Mask Blank Conductive Layer Charge-Up Suppression
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Solution Overview
Problem
Existing mask blanks with resist layers face challenges in suppressing charge-up during electron beam irradiation due to high electric resistance of organic conductive layers and low solubility of metal conductive layers, leading to positional inaccuracies in resist patterns.
Innovation Solution
A mask blank configuration with a resist layer featuring a conductive layer comprising a first metal layer of aluminum and a second metal layer made of a higher oxidation-reduction potential metal, such as molybdenum, tungsten, or titanium, with specific thickness ranges to ensure effective conductivity and solubility, and optionally a water-soluble resin layer for enhanced removability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If an organic conductive layer is formed on the resist layer, then the layer can be removed by a developer, but the electric resistance is higher and charge-eliminating performance is insufficient
Solution Approach 1:
The patent applies composite materials by forming a multi-layer conductive structure consisting of an organic conductive layer and a metal conductive layer. The organic conductive layer (made of water-soluble materials like polyvinyl alcohol or polyvinylpyrrolidone) provides ease of removal, while the metal conductive layer (aluminum, molybdenum, or tungsten) provides low electric resistance and effective charge elimination. This composite structure resolves the contradiction between removability and charge-eliminating performance.
2Reliability
If a metal conductive layer is formed on the resist layer, then charge-eliminating performance is improved, but solubility in solvents is low and removal becomes difficult
Solution Approach 1:
The patent uses composite materials with a metal conductive layer (aluminum, molybdenum, or tungsten) providing low electric resistance for effective charge elimination, combined with an organic conductive layer (water-soluble materials) that enables easy removal by developers. The organic layer acts as a removable carrier that dissolves in water or alkaline solutions, taking the metal layer with it, thus resolving the contradiction between charge-eliminating performance and removability.
Solution Approach 2:
The organic conductive layer serves as an intermediary between the metal conductive layer and the developer solution. It provides a water-soluble interface that allows the insoluble metal layer to be removed indirectly through dissolution of the organic component, solving the removal difficulty while maintaining the metal layer's charge-eliminating function.
3Ease of manufacture
If an aluminum thin film is used, then solubility in alkaline developer is improved, but natural oxidation forms an insulator layer reducing charge-eliminating performance
Solution Approach 1:
The patent applies preliminary action by forming the organic conductive layer over the aluminum thin film before electron beam irradiation. This organic layer prevents natural oxidation of the aluminum surface by acting as a protective barrier, ensuring the aluminum maintains its conductive properties and charge-eliminating performance throughout the lithography process. The preliminary protective coating prevents the harmful oxidation effect before it can occur.
Solution Approach 2:
The composite structure combines the water-soluble organic conductive layer with the aluminum thin film. The organic layer provides both protection against oxidation and the necessary water solubility for removal. This composite approach allows the aluminum to maintain its low resistance and charge-eliminating capability while remaining removable through dissolution of the organic component in alkaline developers.
4Ease of manufacture
If an aluminum thin film is used, then solubility in alkaline developer is improved, but surface roughness is increased due to natural oxidation
Solution Approach 1:
The patent applies preliminary action by depositing the organic conductive layer on the aluminum surface before oxidation can occur. This pre-formed organic coating acts as a protective barrier that prevents natural oxidation of the aluminum, thereby maintaining smooth surface morphology and preventing roughness increase during storage and processing.
Solution Approach 2:
The composite structure of organic conductive layer plus aluminum thin film provides both the desired water solubility (through the organic component) and smooth surface finish (by preventing oxidation-induced roughness). The organic layer protects the aluminum surface while maintaining overall surface smoothness.
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 configuration effectively suppresses charge-up during electron beam irradiation, ensuring accurate positional accuracy of resist patterns and facilitating easy removal of the conductive layer, thereby improving the quality of the mask blank.
Implementation Method 1
a conductive layer which is formed on the resist layer and suppresses charge-up during electron beam irradiation
Implementation Method 2
a resist pattern is formed on the resist layer by irradiating the resist layer with electron beams
Implementation Method 3
on a surface of an aluminum thin film, an insulator layer having a depth of from about 2 nm to about 5 nm is formed by natural oxidation
Data Source
AI summary
A mask blank having a resist layer, which enables charge-up to be suppressed during electron beam irradiation. The mask blank having a resist layer includes a substrate having a thin film, a resist layer formed on a surface of the thin film, and a conductive layer formed on the resist layer. The conductive layer includes a first metal layer containing aluminum as a main component thereof and a second metal layer made of a metal other than aluminum. The first metal layer is formed on the resist layer side of the second metal layer.