Automotive Power Mosfets

Automotive Power MOSFETs

Koji Horiuchi Yasuhiko Arita Takeyoshi Nishimura

1. Introduction bulbs.

As the automobile industry has increasingly used 3. Features of Fuji Electric’s Automotive Power electronic components and systems in recent years for MOSFETs the purpose of making car bodies that are lighter in weight and achieving better fuel efficiency, the use of 3.1 Features of MOSFETs for electronic power steering electronic control units (ECUs) has advanced. systems In particular, the transition from power steering Electric power steering ECUs mainly use 60 V systems that use conventional oil pressure control to MOSFETs, but the upcoming changeover to a 42 V DC motors that use electronic control (hereafter re- power source has led to requests for 75 V products. ferred to as electric power steering ECUs) has been These 60 V and 75 V MOSFET products utilize particularly rapid, and similarly, headlights are transi- trench structure technology to realize lower ON- tioning from conventional halogen bulbs to discharge resistance and smaller package size. Features of the bulbs that use electronically controlled ballast devices. electric power steering MOSFETs are introduced be- Additionally, environmental problems such as glo- low. bal warming have led to the commercialization of (1) Low ON-resistance chip structure and high gate products one-after-another such as hybrid vehicles, reliability electric vehicles and fuel-cell vehicles. In accordance Figure 2 shows a cross-sectional comparison of the with the trends in these automotive fields, there is conventional planar chip structure and the trench chip strong demand for the improved performance of power structure. MOSFETs which are used as the switching devices in A characteristic of the trench chip structure is a ECUs. concave structure fabricated at the gate by means of Fuji Electric has responded to the trend of in- precision controlled etching. This structure enables creased usage of electronic components and systems in the channel resistance component to be decreased, automobiles by developing and commercializing vari- which had been difficult to achieve with the conven- ous power MOSFETs. tional planar chip construction, and also drastically This paper will introduce the product line, features reduces the resistance component due to a JFET effect. and future development trends of Fuji Electric’s auto- Figure 3 shows a comparison of the ON-resistance motive power MOSFETs. components of a 60 V conventional planar chip and a trench chip. 2. Fuji Electric’s Product Line of Automotive Fuji Electric has optimized the trench shape, Power MOSFETs uniform gate oxidation layer and the polysilicon layer that forms the gate electrode to achieve gate reliability Table 1 lists Fuji Electric’s product line of automo- capable of maintaining a high gate voltage (VGS = 30 V) tive power MOSFETs and Fig. 1 shows the external simultaneously with low ON-resistance. appearance of those packages. As MOSFETs for (2) Optimization of the gate threshold voltage electric power steering ECUs, Fuji provides a 60 V The MOSFETs used in electric power steering product line for 12 V battery-use and provides a partial ECUs are selected based on their low ON-resistance lineup of 75 V products capable of supporting the characteristics, and because the chip design involves a upcoming changeover to 42 V power sources (36 V tradeoff between ON-resistance characteristics and battery voltage) in the future. Fuji also has a line of gate threshold voltage, MOSFETs having a low gate 100 to 200 V MOSFETs for use in the DC-DC converter threshold voltage of approximately 1 to 2 V are com- of hybrid vehicles and a line of 500 to 600 V MOSFETs monly used. However, a low gate threshold voltage is for use in the electronic ballast circuits for discharge susceptible to malfunction caused by noise and the

Automotive Power MOSFETs 53 Table 1 Fuji Electric’s product line of automotive power MOSFETs

Main product specification Targeted application Model number Remark such as ECUs VDSS ID RDS (on) (V) (A) (Ω) Package 2SK3270-01 60 80 6.5 m TO-220AB 2SK3271-01 60 100 6.5 m TO-3P 2SK3272-01L, S 60 80 6.5 m D2-Pack

ECUs for electric 2SK3273-01MR 60 70 6.5 m TO-220 full-mold power steering F1519 60 80 6.0 m D2-Pack Under development 2SK3730-01MR 75 70 8.5 m TO-220 full-mold 2SK3804-01S 75 70 8.5 m D2-Pack Under development F1515 75 80 8.5 m TO-247 Under development 2SK3644-01 100 30 44 m TO-220AB 2SK3645-01MR 100 30 44 m TO-220 full-mold 2SK3646-01L, S 100 30 44 m D2-Pack Hybrid electric vehicles, 2SK3590-01 150 40 41 m TO-220AB Electric vehicles, DC-DC converters, 2SK3591-01MR 150 40 41 m TO-220 full-mold Electronic ballast for 2SK3592-01L, S 150 40 41 m D2-Pack discharge bulbs (DC-DC converter/ 2SK3594-01 200 30 66 m TO-220AB inverter units) 2SK3595-01MR 200 30 66 m TO-220 full-mold 2SK3596-01L, S 200 30 66 m D2-Pack 2SK3504-01 500 14 0.46 TO-220AB 2SK3505-01MR 500 14 0.46 TO-220 full-mold 2SK3450-01 600 12 0.65 TO-220AB 2SK3451-01MR 600 12 0.65 TO-220 full-mold

Fig.1 External appearance of packages Fig.3 Comparison of the ON-resistance components of a 60 V conventional planar chip and a trench chip (60 V) [per unit area: Roná A]

Comparison of Ron·A components 120

100 Other D2-Pack 80 Channel 60 JFET TO-220 percentage (%) 40 A TO-220AB full-mold ·

on Epitaxial TO-3P R 20 Substrate 0 Planar chip structure Trench chip structure

Fig.2 Planar chip structure and trench chip structure

Gate oxide GateSource Source Gate like. Fuji Electric’s MOSFETs for electric power steer- n+ n+ n+ n+ n+ n+ p+ p+ p+ ing applications have an optimized gate threshold (RCH)(RCH)

(RCH) p p p ppvoltage of 3 V (typical value) and therefore the target (RJFET) circuitry can easily be configured to include anti-noise Gate oxide measures to prevent malfunction due to noise generat- Trench ed in the interconnects to gate peripheral circuitry. n- n- (3) Highly reliable package compatible with large + + n n currents Drain Drain An ECU system for electric power steering use as (a) Planar chip structure (b) Trench chip structure shown in Fig. 4 must have a highly reliable package capable of withstanding instantaneous large currents

54 Vol. 50 No. 2 FUJI ELECTRIC REVIEW due to: 1) a load short-circuit of the DC motor, 2) a present, in order to support the future transition to a short-circuit to ground in the wiring harness that 42 V power source (36 V battery), Fuji Electric also connects the DC motor and ECU, 3) an arm short- provides a 75 V product line. Table 2 shows the main circuit between upper and lower devices that comprise ratings and Table 3 shows the electrical characteristics of an H bridge or a 3-phase bridge, and so forth. of the 75 V product line. This product line is character- Figure 5 shows the internal structure of Fuji ized by a high voltage of 75 V and by low ON- Electric’s trench power MOSFET. When an electric resistance (8.5 mΩ maximum). power steering ECU operates at maximum torque (motor current of approximately 30 to 65 A), the large 3.2 Features of Fuji Electric’s MOSFETs for use in DC-DC current flow causes power loss to occur in the chip and converters and electronic ballast circuits is dissipated as thermal energy and an even larger Figure 6 shows a ballast device system for control- emission of thermal energy is dissipated in the lead ling a discharge bulb. 100 to 200 V MOSFETs are used wiring that connects to external pins. In consideration in DC-DC converters to boost the battery voltage and of the above problem, Fuji Electric has optimized the 500 to 600 V MOSFETs are used in inverter units to chip design by, (1) increasing the diameter of the generate a high voltage for a discharge bulb. A DC-DC internal connecting wire, and (2) by using multiple converter requires a MOSFET capable of high-frequen- internal connecting wires. cy switching operation in order to realize a compact Provided with the above features, Fuji Electric’s and lightweight step-up transformer, and an inverter electric power MOSFETs are being used in a wide requires a high-voltage and high-speed MOSFET capa- range of applications in addition to those listed above. ble of withstanding the high voltage during the bulb (4) 75 V MOSFET product line unloaded output state of approximately 380 V and the Although a battery voltage of 12 V is used at high dv/dt at the beginning of bulb discharge. In response to these requests, Fuji Electric provides the Fig.4 Equivalent circuit of electric power steering ECU system SuperFAP-G product line which has high speed and (3-phase motor control) low ON-resistance. This SuperFAP-G product line incorporates the new technology of a quasi-planar

Input battery voltage junction (QPJ) shown in Fig. 7 and achieves a high +VCC 3) Short-circuited- level of performance that is only 10 % less than the arm mode theoretical performance limit of silicon (Si). 1) Short-circuited- load mode Features of this product line are listed below (in comparison to the conventional 600 V product line. To drive Drive To each circuit circuit (1) 75 % decrease in turn-off loss gate (6 channels) 3-phase motor (2) 60 % decrease in gate charge (3) High avalanche withstand capability (4) Package product line that includes various surface 2) Short-circuited- to-ground mount packages Micro- mode By providing the above SuperFAP-G product line, computer – + Fuji Electric is able to supply MOSFETs that are ideally suited for DC-DC converter and electronic ballast applications.

Table 2 Main ratings of Fuji Electric’s 75 V automotive power MOSFET (T = 25°C) Fig.5 Internal structure of Fuji Electric’s trench power MOSFET C (surface mount type) Item Symbol Rating Unit Remark V 75 V Base frame Drain-source voltage DS VDSX 40 V VGS= -20 V Continuous drain ± ID 70 A Epoxy resin current ± Pulsed drain current IDP 280 A

Semiconductor Gate-source voltage VGS +30/-20 V chip Maximum avalanche L= 84.5 µH, EAV 443.8 mJ Lead wire energy VCC= 48 V Maximum power P 162 W Heat dissipation D generating Operating part T 175 °C temperature range ch Storage T -55 to +175 °C temperature range stg

Automotive Power MOSFETs 55 Table 3 Electrical characteristics of Fuji Electric’s 75 V Fig.6 Ballast device system automotive power MOSFET (TC = 25°C unless specified otherwise) Input (a) Static characteristics battery voltage +VCC Measurement Standard value DC-DC converter Inverter (bridge) Item Symbol Unit condition Min. Typ. Max.

Drain- ID = 1 mA BVDSS 75 – – V Starter/bulb source VGS = 0 V

breakdown ID = 1 mA BVDSX 40 – –V voltage VGS = – 20 V Gate ID = 10 mA threshold VGS (th) 2.5 3.0 3.5 V V = V voltage DS GS Zero gate ° µ VDS = 75 V Tch =25 C – 1.0 100 A voltage I DSS VGS = 0 V ° µ drain current Tch =125 C –10500 A Gate-source VGS = +30 /-20 leakage IGSS –10100 nA V = 0 V Fig.7 Chip structure of SuperFAP-G product line current DS Drain-source ID = 35 A ON-state RDS (on) – 6.4 8.5 mΩ Gate V = 10 V Source resistance GS (b) Dynamic characteristics

CGD Measurement Standard value n+ n+ n+ n+ n+ Item Symbol Unit condition + Min. Typ. Max. p p- p- p+ p- p- p+ p-

Forward ID = 35 A gfs 25 50 – S transconductance VDS = 10 V n- Input capacitance Ciss – 7,500 – VDS = 25 V Output capacitance Coss – 1,050 – VGS = 0 V pF Reverse transfer f = 1 MHz n+ Crss – 500 – capacitance t –50– Drain Turn-on time d (on) V = 38 V cc (a) Conventional power MOSFET tr V = 10 V –90– GS ns ID = 70 A td (off) – 150 – Turn-off time R = 10 Ω Gate G Source tf –90–

Total gate chargeQg – 150 – Vcc = 38 V Gate-source charge Q I = 70 A –30–nC C GD gs D + + + + + + + + + + + + V = 10 V n p+ n n p+ n n p+ n n p+ n n p+ n n p+ n GS ------Gate-drain chargeQgd – 45 – p p p p p p (c) Parasitic diode characteristics n- Measurement Standard value Item Symbol Unit condition Min. Typ. Max. n+ Avalanche L = 84.5 µH withstand I 70 – A AV T = 25°C – Drain capability ch (b) SuperFAP-G Diode IF = 75 A forward VSD VGS = 0 V – 1.3 1.65 V ° ON-voltage Tch = 25 C

Reverse IF = 35 A trr – 95 –ns recovery time VGS = 0 V -di /dt = 100 A/µs 4. Future Development Trends Reverse Q T = 25°C – – µC recovery charge rr ch 0.30 In addition to Fuji Electric’s existing 60 V product (d) Thermal characteristics line that has a track record of successful use in electric Measurement Standard value Item Symbol Unit power steering application and the new 75 V product condition Min. Typ. Max. line, we are also endeavoring to develop high perfor- ° Thermal Rth (ch-c) – – 0.926 C/W mance products that utilize next generation technolo- resistance ° Rth (ch-a) – – 75.0 C/W gy. The design goals for these high performance prod- ucts, for which development and commercialization being advanced, are listed below. (1) Product voltage VDS: 60 V, 75 V

56 Vol. 50 No. 2 FUJI ELECTRIC REVIEW Fig.8 Comparison of switching characteristics (gate charge) of Fig.9 Comparison of loss generated by a conventional 60 V a conventional 60 V MOSFET and a new high-perfor- MOSFET and a new high-performance 60 V MOSFET mance 60 V MOSFET (simulated results)

Measurement conditions ( VDS = 30 V, ID = 80 A, VGS = 10 V)

Measurement conditions ( ID = 80 A, VDS = 30 V, VGS = 10 V, Ω Conventional MOSFET High-performance MOSFET Rg = 100 , fC = 20 kHz, Duty = 50 %) 40 VDS VGS

31.4 W

ID 30 26.0 W

00 Turn-off loss 20 22.1 W V : 5 V/div Sample Qg (nC) Qgs (nC) Qgd (nC) DS 18.2 W ID : 20 A/div Conventional Total loss (W) 126 38 37 VGS : 2 V/div MOSFET T : 2 µs/div 10 ON-state High-performance 4.0 W 88 32 22 loss 4.0 W MOSFET Turn-on 5.3 W loss 3.8 W 0 Conventional MOSFET High-performance MOSFET

(2) Rated current ID: 70 to 80 A (3) Gate threshold voltage: 2.5 to 3.5 V improve the various main specifications and to en- (4) ON-resistance, Ron · A: 20 % less than conventional hance performance, higher performance can be products achieved not only as a MOSFET for electric power (5) Input capacitance Ciss: 30 % less than convention- steering applications, but by developing other product al products lines, higher performance can be achieved for addition- (6) Package lineup: Stand-alone packages (as typified al applications as well. by the TO-220) and surface mount packages Figure 8 shows a comparison of the switching 5. Conclusion waveforms (gate charge) for a 60 V engineering sample of a product presently under development and a Fuji Electric has developed and commercialized conventional MOSFET and Fig. 9 compares the results various automotive power MOSFETs including those of a simulation of loss generation for these two devices described herein. We are committed to continue assuming use as in an electric power steering applica- developing and providing distinctive products to satisfy tion and a carrier frequency of 20 kHz. the needs for electronic parts and systems and to According to these comparative results, an approxi- expand the field of automotive electronics. mate 40 % improvement in gate charge quantity (Qg), effective in reducing loss during gate driving, and an Reference approximate 18 % in loss generation at 20 kHz are (1) Yamazaki, T. et al. Low Qgd Trench Power MOSFETs achieved. with Robust Gate for Automotive Applications. Based on the above results, by endeavoring to PCIM2003.

Automotive Power MOSFETs 57