A Method for Optimizing Overlay Mark Shape and Measurement Conditions

Abstract

The invention discloses an overlay mark morphology and measurement condition optimization method, and belongs to the field of photoetching. Firstly, an overlay mark morphology structure and a material optical constant are determined according to a photoetching process; secondly, an overlay optical characterization curve can be calculated through an analysis or numerical modeling method; thirdly, an expression of overlay measurement repeatability precision and accuracy are obtained according to a Taylor formula; then, a variable to be optimized and an appropriate multi-objective algorithm are selected, and the repeatability precision and accuracy of overlay measurement are optimized to obtain a plurality of Pareto optimization results; and finally, the robustness of a plurality of Pareto optimization results is verified, and a result with better robustness is selected as a final optimization result. According to the method disclosed by the invention, the overlay mark morphology and the measurement condition of the eDBO method are optimized at the same time, the final optimization result has the characteristics of high repeatability precision, high measurement accuracy and good measurement robustness, and the requirement of overlay error measurement in a photoetching process is met.

Description

technical field [0001] The invention belongs to the field of photolithography, and more specifically relates to a method for optimizing the shape of overlay marks and measurement conditions. Background technique [0002] With the rapid development of integrated circuit technology, integrated circuits have developed from small scale to extremely large scale, and their critical dimensions (Critical Dimension, CD) have also been continuously reduced from micron level to today's 7nm node. The manufacturing process of integrated circuits includes multiple processes such as material preparation, photolithography, cleaning, etching, doping, and chemical mechanical polishing, among which the photolithography process is the most critical. The main indicators of the lithography process include resolution, depth of focus, key dimensions, alignment and overlay accuracy, etc. Among them, overlay refers to the alignment relationship between the current photolithography process layer and ...

AI Technical Summary

Problems solved by technology

[0023] Aiming at the above defects or improvement needs of the prior art, the present invention provides a method for optimizing the shape of the overlay mark and the measurement conditions. Repeatability measurement accuracy σ and accuracy μ are two optimization objectives, and multiple Pareto optimal results with good robustness are obtained, thereby solving the problem of low repeatability, low accuracy, and robustness of existing overlay error measurement. Poor technical issues

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