U-series of IGBT-IPMs (600 V) Kiyoshi Sekigawa Hiroshi Endo Hiroki Wakimoto 1. Introduction and thin wafer processing technology to develop an RIPM3 series that realizes low conduction loss. With the goal of reducing loss even further, Fuji Electric has developed an IGBT device that employs a trench NPT structure to realize lower conduction loss and has developed a new free wheeling diode (FWD) structure to improve the tradeoff between switching noise and loss. Both of these technologies are incorporated into Fuji Electric's newly developed U-series IGBT-IPM (U-IPM) which is introduced below. Intelligent power modules (IPMs) are intelligent power devices that incorporate drive circuits, protection circuits or other functionality into a modular configuration. IPMs are widely used in motor driving (general purpose inverter, servo, air conditioning, elevator, etc.) and power supply (UPS, PV, etc.) applications. The equipment that uses these IPMs are required to have small size, high efficiency, low noise, long service life and high reliability. In response to these requirements, in 1997, Fuji Electric developed the industry's first internal overheat protection function for insulated gate bipolar transistors (IGBTs) and developed an R-IPM series that achieved high reliability by employing an allsilicon construction that enabled a reduction in the number of components used. Then in 2002, Fuji Electric changed the structure of its IGBT chips from the punch through (PT) structure, which had been in use previously, to a non-punch through (NPT) structure, for which lifetime control is unnecessary, in order to realize lower turn-off loss at high temperature, and also established finer planar gate 2. U-IPM Development Concepts and Product Line-up The concepts behind the development of the U-IPM are listed below. (1) Realization of lower loss Lower loss can be realized by developing new power elements and optimizing the drive performance. Increasing the carrier frequency of the equipment contributes to improved control performance. Also, larger output can be obtained from the equipment during the operation at the same carrier frequency. (2) Continued use of the same package as prior products Table 1 Product line-up, characteristics and internal functions of the U-IPM series Inverter part No. of elements 6 in 1 7 in 1 Model VDC (V) VCES (V) IC (A) PC (W) Brake part IC (A) PC (W) Internal function Both upper and lower arms Upper arm Lower arm Dr OC ALM OC ALM TcOH None None UV TjOH 6MBP 20RUA060 20 84 - - Yes Yes Yes 6MBP 50RUA060 50 176 - - Yes Yes Yes 6MBP 80RUA060 450 600 Yes Package type Yes Yes None P619 None Yes Yes Yes P610 80 283 - - Yes Yes Yes Yes None Yes Yes Yes P610 6MBP100RUA060 100 360 - - Yes Yes Yes Yes None Yes Yes Yes P611 6MBP160RUA060 160 431 - - Yes Yes Yes Yes None Yes Yes Yes P611 7MBP 50RUA060 50 176 30 120 Yes Yes Yes Yes None Yes Yes Yes P610 7MBP 80RUA060 7MBP100RUA060 7MBP160RUA060 450 600 80 283 50 176 Yes Yes Yes Yes None Yes Yes Yes P610 100 360 50 176 Yes Yes Yes Yes None Yes Yes Yes P611 160 431 50 176 Yes Yes Yes Yes None Yes Yes Yes P611 Dr: IGBT driving circuit, UV : Under voltage lockout for control circuit, TjOH: Device overheat protection, OC: Over-current protection, ALM: Alarm output, TcOH: Case temperature over-heat protection *6MBP20RUA060 uses a shunt resistance-based over-current detection method at the N line. 48 Vol. 51 No. 2 FUJI ELECTRIC REVIEW Fig.1 External view of U-IPM packages Table 2 Changes in IGBT technology IGBT technology Wafer Wafer thickness P610 P619 R-IPM R-IPM3 N-IGBT T-IGBT U-IPM U-IGBT Epitaxial FZ 350 m 100 m PT NPT Structure Gate structure Planar Lifetime control Yes Trench Carrier injection High Low Transportation factor Low High None P611 Fig.3 Change in cross-sectional structure of 600 V IGBT chip Fig.2 Comparison of planar IGBT and trench IGBT chip cross sections G E n+ V-pn p+ layer (a) Planar IGBT n+ source Gate oxide layer n- silicon substrate Collector electrode pchannel p+ substrate n- n- p p C R-IPM3 Planar NPT structure thinner surface C U-IPM Trench NPT structure C R-IPM Planar PT structure (b) Trench IGBT The continued use of the same package as with prior products makes it possible to improve equipment performance by replacing the IPM without having to modify the design of the equipment. Table 1 lists the product line-up, characteristics and internal functions of Fuji Electric's 600 V U-IPM series. The U-IPM series maintains internal functions and a package size that are interchangeable with the R-IPM series; its rated current is 20 to 160 A for the "6 in 1" pack and 50 to 160 A for the "7 in 1" pack (containing an internal IGBT for braking use). Figure 1 shows an external view of the packages. 3. Characteristics of the Power Devices A fifth-generation U-series IGBT (U-IGBT) is used as the power device. This U-IGBT combines trench gate technology with a basic design comprising Fuji Electric's floating zone (FZ) wafer technology, thin wafer processing technology, carrier injection control technology, and transportation factor improving technology. Figure 2 compares the structures of the conventional planar IGBT and the trench IGBT. The adoption of U-series of IGBT-IPMs (600 V) n+ n+ buffer V-pn R-drift R-acc R-ch R-acc n+ source R-drift R-JFET pchannel GE n- Emitter electrode Insulation layer Gate electrode R-ch p G E a trench gate structure results in a smaller voltage drop at the channel (R-ch) due to increased surface cell density and results in a lower saturation voltage due to the smaller voltage drop resulting from the elimination of the planar device's characteristic JFET region (RJFET). Moreover, short circuit immunity capability is realized through optimization of the design of the surface structure. Figure 3 illustrates the changes that have occurred in the cross-sectional IGBT structure in the transition from the conventional IGBT to the UIGBT, and Table 2 compares their applied technologies. The FWD, in accordance with the U-IGBT, incorporates a new design featuring optimized wafer specification, control of anode-side injection and optimal lifetime control technology to realize the characteristics of low peak current during reverse recovery operation, low generated loss, and soft recovery. 4. U-IPM Loss 4.1 Comparison of total loss The marketplace requires that new IPM products achieve lower levels of loss. (1) Increased carrier frequency to enhance controllability and (2) larger output current at the same carrier frequency are necessary for the achievement of the goal. The loss 49 Fig.4 Comparison of total loss (at same current) for the U-IPM, R-IPM3 and R-IPM series 100 Total loss (W) 80 Tj = 125C, Ed = 300 V VCC = 15 V, Io = 50 Arms Power factor = 0.85, =1 R-IPM : 6MBP150RA060 R-IPM3 : 6MBP150RTB060 U-IPM : 6MBP160RUA060 88.79 5.37 4.12 71.67 Prr Pf Poff Pon Psat 60 6.38 27.9 59.80 3.89 2.68 4.12 12.1 45.50 1.34 4.12 40 14.0 40.55 1.59 3.90 3.03 7.01 6.13 3.18 3.90 1.22 3.89 3.85 12.3 4.89 3.89 44.57 15.3 2.44 3.89 6.04 35.37 5.76 50.90 63.08 24.7 23.2 7.68 11.6 17.0 8.46 4.21 20 0 26.9 26.3 R-IPM R-IPM3 fc = 4 kHz 26.7 26.2 R-IPM R-IPM3 fc = 8 kHz 22.2 U-IPM Fig.5 Current vs. total loss (at same frequency) for U-IPM, RIPM3 and R-IPM 22.1 U-IPM 26.7 26.1 R-IPM R-IPM3 fc = 16 kHz 22.0 U-IPM Fig.6 I C -VCE characteristics for U-IPM, R-IPM3 and R-IPM 150 Tj = 125C, VCC = 15 V VCE (sat) at IPM pin Tj = 125C, Ed = 300 V fc = 4 kHz, Vcc = 15 V Power factor = 0.85, =1 R-IPM : 6MBP150RA060 R-IPM3 : 6MBP150RTB060 U-IPM : 6MBP160RUA060 100 R-IPM R-IPM R-IPM3 100 R-IPM3 U-IPM Ic (A) Total loss (W) 150 U-IPM 50 50 53 A 58 A 66 A 0 0 0 20 40 60 Io (Arms) 80 100 120 generated by existing models and by the U-IPM is described below. Figure 4 compares the loss of the U-IPM and the existing R-IPM and R-IPM3 devices in the case of operation at carrier frequencies of 4, 8 and 16 kHz, and a current of 50 Arms (1 /3 of the rated current). As can be seen in the figure, the newly developed U-IPM realizes a total loss that is approximately 22 to 28 % lower than that of the R-IPM and approximately 11 to 12 % lower than that of the R-IPM3. In particular, it can be seen that the loss generated when using the UIPM at a carrier frequency of 8 kHz is less than the 50 0 0.5 1 1.5 2 VCE (sat) (V) 2.5 3 3.5 loss generated by a R-IPM operating at a carrier frequency of 4 kHz, and therefore, the carrier frequency can be increased from 4 kHz to 8 kHz by replacing a R-IPM with a U-IPM of the same size package. Moreover, according to Fig. 5 which shows the relationship between current and total loss at fc = 4 kHz, to generate the same amount of loss (50 W) as the R-IPM, the output current of the U-IPM can be increased by 24.5 % compared to that of the R-IPM, or increased by 13.7 % compared to that of the R-IPM3. These techniques for reducing loss were focused on reducing the conduction loss, which accounts for more than 50 % of the total loss, and on reducing the turn-on Vol. 51 No. 2 FUJI ELECTRIC REVIEW Fig.7 Characteristics of turn-on waveform and emission noise Fig.8 Emission noise Emission noise level (dBV/m) Measurement conditions: Distance between servo amplifier and antenna is 2 m, vertical direction, standby state 100 VGE VCE IC Low noise 50 Low loss 30 t1 t2 80 Frequency (MHz) 130 (a) R-IPM3 (150RTB) t1 : Time from IC = 0 until IC = ICP t2 : Time from IC = ICP until VCE = 0 low emission noise low loss Table 3 Characteristics of gate resistance and turn-on waveform Turn-on di/dt High Gate resistance RG Low Turn-on dv/dt Loss Emission noise Low Low Increases Decreases High High Decreases Increases Emission noise level (dBV/m) di/dt is small and t1 is long dv/dt is large and t2 is short 100 50 30 80 Frequency (MHz) 130 (b) U-IPM (160RUA) loss, which accounts for a large percentage of the switching loss of the R-IPM3. Each type of loss reduction is described below. 4.2 Reduction of conduction loss Figure 6 shows IC-VCE(sat) characteristics for UIPM, R-IPM3 and R-IPM devices. It can be seen that when IC = 150 A, the VCE(sat) of the U-IPM is 0.45 V less than that of the R-IPM and 0.55 V less than that of the I-RPM3. This is the VCE(sat) reduction effect due to the trench IGBT described in chapter 3. 4.3 Turn-on loss and emission noise Figure 7 shows a schematic drawing of the current ( IC) and voltage (VCE) at the time when the device is turned on. As can be seen in the figure, typically, loss can be reduced by making dv/dt larger and emission noise can be reduced by making di/dt smaller. However, in the case where turn-on operation is controlled by the typical method of gate resistance only, there is a tradeoff relation as shown in Table 3, and it is difficult to establish both high dv/dt and low di/dt simultaneously. In the newly developed U-IPM, the following two techniques suppress the emission noise that usually increases when gate resistance is decreased and di/dt is increased, thereby enabling di/dt to be increased and turn-on loss to be decreased without any increase in U-series of IGBT-IPMs (600 V) the emission noise. (1) Application of the new soft recovery FWD suppresses dv/dt. (2) The capacitance between the gate and emitter is optimized in order to reduce di /dt, which increased as a result of the lower gate resistance, without reducing dv/dt Through application of the above techniques, even if currents of all sizes are controlled with the same gate resistance, emission noise will be maintained at the same level as that of the R-IPM3 as shown in Fig. 8, and lower loss can be realized. Accordingly, the total loss generated in all these products is linearly proportional to the current, and the total loss and temperature rise that occur during actual use can easily be estimated. 5. Conclusion Fuji Electric's 600 V U-IPM that uses a U-series IGBT chip having a trench NPT structure has been described above. This U-IPM provides suitable performance to satisfy the marketplace in which lower loss is required. In the future, Fuji Electric intends to continue to develop new IPMs that will satisfy market requirements. 51