Theory And Method Research On SPR Phase Detection For The Thickness Of Nanometer Scale Metal Film

Nanometer scale metal film has played a significant role in such fields as semiconductor manufacturing,photovoltaic cells,aerial materials biochemical technology and so on in recent years.The thickness of it is not only the critical factor affecting the properties of materials,but one of the crucial technical indexes evaluating the qualities of thin films.Therefore,it is of much significance to measure the thickness of nanometer scale metal film accurately.Surface Plasmon Resonance(SPR)technology has been studied and applied to a certain extent in the field of thin film sensors,particularly in the measurement of the characteristic parameters of thin films.As SPR effect is extremely sensitive to the small changes at the interfaces of varied metal film-dielectric,it can be applied to measure the thickness of nanometer scale metal film.In addition,compared with other detecting methods,SPR phase detection method possesses a higher sensitivity.Based on analysis and elaboration above,a novel method is put forward in this thesis,which SPR phase detection method is utilized to determine the thickness of nanometer scale metal film.The concrete tasks in the thesis mainly include:First,the measurement model is constructed to apply SPR phase detection method to measure the thickness of nanometer scale metal film.According to the basic principles and methods of SPR,the theoretical model based on the multilayer Kretschmann configuration is derived and the impact of the thickness of thin metal films on the reflectance spectrum is analyzed.The gold film and silver film are taken as main research objects.The measurement model is established by utilizing the phase difference between TM and TE polarized waves coupled with numerical calculation and curve fitting methods to calculate the thickness of nanometer scale metal film.Second,the measurement system is established using SPR phase detection method to measure the thickness of nanometer scale metal film.Based on the measurement model,the method is designed by utilizing the image of interference fringes to calculate the phase difference between TM and TE polarized waves.The appropriate experimental devices are selected and the SPR prism coupler with Kretschmann configuration is prepared.In addition,the measurement system is also combined with the monochromatic light polarization modulation structure,Mach-Zehnder interference configuration and the image collection module.Third,the experimental study is conducted by utilizing SPR phase detection method to measure the thickness of nanometer scale metal film.On the basis of the measurement model constructed and the measurement system established,the measurement experiments on the thickness of nanometer scale metal film are carried out with the SPR prism coupler of monolayer and double-layer thin metal films structures respectively.AFM and ellipsometer are utilized to verify the measuring results.Furthermore,the characteristics and shortcomings of the measurement scheme are also analyzed to point out the way for the further improvement of the theoretical model and the measurement system.Theoretical analysis and experimental results show that the measurement range of the novel detection scheme proposed in this thesis is 0~80 nm and the highest measurement resolution is better than 0.1 nm.The measurement system has the advantages of simple structure,better stability and stronger antijamming capability as well as the reliable,stable and accurate measuring results.The results mentioned above indicate that this method can be used to measure the thickness of nanometer scale metal film accurately.