Plasma Electron Density Measurement via Multi-Beam Laser Absorption
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Solution Overview
Problem
Current diagnostic tools for high-density plasma in semiconductor processes, such as EUV lithography and PLD, are invasive, costly, or require sophisticated equipment and expertise, making them unsuitable for continuous, non-invasive measurement of electron density.
Innovation Solution
A method and apparatus using multiple laser beams to measure electron density through inverse bremsstrahlung process absorption, combined with tomographic reconstruction and Beer-Lambert law, to calculate electron density in concentric zones of high-density plasma.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If optical emission spectroscopy is used to measure electron density, then measurement can be performed non-invasively, but the method is limited by overlapping emission lines and self-absorption in high-density plasma, making it difficult to clearly identify peaks
Solution Approach 1:
The patent changes the measurement parameter from emission line analysis to absorption coefficient analysis. By measuring the absorption of laser beams at different wavelengths and paths, the system can determine electron density without relying on emission line peaks, thereby avoiding the limitations of overlapping lines and self-absorption effects in high-density plasma
Solution Approach 2:
The patent introduces laser beams as an intermediary probe to measure plasma properties. Instead of directly analyzing plasma emission, the system uses laser beams that pass through the plasma and measures their absorption characteristics, which are then used to calculate electron density through tomographic reconstruction
2Measurement precision
If Thomson scattering is used to measure electron density and temperature, then accurate measurement can be achieved, but highly sophisticated equipment and high level of expertise are required, making it difficult to apply experimentally
Solution Approach 1:
The patent replaces expensive and complex Thomson scattering equipment with simpler, more affordable laser diodes and photodiodes. The system uses commercially available components that can be easily implemented without requiring specialized expertise, while still achieving accurate electron density measurements through absorption-based tomographic reconstruction
Solution Approach 2:
The patent substitutes the complex mechanical and optical setup of Thomson scattering with a simpler laser absorption system. Instead of using sophisticated scattering detection equipment, the system uses laser beams and photodetectors to measure absorption coefficients, which are then processed to obtain plasma parameters
3Ease of operation
If contact sensor is used to measure plasma state, then measurement can be performed, but the sensor is damaged during diagnosis process and sensor surface is coated with metal material, making it unsuitable for continuous condition monitoring
Solution Approach 1:
The patent uses laser beams as a non-contact intermediary to probe plasma properties. The laser beams pass through the plasma without physical contact, avoiding sensor damage and contamination while still enabling continuous measurement of plasma state parameters
Solution Approach 2:
The patent replaces the mechanical contact sensor system with an optical laser absorption system. This substitution eliminates the physical contact between sensor and plasma, preventing sensor damage and metal coating accumulation, thereby enabling continuous and reliable plasma monitoring
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
Enables real-time, non-invasive, and cost-effective measurement of high-density plasma electron density, facilitating continuous monitoring and process optimization in semiconductor manufacturing.
Implementation Method 1
generating absorption data indicating an extent to which energy of each laser beam is reduced by an inverse bremsstrahlung process occurring in the plasma
Data Source
AI summary
Disclosed herein are an apparatus and a method for measuring an electron density of plasma. The method of measuring an electron density of plasma includes emitting multiple laser beams into plasma through different paths through a laser diode, detecting an intensity of each of the multiple laser beams passing through the plasma through a photodiode and generating absorption data indicating an extent to which energy of each laser beam is reduced by an inverse bremsstrahlung process occurring in the plasma, and calculating an electron density of the plasma for each concentric zone on the basis of the absorption data.