Gallium nitride power device with wide operating gate voltage

Abstract

Disclosed in the present invention is a gallium nitride power device with a wide operating gate voltage. The gallium nitride power device structurally comprises a base, which is sequentially provided with a substrate, a nucleation layer, a buffer layer, a channel layer, a barrier layer and a passivation layer from bottom to top; and an isolation layer, wherein the barrier layer is provided with a voltage limiting-transistor area, a power transistor area and a discharge transistor area, a first drain metal of the voltage-limiting transistor area is connected to a third gate metal of the discharge transistor area by means of a first interconnection metal and is connected to an input gate voltage, and a first source metal of the voltage-limiting transistor area is connected to a second gate metal of the power transistor area and a third drain metal of the discharge transistor area by means of a second interconnection metal. In the present invention, the electric potential of a second gate metal of a power transistor area is clamped by means of the saturation characteristics of a gallium nitride HEMT, thereby increasing the gate voltage swing of the overall device; moreover, a charge discharge path of a second P-type gallium nitride cap layer of the power transistor area is established by means of the switching characteristics of a depletion-mode gallium nitride PFET, thereby enhancing the gate stability of the overall device.

Description

Gallium nitride power device with wide working gate voltage TECHNICAL FIELD

[0001] The present application belongs to the field of power semiconductor devices, and in particular to a gallium nitride power device with wide working gate voltage. BACKGROUND

[0002] Gallium nitride (GaN) is one of the typical representatives of wide bandgap semiconductors, with characteristics such as wide bandgap, high breakdown field, high electron mobility, high thermal conductivity, etc. It has smaller on-resistance and faster response speed, and is widely used in high-frequency and high-temperature power circuits.

[0003] Taking AlGaN / GaN heterojunction as an example, due to the effects of spontaneous polarization and piezoelectric polarization inside the structure, a two-dimensional electron gas (2DEG) with high mobility and high electron saturation velocity can be generated on the surface layer of GaN without doping, which behaves as a depletion mode device in normal conditions. In view of safety and energy issues in device use, the research of enhancement mode devices is more urgent, among which p-GaN technology is widely concerned.

[0004] The traditional gallium nitride device with p-GaN cap layer and Schottky gate structure has the problem of small gate voltage swing range due to the limitations of epitaxial structure and growth process. The gate voltage swing of Si-based MOSFET can reach 20V, while the gate swing of gallium nitride device with p-GaN cap layer and Schottky gate structure does not exceed 8V, greatly increasing the complexity of circuit design and packaging requirements. At the same time, the traditional gallium nitride device with p-GaN cap layer and Schottky gate structure has a pair of back-to-back diodes in equivalent, due to the charge storage effect, the device cannot release the electrons in the p-type gallium nitride cap layer in time under repeated switching conditions, resulting in unstable threshold value of the device. Although the gallium nitride device with p-GaN cap layer and ohmic gate structure has a relatively more stable threshold value, its gate leakage is larger and the gate voltage swing is smaller, which cannot work stably under high gate voltage conditions. The above problems of small gate swing and unstable threshold value will cause a series of reliability problems in the application of the device in the system and seriously affect the practical application development of the gallium nitride device with p-GaN cap layer and Schottky gate structure.

[0005] In addition, in the traditional GaN / AlGaN heterojunction, due to the effects of spontaneous polarization and piezoelectric polarization inside the structure, a two-dimensional hole gas (2DHG) can be generated on the lower surface of GaN without doping, but due to its low mobility, it cannot be used as a main power device in high-power circuits. SUMMARY

[0006] Technical problems: In view of the problems of small gate swing and unstable threshold value of the conventional enhanced gallium nitride power device, the application provides a gallium nitride power device with wide working gate voltage, which can effectively improve the gate voltage swing of the device and enhance the threshold stability of the device.

[0007] Technical scheme: A gallium nitride power device with wide working gate voltage, the device comprises a substrate, the substrate comprises a substrate, a nucleation layer, a buffer layer, a channel layer, a barrier layer and a passivation layer are sequentially arranged on the substrate, an isolation layer, a limiting voltage tube area, a power tube area and a discharge tube area are arranged on the barrier layer;

[0008] The limiting voltage tube area comprises a first source metal connected to the upper surface of the barrier layer, a first P-type gallium nitride cap layer and a first drain metal, and the upper surface of the first P-type gallium nitride cap layer is provided with a first gate metal;

[0009] The power tube area comprises a second source metal connected to the upper surface of the barrier layer, a second P-type gallium nitride cap layer and a second drain metal, and the upper surface of the second P-type gallium nitride cap layer is provided with a second gate metal;

[0010] The discharge tube area comprises a third source metal connected to the upper surface of the barrier layer, a third P-type gallium nitride cap layer and a third drain metal, the upper surface of the third P-type gallium nitride cap layer is provided with a PFET gate dielectric layer, and the upper surface of the PFET gate dielectric layer is provided with a third gate metal.

[0011] Preferably, the discharge tube area has the characteristics of a depletion mode gallium nitride PFET device: when the voltage of the third gate metal is less than the positive threshold voltage, the device is turned on; when the voltage of the third gate metal is greater than the positive threshold voltage, the device is turned off.

[0012] Preferably, the thickness of the third P-type gallium nitride cap layer is 50-300 nm.

[0013] Preferably, the third P-type gallium nitride cap layer is in a groove shape.

[0014] Preferably, the maximum groove depth of the third P-type gallium nitride cap layer is 270 nm.

[0015] Preferably, the thickness of the PFET gate dielectric layer is 1-50 nm.

[0016] Preferably, the PFET gate dielectric layer is one or a combination of silicon nitride, aluminum nitride, aluminum oxide and silicon oxide.

[0017] Advantages: Compared with the prior art, the application has the following advantages:

[0018] (1) Increase the gate voltage swing. The present application takes advantage of the saturation characteristics of GaN HEMT, when the first gate metal voltage of the voltage limiting tube area is greater than its positive threshold voltage, the increased part of the input gate voltage is applied between the drain and source of the voltage limiting tube area, so that the second gate metal voltage of the power tube area is stabilized in its working voltage range, thereby greatly increasing the gate voltage swing of the overall device.

[0019] (2) Enhance threshold stability. The present application takes advantage of the switching characteristics of depletion-mode GaN PFET, when the third gate metal voltage of the discharge tube area is less than its positive threshold, a discharge channel is established for the stored charge in the second P-type GaN cap layer of the power tube area, effectively eliminating the charge storage effect, thereby significantly enhancing the threshold stability of the device.

[0020] (3) High integration, less parasitic. In the present application, an isolation layer is introduced between the N-channel GaN device and the P-channel GaN device, and the devices are directly connected by metal lines, making the device integration higher and reducing the adverse effects caused by parasitic. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 is a schematic diagram of a conventional p-GaN GaN power device structure;

[0022] Figure 2 is a transfer characteristic curve of the device of the present application;

[0023] Figure 3 is a curve graph of the relationship between the second metal gate voltage of the device of the present application and the input gate voltage;

[0024] Figure 4 is a schematic diagram of a wide working gate voltage GaN power device proposed by the present application;

[0025] Figure 5 is an equivalent circuit diagram of the present application;

[0026] Figure 6 is a schematic diagram of another wide working gate voltage GaN power device proposed in Example 2 of the present application;

[0027] Figure 7 is an equivalent circuit diagram of another wide working gate voltage GaN power device proposed in Example 2 of the present application. DETAILED DESCRIPTION

[0028] The present application will be further described in detail below in conjunction with the drawings and specific embodiments.

[0029] Example 1:

[0030] A wide working gate voltage GaN power device, its structure includes: a substrate 10, the substrate 10 includes a substrate 11, a nucleation layer 12, a buffer layer 13, a channel layer 14, a barrier layer 15 and a passivation layer 60 are sequentially arranged on the substrate 11, an isolation layer 50, a voltage limiting tube area 20, a power tube area 30 and a discharge tube area 40 are arranged on the barrier layer 15;

[0031] The voltage limiting tube area 20 includes a first source metal 21 connected to the upper surface of the barrier layer 15, a first P-type gallium nitride cap layer 22, and a first drain metal 24, and the upper surface of the first P-type gallium nitride cap layer 22 is provided with a first gate metal 23;

[0032] The power tube area 30 includes a second source metal 31 connected to the upper surface of the barrier layer 15, a second P-type gallium nitride cap layer 32, and a second drain metal 34, and the upper surface of the second P-type gallium nitride cap layer 32 is provided with a second gate metal 33;

[0033] The discharge tube area 40 includes a third source metal 45 connected to the upper surface of the barrier layer 15, a third P-type gallium nitride cap layer 42, and a third drain metal 41, and the upper surface of the third P-type gallium nitride cap layer 42 is provided with a PFET gate dielectric layer 43, and the upper surface of the PFET gate dielectric layer 43 is provided with a third gate metal 44;

[0034] The first source metal 21 and the third gate metal 44 are connected by a first interconnection metal V1 and connected to an input gate voltage, the first drain metal 24, the second gate metal 33, and the third drain metal 41 are connected by a second interconnection metal V2, the potential of the second source metal 31 and the third source metal 45 is grounded, and the first gate metal 23 is connected to a 5V potential;

[0035] The working principle of the device of the present application is shown in FIG. 5. When the first gate metal 23 is connected to a 5V potential, the channel of the voltage limiting tube area 20 is fully opened, and when the whole device starts to work with the increase of the voltage of the first source metal 21, i.e. the input gate voltage, the voltage of the second gate metal 33 increases with the increase of the input gate voltage, and then due to the saturation characteristics of the gallium nitride HEMT device, the voltage of the second gate metal 33 is clamped within its working voltage range, and the gate current thereof is limited by the saturation current of the voltage limiting tube area; when the whole device is turned off and the input gate voltage decreases to the positive threshold voltage of the depletion-mode gallium nitride PFET, the channel of the discharge tube area 40 is opened, and the stored charge in the second P-type gallium nitride cap layer 32 is quickly discharged.

[0036] Embodiment 2:

[0037] Based on the structure described in Embodiment 1, in this embodiment, the feature is that the voltage limiting tube area can be a depletion-mode gallium nitride HEMT device, and referring to FIG. 6, the voltage limiting tube area 20 includes a first source metal 21 connected to the upper surface of the barrier layer 15, a depletion-mode gallium nitride gate dielectric layer 25, and a first drain metal 24, and the upper surface of the depletion-mode gallium nitride gate dielectric layer 25 is provided with a first gate metal 23;

[0038] The first source metal 21 and the third gate metal 44 are connected by the first interconnection metal V1 and connected to the input gate voltage, the first drain metal 24, the second gate metal 33 and the third drain metal 41 are connected by the second interconnection metal V2, and the second source metal 31 and the third source metal 45 are grounded;

[0039] Different from the embodiment 1, the potential of the first gate metal 23 is grounded in the embodiment.

[0040] The voltage limiting tube region improves the gate voltage swing of the device, the potential of the first gate metal is constant and always greater than its threshold voltage, which ensures that the channel of the voltage limiting tube region is fully opened, the drain current on the second gate metal of the power tube region increases with the increase of the input gate voltage at first, and then remains unchanged due to the saturation current limitation of the voltage limiting tube region, the voltage of the second gate metal of the power tube region is stable in its working voltage range, and the part of the increase of the input gate voltage is applied between the drain and the source of the voltage limiting tube region, which realizes the function of improving the gate voltage swing of the device.

[0041] The above description is only a description of the preferred embodiments of the present application, and does not limit the scope of the present application in any way, and any modification or modification made by a person skilled in the art according to the above disclosure is within the protection scope of the claims.

Claims

1. A gallium nitride power device with wide operating gate voltage, characterized in that, The device comprises a substrate (10) including a substrate (11), a nucleation layer (12), a buffer layer (13), a channel layer (14), a barrier layer (15) and a passivation layer (60) arranged in sequence on the substrate (11), an isolation layer (50), a voltage limiting tube region (20), a power tube region (30) and a discharge tube region (40) arranged on the barrier layer (15); The voltage limiting tube region (20) comprises a first source metal (21) connected to the upper surface of the barrier layer (15), a first P-type gallium nitride cap layer (22) and a first drain metal (24), and the upper surface of the first P-type gallium nitride cap layer (22) is provided with a first gate metal (23). The power tube region (30) comprises a second source metal (31) connected to the upper surface of the barrier layer (15), a second P-type gallium nitride cap layer (32) and a second drain metal (34), and the upper surface of the second P-type gallium nitride cap layer (32) is provided with a second gate metal (33). The discharge tube region (40) comprises a third source metal (45) connected to the upper surface of the barrier layer (15), a third P-type gallium nitride cap layer (42) and a third drain metal (41), and the upper surface of the third P-type gallium nitride cap layer (42) is provided with a PFET gate dielectric layer (43), and the upper surface of the PFET gate dielectric layer (43) is provided with a third gate metal (44).

2. The GaN power device with wide operating gate voltage according to claim 1, characterized in that: The discharge tube region (40) has the characteristics of a depletion-mode gallium nitride PFET device: when the voltage of the third gate metal (44) is less than a positive threshold voltage, the device is turned on; when the voltage of the third gate metal (44) is greater than the positive threshold voltage, the device is turned off.

3. The GaN power device with wide operation gate voltage according to claim 1 or 2, characterized in that: The thickness of the third P-type gallium nitride cap layer (42) is 50-300 nm.

4. The GaN power device with wide operation gate voltage according to claim 1 or 2, characterized in that: The third P-type gallium nitride cap layer (42) is in a groove shape.

5. The GaN power device with wide operation gate voltage according to claim 1 or 2, characterized in that: The maximum groove depth of the third P-type gallium nitride cap layer (42) is 270 nm.

6. The GaN power device with wide operating gate voltage according to claim 1, wherein: The thickness of the PFET gate dielectric layer (43) is 1-50 nm.

7. The GaN power device with wide operation gate voltage according to claim 1 or 6, characterized in that: The PFET gate dielectric layer (43) is one or a combination of silicon nitride, aluminum nitride, aluminum oxide and silicon oxide.

8. The GaN power device with wide operating gate voltage according to claim 1, wherein: The first source metal (21) and the third gate metal (44) are connected by a first interconnection metal (V1) and are connected to an input gate voltage, the first drain metal (24) and the second gate metal (33) are connected to the third drain metal (41) by a second interconnection metal (V2), and the second source metal (31) and the third source metal (45) are grounded.

9. The GaN power device with wide operating gate voltage according to claim 1, wherein, The voltage limiting tube region (20) can also be a first source metal (21) connected to the upper surface of the barrier layer (15), a depletion-mode gallium nitride gate dielectric layer (25) and a first drain metal (24), and the upper surface of the depletion-mode gallium nitride gate dielectric layer (25) is provided with a first gate metal (23).

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