Trench Insulated Gate Bipolar Transistor Research Articles

Grid-patterned trench insulated gate bipolar transistor for 1.2 kV hybrid/plug-in hybrid electric vehicle silicon power devices

This paper reports on the newly developed silicon insulated gate bipolar transistor (IGBT) for Toyota’s fifth generation power devices. The designed IGBTs with a grid-patterned trench provide a lower on-state voltage (V ON ) while maintaining a wide mesa width. A successful 15% reduction of V ON was accomplished by enhancement of the two-dimensional hole storage effect. Furthermore, the grid-patterned trench IGBT merged with Schottky and multi-layered anode technology demonstrated a significant improvement in the trade-off curve between the reverse recovery current (I rr ) and V ON in a reverse conducting IGBT without a lifetime control process. As a result, the grid-patterned trench IGBT has contributed to reduce power loss and volume in the new power control units.

Simulation study on total ionizing dose effect of IGBT gamma irradiation

The insulated gate bipolar transistor (IGBT) has emerged as a prominent high-power semiconductor device due to its excellent overall performance. It is widely utilized in various fields, including aerospace. Due to prolonged operation in complex irradiation environments, the performance of IGBTs is susceptible to degradation and damage. Therefore, conducting research on the variation of IGBT characteristics under irradiation environments is crucial to ensuring their long-term functionality in extended space missions. To evaluate and analyze the total ionizing dose (TID) effect of IGBTs during operation, this study adopts a trench IGBT as the device model. Utilizing the finite element method, technology computer-aided design (TCAD) is employed to simulate and analyze the electrical characteristic changes of IGBTs under different total radiation doses. The simulation results are subsequently validated through theoretical analysis. The simulation results indicate that gamma radiation significantly affects the overall electrical characteristics of IGBTs.

Improving dynamic characteristics for IGBTs by using interleaved trench gate

A novel trench insulated gate bipolar transistor (IGBT) with improved dynamic characteristics is proposed and investigated. The poly gate and poly emitter of the proposed IGBT are arranged alternately along the trench. A self-biased p-MOSFET is formed on the emitter side. Owing to this unique three-dimensional (3D) trench architecture, both the turn-off characteristic and the turn-on characteristic can be greatly improved. At the turn-off moment, the maximum electric field and impact ionization rate of the proposed IGBT decrease and the dynamic avalanche (DA) is suppressed. Comparing with the carrier-stored trench gate bipolar transistor (CSTBT), the turn-off loss (E off) of the proposed IGBT also decreases by 31% at the same ON-state voltage. At the turn-on moment, the built-in p-MOSFET reduces the reverse displacement current (I G_dis), which is conducive to lowing dI C/dt. As a result, compared with the CSTBT with the same turn-on loss (E on), at I C = 20 A/cm2, the proposed IGBT decreases by 35% of collector surge current (I surge) and 52% of dI C/dt.

3-D Segmented Gate Concept: A New IGBT Solution for Reduced Loss and Improved Safe-Operating Area

In this article, the “segmented gate (SG)” concept is proposed and implemented in trench gate to realize both low loss and wide safe-operating area (SOA) for insulated-gate bipolar transistors (IGBTs). The poly gate of the proposed IGBT is split into segments along the trench and each segmented poly gate is surrounded by the poly emitter. This unique 3-D trench architecture is demonstrated under numerical studies to be highly effective in enhancing the short-circuit ruggedness, the turn-off capability, and the latch-up immunity. It enables a 37% reduction in saturation current and a 90% reduction in Miller capacitance. The proposed design also shows an improved trade-off relationship between ON-state voltage and turn-off loss. For the same turn-off loss, the ON-state voltage of the proposed IGBT is reduced by 0.25 V when compared with the conventional carrier-stored trench IGBT.

Improvement Breakdown Voltage by a Using Crown-Shaped Gate

In this paper, a crown-shaped trench gate formed by a sidewall spacer in insulated gate bipolar transistors (IGBT) is proposed to improve breakdown voltage. When a sidewall spacer is added to trench bottom corners, the electric field is distributed to the surface of the sidewall spacer and decreased to 48% peak value of the electric field. Thus, the sidewall spacer IGBT improved to 5% breakdown voltage. Another study proposed an additional oxide layer for trench bottom corners and improved breakdown voltage similar to the proposed IGBT. Previous studies have shown degradation in other electrical characteristics. However, this study shows a sidewall spacer IGBT that increases the current over 3% compared to a conventional trench IGBT when the applied gate voltage is under 4 V. Additionally, the turn-off loss characteristic is similar to conventional trench IGBT. Therefore, the breakdown voltage of the IGBT was improved while maintaining similar electrical properties to existing IGBTs through the crown-shaped gate.

1.2 kV Stepped Oxide Trench Insulated Gate Bipolar Transistor with Low Loss for Fast Switching Application

In this article, a gate engineering technique is used in Insulated gate bipolar transistor (IGBT) for fast switching applications. The modification consists of stepped oxide pattern at gate terminal with n-poly layer sandwiched between two p-poly layers. The oxide thickness increases from top to bottom so as to create a stepped structure. The oxide thickness is lesser on channel side and higher on collector side. The less thickness beside the channel increases gate to emitter charges (QGE) by extracting extra charges along the channel. The presence of these extra charges also increases the collector current density resulting reduction in the area specific on-resistance (Ron.A). On the other hand, the higher thickness at the bottom side of gate offers reduction in gate to collector charges (QGC). Furthermore, to elongate the impact of QGC reduction, the low doped p-col region has been facilitated which also play an important role to increase the breakdown voltage by reducing corner electric field. This p-col region creates charge extraction path to swept out charges from the drift region while turn-off event and makes the device to turn-off quickly. The collective improvement in QGE and QGC provides fast switching to the proposed device by improving turn-off time by 63% and also reduces turn-off loss (Eoff) by 55% as compared to the conventional device. Furthermore, the change in the workfunction also provides the reduction of channel peak electric field and offers 10% increment in the BV as compared to the conventional IGBT.

A 4H-SiC trench IGBT with controllable hole-extracting path for low loss

A novel 4H-SiC trench insulated gate bipolar transistor (IGBT) with a controllable hole-extracting (CHE) path is proposed and investigated in this paper. The CHE path is controlled by metal semiconductor gate (MES gate) and metal oxide semiconductor gate (MOS gate) in the p-shield region. The grounded p-shield region can significantly suppress the high electric field around gate oxide in SiC devices, but it weakens the conductivity modulation in the SiC trench IGBT by rapidly sweeping out holes. This effect can be eliminated by introducing the CHE path. The CHE path is pinched off by the high gate bias voltage at on-state to maintain high conductivity modulation and obtain a comparatively low on-state voltage (V ON). During the turn-off transient, the CHE path is formed, which contributes to a decreased turn-off loss (E OFF). Based on numerical simulation, the E OFF of the proposed IGBT is reduced by 89% compared with the conventional IGBT at the same V ON and the V ON of the proposed IGBT is reduced by 50% compared to the grounded p-shield IGBT at the same E OFF. In addition, the average power reduction for the proposed device can be 51.0% to 81.7% and 58.2% to 72.1% with its counterparts at a wide frequency range of 500 Hz to 10 kHz, revealing a great improvement of frequency characteristics.

Application of SiGe layer for reinforcing conductivity modulation in trench insulated gate bipolar transistor

In this work, an investigation for inserting a SiGe layer in an insulated-gate bipolar transistor (IGBT) has been performed to analyze the relation between on-state property and breakdown voltage (BV) with the help of technology computer-aided design simulation. For a carrier storage (CS) IGBT, which is widely studied for enhancing conductivity modulation by increasing hole density, the BV decreases by increased conductivity in the CS layer. However, by using the SiGe layer instead of the CS layer, the on-state property is improved with lower BV reduction than a CS IGBT due to the absence of impurity doping. Finally, an optimization for a Ge mole fraction is performed. Based on the results, it is found that the SiGe with 0.3 mole fraction shows the best performance because over 0.3 Ge mole fraction, the excessive energy band bending induced by over-accumulated holes makes low carrier velocity in the n-drift layer.

A novel 3300 V trench IGBT with P-N-doped polysilicon split gate for low EMI noise

A novel 3300 V trench insulated gate bipolar transistor (IGBT) with p-n-doped polysilicon split gate (PNSG-IGBT) is proposed for low electromagnetic interference noise. The reverse-biased polysilicon PN junction is laterally depleted and charged by displacement current during the turn-off transient, which raises electrostatic potential in n-region of the polysilicon PN junction (V N) and electrostatic potential under the gate oxide (V ACC) simultaneously. By technology computer aided design simulation, during the turn-on transient, the maximum dV ACC /dt is 57.1% lower than that of the split gate (SG)-IGBT with the same R G and the excess V GE overshoot caused by reverse displacement current is effectively suppressed. Moreover, for the same E ON, the maximum reverse recovery dV KA /dt of the freewheeling diode can be reduced by 77.3% and 30.7% compared with that of the floating P region-IGBT and the SG-IGBT respectively, which is of great merit in suppressing dV/dt noise. Consequently, the PNSG-IGBT shows less common-mode noise at high frequency, especially in the range of 20–40 MHz.

Investigation and improvement of single-event burn-out in 4H-SiC trench insulated gate bipolar transistors

In this paper, the triggering process for single-event burnout (SEB) in conventional 4H-SiC trench insulated gate bipolar transistors (C-TIGBTs) is described. Furthermore, SEB is studied for both a conventional structure and a new structure. The new structure has a Schottky contact at the collector side (S-TIGBT) and is investigated using a 2D numerical-simulation. The simulation results indicate that the Schottky-junction improves the SEB threshold voltage from 4000 V, in the C-TIGBT, to 4600 V, in the S-TIGBT, while the SEB-induced breakdown voltage for 75 MeV/(mg⋅cm−2) is improved by about 15.0%.

A low-loss variable-doped trench-insulated gate bipolar transistor with reduced on-state voltage

The performance of a superjunction trench-insulated gate bipolar transistor with variable vertical doping in the epitaxial region along with variation in the collector layer is investigated. The concept of vertical variation transfers the avalanche multiplication point from the epitaxial edges to the middle of the pillar. The proposed device offers increased effective doping in the drift region, which reduces the on-state voltage () without any degradation in the breakdown voltage. Furthermore, the horizontal doping variation in the collector layer supports the phenomenon in two ways: the left section of the collector layer reduces whereas the right portion enables an efficient discharging path, which allows improved switching performance. In addition to this, a reduction in the gate to collector charge () is observed because of the presence of a lightly doped n-region below the gate terminal. A two-dimensional numerical simulation revealed that the proposed device offers a 15.30% reduction in compared with the conventional device. The structural modification offers a 40% reduction in turn-off time, resulting in a reduction in turn-off energy loss ().

Experimental investigation on the single event gate rupture and hardening of the 600 V trench IGBT

In this paper, a single particle irradiation experiment is performed on the 600 V trench insulated gate bipolar transistor for the first time. The experimental results show that, at the collector voltages of 100 V and 300 V, single event gate rupture occurs in the device under the linear energy transfer of 81.35 MeV cm2/g. The damage occurs in the gate oxide layer near the bottom of the trench gate. The simulation results show that the holes accumulated at the bottom of the trench gate increase the electric field under irradiation, which causes the failure of the gate oxide. Furthermore, the hardening device structure is proposed by increasing the thickness of the bottom gate oxide.

A split-gate trench IGBT with low Miller capacitance and dV/dt noise

A novel trench insulated gate bipolar transistor (IGBT) with a split-gate structure is proposed herein, where the polysilicon electrode in the trench is divided into two parts and insulated by the polysilicon oxide, thus decreasing the overlap between the gate electrode and n-drift region. Due to this split-gate structure, much lower Miller capacitance can be achieved. The performance of the proposed split-gate IGBT device, in particular the turn-on dV/dt controllability, is discussed. The simulation results show that the proposed split-gate IGBT can achieve a much better tradeoff between the maximum reverse-recovery dVKA/dt of the free-wheeling diode and the turn-on loss (Eon) of the IGBT compared with the conventional IGBT design. The reverse-recovery dVKA/dt can be decreased by 56% at the same Eon as in the IGBT. Moreover, a feasible manufacturing process for the split-gate structure is proposed.

High voltage trench insulated gate bipolar transistor with MOS structure for self-adjustable hole extraction

In this letter, a novel high voltage trench insulated gate bipolar transistor (IGBT) with MOS structure for self-adjustable hole extraction (MOS-SH-IGBT) is proposed. It features the adjustable hole path (AHP) region controlled by the MOS structure. The AHP region stores holes during on-state, extracts holes swiftly to reduce switching loss during turn-off and provides an extra hole path to avoid latch-up during short-circuit. Because of shielding effects of the AHP region, MOS-SH-IGBT could also increase breakdown voltage (BV) and decrease Miller capacitance. Based on simulated results, the BV of the proposed device is increased by 10% compared with the conventional separate floating P-base IGBT. Furthermore, the Miller capacitance and switching loss of MOS-SH-IGBT are decreased by 64% and 29%, respectively. As for the same E on of 117.3mJ cm−2, the dIce/dt of the MOS-SH-IGBT is decreased by 38.7%, and for the same E off of 64.1mJ cm−2, the |dIce/dt| is decreased by 23.4%, which realizes lower EMI noise.

Turn-OFF dV/dt Controllability in 1.2-kV MOS-Bipolar Devices

Turn- off dV/dt controllability is an essential feature in insulated gate bipolar transistors (IGBTs) for flexible design in power switching applications. However, the occurrence of dynamic avalanche (DA) during the turn- off transients plays a key role on the turn- off power loss, dV/dt controllability and safe operating area of IGBTs. This article aims to clarify the impact of DA on the turn- off characteristics of 1.2-kV trench IGBTs through three-dimensional technology computer aided design (TCAD) simulations as well as experimental demonstrations. Measurement results show that DA is enhanced at high current density and high supply voltage conditions, which aggravates its influence on the dV/dt controllability as well as turn- off power loss. To eliminate the DA for high current density and low loss operations, a DA free design is experimentally demonstrated in the Trench Clustered IGBT (TCIGBT). Due to effective management of electric field and unique p-channel metal oxide semiconductor (PMOS) actions during turn- off, TCIGBT can retain high dV/dt controllability and low power loss at high current density operations.

Exploring SiC Planar IGBTs towards Enhanced Conductivity Modulation Comparable to SiC Trench IGBTs

The state-of-the-art silicon insulated-gate bipolar transistor (IGBT) features a trench gate, since it enhances the conductivity modulation. The SiC trench IGBT, however, faces the critical challenge of a high electric field in the gate oxide, which is a crucial threat to the device’s reliability. In this work, we explore the possibility of using a SiC planar IGBT structure to approach high performance to the level of a SiC trench IGBT, without suffering the high gate oxide field. The proposed SiC planar IGBT features buried p-layers directly under the p-bodies, and thus can be formed using the same mask set. The region between the buried p-layer and the p-body is heavily doped with n-type dopants so that the conductivity modulation is improved. Comprehensive TCAD simulations have been carried out to verify this concept, and the simulation results show the new SiC planar IGBT exhibits a high performance comparable to the trench IGBT, and also exhibits a low gate oxide field.

Simulation Study of 4H-SiC Trench Insulated Gate Bipolar Transistor with Low Turn-Off Loss.

In this work, an insulated gate bipolar transistor (IGBT) is proposed that introduces a portion of the p-polySi/p-SiC heterojunction on the collector side to reduce the tail current during device turn-offs. By adjusting the doping concentration on both sides of the heterojunction, the turn-off loss is further reduced without sacrificing other characteristics of the device. The electrical characteristics of the device were simulated through the Silvaco ATLAS 2D simulation tool and compared with the traditional structure to verify the design idea. The simulation results show that, compared with the traditional structure, the turn-off loss of the proposed structure was reduced by 58.4%, the breakdown voltage increased by 13.3%, and the forward characteristics sacrificed 8.3%.

An Ultralow Loss Insulated Gate Bipolar Transistor With Emitter Dual Injection

A novel trench insulated gate bipolar transistor (IGBT) with emitter dual injection (EDI-IGBT) is proposed and investigated. The device features the hybrid gate electrode and the tiny P-base. The hybrid gate is a combination of the conventional trench gate (TG) and the accumulation gate (AG). The TG contacts the P-base region and the N-drift region, while the AG contacts the N-drift region only. In the ON-state, the accumulation layer formed by the AG makes an additional accumulation injection in the emitter side, leading to the EDI phenomenon, and hence a low forward voltage drop ( ${V}_{ \mathrm{\scriptscriptstyle ON}}$ ). Simultaneously, the tiny P-base region reduces holes extracted by the reverse-biased p-base/n-drift junction, which also contributes to the reduction in ${V}_{ \mathrm{\scriptscriptstyle ON}}$ . The simulation results show that the EDI-IGBT delivers comparable breakdown voltage and safe operating area (SOA) while featuring a 28% lower ${V}_{ \mathrm{\scriptscriptstyle ON}}$ , resulting in a reduction in total energy loss. Moreover, the existence of the AG suppresses the gate self-charging effect during the turn-on transient, leading to an improved turn-on performance. The excellent device performance, coupled with industry-standard IGBT-compatible fabrication process, makes the proposed EDI-IGBT a promising candidate for power switching applications.

Modeling of Large Area Trench IGBTs: The Effect of Birds-Beak

Three-dimensional (3-D) modeling is becoming an increasingly prevalent technique to model more complex device structures. However, this alone is insufficient to accurately model large area devices. This study images the birds-beak in a commercial insulated gate bipolar transistor (IGBT) and highlights how this processing uncertainty, which impacts the channel properties, has a strong effect on the accuracy of technology computer-aided design (TCAD) simulations; resulting in the designer struggling to validate models and underappreciating the true behavior of the device. It has been demonstrated that the birds-beak effect can be accounted for by a simple two-device model which allows for small-scale and large-scale device behaviors to be matched while limiting the computational effort for designers. The practical effects of birds-beaking on device performance have also been considered, and it has been shown that the variation in threshold voltage across the chip area results in a 32% reduction in short-circuit endurance time for the device. To overcome this, an alternative n+ emitter implantation is proposed, using a combination of arsenic and phosphorus, so that the device threshold is unaffected by the presence of birds-beaking and its variation during processing.

Simulation Study of a Low ON-State Voltage and Saturation Current TCIGBT With Diodes

In this brief, a novel trench clustered insulated gate bipolar transistor (TCIGBT) is proposed and investigated by the simulation. In comparison with the conventional TCIGBT, the p-well region is connected to the cathode through two integrated series diodes and a field stop structure is utilized. In the blocking state, the anode voltage is sustained by the p-well/n-drift junction, which makes the breakdown voltage (BV) independent on the dose of n-layer region, eliminating the contradictionbetween theBV and ON-state voltage appearing in the conventional trench insulated gate bipolar transistor (TIGBT). Accordingly, the ON-state voltage can be reduced by increasing the dose of n-layer region. In the ON-state, the electron quasi-Fermi potential of intrinsic drain is clamped at approximately 0.7 V, so that the saturation current is effectively decreased. The results from TCAD simulation indicate that under the same level of BV of the conventional TIGBT the ON-state voltage and saturation current of the proposed device are decreased by 33.6% and 66.6%, respectively. Moreover, a better tradeoff between the turnoff energy loss and ON-state voltage is achieved, i.e., with the same ON-state voltage of 1.29 V, the proposed device shows an improvement of 51.9% in turn-off energy loss.