Optical Line Width Estimation via Absorption Spectroscopy
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Solution Overview
Problem
Traditional methods for measuring line width in photolithography are time-consuming, costly, and require specialized equipment, often disrupting the manufacturing process and providing inaccurate measurements for smaller line widths.
Innovation Solution
A method and system that use a light source to generate a light beam with a spectrum of wavenumbers, exposing a patterned layer to estimate line width by measuring the absorption spectrum and integrating it over a range corresponding to the material's absorption spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional methods such as SEM or AFM are used for line width measurement, then measurement accuracy is improved, but measurement time and cost increase significantly
Solution Approach 1:
The patent replaces mechanical measurement systems (SEM, AFM) with an optical measurement system that uses light absorption spectroscopy. The system shines light through the photoresist layer and measures the absorbed light intensity at specific wavelengths, allowing rapid non-contact measurement of line width without physical contact or complex mechanical scanning
Solution Approach 2:
The patent introduces light as an intermediary medium to measure line width indirectly through absorption characteristics. Instead of directly imaging or physically probing the features, the system uses light absorption at specific wavelengths (e.g., 2930 cm⁻¹ for C-H bonds) to infer line width, providing a faster and less intrusive measurement method
2Loss of information
If traditional measurement methods are used, then detailed feature information can be obtained, but the manufacturing process is disrupted
Solution Approach 1:
The measurement system is designed to be self-contained and rapidly executable, allowing line width measurement to be performed as an integrated step within the existing photolithography process flow. The system uses the photoresist layer's inherent optical properties without requiring additional preparation or stopping the manufacturing workflow
Solution Approach 2:
The patent performs measurement using light absorption that occurs during or immediately after the photolithography exposure process, before subsequent processing steps. By measuring the absorption spectrum of the photoresist layer in situ, the system obtains line width information without requiring wafer removal or additional processing interruptions
3Measurement precision
If specialized equipment like SEM or AFM is used, then accurate measurements are achieved, but equipment complexity and cost increase
Solution Approach 1:
The patent uses a relatively simple optical setup with common light sources (lasers or LEDs) and detectors that can be integrated into existing photolithography tools. This replaces expensive, complex specialized equipment like SEM or AFM with more accessible optical components that leverage the existing infrastructure
Solution Approach 2:
The optical measurement system can be integrated into existing photolithography equipment, allowing the same tool to perform both pattern formation and line width measurement. The system uses the photoresist layer's optical absorption properties, which are inherent to the materials already being processed, making the measurement capability universally applicable across different photolithography processes
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 allows for rapid and accurate estimation of line width without physically damaging the patterned layer, eliminating dependence on feature size and throughput, and can be integrated into existing photolithography systems.
Implementation Method 1
measuring a first spectrum of the first illuminated area using a light detector, the first spectrum including a first variation in light intensity with a wavenumber of the light beam received at the light detector
Implementation Method 2
determining a first spectrum area by integrating the first variation in light intensity over a range of the plurality of wavenumbers, the range of the plurality of wavenumbers being selected to match an absorption spectrum of the material of the patterned layer
Data Source
AI summary
A method for estimating line width of a patterned layer of a substrate includes generating a light beam with a light spectrum including a plurality of wavenumbers, and exposing the patterned layer of a substrate to the light beam to form a first illuminated area. The method includes measuring a first spectrum of the first illuminated area using a light detector, the first spectrum including a first variation in light intensity with a wavenumber of the light beam received at the light detector. The method includes determining a first spectrum area by integrating the first variation in light intensity over a range of the plurality of wavenumbers, the range of the plurality of wavenumbers being selected to match an absorption spectrum of the material of the patterned layer. And the method further includes determining the line width of the patterned layer based on the first spectrum area.