Transmission Filter Adjusts Pupil Intensity in Exposure Apparatus
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Solution Overview
Problem
Conventional exposure apparatuses face challenges in achieving uniform pupil intensity distributions across the illumination region, leading to variations in pattern line width and reduced precision in transferring microscopic patterns onto substrates during microdevice manufacturing.
Innovation Solution
The illumination optical system incorporates a transmission filter with varying transmittance characteristics, positioned along the optical axis, and a movement mechanism to adjust its position, ensuring uniform pupil intensity distributions by equalizing light intensities across the illumination pupil plane, thereby correcting intensity variations and enhancing pattern transfer precision.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional illumination optical system is used, then the system structure is simple, but the pupil intensity distribution is non-uniform causing line width variations
Solution Approach 1:
A transmission filter is introduced as an intermediary component between the light source and the mask. This filter selectively transmits light rays based on their incident angles, acting as a mediator to equalize the intensity distribution across the illumination pupil plane and eliminate line width variations without fundamentally changing the overall system architecture
Solution Approach 2:
The transmission filter modifies the intensity parameter of light rays by varying its transmittance according to the incident angle. By changing the transmission parameter across different angular regions, the system achieves uniform pupil intensity distribution, transforming a non-uniform illumination problem into a controlled parameter adjustment solution
2Adaptability or versatility
If the transmission filter is fixed in position, then the device complexity is reduced, but the adaptability to different illumination conditions is limited
Solution Approach 1:
The transmission filter is designed to be movable along the optical axis rather than fixed, enabling dynamic adjustment of its position. This allows the filter to adapt to different illumination conditions and optimization requirements by changing its axial location, transforming a static component into a dynamically adjustable element with minimal added complexity
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 solution allows for precise adjustment of pupil intensity distributions, ensuring uniform illumination and faithful pattern formation across the substrate, reducing line width variations and improving the overall precision of microdevice manufacturing processes.
Implementation Method 1
a transmission filter which is arranged on the illumination pupil plane side with respect to the optical integrator and in at least one region out of a first adjustment region set including the illumination pupil plane in an optical-axis direction of the illumination optical system and a second adjustment region set including a pupil conjugate plane optically conjugate with the illumination pupil plane, and having a transmittance characteristic varying according to positions of the light incident thereinto
Data Source
AI summary
According to one embodiment, an illumination optical system is provided with an optical integrator which forms a predetermined light intensity distribution on an illumination pupil plane in an illumination optical path of the illumination optical system with incidence of exposure light from a light source device thereinto; a transmission filter arranged on the reticle side with respect to the optical integrator and in a first adjustment region set including the illumination pupil plane in an optical-axis direction of the illumination optical system, and having a transmittance characteristic varying according to positions of the exposure light incident thereinto; and a movement mechanism which moves the transmission filter along the optical-axis direction in the first adjustment region.