Field modulation type Schottky diode and manufacturing method thereof

Abstract

The invention discloses a field modulation type Schottky diode and a manufacturing method thereof, which mainly solve the problems of high turn-on voltage, small conduction current and low breakdown voltage of the existing Schottky diode, and comprises a cathode (7), a substrate (1), a drift layer (2) and a gradient contact layer (3) from bottom to top, 2n-1 rectangular tunneling holes (8) with unequal intervals and the same size are formed in the middle of the gradient contact layer; a high-K tunneling layer (4) is arranged in the tunneling hole, and the high-K tunneling layer (4) and the gradient contact layer (3) are distributed in a staggered manner; p-type grooves (9) with the same size are formed in the middle of the high-K tunneling layer, and P-type modulation layers (5) are arranged in the P-type grooves; anodes (6) cover the gradient contact layer (3), the high-K tunneling layer (4) and the P-type modulation layer (5), and the high-K tunneling layer (4) and the P-type modulation layer (5) form a field modulation junction (10). According to the invention, the turn-on voltage and the off-state leakage current are reduced, the conduction current and the breakdown voltage are improved, and the device can be used as a power switch device of a power electronic system.

Description

Technical Field

[0001] The invention belongs to the field of microelectronic technology, and in particular relates to a Schottky diode device which can be used in a power electronic system. Technical Background

[0002] As the core support of modern energy conversion, power electronics technology has been widely used in many fields such as aerospace propulsion systems, new energy vehicle electronic systems, medical equipment power modules, and smart home appliance frequency conversion control. In such applications, Schottky diodes, with their low forward voltage drop and fast switching characteristics, undertake the core functions of power regulation and topology conversion, and their performance parameters are directly related to the overall energy efficiency and operational reliability of the system. Current silicon-based power devices are limited by narrow bandgap width and low critical breakdown electric field, and their power density has approached the theoretical limit of materials. Faced with the stringent requirements of the next generation of power electronic systems for high temperature, high voltage and high frequency, traditional silicon-based power devices have shown limitations in conduction loss and thermal management efficiency. The third-generation wide bandgap semiconductor materials represented by gallium nitride have outstanding physical properties: high breakdown field strength, high electron saturation velocity, excellent thermal conductivity, etc., which provide a breakthrough path for the construction of new power devices with low on-resistance, high switching frequency and high power density, and are expected to promote the evolution of power electronic systems towards higher energy efficiency and more compactness.

[0003] Vertical GaN Schottky diodes are widely used in power electronic systems as rectifying devices. How to obtain high-performance vertical GaN Schottky diodes has become a research hotspot at home and abroad. When the vertical GaN Schottky diode is reverse blocked, the device has a large reverse leakage current and high off-state loss due to the Schottky barrier lowering effect. In addition, the reverse electric field tends to gather at the edge of the anode, generating a high electric field peak, causing the device to break down prematurely, resulting in a low breakdown voltage.

[0004] References 1.7-kV Vertical GaN-on-GaN Schottky Barrier Diodes WithHelium-Implanted Edge Termination, IEEE Transactions on Electron Devices, Vol. 69, No. 4, April 2022, such as Figure 1As shown, it includes: substrate 1, drift layer 2, anode 3, cathode 4 and terminal 5; in this structure, anode 3 and drift layer 2 form a Schottky junction. When a positive bias is applied, the Schottky junction forward conduction device is turned on, and terminal 5 does not participate in forward conduction. When a reverse bias is applied, the charge in the terminal structure redistributes the electric field at the edge of the anode, weakens the electric field peak at the edge, and increases the device breakdown voltage. Although this structure can suppress part of the edge electric field, there is still an electric field peak at the edge of the terminal, resulting in uneven electric field distribution under the anode and limited device withstand voltage; and when the device is forward-conducted, the terminal does not participate in conduction and occupies the effective conduction area, resulting in an increase in the device on-resistance and a decrease in the forward conduction current. In addition, due to the influence of the Schottky barrier lowering effect, this structure leads to a large reverse leakage current and a high device turn-off loss. Therefore, it is necessary to develop more effective electric field modulation technology to realize a vertical gallium nitride Schottky diode with high breakdown voltage, low reverse leakage, high forward conduction current and low on-resistance. Summary of the invention

[0005] The purpose of the present invention is to propose a field modulation Schottky diode to solve the problems of low breakdown voltage and large reverse leakage of traditional junction barrier Schottky diodes, to reduce the reverse leakage of the device while achieving low turn-on voltage and improve the reverse breakdown voltage.

[0006] To achieve the above object, the technical solution of the present invention is as follows:

[0007] 1. A field-modulated Schottky diode, comprising: a substrate 1, a drift layer 2, an anode 6, and a cathode 7, characterized in that:

[0008] A gradient contact layer 3 is disposed above the drift layer 2, and 2n-1 rectangular tunnel holes 8 of different intervals and the same size are disposed in the middle of the gradient contact layer 3, and a high-K tunnel layer 4 is disposed in the tunnel hole 8, where n is the number of tunnel holes from the edge to the center;

[0009] A P-type groove 9 of the same size is provided in the middle of the high-K tunneling layer 4, a P-type modulation layer 5 is provided in the P-type groove 9, and the P-type modulation layer and the high-K tunneling layer 4 form a field modulation junction 10;

[0010] The anode 6 covers the upper surfaces of the graded contact layer 3 , the high-K tunneling layer 4 and the P-type modulation layer 5 , and forms a Schottky contact with the graded contact layer 3 .

[0011] Furthermore, the substrate 1 is made of gallium nitride material; the gradient contact layer 3 is made of AlGaN material with an Al component gradually increasing from bottom to top, and the Al component x satisfies 5%≤x≤60%. When the device is forward-conducted, it forms an AlGaN / GaN heterojunction structure with the drift layer 2, polarizes a three-dimensional electron gas, increases the forward conduction current density of the device, and can increase the current during the turn-on process by improving the tunneling probability of carriers, thereby reducing the forward turn-on voltage of the device; when the device is reverse-blocked, it is beneficial to increase the barrier layer height of the Schottky junction and reduce the reverse leakage current.

[0012] Furthermore, the high-K tunneling layer 4 is made of any one of Ta2O5, ZrO2, HfO2, and TiO2, which has a dielectric constant greater than that of the AlGaN material, to increase the tunneling probability of carriers, increase the forward conduction current, and reduce the turn-on voltage;

[0013] The P-type modulation layer 5 is made of P-type NiO or P-type GaN material, and the hole concentration is 1×10 18 ~8×10 20 cm -3 , which is used to weaken the electric field at the edge of the device and improve the uniformity of the surface electric field distribution, thereby reducing the reverse leakage current of the device and increasing the breakdown voltage of the device.

[0014] Furthermore, the tunnel hole 8 is composed of 2n-1 holes of the same size, and is bilaterally symmetrical with the middle nth hole as the center. The width a of each tunnel hole is 0.5-0.8 μm, and the distance between two adjacent tunnel holes is r. n , the tunnel hole spacing increases from the left and right sides to the middle, that is, r 1 <r 2 <r 3 <r 4 < <r n ;

[0015] The P-type groove 9 is composed of 2n-1 grooves of the same size, and the width m of each P-type groove is 0.2-0.6 μm and meets 0 <m<a。

[0016] Furthermore, the high-K tunneling layer 4 and the gradient contact layer 3 are staggeredly distributed, and the difference in dielectric constants of the two adjacent materials is utilized to cause a new electric field peak to be generated at the interface, so as to reduce the barrier width at the interface between the high-K tunneling layer 4 and the gradient contact layer 3, improve the probability of forward electron tunneling, increase the forward conduction current, and reduce the turn-on voltage.

[0017] 2. A method for manufacturing a field-modulated Schottky diode, comprising the following steps:

[0018] S1) epitaxially growing an n-type gallium nitride semiconductor material on a substrate 1 to form a drift layer 2;

[0019] S2) epitaxially growing an AlGaN semiconductor material whose Al component gradually increases from bottom to top on the drift layer 2 to form a graded contact layer 3;

[0020] S3) making a mask on the graded contact layer 3 for the first time, and using the mask to etch on the graded contact layer 3 to form a tunnel hole 8;

[0021] S4) making a mask for the second time on the graded contact layer 3, and using the mask to deposit a high-K dielectric in the tunnel hole 8 to form a high-K tunnel layer 4 that is staggered with the graded contact layer 3;

[0022] S5) making a mask for the third time on the graded contact layer 3 and the high-K tunneling layer 4, and using the mask to etch the high-K tunneling layer 4 to form a P-type groove 9;

[0023] S6) making a mask for the fourth time on the graded contact layer 3 and the high-K tunneling layer 4, and using the mask to deposit a P-type semiconductor material in the P-type groove 9 to form a P-type modulation layer 5;

[0024] S7) making a mask for the fifth time on the back of the substrate 1, using the mask to deposit metal on the back of the substrate 1, and performing rapid thermal annealing to form a cathode (7);

[0025] S8) A mask is made for the sixth time on the graded contact layer 3, the high-K tunneling layer 4 and the P-type modulation layer 5, and a metal is deposited using the mask to form an anode 8, thereby completing the preparation of the entire device.

[0026] Compared with the junction barrier Schottky diode device, the device of the present invention has the following advantages:

[0027] Firstly, since the device of the present invention is additionally provided with a gradient contact layer formed of AlGaN material and a high-K tunneling layer formed of a high-K dielectric material, on the one hand, multiple layers of two-dimensional electron gas can be formed between AlGaN materials with different Al components, and three-dimensional electron gas is generated through superposition, so that a high-concentration electron distribution can be formed in the gradient contact layer; on the other hand, the staggered distribution of the gradient contact layer and the high-K tunneling layer can utilize the difference in dielectric constants of the two adjacent materials to promote the generation of a new electric field peak at the interface, generate a high electron tunneling probability under a relatively small positive bias voltage, form a high output current, and reduce the turn-on voltage and the on-resistance.

[0028] Secondly, since the device of the present invention is additionally provided with a gradient contact layer and a P-type modulation layer structure formed of AlGaN material, on the one hand, the height and width of the Schottky barrier can be significantly increased through the gradient contact layer with a high bandgap width, thereby suppressing the probability of electrons in the metal tunneling into the semiconductor during reverse bias, and reducing the reverse leakage current of the device; on the other hand, when the device is reverse blocked, the space charge region formed by the P-type modulation layer and the drift layer can be merged to cut off the conductive path on the surface of the Schottky junction and reduce the reverse leakage of the device; in addition, the PN junction formed by the P-type modulation layer and the drift layer can also be reverse biased to generate 2n-1 electric field peaks on the surface of the device, thereby maximally weakening the electric field at the edge of the device and improving the uniformity of the surface electric field distribution, thereby reducing the reverse leakage current of the device and improving the breakdown voltage of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a structural diagram of a traditional vertical GaN Schottky diode with terminal protection;

[0030] Figure 2 It is a structural diagram of the field modulation Schottky diode of the present invention;

[0031] Figure 3 It is a schematic diagram of the process of preparing a field modulation Schottky diode according to the present invention;

[0032] Figure 4 It is to simulate the forward conduction characteristic curves of the device of the present invention and the traditional device;

[0033] Figure 5 It is a reverse breakdown characteristic curve of the simulated device of the present invention and the traditional device. DETAILED DESCRIPTION

[0034] The embodiments and effects of the present invention are further described in detail below with reference to the accompanying drawings.

[0035] Reference Figure 2 The vertical gallium nitride tunneling power diode of this example includes: a substrate 1, a drift layer 2, a graded contact layer 3, a high-K tunneling layer 4, a P-type modulation layer 5, an anode 6, a cathode 7, a tunneling hole 8, a P-type groove 9 and a field modulation junction 10. Among them:

[0036] The substrate 1 is a gallium nitride homogeneous substrate;

[0037] The drift layer 2 is located on the upper part of the substrate 1;

[0038] The gradient contact layer 3 is located on the upper part of the drift layer 2 and is made of AlGaN material with Al component gradually increasing from bottom to top, and the Al component x satisfies 5%≤x≤60%;

[0039] The tunnel hole 8 is located inside the gradient contact layer 3, and is composed of 2n-1 holes of the same size, and is symmetrical with the middle nth hole as the center. The width a of each tunnel hole is 0.5-0.8 μm, and the distance between two adjacent tunnel holes is r. n , the tunnel hole spacing increases from the left and right sides to the middle, that is, r 1 <r 2 <r 3 <r 4 < <r n ;

[0040] The high-K tunnel layer 4 is located inside the tunnel hole 8, and is staggered with the gradient contact layer 3. The high-K dielectric material with a dielectric constant greater than that of the AlGaN material is used, that is, Ta 2 O 5 、ZrO 2 , HfO 2 、TiO 2 Any of the following;

[0041] The P-type groove 9 is located inside the high-K tunneling layer 4 and is composed of 2n-1 grooves of the same size. The width m of each P-type groove is 0.2-0.6 μm and meets 0 <m<a;

[0042] The P-type modulation layer 5 is located inside the P-type groove 9 and is made of one of P-type NiO or P-type GaN materials, with a hole concentration of 1×10 18 ~8×10 20 cm -3 ;

[0043] The anode 6 is located on the upper surfaces of the graded contact layer 3, the high-K tunneling layer 4 and the P-type modulation layer 5;

[0044] The cathode 7 is located on the back side of the substrate 1;

[0045] The field modulation junction 10 is composed of a high-K tunneling layer 4 and a P-type modulation layer 5 .

[0046] Reference Figure 3 The present invention provides a method for manufacturing a vertical gallium nitride tunneling power diode, and provides the following three embodiments.

[0047] Example 1: Making the high-K tunneling layer 4 as TiO 2 Materials, the P-type modulation layer 5 is a P-type NiO material, the tunnel hole 8 is composed of 11 holes of the same size, each tunnel hole has a width a of 0.8 μm, the P-type groove 9 is composed of 9 grooves of the same size, and the width m of each P-type groove is 0.6 μm, which is a field-modulated Schottky diode.

[0048] Step 1. Make a drift layer 2, such as Figure 3(a).

[0049] Using metal organic chemical vapor deposition technology, under the process conditions of temperature of 900 ° C, pressure of 45 Torr, hydrogen flow rate of 5000 sccm, ammonia flow rate of 4600 sccm, and gallium source flow rate of 160 μmol / min, an epitaxial layer with a thickness of 10 μm and a doping concentration of 5×10 15 cm -3 n - type GaN, forming the drift layer 2.

[0050] Step 2. Make a gradient contact layer 3, such as Figure 3 (b).

[0051] Under the process conditions of temperature of 950°C, pressure of 45 Torr, hydrogen flow rate of 5000sccm, ammonia flow rate of 3800sccm, gallium source flow rate of 40μmol / min, and aluminum source flow rate of 5μmol / min, AlGaN material is epitaxially grown on the drift layer 2 using metal organic chemical vapor deposition technology to form a gradient contact layer 3.

[0052] Step 3. Make tunnel hole 8, such as Figure 3 (c).

[0053] The mask is first made on the graded contact layer 3. 2 Under the process conditions of a flow rate of 15 sccm, a pressure of 10 mTorr, and a power of 110 W, the mask is used to perform etching with a width of 0.8 μm on the graded contact layer 3 using reactive ion etching technology to form a tunnel hole 8 .

[0054] Step 4. Make a high-K tunneling layer 4, such as Figure 3 (d).

[0055] A mask is made on the gradient contact layer 3 for the second time. The sputtering pressure in the reaction chamber is about 50 Pa. 2 Under the process conditions of Ar flow rate of 10 sccm and 50 sccm respectively and temperature of 200°C, TiO is deposited in the tunnel hole 8 by using the mask using radio frequency magnetron reactive sputtering technology. 2 , forming a high-K tunneling layer 4.

[0056] Step 5. Make a P-type groove 9, such as Figure 3 (e).

[0057] A mask is fabricated for the third time on the graded contact layer 3 and the high-K tunneling layer 4. 2Under the process conditions of a flow rate of 10 sccm, a pressure of 5 mTorr, and a power of 50 W, the high-K tunneling layer 4 is etched with a width of 0.6 μm using the mask using reactive ion etching technology to form a P-type groove 9 .

[0058] Step 6. Make a P-type modulation layer 5, such as Figure 3 (f).

[0059] The fourth mask is made on the graded contact layer 3 and the high-K tunneling layer 4 at a vacuum degree of 3.0×10 -4 Pa, RF power is 100W, O 2 Under the process conditions that the Ar flow rate is 1 sccm and the Ar flow rate is 1 sccm, the P-type NiO material is sputtered on the P-type groove 9 using the mask using the radio frequency magnetron reactive sputtering technology to form the P-type modulation layer 5.

[0060] Step 7. Make cathode 7, such as Figure 3 (g).

[0061] 7.1) The fifth mask is made on the back of substrate 1 at a vacuum degree of 8×10 -4 Pa, the power is 400W, and the evaporation rate is Under the process conditions, the Ti / Al / Au / Ni metal combination is deposited on the back of the substrate 1 by electron beam evaporation technology using the mask, and the thicknesses thereof are 0.02 μm, 0.14 μm, 0.055 μm, and 0.045 μm, respectively;

[0062] 7.2) The deposited metal is subjected to rapid thermal annealing at a temperature of 860° C. for 30 seconds to form a cathode 7.

[0063] Step 8. Make anode 8, such as Figure 3 (h).

[0064] The sixth mask is made on the graded contact layer 3, the high-K tunneling layer 4 and the P-type modulation layer 5. -3 Pa, the power is 350W, and the evaporation rate is Under the process conditions, the mask is used to use electron beam evaporation technology to deposit metal Wu on the gradient contact layer 3, the high-K tunneling layer 4 and the P-type modulation layer 5 to form an anode 8, thereby completing the preparation of the entire device.

[0065] Example 2: Making the high-K tunneling layer 4 HfO 2 Materials, the P-type modulation layer 5 is a P-type NiO material, the tunnel hole 8 is composed of 9 holes of the same size, each tunnel hole has a width a of 0.5 μm, the P-type groove 9 is composed of 9 grooves of the same size, and each P-type groove has a width m of 0.3 μm, which is a field-modulated Schottky diode.

[0066] Step 1. Prepare the drift layer 2, such as Figure 3 (a).

[0067] Using metal organic chemical vapor deposition technology, a 5 μm thick epitaxial layer with a doping concentration of 1×10 14 cm -3 n-type GaN is used to form the drift layer 2. The process conditions are: temperature 800°C, pressure 30 Torr, SiH 4 As the doping source, the hydrogen flow rate is 4000sccm, the ammonia flow rate is 4000sccm, and the gallium source flow rate is 100μmol / min.

[0068] Step 2. Make a gradient contact layer 3, such as Figure 3 (b).

[0069] Using metal organic chemical vapor deposition technology, AlGaN material is epitaxially grown on the drift layer 2 to form a graded contact layer 3, and the process conditions are: temperature of 800°C, pressure of 30 Torr, hydrogen flow rate of 4000sccm, ammonia flow rate of 3500sccm, gallium source flow rate of 30μmol / min, and aluminum source flow rate of 5μmol / min.

[0070] Step 3. Make tunnel hole 8, such as Figure 3 (c).

[0071] A mask is first made on the gradient contact layer 3, and the gradient contact layer 3 is etched by using the mask using reactive ion etching technology to form a tunnel hole 8. The etching process conditions are: Cl 2 The flow rate is 15sccm, the pressure is 10mTorr, and the power is 100W.

[0072] Step 4. Make a high-K tunneling layer 4, such as Figure 3 (d).

[0073] A mask is made on the graded contact layer 3 for the second time, and HfO is deposited in the tunnel hole 8 by using the mask using the radio frequency magnetron reactive sputtering technology. 2 The process conditions for forming the high-K tunneling layer 4 are as follows: the sputtering pressure in the reaction chamber is 0.1 Pa, O 2 The flow rates of Ar and Ar were 1 sccm and 8 sccm respectively, and the temperature was 200°C.

[0074] Step 5. Make a P-type groove 9, such as Figure 3 (e).

[0075] A mask is made on the graded contact layer 3 and the high-K tunneling layer 4 for the third time, and the high-K tunneling layer 4 is etched using the mask using reactive ion etching technology to form a P-type groove 9. The process conditions are: Cl2 The flow rate is 10sccm, the pressure is 5mTorr, and the power is 50W.

[0076] Step 6. Make a P-type modulation layer 5, such as Figure 3 (f).

[0077] A fourth mask is made on the graded contact layer 3 and the high-K tunneling layer 4. The mask is used to sputter a P-type NiO material in the P-type groove 9 using a low-temperature sputtering technique to form a P-type modulation layer 5. The process conditions are: vacuum degree 4.0×10 -4 Pa, RF power is 100W, O 2 The flow rates are 1 sccm and the Ar flow rate is 1 sccm respectively.

[0078] Step 7. Prepare cathode 7, such as Figure 3 (g).

[0079] A mask is made for the fifth time on the back of the substrate 1, and the mask is used to deposit metal on the back of the substrate 1 using electron beam evaporation technology. The deposited metal is a combination of Ti / Au / Ni metals, that is, Ti, Au and Ni from bottom to top, with thicknesses of 0.02μm, 0.3μm and 0.05μm, respectively. The process conditions of electron beam evaporation are: vacuum degree of 1.8×10 -3 Pa, the power is 350W, and the evaporation rate is

[0080] The deposited metal is then rapidly thermally annealed to form a cathode 7, wherein the thermal annealing process conditions are: temperature of 850° C. and time of 35 seconds.

[0081] Step 8. Make anode 8, such as Figure 3 (h).

[0082] The sixth mask is made on the graded contact layer 3, the high-K tunneling layer 4 and the P-type modulation layer 5. The mask is used to deposit metal on the graded tunneling layer 4 and the modulation layer 7 by electron beam evaporation technology. The deposited metal is Ni with a thickness of 0.207 μm. The process conditions are: vacuum degree 5×10 -4 Pa, the power is 200W, and the evaporation rate is The anode 8 is formed to complete the fabrication of the entire device.

[0083] Example 3: Making the High-K Tunneling Layer 4 Ta 2 O 5 Materials, the P-type modulation layer 5 is a P-type GaN material, the tunnel hole 8 is composed of 13 holes of the same size, each tunnel hole has a width a of 0.4 μm, the P-type groove 9 is composed of 9 grooves of the same size, and the width m of each P-type groove is 0.2 μm, which is a field-modulated Schottky diode.

[0084] Step A. Prepare the drift layer 2, such as Figure 3 (a).

[0085] Set the vacuum degree to 1.0×10 -10 mbar, the RF power is 400W, and the reactant is N 2 , the process conditions of high-purity Ga source, using molecular beam epitaxy technology on substrate 1 with an epitaxial thickness of 12μm and a doping concentration of 1×10 16 cm -3 n - type GaN, forming the drift layer 2.

[0086] Step B. Making a gradient contact layer 3, such as Figure 3 (b).

[0087] The process conditions are set to 900°C, 80 Torr, 4800 sccm hydrogen flow, 4900 sccm ammonia flow, 150 μmol / min gallium source flow, and 50 μmol / min aluminum source flow. AlGaN material is epitaxially grown on the drift layer 2 using metal organic chemical vapor deposition technology to form a gradient contact layer 3.

[0088] Step C. Making tunnel hole 8, such as Figure 3 (c).

[0089] Setting Cl 2 Under the process conditions of flow rate of 60 sccm, pressure of 100 mTorr and power of 500 W, a mask is first made on the graded contact layer 3, and a groove is etched on the graded contact layer 3 using reactive ion etching technology using the mask to etch a tunnel hole 8 with a width of 0.4 μm.

[0090] Step D. Fabricate a high-K tunneling layer 4, such as Figure 3 (d).

[0091] The sputtering pressure in the reaction chamber was set to 300 Pa, O 2 Under the process conditions of Ar flow rate of 50sccm and 100sccm respectively and temperature of 900°C, a mask is made on the graded contact layer 3 for the second time, and Ta is deposited in the tunnel hole 8 by using the mask using radio frequency magnetron reactive sputtering technology. 2 O 5 , forming a high-K tunneling layer 4.

[0092] Step E. Make a P-type groove 9, such as Figure 3 (e).

[0093] Setting Cl 2Under the process conditions of flow rate of 10 sccm, pressure of 5 mTorr and power of 50 W, a mask is made on the gradient contact layer 3 and the high-K tunneling layer 4 for the third time. The high-K tunneling layer 4 is etched with a width of 0.2 μm using the mask using reactive ion etching technology to form a P-type groove 9.

[0094] Step F. Make a P-type modulation layer 5, such as Figure 3 (f).

[0095] A mask is made for the fourth time on the gradient contact layer 3 and the high-K tunneling layer 4, and the process conditions are set to 900°C, 80 Torr, 4800 sccm of hydrogen, 4900 sccm of ammonia, 150 μmol / min of gallium source flow, and 50 μmol / min of aluminum source flow. The mask is used to epitaxially grow GaN material on the P-type groove 9 using metal organic chemical vapor deposition technology to form a P-type modulation layer 5.

[0096] Step G. Prepare cathode 7, such as Figure 3 (g).

[0097] The fifth mask is made on the back of the substrate 1, and the vacuum degree is less than 1.8×10 -3 Pa, the power is 500W, and the evaporation rate is Under the process conditions of , the mask is used to deposit metal on the back of the substrate 1 by electron beam evaporation technology, wherein the deposited metal is a combination of Ti / Al / Mo / Au metals, that is, Ti, Al, Mo and Au from bottom to top, and their thicknesses are 0.02μm, 0.1μm, 0.03μm and 0.03μm respectively;

[0098] Under the conditions of a temperature of 860° C. and a time of 30 seconds, a rapid thermal annealing is performed on the sample deposited with the Ti / Al / Mo / Au composite metal to form a cathode 7 .

[0099] Step H. Make anode 8, such as Figure 3 (h).

[0100] The sixth mask is made on the graded contact layer 3, the high-K tunneling layer 4 and the P-type modulation layer 5, and the vacuum degree is set to 1.8×10 -3 Pa, the power is 1000W, and the evaporation rate is Under the process conditions, the mask is used to use electron beam evaporation technology to deposit metal Mo on the gradient contact layer 3, the high-K tunneling layer 4 and the P-type modulation layer 5 to form the anode 8, thereby completing the production of the entire device.

[0101] The effect of the present invention can be further illustrated by the following simulation results.

[0102] Simulation 1: Using the simulation software Silvaco, the forward conduction characteristics of the conventional vertical GaN Schottky diode with terminal protection and the device of the first embodiment of the present invention are simulated respectively. The results are as follows: Figure 4 As shown. Figure 4 It can be seen that the turn-on voltage of the device of the present invention is 0.27 V, and the turn-on voltage of the conventional vertical gallium nitride Schottky diode with terminal protection is 0.7 V. This indicates that the device of the present invention can significantly increase the on-state current and significantly reduce the on-state resistance.

[0103] Simulation 2: Using the simulation software Silvaco, the breakdown characteristics of the conventional vertical GaN Schottky diode with terminal protection and the device of the first embodiment of the present invention are simulated. The results are as follows: Figure 5 As shown. Figure 5 It can be seen that the breakdown voltage of the device of the present invention is about 1390V, the breakdown voltage of the traditional junction barrier Schottky diode is about 850V, and the breakdown voltage of the device of the present invention is 540V higher than the breakdown voltage of the traditional device, indicating that the device of the present invention has better voltage resistance than the traditional device.

[0104] The above descriptions are only three specific embodiments of the present invention and do not constitute a limitation of the present invention. Obviously, for professionals in this field, after understanding the content and principles of the present invention, they can make various modifications and changes in form and details according to the method of the present invention without departing from the principles and scope of the present invention. For example, in addition to using metal organic chemical vapor deposition technology and molecular beam epitaxy technology to prepare AlGaN and GaN materials, hydride vapor phase epitaxy technology and atomic layer deposition technology can also be used; in addition to using radio frequency magnetron reactive sputtering technology to prepare high-K tunneling layers, atomic layer deposition technology and plasma enhanced chemical vapor deposition technology can also be used; in addition to using Ta to prepare high-K tunneling layers 2 O 5 、TiO 2 , HfO 2 In addition to the medium, ZrO 2 Medium; molecular beam epitaxy technology uses a pressure of 1.0×10 - 10 mbar, the RF power is 400W, and the pressure can also be 1.0×10 -10 ~7.0×10 -10 mbar, and other process parameters within the range of RF power of 100 to 800 W, but these modifications and changes based on the present invention are still within the scope of protection of the claims of the present invention.

Claims

1. A field-modulated Schottky diode, comprising: A substrate (1), a drift layer (2), an anode (6), and a cathode (7), characterized in that: A gradient contact layer (3) is arranged above the drift layer (2), 2n-1 rectangular tunnel holes (8) of unequal intervals and the same size are arranged in the middle of the gradient contact layer (3), a high-K tunnel layer (4) is arranged in the tunnel hole (8), and n is the number of tunnel holes from the edge to the center; A P-type groove (9) of the same size is provided in the middle of the high-K tunneling layer (4), a P-type modulation layer (5) is provided in the P-type groove (9), and the P-type modulation layer and the high-K tunneling layer (4) form a field modulation junction (10); The anode (6) covers the upper surfaces of the gradient contact layer (3), the high-K tunneling layer (4) and the P-type modulation layer (5), and forms a Schottky contact with the gradient contact layer (3).

2. The device according to claim 1, characterized in that: The substrate (1) is made of gallium nitride material; The gradient contact layer (3) is made of AlGaN material whose Al component increases gradually from bottom to top, and the Al component x satisfies 5%≤x≤60%. When the device is forward-conducted, it forms an AlGaN / GaN heterojunction structure with the drift layer (2), polarizes a three-dimensional electron gas, increases the forward conduction current density of the device, and can increase the current during the turn-on process by improving the tunneling probability of carriers, thereby reducing the forward turn-on voltage of the device; when the device is reverse-blocked, it is beneficial to increase the barrier layer height of the Schottky junction and reduce the reverse leakage current.

3. The device according to claim 1, characterized in that: The high-K tunneling layer (4) is made of any one of Ta2O5, ZrO2, HfO2 and TiO2, a high-K dielectric material with a dielectric constant greater than that of AlGaN material, and is used to increase the tunneling probability of carriers, increase the forward conduction current and reduce the turn-on voltage; The P-type modulation layer (5) is made of one of P-type NiO and P-type GaN materials, and the hole concentration is 1×10 18 ~8×10 20 cm -3 , which is used to weaken the electric field at the edge of the device and improve the uniformity of the surface electric field distribution, thereby reducing the reverse leakage current of the device and increasing the breakdown voltage of the device.

4. The device according to claim 1, characterized in that: The tunnel hole (8) is composed of 2n-1 holes of the same size and is bilaterally symmetrical with the middle nth hole as the center. The width a of each tunnel hole is 0.5-0.8 μm, and the distance between two adjacent tunnel holes is r. n , the tunnel hole spacing increases from the left and right sides to the middle, that is, r1 <r2<r3<r4<···<r n ; The P-type groove (9) is composed of 2n-1 grooves of the same size, the width m of each P-type groove is 0.2-0.6 μm, and meets 0 <m<a。 5. The device according to claim 1, characterized in that: The high-K tunneling layer (4) and the gradient contact layer (3) are staggeredly distributed, and the difference in dielectric constants between two adjacent materials is utilized to promote the generation of a new electric field peak at the interface, thereby reducing the potential barrier width at the interface between the high-K tunneling layer (4) and the gradient contact layer (3), improving the probability of electron forward tunneling, increasing the forward conduction current, and reducing the turn-on voltage.

6. A method for manufacturing a field-modulated Schottky diode, comprising the following steps: S1) epitaxially growing an n-type gallium nitride semiconductor material on a substrate (1) to form a drift layer (2); S2) epitaxially growing an AlGaN semiconductor material whose Al component gradually increases from bottom to top on the drift layer (2) to form a graded contact layer (3); S3) making a mask on the gradient contact layer (3) for the first time, and using the mask to etch on the gradient contact layer (3) to form a tunnel hole (8); S4) making a mask for the second time on the graded contact layer (3), and using the mask to deposit a high-K dielectric in the tunnel hole (8), so as to form a high-K tunnel layer (4) staggered with the graded contact layer (3); S5) forming a mask for the third time on the graded contact layer (3) and the high-K tunneling layer (4), and using the mask to etch the high-K tunneling layer (4) to form a P-type groove (9); S6) forming a mask for the fourth time on the graded contact layer (3) and the high-K tunneling layer (4), and using the mask to deposit a P-type semiconductor material in the P-type groove (9) to form a P-type modulation layer (5); S7) making a mask for the fifth time on the back of the substrate (1), using the mask to deposit metal on the back of the substrate (1), and performing rapid thermal annealing to form a cathode (7); S8) A mask is fabricated for the sixth time on the graded contact layer (3), the high-K tunneling layer (4) and the P-type modulation layer (5), and metal is deposited using the mask to form an anode (8), thereby completing the fabrication of the entire device.

7. The method according to claim 6, characterized in that: The tunnel hole in step S3) and the P-type groove in step S5) are both made by reactive ion etching technology, and the process conditions are as follows: Cl2 flow rate is 10~60sccm, The pressure is 5~100mTorr, The power is 50~500W.

8. The method according to claim 6, characterized in that: The step S1) epitaxially grows n - The step S2) of epitaxially growing AlGaN semiconductor material is performed by metal organic chemical vapor deposition technology or molecular beam epitaxy technology, wherein: The process conditions of the metal organic chemical vapor deposition technology are as follows: The temperature is 800-1000°C, the pressure is 30-100 Torr, and the hydrogen flow rate is 4000-6000 sccm. The ammonia flow rate is 3500-5500 sccm, and the gallium source flow rate is 100-300 μmol / min. The aluminum source flow rate is 5-50 μmol / min; The molecular beam epitaxy technology has the following process conditions: The pressure is 1.0×10 -10 ~7.0×10 -10 mbar, RF power is 100~800W, The reactants are N2 and a high-purity Ga source.

9. The method according to claim 6, characterized in that: The high-K tunneling layer in step S4) and the NiO semiconductor material in step S6) are both prepared by radio frequency magnetron reactive sputtering technology, and the process conditions are as follows: The sputtering gas pressure in the reaction chamber is about 0.1 to 300 Pa. O2 flow rate is 1~50sccm, Ar flow rate is 1~100sccm, The temperature is 100~600℃.

10. The method according to claim 6, characterized in that: The cathode in step S7) and the anode in step S8) are both made by electron beam evaporation process to deposit metal, and the process conditions are as follows: The vacuum degree is 5×10 -4 ~1.8×10 -3 Pa, The power is 200~1000W, and the evaporation rate is less than The rapid thermal annealing process conditions are: temperature of 800-900° C. and time of 30-75 seconds.

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