Springer Series in Advanced Microelectronics

2 primary works

High Mobility and Quantum Well Transistors

by Geert Hellings and Kristin De Meyer

Published 1 January 2013

For many decades, the semiconductor industry has miniaturized transistors, delivering increased computing power to consumers at decreased cost. However, mere transistor downsizing does no longer provide the same improvements. One interesting option to further improve transistor characteristics is to use high mobility materials such as germanium and III-V materials. However, transistors have to be redesigned in order to fully benefit from these alternative materials.

High Mobility and Quantum Well Transistors: Design and TCAD Simulation investigates planar bulk Germanium pFET technology in chapters 2-4, focusing on both the fabrication of such a technology and on the process and electrical TCAD simulation. Furthermore, this book shows that Quantum Well based transistors can leverage the benefits of these alternative materials, since they confine the charge carriers to the high-mobility material using a heterostructure. The design and fabrication of one particular transistor structure - the SiGe Implant-Free Quantum Well pFET – is discussed. Electrical testing shows remarkable short-channel performance and prototypes are found to be competitive with a state-of-the-art planar strained-silicon technology. High mobility channels, providing high drive current, and heterostructure confinement, providing good short-channel control, make a promising combination for future technology nodes.

Poly-SiGe for MEMS-above-CMOS Sensors

by Pilar Gonzalez Ruiz, Kristin De Meyer, and Ann Witvrouw

Published 30 July 2013

Polycrystalline SiGe has emerged as a promising MEMS (Microelectromechanical Systems) structural material since it provides the desired mechanical properties at lower temperatures compared to poly-Si, allowing the direct post-processing on top of CMOS. This CMOS-MEMS monolithic integration can lead to more compact MEMS with improved performance. The potential of poly-SiGe for MEMS above-aluminum-backend CMOS integration has already been demonstrated. However, aggressive interconnect scaling has led to the replacement of the traditional aluminum metallization by copper (Cu) metallization, due to its lower resistivity and improved reliability.

Poly-SiGe for MEMS-above-CMOS sensors demonstrates the compatibility of poly-SiGe with post-processing above the advanced CMOS technology nodes through the successful fabrication of an integrated poly-SiGe piezoresistive pressure sensor, directly fabricated above 0.13 m Cu-backend CMOS. Furthermore, this book presents the first detailed investigation on the influence of deposition conditions, germanium content and doping concentration on the electrical and piezoresistive properties of boron-doped poly-SiGe. The development of a CMOS-compatible process flow, with special attention to the sealing method, is also described. Piezoresistive pressure sensors with different areas and piezoresistor designs were fabricated and tested. Together with the piezoresistive pressure sensors, also functional capacitive pressure sensors were successfully fabricated on the same wafer, proving the versatility of poly-SiGe for MEMS sensor applications. Finally, a detailed analysis of the MEMS processing impact on the underlying CMOS circuit is also presented.