Shrinking Device Dimensions in Microelectronics

Shrinking Device Dimensions

The increasing integration of functions and the shrinking dimensions of microelectronic devices have significant implications for power consumption and device reliability. As more functions are integrated into a single device, power density increases, leading to higher heat generation. This heat can cause material degradation, such as di-electric breakdown and altered component characteristics. It can also create hot spots within the device. To manage this, additional cooling arrangements become necessary to maintain the operational temperature within acceptable limits. Moreover, the increased power consumption due to higher integration places greater demands on batteries, which can be problematic for small, portable devices.

Dynamic and Static Power consumption

There are two main categories of power consumption in microelectronics: dynamic and static.

Dynamic power is associated with the normal functionality of devices during input and output switching. It includes components like switching power and glitching power. In contrast, static power occurs when the circuit is in standby or runtime mode and no switching occurs at the input and output. Ideally, static power dissipation should be zero, but in practice, there is some undesired leakage of current through semiconductor devices. Various sources contribute to static leakage, such as P-N junction leakage, gate oxide tunneling, DIBL, hot carrier injection, and sub-threshold leakage. Notably, the power dissipation due to leakage currents can account for a significant portion of the overall power dissipation, up to 50% in some cases.

What challenges arise in micro-electronics devices due to technological advances?

Technological advances result in increased integration of functions per device and a significant reduction in device dimensions, leading to higher power density and escalating heat generation. Challenges include di-electric breakdown, altered component characteristics, hot-spot creation, and increased power consumption.

What are the major sources of static power in microelectronics devices?

Static power is due to different leakage components when the circuit is in standby and runtime mode. Major sources of static power include P-N junction leakage, gate oxide tunneling, DIBL, hot carrier injection, and sub-threshold leakage. Static power can contribute up to 50% of the total power dissipation, and this contribution grows further below 65nm technology.

What techniques have been developed to reduce leakage power loss in micro-electronics devices?

Various techniques have been developed, such as leakage control using Body-Biasing (VTCMOS and DTCMOS), multi-threshold design approaches, dual-threshold assignment, and runtime leakage minimization via input state assignment. Aggressive scaling of gate oxide thickness and efficient techniques for gate leakage estimation have also been explored.

Describe the proposed approach for reducing runtime leakage in CMOS gates at 65nm technology.

The proposed approach involves modifying a 2-input NAND gate by adding a high Vth NMOS transistor in series between VDD and ground. This added transistor is used as a capacitor to block static current flow during specific input combinations, reducing leakage power. The gate of the added transistor is tied to the drain of the lowermost NMOS transistor in the normal CMOS NAND gate, simplifying hardware complexity. The approach demonstrates significant improvement in leakage saving and correct logic operation in high-frequency ranges during active mode.

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