Lithographic Radiation Source Adaptive Power Control
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Solution Overview
Problem
Lithographic systems operating with fixed time-averaged energy levels are inefficient, leading to suboptimal throughput due to unnecessary energy constraints and increased instability, requiring re-exposure passes to ensure accurate dosing, which increases processing time.
Innovation Solution
Adaptive control of the radiation source's power level based on the required dose to optimize throughput by minimizing the total exposure time, including a first pass and potential re-exposure pass, while monitoring and adjusting energy delivery to specific target areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a fixed time-averaged energy level is used to ensure accurate dosing for all photoresists, then manufacturing precision is maintained, but productivity decreases due to suboptimal throughput
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed time-averaged energy level to a dynamic power level that varies over time within each pulse cycle. The radiation source power is modulated to deliver higher peak power followed by lower power, allowing optimized energy delivery while maintaining dose accuracy. This dynamic approach enables throughput improvement without sacrificing manufacturing precision.
Solution Approach 2:
The patent changes the power level parameter of the radiation source from a constant fixed value to a time-varying profile. By adjusting the power level in dependence on the required dose and using different power levels during different phases of the pulse cycle, the system optimizes both throughput and dose accuracy. The parameter change allows the system to adapt to different photoresist sensitivities and exposure requirements.
2Productivity
If the radiation source power is increased to reduce exposure time and improve throughput, then productivity increases, but stability deteriorates leading to more re-exposure passes
Solution Approach 1:
The patent applies periodic action by using pulsed radiation with structured power levels within each pulse. The power is modulated periodically with higher peak power followed by lower power phases. This periodic structure allows the system to deliver sufficient energy for high throughput while the controlled pulse structure maintains stability and reduces the need for re-exposure passes compared to continuously high power operation.
Solution Approach 2:
The patent applies beforehand cushioning by delivering a higher power level at the beginning of each pulse cycle to ensure adequate energy delivery, then reducing power afterward. This initial high power phase acts as a cushion to guarantee sufficient exposure even if subsequent power delivery varies, thereby maintaining stability and reducing re-exposure requirements while still enabling overall throughput improvement.
3Device complexity
If a fixed time-averaged energy level is used, then device complexity remains low, but loss of time increases due to unnecessary energy constraints
Solution Approach 1:
The patent implements dynamic power level control that adjusts radiation source output in real-time based on exposure requirements. This dynamic control optimizes energy delivery to reduce processing time without requiring complex additional hardware. The control system modulates power levels within existing pulse structures, achieving time reduction while maintaining acceptable device complexity through software-based power management.
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 maximizes lithographic system throughput by optimizing energy usage, reducing the need for re-exposure passes and minimizing total processing time, with benefits such as a 3.5% increase in substrates per hour at a dose of 40 mJ/cm2 with up to 0.5% re-exposure.
Implementation Method 1
The radiation source is typically of the laser-produced-plasma (LPP) source, wherein a high-power laser converts mass-limited fuel targets into plasma, one at the time
Implementation Method 2
The lithographic apparatus is configured to use the radiation for imaging a pattern onto multiple target areas on a layer of photo-resist on a semiconductor substrate
Data Source
AI summary
A lithographic system comprises a radiation source and a lithographic apparatus. The radiation source provides radiation to the lithographic apparatus. The lithographic apparatus uses the radiation for imaging a pattern onto multiple target areas on a layer of photo-resist on a semiconductor substrate. The imaging requires a pre-determined dose of radiation. The system is controlled so as to set a level of a power of the radiation in dependence on a magnitude of the pre-determined dose.