A T-groove anode GaN MIS temperature sensor and its fabrication method

Abstract

This invention discloses a T-groove anode GaN MIS temperature sensor and its fabrication method. The sensor includes: a substrate layer; a nucleation layer, a buffer layer, a channel layer, and a barrier layer sequentially disposed on the substrate layer; a circular P-type GaN layer located in the middle region of the barrier layer; an anode groove located within the annular ring of the circular P-type GaN layer and penetrating the barrier layer to the channel layer; a circular cathode groove surrounding the circular P-type GaN layer and spaced at a certain distance from it, penetrating the barrier layer to the channel layer; a first insulating layer located on the barrier layer, the circular P-type GaN layer, and the bottom and sidewalls of the anode groove; a T-groove anode for MIS contact located within the anode groove and on the first insulating layer above the circular P-type GaN layer; and a circular cathode located within the circular cathode groove and on the first insulating layer surrounding the circular cathode groove. This invention has high temperature sensitivity and reliability.

Description

Technical Field

[0001] This invention belongs to the field of temperature sensors, specifically relating to a T-groove anode GaN MIS temperature sensor and its fabrication method. Background Technology

[0002] In recent years, GaN HEMT devices have become core components in high-frequency power conversion applications, finding widespread use in electric vehicles and new energy fields. However, these new applications place higher reliability demands on GaN-based HEMT devices. With the widespread application of GaN HEMT devices in high-power and high-frequency applications, the need for monitoring and controlling their operating environment is also increasing. Temperature is one of the key factors affecting the performance and reliability of GaN HEMT power devices. Therefore, integrated GaN temperature sensors have emerged.

[0003] By using a GaN temperature sensor on the same gallium nitride (GaN) HEMT chip, system complexity and cost can be reduced, while system response speed and measurement accuracy can be improved. This allows for effective monitoring and control of the GaN HEMT device's operating status, preventing failure due to excessively high temperatures. However, because the reverse current varies drastically with temperature, this can cause problems in any sensing circuitry that may be in use. Excessive leakage current in the temperature sensor diode can reduce circuit reliability, and leakage paths into high-impedance circuits can lead to erroneous readings. Therefore, this must be considered in the device or circuit design.

[0004] However, due to the late start of the development of all-gallium nitride integrated circuits, there is little research on integrated temperature sensors, and there is still much room for improvement in temperature measurement performance. Furthermore, existing temperature sensing devices lack hardening measures to cope with high temperature and high electrical stress conditions, and the reliability problem of GaN HEMT devices has not been well solved. Summary of the Invention

[0005] To address the aforementioned problems in the prior art, this invention provides a T-groove anode GaN MIS temperature sensor and its fabrication method. The technical problem to be solved by this invention is achieved through the following technical solution:

[0006] In a first aspect, embodiments of the present invention provide a T-groove anode GaN MIS temperature sensor, the GaN MIS temperature sensor comprising:

[0007] Substrate layer; AlN nucleation layer, AlGaN buffer layer, GaN channel layer and AlGaN barrier layer are sequentially disposed on the substrate layer;

[0008] A ring-shaped P-type GaN layer is located in the middle region of the AlGaN barrier layer;

[0009] An anode groove is located inside the annular P-type GaN layer and extends through the AlGaN barrier layer to the GaN channel layer; wherein the depth of the anode groove is equal to the thickness of the annular P-type GaN layer, the AlGaN barrier layer, and part of the GaN channel layer.

[0010] An annular cathode groove surrounds the annular P-type GaN layer and is spaced a certain distance from the annular P-type GaN layer, and penetrates the AlGaN barrier layer to the GaN channel layer;

[0011] The first insulating layer is located on the AlGaN barrier layer, the annular P-type GaN layer, and the bottom and sidewalls of the anode groove; wherein the first insulating layer is an insulating layer with a thickness of less than 10 nm.

[0012] The T-shaped groove anode of the MIS contact is located on the first insulating layer inside the anode groove and on the first insulating layer above the annular P-type GaN layer;

[0013] An annular cathode is located within the annular cathode groove and on the first insulating layer surrounding the annular cathode groove.

[0014] Specifically, the first insulating layer is introduced below the T-shaped groove anode of the MIS contact. The first insulating layer passivates the interface state defects of the anode groove and reduces the interface state-related forward leakage current. At the same time, the anode groove reduces the forward leakage current of the longitudinal dislocations of the epitaxial structure. This allows the forward conduction of the GaN MIS temperature sensor to have both thermionic emission and direct tunneling mechanisms. Since the on-state voltage drop of the thermionic emission and direct tunneling models changes linearly with temperature under the temperature measurement current, and the linearity is close to the ideal value, the GaN MIS temperature sensor reduces the reverse leakage current under forward conduction. The temperature sensitivity increases with the decrease of reverse leakage current, and the reliability increases with the decrease of reverse leakage current.

[0015] In one embodiment of the present invention, the thickness of the first insulating layer is 1 nm to 4 nm.

[0016] In one embodiment of the present invention, the material of the first insulating layer is AlN or Al2O3.

[0017] In one embodiment of the present invention, the GaN MIS temperature sensor further includes:

[0018] The isolation platform is located at both ends of the device and extends through the AlGaN barrier layer to the lower surface of the GaN channel layer;

[0019] The second insulating layer is located on the isolation platform, the annular cathode, the T-shaped groove anode of the MIS contact, and the first insulating layer;

[0020] The first insulating layer is also located on the isolation platform.

[0021] In one embodiment of the present invention, the thickness of the second insulating layer is 200 nm to 250 nm.

[0022] In one embodiment of the present invention, the material of the second insulating layer is SiN or SiO2.

[0023] Secondly, embodiments of the present invention provide a method for fabricating a T-groove anode GaN MIS temperature sensor, the method comprising:

[0024] An epitaxial wafer is prepared; the epitaxial wafer comprises, from bottom to top, a substrate layer, an AlN nucleation layer, an AlGaN buffer layer, a GaN channel layer, an AlGaN barrier layer, and a P-type GaN layer;

[0025] Etch the P-type GaN layers at both ends of the device down to the lower surface of the GaN channel layer to form an isolation mesa.

[0026] A ring-shaped region is defined on the surface of the P-type GaN layer, and the region outside the ring-shaped region is etched downwards, with the etching depth extending to the upper surface of the AlGaN barrier layer, to form a ring-shaped P-type GaN layer.

[0027] The region inside the annular P-type GaN layer is defined as the anode region. The anode region is etched downwards, with the etching depth extending into the GaN channel layer to form an anode groove.

[0028] A first insulating layer is deposited on the isolation platform, the AlGaN barrier layer, the annular P-type GaN layer, and inside and on the sidewalls of the anode groove; wherein the first insulating layer is an insulating layer with a thickness of less than 10 nm;

[0029] A cathode region is defined around the annular P-type GaN layer on the surface of the first insulating layer. The cathode region is etched downwards to the depth of the etching, which extends into the GaN channel layer, forming an annular cathode groove. The cathode region is spaced a certain distance from the annular P-type GaN layer.

[0030] An annular cathode with ohmic contact is formed by depositing ohmic metal on the first insulating layer inside and around the annular cathode groove and annealing it.

[0031] MIS metal is deposited on the first insulating layer inside the anode groove and on the first insulating layer above the annular P-type GaN layer to form a T-shaped groove anode with MIS contact.

[0032] In one embodiment of the present invention, a first insulating layer is deposited on the isolation mesa, the AlGaN barrier layer, the annular P-type GaN layer, and within and on the sidewalls of the anode groove, comprising:

[0033] Using ALD technology, a first insulating layer with a thickness of 1 nm to 4 nm is deposited on the isolation platform, the AlGaN barrier layer, the annular P-type GaN layer, and inside and on the sidewalls of the anode groove.

[0034] In one embodiment of the present invention, the preparation method further includes:

[0035] A second insulating layer is deposited on the annular cathode, the T-groove anode of the MIS contact, and the first insulating layer, and photolithography is performed on the anode region and the cathode region to bring out the T-groove anode of the MIS contact and the annular cathode.

[0036] In one embodiment of the present invention, a second insulating layer is deposited on the annular cathode, the T-groove anode of the MIS contact, and the first insulating layer, comprising:

[0037] Using PECVD technology, a second insulating layer with a thickness of 200 nm to 250 nm is deposited on the annular cathode, the T-groove anode of the MIS contact, and the first insulating layer.

[0038] The beneficial effects of this invention are:

[0039] The T-groove anode GaN MIS temperature sensor proposed in this invention innovatively introduces a first insulating layer beneath the T-groove anode of the MIS contact. This first insulating layer passivates interface state defects in the anode groove, reducing interface state-related forward leakage current. Simultaneously, the anode groove reduces forward leakage current from longitudinal dislocations in the epitaxial structure. This allows the GaN MIS temperature sensor to exhibit both thermionic emission and direct tunneling mechanisms for forward conduction. Since both thermionic emission and direct tunneling models show linear changes in conduction voltage drop with temperature under the temperature-sensing current, with linearity approaching the ideal value, the GaN MIS temperature sensor reduces reverse leakage current under forward conduction conditions. Temperature sensitivity increases with decreasing reverse leakage current, and reliability also improves with decreasing reverse leakage current, thereby enhancing the GaN... The MIS temperature sensor operates more stably under high temperature and high electrical stress environments. The annular P-type GaN layer in the structure proposed in this invention depletes the two-dimensional electron gas and can act as an equivalent resistor, further reducing reverse leakage current and improving temperature sensitivity and reliability. At the same time, the MIS barrier diode with a lateral structure of 2DEG channel proposed in this invention can be fabricated on the same epitaxial wafer as HEMT devices based on the same structure. The temperature sensor has a simple structure and is consistent with the structure of HEMT devices. During integration, the temperature sensor can be well integrated with HEMT devices without additional processes, making high-density integration feasible for this T-groove anode GaN MIS temperature sensor.

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the structure of an existing GaN Schottky temperature sensor;

[0042] Figure 2 This is a schematic diagram of the experimental results of the forward conduction IV curve of the existing structure;

[0043] Figure 3 This is a schematic diagram of the structure of a T-groove anode GaN MIS temperature sensor provided in an embodiment of the present invention;

[0044] Figure 4 This is a schematic diagram of the experimental results of the forward conduction IV curve of the structure proposed in this invention;

[0045] Figure 5 This is a schematic flowchart of a method for fabricating a T-groove anode GaN MIS temperature sensor according to an embodiment of the present invention;

[0046] Figures 6(a) to 6(i) This is a schematic diagram of the fabrication process of the T-groove anode GaN MIS temperature sensor provided in this embodiment of the invention.

[0047] Explanation of reference numerals in the attached figures:

[0048] 1-Substrate layer; 2-AlN nucleation layer; 3-AlGaN buffer layer; 4-GaN channel layer; 5-AlGaN barrier layer; 6-P-type GaN layer; 7-First insulating layer; 8-Annular cathode; 9-T-groove anode with MIS contact; 10-Second insulating layer. Detailed Implementation

[0049] The present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto.

[0050] Figure 1 This paper illustrates a conventional GaN Schottky temperature sensor. While it improves the measurement accuracy of GaN heterojunction temperature and possesses advantages such as high linearity, low on-state voltage, and low reverse leakage current, the inventors discovered during experiments that the forward conduction IV curve of this conventional structure has a turning point, as shown in the diagram. Figure 2 The area circled in blue (indicated by the dotted line) shows a plateau in the experimental results, which severely affects the range of the temperature measurement current. Without this plateau, a lower reverse leakage current could be used to achieve greater temperature sensitivity. However, the inherent high reverse leakage current of Schottky diodes persists, as shown by the area circled in red (indicated by the dotted line) in diagram 2. The final test results are as follows: Figure 1 The structure shown has a temperature sensitivity of 5.32 mV / K and a linearity of 0.98293. Among these, Figure 2 In this context, Ra represents the radius of the annular cathode, Lac represents the distance between the cathode and anode, 25–200 represents the temperature, and J represents the magnitude of the measuring current. Figure 2 The horizontal axis represents the magnitude of the reverse leakage current (Current), measured in amperes (A), and the horizontal axis represents the forward conduction voltage (V), measured in volts (V).

[0051] Based on the above research, the inventors have innovatively proposed a T-groove anode GaN MIS temperature sensor and its fabrication method, specifically:

[0052] Firstly, please see Figure 3 This invention provides a T-groove anode GaN MIS temperature sensor, the GaN MIS temperature sensor comprising:

[0053] Substrate 1; AlN nucleation layer 2, AlGaN buffer layer 3, GaN channel layer 4 and AlGaN barrier layer 5 are sequentially disposed on substrate 1;

[0054] The annular P-type GaN layer 6 is located in the middle region of the AlGaN barrier layer 5;

[0055] The anode groove is located inside the annular P-type GaN layer 6 and extends through the AlGaN barrier layer 5 to the GaN channel layer 4; wherein, the depth of the anode groove is equal to the thickness of the annular P-type GaN layer 6, the AlGaN barrier layer 5 and part of the GaN channel layer 4.

[0056] An annular cathode groove surrounds the annular P-type GaN layer 6 and is spaced a certain distance from the annular P-type GaN layer 6, and penetrates the AlGaN barrier layer 5 into the GaN channel layer 4.

[0057] The first insulating layer 7 is located on the AlGaN barrier layer 5, the annular P-type GaN layer 6, and the bottom and sidewalls of the anode groove; wherein, the first insulating layer 7 is an insulating layer with a thickness of less than 10 nm.

[0058] The T-shaped groove anode 9 of the MIS contact is located on the first insulating layer 7 inside the anode groove and on the first insulating layer 7 above the annular P-type GaN layer 6.

[0059] The annular cathode 8 is located within the groove of the annular cathode 8 and on the first insulating layer 7 surrounding the groove of the annular cathode 8.

[0060] In this embodiment of the invention, the GaN MIS temperature sensor further includes:

[0061] The isolation mesa is located at both ends of the device and extends through the AlGaN barrier layer 5 to the lower surface of the GaN channel layer 4.

[0062] The second insulating layer 10 is located on the isolation platform, the annular cathode 8, the T-shaped groove anode 9 of the MIS contact and the first insulating layer 7;

[0063] The first insulating layer 7 is still located on the isolation platform.

[0064] In this embodiment of the invention, the substrate layer 1 can be a silicon material with a P-type (1,1,1) crystal orientation.

[0065] In this embodiment of the invention, the AlN nucleation layer 2 includes a low-temperature AlN nucleation layer 2 and a high-temperature AlN nucleation layer 2. The thickness of the low-temperature AlN nucleation layer 2 can be 30 nm, and the thickness of the high-temperature AlN nucleation layer 2 can be 170 nm. The thickness of the AlGaN buffer layer 3 can be 5 μm. The thickness of the GaN channel layer 4 can be 200 nm. The thickness of the AlGaN barrier layer 5 can be 15 nm. The thickness of the annular P-type GaN layer 6 is 70 nm, and the width of the annular ring is 10 μm.

[0066] In this embodiment of the invention, the thickness of the first insulating layer 7 is 1 nm to 4 nm; the material of the first insulating layer 7 is AlN or Al2O3.

[0067] In this embodiment of the invention, the thickness of the second insulating layer 10 is 200nm to 250nm; the material of the second insulating layer 10 is SiN or SiO2.

[0068] In this embodiment of the invention, the T-shaped groove anode 9 of the MIS contact is an anode MIS contact metal, which may include Ti, Al, and Au. The anode MIS contact metal in the anode groove has a radius of 35 μm.

[0069] In this embodiment of the invention, the annular cathode 8 is a cathode ohmic metal, which may include Ti, Al, Ni, and Au. The spacing between the annular cathode 8 and the annular P-type GaN layer 6 is 25 μm to 35 μm; the annular width of the annular cathode 8 is 10 μm.

[0070] In this embodiment of the invention, the first insulating layer 7 is the insulating layer in the metal-insulator-semiconductor (MIS) structure. This insulating layer differs from the insulating layer in the MOS structure. In the MOS structure, the insulating layer provides electrical isolation, prevents leakage current, and improves reliability; the gate voltage can be used to control the channel's turn-on and turn-off. Typically, diodes do not incorporate an MIS structure because the insulating layer in a normal MIS structure needs to be tens to hundreds of nanometers thick for isolation, while diodes require forward conduction, and generally, an insulating layer is not added to the anode recess. In this embodiment of the invention, leakage current from the side of the anode recess is the primary leakage path. An extremely thin insulating layer, with a thickness requirement of less than 10 nm, is introduced into the T-shaped recess anode of the MIS contact. Its function is completely different from the existing insulating layer in the anode region. In this invention's structure, the first insulating layer 7 can be considered a Schottky contact in terms of the metal-semiconductor contact type, effectively increasing the height of the Schottky barrier, increasing the on-resistance, and passivating the numerous interface state defects generated during the etching of the anode recess. This reduces reverse leakage current while ensuring forward conduction, improving the reliability of the MIS structure diode under high temperature and high electrical stress.

[0071] The forward conduction mechanism of this invention mainly includes thermionic emission across the Schottky barrier and direct tunneling through the Schottky barrier. The groove and passivation reduce conduction mechanisms related to dislocations and interface state defects. Since the thermionic emission and direct tunneling models show linear changes in forward voltage drop with temperature under the temperature-sensing current, the linearity of temperature measurement is not degraded compared to typical Schottky diodes; the linearity is close to the ideal value, which is 1.0. While this structure might affect the forward characteristics of diodes outside the temperature sensor field, resulting in very low reverse leakage current, it not only improves the forward temperature sensitivity of temperature sensors but also significantly reduces the reverse leakage current, improving reliability. In summary, the structure proposed in this invention utilizes the MIS structure, which is not commonly used in diodes. Because such a structure results in very low reverse leakage current, it sacrifices forward characteristics. Therefore, MIS diodes are a compromise in specific situations. However, in the field of temperature sensors, sensitivity increases as the forward current decreases. Therefore, the MIS structure is no longer a compromise but a bidirectional optimization, offering significant advantages.

[0072] To verify the effectiveness of the T-groove anode GaN MIS temperature sensor provided in this embodiment of the invention, a method was adopted... Figure 1 Experiments were conducted with the same structural parameters, and the results are as follows: Figure 4 As shown, from Figure 4 It can be seen that the forward conduction IV curve of the structure proposed in this invention does not have the following characteristics: Figure 2 The platform issue circled in blue dotted circle has more than... Figure 1 Existing structures exhibit significantly lower reverse leakage current, by at least three orders of magnitude. In summary, the structure proposed in this invention effectively solves the problem... Figure 1 The existing structure shown has problems. Final testing revealed the following: Figure 3 The temperature sensitivity of the structure proposed in this invention is 3.33 mV / K, and the linearity is 0.99724. The lower the temperature sensitivity value, the better, and the closer the linearity value is to 1, the better. This invention has greatly improved both of these indicators.

[0073] In summary, the T-groove anode GaN MIS temperature sensor proposed in this invention innovatively introduces a first insulating layer 7 below the T-groove anode 9 of the MIS contact. The first insulating layer 7 passivates interface state defects in the anode groove, reducing interface state-related forward leakage current. Simultaneously, the anode groove reduces forward leakage current from longitudinal dislocations in the epitaxial structure. This allows the GaN MIS temperature sensor to achieve forward conduction via both thermionic emission and direct tunneling mechanisms. Since both thermionic emission and direct tunneling models exhibit linear changes in conduction voltage drop with temperature under the temperature-sensing current, with linearity approaching the ideal value, the GaN MIS temperature sensor reduces reverse leakage current under forward conduction conditions. Temperature sensitivity increases with decreasing reverse leakage current, and reliability also improves with decreasing reverse leakage current, thereby enhancing the GaN... The MIS temperature sensor operates more stably under high temperature and high electrical stress environments. The annular P-type GaN layer 6 in the structure proposed in this invention depletes the two-dimensional electron gas and can act as an equivalent resistor, further reducing reverse leakage current and improving temperature sensitivity and reliability. At the same time, the MIS barrier diode with a lateral structure of 2DEG channel proposed in this invention can be fabricated on the same epitaxial wafer as HEMT devices based on the same structure. The temperature sensor has a simple structure and is consistent with the structure of HEMT devices. During integration, the temperature sensor can be well integrated with HEMT devices without additional processes, making high-density integration feasible for this T-groove anode GaN MIS temperature sensor.

[0074] Secondly, please see Figure 5 This invention provides a method for fabricating a T-groove anode GaN MIS temperature sensor, the method comprising:

[0075] S10. Prepare an epitaxial wafer; the epitaxial wafer includes, from bottom to top, a substrate layer 1, an AlN nucleation layer 2, an AlGaN buffer layer 3, a GaN channel layer 4, an AlGaN barrier layer 5, and a P-type GaN layer.

[0076] In this embodiment of the invention, a low-temperature AlN nucleation layer 2 is first epitaxially grown on the upper surface of a Si material substrate 1 using MOCVD (Metal-organic Chemical Vapor Deposition) technology. Subsequently, a high-temperature AlN nucleation layer 2 is epitaxially grown on the upper surface of the low-temperature AlN nucleation layer 2. The low-temperature AlN nucleation layer 2 and the high-temperature AlN nucleation layer 2 together constitute the AlN nucleation layer 2. The thickness of the low-temperature AlN nucleation layer 2 can be 30 nm, and the thickness of the high-temperature AlN nucleation layer 2 can be 170 nm.

[0077] After the AlN nucleation layer 2 is prepared, an AlGaN buffer layer 3 with a thickness of 5 μm is deposited on the AlN nucleation layer 2 using MOCVD. For example, using trimethylaluminum as the aluminum source, trimethylgallium as the gallium source, and ammonia as the ammonia source, undoped Al is deposited on the surface of the nucleation layer using MOCVD technology. 0.3 Ga 0.7 N buffer layer, the thickness of which can be 5μm.

[0078] After the AlGaN buffer layer 3 is prepared, a GaN channel layer 4 with a thickness of 200 nm is deposited on the AlGaN buffer layer 3 using MOCVD. For example, using trimethylgallium as the gallium source and ammonia as the ammonia source, an undoped GaN channel layer 4 is deposited on the upper surface of the buffer layer using MOCVD technology. The thickness of the GaN channel layer 4 can be 200 nm.

[0079] After the GaN channel layer 4 is fabricated, an AlGaN barrier layer 5 with a thickness of 15 nm is deposited on the GaN channel layer 4 using MOCVD. For example, using trimethylgallium as the gallium source, trimethylaluminum as the aluminum source, and ammonia as the ammonia source, undoped Al is deposited on the surface of the GaN channel layer 4 using MOCVD technology. 0.2 Ga 0.8 The thickness of the N-type barrier layer and the AlGaN barrier layer 5 is 15 nm.

[0080] After the AlGaN barrier layer 5 is prepared, a 70 nm thick P-type GaN layer is epitaxially grown on the AlGaN barrier layer 5 using MOCVD technology. For example, a 70 nm thick Mg+ ion doping concentration of 10 is epitaxially grown on the AlGaN barrier layer 5 using MOCVD technology. 19 cm -3 A GaN layer was formed, and then a P-type GaN layer was formed through high-temperature annealing. Finally, the structure shown in Figure 6(a) was formed.

[0081] S20. Etch the P-type GaN layers at both ends of the device until the lower surface of the GaN channel layer 4 to form an isolation mesa.

[0082] In this embodiment of the invention, the P-type GaN layer at both ends of the device in Figure 6(a) is etched using an ICP (Inductively Coupled Plasma) etching process, up to the lower surface of the GaN channel layer 4, to form an isolation mesa as shown in Figure 6(b).

[0083] S30. Define a ring-shaped region on the surface of the P-type GaN layer, and etch downwards into the region outside the ring-shaped region, extending the etching depth to the upper surface of the AlGaN barrier layer 5 to form a ring-shaped P-type GaN layer 6.

[0084] In this embodiment of the invention, Si3N4 is deposited on the surface of the prepared device shown in 6(b) to passivate and form a Si3N4 passivation layer. The Si3N4 layer deposited on the surface of the P-type GaN layer is removed by a hydrogen ion wet process to introduce hydrogen ions into the P-type GaN layer. A photoresist is spin-coated on the Si3N4 passivation layer to define a first annular region and exposed and developed. The Si3N4 passivation layer is removed by a BHF (Buffered Hydrofluoric Acid) solution wet process. The P-type GaN layer outside the annular region is etched downwards to the upper surface of the AlGaN barrier layer 5 to form an annular P-type GaN layer 6 as shown in Figure 6(c). The annular width of the annular P-type GaN layer 6 is 10 μm. The BHF solution is prepared by mixing 6 volumes of ammonium fluoride (NH4F, 40% solution) and 1 volume of hydrofluoric acid (HF). Before use, it is diluted in water at a ratio of 7:1 to better control the etching rate. By removing the Si3N4 passivation layer by wet method, the defect states in the P-type GaN layer can be passivated.

[0085] S40. Define the area inside the annular P-type GaN layer 6 as the anode region. Etch the anode region downwards, extending the etching depth into the GaN channel layer 4 to form an anode groove.

[0086] In this embodiment of the invention, the region inside the annular P-type GaN layer 6 is defined as the anode region. That is, the diameter of the annular P-type GaN layer 6 is used as the width of the anode groove. Using the ICP etching process, the anode region is etched downwards, and the etching depth extends into the GaN channel layer 4 to form the anode groove as shown in Figure 6(d). The radius of the anode groove is 35μm.

[0087] S50. A first insulating layer 7 is deposited on the isolation platform, the AlGaN barrier layer 5, the annular P-type GaN layer 6, and inside and on the sidewalls of the anode groove; wherein the first insulating layer 7 is an insulating layer with a thickness of less than 10 nm.

[0088] In this embodiment of the invention, an ALD (Atomic Layer Deposition) technique is used to deposit a first insulating layer 7 on the isolation mesa, AlGaN barrier layer 5, annular P-type GaN layer 6, and inside and on the sidewalls of the anode groove, as shown in Figure 6(e). For example, using trimethylaluminum as the aluminum source and ozone as the oxygen source, an AlN or Al2O3 first insulating layer 7 with a thickness of 1 nm to 4 nm is deposited on the isolation mesa, AlGaN barrier layer 5, annular P-type GaN layer 6, and inside and on the sidewalls of the anode groove using ALD technique.

[0089] S60. A cathode region is defined around the annular P-type GaN layer 6 on the surface of the first insulating layer 7. The cathode region is etched downwards, and the etching depth extends into the GaN channel layer 4 to form an annular cathode 8 groove. The cathode region is spaced a certain distance from the annular P-type GaN layer 6.

[0090] In this embodiment of the invention, photoresist is spin-coated onto the first insulating layer 7 to define the cathode region, which is then exposed and developed. ICP etching is used to etch the cathode region downwards, extending the etching depth into the GaN channel layer 4, forming a circular annular cathode 8 groove as shown in Figure 6(f). The cathode region is spaced a certain distance from the circular p-type GaN layer 6, for example, 25 μm to 35 μm; the radius of the cathode region is 10 μm.

[0091] S70. An annular cathode 8 is formed by depositing ohmic metal in the groove of the annular cathode 8 and on the first insulating layer 7 around the groove of the annular cathode 8 and performing high-temperature annealing.

[0092] In this embodiment of the invention, an annular cathode 8 with ohmic contact is prepared by sputtering Ti, Al, Ni and Au metals from bottom to top in the groove of the annular cathode 8 using PVD (Physical Vapor Deposition) technology. The thicknesses of each metal layer are 20 nm, 140 nm, 50 nm and 30 nm, respectively. The metals of the sputtered annular cathode 8 are subjected to rapid thermal annealing in N2 atmosphere at a temperature of 865 °C for 35 s to complete the preparation of the annular cathode 8 with ohmic contact, as shown in Figure 6(g).

[0093] S80. MIS metal is deposited on the first insulating layer 7 inside the anode groove and on the first insulating layer 7 above the annular P-type GaN layer 6 to form a T-shaped groove anode 9 with MIS contact.

[0094] In this embodiment of the invention, Ti, Al and Au metals are sputtered from bottom to top in the anode groove using PVD technology to prepare a T-shaped groove anode with MIS contact. The thicknesses of each metal layer are 20 nm, 250 nm and 30 nm, respectively. The sputtered T-shaped groove anode metal with MIS contact is annealed in N2 atmosphere at 450 °C for 300 s to complete the preparation of the T-shaped groove anode with MIS contact, as shown in Figure 6(h).

[0095] Furthermore, the preparation method of this embodiment of the invention further includes:

[0096] A second insulating layer 10 is deposited on the annular cathode 8, the T-groove anode 9 with MIS contact, and the first insulating layer 7. Photolithography is then used to expose the T-groove anode 9 and the annular cathode 8 with MIS contact. Specifically, using PECVD (Plasma Enhanced Chemical Vapor Deposition) technology, a second insulating layer 10 of SiN or SiO2 with a thickness of 200nm–250nm is deposited on the annular cathode 8, the T-groove anode 9 with MIS contact, and the first insulating layer 7, as shown in Figure 6(i). Photolithography is then used to open contact holes in the cathode and anode regions, and electrodes are exposed to complete the fabrication of the entire T-groove anode GaN MIS temperature sensor.

[0097] As for the method embodiment of the second aspect, since it is basically similar to the structural embodiment of the first aspect, the description is relatively simple, and relevant details can be found in the description of the structural embodiment of the first aspect.

[0098] In the description of this invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0099] Although the invention has been described herein in conjunction with various embodiments, those skilled in the art, by reviewing the specification and accompanying drawings, will understand and implement other variations of the disclosed embodiments in carrying out the claimed invention. In the specification, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude a plurality. While certain measures are described in different embodiments, this does not mean that these measures cannot be combined to produce good results.

[0100] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A T-groove anode GaN MIS temperature sensor, characterized in that, The GaN MIS temperature sensor includes: Substrate layer; AlN nucleation layer, AlGaN buffer layer, GaN channel layer and AlGaN barrier layer are sequentially disposed on the substrate layer; A ring-shaped P-type GaN layer is located in the middle region of the AlGaN barrier layer; An anode groove is located inside the annular P-type GaN layer and extends through the AlGaN barrier layer to the GaN channel layer; wherein the depth of the anode groove is equal to the thickness of the annular P-type GaN layer, the AlGaN barrier layer, and part of the GaN channel layer. An annular cathode groove surrounds the annular P-type GaN layer and is spaced a certain distance from the annular P-type GaN layer, and penetrates the AlGaN barrier layer to the GaN channel layer; The first insulating layer is located on the AlGaN barrier layer, the annular P-type GaN layer, and the bottom and sidewalls of the anode groove; wherein the first insulating layer is an insulating layer with a thickness of less than 10 nm. The T-shaped groove anode of the MIS contact is located on the first insulating layer inside the anode groove and on the first insulating layer above the annular P-type GaN layer; An annular cathode is located within the annular cathode groove and on the first insulating layer surrounding the annular cathode groove. Specifically, the first insulating layer is introduced below the T-shaped groove anode of the MIS contact. The first insulating layer passivates the interface state defects of the anode groove and reduces the interface state-related forward leakage current. At the same time, the anode groove reduces the forward leakage current of the longitudinal dislocations of the epitaxial structure. This allows the forward conduction of the GaN MIS temperature sensor to have both thermionic emission and direct tunneling mechanisms. Since the on-state voltage drop of the thermionic emission and direct tunneling models changes linearly with temperature under the temperature measurement current, and the linearity is close to the ideal value, the GaN MIS temperature sensor reduces the reverse leakage current under forward conduction. The temperature sensitivity increases with the decrease of reverse leakage current, and the reliability increases with the decrease of reverse leakage current.

2. The T-groove anode GaN MIS temperature sensor according to claim 1, characterized in that, The thickness of the first insulating layer is 1 nm to 4 nm.

3. The T-groove anode GaN MIS temperature sensor according to claim 1, characterized in that, The material of the first insulating layer is AlN or Al2O3.

4. The T-groove anode GaN MIS temperature sensor according to claim 1, characterized in that, The GaN MIS temperature sensor also includes: The isolation platform is located at both ends of the device and extends through the AlGaN barrier layer to the lower surface of the GaN channel layer; The second insulating layer is located on the isolation platform, the annular cathode, the T-shaped groove anode of the MIS contact, and the first insulating layer; The first insulating layer is also located on the isolation platform.

5. The T-groove anode GaN MIS temperature sensor according to claim 4, characterized in that, The thickness of the second insulating layer is 200nm to 250nm.

6. The T-groove anode GaN MIS temperature sensor according to claim 4, characterized in that, The material of the second insulating layer is SiN or SiO2.

7. A method for fabricating a T-groove anode GaN MIS temperature sensor, characterized in that, The preparation method includes: An epitaxial wafer is prepared; the epitaxial wafer comprises, from bottom to top, a substrate layer, an AlN nucleation layer, an AlGaN buffer layer, a GaN channel layer, an AlGaN barrier layer, and a P-type GaN layer; Etch the P-type GaN layers at both ends of the device down to the lower surface of the GaN channel layer to form an isolation mesa. A ring-shaped region is defined on the surface of the P-type GaN layer, and the region outside the ring-shaped region is etched downwards, with the etching depth extending to the upper surface of the AlGaN barrier layer, to form a ring-shaped P-type GaN layer. The region inside the annular P-type GaN layer is defined as the anode region. The anode region is etched downwards, with the etching depth extending into the GaN channel layer to form an anode groove. A first insulating layer is deposited on the isolation platform, the AlGaN barrier layer, the annular P-type GaN layer, and inside and on the sidewalls of the anode groove; wherein the first insulating layer is an insulating layer with a thickness of less than 10 nm; A cathode region is defined around the annular P-type GaN layer on the surface of the first insulating layer. The cathode region is etched downwards to the depth of the etching, which extends into the GaN channel layer, forming an annular cathode groove. The cathode region is spaced a certain distance from the annular P-type GaN layer. An annular cathode with ohmic contact is formed by depositing ohmic metal on the first insulating layer inside and around the annular cathode groove and annealing it. MIS metal is deposited on the first insulating layer inside the anode groove and on the first insulating layer above the annular P-type GaN layer to form a T-shaped groove anode with MIS contact.

8. The method for fabricating the T-groove anode GaN MIS temperature sensor according to claim 7, characterized in that, A first insulating layer is deposited on the isolation platform, the AlGaN barrier layer, the annular P-type GaN layer, and within and on the sidewalls of the anode groove, comprising: Using ALD technology, a first insulating layer with a thickness of 1 nm to 4 nm is deposited on the isolation platform, the AlGaN barrier layer, the annular P-type GaN layer, and inside and on the sidewalls of the anode groove.

9. The method for fabricating the T-groove anode GaN MIS temperature sensor according to claim 7, characterized in that, The preparation method further includes: A second insulating layer is deposited on the annular cathode, the T-groove anode of the MIS contact, and the first insulating layer, and photolithography is performed on the anode region and the cathode region to bring out the T-groove anode of the MIS contact and the annular cathode.

10. The method for fabricating the T-groove anode GaN MIS temperature sensor according to claim 9, characterized in that, A second insulating layer is deposited on the annular cathode, the T-groove anode of the MIS contact, and the first insulating layer, comprising: Using PECVD technology, a second insulating layer with a thickness of 200 nm to 250 nm is deposited on the annular cathode, the T-groove anode of the MIS contact, and the first insulating layer.

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