MOSFET Technology Comparison Guide

Evolution of MOSFET Technologies

MOSFET technology has evolved significantly over the decades to meet the increasing demands of power electronics applications. Each technology addresses specific challenges related to conduction losses, switching losses, and device ruggedness.

Planar MOSFETs

Planar MOSFETs represent the original MOSFET structure, where the gate electrode is formed on the surface of the silicon substrate.

Structure and Operation

Planar MOSFETs have a simple structure where the channel is formed at the surface of the silicon. The on-resistance is primarily determined by the drift region resistance and channel resistance.

Advantages

• Proven reliability and ruggedness
• Simpler manufacturing process
• Good avalanche capability
• Larger safe operating area

Disadvantages

• Higher on-resistance for given area compared to other technologies
• Limited performance at higher voltage ratings
• Less efficient for modern high-frequency applications

Typical Applications

Planar MOSFETs are still suitable for applications where ruggedness and simplicity are more important than efficiency, such as motor control with high inductive loads and some industrial applications.

Trench MOSFETs

Trench MOSFETs improve upon planar technology by etching trenches into the silicon surface and forming the gate electrode in these trenches.

Structure and Operation

In trench MOSFETs, the channel is formed on the walls of the trenches, allowing for a higher channel density per unit area. This results in significantly lower on-resistance compared to planar devices of the same die size.

Advantages

• Lower on-resistance compared to planar for the same die size
• Lower gate charge, enabling faster switching
• Better performance at moderate voltage ratings (20V to 200V)

Disadvantages

• Higher di/dt capability can cause ringing in circuits
• Increased gate-drain capacitance (Miller capacitance)
• More susceptible to gate damage during switching

Typical Applications

Trench MOSFETs are widely used in DC-DC converters, power adapters, and other applications requiring good efficiency at moderate voltage ratings.

Super Junction (SJ) MOSFETs

Super junction MOSFETs represent a significant advancement for high-voltage applications (typically 600V to 900V), featuring alternating p-type and n-type columns in the drift region.

Structure and Operation

The super junction structure allows for a high doping concentration in the drift region while maintaining high breakdown voltage. When properly balanced, the p-type and n-type columns completely deplete in the off-state, enabling high breakdown voltage with very low on-resistance.

Advantages

• Significantly lower on-resistance compared to other technologies for high-voltage ratings
• Better figure of merit (RDS(on) × Qg)
• Excellent performance in PFC circuits and adapters
• Reduced conduction losses at high voltage ratings

Disadvantages

• Complex manufacturing process
• More sensitive to charge imbalance
• Higher cost compared to conventional technologies
• Can have higher switching losses at very high frequencies

Typical Applications

Super junction MOSFETs excel in PFC boost circuits, high-voltage adapters, and other applications where high efficiency at high voltage ratings is critical.

Shielded Gate (SGT) MOSFETs

Shielded gate MOSFETs represent the latest advancement in trench technology, featuring a conductive shield electrode between the gate and drain.

Structure and Operation

The shield electrode in SGT MOSFETs creates a field plate effect that reduces the electric field across the gate oxide during switching. This allows for better optimization of the trade-off between on-resistance and input capacitance.

Advantages

• Superior figure of merit (RDS(on) × Qg) compared to conventional trench
• Optimized for high-frequency operation
• Lower switching losses
• Reduced Miller effect

Disadvantages

• More complex manufacturing process
• Higher cost compared to conventional technologies
• Requires careful design for optimal performance

Typical Applications

SGT MOSFETs are ideal for LLC resonant converters, high-frequency adapters, and other applications requiring optimal performance in RDS(on) × Qg trade-offs.

Technology Comparison Table

Selection Criteria

When selecting a MOSFET technology, consider the following criteria:

Voltage Rating

The voltage rating is determined by the maximum drain-to-source voltage in your application with sufficient margin. For high-voltage applications (600V+), super junction technology typically offers the best performance.

Switching Frequency

At low frequencies, conduction losses dominate, so on-resistance is the primary concern. At high frequencies, switching losses become significant, making charge-related parameters more important.

Thermal Considerations

Consider the thermal resistance and how the MOSFET will be mounted. Technologies with lower on-resistance generally generate less heat during conduction.

Cost Constraints

While newer technologies offer better performance, they often come at a higher cost. Balance performance needs with budget constraints.

CRMICRO MOSFET Portfolio

CRMICRO offers comprehensive MOSFET solutions across all major technology categories:

SGT Series

CRMICRO's Shielded Gate Trench MOSFETs feature the lowest RDS(on) × Qg figure of merit, making them ideal for high-frequency applications such as LLC resonant converters and high-efficiency adapters.

SJ Series

CRMICRO's Super Junction MOSFETs provide excellent performance in PFC applications and high-voltage adapters, with some of the lowest on-resistance values in the industry.

Trench Series

CRMICRO's standard trench MOSFETs offer a good balance of performance and cost for general-purpose power conversion applications.

Design Considerations

When implementing different MOSFET technologies, consider:

Gate Drive Requirements

Different technologies may have different gate charge characteristics, affecting the gate driver requirements. More charge typically requires more drive capability.

Parasitic Effects

Higher-performance MOSFETs often have faster switching speeds, which can exacerbate parasitic inductance issues. Careful PCB layout becomes increasingly important.

Protection Circuitry

Consider the need for additional protection circuits such as snubbers or active clamps, particularly with fast-switching devices.