EUV Collector Mirror Debris Removal via Inductively Coupled Plasma
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Solution Overview
Problem
The collector mirror in extreme ultraviolet lithography systems, used in semiconductor manufacturing, experiences degradation and contamination due to tin debris, leading to reduced reflectivity and increased maintenance frequency, which affects the longevity and efficiency of EUV scanners.
Innovation Solution
The implementation of inductively coupled plasma (ICP) using chlorine radicals to etch and remove tin debris, forming stable SnCl4, which is more stable than SnH4, thereby preventing re-deposition and extending the collector mirror's lifespan and reducing maintenance needs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If inductively coupled plasma with chlorine radicals is used to etch tin debris, then the collector mirror lifetime is extended and reflectivity is maintained, but the device complexity and process complexity increase
Solution Approach 1:
Inductively coupled plasma acts as an intermediary medium that facilitates the removal of tin debris from the collector mirror surface. The plasma, generated through electromagnetic induction in a coil, creates a reactive environment where chlorine radicals efficiently etch tin compounds without requiring direct mechanical contact, thus extending mirror lifetime while managing complexity through a controlled chemical process
Solution Approach 2:
The invention changes the physical and chemical parameters of the environment surrounding the collector mirror by introducing inductively coupled plasma. By controlling plasma power, gas composition (chlorine-containing gases), and pressure, the system optimizes tin debris removal while maintaining acceptable device complexity through parameter control rather than structural complexity
2Illumination intensity
If frequent mirror swapping is performed to maintain exposure power, then high exposure power is maintained, but productivity decreases due to increased downtime
Solution Approach 1:
The inductively coupled plasma system performs preliminary cleaning of tin debris from the collector mirror surface during idle periods or between production cycles. This preventive maintenance approach maintains mirror reflectivity and exposure power without requiring frequent interruptions for mirror replacement, thus preserving scanner productivity
Solution Approach 2:
The plasma cleaning process enables continuous operation of the EUV scanner by maintaining collector mirror performance throughout extended periods. Rather than interrupting production for mirror swaps, the system continuously or periodically removes tin debris, ensuring sustained exposure power and uninterrupted productivity
3Ease of manufacture
If traditional debris removal methods are used, then the process is simple, but tin debris re-deposition occurs and mirror performance degrades
Solution Approach 1:
The inductively coupled plasma generates highly reactive chlorine radicals that act as strong chemical agents to etch and remove tin debris from the collector mirror surface. This chemical etching process converts tin metal into volatile tin chloride compounds that are easily removed, preventing re-deposition and maintaining mirror performance reliability
Solution Approach 2:
The invention replaces mechanical or physical cleaning methods with an inductively coupled plasma chemical etching process. This substitution provides more effective and reliable tin debris removal that prevents re-deposition, while the inductive coupling method maintains relative simplicity through non-contact plasma 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 effectively extends the usable lifetime of the collector mirror, maintains high exposure power and throughput, and reduces the frequency of mirror swapping, minimizing downtime in EUV scanners.
Implementation Method 1
inductively coupled plasma (ICP) using chlorine radicals to etch and remove tin debris
Implementation Method 2
inductively coupled plasma (ICP) using chlorine radicals to etch and remove tin debris
Implementation Method 3
etch and remove tin debris, forming stable SnCl4
Data Source
AI summary
An extreme ultra violet (EUV) radiation source apparatus includes a collector mirror, a target droplet generator for generating a tin (Sn) droplet, a rotatable debris collection device, one or more coils for generating an inductively coupled plasma (ICP), a gas inlet for providing a source gas for the ICP, and a chamber enclosing at least the collector mirror and the rotatable debris collection device. The gas inlet and the one or more coils are configured such that the ICP is spaced apart from the collector mirror.