EUV Photoresist Top Coating for DUV Blocking and CD Uniformity
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Solution Overview
Problem
The reflection of out-of-band deep ultraviolet (DUV) radiation by a pellicle in EUV lithography systems degrades critical dimension (CD) uniformity due to additional exposure, causing blurred images and non-uniformity in the photoresist layer, which is sensitive to both EUV and DUV radiation.
Innovation Solution
A thin layer, referred to as a spectral filter or top coating (TC), is applied over the photoresist layer to absorb out-of-band DUV radiation while allowing EUV radiation to pass through, thereby maintaining CD uniformity by preventing DUV radiation from reaching the photoresist.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a pellicle is used on a reflective mask to protect it, then the mask is protected from contamination, but out-of-band DUV radiation is reflected by the pellicle and causes additional exposure on the photoresist layer, degrading critical dimension uniformity
Solution Approach 1:
A spectral filter layer is introduced as an intermediary component between the pellicle and the photoresist layer. This filter selectively transmits EUV radiation while absorbing out-of-band DUV radiation, thereby mediating the interaction between the reflected DUV radiation and the photoresist to prevent CD uniformity degradation
Solution Approach 2:
The harmful out-of-band DUV radiation is extracted or removed from the radiation spectrum that reaches the photoresist layer through the spectral filter. The filter absorbs the DUV wavelengths while allowing the desired EUV radiation to pass through, effectively separating the harmful component from the useful radiation
2Use of energy by moving object
If out-of-band DUV radiation reaches the photoresist layer, then additional exposure occurs, but this creates a blurred image of the layout pattern and degrades critical dimension uniformity
Solution Approach 1:
The spectral filter exhibits local quality in its wavelength-selective transmission properties. It is designed to be transparent to EUV radiation (13.5 nm wavelength) while being opaque to out-of-band DUV radiation (wavelengths longer than 13.5 nm), allowing different portions of the electromagnetic spectrum to be treated differently based on their utility for the lithography process
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 solution effectively blocks DUV radiation, ensuring a sharp image of the mask pattern on the photoresist layer, reducing the degradation of critical dimensions and maintaining uniformity without appreciably affecting EUV radiation transmission.
Implementation Method 1
A thin layer, referred to as a spectral filter or top coating (TC), is applied over the photoresist layer to absorb out-of-band DUV radiation while allowing EUV radiation to pass through
Data Source
AI summary
A method of generating a layout pattern includes disposing a photoresist layer of a resist material on a substrate and disposing a top layer over of the photoresist layer. The top layer is transparent for extreme ultraviolet (EUV) radiation and the top layer is opaque for deep ultraviolet (DUV) radiation. The method further includes irradiating the photoresist layer with radiation generated from an EUV radiation source. The radiation passes through the top layer to expose the photoresist layer.