EUV Source Mirror Selection for Pattern Uniformity
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Solution Overview
Problem
Existing EUV exposure processes face challenges in achieving optimal optical performance due to the limitations of EUV illumination modes and the need for improved configuration of EUV sources to handle finer semiconductor circuit line widths.
Innovation Solution
A method involving generating an object spectrum map and a pupil map for EUV illumination, selecting mirrors in specific regions of the pupil map, and applying perturbation of pole balance to introduce asymmetry, thereby optimizing the EUV illumination mode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional EUV illumination modes are used, then the exposure process can be performed, but optical performance is not optimal for finer semiconductor circuit line widths
Solution Approach 1:
The patent implements dynamic illumination mode configuration by allowing selective activation of multiple mirrors in the EUV optical system. The control unit dynamically adjusts which mirrors are activated based on the specific exposure requirements, enabling the system to adapt illumination characteristics to match the target pattern and achieve optimal optical performance for varying line widths
Solution Approach 2:
The patent applies local quality by selectively activating specific mirrors corresponding to specific regions in the pupil map. Different mirrors are activated based on the spatial frequency requirements of the mask pattern, with each activated mirror contributing specific spatial frequency components to the illumination, thereby optimizing local optical characteristics for different pattern regions
2Area of stationary object
If more mirrors are selected in the pupil map, then illumination coverage is improved, but system complexity increases
Solution Approach 1:
The patent segments the EUV illumination system into multiple independently controllable mirrors, each corresponding to specific spatial frequency components. The control unit selectively activates only the necessary number of mirrors based on the illumination mode requirements, allowing the system to achieve adequate illumination coverage with a manageable subset of mirrors rather than requiring all possible mirrors to be active simultaneously
3Manufacturing precision
If asymmetric perturbation of pole balance is applied, then pattern uniformity is improved, but illumination efficiency may be reduced
Solution Approach 1:
The patent applies asymmetric perturbation of pole balance by intentionally creating asymmetric illumination patterns through selective mirror activation. The control unit configures mirrors to produce asymmetric illumination that matches the asymmetry of the target pattern, thereby improving pattern uniformity. The system compensates for any illumination efficiency loss by optimizing which specific mirrors are activated to maintain adequate overall illumination while achieving the desired asymmetric pattern uniformity
Data Source
AI summary
Provided are a method of configuring an extreme ultraviolet (EUV) source capable of improving optical performance before an exposure process and an EUV exposure method using the EUV source. The method of configuring an EUV source includes generating an object spectrum map for a layout of a mask pattern, generating a pupil map corresponding to the object spectrum map, and configuring an EUV illumination mode by selecting mirrors in at least a portion of a first region of the pupil map in which a certain condition is satisfied, and applying perturbation of a pole balance to the plurality of mirrors.