计算机硬磁盘CMP中抛光工艺参数对去除率的影响

对于计算机硬磁盘的生产,为了最大限度地提高盘片生产量,降低生产成本,要求化学机械抛光(chemieal mechanical polishing,简称CMP)中在保证优质表面质量情况下,实现最大去除量(Material Removal,简称MR)和去除率(Material Removal Rate,简称MRR)。本文讨论了硬盘片的化学机械抛光过程中的外加压力、转速和抛光时间对去除率的影响。实验采用含多种添加剂的纳米二氧化硅(SiO_2)胶体作为研磨液在双面抛光机上对镍磷敷镀铝镁合金基片进行精抛光。结果表明,不降低表面质量,MRR随着压力的增加而增大到一个最大值,随后随着压力继续增加而减小;增加抛光机下盘的转速将使MRR变大到一定值后再下降;增加抛光时间将使MR增大,而MRR变化是非线性的。     

氧化铝复合磨粒的抛光特性研究

为提高氧化铝磨料分散稳定性,利用接枝聚合对氧化铝粒子进行了表面改性,并研究了改性后氧化铝粒子在数字光盘玻璃基片中的化学机械抛光特性。结果表明,氧化铝复合磨粒的抛光性能与其表面接枝率密切相关。接枝率上升,材料去除速率下降;试验条件下,当接枝率为2.93%时,氧化铝磨粒体现出较高的表面平整性、较低的表面粗糙度及较低的表面损伤。     

数字光盘玻璃基片的三步抛光技术

为得到超光滑的数字光盘母盘玻璃基片表面,研究玻璃基片的亚纳米级抛光技术。分别采用2 m、0.3 m超细氧化铈抛光液以及纳米氧化硅抛光液进行三步化学机械抛光(Chemical mechanical polishing, CMP),抛光后最终表面粗糙度Ra达到0.44 nm,为目前报道的数字光盘母盘玻璃基片抛光的最低值。原子力显微镜分析表明,抛光后的表面超光滑且无微观缺陷。通过对玻璃基片CMP中机械作用及化学作用进行分析,对抛光机理进行了探讨。     

蓝宝石衬底化学机械抛光中材料去除特性的研究

衬底基片的化学机械抛光(CMP)同时兼顾材料去除率及衬底表面质量,在抛光过程中,化学作用与机械作用相辅相成同时参与抛光,化学作用与机械作用的平衡对能否得到满意的衬底表面有重要有意义。针对蓝宝石衬底基片的CMP材料去除率进行了研究,分析了材料去除机理。使用单因素实验法测得:压力的增加会导致材料去除率的增加,但当压力增加到某一点后,材料去除率的增加反而减缓,与此同时衬底基片表面粗糙度达到最小。这一点附近的抛光参数可以达到机械与化学作用的平衡。在实验中,当抛光压力为6kg时材料去除率达到80nm/min,表面粗糙度达到0.2nm。     

CeO_2/SiO_2复合磨粒抛光性能及机制研究

为提高硅片抛光质量与效率,利用均相沉淀法制备CeO2/SiO2复合磨粒,配制绿色环保水基型抛光液对硅片进行化学机械抛光,研究pH值、抛光时间、抛光速度、抛光压力等抛光工艺参数对硅片抛光性能的影响。结果表明:随抛光液pH值增加,材料去除率相应增大;材料去除率在一定时间范围内随抛光时间增加而下降;材料去除量随抛光速度、抛光压力的增加均先增大后减小。推测CeO2/SiO2复合磨粒抛光机制为由于水合作用,在硅片表面形成一层易于磨削的软质层。     

抛光液pH值等对硬盘玻璃盘基片化学机械抛光的影响

随着硬盘存储密度的增大、转速的提高、磁头飞行高度的降低,对硬盘基板材料及基板表面质量提出了更高的要求。采用纳米SiO2作为抛光磨料,在不同抛光液条件下(pH值、表面活性剂、润滑剂等),对玻璃基片化学机械抛光去除速率和表面质量的变化规律进行了研究,并利用原子力显微镜(AFM)和光学显微镜观察了抛光表面的微观形貌。结果表明,玻璃基片去除速率在酸性、碱性条件下变化趋势相近,即随着pH值的升高,材料去除速率先增大后减小。加入一定量的表面活性剂和润滑剂使得去除速率有一定程度的下降,但是表面粗糙度明显降低,并且表面没有出现颗粒吸附现象。     

镁合金AZ91D化学机械抛光工艺研究

将化学机械抛光技术(Chemical Mechanical Polishing,CMP)引入到镁合金片的抛光中,以硅溶胶、表面活性剂、螯合剂及p H调节剂为原料,以涡流搅拌的方法制备镁合金(AZ91D)抛光液。采用单因素法分析抛光过程中压力、转速、抛光液流量及抛光时间等参数对抛光效果的影响。实验结果表明:在压力为0.06MPa,抛光盘上盘转速为10r/min、下盘转速为50r/min,抛光液流量为160m L/min,抛光时间为8min的条件下,镁合金表面形貌良好;在此工艺条件下经过化学机械抛光后,镁合金表面粗糙度Ra能达到10nm。     

CeO2/SiO2复合磨粒抛光性能及机理研究

为提高硅片抛光质量与效率,利用均相沉淀法制备ＣｅＯ２／ＳｉＯ２ 复合磨粒,配制绿色环保水基型抛光液对硅片进行化学机械抛光,研究ｐＨ值、抛光时间、抛光速度、抛光压力等抛光工艺参数对硅片抛光性能的影响。结果表明：随抛光液ｐＨ值增加,材料去除率相应增大;材料去除率在一定时间范围内随抛光时间增加而下降;材料去除量随抛光速度、抛光压力的增加均先增大后减小。推测ＣｅＯ２／ＳｉＯ２复合磨粒抛光机制为由于水合作用,在硅片表面形成一层易于磨削的软质层。     

基于遗传算法优化神经网络的镁合金化学机械抛光材料去除模型

镁合金化学机械抛光(CMP)的材料去除与其工艺参数具有高度非线性的特点,难以采用精确的数学模型来描述。以遗传算法(GA)优化神经网络(NN)建模为基础,利用正交试验设计获取镁合金CMP材料去除样本数据和测试数据,建立镁合金CMP材料去除模型。该模型以抛光压力、抛光盘转速、抛光液流量和抛光时间为输入参数,以材料去除速率为输出目标。结果表明:GA-NN协同模型能够构建镁合金CMP工艺参数与材料去除速率的基本关系;其拟合度波动范围为93.22%~97.97%,大大高于NN模型的拟合度波动范围71.56%~93.56%,因而具有更优的预测能力,基本满足工程实际的需求。     

基于遗传算法优化神经网络的镁合金化学机械抛光材料去除模型与仿真

镁合金化学机械抛光(CMP)的材料去除与其工艺参数具有高度非线性的特点,难以采用精确的数学模型来描述。以遗传算法(GA)优化神经网络(NN)建模为基础,利用正交试验设计获取镁合金CMP材料去除样本数据和测试数据,建立镁合金CMP材料去除模型。该模型以抛光压力、抛光盘转速、抛光液流量和抛光时间为输入参数,以材料去除速率为输出目标。结果表明：GA NN协同模型能够构建镁合金CMP工艺参数与材料去除速率的基本关系;其拟合度波动范围为93.22%~97.97%,大大高于NN模型的拟合度波动范围71.56%~93.56%,因而具有更优的预测能力,基本满足工程实际的需求。     

Prediction of the surface roughness and material removal rate in chemical mechanical polishing of single-crystal SiC via a back-propagation neural network

Chemical mechanical polishing (CMP) is a common method for realising the global planarisation and polishing of single-crystal SiC and other semiconductor substrates. The strong oxidant hydroxyl radicals (·OH) generated by the Fenton reaction can effectively oxidise and corrode the SiC substrate, and are thus used to improve the material removal rate (MRR) and surface roughness (Ra) after polishing of SiC during CMP. Therefore, it is necessary to study the material removal mechanism in detail. Based on the modified Preston equation, the effects of the CMP process parameters on the MRR and Ra after polishing of SiC and their relationship were studied, and a prediction model of the CMP process parameters, MRR, and Ra after polishing was also established based on a back-propagation neural network. The MRR initially increased and then decreased, and the Ra after polishing initially decreased and then increased, with increasing FeSO₄ concentration, H₂O₂ concentration, and pH value. The MRR continuously increased with increasing abrasive particle size, abrasive concentration, polishing pressure, and polishing speed. However, the Ra continuously decreased with increasing abrasive particle size and abrasive concentration, increased with increasing polishing pressure, and initially decreased and then increased with increasing polishing speed. The established prediction model could accurately predict the relationship between the process parameters, MRR and Ra after polishing in CMP (relative prediction error of less than 10%), which could provide a theoretical basis for CMP of SiC.     

A study of material removal amount of sapphire wafer in application of chemical mechanical polishing with different polishing pads

The study mainly explores the fabrication mechanism for fabricating sapphire wafer substrate, by using chemical mechanical polishing (CMP) method. A slurry containing the abrasive particles of SiO₂ is used to contact with the sapphire substrate polish and to produce chemical reaction for removal of sapphire wafer substrate when CMP method is used. The study observes the changes of the removal amount of sapphire wafer substrate when the pattern-free polishing pad and hole-pattern polishing pad are used under different down forces, polishing velocities, abrasive particle sizes and slurry concentrations. Employing regression analysis theory, the study makes improvement of the equation of material removal rate (MRR) to be the material removal height per 30 minutes (MRRh), and develops a compensation parameter C_rv of the error caused by the volume concentration of slurry. The results of experimental analysis show that under a certain down force, if the polishing velocity is greater, the material removal amount will be greater. Generally speaking, the material removal amount of hole-pattern polishing pad is greater than that of pattern-free polishing pad. As to the relationship between abrasive particle size and slurry concentration, when particle size is smaller, the volume concentration of slurry will be higher, and the number of abrasives for polishing wafer will be greater. As a result, a better material removal depth can be acquired. Through the above analytical results, considerable help is offered to the polishing of sapphire wafer.     

A neural-Taguchi-based quasi time-optimization control strategy for chemical-mechanical polishing processes

Besides the major factors such as the down force, back pressure and the rotating speed of wafer carrier, effect of polishing time is also an important issue in CMP processes. In this study, a neural-Taguchi method based on a cost-effective quasi time-optimisation technique for chemical-mechanical polishing (CMP) processes is developed. The key concept of this new technique is that an optimal process parameter set is obtained through a neural-network-simulated CMP process model. Under such an optimal parameter set, the desired material removal rate within-wafer-nonuniformity can be reached with the optimal polishing time. It has been proved by experiment that the proposed method can offer a better polishing performance while reducing the polishing time by 1/3.     

Ta-W合金的化学机械抛光实验研究

针对Ta-W合金材料圆薄片零件化学机械抛光工艺，设计了Ta-W合金材料化学机械抛光抛光液，并探讨了抛光液各组分的含量及抛光工艺参数对抛光速率和抛光件表面质量的影响。结果表明，当抛光液中磨料SiO2溶胶质量分数为40％-65％时，抛光速率也达到较高值并在一定的硅溶胶含量范围内波动不大；当抛光液中有机碱的质量分数为4％-6％时，抛光速率达到最大值；随着氧化剂含量的增加，去除速率几乎成线性增加，但随氧化剂含量的增大表面状态变差，故应控制氧化剂的含量；随着抛光液流量的增加，抛光速率也增大，但在流量增加到200mL／min后，速率的增加变得缓慢。     

Estimating the mechanical properties of polyurethane-impregnated felt pads

Chemical mechanical polishing (CMP) is an essential process in semiconductor fabrication. The results of CMP process are determined with the selection of consumables and process parameters. The polishing pad transports the slurry to the interface between the polishing pad and wafer and obtains material removal planarity. The mechanical properties of the polishing pad should be studied to analyze the material removal mechanism of CMP because polishing pad deformation is directly related to material removal rate and its uniformity. Various studies have investigated the stress distribution of the CMP process by using the elastic modulus and Poisson’s ratio of the polishing pad. However, these aspects of polishing pad have not been fully elucidated. In this study, we estimated the mechanical properties of commercial polyurethane-impregnated felt pads by comparing the experimentally measured compressive deformation amounts with finite element analysis results.     

Preparation of La-doped colloidal SiO2 composite abrasives and their chemical mechanical polishing behavior on sapphire substrates

Chemical mechanical polishing (CMP) has become a widely accepted global planarization technology. Abrasive is one of the key elements in CMP process. In order to enhance removal rate and improve surface quality of sapphire substrate, a series of novel La-doped colloidal SiO₂ composite abrasives were prepared by seed-induced growth method. The CMP performance of the La-doped colloidal SiO₂ composite abrasives on sapphire substrate were investigated using UNIPOL-1502 polishing equipment. The analyses on the surface of polished sapphire substrate indicate that slurries containing the La-doped colloidal SiO₂ composite abrasives achieve lower surface roughness, higher material removal rate than that of pure colloidal SiO₂ abrasive under the same testing conditions. Furthermore, the acting mechanism of the La-doped colloidal silica in sapphire CMP was investigated. X-ray photoelectron spectroscopy analysis shows that solid-state chemical reactions between La-doped colloidal SiO₂ abrasive and sapphire surface occur during CMP process, which can promote the chemical effect in CMP and lead to the improvement of material removal rate.     

Research on chemo-mechanical grinding of large size quartz glass substrate

Finishing process of quartz glass substrate is meeting great challenges to fulfill the requirements of photomask for photolithography applications. For the final finishing of the substrate surface, chemical mechanical polishing (CMP) is often utilized. Those free abrasive processes are able to offer a great surface roughness, but sacrifice profile accuracy. On the other hand, the fixed abrasive process or grinding is known as a promising solution to improve accuracy of profile geometry, but always introduces damaged layer. Chemo-mechanical grinding (CMG) is potentially emerging defect-free machining process which combines the advantages of fixed abrasive machining and CMP. In order to simultaneously achieve high surface quality and high profile accuracy, CMG process has been applied into machining of large size quartz glass substrates for photomask use. Reported in this paper are CMG performances in finishing of quartz glass substrates including material removal rate (MRR), surface roughness, flatness and optical characteristics.