Application of aberration optimization for specific pattern using Nikon's TAO method

Abstract

A layer specific aberration control and optimization method is introduced with some field examples. For the first time lens tuning to application specific and product type mask features will be demonstrated. The adjusted lens set-up can be selected within the scanners process program, i.e. the exposure recipe, thus facilitating utmost flexibility. The application is using Nikon's TAO (Technology for Aberration Optimization) software method for specific pattern. Simulated imaging performance data using the Zernike sensitivity method is used as input. The optimization result is used for direct scanner lens element position change to reach a pre-calculated, well defined new wavefront signature. The new lens element position can be directly applied to the layer specific illumination setting via process program of the scanner tool. Specific imaging performance tolerances can be set. Several imaging parameters can be observed separately and various tolerances can be applied during software run, to reach optimized performance. In this paper two product type patterns, like lines and spaces and a dense hole array, and the way of optimization for a high NA 193nm scanner, like minimizing aberration offsets, will be shown. Special attention to the application at already very low aberration levels of a scanner lens is highlighted. Here the method shows the ability of further reduction of aberration specific CD effects in the field. Optimization targets, results, metrology interactions and possible limitations are discussed.