TW201810710A - Substrate for ultraviolet light emitting diode and production method thereof providing the low-defect-density substrate for the ultraviolet light emitting diode so as to achieve high light emitting efficiency - Google Patents

Abstract

This invention discloses a substrate for an ultraviolet light emitting diode. The substrate is produced by the following steps: providing a sapphire substrate; arranging an AlNxOy film on the surface of the sapphire substrate, wherein x is a number ranging from 0.7 to 1, y is a number ranging from 0.02 to 0.3, and the thickness of the AlNxOy film ranges from 15nm to 2000nm; annealing the sapphire substrate provided with the AlNxOy film at an atmosphere, wherein the annealing temperature ranges from 1500 DEG C to 1900 DEG C; and arranging an epitaxial layer on the annealed AlNxOy film, wherein the content of oxygen atoms in the epitaxial layer is smaller than or equal to 10 atom% (atom%). The epitaxial layer is selected from aluminum nitride (AIN) and gallium nitride (AlGaN) groups, and the thickness of the epitaxial layer ranges from 20nm to 5000nm. Therefore, this invention provides the low-defect-density substrate for the ultraviolet light emitting diode so as to achieve high light emitting efficiency.

Description

Substrate for ultraviolet light emitting diode and manufacturing method thereof

The invention relates to an ultraviolet light emitting diode; in particular, it relates to a substrate for an ultraviolet light emitting diode and a manufacturing method thereof.

At present, blue-light LED lighting has gradually entered the Red Sea market, and its sales price and gross profit have become increasingly thin. Even some manufacturers have shown negative gross profit. Therefore, various manufacturers and enterprises are actively looking for other high-margin blue ocean markets that can be explored. Among them, the UV LED market is in its growth stage, and it is a blue ocean market worth developing.

There are two types of UV LED substrates commonly used in the industry, one is a block aluminum nitride substrate, and the other is a substrate (AlN templates) that is epitaxially grown on sapphire or silicon carbide. Among them, the density of crystal defects of the bulk aluminum nitride substrate is lower than that of AlN templates, and the lower the density of crystal defects, the higher the light emitting efficiency. Therefore, compared to AlN templates, the aluminum nitride substrate has higher light emitting efficiency and Long life, but limited by the difficulty of AlN crystal growth technology, low substrate production capacity and high price, it is not easy to promote. Therefore, many studies are trying to improve the crystal defect density of AlN templates to improve the efficiency of UV LEDs.

However, the technology currently available on the market has limited reduction in the defect density of AlN crystals, and there is room for improvement.

In view of this, an object of the present invention is to provide a substrate for an ultraviolet light emitting diode and a manufacturing method thereof, which can effectively reduce the defect density of the epitaxial layer and improve the light emitting efficiency.

In order to achieve the above object, the present invention provides a substrate for an ultraviolet light emitting diode, which includes a sapphire substrate having a surface; an AlN _x O _y film is disposed on the surface of the sapphire substrate, wherein , X is a number between 0.7 and 1, y is a number between 0.02 and 0.3, and the thickness of the AlN _x O _y film is between 15 nm and 2000 nm; and an epitaxial layer is provided at On the AlN _x O _y film, the content of oxygen atoms in the epitaxial layer is less than or equal to 10% of atomic percentage. The epitaxial layer is composed of aluminum nitride (AlN) and aluminum gallium nitride (AlGaN) groups. And the thickness of the epitaxial layer is between 20 and 5000 nm.

In order to achieve the above object, the present invention further provides a method for manufacturing a substrate for an ultraviolet light emitting diode, which includes the following steps: A. providing a sapphire substrate having a surface; and B. providing the sapphire substrate An AlN _x O _y film is provided on the surface of the material, where x is a number between 0.7 and 1, and y is a number between 0.02 and 0.3. The thickness of the AlN _x O _y film is between 15 nm. Between 2000 and 2000 nm; C. placing the sapphire substrate provided with the AlN _x O _y film in an atmosphere for annealing treatment, wherein the annealing temperature is between 1500 ° C and 1900 ° C; and D. after the annealing An epitaxial layer is provided on the AlN _x O _y film, and the content of oxygen atoms in the epitaxial layer is less than or equal to 10% atomic percentage. The epitaxial layer is composed of aluminum nitride (AlN) and gallium aluminum nitride ( AlGaN) group, and the thickness of the epitaxial layer is between 20 and 5000 nm.

The effect of the present invention is that the AlN _x O _y film can effectively reorganize atoms to reduce defects after annealing treatment, and is beneficial to epitaxial growth when the substrate is subsequently made into an ultraviolet light emitting diode.

In order to explain the present invention more clearly, a preferred embodiment is described in detail below with reference to the drawings. Please refer to FIG. 1, which is a flowchart of a method for manufacturing a substrate for an ultraviolet light emitting diode according to a first preferred embodiment of the present invention, and please refer to FIGS. 2 to 4 to fabricate the substrate 1 (refer to FIG. 4) )A step of.

First, step A is performed: a sapphire substrate 10 is first provided. In this embodiment, the sapphire substrate 10 is substantially flat, and the sapphire substrate 10 has a surface 10a.

Next, step B is performed: an AlN _x O _y film 12 is disposed on the surface 10 a of the sapphire substrate 10, wherein _{x in} the AlN _x O _y film 12 is a number between 0.7 and 1, and y is an intermediary A number between 0.02 and 0.3, the thickness of the AlN _x O _y film 12 is between 15 nm and 2000 nm; more preferably, the thickness of the AlN _x O _y film 12 is between 15 nm and 600 nm .

Next, step C is performed: the sapphire substrate 10 provided with the AlN _x O _y film 12 is placed in an annealing furnace (not shown), and an annealing treatment is performed in an atmosphere. The annealing temperature during the annealing process is above 1500 ° C. Preferably, the annealing temperature is between 1500 ° C and 1900 ° C, and more preferably, the annealing temperature is between 1680 ° C and 1750 ° C. The atmosphere is mainly composed of inert gas (for example, helium, argon, etc. or a combination thereof), or mainly composed of nitrogen, or mainly composed of a mixture of two or more gases such as inert gas and nitrogen, For example: a mixture of helium, argon, and nitrogen constitutes the main gas in this atmosphere. In addition, it is preferable that the gas containing carbon or oxygen element is not substantially contained in the atmosphere. In this way, the problem of light absorption or exchange reaction with carbon atoms caused by aluminum precipitation can be effectively avoided.

Next, step D is performed: an epitaxial layer 14 is disposed on the annealed AlN _x O _y film 12. The epitaxial layer 14 has an oxygen atom content of 10% or less, and the epitaxial layer 14 is selected from the group consisting of aluminum nitride (AlN) and / or aluminum gallium nitride (AlGaN). It is selected, and the thickness of the epitaxial layer 14 is between 20 and 5000 nm. For example, in this embodiment, aluminum nitride is used as the epitaxial layer 14. In addition, in one embodiment, gallium aluminum nitride may be used as the epitaxial layer, without being limited thereto. For example, in the epitaxial process, the Al / Ga composition is a graded AlGaN film formed by adjusting the ratio of the organic metal precursors of graded Ga and Al, or the epitaxial modulation method such as forming a multilayer arrangement of AlN / AlGaN.

Thereby, through the above-mentioned manufacturing method, the substrate 1 for ultraviolet light emitting diodes can be manufactured, and a semiconductor structure (not shown) can be provided on the surface of the epitaxial layer 14. Among them, the penetration density of the epitaxial layer 14 of the manufactured substrate 1 can be effectively controlled at 1 10 ⁸ / cm ³ or less, good luminous efficiency can be achieved.

Please refer to FIG. 5 to FIG. 9, which is the second preferred embodiment of the substrate 2 for ultraviolet light emitting diodes of the present invention (refer to FIG. 11). The manufacturing method is as follows:

First, in step A, a sapphire substrate 20 is provided. On the surface 20a of the sapphire substrate 20, a plurality of structures with ridges 22 as an example are produced (refer to FIGS. 6 and 7). The ridges 22 Forms a micronanostructure. In this embodiment, the bulges 22 are periodically arranged, and each of the bulges 22 is hemispherical, and the minimum width W of the bottom of each of the bulges 22 is between 100 and 5000 nm. And the ratio of the height H (or depth) of each of the humps 22 to the minimum width W of the bottom is greater than or equal to 0.2. Another mention is that the humps 22 may be a spherical structure or an aspherical structure. For example, in this embodiment, the humps 22 are a spherical structure, but in other practical implementations, this is not the case. Limited.

Among them, the humps 22 (micro-nano structure) can be made in the following ways: (1) the use of nano-transfer technology, such as hot-pressed form nano transfer, light-sensed form nano transfer (2) using nanosphere lithography technology, that is, a layer of a solution mixed with nanospheres is applied in advance of the surface 20a of the sapphire substrate 20, and the nanospheres have a self-assembly ) Effect characteristics, after forming a periodic periodic arrangement on the surface 20a of the sapphire substrate 20, the nanosphere is used as an etching mask, and then formed by etching transfer; (3) using anodized aluminum (AAO) process technology, During the anodizing process of metal aluminum, the nano-hole alumina formed by self-assembly is used as a mold and formed by etching and transfer; (4) formed by yellow light lithography and etching technology.

Next, step B is performed: an AlN _x O _y film 24 is disposed on the sapphire substrate 20, and the AlN _x O _y film 24 covers the convex hills 22. Wherein, x is a number between 0.7 and 1, and y is a number between 0.02 and 0.3. The thickness of the AlN _x O _y film 24 is between 15 nm and 2000 nm.

Next, step C is performed: the sapphire substrate 20 provided with the AlN _x O _y film 24 is placed in an annealing furnace (not shown), and an annealing treatment is performed in an atmosphere. The annealing temperature during the annealing process is above 1500 ° C. Preferably, the annealing temperature is between 1500 ° C and 1900 ° C, and more preferably, the annealing temperature is between 1680 ° C and 1750 ° C. The composition of the atmosphere is substantially the same as that of the foregoing embodiments, and may be mainly composed of inert gas (for example, helium, argon, etc. or a combination thereof), or mainly composed of nitrogen, or mainly composed of inert gas and nitrogen. Composed of more than two gases.

Next, step D is performed: an epitaxial layer 26 is disposed on the annealed AlN _x O _y film 24. The epitaxial layer 26 has an oxygen atom content of 10% or less, and the epitaxial layer 26 is selected from the group consisting of aluminum nitride (AlN) and / or aluminum gallium nitride (AlGaN). It is selected, and the thickness of the epitaxial layer 26 is between 20 and 5000 nm. For example, in this embodiment, gallium aluminum nitride is used as the epitaxial layer 26. In addition, in one embodiment, aluminum nitride may also be used as the epitaxial layer, without being limited thereto.

Thereby, the substrate for ultraviolet light emitting diodes manufactured by the manufacturing method of the present invention can effectively reduce the density of the penetration difference of the epitaxial layer, and the density of the penetration difference of the epitaxial layer can be reduced. Reduced to 1 10 ⁸ / cm ³ or less. Since the density of the penetrating differential emission row is reduced, the ultraviolet light emitting diode manufactured by using the substrate can help reduce the chance of recombination of the generated ultraviolet light and the differential emission defect, thereby improving the luminescence of the ultraviolet light emitting diode. effectiveness. In addition, the formed micronanostructure can also increase the effect of ultraviolet light reflection, so that ultraviolet light can be reflected by the micronanostructure away from the substrate, and the luminous efficiency of the ultraviolet light emitting diode is improved.

Wherein, based on the structure of the foregoing embodiment, in one embodiment, the aforementioned AlN _x O _y film and / or the epitaxial layer system may adopt organic metal chemical vapor deposition (MOCVD), atomic layer deposition (ALD) ), Molecular beam epitaxy (MBE), high-temperature reactive sputtering (sputtering) and other processes or a combination of the above processes.

In addition, on the basis of the foregoing preferred embodiment, in step C of an embodiment, a hydrogen gas accounting for 10% or less of the total gas may be further added to the atmosphere, so as to perform the annealing heat treatment The surface defects of the AlN _x O _y film are etched through hydrogen to reduce its defect density.

In addition, based on the foregoing preferred embodiment, a pre-stressed layer may be formed on the surface of the sapphire substrate in step A of an embodiment, and in step B, the AlN _x O _y film is formed. It is arranged on the prestressed layer. Among them, the provision of the prestressed layer can effectively reduce the warpage caused by the stress of the sapphire substrate, and can help to relieve the stress during the subsequent heat treatment such as annealing. The prestressed layer may be formed by polishing or inductively coupled plasma etching (ICP) on the surface of a sapphire substrate, for example, polishing a sapphire substrate using a nano-grade alumina polishing solution. Processing so that the surface of the sapphire substrate forms a prestressed layer with a thickness of about several or tens of atoms; then, the AlN _x O _y film is disposed on the prestressed layer and annealed, and It helps to solve the problem of lattice mismatch between the sapphire substrate and the AlN _x O _y film, that is, it can improve the lattice matching between the sapphire substrate and the AlN _x O _y film.

In addition, please refer to FIG. 10. As shown in the spectral absorbance analysis chart, when the AlN _x O _y film is initially plated, its absorbance is relatively high. In addition, the sapphire substrate with AlN _x O _y film is relatively high. After the material is annealed in an atmosphere mainly dominated by argon gas, or after being annealed in an atmosphere dominated by nitrogen with a trace amount of nitrogen, it can be clearly seen that the absorbance at short wavelengths has decreased significantly. In other words, the substrate for an ultraviolet light emitting diode manufactured by the manufacturing method provided by the present invention can indeed exhibit a good defect improving effect.

In addition, when the AlN _x O _y film was initially plated, the defect density was measured to be about 10 ⁹ to 10 ¹¹ / cm ² , and the atmosphere was composed of about 95% nitrogen and about 5% helium. After the annealing treatment is performed next, it can be seen from Fig. 11 (a) that there are no obvious etch holes after etching, and it can be seen that it has a significant effect of reducing the density of the differential defect. In an atmosphere dominated by argon, After annealing treatment, it can be seen from FIG. 11 (b) that the differential defect density can also be effectively reduced, and it can be seen that the defect density after etching can be reduced to about 5 10 ⁷ / cm ² .

It is worth mentioning that the micronano structure on the sapphire substrate of the substrate provided by the present invention can be shaped as shown in FIG. 12 to FIG. 17 in addition to the hemispherical shape as in the aforementioned second preferred embodiment. among them:

FIG. 12 shows a sapphire substrate 30 of a substrate according to a third preferred embodiment of the present invention. The micro-nano structure 32 has a conical shape.

FIG. 13 shows a sapphire substrate 40 of a substrate according to a fourth preferred embodiment of the present invention. The structure 42 of the micro-nano structure has an arc shape.

FIG. 14 shows a sapphire substrate 50 of a substrate according to a fifth preferred embodiment of the present invention. The structure 52 of the micro-nano structure has a pyramidal shape.

FIG. 15 shows a sapphire substrate 60 of a substrate according to a sixth preferred embodiment of the present invention. The structure 62 of the micro-nano structure has a cylindrical shape, and the structure 62 has an arc-shaped depression.

FIG. 16 shows a sapphire substrate 70 of a substrate according to a seventh preferred embodiment of the present invention. The structure 72 of the micro-nano structure has a platform shape and has a flat surface 722 on the top.

FIG. 17 shows a sapphire substrate 80 of a substrate according to an eighth preferred embodiment of the present invention. The structure 82 of the micronano structure has a basin shape.

Wherein, the structures described in the above embodiments have the function of causing ultraviolet light to be destroyed by total reflection in the epitaxial layer and unable to effectively emit light, thereby improving its luminous efficiency. At the same time, the adjustment of the epitaxial process can also have the effect of reducing defects.

The above descriptions are only the preferred and feasible embodiments of the present invention, and any equivalent changes made by applying the description of the present invention and the scope of patent application should be included in the patent scope of the present invention.

[this invention]
1‧‧‧ substrate
10‧‧‧ Sapphire Substrate
10a‧‧‧ surface
12‧‧‧AlN _x O _y film
14‧‧‧ epitaxial layer
2‧‧‧ substrate
20a‧‧‧ surface
22‧‧‧ convex hill
24‧‧‧AlN _x O _y film
26‧‧‧Epitaxial layer
H‧‧‧ height
W‧‧‧Width
30, 40, 50, 60, 70, 80‧‧‧ sapphire substrate
32, 42, 52, 62, 72, 82‧‧‧ Structure

FIG. 1 is a flowchart of a method for manufacturing a substrate for an ultraviolet light emitting diode according to a first preferred embodiment of the present invention. FIG. 2 is a schematic diagram illustrating the sapphire substrate of the above preferred embodiment. FIG. 3 is a schematic diagram showing that an AlN _x O _y film is disposed on a sapphire substrate. FIG. 4 is a schematic diagram showing that an epitaxial layer is provided on the AlN _x O _y film. FIG. 5 is a sapphire substrate of a substrate for an ultraviolet light emitting diode according to a second preferred embodiment of the present invention. FIG. 6 is a schematic diagram illustrating a sapphire substrate having a micronanostructure in the preferred embodiment. FIG. 7 is a perspective view illustrating a sapphire substrate having a micronanostructure in the preferred embodiment. FIG. 8 is a schematic diagram showing the micronanostructure of the AlN _x O _y film covering the sapphire substrate. FIG. 9 is a schematic diagram illustrating that the epitaxial layer is disposed on the AlN _x O _y film. FIG. 10 is a spectral absorbance analysis chart, which reveals that defects can be effectively improved after annealing. 11 (a) and 11 (b) show measurement results of the surface of the AlN _x O _y film measured by an atomic force microscope (AFM). FIG. 12 is a schematic diagram illustrating a sapphire substrate having a micronanostructure according to a third preferred embodiment of the present invention. FIG. 13 is a schematic view illustrating a sapphire substrate having a micronanostructure according to a fourth preferred embodiment of the present invention. FIG. 14 is a schematic view illustrating a sapphire substrate having a micronanostructure according to a fifth preferred embodiment of the present invention. FIG. 15 is a schematic diagram illustrating a sixth preferred embodiment of the sapphire substrate having a micronanostructure of the present invention. FIG. 16 is a schematic diagram illustrating a seventh preferred embodiment of the present invention with a sapphire substrate having a micronanostructure. FIG. 17 is a schematic diagram illustrating a sapphire substrate having a micronanostructure according to an eighth preferred embodiment of the present invention.

Claims (17)

A substrate for an ultraviolet light-emitting diode, comprising: a sapphire substrate having a surface; an AlN _x O _y film disposed on the surface of the sapphire substrate, wherein x is between 0.7 and 1 Y is a number between 0.02 and 0.3, and the thickness of the AlN _x O _y film is between 15 nm and 2000 nm; and an epitaxial layer is disposed on the AlN _x O _y film, The epitaxial layer has an oxygen atom content of 10% or less. The epitaxial layer is selected from the group consisting of aluminum nitride (AlN) and aluminum gallium nitride (AlGaN). The thickness of the layer is between 20 and 5000 nm. The substrate for an ultraviolet light emitting diode according to claim 1, wherein the thickness of the AlN _x O _y film is between 15 nm and 600 nm. The substrate for an ultraviolet light-emitting diode according to claim 1, wherein the differential transmission density of the epitaxial layer is 1 10 ⁸ / cm ³ or less. The substrate for an ultraviolet light emitting diode according to claim 1, wherein the surface of the sapphire substrate is formed with a micronanostructure, and the AlN _x O _y film system covers the micronanostructure. The substrate for an ultraviolet light emitting diode according to claim 4, wherein the micronanostructure includes a plurality of structures, and the minimum width of the bottom of each structure is between 100 and 5000nm. The substrate for an ultraviolet light emitting diode according to claim 5, wherein a ratio of a height or a depth of each structure to a minimum width of a bottom portion thereof is 0.2 or more. A method for manufacturing a substrate for an ultraviolet light-emitting diode includes the following steps: A. providing a sapphire substrate having a surface; B. setting an AlN _x O _y on the surface of the sapphire substrate Film, where x is a number between 0.7 and 1, and y is a number between 0.02 and 0.3, and the thickness of the AlN _x O _y film is between 15 nm and 2000 nm; The sapphire substrate of the AlN _x O _y film is annealed in an atmosphere, wherein the annealing temperature is between 1500 ° C and 1900 ° C; and D. An epitaxial crystal is provided on the annealed AlN _x O _y film. The epitaxial layer has an oxygen atom content of 10% or less (atom%). The epitaxial layer is selected from the group consisting of aluminum nitride (AlN) and aluminum gallium nitride (AlGaN), and the The thickness of the epitaxial layer is between 20 and 5000 nm. The method for manufacturing a substrate for an ultraviolet light emitting diode according to claim 7, wherein the thickness of the AlN _x O _y film is between 15 nm and 600 nm. The method for manufacturing a substrate for an ultraviolet light emitting diode according to claim 7, wherein the temperature of the step C annealing is between 1680 ° C and 1750 ° C. The method for manufacturing a substrate for an ultraviolet light emitting diode according to claim 7, wherein in step A, a micronanostructure is fabricated on the surface of the sapphire substrate; in step B, the AlN _x O _{A y} film is disposed on the surface and covers the micronanostructure. The method for manufacturing a substrate for an ultraviolet light emitting diode according to claim 10, wherein the micronanostructure includes a plurality of structures, and the minimum width of the bottom of each structure is between 100 and 5000nm. The method for manufacturing a substrate for an ultraviolet light emitting diode according to claim 11, wherein a ratio of a height or a depth of each structure to a minimum width of a bottom portion thereof is 0.2 or more. The method for manufacturing a substrate for an ultraviolet light emitting diode according to claim 7, wherein the atmosphere in step C is mainly composed of inert gas, nitrogen, or a combination thereof, and the atmosphere contains substantially no carbon or Oxygen gas. The method for manufacturing a substrate for an ultraviolet light-emitting diode according to claim 13, wherein in step C, hydrogen is added to the atmosphere in an amount of 10% or less. The method for manufacturing a substrate for an ultraviolet light emitting diode according to claim 7, wherein step A includes: forming a prestressed layer on the surface of the sapphire substrate; and in step B, the AlN _x O _{A y} film is disposed on the prestressed layer. The method for manufacturing a substrate for an ultraviolet light emitting diode according to claim 15, wherein the prestressed layer is formed by polishing or inductively coupled plasma etching (ICP) on the surface of the sapphire substrate. The method for manufacturing a substrate for an ultraviolet light emitting diode according to claim 7, wherein the AlN _x O _y film and / or the epitaxial layer adopts an organic metal chemical vapor deposition method (MOCVD) or an atomic layer deposition method. (ALD), molecular beam epitaxy (MBE), high temperature reactive sputtering (sputtering), or a combination thereof.