Research And Application Of White Light Interference In Vertical Measurement Of Semiconductor Measuring Equipment

In the process of photolithography,the nesting error is an important index reflecting the accuracy of nesting between chip layers,and a clear image is needed to ensure the measurement accuracy when measuring it,while the detection accuracy of the existing focusing technology does not meet the actual demand.To address this problem,this paper conducts an in-depth study of white light scanning interference technology and white light spectral interference technology,and improves the detection rate by calibrating the vertical distance between the best focal plane position of the camera and the zero light range difference position of the white light interference during the check-focus measurement,taking the zero light range difference position as the detection object.A check-focus system that can realize two measurement methods simultaneously is built,and the effectiveness and accuracy of the algorithm are experimentally verified.The main research contents of this paper are as follows:1.For white light interference technology,analyze in detail the principle of zero optical range difference positioning algorithm,and optimize the algorithm according to the actual situation;propose the evaluation method of scanning white light interference signal as the basis for system parameter selection;explain the advantages of white light interference detection focusing compared with image sharpness based detection focusing.2.Design the focusing process,through the calibration of the vertical distance compensation amount,to achieve the conversion of the white light interference zero optical range difference position to the best focal plane position of the silicon;build a Linnik type microscopic interferometric focusing system,the system is compatible with both white light scanning interferometric focusing and white light spectral interferometric focusing two kinds of measurement methods.3.The results of the experiments on the accuracy of the scanning interferometric focusing measurement are: the maximum average absolute error of the focusing measurement is 57 nm and the minimum is 8 nm;the maximum root mean square error is81.6 nm and the minimum is 9.5 nm;the measurement error is smaller and more concentrated than the traditional focal plane measurement technique,and the measurement stability is good;the results of the experiments on the repeatability of the measurement of different marker types of silicon wafers are: The average standard deviation of measurement for BIB marker type wafers was 87.7 nm,and the average standard deviation of measurement for AIM marker type wafers was 72.9 nm.The experiments proved that the measurement repeatability for BIB marker is lower than that for AIM marker.