A gallium oxide micropillar array based on a schottky diode and a preparation method thereof

Abstract

The application discloses a gallium oxide micropillar array based on a Schottky diode and a preparation method thereof. The Schottky diode comprises, from bottom to top, a substrate layer, a gallium oxide layer and a Schottky array of gallium oxide micropillars. The gallium oxide layer is made of alpha-phase, kappa-phase, gamma-phase or beta-phase gallium oxide, and the gallium oxide micropillar is made of alpha-phase, kappa-phase, gamma-phase or beta-phase gallium oxide. The application combines HVPE and Mist CVD to quickly prepare the gallium oxide micropillar array and prepare high-quality gallium oxide array material, so as to realize the Schottky diode of the gallium oxide micropillar array with low opening voltage, fast switching speed and low energy loss. Compared with other methods of gallium oxide Schottky diode, the gallium oxide micropillar array prepared by the application is accurate and controllable in morphology, good in repeatability, high in efficiency and simple in manufacturing process, and can be effectively integrated and mass-produced.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor, in particular to a gallium oxide micropillar array based on Schottky diode and a preparation method thereof. BACKGROUND

[0002] At present, compared with Si, GaAs and other materials, the ultra-wide bandgap semiconductor gallium oxide (Ga2O3) material has advantages of wide bandgap, high electron saturation drift speed, high thermal conductivity, high breakdown electric field strength, high Baliga figure of merit, etc., and is the preferred material of advanced power electronic devices. In recent years, the performance of gallium oxide Schottky diode (Ga2O3 SBD) devices has been improved. In 2016, FLOSFIA company in Japan prepared a gallium oxide SBD device with a withstand voltage of 531V and an on-resistance of only 0.1mΩ·cm2; in 2017, the National Institute of Information and Communications Technology (NICT) in Japan used a field plate structure to reduce the peak electric field and prepared a vertical β-phase gallium oxide SBD device with a withstand voltage of 1076V, a breakdown voltage of 190V and a peak breakdown field strength of 5.9MV / cm, which is much higher than the theoretical value of the breakdown field strength of SiC (3.18MV / cm), which proves that gallium oxide material has the characteristics of high withstand voltage. In 2018, Cornell University used a groove structure to reduce the surface electric field and realized a 2440V vertical structure of β-phase gallium oxide SBD device, which is the highest level of vertical structure of gallium oxide SBD device reported so far. However, the breakdown voltage and on-state characteristics of the hetero-substrate gallium oxide SBD device studied at present are far lower than the expected value of the material.

[0003] The gallium oxide SBD device described above has the following disadvantages: 1. For gallium oxide material itself, especially for gallium oxide on a hetero-substrate, the dislocation density caused by the lattice mismatch between the gallium oxide and the substrate is as high as 10 10 cm -2 . Generally, dislocations are as carrier trapping centers and scattering centers, forming a path for conduction channel leakage, which seriously reduces the migration rate of carriers. 2. The interface state of the existing gallium oxide SBD device has a great influence on the leakage of the device, and the on-voltage is very high, which cannot meet the requirements of low on-voltage, fast switching speed and low energy loss, etc. SUMMARY

[0004] In order to solve the problems in the prior art, the application provides a gallium oxide micropillar array based on a Schottky diode and a preparation method thereof, which combines hydride vapor phase epitaxy (HVPE) and mist chemical vapor deposition (Mist CVD) to quickly prepare a Ga2O3 micropillar array, and prepare a high-quality gallium oxide array material, so as to realize a Schottky diode of the gallium oxide micropillar array with low opening voltage, fast switching speed and low energy loss. Compared with other methods of gallium oxide Schottky diodes, the gallium oxide micropillar array prepared by the application has precise and controllable morphology, good repeatability, high efficiency and simple manufacturing process, and can be effectively integrated and mass-produced.

[0005] The application adopts the following technical solutions to solve the above technical problems:

[0006] The application adopts the following technical solutions to solve the above technical problems:

[0007] A gallium oxide micropillar array based on a Schottky diode, the Schottky diode sequentially comprises a substrate layer, a gallium oxide layer and a Schottky array of gallium oxide micropillars from bottom to top; the Schottky array of gallium oxide micropillars comprises gallium oxide micropillars, a bottom electrode and a top electrode, the bottom electrode and the top electrode adopt a one-to-many structure; the gallium oxide layer is a flat film, the gallium oxide layer material is alpha-phase, kappa-phase, gamma-phase or beta-phase gallium oxide, and the gallium oxide micropillar material is alpha-phase, kappa-phase, gamma-phase or beta-phase gallium oxide.

[0008] Further, the gallium oxide micropillar has a hexagonal prism structure, the bottom surface is a hexagon, the top is an equilateral triangle with three top corners removed, and the side surface is composed of three hexagons, three downward pentagons and six upward pentagons; the gallium oxide micropillar has a pore size of 1-10 microns, a height of 50-10000 nanometers, and a micropillar spacing of 1-20 microns.

[0009] Further, the top electrode is a Schottky contact electrode arranged on the top of the gallium oxide micropillar, and the bottom electrode is two ohmic contact electrodes arranged on the bottom of the gallium oxide micropillar.

[0010] Further, the Schottky contact electrode is Ni / Au, the ohmic contact electrode is Ti / Au or Ti / Al / Ni / Au, and the electrode thickness is 10-500 nanometers.

[0011] Further, the gallium oxide layer has a thickness of 50-1000 nanometers.

[0012] Further, the substrate is an insulating or conductive substrate, such as a gallium oxide single crystal, a sapphire, a silicon, an ITO conductive glass substrate and the like.

[0013] The preparation method of the gallium oxide micropillar array based on Schottky diodes comprises the following steps:

[0014] (1) First, a gallium oxide layer is prepared on a substrate using Mist CVD. By adjusting the temperature, doping concentration and power of the atomizer during the Mist CVD process, gallium oxide with different crystal orientations and different doping concentrations is prepared;

[0015] (2) Then, a silicon dioxide layer is grown on the gallium oxide layer using PECVD or ALD technology;

[0016] (3) Based on integrated circuit process technology, a certain thickness of photoresist is applied on the silicon dioxide layer, a mask plate is covered on the photoresist, and exposure and development steps are performed;

[0017] (4) Using EUV lithography technology, the unprotected areas are etched to form patterns;

[0018] (5) Using RIE, ICP and other etching technologies, the patterns on the photoresist are transferred to the silicon dioxide layer, and the silicon dioxide layer is used as a pattern mask for the next preparation process;

[0019] (6) Then, the photoresist is washed away to obtain a silicon dioxide mask structure, and the substrate with patterns is placed in an HVPE chamber;

[0020] (7) By adjusting the growth temperature, growth time, ratio and pressure of oxygen and hydrogen chloride during the HVPE secondary epitaxial growth process, gallium oxide materials with the required crystal orientation are prepared;

[0021] (8) After washing away the silicon dioxide with HF, the gallium oxide micropillar array with the required crystal orientation is obtained;

[0022] (9) An ohmic contact electrode is deposited on the bottom plane of the obtained gallium oxide micropillar structure;

[0023] (10) A Schottky contact electrode is deposited on the top of the gallium oxide micropillar.

[0024] Further, in step (1), the Mist CVD preparation and growth of the high-doped gallium oxide layer has a gallium oxide doping concentration of 10 18 -10 19 cm -3 .

[0025] Further, in step (2), the thickness of the silicon dioxide layer is 50-500 nm.

[0026] Further, in step (7), the HVPE preparation and growth of the low-doped gallium oxide micropillar array has a gallium oxide doping concentration of 10 15 -10 17 cm-3 .

[0027] Advantages

[0028] (1) The gallium oxide micropillar of the application has a lower dislocation density (including edge dislocation density and screw dislocation density) than a conventional gallium oxide film, effectively improving the crystal quality of the gallium oxide.

[0029] (2) The gallium oxide micropillar array of the application has the advantages of simple structure, low power consumption, simple process, low cost, and strong repeatability. Compared with traditional nanoscale gallium oxide, it has a precise controllable structure and repeatability, which is convenient for large-scale integration and use.

[0030] (3) The semiconductor material structure of the application preferably uses gallium oxide with different crystal orientations as the raw material, wherein the beta phase gallium oxide is monoclinic structure, the alpha phase gallium oxide is hexagonal structure, the kappa phase gallium oxide is orthogonal structure, and the gamma phase gallium oxide is cubic structure. The unique gallium oxide structure will exhibit unique gallium oxide structure after specific selective growth.

[0031] (4) The Schottky structure of the gallium oxide micropillar structure of the application has a core material of oxide, which can effectively avoid air oxidation.

[0032] (5) The Schottky of the gallium oxide micropillar structure of the application adopts a one-to-many structure for the bottom electrode and the top electrode, which can independently control the switching characteristics of each Schottky, reduce the cost, and improve the switching efficiency.

[0033] (6) The technical means adopted by the application discards the material quality problems and disorder and non-repeatability problems caused by large lattice mismatch on a heterogeneous substrate of traditional gallium oxide film and gallium oxide nanowire materials, and combines different doping concentrations and different crystal orientations of gallium oxide on the premise of improving the crystal quality of gallium oxide, realizes the use range, miniaturization and integration of the device, has simple process, strong modulation ability, flexible design, can change the design according to different band gap characteristics, and is convenient for large-scale use. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 The gallium oxide micropillar array structure of the embodiment of the application is prepared.

[0035] Figure 2 The gallium oxide micropillar of the embodiment of the application is prepared.

[0036] Figure 3 The gallium oxide micropillar of the embodiment of the application is prepared.

[0037] Figure 4This is a schematic diagram of the structure of the κ-phase gallium oxide layer and the α-phase gallium oxide micropillar in an embodiment of the present invention.

[0038] Figure 5 This is a physical diagram of the α-gallium oxide micropillar array structure according to an embodiment of the present invention. Detailed Implementation

[0039] The embodiments of the present invention will now be described in further detail with reference to the accompanying drawings. Obviously, the described embodiment is an α-phase gallium oxide micropillar array embodiment, which is only a part of the present invention, and not all of the embodiments. Gallium oxide micropillar arrays with other crystal orientations are all within the protection scope of the present invention. The described embodiments are for illustrative purposes only and are not intended to limit the scope 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 protection scope of the present invention.

[0040] Example 1: Alpha-phase gallium oxide micropillar array based on Schottky diodes

[0041] like Figures 1-3 As shown, this embodiment is an α-phase gallium oxide micropillar array based on Schottky diodes. The Schottky diodes, from bottom to top, include a substrate layer 101, a gallium oxide layer 102, and an α-phase gallium oxide micropillar Schottky array 301. The α-phase gallium oxide micropillar Schottky array 301 includes α-phase gallium oxide micropillars 201, a bottom electrode 203, and a top electrode 204. The bottom electrode 203 and the top electrode 204 adopt a one-to-many structure, which can independently and accurately control the switching characteristics of each Schottky. The gallium oxide layer 102 is a flat thin film. The α-phase gallium oxide micropillars 201 have a hexagonal frustum structure, with a hexagonal base, an equilateral triangle with three vertices removed at the top, and sides composed of three hexagons, three downward-facing pentagons, and six upward-facing pentagons. The aperture size of the α-phase gallium oxide micropillars 201 is 1-10 μm, the height is 50 nm-10000 nm, and the micropillar spacing is 1-20 μm.

[0042] like Figure 1 The diagram shows the fabrication process of an α-phase gallium oxide micropillar array structure, which includes the following steps:

[0043] (1) First, a highly doped gallium oxide layer 102 was prepared on a sapphire substrate 101 using ultrasonic atomization-assisted chemical vapor deposition (Mist CVD). By adjusting the growth temperature and atomizer power during the Mist CVD process, gallium oxide with different crystal orientations was prepared; the gallium oxide doping concentration was 10. 18 -10 19 cm -3 The thickness of the gallium oxide layer 102 is 50nm-1000nm;

[0044] (2) Reuse PECVD or ALD technology, grow a silicon dioxide layer 103 on the gallium oxide layer, the thickness of the silicon dioxide 103 is 50nm-500nm;

[0045] (3) Based on integrated circuit technology, apply a certain thickness of photoresist on the silicon dioxide layer, cover the mask on the photoresist, and perform exposure and development steps;

[0046] (4) Use EUV lithography technology to etch the unprotected area to make pattern 104, which is not limited to this pattern, such as circle, triangle, hexagon, etc.

[0047] (5) Use RIE, ICP and other etching technologies to transfer the pattern 104 on the photoresist to the silicon dioxide layer, and use the silicon dioxide layer 103 as a pattern mask 105 for the next preparation process;

[0048] (6) Then wash off the photoresist to obtain a silicon dioxide mask structure, and place the substrate with the pattern into the HVPE chamber;

[0049] (7) By adjusting the growth temperature, growth time, ratio and pressure of oxygen and hydrogen chloride and other conditions in the HVPE secondary epitaxial growth process, a low-doped concentration α-phase gallium oxide material 106 is prepared; the doping concentration of the gallium oxide is 10 15 -10 17 cm -3 ;

[0050] (8) After washing off the silicon dioxide with HF, an α-phase gallium oxide micropillar array 107 is obtained. By selective growth of the α-phase gallium oxide micropillar array 107, the dislocation density (including edge dislocations and screw dislocations) caused by the lattice mismatch between the gallium oxide and the substrate 101 in the gallium oxide layer 102 is effectively reduced, and the crystal quality of the gallium oxide is effectively improved.

[0051] As Figure 2 shown is a preparation process cross-sectional schematic diagram of a Schottky structure 205 based on α-phase gallium oxide micropillars,

[0052] (a) The bottom plane of the obtained α-phase gallium oxide micropillar structure 201 is deposited with the bottom electrode 203, which is an ohmic contact electrode (Ti / Au or Ti / Al / Ni / Au);

[0053] (b) The top of the α-phase gallium oxide micropillar 201 is deposited with the top electrode 204, which is a Schottky contact electrode (Ni / Au).

[0054] The electrode preparation process uses SUSS lithography technology and PVD metal deposition technology. The thickness of the ohmic contact electrode and the Schottky contact electrode is 10-500nm.

[0055] Example 2: Alpha phase gallium oxide micropillar array structure 403 based on kappa phase gallium oxide layer

[0056] As shown in Figure 4 the difference from example 1 is that the gallium oxide layer 102 adopts a kappa phase gallium oxide layer 402.

[0057] The present application does not list all the combinations between layers and micropillars among other gallium oxide crystal orientations, but they are all within the scope of protection.

[0058] Compared with other Schottky structures, high-quality gallium oxide, especially metastable phase gallium oxide, reduces the dislocation density by two orders of magnitude after selective growth, greatly improves the crystal quality, makes the on-resistance of gallium oxide micropillar Schottky very low, and the power consumption is more, which can greatly reduce the electrical energy loss of device work. Compared with conventional gallium oxide device preparation, the gallium oxide micropillar Schottky of the present application has higher gallium oxide quality, strong repeatability, low cost, which is conducive to large-scale integration and production. For nanoscale gallium oxide, the gallium oxide micropillar array has higher repeatability, can accurately control and design the unique structure of the required gallium oxide structure.

Claims

1. A gallium oxide micropillar array based on Schottky diodes, characterized in that, The Schottky diode comprises, from bottom to top, a substrate layer, a highly doped n-type gallium oxide conductive layer fabricated by Mist-CVD, and a Schottky array of gallium oxide micropillars. The Schottky array of gallium oxide micropillars includes a lightly doped gallium oxide micropillar drift layer fabricated by HVPE, a bottom electrode, and a top electrode, wherein the bottom electrode and the top electrode adopt a one-to-many structure. The gallium oxide conductive layer is a flat thin film, and the material of the gallium oxide conductive layer is α-phase, κ-phase, γ-phase, or β-phase gallium oxide. The material of the gallium oxide micropillars is α-phase, κ-phase, γ-phase, or β-phase gallium oxide. The doping concentration of the highly doped n-type gallium oxide conductive layer is 10. 18 -10 19 cm -3 ; The doping concentration of the low-doped gallium oxide micropillar drift layer is 10. 15 -10 17 cm -3 ; The top electrode is a Schottky contact electrode disposed at the top of the gallium oxide micropillar, and the bottom electrode is two ohmic contact electrodes disposed at the bottom of the gallium oxide micropillar.

2. The gallium oxide micropillar array based on Schottky diodes according to claim 1, characterized in that, The gallium oxide micropillars have a hexagonal frustum structure with a hexagonal base; the diameter of the gallium oxide micropillars is 1-10 micrometers, the height is 50 nm-10000 nm, and the spacing between the micropillars is 1-20 micrometers.

3. The gallium oxide micropillar array based on Schottky diodes according to claim 1, characterized in that, The Schottky contact electrode is Ni / Au; the ohmic contact electrode is Ti / Au or Ti / Al / Ni / Au, and the electrode thickness is 10-500 nm.

4. The gallium oxide micropillar array based on Schottky diodes according to claim 1, characterized in that, The thickness of the gallium oxide conductive layer is 50 nm-1000 nm.

5. The gallium oxide micropillar array based on Schottky diodes according to claim 1, characterized in that, The substrate is an insulating or conductive substrate.

6. The method for fabricating a gallium oxide micropillar array based on a Schottky diode according to any one of claims 1-5, characterized in that, Includes the following steps: (1) First, gallium oxide layers are prepared on the substrate using Mist CVD. By adjusting the growth temperature, doping concentration and atomizer power during the Mist CVD process, gallium oxide with different crystal orientations and different doping concentrations can be prepared. (2) Then use PECVD or ALD technology to grow a silicon dioxide layer on the gallium oxide layer; (3) Based on integrated circuit process technology, a certain thickness of photoresist is applied to the silicon dioxide layer, and a mask is covered on the photoresist for exposure and development steps; (4) Use EUV lithography to etch the unprotected areas to create patterns; (5) Using RIE and ICP etching techniques, the pattern on the photoresist is transferred to the silicon dioxide layer, and the silicon dioxide layer is used as the pattern mask for the next fabrication process; (6) After washing away the photoresist, a silicon dioxide mask structure is obtained, and the patterned substrate is placed into the HVPE chamber; (7) Gallium oxide material with the desired crystal orientation was prepared by adjusting the growth temperature, growth time, oxygen and hydrogen chloride ratio and pressure during the secondary epitaxial growth process of HVPE. (8) After washing away the silicon dioxide with HF, a gallium oxide micropillar array with the desired crystal orientation is obtained; (9) Deposit an ohmic contact electrode on the bottom plane of the obtained gallium oxide micropillar; (10) A Schottky contact electrode is deposited on the top of a gallium oxide micropillar; the Schottky array of the gallium oxide micropillar includes a lightly doped gallium oxide micropillar drift layer prepared by HVPE, a bottom electrode and a top electrode, wherein the bottom electrode and the top electrode adopt a one-to-many structure.

7. The method for fabricating a gallium oxide micropillar array based on a Schottky diode according to claim 6, characterized in that, In step (1), the doping concentration of the Mist CVD-grown material is 10. 18 -10 19 cm -3 Gallium oxide layer.

8. The method for fabricating a gallium oxide micropillar array based on a Schottky diode according to claim 6, characterized in that, In step (2), the thickness of the silicon dioxide layer is 50 nm-500 nm.

9. The method for fabricating a gallium oxide micropillar array based on a Schottky diode according to claim 6, characterized in that, In step (7), the doping concentration of HVPE prepared and grown is 10. 15 -10 17 cm -3 Gallium oxide micropillar array.

Images