Quasi-Neutral Plasma Masking for EUV Contamination Control
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Solution Overview
Problem
EUV lithographic apparatuses face contamination issues due to the absorption of radiation by pellicles, leading to reduced throughput and the need for a pellicle-free solution that maintains radiation intensity and prevents contamination particle defects.
Innovation Solution
A lithographic patterning device contamination control assembly using a support structure, masking apparatus, gas supply, and ionizer to create a quasi-neutral plasma between the masking apparatus and patterning device, which neutralizes charged contamination particles without electric field acceleration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pellicle is used in EUV lithographic apparatus, then contamination particles are blocked from reaching the patterning device, but EUV radiation is absorbed by the pellicle reducing throughput
Solution Approach 1:
The patent removes the pellicle from the EUV lithographic apparatus entirely, extracting the problematic component that caused radiation absorption. Instead of using a physical barrier (pellicle), the invention employs a plasma environment to protect the patterning device from contamination, thereby maintaining high radiation transmission and throughput while still preventing particle defects.
Solution Approach 2:
The patent introduces a plasma as an intermediary medium between the contamination particles and the patterning device. This plasma environment acts as a mediator that neutralizes charged particles through ionization, preventing them from reaching and damaging the patterning device without requiring a physical pellicle that would absorb EUV radiation.
2Productivity
If no pellicle is used, then EUV radiation intensity is maintained and throughput increases, but contamination particles can reach the patterning device causing defects
Solution Approach 1:
The patent changes the physical state and electrical properties of the environment around the patterning device by creating a plasma. This parameter change (from neutral gas to ionized plasma) fundamentally alters how contamination particles interact with the patterning device, neutralizing their charge and preventing adhesion without requiring a physical barrier that would reduce radiation intensity.
3Object-affected harmful factors
If charged contamination particles are present near the patterning device, then particles are accelerated towards the patterning device by electric fields, but using a plasma neutralizes particles preventing acceleration
Solution Approach 1:
The patent converts the harmful effect of charged particles (which are accelerated by electric fields toward the patterning device) into a beneficial effect by ionizing the gas environment. The same electric fields that would normally accelerate particles are used to create a plasma that neutralizes particle charges, thereby stopping acceleration and preventing contamination.
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
The quasi-neutral plasma effectively prevents charged contamination particles from reaching the patterning device, maintaining EUV radiation intensity and reducing defects without the need for a pellicle, thus enhancing apparatus throughput.
Implementation Method 1
the ionizer being configured to convert the gas to a quasi-neutral plasma which is located in a region between the masking apparatus and the lithographic patterning device
Implementation Method 2
there is substantially no electric field within the quasi-neutral plasma and thus charged contamination particles are not accelerated towards the patterning device
Data Source
AI summary
A lithographic patterning device contamination control assembly comprising a support structure configured to support a patterning device floating with respect to ground, a masking apparatus configured to selectively mask the lithographic patterning device, the masking apparatus being connected to ground, a gas supply and an ionizer, the gas supply being configured to supply gas to the ionizer, and the ionizer being configured to convert the gas to a quasi-neutral plasma which is located in a region between the masking apparatus and the lithographic patterning device.