Thermoreflectance based thermal microscope

TLDR

The system uses a 16×16 AC‑coupled photodiode array with synchronous frequency‑domain filtering to acquire visible‑light thermoreflectance images in real time, achieving 34 mK sensitivity, 123 dB dynamic range (1 s averaging), 40 kHz frame rate, and sub‑micron resolution via 160×160 pixel enhancement. Amplitude and phase thermoreflectance images of 50 × 50 µm SiGe microcoolers were obtained, demonstrating that a stable, higher‑power light source enables the camera to achieve 6 mK sensitivity over a sub‑micron area.

Abstract

Thermal images of active semiconductor devices are acquired and processed in real time using visible light thermoreflectance imaging with 34mK sensitivity. By using a 16×16 alternating current coupled photodiode array with synchronous frequency domain filtering a dynamic range of 123dB is achieved for 1s averaging. Thus with a stable and higher power light source, fundamentally the camera can reach 6mK sensitivity over a submicron area. The number of pixels in the image is increased to 160×160 by multiple frame image enhancement and submicron spatial resolution is achieved. The photodiode array system has a maximum 40kHz frame rate and generates a synchronous trigger for recovery of the phase signal. Amplitude and phase images of the thermoreflectance signal for 50×50 micron square active SiGe based microcoolers are presented.