用于GaN薄膜生长的γ-LiAlO_2晶体基片制备工艺研究
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摘要
研究了铝酸锂晶体的化学机械抛光工艺。自制了SiO2悬浮液作为抛光剂,主要研究抛光过程中抛盘转速、抛光时间以及抛光压力等系列抛光工艺参数对抛光晶片表面质量的影响规律。通过优化抛光工艺参数获得了适宜制备氮化镓薄膜的铝酸锂晶体基片,最小的表面粗糙度为2.695 nm。结合氮化镓薄膜的制备条件,对抛光好的铝酸锂晶体基片采用退火的方法去除生长态晶体的热应力和机械应力。利用扫描电子显微镜研究了退火后晶片的表面质量,同时用激光共聚焦技术研究了晶体表面腐蚀坑的三维形貌。退火处理导致了铝酸锂晶体表面腐蚀坑的数目和深度增加。随着退火温度的升高和退火的保温时间的增加,铝酸锂晶体中锂元素挥发,晶体表面质量下降。但是适当的保温时间能够改善铝酸锂晶体的完整性,释放在晶体生长和试样制备过程中存在的热应力和机械应力,改善了晶体质量。
LiAlO2 crystal was polished by chemical and mechanical polishing( CMP) method with SiO2 soliquoid. The effect of polishing velocity,time and pressure on the property of γ-LiAlO2 crystal surface was investigated. After being polished at the optimum conditions,the roughness of crystal surface is up to2. 695 nm,which meets the requirement for epitaxial growth of Ga N thin film. The polished LAO crystal is annealed to release thermal and mechanical stress formed in crystal growth and processing. The threedimension topography of crystal surface pits is observed with laser scanning confocal microscopy( LSCM)technology. Annealing caused the number and depth of etching pits on the surface of γ-LiAlO2 increasing. The results show that as the annealing temperature increasing,Li element will volatilize,which deteriorates the crystal surface. The crystal surface perfection can be improved and the thermal stress generated in crystal growth can be released by choosing the appropriate annealing time.
LiAlO2 crystal was polished by chemical and mechanical polishing( CMP) method with SiO2 soliquoid. The effect of polishing velocity,time and pressure on the property of γ-LiAlO2 crystal surface was investigated. After being polished at the optimum conditions,the roughness of crystal surface is up to2. 695 nm,which meets the requirement for epitaxial growth of Ga N thin film. The polished LAO crystal is annealed to release thermal and mechanical stress formed in crystal growth and processing. The threedimension topography of crystal surface pits is observed with laser scanning confocal microscopy( LSCM)technology. Annealing caused the number and depth of etching pits on the surface of γ-LiAlO2 increasing. The results show that as the annealing temperature increasing,Li element will volatilize,which deteriorates the crystal surface. The crystal surface perfection can be improved and the thermal stress generated in crystal growth can be released by choosing the appropriate annealing time.
引文
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[9]Huang T,Zhou S,Teng H,et al.Growth,Etching Morphology and Spectra of Li Al O2Crystal[J].Crystal Research and Technology,2008,43(8):801.
[10]刘立新,张学建,张莹,等.铌酸锂晶体的抛光机理及精密加工工艺[J].硅酸盐学报,2008,36(11):1609.
[11]徐科,邓佩珍,徐军,等.两种新型衬底材料Li Al O2和Li Ga O2晶体的腐蚀形貌和缺陷研究[J].硅酸盐学报,1998,26(3):281.
[12]Waltereit P,Brandt O,Trampert A,et al.Nitride Semiconductors Free of Electrostatic Fields for Efficient White Light Emitting Diodes[J].Nature,2000,406:865.
[13]Chou M,Huang H,Gan D,et al.Defect Characterizations ofγ-Li Al O2Single Crystals[J].Journal of Crystal Growth,2006,291(2):485.
[14]Brik M G,Avram N M,Avram C N.Crystal Field Analysis of Energy Level Structure of Li Al O2∶V3+and Li Ga O2∶V3+[J].Spectrochimica Acta,2006,(63A):759.