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.

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.

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.

Material removal mechanism of copper chemical mechanical polishing with different particle sizes based on quasi-continuum method

In this paper,the material removal mechanism of copper chemical mechanical polishing was studied by the quasicontinuum method that integrated molecular dynamics and the finite element method.By analyzing the abrasive process of different particle sizes on single crystal copper,we investigated the internal material deformation,the formation of chips,the stress distribution,and the change of cutting force.Results showed that shear band deformation was generated along the cutting direction at approximately 45° inside the workpiece material.The deformation was accompanied by dislocations and sliding phenomena in the shear band region.Smaller abrasive particle size led to poor quality of the workpiece,while a larger particle size led to better quality.However,larger particle size resulted in greater plastic deformation and deeper residual stress inside the workpiece.Size change of abrasive particles had little effect on the tangential cutting force.

Chemical mechanical polishing: Theory and experiment

For several decades,chemical mechanical polishing(CMP)has been the most widely used planarization method in integrated circuits manufacturing.The final polishing results are affected by many factors related to the carrier structure,the polishing pad,the slurry,and the process parameters.As both chemical and mechanical actions affect the effectiveness of CMP,and these actions are themselves affected by many factors,the CMP mechanism is complex and has been a hot research area for many years.This review provides a basic description of the development,challenges,and key technologies associated with CMP.We summarize theoretical CMP models from the perspectives of kinematics,empirical,its mechanism(from the viewpoint of the atomic scale,particle scale,and wafer scale),and its chemical-mechanical synergy.Experimental approaches to the CMP mechanism of material removal and planarization are further discussed from the viewpoint of the particle wear effect,chemical-mechanical synergy,and wafer-pad interfacial interaction.

Mechanical model of nanoparticles for material removal in chemical mechanical polishing process

Chemical mechanical polishing (CMP) is the most effective method for surface planarization in the semiconductor industry. Nanoparticles are significant for material removal and ultra-smooth surface formation. This research investigates the mechanical effects of the material removal in the CMP process. The various contact states of pad, individual particle, and wafer caused by the variations of working conditions and material properties are analyzed. Three different mechanical models for the material removal in the CMP process, i.e., abrasive wear, adhesive wear, and erosive wear are investigated, with a focus on the comparison of the results for different models. The conclusions and methods obtained could potentially contribute to the understanding and evaluation of the CMP process in further work.

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.

Scratch-concerned yield modeling for IC manufacturing involved with a chemical mechanical polishing process

In existing integrated circuit (IC) fabrication methods,the yield is typically limited by defects generated in the manufacturing process.In fact,the yield often shows a good correlation with the type and density of the defect.As a result,an accurate defect limited yield model is essential for accurate correlation analysis and yield prediction.Since real defects exhibit a great variety of shapes,to ensure the accuracy of yield prediction,it is necessary to select the most appropriate defect model and to extract the critical area based on the defect model.Considering the realistic outline of scratches introduced by the chemical mechanical polishing (CMP) process,we propose a novel scratch-concerned yield model.A linear model is introduced to model scratches.Based on the linear model,the related critical area extraction algorithm and defect density distribution are discussed.Owing to higher correspondence with the realistic outline of scratches,the linear defect model enables a more accurate yield prediction caused by scratches and results in a more accurate total product yield prediction as compared to the traditional circular model.

MORPHOLOGY CONTROL OF ULTRAFINE CeO_2 AND ITS POLISHING EFFICACY

Homogenous precipitation and subsequent calcination has been used tosynthesize ultrafine ceria from cerium nitrate and urea solution. The ceria calcined from theprecursor inherit the size and morphology of it. The size and morphology of the precursor areclosely related to the preparation process. The morphology, size and distribution of the precursorcould be tailored by changing the reaction condition and the ageing time. Monodispersed 200 nm sizedspherical particles is prepared by this method. The powder is used in the chemical-mechanicalpolishing of Si wafer. The average surface roughness of the polished Si wafer is 0.171 nm measuredby AFM.

Exploring the role of --NH2 functional groups of ethylenediamine in chemical mechanical polishing of GCr15 bearing steel

Ethylenediamine with two-NH2 functional groups was used as a critical complexing agent in chemical mechanical polishing(CMP)slurries for a high carbon chromium GCr15 bearing steel(equivalent to AISI 52100).The polishing performance and corresponding mechanism of-NH2 functional groups were thoroughly investigated as a function of pH.It is revealed that,when polished with ethylenediamine and H2O2-based slurries,the material removal rate(MRR)and surface roughness Ra of GCr15 steel gradually decrease as pH increases.Compared with acidic pH of 4.0,at alkaline pH of 10.0,the surface film of GCr15 steel has much higher corrosion resistance and wear resistance,and thus the material removal caused by the pure corrosion and corrosion-enhanced wear are greatly inhibited,resulting in much lower MRR and Ra.Moreover,it is confirmed that a more protective composite film,consisting of more Fe3+hydroxides/oxyhydroxides and complex compounds with-NH2 functional groups of ethylenediamine,can be formed at pH of 10.0.Additionally,the polishing performance of pure iron and a medium carbon 45 steel exhibits a similar trend as GCr15 steel.The findings suggest that acidic pH could be feasible for amine groups-based complexing agents to achieve efficient CMP of iron-based metals.

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.

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。

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。

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。

BTA与TT-LYK对铜CMP缓蚀效果和协同效应研究

在铜化学机械抛光中,由于典型缓蚀剂苯并三氮唑(BTA)对铜表面化学保护作用非常强烈,造成铜去除速率过低的现象。为了获得更好的缓蚀效果和铜表面质量,在近中性溶液中,对BTA缓蚀剂和新型缓蚀剂2,2′-[[(甲基-1H-苯并三唑-1-基)甲基]亚氨基]双乙醇-(TT-LYK)的缓蚀效果进行比较,并对2种缓蚀剂的复配效果进行研究。结果表明:在近中性溶液中,BTA和TT-LYK均可以有效抑制铜表面腐蚀;2种缓蚀剂复配后具有协同作用,添加到抛光液中可得到更好的铜表面质量和更低的粗糙度,这可能是由于2种缓蚀剂的钝化膜类别相似,使得在一种缓蚀剂形成配合物的基础上,另一种缓蚀剂对生成的钝化膜进行补充,使得双层钝化膜更致密,能更好地保护铜表面不受腐蚀。