CN113990918B - Vertical III-nitride power semiconductor device with stepped shielding ring and preparation method thereof - Google Patents

Abstract

The invention relates to a vertical III-nitride power semiconductor device with a stepped shielding ring and a preparation method thereof, wherein the vertical III-nitride power semiconductor device sequentially comprises a cathode electrode, a heavily doped N-nitride substrate region, a lightly doped N-nitride drift region, a heavily doped P-nitride region and an anode electrode from bottom to top, wherein a lightly doped P-nitride shielding ring is embedded below the heavily doped P-nitride region in the lightly doped N-nitride drift region; through a large number of simulation calculation analyses, the lightly doped P-type nitride shielding ring is embedded in the lightly doped N-type nitride drift region, so that the reverse voltage withstand capability of the device can be greatly improved on the premise of keeping the size of the device unchanged, and meanwhile, the reverse leakage is further reduced, so that the device can be applied to a higher voltage scene.

Description

A vertical type III nitride power semiconductor device with a stepped shielding ring and Its preparation method

Technical field

The invention relates to a Group III nitride vertical power device structure with a shielding ring structure and its preparation method and application, and belongs to the technical field of semiconductor devices.

Background technique

Compared with the first-generation semiconductors represented by silicon and the second-generation semiconductors represented by gallium arsenide, the third-generation semiconductors represented by silicon carbide and group III nitrides have large bandgaps and high criticality. With excellent characteristics such as breakdown field strength, high thermal conductivity, and high electron saturation drift rate, it has broad application prospects in high-frequency communications, power electronics and other fields.

At present, gallium nitride-based devices that can be widely used are mainly lateral high electron mobility transistors (HEMT). However, the main disadvantage of lateral devices is that the reverse breakdown voltage of the device is proportional to the lateral electrode spacing of the device, resulting in the need for larger device sizes in high-voltage working scenarios, which greatly increases the process preparation cost of the device. In order to solve this problem, fully vertical devices can achieve a larger reverse breakdown voltage by increasing the thickness of the vertical drift layer of the device, while effectively avoiding the current crowding effect that occurs in lateral structures and quasi-vertical structures, and reducing forward conduction. resistance.

During the reverse blocking process of the device, excellent reverse breakdown characteristics can be achieved by adjusting the electric field distribution inside the device to be uniform. However, during the optimization of the device structure parameters, premature breakdown of the device will occur due to local electric field accumulation. .

Schottky barrier diodes have become an important part of modern power electronic systems due to their advantages such as voltage drop and fast switching speed. In order to meet the application of consumer electronics and high-frequency communication devices, higher requirements have been put forward for traditional Schottky diodes in high-voltage and high-power application scenarios, and the performance limitations of the devices have become increasingly prominent.

In a high reverse bias scenario, Planar Schottky Barrier Diode (SBD) often produces an obvious barrier lowering effect due to the strong electric field accumulation under the Schottky contact barrier, resulting in a large The reverse leakage current limits the reverse breakdown characteristics of the Schottky barrier diode. This problem can be solved by using a new structure of a mixed PiN junction barrier Schottky diode (Merged PiN Schottky diode, MPS diode). Compared with traditional planar Schottky barrier diodes, gallium nitride vertical hybrid PiN junction barrier Schottky diodes can effectively modulate the electric field distribution under the Schottky contact barrier and utilize the depletion region of adjacent PN junctions. Superposition can form a good electric field shielding effect on the Schottky contact barrier and avoid large leakage current and early breakdown problems caused by the barrier reduction effect. However, when the doping concentration of p-GaN is too high, strong electric field accumulation occurs at the corners at the bottom of the p-GaN structure, causing premature breakdown of the device again and limiting the reverse blocking performance of the device.

Contents of the invention

In view of the shortcomings of the existing technology, the present invention provides a Group III nitride vertical power device structure with a shielding ring structure; the present invention proposes an effective solution to the problem of vertical gallium nitride mixed PiN under the condition of high p-GaN doping. The technical solution to the local electric field accumulation problem of junction barrier Schottky diodes is as follows:

1. Through the growth method of secondary epitaxy or multiple epitaxy plus ion implantation, a shallowly doped stepped shielding ring structure under the heavily doped p-GaN is realized. The depletion effect of the shielding ring can effectively alleviate the heavily doped p-GaN. The strong electric field gathers at the corners at the bottom of the structure, forming an electric field shielding protection for it;

2. By optimizing the parameters of the p-GaN shallowly doped stepped shielding ring (magnesium ion doping concentration, upper step thickness, lower step thickness), the reverse blocking characteristics are greatly improved. The physical mechanism of the device structure is that lightly doped p-GaN and the n-type drift layer form a space charge depletion region of the PN junction. The width of the space charge depletion region will change with the change of the reverse bias voltage, thereby achieving Evacuate the accumulated local electric field to make the electric field distribution more uniform, so as to improve the reverse breakdown voltage of the device.

Terminology explanation:

1. Dry etching is a technology that uses plasma to etch thin films.

2. MOCVD method is a new vapor phase epitaxial growth technology developed on the basis of vapor phase epitaxial growth (VPE) in MOCVD furnace.

The technical solution of the present invention is:

A Group III nitride vertical power device structure with a shielding ring structure, including from bottom to top a cathode electrode, a heavily doped N-type nitride substrate region, a lightly doped N-type nitride drift region, a heavily doped P-type nitride region, anode electrode, and a lightly doped P-type nitride shielding ring embedded below the heavily doped P-type nitride region in the lightly doped N-type nitride drift region;

According to the preferred embodiment of the present invention, the lightly doped P-type nitride shielding ring is in the shape of a step. The thickness T ₁ of the upper step is 0.5-2.0 μm, the thickness T ₂ of the lower step is 1.0-10.0 μm, and the width W of the lower step is is 1.0-4.0μm;

Most preferably, the thickness T ₁ of the upper step is 2.0 μm, the thickness T ₂ of the lower step is 8.0 μm, and the width W of the lower step is 2 μm.

According to the preferred embodiment of the present invention, the magnesium ion doping concentration in the lightly doped P-type nitride shielding ring is 1e15cm ^-3 -5e17cm ^-3 .

Further preferably, the magnesium ion doping concentration in the lightly doped P-type nitride shielding ring is 1e16cm ^-3 -8e16cm ^-3 .

Most preferably, the magnesium ion doping concentration in the lightly doped P-type nitride shielding ring is 3e16cm ^-3 .

According to the preferred embodiment of the present invention, the heavily doped N-type nitride substrate region is a heavily doped N-type gallium nitride substrate region, and the lightly doped N-type nitride drift region is a lightly doped N-type nitride Gallium drift region, the heavily doped P-type nitride region is a heavily doped P-type gallium nitride region.

The preparation method of the above-mentioned Group III nitride vertical power device structure with a shielding ring structure includes the following steps:

(1) Sequentially grow a heavily doped N-type nitride substrate region and a lightly doped N-type nitride drift region on the cathode electrode;

(2) After ICP etching the lightly doped N-type nitride drift region, perform secondary epitaxial growth to form a stepped lightly doped P-type nitride shielding ring;

(3) Continue to epitaxially grow the heavily doped P-type nitride region and the anode electrode in sequence, and the result is obtained.

According to the preferred embodiment of the present invention, in step (2), secondary epitaxial growth is performed to form a stepped lightly doped P-type nitride shielding ring. The specific implementation steps include:

①Use a dry etching process to etch the trench area on the lightly doped N-type nitride drift area, and damage the etched surface;

②Use silicon dioxide as a hard mask to block the unetched lightly doped N-type nitride drift region, use ammonia as the N source, magnesium dicene as the doping source, H ₂ as the carrier gas, and use MOCVD The method is to homoepitaxially grow a layer of P-type nitride on the surface of the lightly doped N-type nitride drift region;

③ In-situ annealing in the MOCVD furnace activates P-type doped magnesium ions and grows to form a stepped lightly doped P-type nitride shielding ring.

According to the preferred embodiment of the present invention, in step (2), after ICP etching, multiple epitaxy and ion implantation processes are performed to grow a stepped lightly doped P-type nitride shielding ring. The specific implementation steps include:

A. Use a dry etching process to etch the trench area on the lightly doped N-type nitride drift area, and damage the etched surface;

B. Use an ion implanter to implant Mg ions on the bottom surface of the trench area of the lightly doped N-type nitride drift region. The power energy of the ion implantation is set to 150~300keV, and the implantation depth is 0.3~0.6μm;

C. Perform rapid thermal annealing treatment in a gas atmosphere of one or more mixtures of nitrogen, ammonia, argon, and hydrogen in any proportion. The temperature range of the rapid thermal annealing treatment is 400 to 1500°C. Time is 10~90min;

D. Use the MOCVD method to epitaxially grow N-type nitride of 0.3 to 0.6 μm, and the doping concentration of silicon is 2e16cm ^-3 ;

E. Repeat steps B to D multiple times until a lightly doped P-type nitride shielding ring with a specified thickness is generated.

Group III nitride material systems can be gallium nitride materials.

The above-mentioned Group III nitride vertical power device structure with a shielding ring structure is used in high-frequency, high-voltage and high-power power electronics and integrated systems.

The beneficial effects of the present invention are:

1. The present invention sets a stepped lightly doped stepped p-GaN region at the bottom of the heavily doped p-GaN region of the vertical mixed PiN junction barrier Schottky diode to form a shielding ring structure, which effectively alleviates the problem of heavy doping. The problem of local electric field concentration at the corners of the p-GaN region improves the reverse blocking performance of the device.

2. The present invention uses ICP dry etching to form the trench area, and then uses MOCVD secondary epitaxial growth to grow a shallowly doped stepped p-GaN shielding ring. The preparation method of the present invention is suitable for Group III nitride systems, the process is relatively simple, the activation efficiency is high, and the obtained P-type structure is relatively stable. The relevant processes involved in the present invention are existing, and the specific process conditions and deposition temperatures are also well known to those skilled in the art.

Description of the drawings

Figure 1 is a schematic structural diagram of a hybrid PiN junction barrier Schottky diode with a lightly doped stepped p-GaN shielding ring proposed by the present invention;

Figure 2 is a schematic structural diagram of a traditional planar hybrid PiN junction barrier Schottky diode;

Figure 3 is a graph showing the relationship between the magnesium doping concentration of the stepped p-GaN shielding ring and the reverse breakdown voltage of the device.

Figure 4 shows the relationship between the upper step thickness of the stepped p-GaN shielding ring and the reverse breakdown voltage of the device;

Figure 5 shows the relationship between the lower step thickness of the stepped p-GaN shielding ring and the reverse breakdown voltage of the device.

Detailed ways

The present invention will be further limited below with reference to the accompanying drawings and examples of the description, but is not limited thereto.

Example 1

A Group III nitride vertical power device structure with a shielded ring structure, as shown in Figure 1, including from bottom to top a cathode electrode, a heavily doped N-type gallium nitride substrate region, a lightly doped N-type nitrogen Gallium drift region, heavily doped P-type gallium nitride region, anode electrode, lightly doped P-type gallium nitride is embedded below the heavily doped P-type gallium nitride region in the lightly doped N-type gallium nitride drift region Shielding ring; the shallowly doped stepped p-GaN shielding ring is located below the heavily doped p-GaN. It can form a PN junction with the n-type shallowly doped drift layer, and the depletion effect can regulate the heavily doped p-GaN structure. Strong electric field around the corner.

The structure of a traditional planar hybrid PiN junction barrier Schottky diode is shown in Figure 2. Through a large number of simulation calculations and analysis, it is known that a lightly doped P-type gallium nitride shielding ring is embedded in the lightly doped N-type gallium nitride drift region. , the reverse voltage withstand capability of the device can be greatly improved while keeping the size of the device unchanged. At the same time, the reverse leakage has been further reduced, making it possible for the device to be applied in higher voltage scenarios.

Example 2

The difference between a Group III nitride vertical power device structure with a shielding ring structure according to Embodiment 1 is:

The lightly doped P-type gallium nitride shielding ring is in the shape of a step. The thickness of the upper step _T1 is 0.5-2.0μm, the thickness of the lower step _T2 is 1.0-10.0μm, and the width W of the lower step is 1.0-4.0μm; light The magnesium ion doping concentration in the doped P-type gallium nitride shielding ring is 1e15cm ^-3 -5e17cm ^-3 .

When the step thickness T ₁ and T ₂ are larger, the shielding ring structure goes deeper into the device, the depletion region can be expanded to the depth of the drift layer, and the area that bears the voltage increases, so a higher reverse voltage can be achieved. through voltage. The selection of the magnesium ion doping concentration can ensure the effective depletion protection of the shielding ring structure, and avoid the depletion effect of the shielding ring being too small and negligible when the concentration is too low, and the strong depletion effect causing local electric field accumulation when the concentration is too high. Cause premature breakdown of the device.

Example 3

The difference between a Group III nitride vertical power device structure with a shielding ring structure according to Embodiment 2 is:

The thickness T ₁ of the upper step is 2.0 μm, the thickness T ₂ of the lower step is 8.0 μm, and the width W of the lower step is 2 μm.

The magnesium ion doping concentration in the lightly doped P-type gallium nitride shielding ring is 3e16cm ^-3 .

The thickness of the heavily doped N-type gallium nitride substrate region is 2 μm, the doping element is silicon, and the doping concentration is 5e18cm ^-3 ; the thickness of the lightly doped N-type gallium nitride drift region is 15 μm, the doping element is silicon, and the doping concentration is 5e18cm -3 The impurity concentration is 2e16cm ^-3 . The structure of the heavily doped P-type gallium nitride region is square, with a depth of 2 μm and a width of 4 μm. The doping ions are Mg ions, and the doping concentration is 1e18cm ^-3 . The middle Schottky contact width is set to 2μm.

Example 4

The method for preparing a Group III nitride vertical power device structure with a shielded ring structure as described in either embodiment 1 or 2 includes the following steps:

(1) Sequentially grow a heavily doped N-type gallium nitride substrate region and a lightly doped N-type gallium nitride drift region on the cathode electrode;

(2) After ICP etching the lightly doped N-type gallium nitride drift region, perform secondary epitaxial growth to form a stepped lightly doped P-type gallium nitride shielding ring; that is, a lightly doped stepped p- Vertical MPS diode with GaN shielding ring; secondary epitaxial growth is performed using MOCVD. The outlines between the material layers are clear and evenly distributed, which avoids lattice damage to the material during ion implantation.

Specific implementation steps include:

①Use a dry etching process to etch the trench area on the lightly doped N-type gallium nitride drift area, and damage the etched surface;

②Use silicon dioxide as a hard mask to block the unetched lightly doped N-type gallium nitride drift region, use ammonia (NH ₃ ) as the N source, and magnesium cyclocene (Cp ₂ Mg) as the dopant. Source, H ₂ as carrier gas, use MOCVD method to homoepitaxially grow a layer of P-type gallium nitride on the upper surface of the lightly doped N-type gallium nitride drift region;

③ In-situ annealing in the MOCVD furnace activates P-type doped magnesium ions and grows to form a stepped lightly doped P-type gallium nitride shielding ring.

(3) Continue to epitaxially grow the heavily doped P-type gallium nitride region and the anode electrode in sequence, and the result is obtained.

Example 5

According to the preparation method of a Group III nitride vertical power device structure with a shielding ring structure described in Embodiment 4, the difference is that:

In step (2), after ICP etching, multiple epitaxy and ion implantation processes are performed to grow a stepped lightly doped P-type gallium nitride shielding ring. The specific implementation steps include:

A. Use a dry etching process to etch the trench area on the lightly doped N-type gallium nitride drift area, and damage the etched surface;

B. Use an ion implanter to implant Mg ions on the bottom surface of the trench area of the lightly doped N-type gallium nitride drift region. The power energy of the ion implantation is set to 150~300keV, and the implantation depth is 0.3~0.6μm;

C. Perform rapid thermal annealing treatment in a gas atmosphere of one or more mixtures of nitrogen, ammonia, argon, and hydrogen in any proportion. The temperature range of the rapid thermal annealing treatment is 400 to 1500°C. The time is 10~90min; to increase the activation rate of Mg ions in gallium nitride;

D. Use MOCVD method to epitaxially grow 0.3-0.6μm N-type gallium nitride, and the doping concentration of silicon is 2e16cm ^-3 ;

E. Repeat steps B to D multiple times until a lightly doped P-type gallium nitride shielding ring with a specified thickness is generated.

The ion implantation process achieves no interface between the implanted layer and the substrate, high bonding strength and good adhesion, and does not change the external dimensions and surface finish of the device.

Example 6

The preparation method of a Group III nitride vertical power device structure with a shielding ring structure described in Embodiment 3 includes the following steps:

(1) Use trimethylammonium (TMGa) and ammonia (NH ₃ ) as Ga source and N source respectively, _Si H ₃ CH ₃ as N-type impurity source, and H ₂ as carrier gas to achieve 2 μm in MOCVD. Thick, low-defect, low-dislocation heavily doped N-type gallium nitride substrate region, the silicon doping concentration is 5e18cm ^-3 ;

(2) Use trimethylammonium (TMGa) and ammonia (NH ₃ ) as the Ga source and N source respectively, _Si H ₃ CH ₃ as the N-type impurity source, H ₂ as the carrier gas, and heavily dope the N-type A 15 μm thick lightly doped N-type gallium nitride drift region is homoepitaxially formed on the surface of the gallium nitride substrate area, and the silicon doping concentration is 2e16cm ^-3 ;

(3) Use _Si O ₂ as a hard mask on the epitaxial wafer to block some areas of the epitaxial wafer that will not be etched, and use inductively coupled plasma in a mixed atmosphere of Cl ₂ /BCl ₃ /Ar Etching (ICP) is used to etch the step trench area;

(4) After dry etching, there are a large number of sharp peaks and burrs with slopes on the material surface. Put the sample into a 25% TMAH solution and treat it at 85°C for 1 hour to remove the surface damage caused by etching: Then put the sample into acetone and heat it to 85°C, and heat it in a water bath for 10 minutes; ultrasonically clean it with isopropyl alcohol for 5 minutes, rinse it 6 times with deionized water, blow it dry with nitrogen and dry it using a hot plate; add an ammonia solution with a concentration of 25wt% Heat the water bath to 85°C, put the sample in, and heat in the water bath for 10 minutes; remove the sample from the ammonia water and rinse it with deionized water 6 times to remove the ammonia water on the surface, terminate the surface treatment effect of the ammonia water, blow dry and dry using a hot plate; Use atomic force microscopy to test the etching depth and etching morphology;

(5) Use trimethylgallium (TMGa), magnocene (Cp ₂ Mg) and ammonia (NH ₃ ) as the Ga, Mg and N sources respectively, H ₂ as the carrier gas, and use the MOCVD method to create a step-shaped trench. Regional homoepitaxial growth of P-type lightly doped gallium nitride layer to form a stepped shielding ring, the magnesium doping concentration range is 1e16cm ^-3 -8e16cm ^-3 ;

(6) Continue to epitaxially grow the heavily doped P-type gallium nitride region and the anode electrode in sequence.

Example 7

The preparation method of the Group III nitride vertical power device structure with a shielded ring structure described in Example 3 is prepared by multiple epitaxy plus ion implantation, including the following steps:

(1) Use trimethylammonium (TMGa) and ammonia (NH ₃ ) as Ga source and N source respectively, _Si H ₃ CH ₃ as N-type impurity source, and H ₂ as carrier gas to achieve 2 μm in MOCVD. Thick N-type heavily doped gallium nitride substrate layer with low defects and low dislocations, the silicon doping concentration is 5e18cm ^-3 ;

(2) Use trimethylammonium (TMGa) and ammonia (NH ₃ ) as Ga source and N source respectively, _Si H ₃ CH ₃ as N-type impurity source, H ₂ as carrier gas, and heavily doped in N-type A 15 μm thick N-type lightly doped gallium nitride drift layer is homoepitaxially formed on the surface of the gallium nitride substrate layer, and the silicon doping concentration is 2e16cm ^-3 ;

(3) Use _Si O ₂ as a hard mask on the epitaxial wafer to block some areas of the epitaxial wafer that will not be etched, and use inductively coupled plasma in a mixed atmosphere of Cl ₂ /BCl ₃ /Ar Etching (ICP) is used to etch the step trench area;

(4) After dry etching, there are a large number of sharp peaks and burrs with slopes on the material surface. Put the sample into a 25% TMAH solution and treat it at 85°C for 1 hour to remove the surface damage caused by etching: Then put the sample into acetone and heat it to 85°C, and heat it in a water bath for 10 minutes; ultrasonically clean it with isopropyl alcohol for 5 minutes, rinse it 6 times with deionized water, blow it dry with nitrogen and dry it using a hot plate; add an ammonia solution with a concentration of 25wt% Heat the water bath to 85°C, put the sample in, and heat in the water bath for 10 minutes; remove the sample from the ammonia water and rinse it with deionized water 6 times to remove the ammonia water on the surface, terminate the surface treatment effect of the ammonia water, blow dry and dry using a hot plate; Use atomic force microscopy to test the etching depth and etching morphology;

(5) Use trimethylgallium (TMGa) and ammonia (NH ₃ ) as the Ga source and N source respectively, H ₂ as the carrier gas, and use the MOCVD method to homoepitaxially grow 300nm to 500nm thick in the stepped trench area. N-type gallium nitride layer;

(6) Use an ion implanter to implant Mg ions into the epitaxially grown N-type gallium nitride layer at the bottom of the stepped trench, and adjust the energy of the ion implantation to achieve a 300nm to 500nm thick P-type gallium nitride layer as the shielding ring area, and then Remove the surface SiO ₂ hard mask and perform rapid thermal annealing (PIA). The process is rapid thermal annealing in a nitrogen atmosphere. The temperature range of high-temperature annealing is 450°C and the annealing time is 20 minutes to improve the P-type Hole activation rate inside the gallium nitride layer.

(7) Repeat steps (5) and (6) multiple times to grow a p-GaN shielding ring with a specified thickness;

(8) Continue to epitaxially grow the heavily doped P-type gallium nitride region and the anode electrode in sequence.

Example 8

The magnesium ion doping concentration of the shielding ring in the planar mixed PiN junction barrier Schottky diode structure with a shallowly doped stepped p-GaN shielding ring in Variation Embodiment 1 (the variation range is 1e16cm ^-3 -8e16cm ^-3 ), Through numerical simulation, the relationship between the reverse breakdown voltage of the device and the magnesium ion doping concentration in the shallowly doped stepped p-GaN shielding ring region is obtained, as shown in Figure 3.

The reverse breakdown voltage of a traditional planar hybrid PiN junction barrier Schottky diode without a shielding ring structure is marked as 1123V in Figure 3, which is used as a reference. At this time, the concentration of the N-type lightly doped drift layer is set to 2e16cm ^-3 . Compared with the reverse breakdown voltage (1123V) of the traditional planar hybrid PiN junction barrier Schottky diode, the device with a shallowly doped stepped p-GaN shielding ring shows a higher reverse breakdown voltage; further , the optimal magnesium ion doping concentration is 3e16cm ^-3 . As the magnesium ion doping concentration increases, the reverse breakdown voltage shows a trend of first increasing and then decreasing, but all show reverse breakdown voltage values higher than 1123V. Through the analysis of TCAD simulation results, it can be seen that with the stepped shielding ring structure, the reverse breakdown voltage can be effectively improved and better reverse blocking characteristics can be achieved. By optimizing the doping concentration of magnesium ions, this can be further achieved. Better reverse pressure resistance. The quality of reverse blocking performance is mainly reflected in the magnitude of reverse breakdown voltage.

Example 9

The upper step thickness of the shielding ring in the planar mixed PiN junction barrier Schottky diode structure with a lightly doped stepped p-GaN shielding ring in Variation Embodiment 1 (variation range is 0.5μm-2.0μm), obtained through numerical simulation The relationship between the reverse breakdown voltage of the device and the step thickness on the shallowly doped stepped p-GaN shielding ring is shown in Figure 4. At this time, the magnesium doping concentration of the stepped p-GaN shielding ring is set to 4e16cm ^-3 . The larger the value of _T1 , the higher the reverse breakdown voltage is exhibited. As the thickness of the step on the shielding ring increases, the reverse breakdown voltage shows a monotonous rising trend, and the highest reverse breakdown voltage of 1811V is achieved under the condition that _T1 is 2.0μm.

Example 10

In Variation Embodiment 1, the lower step thickness of the shielding ring in the planar mixed PiN junction barrier Schottky diode structure with a shallowly doped stepped p-GaN shielding ring (the variation range is 1 μm-10 μm) was obtained through numerical simulation. The relationship between the reverse breakdown voltage and the step thickness under the lightly doped stepped p-GaN shielding ring is shown in Figure 5. At this time, the magnesium doping concentration of the stepped p-GaN shielding ring is set to 4e16cm ^-3 . The larger the value of T ₂ is, the higher the reverse breakdown voltage will be, and it will tend to be saturated when its width reaches 8μm. The internal structure of the device appears to be that the lower step of the p-GaN shielding ring is close to the n-type heavily doped substrate. district. As the thickness of the step under the shielding ring increases, the reverse breakdown voltage shows an almost monotonic rising trend. Under the condition of _T2 of 10μm, the highest reverse breakdown voltage of 2381V is achieved. Through the analysis of TCAD simulation results, it can be seen that the larger the step thickness, the deeper the depletion region depth can be achieved, and the N-type lightly doped gallium nitride drift layer can be effectively used to uniform the electric field distribution to achieve better reverse resistance. interruption performance.

Claims (10)

1. The III-nitride vertical power device structure with the shielding ring structure is characterized by comprising a cathode electrode, a heavily-doped N-type nitride substrate region, a lightly-doped N-type nitride drift region, a heavily-doped P-type nitride region and an anode electrode from bottom to top in sequence, wherein a lightly-doped P-type nitride shielding ring is embedded below the heavily-doped P-type nitride region in the lightly-doped N-type nitride drift region;

the lightly doped P-type nitride shielding ring is stepped and has the thickness T of the upper step ₁ Thickness T of the lower step is 0.5-2.0 μm ₂ The width W of the lower step is 1.0-4.0 μm and is 1.0-10.0 μm.

2. The group iii nitride vertical power device structure with shield ring structure of claim 1, wherein the thickness T of the upper step ₁ Thickness T of the lower step of 2.0 μm ₂ The width W of the lower step was 8.0 μm and 2. Mu.m.

3. The group iii nitride vertical power device structure with shield ring structure of claim 1, wherein the lightly doped P-type nitride shieldThe doping concentration of magnesium ions in the ring is 1e15cm ^-3 -5e17cm ^-3 。

4. The vertical power device structure of group iii nitride with shielding ring structure of claim 1, wherein the doping concentration of magnesium ions in the lightly doped P-type nitride shielding ring is 1e16cm ^-3 -8e16cm ^-3 。

5. The group iii nitride vertical power device structure of claim 1, wherein the magnesium ion doping concentration in the lightly doped P-type nitride shield ring is 3e16cm ^-3 。

6. The vertical power device structure of claim 1, wherein the heavily doped N-type nitride substrate region is a heavily doped N-type gallium nitride substrate region, the lightly doped N-type nitride drift region is a lightly doped N-type gallium nitride drift region, and the heavily doped P-type nitride region is a heavily doped P-type gallium nitride region.

7. The method for manufacturing a group iii nitride vertical power device structure having a shield ring structure as set forth in any one of claims 1 to 6, comprising the steps of:

(1) Sequentially growing a heavily doped N-type nitride substrate region and a lightly doped N-type nitride drift region on the cathode electrode;

(2) Performing ICP etching on the lightly doped N-type nitride drift region, and performing secondary epitaxial growth to form a stepped lightly doped P-type nitride shielding ring;

(3) And continuing to epitaxially grow a heavily doped P-type nitride region and an anode electrode in sequence to obtain the semiconductor device.

8. The method for manufacturing a group iii nitride vertical power device structure with a shielding ring structure according to claim 7, wherein in the step (2), the step of performing a second epitaxial growth to form a stepped lightly doped P-type nitride shielding ring, the specific implementation steps include:

(1) etching a groove region on the lightly doped N-type nitride drift region by using a dry etching process, and performing damage treatment on the etched surface;

(2) the silicon dioxide is used as a hard mask to shield an unetched lightly doped N-type nitride drift region, ammonia is used as an N source, magnesium oxide is used as a doping source, and H ₂ As carrier gas, adopting MOCVD method to homoepitaxial a layer of P-type nitride on the upper surface of lightly doped N-type nitride drift region;

(3) and (3) in-situ annealing in the MOCVD furnace, activating P-type doped magnesium ions, and growing to form a stepped lightly doped P-type nitride shielding ring.

9. The method for manufacturing a group iii nitride vertical power device structure with a shielding ring structure according to claim 7, wherein in the step (2), after performing ICP etching, a step-shaped lightly doped P-type nitride shielding ring is formed by performing epitaxial and ion implantation for a plurality of times, and the specific implementation steps include:

A. etching a groove region on the lightly doped N-type nitride drift region by using a dry etching process, and performing damage treatment on the etched surface;

B. carrying out Mg ion implantation on the bottom surface of the groove area of the lightly doped N-type nitride drift region by using an ion implanter, wherein the power energy of the ion implantation is set to be 150-300 keV, and the implantation depth is 0.3-0.6 mu m;

C. carrying out rapid thermal annealing treatment in a gas atmosphere of a mixture of one or more than two of nitrogen, ammonia, argon and hydrogen in any proportion, wherein the temperature range of the rapid thermal annealing treatment is 400-1500 ℃ and the annealing time is 10-90 min;

D. epitaxially growing N-type nitride with thickness of 0.3-0.6 μm by MOCVD method, and doping concentration of silicon is 2e16cm ^-3 ；

E. Repeating the steps B to D for a plurality of times until the lightly doped P-type nitride shielding ring with the specified thickness is generated.

10. Use of a group iii nitride vertical power device structure with a shield ring structure according to any of claims 1-6, characterized in that the group iii nitride vertical power device structure with a shield ring structure is used in high frequency, high voltage and high power electronics and integration systems.