-3094.