Electrodeless Lamp Illumination for Semiconductor Wafer Inspection
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Solution Overview
Problem
Existing semiconductor inspection systems face limitations with electrode-based high-intensity discharge arc lamps due to brightness and power constraints, electrode erosion, and inability to control dopants, which affect the quality and duration of illumination for defect detection on specular or quasi-specular surfaces like semiconductor wafers.
Innovation Solution
The use of an electrodeless lamp system that generates light through a plasma excited by a laser, with focusing optics to direct excitation light and maintain a plasma geometry matching collection optics, providing deep ultraviolet (DUV) or broadband light for improved illumination without electrodes, thus overcoming the limitations of traditional lamps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If electrode-based high-intensity discharge arc lamps are used, then illumination is provided for specimen inspection, but brightness and power are limited due to electrostatic constraints on current density from the electrodes
Solution Approach 1:
The patent removes electrodes from the discharge lamp system entirely, extracting the limiting component that constrained current density and brightness. This electrodeless design allows energy to be deposited directly into the gas fill without electrode interference, enabling higher power operation and increased illumination intensity for specimen inspection.
Solution Approach 2:
The patent replaces the mechanical/electrical electrode-based energy transfer system with an electromagnetic field-based energy deposition system. Instead of using physical electrodes to conduct current, the invention uses electromagnetic fields to directly energize the gas fill, eliminating the electrostatic constraints that limited brightness and power in traditional electrode-based lamps.
2Illumination intensity
If electrode-based lamps operate at high current densities, then illumination is achieved, but electrodes erode rapidly due to presence of relatively large current densities at the cathodes
Solution Approach 1:
By removing electrodes from the system, the patent eliminates the component that suffered from rapid erosion. Without physical electrodes to degrade, the illumination system can operate continuously at high current densities without the lifespan limitations that plagued electrode-based lamps, significantly extending operational duration.
Solution Approach 2:
The patent substitutes the mechanical electrode-based current conduction system with an electromagnetic field-based energy deposition system. This replacement eliminates the physical wear and erosion mechanisms that limited electrode lifespan, allowing the illumination system to maintain stable operation for extended periods without component degradation.
3Illumination intensity
If electrode-based lamps are used, then light is generated for inspection, but ability to control dopants is limited for relatively long periods of time at the required emission current
Solution Approach 1:
The patent replaces the electrode-based current delivery system with an electromagnetic field-based energy deposition system. This substitution provides superior control over the timing and duration of dopant emission, as electromagnetic fields can be precisely modulated to deliver required emission currents for extended periods without the degradation and control limitations inherent in electrode-based systems.
4Power
If electrodeless lamp with laser excitation is used, then higher excitation power densities are achieved, but system complexity increases due to laser and focusing optics requirements
Solution Approach 1:
The patent changes the fundamental operating parameters of the discharge lamp by introducing laser excitation with specific wavelengths (e.g., 308 nm UV or 10.6 μm infrared) and controlling plasma conditions (pressure, gas composition, temperature). These parameter changes enable higher excitation power densities that produce more intense illumination, justifying the added complexity of laser and focusing optics components.
Solution Approach 2:
The patent creates a multi-functional system where the laser serves multiple purposes: providing precise wavelength-selective excitation, controlling plasma generation timing, and enabling higher power density operation. The focusing optics similarly serve dual functions of concentrating energy to the plasma region and defining the illumination geometry, reducing the need for separate illumination shaping components.
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 solution provides high brightness and extended operational life by concentrating excitation energy within the plasma region, reducing ohmic losses and allowing for higher excitation power densities, resulting in more efficient and stable illumination for semiconductor wafer inspection.
Implementation Method 1
a laser configured to generate excitation light
Implementation Method 2
focusing optics configured to focus the excitation light to a plasma in an electrodeless lamp such that the plasma generates light
Data Source
AI summary
Methods and systems for providing illumination of a specimen for a process performed on the specimen are provided. One system configured to provide illumination of a specimen for a process performed on the specimen includes a laser configured to generate excitation light. The system also includes focusing optics configured to focus the excitation light to a plasma in an electrodeless lamp such that the plasma generates light. The system is also configured such that the light illuminates the specimen during the process.