Abstract
In this article, we present the design, fabrication, and characterization of a thermopile infrared sensor array (TISA) pixel. This TISA pixel is composed of a dual-layer p+/n- poly-Si thermopile with a closed membrane and an n-channel metal oxide semiconductor (NMOS) switch. To address the challenges in fabrication through the 3D integration method, the anode of the thermopile is connected to the drain of the NMOS, both of which are fabricated on the same bulk wafer using a CMOS compatible monolithic integration process. During a single process sequence, deposition, etching, lithography, and ion implantation steps are appropriately combined to fabricate the thermopile and the NMOS simultaneously. At the same time as ensuring high thermoelectric characteristics of the dual-layer p+/n- poly-Si thermopile, the basic switching functions of NMOS are achieved. Compared with a separate thermopile, the experimental results show that the thermopile integrated with the NMOS maintains a quick response, high sensitivity and high reliability. In addition, the NMOS employed as a switch can effectively and quickly control the readout of the thermopile sensing signal through the voltage, both on and off, at the gate of NMOS. Thus, such a TISA pixel fabricated by the monolithic CMOS-compatible integration approach is low-cost and high-performance, and can be applied in arrays for high-volume production.
Highlights
The three-dimensional (3D) integration of micro-electro-mechanical system (MEMS)devices or microsensors with CMOS signal processing circuits on separate chips by stacked bonding and electrically connecting neighboring chips with through-silicon-vias (TSVs) offers significant advantages, such as a low cost, high performance, and multiple functions within a single package [1–3].a large volume of high-power-density thermal accumulation, complex 3D architecture, diverse design tools and a high alignment accuracy all present technical challenges for 3D integration [4–8]
Compared to 3D integration, monolithic integration, which integrates MEMS sensors and CMOS ICs on the same substrate using consecutive or interlaced processing schemes, has shown great potential for MEMS devices fabricated by a monolithic integration process
Such an n-channel metal oxide semiconductor (NMOS) can function as a switch that reads the drain voltage by controlling V GS
Summary
Devices or microsensors with CMOS signal processing circuits on separate chips by stacked bonding and electrically connecting neighboring chips with through-silicon-vias (TSVs) offers significant advantages, such as a low cost, high performance, and multiple functions within a single package [1–3]. A large volume of high-power-density thermal accumulation, complex 3D architecture, diverse design tools and a high alignment accuracy all present technical challenges for 3D integration [4–8]. These challenges could be overcome by elaborate optimization, they inevitably lead to additional cost and technical risk. Various 3D integration schemes have been developed, only the heterogeneous integration of devices with different processes shows performance and cost advantages [9–12]. By fabricating MEMS and CMOS on the same chip with a single process sequence, a system Compared to 3D integration, monolithic integration, which integrates MEMS sensors and CMOS ICs on the same substrate using consecutive or interlaced processing schemes, has shown great potential for MEMS devices fabricated by a monolithic integration process.
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