Projection Lens Focus Control via Dual Beam Measurement
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Solution Overview
Problem
Conventional exposure processes in semiconductor fabrication struggle to maintain accurate focus and level conditions due to mechanical vibrations and variations in the projection lens unit's inner conditions, leading to deformation of circuit patterns.
Innovation Solution
A projection lens unit with adjustable properties, incorporating a dual light beam system where one beam passes through the lens and another does not, allowing for precise measurement and correction of focus and level errors by comparing the intensity of measurement light and reference light reflected from the semiconductor substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional focus and level measurement units are used that operate independently of the projection lens, then the measurement process is simple, but the measurement precision deteriorates because variations in the projection lens unit's inner conditions are not accounted for
Solution Approach 1:
The patent combines the focus and level measurement functions with the projection lens unit into an integrated system. The measurement light emitting unit, measurement light receiving unit, and projection lens unit work together as a coordinated system, allowing the measurement process to account for variations in the projection lens unit's inner conditions while maintaining reasonable system complexity through functional integration.
Solution Approach 2:
The patent introduces a measurement light emitting unit and measurement light receiving unit as intermediary components that facilitate precise measurement. These units act as mediators between the projection lens unit and the control system, enabling accurate detection of focus and level conditions by measuring light reflected from the semiconductor substrate through the projection lens unit.
2Productivity
If mechanical vibrations are present during rapid semiconductor manufacturing, then productivity increases, but the stability of focus and level conditions deteriorates
Solution Approach 1:
The patent implements a feedback control system where the measurement light receiving unit continuously monitors focus and level conditions by detecting reflected light, and the control unit adjusts the semiconductor substrate stage position based on these measurements. This feedback mechanism maintains stable focus and level conditions even during rapid manufacturing operations with mechanical vibrations.
Solution Approach 2:
The patent performs focus and level measurement and adjustment operations before the actual exposure process. By preliminarily establishing accurate focus and level conditions through measurement and control adjustments, the system ensures stable pattern transfer during the subsequent high-speed exposure process, even in the presence of mechanical vibrations.
3Adaptability or versatility
If the projection lens unit's inner conditions vary, then adaptability to different manufacturing conditions improves, but manufacturing precision deteriorates due to unaccounted focus errors and distortion
Solution Approach 1:
The patent measures and compensates for changes in the projection lens unit's inner conditions by monitoring focus and level parameters through light intensity measurements. The system detects variations in lens conditions and adjusts the semiconductor substrate stage position accordingly, maintaining manufacturing precision despite changes in lens adaptability or operating conditions.
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
This approach effectively accounts for focus errors and distortion effects within the projection lens, ensuring accurate transfer of circuit patterns and improving manufacturing yield by enabling precise control of the semiconductor substrate's position relative to the projection lens.
Implementation Method 1
a measurement light emitting unit adapted to provide measurement light of second wavelength different from the first wavelength, such that the measurement light passes through a second plurality of the lenses (M) in the projection lens and irradiates the semiconductor substrate
Implementation Method 2
a reference light emitting unit adapted to provide reference light of third wavelength different from the first wavelength, such that the reference light irradiates the semiconductor substrate without passing through the first plurality of lenses in the projection lens
Implementation Method 3
a reflected measurement light receiving unit adapted to receive a portion of the measurement light reflected from the semiconductor substrate and a reflected reference light receiving unit adapted to receive a portion of the reference light reflected from the semiconductor substrate
Data Source
AI summary
A projection lens unit, related exposure apparatus and control method are described in which measurement light irradiating a semiconductor substrate after passing through lenses in the projection lens unit and reference light irradiating the semiconductor substrate without passing through the lenses in the projection lens unit are used to derive a control signal adapted to adjust the position of the semiconductor substrate under the projection lens unit.