ITO film and preparation method, LED chip

Abstract

The present invention provides an inertial (ITO) film and a preparation method, as well as an LED chip. An ITO target material is subjected to electron beam evaporation to prepare an ITO gas-phase reactant, and a metal base material and the ITO gas-phase reactant are then heated at a preset temperature to form metal droplets. The metal droplets are controlled to precipitate at a preset oxygen flow rate and a preset ITO target material evaporation rate to form an ITO film with an interconnected nanostructure. Specifically, total internal reflection light scattering (Rayleigh scattering) is regulated at the nanoscale. The ITO film with the surface nanostructure is applied to an LED and can cause changes in total internal reflection of light through changes in the refractive index in the nanometer-scale space, thereby improving light extraction efficiency.

Description

Technical Field

[0001] The present invention relates to the technical field of LEDs, and in particular to an ITO film and a preparation method thereof, and an LED chip. Background Art

[0002] Light Emitting Diode (LED) is a semiconductor electronic component that can emit light. Due to its small size, high brightness and low energy consumption, it has attracted the attention of more and more researchers.

[0003] In the current standard LED chips, the following methods can be used to improve the LED luminous efficiency, but each has its own drawbacks:

[0004] 1) By wet etching and roughening the ITO conductive film, the luminous power of the LED chip can be improved to a certain extent. However, this method requires additional chip process steps, and the process control is greatly affected by the environment and materials.

[0005] 2) Preparing the ITO conductive film into a periodic hole structure can improve the luminous power of the LED chip to a certain extent, but this periodic hole structure increases the chip operating voltage by about 0.15V, which has little significance for the luminous efficiency of the packaged white light;

[0006] 3) Based on the high-temperature agglomeration characteristics of the Ni thin layer, etching the surface of the nanostructured P-type layer using the agglomerated Ni as a mask can improve the luminous power of the LED chip to a certain extent. However, due to the fragile and easily damaged characteristics of the P-type layer, it is easy to cause the LED chip to fail. Summary of the Invention

[0007] Based on this, the purpose of the present invention is to provide an ITO film and a preparation method, and an LED chip, aiming to improve the luminous power of the LED chip without affecting other properties of the LED chip.

[0008] According to an embodiment of the present invention, a method for preparing an ITO thin film includes:

[0009] Providing an ITO target material, and preparing an ITO gas-phase reactant by electron beam evaporation of the ITO target material;

[0010] Providing a metal base material, and heating the metal base material and the ITO gas phase reactant at a preset temperature to form metal droplets;

[0011] The metal droplets are controlled to precipitate under a preset oxygen flow rate and a preset ITO target material evaporation rate to form a nanostructured ITO film.

[0012] Furthermore, in the step of preparing an ITO gas-phase reactant by electron beam evaporation of the ITO target, the ITO target is first placed in an electron beam evaporation device and vacuumed, and then the electron beam is controlled to bombard the ITO target, and the evaporation temperature is controlled to be 280°C to 300°C to obtain the ITO gas-phase reactant.

[0013] Furthermore, the ITO target is InSn oxide.

[0014] Furthermore, the metal base material is one of Au, Ni or Fe.

[0015] Furthermore, in the step of heating the metal base material and the ITO gas-phase reactant at a preset temperature to form metal droplets, the preset temperature is 290° C. to 310° C.

[0016] Furthermore, in the step of controlling the metal droplets to precipitate under a preset oxygen flow rate and a preset ITO target evaporation rate to form a nanostructured ITO film, the oxygen flow rate is first controlled to be 0 sccm, and the evaporation rate of the ITO target is The first ITO film with a thickness of 50nm to 100nm is deposited, and the oxygen flow rate is controlled to be 9sccm to 11sccm. The evaporation rate of the ITO target is A second ITO film with a thickness of 150 nm to 200 nm is deposited, wherein the ITO film is composed of the first ITO film and the second ITO film.

[0017] Furthermore, the roughness of the ITO film is greater than 35 nm.

[0018] An ITO thin film according to an embodiment of the present invention is prepared by the above-mentioned ITO thin film preparation method.

[0019] Furthermore, the thickness of the ITO film is 200nm to 300nm.

[0020] An LED chip according to an embodiment of the present invention includes an ITO thin film prepared according to the above-mentioned ITO thin film preparation method.

[0021] Compared with the existing technology: the ITO target is prepared into an ITO gas-phase reactant through electron beam evaporation, and the metal base material and the ITO gas-phase reactant are heated at a preset temperature to form metal droplets, and the metal droplets are controlled to precipitate under a preset oxygen flow rate and a preset ITO target evaporation rate to form an interconnected nanostructured ITO film. Specifically, the total internal reflection light scattering (Rayleigh scattering) is regulated at the nanoscale. The surface nanostructured ITO film is used in LEDs, which can cause changes in the total internal reflection of light through changes in the refractive index in the nanoscale space, thereby improving the light extraction efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 A flowchart of a method for preparing an ITO thin film according to an embodiment of the present invention;

[0023] Figure 2 The current-voltage curves of the ITO films obtained in Example 2 and Comparative Examples 1-3 when applied to LED chips;

[0024] Figure 3 The current and luminous power curves of the ITO films obtained in Example 2 and Comparative Examples 1-3 when applied to LED chips. DETAILED DESCRIPTION

[0025] To facilitate understanding of the present invention, the present invention will be described more fully below with reference to the accompanying drawings. The drawings illustrate several embodiments of the present invention. However, the present invention may be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and comprehensive understanding of the present invention.

[0026] It should be noted that when an element is referred to as being "fixed to" another element, it may be directly on the other element or there may be an intermediate element. When an element is referred to as being "connected to" another element, it may be directly connected to the other element or there may be an intermediate element. The terms "vertical," "horizontal," "left," "right," and similar expressions used herein are for illustrative purposes only.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this invention pertains. The terms used in this specification of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0028] refer to Figure 1 , a method for preparing an ITO thin film provided by an embodiment of the present invention, specifically comprising the following steps:

[0029] S100: providing an ITO target material, and preparing an ITO gas-phase reactant by electron beam evaporation of the ITO target material;

[0030] It should be noted that the ITO film is generally deposited on the LED epitaxial wafer, wherein the LED epitaxial wafer includes at least a substrate, an N-type layer, an active layer and a P-type layer. Before the ITO film is deposited on the LED epitaxial wafer, the LED epitaxial wafer needs to be processed. Specifically, the N-GaN morphology is first etched and exposed by the inductively coupled plasma (ICP) etching technology, and then CB-SiO2 is deposited on the surface of the P-type layer as a current blocking layer using plasma enhanced chemical vapor deposition (PECVD) equipment to improve the current crowding phenomenon near the P electrode. Finally, the GaN-based epitaxial wafer is cleaned with SPM solution, wherein the SPM solution includes H2SO4, H2O2 and H2O. After cleaning, it is dried. After drying, the subsequent ITO film deposition is carried out.

[0031] Furthermore, after obtaining the ITO target material, the ITO target material is subjected to electron beam evaporation to prepare an ITO gas-phase reactant. Specifically, the ITO target material is InSn oxide, that is, the InSn oxide is placed in an electron beam evaporation device and vacuumed. During the vacuuming process, the temperature in the cavity is maintained at 280°C to 300°C, and then the electron beam is controlled to bombard the InSn oxide, and the evaporation temperature is controlled to 280°C to 300°C. The InSn oxide will evaporate from the solid phase to the gas phase to obtain the ITO gas-phase reactant.

[0032] S200: providing a metal base material, and heating the metal base material and the ITO gas-phase reactant at a preset temperature to form metal droplets;

[0033] Specifically, the metal base material is any one of Au, Ni or Fe. Taking Au as an example, the metal base material Au, gas-phase InSn oxide and the processed LED epitaxial wafer are placed in the cavity, and the preset temperature is controlled to be 290°C to 310°C. Since Au is heated in a high-temperature environment, after absorbing the gas-phase components of InSn oxide, its melting point becomes lower and it melts into metal droplets, that is, a mixture of Au / InSn oxide. In the atmosphere of InSn oxide gas-phase reactants, the Au / InSn oxide mixture continuously absorbs the target element In-Sn oxide, that is, whisker elements, in the InSn oxide gas-phase reactant, thereby forming metal droplets with a lower melting point.

[0034] The target element In-Sn oxide is continuously adsorbed and dissolved into the metal droplets, gradually reaching a supersaturated state. Then, it will precipitate in the metal droplets to form crystal nuclei of the target element. As the target element continues to precipitate at the interface between the droplets and the LED epitaxial wafer, that is, when the number of atoms in the droplets exceeds the equilibrium concentration in the liquid phase, crystals will precipitate under the metal droplets and gradually grow in a direction to form a nanostructured ITO film. This nanostructured ITO film is a granular porous film.

[0035] S300: controlling the metal droplets to precipitate under a preset oxygen flow rate and a preset ITO target evaporation rate to form a nanostructured ITO film.

[0036] It should be noted that the specific process of forming the ITO film into a granular porous film is as follows: first, the oxygen flow rate is controlled to be 0 sccm, and the evaporation rate of the ITO target is The first ITO film with a thickness of 50nm to 100nm is deposited, and the oxygen flow rate is controlled to be 9sccm to 11sccm. The evaporation rate of the ITO target is A second ITO film with a thickness of 150nm to 200nm is precipitated, wherein the ITO film is composed of a first ITO film and a second ITO film. It can be understood that by controlling the amount of oxygen permeation at different stages, an ITO film with a thickness of 200nm to 300nm is obtained. In addition, the roughness of the ITO film prepared by the above process is greater than 35nm.

[0037] Specifically, after the ITO film deposition is completed, the PN metal electrode of the chip is prepared. The electrode structure is Cr / Al / Ti / Ni / Pt / Ni / Pt / Au in sequence, and a SiO2 passivation layer is deposited on the outermost surface of the chip, finally obtaining an LED chip including an ITO film.

[0038] The present invention will be further described below with specific embodiments:

[0039] Example 1

[0040] This embodiment provides an ITO film for deposition on an LED epitaxial wafer. The LED epitaxial wafer includes at least a substrate, an N-type layer, an active layer, and a P-type layer. Before the ITO film is deposited on the LED epitaxial wafer, the LED epitaxial wafer needs to be processed. Specifically, the N-GaN morphology is first etched and exposed using an inductively coupled plasma (ICP) etching technique. Then, CB-SiO2 is deposited on the surface of the P-type layer using a plasma enhanced chemical vapor deposition (PECVD) device as a current blocking layer to improve current crowding near the P electrode. Finally, the GaN-based epitaxial wafer is cleaned using an SPM solution (H2SO4:H2O2:H2O=5:1:1) and then dried. After drying, the subsequent ITO film deposition is performed.

[0041] The deposition process of ITO thin film can be:

[0042] 1) providing an ITO target material, and preparing an ITO gas-phase reactant by electron beam evaporation of the ITO target material;

[0043] After obtaining the ITO target material, the ITO target material is subjected to electron beam evaporation to prepare an ITO gas-phase reactant. Specifically, the ITO target material is InSn oxide, that is, the InSn oxide is placed in an electron beam evaporation device and vacuumed. During the vacuuming process, the temperature in the cavity is maintained at 300°C, and then the electron beam is controlled to bombard the InSn oxide, and the evaporation temperature is controlled to 300°C. The InSn oxide will evaporate from the solid phase to the gas phase to obtain the ITO gas-phase reactant.

[0044] 2) providing a metal base material, and heating the metal base material and the ITO gas-phase reactant at a preset temperature to form metal droplets;

[0045] In this embodiment, the metal base material is Au. The metal base material Au, the gas phase InSn oxide and the processed LED epitaxial wafer are placed in the cavity, and the preset temperature is controlled to 300°C. Since Au is heated in a high temperature environment, after absorbing the gas phase components of the InSn oxide, the melting point becomes lower and it melts into metal droplets, that is, a mixture of Au / InSn oxide.

[0046] 3) controlling the metal droplets to precipitate under a preset oxygen flow rate and a preset ITO target evaporation rate to form a nanostructured ITO film;

[0047] In this embodiment, the specific process of forming the ITO thin film into a granular porous film is as follows: first, the oxygen flow rate is controlled to be 0 sccm, and the evaporation rate of the ITO target is The first ITO film with a thickness of 50 nm was deposited, and the oxygen flow rate was controlled to be 10 sccm. The evaporation rate of the ITO target was A second ITO film with a thickness of 150 nm is precipitated, wherein the ITO film is composed of a first ITO film and a second ITO film. It can be understood that by controlling the amount of oxygen permeation in different stages, an ITO film with a thickness of 200 nm is obtained. In addition, the roughness of the ITO film prepared by the above process is 36.5 nm.

[0048] Example 2

[0049] This embodiment also provides an ITO film, which differs from embodiment 1 in that the thickness of the first ITO film is 75 nm, and the thickness of the second ITO film is 175 nm, that is, the thickness of the ITO film is 250 nm, and the roughness of the ITO film is 38.0 nm.

[0050] Example 3

[0051] This embodiment also provides an ITO film, which differs from embodiment 2 in that the thickness of the first ITO film is 100 nm, and the thickness of the second ITO film is 200 nm, that is, the thickness of the ITO film is 300 nm, and the roughness of the ITO film is 37.1 nm.

[0052] Comparative Example 1

[0053] This comparative example provides an ITO thin film, which differs from Example 2 in that oxygen is not introduced during the growth of the ITO thin film, thereby obtaining a columnar ITO thin film having a roughness of 29.5 nm.

[0054] Comparative Example 2

[0055] This comparative example provides an ITO film, which differs from Example 2 in that, during the process of growing the ITO film, the oxygen flow rate is first controlled to 10 sccm to grow the first ITO film, and then the oxygen flow rate is controlled to 0 sccm to grow the second ITO film to obtain a tree-like ITO film, and the roughness of the tree-like ITO film is 30.0 nm.

[0056] Comparative Example 3

[0057] This comparative example provides an ITO film, which differs from Example 2 in that, in the process of growing the ITO film, the oxygen flow rate is first controlled to be 10 sccm to grow the first ITO film, and then the oxygen flow rate is controlled to be 10 sccm to grow the second ITO film to obtain a granular ITO film, and the roughness of the tree-like ITO film is 7.1 nm.

[0058] The ITO films obtained in Examples 1-3 and Comparative Examples 1-3 were applied to LED chips, and the voltage of the LED chips was tested under a certain operating current. Figure 2 and Figure 3 As shown, Figure 2 The current-voltage curves of the ITO films obtained in Example 2 and Comparative Examples 1-3 when applied to LED chips are shown. Figure 3 The current and luminous power curves of the ITO films obtained in Example 2 and Comparative Examples 1-3 when applied to LED chips.

[0059] The specific results are as follows:

[0060]

[0061] As can be seen from the table, the ITO film prepared by the method in the embodiment of the present invention is applied to the LED chip, which effectively improves the luminous power compared with the prior art. Among them, the granular porous ITO film prepared in Example 2 is particularly obvious when applied to the LED chip. The luminous performance of the ITO films prepared in other embodiments when applied to the LED chip is slightly worse than that of Example 2. In addition, this method is simple, controllable, does not increase additional costs, and has no effect on the operating voltage of the LED.

[0062] In summary, the ITO film, preparation method, and LED chip in the embodiments of the present invention are achieved by preparing an ITO gas-phase reactant by electron beam evaporation of an ITO target material, and then heating the metal base material and the ITO gas-phase reactant at a preset temperature to form metal droplets, and controlling the metal droplets to precipitate at a preset oxygen flow rate and a preset ITO target evaporation rate to form an interconnected nanostructured ITO film. Specifically, the total internal reflection light scattering (Rayleigh scattering) is regulated at the nanoscale. The ITO film with a surface nanostructure is used in LEDs, which can cause changes in the total internal reflection of light through changes in the refractive index in the nanoscale space, thereby improving the light extraction efficiency.

[0063] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing an ITO thin film, characterized in that: The method comprises: An ITO target is provided, and an ITO gas-phase reactant is prepared by electron beam evaporation of the ITO target. The ITO target is first placed in an electron beam evaporation device and vacuumed. Then, an electron beam is controlled to bombard the ITO target, and the evaporation temperature is controlled to be 280° C. to 300° C. to obtain the ITO gas-phase reactant. The ITO target is InSn oxide. Providing a metal base material, and heating the metal base material and the ITO gas phase reactant at a preset temperature to form metal droplets, wherein the metal base material is one of Au, Ni, or Fe, and the preset temperature is 290° C. to 310° C.; The metal droplets are controlled to precipitate under a preset oxygen flow rate and a preset ITO target evaporation rate to form a nanostructured ITO film. First, the oxygen flow rate is controlled to be 0 sccm and the evaporation rate of the ITO target is 0.9 Å / S to 1.1 Å / S to precipitate a first ITO film with a thickness of 50 nm to 100 nm. Then, the oxygen flow rate is controlled to be 9 sccm to 11 sccm and the evaporation rate of the ITO target is 0.9 Å / S to 1.1 Å / S to precipitate a second ITO film with a thickness of 150 nm to 200 nm. The ITO film is composed of the first ITO film and the second ITO film.

2. The ITO film preparation method according to claim 1, wherein The roughness of the ITO film is greater than 35 nm.

3. An ITO film, characterized in that The ITO film is prepared by the ITO film preparation method according to any one of claims 1 to 2.

4. The ITO film according to claim 3, characterized in that The thickness of the ITO film is 200nm~300nm.

5. An LED chip, characterized in that: The invention comprises an ITO film prepared by the ITO film preparation method according to any one of claims 1-2.

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