What is FinFET?
FinFET is a type of multi gate (MOSFET). It was first developed at the University of Berkley, California. It is named as FinFET because the 3D structure above the substrate looks like set of fins. It is a 3D transistor and widely used in integration circuits recently instead of planar CMOS FinFet. It is used more than other FETs because of its area of performance, lower leakage power, low voltage operation, intra- die variability and lower retention voltages for SRAM.
Structure of FinFET
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| Structure of Planar FET |
In planar FET the Gate is placed above the channel and there is leakage current flowing from source to drain even when the gate is off. Like the normal FET , FinFET consists of a source, drain and also a gate to control the current flow.In the FinFET the channel is thin vertical fin and gate is wrapped around it. This helps in better controlling of the channel and thus the electrical properties are better. FinFET can have two to four fins in the same structure.
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| Structure of FinFET |
The manufacturing process of the FinFET includes the following steps.
• Substrate:
In the fabrication process first a lightly doped P type substrate is used and a hard mask over it.
• Fin etch:
Then by a highly anisotropic process fins are formed
• Oxide deposition:
Over the fins oxide layers are formed to isolate the fins.
• Planarization:
It is planarized by chemical mechanical polishing process.
• Recess etch:
Excess oxide is etched
• Gate oxide:
To isolate the channel from the gate by thermal oxidization process gate oxide is deposited over the fins.
• Deposition of the gate:
Finally gate layer is formed of highly doped N+ poly silicon layer and deposited over the fins.
V-I Characteristics of FinFET:
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| V-I Characteristics of FinFET |
The drain current increases when the drain source voltage is applied. Initially it increases linearly and after that it enters into saturation region where the curve is almost most.
Advantages of FinFET over other FETs:
1) Lower power consumption
2) Operates at lower voltage
3) Operating speed is higher
4) Static leakage current is reduced upto 90%
5) More compact
Disadvantages of FinFET
1) For building the FinFET it involves many additional steps, so the fabrication cost is high
2) Controlling the Fin depth is difficult
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