基于磨损行为的单晶硅片化学机械抛光材料的去除特性

为了掌握化学机械抛光（CMP）过程中硅片表面材料的去除行为,根据CMP过程中硅片表面材料的磨损行为,建立了硅片CMP时的材料去除率构成成分模型,设计了不同成分的抛光液并进行了材料去除率实验,得出了机械、化学及其交互作用所引起的材料去除率.结果显示,机械与化学的交互作用率为85.7%～99.1%.磨粒的机械作用率为69.5%～94.0%,磨粒的机械与化学交互作用率为55.1%～93.1%.由此可见,磨粒的机械作用是化学机械抛光中的主要机械作用,磨粒与抛光液的机械化学交互作用引起的材料去除率是主要的材料去除率.研究结果可为进一步研究硅片CMP时的材料去除机理提供理论参考依据.     

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正碳化硅作为具有良好性能的第三代半导体材料,在MEMS、高能半导体器件等领域具有很大发展潜力.但该类材料硬度高、脆性大,加工困难,通常采用化学机械抛光(CMP)实现其基片表面的全局平坦化加工.CMP依靠嵌入抛光垫的磨粒对基片表面化学改性层进行机械去除,切削深度为纳米级.由于尺寸效应,传统切削理论无法很好地解释其机理,而分子动力学(MD)是探究原子尺度过     

轴向超声振动磨削硬脆性材料表面粗糙度建模研究

假设磨粒切削沟槽轮廓截面为一系列顶角等于磨粒的锥顶角、深度服从瑞利分布的三角形,并考虑磨粒运动轨迹重叠效应的影响,建立了轴向超声振动磨削硬脆性材料的表面粗糙度模型。以K9光学玻璃为实验材料,对比分析了未考虑和考虑了磨粒运动轨迹重叠效应的表面粗糙度模型的拟合精度,结果表明:后者表征超声磨削表面粗糙度更接近实验结果,且超声磨削表面粗糙度模型反映的磨削参数和振动参数对表面粗糙度的影响趋势与实验结果相一致,从而验证了所建模型的正确性和有效性。     

立方碳化硅CMP过程中机械作用分子动力学仿真

为了更好地理解立方碳化硅在化学机械抛光(CMP)过程中原子层面的材料去除机理,利用分子动力学(MD)方法建立了金刚石磨粒刻划碳化硅的原子模型,仿真研究了金刚石磨粒半径、刻划深度和刻划速度对碳化硅表面形貌、晶体结构、摩擦力和原子去除率的影响规律,并与无定型二氧化硅氧化膜的机械刻划作用的仿真结果进行了对比分析.结果发现:碳化硅在机械刻划过程中局部会出现非晶态变化;刻划深度增大会导致切削力和切削温度增大,原子去除率也随之增加;刻划速度的改变会影响温度和原子去除率,而对切削力几乎无影响;磨粒半径的增加会导致切削力和温度的增加,在压入深度相同的情况下对原子去除率影响不大;碳化硅表面生成的二氧化硅膜能大幅度降低切削力,但由于其结构的影响,机械刻划作用仅使氧化膜产生明显的致密化,而不产生磨屑.     

3英寸SiC衬底无架行星式双面抛光运动学分析

针对3英寸SiC衬底的精密抛光加工,设计了其无架行星式适应性双面抛光机构的几何模型。推导了抛光垫上任一点磨粒A相对SiC衬底的运动轨迹方程。利用C#和Matlab联合仿真对太阳轮、行星轮、齿圈以及抛光盘转速和运动轨迹的曲率等工艺参数进行了分析。基于ADAMS工具,进行了双面抛光的运动学仿真,得到了3英寸SiC衬底表面5点的位移、速度、加速度随时间变化的曲线。仿真结果表明,当齿圈和太阳轮转速比m=-1.25;抛光盘和太阳轮转速比n=1;磨粒分布半径(RA)适当增加时,磨粒在晶片上走过的轨迹范围增大;得到的抛光轨迹更加均匀。根据仿真的最优参数进行实验,机械抛光后获得了材料去除率(MRR)为1~2μm/h,表面粗糙度(Ra)小于2nm,总厚度变化(TTV)、弯曲度(BOW)、翘曲度(Warp)均小于15μm的SiC衬底。验证了理论模型的正确性和虚拟样机的合理性。     

轴向超声振动辅助磨削的表面残余应力建模EI北大核心CSCD

以单颗磨粒为对象,分析了轴向超声振动下磨粒的运动特性;在此基础上,将磨削力分为切削变形力和摩擦力两部分,分别分析了轴向超声振动对切屑变形力和摩擦力的影响。在切削变形力方面,轴向超声振动改变了磨粒的运动方向和运动轨迹;在摩擦力方面,轴向超声振动降低了磨粒与工件间的摩擦因数;结合切向磨削力与热源强度的关系,以及温升是磨削表面残余应力产生的主要因素,建立了轴向超声振动辅助磨削的表面残余应力模型。进行轴向超声振动辅助磨削45钢的表面残余应力实验,确定了模型的常数,并验证了所建模型的正确性。     

不同磨料对微晶玻璃化学机械抛光的影响

为了提高微晶玻璃化学机械抛光(CMP)的材料去除速率(MRR),降低其表面粗糙度,利用自制的抛光液对微晶玻璃进行化学机械抛光,研究了4种含不同磨料(Si O2、Al2O3、Fe2O3、Ce O2)的抛光液对微晶玻璃化学机械抛光MRR和表面粗糙度的影响.利用纳米粒度仪检测抛光液中磨料的粒径分布和Zeta电位,利用原子力显微镜观察微晶玻璃抛光前后的表面形貌.实验结果表明,在相同条件下,采用Ce O2作为磨料进行化学机械抛光时可以获得最好的表面质量,抛光后材料的表面粗糙度Ra=0.4 nm,MRR=100.4 nm/min.进一步研究了抛光液中不同质量分数的Ce O2磨料对微晶玻璃化学机械抛光的影响,结果表明,当抛光液中Ce O2质量分数为7%时,最高MRR达到185 nm/min,表面粗糙度Ra=1.9 nm;而当抛光液中Ce O2质量分数为5%时,MRR=100.4 nm/min,表面粗糙度最低Ra=0.4 nm.Ce O2磨料抛光后的微晶玻璃能获得较低表面粗糙度和较高MRR.     

兆声化学机械复合抛光及其抛光均匀性的实现

在匹配层结构压电换能器的基础上,通过对兆声压电振子的振动模式进行控制,在横向尺度上实现了兆声抛光工具头振动振幅的均匀化,进而开展了有/无兆声作用下硅片的化学机械抛光实验.抛光后,无兆声作用硅片的表面粗糙度Ra均值达到0.072μm,兆声作用硅片的表面粗糙度Ra均值达到0.020μm.测量了被抛光硅片的平面度,相对于无兆声作用硅片的平面度的PV值28μm,兆声作用硅片PV值显著下降,为21μm.可见,相对于传统化学机械抛光,兆声化学机械复合抛光能够有效地改善原有抛光工艺,提高硅片抛光表面质量,实现其抛光均匀性.     

海外文献速递

电　镀2 0 0 0 0 5 0 1　 W在化学机械抛光过程中的电化学行为研究——Stein D J. JElectrochem Soc,1998,145 (9) :3190 (英文 )通过观察 W在化学机械抛光过程中的电化学行为 ,研究了W表面的钝化和研磨机理 ,在实验槽中进行了电化学检测 ,测定了抛光速度。氧化铝类抛光膏含 KI、Fe(NO3) 3或过硫酸铵 ,测定了抛光期间 W的氧化速度及静电位下的抛光速度。2 0 0 0 0 5 0 2　氮化硅的化学机械抛光机理—— Hu Y Z.JElectrochem Soc,1998,145 (11) :3919(英文 )为了阐明 Si3N4的化学机械抛光原理 ,分析了化学抛光前后的低压 CVD Si3…     

超声振动辅助固结磨粒抛光硅片表面形貌及粗糙度研究

高面型精度和高表面质量的硅片表面加工是目前研究的难点和热点问题之一,基于超声加工所具有的加工效率和加工表面质量高的特性,以及固结磨粒的加工质量易控制和对环境污染小的特点,开展超声椭圆振动辅助固结磨粒抛光硅片的材料去除、抛光表面面型精度及粗糙度的加工机理及实验研究。研究认为抛光工具运动轨迹是影响上述问题的主要因素,为此在对抛光实验系统描述基础上,分析并建立了抛光工具运动轨迹及轨迹密度模型,进而完成硅片材料去除,抛光表面形貌和表面粗糙度的建模仿真。开展相应的实验研究,发现理论分析与实验的结果相一致,基于抛光工具运动轨迹建模的可行性。该研究方法和得出结论为今后开展固结磨粒抛光硅片表面实验的工艺参数的选择和优化,提供了可供借鉴的研究成果,为实际生产提供了可供参考的理论依据。     

Modeling and calculation of slurry-chemistry effects on chemical–mechanical planarization with a grooved pad

During chemical–mechanical planarization (CMP), a rotating wafer is pressed against a rotating pad, while a slurry is dragged into the pad–wafer interface. Here, taking into account the dependence of local material removal rate (MRR) on the slurry’s chemical activity, the effects of pad groove geometry and various other process parameters on the spatial average and non-uniformity of MRR are examined. Technically, the slurry flow is calculated by following an existing approach that integrates two-dimensional fluid-film lubrication theory and contact-mechanics models. A slurry impurity transport equation is then used to calculate the impurity concentration that determines the slurry’s chemical activity and hence the local MRR. The numerical results obtained here indicate that the presence of pad grooves generally decreases the average slurry impurity concentration, and increases the average contact stress on the pad–wafer interface. However, as a grooved pad has less contact area for effective interaction with the wafer surface, the average MRR may or may not be increased, depending upon the specific setting of process parameters. Meanwhile, it appears that the retaining ring generally used to keep the wafer in place also plays an important part in reducing the MRR non-uniformity.     

Surface Removal Rate in Chemical-Mechanical Polishing

Variation of the surface removal rate with down pressure, pad asperity, and relative velocity in chemical-mechanical polishing (CMP) was studied. A phenomenological model for contact of pad asperities with abrasive particles and wafer is described. The functional dependence of the polishing rate on pressure and velocity was found to be related to the distribution of pad asperities. Simple argument based on the mechanical contact theory suggests that the linear variation predicted by Preston's equation follows when the pad asperities have a random distribution. The sublinear dependence of the removal rate, however, is obtained when the pad asperities have a wavy distribution. The use of the statistical least-square method is suggested as a way to determine the relationship between the removal rate and pressure for different industrial pads used in CMP processes.

CMP polishing planarization surface removal     

A chemical mechanical polishing model incorporating both the chemical and mechanical effects

A comprehensive model for the material removal in a chemical mechanical polishing (CMP) process is presented in which both chemical and mechanical effects are taken into consideration. The chemical effects come into play through the formation of chemically modified surface layer on the wafer surface that, in turn, is removed mechanically by the plastic deformation induced by slurry particles. This model describes the influence of most, if not all, variables involved in the CMP process including slurry characteristics (solid loading, particle size and distribution, modulus), pad properties (modulus, hardness, asperity sizes and distribution) and processing conditions (down-pressure, velocity). Although more elaborate experimental verification of the model is yet to follow, this model appears to be capable of explaining many experimental observations on both oxide and metal CMP that, otherwise, could not be explained properly.     

Macroscopic and microscopic investigation on chemical mechanical polishing of sapphire wafer

Sapphire (alpha-Al2O3) is an important ceramic material that is widely used in substrate material for electronics. We investigate the chemical reaction layer on a sapphire wafer using X-ray photoelectron microscopy (XPS) and atomic force microscopy (AFM). The frictional characteristics of sapphire chemical mechanical polishing (CMP) was studied using in-situ friction force monitoring system. From XPS analysis and AFM experiment, a chemically-reacted layer was verified on the sapphire surface through a chemical reaction between the sapphire and chemicals in a slurry. During sapphire CMP, the friction force mainly depended on the applied pressure. The material removal efficiency per unit friction energy in sapphire CMP was 6.18 nm/kJ.     

Quality improvement of chemical-mechanical wafer planarization process in semiconductor manufacturing using a combined generalized linear modelling - non-linear programming approach

This paper is aimed at how to develop and utilize a specialized response surface method, combined with state-of-the-art mathematical programming techniques, for quality improvements of the chemical-mechanical planarization (CMP) process in semiconductor manufacturing. CMP is one of the fastest growing technologies that enables to polish the topography of interlayer dielectrics (ILDs) and to obtain a high degree of global planarity due to increasingly stringent requirements of photolithography between process steps. A wafer held on a carrier is rotated against a polishing pad in the presence of a silica-based alkaline slurry while applying a down-force onto it. Two major challenging works posed by CMP involve maintaining stable removal rate with polishing time and achieving acceptable within-wafer non-uniformity (WIWNU) over an entire die. In this research, to robustly characterize and therefore optimize such a still unclear and fully complex process, the response surface methodology (RSM) as an external modelling technique and non-linear programming (NLP) approaches as an optimum-seeking procedure are proposed to the bicriteria situation. An example with real CMP data is rigorously investigated, revealing that not only does the proposed method flexibly and appropriately portray CMP, but also helps locate the optimal parameter settings that attain better polishing quality.     

材料特性对亲水性固结磨料研磨垫加工性能的影响

为研究材料特性对亲水性固结磨料研磨垫的加工性能影响,本文研究了K9玻璃和硅片两种材料在不同加工顺序下研磨过程中的声发射信号和摩擦系数特征,采用扫描电镜分析磨屑的尺寸与形态.结果表明:不同加工顺序下工件的材料去除速率差别很大.与直接研磨硅片相比,先研磨K9玻璃再研磨硅片,硅片的材料去除速率大幅下降;相反,先研磨硅片再研磨K9玻璃,与直接研磨K9玻璃相比,K9玻璃的材料去除速率变化不大.无论采用哪种加工顺序,后研磨的工件表面粗糙度均比直接研磨的同种工件要大.扫描电镜的分析表明,硅片的磨屑尺寸集中在600 nm~1.5μm,磨屑大部分都棱角完整;而K9玻璃的磨屑尺寸集中在300 nm~500 nm左右,无明显棱角.硅片磨屑较大的尺寸与完整的棱角促进了研磨垫的自修正过程,所以硅片这类脆性较大的材料有利于研磨垫的自修正过程.     

铝化学机械抛光中1,2,4-三唑和苯并三氮唑的缓蚀机制

揭示铝低压力化学机械抛光(CMP)中的弱缓蚀机制是铝CMP研究的关键问题。采用CMP试验,研究了1,2,4-三唑(TAZ)和苯并三氮唑(BTA)对铝表面去除率的影响规律;通过接触角和表面原子力显微镜(AFM)试验,分析了TAZ和BTA薄膜在铝表面的亲水性能,发现由TAZ作用形成的缓蚀薄膜比由BTA形成的缓蚀薄膜更厚,更易渗透与去除。结合摩擦磨损试验和Arrhenius公式,探讨了TAZ和BTA在CMP过程中对铝表面化学反应活化能的影响。结果显示:TAZ的活化能小于BTA,更容易形成弱缓蚀薄膜,机械促进化学作用的效果更明显。     

Chemical mechanical polishing (CMP) of on-axis Si-face 6H-SiC wafer for obtaining atomically flat defect-free surface

Due to its high mechanical hardness and excellent chemical inertness, SiC single-crystal wafer is extremely difficult to realize effectively removed total planarization. Owing to crystalline polarity and anisotropy, material removal rate (MRR) on Si-face (0001) of SiC wafer is significantly lower than C-face (000 $ \bar{1} $ ) for a defect-free surface. In the paper, the slurry containing hydrogen peroxide (H₂O₂), potassium hydroxide and abrasive colloidal silica, is introduced to chemical mechanical polishing (CMP) of on-axis Si-face 6H-SiC wafer, resulting in acquiring high MRR with 105 nm/h, and atomically flat defect-free surface with atomic step-terrace structure and roughness of 0.0667 nm by atomic force microscope (AFM), in order to satisfy further demands of electronic device fabrication towards substrate wafer performance. The effects of the three ingredients in the slurry towards MRR of SiC wafer, polished surface quality and coefficient of friction in polishing process are studied. Optical microscope, optical interferometry profiler and AFM are used to observe the polished surface. In addition, the CMP removal mechanism of SiC wafer and the formation of ultra-smooth surface are discussed.     

Surface-complex films of guanidine on tantalum nitride electrochemically characterized for applications in chemical mechanical planarization

Chemical mechanical planarization (CMP) of tantalum nitride is an essential step of material processing in the fabrication of integrated circuits. This CMP step often involves the chemical formation of a structurally weak oxide-complex film on the wafer surface, followed by selective removal of the film with mechanical abrasion under reduced loading. The present work investigates certain chemical aspects of this strategy of TaN-CMP by using guanidine carbonate (GC) as a surface complexing agent, and employing electrochemical experiments. The experiments are designed to study the chemical and electrochemical origins of the CMP-specific surface complex films formed on a TaN wafer in acidic solutions of GC and hydrogen peroxide. Open circuit potential, polarization resistance, and electrochemical impedance measurements are employed to probe the surface effects that facilitate material removal in chemically prevailing CMP of TaN. The results are discussed in view of designing slurry variables to support barrier layer planarization with reduced roles of mechanical abrasion.