散射测量技术在纳米级晶圆复杂轮廓上的优势测量

【作者】 陈亮；

【导师】 刘冉； 迟玉山；

【作者基本信息】 复旦大学 ， 集成电路工程， 2009， 硕士

【摘要】 近四十年以来,半导体技术沿摩尔定律非常迅速地发展,其技术节点的推进都是由一个重要特征表示的,即:制造集成电路的最小特征尺寸CD(CriticalDimension)不断成倍地迅速缩小。随着技术节点的提升,晶圆的制造过程中更多的应用了各种各样的新型材料与纳米尺寸结构,这对测量技术提出了日益严峻的挑战。根据国际半导体技术蓝图ITRS(Internat ional Technology Roadmap forSemiconductors),生产中对晶圆内各式各样的线条尺寸与轮廓进行监控变得越来越关键。在先进的工艺中,除了CD外,轮廓的测量也非常重要,很小的倾角变化就会使大深宽比结构的尺寸发生很大的改变,从而导致器件失效。然而,对于传统的测量技术来讲,特征尺寸扫描电子显微镜CD-SEM(Scanning ElectronMicroscope)由于仅限于自上而下的观测而无法提供真正的轮廓信息,破坏性的截面测量方法则不适用于生产中。为了解决CD-SEM等方法所面临的局限性,以及提供强有力的晶圆纳米级轮廓检测方案以满足生产的需求,基于散射测量法(Scatterometry)的光学轮廓测量得到了迅猛发展,其成为了很多国际化生产厂的重要CD兼轮廓测量的手段。在90纳米及以下的晶圆制程中,散射测量技术,或者称为光学特征尺寸OCD(Optical critical dimension)量测,不管在特征尺寸量测或者复杂轮廓分析的应用上都获得快速的进步。这项技术可以提供CD-SEM或原子力显微镜AFM(Atomic Force Microscope)所无法提供的资讯,包括足部(footing)、缺角(notch)、底切(undercut)与侧壁角度(sidewall angle)等结构细节,同时也能计算出蚀刻深度。现在,这种技术已经成为半导体业中一种很重要的测量检测手段,它的轮廓分析能力、快速量测及集成能力是其他一些测量技术无法比拟的。据统计,目前世界前20大的300毫米先进晶圆厂均已采用了基于这种技术的平台进行日常产品测量检测。散射光学的量测是从具有光栅结构的测试图案上所反射回来的光谱,再从中设法得到有关光栅尺寸与线宽轮廓的资讯。这些栅线代表的是实际制造的元件尺寸。OCD采用宽频光谱与入射的线性极化光来达成测量的目的,再借由复杂的数学模型分析反射光谱,获取有关包括CD与线宽轮廓等资讯。由于散射测量的快速性,晶圆到晶圆的采样正变成一种日益熟知的用于预见的方法。OCD提供了线宽量测以及复杂的结构轮廓分析的强大工具,可以快速测定全面CD以提供先进的制程控制。近年来,基于椭偏仪结构的散射测量技术在国外已经得到了广泛应用,但对于批量测量来说,其速度还满足不了量产的需求。因此,许多工厂引入了速度更快的基于反射法的散射测量技术。本课题就是针对反射法OCD在国内的300毫米先进晶圆厂的首次应用,对其技术能力进行了一系列实验评估。在90纳米栅极蚀刻测量实验中,评估了特征尺寸和侧墙倾角等参数的动态精度与准确性。通过对栅极侧面轮廓的测量,研究了散射测量技术在缺陷检测上面的能力。对于复杂轮廓的测量,评估了散射测量技术在90纳米ONOSpacer结构的动态精度与准确性。在纳米级技术节点,因为缺乏芯片与划片槽上测试点之间的相关性,测量必须在芯片图形上完成,实验采用了片内浮栅厚度测量,评估了OCD建模能力及片内测量的准确性,此外,还对缺陷检测方面进行了研究。本课题还对整合散射测量和先进工艺控制(APC)进行了一些探讨,先进的APC系统能为更先进的技术节点提供可靠的工艺控制。本课题对于国内300毫米晶圆蚀刻制程首次采用的APC应用进行了试探性的实验,研究了离线APC对栅极蚀刻工艺的影响,这为日后在线的APC应用提供了必要的技术支持。更多还原

【Abstract】 Over the past forty years,semiconductor technology has been progressing rapidly following the Moore’s Law.The advancement of the technical node is primarily characterized by the smallest critical dimension(CD) in integrated circuit manufacturing.With the downscaling of devices,more and more new materials and nano-scale structures are adopted in wafer fabrication.Therefore,metrology is facing increasing challenges.According to International Technology Roadmap for Semiconductors(ITRS),monitoring various lines and profiles during wafer manufacturing becomes extremely critical.In the advanced processes,the profile measurement is almost as important as the CD measurement.Slight sidewall angle changes can cause big changes the structures with large aspect ratio and leads to device failure.However,for the traditional metrology techniques,the commonly used CD-SEM cannot provide actual profile information due to its top-view scanning mode,while other destructive cross-section metrology also cannot meet the in-line monitoring requirement.To break the limitation of traditional methods and provide robust and non-destructive measurement solution for the nano-scale profiles in the wafer fabrication,scatterometry base optical profile measurement has been developed rapidly and already implemented in most advanced fabs.In the 90nm and below technical node,scatterometry,or so called optical critical dimension(OCD) measurement has been applied for both CD measurement as well as complicated profile analyses.This technology can provide the detail structure information such as footing,notch,undercut and sidewall angle and etch depth which CD-SEM or AFM can hardly provide. Now,this technology becomes a very important monitoring method in the semiconductor industry.Its capability of profile analysis,quick measurement and easy for integration is unique among other metrology. Statistics shows that the top 20 world 300mm advanced wafer fabs all equipped scatterometry tools for daily production measurement.Scatterometry is a technique that measuring reflection spectra from test patterns with grating structures,and calculating information about grating size and line width.These lines mimic the real device dimension. OCD simplifies the measurements by using broad band wavelength and polarized light and analyzing the reflected spectra with complicated mathematical model in order to acquire information on CD and profile parameters.Due to the fast measurement speed of scatterometry,sampling wafer to wafer becomes a well-known way for process prediction.OCD provides robust analysis tool for CD and complicate profile measurement.It can measure all CD related parameters in order to provide advanced process control.Nowadays,SE base scatterometry has been widely used in the worldwide.But for the needs of measurement by wafer,its speed cannot well meet full production requirement.Therefore,many manufactures have been adopting SR base scatterometry which is much faster.This thesis researches the first SR OCD applications in domestic 300mm advanced wafer fab and evaluates the technology capabilities base on several experiments. In the 90nm gate etch measurement experiment,the thesis evaluates the dynamic precision and accuracy for CD and SWA,etc.parameters and investigates the defect detection capability of scatterometry.For the complicate profile measurement,the thesis evaluates the dynamic precision and accuracy of 90nm ONO spacer structure.At nano-level technical node,measurements have to be done on the chip pattern due to lack of correlation between chip cell and monitor pad.This thesis chooses in-die floating gate thickness as measurement experiment and evaluates OCD modeling capability and in-die measurement accuracy.Besides,some researches on defect detection are also performed.In addition,this thesis puts some investigations on integrated metrology and advanced process control.APC system shows robust process control capability for advanced technical node.This thesis experiments etch process with APC enabled on the first adopted APC system in domestic 300mm wafer.The evaluation shows offline APC influence to gate etch process which gives necessary technical support for the future inline APC uses.更多还原