With the advancement of silicon electronics under threat from physical limits to dimensional scaling, the International Technology Roadmap for Semiconductors (ITRS) released a white paper in 2008, detailing the ways in which the semiconductor industry can keep itself continually growing in the twenty-first century. Two distinct paths were proposed: More-Moore and More-than-Moore. While More-Moore approach focuses on the continued use of state-of-the-art, complementary metal oxide semiconductor (CMOS) technology for next generation electronics, More-than-Moore approach calls for a disruptive change in the system architecture and integration strategies. In this doctoral thesis, we investigate both the approaches to obtain performance improvement in the state-of-the-art, CMOS electronics. We present a novel channel material, SiSn, for fabrication of CMOS circuits. This investigation is in line with the More-Moore approach because we are relying on the established CMOS industry infrastructure to obtain an incremental change in the integrated circuit (IC) performance by replacing silicon channel with SiSn. We report a simple, low-cost and CMOS compatible process for obtaining single crystal SiSn wafers. Tin (Sn) is deposited on silicon wafers in the form of a metallic thin film and annealed to facilitate diffusion into the silicon lattice. This diffusion provides for sufficient SiSn layer at the top surface for fabrication of CMOS devices. We report a lowering of band gap and enhanced mobility for SiSn channel MOSFETs compared to silicon control devices. We also present a process for fabrication of vertically integrated flexible silicon to form 3D integrated circuits. This disruptive change in the state-of-the-art, in line with the More-than-Moore approach, promises to increase the performance per area of a silicon chip. We report a process for stacking and bonding these pieces with polymeric bonding and interconnecting them using copper through silicon vias (TSVs). We report a process for fabricating through polymer vias (TPVs) facilitating the fabrication of sensor arrays and control electronics on the opposite sides of the same flexible polymer. Finally, we present a process to fabricate stretchable metallic thin films with up to 800% stretchability, and report two distinct applications for these devices which cannot be done using current techniques.

The growth of flexible electronics industry has given rise to light-weight, flexible devices which have a wide range of applications such as wearable electronics, flexible sensors, conformal antennas, bio-medical applications, solar cells etc. Though several techniques exist to fabricate flexible devices, the limiting factors have been durability, cost and complexity of the approach. In this research, the focus has been on developing stretchable (flexible) conductors using a multi-layer structure of metal and conductive rubber. The stretchable conductors developed using this approach do not lose electrical connection when subjected to large strains up to 25%. Also, the conductivity of the conductive rubber has been improved by ~20 times using the multi-layer approach. Furthermore, the multi-layer approach was used to fabricate devices for RF and antenna applications. A flexible micro-stripline was fabricated using the multi-layer approach to study the performance at microwave frequencies up to 5 GHz. It was observed that using an optimal metal and conductive rubber layer structure can help to reduce the loss of the device by 58% and also the device does not get damaged due to bending. In addition to this, an aperture-coupled patch antenna at 3.1 GHz was fabricated using the multi-layer approach to demonstrate reconfigurability. Ideally, the multi-layer patch antennas can be stretched up to 25% which helps to tune the resonance frequency from 3.1 GHz to 2.5 GHz. The multi-layer patch antennas were tested up to ~10% strains to study their radiation properties. It was demonstrated that using an ideal multi-layer structure of metal and conductive rubber layer can help to improve the antenna's peak gain by 3.3 dBi compared to a conductive rubber based antenna.