Towards Single-Chip Nano-Systems
Important scientific discoveries are being propelled by the advent of nano-scale sensors that capture weak signals from their environment and pass them to complex instrumentation interface circuits for signal detection and processing. The highlight of this research is to investigate fabrication technologies to integrate such precision equipment with nano-sensors on a single complementary metal oxide semiconductor (CMOS) chip. In this context, several demonstration vehicles are proposed. First, an integration technology suitable for a fully integrated flexible microelectrode array has been proposed. A microelectrode array containing a single temperature sensor has been characterized and the versatility under dry/wet, and relaxed/strained conditions has been verified. On-chip instrumentation amplifier has been utilized to improve the temperature sensitivity of the device. While the flexibility of the array has been confirmed by laminating it on a fixed single cell, future experiments are necessary to confirm application of this device for live cell and tissue measurements. The proposed array can potentially attach itself to the pulsating surface of a single living cell or a network of cells to detect their vital signs. Next, a fabrication process has been developed to integrate arrays of electron field emitters within a CMOS SOI chip. The proposed integration technology enables engineered electrodes with uniform tip shapes and highly controlled electrode distances. Field emission experiments from both vertical and horizontal nano-tips within a CMOS chip is demonstrated. A fabrication approach based on engineering the CMOS substrate has also been developed to improve the characteristics of electronic components and circuits. By transferring or removing the silicon substrate of a CMOS SOI chip, the loss of Si substrate has been eliminated, leading to improved performance of two circuit demonstration vehicles. In the first example, a high performance wideband RF power amplifier (PA) is presented with the substrate transferred to Aluminum Nitride (AlN). In the second case, improved performance of an integrated rectifier and antenna (Rectenna) without silicon substrate is presented. Finally, post-processing techniques to integrate nano-fluidic channels and nanoelectromechanical systems (NEMS) on a CMOS chip have been developed. For applications in integrated nano-fluidic channels, post-processing recipes to fabricate both horizontal and vertical channels have been proposed, which may facilitate future single biomolecule detection and characterization. For integrated NEMS, different nanobeams have been fabricated in a standard CMOS SOI technology, with a focus on the development of different suspension methods. Proposed techniques to fabricate NEMS devices may find applications in precision mass sensing, gyroscopes and electromechanical filters. Nano-sensors integrated with CMOS offer a pathway to overcome several challenges, including low detection bandwidth, low signal-to-noise ratios, and low yield and reproducibility. Solving these challenges will propel integrated nano-systems into the commercial market.
Mohammdi, Purdue University.
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