Noise Improvement of a-Si Microbolometers by the Post-Metal Annealing Process.

Jaesub Oh,Jong-Kwon Lee,Jongcheol Park,Hyeong-Sub Song

doi:10.3390/s21206722

Jaesub Oh, Jong-Kwon Lee + Show 2 more

Open Access

https://doi.org/10.3390/s21206722

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Abstract

To realize high-resolution thermal images with high quality, it is essential to improve the noise characteristics of the widely adopted uncooled microbolometers. In this work, we applied the post-metal annealing (PMA) process under the condition of deuterium forming gas, at 10 atm and 300 °C for 30 min, to reduce the noise level of amorphous-Si microbolometers. Here, the DC and temperature coefficient of resistance (TCR) measurements of the devices as well as 1/f noise analysis were performed before and after the PMA treatment, while changing the width of the resistance layer of the microbolometers with 35 μm or 12 μm pixel. As a result, the microbolometers treated by the PMA process show the decrease in resistance by about 60% and the increase in TCR value up to 48.2% at 10 Hz, as compared to the reference device. Moreover, it is observed that the noise characteristics are improved in inverse proportion to the width of the resistance layer. This improvement is attributed to the cured poly-silicon grain boundary through the hydrogen passivation by heat and deuterium atoms applied during the PMA, which leads to the uniform current path inside the pixel.

Highlights

Infrared (IR) sensors detect electromagnetic waves in the range of 0.75 to 1000 μm, which are easy to pass through various media due to their long wavelength and have no sensitivity to the human eye
Thereafter, we described the effect of the post-metal annealing (PMA) process on the improvement of the a-Si based microbolometers
As a result of the measured data, by performing the PMA process under the condition of D2 forming gas, at 10 atm and 300 °C for 30 min, it is observed that the resistance decreased by about 60% compared to the reference microbolometer, and the temperature coefficient of resistance (TCR) values increased up to 48.2%

Summary

Introduction

Infrared (IR) sensors detect electromagnetic waves in the range of 0.75 to 1000 μm, which are easy to pass through various media due to their long wavelength and have no sensitivity to the human eye. By normalizing the noise data with respect to the anode current, it is observed that the noise levels of all the microbolometers treated by the D2 PMA process are lowered in the frequency range compared to those of the reference devices.

Results

Conclusion