Study of loading effect on dry etching process

Abstract

Nowadays, the CD (Critical Dimension) control on masks manufacturing plays an important role in photolithography process for 90-nm node technology and below. The process performance of photolithography will degrade severely even when the mask CD error is small. One of the most important process-induced mask CD errors comes from the dry etching process. With the loading effect due to environment pattern variations, isolated and dense patterns have different etching biases. Furthermore, the loading effect can induce an overall CD variation called global loading effect contributed from the pattern density change in large areas and a CD variation on individual monitor pattern called micro-loading effect contributed from various feature dimensions in the near region. The micro-loading effect can also be classified as the “nearest spacing” effect which is dependent upon the space between the nearest neighbor pattern and the monitor pattern, and the “nearest neighbor” effect which is dependent upon the size of the nearest neighbor feature around the monitor pattern. All of these effects enlarge the total range of mask CD linearity and proximity errors. In this paper we report the result of the global loading effect and micro-loading effect by varying pattern densities and feature dimensions nearby. With the design of test pattern, the global loading effect and the micro-loading effect can be separated. The CD variation dominated by the micro-loading effect in the dry etching process is observed. This large etching bias change resulted from the micro-loading effect is consistent with the depletion of radical species in the narrow space during the etching process.