CN107170810A - A kind of inverse-impedance type gallium nitride device - Google Patents

Abstract

The invention belongs to the technical field of semiconductors, and in particular relates to a reverse-resistance gallium nitride device. Aiming at the incompatibility between the conventional reverse-resistance AlGaN/GaN heterojunction high electron mobility transistor and the traditional silicon CMOS process and the high temperature of device fabrication, the present invention proposes a reverse-resistance gallium nitride device without ohmic contact . The reverse-resistance gallium nitride device proposed by the invention has the advantages of being compatible with traditional silicon technology, being able to be prepared at low temperature, and the like.

Description

A reverse-resistance gallium nitride device

technical field

The invention belongs to the technical field of semiconductors, and in particular relates to a reverse-resistance gallium nitride device.

Background technique

Power electronics technology is an important supporting technology for modern science, industry and national defense. Among them, power semiconductor devices are not only the foundation of power electronics technology, but also a powerful driving force for the development of power electronics technology. The development of power semiconductor devices plays a decisive role in the development of power electronics technology. . Among them, new power semiconductor devices represented by power MOS field effect transistors (MOSFETs) and insulated gate transistors (IGBTs) occupy a dominant position and play an important role in the fields of 4C electronic products, industrial control, and national defense equipment. However, power MOSFET devices based on silicon materials are increasingly showing their shortcomings and limitations. Wide bandgap semiconductor materials have better material properties and are expected to solve the "silicon limit" problem faced by the development of power semiconductor devices today.

The wide bandgap semiconductor material GaN has outstanding advantages such as wide band gap, high electron saturation drift velocity, high thermal conductivity, high critical breakdown electric field, etc., which greatly improves the withstand voltage capacity, operating frequency and current density of GaN power electronic devices, and greatly reduces The conduction loss of the device enables the device to work under harsh conditions such as high power and high temperature. In particular, gallium nitride on silicon technology combines the performance advantages of GaN materials and the cost advantages of silicon technology. It has become a strategic commanding height in the field of international power semiconductors and has been highly valued by governments around the world. Compared with traditional Si-based power electronic devices, the wide-bandgap semiconductor power electronic devices that have been practical at present can reduce power consumption by half, thereby reducing or even eliminating cooling systems, and greatly reducing the size and weight of power converters.

Wide bandgap semiconductor power electronic devices have a very wide range of military and civilian values, such as tanks, ships, aircraft, artillery and other military equipment in the field of power electronic systems, as well as civilian power electronic equipment, household appliances, train traction equipment, high-voltage direct current transmission equipment , It is also being applied to systems such as PCs, hybrid vehicles, electric vehicles, and solar power generation. In these new power electronic systems, GaN power electronic devices are one of the core key technologies, which can greatly reduce power consumption, so they are also known as "green energy" devices that drive the "new energy revolution".

AlGaN/GaN heterojunction-based high electron mobility transistors (HEMTs) (or heterojunction field effect transistors HFETs) have been widely used in the semiconductor field. However, conventional AlGaN/GaN heterojunction high electron mobility transistors do not have reverse blocking capability, and when the drain voltage is reversed, a large reverse current will appear. This situation may cause damage to devices or systems in actual work. To solve these problems, several reverse-resistance AlGaN/GaN heterojunction high electron mobility transistors have been proposed in recent years. However, conventional reverse-resistance AlGaN/GaN heterojunction high electron mobility transistors have ohmic contacts, require heavy metals such as gold, and are prepared under high temperature conditions, making the device incompatible with traditional silicon processes. And during the high-temperature ohmic annealing process, the surface of the device will be oxidized, which will lead to the generation of surface states. These surface traps trap electrons, resulting in a large dynamic resistance during dynamic switching of the device.

Contents of the invention

The purpose of the present invention is to solve the problems that the conventional reverse resistance type AlGaN/GaN heterojunction high electron mobility transistor is not compatible with the traditional silicon CMOS process and the device preparation temperature is high. The present invention proposes a reverse resistance type without ohmic contact GaN devices. The reverse-resistance gallium nitride device proposed by the invention has the advantages of being compatible with traditional silicon technology, being able to be prepared at low temperature, and the like.

The technical solution of the present invention is: a reverse-resistance gallium nitride device, including a substrate 1, a GaN layer 2 and an MGaN layer 3 stacked sequentially from bottom to top, and the GaN layer 2 and MGaN layer 3 form a heterojunction The M is a Group III element other than Ga; one end of the upper surface of the MGaN layer 3 has a drain metal 5, and the drain metal 5 forms a Schottky barrier contact with the MGaN layer 3; it is characterized in that, There is an insulating gate structure 6 at the other end of the MGaN layer 3, and the insulating gate structure 6 is composed of an insulating gate dielectric 8 and a metal gate electrode 9, wherein the metal gate electrode 9 is located in the insulating gate groove 7, and the insulating gate The gate groove 7 is a groove that penetrates the MGaN layer 3 and extends into the upper surface of the GaN layer 2, and the metal gate electrode 9 is isolated from the MGaN layer 3 and the GaN layer 2 by an insulating gate dielectric 8; it is adjacent to the insulating gate structure 6 The upper surface of the MGaN layer 3 has a source metal 4, the source metal 4 is isolated from the metal gate electrode 9 by an insulating gate dielectric 8, and the insulating gate dielectric 8 completely covers the surface of the source metal 4 and along the MGaN layer 3 The upper surface extends to contact with a portion of the lower surface of the drain metal 5 .

Further, the part of the bottom of the drain metal 5 that is not in contact with the insulating gate dielectric 8 extends down to the upper layer of the embedded GaN layer 2 .

Further, the material used for the substrate 1 is one of silicon, sapphire, silicon carbide and gallium nitride.

Further, the material used for the insulating gate dielectric 8 is one of SiO ₂ , Si ₃ N ₄ , AlN, Al ₂ O ₃ , MgO and Sc ₂ O ₃ .

The beneficial effects of the present invention are: for the problems of conventional reverse resistance AlGaN/GaN heterojunction high electron mobility transistors being incompatible with the traditional silicon CMOS process and high device manufacturing temperature, the present invention proposes a non-ohmic contact Reverse-resistance gallium nitride device, because there is no ohmic contact, the device is compatible with traditional silicon technology and can be prepared at low temperature.

Description of drawings

Fig. 1 is a device structure schematic diagram of the present invention;

Fig. 2 is a schematic diagram of the working principle of the device of the present invention;

Fig. 3 is a schematic diagram of epitaxial wafers in the device manufacturing process flow of the present invention;

Fig. 4 is a schematic diagram of the structure after growing source Schottky metal and drain Schottky metal in the device manufacturing process flow of the present invention;

5 is a schematic diagram of the structure after etching MGaN to form insulating gate grooves in the device manufacturing process flow of the present invention;

6 is a schematic diagram of the structure after growing an insulating layer in the device manufacturing process flow of the present invention;

FIG. 7 is a schematic diagram of the structure after growing an insulating gate metal in the device manufacturing process flow of the present invention.

FIG. 8 is a schematic diagram of another device structure of the present invention.

detailed description

Below in conjunction with accompanying drawing, describe technical scheme of the present invention in detail:

As shown in FIG. 1, it is a reverse-resistance gallium nitride device of the present invention, which includes a substrate 1, a GaN layer 2, and an MGaN layer 3 that are sequentially stacked from bottom to top, and the GaN layer 2 and MGaN layer 3 form a heterogeneous Junction; the M is a group III element except Ga; one end of the upper surface of the MGaN layer 3 has a drain metal 5, and the drain metal 5 forms a Schottky barrier contact with the MGaN layer 3; it is characterized in that , there is an insulating gate structure 6 at the other end of the MGaN layer 3, the insulating gate structure 6 is composed of an insulating gate dielectric 8 and a metal gate electrode 9, wherein the metal gate electrode 9 is located in the insulating gate groove 7, the The insulating gate groove 7 is a groove that penetrates the MGaN layer 3 and extends into the upper surface of the GaN layer 2, and the metal gate electrode 9 is isolated from the MGaN layer 3 and the GaN layer 2 by an insulating gate dielectric 8; The upper surface of the adjacent MGaN layer 3 has a source metal 4, the source metal 4 is isolated from the metal gate electrode 9 by an insulating gate dielectric 8, and the insulating gate dielectric 8 completely covers the surface of the source metal 4 and along the MGaN layer 3. The upper surface extends to contact with the lower surface of part of the drain metal 5.

Traditional reverse-resistance GaN field effect transistors have ohmic contacts, require heavy metals such as gold, and are prepared under high temperature conditions, making the device incompatible with traditional silicon processes. And during the high-temperature ohmic annealing process, the surface of the device will be oxidized, which will lead to the generation of surface states. These surface traps trap electrons, resulting in a large dynamic resistance during dynamic switching of the device. In order to solve these problems, the present invention proposes a reverse-resistance gallium nitride field effect transistor without ohmic contact (as shown in FIG. 1 ). The source and the drain of the device of the present invention are both Schottky contact structures instead of traditional ohmic contact structures, and at the same time, a gate structure is introduced near the Schottky source structure to control the potential barrier below the source Schottky contact The energy band structure of the layer is used to realize the turn-on and turn-off of the device. Since the reverse-resistance gallium nitride field effect transistor of the present invention has no ohmic contact, it does not need to use heavy metals and is compatible with CMOS technology. At the same time, the invention does not require a high-temperature annealing process, the device can be prepared at a lower temperature, and problems such as oxidation of the device surface can be avoided.

In the structure shown in Figure 1, growing SiO2, Si3N4, AlN, Al2O3, MgO or Sc2O3 on the surface of the AlGaN layer as a passivation layer can further reduce leakage and improve performance. The groove depth of the source Schottky contact electrode embedded in the upper layer of the GaN layer is hundreds of nanometers. The Schottky source structure and the insulated gate structure are separated by an insulating medium, and the quality of the medium directly affects the performance of the device.

Basic working principle of the present invention is:

First, the energy band structure of the barrier layer under the Schottky contact is controlled by the insulated gate structure near the Schottky source contact to change the working state of the device, and the device is turned on and off. When a positive voltage is applied to the gate, the thickness of the potential barrier under the source Schottky becomes thinner (Figure 2), and the tunneling probability of electrons increases, which can make the device have a current characteristic similar to an ohmic contact; when a negative voltage on the gate When , the Schottky barrier thickness becomes thicker, the electron tunneling probability decreases, electrons can hardly pass through the barrier, and the device can achieve forward blocking capability. At the same time, the invention utilizes the Schottky drain to realize the reverse blocking of the device.

The device of the present invention is compatible with the traditional CMOS process, and can utilize the traditional CMOS process line to prepare the device. It should be noted that:

1. The substrate 1 can be silicon, sapphire, silicon carbide or gallium nitride.

2. Other materials may exist between the substrate 1 and the GaN layer 2 .

3. The drain metal 5 can extend to the GaN layer 2 .

4. A Schottky contact rather than a traditional ohmic contact is formed between the source metal 4 and the drain metal 5 and the MGaN layer 3 .

5. The material used for the insulating gate dielectric 8 is one of SiO2, Si3N4, AlN, Al2O3, MgO or Sc2O3.

6. The insulating gate structure 6 must be near the source metal 4 .

7. The insulating gate structure 6 must extend to the GaN layer 2 .

8. Extending the metal length of the Schottky drain metal 5 on the insulating gate dielectric 8 to form a drain field plate can improve the reverse blocking capability of the device.

9. Extending the metal length of the Schottky drain metal 4 on the surface of the insulating gate dielectric 8 to form a source field plate can improve the forward blocking capability of the device.

10. The source metal 4 , the drain metal 5 and the metal gate electrode 9 may not contain heavy metals such as gold.

In the present invention, the following two schemes can be used to prepare the insulating dielectric material.

(a) Al ₂ O ₃ , HfO ₂ , TiO ₂ and other dielectric materials were prepared by atomic layer deposition (ALD). The film grown by ALD is self-limiting, can precisely control the thickness and chemical composition of the film, and the deposited film has good uniformity and shape retention. It should be considered to realize the method of composite lamination, such as HfO ₂ /Al ₂ O ₃ and so on.

(b) Using MOCVD equipment to prepare Ga ₂ O ₃ , Al ₂ O ₃ , AlGaO or AlGaO/Al ₂ O ₃ various single layers, mixed layers and various stacked structures to prepare high-performance insulating gate dielectrics. The MOCVD method has the advantages of dense film-forming state of dielectric materials, precise thickness control, easy formation of mixed films and good repeatability of multi-layer films, especially the large controllable space for interface state control.

The manufacturing process flow of the present invention is shown in Fig. 3-Fig. 7, mainly comprises:

Figure 3 is an epitaxial wafer with a heterojunction structure, Figure 4 grows Schottky source metal and Schottky drain metal, Figure 5 and Figure 6 are etching shallow grooves of the insulating gate and growing insulating gate dielectric, Figure 7 Grow insulating gate metal.

Claims (4)

1. a kind of inverse-impedance type gallium nitride device, including substrate (1), GaN layer (2) and MGaN layers being cascading from bottom to up (3), the GaN layer (2) and MGaN layers (3) form hetero-junctions；The M is III race's element in addition to Ga；Described MGaN layers (3) Upper surface one end has drain metal (5), and the drain metal (5) forms Schottky Barrier Contact with MGaN layers (3)；Its feature It is there is insulated gate structures (6) in described MGaN layers (3) other end, the insulated gate structures (6) are by insulation gate medium (8) constituted with metal gate electrode (9), wherein metal gate electrode (9) is located in insulation grid recess (7), the insulation grid recess (7) Through MGaN layers (3) and to extend into the groove of GaN layer (2) upper surface, metal gate electrode (9) and MGaN layers (3) and GaN layer (2) isolated between by the gate medium that insulate (8)；MGaN layer (3) upper surface adjacent with insulated gate structures (6) has source electrode gold Belong to (4), isolated between the source metal (4) and metal gate electrode (9) by the gate medium that insulate (8), and insulation gate medium (8) The surface of source metal (4) is completely covered and is extended to along MGaN layers of (3) upper surface and is connect with the lower surface of part drain metal (5) Touch.

2. a kind of inverse-impedance type gallium nitride device according to claim 1, it is characterised in that drain metal (5) bottom The part not contacted with insulation gate medium (8), extends downward into embedded GaN layer (2) upper strata.

3. a kind of inverse-impedance type gallium nitride device according to claim 1 or 2, it is characterised in that what the substrate (1) used Material is one kind in silicon, sapphire, carborundum and gallium nitride.

4. a kind of inverse-impedance type gallium nitride device according to claim 3, it is characterised in that the insulation gate medium (8) is adopted Material is SiO₂、Si₃N₄、AlN、Al₂O₃, MgO and Sc₂O₃In one kind.