A patterned substrate doped with quantum dots, a preparation method thereof, and an LED epitaxial wafer

Abstract

An embodiment of the present invention discloses a patterned substrate doped with quantum dots, a preparation method thereof, and an LED epitaxial wafer. The preparation method of the patterned substrate doped with quantum dots includes: providing a substrate; forming a hetero-layer on the substrate, and synchronously doping quantum dots during the formation of the hetero-layer; patterning the hetero-layer to form a plurality of hetero-microstructures, and the quantum dots are doped in the hetero-microstructures. The embodiment of the present invention solves the problem of low reliability of phosphors in traditional white LEDs. It can not only enable the hetero-microstructures to realize the function of light excitation to convert the LED color, reducing the process steps of coating phosphors during the packaging process; at the same time, it can also seal the quantum dots in the hetero-microstructures to isolate the external environment, overcoming the disadvantage that traditional coated phosphors are prone to aging and peeling, and contributing to the realization of white LEDs with good color rendering and anti-aging yellowing.

Description

Technical Field

[0001] Embodiments of the present invention relate to the technical field of semiconductor manufacturing, and in particular, to a patterned substrate doped with quantum dots, a preparation method thereof, and an LED epitaxial wafer. Background Art

[0002] In the packaging process of traditional white LEDs, a blue InGaN chip is often used to excite a YAG yellow phosphor to generate yellow-green light, and white light is produced by mixing the yellow-green light and the blue light. Such white LEDs have poor color difference reduction and are easily affected by the thickness of the YAG yellow phosphor. In addition, the packaging process usually adopts the method of mixing phosphor particles with an organic polymer and then coating it on the LED package. The mixture coating layer prepared by this method has poor thermal stability and is prone to aging and yellowing under long-term light and heat conditions, ultimately resulting in a reduction in the light efficiency and reliability of the white LED. Summary of the Invention

[0003] The present invention provides a patterned substrate doped with quantum dots, a preparation method thereof, and an LED epitaxial wafer to dope quantum dots in the substrate and form white light by exciting and mixing the quantum dots.

[0004] In a first aspect, embodiments of the present invention provide a method for preparing a patterned substrate doped with quantum dots, including:

[0005] Providing a substrate;

[0006] Forming a hetero-layer on the substrate, and synchronously doping quantum dots during the formation of the hetero-layer;

[0007] Patternizing the hetero-layer to form a plurality of hetero-microstructures doped with the quantum dots.

[0008] Optionally, forming a hetero-layer on the substrate, and synchronously doping quantum dots during the formation of the hetero-layer, including:

[0009] Doping quantum dots in a hetero-material;

[0010] Depositing the hetero-material doped with the quantum dots on the substrate to form a hetero-layer.

[0011] Optionally, forming a hetero-layer on the substrate, and synchronously doping quantum dots during the formation of the hetero-layer, including:

[0012] Depositing a hetero-material on the substrate, and dynamically injecting quantum dots into the deposition gas simultaneously to form the hetero-layer.

[0013] Optionally, forming a hetero-layer on the substrate includes:

[0014] A heterogeneous layer is deposited and formed on the substrate by physical vapor deposition or aerosol jet process.

[0015] In a second aspect, an embodiment of the present invention further provides a patterned substrate doped with quantum dots, which is made by the method for preparing a patterned substrate doped with quantum dots according to any one of the first aspects. The patterned substrate doped with quantum dots includes a substrate and a plurality of heterogeneous microstructures located on the substrate, and the heterogeneous microstructures are doped with quantum dots.

[0016] Optionally, the doping ratio of the quantum dots is 0.5%-20%.

[0017] Optionally, the material of the quantum dots includes at least one semiconductor material of II-VI group elements and III-V group elements.

[0018] Optionally, the shape of the heterogeneous microstructure includes a polygonal cone, a cone, an elliptical cone, a cylinder, and a frustum of a cone.

[0019] Optionally, the heterogeneous material of the heterogeneous microstructure includes at least one of a transparent oxide, a nitride, and an element.

[0020] In a third aspect, an embodiment of the present invention further provides an LED epitaxial wafer, including the patterned substrate doped with quantum dots according to any one of the second aspects.

[0021] In the embodiment of the present invention, by forming a heterogeneous layer on the substrate, synchronously doping quantum dots during the formation of the heterogeneous layer, and then patterning the heterogeneous layer to form a plurality of heterogeneous microstructures, quantum dots can be doped in the heterogeneous microstructures, which not only enables the heterogeneous microstructures to realize the adjustment and conversion of the light output color, but also can seal and protect the quantum dots. The embodiment of the present invention solves the problem of low reliability of phosphors in traditional white LEDs. By using quantum dots synchronously doped in the heterogeneous layer to form heterogeneous microstructures, not only does the heterogeneous microstructure realize the function of light excitation to convert the LED color, reducing the process steps of coating phosphors during the packaging process, helping to simplify the process difficulty and reduce the cost; at the same time, the quantum dots can be sealed in the heterogeneous microstructures to isolate the external environment, overcoming the disadvantage that traditional coated phosphors are prone to aging and falling off, and helping to realize white LEDs with good color rendering and anti-aging yellowing. Description of the Drawings

[0022] Figure 1 is a flowchart of a method for preparing a patterned substrate doped with quantum dots provided by an embodiment of the present invention;

[0023] Figure 2 is Figure 1 the structural flowchart of the method for preparing the patterned substrate doped with quantum dots shown;

[0024] Figure 3 is a patterned substrate doped with quantum dots provided by an embodiment of the present invention;

[0025] Figure 4 is a schematic structural diagram of a white LED provided by an embodiment of the present invention

[0026] Figure 5 is a flowchart of another method for preparing a patterned substrate doped with quantum dots provided by an embodiment of the present invention;

[0027] Figure 6 is Figure 5 a structural flowchart of the method for preparing the patterned substrate doped with quantum dots shown;

[0028] Figure 7 is a flowchart of yet another method for preparing a patterned substrate doped with quantum dots provided by an embodiment of the present invention;

[0029] Figure 8 is a flowchart of yet another method for preparing a patterned substrate doped with quantum dots provided by an embodiment of the present invention;

[0030] Figure 9 is a schematic structural diagram of an LED epitaxial wafer provided by an embodiment of the present invention. Detailed implementation manners

[0031] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It can be understood that the specific embodiments described herein are only used to explain the present invention, rather than limiting the present invention. Additionally, it should be noted that for the sake of description, only parts related to the present invention are shown in the accompanying drawings rather than all the structures.

[0032] Figure 1 is a flowchart of a method for preparing a patterned substrate doped with quantum dots provided by an embodiment of the present invention, Figure 2 is Figure 1 a structural flowchart of the method for preparing the patterned substrate doped with quantum dots shown, Figure 3 is a patterned substrate doped with quantum dots provided by an embodiment of the present invention, referring to Figures 1-3 , the patterned substrate doped with quantum dots includes:

[0033] S110. Provide a substrate;

[0034] Referring to Figure 2 in FIG. a), wherein the substrate 10 is a substrate with a smooth surface after being polished, that is, the substrate 10 has a well-quality C plane, which can help the epitaxial crystal form nuclei and grow into an epitaxial layer. The substrate can specifically be a sapphire substrate, etc., which is not limited herein.

[0035] S120. Form a hetero-layer on the substrate. During the formation of the hetero-layer, quantum dots are doped synchronously.

[0036] Reference Figure 2 Referring to FIG. b) of [], the hetero-layer 20 is a film layer made of a hetero-material. The thickness of the hetero-layer 20 can be optionally set to 0.5 μm - 3.5 μm. The hetero-material is essentially a material that is different from the substrate 10 and the epitaxial layer material such as gallium nitride. That is, it is a material different from the substrate 10 and the epitaxial material. Since it is difficult for the epitaxial material to grow on this hetero-material, the hetero-material has the effect of inhibiting the growth of the epitaxial material. The hetero-layer 20 can be optionally a film layer formed of one material on the substrate 10, or can also be multiple film layers formed of multiple materials on the substrate in sequence. It can be understood that in order to achieve a gradual or sudden change in refractive index in the subsequently prepared patterned substrate, multiple film layers of hetero-materials with different refractive indices can be provided in the hetero-layer 20, which is not limited here. Specifically, the hetero-material used in the hetero-layer 20 can specifically include at least one of transparent oxides, nitrides, and carbides. Exemplarily, the oxide can specifically be SiOx, AlOx, etc., the nitride can specifically be SiNx, BN, etc., and the single substance can be diamond.

[0037] As a zero-dimensional nanomaterial, quantum dots are atomic clusters composed of hundreds to thousands of atoms, with a size between 1 - 10 nm and usually spherical. Quantum dots are doped into the hetero-layer during the formation of the hetero-layer, so that the quantum dots are doped into the hetero-layer relatively uniformly. The laser radiation ability of the quantum dots can be utilized to endow the hetero-layer with the ability to convert the color of light. Exemplarily, when the quantum well structure of the LED emits blue light, yellow-green light can be excited from the blue light by using quantum dots of an appropriate size. At this time, the yellow-green light can be mixed with the blue light to form white light. In addition, the hetero-layer 20 can also be used as a film layer structure for sealing quantum dots, which can not only ensure the excitation conversion of color, but also protect the quantum dots from the external environment and prevent the quantum dots from deteriorating.

[0038] It should be noted that the preparation of quantum dots can be composed of II-VI group elements (such as ZnO, ZnS, ZnSe, CdS, CdSe, CdTe, etc.) or III-V group elements (such as GaN, GaP, GaAs, InP, InAs, etc.), or can also be composed of two or more semiconductor materials, such as CdSe / ZnS, CdSe / CdS, etc.; in addition to the above traditional quantum dots, it can also be carbon quantum dots, which are not limited too much here.

[0039] The size of the quantum dots is a key factor affecting the light excitation band. In actual process design, the size of the quantum dots needs to be set according to the light emission requirements of the LED chip, and no restrictions are imposed here. In addition, in order to ensure the light excitation effect of the quantum dots, realize blue light excitation to form yellow-green light, and thus mix to form white light, in this embodiment, the doping ratio of the quantum dots can be set to 0.5%-20%.

[0040] S130. Pattern the heterolayer to form a plurality of heteromicrostructures, and the heteromicrostructures are doped with quantum dots.

[0041] Reference Figure 2 Figure c) of Figure 3 This step is a process of making the heterolayer 20 uneven. It can be understood that a plurality of heteromicrostructures 21 are formed on the substrate 10, and the heteromicrostructures 21 can be used to cover a certain area of the substrate 10, reducing the C-plane area on the substrate 10, so as to ensure that when growing an epitaxial layer (not shown in the figure), the epitaxial material forms nuclei using the C-plane not covered by the hetero material, and then grows into a film along the side surface of the heteromicrostructure 21. During this process, the mutual stress between positions of the epitaxial layer is reduced due to the setting of the heteromicrostructure 21, the epitaxial layer has fewer defects, and the dislocation density is lower. The optional heteromicrostructure is a periodic convex structure or a concave pit structure, and it can be understood that because the concave pit structure and the convex structure are complementary in structure, the epitaxial material actually grows in the concave pit structure and covers the patterned heterolayer during growth, thereby forming an epitaxial layer. Taking the convex structure as an example, in the embodiment of the present invention, the optional shapes of the heteromicrostructures include polygonal cones, conical cones, elliptical cones, cylinders, and truncated cones. For the specific improvement effect of the heteromicrostructure on the quality of the epitaxial layer and the excitation and radiation ability of the quantum dots, those skilled in the art can make a reasonable selection according to the test results, and no excessive restrictions are imposed here.

[0042] Next, the LED structure and white light principle using the above-mentioned patterned substrate will be introduced. Figure 4 is a schematic structural diagram of a white light LED provided by an embodiment of the present invention. Refer to Figure 4 This white light LED chip includes a patterned substrate, an n-type gallium nitride layer located on the patterned substrate, a quantum well, and a p-type gallium nitride layer. After the quantum well emits blue light, it exits through the patterned substrate. In this patterned substrate, since the heterolayer 20 is doped with quantum dots, the heteromicrostructures 21 formed by patterning also have the ability of excitation and radiation by using the quantum dots, so that they can be excited by part of the blue light to radiate yellow-green light. At this time, the unexcited part of the blue light and the yellow-green light are mixed to form white light, thus realizing the white light LED chip. Obviously, setting the heteromicrostructures 21 in the patterned substrate to be doped with quantum dots can use the heteromicrostructures 21 to improve the quality of the epitaxial layer while performing color conversion on the light emitted by the quantum well, realizing the adjustment of the light emission color of the LED chip.

[0043] In the embodiment of the present invention, by forming a heterogeneous layer on a substrate, and synchronously doping quantum dots during the formation of the heterogeneous layer, and then patterning the heterogeneous layer to form a plurality of heterogeneous microstructures, the doped quantum dots in the heterogeneous microstructures can not only enable the heterogeneous microstructures to achieve the adjustment and conversion of the light-emitting color, but also can seal and protect the quantum dots. The embodiment of the present invention solves the problem of low reliability of phosphors in traditional white LEDs. By using synchronous doping of quantum dots in the heterogeneous layer to make heterogeneous microstructures, not only does the heterogeneous microstructure achieve the function of light excitation conversion of LED color, reducing the process steps of coating phosphors during packaging, which helps to simplify the process difficulty and reduce costs; at the same time, the quantum dots can be sealed in the heterogeneous microstructures to isolate the external environment, overcoming the disadvantage that traditional coated phosphors are prone to aging and falling off, which helps to achieve white LEDs with good color rendering and anti-aging yellowing.

[0044] Specifically, in the process of patterning the heterogeneous layer in step S130, the embodiment of the present invention provides specific process steps. Figure 5 It is a flowchart of another method for preparing a patterned substrate doped with quantum dots provided by the embodiment of the present invention. Figure 6 is Figure 5 The structural flowchart of the method for preparing the patterned substrate doped with quantum dots shown. Specifically, step S130 may include:

[0045] S131. Form a photoresist layer on the heterogeneous layer;

[0046] Referring to Figure 6 FIG. c), in this step, when preparing the photoresist layer 40, the photoresist can be a positive photoresist or a negative photoresist. The photoresist layer 40 can be prepared by a spin coating or spraying process, and its thickness range can be set at 1.0 μm - 3.0 μm.

[0047] S132. Adopt a photolithography exposure process or a nanoimprinting technology to form periodic photoresist pillars;

[0048] Referring to Figure 6 FIG. d), where the photoresist pillars 41 are the pattern masks for patterning the heterogeneous layer 20, and the pattern of the photoresist pillars 41 corresponds to the pattern of the microstructures on the final patterned substrate. When preparing the photoresist pillars 41, it can be achieved through a pattern transfer technology such as photolithography exposure or nanoimprinting. Taking the photolithography exposure process as an example, by exposing the photoresist layer 40 through a photomask, and then removing the soluble photoresist by a developing step, the patterning of the photoresist layer 40 is realized, and the pattern of the photomask is transferred to the photoresist layer 40 to form the photoresist pillars 41.

[0049] S133. Using the periodic photoresist columns as a mask, multiple heterogeneous microstructures are etched and formed on the heterogeneous layer by dry etching.

[0050] Reference Figure 6 Figure e) of. This step is a process of pattern transfer according to the photoresist columns. Specifically, dry or wet etching processes can be used to etch the heterogeneous layer to complete patterning. Taking dry etching as an example, the etching gases used may include BCl3, Cl2, CF4, etc.

[0051] Such as Figure 6 Figure e) of is the schematic structure of the patterned substrate doped with quantum dots provided by the embodiment of the present invention. The patterned substrate may include a substrate 10 and multiple heterogeneous microstructures 21 located on the substrate 10. In addition, quantum dots are doped in the heterogeneous microstructures 21. It should be noted that referring to Figure 6 Figure e of, in the patterned substrate provided by this embodiment, when the heterogeneous microstructures 21 are formed by etching, an over-etching method can be used to etch a certain part of the structure of the substrate 10 to ensure that the substrate 10 is exposed from the heterogeneous layer. Therefore, in this embodiment, the heterogeneous microstructures 21 can be formed by etching the heterogeneous layer 20 doped with quantum dots and the substrate 10 together. The heterogeneous microstructures 21 are divided into two layers, the upper layer is the heterogeneous layer doped with quantum dots, and the lower layer is a structural layer integrated with the substrate.

[0052] For the process of synchronously preparing quantum dots and the heterogeneous layer and achieving uniform doping, the embodiment of the present invention provides two implementation methods. Specifically, Figure 7 is the flowchart of another method for preparing a patterned substrate doped with quantum dots provided by the embodiment of the present invention. Referring to Figure 7 , this method for preparing a patterned substrate includes:

[0053] S110. Provide a substrate.

[0054] S121. Dope quantum dots in the heterogeneous material.

[0055] S122. Deposit the heterogeneous material doped with quantum dots on the substrate to form a heterogeneous layer.

[0056] The process of doping quantum dots adopted in steps S121 and S122 can actually be realized by processes such as physical vapor deposition or aerosol spraying. Before physical vapor deposition or aerosol spraying, the quantum dots need to be uniformly mixed in the heterogeneous material. During the specific deposition process, the quantum dots are naturally deposited synchronously with the heterogeneous material and doping is ensured. It can be understood that before actual deposition, the concentration of quantum dots when mixed into the heterogeneous material is the doping concentration of quantum dots in the final heterogeneous layer. Therefore, the process of realizing quantum dot doping by synchronous deposition is easier to control the doping concentration and can also ensure the uniformity of quantum dot doping.

[0057] S130. Pattern the heterogeneous layer to form a plurality of heterogeneous microstructures, and the heterogeneous microstructures are doped with quantum dots.

[0058] Based on the method for preparing a patterned substrate as shown in Figure 7 the embodiments of the present invention also provide a specific implementation manner. In a specific embodiment of the present invention, the steps for preparing the patterned substrate doped with quantum dots include:

[0059] ((1) Add CdSe quantum dots to high-purity aluminum in a vacuum molten state to prepare an aluminum target with a quantum dot concentration of 5%. Use He and N2 as reaction gases, set the sputtering voltage to 300V, and deposit a 0.5-μm-thick AlN layer (heterogeneous layer) on a sapphire substrate. The AlN layer contains a certain concentration of CdSe quantum dots, and the content of quantum dots in the actual AlN layer can be adjusted by the content of quantum dots in the target aluminum. The content of quantum dots in the target aluminum is 0.5% - 20%;

[0060] ((2) Adopt the spin coating method to coat a 0.6-μm-thick positive photoresist on the substrate, and through exposure and development, obtain a photoresist column with a bottom width of 0.6 μm;

[0061] ((3) Perform dry etching on it by ICP to obtain a triangular pyramid protrusion (bottom width 0.85 μm, height 0.45 μm, and the proportion of the patterned heterogeneous layer in the patterned height is 55%). Specifically, refer to the etching formula as shown in the following table:

[0062]

[0063] Figure 8 is a flowchart of another method for preparing a patterned substrate doped with quantum dots provided by the embodiments of the present invention. Refer to Figure 8 and this method for preparing a patterned substrate includes:

[0064] S110. Provide a substrate;

[0065] S123. Deposit the heterogeneous material on the substrate, and simultaneously dynamically inject quantum dots into the deposition gas to form a heterogeneous layer;

[0066] The process of realizing quantum dot doping in this step can also be achieved by physical vapor deposition process or aerosol spray coating process. Specifically, when performing vapor deposition or aerosol spray coating of heterogeneous materials, structures such as nozzles can be used to synchronously and dynamically inject quantum dots into the heterogeneous material gas flow. It can be understood that in the gas state, the heterogeneous materials can be naturally and uniformly mixed with the quantum dots. In addition, the doping ratio of the quantum dots can be controlled according to gas concentration, flow rate ratio, etc. Those skilled in the art can adjust according to actual process conditions and no excessive limitations are imposed here.

[0067] S130. Pattern the heterolayer to form a plurality of heterogeneous microstructures doped with quantum dots.

[0068] Similarly, based on the preparation method of the patterned substrate as shown in Figure 8 , the embodiments of the present invention also provide specific implementation manners. In this specific embodiment, the steps for preparing the patterned substrate doped with quantum dots include:

[0069] (1) Using a sapphire wafer as the substrate, grow a SiO2 layer (heterolayer) with a thickness of 2.1 μm by PECVD, with an electrode power of 200 W, a temperature of 260 °C, a gas flow rate ratio of SiH4:N2O:N2 = 1:4:5, and a deposition rate of 100 nm / min; during the deposition process, use aerosol jet technology to spray a colloidal solution in which 10% concentration of CdTe quantum dots are uniformly dispersed in the form of nanoscale droplets into the chamber interior and be encapsulated in the heterolayer as SiO2 is deposited.

[0070] (2) Adopt the spin coating method to coat a positive photoresist with a thickness of 2.0 μm on the substrate, and obtain a photoresist column with a bottom width of 2.0 μm through imprinting technology;

[0071] (3) Perform dry etching on it by ICP to obtain a triangular pyramid protrusion (bottom width 2.80 μm, height 1.65 μm, and the proportion of the patterned heterolayer in the pattern height is 70%). Specifically, refer to the etching recipe as follows:

[0072]

[0073] Based on the same inventive concept, the embodiments of the present invention also provide an LED epitaxial wafer. Figure 9 It is a schematic structural diagram of an LED epitaxial wafer provided by the embodiments of the present invention. Referring to Figure 9 , this LED epitaxial wafer includes the patterned substrate 1 doped with quantum dots provided in the above embodiments, and further includes an epitaxial layer 2 formed on the patterned substrate 1.

[0074] For forming an epitaxial layer on heterogeneous microstructures of different materials, different LED epitaxial wafer growth technologies are required. For the patterned composite substrate provided in the embodiments of the present invention, the epitaxial layer 2 on the LED epitaxial wafer can be a GaN, AlGaN epitaxial layer, etc. Since the LED epitaxial wafer uses the patterned substrate 1 provided in the above embodiments, it has the same beneficial effects as the patterned substrate 1.

[0075] Note that the above is only the preferred embodiment of the present invention and the technical principles applied. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein. Various obvious changes, re-adjustments, combinations with each other, and substitutions can be made by those skilled in the art without departing from the protection scope of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments. Without departing from the concept of the present invention, more other equivalent embodiments can be included, and the scope of the present invention is determined by the scope of the appended claims.

Claims

1. A method for preparing a patterned substrate doped with quantum dots, characterized in that, Comprising: Providing a substrate; Forming a heterolayer on the substrate, and synchronously doping quantum dots during the formation of the heterolayer; Patterning the heterolayer to form a plurality of heteromicrostructures, wherein the quantum dots are doped in the heteromicrostructures; The heteromaterial of the heteromicrostructure comprises at least one of a transparent oxide, a nitride, and an element; Forming a heterolayer on the substrate, and synchronously doping quantum dots during the formation of the heterolayer, comprising: Depositing a heteromaterial on the substrate, and dynamically injecting quantum dots into the deposition gas simultaneously to form the heterolayer.

2. The method for preparing a patterned substrate according to claim 1, wherein Forming a heterolayer on the substrate, comprising: Depositing a heterolayer on the substrate by physical vapor deposition or aerosol jet process.

3. A patterned substrate doped with quantum dots, characterized in that, Prepared by the method for fabricating a patterned substrate doped with quantum dots according to any one of claims 1-2, the patterned substrate doped with quantum dots comprises a substrate and a plurality of heteromicrostructures located on the substrate, and the quantum dots are doped in the heteromicrostructures.

4. The patterned substrate according to claim 3, wherein The doping ratio of the quantum dots is 0.5%-20%.

5. The patterned substrate according to claim 3, wherein The material of the quantum dots comprises at least one semiconductor material of II-VI group elements and III-V group elements.

6. The patterned substrate according to claim 3, wherein The shape of the heteromicrostructure comprises a polygonal pyramid, a cone, an elliptical cone, a cylinder, and a frustum of a cone.

7. The patterned substrate according to claim 3, wherein The heteromaterial of the heteromicrostructure comprises at least one of a transparent oxide, a nitride, and an element.

8. An LED epitaxial wafer, characterized in that, Comprising the patterned substrate doped with quantum dots according to any one of claims 3-7.

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