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High-Resolution Temperature Sensing for Human Health Using Si-Photonics Technologies
Professor Ching-Fuh Lin
Graduate Institute of Photonics and Optoelectronics, National Taiwan University
台湾大学光电所 林清富教授
Accurate and non-contact temperature sensing is important for healthcare monitoring, smart sensing systems, and thermal imaging, particularly in the human-body-temperature range where small temperature variations must be reliably distinguished. Conventional infrared thermal sensors often require specialized materials or complex device architectures. In this work, we investigate a silicon-compatible approach based on Cu/p-Si Schottky hot-carrier photodetectors with periodic inverted-pyramid structures (IPSs) for detecting blackbody radiation from 35 to 42 °C. Under reverse bias, the electric field near the metal–semiconductor interface promotes carrier transport and enhances the photothermal response associated with hot-carrier relaxation. The inverted-pyramid geometry further modifies the optical-field distribution at the Cu/Si interface and, together with localized surface plasmon resonance (LSPR), promotes hot-carrier generation and improves the temperature-dependent response.
To quantitatively evaluate the detector response, the transient current slope was extracted using local linear regression and used as the sensing metric. Reverse bias produced a substantially stronger temperature-dependent response than forward bias. For the planar device at 42 °C, the response at −0.3 V reached 52.548 µA/s, approximately 2.6 times of that at +0.3 V and 3.8 times that at +0.5 V. After introducing an 8 µm IPS, the response under −0.3 V nearly doubled compared with the planar device, increasing from 7.631 to 15.563 µA/s at 35 °C and from 52.548 to 103.387 µA/s at 42 °C. The enhanced response enabled clear discrimination of controlled 0.1 °C source-temperature steps.
The dimensions of the inverted-pyramid structures were also found to play an important role in the sensitivity. As the IPS size increased from 8 to 14 µm, the response increased from 15.563 to 21.074 µA/s at 35 °C and from 103.387 to 162.960 µA/s at 42 °C. Linear fitting over 35–42 °C yielded sensitivities of approximately 12.20, 13.57, 16.37, and 20.60 µA/s°C for the 8, 10, 12, and 14 µm IPS devices, respectively. These results demonstrate that engineering the surface microstructure provides an effective means of tailoring the optical-field distribution and hot-carrier response, thereby improving the performance of Cu/p-Si Schottky detectors for low-temperature thermal-radiation sensing.
Device miniaturization was further demonstrated using a 3 mm × 3 mm detector with 14-µm IPSs. Under a −1 V bias, the miniaturized device maintained a clear temperature-dependent response, with the current slope increasing from 0.771 µA/s at 35 °C to 4.725 µA/s at 42 °C. Despite the substantial reduction in device area, the detector retained the ability to discriminate controlled 0.2 °C source-temperature steps. Overall, the Cu/p-Si platform combines room-temperature operation, silicon-process compatibility, microstructure-enhanced thermal-radiation response, and strong potential for device miniaturization, highlighting its promise for compact non-contact temperature-sensing applications.
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Fig. 1. (a) SEM images of periodic inverted-pyramid structures with characteristic sizes of 8, 10, 12, and 14 µm. (b) Temperature-dependent current-slope responses of Cu/p-Si hot-carrier photodetectors with different inverted-pyramid sizes.
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Ultra-Thin Ferroelectric Capacitor with 1.2 V NVSRAM Application
Professor Chee-Wee Liu
Graduate Institute of Photonics and Optoelectronics, National Taiwan University
台湾大学光电所 刘致为教授
Scaling Hf1-xZrxO (HZO) films to <5 nm typically induces severe polarization degradation and high leakage. In alignment with this trajectory, our group resolved these constraints by fabricating 3 nm HZO capacitors on
b-W electrodes (Figure 1 (a)) using an initial solid-phase epitaxy (ISPE) method for larger crystallization of the orthorhombic (o-) phase in HZO and water quenching to reduce leakage current by four orders of magnitude (Figure 1 (b)). This resulted in a low operating voltage (VOP) of 0.55 V while still maintaining 2 Pr = 29 mC/cm2, exceeding the 2023 IRDS target (Figure 1 (c)), and a record 2 Pr/Vop ratio of 60 (Figure 1 (d)). Furthermore, we demonstrated low-operating-voltage non-volatile SRAM (NVSRAM) (Figure 2 (a)). Integrating 3.5 nm ferroelectric capacitors via standard routing enables complete data store and recall operations at 1.2 V. This closely matches the required non-volatile store voltage directly to the regular SRAM VDD, successfully eliminating conventional operational voltage mismatches (Figure 2 (b))[1].
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Fig. 1. (a) Process flow for MFM capacitor with 3 nm HZO. (b) DC I-V curves. (c) 2 Pr vs Vop. ISPE reaches 2 Pr of 29 μC/cm2 at 0.55 V Vop. (d) Benchmark 2 Pr/Vop ratios.
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Fig. 2. (a) Top view OM image of NVSRAM and cross-section schematics. (b) Stored and measured Recall waveforms in NVSRAM.
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Reference:
[1] Yu-Tsung Liao et al., IEDM 2025
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