Mirror Array Gap Sensing for EUV Power Control
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Solution Overview
Problem
Lithographic apparatuses using EUV radiation face challenges in accurately measuring radiation power, leading to potential damage from high power levels and reduced throughput due to low power levels, necessitating a reliable method to adjust and monitor EUV radiation power.
Innovation Solution
A mirror array with sensing apparatuses that measure gaps between the sensing apparatuses and the arms extending from the mirrors, which are temperature-dependent and directly related to the absorbed radiation power, utilizing eddy current sensors and a processor to calculate radiation power changes based on thermal expansion models.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If EUV radiation power is increased to improve throughput, then the number of substrates exposed per hour increases, but damage to components occurs
Solution Approach 1:
The patent implements a feedback control system where radiation power is continuously measured using the mirror array and sensing apparatuses. The measured power information is fed back to control the EUV radiation source, allowing dynamic adjustment of radiation power to maintain optimal levels that maximize throughput while preventing component damage.
Solution Approach 2:
The system monitors and adjusts the radiation power parameter in real-time. By changing the power parameter based on measured values and predefined thresholds, the system optimizes the balance between throughput and component safety, allowing operation at higher power levels when conditions permit while preventing dangerous power levels.
2Object-affected harmful factors
If EUV radiation power is decreased to prevent component damage, then component safety is improved, but throughput reduces
Solution Approach 1:
The continuous feedback mechanism allows the system to operate at the maximum safe power level by dynamically adjusting based on real-time measurements. This eliminates the need for conservative static power limits, enabling the system to maintain high throughput while staying within safe operating boundaries through active monitoring and control.
Solution Approach 2:
The system transitions from static power setting to dynamic power control. The radiation power is continuously adjusted based on real-time measurements and changing operational conditions, allowing the system to maximize throughput during safe operating windows while automatically reducing power when thresholds are approached, thus preventing component damage without unnecessarily limiting productivity.
3Measurement precision
If traditional radiation power measurement methods are used, then measurement capability is provided, but accuracy and reliability are insufficient
Solution Approach 1:
The patent uses a mirror array as an intermediary element to indirectly measure radiation power. Instead of directly measuring the challenging EUV radiation, the system measures the thermal expansion of mirror arms caused by absorbed radiation, which serves as a reliable proxy for power measurement, achieving high accuracy without direct radiation sensing complexity.
Solution Approach 2:
The system replaces complex optical or electromagnetic radiation detection mechanisms with a simpler thermal-mechanical measurement approach. By measuring the mechanical expansion of mirror arms through sensing apparatuses, the system achieves accurate radiation power measurement using well-established thermal expansion principles rather than complex radiation detection technology.
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
Enables accurate measurement of EUV radiation power without determining absolute values, allowing for adjustments to maintain optimal power levels, prevent damage, and improve throughput by identifying power changes and potential issues like contamination or mirror damage.
Implementation Method 1
The gaps between the sensing apparatuses and the arms which extend from the mirrors are determined by the temperatures of the mirrors and the arms. The temperatures of the mirrors and the arms is in turn determined by the power of radiation which is absorbed by the mirrors.
Implementation Method 2
At least some of the sensing apparatuses may comprise a plurality of eddy current sensors.
Data Source
AI summary
A mirror array, at least some of the mirrors of the array comprising a reflective surface and an arm which extends from a surface opposite to the reflective surface, wherein the mirror array further comprises a support structure provided with a plurality of sensing apparatuses, the sensing apparatuses being configured to measure gaps between the sensing apparatuses and the arms which extend from the mirrors.