硅酸盐学报2025，Vol.53Issue(12)：3494-3505,12.DOI:10.14062/j.issn.0454-5648.20250536
直拉单晶硅氧浓度控制技术研究进展
Research Progress on Oxygen Concentration Control Technology of Czochralski Monocrystalline Silicon
摘要
Abstract
Czochralski(CZ)monocrystalline silicon is a dominant substrate material for integrated circuit manufacturing,accounting for over 90%of global silicon wafer production.During CZ silicon growth,oxygen impurities dissolve from quartz crucibles(SiO2)into silicon melt at sustained high temperatures,ultimately incorporating into the crystal lattice.Oxygen in silicon affects essential substrate properties,including resistivity,mechanical strength,metal gettering capability,and carrier lifetime.Different applications impose divergent oxygen specifications.For instance,solar cells require concentrations of<7×1017 atoms·cm-3 to minimize minority carrier lifetime degradation.Insulate Gate Bipolar Transistor(IGBT)power devices demand ultra-low oxygen(i.e.,<2.5×1017 atoms·cm-3)to suppress leakage current and breakdown voltage fluctuations.Furthermore,3D-NAND flash memory necessitates a precise oxygen precipitate control to balance thermo-mechanical stress in multi-layer architectures.It is thus paramount for device performance and manufacturing yield to understand oxygen transport physics and achieve precise concentration control. Oxygen transport in Cz silicon growth involves four primary mechanisms,i.e.,1)Crucible Dissolution:Oxygen dissolves from the quartz crucible wall into the silicon melt via the reaction(SiO2(s)Si(l)+2O(l)).The temperature dependence of oxygen solubility remains a subject of debate,2)Melt Transport:Dissolved oxygen moves through the melt via convection and diffusion(governed by convection-diffusion equations),heavily influenced by melt flow dynamics,3)Free Surface Volatilization:Oxygen evaporates at the melt surface as SiO gas(Si(l)+O(l) SiO(g)),affected by argon ambient pressure and flow rate,and 4)Crystallization Segregation:The amount of oxygen that incorporates into crystal at the solid-liquid interface is affected by the solubility difference of oxygen between the silicon melt and the crystal.The complex,highly nonlinear interplay between these mechanisms presents a core scientific challenge.As segregation effects are dominated by the intrinsic characteristics of oxygen and silicon atoms and are difficult to control,the related research advancements involve. 1)Crucible Dissolution Control:Conventional approaches focus on thermal field optimization.Implementing dual-heater systems improves power distribution,compared to single heaters,effectively lowering localized crucible temperatures and subsequently reducing crystal oxygen content.Alternative strategies involve material modifications,such as applying Si3N4 coatings to quartz crucibles or using graphite crucibles with similar coatings,which can significantly suppress oxygen dissolution.However,these material substitutions introduce substantial trade-offs,including elevated carbon contamination(i.e.,>5×1017 atoms·cm-3)and nitrogen doping(i.e.,>3×1015 atoms·cm-3),requiring a further evaluation. 2)Melt Flow Control:Melt convection plays a pivotal role in oxygen transport.Precise manipulation of crystal and crucible rotation rates and directions impacts flow patterns and oxygen distribution,though identifying optimal settings becomes a challenge due to complex,field-dependent behavior.Magnetic fields are essential for stabilizing turbulent flow in large melts and reducing oxygen concentration consequently.Transverse Magnetic Fields(TMF)provide a strong turbulence suppression(i.e.,0.5 T)but often induce radial oxygen non-uniformity.Conversely,Cusp Magnetic Fields(CMF)offer a better radial uniformity but with lower field strengths(i.e.,0.1 T).The impact of Zero-Gauss plane(ZGP)position and coil current ratio varies considerably,indicating context-specific dependence.Innovations like quadrupole magnetic fields show a promise for unifying transverse-field stability with an enhanced radial homogeneity. 3)Free surface Volatilization Control:This strategy is to control oxygen concentration via SiO evaporation via manipulating the ambient argon environment.Lower argon pressure and higher argon flow rates generally promote SiO volatilization kinetics and reduce crystal oxygen incorporation,as reduced gas-phase partial pressure facilitates oxygen evaporation at the melt-gas interface.This relationship is consistently determined in both experimental measurements and theoretical models.Complementing gas parameter adjustments,heat shield design optimization offers a secondary control via altering the gas flow geometry above the melt.Specifically,tailored shield structures minimize argon recirculation zones that otherwise trap SiO vapor,thereby reducing local saturation and enhancing overall volatilization efficiency.However,shield modifications are less common in semiconductor-grade silicon production because they affect thermal gradients near the crystal,potentially disrupting the critical v/G ratio required for defect-free crystal growth.Furthermore,volatilization efficiency is not solely governed by gas dynamics.Complex interface phenomena on the melt surface(i.e.,Marangoni convection and argon shear stress effects)also significantly affect oxygen evaporation rates.The interaction between these melt-surface flows and gas-phase mass transfer remains inadequately quantified,representing an important area for future fundamental research to fully exploit volatilization-based oxygen control strategies. Summary and prospects This review analyzes critical oxygen control strategies in CZ silicon growth,essential for achieving substrate specifications across diverse applications.The primary approaches focus on reducing oxygen dissolution through thermal field design and crucible modification,optimizing melt convection and oxygen transport via rotation and magnetic fields,and enhancing free surface volatilization by controlling argon atmosphere. Some challenges persist,requiring a further research to clarify fundamental mechanisms.Key uncertainties include the temperature dependence of oxygen solubility and the precise mechanism relating crucible temperature reduction to lower crystal oxygen levels(primarily due to reduced dissolution or altered flow patterns).Understanding the complex coupling among detailed magnetic field distributions,resulting melt flow patterns and oxygen transport also requires a further investigation.Quantifying the influence of argon shear stress interacting with Marangoni forces on the melt surface is equally essential for refining volatilization models. Furthermore,complicating these challenges is the multi-variable,strongly coupled nature of the CZ system,which makes conventional trial-and-error optimization approaches time-consuming and costly.A future research should therefore prioritize the developing intelligent control systems that leverage artificial intelligence(AI)and machine learning for data-driven modeling,prediction,and efficient multi-parameter optimization.关键词
直拉单晶硅/氧输运/坩埚溶解/熔体流动/自由液面挥发Key words
Czochralski monocrystalline silicon/oxygen transport/crucible dissolution/melt flow/melt free surface volatilization分类
信息技术与安全科学引用本文复制引用
LIU Wenkai,LIU Yun,XUE Zhongying,WEI Xing..直拉单晶硅氧浓度控制技术研究进展[J].硅酸盐学报,2025,53(12):3494-3505,12.基金项目
中国科学院基础与交叉前沿科研先导专项(B类先导专项)(XDB0670102) （B类先导专项）
国家自然科学基金(62074152,62304232,62304233). （62074152,62304232,62304233）
