HEMT device

Abstract

The invention discloses an HEMT device. The HEMT device comprises a substrate; the channel layer is arranged on one side of the substrate, and the material of the channel layer comprises undoped GaN; the heteroepitaxial structure comprises at least one superlattice structure formed by stacking an AlGaN layer and a GaN layer, and in each superlattice structure, the GaN layer is arranged on the side, away from the channel layer, of the AlGaN layer; the barrier layer is arranged on the side, away from the channel layer, of the heteroepitaxial structure, and the material of the barrier layer comprises AlGaN; and the total thickness of the channel layer and the heteroepitaxial structure is 150-350 nanometers. According to the embodiment of the invention, the heteroepitaxial structure is arranged between the channel layer and the barrier layer, so that a plurality of two-dimensional electron gas channels can be formed, the crowding condition of electrons in the single and two-dimensional electron gas channels is reduced, the electron mobility is improved, and the on-resistance is reduced; by designing the total thickness of the channel layer and the heteroepitaxial structure, the chip manufacturing process does not need to be redesigned in the subsequent process, and the situation that the processing difficulty of the chip manufacturing process in the subsequent process is increased is avoided.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a HEMT device. Background Art

[0002] With the development of semiconductor technology, gallium nitride HEMT (High electron mobility transistor) has been increasingly used. HEMT uses two materials with different energy gaps to form a heterojunction, which can obtain 2-DEG (Two-dimensional electron gas) to provide a channel for carriers. The gallium nitride HEMT developed in recent years has attracted a lot of attention due to its good high-frequency characteristics.

[0003] Conventional GaN HEMTs have a single-channel two-dimensional electron gas. The electrons in the single-channel device are tightly packed, which increases the rate of electron-electron collisions, thereby increasing resistance and the power consumption of the HEMT device. Therefore, existing solutions improve GaN HEMTs to achieve multiple two-dimensional electron gases in GaN HEMTs. However, most of these improvements require redesigning the structure of GaN HEMTs, which increases the difficulty of processing the chip manufacturing process in subsequent processes. Summary of the invention

[0004] In view of at least some of the problems and shortcomings in the prior art, an embodiment of the present invention discloses a HEMT device to realize multi-channel two-dimensional electron gas without changing the processing difficulty of the existing chip manufacturing process.

[0005] On the one hand, an embodiment of the present invention provides a HEMT device, for example, including: a substrate; a channel layer, arranged on one side of the substrate, the material of the channel layer includes undoped GaN; a heteroepitaxial structure, including at least one superlattice structure formed by stacking an AlGaN layer and a GaN layer, in each of the superlattice structures, the GaN layer is arranged on a side of the AlGaN layer away from the channel layer; a barrier layer, arranged on a side of the heteroepitaxial structure away from the channel layer, the material of the barrier layer includes AlGaN; wherein the total thickness of the channel layer and the heteroepitaxial structure is 150 to 350 nanometers.

[0006] It can be seen from the above that the above technical features of the present invention can have one or more of the following beneficial effects: the embodiment of the present invention can form a plurality of two-dimensional electron gas channels by arranging a heteroepitaxial structure between the channel layer and the barrier layer, thereby reducing the crowding of electrons in a single two-dimensional electron gas channel, thereby improving the electron mobility and reducing the on-resistance; in addition, by designing the total thickness of the channel layer and the heteroepitaxial structure to be 150 to 350 nanometers, there is no need to redesign the chip process in subsequent processes, thereby avoiding the situation in which the processing difficulty of the chip process in subsequent processes is increased due to the long distance between the channels of the multi-channel HEMT device. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0008] Figure 1 A schematic diagram of the structure of a HEMT device provided in an embodiment of the present invention.

[0009] Figure 2 Another schematic diagram of the structure of a HEMT device provided in an embodiment of the present invention.

[0010] Figure 3 for Figure 1 Schematic diagram of the specific structure of the HEMT device.

[0011] Figure 4 for Figure 2 Schematic diagram of the specific structure of the HEMT device.

[0012] Figure 5 It is a schematic structural diagram of a HEMT device provided in a specific embodiment of the present invention.

[0013] Figure 6 A flow chart of a method for preparing a HEMT device provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0014] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0015] See also Figure 1 The embodiment of the present invention provides a HEMT device 10, for example, including: a substrate 100, a channel layer 500, a heteroepitaxial structure 600 and a barrier layer 700. The channel layer 500 is, for example, disposed on one side of the substrate 100, and the material of the channel layer 500 includes undoped GaN. Figure 2 The heteroepitaxial structure 600, for example, includes at least one superlattice structure 610 formed by stacking an AlGaN layer 611 and a GaN layer 612. In each of the superlattice structures 610, the GaN layer 612 is disposed on a side of the AlGaN layer 611 away from the channel layer 500. The GaN layer 612 is, for example, undoped GaN. The barrier layer 700 is, for example, disposed on a side of the heteroepitaxial structure 600 away from the channel layer 500, and the material of the barrier layer includes AlGaN. Specifically, the total thickness of the channel layer and the heteroepitaxial structure is 150 to 350 nanometers.

[0016] For example, the material of the substrate 100 is, for example, Al2O3, for example, a sapphire substrate. The superlattice structure mentioned above is, for example, a layered fine composite material, which is, for example, formed by alternating the growth of a periodic structure of two materials with good lattice matching. In an embodiment of the present invention, the AlGaN layer 611 of the superlattice structure 610 in the heteroepitaxial structure 600, for example, forms a heterostructure with the channel layer 500, thereby obtaining 2-DEG (Two-dimensional electron gas) to form a two-dimensional electron gas channel. And the GaN layer 612, for example, can form a heterostructure with the barrier layer 700, thereby obtaining 2-DEG to form a two-dimensional electron gas channel. Therefore, when the heteroepitaxial structure 600 includes only one superlattice structure 610, the embodiment of the present invention can provide two two-dimensional electron gas channels. In other words, based on the fact that the heteroepitaxial structure 600 includes at least one superlattice structure 610, the embodiment of the present invention can provide at least two two-dimensional electron gas channels, which can increase the mobility of electrons and reduce the crowding of electrons in a single two-dimensional electron gas channel, thereby improving the electron mobility and reducing the on-resistance.

[0017] As mentioned above, since the thickness of the channel layer in the existing solution is 150-350 nanometers, in the embodiment of the present invention, the total thickness of the channel layer 500 and the heteroepitaxial structure 600 is designed to be 150-350 nanometers, so that there is no need to redesign the chip process in the subsequent process, thereby avoiding the situation where the chip process in the subsequent process is more difficult due to the long distance between the channels of the multi-channel HEMT device.

[0018] The HEMT device 10 is described below by way of example with reference to a specific embodiment.

[0019] See also Figure 3 The HEMT device 10 provided in the embodiment of the present invention, for example, includes: a substrate 100 , a high resistance layer 400 , a channel layer 500 , a heteroepitaxial structure 600 , an isolation layer 700 , a barrier layer 800 and a protective layer 900 .

[0020] See also Figure 3, for example, a buffer layer is provided on the substrate 100, and the thickness of the buffer layer is, for example, 20 to 80 nanometers. For example, the buffer layer includes, for example, a first buffer layer 200 and / or a second buffer layer 300. Specifically, the first buffer layer 200 is provided on the substrate 100 by a plasma enhanced chemical vapor deposition method. For example, the material of the first buffer layer 200 provided is, for example, AlN, and its thickness is, for example, 20 to 40 nanometers. By heat treatment in a hydrogen environment at 1000 to 1200° C. for 8 to 12 minutes, it is helpful for the first buffer layer 200 to obtain AlN material with higher crystal quality. Based on the above, the second buffer layer 300 is, for example, provided on the side of the first buffer layer 200 away from the substrate 100. Specifically, the second buffer layer 300 is deposited on the side of the first buffer layer 200 away from the substrate 100 by a metal organic compound chemical vapor deposition method. Among them, the material of the second buffer layer 300 is, for example, AlN or AlGaN, and its thickness is, for example, 20 to 40 nanometers.

[0021] Specifically, compared to substrate 100 (sapphire substrate, material is Al2O3), AlN, for example, has a smaller lattice mismatch and thermal expansion coefficient mismatch with GaN, and GaN is epitaxially grown on the AlN surface, and the obtained GaN material has a lower XRD(102) / XRD(002) and a smoother surface. Among them, XRD(102) is the characteristic peak of the crystal plane of GaN material 102 in the XRD diffraction spectrum, and XRD(002) is the characteristic peak of the crystal plane of GaN material 002 in the XRD diffraction spectrum. That is, the first buffer layer 200 and the second buffer layer 300 are used, for example, to buffer the problem of mismatch between the Al2O3 lattices in GaN and the substrate 100.

[0022] See also Figure 3 The high resistance layer 400 is, for example, disposed on a side of the second buffer layer 300 away from the first buffer layer 200, wherein the high resistance layer 400 is, for example, a flat high-resistance GaN layer structure. For example, the roughness of the high resistance layer 400 is, for example, less than 0.3 nanometers, and the resistance Rs of the high resistance layer 400 is, for example, greater than 1e9Ω / □. The material of the high resistance layer 400 includes GaN, and the thickness of the high resistance layer 400 is, for example, greater than 1 micron. In a specific embodiment, the high resistance layer 400 is a GaN layer doped with Fe and / or C, and the doping concentration of the high resistance layer 400 is greater than 2e18cm -3. The high resistance layer 400 is doped with Fe and / or C to increase the resistance of the high resistance layer 400. In another specific embodiment, the high resistance layer 400 is, for example, an undoped GaN layer, and a flat high resistance high resistance layer 400 can be obtained by direct growth under epitaxial conditions, for example, the V / III ratio (NH3 / Ga ratio) of the high resistance layer 400 and the growth temperature of the high resistance layer 400 can be optimized, for example, the V / III ratio of the GaN high resistance layer is 900-2000, and the growth temperature is 1000°C-1150°C, so as to obtain an undoped GaN high resistance layer 400 with a flat high resistance characteristic. By providing a flat high resistance high resistance layer 400, leakage can be suppressed and the voltage resistance of the HEMT device 10 can be improved.

[0023] As mentioned above, the channel layer 500 is, for example, disposed on a side of the high resistance layer 400 away from the second buffer layer 300, and the material of the channel layer 500 is undoped GaN. The thickness of the channel layer 500 is in the range of 100 to 200 nanometers, and the thickness of the channel layer 500 is designed to avoid the channel layer 500 of the HEMT device 10 being too thick, which causes the HEMT device 10 to fail to shut down normally and cause leakage problems.

[0024] Preferably, the heteroepitaxial structure 600 includes at most three superlattice structures 610 . Figure 4 That is, it shows the case where the heteroepitaxial structure 600 includes three superlattice structures 610. For example, a heterostructure is formed between the AlGaN layer 611 and the channel layer 500, for example, at the surface of the channel layer 500 close to the AlGaN layer 611, and then 2-DEG is obtained to form a two-dimensional electron gas channel 620. A heterostructure is formed between the GaN layer 612 and the AlGaN layer 611, for example, at the surface of the GaN layer 612 close to the AlGaN layer 611, and then 2-DEG is obtained to form a two-dimensional electron gas channel 620. And a heterostructure is formed between the GaN layer 612 and the barrier layer 800, for example, at the surface of the GaN layer 612 close to the barrier layer 800, and then 2-DEG is obtained to form a two-dimensional electron gas channel 620. That is, in Figure 4 For example, four two-dimensional electron gas channels are formed in the solution, which can effectively reduce electron crowding and thus improve electron mobility. However, when the number of superlattice structures 610 exceeds three, the effect of reducing electron crowding is not significant enough due to the large number of two-dimensional electron gas channels generated. Moreover, when the number of superlattice structures 610 is large, the difficulty of subsequent chip manufacturing process will increase significantly, and the resistance of the chip manufacturing process may also increase.

[0025] Furthermore, the thickness of each of the superlattice structures 610 is, for example, less than or equal to 40 nanometers. This is to avoid the problem of processing difficulties or leakage caused by the long distance between the channels of the heteroepitaxial structure 600, which requires the subsequent chip process to change the design. Preferably, the thickness of the channel layer 500 ranges from 100 to 200 nanometers, the thickness of the AlGaN layer 611 is less than or equal to 10 nanometers, and the thickness of the GaN layer 612 is greater than the thickness of the AlGaN layer 611 and less than or equal to 30 nanometers. When the thickness of the AlGaN layer 611 is too large, it will affect the formed two-dimensional electron gas channel, resulting in poor dispersion of electrons in the two-dimensional electron device channel.

[0026] In one embodiment, see Figure 5 , the superlattice structure 610 also includes an InGaN layer 613. In each of the superlattice structures 610, the InGaN layer 613 is arranged between the AlGaN layer 611 and the GaN layer 612. By setting the InGaN layer 613, the high electron mobility thereof is utilized to effectively improve the mobility of electrons in the formed two-dimensional electron gas channel. That is, the AlGaN / InGaN / GaN heterojunction formed by inserting the InGaN layer into the AlGaN / GaN heterojunction interface is superior to the conventional AlGaN / GaN heterojunction. It should be noted that although the addition of the InGaN layer 613 can improve the electron mobility, it will also increase the thickness of the superlattice structure 610 accordingly. The thickness of the superlattice structure 610 still needs to be less than or equal to 40 nanometers, so as to avoid the long distance between the channels of the heteroepitaxial structure 600, which may cause the subsequent chip process to change the design or leakage problems.

[0027] Preferably, see Figure 3 The isolation layer 700 is disposed on a side of the heteroepitaxial structure 600 away from the channel layer 500 . The material of the isolation layer 700 is AlN. The thickness of the isolation layer 700 is, for example, 1 to 2 nanometers. The mobility performance of the HEMT device 10 can be improved by disposing the isolation layer 700 .

[0028] Further, see Figure 3 The barrier layer 800 is, for example, disposed on a side of the isolation layer 700 away from the heteroepitaxial structure 600, and the material of the barrier layer 800 is AlGaN. The proportion of aluminum in the barrier layer 800 is, for example, 20% to 30%, and the thickness of the barrier layer 800 is, for example, 15 to 30 nanometers. The AlGaN in the barrier layer 800, for example, forms a heterostructure with the GaN layer 612 in the superlattice structure 610 in the heteroepitaxial structure 600, thereby obtaining 2-DEG.

[0029] Specifically, by providing an isolation layer 700 (AlN thin layer) between the barrier layer 800 (AlGaN) and the GaN layer 612 in the superlattice structure 610 in the heteroepitaxial structure 600, the electron density of the two-dimensional electron gas can be increased, the resistance can be reduced, the mobility can be increased, and a larger current can be achieved. Specifically, the effective ΔEc (cathode polarization value) caused by the polarization effect of the AlGaN / AlN / GaN structure is increased, a deeper quantum well is generated, and thus a higher electron concentration is generated; the penetration of the two-dimensional electron gas into the barrier layer 800 is significantly reduced, so the alloy disorder scattering can be reduced, thereby improving the mobility. That is, the AlGaN / AlN / GaN heterojunction formed by inserting an AlN thin layer at the AlGaN / GaN heterojunction interface is superior to the conventional AlGaN / GaN heterojunction.

[0030] In addition, see Figure 3 , the HEMT device 10 further includes, for example, a protective layer 900, and the surface protective layer 900 includes, for example, a protective layer and / or a passivation layer. The protective layer 900 is disposed on the side of the barrier layer 800 away from the isolation layer 700. For example, a first protective layer may be disposed on the side of the barrier layer 800 away from the isolation layer 700, and the material of the first protective layer may be, for example, GaN; or a second protective layer may be disposed on the side of the barrier layer 800 away from the isolation layer 700, and the material of the second protective layer may be, for example, SiNx; or a first protective layer may be disposed on the side of the barrier layer 800 away from the isolation layer 700, and a second protective layer may be disposed on the first protective layer. The thickness of the protective layer is, for example, 1 to 4 nanometers. Among them, the first protective layer can protect the HEMT device, and the second protective layer can improve the dynamic resistance and reduce leakage.

[0031] In summary, the embodiment of the present invention forms a plurality of two-dimensional electron gas channels by arranging a heteroepitaxial structure between the channel layer and the barrier layer, thereby reducing the crowding of electrons in a single two-dimensional electron gas channel, thereby improving the electron mobility and reducing the on-resistance; in addition, by designing the total thickness of the channel layer and the heteroepitaxial structure to be 150 to 350 nanometers, it is unnecessary to redesign the chip process in subsequent processes, thereby avoiding the increased difficulty of chip process in subsequent processes due to the long distance between channels of the multi-channel HEMT device.

[0032] In addition, see Figure 6 The following is a method for preparing the HEMT device 10 provided in an embodiment of the present application, and the preparation method includes, for example:

[0033] S11: providing a substrate;

[0034] S13: growing a high resistance layer on the substrate;

[0035] S15: sequentially growing a channel layer, a heteroepitaxial structure, an isolation layer and a barrier layer on the high resistance layer.

[0036] Wherein, step S12 is further included between step S11 and step S13, and step S12 specifically includes:

[0037] S121: growing AlN on the substrate by plasma enhanced chemical vapor deposition method, and heat treating in a hydrogen environment at 1000-1200° C. for 8-12 minutes to improve the lattice quality of the first buffer layer;

[0038] S123: growing a second buffer layer on the first buffer layer by metal organic chemical vapor deposition.

[0039] Based on the above, step S13 specifically includes: growing the high resistance layer on the second buffer layer under the conditions of epitaxial GaN flow field and temperature field.

[0040] Furthermore, step S15 specifically includes:

[0041] S151: growing a channel layer on the high resistance layer;

[0042] S153: growing a heteroepitaxial structure on the channel layer;

[0043] S155: growing an isolation layer on the heteroepitaxial structure;

[0044] S157: Growing a barrier layer on the heteroepitaxial structure.

[0045] Wherein, step S153 specifically includes: growing at least one superlattice structure on the channel layer; wherein the superlattice structure includes an AlGaN layer and a GaN layer grown sequentially.

[0046] In addition, step S17 is included after step S15, and step S17 specifically includes:

[0047] S171: growing a protective layer on the barrier layer.

[0048] Step S171 specifically includes: growing a first protective layer on the barrier layer; and growing a second protective layer on the first protective layer.

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A HEMT device, characterized in that: include: substrate; A channel layer is disposed on one side of the substrate, wherein the material of the channel layer includes undoped GaN; A heteroepitaxial structure, comprising at least one superlattice structure formed by stacking an AlGaN layer and a GaN layer, wherein in each of the superlattice structures, the GaN layer is disposed on a side of the AlGaN layer away from the channel layer; A barrier layer is arranged on a side of the heteroepitaxial structure away from the channel layer, and the material of the barrier layer includes AlGaN; Wherein, the total thickness of the channel layer and the heteroepitaxial structure is 150 to 350 nanometers.

2. The HEMT device according to claim 1, characterized in that The heteroepitaxial structure includes at most three of the superlattice structures.

3. The HEMT device according to claim 1, wherein: The thickness of each of the superlattice structures is less than or equal to 40 nanometers.

4. The HEMT device according to claim 3, characterized in that The thickness of the AlGaN layer is less than or equal to 10 nanometers, and the thickness of the GaN layer is greater than the thickness of the AlGaN layer and less than or equal to 30 nanometers.

5. The HEMT device according to claim 3, characterized in that The thickness of the channel layer ranges from 100 to 200 nanometers.

6. The HEMT device according to claim 1, wherein: The superlattice structure further includes an InGaN layer, and in each of the superlattice structures, the InGaN layer is disposed between the AlGaN layer and the GaN layer.

7. The HEMT device according to any one of claims 1 to 6, characterized in that: The proportion of Al element in the barrier layer is 20% to 30%, and the proportion of Al element in the AlGaN layer is the same as the proportion of Al element in the barrier layer.

8. The HEMT device according to claim 7, characterized in that It also includes an isolation layer, which is arranged between the heteroepitaxial structure and the barrier layer. The material of the isolation layer includes AlN, and the thickness of the isolation layer ranges from 1 to 2 nanometers.

9. The HEMT device according to claim 8, characterized in that The invention also includes a high resistance layer, which is arranged between the substrate and the channel layer, and the high resistance layer is an undoped GaN layer; or the high resistance layer is a Fe and / or C doped GaN layer, and the doping concentration of the high resistance layer is greater than 2e18cm -3 .

10. The HEMT device according to claim 9, characterized in that Also includes: a buffer layer, disposed between the high resistance layer and the substrate, the thickness of the buffer layer being 20 to 80 nanometers, and the material of the buffer layer comprising AlN and / or AlGaN; and, The protective layer is arranged on a side of the barrier layer away from the heteroepitaxial structure. The material of the protective layer is GaN and / or SiNx. The thickness of the protective layer is 1 to 4 nanometers.

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