04-04-2012, 03:59 PM
Silicon-On-Insulator Technology
SOI_Presentation.ppt (Size: 422.5 KB / Downloads: 46)
Short-Channel Effects(SCES)
A MOSFET device is considered to be short when the channel length is the same order of magnitude as the depletion-layer widths of the source and drain junction.
The short-channel effects are attributed to two physical phenomena:-
1.the limitation imposed on electron drift characteristics in the channel.
2.the modification of the threshold voltage due to the shortening of channel length.
Sub-Threshold Current
Sub-threshold leakage current is the current that flows between the source and drain of a MOSFET under the condition (VGS<VT0).
Current flows in the channel because potential barrier of channel is reduced due to increase in the drain-to-source voltage.
In the past, the subthreshold leakage of transistors has been very small, but as transistors have been scaled down, subthreshold leakage can compose nearly 50% of total power consumption.
Scaling reduces the threshold voltage
in the same proportion. As threshold
voltages are reduced, subthreshold.
leakage rises exponentially.
Introduction
The first implementation of SOI was announced by IBM in August 1998.
Implementation of SOI technology is one of the manufacturing strategies employed to allow continued miniaturization of microelectronic devices.
Performance gains 20-35% when design is moved from bulk Si to SOI.
Benefits of SOI technology relative to conventional silicon (bulk CMOS) :-
Lowers parasitic capacitance due to isolation from the bulk silicon, which improves power consumption and thus high speed performance.
Reduced short channel effects.
Reduced Short channel effects
SOI Fabrication
Different methods used to fabricate SOI wafers:
SIMOX(Separation by IMplantation of OXygen) -uses an oxygen ion beam implantation process followed by high temperature annealing to create a buried SiO2 layer.
Application
SOI has opened the door for opportunities in the low-power arena.
Used in wireless technology which requires the use of high resistivity substrates.
Used in case of faster speed operations.
Microprocessors are built with SOI as substrate.
SOI is an attractive alternative for low-voltage digital CMOS logic, microprocessors, memories, sensors and integrated optical electronics.
Conclusion
Today SOI is being used by many companies despite of the fact that it is expensive and bringing it into the mainstream of Si technology has been challenging.
However,as we move to the 0.1micro-meter generation and beyond,SOI offers the total solution to problems of bulk-Si substrate and SOI will be the technology of choice.