Laser Beam Formatting Module for EUV Lithography
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Solution Overview
Problem
Conventional lithographic systems using laser-produced plasma (LPP) light sources often emit a distribution of wavelengths due to varying laser beam intensities, resulting in significant out-of-band radiation that reduces image quality and generates excess heat, as they fail to achieve uniform intensity necessary for efficient patterning radiation at specific wavelengths like 13.5 nanometers in EUV lithography.
Innovation Solution
A laser beam formatting module comprising an aperture plate and lens assembly that shapes and demagnifies the laser beam to achieve uniform intensity across the target, reducing out-of-band radiation by ensuring consistent energy delivery for optimal patterning radiation production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a focusing lens is used to focus the laser beam onto the target, then the laser beam intensity is concentrated to produce plasma, but the laser beam intensity distribution becomes non-uniform resulting in a distribution of wavelengths including out-of-band radiation
Solution Approach 1:
The patent changes the intensity distribution parameter of the laser beam from a focused Gaussian distribution to a uniform top-hat distribution by using an aperture plate and demagnification optics. This parameter change ensures that the entire target surface receives uniform intensity, producing plasma that emits primarily at the desired wavelength (13.5 nm) rather than a distribution of wavelengths, thereby reducing out-of-band radiation.
2Power
If conventional focusing techniques are used, then the laser beam is concentrated on the target, but the non-uniform intensity distribution reduces energy conversion efficiency to patterning radiation
Solution Approach 1:
The patent modifies the intensity distribution parameter from focused to uniform, and scales the intensity through demagnification. This ensures that the laser energy is distributed uniformly across the target surface at an optimized intensity level, maximizing the conversion efficiency of laser energy to patterning radiation at 13.5 nm while minimizing energy loss to out-of-band radiation.
Solution Approach 2:
The patent replaces the conventional focusing lens optical system with an aperture plate and demagnification optics system. This substitution changes the fundamental approach from concentrating energy at a point to distributing energy uniformly across the target surface, thereby improving energy conversion efficiency and reducing wasteful out-of-band radiation emission.
3Productivity
If out-of-band radiation is produced, then the lithographic process can proceed, but image quality is reduced and excess heat is generated
Solution Approach 1:
By changing the laser beam intensity distribution parameter to uniform and optimizing the intensity through demagnification, the patent ensures that plasma is produced at a consistent intensity across the entire target surface. This produces patterning radiation primarily at the desired 13.5 nm wavelength, minimizing out-of-band radiation that would otherwise degrade image quality and generate excess heat in the lithographic 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 solution significantly reduces out-of-band radiation emission, improving energy conversion efficiency, maintaining image quality, and eliminating the need for out-of-band radiation filters, while protecting optical components from heat damage.
Implementation Method 1
A laser beam formatting module comprising an aperture plate and lens assembly that shapes and demagnifies the laser beam to achieve uniform intensity across the target
Implementation Method 2
In EUV lithography, for example, a laser-produced plasma (LPP) serves as a lithographic light source, at extreme ultraviolet (EUV) wavelengths
Implementation Method 3
a pattern formed on a lithographic mask can be transferred to a semiconductor wafer by exposing a photoresist formed on the semiconductor wafer to the image of the lithographic mask
Data Source
AI summary
According to one exemplary embodiment, a laser beam formatting module for use in a lithographic system to fabricate a semiconductor wafer comprises an aperture plate having, for example, a circular aperture and capable of being situated between a laser source and a target, and a lens assembly, in a light path between the aperture plate and the target. The laser beam formatting module can produce a substantially uniform laser beam intensity across a target during fabrication of a semiconductor wafer in a laser-produced plasma (LPP) lithographic process using, for example, extreme ultraviolet light (EUV). In one embodiment, a laser beam formatting module improves energy conversion efficiency, reduces out-of-band radiation emission, avoids heating of reflective optics, and eliminates the need for an out-of-band radiation filter.