Reflective Mask Antireflective Layer Out-of-Band Light Control
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Solution Overview
Problem
In EUV lithography, reflective masks suffer from out-of-band light transmission and charging issues due to the design of conventional light shielding frames, leading to blurred patterns and dimensional inaccuracies in semiconductor fabrication.
Innovation Solution
A reflective mask blank with a multi-layer reflective layer, a protective layer, and an absorbing layer, where the absorbing layer includes a light shielding frame with an antireflective layer made of inorganic materials like Si, Mo, or Cr, which reduces out-of-band light reflection by causing surface reflection in antiphase with the substrate, minimizing charging during electron microscope observations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional light shielding frame is used in EUV lithography, then the absorbing layer can block EUV light, but out-of-band light is transmitted and causes blurred patterns and dimensional inaccuracies
Solution Approach 1:
The light shielding frame is constructed using a composite structure combining the absorbing layer with an antireflective layer made of inorganic materials (Si, Mo, Cr). This composite configuration enables the frame to simultaneously block EUV light and reflect out-of-band light, resolving the contradiction between light blocking effectiveness and out-of-band light transmission
Solution Approach 2:
The patent modifies the optical parameters of the light shielding frame by introducing an antireflective layer with specific refractive index properties. This layer changes the reflectivity characteristics at the interface, causing out-of-band light to reflect in antiphase and cancel reflected light, thereby preventing blurred patterns while maintaining EUV light blocking
2Manufacturing precision
If the absorbing layer is made thicker to improve light shielding, then light blocking improves, but shadowing effects increase causing blurred edges and displacement
Solution Approach 1:
The patent employs a composite structure where the absorbing layer is combined with an antireflective layer. This composite configuration allows the absorbing layer to be optimized for light blocking without excessive thickness, as the antireflective layer compensates for shadowing effects by managing out-of-band light reflection
Solution Approach 2:
The antireflective layer acts as an intermediary between the absorbing layer and the incoming light. It mediates the interaction by reflecting out-of-band light in antiphase, thereby reducing shadowing effects while allowing the absorbing layer to maintain effective EUV light blocking at optimized thickness
3Object-affected harmful factors
If the absorbing layer is made thinner to reduce shadowing, then shadowing effects decrease, but light shielding properties and transfer contrast degrade
Solution Approach 1:
The composite structure of absorbing layer plus antireflective layer enables the absorbing layer to be thinner while maintaining effective light shielding. The antireflective layer compensates for the reduced shielding capability by managing out-of-band light, thereby preserving transfer contrast without excessive shadowing
4Object-affected harmful factors
If a light shielding frame is provided to block out-of-band light, then out-of-band light reflection is reduced, but charging occurs during electron microscope observations
Solution Approach 1:
The patent changes the electrical parameters of the light shielding frame by selecting inorganic materials (Si, Mo, Cr) with appropriate electrical conductivity. This parameter change allows the frame to reflect out-of-band light while conducting away accumulated charge, preventing charging effects during electron microscope observations
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 reduces out-of-band light reflection and minimizes charging, enhancing the dimensional accuracy and productivity of semiconductor patterns by optimizing the reflectivity and electrical conductivity of the antireflective layer.
Implementation Method 1
the antireflective layer causes surface reflection in antiphase to out-of-band light reflected from a rear-surface conductive film
Implementation Method 2
the antireflective layer causes surface reflection in antiphase to out-of-band light reflected from a rear-surface conductive film formed on a rear surface of the substrate
Implementation Method 3
The absorbing layer absorbs the wavelength of the exposure light source
Implementation Method 4
The multi-layer reflective layer has a high reflectance relative to the wavelength of an exposure light source
Data Source
AI summary
There are provided a reflective mask and a reflective mask blank reducing reflection of out-of-band light and a manufacturing method therefor. A light shielding frame is formed on a mask region corresponding to a multiply exposed boundary region between a chip and a semiconductor substrate. The frame is provided with an antireflective layer causing surface reflection in antiphase to out-of-band light reflected from the surfaces of a rear-surface conductive film and the substrate to provide a reflective mask reducing reflection of out-of-band light. The antireflective layer of the present disclosure has an electrical conductivity of 1×104/mΩ or greater to minimize charging occurring in a pattern region in observing the region using an electron microscope.