KR20100085508A - Trench insulated gate bipolar trangistor - Google Patents

Abstract

PURPOSE: A vertical gate type bipolar transistor with an electric field dispersion effect is provided to improve a breakdown voltage by inducing a part of electric field, which is concentrated to the edge of a gate, toward a junction part. CONSTITUTION: Hole-injection efficiency toward an N-type drift layer is maximized by isolating a P-type positive collector in a trench insulated gate bipolar transistor(TIGBT) structure using an oxide film. A P-type base(26) is formed between gates(29) in the TIGBT structure. A part of electric field, which is concentrated toward the gates, is induced toward a junction part. The flow of holes is improved in a turn-off operation.

Description

Vertical Insulated Gate Bipolar Trangistor with Field Dispersion Effect

Recently, with the rapid development of the IT industry, the energy efficiency problem has emerged, the power industry is becoming more important. It is clear that the power industry is a semiconductor technology centered on silicon. Therefore, IGBT is a power switching device that combines the advantages of MOSFET and BJT. It can overcome the problems of BJT's complex current control circuit, slow switching speed, low breakdown and poor current control capability of MOSFET. It is attracting attention as an alternative element. However, in the case of the horizontal gate IGBT (FIG. 2), the IGBT has many problems that need to be improved such as a forward voltage drop caused by the JFET 10 region and a time delay caused by hole current during turn-off. Unlike the horizontal gate IGBT (FIG. 2), the vertical gate IGBT (FIG. 3) has no JFET 10 region, so that a lower forward voltage drop can be obtained, in particular, the unit cell size. Can be reduced to less than half the horizontal gate IGBT (Fig. 2), which is advantageous for miniaturization of the module. However, in the case of the vertical IGBT (FIG. 3), the yield characteristic due to the field concentration may be somewhat reduced at the edge 37 of the gate 29. FIG. Therefore, as a method to reduce turn-off time of IGBT, technology for reducing hole life time by irradiation and PT-IGBT (Punch Through IGBT) using N-Buffer (31) layer is used. Recently, a collector structure in which N + (31) / P + (32) is shorted by changing the collector structure in order to reduce turn-off time through structural improvement has been proposed. . However, the structural change of the IGBT device to reduce the turn-off time can increase the forward voltage drop in the trade-off relationship. Therefore, the present invention overcomes the structural limitations of the general TIGBT (Trench Insulated Gate Bipolar Transistor) and further satisfies the existing IGBT performance index while improving the breakdown voltage characteristics due to the structural change of the TIGBT of the new structure, and forward voltage drop and turn-off. The purpose is to improve the trade-off relationship of off time.

The present invention relates to a TIGBT having a TIGBT (FIG. 6) structure having improved forward voltage drop, breakdown characteristics, and electrical characteristics of turn-off.

  The general Insulated Gate Bipolar Transistor (IGBT) has the same characteristics as that of MOS-Gate thyristors, but has different characteristics in that the structure of parasitic thyristor (PNPN) is operated so as not to turn on. In addition, IGBTs can be implemented in planar cellular, stripe, or topology, and these devices have intrinsic JFETs. JFETs increase the forward voltage drop (Vce, sat) by increasing device on-resistance.

  The IGBT (Fig. 2) is a planar IGBT, which is a junction field effect due to diffusion of a depletion layer between the P-base 12 and the P + 13 under the gate 29. Transistor) 10 is provided. However, the JFET has a problem of increasing the forward voltage drop (Vce, sat) by increasing the device on-resistance. In addition, the horizontal IGBT (FIG. 2) has problems such as turn-off time delay due to hole current during turn-off.

  TIGBT (FIG. 3) has no isolated JFET 10 region from the planar IGBT (FIG. 2), resulting in a lower forward voltage drop, in particular the channel between N + (28) and Gate (29). Since the channel length can be reduced, the cell size can be reduced to less than half of the horizontal IGBT (FIG. 2), which is advantageous for miniaturization of the module. However, there is a problem in that the yield characteristic is somewhat reduced by the field concentration at the lower edge 37 of the gate 29.

Therefore, it is necessary to improve the breakdown characteristics due to low yield and slow turn-off time in the planar IGBT (FIG. 2) and the field concentration occurring in the TIGBT (FIG. 3).

According to the present invention, the hole injection efficiency into the N-drift layer 11 is maximized by isolating the P + collector 15 region under the existing TIGBT (Fig. 3) with an oxide film 33. Gate gate by introducing convex 34 into the structure of the TIGBT (FIG. 4), which is characterized by a lower forward voltage drop than the conventional TIGBT (FIG. 3) and the bottom of the P-base 26 region. TIGBT (FIG. 6) combines the TIGBT (FIG. 5) structure with higher breakdown voltage and faster turn-off time than the existing TIGBT (FIG. 3) into one structure by inducing part of the electric field concentrated toward (29). to be. Therefore, the present invention improves forward voltage drop, breakdown, and turn-off characteristics as a structure of TIGBT (FIG. 6) combined to have excellent electrical characteristics of the two structures of TIGBT Figures 4 and 5. You can.

The present invention can reduce the forward voltage by maximizing the hole injection efficiency from the TIGBT to the N-drift region (11) layer, the portion of the electric field concentrated toward the gate edge (37) The breakdown voltage can be increased by inducing to the junction. In addition, the turn-off time can be lowered by improving the flow of holes during turn-off.

In the present invention, the structure of TIGBT (Figs. 4, 5, 6) for improving the electrical characteristics of the IGBT, using the TIGBT (Fig. 3) to obtain a low forward voltage drop without changing the concentration of the P + collector (Collector) at the bottom of the device The P + collector (32) is isolated to isolate the portion of the (32) portion from the oxide film (Sio2) 33 so as to reduce the effect of the turn-off loss in the trade-off relationship according to the forward voltage drop. In order to obtain a high yielding characteristic without changing the concentration by using the structure of TIGBT (Fig. 4) and the existing TIGBT (Fig. 3) in which the N + diffusion region 31 is formed around the oxide film (Sio2) 33 on both sides. By designing the region of the P-base 26 between the gates 29 to be convex 34, a portion of the electric field concentrated on the gate edge 37 is relaxed to gate ) Better yield characteristics than the existing TIGBT (Fig. 3), which yields first at the edge (37), can be obtained. In the turn-off, due to the influence of the convex (34) P-base area (26), the hole current exiting to the emitter (30) rather than the existing TIGBT (Fig. 3). The flow is distributed and has a faster turn-off characteristic. In addition, the TIGBT structure shown in FIG. 6 is a structure considering the electrical characteristics of the TIGBT structure shown in FIG. 4 and the electrical characteristics of the TIGBT structure shown in FIG. 5, and the forward voltage is reduced by maximizing the hole injection efficiency to the N-drift layer 11. The breakdown voltage can be increased by inducing a portion of the electric field concentrated toward the gate edge region 37 toward the junction portion. In addition, the turn-off time can be lowered by improving the flow of holes during turn-off.

  The semiconductor device embodied in the present invention includes a collector electrode 16, a collector region group 31 and 32, an insulating layer 33, a drift region 11, and a base ( It has a base region 26, emitter regions 27 and 28, a gate electrode 29, and an emitter electrode 30. The collector region group 31 is distributed on the collector electrode 16 due to the insulator 33 and is of the first conductivity type. The insulating layer 33 is formed at intervals between the collector region 32 and the N + region 31 on the collector electrode 16. The drift region 11 is in contact with the collector region 32, the N + region 31, and the insulating layer 33, and is of a second conductivity type. The base region 26 is separated from the collector region 32 in accordance with the drift region 11 and is of the first conductivity type. The emitter regions 27 and 28 are separated from the drift region 11 along the base region 26 and are of the second conductivity type. The gate electrode 29 is in contact with the emitter region 28 and the base region 26 and also in contact with the drift region 11. The shape of the gate electrode 29 is not specifically limited, For example, a planar gate type | mold, a trench gate type, etc. can be employ | adopted suitably.

The operation when the semiconductor device is on will be described. If a predetermined on voltage is applied to the gate electrode 29, a base region having an emitter region 27 and 28 and a drift region 11 therebetween. An inversion layer is formed at 26, and the second conductive carrier is supplied to the drift region 11 via the inversion layer. The second conductive carrier flows to the collector electrode side 11 via a drift region. Since there is a localized region of the blocking film 33 on the collector electrode, the second conductivity type carrier is directly from the drift region 11 to the collector electrode 16. Cannot be moved to the collector electrode 32 via the collector region 32. In the semiconductor structure described above, the collector region 32 is dispersedly arranged on the collector electrode 16. In the conventional semiconductor structure (FIG. 3), the collector region 32 is formed on the entire surface of the collector electrode 16, whereas in the semiconductor structure described above, the collector region 32 is formed. have. Therefore, the second conductivity type carrier is concentrated in the collector region distributed on the collector electrode 16. If the second conductivity type carriers are concentrated, the first conductivity type carriers corresponding to the second conductivity type carriers supplied from the collector electrode to the collector region increase. As a result, conductivity modulation in the drift region becomes active, and the on voltage of the semiconductor device decreases.

(1) Embodiment 1

  The TIGBT included in the semiconductor device according to the first embodiment of the present invention will be described below with reference to FIG. 4. First, in order to realize a low on-voltage increase in TIGBT, it is preferable that the trench gate width is wider in consideration of the charge density efficiency of the cell. The trench gate is wide and the area of the P-type base layer 26 is reduced. This weakens the effect of the holes injected from the collector 32, which is a P + type semiconductor, into the N-drift region 11, which is a high resistance N-type semiconductor layer, and makes up for and supplements the charge neutral conditions. This is because the injection of electrons from the emitter layer 30 is facilitated and modulated when conducted more effectively to the N-drift region 11, which is a high resistance N-type semiconductor layer.

(2) Embodiment 2

  A trench gate type IGBT included in the semiconductor device according to the second embodiment of the present invention will be described below with reference to FIG. 5.

(3) Embodiment 3

A trench gate type IGBT included in the semiconductor device according to Embodiment 3 of the present invention will be described below with reference to FIG. 6.

1 is an internal drive circuit diagram of the IGBT.

2 is a cross-sectional view of a planar IGBT structure of the existing structure.

3 is a cross-sectional view of the TIGBT structure of the existing structure.

4 is a cross-sectional view of a TIGBT structure for low forward voltage drop according to the present invention.

5 is a cross-sectional view of a vertical TIGBT structure for high breakdown voltage and fast turn-off time according to the present invention.

Figure 6 is a cross-sectional view of a TIGBT structure for low forward voltage drop and high breakdown voltage fast turn-off time in accordance with the present invention.

10 Junction Field Effect Transistor (JFET) area

11 N-type semiconductor layer

12 P type base layer

13 P-Latch

14 N-type emitter

15 P-type semiconductor substrate

16 Collector Electrode

17 Gate Electrode

18 emitter electrode

26 P-type base layer

27 P-type emitter area

28 N-type emitter area

29 Gate Area

30 emitter electrodes

31 N-type impurity diffusion layer

32 P-type collector area

33 Oxide (Sio2)

34 P-type base diffusion layer

37 Gate Edge Area

38 gate oxide

Claims (3)

In Insulated Gate Bipolar Transistor (IGBT), The proposed TIGBT device in FIG. 4 isolates the P + collector 32 into an oxide film (Sio2) 33 in the existing TIGBT structure (FIG. 3) to inject holes into the N-drift (11) layer. TIGBT characterized by a lower forward voltage drop than conventional TIGBT structures (Figure 3). In Insulated Gate Bipolar Transistor (IGBT), The structure of FIG. 5 shows that the P-base 26 is convex 34 between both gates 29 in the existing TIGBT structure (FIG. 3). Leading part toward the junction improves breakdown voltage higher than conventional TIGBT (Figure 3) and flow of holes at turn-off, resulting in faster turn-off than conventional TIGBT (Figure 3) TIGBT featuring time. The method according to claim 1 or 2, The structure of FIG. 6 is combined to have both excellent electrical characteristics of the structures of FIGS. 4 and 5, and the TIGBT has improved forward voltage drop, breakdown, and turn-off characteristics over the existing TIGBT (FIG. 3) structure.

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