Global Critical Dimension Correction: II

概要

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In LSI production, various factors contribute to critical dimension (CD) errors. Factors that gradually affect CD over a several mm–cm area are referred to as global CD errors. In this paper, a method of correcting global CD errors (GCD correction) that appear in processes following an electron-beam mask-writing process is discussed. Examples of GCD errors are the loading effects in wafer and mask processes, and the flare in lithography processes. In this paper, we propose a new method of calculating the optimum dimension to correct GCD errors. The correction method is based on a pattern modulation method; i.e., modification of the sizes of figures in an LSI pattern depending on their position. A feature of our method is the use of two newly introduced factors, a “figure edge contribution” and a “corner adjustment term”, in addition to conventional pattern density. As an example, the correction accuracy of our method is evaluated for mask fabrication by numerical calculation. It is shown that our method can suppress the GCD correction error to less than 0.01 nm when the maximum GCD error depending on the pattern density is 20 nm. Our method will provide the CD accuracy required in the future. The relation between global CD correction and proximity effect correction is also discussed in the case that an electron-beam writing system is used to control figure sizes.
2007-06-15