GaN cap layer structure
By etching the annular trench array on the surface of the GaN cap layer and filling it with high thermal conductivity materials, combined with the sidewall inclination angle design, the problems of heat management and charge shielding effects of traditional p-GaN cap layer structure under high power density are solved, and the problem of heat management and charge shielding effect of traditional p-GaN cap layer structure is improved. The thermal stability and reliability of the device.
Patent Information
- Application Number
- CN202420872930.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-25
- Publication Date
- 2024-12-17
- Estimated Expiration
- 2034-04-25
AI Technical Summary
Traditional p-GaN cap layer structure is difficult to effectively manage heat in high power density applications, resulting in an increase in local hot spot temperature, affecting device performance and reliability. At the same time, there are charge shielding effects and ohmic contact problems, and the surface defects and trap suppression capabilities are limited. .
A GaN cap layer structure was designed, including etching annular trench arrays on the surface of the p-GaN cap layer and filling with high thermal conductivity materials, sidewall tilt angle design to optimize the direction of heat flow, reduce heat flow reflux and accumulation, and through chemical bonding Or intermetallic compound filling method to improve heat conduction efficiency.
It significantly improves the local heat dissipation ability of the device, reduces the hot spot temperature, extends the device life, improves the stability and reliability under high temperature conditions, and optimizes the thermal diffusion efficiency.
Smart Images
Figure CN222190736U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of GaN cap layers, and in particular relates to a GaN cap layer structure. Background Art
[0002] Gallium nitride (GaN), as a typical representative of the third generation of semiconductor materials, has shown great application potential in power electronics, radio frequency communications, optoelectronics and other fields with its excellent physical and electrical properties, such as wide bandgap, high breakdown electric field, high saturation electron mobility, high temperature stability and high thermal conductivity. In the GaN device structure, the p-GaN cap layer, as a key component, is located above the two-dimensional electron gas (2DEG) channel and is responsible for providing ohmic contact, regulating the gate's control of the 2DEG electric field and improving surface properties. The traditional p-GaN cap layer structure is usually a uniform, continuous single-layer film formed by doping p-type impurities (such as magnesium, zinc, cadmium, etc.).
[0003] With the popularity of GaN devices in high power density and high frequency applications, the traditional p-GaN cap layer structure has exposed technical problems: Thermal management problem: Although GaN itself has high thermal conductivity, under high power density applications, due to the large amount of heat generated inside the device concentrated in local areas, especially the p-GaN cap layer and metal contact area, the traditional single, uniform p-GaN cap layer structure is difficult to quickly and effectively transfer heat from the heat source to the external heat sink, resulting in local hot spot temperature increase, affecting device performance, life and reliability. Charge screening effect: The thickness of the traditional p-GaN cap layer is usually limited by process conditions and the requirements for ohmic contact. Excessively thick cap layers will increase the difficulty of gate voltage control of 2DEG, the so-called charge screening effect, resulting in threshold voltage drift, switching speed reduction and transconductance reduction, affecting the high-speed switching performance and power efficiency of the device. Ohmic contact problem: Due to the work function mismatch between GaN and metal, it is difficult to form a good ohmic contact. The traditional p-GaN cap layer structure often requires additional complex surface treatment and metal selection to reduce contact resistance. However, even so, the contact resistance may still be high, affecting the conduction loss and thermal management of the device. Surface defects and traps: The traditional p-GaN cap layer structure has limited ability to suppress surface defects and traps. These non-ideal structures can capture or release charges, resulting in increased device leakage current, unstable dynamic behavior, and reduced reliability. Utility Model Content
[0004] In view of this, the utility model provides a GaN cap layer structure to solve the problem that a large amount of heat generated inside a traditional GaN device is concentrated in a local area, thereby improving the local heat dissipation capacity of the device.
[0005] The utility model is achieved in this way:
[0006] The utility model provides a GaN cap layer structure, which is used in a gallium nitride device, including a GAN device, wherein the GAN device is provided with a 2DEG channel, wherein the GAN device is provided with a p-GaN cap layer, the p-GaN cap layer is arranged on the 2DEG channel of the GAN device, an annular groove array is etched on the surface of the p-GaN cap layer, the annular groove array includes a plurality of annular grooves, each of the annular grooves is annularly distributed along the radial direction surrounding the extension direction of the 2DEG channel, and the annular groove array is filled with a filling material;
[0007] Wherein, the sidewall of the annular groove array forms an inclined angle with the surface of the p-GaN cap layer.
[0008] On the basis of the above technical solution, a GaN cap layer structure of the utility model can also be improved as follows:
[0009] Wherein, the axis of the annular groove array coincides with the central axis of the 2DEG channel.
[0010] Furthermore, the depth of the annular groove array is 10% to 50% of the thickness of the p-GaN cap layer.
[0011] Furthermore, the ratio of the width of the annular groove to the spacing between adjacent annular grooves is 1:1 to 1:3.
[0012] Furthermore, the cross-sectional shape of the annular groove array is one of rectangular, semicircular, trapezoidal or V-shaped.
[0013] Furthermore, the number of the annular grooves is 2 to 20, and the center distance between two adjacent annular grooves is arranged according to the golden section ratio, the Fibonacci sequence or the arithmetic progression.
[0014] Furthermore, the inclination angle is 30° to 45°.
[0015] The beneficial effect of adopting the above-mentioned improvement scheme is that the inclined sidewall design makes the flow direction of heat offset from the direction perpendicular to the surface of the p-GaN cap layer when it propagates along the sidewall, that is, the flow path of heat in the groove is no longer simply vertically upward, but forms an oblique upward propagation at a certain angle.
[0016] When the heat flow diffuses upward through the inclined sidewall, due to the angle between the sidewall and the surface of the p-GaN cap layer, the heat flow diffuses to the outside of the trench after reaching the top of the trench, rather than directly returning vertically upward to the surface of the p-GaN cap layer. This design helps guide the heat flow to diffuse radially outward along the trench, promotes faster transfer of heat to the external heat dissipation environment, and reduces the reflux and accumulation of heat inside the trench.
[0017] The sidewall tilt design reduces the vertical thermal resistance of the heat flow inside the groove by optimizing the heat flow direction, increases the radial diffusion path of the heat flow, makes it easier for heat to transfer from the inside of the groove to the outside, thereby improving the heat diffusion efficiency.
[0018] At the same time, the inclined sidewall design can effectively reduce the reflection and scattering of heat flow on the inner wall of the groove, reduce the residence time of heat flow inside the groove, further improve the heat diffusion rate, help reduce the hot spot temperature of the device, and improve the thermal stability of the device.
[0019] Furthermore, the filling material and the p-GaN cap layer are tightly combined by chemical bonding, intermetallic compound formation or hot pressing filling.
[0020] Furthermore, the filling material is a filling material with high thermal conductivity.
[0021] Furthermore, the thermal conductivity of the filling material is at least twice that of the p-GaN cap layer material, and the high thermal conductivity filling material is one of silicon, silicon carbide, diamond, metal alloy, and composite material.
[0022] The p-GaN cap layer material specifically refers to gallium nitride (GaN) material doped with p-type impurities (such as magnesium, zinc, cadmium, etc.). In GaN devices, the p-GaN cap layer is located above the two-dimensional electron gas (2DEG) channel as part of the device structure. Its main functions include providing ohmic contact, regulating the electric field control of the gate on the 2DEG, and improving surface characteristics.
[0023] Compared with the prior art, the GaN cap layer structure provided by the utility model has the following beneficial effects: heat can be rapidly diffused outward along the radial direction of the groove, reducing the lateral diffusion resistance of heat flow inside the cap layer. The high thermal conductivity material filled has a thermal conductivity at least twice that of the p-GaN cap layer material, which greatly enhances the thermal conduction efficiency and significantly improves the local heat dissipation capacity of the device;
[0024] Effectively reduce thermal resistance: By rationally designing the depth, width, spacing of the annular grooves and the selection of filling materials, the heat flow path is optimized, the heat flow backflow and accumulation inside the p-GaN cap layer are reduced, the thermal resistance is reduced, and heat is more easily transferred from the heat source to the external heat dissipation environment, further improving the heat diffusion efficiency;
[0025] Reduce hot spot temperature: The annular groove structure effectively disperses local hot spots, reduces the hot spot temperature, reduces the impact of high temperature on device performance, extends the service life of the device, and reduces the risk of thermal runaway, improving the stability and reliability of the device under high temperature working conditions. BRIEF DESCRIPTION OF THE DRAWINGS
[0026] In order to more clearly illustrate the technical solutions of the embodiments of the utility model, the drawings required for use in the description of the embodiments of the utility model will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.
[0027] Figure 1 An example diagram of a GaN cap layer structure;
[0028] In the accompanying drawings, the components represented by the reference numerals are listed as follows:
[0029] 10. GAN device; 11. p-GaN cap layer; 12. 2DEG channel; 20. annular trench array; 21. filling material. DETAILED DESCRIPTION
[0030] In order to make the purpose, technical solution and advantages of the implementation mode of the present invention clearer, the technical solution in the implementation mode of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the implementation mode of the present invention.
[0031] like Figure 1 As shown, it is a first embodiment of a GaN cap layer structure provided by the utility model. In this embodiment, it is used in a gallium nitride device, including a GAN device 10, the GAN device 10 is provided with a 2DEG channel 12, wherein the GAN device 10 is provided with a p-GaN cap layer 11, the p-GaN cap layer 11 is arranged on the 2DEG channel 12 of the GAN device 10, and an annular groove array 20 is etched on the surface of the p-GaN cap layer 11, the annular groove array 20 includes a plurality of annular grooves, each of the annular grooves is annularly distributed along the radial direction surrounding the extension direction of the 2DEG channel 12, and the annular groove array 20 is filled with a filling material;
[0032] The sidewall of the annular groove array 20 forms an inclined angle with the surface of the p-GaN cap layer 11 .
[0033] In the above technical solution, the axis of the annular groove array 20 coincides with the central axis of the 2DEG channel 12 .
[0034] Furthermore, in the above technical solution, the depth of the annular groove array 20 is 10% to 50% of the thickness of the p-GaN cap layer 11 .
[0035] Furthermore, in the above technical solution, the ratio of the width of the annular groove to the spacing between adjacent annular grooves is 1:1 to 1:3.
[0036] Furthermore, in the above technical solution, the cross-sectional shape of the annular groove array 20 is one of a rectangular, semicircular, trapezoidal or V-shaped.
[0037] Furthermore, in the above technical solution, the number of the annular grooves is 2 to 20, and the center distance between two adjacent annular grooves is arranged according to the golden ratio, the Fibonacci sequence or the arithmetic sequence.
[0038] Golden ratio arrangement:
[0039] In the annular groove array, the center distance between two adjacent annular grooves (i.e., the difference in the radius of the annular grooves) follows the golden ratio (approximately 1:0.618). The ratio of the radius of the second annular groove to the radius of the first annular groove is 0.618. The subsequent annular grooves are similar, and the distance between each newly added annular groove and the previous annular groove maintains the golden ratio.
[0040] The golden ratio has self-similarity and good aesthetic properties. Applying it to the layout of annular groove spacing helps to form a uniform, coordinated and efficient heat diffusion path. This layout is conducive to the smooth transition of heat flow between annular grooves of different scales, reduces local heat flow aggregation, and improves heat diffusion efficiency.
[0041] Fibonacci sequence arrangement:
[0042] In the annular groove array, the center distance between two adjacent annular grooves is determined according to the Fibonacci sequence. For example, the radius of the first annular groove is F1, the radius of the second annular groove is F2, and the radius of the subsequent annular grooves is F3, F4, etc., where F n+1 =F n +F n-1 (n≥2, F1=1, F2=1) n represents the number of annular grooves.
[0043] The Fibonacci sequence has good self-similarity and convergence. When applied to the layout of annular groove spacing, it can naturally form a series of increasing but gradually converging spacings, so that the heat flow is transferred in an orderly and balanced manner between annular grooves of different scales, avoiding excessive concentration of heat flow at a certain scale, thereby optimizing the heat diffusion path.
[0044] Arithmetic sequence arrangement:
[0045] In the annular groove array, the center distances of two adjacent annular grooves form an arithmetic progression. That is, if the initial radius is set to A1 and the tolerance is d, then the radius A of the nth annular groove is n =A1+(n-1)d. The radii of all annular grooves increase according to this rule.
[0046] Furthermore, in the above technical solution, the inclination angle is 30° to 45°.
[0047] Furthermore, in the above technical solution, the filling material and the p-GaN cap layer 11 are tightly combined by chemical bonding, intermetallic compound formation or hot pressing filling.
[0048] Furthermore, in the above technical solution, the filling material is a high thermal conductivity filling material.
[0049] Furthermore, in the above technical solution, the thermal conductivity of the filling material is at least twice that of the p-GaN cap layer 11 material, and the high thermal conductivity filling material is one of silicon, silicon carbide, diamond, metal alloy, and composite material.
[0050] As a wide bandgap semiconductor material, GaN has a high thermal conductivity, usually in the range of 100W / m·K to 200W / m·K, and the specific value depends on factors such as material purity, crystal quality, doping concentration, and the presence of defects. However, compared with traditional semiconductor materials such as silicon (Si) and silicon carbide (SiC), the thermal conductivity of GaN is still at a relatively high level, which helps it effectively dissipate heat in high power density applications.
[0051] The filling material should have a thermal conductivity of at least 200W / m·K to 400W / m·K to ensure that it serves as an efficient heat diffusion path and significantly improves the local heat dissipation capacity of the device. Such high thermal conductivity filling materials can be:
[0052] Silicon (Si): Although the intrinsic thermal conductivity of silicon (about 150W / m·K) is slightly lower than that of GaN, its thermal conductivity can be increased to about 180W / m·K or more by using high-purity single crystal silicon or polycrystalline silicon prepared by directional solidification, which meets the requirements.
[0053] Silicon Carbide (SiC): SiC is a high thermal conductivity semiconductor material. Its thermal conductivity is usually between 400W / m·K and 500W / m·K, which is much higher than p-GaN. It is very suitable as a high thermal conductivity filling material.
[0054] Diamond: Diamond has the highest thermal conductivity known in nature, reaching over 2000W / m·K, far exceeding GaN, but its application may be limited by cost and process compatibility.
[0055] Metal alloys: Certain metal alloys, such as copper (Cu), aluminum (Al) and their alloys, have thermal conductivity as high as 300W / m·K to 400W / m·K and good compatibility with semiconductor processes, making them suitable as filling materials.
[0056] Composite materials: Thermal interface materials composed of high thermal conductivity components (such as the above-mentioned metals or ceramics) and polymers or other materials. After optimized design, their thermal conductivity may reach or even exceed twice that of p-GaN.
[0057] Specifically, the principle of the utility model is:
[0058] Heat diffusion mechanism of annular grooves: The design concept of annular grooves is based on the principle of heat diffusion in complex geometric structures. When heat flows in the grooves, due to the guiding effect of the groove sidewalls, the heat flow is no longer limited to vertical conduction, but diffuses radially outward along the grooves, forming a three-dimensional heat diffusion network. This design effectively breaks the heat flow limitation of traditional planar structures and promotes the rapid transfer of heat in three-dimensional space;
[0059] The role of high thermal conductivity filling materials: The high thermal conductivity materials filled in the annular groove, such as silicon, silicon carbide, diamond or metal alloy, have much higher thermal conductivity than the p-GaN cap layer, forming an efficient heat conduction channel. These materials can not only quickly absorb and transfer the heat generated from the bottom of the groove (i.e. the contact area between the p-GaN cap layer and the 2DEG), but also quickly transfer the heat to the edge of the groove through their own high thermal diffusion ability and further dissipate it to the external heat dissipation environment, greatly improving the thermal diffusion efficiency;
[0060] Optimization of heat flow direction: The sidewalls of the annular grooves are inclined at an angle, so that the sidewalls form a certain angle with the surface of the p-GaN cap layer. This design further optimizes the heat flow direction. When the heat flow diffuses upward along the sidewalls, due to the inclination of the sidewalls, the heat flow will diffuse to the outside of the groove after reaching the top of the groove, rather than directly returning vertically upward to the surface of the p-GaN cap layer. This design helps to guide the heat flow to diffuse radially outward along the groove, reduce the reflux and accumulation of heat inside the groove, and further reduce the thermal resistance.
Claims
1. A GaN cap layer structure for use in a gallium nitride device, comprising a GaN device (10), wherein the GaN device (10) is provided with a 2DEG channel (12), characterized in that: The GAN device (10) is provided with a p-GaN cap layer (11), the p-GaN cap layer (11) is provided on the 2DEG channel (12) of the GAN device (10), an annular groove array (20) is etched on the surface of the p-GaN cap layer (11), the annular groove array (20) comprises a plurality of annular grooves, each of the annular grooves is distributed in an annular shape along a radial direction surrounding the extension direction of the 2DEG channel (12), and the annular groove array (20) is filled with a filling material (21); Wherein, the side wall of the annular groove array (20) forms an inclined angle with the surface of the p-GaN cap layer (11).
2. A GaN cap layer structure according to claim 1, characterized in that: The axis of the annular groove array (20) coincides with the central axis of the 2DEG channel (12).
3. A GaN cap layer structure according to claim 2, characterized in that: The depth of the annular groove array (20) is 10% to 50% of the thickness of the p-GaN cap layer (11).
4. A GaN cap layer structure according to claim 3, characterized in that: The ratio of the width of the annular groove to the spacing between adjacent annular grooves is 1:1 to 1:
3.
5. A GaN cap layer structure according to claim 4, characterized in that: The cross-sectional shape of the annular groove array (20) is one of a rectangular, semicircular, trapezoidal or V-shaped.
6. A GaN cap layer structure according to claim 5, characterized in that: The number of the annular grooves is 2 to 20, and the center distance between two adjacent annular grooves is arranged according to the golden section ratio, the Fibonacci sequence or the arithmetic sequence.
7. A GaN cap layer structure according to claim 6, characterized in that: The inclination angle is 30° to 45°.
8. A GaN cap layer structure according to claim 7, characterized in that: The filling material (21) and the p-GaN cap layer (11) are tightly combined by chemical bonding, intermetallic compound formation or hot pressing filling.
9. A GaN cap layer structure according to claim 8, characterized in that: The filling material (21) is a filling material with high thermal conductivity.
10. A GaN cap layer structure according to claim 9, characterized in that: The thermal conductivity of the filling material (21) is at least twice that of the material of the p-GaN cap layer (11), and the high thermal conductivity filling material is one of silicon, silicon carbide, diamond, metal alloy and composite material.