Chemical Mechanical Polishing of Glass Substrate with α-Alumina-g-Polystyrene Sulfonic Acid Composite Abrasive

Abrasive is the one of key influencing factors during chemical mechanical polishing（CMP） process. Currently, α-Alumina （α-Al2O3） particle, as a kind of abrasive, has been widely used in CMP slurries, but their high hardness and poor dispersion stability often lead to more surface defects. After being polished with composite particles, the surface defects of work pieces decrease obviously. So the composite particles as abrasives in slurry have been paid more attention. In order to reduce defect caused by pure α-Al2O3 abrasive, α-alumina-g-polystyrene sulfonic acid （α-Al2O3-g-PSS） composite abrasive was prepared by surface graft polymerization. The composition, structure and morphology of the product were characterized by Fourier transform infrared spectroscopy（FTIR）, X-ray photoelectron spectroscopy（XPS）, time-of-flight secondary ion mass spectroscopy（TOF-SIMS）, and scanning electron microscopy（SEM）, respectively. The results show that polystyrene sulfonic acid grafts onto α-Al2O3, and has well dispersibility. Then, the chemical mechanical polishing performances of the composite abrasive on glass substrate were investigated with a SPEEDFAM-16B-4M CMP machine. Atomic force microscopy（AFM） images indicate that the average roughness of the polished glass substrate surface can be decreased from 0.835 nm for pure α-Al2O3 abrasive to 0.583 nm for prepared α-Al2O3-g-PSS core-shell abrasive. The research provides a new and effect way to improve the surface qualities during CMP.

TWO STEPS CHEMICAL-MECHANICAL POLISHING OF RIGID DISK SUBSTRATE TO GET ATOM-SCALE PLANARIZATION SURFACE

In order to get atomic smooth rigid disk substrate surface, ultra-fined alumina slurry and nanometer silica slurry are prepared, and two steps chemical-mechanical polishing （CMP） of rigid disk substrate in the two slurries are studied. The results show that, during the first step CMP in the alumina slurry, a high material removal rate is reached, and the average roughness （Ra） and the average waviness （Wa） of the polished surfaces can be decreased from previous 1.4 nm and 1.6 nm to about 0.6 nm and 0.7 nm, respectively. By using the nanometer silica slurry and optimized polishing process parameters in the second step CMP, the Ra and the Wa of the polished surfaces can be further reduced to 0.038 nm and 0.06 am, respectively. Atom force microscopy （AFM） analysis shows that the final polished surfaces are ultra-smooth without micro-defects.

Effect of Abrasive Concentration on Chemical Mechanical Polishing of Sapphire

Effects of abrasive concentration on material removal rate CMRR） and surtace quality m the chemical mecnamcal polishing （CMP） of light-emitting diode sapphire substrates are investigated. Experimental results show that the MRR increases linearly with the abrasive concentration, while the rms roughness decreases with the increasing abrasive concentration. In addition, the in situ coefficient of friction （COF） is also conducted during the sapphire polishing process. The results present that COF increases sharply with the abrasive concentration up to 20 wt% and then shows a slight decrease from 20wt% to 40wt%. Temperature is a product of the friction force that is proportional to COF, which is an indicator for the mechanism of the sapphire CMP.

Electrochemical behavior and polishing properties of silicon wafer in alkaline slurry with abrasive CeO_2

The electrochemical behavior of silicon wafer in alkaline slurry with nano-sized CeO2 abrasive was investigated.The variations of corrosion potential(φcorr)and corrosion current density(Jcorr)of the P-type(100)silicon wafer with the slurry pH value and the concentration of abrasive CeO2 were studied by polarization curve technologies.The dependence of the polishing rate on the pH and the concentration of CeO2 in slurries during chemical mechanical polishing(CMP)were also studied.It is discovered that there is a large change of φcorr and Jcorr when slurry pH is altered and the Jcorr reaches the maximum(1.306 μA/cm2)at pH 10.5 when the material removal rate(MRR)comes to the fastest value.The Jcorr increases gradually from 0.994 μA/cm2 with 1% CeO2 to 1.304 μA/cm2 with 3% CeO2 and reaches a plateau with the further increase of CeO2 concentration.There is a considerable MRR in the slurry with 3% CeO2 at pH 10.5.The coherence between Jcorr and MRR elucidates that the research on the electrochemical behavior of silicon wafers in the alkaline slurry could offer theoretic guidance on silicon polishing rate and ensure to adjust optimal components of slurry.

Atomistic understanding of rough surface on the interfacial friction behavior during the chemical mechanical polishing process of diamond

The roughness of the contact surface exerts a vital role in rubbing.It is still a significant challenge to understand the microscopic contact of the rough surface at the atomic level.Herein,the rough surface with a special root mean square(RMS)value is constructed by multivariate Weierstrass–Mandelbrot(W–M)function and the rubbing process during that the chemical mechanical polishing(CMP)process of diamond is mimicked utilizing the reactive force field molecular dynamics(ReaxFF MD)simulation.It is found that the contact area A/A0 is positively related with the load,and the friction force F depends on the number of interfacial bridge bonds.Increasing the surface roughness will increase the friction force and friction coefficient.The model with low roughness and high lubrication has less friction force,and the presence of polishing liquid molecules can decrease the friction force and friction coefficient.The RMS value and the degree of damage show a functional relationship with the applied load and lubrication,i.e.,the RMS value decreases more under larger load and higher lubrication,and the diamond substrate occurs severer damage under larger load and lower lubrication.This work will generate fresh insight into the understanding of the microscopic contact of the rough surface at the atomic level.

Optimization of Polishing Parameters with Taguchi Method for LBO Crystal in CMP

Chemical mechanical polishing （CMP） was used to polish Lithium triborate （LiB3O5 or LBO） crystal. Taguchi method was applied for optimization of the polishing parameters. Material removal rate （MRR） and surface roughness are considered as criteria for the optimization. The polishing pressure, the abrasive concentration and the table velocity are important parameters which influence MRR and surface roughness in CMP of LBO crystal. Experiment results indicate that for MRR the polishing pressure is the most significant polishing parameter followed by table velocity; while for the surface roughness, the abrasive concentration is the most important one. For high MRR in CMP of LBO ctystal the optimal conditions are： pressure 620 g/cm^2, concentration 5.0 wt pct, and velocity 60 r/min, respectively. For the best surface roughness the optimal conditions are： pressure 416 g/cm^2, concentration 5.0 wt pct, and velocity 40 r/min, respectively. The contributions of individual parameters for MRR and surface roughness were obtained.

Chemically-induced active micro-nano bubbles assisting chemical mechanical polishing:Modeling and experiments

The material loss caused by bubble collapse during the micro-nano bubbles auxiliary chemical mechanical polishing(CMP)process cannot be ignored.In this study,the material removal mechanism of cavitation in the polishing process was investigated in detail.Based on the mixed lubrication or thin film lubrication,bubble-wafer plastic deformation,spherical indentation theory,Johnson-Cook(J-C)constitutive model,and the assumption of periodic distribution of pad asperities,a new model suitable for micro-nano bubble auxiliary material removal in CMP was developed.The model integrates many parameters,including the reactant concentration,wafer hardness,polishing pad roughness,strain hardening,strain rate,micro-jet radius,and bubble radius.The model reflects the influence of active bubbles on material removal.A new and simple chemical reaction method was used to form a controllable number of micro-nano bubbles during the polishing process to assist in polishing silicon oxide wafers.The experimental results show that micro-nano bubbles can greatly increase the material removal rate(MRR)by about 400%and result in a lower surface roughness of 0.17 nm.The experimental results are consistent with the established model.In the process of verifying the model,a better understanding of the material removal mechanism involved in micro-nano bubbles in CMP was obtained.

Preparation of CeO_(2) abrasives by reducing atmosphere-assisted molten salt method for enhancing their chemical mechanical polishing performance on SiO_(2)substrates

Ce^(3+)as the active site on the CeO_(2)abrasive surface is the key to enhancing the material removal rate(MRR).The CeO_(2)abrasives with high chemical activity were prepared by the molten salt method under a reducing atmosphere.The crystal structure and morphology of CeO_(2)abrasive s were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),Fourier transform infrared spectroscopy(FT-IR),ultraviolet—visible diffuse reflectance spectroscopy(UV-Vis DRS),and X-ray photoelectron spectroscopy(XPS).The CeO_(2)abrasives were obtained under different atmospheres(Air,Ar,and Ar/H_(2)).With the enhancement of the reducing atmosphere,the morphology of the abrasives transforms from spherical to octahedral,while more oxygen vacancies and Ce^(3+)are generated on the surface of CeO_(2)abrasives.The CMP experiments show that the MRRs of the CeO_(2)-Air,CeO_(2)-Ar,and CeO_(2)-Ar/H_(2)abrasives on SiO_(2)substrates are 337.60,578.74,and 691.28 nm/min,respectively.Moreover,as confirmed by atomic force microscopy(AFM),the substrate surfaces exhibit low roughness(20.5 nm)after being polished using all of the prepared samples.Especially,the MRR of CeO_(2)-Ar/H_(2)abrasives is increased by 104.76%compared with CeO_(2)-air abrasives.The improved CMP performance is attributed to the increased Ce^(3+)concentration and the octahedral morphology of the abrasives enhancing the chemical reaction and mechanical removal at the abrasive-substrate interface.

蓝宝石衬底CMP中氧化硅磨粒粒度分布对抛光液体系性能影响研究

目的 化学机械抛光(CMP)包含化学腐蚀和机械磨削两方面,抛光液p H、磨粒粒径和浓度等因素均会不同程度地影响其化学腐蚀和机械磨削能力,从而影响抛光效果。方法 采用30~150 nm连续粒径磨粒抛光液、120 nm均一粒径磨粒抛光液、50 nm和120 nm配制而成的混合粒径磨粒抛光液,分别对蓝宝石衬底晶圆进行循环CMP实验,研究CMP过程中抛光液体系的变化。结果 连续粒径磨粒抛光液中磨粒大规模团聚,满足高材料去除率的抛光时间仅有4 h,抛光后的晶圆表面粗糙度为0.665 nm;均一粒径磨粒抛光液中磨粒稳定,无团聚现象,抛光9 h内材料去除率较连续粒径磨粒抛光液高94.7%,能至少维持高材料去除率18 h,抛光后的晶圆表面粗糙度为0.204 nm;混合粒径磨粒抛光液初始状态下磨粒稳定性较高,抛光9 h内材料去除率较连续粒径磨粒抛光液高114.8%,之后磨粒出现小规模团聚现象,后9h材料去除率仅为均一粒径磨粒抛光液的59.6%,18 h内材料去除率仅为均一粒径磨粒抛光液的87.7%,但抛光后的晶圆表面粗糙度为0.151 nm。结论 一定时间内追求较高的材料去除率和较好的晶圆表面粗糙度选用混合粒径磨粒抛光液,但需要长时间CMP使用均一粒径磨粒抛光液更适合,因此,在工业生产中需要根据生产要求配合使用混合粒径磨粒抛光液和均一粒径磨粒抛光液。

阴/非离子型表面活性剂对CMP后SiO_(2)颗粒的去除效果

为了更有效地去除铜晶圆化学机械抛光(CMP)后清洗残留的SiO_(2)颗粒,选择了2种阴离子型表面活性剂(SLS、TD⁃40)和2种非离子型表面活性剂(AEO⁃5、JFC⁃6),通过接触角、表面张力、电化学、分子动力学模拟实验探究了4种表面活性剂在铜表面的润湿性、吸附构型及吸附稳定性。通过优化表面活性剂质量浓度,选择达到吸附稳定时的质量浓度配置4种表面活性剂来清洗铜晶圆,利用扫描电子显微镜观测铜表面形貌,对比它们的清洗效果。随后选择TD⁃40和JFC⁃6进行复配,研究复配后表面活性剂对硅溶胶颗粒的去除效果。实验结果表明,使用体积比为2∶1的TD⁃40与JFC⁃6进行复配得到的CMP清洗液对SiO_(2)颗粒的去除效果比单一表面活性剂的更好。

磨粒振动对碳化硅CMP的微观结构演变和材料去除的影响

针对化学机械抛光中磨料易团聚、机械和化学作用不能充分发挥等问题,采用振动辅助的方法进行优化。通过分子动力学模拟,分析磨粒振动的频率、振幅及其压入深度、划切速度对工件表面微观原子迁移的演变规律,揭示振动对材料去除和表面改善的促进机制;并通过振动辅助化学机械抛光工艺试验和表面成分分析,验证振动辅助的抛光效果和去除机制。结果表明:适当增大磨粒的振动频率、振动振幅及其压入深度、划切速度,可有效提高工件表面的原子势能和温度;磨粒振动有利于提高工件表面原子的混乱度,促进碳化硅参与氧化反应,形成氧化层并以机械方式去除;抛光试验和成分分析也证实振动可以提高材料去除率约50.5%,改善表面质量约25.4%。

半导体材料CMP过程中磨料的研究进展

对磨料在半导体材料化学机械抛光(CMP)中的应用和研究进展进行了简单阐述,从各代半导体材料制成半导体器件的加工要求介绍了磨料在半导体材料CMP中的重要性,从CMP过程中磨料与半导体材料的相互作用介绍了磨料在半导体材料CMP中的环保性,从磨料的改性和制备介绍了磨料在半导体材料CMP中应用的限制性,重点从半导体材料的去除速率和表面质量介绍了磨料对半导体材料抛光性能的影响,并对国内外研究中单一磨料、混合磨料和复合磨料对半导体材料抛光性能的影响进行了评述,总结了近年来磨料在半导体材料CMP中的研究进展。最后,对磨料在半导体材料CMP中存在的共性问题进行了总结,并对该领域所面临的挑战及发展方向进行了展望。

pH调节剂在CMP工艺中的应用研究进展

pH调节剂在化学机械抛光(CMP)工艺中有重要应用,可以调节抛光液的pH值以确保抛光过程的化学反应在理想的pH值下进行,同时保持抛光化学环境的稳定等。对无机酸、有机酸、无机碱和有机碱四大类pH调节剂在合金、金属和金属化合物等材料的CMP中的应用及其作用机理进行综述。无机酸pH调节剂的主要作用机理是快速腐蚀材料表面,但其主要缺点是会将多余的金属离子引入抛光液中污染金属表面。有机酸pH调节剂的主要作用机理是螯合金属离子形成大分子络合物,但其主要缺点是稳定性差,难以保存。无机碱pH调节剂的主要作用机理是在基底表面生成一层软化层,使其在机械作用下更容易被去除,但其主要缺点是仍会引入金属离子污染材料表面。有机碱pH调节剂的主要作用机理是加速钝化膜的形成,但其主要缺点是制备困难、成本高。最后对pH调节剂在CMP中的应用前景进行了展望。

CMP抛光垫表面及材料特性对抛光效果影响的研究进展

对化学机械抛光(CMP)工艺中的抛光垫特性、劣化以及修整进行了简单阐述,重点先从抛光垫表面特性(抛光垫表面微形貌、微孔及抛光垫的结构、表面沟槽纹理的形状、微凸体的分布)和材质特性(硬度、弹性模量和化学性能)入手,对近年来国内外的实验研究与理论模拟分析两方面进行了概括,总结了目前各个特性参数对抛光垫性能以及对CMP过程影响的进展,此外,从机械磨损和化学腐蚀两方面对抛光垫的劣化机理进行简要分析。随后,为进一步探究抛光垫修整对抛光性能影响,对抛光垫的两种修整方式和修整参数对修整的效果进行了归纳,介绍了几种新型自修整材料。最后,指出了抛光垫特性和修整在发展现状中存在的问题,未来抛光垫的发展趋势将逐渐走向创新化、智能化、理论化以及应用集成化。

表面活性剂在集成电路多层布线CMP工艺中的应用研究

随着集成电路(IC)特征尺寸不断缩小,集成电路多层布线加工精度面临更高的要求,而化学机械抛光(CMP)凭借化学腐蚀和机械磨削的耦合协同作用,成为实现晶圆局部和全局平坦化的唯一可靠技术。抛光液作为CMP工艺中关键要素之一,其主要成分表面活性剂的选择以及含量会严重影响晶圆的表面质量。介绍表面活性剂的特性及其类型,回顾近年来国内外表面活性剂在集成电路多层布线相关材料CMP中的应用及作用机制,归纳总结得出表面活性剂在CMP过程中可以起到缓蚀保护、增强润湿、分散磨料、去除晶圆表面残留污染等多种作用,具有广泛的应用领域。同时,对表面活性剂在CMP中的应用前景进行了展望。

复合磨料的制备及其对层间介质CMP性能的影响

以SiO_(2)为内核、CeO_(2)为外壳制备出了核壳结构复合磨料,用以提升集成电路层间介质的去除速率及表面一致性。采用扫描电子显微镜(SEM)观察复合磨料的表面形貌,利用X射线衍射仪(XRD)、傅里叶变换红外光谱仪(FTIR)和X射线光电子能谱仪(XPS)分析复合磨料的表面物相结构及化学键组成。研究结果表明,所制备的复合磨料呈现出“荔枝”形,平均粒径为70~90 nm,CeO_(2)粒子主要以Si—O—Ce键与SiO_(2)内核结合。将所制备的复合磨料配置成抛光液进行层间介质化学机械抛光(CMP)实验。实验结果表明,Zeta电位随着pH值的降低而升高,当pH值约为6.8时达到复合磨料的等电点。当pH值为3时,层间介质去除速率达到最大,为481.6 nm/min。此外,研究发现去除速率还与摩擦力和温度有关,CMP后的SiO_(2)晶圆均方根表面粗糙度为0.287 nm。

基于SSA-GRNN的铜CMP抛光液抛光速率预测

铜化学机械抛光(CMP)是集成电路制造的关键步骤之一,其中铜抛光速率是衡量抛光液性能的关键指标。在CMP过程中,由于铜抛光液中各组分与铜之间的化学反应复杂,需要大量的数据实验来实现可调的抛光速率。为提高铜CMP抛光速率预测的准确性,利用麻雀搜索算法对广义回归神经网络的平滑因子进行优化,提出了一种基于麻雀搜索算法的广义回归神经网络(SSA-GRNN)铜CMP抛光液抛光速率预测模型。首先,在MATLAB中建立SSA-GRNN网络模型,然后输入抛光液各组分数据,预测在不同组分下抛光液的抛光速率,最后将SSA-GRNN模型的预测结果与BP神经网络模型(BP-NCABC)的预测结果对比。结果表明,SSA-GRNN模型在训练集上的平均绝对百分比误差(MAPE)比BP-NCABC模型降低4.82百分点,在测试集上的MAPE比BP-NCABC模型降低1.78百分点;SSA-GRNN模型在训练集上的最优预测精度比BP-NCABC模型提高0.09百分点,在测试集上的最优预测精度比BP-NCABC模型提高0.32百分点。上述研究结果表明,在CMP抛光速率的预测上SSA-GRNN模型比BP-NCABC模型的准确性更高,这为指导CMP实验、提升实验效率、降低研发成本和优化抛光液组分提供了一种可选的模型。

CMP抛光液中SiO_(2)磨料分散稳定性的研究进展

对SiO_(2)磨料在化学机械抛光(CMP)抛光液中的应用以及影响抛光液分散稳定性的因素进行了阐述,重点从SiO_(2)磨料分散稳定性的角度介绍了SiO_(2)磨料质量分数和粒径、抛光液pH值、表面活性剂种类和表面改性等对抛光液稳定性的影响,通过分析Zeta电位绝对值的范围、凝胶时间的长短、粒径随时间的变化和接触角等,总结了小粒径(35 nm左右)SiO_(2)磨料在抛光液中的分散机理,同时探讨了弱碱性环境对磨料Zeta电位的影响,阳离子、阴离子和非离子表面活性剂对磨料表面的作用机理和复配使用的效果,以及表面疏水化或亲水化改性对磨料分散稳定性的影响。最后对该领域未来的发展方向进行了展望。

基于流固耦合的碳化硅衬底CMP过程温度场仿真分析

在碳化硅衬底化学机械抛光过程中,抛光界面温度是影响抛光效率的关键因素之一,掌握抛光界面温度分布情况,有助于更深入理解CMP机理并为工艺优化提供理论指导。为此,对碳化硅衬底的CMP过程中温度场分布情况进行了探究,分析了不同抛光工艺参数和抛光液组分对抛光界面温度的影响。利用有限元分析软件ANSYS的流固耦合模块,综合考虑抛光垫与抛光液对SiC衬底的磨削作用,得到抛光过程中SiC衬底表面温度分布。仿真结果表明,SiC衬底径向温度从中心到边缘逐渐增大,边缘处上升趋势逐渐减小甚至出现温度小幅下降,最大温差接近0.4℃(约为4%)。通过单因素实验探究不同影响因素与温度之间的关系,得出结论:随着抛光转速和抛光压力的增大,SiC表面平均温度上升,均近似成线性关系,并且边缘点与中心点温度变化相差越来越大;同时,衬底界面温度随着抛光液磨料浓度的增加而上升,但变化相对较小。

E1310P和FMEE复配对铜膜CMP性能的影响

针对化学机械抛光(CMP)中传统唑类缓蚀剂毒性强、成本高,在表面形成坚硬钝化膜难以去除等问题,在甘氨酸-双氧水体系下,使用阴离子表面活性剂聚氧乙烯醚磷酸酯(E1310P)和非离子表面活性剂脂肪酸甲酯乙氧基化物(FMEE)复配替代传统唑类缓蚀剂。通过去除速率、表面粗糙度和表面形貌等的实验结果研究了E1310P和FMEE协同作用对CMP过程中表面质量的影响。通过表面张力、电化学性能、X射线光电子能谱(XPS)和密度泛函理论(DFT)揭示了E1310P和FMEE的协同吸附行为及其机理。结果表明,E1310P可以吸附在Cu的表面,降低Cu的去除速率;FMEE的加入能有效屏蔽E1310P离子头基间的电性排斥作用,使更多的E1310P吸附在Cu的表面,在协同作用下形成了更致密的抑制膜,使得CMP抛光性能得以提升。