A method for measuring the process window of photolithography

Abstract

The invention discloses a measuring method of a photolithographic process window, comprising the following steps: providing a wafer with a plurality of structures to be measured in array distribution formed by photoetching a focus value and exposing energy matrixes; acquiring a line imaging chart of the structures to be measured through an electron beam microscope; analyzing the line imaging chart by a multi-pixel threshold method, acquiring a marginal distribution curve of the lines in one-dimension direction, computing the line roughness according to the marginal distribution curve, and drawing a relation curve between pixel value and line roughness; taking the marginal pixel value corresponding to the continually varying minimal line roughness as a line marginal position reference, and computing a line reference width according to the line marginal position reference; and carrying out data analysis on the line reference width and minimal line roughness of all the structures to be measured, and computing the numerical range of the photolithographic process window. The measuring method improves the accuracy in measuring the photolithographic process window.

Description

technical field [0001] The invention relates to the technical field of integrated circuits, and more specifically, relates to a method for measuring a photolithography process window. Background technique [0002] In the development and manufacturing process of new integrated circuit products, determining the optimal process window of lithography, that is, determining the optimal exposure energy, optimal focus value and its range is the most important process, and this process is highly dependent on accurate electron beam scan imaging. With the continuous improvement of integrated circuit integration, the feature size of the device is continuously reduced, and the imaging of nanoscale lines by electron beam microscopy (SEM) is affected by the edge effect of the electron beam, which increases the imaging error. Especially when measuring the structure to be tested in the wafer containing the focus value and exposure energy matrix (Focus Energy Matrix, FEM), the SEM imaging re...

AI Technical Summary

Problems solved by technology

But when the line width is less than 100 nanometers, especially after using double or multiple lithography techniques, the line width after lithography is already much smaller than 100 nanometers, and after etching, cutting or other processes, the minimum line width may drop below 50 nanometers , resulting in an unusually significant edge effect in the SEM imaging process

In this case, the existing technology has a large error in determining the optimal photolithography process window, especially slight edge threshold fluctuations or image noise fluctuations will have a measurement width change of several nanometers, so it is difficult to achieve such a large The regular relationship curve when the size line determines the FEM process window leads to a decrease in the accuracy and comparability of the measurement results, and the relationship curve of line width with exposure energy or focus value fluctuates seriously

[0004] From the above description, it can be seen that the existing measurement method that only relies on the relationship between line width, exposure energy and focus value, as the lines of the structure to be tested become narrower, it becomes more and more difficult to accurately measure the optimal lithography process window

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