光程补偿近红外光透射反射干涉重构微结构内部形貌

Internal profile reconstruction of microstructures based on near-infrared light transmission reflection interferometry with optical path compensation

高深宽比微结构的底部及侧壁形貌重构是微机电系统领域亟待解决的一个问题。本文提出光程补偿近红外光透射反射干涉技术重构微结构内部形貌的方法,所采用的近红外光干涉技术将白光干涉系统中的光源扩展至近红外光源,将反射干涉技术扩展至透射反射干涉技术,近红外光干涉测量系统由近红外光光源、干涉显微镜、红外光CCD、高精度压电陶瓷和数据采集系统组成。设计了具有两个台阶的GaAs半导体微结构待测样品,采用近红外光垂直扫描干涉法并通过光程补偿,重构了微结构的内部三维形貌,并与扫描电镜结果进行对比。光程补偿近红外光透射反射干涉技术测量的台阶相对高度分别为2. 132μm和0. 766μm,与扫描电镜和近红外光反射干涉测量结果基本一致,分别对应2. 16%和2. 68%的相对误差。测量结果表明,该测量系统能够测量高深宽比微结构底部及侧壁形貌。

The bottom and sidewall profile reconstruction of microstructures with a high aspect ratio is a problem that urgently needs to be solved in the field of MEMS(Micro-Electro-Mechanical system).Microstructures profile reconstruction method is presented based on near-infrared light transmission reflection interferometry with optical path compensation(OPC),which is extended from white light to near-infrared light and from reflection interference to transmission interference.The near-infrared light transmission interferometry system is composed of a near-infrared light source,an interference microscope,an infrared light CCD,piezoelectric ceramics with high accuracy and a data acquisition system.A GaAs sample microstructure with two steps was designed and the method of vertical scanning interference of near-infrared light with OPC was adopted to reconstruct the internal profile of a microstructure,which was then compared with the results of scanning electron microscopy(SEM).Test results show that the relative heights of the measured microstructure steps using nearinfrared light transmission reflection interferometry were 2.132μm and 0.766μm with 2.16%and 2.68%relative errors,respectively,which agree with the results of SEM and that of the near-infrared light reflection interferometer.The measurement system has the ability to reconstruct the bottom and sidewall profile of microstructures with a high aspect ratio.