TWI835103B - Nitride semiconductor epitaxial stack structure and power device thereof - Google Patents

Abstract

A nitride semiconductor epitaxial stack structure includes a silicon substrate; an aluminum-included nucleation layer disposed on the silicon substrate; a buffer structure disposed on the aluminum-included nucleation layer, including: a first superlattice structure, a first GaN based layer disposed on the first superlattice structure, and a second superlattice structure disposed on the first GaN based layer; a channel layer disposed on the buffer structure; and a barrier layer disposed on the channel layer; wherein the first superlattice structure has a first average aluminum composition ratio, the first GaN based layer has a first aluminum composition ratio, and the second superlattice structure has a second average aluminum composition ratio; wherein an aluminum composition ratio of the aluminum-included nucleation layer≧the first average aluminum composition ratio＞the first aluminum composition ratio＞the second average aluminum composition ratio.

Description

Nitride semiconductor epitaxial stack structure and its power components

The present disclosure relates to a nitride semiconductor epitaxial stack structure and power components thereof, and more specifically, to a gallium nitride semiconductor epitaxial stack structure and power components used in semiconductor power components.

In recent years, due to the increasing demand for high-frequency and high-power component products, the energy gap of the III-V semiconductor material gallium nitride (GaN) is about 3.4eV and the thermal conductivity is >1.5W/cm. Its wide energy gap and high thermal conductivity (Easy to dissipate heat) Suitable for operation in high temperature and chemically resistant environments. In addition, the collapse electric field of gallium nitride material is (3×10 ⁶ V/cm), and the carrier transmission speed can reach 3×10 ⁷ cm/s, making gallium nitride material suitable as a microwave high-power component that can apply high voltage on it without breaking down. Therefore, nitride semiconductor power components based on gallium nitride materials, such as aluminum gallium nitride/gallium nitride (AlGaN/GaN) semiconductor power components, can achieve very fast switching speeds due to their high electron mobility. The characteristics of components operating in high-frequency, high-power and high-temperature working environments are widely used in industrial applications, including electronic products, uninterruptible power systems, automobiles, motors, wind power and other fields. They are especially used in power supplies. ), DC/DC converter (DC/DC converter), DC/AC inverter (AC/DC inverter).

However, based on competitive considerations such as efficiency and price, existing products use cheaper substrate materials that have different lattice constants and thermal expansion coefficients from nitride semiconductor materials. Therefore, due to differences in lattice constants and thermal expansion coefficients between the substrate material and the nitride semiconductor material, epitaxial defects are easily generated between the epitaxial layers when the epitaxial layer is formed on the substrate. When the density of epitaxial defects is high, the surface flatness of the epitaxial layer is likely to be reduced. If the epitaxial defects extend to the surface of the epitaxial layer, they will cause cracks on the surface of the epitaxial layer. One of the causes. Therefore, it is not easy to form a high-quality nitride semiconductor epitaxial stack structure with low epitaxial defect density, smooth surface, fewer and/or smaller surface cracks on a substrate. Among various substrate materials, silicon substrates are widely used in the growth of nitride semiconductor epitaxial stack structures with a reasonable cost structure. However, growing high-quality nitride semiconductor epitaxial stack structures on silicon substrates is still a problem to be solved in this technical field until now. In addition, the performance of components manufactured through this nitride semiconductor epitaxial stack structure, such as power components and Schottky diode components, will also be affected by the quality of the nitride semiconductor epitaxial stack structure.

Please refer to Figure 1. Figure 1 shows a transmission electron microscope (TEM) image of a conventional nitride semiconductor epitaxial stack structure 100 that can be used in power device manufacturing. The nitride semiconductor epitaxial stacked structure 100 is first directly formed with a layer of nitrogen on the (111) surface of the silicon substrate 110 along the [0001] direction by metal-organic chemical vapor deposition (MOCVD). aluminum nitride nucleation layer 120, and then use the same MOCVD method to form a plurality of aluminum nitride superlattice layers 131 (18 nm thick) and gallium nitride superlattice layers 132 ( 5 nm thick) staggered superlattice stack 130. Next, a thick gallium nitride layer 140 with a thickness greater than 1000 nanometers is formed on the superlattice stack 130 by MOCVD. Then, a barrier layer 152 is formed on it by MOCVD method, and a two-dimensional electron gas (2DEG, not shown) is generated near the interface between the gallium nitride thick layer 140 and the barrier layer 152 .

It can be found from Figure 1 that even if the nitride semiconductor epitaxial stack structure 100 has a superlattice stack 130 underneath, many epitaxial defects 145 are still formed in the gallium nitride thick layer 140, and Extend upward to the upper half of the gallium nitride thick layer 140 and even into the barrier layer 152 .

The present disclosure relates to a nitride semiconductor epitaxial stack structure, which includes a silicon substrate; an aluminum-containing nucleation layer disposed on the silicon substrate; and a buffer structure disposed on the aluminum-containing nucleation layer, which in sequence includes: an aluminum-containing nucleation layer a first superlattice stack structure; a first gallium nitride layer, disposed on the first superlattice stack structure; and a second superlattice stack structure, disposed on the first gallium nitride layer; A channel layer is disposed on the buffer structure; and a barrier layer is disposed on the channel layer; wherein the first superlattice epitaxial structure includes a first average aluminum composition ratio, and the first gallium nitride layer includes a first An aluminum composition ratio, the second superlattice epitaxial structure includes a second average aluminum composition ratio; wherein, the aluminum composition ratio of the aluminum-containing nucleation layer ≧ the first average aluminum composition ratio > the first aluminum composition ratio > the second average Aluminum composition ratio.

A semiconductor power element, including the aforementioned nitride semiconductor epitaxial stack structure; and a source electrode, a gate electrode, and a drain electrode, or a cathode and an anode respectively disposed on the aforementioned nitride semiconductor epitaxial stack Structurally, the gate electrode is located between the source electrode and the drain electrode.

In order to make the above and other objects, features and advantages of the present disclosure more obvious and understandable, preferred embodiments are described in detail below along with the accompanying drawings.

60, 60’: dielectric layer

70: Source electrode

80: Drain electrode

90: Gate electrode

100, 200, 500: Nitride semiconductor epitaxial stack structure

100’, 200’: local epitaxial layering

110, 210: Substrate

120, 220: Aluminum nitride nucleation layer

130:Superlattice stack

131:Aluminum nitride superlattice layer

132:GaN superlattice layer

140:Thick layer of gallium nitride

145, 245: Epitaxial defects

400: Component functional structure

300, 430, 460, 490: buffer structure

410: Channel layer

152, 420: Barrier layer

310, 432, 461, 492: The first superlattice epitaxial structure

320, 320’, 431, 462, 491: The first gallium nitride series thick layer

330, 434, 463, 494: Second superlattice epitaxial structure

340, 340’, 433, 464, 493: Second gallium nitride series thick layer

465, 496: The third superlattice epitaxial structure

466, 495: The third gallium nitride series thick layer

510: Cap layer

550:Rear barrier layer

A:Anode

C: cathode

E0, E1: power component unit

E2: Schottky diode element unit

E3, E4: Power component test unit

O1~O4: Ohmic electrode

S: power component

S70: Source pad

S80: drain pad

S90: Gate pad

FF’: section line

Figure 1 is a TEM image of a conventional nitride semiconductor epitaxial stack structure.

Figure 2 is a schematic side view of the nitride semiconductor epitaxial stack structure according to the first embodiment of the present disclosure.

Figure 3A is a partial TEM image of a conventional nitride semiconductor epitaxial stack structure including a buffer structure portion.

Figure 3B is a partial TEM image of the buffer structure portion of the nitride semiconductor epitaxial stack structure according to the second embodiment of the present disclosure.

Figures 4A to 4C are schematic side views showing partial epitaxial stack structures of the nitride semiconductor epitaxial stack structure including the buffer structure portion according to the third to fifth embodiments of the present disclosure.

Figure 5 is a top view of a power device using a nitride semiconductor epitaxial stack structure according to the sixth embodiment of the present disclosure.

Figure 6A is a partially enlarged top view of a nitride semiconductor power device unit using a nitride semiconductor epitaxial stack structure according to the sixth embodiment of the present disclosure.

Figure 6B is a schematic cross-sectional view along section line FF' of Figure 6A.

FIG. 7 is a detailed side view of the nitride semiconductor epitaxial stack structure according to the sixth embodiment of the present disclosure.

Figure 8 is a schematic side view of a Schottky diode device unit according to the seventh embodiment of the present disclosure.

Figure 9A shows the electrical test results of a power device test unit using a conventional nitride semiconductor epitaxial stack structure.

Figure 9B is a diagram of electrical test results of a power device test unit using the nitride semiconductor epitaxial stack structure of the first embodiment of the present disclosure.

Figure 10A is a schematic side view of a power device test unit using a conventional nitride semiconductor epitaxial stack structure.

Figure 10B is a schematic side view of a power device testing unit using the nitride semiconductor epitaxial stack structure according to the first embodiment of the present disclosure.

The following embodiments will be accompanied by drawings to illustrate the concepts of the present disclosure. In the drawings or descriptions, similar or identical parts use the same reference numerals, and in the drawings, the shape or thickness of elements may be enlarged or reduced. It should be noted that components not shown or described in the drawings may be in forms known to those skilled in the art.

Please refer to Figure 2. Figure 2 shows a side view of a nitride semiconductor epitaxial stack structure 200 according to the first embodiment of the present disclosure. The nitride semiconductor epitaxial stack structure 200 includes a silicon substrate 210. An aluminum nitride nucleation layer 220 is formed on the silicon substrate 210. A buffer structure 300 is formed on the aluminum nitride nucleation layer 220. Among them, the buffer structure 300 sequentially includes a first aluminum gallium nitride superlattice layer (Al _x1 Ga _1-x1 N, thickness d ₁ ) and a second aluminum gallium nitride superlattice layer (Al _y1 Ga _1-y1 N, thickness d ₂ ) The first superlattice epitaxial structure 310, a staggered stack combination of two superlattice layers, and a first gallium nitride series thick layer (Al _z1 Ga _{1- z1} N) 320, consisting of the third aluminum gallium nitride superlattice layer (Al _x2 Ga _1-x2 N, thickness d ₃ ) and the fourth aluminum gallium nitride superlattice layer (Al _y2 Ga _1-y2 N, thickness d4) The second superlattice epitaxial structure 330 of a staggered stacking combination of two superlattice layers, and a second gallium nitride series thick layer (Al _z2 Ga _1-z2 N) 340 with a thickness greater than 1000 nanometers. Then, a component functional structure 400 is formed on the buffer structure 300 . Among them, the element functional structure 400 includes a channel layer 410 composed of aluminum gallium nitride (Al _a Ga _1-a N), 0≦a<1, and a channel layer 410 formed of aluminum gallium nitride (Al _b Ga _1-b N). For the barrier layer 420, 0<b<1, and a<b. Finally, a cap layer 510 composed of undoped gallium nitride (u-GaN) is formed above the barrier layer 420 .

In this embodiment, the device functional structure 400 is, for example, the gallium nitride channel layer 410 and the aluminum gallium nitride barrier layer 420 of the power device, which can generate 2DEG near the junction thereof. Of course, in another embodiment, the functional structure of the device may also be the active layer (not shown) of the light-emitting diode device. When the light-emitting diode device is injected with current, electron holes recombine in the active layer. Produce light.

In this embodiment, the aluminum nitride nucleation layer 220 is formed along the [0001] direction on the (111) surface of the substrate 210 in the nitride semiconductor epitaxial stack structure 200 . It is worth noting that the material of the substrate 210 is not limited to a silicon substrate, and can be a semiconductor material or an oxide material. The above-mentioned semiconductor material can include, for example, silicon (Si), gallium nitride (GaN), silicon carbide (SiC). ), gallium arsenide (GaAs), aluminum nitride (AlN), etc., and the above-mentioned oxide material may include, for example, sapphire. In addition, when distinguished by conductivity, the substrate 210 itself can be a conductive substrate or an insulating substrate. The above-mentioned conductive substrate includes a silicon (Si) substrate, a gallium nitride (GaN) substrate, a gallium arsenide (GaAs) substrate, and other substrates. The above-mentioned insulating substrates include sapphire (sapphire) substrates, silicon on insulator (SOI) substrates, aluminum nitride (AlN) and other substrates. In addition, the substrate 210 can be selectively doped with substances to change its conductivity to form a conductive substrate or a non-conductive substrate. For a silicon (Si) substrate, it can be doped with boron (B), arsenic ( As), or phosphorus (P) makes it conductive. In this embodiment, the substrate 210 is a p-type conductive semiconductor silicon substrate (Si) doped with boron (B) and has a thickness of approximately 175~1500 μm.

Next, the aforementioned aluminum nitride nucleation layer 220 is epitaxially grown on the (111) surface of the silicon substrate 210, where the aluminum nitride nucleation layer 220 grows along the [0001] direction, and the thickness can be about tens of tens. Nanometers or hundreds of nanometers can be used to reduce the lattice difference between the substrate 10 and the upper semiconductor layer. Epitaxial growth methods include physical vapor deposition (PVD), atomic layer deposition (ALD), metal-organic chemical vapor deposition (MOCVD), Or molecular-beam epitaxy (MBE). The aluminum nitride nucleation layer 220 can improve the epitaxial quality of semiconductor epitaxial stacks such as buffer structures and channel layers that are subsequently formed thereon. The material of the aluminum nitride nucleation layer 220 is, for example, a Group III or V semiconductor material, including aluminum nitride (AlN), gallium nitride (GaN), aluminum gallium nitride (AlGaN), or a stack of mixed compositions thereof, etc., and The structure of the aluminum nitride nucleation layer 220 may be, for example, amorphous, polycrystalline, single crystal or crystalline graded. Blending layer. In this embodiment, the aluminum nitride nucleation layer 220 is aluminum nitride (AlN), has a thickness of about 20~50 nm, and is formed by the MOCVD method.

After the aluminum nitride nucleation layer 220 is formed, a buffer structure 300 is grown above the aluminum nitride nucleation layer 220. As mentioned above, the buffer structure 300 can be used to reduce the friction between the nucleation layer 220 and the upper channel layer 410. The lattice difference between them and the reduction of epitaxial defect density. The preparation method of the buffer structure 300 is similar to the above, such as physical vapor deposition (PVD), atomic layer deposition (ALD), metal-organic chemical vapor deposition (metal-organic chemical). One of the possible epitaxy methods is vapor deposition (MOCVD) or molecular-beam epitaxy (MBE). Through the buffer structure 300, a high-quality device functional structure 400 with low epitaxial defect density, smooth surface, fewer surface cracks, and/or smaller size can be formed above it. In this embodiment, the buffer structure 300 consists of the following four parts and is formed by the MOCVD method. The growth steps are described below.

First, a first aluminum gallium nitride superlattice layer (Al _x1 Ga _1-x 1N, thickness d ₁ ) and a second aluminum gallium nitride superlattice layer are formed on the aluminum nitride nucleation layer 220 using the MOCVD method. (Al _y1 Ga _1-y1 N, thickness d ₂ ) The first superlattice epitaxial structure 310 of a staggered and stacked combination of two superlattice layers. Among them, in order to avoid excessive stress due to excessive differences in lattice constants between the first superlattice epitaxial structure 310 and the underlying aluminum nitride nucleation layer 220, two types of nitride in the first superlattice epitaxial structure 310 are The preferred range of the average aluminum content of the aluminum gallium superlattice layer is 0.3≦(x1×d ₁ +y1×d ₂ )/(d ₁ +d ₂ )≦1, x1≠y1. In addition, the thickness d ₁ and d ₂ of each superlattice layer in the first superlattice epitaxial structure 310 is preferably no more than 50 nanometers. Through the structural characteristics of the first superlattice epitaxial structure 310, the stress accumulation in the overall nitride semiconductor epitaxial stack structure 200 can be released, and the stress originating from the silicon substrate 210 and the aluminum nitride nucleation layer 220 can be blocked. For example, epitaxial defects generated due to lattice mismatch or stress extend along a direction quasi-perpendicular to the surface of the silicon substrate 210 and continue to the upper part of the nitride semiconductor epitaxial stack structure 200, thereby affecting the quality of the upper channel layer 410. If the defect continues to extend to the surface, cracks will occur. Here, the appropriate average aluminum composition ratio, 0.3≦(x1×d ₁ +y1×d ₂ )/(d ₁ +d ₂ )≦1, can reduce the relationship between the aluminum nitride nucleation layer 220 and the first superlattice The difference in lattice constants between the epitaxial structures 310 can reduce stress generation during epitaxial crystallization and can also reduce cracks on the surface of the epitaxial laminated layer. In this embodiment, the first superlattice epitaxial structure 310 having a composition layer number of 100 (50 pairs) is formed through the MOCVD method. However, the actual number of composition layers is not limited to this number. A preferred superlattice epitaxial structure 310 The number of layers of the lattice epitaxial structure can range from 20 layers (10 pairs) to 300 layers (150 pairs); in the experiment of this embodiment, it is found that when the number of layers is less than 20 layers, the super lattice epitaxial structure will The effect of slowing down stress accumulation and blocking epitaxial defects is extremely low, and it is impossible to prevent the subsequent growth of semiconductor epitaxial stacks from producing too many or too large cracks at a sufficient thickness; and when the superlattice epitaxial structure consists of more than When there are 300 layers, the epitaxial process will be too time-consuming, which is not conducive to the process economy of the overall nitride semiconductor epitaxial structure 200, and the superlattice epitaxial structure itself will also cause superlattice epitaxy due to excessive thickness. The surface of the structure begins to deteriorate and produces undesirable stresses and other side effects.

In addition, in another embodiment, the first superlattice epitaxial structure 310 may also be doped with elements such as carbon or iron to increase the intra-layer resistance of the first superlattice epitaxial structure 310 . In this embodiment, the first superlattice epitaxial structure 310 formed by the MOCVD method is an aluminum gallium nitride layer doped with carbon impurities. The doped carbon impurities in this embodiment include intentional doping or unintentional doping. The preferred carbon impurity concentration range is the range of 5×10 ¹⁷ /cm ³ ~1×10 ²⁰ /cm ³ when measured with a secondary ion mass spectrometer (SIMS). From the experimental results of this embodiment, it can be found that when the carbon concentration range is lower than 5×10 ¹⁷ /cm ³ , the resistance of the first superlattice epitaxial structure 310 is too low. Subsequently, when a nitride with too low resistance is used, When a semiconductor epitaxial laminated structure is used to make a power device, the device cannot withstand the injected voltage and cannot provide a higher breakdown voltage. When the measured carbon concentration range is higher than 1×10 ²⁰ /cm ³ When the concentration is too high, the first superlattice epitaxial structure 310 will generate epitaxial defects, thereby degrading its epitaxial quality.

Next, a first gallium nitride series thick layer (Al _z1 Ga _1-z1 N) 320 with a thickness greater than 1000 nanometers is formed on the first superlattice epitaxial structure 310 using the MOCVD method. Here, the first The composition of the gallium nitride thick layer 320 may be, for example, pure gallium nitride or an aluminum gallium nitride layer containing low aluminum content. Among them, adding appropriate aluminum elements, for example, the aluminum content is 0≦z1≦0.05, can increase the energy gap width of the first gallium nitride thick layer 320. If the nitride semiconductor epitaxial stacked structure 200 is manufactured, When a high-efficiency component is used, theoretically, the component as a whole can have a higher vertical withstand operating voltage capability, that is, a higher component breakdown voltage. Similarly, elements such as carbon or iron can also be doped into the first gallium nitride thick layer 320 to increase the intra-layer resistance of the first gallium nitride thick layer 320 . In this embodiment, the first gallium nitride thick layer 320 formed by the MOCVD method is an aluminum gallium nitride layer doped with carbon impurities. The doped carbon impurities in this embodiment include intentional doping or unintentional doping. The preferred carbon impurity concentration range is 5×10 ¹⁷ /cm ³ ~1×10 ²⁰ /cm ³ when measured by SIMS. Through the experimental results of this embodiment, it can be found that when the carbon concentration range is lower than 5×10 ¹⁷ /cm ³ , the resistance of the first gallium nitride thick layer 320 is too low. Subsequently, when a nitride semiconductor with too low resistance is used, When a power device is made of an epitaxial laminated structure, the device cannot withstand the injected voltage and cannot provide a higher breakdown voltage. When the measured carbon concentration range is higher than 1×10 ²⁰ /cm ³ , the first gallium nitride thick layer 320 will produce epitaxial defects due to too high concentration, thereby reducing its epitaxial quality.

Then, a third aluminum gallium nitride superlattice layer (Al _x2 Ga _1-x2 N, thickness d ₃ ) and a fourth aluminum nitride layer are formed on the first gallium nitride thick layer 320 by the MOCVD method. The second superlattice epitaxial structure 330 is a staggered and stacked combination of two superlattice layers of gallium superlattice layer (Al _y2 Ga _1-y2 N, thickness d ₄ ). Among them, in order to avoid excessive stress due to excessive differences in lattice constants between the second superlattice epitaxial structure 330 and the underlying first gallium nitride thick layer 320, two types of the second superlattice epitaxial structure 330 are The preferred range of the average aluminum content of the aluminum gallium nitride superlattice layer is 0≦(x2×d ₃ +y2×d ₄ )/(d ₃ +d ₄ )≦0.05, x2≠y2, and each layer of supercrystal The thickness of the grid layer is preferably no more than 50 nanometers. The stress accumulation in the overall nitride semiconductor epitaxial stack structure 200 is released through the second superlattice epitaxial structure 330, and can continuously block the stress from the first gallium nitride thick layer 320 side such as lattice mismatch or The epitaxial defects generated by the stress continue to extend upward along the direction perpendicular to the surface of the silicon substrate 210 as the subsequent semiconductor epitaxial stack grows. Here, the appropriate aluminum composition ratio, 0≦(x2×d ₃ +y2×d ₄ )/(d ₃ +d ₄ )≦0.05, can reduce the distance between the first gallium nitride series thick layer 320 and the second supercrystal The difference in lattice constants between the lattice epitaxial structures 330 reduces stress generation during epitaxial crystallization and can also reduce cracks on the surface of the epitaxial layer. In this embodiment, the second superlattice epitaxial structure 330 is formed with 60 layers (30 pairs), but in fact, the number of layers is not limited to this number. The preferred number of layers of the superlattice epitaxial structure can be from 20 layers (10 pairs) to 300 layers (150 pairs). When the number of layers is less than 20 layers, the superlattice epitaxial structure can slow down stress accumulation and barrier. The effect of epitaxial defects is extremely low, and it is impossible to prevent the subsequent growth of semiconductor epitaxial stacks from producing too many or too large cracks at a sufficient thickness; and when the superlattice epitaxial structure has more than 300 layers, the epitaxial layer will be The process is too time-consuming and is not conducive to the process economy of the overall nitride semiconductor epitaxial stacked structure 200. The fixed stacked superlattice epitaxial structure itself will also cause the surface of the superlattice epitaxial structure to begin to deteriorate due to its excessive thickness. and unexpected stress and other side effects.

Finally, a second gallium nitride series thick layer (Al _z2 Ga _1-z2 N) 340 with a thickness greater than 1000 nanometers is formed on the second superlattice epitaxial structure 330 using the MOCVD method. Here, the second The composition of the gallium nitride thick layer 340 may be, for example, pure gallium nitride or an aluminum gallium nitride layer containing appropriately added low aluminum content. Among them, adding appropriate aluminum elements, for example, the aluminum content is 0≦z2≦0.05, can increase the energy gap width of the second gallium nitride series thick layer 340. Subsequently, the nitride semiconductor epitaxial stacked structure 200 is made. When using power components, the overall component can theoretically have a higher vertical withstand operating voltage capability, that is, a higher component breakdown voltage. In addition, elements such as carbon or iron can also be doped into the second gallium nitride thick layer 340 to increase the intra-layer resistance of the second gallium nitride thick layer 340 . In this embodiment, the second gallium nitride thick layer 340 formed by the MOCVD method is an aluminum gallium nitride layer doped with carbon impurities. The doped carbon impurities in this embodiment include intentional doping or unintentional doping. The carbon impurity concentration range in this embodiment is a range of 5×10 ¹⁷ /cm ³ ~1×10 ²⁰ /cm ³ when measured by SIMS. Through the experimental results of this embodiment, it can be found that when the carbon concentration range is lower than 5×10 ¹⁷ /cm ³ , the resistance of the second gallium nitride thick layer 340 is too low. Subsequently, when a nitride with too low resistance is used, When a semiconductor epitaxial laminated structure is used to make a power device, the device cannot withstand the injected voltage and cannot provide a high breakdown voltage. When the measured carbon concentration range is higher than 1×10 ²⁰ /cm ³ When the carbon concentration is too high, epitaxial defects will occur in the second gallium nitride thick layer 340 and its epitaxial quality will be degraded.

Similarly, elements such as carbon or iron can also be doped into the second superlattice epitaxial structure 330 to increase the intra-layer resistance of the superlattice epitaxial structure 330 . In this embodiment, the superlattice epitaxial structure 330 formed by the MOCVD method is an aluminum gallium nitride layer doped with carbon impurities. Similarly, the doping of carbon impurities in this embodiment includes intentional doping or unintentional doping. The preferred carbon impurity concentration range is 5×10 ¹⁷ /cm ³ ~1×10 ²⁰ /cm ³ when measured by SIMS. Through relevant experimental results, it can be found that when the carbon concentration range is lower than 5×10 ¹⁷ /cm ³ , the resistance value of the second superlattice epitaxial structure 330 is too low. Subsequently, when a nitride semiconductor epitaxial structure with too low resistance value is used, When a power device is made of a crystal laminated structure, the device cannot withstand the injected voltage and cannot provide a higher breakdown voltage. When the measured carbon concentration range is higher than 1×10 ²⁰ /cm ³ , In the second superlattice epitaxial structure 330, epitaxial defects may occur due to excessive carbon doping concentration, resulting in reduced epitaxial quality.

After the buffer structure 300 is completed, the device functional structure 400 can be epitaxially formed on the buffer structure 300 . The growth methods of epitaxial crystals can be referred to the growth methods listed above and will not be described again here. In this embodiment, the device functional structure 400 of the power device includes a channel layer 410 and a barrier layer 420. The channel layer 410 has a thickness ranging from 50 to 500 nm and is formed on the buffer structure 300. It is composed of a Group III nitride material and has a first energy gap. The barrier layer 420 has a thickness ranging from 10 to 50 nm and is formed on the channel layer 410. , composed of Group III nitride materials and having a second energy gap. The second energy gap is larger than the first energy gap. Therefore, the lattice constant of the barrier layer 420 is smaller than that of the channel layer 410 . Among them, the channel layer 410 can be composed of pure gallium nitride or a gallium nitride-based material (Al _a Ga _1-a N) composed of aluminum gallium nitride with an appropriate addition of low aluminum content, 0≦a<0.05, and the barrier layer 420 It contains aluminum gallium nitride (Al _b Ga _1-b N), 0<b<1, and a<b. The channel layer 410 and the barrier layer 420 themselves form spontaneous polarization (spontaneous polarization), and their different lattice constants form piezoelectric polarization (piezoelectric polarization), thereby generating two heterojunctions between the channel layer 410 and the barrier layer 420. For dimensional electron gas, please refer to the dotted line in Figure 2. In this embodiment, the channel layer 410 and the barrier layer 420 are formed by the MOCVD method. The material of the channel layer 410 is gallium nitride, and the material of the barrier layer 420 is aluminum gallium nitride, which is an undoped intrinsic semiconductor. This disclosure is not limited to this embodiment. The barrier layer 420 and the channel layer 410 may also be doped with donor impurities or acceptor impurities according to device performance requirements to change the characteristics of their semiconductor layers. The location where the two-dimensional electron gas is generated is not limited to the channel layer 410 as shown in FIG. 2 in this embodiment, and may also be generated in the barrier layer 420 depending on the embodiment.

In this embodiment, in order to reduce unnecessary stress accumulation caused by the difference in lattice constants, when the material of the aluminum nitride nucleation layer 220 is a material with a higher aluminum composition ratio, such as aluminum nitride; and the functional structure of the upper device is as follows When the material of the channel layer 410 is a material with a low aluminum composition ratio, such as gallium nitride; a preferred embodiment of the buffer structure 300 is to use an aluminum composition ratio of all or part of the plurality of layers in the nitride semiconductor epitaxial stacked structure. It is located between the aluminum composition ratio of the nucleation layer 220 material and the aluminum composition ratio of the element functional layer material, and gradually changes along the epitaxial growth direction, wherein the aluminum composition gradient may be continuous or discontinuous. That is, for example, as shown in this embodiment, the aluminum composition ratio of the aluminum nitride nucleation layer 220 ≧ the average aluminum composition ratio of the first superlattice epitaxial structure 310 ≧ the aluminum composition ratio of the first gallium nitride series thick layer 320 ≧ The average aluminum composition ratio of the second superlattice epitaxial structure 330 ≧ the aluminum composition ratio of the second gallium nitride series thick layer 340 .

In another embodiment, the channel layer 410 in the nitride semiconductor epitaxial stack structure can also be formed simultaneously when the second gallium nitride thick layer 340 is formed. In other words, in the second superlattice Lei A second gallium nitride-based semiconductor layer (not shown) is grown on the crystal structure 330, in which the upper half of the second gallium nitride-based semiconductor layer constitutes the channel layer 410, and the lower half of the second gallium nitride-based semiconductor layer The second gallium nitride thick layer 340 is formed. A barrier layer 420 is then formed thereon, and a two-dimensional electron gas is generated adjacent to the interface between the barrier layer 420 and the channel layer 410 .

In addition, after the barrier layer 420 is grown, the cap layer 510 can be selectively grown on the barrier layer 420 by any of the above-mentioned growth methods, which will not be described in detail here. In this embodiment, the cap layer 510 is, for example, an undoped gallium nitride semiconductor layer, and substantially covers the surface of the barrier layer 420, which can prevent the surface of the barrier layer 420 from being degraded due to oxidation and other reactions, and can improve the surface leakage current phenomenon of the barrier layer 420. It is worth noting that in order to maintain good electrical contact between the electrode structure (not shown) to be formed on the surface of the nitride semiconductor epitaxial stack structure 200 and the barrier layer 420 when the device is subsequently manufactured, the thickness of the cap layer 510 in this embodiment is between 0 and 20 nanometers, so that electrons can tunnel through the cap layer 510 through the electrode structure.

Please refer to Figures 3A and 3B, which respectively show a conventional nitride semiconductor epitaxial stacked structure 100 and a nitride semiconductor epitaxial stacked structure (not shown) using the second embodiment of the present disclosure including a buffer structure. TEM images of portions of partial epitaxial stacks 100' and 200'. Referring to Figures 3A and 3B, in Figure 3A, the buffer structure of the local epitaxial layer 100' is composed of a superlattice stack 130 and a gallium nitride thick layer 140; in Figure 3B, the local epitaxial layer 100' The buffer structure 300 of the crystal stack 200' is composed of a first superlattice epitaxial structure 310, a first gallium nitride thick layer 320', a second superlattice epitaxial structure 330, and a second gallium nitride thick layer. Composed of 340'. It can be found from the image that the local epitaxial stack 100' still has most of the epitaxial defects 145 extending from the superlattice stack 130 to the upper gallium nitride thick layer 140; in contrast, as shown in Figure 3B shows that in the second embodiment, the difference from the first embodiment is that the thickness of the first gallium nitride thick layer 320' is 1.3 microns, while the thickness of the second gallium nitride thick layer 340' is 0.9 Micron. It can be found from the image that there are some epitaxial defects in the local epitaxial stack 200'. 245 is turned or stopped in the first gallium nitride thick layer 320', another part of the epitaxial defects 245 is interrupted in the second superlattice epitaxial structure 330, and there is another part of the epitaxial defects 245. It is turned or stopped again in the second gallium nitride thick layer 340'. It can be seen from this that, compared with the conventional partial epitaxial stack 100' in Figure 3A, the partial epitaxial stack 200' of the second embodiment of the present disclosure can relatively significantly reduce epitaxy defects in the epitaxial stack. density, thereby reducing surface cracks on the subsequently generated component functional structure (not shown), improving its epitaxial quality, and enabling subsequent power components to be manufactured using this nitride semiconductor epitaxial stack structure 200' to have higher Component performance. From the experimental results of the embodiment, it can be found that the overall thickness of the first gallium nitride-based thick layer 320' and the second gallium nitride-based thick layer 340' has a steering effect on the epitaxial defects 245 in the nitride semiconductor epitaxial stack structure. or the effect of discontinued contributions. As shown in the results of the first embodiment and the second embodiment, in a better case, the total thickness of the two gallium nitride thick layers should be greater than two microns.

Please refer to Figures 4A to 4C, which are partial schematic diagrams of nitride semiconductor epitaxial stacked structures according to the third to fifth embodiments of the present disclosure, respectively illustrating parts of the buffer structures 430, 460, and 490. Schematic side view of the epitaxial stack structure. Figure 4A shows a schematic side view of a partial epitaxial stack structure including a buffer structure 430 part according to the third embodiment of the present disclosure. The nitride semiconductor epitaxial stack structure of this embodiment is different from the first embodiment in that the buffer structure The other differences between the structure 430 and the buffer structure 300 are the same as those in the first embodiment. In this embodiment, on the aluminum nitride nucleation layer 220, the buffer structure 430 sequentially includes a first gallium nitride series thick layer 431, a first superlattice epitaxial structure 432, and a second gallium nitride series thick layer 431. layer 433, and a second superlattice epitaxial structure 434. That is, in this embodiment, the buffer structure 430 is composed of two groups of sequentially grown thick layers of gallium nitride and a superlattice epitaxial structure. In the first embodiment, the buffer structure 300 first grows a superlattice epitaxial structure. crystal structure, and then the order of growing a thick layer of gallium nitride is reversed. Subsequently, a single-layer or multi-layer component functional structure can be formed on the buffer structure 430 according to different requirements.

Among them, in order to reduce unnecessary stress accumulation caused by the difference in lattice constants, when the material of the aluminum nitride nucleation layer 220 is a material with a high aluminum composition ratio, such as aluminum nitride; and the upper component functional structure such as the channel layer (Fig. When the material (not shown) is a material with a low aluminum composition ratio, such as gallium nitride; a preferred embodiment of the buffer structure is to adjust the aluminum composition ratio of all or part of the plurality of layers in the nitride semiconductor epitaxial stacked structure It is located between the aluminum composition ratio of the nucleation layer material and the aluminum composition ratio of the component functional layer material, and gradually changes along the epitaxial growth direction. The gradient may be continuous or discontinuous. That is, as shown in this embodiment, the aluminum composition ratio of the aluminum nitride nucleation layer 220 ≧ the aluminum composition ratio of the first gallium nitride thick layer 431 ≧ the average aluminum composition ratio of the first superlattice epitaxial structure 432 ≧ The aluminum composition ratio of the second gallium nitride thick layer 433 is ≧ the average aluminum composition ratio of the second superlattice epitaxial structure 434 .

Figure 4B shows a schematic side view of a partial epitaxial stack structure including a buffer structure 460 part according to the fourth embodiment of the present disclosure. The difference from the first embodiment is that in this embodiment, nitride is formed on the silicon substrate 210 After the aluminum nucleation layer 220 is formed, the buffer structure 460 formed thereon sequentially consists of a first superlattice epitaxial structure 461, a first gallium nitride thick layer 462, a second superlattice epitaxial structure 463, It is composed of a gallium nitride thick layer 464 , a third superlattice epitaxial structure 465 , and a third gallium nitride thick layer 466 . That is, in this embodiment, the buffer structure 460 is composed of three sets of superlattice epitaxial structures and gallium nitride thick layers, which is smaller than the two sets of superlattice epitaxial structures and gallium nitride thick layers in the first embodiment. The thick layer consists of one more group. It is worth noting that buffer structures including two or more groups of superlattice epitaxial structures and gallium nitride thick layers should be able to achieve the spirit of the disclosure. The disclosure is not limited to the number of groups in this embodiment. .

Among them, in order to reduce unnecessary stress accumulation caused by the difference in lattice constants, when the material of the aluminum nitride nucleation layer 220 is a material with a high aluminum composition ratio, such as aluminum nitride; and the upper component functional structure such as the channel layer (Fig. When the material (not shown) is a material with a low aluminum composition ratio, such as gallium nitride; a preferred embodiment of the buffer structure is to adjust the aluminum composition ratio of all or part of the plurality of layers in the nitride semiconductor epitaxial stacked structure It is between the aluminum composition ratio of the nucleation layer material and the aluminum composition ratio of the component functional layer material, and Gradient along the epitaxial growth direction, the gradient can be continuous or discontinuous. That is, as shown in this embodiment, the aluminum composition ratio of the aluminum nitride nucleation layer 220 ≧ the average aluminum composition ratio of the first superlattice epitaxial structure 461 ≧ the aluminum composition ratio of the first gallium nitride series thick layer 462 ≧ The average aluminum composition ratio of the second superlattice epitaxial structure 463 ≧ the aluminum composition ratio of the second gallium nitride series thick layer 464 ≧ the average aluminum composition ratio of the third superlattice epitaxial structure 465 ≧ the third gallium nitride series Aluminum composition ratio of thick layer 466.

Figure 4C shows a schematic side view of a partial epitaxial laminated structure including a buffer structure 490 part according to the fifth embodiment of the present disclosure. The difference from the fourth embodiment is that the buffer structure 490 in this embodiment sequentially consists of the first Gallium nitride series thick layer 491, first superlattice epitaxial structure 492, second gallium nitride series thick layer 493, second superlattice epitaxial structure 494, third gallium nitride series thick layer 495, and It is composed of three superlattice epitaxial structures 496. That is, in this embodiment, the buffer structure 490 is composed of three groups of gallium nitride thick layers and a superlattice epitaxial structure, which is larger than the two groups of gallium nitride thick layers and superlattice structures in the first embodiment. There is one more set of epitaxial structures. In addition, the order of growing the superlattice epitaxial structure first and then growing the gallium nitride thick layer is opposite to that of the buffer structure 460 in the fourth embodiment. It is worth noting that buffer structures including two or more groups of gallium nitride thick layers and superlattice epitaxial structures should be able to achieve the spirit of this disclosure, and this disclosure is not limited to the number of groups in the embodiment.

Among them, in order to reduce unnecessary stress accumulation caused by the difference in lattice constants, when the material of the aluminum nitride nucleation layer 220 is a material with a high aluminum composition ratio, such as aluminum nitride; and the upper component functional structure such as the channel layer (Fig. When the material (not shown) is a material with a low aluminum composition ratio, such as gallium nitride; a preferred embodiment of the buffer structure is to adjust the aluminum composition ratio of all or part of the plurality of layers in the nitride semiconductor epitaxial stacked structure It is located between the aluminum composition ratio of the nucleation layer material and the aluminum composition ratio of the component functional layer material, and gradually changes along the epitaxial growth direction. The gradient may be continuous or discontinuous. That is, for example, as shown in this embodiment, the aluminum composition ratio of the aluminum nitride nucleation layer 220 ≧ the aluminum composition ratio of the first gallium nitride thick layer 491 ≧ the first The average aluminum composition ratio of the superlattice epitaxial structure 492 ≧ the aluminum composition ratio of the second gallium nitride series thick layer 493 ≧ the average aluminum composition ratio of the second superlattice epitaxial structure 494 ≧ the third gallium nitride series thick layer The aluminum composition ratio of 495≧the average aluminum composition ratio of the third superlattice epitaxial structure 496.

Next, please refer to Figures 5, 6, and 7A-7B. Figure 5 is a top view of a power element S according to the sixth embodiment of the present disclosure. The semiconductor power element S is, for example, a three-terminal element. In this embodiment, the power device S includes a source pad S70, a drain pad S80, a gate pad S90 and at least one power device unit E1. The power element unit E1 is, for example, a field effect transistor (FET), specifically a high electron mobility field effect transistor (HEMT).

Figures 6A to 6B show a schematic structural diagram of the power element unit E1 in the top view of the power element S in Figure 5. In order to clearly illustrate the detailed structure of the power device unit E1, Figure 6A shows a partially enlarged top view of the power device unit E1, and Figure 6B shows a cross-sectional view along the section line FF' in Figure 6A. The power element unit E1 is, for example, a high electron mobility field effect transistor, including a nitride semiconductor epitaxial stack structure 500 using the sixth embodiment of the present disclosure, a source electrode 70, a drain electrode 80, and A gate electrode 90. As shown in Figure 5, in the power element unit E1, the source pad S70 is electrically connected to the source electrode 70, the drain pad S80 is electrically connected to the drain electrode 80, and the gate pad S90 is electrically connected to the gate electrode. The electrodes 90 are electrically connected, and the nitride semiconductor epitaxial stack structure 500 is correspondingly located under the electrodes, as shown in Figure 6B.

A protective layer (not shown) may be further formed on the surface of the power element unit E1 to cover the surfaces of the dielectric layer 60, the source electrode 70, the drain electrode 80 and the gate electrode 90 to prevent the overall electrical damage of the power element unit E1. affected. The protective layer can be an oxide or a nitride, such as an oxide such as silicon oxide or aluminum oxide, or a nitride such as silicon nitride or gallium nitride. Then the protective layer is etched to expose part of the source electrode 70 , the drain electrode 80 and the gate electrode 90 . That is, part of the surface of the source electrode 70 , the drain electrode 80 and the gate electrode 80 may not be covered by the protective layer. , to increase the electrical connection with the outside world Convenience. In the present disclosure, the locations not covered by the protective layer may be, for example, the source pad S70 , the drain pad S80 , and the gate pad S90 that are directly electrically connected to the source electrode 70 , the drain electrode 80 , and the gate electrode 90 .

FIG. 7 shows a detailed side view of the nitride semiconductor epitaxial stack structure 500 in the power device S according to the sixth embodiment of the present disclosure. In this embodiment, the nitride semiconductor epitaxial stack structure 500 is similar to the first embodiment and uses the same reference numerals as the first embodiment. It is worth noting that in this embodiment, a back barrier layer (Back Barrier) 550 is inserted between the buffer structure 300 and the channel layer 410. The preferred composition of the rear barrier layer 550 is an aluminum gallium nitride layer with a higher aluminum composition ratio than that of the second gallium nitride thick layer 340 . When the nitride semiconductor epitaxial stacked structure 500 is subsequently fabricated into a power device, the rear barrier layer 550 has a higher aluminum composition ratio than the second gallium nitride thick layer 340 and will have a higher energy gap to provide localized electronic capabilities to avoid When the device is operated, electrons enter the buffer structure 300 and are captured by epitaxial defects in the buffer structure 300 , thereby affecting the stability of the two-dimensional electron gas concentration between the heterogeneous interfaces during subsequent device operation. That is, the degree of current collapse that occurs when the device is repeatedly operated can be reduced.

It is worth noting that in this embodiment, in order to prevent the high energy gap of the rear barrier layer 550 from raising the energy barrier height of the channel layer 410 and further affecting the intensity of the current when the power device is operated, the thickness of the rear barrier layer 550 is no more than 50 Nano is better.

In addition, as shown in FIG. 6B, in this embodiment, before forming the source electrode 70, the drain electrode 80 and the gate electrode 90, a dielectric layer 60 can also be formed on the cap layer 510. above the surface. The dielectric layer 60 may also be selectively located under the gate electrode 90 (not shown). When the dielectric layer 60 is located under the gate electrode, by selecting the dielectric layer 60 with different dielectric constants and adjusting the thickness of the dielectric layer 60 , the surface leakage current can be further reduced, and the operation of the gate electrode 90 can be improved. Bias voltage range improves component reliability. The dielectric layer 60 may be an oxide or a nitride, such as an oxide such as silicon oxide or aluminum oxide, a nitride such as silicon nitride or aluminum nitride, or an oxynitride such as aluminum oxynitride. However, the present disclosure is not limited thereto, and the dielectric layer 60 may not be formed in other embodiments.

In this embodiment, as mentioned above, the source electrode 70 , the drain electrode 80 and the gate electrode 90 are respectively formed above the nitride semiconductor epitaxial stack structure 500 , and are subsequently extended and electrically connected thereto. The source pad S70, the drain pad S80, and the gate pad S90 serve as terminal points for electrical connection with the outside. As shown in Figure 6B, in the side view of a power element unit E1, the source electrode 70 and the drain electrode 80 are respectively placed on both sides of the surface of the nitride semiconductor epitaxial stack structure 500, and the gate electrode 90 is located between the source electrode 70 and the drain electrode 80 . In this embodiment, the source electrode 70 and the drain electrode 80 can be made by selecting appropriate materials for the source electrode 70 and the drain electrode 80 and/or through processes (such as etching, thermal annealing, etc.). Ohmic contact is formed between the pole electrode 80 and the barrier layer 420 . Similarly, a Schottky contact can be formed between the gate electrode 90 and the barrier layer (not shown) by selecting an appropriate material of the gate electrode 90 . The material of the source electrode 70 and the drain electrode 80 can be selected from titanium (Ti), aluminum (Al) or a combination thereof, and the material of the gate electrode 90 can be selected from the group consisting of nickel (Ni), gold (Au), tungsten (W). ), titanium nitride (TiN) or a combination thereof, but is not limited to this.

In other embodiments, the nitride semiconductor epitaxial stacked structure 500 of the power device S can also be replaced or partially replaced with the buffer structure part by the nitride semiconductor epitaxial stacked structure in other embodiments of the present disclosure.

Please refer to FIG. 8 , which is a schematic side view of the Schottky diode unit E2 according to the seventh embodiment of the present disclosure. The Schottky diode element unit E2 is manufactured using the nitride semiconductor epitaxial stack 500 in the sixth embodiment of the present disclosure. In this structure, an anode A and a cathode C are respectively formed on the upper surface of the nitride semiconductor epitaxial layer 500 as terminal points for electrical connection with the outside. The anode A and the cathode C can be placed on both sides of the upper surface of the epitaxial layer 500 respectively, by selecting appropriate materials of the anode A and cathode C, and/or by processing (such as etching, thermal annealing) ) to form ohmic contact between anode A and cathode C and the barrier layer. The materials of anode A and cathode C can be selected from titanium (Ti), aluminum (Al) or their compositions.

Similarly, a dielectric layer 60' may also be formed on the upper surface of the nitride semiconductor epitaxial stack 500, and the forming step may be before or after forming the anode A and cathode C. The dielectric layer 60' can further reduce surface leakage current and improve component reliability. The dielectric layer 60' may be an oxide or a nitride, such as an oxide such as silicon oxide or aluminum oxide, or a nitride such as silicon nitride or aluminum nitride. However, the present invention is not limited to this, and the dielectric layer may not be formed in other embodiments.

Finally, please refer to Figures 9A-9B and Figures 10A-10B. Figures 9A-9B respectively show the power device test unit E3 made by using the conventional nitride semiconductor epitaxial stack structure 100 and the first implementation of the present disclosure. For example, the electrical test results of the horizontal leakage capability of the power device test unit E4 made of the nitride semiconductor epitaxial stack structure 200 are shown.

The power device test units E3 and E4 are formed with a plurality of the aforementioned power device test units on a conventional nitride semiconductor epitaxial wafer and a nitride semiconductor epitaxial wafer (not shown) according to the disclosed first embodiment respectively through a manufacturing process. Units E3 and E4 are divided into power component test units in these areas according to the three areas of the center, periphery, and outside of the semiconductor epitaxial wafer, and electrical tests are performed on a plurality of power component test units E3 and E4 in these areas. As shown in Figures 9A-9B, after making representative measurements of the electrical characteristics of the power components in these areas, three different electrical test result trends can be obtained from the electrical test results in Figures 9A and 9B respectively. String. Figures 10A and 10B show schematic side views of the power component test units E3 and E4 respectively. The power component test unit is prepared by defining a plurality of power component test units in the semiconductor epitaxial wafer, and each unit is The nitride semiconductor epitaxial stacked structures 100 and 200 completed by mid-epitaxial epitaxy, including the channel layer 410, the barrier layer 152, 420, and the central part of the cap layer 510 are removed, and then the semiconductor epitaxial layers that have not been removed on the left and right sides are removed. Ohmic electrodes O1~O4 are formed on the surface of the stacked structure.

The test conditions are to set the ohmic electrodes O1 and O3 on the left side to the ground state (Ground, 0V), and apply the corresponding reverse bias voltage to the ohmic electrodes O2 and O4 on the other side, as shown on the abscissa in Figure 9A-9B. The reverse bias voltage V=0~-1000 volts is used to test the leakage current (I, in milliamps) of the power component test units E3 and E4 in the buffer structure part, as shown on the ordinate in Figure 9A-9B. It can be found from Figures 9A-9B that the leakage current of the power component test unit E3 is approximately 1×10 ^-6 mA when the corresponding bias voltage -600 volts is applied. Compared with the leakage current of the power component test unit E4, When the corresponding bias voltage -600 volts is applied, it is about 5×10 ^-7 milliamps. A similar trend can be obtained under other reverse bias voltages. The leakage current of power component test unit E4 is lower than that of E3. About 0.5~1 series.

Through the implementation of the spirit of the present disclosure, a high-quality nitride semiconductor epitaxial stack structure with low crystal defect density, smooth epitaxial layer surface, fewer and/or smaller surface cracks can be formed, and through this nitride semiconductor epitaxial stack structure Components manufactured with a layered structure, such as power components and Schottky diode components, will also have improved component performance due to the improvement in the quality of the semiconductor epitaxial laminated structure, and have industrial applicability. The above-described embodiments are only for illustrating the technical ideas and features of the present disclosure. Their purpose is to enable those skilled in the art to understand the contents of the present disclosure and implement them accordingly. They should not be used to limit the patent scope of the present disclosure. That is to say, all equivalent changes or modifications made in accordance with the spirit of the disclosure should still be covered by the patent scope of the disclosure.

200:Nitride semiconductor epitaxial stack structure

210:Substrate

220: Aluminum nitride nucleation layer

300: Buffer structure

310: The first superlattice epitaxial structure

320: The first gallium nitride series thick layer

330: Second superlattice epitaxial structure

340: Second gallium nitride series thick layer

400: Component functional structure

410: Channel layer

420: Barrier layer

510: Cap layer

Claims (10)

A nitride semiconductor epitaxial stack structure includes: a silicon substrate; an aluminum-containing nucleation layer disposed on the silicon substrate; a buffer structure disposed on the aluminum-containing nucleation layer, including in sequence: a first a superlattice epitaxial structure; a first gallium nitride system layer disposed on the first superlattice epitaxial structure; and a second superlattice epitaxial structure disposed on the first gallium nitride system layer; a channel layer disposed on the buffer structure; and a barrier layer disposed on the channel layer; wherein the first superlattice epitaxial structure includes a first average aluminum composition ratio, the first average The aluminum composition ratio is greater than 0 and less than or equal to 1, the first gallium nitride layer includes a first aluminum composition ratio, the first aluminum composition ratio is greater than 0 and less than or equal to 1, the second superlattice epitaxial structure Contains a second average aluminum composition ratio, the second average aluminum composition ratio is greater than or equal to 0 and less than 1, the aluminum composition ratio of the aluminum-containing nucleation layer is greater than 0 and less than or equal to 1; wherein, the aluminum-containing nucleation layer The aluminum composition ratio≧the first average aluminum composition ratio≧the first aluminum composition ratio>the second average aluminum composition ratio. The nitride semiconductor epitaxial stack structure described in item 1 of the patent application, wherein the first superlattice epitaxial structure consists of a plurality of aluminum nitride superlattice layers and a plurality of aluminum gallium nitride superlattice layers alternately Stacking; wherein, the second superlattice epitaxial structure consists of a plurality of aluminum gallium nitride superlattice layers and a plurality of gallium nitride superlattice layers alternately stacked. For the nitride semiconductor epitaxial stack described in claim 1, the channel layer is a gallium nitride layer, and the barrier layer is an aluminum gallium nitride layer. The nitride semiconductor epitaxial stack structure described in claim 1 of the patent application further includes an aluminum gallium nitride rear barrier layer located between the channel layer and the buffer structure. The nitride semiconductor epitaxial stacked structure described in item 1 of the patent application further includes a second gallium nitride series layer disposed on the second superlattice epitaxial structure, and the second gallium nitride The system layer includes a second aluminum composition ratio, the second aluminum composition ratio is greater than or equal to 0 and less than 1, and the first aluminum composition ratio is greater than the second aluminum composition ratio. In the nitride semiconductor epitaxial stack structure described in claim 5, the first gallium nitride layer and/or the second gallium nitride layer respectively include a dopant. The nitride semiconductor epitaxial stack structure described in claim 1, wherein the first superlattice epitaxial structure and/or the second superlattice epitaxial structure each contains a dopant. For the nitride semiconductor epitaxial stack structure described in item 6 or 7 of the patent application, the dopant includes at least one of iron or carbon. In the nitride semiconductor epitaxial stack structure described in claim 1, the thickness of the first gallium nitride layer is greater than 1000 nanometers. A power component, including: a nitride semiconductor epitaxial stack structure as described in any one of items 1 to 9 of the patent application; and a source electrode, a gate electrode, and a drain electrode, or A cathode and an anode are respectively disposed on the nitride semiconductor epitaxial stack structure; wherein the gate electrode is located between the source electrode and the drain electrode.

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