Global Critical Dimension Correction: I. Fogging Effect Correction

Abstract

Present LSI technology requires very strict critical dimension (CD) control on masks. An electron beam (EB) mask writer has been widely used but is known to induce a fogging effect that affects CD control. In this paper, a new formula for calculating the optimum dose required to correct both the fogging effect and the proximity effect is proposed. This formula is expressed as the product of the proximity effect and fogging effect correction terms. Features of this new formula are that (1) the fogging effect correction term includes the result of the proximity effect correction, and (2) the formula can provide an accurate value for the optimum dose required to correct both the proximity and fogging effects. Correction accuracy is evaluated under the conditions that the proximity effect parameter η and the fogging effect parameter θ are 0.8 and 0.1, respectively. It is found that when using a conventional fogging effect correction method, a significant correction error (1.7% in energy and 3.4 nm in dimension) appears because the method does not use the results of the proximity effect correction. On the other hand, our method can suppress the correction error to less than 0.15% in energy (0.29 nm in dimension).