Lithography Dose Uniformity via Oblique Light Scattering
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Solution Overview
Problem
Current lithography processes face challenges in accurately determining the consistency and uniformity of exposure radiation dose, leading to inefficiencies in the formation of integrated circuit patterns due to non-uniform energy distribution and the need for prolonged downtime for sensor measurements.
Innovation Solution
A method and system that perform open frame exposures on a substrate, followed by baking and developing, and then analyze the scattered light from the substrate surface using oblique light scanning to create a haze map, which is converted into a graphical image file to determine the effective dose of the lithography tool, allowing for quick and accurate characterization of radiation distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sensor measurements are used to determine exposure radiation dose uniformity, then measurement accuracy can be achieved, but production downtime increases due to prolonged measurement time
Solution Approach 1:
The patent replaces traditional mechanical sensor-based measurement systems with an optical scattering-based measurement system. The inspection tool uses oblique light scattering to detect resist thickness variations, eliminating the need for physical sensor measurements during production and significantly reducing downtime while maintaining measurement accuracy.
Solution Approach 2:
The patent creates an optical copy or representation of the exposure dose distribution by measuring light scattering patterns from the resist layer. Instead of directly measuring the radiation dose with sensors, the system captures an optical imprint of the dose uniformity through scattering intensity variations, enabling rapid non-contact measurement.
2Measurement precision
If traditional measurement methods are used, then device complexity is lower, but measurement sensitivity and area coverage are insufficient
Solution Approach 1:
The inspection tool is designed with multi-functionality, capable of performing both scattering intensity measurements for dose uniformity assessment and haze map generation for comprehensive resist characterization. This universal tool replaces multiple specialized measurement devices, increasing sensitivity and coverage while the added complexity is justified by the enhanced capabilities.
3Productivity
If conventional analysis methods are used, then processing is simpler, but analysis speed and detail resolution are limited
Solution Approach 1:
The patent segments the scattered light signal into two distinct components: the background signal used for haze map generation and the intensity variations used for dose uniformity measurement. This segmentation allows parallel processing of different data aspects, improving analysis speed while managing complexity through structured data separation.
Solution Approach 2:
The patent performs preliminary processing by generating haze maps from background signals before conducting the final dose uniformity analysis. This preliminary action pre-processes the data, organizing it in a way that accelerates the subsequent quantitative analysis and enables faster overall processing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach provides high sensitivity and rapid analysis of large areas, enabling better control over the lithography process, reducing downtime, and improving the uniformity and repeatability of the exposure process, while offering finer sampling and resistance to non-dose related effects like image defocus.
Implementation Method 1
scanning the resultant open frame images with oblique light and capturing the light scattered from the substrate surface
Implementation Method 2
Lithography includes an exposure process in which a layer of resist (also known as photoresist) on a substrate is exposed to radiation
Data Source
AI summary
Embodiments are directed to a method and system for determining effective dose of a lithography tool. The method includes performing a series of open frame exposures with the lithography tool on a substrate to produce a set of controlled exposure dose blocks in resist, and then baking and developing the exposed substrate. The method further includes scanning the resultant open frame images with oblique light and capturing the light scattered from the substrate surface. The method further includes creating a haze map from the background signal of the scattered light data, converting the haze map to a graphical image file, and analyzing the graphical image file to determine effective dose of the lithography tool, wherein a brightness of the graphical image file is related to effective dose of the lithography tool.