化学机械抛光过程中扭矩的模型分析与试验研究

提出了一个计算化学机械抛光（Chemical Mechanical Polishing,CMP）过程中硅片所受扭矩的模型,并通过CMP过程中摩擦力和扭矩的在线检测试验进行了验证。试验结果表明该扭矩计算模型可以较好地描述CMP过程中硅片所受扭矩的特征。该研究可以为基于抛光头旋转轴扭矩变化的CMP终点检测方法提供理论依据。     

On the Wafer/Pad Friction of Chemical–Mechanical Planarization (CMP) Processes—Part I: Modeling and Analysis

Friction characteristics between the wafer and the polishing pad play an important role in the chemical–mechanical planarization (CMP) process. In this paper, a wafer/pad friction modeling and monitoring scheme for the linear CMP process is presented. Kinematic analysis of the linear CMP system is investigated and a distributed LuGre dynamic friction model is utilized to capture the friction forces generated by the wafer/pad interactions. The frictional torques of both the polisher spindle and the roller systems are used to monitor in situ the changes of the friction coefficient during a CMP process. Effects of pad conditioning and patterned wafer topography on the wafer/pad friction are also analyzed and discussed. The proposed friction modeling and monitoring scheme can be further used for real-time CMP monitoring and process fault diagnosis.     

A signal processing method for the friction-based endpoint detection system of a CMP process

A signal processing method for the friction-based endpoint detection system of a chemical mechanical polishing(CMP) process is presented.The signal process method uses the wavelet threshold denoising method to reduce the noise contained in the measured original signal,extracts the Kalman filter innovation from the denoised signal as the feature signal,and judges the CMP endpoint based on the feature of the Kalman filter innovation sequence during the CMP process.Applying the signal processing method,the ...     

一种面向化学机械抛光终点检测系统的信号处理方法

提出了一种针对基于摩擦的化学机械抛光（Chemical Mechanical Polishing,CMP）终点检测系统的信号处理方法。该信号处理方法采用小波阈值去噪的方法去除包含在原始测量信号中的噪声;从去噪后的信号中提取卡尔曼滤波新息作为特征信号;根据CMP过程中卡尔曼滤波新息的特征来判断何时达到CMP终点。应用该信号处理方法,进行了铜CMP过程的终点检测试验。试验结果表明,该信号处理方法可以判断出铜CMP过程的终点。     

Optimization of tribological properties of silicon dioxide during the chemical mechanical planarization process

Chemical mechanical planarization (CMP) has been proved to achieve excellent global and local planarity, and, as feature sizes shrink, the use of CMP will be critical for planarizing multilevel structures. Understanding the tribological properties of a dielectric layer in the CMP process is critical for successful evaluation and implementation of the materials. In this paper, we present the tribological properties of silicon dioxide during the CMP process. A CMP tester was used to study the fundamental aspects of the CMP process. the accessories of the CMP tester were first optimized for the reproducibility of the results. The coefficient of friction (COF) was measured during the process and was found to decrease with both down pressure and platen rotation. An acoustic sensor attached to this tester is used to detect endpoint, delamination, and uniformity. The effects of machine parameters on the polishing performance and the correlation of physical phenomena with the process have been discussed.     

On the Wafer/Pad Friction of Chemical–Mechanical Planarization (CMP) Processes—Part II: Experiments and Applications

This paper presents the experimental validation and some application examples of the proposed wafer/pad friction models for linear chemical–mechanical planarization (CMP) processes in the companion paper. An experimental setup of a linear CMP polisher is first presented and some polishing processes are then designed for validation of the wafer/pad friction modeling and analysis. The friction torques of both the polisher spindle and roller systems are used to monitor variations of the friction coefficient in situ . Verification of the friction model under various process parameters is presented. Effects of pad conditioning and the wafer film topography on wafer/pad friction are experimentally demonstrated. Finally, several application examples are presented showing the use of the roller motor current measurement for real-time process monitoring and control.     

Statistical and Experimental Analysis of Correlated Time-Varying Process Variables for Conditions Diagnosis in Chemical–Mechanical Planarization

During chemical–mechanical planarization (CMP) of semiconductor wafers, chemical and mechanical process variables are strongly correlated and jointly affect polishing performance. The correlation among these process variables could potentially be utilized to characterize process conditions for the purpose of diagnosis. However, process variables measured during CMP, such as the temperature distribution and coefficient of friction between wafer and pad, vary with time and present in a functional form. This significantly increases the complexity of analyzing correlation patterns and relating them with process conditions. The focus of this paper is therefore twofold: 1) experimental investigation of the correlation between sensing process variables and the implication of correlation pattern changes on process conditions and 2) statistical analysis of correlation patterns between process variables in functional form. In the designed CMP experiment, we investigated two failure modes during CMP process: pad failure and slurry failure. Slurry failure was generated by reducing the percentage of oxidizer to investigate its effects on polishing performance and heat generation on the pad. Pad failure was due to variation of diamond abrasive sizes in the conditioner. The post-CMP study of nonuniformity and defects such as scratches on the wafer was conducted to characterize process conditions. The experimental and statistical results support the investigation of correlation among process variables for condition diagnosis.      

Influence of oxides on friction during Cu CMP

In this work, we investigated the frictional behavior of copper CMP. Using a laboratory polishing set up, we polished Cu with designed polishing media. After that the copper surface and the fumed silica particles Cu were analyzed. The surface analysis techniques used are the field emission SEM, the field-emission high-resolution analytical TEM, x-ray spectroscopy, and XPS. We found evident difference in friction value using different polishing media. Discussions lead to three mechanisms during copper CMP. The nature of copper oxides has a profound influence on friction and might be directly related to defects. Argonne National Laboratory     

In situ endpoint detection by pad temperature in chemical-mechanical polishing of copper overlay

As the number of metal levels and the wafer size increase, the global planarity and effective removal of metal overlay across the wafer becomes more crucial. Chemical-mechanical polishing (CMP) has been recognized essential to achieve this goal. Accurate in situ endpoint detection and monitoring method significantly improves the yield and throughput. Previous methods have been proposed, which either require the rearrangement of the machine set-up, or can only be implanted on certain types of machines. In this study, a model for pad temperature capable of predicting the endpoint of CMP in situ is established based on the total consumed kinematic energy between wafer and pad. Limited assumptions of thermal and kinematic conditions are made. The model of temperature rise uses the integral of the relative polishing speed and is verified by on-line measurement. Since the coefficient of friction between the pad and dielectric layer is distinguishably lower than that between the pad and the metal layer, the pad temperature increases milder than polishing the metal layer. In use of the proposed regression method applied to the measured temperature rise, the endpoint of the process can be detected.     

一种基于光学干涉原理的EMP在线终点检测装置

化学机械抛光是晶片全局平坦化的关键技术，其中终点检测系统是影响抛光效果的关键。如果不能有效地检测抛光过程，便无法避免硅片产生抛光过度或抛光不足的缺陷。基于光学干涉薄膜测厚原理，给出了一种CMP在线终点检测装置。     

一种基于光学干涉原理的CMP在线终点检测装置

化学机械抛光是晶片全局平坦化的关键技术,其中终点检测系统是影响抛光效果的关键。如果不能有效地检测抛光过程,便无法避免硅片产生抛光过度或抛光不足的缺陷。基于光学干涉薄膜测厚原理,给出了一种CMP在线终点检测装置。     

Mechanical and tribological properties of interlayer films for the damascene-Cu chemical-mechanical planarization process

Chemical-mechanical planarization (CMP) has emerged as the most preferred method to achieve excellent global and local planarity in the damascene-Cu process. As the feature sizes shrink, understanding the fundamentals of CMP is critical for successful implementation of the CMP process in sub 0.35-μm technology. It is also important to understand the effects of mechanical and tribological properties of the interlayer films on the CMP process to conduct successful evaluation and implementation of these materials. In this paper, we present the mechanical and tribological properties of various interlayer films (SiO₂, SiC, low-k B, low-k C, Ta, and Cu) and discuss the CMP process of the films in an alumina-based Cu slurry. Mechanical properties were evaluated using a nanoindentation technique. A micro-CMP tester was used to study the fundamental aspects of the CMP process. The coefficient of friction (COF) was measured during the process and was found to decrease both with downward pressure and with platen rotation. An acoustic sensor, attached to the substrate carrier, was used to monitor the process, and the signal was recorded to examine the difference in polishing behavior of these films. The acoustic emission (AE) signal was found to increase with the increase in platen velocity and pressure. Effects of machine parameters on the polishing behavior of the interlayer films and the correlation of mechanical properties with tribological properties have been discussed.     

Interfacial transfer between copper and polyurethane in chemical-mechanical polishing

The interactions between a copper and urethane polishing pads were characterized to investigate the effects of friction on removal mechanisms of a polishing system of copper interconnect wafers in water. In-situ characterization of polished copper and urethane were conducted using Auger and x-ray photoelectron spectroscopy (XPS) analysis techniques. These techniques pinpointed the chemical interactions immediately during polishing. Results indicated that, because of the stimulation of friction, the molecules from the pad transferred to the copper surface, and the oxidized copper surface was transferred to the urethane surface. Without friction, however, such a transformation did not occur and passivation of the copper surface took place. This evidence proves a possible new chemical-mechanical polishing (CMP) mechanism. In addition to the formation and removal of a passivation layer, a transformation layer is formed during CMP because of friction stimulation. This layer is found on both copper and pad surfaces with different chemical bonds. Understanding the transformation layer helps to understand the formation of defects, pad conditioning, and pad life.     

Online End Point Detection in CMP Using SPRT of Wavelet Decomposed Sensor Data

Efficient end point detection (EPD) in chemical mechanical planarization (CMP) is critical to quality and productivity of the wafer fabrication process. The cost of over and under polishing, and the cost of ownership of many expensive metrology-based EPD methods have motivated the researchers to seek cost effective and efficient alternatives. This paper presents a novel method for EPD, which uses a sequential probability ratio test (SPRT) on the wavelet decomposed coefficient of friction (CoF) data from the CMP process. The method is made suitable for online application by developing a moving block data processing strategy, which matches the rate of data acquisition. Tests on both oxide and copper metal CMP show that the developed methodology is uniquely capable of identifying the start and finish of the end point event.     

Pad Deflection-Based Model of Chemical–Mechanical Polishing for Use in CAD IC Layout

The use of chemical–mechanical polishing (CMP) during the integrated circuit (IC) fabrication process has allowed for the aggressive interconnect patterning that is necessary for modern microprocessor technology. However, as IC technology has moved into the deep submicron realm, nonidealities during polishing have begun to play a significant role in device yield and circuit performance. In order to accurately predict circuit performance, designers must consider the effects of CMP prior to fabrication. A physics-based model to predict feature-scale wear of devices during polishing is presented and integrated into a CAD framework to test the model on various IC layouts. The model is benchmarked against experimental data and shown to be qualitatively accurate in predicting surface topography evolution.      

化学机械抛光（CMP）过程中抛光盘温度控制的分析研究

在化学机械抛光（CMP）过程中,温度是影响晶片最终抛光效果的主要因素之一,采用合理的温度控制方法,把温度控制在一定的范围内才能满足化学机械抛光的工艺要求。通过化学机械抛光机理分析阐述了抛光过程中热量产生的根源,介绍了一种温度控制系统的设计原理,并通过抛光实验验证并说明了温度控制的必要性。     

Effect of mechanical process parameters on friction behavior and material removal during sapphire chemical mechanical polishing

The effect of mechanical process parameters such as down force and rotation speed on friction behavior and material removal rate (MRR) was investigated during chemical mechanical polishing (CMP) of sapphire substrate. It was found that the increase in both rotation speed and down force can enhance the MRR and friction force almost linearly depends on the down force and rotation speed. The coefficient of friction (COF) decreases with increasing rotation speed under a fixed down force but keeps constant regardless of variation in down force under a fixed rotation speed. Moreover, the relationship between friction force and MRR was obtained. MRR was proportional to friction force with increasing down force whereas converse proportional to that with increasing the rotation speed. In addition, MRR data are fitted to the Preston equation in the sapphire CMP.     

镁合金抛光机理与CMP工艺研究

将化学机械抛光(CMP)技术引入到镁合金片(MB2)的抛光中,打破过去镁合金以单一化学或机械加工为主的加工手段,用自制的抛光液对镁合金片进行抛光实验。结果发现,抛光液中加入双氧水易产生胶体,不利于抛光的进行,因此提出无氧化剂SiO2碱性抛光。同时分析了镁合金的抛光机理,抛光中压力、转速和抛光液流量参数对抛光过程的影响,利用Olympus显微镜对抛光前后镁合金表面进行观察,通过合理控制工艺参数,能够得到较佳的镁合金抛光表面,远优于单一的机械加工,为镁合金抛光工艺和进一步研究抛光液的配比奠定了基础。     

碲锌镉衬底的化学机械抛光液研究

作为碲锌镉衬底表面加工的重要工序,化学机械抛光(Chemical Mechanical Polishing, CMP)的加工效果决定了碲锌镉衬底的表面质量和生产效率。抛光液是CMP的关键影响因素之一,直接影响衬底抛光后的表面质量。对碲锌镉衬底CMP工艺使用的抛光液进行了研究,探究了以二氧化硅溶胶和过氧化氢为主体的抛光液体系在不同pH值、不同磨料浓度下对衬底抛光表面质量和去除速率的影响。结果表明,使用改进后的抛光液体系对碲锌镉衬底进行CMP,能够在获得超光滑表面的同时实现高效率加工,为批量化制备高表面质量的碲锌镉衬底奠定了良好基础。     

W-Mo合金表面超精密加工的CMP技术研究

阐述了金属化学机械抛光的机理。将半导体制造工艺中的nm级平坦化技术、化学机械抛光技术拓展并应用到W-Mo合金工艺中,在实现精密物理材料表面高平坦度、低粗糙度的前提下,提高W-Mo合金去除速率。采用碱性抛光液进行实验,确定了抛光液的成分;分析了W-Mo合金化学机械抛光中压力、流量、转速、pH值、活性剂等参数对W-Mo合金的影响。实验表明,实现W-Mo合金表面超精密抛光的最佳条件为:压力0.06MPa,流速160mL/min,转速60r/min,pH值10.1~10.3。