Accurate measurement of film thickness and its uniformity are very important to the performance of many coated surfaces and for many applications are critical. Effective inspection of the film thickness and uniformity...Accurate measurement of film thickness and its uniformity are very important to the performance of many coated surfaces and for many applications are critical. Effective inspection of the film thickness and uniformity is the key to high performance. Conventionally, film thickness is meas- ured using a spectrophotometer/reflectometer, ellipsometer or a physical step measurement;however, these techniques all have limitations. Coherence Scanning Interferometry (CSI) is an established method to measure surface topography as this technique offers many advantages such as speed, ease of use and accuracy. The measurement of “thick” films (exceeding ~1.5 μm) which gives rise to clearly separate fringe bunches is a well-established CSI capability. However, a methodology known as the ‘helical complex field’ (HCF) [1] [2] function allows film thickness to be measured down to ~25 nm. This new method, combined with Coherence Correlation Interferometry (CCI) [3] offers film thickness measurements with sub-nanometre vertical resolution and ~1 μm lateral resolution. It is ideally suited for detailed analysis of coated optical surfaces. In this paper, the fundamentals of the techniques are described and some case studies are presented.展开更多
The growing demands of optical systems have led to increasingly complex aspheres and freeforms.In this paper,an established measurement system in asphere production,which is also a promising approach in high-precision...The growing demands of optical systems have led to increasingly complex aspheres and freeforms.In this paper,an established measurement system in asphere production,which is also a promising approach in high-precision freeform metrology,is presented.It is based on a scanning-point multiwavelength interferometer approach.The scanning principle enables great fexibility,reduces setup time and costs,and has almost no limitations in spherical departure.Due to the absolute measurement capability,the utilized multiwavelength approach is benefcial for segmented,annular,and discrete surfaces,which are common designs of modern applications’optical elements.The metrology system enables measurements on a nanometer scale on a great variety of apertures—from 1 to 1000 mm.Recently,a new short-coherence multiwavelength interferometer operating in the visible domain has been developed.It enables the high-precision measurement on silicon-coated surfaces,which can be found in space applications and are also commonly used for extreme-ultraviolet(EUV)lithographic setups,which will be used as an example throughout this work.Owing to the large absolute measurement capability,applied grating structures for suppressing infrared light in the EUV process can easily be measured.This paper summarizes the basic working principles of the proposed metrology system,explains the special requirements for diferent felds of application,highlights the capabilities of the visible multiwavelength approach,and shows the measurement results.展开更多
文摘Accurate measurement of film thickness and its uniformity are very important to the performance of many coated surfaces and for many applications are critical. Effective inspection of the film thickness and uniformity is the key to high performance. Conventionally, film thickness is meas- ured using a spectrophotometer/reflectometer, ellipsometer or a physical step measurement;however, these techniques all have limitations. Coherence Scanning Interferometry (CSI) is an established method to measure surface topography as this technique offers many advantages such as speed, ease of use and accuracy. The measurement of “thick” films (exceeding ~1.5 μm) which gives rise to clearly separate fringe bunches is a well-established CSI capability. However, a methodology known as the ‘helical complex field’ (HCF) [1] [2] function allows film thickness to be measured down to ~25 nm. This new method, combined with Coherence Correlation Interferometry (CCI) [3] offers film thickness measurements with sub-nanometre vertical resolution and ~1 μm lateral resolution. It is ideally suited for detailed analysis of coated optical surfaces. In this paper, the fundamentals of the techniques are described and some case studies are presented.
文摘The growing demands of optical systems have led to increasingly complex aspheres and freeforms.In this paper,an established measurement system in asphere production,which is also a promising approach in high-precision freeform metrology,is presented.It is based on a scanning-point multiwavelength interferometer approach.The scanning principle enables great fexibility,reduces setup time and costs,and has almost no limitations in spherical departure.Due to the absolute measurement capability,the utilized multiwavelength approach is benefcial for segmented,annular,and discrete surfaces,which are common designs of modern applications’optical elements.The metrology system enables measurements on a nanometer scale on a great variety of apertures—from 1 to 1000 mm.Recently,a new short-coherence multiwavelength interferometer operating in the visible domain has been developed.It enables the high-precision measurement on silicon-coated surfaces,which can be found in space applications and are also commonly used for extreme-ultraviolet(EUV)lithographic setups,which will be used as an example throughout this work.Owing to the large absolute measurement capability,applied grating structures for suppressing infrared light in the EUV process can easily be measured.This paper summarizes the basic working principles of the proposed metrology system,explains the special requirements for diferent felds of application,highlights the capabilities of the visible multiwavelength approach,and shows the measurement results.
