Research On Linnik Microscopic White Light Spectral Interferometry

With the development of micro-nano manufacturing technology,microstructure testing,especially surface topography testing and film thickness testing,has become one of the important directions of micro-nano measurement technology.The quality of the surface topography,to some extent,can affect the quality and yield of the whole micro-device.And the thickness can influence the electromagnetic,optical and mechanical properties of the thin film in a decisive manner.Therefore,how to detect the surface topography and the thin film thickness accurately has become a key technology.As a kind of optical testing method,white light spectral interference technology,which combines the precision of white light interferometry and the speed of spectral analysis,has the advantages of non-contact and high precision,and can realize fast measurement at the same time.Different from the traditional microscopic interference structure such as Michelson type and Mirau type,Linnik microscopic interference structure can be used to measure samples working in special condition owing to its characteristics of long working distance.In this thesis,the topic focuses on the measuring system of Linnik microscopic white light spectral interferometry,which realizes the measurement of surface topography and thin film thickness.The main works are as follows:1.The research state of thin film technology was introduced,and several methods for measuring surface topography and thin film thickness were summarized.The superiority of Linnik microscopic white light spectral interferometry was described in detail.2.The basic theory of white light spectral interferometry was described in detail from the aspects of principle of two-beam interference,characteristics of white light interference and frequency interference.3.Components of Linnik microscopic white light spectral interference measuring system were introduced.The process of instrument control and interference signal acquisition were described briefly.4.Two kinds of phase extraction algorithms were compared theoretically.On these bases,absolute distance verification experiments and step structure measuring experiment were conducted.Influences of different phase extraction algorithms anddifferent ratio objects were also analyzed.5.The reflection characteristics of thin film were introduced,and the initial estimation method based on the frequency of nonlinear phase of thin film was described.In addition,the effective range of initial value was studied when using the local optimization algorithm.And measuring experiments of thin films with different thicknesses were conducted.Besides,influences of elements such as different phase extraction algorithms and different ratio objects were also analyzed.