Simulation Results of Prospective Next Generation 3-D Thermopile Sensor and Array Circuitry Options

This work presents the simulation results and design rules of a new sensor for IR-detection using the thermoelectric effect. Within the Seebeck-effect, thermopiles generate a voltage based on a temperature gradient inside the structure. State of the art thermopiles are manufactured as two-dimensional structures directly on a substrate. Here, a possible method of 3D integration is shown, where the thermoelectric materials are fabricated as thin tubes using an atomic layer deposition (ALD) process. These tubes are connected to an IR-absorber on top, where the IR-radiation causes a temperature gradient relative to the substrate. This has the advantages to achieve a fill factor of nearly 100%. In comparison to microbolometers, the 3D thermopile is a passive structure, which does not need complex readout and supply circuits. Furthermore, the usage of energy harvesting is possible. Additionally, new array circuitry options are discussed to achieve a better signal-to-noise ratio. An electrical series connection of multiple sensors effects a rising specific detectivity and the noise equivalent temperature difference (NETD) decreases analogously. With this technique, groups of pixels of the detector can be merged to one "super-pixel" for detecting even marginal temperature changes of an object.