Liquid Crystal Reticle Masking for Vibration-Free Aperture Control
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Solution Overview
Problem
Conventional photolithographic scanners experience vibrations due to power-driven reticle masking blades, leading to defects in the exposure process and reduced yield in semiconductor manufacturing.
Innovation Solution
A scanner with a reticle masking device using a liquid crystal display (LCD) to form and adjust a slit-shaped aperture electronically, eliminating the need for mechanical power and thus preventing vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If power-driven reticle masking blades are used to form and adjust the aperture, then the aperture can be precisely controlled, but vibrations are generated that cause defects in the exposure process
Solution Approach 1:
The patent replaces the mechanical power-driven reticle masking blades with a liquid crystal display (LCD) that is optically coupled to the reticle. The LCD electronically controls the aperture formation and dimension adjustment using electrical signals rather than mechanical movement, thereby eliminating vibrations generated by motor-driven blades while maintaining precise aperture control.
Solution Approach 2:
The patent introduces an LCD as an intermediary component between the control system and the reticle. The LCD acts as a mediator that converts electrical control signals into optical aperture patterns, eliminating the need for direct mechanical contact and power-driven movement of masking blades, thus preventing vibration transmission to the exposure system.
2Device complexity
If mechanical reticle masking blades are used, then the device structure is simple, but vibrations propagate throughout the scanner and shake the reticle stage
Solution Approach 1:
The patent replaces the simple mechanical masking blade structure with an LCD-based optical system. Although the LCD structure may appear more complex, it eliminates the harmful mechanical vibrations that propagate through the scanner and shake the reticle stage, thereby significantly improving exposure process stability and reliability.
Solution Approach 2:
The LCD serves as an intermediary that decouples the control mechanism from the optical path. By positioning the LCD in the optical path and using optical coupling rather than direct mechanical connection to the reticle, the system prevents vibration propagation while maintaining the ability to control aperture dimensions.
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 allows for precise control of the aperture dimensions without inducing vibrations, enabling flawless exposure processes and improving the accuracy and reliability of semiconductor device manufacturing.
Implementation Method 1
reticle masking means for forming a slit-shaped aperture electronically without the use of motive power in an optical path of the equipment extending between the light source and the reticle stage
Data Source
AI summary
A scanner of photolithographic equipment has a reticle masking device capable of forming an aperture, in the shape of a slit, without inducing vibrations in the scanner. The reticle masking device forms the slit electronically, without the use of motive power, and can likewise vary the width of the slit in a direction parallel to the direction of movement of a reticle stage. In particular, the width of the slit is increase at the beginning and decreased at the end of a scan. Preferably, the reticle masking device is a liquid crystal display. It is thus possible to isolate and compensate for vibrations induced by the movement of the reticle stage or wafer stage during a scan, and thus to prevent flaws in the exposure process due to relative positional errors and thereby enhance the production yield.