A P-GaN HEMT composite structure with high total dose tolerance

Abstract

This application provides a P-GaN HEMT composite structure with high total dose tolerance. Applied to the field of semiconductor device technology, it includes, from bottom to top, a substrate layer, an AlN nucleation layer, a superlattice buffer layer, a GaN channel layer, an AlGaN barrier layer, an ALD-AlN interface layer, and a P-GaN layer. The upper surface of the AlGaN barrier layer further comprises a metal source, a metal drain, a passivation layer, and a field plate structure. The upper surface of the P-GaN layer contains a metal gate. This structure improves total dose tolerance by passivating defects through the AlN interface layer, blocking holes through the superlattice buffer layer, and dispersing the electric field through the field plate structure.

Description

Technical Field

[0001] This application relates to the field of semiconductor device technology, and in particular to a P-GaN HEMT composite structure with high total dose tolerance. Background Technology

[0002] P-GaN HEMTs (P-gate GaN-based high electron mobility transistors), as third-generation wide-bandgap semiconductor power devices, have been widely used in 5G communications, power electronics, and aerospace due to their advantages such as normally-off characteristics, high breakdown field strength, and low on-resistance. Especially in extreme environments such as aerospace and nuclear energy, power devices need to withstand long-term space radiation such as gamma rays, high-energy protons, and electrons, with total cumulative doses reaching hundreds of krad(Si) or even Mrad(Si). Therefore, the device's resistance to total radiation dose becomes a key indicator determining system reliability.

[0003] Conventional P-GaN HEMT structures exhibit problems such as nitrogen vacancy defect proliferation at the AlGaN / GaN interface, hole accumulation in the buffer layer leading to increased off-state leakage current, and threshold voltage drift after a total dose exceeding 1000 krad. Existing research has used a single Al2O3 passivation layer to improve the radiation resistance of P-GaN HEMT structures, but the passivation effect is limited, the charge migration problem in the buffer layer remains unresolved, and electric field concentration at high doses can still induce defect generation. Summary of the Invention

[0004] This application provides a P-GaN HEMT composite structure with high total dose tolerance to solve the problems of interface defect proliferation, increased leakage current of buffer layer, and threshold voltage drift of existing P-GaN HEMT structures under high total dose irradiation.

[0005] This application provides a high total dose tolerance P-GaN HEMT composite structure, comprising, from bottom to top, a substrate layer, an AlN nucleation layer, a superlattice buffer layer, a GaN channel layer, an AlGaN barrier layer, an ALD-AlN interface layer, and a P-GaN layer. The upper surface of the AlGaN barrier layer is further provided with a metal source, a metal drain, a passivation layer, and a field plate structure, and the upper surface of the P-GaN layer is provided with a metal gate.

[0006] Optionally, the field plate structure is formed by extending from the metal source to the metal drain, the field plate structure covers the passivation layer between the metal gate and the metal drain, and a gap is left between the end of the field plate structure and the metal drain.

[0007] Optionally, the extension length of the field plate structure is 0.3μm-0.6μm.

[0008] Optionally, the superlattice buffer layer is formed by alternating stacking of multiple periods of AlGaN and GaN layers. The superlattice buffer layer has 5-8 repeating periods, each period including one AlGaN sublayer and one GaN sublayer. The sum of the thicknesses of the AlGaN sublayer and the GaN sublayer in each period is 20 nm. The Al composition in the AlGaN sublayer gradually changes from 15% to 25% along the direction from the substrate layer to the GaN channel layer.

[0009] Optionally, the thickness of the AlN nucleation layer is 50 nm.

[0010] Optionally, the ALD-AlN interface layer is grown using an atomic layer deposition process at a deposition temperature of 300°C, and the thickness of the ALD-AlN interface layer is 3nm-5nm.

[0011] Optionally, the passivation layer includes: Layers and Layer, the The layer was grown using a plasma-enhanced chemical vapor deposition process. The thickness of the layer is 100nm-120nm, the The layer is grown using atomic layer deposition technology. The thickness of the layer is 50nm-80nm.

[0012] Optionally, the metal gate is formed by depositing TiN using a physical vapor deposition process, and the thickness of the metal gate is 100nm-150nm.

[0013] Optionally, the distance between the metal gate and the metal drain is 1.4 μm, and the length of the metal gate is 0.4 μm.

[0014] Optionally, the thickness of the P-GaN layer is 80 nm, and the Mg doping concentration of the P-GaN layer is... The upper surface of the P-GaN layer is adopted and Plasma etching is performed.

[0015] This application provides a high total dose tolerance P-GaN HEMT composite structure, comprising, from bottom to top, a substrate layer, an AlN nucleation layer, a superlattice buffer layer, a GaN channel layer, an AlGaN barrier layer, an ALD-AlN interface layer, and a P-GaN layer. The upper surface of the AlGaN barrier layer further comprises a metal source, a metal drain, a passivation layer, and a field plate structure. The upper surface of the P-GaN layer comprises a metal gate. This structure improves total dose tolerance by passivating defects through the AlN interface layer, blocking holes through the superlattice buffer layer, and dispersing the electric field through the field plate structure. Attached Figure Description

[0016] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0017] Figure 1 A cross-sectional schematic diagram of a P-GaN HEMT composite structure with high total dose tolerance provided in an embodiment of this application;

[0018] Figure 2 This is a schematic diagram of the structure of the superlattice buffer layer provided in an embodiment of this application.

[0019] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] The terms "first," "second," "third," "fourth," etc. (if present) in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein.

[0022] In this application, the terms "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in this application should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of terms such as "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0023] The technical solution of this application and how the technical solution of this application solves the above-mentioned technical problems are described in detail below with specific embodiments. These specific embodiments can be combined with each other, and the same or similar concepts or processes may not be described again in some embodiments. The embodiments of this application will now be described with reference to the accompanying drawings.

[0024] Figure 1 This is a cross-sectional schematic diagram of a P-GaN HEMT composite structure with high total dose tolerance provided in an embodiment of this application. Figure 1 As shown, this embodiment provides a high total dose tolerance P-GaN HEMT composite structure, comprising: a substrate layer 1, a superlattice buffer layer 2, a GaN channel layer 3, an AlGaN barrier layer 4, and a P-GaN layer 7 arranged sequentially from bottom to top. The upper surface of the AlGaN barrier layer 4 is further provided with a metal source 6, a metal drain 8, a passivation layer 5, and a field plate structure. The upper surface of the P-GaN layer 7 is provided with a metal gate 9.

[0025] The epitaxial growth process for fabricating an enhancement-mode GaN HEMT on a Si substrate includes: depositing a thin AlN layer on the Si substrate, which serves only as a mechanical support. This layer acts as both an insulator and a nucleation center for subsequent crystal growth. Next, an AlGaN transition layer is deposited to alleviate lattice mismatch and stress between the different materials. Then, a thick GaN layer is epitaxially grown, forming the main channel of the device. Following this, a thin AlGaN layer is deposited, utilizing the band shift and piezoelectric polarization effect between GaN and AlGaN to form a high-concentration, high-mobility 2DEG at the interface, which is the core channel for transistor conduction. Finally, a p-GaN barrier layer is deposited. This layer depletes electrons in the 2DEG, achieving the always-on characteristic of the enhancement-mode device, thus significantly improving the safety and reliability of the application.

[0026] Specifically, the field plate structure extends from the metal source 6 towards the metal drain 8, covering the passivation layer 5 between the metal gate 9 and the metal drain 8, with a gap between the end of the field plate structure and the metal drain 8. The field plate structure is deposited in the same layer as the metal source 6, with an extension length of 0.3 μm-0.6 μm. In a preferred embodiment, the length of the source-extending field plate is 0.5 μm, and the width is the same as that of the source.

[0027] Figure 2 This is a schematic diagram of the superlattice buffer layer provided in an embodiment of this application. Specifically, the superlattice buffer layer 2 is composed of multiple alternating stacks of AlGaN and GaN layers. The number of repeating cycles of the superlattice buffer layer 2 is 5-8 cycles. In a preferred embodiment, the number of cycles is 6. Each cycle includes one AlGaN sublayer and one GaN sublayer. The sum of the thicknesses of the AlGaN and GaN sublayers in each cycle is 20 nm (e.g., the thickness of the AlGaN sublayer is 8 nm and the thickness of the GaN sublayer is 12 nm). The Al composition in the AlGaN sublayer gradually changes from 15% to 25% along the direction from the substrate layer 1 to the GaN channel layer 3, forming a potential energy gradient and suppressing hole migration and trapping into the channel. The superlattice buffer layer 2 is grown using a metal-organic chemical vapor deposition process, with a single-cycle growth temperature of 950-1050℃.

[0028] For example, the superlattice buffer layer is composed of six alternating AlGaN / GaN layers, with the AlGaN sublayer having a thickness of 8 nm and the GaN sublayer having a thickness of 12 nm in each period; wherein, the Al molar fraction of the AlGaN sublayer in the first to sixth periods is 15%, 17%, 19%, 21%, 23%, and 25% respectively, forming an Al composition distribution that increases stepwise from the substrate side to the channel side.

[0029] Specifically, the high total dose tolerance P-GaN HEMT composite structure provided in this embodiment further includes: an AlN nucleation layer, which is formed between the substrate layer 1 and the superlattice buffer layer 2, with a thickness of 50 nm. The AlN nucleation layer is grown using a metal-organic chemical vapor deposition process at a growth temperature of 1000 °C.

[0030] Specifically, the thickness of GaN channel layer 3 is 1 μm, and it is an intrinsic GaN layer that is not intentionally doped.

[0031] Specifically, the AlGaN barrier layer 4 has a thickness of 15 nm and an Al composition of 25%.

[0032] Specifically, the high total dose-tolerant P-GaN HEMT composite structure provided in this embodiment further includes an ALD-AlN interface layer. The ALD-AlN interface layer is grown using atomic layer deposition (ALD) at a deposition temperature of 300°C to ensure interface compactness. The thickness of the ALD-AlN interface layer is 3 nm-5 nm. In a preferred embodiment, the thickness of the ALD-AlN interface layer is 4 nm. The ALD-AlN interface layer is inserted between the P-GaN layer 7 and the AlGaN barrier layer 4, and the dangling bonds at the interface are passivated using ALD-AlN deposition, reducing irradiation-induced nitrogen vacancy defects.

[0033] Specifically, the passivation layer 5 includes: Layers and layer, The layer was grown using plasma-enhanced chemical vapor deposition. The layer thickness is 100nm-120nm. The layers were grown using atomic layer deposition (ALD) technology. The thickness of the layer is 50nm-80nm. The layer deposition temperature is 350℃. The layer deposition temperature is 300°C. In a preferred embodiment, The layer thickness is 110 nm. The layer thickness is 60nm. It is bonded via source extension field plate. The composite passivation structure can disperse the high electric field of the gate drain and reduce the charge accumulation under irradiation.

[0034] Specifically, the metal gate 9 is formed by depositing TiN using a physical vapor deposition process, and the thickness of the metal gate 9 is 100nm-150nm. The PVD sputtering power used for the TiN metal gate deposition is 300W, and the deposition temperature is 200℃.

[0035] Specifically, the distance between the metal gate 9 and the metal drain 8 is 1.4 μm, and the length of the metal gate 9 is 0.4 μm.

[0036] Specifically, the thickness of P-GaN layer 7 is 80 nm, and the Mg doping concentration of P-GaN layer is... The upper surface of P-GaN layer 7 is used and Plasma etching is performed at a rate controlled at 5-8 nm / min to avoid interface damage. The flow ratio is 2:1, the ICP power is 200W, and the RF bias is 30W.

[0037] In this embodiment, the strong polarization effect at the AlGaN-GaN interface induces a high concentration of two-dimensional electron gas, forming a conductive channel. The built-in electric field generated by P-GaN effectively depletes the two-dimensional electron gas in the channel, thereby automatically turning off the device at zero gate voltage and achieving a reliable enhancement-mode operation. This characteristic provides higher safety and energy efficiency in power switching applications. The source metal extension forms a field plate structure covering the gate and drift region to effectively alleviate the electric field concentration at the gate edge, improving the device's breakdown voltage and dynamic reliability.

[0038] The field plate structure can also modulate the electric field lines in the depletion region of the barrier layer, thereby weakening the electric field spikes at the gate edge, reducing self-heating effects, and improving device reliability. Furthermore, the dielectric and passivation layers of the device ensure its long-term stability and reliability.

[0039] In terms of radiation resistance, the electric field distribution plays a decisive role in defect migration and recapture, especially the high-field regions at the gate edge and drain, which are the most sensitive areas for neutron-induced defect accumulation. By introducing a field plate structure and optimizing the electric field gradient between the gate and drain, the local electric field peak can be significantly weakened, reducing the redistribution and aggregation of charged defects in the high-field region, and suppressing the threshold positive drift and breakdown voltage drop caused by defect charge migration. For device resistance to single-event burn-out (SEB), the field plate avoids the appearance of secondary high-field regions at the gate-source edges, reducing the lateral migration of electrons near the source and the probability of them being trapped by gate-source traps. This reduces the depletion of the two-dimensional electron gas (2DEG) at the heterojunction interface, completely eliminating the triggering condition of "electron acceleration-trapping." This not only allows the device to maintain a near-static level of dynamic on-resistance (Ron) after blocking, but also weakens hole accumulation below the gate during heavy-ion irradiation.

[0040] This application provides a high total dose tolerance P-GaN HEMT composite structure. After irradiation with a total dose of 2000 klad, the off-state leakage current increase is ≤30%, which is a significant improvement compared to the existing pure P-GaN structure (which increases by more than 80%). The threshold voltage drift is ≤0.08V, and the breakdown voltage retention rate is ≥95%, meeting the long-term operation requirements in extreme irradiation scenarios. All structures and processes are optimized based on existing GaN production lines, requiring no additional dedicated equipment and facilitating mass production. It can cover multiple voltage levels of P-GaN HEMTs, such as 40V, 100V, and 200V, and is suitable for high-end applications in aerospace, nuclear industry, and other fields.

[0041] Other embodiments of this application will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein. The specification and examples are to be considered exemplary only, and the true scope and spirit of this application are indicated by the following claims.

[0042] It should be understood that this application is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A P-GaN HEMT composite structure with high total dose tolerance, characterized in that, include: The following layers are arranged sequentially from bottom to top: substrate layer, AlN nucleation layer, superlattice buffer layer, GaN channel layer, AlGaN barrier layer, ALD-AlN interface layer, and P-GaN layer. The upper surface of the AlGaN barrier layer is also provided with a metal source, a metal drain, a passivation layer, and a field plate structure. The upper surface of the P-GaN layer is provided with a metal gate.

2. The high total dose tolerance P-GaN HEMT composite structure according to claim 1, characterized in that, The field plate structure is formed by extending from the metal source to the metal drain. The field plate structure covers the passivation layer between the metal gate and the metal drain, and a gap is left between the end of the field plate structure and the metal drain.

3. The high total dose tolerance P-GaN HEMT composite structure according to claim 2, characterized in that, The extension length of the field plate structure is 0.3μm-0.6μm.

4. The high total dose tolerance P-GaN HEMT composite structure according to claim 1, characterized in that, The superlattice buffer layer is composed of multiple alternating stacks of AlGaN and GaN layers. The superlattice buffer layer repeats for 5-8 cycles. Each cycle includes one AlGaN sublayer and one GaN sublayer. The sum of the thicknesses of the AlGaN and GaN sublayers in each cycle is 20 nm. The Al composition in the AlGaN sublayer gradually changes from 15% to 25% along the direction from the substrate to the GaN channel layer.

5. The high total dose tolerance P-GaN HEMT composite structure according to claim 1, characterized in that, The thickness of the AlN nucleation layer is 50 nm.

6. The high total dose tolerance P-GaN HEMT composite structure according to claim 1, characterized in that, The ALD-AlN interface layer is grown using atomic layer deposition at a temperature of 300°C, and the thickness of the ALD-AlN interface layer is 3nm-5nm.

7. The high total dose tolerance P-GaN HEMT composite structure according to claim 1, characterized in that, The passivation layer includes: Layers and The layer, the The layer was grown using a plasma-enhanced chemical vapor deposition process. The thickness of the layer is 100nm-120nm, the The layer is grown using atomic layer deposition technology. The thickness of the layer is 50nm-80nm.

8. The high total dose tolerance P-GaN HEMT composite structure according to claim 1, characterized in that, The metal gate is formed by depositing TiN using a physical vapor deposition process, and the thickness of the metal gate is 100nm-150nm.

9. The high total dose tolerance P-GaN HEMT composite structure according to claim 1, characterized in that, The distance between the metal gate and the metal drain is 1.4 μm, and the length of the metal gate is 0.4 μm.

10. The high total dose tolerance P-GaN HEMT composite structure according to claim 1, characterized in that, The thickness of the P-GaN layer is 80 nm, and the Mg doping concentration of the P-GaN layer is... The upper surface of the P-GaN layer is adopted and Plasma etching is performed.

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