TWI670864B - Substrate for ultraviolet light emitting diode and manufacturing method thereof - Google Patents

Abstract

A substrate for an ultraviolet light emitting diode is manufactured by: providing a sapphire substrate; and disposing an AlN _x O _y film 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, the thickness of the AlN _x O _y film is between 15 nm and 2000 nm; the sapphire substrate provided with the AlN _x O _y film is placed in an atmosphere for annealing Processing, wherein the annealing temperature is between 1500 ° C and 1900 ° C; an epitaxial layer is disposed on the annealed AlN _x O _y film, and the oxygen atom content in the epitaxial layer is less than or equal to 10% atom% (atom% The epitaxial layer is selected from the group consisting of aluminum nitride (AlN) and aluminum gallium nitride (AlGaN), and the thickness of the epitaxial layer is between 20 and 5000 nm. Thereby, a substrate for a low-density density ultraviolet light-emitting diode is provided to achieve good luminous efficiency.

Description

Substrate for ultraviolet light emitting diode and manufacturing method thereof

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

At present, blue LED lighting has gradually entered the Red Sea market, its sales price and gross profit are becoming meager, and even some manufacturers have already experienced negative gross profit. Therefore, various manufacturers and enterprises are actively looking for other high-margin blue ocean markets that can be exploited. Among them, the market for UV LED is in the growth stage, and it is a blue ocean market worth developing.

There are two kinds of UV LED substrates commonly used in the industry, one is a bulk aluminum nitride substrate, and the other is aluminum nitride on a sapphire or tantalum carbide substrate (AlN templates). Among them, the aluminum nitride substrate has a lower crystal defect density than the AlN templates, and the lower the crystal defect density, the higher the luminous efficiency. Therefore, the aluminum nitride substrate has higher luminous efficiency than the AlN templates. Long life, but limited by the difficulty of AlN crystal growth technology, low substrate productivity and high price, it is not easy to promote. Therefore, many studies have sought to improve the crystal defect density of AlN templates to improve UV LED performance.

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

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

In order to achieve the above object, the present invention provides 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 a number between 0.7 and 1, y is a number between 0.02 and 0.3, the thickness of the AlN _x O _y film is between 15 nm and 2000 nm; and an epitaxial layer is disposed on On the AlN _x O _y film, the oxygen atom content in the epitaxial layer is less than or equal to 10% atom%, and the epitaxial layer is composed of aluminum nitride (AlN) and aluminum gallium nitride (AlGaN) groups. Selected in the layer, 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 fabricating a substrate for an ultraviolet light emitting diode, comprising the steps of: A, providing a sapphire substrate having a surface; B, the sapphire substrate The surface of the material is provided with an AlN _x O _y film, 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 Between 2000 nm; C, the sapphire substrate provided with the AlN _x O _y film is annealed in an atmosphere, wherein the annealing temperature is between 1500 ° C and 1900 ° C; and D, after annealing An epitaxial layer is disposed on the AlN _x O _y film, and the oxygen atom content in the epitaxial layer is less than or equal to 10% atom%, and the epitaxial layer is made of aluminum nitride (AlN) and aluminum gallium nitride ( Selected in the group of AlGaN), and the thickness of the epitaxial layer is between 20 and 5000 nm.

The effect of the invention is that the annealing process of the AlN _x O _y film can effectively reduce the defects of the atom recombination, and is beneficial to the growth of the epitaxial crystal when the substrate is subsequently formed into an ultraviolet light emitting diode.

〔this invention〕

1‧‧‧Substrate

10‧‧‧Sapphire substrate

10a‧‧‧ surface

12‧‧‧AlN _x O _y film

14‧‧‧ epitaxial layer

2‧‧‧Substrate

20a‧‧‧ surface

22‧‧‧ 丘丘

24‧‧‧AlN _x O _y film

26‧‧‧ epitaxial layer

H‧‧‧ Height

W‧‧‧Width

30, 40, 50, 60, 70, 80‧‧‧ sapphire substrates

32, 42, 52, 62, 72, 82‧‧‧ structures

1 is a flow chart showing a method of manufacturing a substrate for an ultraviolet light emitting diode according to a first preferred embodiment of the present invention.

Figure 2 is a schematic view showing the sapphire substrate of the above preferred embodiment.

Figure 3 is a schematic view showing the placement of an AlN _x O _y film on a sapphire substrate.

4 is a schematic view showing the provision of an epitaxial layer on an 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.

Figure 6 is a schematic view showing the above preferred embodiment of a sapphire substrate having a micronanostructure.

Figure 7 is a perspective view showing the sapphire substrate having the micronanostructure of the above preferred embodiment.

Figure 8 is a schematic view showing the micro-nano structure of the AlN _x O _y film covering the sapphire substrate.

Figure 9 is a schematic view showing that the epitaxial layer is disposed on the AlN _x O _y film.

Figure 10 is a graph of spectral absorbance analysis showing that defects can be effectively improved after annealing.

Figures 11(a) and 11(b) show the measurement results of the surface of the AlN _x O _y film measured by atomic force microscopy (AFM).

Figure 12 is a schematic view showing a sapphire substrate having a micro-nano structure according to a third preferred embodiment of the present invention.

Figure 13 is a schematic view showing a sapphire substrate having a micro-nano structure according to a fourth preferred embodiment of the present invention.

Figure 14 is a schematic view showing a sapphire substrate having a micro-nano structure according to a fifth preferred embodiment of the present invention.

Figure 15 is a schematic view showing a sapphire substrate having a micro-nano structure according to a sixth preferred embodiment of the present invention.

Figure 16 is a schematic view showing a sapphire substrate having a micro-nano structure according to a seventh preferred embodiment of the present invention.

Figure 17 is a schematic view showing a sapphire substrate having a micro-nano structure according to an eighth preferred embodiment of the present invention.

In order to explain the present invention more clearly, a preferred embodiment will be described in detail with reference to the drawings. 1 is a flow chart of a method for fabricating a substrate for an ultraviolet light emitting diode according to a first preferred embodiment of the present invention, and the substrate 1 is described with reference to FIGS. 2 to 4 (refer to FIG. 4 )A step of.

First, step A is performed: a sapphire substrate 10 is first provided. In the embodiment, the sapphire substrate 10 has a flat shape, 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 10a 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 The thickness of the AlN _x O _y film 12 is between 15 nm and 2000 nm at a number between 0.02 and 0.3. Further, 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 annealed in an atmosphere. The annealing temperature in the annealing treatment is 1500 ° C or higher. Preferably, the annealing temperature is between 1500 ° C and 1900 ° C. More preferably, the annealing temperature is between 1680 ° C and 1750 ° C. Wherein, the atmosphere may be mainly composed of inert gas (for example, helium gas, argon gas or the like or a combination thereof), or mainly composed of nitrogen gas, or mainly composed of a gas mixture of inert gas and nitrogen or the like. For example, a mixture of helium, argon, and nitrogen constitutes the main gas in the atmosphere. Further, preferably, the gas containing no carbon or oxygen-containing element is substantially not contained in the atmosphere, and as a result, the problem of light absorption or exchange reaction with carbon atoms can be effectively prevented.

Next, step D is performed: an epitaxial layer 14 is disposed on the annealed AlN _x O _y film 12. Wherein, the content of oxygen atoms in the epitaxial layer 14 is less than or equal to 10% atom%, and the epitaxial layer 14 is composed of aluminum nitride (AlN) and/or aluminum gallium nitride (AlGaN) groups. Selected, and the thickness of the epitaxial layer 14 is between 20 and 5000 nm. For example, in the present embodiment, aluminum nitride is used as the epitaxial layer 14. In addition, in one embodiment, aluminum gallium nitride may also be used as the epitaxial layer, and is not limited thereto. For example, in the epitaxial process, an Al/Ga composition is used to form a graded AlGaN film by using a gradient type Ga or Al organic metal precursor, or an epitaxial modulation method such as a multilayer arrangement in which AlN/AlGaN is formed.

Thereby, the substrate 1 for the ultraviolet light emitting diode can be formed by the above-described manufacturing method, and a semiconductor structure (not shown) can be provided on the surface of the epitaxial layer 14. Among them, the difference in the discharge density of the epitaxial layer 14 of the substrate 1 produced can be effectively controlled to be 1 × 10 ⁸ /cm ³ or less, and good luminous efficiency can be achieved.

As shown in FIG. 5 to FIG. 9 , the substrate 2 for ultraviolet light-emitting diodes according to the second preferred embodiment of the present invention is manufactured as follows. First, in step A, a sapphire substrate 20 is provided. The surface 20a of the sapphire substrate 20 is formed with a plurality of structures (see FIGS. 6 and 7) which are exemplified by the humps 22, and the humps 22 constitute a micron structure. In the embodiment, the ridges 22 are periodically arranged, and each of the ridges 22 is hemispherical, and the bottom of each of the humps 22 The minimum width W 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. It is to be noted that the ridges 22 may be a spherical structure or an aspherical structure. For example, in the embodiment, the ridges 22 are exemplified by a spherical structure, but in other practical implementations, Limited.

Among them, the humps 22 (micro-nano structure) can be made in the following manner: (1) using nano transfer technology, such as hot pressing into the form of nano transfer, light-sensing form of nano transfer (2) using the technique of nanosphere lithography, that is, prior to the surface 20a of the sapphire substrate 20, a layer of a solution mixed with nanospheres is preliminarily coated, and the nanosphere is self-assembled by self-assembly. The effect of the effect is that after the surface 20a of the sapphire substrate 20 is formed in a periodic arrangement, the nanosphere is used as an etching mask and is etched and transferred; (3) using anodized aluminum (AAO) process technology, During the anodization process of the metal aluminum, the aluminum oxide formed by self-assembly of the nanopores is used as a plate mold, and is formed by etching transfer; (4) is formed by using 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 humps 22. 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 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 annealed in an atmosphere. The annealing temperature in the annealing treatment is 1500 ° C or higher. Preferably, the annealing temperature is between 1500 ° C and 1900 ° C. More preferably, the annealing temperature is between 1680 ° C and 1750 ° C. Wherein, the composition of the atmosphere is substantially the same as that of the foregoing embodiment, and may be mainly composed of inert gas (for example, helium gas, argon gas or the like or a combination thereof), or mainly composed of nitrogen gas, or mainly by inert gas and nitrogen gas. A mixture of two or more gases.

Next, step D is performed: an epitaxial layer 26 is disposed on the annealed AlN _x O _y film 24. Wherein, the content of oxygen atoms in the epitaxial layer 26 is less than or equal to 10% atom%, and the epitaxial layer 26 is composed of aluminum nitride (AlN) and/or aluminum gallium nitride (AlGaN) groups. Selected, and the thickness of the epitaxial layer 26 is between 20 and 5000 nm. For example, in the present embodiment, aluminum gallium nitride is used as the epitaxial layer 26. In addition, in one embodiment, aluminum nitride may be selected as the epitaxial layer, and is not limited thereto.

Therefore, the substrate for the ultraviolet light emitting diode formed by the manufacturing method of the present invention can effectively reduce the density of the difference between the epitaxial layers, and the density of the epitaxial layer can be reduced to 1×. 10 ⁸ /cm ³ or less. Due to the reduced density of the differential row, the ultraviolet light-emitting diode fabricated by using the substrate can help reduce the chance of the combined ultraviolet light and the poor-discharge defect, thereby improving the luminous efficiency of the ultraviolet light-emitting diode. In addition, the light-emitting efficiency of the ultraviolet light-emitting diode can also be improved by the formed micro-nano structure.

According to the structure of the foregoing embodiment, in an embodiment, the foregoing AlN _x O _y film and/or the epitaxial layer may adopt an organic metal chemical vapor deposition (MOCVD) method or an atomic layer deposition method (ALD). ), molecular beam epitaxy (MBE), high temperature reactive sputtering (sputtering), or the like, or a combination of the above processes.

In addition, in the step C of an embodiment, in the step C of an embodiment, hydrogen gas having a total gas content of 10% or less may be further added to the atmosphere, thereby performing heat treatment for annealing. The surface defects of the AlN _x O _y film are etched by hydrogen gas to reduce the defect density.

In addition, under the basis of the foregoing preferred embodiment, the surface of the sapphire substrate in step A of an embodiment may first form a pre-stress layer, and in step B, the AlN _x O _y film The system is disposed on the prestressed layer. Among them, by the provision of the pre-stress layer, the warpage caused by the stress of the sapphire substrate can be effectively reduced, and the stress can be relieved when the heat treatment such as annealing is performed later. Wherein, the pre-stress layer may be formed by polishing or inductively coupled plasma etching (ICP) on the surface of the sapphire substrate, for example, polishing the sapphire substrate with a nano-alumina polishing solution. Processing, so that the surface of the sapphire substrate forms a pre-stress layer of about several or several tens of atomic thickness; and then, the AlN _x O _y film is disposed on the pre-stress layer, and after annealing, It helps to solve the problem of lattice mismatch between the sapphire substrate and the AlN _x O _y film, that is, the lattice matching between the sapphire substrate and the AlN _x O _y film can be improved.

In addition, as shown in Fig. 10, it can be seen from the spectral absorbance analysis chart that the absorbance is relatively high when the AlN _x O _y film is initially plated; in addition, the sapphire base having the AlN _x O _y film After the material is annealed in an atmosphere mainly composed of argon gas or annealed in an atmosphere mainly containing a trace amount of hydrogen gas under nitrogen, it is apparent that the absorbance at a short wavelength is significantly decreased. In other words, the substrate for the ultraviolet light-emitting diode manufactured by the production method provided by the present invention can surely exhibit a good defect improving effect.

In addition, when the AlN _x O _y film is initially plated, the defect density is measured to be about 10 ⁹ to 10 ¹¹ /cm ² , and the atmosphere is composed of about 95% of nitrogen and about 5% of hydrogen. After the annealing treatment, it can be seen from Fig. 11(a) that no significant etching holes are formed after the etching, and it is seen that it has the effect of significantly reducing the density of the defective defects; and in an atmosphere mainly composed of argon gas. After the annealing treatment, it can be seen from Fig. 11(b) that the density of the defective defects can be effectively reduced, and the density of defects after etching can be reduced to about 5 × 10 ⁷ /cm ² by measurement.

It is to be noted that the micro-nano structure on the sapphire substrate of the substrate provided by the present invention may be in the shape shown in FIG. 12 to FIG. 17 in addition to the hemispherical shape of the second preferred embodiment. Wherein: FIG. 12 shows a sapphire substrate 30 of a substrate according to a third preferred embodiment of the present invention, and the structure 32 of the micro-nano structure has a conical shape.

Figure 13 is a view showing a sapphire substrate 40 of a substrate according to a fourth preferred embodiment of the present invention, wherein the structure 42 of the micro-nano structure has an arc shape.

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 pyramid shape, and the side ring surface of the structure 52 is curvedly recessed.

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 recess.

Figure 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 is in the form of a plate having a flat surface 722 at the top.

Figure 17 is a view showing a sapphire substrate 80 of a substrate according to an eighth preferred embodiment of the present invention, wherein the structure 82 of the micro-nano structure is in the shape of a basin.

The structure described in each of the above embodiments has the function of causing ultraviolet light to be totally reflected in the epitaxial layer and unable to effectively emit light, thereby improving the luminous efficiency. At the same time, the adjustment of the epitaxial process can also have the effect of reducing defects.

The above is only a preferred embodiment of the present invention, and equivalent changes to the scope of the present invention and the scope of the patent application are intended to be included in the scope of the present invention.

Claims (16)

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 a number between y and a number between 0.02 and 0.3, the thickness of the AlN _x O _y film is between 15 nm and 2000 nm; and an epitaxial layer disposed on the AlN _x O _y film, The content of oxygen atoms in the epitaxial layer is less than or equal to 10% atom%, and the epitaxial layer is selected from the group consisting of aluminum nitride (AlN) and aluminum gallium nitride (AlGaN), and the epitaxial layer The thickness of the layer is between 20 and 5000 nm, wherein the epitaxial layer has a poor diffusion density of 1 × 10 ⁸ /cm ² or less. 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 surface of the sapphire substrate is formed with a micro-nano structure, and the AlN _x O _y film covers the micro-nano structure. The substrate for an ultraviolet light-emitting diode according to claim 3, wherein the micro-nano structure comprises a plurality of structures, and a minimum width of a bottom portion of each of the structures is between 100 and 5000 nm. The substrate for an ultraviolet light-emitting diode according to claim 4, wherein a ratio of a height or a depth of each of the structures to a minimum width of the bottom portion is 0.2 or more. A method for manufacturing a substrate for an ultraviolet light emitting diode comprises the steps of: A, providing a sapphire substrate having a surface; B, disposing an AlN _x O _y on the surface of the sapphire substrate a film, 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; The sapphire substrate of the AlN _x O _y film is annealed in an atmosphere in which the annealing temperature is between 1500 ° C and 1900 ° C; and D, an epitaxial layer is disposed on the annealed AlN _x O _y film a layer having an oxygen atom content of 10% atom% or less, the epitaxial layer being selected from the group consisting of aluminum nitride (AlN) and aluminum gallium nitride (AlGaN), and The thickness of the epitaxial layer is between 20 and 5000 nm. The method for producing a substrate for an ultraviolet light-emitting diode according to claim 6, wherein the thickness of the AlN _x O _y film is between 15 nm and 600 nm. The method for producing a substrate for an ultraviolet light-emitting diode according to claim 6, wherein the temperature at which the step C is annealed is between 1680 ° C and 1750 ° C. The method for manufacturing a substrate for an ultraviolet light-emitting diode according to claim 6, wherein in the step A, the micro-nano structure is formed on the surface of the sapphire substrate; and in the step B, the AlN _x O _{A y} film system is disposed on the surface and covers the micro-nano structure. The method for fabricating a substrate for an ultraviolet light-emitting diode according to claim 9, wherein the micro-nano structure comprises a plurality of structures, and a minimum width of a bottom portion of each of the structures is between 100 and 5000 nm. The method for producing a substrate for an ultraviolet light-emitting diode according to claim 10, wherein a ratio of a height or a depth of each of the structures to a minimum width of the bottom portion is 0.2 or more. The method for producing a substrate for an ultraviolet light-emitting diode according to claim 6, wherein the atmosphere in the step C is mainly composed of inert gas, nitrogen gas or a combination thereof, and substantially does not contain carbon or contains in the atmosphere. Oxygen gas. The method for producing a substrate for an ultraviolet light-emitting diode according to claim 12, wherein in the step C, hydrogen gas having a total gas content of 10% or less is added to the atmosphere. The method for manufacturing a substrate for an ultraviolet light-emitting diode according to claim 6, wherein the step A includes: forming a pre-stress layer on the surface of the sapphire substrate; and in the step B, the AlN _x O _{A y} film system is disposed on the prestressed layer. The method for producing a substrate for an ultraviolet light-emitting diode according to claim 14, wherein the pre-stress layer is formed by polishing or inductively coupled plasma etching (ICP) on the surface of the sapphire substrate. The method for producing a substrate for an ultraviolet light-emitting diode according to claim 6, wherein the AlN _x O _y film and/or the epitaxial layer is subjected to an organic metal chemical vapor deposition (MOCVD) method or an atomic layer deposition method. (ALD), molecular beam epitaxy (MBE), high temperature reactive sputtering (sputtering) or a combination of the above.