MOSFET Performance Improvement: Decision Factors of RDS(ON)

(1) The MOSFET device structure is selected according to the required withstand voltage. The factors that determine the on-resistance RDS (ON) are as shown in Figure 3-7 and Equation 3- (1). Depending on the structure of the device, the ratio of factors determining on-resistance will change.
(2) For example, many middle- and high-voltage MOSFETs (250 V or higher) have planar MOS (π-MOS) structure, and products with less than 200 V have more trench MOS (U-MOS). Therefore, when the withstand voltage VDSS = 600 V, Rdrift becomes the dominant factor, and in the case of 30 V, the ratio of Rch is high.

ON resistance decision factors of D-MOS
Fig. 3-7(a) ON resistance decision factors of D-MOS

RDS(ON)= Rsub + Rdrift + RJ-FET + Rch + RN+

ON resistance decision factors of trench MOS
Fig. 3-7(b) ON resistance decision factors of trench MOS

RDS(ON)= Rsub + Rdrift + Rch + RN+  ・・・  Equation 3-(1)

In the case of VDSS=600 V, the order is Rdrift >> Rch > RJ-FET , RN+ , Rsub  and RDS(ON) depends on Rdrift
In the case of VDSS=30V, the order is Rch >> Rdrift > RN+ , Rsub.  Dependence of RDS(ON) on Rch can be minimized by fine patterning of trench MOS structure.

Chapter III : Transistors

Types of Transistors
Bipolar Transistors (BJTs)
Bias Resistor Built-in Transistors (BRTs)
Junction Field-Effect Transistors (JFETs)
Metal-Oxide-Semiconductor Field-Effect Transistors (MOSFETs)
Differences between BJT and MOSFET
Structure and Operation of MOSFET
MOSFET Performance Improvement: Approach to Low RDS(ON)
MOSFET Performance Improvement: Super-Junction MOSFETs (SJ-MOS)
Summary of MOSFET Features by Structure
Performance of MOSFETs: Drain Current and Power Dissipation
Performance of MOSFETs: Avalanche Capability
Performance of MOSFETs: Characteristic of Capacitance
Performance of MOSFETs: Safe Operating Area(or Area of Safe Operation)
Insulated-Gate Bipolar Transistors (IGBTs)
Operation of Insulated-Gate Bipolar Transistors (IGBTs)
Performance Improvement of IGBTs: Evolution of Vertical Design
What are RC-IGBTs and IEGTs?
Application of IGBTs
Comparison of Forward Characteristics of IGBTs and MOSFETs
Comparison of Transistors by Structure
Datasheets of MOSFET: Maximum Ratings
Datasheets of MOSFET: Electrical Characteristics
Datasheets of MOSFET: Capacitance and Switching Characteristics
Datasheets of MOSFET: Body Diode

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