EUV Reflective Mask Substrate Friction Control
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Solution Overview
Problem
In EUV lithography, increasing the movement speed of the stage on which a reflective mask is placed leads to positional shifts during pattern transfer, compromising the precision of the pattern transfer process.
Innovation Solution
A substrate with an electrically conductive film having a coefficient of static friction of 0.25 or greater is used, composed of materials like tantalum and chromium, and with a surface roughness of 0.60 nm or less, to inhibit positional shifts by enhancing the frictional force between the mask and the electrostatic chuck.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the movement speed of the stage is increased to improve productivity, then the manufacturing efficiency is improved, but positional shifts occur during pattern transfer reducing manufacturing precision
Solution Approach 1:
The patent changes the physical parameters of the electrically conductive film, specifically increasing the coefficient of static friction to 0.25 or greater and controlling surface roughness to 0.60 nm or less. These parameter changes enhance the frictional force between the mask and electrostatic chuck, allowing the stage to move at higher speeds without causing positional shifts during pattern transfer, thus resolving the contradiction between productivity and manufacturing precision
Solution Approach 2:
The patent specifies that the electrically conductive film should have an amorphous crystalline state rather than a crystalline structure. This structural modification creates a smoother surface morphology that increases static friction while maintaining electrical conductivity, enabling stable mask positioning at high movement speeds without compromising pattern transfer accuracy
2Manufacturing precision
If an electrically conductive film with high friction is used to prevent positional shifts, then manufacturing precision is improved, but the surface roughness control becomes more difficult increasing device complexity
Solution Approach 1:
The patent establishes specific parameter ranges for the electrically conductive film: coefficient of static friction of 0.25 or greater and surface roughness of 0.60 nm or less. By defining these quantitative parameters, the patent simplifies the control process while ensuring positional stability of the mask during high-speed movement
Solution Approach 2:
The patent specifies that the electrically conductive film should be composed of tantalum and chromium in specific proportions. This composite material composition simultaneously achieves high electrical conductivity, high static friction coefficient, and low surface roughness, thereby improving mask positional stability without excessively complicating the manufacturing 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 prevents positional shifts of the reflective mask during pattern transfer, even at increased movement speeds, ensuring precise and stable pattern formation on semiconductor substrates.
Implementation Method 1
a coefficient of static friction of the surface of the electrically conductive film is not less than 0.25
Implementation Method 2
An electrostatic chuck is used for the substrate support means. Consequently, in order to proceed immobilization of the substrate by the electrostatic chuck
Data Source
AI summary
A substrate with an electrically conductive film for fabricating a reflective mask is obtained that is capable of preventing positional shift of the reflective mask during pattern transfer. Provided is a substrate with an electrically conductive film used in lithography, the substrate with an electrically conductive film having an electrically conductive film formed on one of the main surfaces of a mask blank substrate, and a coefficient of static friction of the surface of the electrically conductive film is not less than 0.25.