GaN-based HEMT (High Electron Mobility Transistor) device with inclined field plate structure

Abstract

The utility model belongs to the field of semiconductor power device manufacturing, and particularly relates to a GaN-based HEMT device with an inclined field plate structure, which comprises a substrate layer, a buffer layer connected above the substrate layer, an AlGaN barrier layer connected above the buffer layer, a GaN cap layer connected above the AlGaN barrier layer, and a GaN layer connected above the GaN cap layer. The left side and the right side of the GaN cap layer are oppositely connected with a source electrode and a drain electrode, the top of the GaN cap layer is connected with SiN passivation, the top of the GaN cap layer is connected with a grid electrode, and Schottky contact is formed between the grid electrode and the GaN cap layer; a field plate is introduced into the grid electrode. By introducing the field plate structure, electric field lines at the edge of the grid electrode are dispersed, and the electric field intensity at the edge of the grid electrode is effectively reduced, so that the electric field distribution in a depletion layer is more uniform, the possibility that electrons tunnel to a surface trap is reduced, the formation of a virtual grid effect is further hindered, and the performance of the device is improved. And the current collapse phenomenon of the device is effectively reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of semiconductor power device manufacturing, in particular to a GaN-based HEMT device with an inclined field plate structure. Background Art

[0002] GaN-based high electron mobility transistors (HEMTs) have broad application prospects in the field of high frequency and high power due to their good operating frequency, output power density, electron mobility and other characteristics. As a third-generation semiconductor material, gallium nitride (GaN) has excellent physical properties such as wide bandgap, high electron mobility, high electron saturation rate, high breakdown electric field, high thermal conductivity, good chemical stability and strong radiation resistance, which makes up for the shortcomings of the previous two generations of Si and GaAs semiconductor devices in terms of high power and high frequency.

[0003] For actual devices, their output power is less than the ideal output power, and the linearity is reduced. According to the formula for the maximum output power of the device, the output power can be increased by increasing the breakdown voltage of the device, thereby improving the linearity of the device. For conventional devices, when a negative bias is applied to the gate and a positive bias is applied to the drain, a depletion layer will form in the area below the gate. When the device is off, the electric field lines are located directly below the gate and perpendicular to the Schottky contact surface, forming a relatively uniform electric field distribution. However, at the edge of the gate close to the drain side, the electric field lines will bend and the electric field lines will be concentrated to the edge of the gate, causing the electric field strength in this area to be much higher than the electric field strength directly below the gate, increasing the risk of device breakdown. For this reason, we propose a GaN-based HEMT device with a tilted field plate structure. Utility Model Content

[0004] The utility model aims to provide a GaN-based HEMT device with an inclined field plate structure, which can effectively reduce the risk of device breakdown.

[0005] To this end, the technical solution adopted in this utility model is:

[0006] A GaN-based HEMT device with a tilted field plate structure comprises a substrate layer, a buffer layer is connected above the substrate layer, an AlGaN barrier layer is connected above the buffer layer, a GaN cap layer is connected above the AlGaN barrier layer, a source electrode and a drain electrode are relatively connected to the left and right sides of the GaN cap layer, a SiN passivation is connected to the top of the GaN cap layer, and a gate electrode is connected to the top of the GaN cap layer, and a Schottky contact is formed between the gate electrode and the GaN cap layer;

[0007] The gate is introduced with a field plate, the side of the field plate facing the drain is set as an inclined surface, and the angle formed by the inclined surface and the horizontal line of the side of the field plate close to the gate is an acute angle.

[0008] Based on the above technical solution, its use principle and the technical effects produced are as follows:

[0009] The introduction of the field plate structure significantly changes the distribution of electric field lines in the depletion layer. Under the action of the field plate, the depletion region expands toward the drain, so that electric field lines pointing to the field plate appear directly below the field plate. Some electric field lines are concentrated toward the edge of the field plate, showing an electric field curvature effect at the edge of the field plate, dispersing the electric field lines originally concentrated at the edge of the gate. The electric field density there drops significantly, and the electric field strength is reduced, thereby increasing the breakdown voltage of the device. By introducing the field plate structure, not only the electric field lines at the edge of the gate are dispersed and the electric field strength there is reduced, but also the electric field distribution in the entire depletion layer is made more uniform.

[0010] In a preferred example, the utility model can be further configured as follows: the initial length of the gate is L g =0.5μm.

[0011] In a preferred example, the present invention can be further configured as follows: the dielectric thickness t of the field plate is in the range of 50-600 nm, and the tilt angle θ is in the range of 13°-80°.

[0012] In a preferred example, the present invention can be further configured as follows: the distance L from the gate to the source sg =1μm, the distance from gate to drain is L gd =3μm.

[0013] In a preferred example, the utility model can be further configured as follows: the substrate layer material is one of SiC, Si, and sapphire, and the substrate layer thickness is set to 20-100 μm.

[0014] In a preferred example, the utility model can be further configured as follows: the material of the buffer layer is any one of GaN, AlGaN, InAlGaN or InGaN, and the thickness of the buffer layer is set to 0.8-2 μm.

[0015] In a preferred example, the present invention can be further configured as follows: the thickness of the GaN cap layer is 3 nm.

[0016] In a preferred example, the utility model can be further configured as follows: a Schottky contact is formed between the gate and the GaN cap layer, and both the source and the drain are ohmic contacts.

[0017] In a preferred example, the present invention can be further configured as follows: the thickness of the SiN passivation layer is 75 nm.

[0018] The nouns, conjunctions or adjectives involved in the above technical solution are explained as follows:

[0019] Fixed connection refers to a connection in which parts or components are fixed without any relative movement. There are two types of connection: detachable and non-detachable.

[0020] (1) A removable connection is a connection that uses screws, splines, wedge pins, etc. to hold parts together. This type of connection can be disassembled for maintenance without damaging the parts. However, the specifications of the connectors used must be correct (such as the length of the bolts, keys, and wedge pins) and they must be properly tightened.

[0021] (2) Non-detachable connections mainly refer to welding, riveting and tenoning. Since they need to be disassembled by forging, sawing or oxygen cutting for maintenance or replacement, spare parts generally cannot be reused. At the same time, when making connections, attention should be paid to process quality, technical inspection and remedial measures (such as calibration, polishing, etc.);

[0022] An active connection is a connection in which parts or components are fixed so that they can move relative to each other.

[0023] The above technical solution of the utility model has the following beneficial technical effects:

[0024] The utility model introduces a field plate structure to disperse the electric field lines at the edge of the gate, and the electric field strength at the edge of the gate is also effectively reduced, making the electric field distribution in the depletion layer more uniform, thereby reducing the possibility of electron tunneling to surface traps, further hindering the formation of the virtual gate effect, and effectively reducing the current collapse phenomenon of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall layer structure of the utility model;

[0026] Figure 2 This is a schematic diagram of the overall layer structure of a traditional GaN HEMT device;

[0027] Figure 3 It is a simulation diagram of the breakdown characteristics of two GaN HEMT devices with a tilted field plate structure and a traditional structure proposed by the utility model;

[0028] Figure 4 This is a channel electric field distribution diagram of two GaN HEMT devices with a tilted field plate structure and a traditional structure under the breakdown state proposed by the utility model.

[0029] Reference numerals:

[0030] 1. Substrate layer; 2. Buffer layer; 3. AlGaN barrier layer; 4. GaN cap layer; 5. Source; 6. Drain; 7. SiN passivation; 8. Gate; 9. Field plate. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present disclosure to clearly and completely describe the technical solutions in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present disclosure. It should be noted that the embodiments of the present utility model and the features in the embodiments can be combined with each other without conflict.

[0032] According to the concept of this application, Figures 1 to 4 An embodiment of a GaN-based HEMT device with a tilted field plate 9 structure for reducing the electric field strength at the edge of the gate 8 is described. Specifically, the GaN-based HEMT device with a tilted field plate 9 structure is constructed as an integrated structure, which has components such as a substrate layer 1, a gate 8 and a field plate 9. By introducing the field plate 9 structure, the electric field lines at the edge of the gate 8 are dispersed, and the electric field strength at the edge of the gate 8 is also effectively reduced, making the electric field distribution in the depletion layer more uniform, thereby reducing the possibility of electron tunneling to the surface trap, further hindering the formation of the virtual gate effect, and effectively reducing the current collapse phenomenon of the device.

[0033] Combination Figure 1-4 As shown, the utility model provides a GaN-based HEMT device with a tilted field plate 9 structure, comprising a substrate layer 1, a buffer layer 2 connected to the top of the substrate layer 1, an AlGaN barrier layer 3 connected to the top of the buffer layer 2, a GaN cap layer 4 connected to the top of the AlGaN barrier layer 3, a source 5 and a drain 6 connected to the left and right sides of the GaN cap layer 4, a SiN passivation 7 connected to the top of the GaN cap layer 4, and a gate 8 connected to the top of the GaN cap layer 4, and a Schottky contact is formed between the gate 8 and the GaN cap layer 4;

[0034] The gate 8 is introduced with a field plate 9 , and the side of the field plate 9 facing the drain 6 is set as an inclined surface, and the angle formed by the inclined surface and the horizontal line of the side of the field plate 9 close to the gate 8 is an acute angle.

[0035] The substrate layer 1 is mainly used for heat dissipation. In some embodiments, the material of the substrate layer 1 can be set to SiC, Si, or sapphire. For the technical solution of this embodiment, the material of the substrate layer 1 is SiC, and the thickness of the SiC substrate layer 1 can be set to 20-100μm. For the technical solution of this embodiment, the thickness is specifically set to 20μm.

[0036] The buffer layer 2 is mainly used to provide a flat surface. In some embodiments, the material of the buffer layer 2 is any one of GaN, AlGaN, InAlGaN or InGaN. For the technical solution of this embodiment, the material of the buffer layer 2 is set to GaN, and the thickness of the buffer layer 2 can be set to 0.8-2μm. For the technical solution of this embodiment, the thickness is specifically set to 2μm.

[0037] In actual use, the AlGaN barrier layer 3 can also be replaced and set to any one of AlInN, AlScN, AlN, AlInGaN, AlInScN or AlGaScN. The Al component value range of the AlGaN barrier layer 3 is 0.15-0.3. For the technical solution of this embodiment, the Al component in the AlGaN barrier layer 3 is fixed to 0.25; the thickness value range of the AlGaN barrier layer 3 is 10-30nm. For the technical solution of this embodiment, its thickness is specifically set to 20nm.

[0038] Furthermore, the thickness of the GaN cap layer 4 is set to 3 nm, and the thickness of the SiN passivation layer 7 is set to 75 nm. The current collapse effect of the GaN HEMT device can be suppressed by using the set SiN passivation layer 7.

[0039] The source 5 and the drain 6 are both ohmic contacts. In order to improve the breakdown characteristics, the distance between the gate 8 and the drain 6 (L gd ) is often greater than the distance between the gate 8 and the source 5 (L gs ), for the technical solution of this embodiment, the distance L from the gate 8 to the source 5 sg =1μm, the distance L from the gate 8 to the drain 6 gd =3μm, the initial length of the gate 8 Lg=0.5μm.

[0040] The dielectric thickness t of the field plate (9) ranges from 50 to 600 nm, and the tilt angle θ ranges from 13° to 80°. For the technical solution of this embodiment, the dielectric thickness t of the field plate 9 is 350 nm, and the tilt angle θ is 15°. The introduction of the field plate 9 structure significantly changes the distribution of electric field lines in the depletion layer. Under the action of the field plate 9, the depletion region expands toward the drain 6, so that electric field lines pointing to the field plate 9 appear directly below the field plate 9. Some of the electric field lines are concentrated to the edge of the field plate 9, and an electric field curvature effect is exhibited at the edge of the field plate 9, dispersing the electric field lines originally concentrated at the edge of the gate 8. The electric field density at this location decreases significantly, and the electric field strength is reduced, thereby improving the breakdown voltage of the device. By introducing the field plate 9 structure, not only the electric field lines at the edge of the gate 8 are dispersed, reducing the electric field strength at this location, but also the electric field distribution in the entire depletion layer is made more uniform. It should be further explained that the tilted field plate is equivalent to the superposition of countless multi-layer field plates, and the effect is better.

[0041] The specific embodiments are as follows:

[0042] In order to verify the advantages of the GaN HEMT device with the inclined field plate 9 structure proposed in the present invention over the traditional GaN HEMT device, the present invention simulates and compares the relevant performance indicators of the two. The structure of the GaN HEMT device with the traditional structure is shown in FIG. Figure 2 As shown, the thickness of the SiN passivation layer is 50nm. Except for the passivation layer, the other parameters are the same as Figure 1 Same as described.

[0043] See also Figure 3 , the breakdown characteristics of the traditional structure and the tilted field plate 9 structure GaN HEMT devices were simulated and compared by using the two-dimensional device simulation tool of Sentaurus TCAD. The gate 8 voltage was scanned to -6V to put the device in the off state; then the drain 6 voltage was gradually scanned to 1000V by DC. When the drain 6 current increased sharply, the device broke down. The breakdown voltage of the traditional structure device was 187V; after adding the tilted field plate 9 structure, the breakdown voltage of the device increased to 283V, an increase of 51%, which was a significant change.

[0044] See also Figure 4 , which shows the comparison of channel electric field distribution in the breakdown state between the traditional structure and the tilted field plate 9 structure GaN-based HEMT devices: the traditional structure device only has an electric field peak of 3.5MV / cm on the side of the gate 8 close to the drain 6, and the electric field intensity in other areas is relatively low; after adding the tilted field plate 9 structure, the electric field peak at the edge of the device gate 8 decreases, and the electric field value between the gate and the drain increases, the ability to regulate the channel electric field is better, and the electric field distribution is more balanced.

[0045] In addition, by introducing the inclined field plate 9 structure, the gate control capability is improved, the electron confinement in the channel is enhanced, the leakage current is reduced, and the current collapse effect is suppressed. Compared with the device with the traditional structure, the device performance stability is improved.

[0046] The following further describes a GaN-based HEMT device with a tilted field plate 9 structure provided by the present invention in conjunction with the accompanying drawings and implementation examples.

[0047] A GaN-based HEMT device with a tilted field plate 9 structure comprises a substrate layer 1, a buffer layer 2 is connected above the substrate layer 1, an AlGaN barrier layer 3 is connected above the buffer layer 2, a GaN cap layer 4 is connected above the AlGaN barrier layer 3, a source 5 and a drain 6 are relatively connected to the left and right sides of the GaN cap layer 4, a SiN passivation 7 is connected to the top of the GaN cap layer 4, and a gate 8 is connected to the top of the GaN cap layer 4, and a Schottky contact is formed between the gate 8 and the GaN cap layer 4;

[0048] The gate 8 is introduced with a field plate 9 , and the side of the field plate 9 facing the drain 6 is set as an inclined surface, and the angle formed by the inclined surface and the horizontal line of the side of the field plate 9 close to the gate 8 is an acute angle.

[0049] In summary, the utility model introduces the field plate 9 structure to disperse the electric field lines at the edge of the gate 8, and the electric field strength at the edge of the gate 8 is also effectively reduced, making the electric field distribution in the depletion layer more uniform, thereby reducing the possibility of electron tunneling to the surface trap, further hindering the formation of the virtual gate effect, and effectively reducing the current collapse phenomenon of the device.

[0050] In the present utility model, the term "plurality" refers to two or more than two, unless otherwise clearly defined. The term "and / or" used in this article includes any and all combinations of one or more related listed items. The terms "install", "connect", "connect", "fix" and the like should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; "connection" can be a direct connection or an indirect connection through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms in the present utility model can be understood according to the specific circumstances.

[0051] It should be noted that when an element is referred to as being "assembled on", "installed on", "fixed on" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0052] In the description of this specification, the description of the terms "one embodiment", "some embodiments", "specific embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the utility model. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0053] Although the embodiments of the present invention have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A GaN-based HEMT device with a tilted field plate structure, comprising a substrate layer (1), characterized in that: A buffer layer (2) is connected above the substrate layer (1), an AlGaN barrier layer (3) is connected above the buffer layer (2), a GaN cap layer (4) is connected above the AlGaN barrier layer (3), a source electrode (5) and a drain electrode (6) are relatively connected to the left and right sides of the GaN cap layer (4), a SiN passivation layer (7) is connected to the top of the GaN cap layer (4), and a gate electrode (8) is connected to the top of the GaN cap layer (4), and a Schottky contact is formed between the gate electrode (8) and the GaN cap layer (4); The gate (8) is introduced with a field plate (9), the side of the field plate (9) facing the drain (6) is arranged as an inclined surface, and the angle formed by the inclined surface and a horizontal line on the side of the field plate (9) close to the gate (8) is an acute angle.

2. A GaN-based HEMT device with a tilted field plate (9) structure according to claim 1, characterized in that: The initial length of the gate (8) is L g =0.5μm.

3. A GaN-based HEMT device with a tilted field plate (9) structure according to claim 2, characterized in that: The dielectric thickness t of the field plate (9) is in the range of 50-600 nm, and the tilt angle θ is in the range of 13°-80°.

4. A GaN-based HEMT device with a tilted field plate (9) structure according to claim 2, characterized in that: The distance L between the gate (8) and the source (5) is sg =1μm, the distance L from the gate (8) to the drain (6) gd =3μm.

5. A GaN-based HEMT device with a tilted field plate (9) structure according to claim 4, characterized in that: The material of the substrate layer (1) is one of SiC, Si and sapphire, and the thickness of the substrate layer (1) is set to 20-100 μm.

6. A GaN-based HEMT device with a tilted field plate (9) structure according to claim 5, characterized in that: The material of the buffer layer (2) is any one of GaN, AlGaN, InAlGaN or InGaN, and the thickness of the buffer layer (2) is set to be 0.8-2 μm.

7. A GaN-based HEMT device with a tilted field plate (9) structure according to claim 6, characterized in that: The GaN cap layer (4) has a thickness of 3 nm.

8. A GaN-based HEMT device with a tilted field plate (9) structure according to claim 7, characterized in that: A Schottky contact is formed between the gate (8) and the GaN cap layer (4), and the source (5) and the drain (6) are both ohmic contacts.

9. A GaN-based HEMT device with a tilted field plate (9) structure according to claim 8, characterized in that: The SiN passivation (7) layer has a thickness of 75 nm.

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