Pellicle Heating System for EUV Lithography
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Solution Overview
Problem
Carbon nanotube pellicles in EUV lithographic apparatuses are susceptible to hydrogen plasma etching, leading to reduced lifetime due to temperature fluctuations and hydrogen ion interactions, which existing heating methods fail to adequately address.
Innovation Solution
A heating system is integrated into the lithographic apparatus to maintain the pellicle at a temperature above a threshold, potentially with the addition of catalysts like transition metals, to reduce hydrogen etching rates and extend pellicle lifetime, and periodic or pulsed heating is employed to minimize power consumption and heat load.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a carbon nanotube pellicle is used to protect the reticle, then particle contamination is prevented, but hydrogen plasma etching reduces pellicle lifetime
Solution Approach 1:
The patent applies parameter changes by heating the pellicle to a specific temperature range (600-800K) to suppress hydrogen plasma etching. This temperature control fundamentally changes the thermal state of the pellicle, reducing the etching rate and thereby extending pellicle lifetime while maintaining its particle protection function
Solution Approach 2:
The patent employs composite materials by incorporating transition metal catalysts (such as iron, cobalt, or nickel) into the carbon nanotube pellicle structure. This creates a composite material that not only protects against particle contamination but also exhibits enhanced resistance to hydrogen plasma etching, thus extending pellicle lifetime
2Duration of action of stationary object
If continuous heating is applied to suppress etching, then pellicle lifetime is extended, but power consumption and heat load increase
Solution Approach 1:
The patent applies periodic action by implementing pulsed or cyclic heating instead of continuous heating. The heating system activates intermittently to maintain the pellicle temperature above the etching suppression threshold, thereby extending pellicle lifetime while significantly reducing average power consumption and heat load on the system
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 heating system effectively maintains the pellicle at a temperature where hydrogen etching is negligible, significantly extending its lifetime and reducing thermal stress on the apparatus, while also optimizing power usage and minimizing heat impact on the reticle.
Implementation Method 1
a heating system operable to heat a pellicle of the reticle and pellicle assembly supported by the support structure
Implementation Method 2
a low pressure hydrogen gas is typically provided within the lithographic apparatus, which forms a hydrogen plasma in the presence of the EUV radiation (during exposure)
Data Source
AI summary
A lithographic apparatus includes: an illumination system configured to condition a radiation beam; a support structure constructed to support a reticle and pellicle assembly for receipt of the radiation beam conditioned by the illumination system; a substrate table constructed to support a substrate; a projection system configured to receive the radiation beam from the reticle-pellicle assembly and to project it onto the substrate; and a heating system configured to heat a pellicle of the reticle-pellicle assembly supported by the support structure. A method for using a reticle-pellicle assembly including: illuminating the reticle-pellicle assembly with a radiation beam so as to form a patterned image on a substrate; and heating the pellicle of the reticle-pellicle assembly using a separate heat source.