Ultra-Large-Charge-Capacity Digital ROIC Technology for Very-Long-Wavelength IRFPAs

Very-long-wavelength infrared (VLWIR) detectors have important applications in infrared imaging systems, spectral detection, and deep space exploration. Compared with medium-wavelength (MW) and long-wavelength (LW) IR detectors, VLWIR detectors exhibit significantly higher photocurrent and dark current, and their bias voltage becomes more discrete and sensitive. This study employs digital integration technology and multi-power-domain technologies to address the challenges of temperature sensitivity constrained by integration time and the wide bias voltage range required for VLWIR detectors. Based on a standard CMOS 0.13 μm process, a digital readout integrated circuit (DROIC) with a 320 × 256 array (30-μm pitch) and a 640 × 512 array (30-μm pitch) was designed and fabricated. In both DROICs, the pixel-level ADC is 16-bit, the charge capacity reaches 11.8Ge-, and the detector bias voltage range is extended to 2.2 V. Measurement results show that the power consumption is 53.1 and 149.6 mW (@100 Hz frame rate), respectively. Coupled with 320 × 256 and 640 × 512 VLWIR detectors, the average noise equivalent temperature difference (NETD) is 8.01 and 9.29 mK (half-well capacity), respectively. When the integration time is less than 10 ms, the dynamic range (DR) exceeds 90 dB. Compared with traditional readout integrated circuit, DROIC significantly expands the charge capacity, prolongs the integration time of VLWIR detectors, and effectively improves temperature sensitivity and dynamic range.