Dual Metal Gates

Dual Metal Gate technology is an advanced semiconductor fabrication technique primarily aimed at improving the performance of CMOS (Complementary Metal Oxide Semiconductor) technology, which forms the basis of many modern electronic devices.

Dual Metal Gate technology involves using two different metal materials for the gate in nMOS and pMOS transistors in a CMOS structure. The nMOS and pMOS transistors in CMOS circuits have different properties and characteristics, and the use of different metal gates helps optimize each type of transistor's performance.

In 2007, taking the final step in the quest for dual metal gates, SEMATECH engineers demonstrated high-k/metal gate stacks that were used to build high-performance nMOS and pMOS transistors in a CMOS configuration. Thes breakthrough removed the obstacles to commercial implementation of high-k metal gate stacks in transistors for the 45nm and 32nm technologies. It also complemented the consortium's identification of effective nMOS materials for metal gates and previous success with developing high mobility high-k dielectrics. The combination of these successes provided a powerful tool for extending CMOS technology.

How Dual Metal Gate Technology Benefits CMOS Design

1. Threshold Voltage Control: The use of different metal materials allows for more precise control over the threshold voltage for both nMOS and pMOS transistors. The threshold voltage is the minimum voltage required to turn on the transistor. By controlling the threshold voltage, we can significantly reduce leakage current and power consumption, which is a major issue in miniaturized, densely packed transistors in modern integrated circuits.
2. Reduced Short Channel Effects: Short channel effects are a prominent issue in miniaturized devices, leading to degradation in transistor performance. This is due to the inability of the gate to control the channel at smaller dimensions. By using a dual metal gate, we can modulate the work function of the gate materials, reducing the impact of short channel effects.
3. Improved Carrier Mobility: Different gate materials can also affect the mobility of charge carriers. By selecting appropriate materials, the carrier mobility in nMOS and pMOS transistors can be increased, leading to better performance and faster switching times.
4. Enhanced Scalability: The dual metal gate technology provides a way to continue to scale down transistor sizes while maintaining control over their electrical properties. This helps to continue the trend of Moore's Law and allows for higher integration density in ICs.
5. Reduced Power Consumption: Dual metal gates reduce leakage current, which is a significant component of power consumption, especially in smaller devices. Reduced leakage means reduced power consumption, leading to more energy-efficient devices.