Diamond Schottky diode with composite anode structure and preparation method thereof

Abstract

The invention discloses a diamond Schottky diode with a composite anode structure and a preparation method of the diamond Schottky diode. The Schottky diode comprises an ohmic electrode, a 100-crystal-orientation p-type heavily-doped monocrystal diamond substrate, an unintentionally-doped diamond layer, a phosphorus-doped diamond layer, a high-conductivity layer and a Schottky electrode, the unintentional doped diamond layer is etched into a slope structure, the phosphorus-doped diamond layer is arranged in an etching area, and the high-conductivity layer is arranged on the surface of the phosphorus-doped diamond layer, so that the surface of the high-conductivity layer and the surface of the unintentional doped diamond layer are alternately arranged, and low-barrier Schottky junctions and high-barrier pn junctions which are alternately arranged are introduced into an anode; because the barrier heights of the pn junction and the Schottky junction are different, the low-barrier Schottky junction is used for leading in forward conduction, and the conduction resistance is low; and during reverse turn-off, the high-barrier pn junction is used for leading, and the reverse breakdown voltage is high. According to the preparation method, two times of self-alignment are introduced, unmasked region etching is isolated from phosphorus-doped diamond layer growth and Schottky electrode self-mask etching, and the process complexity is reduced.

Description

TECHNICAL FIELD

[0001] The application relates to a composite anode structure diamond Schottky diode and a preparation method thereof, and belongs to the technical field of power devices. BACKGROUND

[0002] Schottky diodes play a key role in many fields, and are widely studied due to their fast recovery characteristics, low forward voltage drop and simple structure. Diamond has the characteristics of super-wide band gap (5.5 eV), high thermal conductivity, high intrinsic mobility, high breakdown field, high saturation velocity and low dielectric constant, and is an ideal choice for making Schottky diodes. Due to the difficulty of n-type doping of diamond, the current diamond Schottky diode is mainly p-type diamond.

[0003] The conventional vertical structure p-type diamond Schottky diode faces the contradiction that the on-resistance and the reverse withstand voltage are difficult to balance. In order to improve the withstand voltage of the device, a method combining a low work function metal and a field plate structure and an edge junction termination technology is often used, which effectively improves the breakdown voltage of the device, but has no improvement on the forward on-resistance. In order to reduce the forward on-resistance, a high work function is required, and the high work function metal means that the Schottky barrier height is small, which makes the leakage current too large and the breakdown voltage too small. Therefore, a double-barrier composite anode structure can be considered to balance the forward on-resistance and the reverse withstand voltage.

[0004] The current double-barrier composite anode structure mainly relies on changing the surface termination type to realize the change of the barrier height when the metal is in contact with the diamond surface. However, the diamond surface termination has a strong Fermi pinning effect, so the change of the barrier height is limited, and the balancing effect on the device performance is poor. Considering that the barrier height of the pn junction is much higher than that of the Schottky junction, and the withstand voltage of the pn junction is higher than that of the Schottky junction, the pn junction barrier and the Schottky junction barrier can be combined to realize the composite anode structure Schottky diode. For diamond, the n-type phosphorus doping concentration is low, so it is necessary to improve the phosphorus doping concentration to ensure the reverse shielding of the pn junction barrier to the Schottky junction barrier. SUMMARY

[0005] In order to solve the above problems, the application provides a composite anode structure diamond Schottky diode and a preparation method thereof. The application provides a composite anode structure diamond Schottky diode composed of high-pn junction barriers and low Schottky junction barriers. Due to the different barrier heights of the pn junction and the Schottky junction, the current preferentially flows in the low-barrier Schottky junction in the forward direction, so that the turn-on voltage and the on-resistance are low. When the reverse bias is applied, the depletion region of the high-barrier pn junction is wide, shielding the depletion region of the Schottky junction, so that the breakdown voltage is high.

[0006] The first object of the present application is to provide a preparation method of a composite anode structure diamond Schottky diode, comprising the following steps:

[0007] Step one, growing an unintentionally doped diamond layer on a 100 crystal direction p-type heavily doped single crystal diamond substrate;

[0008] Step two, treating the surface of the unintentionally doped diamond layer into an oxygen terminal to form an anode metal mask array;

[0009] Step three, etching the unmasked area into a slope mesa to grow a phosphorus doped diamond layer;

[0010] Step four, removing the anode metal mask array and depositing an ohmic electrode under the 100 crystal direction p-type heavily doped single crystal diamond substrate;

[0011] Step five, annealing the sample at high temperature to form a high-conductivity layer on the surface of the phosphorus doped diamond layer;

[0012] Step six, forming a Schottky electrode on the alternately arranged high-conductivity layer and unintentionally doped diamond layer and performing self-aligned etching isolation to obtain a Schottky diode.

[0013] In an embodiment of the present application, the doping element of the 100 crystal direction p-type heavily doped single crystal diamond substrate is boron, and the doping concentration is greater than 10 19 cm -3 , and the thickness is 50-1000 μm.

[0014] In an embodiment of the present application, the unintentionally doped diamond layer is realized by epitaxial growth through MPCVD technology, wherein the growth pressure is 90-120 Torr, the methane flow is 5-40 sccm, the hydrogen flow is 400-500 sccm, the temperature is 800-950 ℃, and the thickness is 500-2000 nm.

[0015] In an embodiment of the present application, in step two, the hydrogen terminal surface of the unintentionally doped diamond layer is converted into an oxygen terminal through ultraviolet ozone treatment or oxygen plasma treatment; the anode metal mask adopts high-melting-point Ti and W metals and does not chemically react with methane plasma; the width of the anode metal mask array is 1-3 μm, and the pitch is 2-6 μm.

[0016] In an embodiment of the present application, in step three, the unmasked area is plasma etched to form a slope, the etching depth is 100-1500 nm, and the etching depth is less than the thickness of the unintentionally doped diamond layer, and the slope angle is 30-60°.

[0017] In an embodiment of the present application, the phosphorus-doped diamond layer is epitaxially grown by MPCVD technology, wherein the growth pressure is 90-120 Torr, the methane flow rate is 1-20 sccm, the phosphine flow rate is 40-100 sccm, the hydrogen flow rate is 400-450 sccm, the temperature is 1050-1150 ℃, and the doping concentration is greater than 10 18 cm -3 , and the thickness is 20-80 nm.

[0018] In an embodiment of the present application, in step four, the anode mask metal array is removed by high-temperature etching with a sulfuric acid / nitric acid mixed solution; and the ohmic electrode is deposited under the 100 crystal direction p-type heavily doped single crystal diamond substrate to form a vertical structure diode, and the ohmic electrode is made of one of Ti, Pt, and Ni, and has a thickness of 100-200 nm.

[0019] In an embodiment of the present application, in step five, the high-conductivity layer is formed on the surface of the phosphorus-doped diamond layer by high-temperature annealing, and the surface of the unintentionally doped diamond layer is not formed with the high-conductivity layer; the annealing temperature is greater than 900 ℃, and the annealing time is greater than 2 min.

[0020] In an embodiment of the present application, in step six, the Schottky electrode is a high work function metal of Ni, Au, and Pt, which covers the surfaces of the high-conductivity layer array and the unintentionally doped diamond layer arranged alternately, and is used as a self-aligned mask to realize device isolation by ICP etching.

[0021] A second object of the present application is to provide a composite anode structure diamond Schottky diode prepared by the preparation method, which comprises, from bottom to top, an ohmic electrode, a 100 crystal direction p-type heavily doped single crystal diamond substrate, an unintentionally doped diamond layer, a phosphorus-doped diamond layer, a high-conductivity layer, and a Schottky electrode; wherein the unintentionally doped diamond layer is etched into a slope structure, the phosphorus-doped diamond layer is arranged in the etched region, the high-conductivity layer is arranged on the surface of the phosphorus-doped diamond layer, and the Schottky electrode covers the surfaces of the high-conductivity layer array and the unintentionally doped diamond layer arranged alternately.

[0022] The present application has the following advantages:

[0023] (1) The diode of the present application is composed of an anode of an array of low-barrier Schottky junctions and an array of high-barrier pn junctions arranged alternately, and because the barrier heights of the pn junctions and the Schottky junctions are different, the low-barrier Schottky junctions are dominant in forward conduction, and the high-barrier pn junctions are dominant in reverse blocking, so that the diode has low forward conduction resistance and high reverse breakdown voltage.

[0024] (2) The present application utilizes an anode metal mask to perform self-aligned etching and growth of the phosphorus-doped diamond layer, which can reduce the process complexity, and the slope structure design can effectively improve the phosphorus doping concentration and effectively improve the pn junction barrier height;

[0025] (3) The phosphorus-doped diamond layer of the present application has similar insulating properties as intrinsic diamond, and the pn junction formed thereby has high withstand voltage, which reduces the variation range of the breakdown voltage caused by the thickness reduction of the unintentionally doped diamond layer after etching, and maintains a high breakdown voltage;

[0026] (4) The present application utilizes high-temperature annealing to form a high-conductivity layer on the surface of the phosphorus-doped diamond layer, which is conducive to forming a good pn junction metal contact and reducing the on-resistance;

[0027] (5) The present application utilizes a Schottky electrode to perform self-aligned device isolation etching, which can reduce the process cost and reduce the interface state of the metal / unintentionally doped diamond layer during etching, further reducing the on-resistance; after etching, it is also conducive to optimizing the electric field distribution of the device and improving the breakdown voltage. BRIEF DESCRIPTION OF DRAWINGS

[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and those skilled in the art can obtain the remaining drawings according to these drawings without creative labor.

[0029] Figure 1 It is a cross-sectional structure diagram of the composite anode structure diamond Schottky diode of the present application.

[0030] Figure 2 It is a comparison diagram of the forward conduction characteristics of the improved SBD of embodiment 3 of the present application and the traditional SBD of the comparative example.

[0031] Figure 3 It is a comparison diagram of the reverse withstand voltage characteristics of the improved SBD of embodiment 3 of the present application and the traditional SBD of the comparative example.

[0032] In the figure: 1, 100 crystal direction p-type heavily doped single crystal diamond substrate; 2, unintentionally doped diamond layer; 3, phosphorus-doped diamond layer; 4, ohmic electrode; 5, high-conductivity layer; 6, Schottky electrode. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. The terms "first position" and "second position" refer to two different positions.

[0035] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections or detachable connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal connections between two components. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0036] Example 1

[0037] like Figure 1 As shown, this embodiment provides a method for fabricating a composite anode structure diamond Schottky diode, including the following steps:

[0038] Step 1: Grow an unintentionally doped diamond layer 2 on a 100-oriented p-type heavily doped single-crystal diamond substrate 1;

[0039] Step 2: Treat the surface of the unintentionally doped diamond layer 2 to form an oxygen terminal, thereby forming an anode metal mask array;

[0040] Step 3: Etch the unmasked area into a sloping platform and grow a phosphorus-doped diamond layer 3;

[0041] Step 4: Remove the anode metal mask array and deposit an ohmic electrode 4 under the 100-oriented p-type heavily doped single crystal diamond substrate 1.

[0042] Step 5: Perform high-temperature annealing on the sample to form a highly conductive layer 5 on the surface of the phosphorus-doped diamond layer 3;

[0043] Step six, forming Schottky electrode 6 on the high-conductivity layer 5 and the unintentionally doped diamond layer 2 in alternate arrangement, and performing self-aligned etching isolation to obtain a Schottky diode.

[0044] Optionally, the shape of the crystal direction p-type heavily doped single crystal diamond substrate 1 is not limited, the doping element is boron, the doping concentration is greater than 10 19 cm -3 , and the thickness is 50-1000μm.

[0045] Optionally, the unintentionally doped diamond layer 2 is realized by epitaxial growth through MPCVD technology, wherein the growth pressure is 90-120Torr, the methane flow is 5-40sccm, the hydrogen flow is 400-500sccm, the temperature is 800-950℃, and the thickness is 500-2000nm.

[0046] Optionally, in step two, the hydrogen-terminated surface of the unintentionally doped diamond layer 2 is converted into an oxygen-terminated surface through ultraviolet ozone treatment or oxygen plasma treatment.

[0047] Optionally, in step two, the anode metal mask adopts a metal with high melting point and stable chemical properties in a methane plasma atmosphere, such as Ti, W, etc., to avoid affecting the subsequent etching and phosphorus-doped diamond layer 3 growth process; the width of the anode metal mask array is 1-3μm, and the pitch is 2-6μm, to realize a good high-low barrier composite structure.

[0048] Optionally, in step three, the unmasked area is subjected to plasma etching to form a slope, the etching depth is 100-1500nm, and the etching depth is less than the thickness of the unintentionally doped diamond layer 2, and the slope angle is 30-60°, to realize the growth of the high-concentration phosphorus-doped diamond layer 3.

[0049] Optionally, the phosphorus-doped diamond layer 3 is realized by epitaxial growth through MPCVD technology, wherein the growth pressure is 90-120Torr, the methane flow is 1-20sccm, the phosphine flow is 40-100sccm, the hydrogen flow is 400-450sccm, the temperature is 1050-1150℃, the doping concentration is greater than 10 18 cm -3 , and the thickness is 20-80nm.

[0050] Optionally, in step four, the anode mask metal array is removed by high-temperature etching with a sulfuric acid / nitric acid mixed solution.

[0051] Optionally, in the step four, the ohmic electrode 4 is deposited under the 100 crystal direction p-type heavily doped single crystal diamond substrate 1 to form a vertical structure diode, and the ohmic electrode 4 is made of one of Ti, Pt and Ni, and has a thickness of 100-200 nm.

[0052] Optionally, in the step five, high temperature annealing is performed on the sample, so that a good ohmic contact is formed, and a high-conductivity layer 5 is formed on the surface of the phosphorus-doped diamond layer 3 array, thereby serving as a metal electrode, while the high-conductivity layer 5 is not formed on the surface of the unintentionally doped diamond layer 2 array, thereby maintaining the intrinsic diamond insulating property; the annealing temperature is greater than 900 ℃, and the annealing time is greater than 2 min. Therefore, the high-conductivity layer 5 is formed only on the surface of the phosphorus-doped diamond layer 3 by high temperature annealing, while the surface of the unintentionally doped diamond layer 2 does not form the high-conductivity layer 5,

[0053] Optionally, in the step six, the Schottky electrode 6 is made of a high work function metal such as Ni, Au and Pt, so as to realize a lower Schottky barrier; the Schottky electrode 6 covers the surface of the array of the high-conductivity layer 5 and the unintentionally doped diamond layer 2 arranged alternately, and serves as a self-aligned mask to realize device isolation by ICP etching.

[0054] Embodiment 2

[0055] The embodiment provides a composite anode structure diamond Schottky diode prepared by the preparation method in Embodiment 1, and the Schottky diode comprises, from bottom to top, an ohmic electrode 4, a 100 crystal direction p-type heavily doped single crystal diamond substrate 1, an unintentionally doped diamond layer 2, a phosphorus-doped diamond layer 3, a high-conductivity layer 5 and a Schottky electrode 6; the unintentionally doped diamond layer 2 is etched into a slope structure, the phosphorus-doped diamond layer 3 is arranged in the etched region, the high-conductivity layer 5 is arranged on the surface of the phosphorus-doped diamond layer 3, and the Schottky electrode 6 covers the surface of the array of the high-conductivity layer 5 and the unintentionally doped diamond layer 2 arranged alternately.

[0056] Embodiment 3

[0057] The embodiment provides a preparation method of a composite anode structure diamond Schottky diode, which comprises the following steps:

[0058] (1) a 100 crystal direction p-type heavily boron-doped single crystal diamond substrate with a doping concentration of 3×10 19 cm -3、 The thickness of the 100 crystal direction p-type heavily boron-doped single crystal diamond substrate is 100 μm, and the substrate is sequentially subjected to ultrasonic cleaning with acetone, anhydrous ethanol and deionized water for 10 min, and is subjected to nitrogen blowing for 20 s, and then is placed in an MPCVD device to grow an unintentionally doped diamond layer with a thickness of 500 nm on the front surface, wherein the growth pressure is 90 Torr, the methane flow rate is 5 sccm, the hydrogen flow rate is 480 sccm, and the temperature is 800 ℃.

[0059] (2) UV-ozone treatment was used to convert the surface hydrogen termination of the unintentionally doped diamond layer to oxygen termination, and photolithography was used to obtain 30 rectangular patterns with a length of 100 μm, a width of 1 μm, and a pitch of 2 μm. Then, 100 nm of metal W was deposited by magnetron sputtering, and after stripping, an anode metal mask array was obtained;

[0060] (3) The unmasked area was etched by 200 nm using an ICP device to form a slope structure with a slope of 60°. Then, a 20 nm thick phosphorus-doped diamond layer with a doping concentration of 2×10 18 cm -3 was grown in the unmasked area using an MPCVD device at a growth pressure of 100 Torr, a methane flow rate of 1 sccm, a phosphine flow rate of 40 sccm, a hydrogen flow rate of 450 sccm, and a temperature of 1150℃.

[0061] (4) The anode metal mask array was removed by heating a mixed acid solution of sulfuric acid and nitric acid (1:1) at 300℃ for 2h to form a structure in which the surface of the phosphorus-doped diamond layer alternates with the surface of the unintentionally doped diamond layer. Then, a 200 nm thick metal titanium layer was deposited on the back of the substrate as an ohmic electrode;

[0062] (5) The sample was placed in a rapid annealing device and annealed at 1000℃ for 5 min to form a high-conductivity layer on the surface of the phosphorus-doped diamond layer array and to form a good ohmic contact between the ohmic electrode and the heavily doped p-type single crystal diamond substrate;

[0063] (6) A Schottky electrode pattern with a length of 100 μm and a width of 110 μm was photolithographed on the surface of the high-conductivity layer and the unintentionally doped diamond layer. Then, 100 nm of metal Pt was deposited by magnetron sputtering, and after stripping, the sample was etched by 500 nm in an ICP etching device to finally obtain a Schottky diode.

[0064] Example 4

[0065] The present embodiment provides a method for preparing a composite anode structure diamond Schottky diode, comprising:

[0066] (1) A 100 crystal p-type heavily boron-doped single crystal diamond substrate with a doping concentration of 1×10 20 cm -3 and a thickness of 500 μm was ultrasonically cleaned with acetone, anhydrous ethanol, and deionized water for 10 min, and then was blown with nitrogen for 20 s. Then, a 1000 nm thick unintentionally doped diamond layer was grown on the front surface of the substrate in an MPCVD device at a growth pressure of 100 Torr, a methane flow rate of 15 sccm, a hydrogen flow rate of 480 sccm, and a temperature of 850℃;

[0067] (2) UV-ozone treatment is used to change the surface hydrogen termination of the unintentionally doped diamond layer to oxygen termination, photolithography is used to obtain 30 rectangular patterns with a length of 150 μm, a width of 2 μm and a pitch of 3 μm, and 100 nm of metal W is deposited by magnetron sputtering, and after stripping, an anode metal mask array is obtained;

[0068] (3) The unmasked area is etched by 600 nm by using an ICP device, a slope structure with a slope of 45° is formed, and then a 50 nm thick phosphorus doped diamond layer with a doping concentration of 5×10 18 cm -3 -6 is grown on the unmasked area by using an MPCVD device, the growth pressure is 110 Torr, the methane flow rate is 1 sccm, the phosphine flow rate is 60 sccm, the hydrogen flow rate is 450 sccm, and the temperature is 1100°C.

[0069] (4) The anode metal mask array is removed by using a mixed acid solution of sulfuric acid and nitric acid (1:1) at 300°C for 2 h to form a structure in which the surface of the phosphorus doped diamond layer and the surface of the unintentionally doped diamond layer are arranged alternately, and then a 200 nm thick metal titanium layer is deposited on the back of the substrate as an ohmic electrode;

[0070] (5) The sample is placed in a rapid annealing device and annealed at 1100°C for 3 min to form a high-conductivity layer on the surface of the phosphorus doped diamond layer array and to form a good ohmic contact between the ohmic electrode and the heavily doped single crystal diamond substrate;

[0071] (6) A Schottky electrode pattern with a length of 160 μm and a width of 160 μm is formed on the surface of the high-conductivity layer and the unintentionally doped diamond layer by photolithography, 200 nm of metal Ni is deposited by magnetron sputtering, and after stripping, the sample is etched by 1000 nm in an ICP etching device to finally obtain a Schottky diode.

[0072] Example 5

[0073] The embodiment provides a preparation method of a composite anode structure diamond Schottky diode, which comprises the following steps:

[0074] (1) A 100 crystal direction p-type heavily boron doped single crystal diamond substrate with a doping concentration of 1×10 20 cm -3 -6 and a thickness of 1000 μm is ultrasonically cleaned with acetone, anhydrous ethanol and deionized water for 10 min, and then is blown with nitrogen for 20 s, and then is placed in an MPCVD device to grow a 1900 nm thick unintentionally doped diamond layer on the front surface, the growth pressure is 120 Torr, the methane flow rate is 20 sccm, the hydrogen flow rate is 480 sccm, and the temperature is 950°C;

[0075] (2) UV-ozone treatment was used to change the surface hydrogen termination of the unintentionally doped diamond layer to oxygen termination. A 30-rectangle pattern with length of 180 μm, width of 2 μm and interval of 4 μm was obtained by lithography. Then, 200 nm of Ti was deposited by magnetron sputtering. After stripping, the anode metal mask array was obtained.

[0076] (3) The unmasked area was etched by ICP equipment for 1200 nm to form a slope structure with a slope of 30°. Then, a 80 nm thick phosphorus-doped diamond layer with a doping concentration of 5×10 18 cm -3 was grown on the unmasked area by MPCVD equipment. The growth pressure was 110 Torr, the methane flow rate was 1 sccm, the phosphine flow rate was 60 sccm, the hydrogen flow rate was 450 sccm, and the temperature was 1100 °C.

[0077] (4) The anode metal mask array was removed by heating a mixed acid solution of sulfuric acid and nitric acid (1:1) at 300 °C for 2 h to form a structure in which the surface of the phosphorus-doped diamond layer and the surface of the unintentionally doped diamond layer were arranged alternately. Then, a 200 nm thick titanium metal layer was deposited on the back of the substrate as an ohmic electrode.

[0078] (5) The sample was placed in a rapid annealing device and annealed at 950 °C for 10 min to form a high-conductivity layer on the surface of the phosphorus-doped diamond layer array and to form a good ohmic contact between the ohmic electrode and the heavily doped single crystal diamond substrate.

[0079] (6) A Schottky electrode pattern with a length of 200 μm and a width of 200 μm was formed on the surface of the high-conductivity layer and the unintentionally doped diamond layer by lithography. Then, 200 nm of Au was deposited by magnetron sputtering. After stripping, the sample was etched by ICP for 1500 nm to obtain a Schottky diode.

[0080] Comparative Example

[0081] The difference between the comparative example and Example 3 is that the comparative example is a traditional vertical structure diamond Schottky diode, which comprises, from bottom to top, an ohmic electrode, a 100 heavily doped single crystal diamond substrate, an unintentionally doped diamond layer, and a Schottky electrode. The preparation method is to grow an unintentionally doped diamond layer on the surface of the heavily doped single crystal diamond substrate, and then to treat the surface into an oxygen termination. Then, an ohmic electrode is prepared on the back of the heavily doped single crystal diamond substrate, and a Schottky electrode is prepared on the front of the heavily doped single crystal diamond substrate. It is a single-barrier device without the etching of the unintentionally doped diamond layer, the growth of the phosphorus-doped diamond layer, and the high-conductivity layer.

[0082] The performance of the diode of the comparative example and Example 3 is compared as follows: Figure 2 and Figure 3As shown, it can be seen that the improved SBD (Schottky barrier diode) of Example 3 has a higher reverse withstand voltage on the basis of losing certain conduction performance compared with the conventional SBD of the comparative example.

[0083] The detection process is as follows: the sample is placed on the sample stage of the Agilent B1505A test equipment, the voltage is introduced to the sample surface by the probe, and the current signal of the device is collected. As a result, the on-resistance of the composite anode structure diamond Schottky diode prepared by the application is 4.5 mΩ·cm 2 , and the breakdown voltage is 300 V; the on-resistance of the conventional vertical structure diamond Schottky diode is 1.2 mΩ·cm 2 , and the breakdown voltage is 190 V. The results show that the composite anode structure diamond Schottky diode of the application has a comparable on-resistance level to the conventional Schottky diode, and has a higher reverse withstand voltage.

[0084] In summary, the composite anode structure diamond Schottky diode and the preparation method thereof provided by the application, the Schottky diode comprises an ohmic electrode, a crystal direction p-type heavily doped single crystal diamond substrate, an unintentionally doped diamond layer, a phosphorus doped diamond layer, a high conductivity layer, and a Schottky electrode; wherein the unintentionally doped diamond layer is etched into a slope structure, the phosphorus doped diamond layer is arranged in the etched area, and the high conductivity layer is arranged on the surface of the phosphorus doped diamond layer, so as to realize the alternate arrangement of the high conductivity layer and the surface of the unintentionally doped diamond layer, thereby introducing the alternating low-barrier Schottky junction and high-barrier pn junction into the anode, and realizing the compromise of the forward on-resistance and the reverse breakdown voltage. The preparation method introduces two self-alignments, which are the unmasked area etching and the phosphorus doped diamond layer growth and the Schottky electrode self-masked etching isolation, thereby reducing the process complexity.

[0085] The principles and implementation manners of the application are described by using specific examples in the present application, and the above examples are only used to help understand the method of the application and its core idea. It should be pointed out that for ordinary skilled in the art, without departing from the principles of the application, the application can be improved and modified in several ways, and these improvements and modifications also fall within the protection scope of the claims of the application. Therefore, the protection scope of the application patent should be subject to the appended claims.

Claims

1. A method for fabricating a composite anode structure diamond Schottky diode, characterized in that, The method comprises the following steps: Step one, growing a non-intentionally doped diamond layer (2) on a 100 crystal orientation p-type heavily doped single crystal diamond substrate (1); Step two, treating the surface of the non-intentionally doped diamond layer (2) into an oxygen terminal to form an anode metal mask array; Step three, etching the unmasked area into a slope mesa to grow a phosphorus doped diamond layer (3); Step four, removing the anode metal mask array to deposit an ohmic electrode (4) under the 100 crystal orientation p-type heavily doped single crystal diamond substrate (1); Step five, annealing the sample at high temperature to form a high-conductivity layer (5) on the surface of the phosphorus doped diamond layer (3); Step six, forming a Schottky electrode (6) on the high-conductivity layer (5) and the non-intentionally doped diamond layer (2) arranged alternately and performing self-aligned etching isolation to obtain a Schottky diode.

2. The method of claim 1, wherein the method further comprises: The doping element of the 100 crystal direction p-type heavily doped monocrystalline diamond substrate (1) is boron, the doping concentration is greater than 10 19 cm -3 , and the thickness is 50-1000 μm.

3. The method of claim 1, wherein the method further comprises: The non-intentionally doped diamond layer (2) is realized by epitaxial growth through MPCVD technology, wherein the growth pressure is 90-120 Torr, the methane flow is 5-40 sccm, the hydrogen flow is 400-500 sccm, the temperature is 800-950℃, and the thickness is 500-2000 nm.

4. The method of claim 1, wherein the method further comprises: In step two, the hydrogen terminal surface of the non-intentionally doped diamond layer (2) is converted into an oxygen terminal through ultraviolet ozone treatment or oxygen plasma treatment; the anode metal mask adopts high-melting-point Ti and W metals and does not chemically react with the methane plasma; the width of the anode metal mask array is 1-3 μm, and the pitch is 2-6 μm.

5. The method of claim 1, wherein the method further comprises: In step three, the unmasked area is plasma etched to form a slope, the etching depth is 100-1500 nm, and the etching depth is less than the thickness of the non-intentionally doped diamond layer (2), and the slope angle is 30-60°.

6. The method of claim 1, wherein the method further comprises: The phosphorus-doped diamond layer (3) is realized by epitaxial growth through MPCVD technology, wherein the growth pressure is 90-120 Torr, the methane flow is 1-20 sccm, the phosphine flow is 40-100 sccm, the hydrogen flow is 400-450 sccm, the temperature is 1050-1150℃, and the doping concentration is greater than 10 18 cm -3 , and the thickness is 20-80nm.

7. The method of claim 1, wherein the method further comprises: In step four, the anode mask metal array is removed by high-temperature corrosion with a sulfuric acid / nitric acid mixed solution; the ohmic electrode (4) is deposited under the 100 crystal orientation p-type heavily doped single crystal diamond substrate (1) to form a vertical structure diode, and the material of the ohmic electrode (4) is one of Ti, Pt, and Ni, and the thickness is 100-200 nm.

8. The method of claim 1, wherein the diamond Schottky diode is a composite anode structure diamond Schottky diode. In step five, the high-conductivity layer (5) is formed only on the surface of the phosphorus doped diamond layer (3) by high-temperature annealing, and the non-intentionally doped diamond layer (2) surface will not form a high-conductivity layer (5); the annealing temperature is greater than 900℃, and the annealing time is greater than 2 min.

9. The method of claim 1, wherein the diamond Schottky diode is a composite anode structure diamond Schottky diode. In step six, the Schottky electrode (6) is a high work function metal of Ni, Au, and Pt, which covers the surface of the high-conductivity layer (5) array and the non-intentionally doped diamond layer (2) arranged alternately, and the Schottky electrode (6) is used as a self-aligned mask to realize device isolation by ICP etching.

10. The diamond Schottky diode of claim 1 to 9, wherein the composite anode structure is prepared by the method of any one of claims 1 to 9. The Schottky diode comprises, from bottom to top, an ohmic electrode (4), a 100 crystal direction p-type heavily doped monocrystalline diamond substrate (1), an unintentionally doped diamond layer (2), a phosphorus-doped diamond layer (3), a high-conductivity layer (5), and a Schottky electrode (6); wherein the unintentionally doped diamond layer (2) is etched into a slope structure, the phosphorus-doped diamond layer (3) is arranged in the etched area, the high-conductivity layer (5) is arranged on the surface of the phosphorus-doped diamond layer (3), and the Schottky electrode (6) covers the surface of the array of high-conductivity layers (5) and the unintentionally doped diamond layer (2) arranged alternately.

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