Off-axis Illumination Angle Control via Rotatable Mask Stage
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Solution Overview
Problem
Conventional off-axis illumination methods for semiconductor exposure processes struggle to uniformly control the incident angle of light on a mask, leading to exposure pattern failures and product defects due to the inability to adjust the off-axis angle without changing apertures, resulting in inconsistent light transmissivity and critical dimension control on wafers.
Innovation Solution
An off-axis illumination apparatus and method that varies the incident angle of light on a mask using a system comprising a mask stage, a light source, and an incident angle varying section, which includes drivers and encoders to rotate the mask stage or light source, allowing precise control of the incident angle without requiring different apertures, thereby adjusting the transmissivity and critical dimension on the wafer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional off-axis illumination method is used with modified aperture, then optical resolution is improved, but the off-axis angle cannot be adjusted without changing apertures leading to exposure pattern failures
Solution Approach 1:
The patent introduces a rotatable mask stage that can dynamically adjust the off-axis angle of illumination without requiring physical changes to the aperture structure. This dynamic adjustment capability allows the system to maintain optimal optical resolution while adapting to different exposure requirements by rotating the mask stage to various angles.
Solution Approach 2:
The modified aperture structure is designed to work with multiple off-axis angles through the rotatable mask stage, making a single aperture configuration serve multiple functions. The aperture maintains its optimized shape for high resolution while the system gains versatility by being able to illuminate at different angles through stage rotation.
2Manufacturing precision
If fixed aperture is used for off-axis illumination, then manufacturing precision is improved, but light transmissivity control becomes inconsistent causing product failures
Solution Approach 1:
The system employs a rotatable mask stage that enables dynamic adjustment of the off-axis angle to optimize both critical dimension control and exposure uniformity. By allowing angular adjustment, the system can compensate for variations in light transmissivity and maintain consistent exposure across different manufacturing conditions.
Solution Approach 2:
The patent changes the parameter of illumination angle by rotating the mask stage, allowing optimization of light transmissivity and exposure uniformity. This parameter adjustment enables the system to achieve consistent manufacturing precision while improving reliability by preventing exposure pattern failures.
3Adaptability or versatility
If multiple apertures are used to vary off-axis angle, then adaptability is improved, but device complexity increases
Solution Approach 1:
Instead of providing multiple physical apertures, the patent uses a single modified aperture combined with a rotatable mask stage. This dynamic approach achieves the same adaptability as multiple apertures but with significantly reduced device complexity, as only one aperture needs to be manufactured and maintained.
Solution Approach 2:
A single modified aperture is designed to work effectively at multiple off-axis angles through the rotation capability of the mask stage. This universal design eliminates the need for multiple specialized apertures, reducing device complexity while maintaining full adaptability for varying illumination requirements.
Data Source
AI summary
Provided are an off-axis illumination apparatus, an exposure apparatus, and an off-axis illumination method. The off-axis illumination apparatus may include a mask, a light source for emitting light to the mask, and an incident angle varying section for varying an incident angle of the light. The exposure apparatus may include the off-axis illumination apparatus in addition to a wafer stage and an optical detector. The off-axis illumination method may include irradiating light from the light source to a mask, and moving positions of the light source and the mask to vary an incident angle of the light to the mask.