A transverse-longitudinal composite channel device and a method for manufacturing the same

Abstract

The application discloses a transverse-longitudinal composite channel device and a preparation method thereof. The preparation method comprises a substrate layer, a buffer layer laminated structure and a multi-channel structure arranged in sequence. The buffer layer laminated structure comprises a first buffer layer and a second buffer layer. The second buffer layer and the multi-channel structure form a ring-shaped laminated structure. The multi-channel structure comprises a plurality of channel units arranged in layers. The lower end of the center of the ring-shaped laminated structure comprises a side gate structure. The side gate structure comprises an electrostatic shielding layer and a gate metal layer. A longitudinal aperture is formed in the center of the ring-shaped laminated structure. The longitudinal aperture comprises an aperture dielectric layer and a source electrode. The outer side of the upper surface of the ring-shaped laminated structure comprises a plurality of columnar gate structures. A drain electrode is arranged outside the ring-shaped laminated structure. The application forms a multi-layer two-dimensional electron gas transmission path through a plurality of channel units in the vertical direction. In combination with three-dimensional potential regulation, a multi-path current system continuously conducted from top to bottom is constructed, and the current carrying capacity and power density can be significantly improved.

Description

Technical Field

[0001] This invention belongs to the field of power device technology, specifically relating to a transverse and longitudinal composite channel device and its fabrication method. Background Technology

[0002] Wide-bandgap semiconductors (such as GaN and SiC) are widely used in RF power amplifiers, power electronics, and high-voltage converters due to their advantages such as high breakdown field, high thermal conductivity, and high electron mobility. A typical GaN HEMT (High Electron Mobility Transistor) achieves high lateral conductivity by forming a two-dimensional electron gas through an AlGaN / GaN heterojunction. However, its breakdown voltage is limited by the lateral electric field distribution, making it difficult to balance high voltage and high current.

[0003] To improve breakdown performance, existing research has introduced vertical structures, such as CAVET (Current Aperture Vertical Electron Transistor) and BAVET (Barrier Aligned Vertical Field-Effect Transistor). BAVET significantly improves the on-state performance by combining a lateral InGaAs channel, a vertical aperture drift region, and an electrostatic shielding layer, and reduces the drain voltage drop by utilizing trap modulation.

[0004] However, existing wide-bandgap power semiconductor devices (such as lateral AlGaN / GaN HEMTs, vertical GaN MOSFETs, and CAVET / BAVET structures) mostly employ unidirectional (lateral or vertical) conduction modes. These structures suffer from the following problems: a single conduction path limits current density, making it difficult to achieve high power output; during high-voltage operation, the electric field concentrates at the gate and channel edges, limiting the breakdown voltage; and it is difficult to simultaneously achieve low on-resistance and high breakdown voltage, resulting in a trade-off between power density and electrical performance. Furthermore, traditional lateral HEMTs suffer from high parasitic resistance and difficult thermal management in high-voltage applications; while vertical structures, although having high breakdown voltage, have conduction current limited by the effective channel area, making it difficult to achieve high integration and high efficiency at the chip level. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a transverse and longitudinal composite channel device and its fabrication method. The technical problem to be solved by this invention is achieved through the following technical solution: One aspect of the present invention provides a transverse and longitudinal composite channel device, comprising a substrate layer, a buffer layer stack structure, and a multi-channel structure arranged sequentially from bottom to top, wherein... The buffer layer stack structure includes a first buffer layer and a second buffer layer stacked sequentially on the substrate layer, wherein the second buffer layer is located at the center of the upper surface of the first buffer layer and its surface size is smaller than that of the first buffer layer. The second buffer layer and the multi-channel structure are both ring-shaped, forming a ring-shaped stacked structure. The multi-channel structure includes multiple channel units stacked from bottom to top, and each channel unit includes a channel layer and a barrier layer stacked from bottom to top. A side gate structure is embedded at the lower center of the annular stacked structure. The side gate structure includes an annular electrostatic shielding layer and a gate metal layer disposed in the central region of the electrostatic shielding layer. The annular stacked structure has a longitudinal aperture at its center. The longitudinal aperture extends vertically downward from the center of the upper surface of the multi-channel structure to the interior of the second buffer layer. The interior of the longitudinal aperture is filled with a pore dielectric layer and a source electrode from bottom to top. The outer side of the upper surface of the annular stacked structure includes a plurality of cylindrical gate structures surrounding the electrostatic shielding layer. Each cylindrical gate structure includes a gate dielectric layer extending from the upper surface of the multi-channel structure into the interior of the buffer layer and a cylindrical gate disposed inside the central hole of the gate dielectric layer. A drain electrode is provided on the upper surface of the buffer layer on the outer side of the annular stacked structure.

[0006] Another aspect of the present invention provides a method for fabricating a transverse-vertical composite channel device, the method comprising: S1: Epitaxially grow a buffer layer stack structure and a bottom channel layer on a substrate layer, wherein the buffer layer stack structure includes a first buffer layer and a second buffer layer sequentially stacked on the substrate layer. S2: An opening region extending into the second buffer layer is formed by vertical etching from the center of the upper surface of the bottom channel layer, and an electrostatic shielding layer and a gate metal layer are formed in the opening region, wherein the electrostatic shielding layer surrounds the sidewall of the opening region, and the gate metal layer fills the axial central hole of the electrostatic shielding layer. S3: Multiple channel units are sequentially grown on the upper surface of the bottom channel layer to form a multi-channel structure covering the second buffer layer, the electrostatic shielding layer and the gate metal layer; S4: A plurality of columnar gate structures are formed around the electrostatic shielding layer on the outer side of the upper surface of the multi-channel structure. Each columnar gate structure includes a gate dielectric layer extending from the upper surface of the multi-channel structure to the interior of the second buffer layer and a columnar gate disposed in the axial central hole of the gate dielectric layer. S5: A longitudinal aperture is formed in the central region of the upper surface of the multi-channel structure. The longitudinal aperture extends vertically downward from the center of the upper surface of the multi-channel structure to the interior of the second buffer layer, and a pore medium layer is formed inside the longitudinal aperture. S6: A source electrode is formed in the longitudinal aperture above the aperture dielectric layer, and a drain electrode is formed on the upper surface of the first buffer layer.

[0007] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention proposes a transverse and longitudinal composite channel device, specifically a high-power semiconductor device with a transverse and longitudinal composite channel structure. By stacking multiple channel units in the longitudinal direction to form a multi-layer two-dimensional electron gas (2DEG) transport path, and making the bottom channel layer contact and connect with the longitudinal conductive aperture, a multi-path current system that is continuously conducted from top to bottom is constructed by combining three-dimensional potential modulation, thereby significantly improving the current carrying capacity and power density of the device.

[0008] 2. This invention constructs a composite transverse and longitudinal conduction path within the same heterojunction structure, enabling current transmission between the transverse high-mobility channel and the longitudinal high-voltage drift path. This effectively expands the conductive cross-section, reduces the equivalent on-resistance, and improves the device's current carrying capacity and energy transfer efficiency. Simultaneously, the multi-dimensional shunt current transmission disperses localized heat accumulation, improving the device's thermal stability and reliability. Furthermore, this invention significantly expands the effective conductive cross-section and increases current density through the series conduction of multilayer channel units, resulting in a more uniform current distribution. Simultaneously, the potential distribution of the multilayer channel units forms a natural electric field gradient, effectively mitigating high-field concentration and improving withstand voltage performance.

[0009] 3. Regarding electric field control, this invention employs a multi-column gate structure surrounding the device, combined with a side-gate structure consisting of an electrostatic shielding layer and a gate metal layer, forming a three-dimensional potential control system. This achieves uniform distribution of the electric field in both the horizontal and vertical directions, effectively suppressing electric field concentration, short-channel effects, and trapping behavior, significantly improving the device's withstand voltage performance and stability. This invention achieves a balance between low on-resistance, high breakdown voltage, and high reliability, while also possessing high mobility and excellent switching characteristics. Furthermore, the device structure exhibits good process compatibility and scalability, making it suitable for various wide-bandgap material platforms and high-power integrated applications.

[0010] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0011] Figure 1 This is a cross-sectional schematic diagram of a transverse and longitudinal composite channel device provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a multi-channel structure provided in an embodiment of the present invention; Figure 3 This is a top view schematic diagram of a transverse and longitudinal composite channel device provided in an embodiment of the present invention; Figure 4 This is a top view schematic diagram of another transverse and longitudinal composite channel device provided in an embodiment of the present invention; Figures 5a to 5g This is a schematic diagram of the fabrication process of a transverse and longitudinal composite channel device provided in an embodiment of the present invention.

[0012] Explanation of reference numerals in the attached figures: 1-Substrate layer; 2-Buffer layer stack-up structure; 21-First buffer layer; 22-Second buffer layer; 3-Multi-channel structure; 31-Channel unit; 4-Side gate structure; 41-Electrostatic shielding layer; 42-Gate metal layer; 5-Vertical aperture; 6-Aperture dielectric layer; 7-Source; 8-Gate dielectric layer; 9-Pillar gate; 10-Drain; 11-Bottom channel layer; 12-Opening region; 13-Pillar opening. Detailed Implementation

[0013] To further illustrate the technical means and effects adopted by the present invention to achieve the intended purpose, the following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a detailed explanation of a transverse and longitudinal composite channel device and its preparation method based on the present invention.

[0014] The foregoing and other technical contents, features, and effects of the present invention will be clearly presented in the following detailed description of specific embodiments in conjunction with the accompanying drawings. Through the description of the specific embodiments, a more in-depth and concrete understanding can be gained of the technical means and effects adopted by the present invention to achieve its intended purpose. However, the accompanying drawings are for reference and illustration only and are not intended to limit the technical solutions of the present invention.

[0015] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations are intended to cover non-exclusive inclusion, such that an article or apparatus comprising a list of elements includes not only those elements but also other elements not expressly listed. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the article or apparatus that includes said element.

[0016] Example 1 Please see Figure 1 , Figure 1This is a cross-sectional schematic diagram of a horizontal and vertical composite channel device provided in an embodiment of the present invention. The horizontal and vertical composite channel device includes a substrate layer 1, a buffer layer stack structure 2, and a multi-channel structure 3 arranged sequentially from bottom to top. In this embodiment, the substrate layer 1 is selected from SiC, Si, or sapphire substrates, with a thickness ≥100μm, and is used to provide mechanical support and heat dissipation. The buffer layer stack structure 2 includes a first buffer layer 21 and a second buffer layer 22 sequentially stacked on the substrate layer 1. The first buffer layer 21 has the same surface dimensions as the substrate layer 1, and the second buffer layer 22 is located at the center of the upper surface of the first buffer layer 21 and has a smaller surface dimension than the first buffer layer 21. The material of the buffer layer stack structure 2 in this embodiment is GaN:C / Fe doped, that is, gallium nitride (GaN) is used as the matrix material, and carbon (C) and iron (Fe) are doped. The buffer layer stack structure 2 is used to reduce leakage current and improve withstand voltage, with a total thickness of 1~5μm. In this embodiment, the second buffer layer 22 and the multi-channel structure 3 are both annular structures with the same inner and outer diameters, so that the second buffer layer 22 and the multi-channel structure 3 form an annular stacked structure.

[0017] Please see also Figure 1 and Figure 2 , Figure 2 This is a schematic diagram of a multi-channel structure provided in an embodiment of the present invention. The multi-channel structure 3 includes multiple channel units 31 stacked from bottom to top. Each channel unit 31 includes a channel layer and a barrier layer arranged sequentially from bottom to top. A heterojunction interface is formed between adjacent barrier layers and channel layers. Due to polarization effects and band discontinuities, a high-density two-dimensional electron gas (2DEG) is induced at this heterojunction interface, thereby constituting independent conductive channels.

[0018] The multi-channel structure 3 in this embodiment may include n channel units stacked from bottom to top, where 2≤n≤6, the thickness of each channel layer is 5~10nm, and the thickness of each barrier layer is 10~15nm. The channel layer of each channel unit is made of InGaN material, and the In content in the channel layer gradually increases along the stacking direction from bottom to top; the barrier layer of each channel unit is made of AlGaN or InAlN material.

[0019] Furthermore, such as Figure 2As shown, the multi-channel structure 3 includes bottom channel units, middle channel units, and top channel units stacked from bottom to top. The bottom channel unit includes a first channel layer and a first barrier layer arranged sequentially from bottom to top. The middle channel unit includes a second channel layer and a second barrier layer arranged sequentially from bottom to top. The top channel unit includes a third channel layer and a third barrier layer arranged sequentially from bottom to top. The first channel layer uses InGaN material with an In composition of 0-5%, and the first barrier layer uses AlGaN material with an Al composition of 20-30%. The second channel layer uses InGaN material with an In composition of 5-10%, and the second barrier layer uses AlGaN material with an Al composition of 15-25%. The third channel layer uses InGaN material with an In composition of 10-15%, and the third barrier layer uses AlGaN or InAlN material with an Al composition of 15-25%.

[0020] Preferably, taking a three-channel structure as an example, the structure includes three channel units: the channel layer of the bottom channel unit is In0. 05 Ga0. 95 The N-channel layer (approximately 5 nm thick) is topped with Al₂O₃. 25 Ga0. 75 The N-type barrier layer (approximately 10 nm thick) and the channel layer of the intermediate channel unit are InO. 10 Ga0. 90 The N-channel layer (approximately 5 nm thick) is topped with Al₂O₃. 25 Ga0. 75 The N-type barrier layer (approximately 10 nm thick) and the channel layer of the top channel unit are In0. 15 Ga0. 85 The N-channel layer (approximately 5 nm thick) is topped with Al₂O₃. 25 Ga0. 75 An N-type barrier layer (approximately 10 nm thick) is formed. Two-dimensional electron gases (2DEGs) can be created at the interfaces between each barrier layer and the underlying channel layer, thus constructing multiple parallel conductive channels in the lateral direction. By controlling the thickness of the barrier layers, adjacent channel layers are neither completely isolated nor completely isolated, allowing for carrier transport across layers. Simultaneously, by gradually increasing the In composition in the channel layers from bottom to top (e.g., 5% → 10% → 15%), a stepped potential well distribution is formed in the vertical direction (longitudinal direction), thereby controlling the energy distribution of carriers between different channels.

[0021] It should be further noted that the multi-channel structure 3 of the present invention is not naturally conductive in the longitudinal direction, but rather achieves a controllable through-path through voltage. Specifically, in the low drain voltage or off state, the channel layers are effectively isolated in the longitudinal direction, and no straight conductive path is formed, thereby avoiding short circuits in the device; while in the operating state, by adjusting the electric field distribution by applying an external drain voltage, a controlled carrier transport channel can be established in the longitudinal direction, realizing dynamic coupling between multiple channel units.

[0022] For example, in a multi-channel structure, the coupling mechanism of the intermediate channel unit mainly originates from the real-space transfer of hot electrons. When the device is in a half-open state and a high drain voltage is applied, a strong transverse electric field is formed in the drain region, accelerating electrons inside the channel layer into high-energy hot electrons. When the hot electrons gain sufficient energy, under the combined action of the longitudinal electric field inside the device, they can cross the barrier layer and enter adjacent channels, thereby realizing real-space transfer in the longitudinal direction and establishing coupled conductive paths between multiple channel units. In addition, the coupling strength between intermediate channel units can also be controlled by the material composition of the channel layer. For example, when using an InGaN channel layer, increasing the In composition will reduce the channel well energy level and enhance the carrier localization ability, thereby increasing the probability of real-space transfer of hot electrons and making it easier to form coupled conductive channels between channels. However, considering the practical limitations of material epitaxial growth quality and stress control, it is preferable to control the In composition in the range of 0 to 0.7.

[0023] By setting the aforementioned component gradient, a stepped band structure can be formed in the vertical direction. This allows each two-dimensional electron gas channel to conduct electricity laterally while simultaneously enabling cross-layer carrier transfer in the vertical direction through the band gradient. This establishes a longitudinally coupled transport path between multiple channel units, achieving three-dimensional coordinated conduction. The polarization composition (e.g., Al composition) of each barrier layer preferably decreases gradually from top to bottom, for example, 20%~30%, 15%~25%, and 10%~20%, respectively. This design results in a gradually decreasing two-dimensional electron gas density distribution in multiple channel units, while simultaneously forming a continuous potential gradient in the vertical direction.

[0024] Through the synergistic gradient design of the channel layer and barrier layer components, a stepped band structure is formed in the vertical direction of the device. The conduction band energy levels of each channel layer decrease layer by layer, thereby establishing a built-in electric field that is conducive to the downward transport of electrons under conditions of no external bias or low bias. In the device conduction state, electrons preferentially transport laterally in the upper high-density channel layer and couple downwards layer by layer under the drive of the potential gradient. Finally, they are injected through the vertical conductive aperture in the bottom channel layer, realizing a synergistic conduction mechanism of "lateral multi-layer parallel transport + vertical series output".

[0025] See also Figure 1 In this embodiment, a side gate structure 4 is embedded at the lower center of the annular stacked structure. The side gate structure 4 includes an annular electrostatic shielding layer 41 and a gate metal layer 42 disposed in the central region of the electrostatic shielding layer 41. The electrostatic shielding layer 41 and the gate metal layer 42 have the same height, their lower surfaces are flush and both extend into the interior of the second buffer layer 22, and their upper surfaces are flush and both extend into the interior of the multi-channel structure 3. Furthermore, the upper surfaces of the electrostatic shielding layer 41 and the gate metal layer 42 both extend into the channel layer of the bottom channel unit of the multi-channel structure 3. Preferably, the outer diameter of the electrostatic shielding layer 41 is 0.5~5μm, the height of both the electrostatic shielding layer 41 and the gate metal layer 42 is 0.2~2μm, the distance between the inner and outer diameters of the gate metal layer 42 (i.e., the radial thickness) is 10~80 nm, the distance between the inner and outer diameters of the electrostatic shielding layer 41 (i.e., the radial thickness) is 50~300 nm, and the distance between the upper surface of the electrostatic shielding layer 41 and the upper surface of the multi-channel structure 3 is 0.3~2 μm.

[0026] Furthermore, a longitudinal aperture 5 is formed at the center of the annular stacked structure. This longitudinal aperture 5 extends vertically downward from the center of the upper surface of the multi-channel structure 3, through the center of the gate metal layer 42, and into the interior of the second buffer layer 22. Preferably, the lower surface of the longitudinal aperture 5 is flush with the lower surface of the gate metal layer 42.

[0027] The interior of the longitudinal aperture 5 is sequentially filled from bottom to top with an aperture dielectric layer 6 and a source electrode 7. The height of the aperture dielectric layer 6 is slightly greater than that of the electrostatic shielding layer 41, and the source electrode 7 extends from the upper surface of the aperture dielectric layer 6 to the upper surface of the multi-channel structure 3. Specifically, the lower surface of the aperture dielectric layer 6 contacts the second buffer layer 22, and the upper surface of the aperture dielectric layer 6 extends to the lower surface of the barrier layer of the bottom channel unit.

[0028] In one specific embodiment, both the electrostatic shielding layer 41 and the gate metal layer 42 are annular structures, which can be circular or square rings. The outer surface of the electrostatic shielding layer 41 contacts the inner surface of the annular stacked structure, the inner surface of the electrostatic shielding layer 41 contacts the outer surface of the gate metal layer 42, and the inner surface of the gate metal layer 42 contacts the outer surface of the aperture dielectric layer 6. Adaptively, the aperture dielectric layer 6 can be cylindrical or square. The lower surfaces of the electrostatic shielding layer 41, the gate metal layer 42, and the aperture dielectric layer 6 are all in contact with the upper surface of the second buffer layer 22. Furthermore, the aperture dielectric layer 6 and the source electrode 7 have the same surface shape and size, and their longitudinal projections completely overlap.

[0029] The outer side of the upper surface of the annular stacked structure in this embodiment includes multiple cylindrical gate structures surrounding the side gate structure 4. Each cylindrical gate structure includes an annular gate dielectric layer 8 extending from the upper surface of the multi-channel structure 3 into the interior of the buffer layer stacked structure 2, and a cylindrical gate 9 disposed inside the central hole of the gate dielectric layer 8. Figure 1 As shown, each cylindrical gate structure has the same shape and size, uniformly surrounding the outer periphery of the electrostatic shielding layer 41 and spaced apart from it. In one embodiment, the gate dielectric layer 8 is a ring structure, and adaptively, the cylindrical gate 9 is a cylindrical structure, such as... Figure 3 As shown, preferably, the diameter of the cylindrical gate 9 is 50~500 nm, and the center-to-center spacing between adjacent cylindrical gates 9 is 0.2~2.0 μm. In another embodiment, the gate dielectric layer 8 is a square ring structure, and adaptably, the cylindrical gate 9 is a square pillar structure, such as... Figure 4 As shown. The lower surfaces of both the gate dielectric layer 8 and the pillar gate 9 extend into the interior of the second buffer layer 22, specifically, extending into the interior of the second buffer layer 22 by 0.2~2 μm.

[0030] In this embodiment, the gate dielectric layer 8 can be, for example, made of silicon nitride. This gate dielectric layer 8 has excellent insulation properties, effectively isolating the cylindrical gate 9 from the source / drain region, preventing current leakage and electron leakage, and improving the device's insulation performance. Furthermore, the gate dielectric layer 8 has a low dielectric constant, which helps reduce capacitance and losses, and improves the device's high-frequency performance. It also exhibits excellent heat resistance and reliability, making it adaptable to various operating environments. In this ring structure, applying a bias voltage between two adjacent cylindrical gates 9 allows control of the conduction and pinch-off of the device's lateral channel, thereby achieving effective switching control of the lateral current.

[0031] In this embodiment, a drain electrode 10 is provided on the upper surface of the first buffer layer 21 on the outer side of the annular stacked structure. The drain electrode 10 is in the shape of an annular structure and is located on the upper surface of the second buffer layer 21 of the buffer layer stacked structure 2, and is spaced apart from the inner annular stacked structure.

[0032] The gate metal layer 42 and the aperture dielectric layer 6 together form a vertical current path. This side gate structure 4 can achieve vertical electric field adjustment, and works in conjunction with the lateral channel switching control formed by the cylindrical gate structure to form a three-dimensional potential regulation system. In other words, the lateral conductive channel formed by the multi-channel structure 3 in this embodiment, together with the gate metal layer 42 and the aperture dielectric layer 6 below, forms a vertical current path (vertical conductive channel), enabling electrons to enter the vertical conductive channel from the source through the lateral conductive channel. This structure achieves combined lateral and vertical conduction.

[0033] This embodiment proposes a horizontal and vertical composite channel device, which is a high-power semiconductor device with a horizontal and vertical composite channel structure. By stacking multiple channel layers in the vertical direction to form a multi-layer two-dimensional electron gas (2DEG) transport path, and making the bottom channel layer contact and connect with the vertical conductive aperture, a multi-path current system that is continuously conducted from top to bottom is constructed by combining three-dimensional potential modulation, thereby significantly improving the current carrying capacity and power density of the device.

[0034] Example 2 Based on Example 1, this example provides a method for fabricating a transverse and longitudinal composite channel device. Please refer to [link to example]. Figures 5a to 5g , Figures 5a to 5g This is a schematic diagram illustrating the fabrication process of a transverse and longitudinal composite channel device according to an embodiment of the present invention. The fabrication method includes: S1: A buffer layer stack structure 2 and a bottom channel layer 11 are epitaxially grown on substrate layer 1, such as... Figure 5a As shown.

[0035] In this embodiment, a SiC, Si, or sapphire substrate is selected as the substrate layer 1. A buffer layer stack structure 2 is epitaxially grown on the substrate layer 1 to reduce dislocation density and improve thermal conductivity. In this embodiment, the buffer layer stack structure 2 is made of GaN material. The buffer layer stack structure 2 includes a first buffer layer 21 and a second buffer layer 22 sequentially stacked on the substrate layer 1. The total thickness of the buffer layer stack structure 2 is 1~5 μm.

[0036] Subsequently, the bottom channel layer 11 of the multi-channel structure 3 is epitaxially grown on the upper surface of the second buffer layer 22, such as... Figure 5a As shown.

[0037] S2: Define the longitudinal conduction region: A vertically etched opening region 12 extending into the second buffer layer 22 is formed from the center of the upper surface of the bottom channel layer 11, and an electrostatic shielding layer 41 and a gate metal layer 42 are formed in the opening region 12, wherein the electrostatic shielding layer 41 surrounds the sidewall of the opening region 12, and the gate metal layer 42 fills the axial central hole of the electrostatic shielding layer 41. Specifically, a photolithography process is used to define the central region, and an ICP etching process is used to form an opening region 12 (reserving a vertical structure area) in the central region. The etching depth penetrates the bottom channel layer 11 and extends into the second buffer layer 22 by 0.2~2μm. This opening region 12 will subsequently form a vertical conductive path, such as... Figure 5b As shown.

[0038] Subsequently, an electrostatic shielding layer 41 is filled into the opening region 12, and an axial center hole is formed by etching the electrostatic shielding layer 41. This axial center hole extends downward to contact the second buffer layer 22. Then, a gate structure controlling the longitudinal conductive channel, namely, a gate metal layer 42, is grown within this axial center hole. Figure 5c As shown. By precisely controlling the etching depth and surface area size of the opening region 12, a vertical current path connected to the lateral channel can be established below the lateral channel, enabling electrons to enter the longitudinal aperture from the source electrode through the lateral channel downwards.

[0039] S3: Multiple channel units 31 are sequentially grown on the upper surface of the bottom channel layer 11 to form a multi-channel structure 3 covering the second buffer layer 22, the electrostatic shielding layer 41, and the gate metal layer 42, such as... Figure 5d As shown.

[0040] Specifically, a barrier layer is first grown on the bottom channel layer 11 to form a bottom channel unit, and then multiple channel units 31 are grown. The multiple channel units 31 together form a multi-channel structure 3. Each channel unit 31 includes a channel layer and a barrier layer arranged sequentially from bottom to top. The thickness of each channel layer is 5~10 nm, and the thickness of each barrier layer is 10~15 nm.

[0041] S4: Define the cylindrical gate structure and form a lateral channel switch: Multiple cylindrical gate structures are formed around the electrostatic shielding layer 41 on the outer side of the upper surface of the multi-channel structure 3. Each cylindrical gate structure includes a gate dielectric layer 8 extending from the upper surface of the multi-channel structure 3 into the interior of the second buffer layer 22, and a cylindrical gate 9 disposed inside the central hole of the gate dielectric layer 8, such as... Figure 5e As shown.

[0042] Specifically, a plurality of columnar openings 13 are formed in the outer ring region of the upper surface of the multi-channel structure 3 prepared above, using photolithography and dry etching processes, to penetrate the multi-channel structure 3 and part of the second buffer layer 22. Specifically, the depth of the columnar openings 13 into the second buffer layer 22 is 50~300 nm 0.2~2 μm. The columnar openings 13 are spaced apart from each other and form a ring structure around the center of the upper surface of the multi-channel structure 3, and are spaced apart from the electrostatic shielding layer 41 in the central region.

[0043] Subsequently, an Al2O3 / HfO2 material is deposited in the columnar opening 13 using ALD (Atomic Layer Deposition) to form a gate dielectric layer 8. A groove is then etched in the central region of the gate dielectric layer 8, with a depth equal to the depth of the gate dielectric layer 8. A columnar gate 9, made of a Ni / Au stack, is grown within the groove. Multiple columnar gate structures form a columnar gate array, collectively constituting a lateral channel switch. The conduction and pinch-off of the lateral channel of the device are controlled between adjacent columnar gate structures, thereby achieving effective switching control of the lateral current.

[0044] S5: A longitudinal aperture 5 is formed in the central region of the upper surface of the multi-channel structure 3. The longitudinal aperture 5 extends vertically downward from the center of the upper surface of the multi-channel structure 3 into the interior of the second buffer layer 22, and a pore size dielectric layer 6 is formed inside the longitudinal aperture 5, such as... Figure 5f As shown.

[0045] This step fabricates the longitudinal conductive channel aperture and forms a three-dimensional potential control system. Specifically, a longitudinal aperture 5 with a diameter of 0.5~5 μm is formed in the central region by secondary photolithography, and a dielectric layer 6 is formed at the bottom of the longitudinal aperture 5. The thickness of the dielectric layer 6 is slightly larger than that of the gate metal layer 42, thereby forming a side gate structure 4 between the electrostatic shielding layer 41 and the gate metal layer 42. An array of cylindrical gate structures and the side gate structure 4 are connected to independent electrodes to implement the gate voltage. V G2 and V G1 The coordinated control of these components constitutes a three-dimensional potential regulation system.

[0046] S6: A source electrode 7 is formed in the longitudinal aperture 5 above the aperture dielectric layer 6, and a drain electrode 10 is formed on the upper surface of the second buffer layer 22, such as... Figure 5g As shown.

[0047] In this step, a source electrode 7 is formed in the longitudinal aperture 5 above the aperture dielectric layer 6, and a drain electrode 10 is formed on the upper surface of the second buffer layer 22, followed by annealing to form an ohmic contact. The source electrode 7 needs to be reliably connected to the multi-channel structure 3 (through-hole / stepped contact or regrown contact layer can be used); the drain electrode 10 is located at the bottom / vertical output end of the device.

[0048] Specifically, a multilayer metal Ti / Al / Ni / Au system is deposited in the defined source and drain regions, and annealing is performed to form stable ohmic contacts. The source 7 and drain 10 are connected to the lateral conductive channel and the longitudinal conductive channel, respectively, thereby realizing the transmission of current in both directions. The source metal runs through the multilayer channel unit and makes sequential contact with each channel layer to form a longitudinal series structure. The drain 10 is located in the bottom buffer layer, namely the second buffer layer 22, and serves as the overall current output terminal.

[0049] Furthermore, the preparation method of this embodiment also includes: S7: Perform surface passivation and interconnection.

[0050] Specifically, SiN is deposited on the device surface. x Materials such as Al2O3 form a passivation dielectric layer to stabilize the surface potential, and structural integration can be achieved through metal interconnects or air bridges.

[0051] This invention constructs a composite conduction path in both the transverse and longitudinal directions within the same heterojunction structure. Current can be transmitted between the transverse high-mobility channel and the longitudinal high-voltage drift path, effectively expanding the conductive cross-section, reducing the equivalent on-resistance, and improving the device's current carrying capacity and energy transfer efficiency. Simultaneously, the multi-dimensional shunt current transmission disperses localized heat accumulation, improving the device's thermal stability and reliability. This invention significantly expands the effective conductive cross-section and increases current density through the series conduction of multi-layer channel units, resulting in a more uniform current distribution. Furthermore, the potential distribution of the multi-layer channel units forms a natural electric field gradient, effectively mitigating high-field concentration and improving breakdown voltage performance. Regarding electric field modulation, this invention employs multiple surrounding cylindrical gate structures combined with a side-gate structure composed of an electrostatic shielding layer and a gate metal layer to form a three-dimensional potential modulation system. This achieves a uniform distribution of the transverse and longitudinal electric fields, effectively suppressing electric field concentration, short-channel effects, and trapping behavior, significantly improving the device's breakdown voltage performance and stability. This invention achieves a balance between low on-resistance, high breakdown voltage, and high reliability, while also possessing high mobility and excellent switching characteristics. Meanwhile, the device structure has good process compatibility and scalability, making it suitable for various wide bandgap material platforms and high-power integrated applications.

[0052] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A transverse and longitudinal composite channel device, characterized in that, It includes, from bottom to top, a substrate layer (1), a buffer layer stacked structure (2), and a multi-channel structure (3), wherein, The buffer layer stack structure (2) includes a first buffer layer (21) and a second buffer layer (22) stacked sequentially on the substrate layer (1). The second buffer layer (22) is located at the center of the upper surface of the first buffer layer (21) and its surface size is smaller than that of the first buffer layer (21). The second buffer layer (22) and the multi-channel structure (3) are both ring-shaped, forming a ring-shaped stacked structure. The multi-channel structure (3) includes multiple channel units (31) stacked from bottom to top. Each channel unit (31) includes a channel layer and a barrier layer stacked from bottom to top. A side gate structure (4) is embedded at the lower center of the annular stacked structure. The side gate structure (4) includes an annular electrostatic shielding layer (41) and a gate metal layer (42) disposed in the central region of the electrostatic shielding layer (41). The annular stacked structure has a longitudinal aperture (5) at its center. The longitudinal aperture (5) extends vertically downward from the center of the upper surface of the multi-channel structure (3) to the interior of the second buffer layer (22). The interior of the longitudinal aperture (5) is filled from bottom to top with a pore dielectric layer (6) and a source electrode (7). The outer side of the upper surface of the annular stacked structure includes a plurality of cylindrical gate structures surrounding the electrostatic shielding layer (41). Each cylindrical gate structure includes a gate dielectric layer (8) extending from the upper surface of the multi-channel structure (3) into the interior of the buffer layer (2) and a cylindrical gate (9) disposed inside the central hole of the gate dielectric layer (8). A drain electrode (10) is provided on the upper surface of the buffer layer (2) on the outer side of the annular stacked structure.

2. The transverse and longitudinal composite channel device according to claim 1, characterized in that, The multi-channel structure (3) includes n channel units stacked from bottom to top, where 2≤n≤6. Each channel unit includes a channel layer and a barrier layer stacked from bottom to top. The thickness of the channel layer is 5~10nm and the thickness of the barrier layer is 10~15nm.

3. The transverse and longitudinal composite channel device according to claim 1, characterized in that, The channel layer of each channel unit is made of InGaN material, and the content of In component in the channel layer gradually increases along the stacking direction from bottom to top; the barrier layer of each channel unit is made of AlGaN or InAlN material.

4. The transverse and longitudinal composite channel device according to claim 1, characterized in that, The multi-channel structure (3) includes a bottom channel unit, a middle channel unit and a top channel unit stacked from bottom to top. The bottom channel unit includes a first channel layer and a first barrier layer arranged sequentially from bottom to top. The middle channel unit includes a second channel layer and a second barrier layer arranged sequentially from bottom to top. The top channel unit includes a third channel layer and a third barrier layer arranged sequentially from bottom to top. The first channel layer is made of InGaN material with an In composition of 0-5%, and the first barrier layer is made of AlGaN material with an Al composition of 20-30%. The second channel layer is made of InGaN material with an In composition of 5% to 10%, and the second barrier layer is made of AlGaN material with an Al composition of 15% to 25%. The third channel layer is made of InGaN material with an In composition of 10% to 15%, and the third barrier layer is made of AlGaN or InAlN material with an Al composition of 15% to 25%.

5. The transverse and longitudinal composite channel device according to claim 1, characterized in that, The lower surfaces of the electrostatic shielding layer (41) and the gate metal layer (42) both extend into the interior of the second buffer layer (22), and the upper surfaces of the electrostatic shielding layer (41) and the gate metal layer (42) both extend into the interior of the multi-channel structure (3).

6. The transverse and longitudinal composite channel device according to claim 1, characterized in that, The upper surface of the aperture dielectric layer (6) extends to the lower surface of the barrier layer of the lowest channel unit in the multi-channel structure (3), and the source (7) extends from the upper surface of the aperture dielectric layer (6) to the upper surface of the multi-channel structure (3).

7. The transverse and longitudinal composite channel device according to claim 6, characterized in that, Both the electrostatic shielding layer (41) and the gate metal layer (42) are ring-shaped structures, either circular or square. The outer surface of the electrostatic shielding layer (41) is in contact with the inner surface of the ring-shaped stacked structure, the inner surface of the electrostatic shielding layer (41) is in contact with the outer surface of the gate metal layer (42), and the inner surface of the gate metal layer (42) is in contact with the outer surface of the aperture dielectric layer (6).

8. The transverse and longitudinal composite channel device according to claim 1, characterized in that, The plurality of columnar grid structures are uniformly surrounded around the outer periphery of the electrostatic shielding layer (41) and spaced apart from the electrostatic shielding layer (41); In each cylindrical gate structure, the gate dielectric layer (8) surrounds the outside of the cylindrical gate (9), and both the gate dielectric layer (8) and the cylindrical gate (9) extend from the upper surface of the multi-channel structure (3) into the interior of the second buffer layer (22).

9. The transverse and longitudinal composite channel device according to claim 1, characterized in that, The drain (10) has a ring-shaped structure, is disposed on the upper surface of the first buffer layer (21) and is spaced apart from the ring-shaped stacked structure.

10. A method for fabricating a transverse and longitudinal composite channel device, characterized in that, The method for fabricating the transverse and longitudinal composite channel device according to any one of claims 1 to 9 comprises: S1: A buffer layer stack structure (2) and a bottom channel layer (11) are epitaxially grown on a substrate layer (1). The buffer layer stack structure (2) includes a first buffer layer (21) and a second buffer layer (22) sequentially stacked on the substrate layer (1). S2: An opening region (12) extending into the second buffer layer (22) is formed by vertical etching from the center of the upper surface of the bottom channel layer (11), and an electrostatic shielding layer (41) and a gate metal layer (42) are formed in the opening region (12), wherein the electrostatic shielding layer (41) surrounds the sidewall of the opening region (12), and the gate metal layer (42) fills the axial central hole of the electrostatic shielding layer (41); S3: Multiple channel units (31) are sequentially grown on the upper surface of the bottom channel layer (11) to form a multi-channel structure (3) covering the second buffer layer (22), the electrostatic shielding layer (41) and the gate metal layer (42); S4: A plurality of columnar gate structures are formed around the electrostatic shielding layer (41) on the outer side of the upper surface of the multi-channel structure (3). Each columnar gate structure includes a gate dielectric layer (8) extending from the upper surface of the multi-channel structure (3) into the interior of the second buffer layer (22) and a columnar gate (9) disposed in the axial central hole of the gate dielectric layer (8). S5: A longitudinal aperture (5) is formed in the central region of the upper surface of the multi-channel structure (3). The longitudinal aperture (5) extends vertically downward from the center of the upper surface of the multi-channel structure (3) to the interior of the second buffer layer (22), and a pore medium layer (6) is formed inside the longitudinal aperture (5). S6: A source electrode (7) is formed in the longitudinal aperture (5) above the aperture dielectric layer (6), and a drain electrode (10) is formed on the upper surface of the first buffer layer (21).

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