19-11-2012, 12:01 PM
FinFETs
FinFETs.ppt (Size: 485.5 KB / Downloads: 26)
Introduction
The FinFET is a double gate device, one of a number of geometries being introduced to multigate devices, the effects of short channel & reduce drain induced barrier lowering.
FinFET are design to use multiple fins to achieve larger channel width. Source/Drain pads contacts, the fin is parallel.
As the Fin increased the current through the device increases.
E.g. A 5 Fin device has 5 times more current than single Fin device.
What are FinFETs?
A FinFET is like a FET, but the channel has been “turned on its edge” and made to stand up.
FinFETs are candidates as replacements for bulk MOSFETs
– Better control of short channel effects
– Double drive current
Compact model development
– Compact model required for circuit design
– No (public domain) FinFET models available
This structure is called FinFET because of its silicon body resembles the back fin of a fish
Partially Depleted(PD) SOI
The PD floating-body MOSFET was the first SOI transistor generically adopted for high-performance applications, primarily due to device and processing similarities to bulk CMOS device. & it is the first technology for high performance microprocessor applications.
The PD SOI device is largely identical to the bulk device, except for the addition of a buried oxide(“BOX”) layer.
The device offers several advantages for performance/ power improvement:
reduced junction capacitance,
lower average threshold due to positive V BS during switching.
dynamic loading effects,in which the load device tends to be in high VT state during switching.
The performance comes at the cost of some design complexity resulting from the floating body of the device, such as
parasitic bipolar effect and
hysteretic VT variation.
Parasitic Bipoler Effect
In PDSOI an n-p-n transistor is formed with source and drain as emitter & collector respectively and body as the base.
The topology involves an “OFF” transistor with the source & drain voltage set up in “HIGH” state. When the source is subsequently pulled down large overdrive produced across body-source junction, causing bipolar current to flow through the lateral parasitic bipolar transistor. This may cause circuit failure.
Histeretic Vt Variation
The hysteretic VT variation due to long time constants of various body charging/discharging mechanisms.
A commonly used gauge for hysteretic VT variation is the disparity in the body voltages and delays between the so-called “first switch”(i/p low) and “second switch”(o/p high) .