| Uncooled infrared focus plane array(UIFPA) detectors are widely used in military and civilian fields. And the demand of developing high-performance, small size and long life UIFPA with independent intellectual property rights will become an urgent issue in the high-tech fields of China. Sensitive films with low noise and excellent electrical properties are worth studying. Amorphous silicon(a-Si) thin film has the characteristics of high light absorption rate, high temperature coefficient of resistance(TCR), easily controlled forbidden band width. And due to its advantages of simple production process, large area deposition compatibility at low temperature, compatible with silicon technology, etc, a-Si thin film has a good application prospect in the fields of infrared detectors. However, because of the shortcomings of amorphous silicon thin film, the low frequency noise(1/f noise) level is relatively high, so would directly affect the performance of uncooled infrared detectors based on a-Si thin film. Therefore, the metal element ruthenium(Ru) is doped in amorphous silicon thin film and the a-Si1-xRux films are annealed at different temperature, in order to study the microstructural evolution of and low-frequency noise of the films. The goal of this thesis is to optimize the fabrication parameters of the film materials, and to modify the microstructure of amorphous networks with better stability, less defects, lower noise, and suitable for the application of UIFPAs.Nowadays, there are a lot of uncertainty factors on the noise test of resistance sensitive films. This thesis briefly describes the theory of film noise and the generating mechanism of 1/f noise. Finally, we have successfully set up a system at home in order to carry out the realization of noise characterization in a-Si1-xRux thin films.The a-Si1-xRux thin films were fabricated by radio frequency magnetron sputtering deposition technology. The influence of different doping ratios of Ru atoms on the microstructure and electrical properties of the thin films is studied. The results indicate that the ordered degree of the a-Si1-xRux amorphous network is gradually deteriorated with the incorporation of Ru atoms, and many Ru2 Si nanocrystals appear in the as-deposited microstructure of the thin films. At the same time, the film resistivity at room temperature decreases gradually with an obvious 1/f noise ability improvement of the thin films. When Ru doping ratio is 8 %, the film resistivity declines by nearly eight order of magnitude, compared to that of the intrinsic amorphous one. With the increase of Ru doping ratios, the absolute TCR value of the film is gradually reduced. It is worthy of noticing that a moderate Ru doped ratio of 4 % could make the films realize TCR=2.4 %/K, which might to fulfil the application requirement of micro bolometers.This thesis has also studied the heat annealing effect on the microstructure and low frequency noise of a-Si1-xRux thin films. The results show that the annealing can improve the ordered degree and reduce the structural defects of the amorphous thin films. After annealing of 700 ℃×1 h, the crystallization appears significantly in the microstructure of 6 % Ru-doped amorphous film. Many new nanocrystals of pure silicon appear and the early Ru2 Si nanocrystals have changed into Ru2Si3. It is noted that, annealing can not only improve the structural stability, but also reduce the low frequency noise of the thin films. After the annealing of 700 ℃×1 h, the minimum of the noise parameter comes to 2.80×10-9, declines by two orders of magnitude. Our present study shows that through doping of Ru atoms and afterword annealing of the films, the low frequency noise of a-Si1-xRux thin films can significantly be reduced at some extent. |
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