Abstract
We report a newly developed design/fabrication module with low-cost single-sided “low-stress-silicon-nitride (LS-SiN)/polysilicon (poly-Si)/Al” process for monolithic integration of composite sensors for sensing-network-node applications. A front-side surface-/bulk-micromachining process on a conventional Si-substrate is developed, featuring a multifunctional SiN/poly-Si/Al layer design for diverse sensing functions. The first “pressure + acceleration + temperature + infrared” (PATIR) composite sensor with the chip size of 2.5 mm × 2.5 mm is demonstrated. Systematic theoretical design and analysis methods are developed. The diverse sensing components include a piezoresistive absolute-pressure sensor (up to 700 kPa, with a sensitivity of 49 mV/MPa under 3.3 V supplied voltage), a piezoresistive accelerometer (±10 g, with a sensitivity of 66 μV/g under 3.3 V and a −3 dB bandwidth of 780 Hz), a thermoelectric infrared detector (with a responsivity of 45 V/W and detectivity of 3.6 × 107 cm·Hz1/2/W) and a thermistor (−25–120 °C). This design/fabrication module concept enables a low-cost monolithically-integrated “multifunctional-library” technique. It can be utilized as a customizable tool for versatile application-specific requirements, which is very useful for small-size, low-cost, large-scale sensing-network node developments.
Highlights
Over the past decade, the development of various sensing networks has had great impact on human beings’ life [1,2,3,4]
In sensing networks, sensing nodes play the key role in information gathering, and determine the performance, reliability and cost of the whole system
Along with the rapid increase of complex-environment sensing/monitoring requirements, multifunctional sensing-network nodes are in high demand [5]
Summary
The development of various sensing networks (e.g., wireless sensor networks, Internet-of-Things, etc.) has had great impact on human beings’ life [1,2,3,4]. Along with the rapid increase of complex-environment sensing/monitoring requirements, multifunctional sensing-network nodes are in high demand [5]. Such composite sensing nodes monitor various objects or parameters, and achieve better sensing characteristics by information convergence [6,7]. Single-chip-integrated composite sensors are great candidates for the generation of sensing nodes. By integrating various sensing components on a single chip with microelectromechanical system (MEMS) techniques, the monolithic composite sensors will feature the advantages of smaller size, lower power, and less assembly cost. Researchers have made efforts in developing sensors with combined functions [9,10,11]
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