Beamline Spectroscopy of Integrated Circuits With Hard X-ray Transition Edge Sensors at the Advanced Photon Source

TL;DR

This paper reports on the development and testing of superconducting Transition Edge Sensor arrays for X-ray spectroscopy at the APS, demonstrating significantly improved energy resolution and capabilities in analyzing complex integrated circuits.

Contribution

Introduction of a prototype TES array with multiplexed pixels that achieves ten times better energy resolution than existing detectors at a major beamline.

Findings

Energy resolution improved by a factor of ten

Ability to resolve closely spaced emission lines

Enhanced fluorescence mapping of integrated circuits

Abstract

At Argonne National Laboratory, we are developing hard X-ray (2 to 20 keV) Transition Edge Sensor (TES) arrays for beamline science. The significantly improved energy resolution provided by superconducting detectors compared to semiconductor-based energy-dispersive detectors, but with better collection efficiency than wavelength-dispersive instruments, will enable greatly improved X-ray emission and absorption spectroscopic measurements. A prototype instrument with 24 microwave-frequency multiplexed pixels is now in testing at the Advanced Photon Source (APS) 1-BM beamline. Initial measurements show an energy resolution ten times better (150 eV compared to < 15 eV) than the silicon-drift detectors currently available to APS beamline users, and in particular demonstrate the ability to resolve closely-spaced emission lines in samples containing multiple transition metal elements, such as integrated circuits. Comparing fluorescence spectra of integrated circuits measured with our TESs at the beamline to those measured with silicon detectors, we find emission lines and elements largely hidden (e.g. Hf alongside Cu) from a semiconductor-based detector but well resolved by a TES. This directly shows the strengths of TES-based instruments in fluorescence mapping.