摘要
带电粒子束成像检测技术是一种可以提供纳米级测量精度的技术,广泛应用于半导体检测中。在进行硅片检测时,要求待测硅片在扫描检测过程中一直处于电子束的焦深范围(DoF)内。本文提出一种毫米级控制范围、纳米级控制精度、高度测量时间在亚毫秒量级的粗精结合的闭环硅片高度控制技术。它的核心子系统是一套光学硅片高度测量系统,在进行粗控制时,数字相机的成像面作为一个光栅图像接收面,硅片的高度信息通过测量光栅线条在成像面上的位移获得。在接近目标高度时,数字相机的成像面作为一个虚拟的数字光栅使用。它与光学光栅图像存在一定周期差,两者构成类似机械游标卡尺的结构,本文称为光学游标卡尺,实验表明该技术可以在成像面上细分像素尺寸10×以上。当用其测量硅片高度时,粗测范围达毫米量级,粗测时间小于0. 38 ms,精测分辨率小于80 nm,精测时间小于0. 09 ms。利用该硅片高度测量系统进行硅片高度的初步闭环反馈控制,控制精度达到15 nm,在电子束硅片图形检测系统中具有广阔的应用前景。
Charged particle beam imaging inspection technology is widely applied in semiconductor industry to find defects on wafers with nanometer degree measurement accuracy.During the wafer inspection,the wafer to be measured is supposed to be in the range of depth of focus(DoF)of the electron beam.In this paper we propose a close-loop wafer height control technology with millimeter range,nanometer accuracy and sub-microse-cond height measurement time.It combines coarse control and fine control with an identical optical wafer height measurement system.During the coarse control,the imaging plane of the digital camera functions as a pure optical sensor.The wafer height information is obtained by measuring the displacement of one certain grating line.When approaching to the target position,the imaging plane changes to be a virtual digital grating.The so called optical vernier caliper,analogous with the mechanical vernier caliper,is constructed with the optical grating image and the digital grating image when there is some period difference between them.The experiment shows that such structure subdivides pixels by a factor of 10×or more on the image plane.When the system is used to measure the wafer height,the coarse measurement range is in millimeter degree and the coarse measurement time is 0.38 ms.The fine measurement resolution is less than 80 nm,and the fine measurement time is 0.09 ms.The close-loop feedback control is conducted with the system.The preliminary experiment shows the control accuracy is 15 nm.Such nanometer degree focus control accuracy is most advantageous in the charged particle beam inspection in the future.
作者
郭杰
李世光
赵焱
宗明成
GUO Jie;LI Shi-guang;ZHAO Yan;ZONG Ming-cheng(Institute of Microelectronics of Chinese Academy of Sciences,Beijing 100029,China;University of Chinese Academy of Sciences,Beijing 100049,China;Zhongke Jingyuan Electron(Beijing)Limited,Beijing 100076,China)
出处
《中国光学》
EI
CAS
CSCD
北大核心
2019年第2期242-255,共14页
Chinese Optics
基金
极大规模集成电路制造装备及成套工艺(国家02专项)资助项目(No.2012ZX02701004)~~
关键词
对焦控制
高度测量
高度控制
带电粒子束检测
电子束检测
光学游标卡尺
焦深
focus control
height measurement
height control
charged particle beam inspection
electron beam inspection
optical vernier caliper
depth of focus
作者简介
郭杰(1993-),男,陕西西安人,硕士研究生,主要从事集成电路先导工艺与仪器装备等方面的研究。E-mail:guojie1@ime.ac.cn;通讯作者:李世光(1973-),女,辽宁沈阳人,博士,副研究员,主要从事光电检测技术及光学工程方面的研究。E-mail:lishiguang@tsinghua.org.cn。
