Application Of Low Coherence Scanning Interferometry In Measurement Of Geometric Characteristics Of Silicon Wafers

Low coherent scanning interferometry has been widely used in surface topography measurement.Silicon wafers play an important role in the semiconductor manufacturing industry.The measurement of the geometric characteristics of silicon wafers is becoming more and more important.The current surface topography measurement methods cannot meet the simultaneous measurement of the front and back surfaces of silicon wafers,and the optical thickness of silicon wafers cannot be measured.In this paper,a set of scanning interferometry system is designed for the measurement of silicon wafer geometry.The main work of this paper is as follows:1.This paper analyzes and summarizes the measurement methods of various surface topography and compares their advantages and disadvantages.The theoretical basis of the measurement of the geometrical characteristics of silicon wafers was analyzed to select a method suitable for the measurement of geometric characteristics of silicon wafers.2.A near-infrared low-coherence optical scanning interferometry system based on Michelson's interference was built.The system device was optimized and improved for the characteristics of doped silicon wafers.The light source,CCD camera,stepper motor and optical components were analyzed and selected.The components of the measurement system: optical system,drive and control system,image acquisition and data processing system are introduced in detail.3.The three-dimensional surface reconstruction algorithms of various surfaces are analyzed.Finally,the weight center method is used to improve and optimize.The weighted recursive centroid algorithm is used to reconstruct the surface three-dimensional shape.The front and back surface topography of three doping silicon wafers were measured and analyzed.4.When the optical thickness of the silicon wafer was measured,the low-coherence scanning interferometry method was used for measurement,and the optical thickness of the single point was measured by the SRI method.The two results were compared to verify that the system has high precision.Finally,the refractive index of the doped silicon wafer was measured.5.Low-coherence scanning interferometry system can be well applied in actual measurement,but it still has error source that limits measurement accuracy.The errorsource in this measurement system includes system internal,algorithm and environment.A simple analysis of these error sources was performed.