Dual-Pulse Laser EUV Source Control for Debris Reduction
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Solution Overview
Problem
The existing EUV lithography systems face low efficiency in generating EUV radiation and degradation of LPP collectors due to particle, ion, and debris deposition, which affects wafer throughput and collector lifetime.
Innovation Solution
The system employs a dual-pulse laser-produced plasma mechanism with optimized parameters, including pre-pulses and main pulses, to enhance EUV conversion efficiency and minimize debris deposition on the LPP collector by controlling the speed and size of target plumes, using a controller to adjust laser pulse energy and timing for optimal EUV generation and reduced contamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional single-pulse laser-produced plasma is used, then the system structure is simple, but the EUV conversion efficiency is low and debris deposition on collectors is high
Solution Approach 1:
The laser pulse is segmented into multiple pulses (pre-pulse, main pulse, and optional additional pulses) with different energies and timings. The pre-pulse creates an initial plasma channel, and the main pulse follows to generate high EUV radiation efficiency while the segmented structure reduces debris deposition compared to a single high-energy pulse
Solution Approach 2:
A pre-pulse is applied before the main pulse to prepare the plasma channel and reduce debris formation. The pre-pulse creates initial ionization and plasma structure that facilitates more efficient EUV generation from the subsequent main pulse while minimizing harmful debris deposition on collectors
2Productivity
If high laser power is used to increase EUV output, then productivity improves, but collector degradation accelerates due to increased debris and particle impact
Solution Approach 1:
The system uses periodic pulsed laser operation with optimized pulse sequences (pre-pulse followed by main pulse) to generate EUV radiation. This periodic action with controlled pulse parameters maintains high productivity through sustained EUV output while the specific pulse structure reduces per-pulse debris generation, extending collector lifetime
Solution Approach 2:
The laser pulse parameters are changed and optimized - using multiple pulses with different energies and time delays instead of a single high-power pulse. This parameter optimization achieves high EUV conversion efficiency and productivity while reducing the intensity of particle and debris generation that causes collector degradation
3Illumination intensity
If laser pulse energy is increased to improve EUV generation, then radiation intensity improves, but target plume expansion becomes uncontrolled and debris increases
Solution Approach 1:
The laser energy delivery is segmented into multiple pulses with different energy levels. The pre-pulse uses lower energy to initiate plasma formation, and the main pulse delivers higher energy to generate intense EUV radiation. This segmentation allows controlled plume expansion and stable target interaction while achieving high EUV intensity and reducing uncontrolled debris generation
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 improves EUV conversion efficiency and extends the usable lifetime of LPP collectors by optimizing the generation of EUV radiation and reducing debris accumulation, thereby enhancing wafer throughput and system performance.
Implementation Method 1
LPP technology produces EUV light by focusing a high-power laser beam onto small tin droplets to form highly ionized plasma that emits EUV radiation at about 13.5 nm
Implementation Method 2
The EUV light is then collected by an LPP collector and reflected by optics towards a lithography target
Data Source
AI summary
A method for extreme ultraviolet (EUV) lithography includes loading an EUV mask to a lithography system; loading a wafer to the lithography system, wherein the wafer includes a resist layer sensitive to EUV radiation; producing EUV radiation by heating target plumes using a radiation source; and exposing the resist layer to the EUV radiation while monitoring a speed of the target plumes.