A silicon carbide and silicon heterojunction trench reverse conducting IGBT

Abstract

The present invention relates to a silicon carbide and silicon heterojunction trench reverse-conducting IGBT, which includes a collector structure; the collector structure is a multilayer structure, which is sequentially composed of a P+ collector region and an N+ collector region, an N+ buffer layer located above the P+ collector region and the N+ collector region, an N drift region located above the N+ buffer layer, and a surface structure located above the drift region from the bottom layer to the top layer, wherein the collector contact of the P+ collector region is an ohmic contact, and the collector contact of the N+ collector region is a Schottky contact; the N+ collector region is made of silicon carbide material, and the P+ collector region, the N+ buffer layer, the N drift region, and the surface structure are all made of silicon material. The design is that except for the N+ collector region made of silicon carbide material, the remaining regions are made of silicon material, and the collector contact of the N+ collector region is a Schottky contact, and the voltage foldback phenomenon is eliminated by utilizing the characteristic of the high voltage drop of the silicon carbide Schottky junction.

Description

Technical Field

[0001] The present invention relates to an IGBT (Insulated Gate Bipolar Transistor), and in particular to a silicon carbide and silicon heterojunction trench reverse-conducting IGBT. Background Art

[0002] Nowadays, IGBT (Insulated Gate Bipolar Transistor) devices occupy an important position in power application systems, and application circuits generally require bidirectional conduction capabilities. However, traditional IGBT devices are unidirectional conduction devices, which requires that the IGBT must be reversely connected in parallel with a device (generally a diode) to meet the application of the power system, which increases the complexity of the system and the application cost.

[0003] In response to this situation, some people have proposed reverse-conducting IGBT devices. In order to keep the front structure of traditional IGBT devices unchanged, N-type impurities are doped on the back of the IGBT device, forming a coexistence of N-type impurities and P-type impurities on the back. The N-type impurity area on the back and the P-type impurity area on the front form the cathode and anode structures of the diode respectively. Compared with traditional IGBTs, reverse-conducting IGBTs integrate diode characteristics and can be used alone in applications without parallel diodes, which greatly simplifies the complexity of the system and further reduces the application cost.

[0004] However, this type of reverse-conducting IGBT will have a voltage foldback phenomenon when it is forward-conducting. This is because when it is turned on, electrons are quickly exported from the back N region, which is equivalent to working only in Mosfet mode. Due to the junction barrier of the back PN junction, holes cannot be injected immediately when it is turned on. Only when the current reaches a specific value and the potential superimposed on the PN junction exceeds the junction barrier, holes can be injected into the IGBT drift region. When holes are injected, the conductivity modulation effect is formed. At this time, the voltage drop of the IGBT is significantly reduced compared to when it only works in Mosfet mode. This is also the fundamental reason for the voltage foldback. IGBT devices are generally used in parallel in power application systems. If the device has a voltage foldback output characteristic, it is very easy to have a serious current imbalance during parallel use. The final consequence is that the IGBT device overheats and burns, causing damage to the application system. Summary of the invention

[0005] In order to solve the above problems, the present invention proposes a silicon carbide and silicon heterojunction trench reverse conducting IGBT.

[0006] The technical solution of the present invention:

[0007] A silicon carbide and silicon heterojunction trench reverse-conducting IGBT, comprising a collector structure; the collector structure is a multi-layer structure, which comprises, from the bottom layer to the top layer, a P+ collector region and an N+ collector region, an N+ buffer layer located above the P+ collector region and the N+ collector region, an N drift region located above the N+ buffer layer, and a surface structure located above the N drift region, wherein the collector contact of the P+ collector region is an ohmic contact, and the collector contact of the N+ collector region is a Schottky contact.

[0008] The N+ collector region is made of silicon carbide (SiC) material, and the P+ collector region, N+ buffer layer, N drift region, and surface structure are all made of silicon (Si) material.

[0009] The surface structure includes a P base region, a plurality of trench gates are arranged in the P base region, a plurality of N+ emitter regions and P+ emitter regions are arranged on the P base region, and each group of two N+ emitter regions and one P+ emitter region are located between adjacent trench gates, wherein the N+ emitter region is close to the trench gate, and the P+ emitter region is close to the N+ emitter region and is located between the two N+ emitter regions;

[0010] The surface structure also includes a top emitter disposed above the trench gate, the N+ emitter region, and the P+ emitter region.

[0011] The P+ emitter region is deeply diffused, and its depth is less than that of the P base region.

[0012] The trench gate extends into the N drift region for a certain distance.

[0013] The advantages of the present invention are reasonable design and ingenious conception. Except for the N+ collector region which is made of silicon carbide material, the remaining regions are all made of silicon material, and the collector contact of the N+ collector region is a Schottky contact. The high voltage drop characteristic of the silicon carbide Schottky junction is utilized to eliminate the voltage foldback phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a schematic diagram of the collector structure.

[0015] In the figure, there are P+ collector region 9, ohmic contact 91, N+ collector region 8, Schottky contact 81, N+ buffer layer 7, N drift region 6, surface structure 5, P base region 51, trench gate 52, N+ emitter region 53, P+ emitter region 54, and emitter 55. DETAILED DESCRIPTION

[0016] As shown in the figure, a silicon carbide and silicon heterojunction trench reverse conducting IGBT includes a collector structure; the collector structure is a multi-layer structure, from the bottom to the top, respectively, a P+ collector region 9 and an N+ collector region 8, an N+ buffer layer 7 located above the P+ collector region 9 and the N+ collector region 8, an N drift region 6 located above the N+ buffer layer 7, and a surface structure 5 located above the N drift region 6, the collector contact of the P+ collector region 9 is an ohmic contact 91, and the collector contact of the N+ collector region 8 is a Schottky contact 81; the N+ collector region 8 is made of silicon carbide material, and the P+ collector region 9, the N+ buffer layer 7, the N drift region 6, and the surface structure 5 are all made of silicon material.

[0017] The surface structure 5 includes a P base region 51, in which a plurality of trench gates 52 are arranged, and a plurality of N+ emitter regions 53 and P+ emitter regions 54 are arranged on the P base region 51, wherein two N+ emitter regions 53 and one P+ emitter region 54 form a group and are located between adjacent trench gates 52, wherein the N+ emitter region 53 is close to the trench gates 52, and the P+ emitter region 54 is close to the N+ emitter region 53 and is located between the two N+ emitter regions 53; the surface structure 5 also includes a top emitter 55 arranged above the trench gates 52, the N+ emitter region 53, and the P+ emitter region 54; the P+ emitter region 54 is deeply diffused, and its depth is less than that of the P base region 51; the trench gates 52 extend into a section of the N drift region 6.

[0018] The technical elements described in this specification or drawings are technically useful alone or in various combinations, and are not limited to the combinations described in the claims at the time of application. In addition, the technology exemplified in this specification or drawings achieves multiple purposes at the same time, and achieving one of the purposes itself has technical usefulness.

Claims

1. A silicon carbide and silicon heterojunction trench reverse conducting IGBT, comprising a collector structure; characterized in that: The collector structure is a multi-layer structure, which includes, from the bottom layer to the top layer, a P+ collector region and an N+ collector region, an N+ buffer layer located above the P+ collector region and the N+ collector region, an N drift region located above the N+ buffer layer, and a surface structure located above the N drift region. The collector contact of the P+ collector region is an ohmic contact, and the collector contact of the N+ collector region is a Schottky contact. The N+ collector region is made of silicon carbide material, and the P+ collector region, N+ buffer layer, N drift region, and surface structure are all made of silicon material; The surface structure includes a P base region, a plurality of trench gates are arranged in the P base region, a plurality of N+ emitter regions and P+ emitter regions are arranged on the P base region, and each group of two N+ emitter regions and one P+ emitter region are located between adjacent trench gates, wherein the N+ emitter region is close to the trench gate, and the P+ emitter region is close to the N+ emitter region and is located between the two N+ emitter regions; The surface structure also includes a top emitter disposed above the trench gate, the N+ emitter region, and the P+ emitter region; The P+ emitter region is deeply diffused, and its depth is less than that of the P base region; The trench gate extends into the N drift region for a certain distance.

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