Enabling rotary atomic layer deposition for optical applications

Area of Science:

• Materials Science
• Optical Engineering
• Thin Film Technology

Background:

• Atomic Layer Deposition (ALD) is crucial for high-quality optical coatings.
• Batch ALD suffers from slow deposition rates due to essential purge steps, hindering complex multilayer applications.
• Rotary ALD presents a novel approach to accelerate optical coating processes.

Purpose of the Study:

• To investigate and characterize the performance of a new rotary ALD coating tool for optical applications.
• To evaluate the deposition of silicon dioxide (SiO2) and tantalum pentoxide (Ta2O5) layers using the rotary ALD system.
• To assess key performance metrics including deposition rate, film quality, and uniformity.

Main Methods:

• Utilized a novel rotary ALD reactor where process steps occur in spatially separated zones.
• Substrates were rotated through these zones to complete ALD cycles.
• Characterized SiO2 and Ta2O5 films deposited on fused silica substrates for optical properties and uniformity.

Main Results:

• Achieved high growth rates up to 0.18 nm/s for SiO2 and Ta2O5 layers.
• Demonstrated low optical absorption levels (<3.1 ppm for Ta2O5, <6.0 ppm for SiO2) at 1064 nm.
• Exhibited excellent film uniformity with non-uniformity as low as ±0.53% for Ta2O5 and ±1.07% for SiO2 over a 135x60 mm area.

Conclusions:

• The novel rotary ALD system significantly enhances deposition rates compared to traditional batch ALD.
• The developed rotary ALD process yields high-quality optical coatings with low absorption and excellent uniformity.
• Rotary ALD is a promising technology for efficient and high-performance optical coating production.