EUV Laser System Pressure Stabilization via Pulse Energy Control
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Solution Overview
Problem
Current EUV light generation systems for semiconductor microfabrication face challenges in stabilizing the output of EUV light over long periods due to ablation of the partition wall around the through hole, leading to changes in the size of the through hole and subsequent variations in rare gas pressure, which affect the EUV light output.
Innovation Solution
The system incorporates a primary controller to manage the flow rate control valve and laser output controller, using PID control to maintain the rare gas pressure within a reference range and adjust the pulse energy of the fundamental wave light to stabilize the EUV light output, while also considering the pressure in the light focused position and potential optical element deterioration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the through hole size is kept constant to maintain stable EUV light output, then the EUV light output stability is improved, but the partition wall around the through hole undergoes ablation over time causing the through hole size to change
Solution Approach 1:
The system dynamically adjusts the pulse energy of the laser based on detected EUV light output levels. When the through hole size changes due to ablation, the pulse energy is modified to compensate for the resulting pressure and output variations, thereby maintaining stable EUV light generation over extended periods
Solution Approach 2:
A detection device continuously monitors the EUV light output level, and this information is fed back to the control device. The control device uses this feedback to adjust the pulse energy in real-time, counteracting the effects of partition wall ablation and maintaining consistent through hole characteristics despite material degradation
2Reliability
If the rare gas pressure is maintained within a reference range to stabilize EUV light output, then the EUV light generation stability is improved, but the pressure changes due to through hole size variations require active control
Solution Approach 1:
The system controls the pulse energy parameter to compensate for pressure changes caused by through hole size variations. By adjusting the pulse energy, the system maintains the rare gas pressure within the reference range, ensuring stable EUV light output without requiring complex mechanical pressure adjustment mechanisms
3Reliability
If the pulse energy is rapidly adjusted to counteract pressure changes, then the EUV light output stability is improved, but the control system complexity increases
Solution Approach 1:
The control device receives real-time feedback on EUV light output levels and automatically adjusts the pulse energy accordingly. This closed-loop feedback mechanism enables rapid compensation for pressure changes and through hole size variations without requiring complex manual intervention or multiple control components
Solution Approach 2:
The system performs self-adjustment by automatically modifying the pulse energy in response to detected output variations. The control device independently manages the compensation process, eliminating the need for external intervention or complex multi-component control systems
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 effectively stabilizes the EUV light output for extended periods by rapidly adjusting the pulse energy and flow rate to counteract changes in the through hole size and pressure, ensuring consistent EUV light generation.
Implementation Method 1
a light focusing optical system configured to focus, in the rare gas chamber, the pulsed laser light outputted from the laser apparatus to excite the rare gas
Implementation Method 2
harmonic light produced in the rare gas chamber
Implementation Method 3
an apparatus based on laser produced plasma (LPP) using plasma produced by irradiation of a target substance with pulsed laser light
Implementation Method 4
a filter chamber configured to selectively transmit EUV light contained in harmonic light produced in the rare gas chamber
Data Source
AI summary
A laser system includes A. a laser apparatus configured to output pulsed laser light; B. a rare gas chamber; C. a light focusing optical system configured to focus the pulsed laser light in the rare gas chamber to excite the rare gas; D. a filter chamber configured to selectively transmit EUV light contained in harmonic light produced in the rare gas chamber; E. an exhauster connected to the filter chamber; F. at least one through hole disposed in the optical path between the rare gas chamber and the filter chamber; G. a rare gas supplier; H. a flow rate control valve configured to control the flow rate of the rare gas flowing from the rare gas supplier into the rare gas chamber; I. a first pressure sensor configured to detect the pressure of the rare gas in the rare gas chamber; J. a first controller configured to control the flow rate control valve in such a way that the pressure detected with the first pressure sensor falls within a reference range; and K. a second controller configured to control the pulse energy of the pulsed laser light outputted from the laser apparatus based at least on the pressure detected with the first pressure sensor.