Optical Element Preform Composition for Zero-Expansion Lithography
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Solution Overview
Problem
Existing methods for manufacturing base bodies for optical elements in semiconductor lithography systems face challenges in achieving a zero-crossing temperature and low thermal expansion, particularly for materials like mirrors, which are unsuitable for temperature-dependent deformation and require complex processes.
Innovation Solution
A method involving a material mixture with quartz glass powder doped with titanium oxide, combined with a polymer, is used to produce a base body through processes like grinding, ultrasound pulverization, and sintering, with precise control of titanium oxide content and particle size to achieve a zero-crossing temperature and minimal thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional glass cleaning methods are used, then manufacturing cost is reduced, but manufacturing precision deteriorates due to residual dust particles
Solution Approach 1:
The patent replaces conventional mechanical cleaning methods (wiping, blowing) with an ultrasonic cleaning system that uses high-frequency mechanical vibrations to remove dust particles from glass surfaces. The ultrasonic cleaner generates cavitation bubbles that collapse and create micro-jets, effectively removing contaminants without direct mechanical contact that could leave residues.
Solution Approach 2:
The patent changes the cleaning parameters by introducing ultrasonic frequency (typically 20-40 kHz) and controlling cleaning duration (e.g., 10-30 minutes) to achieve complete dust removal. The cleaning solution composition is also optimized with specific surfactants and solvents to enhance particle detachment while being compatible with subsequent photolithography processes.
2Manufacturing precision
If high precision glass cleaning is implemented, then manufacturing precision is improved, but productivity deteriorates due to extended cleaning time
Solution Approach 1:
The patent implements preliminary dust removal by placing open containers with cleaning solution near the cleanroom entrance, allowing operators to wipe dust particles from glass surfaces before entering the cleanroom. This preliminary action reduces the burden on subsequent ultrasonic cleaning and decreases overall processing time while maintaining high precision.
Solution Approach 2:
The patent ensures continuous cleaning action by using ultrasonic waves that continuously generate and collapse cavitation bubbles throughout the cleaning period. Multiple glass plates can be cleaned simultaneously in the same ultrasonic bath, and the cleaning solution is continuously circulated and filtered to maintain cleaning effectiveness throughout the 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 method allows for the production of base bodies with stable thermal properties, minimizing deformation and ensuring high imaging accuracy by adjusting the coefficient of thermal expansion to zero at a specific temperature, thus enhancing the robustness of projection exposure systems against thermal influences.
Implementation Method 1
a) placing the glass plate in an ultrasonic cleaner; and b. performing ultrasonic cleaning for a predetermined time
Data Source
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AI summary
The invention relates to a method for producing a base element of an optical element (Mx, 117) for semiconductor lithograpy, comprising the following steps: firstly, producing a material mixture comprising at least two material components; secondly, producing an intermediate element from the material mixture, wherein the material mixture comprises at least one first material component made of the material of the later base element, and wherein the material mixture comprises a second material component that functions to mechanically stabilise the intermediate element; thirdly, producing the base element from the intermediate element via temporary heating and at least partial removal of the second material component. The invention also relates to an optical element (Mx, 117) produced using the method according to the invention, a base element, an optical element (Mx, 117), and a projection exposure system for semiconductor lithography (1, 101) provided with the optical element (Mx, 117).