A micromachined silicon thermopile and thermal emitters of infrared radiation have been developed. The thermopile junction materials were highly doped polycrystalline silicon deposited by PECVD or RF sputtering and aluminum metallisation. The hot junctions have been placed on a 0.5μm thick membrane made of silicon nitride, and the cold junctions have been placed on a surface of monolithic silicon. Porous silicon has been used as a thick sacrificial layer to suspend the membrane over the cavity. Alternatively, nanoporous silicon has been exploited as the thermal insulation material. Similar methods have been used for fabrication of electrically modulated microemitters of infrared radiation. This technology enables cost-effective manufacturing of infrared thermal sensors, and high performance emitters.
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