Leakage Power reduction - Nanotechnology

What is Leakage Power?

Leakage power is the power consumed by a digital circuit even when it is not actively switching. It is primarily due to the leakage current that flows through the transistors even in their off state. In nanotechnology, the reduction of leakage power is crucial due to the scaling down of semiconductor devices, which exponentially increases leakage currents.

Why is Leakage Power a Concern in Nanotechnology?

As we scale down to the nanometer scale, leakage power becomes a significant portion of the total power consumption. This is problematic for several reasons:

Battery Life: Increased leakage power drains battery-operated devices faster.
Thermal Management: Excessive leakage power can lead to overheating, which can degrade the performance and reliability of the device.
Cost: Managing leakage power requires more sophisticated cooling solutions, which increase the cost of the device.

Types of Leakage Currents

There are several types of leakage currents in nanometer-scale transistors:

Subthreshold Leakage: Occurs when the transistor is off but a small current flows between the source and drain.
Gate Oxide Leakage: Due to tunneling current through the thin gate oxide layer.
Junction Leakage: Due to reverse-biased diode leakage at the drain and source junctions.

Techniques for Reducing Leakage Power

Multiple techniques can be used to reduce leakage power in nanotechnology:

High-K Dielectrics
Replacing the traditional silicon dioxide gate dielectric with high-K materials can reduce gate oxide leakage. High-K dielectrics allow for a thicker gate insulator while maintaining the same capacitance, thereby reducing leakage.

Multi-Threshold CMOS (MTCMOS)
MTCMOS technology uses transistors with different threshold voltages to optimize power and performance. High-threshold voltage transistors are used in non-critical paths to reduce leakage, while low-threshold voltage transistors are used in critical paths to maintain performance.

Power Gating
Power gating involves shutting off the power supply to inactive blocks of the circuit, thereby reducing leakage power. This technique is particularly useful in systems with significant idle periods.

Dynamic Voltage Scaling (DVS)
DVS reduces the supply voltage during low-performance periods, thereby reducing leakage power. Lowering the supply voltage reduces the subthreshold leakage exponentially.

Body Biasing
Adjusting the body bias of a transistor can control its threshold voltage. Forward body biasing can be used to increase performance, while reverse body biasing can be used to reduce leakage power.

Use of FinFETs
FinFETs are 3D transistors that offer better control over the channel, thereby reducing leakage currents. They are becoming increasingly popular in nanometer-scale technologies.

Future Directions

Research is ongoing to find new materials and techniques to further reduce leakage power. Emerging technologies like quantum dots, carbon nanotubes, and graphene hold promise for significantly reducing leakage power in future nanodevices.

Conclusion

Leakage power reduction is a critical aspect of nanotechnology, especially as devices continue to scale down. By employing a combination of techniques such as high-K dielectrics, MTCMOS, power gating, DVS, body biasing, and FinFETs, it is possible to mitigate the challenges posed by leakage currents. Ongoing research and development will continue to play a vital role in addressing these issues and advancing the field of nanotechnology.