Doped Semiconductor Dose-Reducing Layer for EUV Shot Noise
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Solution Overview
Problem
In extreme ultraviolet lithography, the low photon count due to high energy EUV photons results in poor quality lithography structures because of the photon shot noise effect, especially at small structure sizes. Current solutions either complicate resist structures or suffer from self-limiting effects and electron loss to the substrate.
Innovation Solution
A structure comprising a substrate, a dose reducing layer, and an EUV resist, where the dose reducing layer is a doped semiconductor with a main component and a dopant, enhancing secondary electron generation and absorption of EUV radiation to improve lithography quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high energy EUV photons are used to improve resolution, then wavelength is decreased, but photon count is reduced causing poor lithography quality due to shot noise
Solution Approach 1:
The patent introduces an EUV absorbing layer as an intermediary between the EUV photons and the resist. This layer absorbs the high energy photons and converts them into secondary electrons, which then act as the effective exposure agents for the resist. This mediator approach solves the shot noise problem by multiplying the effective exposure events from each photon.
Solution Approach 2:
The patent changes the parameter of electron multiplication by using materials with high secondary electron yield. By selecting specific materials and optimizing their properties, each absorbed photon generates multiple secondary electrons, effectively amplifying the exposure signal and reducing the impact of photon shot noise.
2Use of energy by moving object
If EUV absorbing materials are added to the resist to increase absorption, then photoelectron production increases, but resist structure becomes complicated and control of SE generation becomes difficult
Solution Approach 1:
The patent segments the lithography stack into distinct functional layers: a separate EUV absorbing layer is created beneath the resist, rather than complicating the resist composition itself. This segmentation allows each layer to be optimized independently for its specific function while maintaining overall system simplicity.
Solution Approach 2:
The EUV absorbing layer serves as an intermediary that handles the complex absorption and secondary electron generation functions, allowing the resist to remain relatively simple while still achieving high absorption efficiency through the underlying layer.
3Quantity of substance
If heavy metal materials are used in underlayers to produce secondary electrons, then electron production increases, but electrons are blocked by upper layers and lost to substrate
Solution Approach 1:
The patent optimizes the thickness parameter of the EUV absorbing layer to match the electron mean free path. This ensures that secondary electrons generated in the absorbing layer can escape into the resist before being lost to the substrate, maximizing electron utilization while maintaining high absorption.
Solution Approach 2:
The patent applies different material properties to different locations in the stack: the EUV absorbing layer uses high-Z materials optimized for photon absorption and secondary electron generation, while the resist layer is optimized for receiving and responding to the generated electrons. Each layer has locally optimized properties for its specific function.
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 proposed solution effectively increases the number of secondary electrons produced per photon, reducing the required EUV dose and improving the quality of lithography structures by minimizing photon shot noise.
Implementation Method 1
The EUV resist can be constructed and arranged for absorbing EUV radiation and generating secondary electrons
Implementation Method 2
Absorption is often improved by simply inserting EUV absorbing materials into the lithography structure. This absorption produces photoelectrons which can cause reactions in the resist, but one electron per photon conversion still produces high shot noise. This problem is solved if the high energy photoelectrons are converted into multiple secondary electrons (SEs) through multiple possible pathways.
Data Source
AI summary
Methods and related systems and structures for reducing EUV dose requirements during lithography steps. Presently disclosed methods can comprise forming a dose reducing layer that comprises a doped semiconductor. The doped semiconductor can comprise at least one of an elemental semiconductor and a compound semiconductor.