GaN HEMT device with back barrier structure with gradually changed components
By adopting the component gradient AlGaN back barrier structure in GaN HEMT devices, the short channel effect problem of the device in high-frequency and high-power applications is solved, and higher gate control capabilities and lower leakage current are achieved, improving the overall performance of the device.
Patent Information
- Application Number
- CN202420719765.X
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-09
- Publication Date
- 2025-03-04
- Estimated Expiration
- 2034-04-09
AI Technical Summary
GaN HEMT devices have short channel effects in high-frequency and high-power applications, resulting in threshold voltage drift, increased leakage current and increased sub-threshold swing. The existing technologies such as the extremely thin barrier layer and the AlGaN back barrier structure with fixed Al components have lattice mismatch and interface scattering problems.
Using an AlGaN back barrier structure with component gradient, a gradient Al component distribution is formed by linearly increasing the components of the first AlGaN back barrier layer and the second AlGaN barrier layer to improve gate control capabilities and reduce interface scattering.
Effectively raise the barrier height of the gate, improve gate control capabilities, enhance electronic constraints in the channel, reduce leakage current, improve the DC and large signal characteristics of the device, and improve power density and power additional efficiency.
Smart Images
Figure CN222564254U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of semiconductor power device manufacturing, in particular to a GaN HEMT device with a back barrier structure with a gradual component change. 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. GaN's high bandgap width brings high electron speed and high voltage resistance. Compared with other semiconductor devices, GaN HEMT devices have higher output power density. High output power density enables the device to obtain the desired output power in a smaller volume, thereby reducing parasitic capacitance and increasing bandwidth. Although the electron mobility of GaN material is lower than that of GaAs, it can carry higher voltages at smaller sizes and higher frequencies. This feature makes it stand out among materials such as GaAs and Si.
[0003] In order to obtain good frequency characteristics, high-frequency devices are generally small-sized and short-gate devices. However, short-gate devices will reduce the gate control ability of the device and cause short channel effects, which are specifically manifested as threshold voltage drift, increased leakage current, increased subthreshold swing, etc. The use of ultra-thin barrier layer technology and AlGaN back barrier structure with fixed Al composition are two common ways to suppress the short channel effect. Ultra-thin barrier technology can reduce the distance between the gate and the two-dimensional electron gas and improve the gate control ability. However, the Al component concentration of the thin barrier is generally high, which will cause serious lattice mismatch with GaN and is difficult to grow; and the interface between the traditional constant composition back barrier and the GaN buffer layer is relatively rough, which increases the interface scattering and has a significant impact on the main channel. Therefore, both technologies have defects and new methods need to be sought to suppress the short channel effect of the device. Utility Model Content
[0004] The utility model aims to provide a GaN HEMT device with a back barrier structure with a gradient composition, so as to solve the problems raised in the above background technology.
[0005] To this end, the technical solution adopted in this utility model is:
[0006] A GaN HEMT device with a component gradient back barrier structure, comprising a SiC substrate layer, a GaN buffer layer connected to the SiC substrate layer, a first AlGaN back barrier layer connected to the GaN buffer layer, a GaN channel layer connected to the first AlGaN back barrier layer, an AlN insertion layer connected to the GaN channel layer, a second AlGaN barrier layer connected to the AlN insertion layer, a source electrode and a drain electrode connected to opposite sides of the second AlGaN barrier layer, and a gate installed near the middle of the second AlGaN barrier layer;
[0007] A Si3N4 passivation layer is connected to the second AlGaN barrier layer;
[0008] The grid comprises a grid cap and a grid foot fixed in the middle of the grid cap, and the grid cap and the grid foot are perpendicular to each other.
[0009] Based on the above technical solution, its use principle and the technical effects produced are as follows:
[0010] By introducing an AlGaN back barrier structure with a gradient composition, the height of the barrier under the gate can be effectively raised, the gate control capability can be improved, the electron confinement in the channel can be enhanced, and the leakage current can be reduced. Compared with devices without a back barrier structure, the device performance is improved.
[0011] In a preferred example, the utility model can be further configured as follows: the Al composition of the side of the first AlGaN back barrier layer close to the GaN channel layer is 0, and increases linearly toward the side away from the GaN channel layer, and the range of the increase of the Al composition in the first AlGaN back barrier layer is 0.05-0.2, and the thickness of the first AlGaN back barrier layer is 10nm.
[0012] In a preferred example, the present invention can be further configured as follows: the thickness of the GaN buffer layer is 0.8-2 μm.
[0013] In a preferred example, the present invention can be further configured as follows: the thickness of the GaN channel layer is 200nm-500nm.
[0014] In a preferred example, the present invention can be further configured as follows: the thickness of the AlN insertion layer is 1 nm.
[0015] In a preferred example, the present invention can be further configured as follows: the Al composition in the second AlGaN barrier layer is fixed at 0.2-0.3, and the thickness thereof is 20 nm.
[0016] In a preferred example, the utility model can be further configured as follows: a groove is etched on the upper surface of the second AlGaN barrier layer, the groove depth is 10 nm, and the gate penetrates the Si3N4 passivation layer and is embedded in the groove.
[0017] In a preferred example, the present invention can be further configured as follows: the thickness of the Si3N4 passivation layer is 60nm.
[0018] In a preferred example, the utility model can be further configured as follows: the gate length Lg=0.1 μm, the gate cap length is 1 μm, the gate cap width is 0.5 μm, and the gate foot height is 0.2 μm.
[0019] In a preferred example, the utility model can be further configured as follows: the distance from the gate to the source Lgs=1.1 μm, the distance from the gate to the drain Lgd=1.6 μm, the source and the drain are both ohmic contacts, and the gate is a Schottky contact.
[0020] The nouns, conjunctions or adjectives involved in the above technical solution are explained as follows:
[0021] 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.
[0022] (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.
[0023] (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.);
[0024] An active connection is a connection in which parts or components are fixed so that they can move relative to each other.
[0025] The above technical solution of the utility model has the following beneficial technical effects:
[0026] 1. The utility model effectively enhances the electron confinement in the channel, suppresses the short channel effect of the device, improves the DC characteristics of the device, and thus improves the power characteristics of the GaN-based HEMT device by introducing a back barrier layer with a gradient composition. In the face of the interface scattering problem caused by the back barrier structure, the gradient composition back barrier structure can reduce the interface scattering and parasitic parameters compared to the fixed composition back barrier structure, reduces the impact on the GaN main channel, and improves the small signal and large signal characteristics of the device.
[0027] 2. The gate structure provided in the present invention can reduce the gate resistance and improve the small signal characteristics of the device compared with the traditional gate structure. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 It is a schematic structural diagram of a GaN HEMT device with a composition-gradient back barrier layer in the utility model;
[0029] Figure 2 It is a schematic diagram of the layer structure of a conventional GaN HEMT device with a fixed composition back barrier layer;
[0030] Figure 3 It is a simulation diagram of small signal characteristics of two GaN HEMT devices with a gradient component back barrier and a fixed component back barrier in the utility model;
[0031] Figure 4 It is a simulation diagram of large signal power characteristics of two types of GaN HEMT devices with a gradient component back barrier and a fixed component back barrier in the utility model. DETAILED DESCRIPTION
[0032] 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.
[0033] According to the concept of this application, Figures 1 to 4 An embodiment of a GaN HEMT device with a back barrier structure having a gradient composition is described, which can effectively improve the quality at the interface and reduce the adverse effects of interface scattering and back barriers on the main channel mobility. Specifically, the GaN HEMT device with a back barrier structure having a gradient composition is constructed as an integrated structure, which has components such as a first AlGaN back barrier layer, a second AlGaN barrier layer, a GaN buffer layer and a GaN channel layer. By introducing a back barrier layer having a gradient composition, the electron confinement in the channel is effectively enhanced, the short channel effect of the device is suppressed, the DC characteristics of the device are improved, and the power characteristics of the GaN-based HEMT device are thereby improved. In the face of the interface scattering problem caused by the back barrier structure, the gradient composition back barrier structure can reduce interface scattering and parasitic parameters compared to the fixed composition back barrier structure, reduce the impact on the GaN main channel, and improve the small signal and large signal characteristics of the device.
[0034] Combination Figure 1-4As shown, the utility model provides a GaN HEMT device with a back barrier structure with a gradual component change, comprising a SiC (silicon carbide) substrate layer, a GaN (gallium nitride) buffer layer connected to the top of the SiC (silicon carbide) substrate layer, a first AlGaN (aluminum gallium nitride) back barrier layer connected to the top of the GaN (gallium nitride) buffer layer, a GaN (gallium nitride) channel layer connected to the top of the first AlGaN (aluminum gallium nitride) back barrier layer, an AlN (aluminum nitride) insertion layer connected to the top of the GaN (gallium nitride) channel layer, a second AlGaN (aluminum gallium nitride) barrier layer connected to the top of the AlN (aluminum nitride) insertion layer, a source electrode and a drain electrode are relatively connected to the two sides of the second AlGaN (aluminum gallium nitride) barrier layer, and a gate is installed near the middle of the second AlGaN (aluminum gallium nitride) barrier layer;
[0035] The second AlGaN (aluminum gallium nitride) barrier layer is connected to Si 3 N 4 (Silicon nitride) passivation layer;
[0036] The grid comprises a grid cap and a grid foot fixed in the middle of the grid cap, and the grid cap and the grid foot are perpendicular to each other.
[0037] The substrate layer is mainly used to provide bearing and protection functions. In some embodiments, the material of the substrate layer can be set to sapphire, silicon or silicon carbide. For the technical solution of this embodiment, the material of the substrate layer is silicon carbide.
[0038] In some embodiments, the Al composition of the side of the first AlGaN back barrier layer close to the GaN channel layer is 0, and increases linearly toward the side away from the GaN channel layer, and the increase range value can be set to 0.05-0.2. According to the technical solution of this embodiment, the Al composition of the side of the first AlGaN back barrier layer close to the GaN channel layer is 0, and increases linearly to 0.1 toward the side away from the GaN channel layer. The thickness of the first AlGaN back barrier layer is 10nm. The first AlGaN back barrier with a gradient Al composition can effectively improve the quality at the interface, reduce the adverse effects of interface scattering and back barriers on the main channel mobility, thereby obtaining better small signal and large signal characteristics.
[0039] In some embodiments, the thickness range of the GaN buffer layer can be set to 0.8-2μm, and the thickness range of the GaN channel layer can be set to 200nm-500nm. For the technical solution of this embodiment, the thickness of the GaN buffer layer is 1.2μm, and the thickness of the GaN channel layer is 480nm.
[0040] According to the technical solution of this embodiment, the thickness of the AlN insertion layer is 1 nm. The AlN insertion layer can suppress the diffusion of the two-dimensional electron gas in the channel to the AlGaN barrier layer, reduce the leakage current, and facilitate the increase of the concentration of the two-dimensional electron gas.
[0041] In some embodiments, the fixed value of the Al component in the second AlGaN barrier layer can be set to 0.2-0.3. For the technical solution of this embodiment, the Al component in the second AlGaN barrier layer is fixed to 0.25, and its thickness is 20nm. A groove is etched on the upper surface of the second AlGaN barrier layer, and the groove depth is 10nm. The gate penetrates the Si3N4 passivation layer and is embedded in the groove. The opened groove can shorten the distance from the gate to the GaN channel layer and improve the gate control capability. It should be noted that the shape of the groove can be set to a square or a wedge. For the technical solution of this embodiment, the shape of the groove is set to a square.
[0042] According to the technical solution of this embodiment, the gate length Lg=0.1μm, the gate cap length is 1μm, the gate cap width is 0.5μm, the gate foot height is 0.2μm, the distance from the gate to the source Lgs=1.1μm, the distance from the gate to the drain Lgd=1.6μm, the source and the drain are both ohmic contacts, and the gate is a Schottky contact.
[0043] Furthermore, the thickness of the Si3N4 passivation layer is 60 nm, and its function is to suppress the current collapse effect of the GaN HEMT device.
[0044] The following is a further description of a GaN HEMT device with a back-barrier structure with a gradient composition provided by the present invention in conjunction with the accompanying drawings and implementation examples.
[0045] A GaN HEMT device with a component-gradient back barrier structure comprises a SiC substrate layer, a GaN buffer layer is connected above the SiC substrate layer, a first AlGaN back barrier layer is connected above the GaN buffer layer, a GaN channel layer is connected above the first AlGaN back barrier layer, an AlN insertion layer is connected above the GaN channel layer, a second AlGaN barrier layer is connected above the AlN insertion layer, a source electrode and a drain electrode are connected to opposite sides of the second AlGaN barrier layer, and a gate is installed near the middle of the second AlGaN barrier layer;
[0046] A Si3N4 passivation layer is connected to the second AlGaN barrier layer;
[0047] The grid comprises a grid cap and a grid foot fixed in the middle of the grid cap, and the grid cap and the grid foot are perpendicular to each other.
[0048] In order to verify the advantages of the GaN HEMT device with a gradient composition back barrier structure proposed in this application over the ordinary GaN HEMT device without back barrier, the inventors of this application conducted a simulation comparison of the relevant performance indicators of the two. Since the Al element contained in the 0-0.1 gradient composition back barrier is the same as the Al element contained in the 0.05 fixed composition back barrier, the first AlGaN back barrier with gradient composition can be compared with the conventional Al0.05Ga0.95N back barrier with fixed composition. The structure of the conventional GaN HEMT device with fixed composition back barrier layer is shown in FIG. Figure 2 As shown in Figure 2, the Al composition of the back barrier layer is fixed at 0.05 and the thickness is 10 nm. Except for the back barrier, the other parameters are the same as Figure 1 same.
[0049] See also Figure 3 , the small signal characteristics of the traditional fixed-composition back-barrier and the gradient-composition back-barrier GaN HEMT devices were simulated and compared by using the Atlas two-dimensional device simulation tool of Silvaco TCAD (semiconductor process simulation and device simulation tool). The gate bias voltage Vgs=0V, the source-drain voltage Vds=15V, when the thickness of the back-barrier layer is less than or equal to 12.5nm, the maximum oscillation frequency of the gradient-composition device is significantly greater than that of the fixed-composition device. This is due to the smaller scattering effect of the gradient-composition back-barrier device; when the thickness of the gradient-composition back-barrier is 10nm, the current gain cutoff frequency is 83.9GHz and the maximum oscillation frequency is 144GHz; and when the thickness of the back-barrier layer is greater than 12.5nm, due to the enhancement of parasitic effects, there is no obvious difference in the small signal characteristics of the two.
[0050] See also Figure 4 , which shows the performance simulation comparison between the traditional Al0.05Ga0.9N back barrier HEMT device with fixed composition and the composition gradient back barrier HEMT device proposed in the present invention:
[0051] The static operating point gate bias is set to -3V, the source-drain voltage is 30V, and Rg = Rd = 50Ω is taken as the impedance matching, so that the power device is in the AB class working state; when the device operating frequency is 10GHz, compared with the fixed component back barrier device, the power density of the gradient component back barrier device is 4.49W / mm, an increase of 0.3W / mm; the power gain is 12.9dB, an increase of 0.7dB; the power added efficiency PAE reaches 21.7%, an increase of 2.5%. Due to the reduction of the influence of scattering on the main channel of the device, the large signal characteristics of the gradient component back barrier device are comprehensively improved compared with the fixed component back barrier device.
[0052] In summary, by introducing an AlGaN back-barrier structure with a gradient composition, the height of the barrier under the gate can be effectively raised, the gate control capability can be improved, the electron confinement in the channel can be enhanced, and the leakage current can be reduced. Compared with devices without a back-barrier structure, the device performance is improved.
[0053] 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.
[0054] 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.
[0055] 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.
[0056] 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 HEMT device having a back barrier structure with a gradient composition, comprising a SiC substrate layer, characterized in that: A GaN buffer layer is connected above the SiC substrate layer, a first AlGaN back barrier layer is connected above the GaN buffer layer, a GaN channel layer is connected above the first AlGaN back barrier layer, an AlN insertion layer is connected above the GaN channel layer, a second AlGaN barrier layer is connected above the AlN insertion layer, a source electrode and a drain electrode are connected to opposite sides of the second AlGaN barrier layer, and a gate is installed near the middle of the second AlGaN barrier layer; A Si3N4 passivation layer is connected to the second AlGaN barrier layer; The grid comprises a grid cap and a grid foot fixed in the middle of the grid cap, and the grid cap and the grid foot are perpendicular to each other.
2. A GaN HEMT device with a back barrier structure with a gradient composition according to claim 1, characterized in that: The Al composition of the first AlGaN back barrier layer is 0 on the side close to the GaN channel layer and increases linearly toward the side away from the GaN channel layer. The Al composition in the first AlGaN back barrier layer increases in the range of 0.05-0.2, and the thickness of the first AlGaN back barrier layer is 10 nm.
3. A GaN HEMT device with a back barrier structure with a gradient composition according to claim 2, characterized in that: The GaN buffer layer has a thickness of 0.8-2 μm.
4. The GaN HEMT device having a back barrier structure with a gradient composition according to claim 2, characterized in that: The thickness of the GaN channel layer is 200nm-500nm.
5. The GaN HEMT device having a back barrier structure with a gradient composition according to claim 4, characterized in that: The thickness of the AlN insertion layer is 1 nm.
6. The GaN HEMT device having a back barrier structure with a gradient composition according to claim 5, characterized in that: The Al composition in the second AlGaN barrier layer is fixed at 0.2-0.3, and the thickness is 20 nm.
7. The GaN HEMT device having a back barrier structure with a gradient composition according to claim 1, characterized in that: A groove is etched on the upper surface of the second AlGaN barrier layer, the depth of the groove is 10 nm, and the gate penetrates the Si3N4 passivation layer and is embedded in the groove.
8. The GaN HEMT device having a back barrier structure with a gradient composition according to claim 7, characterized in that: The Si3N4 passivation layer has a thickness of 60 nm.
9. The GaN HEMT device with a back barrier structure with a gradient composition according to claim 7, characterized in that: The gate length Lg=0.1 μm, the gate cap length is 1 μm, the gate cap width is 0.5 μm, and the gate foot height is 0.2 μm.
10. The GaN HEMT device having a back barrier structure with a gradient composition according to claim 7, characterized in that: The distance from the gate to the source is Lgs=1.1 μm, the distance from the gate to the drain is Lgd=1.6 μm, the source and the drain are both ohmic contacts, and the gate is a Schottky contact.