Microbolometer based on a porous silicon fabrication process with a plasmonic absorber

Low-cost microbolometers are the key to enabling a broader market penetration of uncooled thermal imaging sensors. Nowadays, such devices can be used for commercial applications, ranging from thermal building inspection to automotive night vision. The problem with the presently available microbolometer arrays is the use of exotic materials in the production, such as non-CMOS-compatible materials, e. g. vanadium oxide (VOx). The microbolometer presented in this dissertation follows a radically different approach. The concept involves the fabrication of a completely separate micro-electro-mechanical-system (MEMS) microbolometer chip and a separate read-out-circuit (ROIC) chip. These are combined using wafer-level bonding. In this design the infrared (IR) radiation is exposed from behind (through the substrate) onto the pixels. Fabricating the MEMS chip involves designing and fabricating thermally insulated microbolometer pixels. The temperature-sensitive-devices (TSDs) that detect the heat induced by the IR radiation are PN-junction diodes. Another essential part in this underlying work is the fabrication design of a plasmonic absorber for microbolometer pixels. Comparing the pixels with and without a plasmonic absorber shows that pixels with a plasmonic absorber, absorb LWIR 18 percent better compared to pixels without an absorber, further underlining the fact that the peak absorption approximately coincides the designed wavelength.