MS Thesis

Abstract:

Schottky junctions are well known for their low forward drop and insignificant storage effects. Their application in both the two-terminal and three-terminal devices to enhance the high-speed performance has gained importance due to the technological ability to prepare extremely clean semiconductor surfaces. In the recent past, several novel rectifier as well as transistor structures have been reported using Schottky junctions. SiC Schottky rectifiers have several advantages in high temperature, high speed and high voltage applications. Although a number of vertical SiC Schottky rectifiers have been reported in literature, lateral Schottky rectifiers are increasingly becoming important because of their utility in power ICs.

Due to it’s excellent material properties of SiC, device designers have started using it as emitter in high-performance HBTs where as SiGe is an excellent semiconductor for RF applications. Replacing the collector-base p-n junction by a Schottky junction in BJTs has been proposed to reduce the collector resistance, base widening and to improve the transient response of the transistor. But all these proposed devices are vertical in nature and not compatible with standard CMOS processes, so they could not gain wider acceptability in VLSI BiCMOS applications.

In the present work, to enhance the performance limits of Schottky rectifiers and HBTs, we have proposed four high performance BiCMOS compatible lateral Schottky devices in Silicon-On-insulator (SOI) technology namely, 1) A Novel high voltage 4H-SiC Lateral Dual Sidewall Schottky (LDSS) rectifier, 2) Lateral Dual Sidewall Schottky (LDSS) concept for improved rectifier performance on SOI, 3) A Novel lateral N-SiC emitter P-SiGe base Schottky Metal-collector (NPM) HBT on SOI and 4) A New lateral dual – bandgap P-emitter N-SiGe base Schottky Metalcollector (PNM) HBT on SOI with reduced collector – emitter offset voltage.

We have used carefully calibrated two-dimensional simulations to study the characteristics of the proposed devices in this work. Based on the simulated results, we have analyzed the reasons for the improved performance of the proposed structures over the conventional devices. We have also presented a BiCMOS compatible fabrication procedure for all our proposed devices. The results presented in our work are expected to be an incentive for further experimental exploration by other researchers.

References:

1. Kumar M.J. and C.Linga Reddy, "Silicon-on-Insulator Lateral Dual Sidewall Schottky (SOI-LDSS) Concept for Improved Rectifier Performance: A Two-Dimensional Simulation Study," Microelectronics International, vol. 23, No.1, pp. 16-18, January 2006.

2. Kumar M.J. and C.Linga Reddy, “A New Dual bandgap Emitter Schottky Collector PNM HBT on SOI with Reduced Collector Emitter Offset Voltage,” IEE Proceedings on Circuits, Devices and Systems, Vol.151, April 2004.

3. Kumar M.J. and C.Linga Reddy, “A New High Voltage 4H-SiC Lateral Dual Sidewall Schottky (LDSS) Rectifier: Theoretical Investigation and Analysis,” IEEE Transactions on Electron Devices, Vol.50, pp.1690-1693, July 2003.

4. Kumar M.J. and C.Linga Reddy, “A Novel SiC Emitter, SiGe Base Lateral Schottky Collector NPM HBT on SOI,” Microelectronics Reliability Journal, Vol.43, pp.1145-1149, July 2003.

5. Kumar M.J. and C.Linga Reddy, “A New dual-bandgap SiC-on-Si P-emitter, SiGe N-base, lateral Schottky Metal-collector (PNM) HBT on SOI with reduced collector-emitter offset-voltage,” IEEE TENCON 2003.

6. Kumar M.J. and C.Linga Reddy, “Application of Lateral Dual Sidewall Schottky (LDSS) Concept for Improved Rectifier Performance on SOI - Design and Optimization,” IEEE TENCON - 2003.

7. Kumar M.J. and C.Linga Reddy, “A Novel 4H-SiC Lateral Dual Sidewall Schottky Rectifier with excellent forward and reverse characteristics,” IASTED International Conference on Circuits, Signals, and Systems (CSS' 03) Cancun, Mexico, May 19-21, 2003.

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