GaN HEMT device

Abstract

The invention provides a GaN HEMT (High Electron Mobility Transistor) device. The GaN HEMT device comprises a low-resistance substrate; the grounded back grounding metal is formed on the back side of the substrate; the P-type epitaxial layer is formed on the substrate; a GaN HEMT structure layer, wherein the GaN HEMT structure layer comprises an active region and a high resistance region; the deep hole is formed downwards from the upper surface of the high-resistance region, and the bottom end of the deep hole enters the substrate; the first connecting region is formed in the deep hole in a filling mode, the bottom end of the first connecting region enters the substrate, and the contact between the first connecting region and the substrate is ohmic contact. According to the GaN on SiC HEMT device, the technical problem that the grounding process is complex due to the structure of a traditional GaN on SiC HEMT device is solved.

Description

Technical Field

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

[0002] Gallium nitride high electron mobility transistor (GaN HEMT) is an emerging semiconductor device that has been widely used in many fields due to its excellent performance. Compared with traditional silicon-based devices, GaN HEMT has higher switching speed and higher breakdown voltage, which enables it to perform well in high-frequency, high-power and high-temperature environments.

[0003] GaN HEMT devices have applications in a variety of fields, including the following: 1. Wireless communication: GaN HEMT devices play an important role in 5G and future 6G communication systems. Their high-frequency characteristics enable signals to be transmitted at higher frequencies, improving data transmission rates and network capacity.

[0004] 2. Radar system: Due to the high power and high efficiency of GaN HEMT devices, many modern radar systems choose to adopt this technology. It can effectively improve the detection range and accuracy of radar and is widely used in military and civil aviation fields.

[0005] 3. Power conversion: GaN HEMT devices are widely used in power management, especially in high-efficiency power converters and inverters. Their high switching speed and low on-resistance significantly improve power efficiency and help reduce energy consumption.

[0006] 4. Electric vehicles and renewable energy: With the popularization of electric vehicles and renewable energy, GaN HEMT devices have gradually become the core components of electric vehicle charging piles and inverters, which can improve the efficiency and performance of the overall system.

[0007] In recent years, GaN HEMT device technology has developed rapidly. Many semiconductor companies and research institutions have increased their investment in the research and production of GaN materials. Compared with early technologies, today's GaN HEMT devices have made significant progress in cost, stability and production processes. With the maturity of manufacturing processes, GaN HEMT devices are increasingly widely used in the market, and prices are gradually falling, which has promoted their popularity in various fields.

[0008] Figure 1 Schematic diagram of a GaN on SiC HEMT device in the prior art. Figure 1 From the document "RF GaN on Silicon: The Best of Two Worlds". Figure 1 As shown, GaN epitaxial layer 1-1 and two-dimensional electron gas 1-2.

[0009] While the existing GaN on SiC HEMT devices are developing, they are also facing problems such as process difficulties. Figure 2 Schematic diagram of another GaN on SiC HEMT device in the prior art. GaN on SiC HEMT devices are generally used in power applications and RF applications, among which RF applications have very high requirements for the grounding resistance and inductance of the device. Currently, GaN on SiC HEMT devices use a high-resistance substrate, so TSV is generally used to achieve grounding. The brief process is to etch the surface GaN first, align it on the back, and etch the TSV hole.

[0010] TSV (Through Silicon Via) is a vertical interconnection technology that penetrates silicon wafers or chips and is mainly used in three-dimensional packaging and three-dimensional integrated circuits.

[0011] TSV via 2-1 has excellent performance and its cross-sectional morphology is as follows Figure 2 As shown, the diameter of the TSV through hole 2-1 is greater than 30 μm, the depth of the TSV through hole 2-1 is greater than 60 μm, and the TSV through hole 2-1 is filled with gold. The existing TSV through hole 2 process has the problems of complex process and high price.

[0012] Figure 2 The TSV vias used for grounding in GaN on SiC HEMT devices have the following shortcomings: 1. The etching process is complicated. Since SiC materials are difficult to etch using ordinary etching processes, ICP (Inductively Coupled Plasma) is required for etching. Therefore, a special etching barrier layer is required, and then a liftoff process (i.e., stripping process) is used to remove it. Figure 2 , ICP etching is performed after the liftoff process, and the etching barrier layer on the front side of the device needs to select a gold layer that is difficult to etch.

[0013] 2. The process cost is very high. After etching is completed, metal filling is required. A gold layer of several microns is required. The cost of the gold layer is high. Due to the selection of the etching stop layer on the front of the device, gold is also selected, which is very costly.

[0014] 3. The etched hole occupies a large area. Since the etching selectivity cannot be very high, the diameter of the device TSV through hole cannot be reduced. When it is above 30μm, the area occupied is larger than the active area.

[0015] Therefore, the structure of the traditional GaN on SiC HEMT device leads to a complicated grounding process, which is a technical problem that technical personnel in this field urgently need to solve.

[0016] The above information disclosed in the background section is only for enhancing understanding of the background of the present application and therefore it may contain information that does not form the prior art known to a person of ordinary skill in the art. Summary of the invention

[0017] The present application provides a GaN HEMT device to solve the technical problem that the structure of a traditional GaN on SiC HEMT device leads to a complicated grounding process.

[0018] The present application provides a GaN HEMT device, including: Low-resistance substrate; A grounded back side grounding metal formed on the back side of the substrate; A P-type epitaxial layer is formed on the substrate; ‌GaN HEMT structural layer, the GaN HEMT structural layer comprising an active region and a high resistance region; A deep hole is formed downward from the upper surface of the high resistance region, and the bottom end of the deep hole enters into the substrate; A first connection region of metal is filled in the deep hole, the bottom of the first connection region enters into the substrate, and the contact between the first connection region and the substrate is an ohmic contact.

[0019] Due to the adoption of the above technical solution, this application has the following technical effects: The advantages of the GaN HEMT device of this application are: Simple process: TSV through-holes are eliminated, and TSV process is no longer needed. Instead, deep holes and the first connection area 30 of metal filled in the deep holes and a low-resistance substrate are used, and there is no need to etch through-holes that penetrate the entire thickness of the device. Only a deep hole of a few microns is needed, so the deep hole etching process is simple, the process steps are simple, and the process difficulty is low. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings described herein are used to provide a further understanding of the present application and constitute a part of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings: Figure 1 is a schematic diagram of a GaN on SiC HEMT device in the prior art; Figure 2 is a schematic diagram of another GaN on SiC HEMT device in the prior art; Figure 3-A A schematic diagram of an implementation of the GaN HEMT device of the present application; Figure 3-B A schematic diagram of another implementation of the GaN HEMT device of the present application; Figure 4 A schematic diagram of completing step S1 of the method for preparing a GaN HEMT device of the present application; Figure 5 A schematic diagram of completing step S2 of the method for preparing a GaN HEMT device of the present application; Figure 6 A schematic diagram of completing step S3 of the method for preparing a GaN HEMT device of the present application; Figure 7 A schematic diagram of completing step S4 of the method for preparing a GaN HEMT device of the present application; Figure 8 A schematic diagram of completing step S5 of the method for preparing a GaN HEMT device of the present application; Fig. 9 A schematic diagram of completing step S6 of the method for preparing a GaN HEMT device of the present application; Fig.10 This is a schematic diagram of completing step S4-1 of the method for preparing a GaN HEMT device of the present application.

[0021] Reference numerals: In the background technology: GaN epitaxial layer 1-1, two-dimensional electron gas 1-2, TSV through hole 2-1; In this application: Back grounding metal 10, substrate 11, epitaxial layer 12, second connection region 20, AlN layer 22, GaN buffer layer 23, GaN layer 24, AlGaN layer 25, Gate metal 26, SiN layer 27, source 28-1, drain 28-2, A first connection region 30 and a source metal 31 . DETAILED DESCRIPTION

[0022] In order to make the technical solutions and advantages of the present application more clearly understood, the exemplary embodiments of the present application are further described in detail below in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than an exhaustive list of all the embodiments. It should be noted that the embodiments and features in the embodiments of the present application can be combined with each other without conflict. Embodiment 1

[0023] like Figure 3-A , Figure 3-BAs shown, the GaN HEMT device of the present application includes: A low-resistance substrate 11; A grounded backside grounding metal 10 is formed on the back side of the substrate 11; A P-type epitaxial layer 12 is formed on the substrate 11; ‌GaN HEMT structural layer, the GaN HEMT structural layer comprising an active region and a high resistance region; A deep hole is formed downward from the upper surface of the high resistance region, and the bottom end of the deep hole enters into the substrate 11; A first connection region 30 of metal is filled in the deep hole, and the bottom of the first connection region 30 enters into the substrate 11 . The contact between the first connection region 30 and the substrate 11 is an ohmic contact.

[0024] In the GaN HEMT device of the present application, the epitaxial layer of the P-type SIC material formed on the substrate 11 is a necessary structure of the GaN HEMT device. Above the epitaxial layer 12 is the GaN HEMT structural layer, which includes an active region and a high resistance region.

[0025] The deep hole is formed by etching downward from the upper surface of the high resistance region, and the bottom of the deep hole enters into the substrate 11. That is, the starting point of the etching for forming the deep hole is the upper surface of the high resistance region, and the end point is to enter into the substrate 11. The etching for forming the deep hole only needs to penetrate the thickness of the epitaxial layer of the SIC material and enter deeper into the substrate 11.

[0026] The first metal connection area 30 formed in the deep hole is filled, and the bottom of the first metal connection area 30 enters the substrate 11. At the same time, since the contact between the first metal connection area 30 and the substrate 11 is an ohmic contact, a good connection between the back grounding metal 10, the substrate 11 and the first metal connection area 30 is achieved, which is an ohmic contact.

[0027] The distance between the back grounding metal 10 and the upper surface of the GaN HEMT structure layer is the total thickness of the GaN HEMT device of the present application. Therefore, the deep hole etching is performed for the SIC material with greater etching difficulty, and the etching depth does not penetrate the substrate 11, and there is still a distance from the bottom of the substrate 11, so that the deep hole etching depth is small, which is less than the thickness of the GaN HEMT device of the present application. Therefore, the etching to form the deep hole does not need to adopt the TSV through-hole process, but only needs to adopt the semi-through-hole etching process, and the etching process is simple and the process implementation difficulty is relatively low.

[0028] The depth of the deep hole is small, and correspondingly, the diameter of the deep hole is also small, which makes the area occupied by the deep hole also small.

[0029] Since the back grounding metal 10 is grounded, the zero potential of the grounded back grounding metal 10 has been connected to the upper surface of the first connection area 30 (corresponding to the height of the upper surface of the GaN HEMT structure layer) through the back grounding metal 10, the substrate 11 and the first metal connection area 30, providing conditions for the GaN HEMT device of the present application to be grounded from the front. In this way, the structural form of the GaN HEMT device of the present application realizes that the front grounding no longer needs to penetrate the thickness of the entire device, and thus no longer needs to use the TSV through-hole process.

[0030] The advantages of the GaN HEMT device of this application are: (1) Simple process: TSV through-holes are eliminated and TSV process is no longer needed. Instead, deep holes and the first connection area 30 of metal filled in the deep holes and a low-resistance substrate are used. There is no need to etch through-holes that penetrate the entire thickness of the device. Only a deep hole with a depth of several microns is needed, so the deep hole etching process is simple, the process steps are simple, and the process difficulty is low.

[0031] (2) Small deep hole area: By using a deep hole and the first connection area 30 filled in the deep hole, the area occupied by the deep hole is small, and the device area utilization rate is high. Since the depth of the deep hole is only a few microns, the diameter of the deep hole only needs to be 0.5-5μm.

[0032] (3) Low material cost: Since the GaN HEMT device of the present application does not need to adopt the TSV process, it does not need to use gold as the metal material and TSV filling material, which greatly reduces the material cost. In addition, since the GaN HEMT device of the present application adopts a low-resistance substrate on a large scale, the cost is lower than that of a high-resistance substrate.

[0033] The GaN HEMT device in the prior art uses a back-side opening for grounding, which needs to penetrate the entire thickness of the device. The GaN HEMT device in the prior art cannot use a front-side opening for grounding. The reasons are as follows: In the prior art, the GaN HEMT device has a very deep etched hole, so it can only be etched using a hard mask. Then, it is difficult to remove the hard mask on the front side, which will affect the device characteristics on the front side. Therefore, it is usually done on the back side. In this application, the substrate 11 is used for contact, so the hole does not need to be made very deep, so it can be etched without a hard mask.

[0034] Specifically, the epitaxial layer is an epitaxial layer of a P-type SiC material.

[0035] The present application adopts a low-resistance substrate 11 and a P-type SiC epitaxial layer to replace the high-resistance substrate in the prior art. The reason for the SiC epitaxial layer is that SiC has a high lattice matching degree with GaN, the growth of GaN has few defects, and SiC has a high thermal conductivity, which can better dissipate heat.

[0036] In this way, the combination of the low-resistance substrate 11 and the epitaxial layer of the P-type SiC material can also meet the requirements of improving the electrical performance, reliability and stability of the device.

[0037] If only a low-resistance substrate is used, leakage will occur, but the P-type epitaxial layer can prevent electron leakage.

[0038] In implementation, such as Figure 3-B As shown, the GaN HEMT device of the present application also includes: A second connection area 20 formed at the bottom end of the first connection area 30; The second connection region 20 and the substrate 11 have the same doping type, and the doping concentration of the second connection region 20 is greater than the doping concentration of the substrate 11 .

[0039] The doping concentration of the substrate 11 is low, the second connection area 20 and the substrate 11 have the same doping type, and the doping concentration of the second connection area 20 is greater than the doping concentration of the substrate 11. In this way, the contact between the second connection area 20 and the first connection area 30 can more easily achieve ohmic contact. Thus, good connection is achieved among the back grounding metal 10, the substrate 11, the second connection area 20 and the first connection area 30, and good grounding is achieved.

[0040] As an optional method, the substrate 11 and the second connection region 20 are both P-type doped; As another optional manner, both the substrate 11 and the second connection region 20 are N-type doped. Currently, N-type substrates and their corresponding GaN HEMT devices are more mature.

[0041] In implementation, such as Figure 3-A and Figure 3-B As shown, the depth of the first connection region 30 entering the substrate 11 is in a range of greater than or equal to 0.1 μm.

[0042] In this way, the depth requirement of the deep hole etching process is relatively loose, and at the same time, it can also ensure that the first connection area 30 and the substrate 11 can be fully connected.

[0043] In implementation, the second connection region 20 completely wraps the portion of the first connection region 30 that enters into the substrate; Alternatively, the second connection region at least wraps around the bottom of the portion of the first connection region 30 that enters the substrate.

[0044] The larger the area of ​​the second connection region 20 that completely wraps around the first connection region 30 and enters into the substrate, the larger the contact area between the two.

[0045] In the implementation, the second connection region 20 is a second connection region 20 of SIC material, and the doping concentration of the second connection region 20 is in the range of 1×10 18 cm -3 Less than or equal to 1×10 22 cm -3 ; The doping concentration of the second connection region 20 is at least 2 orders of magnitude higher than the doping concentration of the substrate.

[0046] As a first optional manner, the second connection region 20 is an N-type second connection region 20 made of Si material, and the substrate 11 is a substrate made of Si material.

[0047] As a second optional manner, the second connection region 20 is an N-type second connection region 20 made of a SIC material, and the substrate 11 is a substrate made of a SIC material.

[0048] The substrate of the SIC material has a high degree of matching with the GaN in the GaN HEMT device. Therefore, the second optional method is better. The second connection area 20 of the SIC material can be selected from either single crystal or polycrystalline. However, the growth conditions of the polycrystalline SIC material are lower and the conductivity is higher, so it is better.

[0049] The higher the doping concentration of the second connection region 20, the better. In actual preparation, the doping concentration of the second connection region 20 is limited by the ion implantation process.

[0050] In practice, the resistivity of the first metal connection area 30 is generally less than 100 uohm. cm.

[0051] In implementation, the metal material of the first connection region 30 is copper, tin, aluminum, tungsten, titanium or nickel.

[0052] In practice, the deep hole is formed by a semi-through hole etching process.

[0053] In implementation, such as Figure 3-A and Figure 3-B As shown, it also includes: The source metal 31 is connected to the source of the active region.

[0054] The top of the first connection region 30 is connected to the source metal 31 .

[0055] like Figure 3-A , Figure 3-BAs shown, the GaN HEMT structure layer includes: An AlN layer 22 formed on the epitaxial layer 12; A GaN buffer layer 23 formed on the AlN layer 22; A GaN layer 24 formed on the GaN buffer layer 23; An AlGaN layer 25 is formed on the GaN layer 24, and a two-dimensional electron gas is between the GaN layer 24 and the AlGaN layer 25; A SiN layer 27 formed on the AlGaN layer 25; The area where the two-dimensional electron gas is destroyed serves as the high resistance area of ​​the GaN HEMT structure layer, and the area where the two-dimensional electron gas is not destroyed serves as the active area of ​​the GaN HEMT structure layer; like Figure 3-A , Figure 3-B As shown, the GaN HEMT device also includes: A gate metal 26 is formed on the SiN layer 27 and connected to the AlGaN layer 25 through a contact hole through the SiN layer 27; the gate metal 26 is used to control the opening and closing of the two-dimensional electron gas; The source electrode 28-1 and the drain electrode 28-2 respectively penetrate the SiN layer 27 and the AlGaN layer 25 and enter the GaN layer 24, and are respectively connected to the two ends of the GaN layer 24; wherein the source electrode 28-1 and the drain electrode 28-2 are respectively formed in the high resistance region and are respectively located at the two sides of the active region; The source metal 31 is connected to the source 28 - 1 .

[0056] The performance comparison between the conventional GaN HEMT device and the GaN HEMT device of the present application is shown in the following table:

[0057] It can be seen from the table that, under similar performance conditions, the breakdown voltage BV of the GaN HEMT device of the present application is higher.

[0058] This application Figure 3-A The preparation process of the GaN HEMT device includes the following steps: Step S1: Figure 4 As shown, a back grounding metal 10 is formed on the back side of a P-type low-resistance substrate 11, and an epitaxial layer 12 of a P-type SIC material is formed from the upper surface of the substrate 11; Step S2: Figure 5 As shown, an AlN layer 22, a GaN buffer layer 23, a GaN layer 24, an AlGaN layer 25, and a SiN layer 27 are sequentially formed on the epitaxial layer 12 from bottom to top by ion implantation; Step S3: Figure 6 As shown, the high resistance region is formed downward by ion implantation from the upper surface of the SiN layer 27, and the region not implanted with ions is used as the active region; Step S4: Figure 7 As shown, a deep hole is formed by etching from the upper surface of the high resistance region downward, and the bottom of the deep hole enters into the substrate 11; a part of the deep hole is subjected to high temperature annealing, which can enhance the ohmic contact and reduce the resistance; Step S5: Figure 8 As shown, metal or P-type polysilicon is filled in the deep hole to form a first connection region 30; Step S6: Fig. 9 As shown, source 28 - 1 , drain 28 - 2 , source metal 31 and drain metal are formed.

[0059] This application Figure 3-B The preparation process of GaN HEMT devices is Figure 3-A The preparation process of GaN HEMT devices also includes the following steps: Step S4-1: Fig.10 As shown, a P-type second connection region 20 is formed on the inner bottom and sidewall of the deep hole by ion implantation.

[0060] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0061] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0062] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0063] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0064] Although the preferred embodiments of the present application have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the present application.

[0065] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A GaN HEMT device, characterized in that: include: A low-resistance substrate (11); A grounded back side grounding metal (10) formed on the back side of the substrate (11); A P-type epitaxial layer (12) formed on the substrate (11); ‌GaN HEMT structural layer, the GaN HEMT structural layer comprising an active region and a high resistance region; A deep hole is formed downward from the upper surface of the high resistance region, and the bottom end of the deep hole enters into the substrate (11); A first connection area (30) of metal is filled and formed in the deep hole, the bottom end of the first connection area (30) enters into the substrate (11), and the contact between the first connection area (30) and the substrate (11) is an ohmic contact.

2. The GaN HEMT device according to claim 1, characterized in that: Also includes: a second connection area (20) formed at the bottom end of the first connection area (30); The second connection region (20) and the substrate (11) have the same doping type, and the doping concentration of the second connection region (20) is greater than the doping concentration of the substrate (11).

3. The GaN HEMT device according to claim 2, characterized in that: The substrate (11) and the second connection region (20) are both P-type doped; Alternatively, the substrate (11) and the second connection region (20) are both N-type doped.

4. The GaN HEMT device according to claim 1 or 2, characterized in that: The depth of the first connection area (30) entering the substrate (11) is in a range of greater than or equal to 0.1 μm.

5. The GaN HEMT device according to claim 2, characterized in that: The second connection area (20) completely wraps around the portion of the first connection area (30) that enters into the substrate; Alternatively, the second connection area at least wraps around the bottom of the portion of the first connection area (30) that enters the substrate.

6. The GaN HEMT device according to any one of claims 1 to 3, characterized in that: Also includes: A source metal (31) connected to the source of the active region; Wherein, the top of the first connection area (30) is connected to the source metal (31).

7. The GaN HEMT device according to claim 2, characterized in that: The second connection region (20) is a second connection region (20) of SIC material; the doping concentration of the second connection region (20) is in a range of greater than or equal to 1×10 18 cm -3 Less than or equal to 1×10 22 cm -3 ; The doping concentration of the second connection region (20) is at least 2 orders of magnitude higher than the doping concentration of the substrate.

8. The GaN HEMT device according to any one of claims 1 to 3, characterized in that: The resistivity of the first metal connection area (30) is generally less than 100 uohm cm.

9. The GaN HEMT device according to any one of claims 1 to 3, characterized in that: The metal material of the first connection area (30) is copper, tin, aluminum, tungsten, titanium or nickel.

10. The GaN HEMT device according to any one of claims 1 to 3, characterized in that: The deep hole is formed by adopting a semi-through hole etching process.

Images