Detection Of Nanometer Scale Thin Metal Film's Thickness Based On Surface Plasmon Resonance Effect

Nanometer scale metal thin film are widely used for lots of modern high-tech products such as nano-micro optoelectronic devices, because of their special features, which are closely related to their thickness. So it is important to measure the film's thickness with high accuracy. At present, there are several instruments which can complete the above task, such as scanning probe microscope, ellipsometer and step profiler and so on. However, high price and complex structure limit their application. In order to solve the above problems, a Mach-Zehnder interference structure based on surface plasmon resonance effect is designed and measurement system is trail established. It belongs to phase detection method. The variation of film's thickness can be transformed as phasse phase variation of the interference. The method can provide a detection method method on metal film's thickness with the range from 30nm to 100nm, with high sensitivity and simpler structure. Its accuracy is about 1nm.The major contribution and innovations of this dissertation are as follows:1. S-polarized light is taken as reference and p-polarized light is adopted to measure the change of the phase. Mathematical relations between the thickness and the phase of two kinds of polarized lights are set up.2. According to the feture of SPR and laser interferometer, Mach-Zehnder interference structure is set up.3. The method of searching the center of bright stripes is as follow: in the first place rough search, and then detailed search. According to the center of bright stripes, the offset and cycle of the fringe can be calculated.4. As a result of the complex relationship between the thickness and the phase, it is difficult to solve the problem directly. Through making use of piecewise quadratic fitting, not only computing difficulty is reduced but also computing precision is ensured.