Radiation Source Modulation for Lithographic Dose Uniformity
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Solution Overview
Problem
Existing lithographic apparatuses face challenges in accurately controlling the radiation dose delivered to a substrate, particularly due to non-uniform radiation profiles and varying system parameters, which can result in inconsistent exposure across different points on the substrate.
Innovation Solution
A method is introduced to select a periodic modulation frequency for a radiation source, calculated as a convolution of the radiation profile and irradiance, ensuring that the radiation dose received by a point on the substrate meets specific criteria, thereby allowing for precise control over the energy dose delivered. This involves determining the optimal modulation frequency to minimize dose variation across the substrate, considering parameters like scan speed, pulse frequency, and profile shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a radiation source operates without periodic modulation, then the control system is simpler, but the radiation dose delivered to the substrate is inconsistent and non-uniform
Solution Approach 1:
The patent applies periodic modulation to a variable of the radiation source at a specifically selected frequency. This periodic action creates a controlled variation in radiation output that, when combined with substrate movement, produces a uniform average dose distribution across the substrate, resolving the non-uniformity issue without requiring complex real-time control adjustments.
Solution Approach 2:
The patent changes the operating parameters of the radiation source by introducing periodic modulation at an optimized frequency. This parameter change transforms the radiation delivery pattern from static and non-uniform to dynamically modulated, achieving uniform dose distribution while maintaining relatively simple control architecture.
2Productivity
If the radiation source delivers high energy dose, then the lithographic process is more efficient, but the dose uniformity across different points on the substrate deteriorates
Solution Approach 1:
By applying periodic modulation to the radiation source variable, the system achieves both high average energy dose delivery and uniform distribution. The modulation frequency is selected to ensure that the time-averaged dose is uniform across the substrate, allowing efficient high-dose processing without sacrificing uniformity.
Solution Approach 2:
The patent introduces dynamic modulation to the radiation source operation, transforming it from a static high-dose delivery system to a dynamically controlled system. This dynamic approach allows the radiation output to vary periodically in a controlled manner, achieving both high efficiency and uniformity through temporal variation.
3Measurement precision
If periodic modulation is applied to the radiation source variable, then the radiation dose control is improved, but the system complexity increases
Solution Approach 1:
The patent achieves precise radiation dose control by changing the modulation frequency parameter to an optimized value. This single parameter optimization enables accurate dose control through periodic modulation while avoiding the need for complex multi-parameter control systems, maintaining relative system simplicity.
Solution Approach 2:
The periodic modulation approach provides precise dose control through temporal variation rather than spatial adjustment. By modulating the radiation source variable periodically at an optimized frequency, the system achieves accurate dose control without requiring complex real-time measurement and adjustment mechanisms.
Data Source
AI summary
A method of selecting a periodic modulation to be applied to a variable of a radiation source, wherein the source delivers radiation for projection onto a substrate and wherein there is relative motion between the substrate and the radiation at a scan speed, the method including: for a set of system parameters and for a position on the substrate, calculating a quantity, the quantity being a measure of the contribution to an energy dose delivered to the position that arises from the modulation being applied to the variable of the source, wherein the contribution to the energy dose is calculated as a convolution of: a profile of radiation, and a contribution to an irradiance of radiation delivered by the source; and selecting a modulation frequency at which the quantity for the set of system parameters and the position on the substrate satisfies a certain criteria.