Inert Gas Flow for EUV Lithography Outgassing Control
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Solution Overview
Problem
EUV lithography systems face challenges with outgassing during patterning operations, leading to contaminant deposition on components and reduced efficiency due to air absorption of EUV photons, which necessitates vacuum conditions but still results in outgassed contaminants affecting tool performance.
Innovation Solution
A method and apparatus that utilize a thin layer of inert gases, such as helium, neon, or argon, to flow across the photoresist-coated substrate and reflective surfaces, preventing contaminant deposition and maintaining low pressure in the lithography chamber, with a controlled flow rate and exhaust system to minimize resonance time and photon absorption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If vacuum conditions are maintained in the lithography chamber to prevent air absorption of EUV photons, then photon transmission efficiency is improved, but outgassing from the photoresist substrate still produces contaminants that deposit on components
Solution Approach 1:
A nitrogen gas flow is introduced as an intermediary substance between the photoresist substrate and the reflective surfaces. This nitrogen flow serves as a protective mediator that captures outgassed contaminants before they can deposit on the mirrors and optical components, while simultaneously maintaining conditions that allow EUV photons to reach the substrate efficiently.
Solution Approach 2:
The patent utilizes an inert nitrogen atmosphere flowing through the chamber to create a protective environment. The nitrogen gas, being chemically inert, does not react with the EUV photons or the photoresist, but effectively suppresses the deposition of outgassed contaminants on surfaces by maintaining a controlled atmospheric condition throughout the exposure process.
2Object-generated harmful factors
If inert gas flow rate is increased to improve contaminant removal, then cleaning effectiveness is improved, but absorption of EUV photons by the inert gas increases
Solution Approach 1:
The patent optimizes the nitrogen gas flow rate to a specific parameter range that balances two competing requirements: sufficient flow to carry away outgassed contaminants, but not so high as to cause significant EUV photon absorption. This parameter optimization ensures the gas flow velocity and pressure are tuned to achieve effective contaminant removal while minimizing energy loss.
Solution Approach 2:
Instead of using excessive gas flow that would guarantee complete contaminant removal but cause significant photon absorption, the patent applies partial action by using a controlled, moderate nitrogen flow that achieves sufficient contaminant management for practical purposes while accepting a small, manageable level of photon absorption loss.
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 inert gas flow effectively reduces outgassing and prevents contaminant buildup on components, maintaining high efficiency by minimizing the absorption of EUV photons and ensuring clean reflective surfaces, thereby enhancing the patterning process in EUV lithography systems.
Implementation Method 1
The inert gas flow is a laminar layer of inert gas produced over the substrate surface
Implementation Method 2
Inert gasses are advantageous because they will not easily react with the photons from EUV light to produce reactive radicals. The inert gasses are exhausted quickly and the flow rate is controlled to produce a short resonance time of the inert gas in the lithography system to avoid significant absorption of the EUV photons by the inert gas.
Implementation Method 3
The EUV light beams are reflected from the reticle and impinge upon the substrate surface where the light radiation chemically alters the exposed photoresist
Data Source
AI summary
A method and apparatus for ultraviolet (UV) and extreme ultraviolet (EUV) lithography patterning is provided. A UV or EUV light beam is generated and directed to the surface of a substrate disposed on a stage and coated with photoresist. A laminar flow of a layer of inert gas is directed across and in close proximity to the substrate surface coated with photoresist during the exposure, i.e. lithography operation. The inert gas is exhausted quickly and includes a short resonance time at the exposure location. The inert gas flow prevents flue gasses and other contaminants produced by outgassing of the photoresist, to precipitate on and contaminate other features of the lithography apparatus.