Research On LER Effect Of Linewidh Measurement Accuracy On Nano-Scale

The measurement of nano-scale linewidth is an important content in nanometrology research. It is a technology that measures the width of reticle or other features in nano-scale. Nowadays, the growing semiconductor integrate circuit industry is the main motivation which drives the development of measurement technology of nano scale linewidth. The developing of MEMS and the data storage industry also need measurement of linewidth with high precision. Atomic force microscopy(AFM) has begun to be used in linewidth measurement and has become an important technique for its insensitivity to sample materials and its capability for working at ambient conditions. Aimed on some questions existing in linewidth measurement using AFM, this paper studied nano-scale linewidth measurement technology based on AFM.The working principle, device structure and working mode of AFM are briefly introduced, and the geometric explanation for scanning image of the sample with AFM is proposed. The application of linewidth measurement and the main factor that affects measurement image with AFM are analyzed. Such as expansion effect of AFM probe, nonlinearity of piezoelectricity, change of measurement environment and setup of instrument parameter, etc. are explained in detail. The research trends aimed at these questions in nano scale linewidth measurement at present are discussed and the farther research work is based. A detailed analysis of the differences between the two was established. The effects of LER on linewidth under the new line edge roughness measurement model is introduced.Based on the results of laboratory experiments, linewidth measurement model has been improved. Line edge roughness were accurately characterized by measuring the three widths of the bottom, middle and top of the line width and the corresponding six key points. The data was calculated by Matlab and compared with the existing results.Based on the scanning course and characteristic of AFM, filter methods for several noise induced in scan course are discussed. Effect on linewidth measurement by different filter method is introduced. The principle and calculation method of rigid body rotation and displacement and the interpolation and fitting of the scan image element after rotation are expatiated. In order to reduce the method divergences caused by different measurement methods and instruments for an accurate determination of nano-scale linewidth parameters, in this paper, a measurement model and algorithm for linewidth measurement is established based on AFM measurements. The model and calculation method based on scan image are explained in detail. And the software to calculate involved parameters is developed with Matlab.The calculation and modification method of sample position error is described. The nano-scale reticle sample is measured with AFM installed normal probe. Then image rotation is implemented. In light of the uncertainty evaluation theory, manifold methods of evaluating uncertainty root in variety of errors including image rotation. The uncertainty evaluation system of linewidth measurement with Innova AFM is established and the evaluations are implemented. The synthesization standard uncertainty and extend uncertainty of top linewidth, middle linewidth and bottom linewidth are calculated.