This paper shows the current status of cooled IR detector technologies at i3system, South Korea. Mass production technology of i3system has successfully supplied lots of QVGA cooled IR detectors to camera customers. i3system has also developed small pitch cooled IR detectors with 320×256 and 640×512 formats for several different applications such as thermal sights and 24-hour operation observation units. In 2013, i3system’s cooled IR detector has been launched in STSAT(Science and Technology SATellite)-2C through Naro-1 program which was South Korea’s first successful launch vehicle for satellite. Owing to i3system’s robust, intensive design and test programs, IR detector technologies have been space qualified without any further efforts by the space program. Currently, development programs for SXGA(1280×1024) with small pitch cooled detector are being progressed and its status is addressed.
Heat-sensitive material is one of the most essential parts of microbolometer fabrication. Vanadium oxide (VOx) and amorphous silicon (a-Si) are widely accepted materials for commercialized focal plane arrays. Meanwhile, there are a lot of efforts for finding alternative materials having better performance, lower process cost and higher yield. In this study, reactively sputtered titanium oxide (TiO2-δ) films were investigated for heat sensitive material. Microbolometer device was also fabricated by using the TiO2-δ film as a heat sensitive material.
It is well known that the TiO2-δ can have several phases according to film deposition condition. Properties of TiO2-δ film could be largely varied by controlling the deposition condition. Resistivity of the fabricated TiO2-δ film was ranged from 10-2 Ω•cm to 10 Ω•cm. Negative TCR(temperature coefficient of resistance) value up to 2.8 %/K was obtained. 1/f noise of the TiO2-δ film was comparable to that of VOx film. From the fabrication result of microbolometer device, feasibility of the reactively sputtered TiO2-δ film was demonstrated. NETD(Noise equivalent temperature difference) of the 50μm-pitch simple single-level membrane structure microbolometer was 34mK with conditions of 1V bias and 30Hz operation frequency.
This paper reports the development of mid-wave 320x256 HgCdTe IRFPA with 30μm pixel pitch since 2002 in Korea.
All key technologies such as HgCdTe photodiode array fabrication process, the design of silicon readout integrated
circuit and hybridization process between HgCdTe photodiode array and ROIC including underfill encapsulation process
are studied and realized. The fabricated IRFPA shows good electro-optical performances such as operability over 99%,
NETD of ~ 17mK and there is no degradation in the operability during 500 thermal cycles.
At present, infrared photodetectors are being increasingly used in space systems, where they are exposed to the space radiation environment. Consequently, the radiation-hardness-related problem in HgCdTe photodetectors has become a critical issue.
In this study, the gamma radiation effects on ZnS- and CdTe-passivated mid-wavelength infrared (MWIR) HgCdTe photodiodes were investigated. Although ZnS has an excellent insulating property, its radiation-tolerant property was revealed very poor in comparison with CdTe. After 1 Mrad of gamma irradiation, the resistance-area product at zero bias (R0A) value of the ZnS-passivated photodiode was drastically reduced by roughly 5 orders from ~107 Ω cm2 to 102 Ω cm2, whereas the CdTe-passivated photodiode showed no degradation in R0A values.