The main MOSFETs in the market including VDMOS，Trench MOSFET，SGT MOSFET and SJ MOSFET.
The most common and typical planar gate structure of a MOSFET includes the following main parts.
Gate: It is the control element of the MOSFET, used to control the opening and closing of the channel, corresponding to one pin.
Source: It is the input terminal where electrons enter the MOSFET, corresponding to one pin.
Drain: It is the outlet for electrons to flow out, corresponding to one pin.
Substrate: The substrate is the base material of the MOSFET, providing carriers for the conductive channel of the MOSFET.
Oxide Insulator: Typically SiO2, placed between the source/drain regions and the gate to provide insulation.
1.（VDMOS）
In a VDMOS structure, the drain, source, and gate terminals are not on the same plane.
In the VDMOS structure, the channel is vertical and the gate is planar. This design has the following advantages.
·Higher voltage resistance: The vertical channel can withstand higher voltage, thus improving the voltage resistance of MOSFET.
·Smaller area: The vertical channel makes the MOSFET area smaller, and the finished product package volume can be smaller.
·Lower parasitic capacitance: The vertical channel can make the gate metal area of MOSFET smaller and the parasitic capacitance lower, thus improving the switching speed.
2. Trench MOS
The gate of the trench MOS is made by digging a groove inward and then filling the groove with silicon oxide. This process is called gate oxidation.
Compared with planar gate MOSFET, trench gate MOSFET constructs a trench structure that passes through the bottom of the P-type base region. The formed channel is located between the N+ source and the N drift region, eliminating the JFET area and the JFET resistance. Therefore, the total characteristic resistance is greatly reduced compared to the planar gate structure.
3. SGT MOS
SGT-MOS is an improved structure of Trench MOS, which is usually suitable for medium and low voltage scenarios (as shown in Figure 4). Compared with traditional Trench MOSFET, SGT-MOSFET adds a polysilicon electrode under the gate electrode, namely the shielding electrode or coupling electrode. The shielding electrode is connected to the source electrode, which realizes the function of shielding the gate and the drift region, reduces the Miller capacitance, and speeds up the switching speed of the device. At the same time, it realizes the charge coupling effect, reduces the critical electric field strength of the drift region, reduces the on-resistance of the device, and can reduce the switching loss.
4. SJ MOS
In terms of power MOS, compared with the conventional VDMOS device structure, there is a contradictory relationship between RDS(on) and BVSS. To improve BVSS, it is generally necessary to reduce the EPI doping concentration (Epi doping refers to depositing a layer of doping material on the surface of the wafer to change the conductive properties of the wafer. By controlling the type and concentration of the doping material, the electrical properties of the wafer can be precisely controlled). However, the epitaxial layer is the channel for the forward current to flow. If the EPI doping concentration is reduced, the resistance will inevitably increase, and RDS(on) will increase. Otherwise, it is necessary to increase the chip area, increase the package size, and increase a lot of production costs. Therefore, for ordinary VDMOS, the contradiction between the two is irreconcilable.
High-voltage power MOSFETs using the Super Junction (SJ) process significantly reduce the on-resistance per unit area by setting a P-pillar region deep into the EPI layer and increasing the doping concentration of the current conduction region, but at the same time The withstand voltage is not affected, making it a new type of device with high withstand voltage and low resistance characteristics. The special super-junction structure allows the internal resistance of high-voltage super-junction MOSFET to be reduced to 1/5 of that of traditional planar MOSFET under the same area, and the switching loss is therefore reduced to 1/2 of that of ordinary VDMOSFET.
Compared with traditional power MOSFET, SJ-MOSFET has the advantages of low conduction loss, large current driving capability, low gate charge, low turn-on voltage and fast switching speed.
5. Summary
In summary, the advantages and disadvantages of MOS tubes of various processes are as follows.
VDMOS
Advantages: high withstand voltage, smaller area with the same specification, low parasitic capacitance.
Disadvantages: large on-resistance and large leakage current.
Trench MOS
Advantages: small on-resistance, small parasitic capacitance, and excellent switching performance.
Disadvantages: cannot withstand high voltage, often used in low-voltage fields below 100V, and weak impact resistance.
SGT MOS
Advantages: small Miller capacitance, low switching loss, low conduction loss, often used in medium and low voltage fields (about 200V).
Disadvantages: complex process and high cost.
SJ MOS
Advantages: small internal resistance, small gate charge, fast switching speed, often used in high voltage fields (600-800V).
Disadvantages: weak surge resistance.
Din-Tek has all the MOSFETS mentioned above, and can also do customization based customer requirements. Please kindly let us know your requirements.
