Electrostatic Chuck Particle Control for EUV Photomasks
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Solution Overview
Problem
In extreme ultraviolet lithography (EUVL), conventional pellicles absorb EUV radiation, leading to photomask contamination and pattern distortion on semiconductor wafers due to particulate contamination, as they cannot be used in EUVL and provide inadequate protection during the process.
Innovation Solution
An electrostatic chuck apparatus with a coulomb-force-type electrostatic chuck and collecting plates generates electric fields to attract, detach, and collect charged particles, utilizing a magnetic field to prevent contamination by driving particles away from the photomask, ensuring accurate pattern reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional pellicles are used to protect photomasks, then photomask protection is improved, but EUV radiation absorption increases leading to pattern distortion
Solution Approach 1:
The patent removes the pellicle from the photomask system entirely, extracting the harmful EUV-absorbing component while maintaining photomask protection through an alternative approach using electric fields to repel charged particles away from the photomask surface
Solution Approach 2:
The patent replaces the mechanical pellicle protection system with an electric field-based particle control system, substituting a physical barrier that absorbed EUV radiation with an electromagnetic field that selectively influences charged particles without interfering with EUV transmission
2Object-affected harmful factors
If no pellicle is used in EUVL, then EUV radiation absorption is reduced, but photomask particulate contamination increases
Solution Approach 1:
The patent introduces electric fields as an intermediary between the charged particles and the photomask, using the electrostatic chuck to generate fields that attract and hold charged particles away from the photomask surface, providing protection without direct contact or EUV absorption
Solution Approach 2:
The patent changes the operational parameters of the electrostatic chuck by applying different voltages at different stages: initially applying a first voltage to attract particles onto the chuck, then switching to a second voltage to detach particles, and using a third voltage to collect particles, dynamically controlling particle positions to prevent contamination
3Reliability
If electric fields are used to control charged particles, then particle collection is improved, but device complexity increases
Solution Approach 1:
The patent makes the electrostatic chuck multi-functional by using it not only for its primary function of holding the photomask during lithography but also for particle control through voltage switching, enabling attraction, detachment, and collection of charged particles through the same device without adding separate complex particle manipulation systems
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 method effectively prevents photomask particulate contamination by efficiently attracting and collecting charged particles, maintaining light intensity and improving wafer yield by reducing particle impact on the photomask during EUVL.
Implementation Method 1
generating a first electric field from an electrostatic chuck to attract a charged particle onto the electrostatic chuck
Implementation Method 2
controlling the first electric field to detach the charged particle from the electrostatic chuck
Implementation Method 3
generating a second electric field below the electrostatic chuck to attract the charged particle
Implementation Method 4
utilizing a magnetic field to prevent contamination by driving particles away from the photomask
Data Source
AI summary
A method for preventing photomask contamination includes securing a photomask on a bottom surface of an electrostatic chuck; generating a first voltage at a peripheral area of the bottom surface of the electrostatic chuck to attract a particle onto the peripheral area of the bottom surface of the electrostatic chuck, wherein the peripheral area of the bottom surface of the electrostatic chuck is not directly above the photomask; after generating the first voltage, generating a second voltage at the peripheral area of the bottom surface of the electrostatic chuck to repulse the particle, wherein the first voltage and the second voltage have opposite electrical properties; and generating a third voltage, by using a collecting plate, near a sidewall of the photomask to attract the repulsed particle.