PVD Chamber Shield Holes for EUV Multilayer Reflectivity
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Solution Overview
Problem
In the manufacturing of extreme ultraviolet (EUV) mask blanks, there is a need to reduce defect sources such as particles and cross-contamination of targets in multi-cathode PVD chambers, while also improving the reflectivity of the multilayer stack at EUV wavelengths like 13.5 nm.
Innovation Solution
A method involving the formation of reflective layer pairs comprising silicon and molybdenum, where silicon is sputtered using a DC power source and inert gas, followed by the deposition of Si3N4 interface layers using RF and DC power sources, alternating with molybdenum layers, to create a multilayer stack with enhanced reflectivity, and a capping and absorber layer are added to the EUV mask blank.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high power density PVD sputtering with high magnetic fields and high DC power is used, then sputtering rate is enhanced, but surface temperature of the sputtering target rises significantly
Solution Approach 1:
The patent divides the sputtering process into multiple lower-power pulses rather than using continuous high power. The controller applies a sequence of pulses with duty cycles less than 100%, allowing the target surface to cool between pulses while still achieving high overall deposition rates through cumulative effect.
Solution Approach 2:
The patent employs periodic pulsed DC power application to the magnetron cathode instead of continuous power. The pulsed operation with controlled duty cycles creates periodic sputtering cycles that prevent excessive heat accumulation while maintaining productive deposition through repeated pulses.
2Productivity
If multiple cathodes are used in a PVD chamber to deposit alternating layers, then manufacturing efficiency is improved, but cross-contamination between targets increases
Solution Approach 1:
The patent applies a pulsed cleaning cycle to each cathode before depositing material from that target. This preliminary cleaning action removes any accumulated contamination or stray material from the target surface, ensuring that subsequent deposition starts with a clean surface and reducing cross-contamination between alternating layers.
Solution Approach 2:
The patent uses rapid pulsed cycling between different cathodes with minimal transition time. By rushing through the deposition sequence with short pulses and quick switching between targets, the system minimizes the time each target is exposed to potential contamination from other materials while maintaining high manufacturing efficiency.
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 reduces cross-contamination and particle defects, achieving improved reflectivity and reducing material waste by preventing contamination between targets, thereby enhancing the quality and efficiency of EUV mask blank production.
Implementation Method 1
sputtering a silicon target in a physical vapor deposition (PVD) chamber using a DC power source and an flowing inert gas in the PVD chamber to form a silicon layer on a substrate
Implementation Method 2
sputtering the silicon target using an RF power source and flowing nitrogen gas in the PVD chamber to form a first Si3N4 interface layer on the silicon layer
Implementation Method 3
sputtering a molybdenum target using a DC power source and flowing an inert gas in the PVD chamber to form a molybdenum layer on the Si3N4 layer
Data Source
AI summary
A physical vapor deposition (PVD) chamber and a method of operation thereof are disclosed. Chambers and methods are described that provide a chamber comprising an upper shield with two holes that are positioned to permit alternate sputtering from two targets. A process for improving reflectivity from a multilayer stack is also disclosed.