The Simons Observatory: Production-Level Fabrication of the Mid- and Ultra-High-Frequency Wafers

Area of Science:

• Cosmology and Astrophysics
• Instrumentation and Measurement

Background:

• The Simons Observatory (SO) is a suite of instruments designed to study the cosmic microwave background (CMB).
• SO will deploy over 65,000 polarization-sensitive transition-edge sensor (TES) bolometers across a wide frequency range (27–280 GHz).
• Key components include mid-frequency (90/150 GHz) and ultra-high-frequency (220/280 GHz) detector arrays.

Purpose of the Study:

• To establish and validate a production-level fabrication framework for SO's detector arrays and associated routing wafers.
• To ensure the timely and high-yield production of superconducting focal plane components.

Main Methods:

• Development of a comprehensive fabrication framework encompassing single device prototyping, process monitoring, in-process metrology, and cryogenic measurements.
• Implementation of this framework for the production of detector arrays and monolithic DC/RF routing wafers.
• Rigorous testing and validation of critical film properties and device performance.

Main Results:

• Successful development and application of a robust, production-level fabrication framework.
• Timely delivery of nearly 100 superconducting focal plane components to the Simons Observatory.
• Achieved high channel yield ($$) and wafer yield ($$) meeting nominal criteria for module integration.

Conclusions:

• The established fabrication framework is effective for producing high-quality superconducting detector arrays at scale.
• The framework ensures the timely delivery of critical components with high yields, supporting the SO's scientific goals.
• This work demonstrates a reliable method for fabricating complex detector modules for CMB research.