CN115832038A

CN115832038A - RC-IGBT with double gates

Info

Publication number: CN115832038A
Application number: CN202211453932.2A
Authority: CN
Inventors: 伍伟; 喻明康; 高崇兵
Original assignee: University of Electronic Science and Technology of China
Current assignee: University of Electronic Science and Technology of China
Priority date: 2022-11-21
Filing date: 2022-11-21
Publication date: 2023-03-21

Abstract

The invention provides an RC-IGBT with a double grid, which is characterized in that on the basis of a conventional RC-IGBT structure, a sub-control trench grid is added in a collector region, a P-type collector base region is added to a back injection structure, and an N + collector region is not directly connected with an N-type buffer region but is connected with the buffer region when an electronic channel is opened by the sub-control grid, so that the working state of a device can be completely controlled. When the main control grid is opened and the auxiliary control grid is closed, the device is conducted in the forward direction, and at the moment, the device does not have a single-pole conducting state, so that the inherent snapback phenomenon of the conventional RC-IGBT is eliminated. When the main control grid and the auxiliary control grid are closed simultaneously, the device works in a blocking state, and at the moment, the device can be blocked in a forward direction and also can be blocked in a reverse direction. When the main control gate is closed and the auxiliary control gate is opened, the device is conducted in the reverse direction, current is uniformly distributed at the moment, reverse conduction voltage drop is reduced, and the characteristics of the diode are remarkably optimized.

Description

RC-IGBT with double gates

Technical Field

The invention relates to the field of semiconductors, in particular to an RC-IGBT with a double grid.

Background

Insulated Gate Bipolar Transistors (IGBTs) are currently the most prevalent fully-controlled power semiconductor devices. When the IGBT is used in the field of power electronics, the IGBT is usually connected in parallel with a reverse conducting diode to achieve the purpose of follow current protection, so the reverse conducting insulated gate bipolar transistor (RC-IGBT) has the advantage of integrating an anti-parallel diode therein, and becomes a hot point for research in the technical field of semiconductor power devices at present.

One of the challenges facing RC-IGBTs is the phenomenon of negative differential resistance, also known as voltage foldback (snapback), that occurs in their forward characteristic curves. Due to the presence of the N + region of the collector of the RC-IGBT, it will operate in a unipolar conduction state at the start of conduction, i.e. only electron current is generated. When the external voltage is sufficiently high, the potential difference between the P + collector region and the N region thereon exceeds a critical point, and thus a bipolar conduction state is entered. During the switching of the on-mode of the RC-IGBT, a voltage folding-back phenomenon can be observed from a voltage current curve. The traditional RC-IGBT eliminates snapback phenomenon by increasing the length of a P + collector region, the method is simple to realize, but current distribution is uneven when reverse conduction is carried out, and the characteristics of an integrated diode are poor. Therefore, a structure for simultaneously eliminating the voltage folding phenomenon of the RC-IGBT and improving the characteristics of the integrated diode is in urgent need of research.

Disclosure of Invention

Aiming at the requirements of eliminating the voltage folding phenomenon of the RC-IGBT and improving the characteristics of an integrated diode, the invention provides the RC-IGBT with the double gates as shown in figure 2.

The technical scheme adopted by the invention for solving the technical problems is as follows: a RC-IGBT with a double gate comprises cell structures as follows from bottom to top in sequence: the solar cell comprises a back structure and an N-type drift region (5), wherein the back structure consists of an N + collector region (1), a P + collector region (2), a P-type collector base region (3) and an N-type buffer layer (4), the front structure comprises a carrier storage layer (6), a P-type base region (7), a P + type emitter region (8) and an N + type emitter region (9), and SiO is arranged between the collector region and the emitter region ₂ A gate electrode made of an oxide layer (10) and polysilicon (11). In the structure diagram, the trench gate of the emitter region is the main control gate MG, and the trench gate of the collector region is the sub-control gate SG.

Compared with the conventional RC-IGBT device, the technical scheme of the invention mainly aims at improving the back structure. And a sub-control trench gate SG is added in the collector region, the positions of an N + collector region (1) and a P + collector region (2) are changed, a P-type collector base region (3) is added, and finally a structure similar to the front side is formed on the back side of the device, so that the elimination of a voltage folding phenomenon and the optimization of the characteristics of the IGBT and the integrated diode are realized through the control of the double gates.

Furthermore, the structure between all adjacent secondary control trench gates in the structure is fixed to be that two N + collector regions (1) are respectively attached to the left trench gate and the right trench gate and connected with a collector, a P + collector region (2) is also connected with the collector and located between the two N + collector regions (1), and a P-type collector base region (3) and an N-type buffer layer (4) are sequentially arranged above the N + collector region (1) and the P + collector region (2).

Furthermore, the structure between adjacent secondary control trench gates in the structure is not fixed, an N + collector region (1) is not arranged between part of adjacent secondary control trench gates, a P + collector region (2) is tightly attached to the left and right trench gates, and a P-type collector base region (3) and an N-type buffer layer (4) are sequentially arranged above the P + collector region (2).

Furthermore, the number of the secondary control groove gates SG is changed, the number of the secondary control groove gates SG is increased, the number of electronic paths on the back of the device in the working state of the diode is increased, and the current distribution is more uniform.

The invention has the beneficial effects that: the invention provides an RC-IGBT with a double gate, which is improved aiming at a back structure on the basis of a conventional RC-IGBT structure. And adding a secondary control trench gate and a P-type collector base region (3) to finally enable the structure of the back side of the new device to be similar to the structure of the front side. The structure can realize the switching of different working states by respectively controlling the double gates, so that the direct bipolar conduction can be realized without entering a unipolar conduction mode when the structure is started, and the voltage folding phenomenon is eliminated. Meanwhile, the back electronic channels are uniformly distributed, so that the current of the device is uniformly distributed when the device is conducted reversely, and the characteristics of the integrated diode are optimized. And the new device can also realize reverse blocking through the control of the secondary control groove gate.

Drawings

FIG. 1 is a schematic structural diagram of a conventional RC-IGBT;

FIG. 2 is a schematic structural view of embodiment 1;

FIG. 3 is a schematic structural view of example 2;

Detailed Description

The following description of the embodiments of the present invention is provided to facilitate the understanding of the present invention by those skilled in the art, but it should be understood that the present invention is not limited to the scope of the embodiments, and it will be apparent to those skilled in the art that various changes may be made without departing from the spirit and scope of the invention as defined and defined in the appended claims, and all matters produced by the invention using the inventive concept are protected.

Example 1

As shown in fig. 2, the cell structure of the RC-IGBT with the dual gates of this example is, from bottom to top: the solar cell comprises a back structure and an N-type drift region (5), wherein the back structure consists of an N + collector region (1), a P + collector region (2), a P-type collector base region (3) and an N-type buffer layer (4), the front structure comprises a carrier storage layer (6), a P-type base region (7), a P + type emitter region (8) and an N + type emitter region (9), and SiO is arranged between the collector region and the emitter region ₂ A gate electrode made of an oxide layer (10) and polysilicon (11). In the structure diagram, the trench gate of the emitter region is the main control gate MG, and the trench gate of the collector region is the sub-control gate SG. Compared with the conventional RC-IGBT device, the RC-IGBT device is mainly improved on the basis of a back structure, and the front structure of the RC-IGBT device is the same as that of the conventional RC-IGBT device in the figure 1. The specific improvement scheme of the collector region structure is as follows: and adding a plurality of sub-control trench gates SG in the collector region, wherein the number ratio of the sub-control gates to the main control gates is about 2. In the embodiment, the structures between all adjacent secondary control trench gates are fixed to be that two N + collector regions (1) are respectively attached to the left trench gate and the right trench gate and are connected with a collector, a P + collector region (2) is also connected with the collector and is positioned between the two N + collector regions (1), and a P-type collector base region (3) and an N-type buffer layer (4) are sequentially arranged above the N + collector region (1) and the P + collector region (2).

The working principle of the embodiment is as follows:

when the device is conducted in the forward direction, the main control gate MG is connected with a positive voltage, the auxiliary control gate SG is in short circuit with the collector, at the moment, the electron channel on the emitter side is opened, the electron channel on the collector side is closed, the working state is the same as that of the IGBT, the switching process of the single-pole working state and the double-pole working state of the traditional RC-IGBT is avoided, and the voltage folding phenomenon is avoided. The secondary control grid SG can also be connected with a certain negative pressure relative to the collector electrode, so that the N doped region near the secondary control grid groove is inverted into a P doped region and is connected with the P + collector region (2), and the hole injection area of the device is increased. When the device is conducted reversely, the emitting electrode is connected with high voltage, the collecting electrode is grounded, the sub-control grid SG is connected with positive voltage, at the moment, the electron channel on the collecting electrode side is opened, a P + type emitting region (8), a P type base region (7), an N type drift region (5), an N type buffer layer (4), an N type inversion layer in the P type collecting electrode base region (3) and an N + collecting region (1) form a PN diode, the working state of the device is the same as that of the conducting diode, because the electron channel on the collecting electrode region is uniformly distributed, the current distribution is also uniform, and the conducting characteristic of the diode is greatly improved compared with that of the conventional RC-IGBT shown in the figure 1. When the device is turned off, only the main control gate MG and the auxiliary control gate SG are grounded at the same time, and both forward voltage and reverse voltage can be blocked.

Example 2

As shown in fig. 3, the difference between this example and example 1 is that in the back structure of this example, the structure between adjacent sub-control trench gates is not fixed, the N + collector region (1) is not included between part of adjacent sub-control trench gates, the P + collector region (2) is closely attached to the left and right trench gates, and the P-type collector base region (3) and the N-type buffer layer (4) are sequentially above the P + collector region (2). Compared with the device of the embodiment 1, the device of the embodiment has larger injection area in the forward direction conduction.

Furthermore, the number of the sub-control trench gates SG is increased, the number of electronic paths on the back of the device in the working state of the diode is increased, and the current distribution is more uniform.

In summary, the invention provides an RC-IGBT structure with a dual gate, which is improved for a back structure based on a conventional RC-IGBT structure, so that the back structure of a new device is similar to a front structure. The device can realize the switching of different working states by respectively controlling the double gates, thereby realizing that the device does not enter a single-pole conduction mode when being started so as to eliminate the voltage folding phenomenon. Meanwhile, when the device is conducted reversely, the electronic channels of the collector are uniformly distributed, the current is uniformly distributed, and the conduction characteristic of the integrated diode is optimized. And the new device can also realize reverse blocking through controlling the secondary control trench gate.

Claims

1. A RC-IGBT with a double gate comprises cell structures as follows from bottom to top in sequence: the N + collector region (1), the P + collector region (2), the P type collector base region (3) and the N type buffer layer (4) form a back structure and an N type drift region (5), the front structure comprises a carrier storage layer (6), a P type base region (7), a P + type emitter region (8) and an N + type emitter region (9), and S is arranged between the collector region and the emitter regioniO ₂ A grid electrode formed by an oxide layer (10) and polycrystalline silicon (11); in the structure diagram, the trench gate of the emitter region is the main control gate MG, and the trench gate of the collector region is the sub-control gate SG.

2. The RC-IGBT with the double gates according to claim 1, wherein compared with a conventional RC-IGBT device, a sub-control trench gate SG is added in a collector region, the positions of an N + collector region (1) and a P + collector region (2) are changed, and a P-type collector base region (3) is added to a back injection structure, so that the N + collector region (1) and an N-type buffer layer (4) are not directly connected, and the MOS working state of the device is controlled by controlling the sub-control gate, thereby achieving the effect of completely controlling the working state of the device.

3. The RC-IGBT with the double gates according to claims 1 and 2, wherein the structure between every two sub-control trench gates is fixed as two N + collector regions (1) respectively clinging to the left and right trench gates and connected with the collector, the P + collector region (2) is also connected with the collector and located between the two N + collector regions (1), and a P-type collector base region (3) and an N-type buffer layer (4) are sequentially arranged above the N + collector region (1) and the P + collector region (2).

4. The RC-IGBT with the double gates according to claims 1 and 2, wherein the structure between every two sub-control trench gates SG is not fixed, a part of the structure is as in claim 3, an N + collector region (1) is not included between part of adjacent sub-control trench gates, a P + collector region (2) is tightly attached to the left and right trench gates, and a P-type collector base region (3) and an N-type buffer layer (4) are sequentially arranged above the P + collector region (2).

5. The RC-IGBT with the double gates of claims 1-4, wherein the number of the sub-control trench gates SG is changed, the number of the sub-control trench gates SG is increased, the number of back side electron paths of the device in the diode working state is increased, and the current distribution is more uniform.