Method for manufacturing a light emitting device

Abstract

The application discloses a manufacturing method of a light-emitting device, which comprises the following steps: depositing a transparent conductive layer on the surface of a semiconductor epitaxial wafer; etching the transparent conductive layer by using a first etching gas to form a predetermined pattern, wherein the first etching gas comprises a bromine-containing gas; and etching the semiconductor epitaxial wafer by using a second etching gas. The application can improve the surface roughness of the semiconductor epitaxial wafer and the consistency of etching topography, and simplify the process flow.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of semiconductor device manufacturing, and more particularly, to a manufacturing method of a light emitting device. BACKGROUND

[0002] High-efficiency, high-power GaN-based blue LED is widely used in indoor lighting, night decoration, medical treatment, automobile lighting, large screen display, mobile phone backlight and other fields, and LED chip is an important part of LED light source. Among them, the forward LED GaN-based chip has the advantages of simple process, low cost and high yield, and is the mainstream choice of current solid-state lighting and backlight industry. Due to the low hole concentration of P-type GaN material, current spreading problem will occur, in order to solve this problem, many people propose to use ITO (tin oxide) film layer as current spreading layer.

[0003] ITO is an indium tin compound, its band gap Eg=3.5-4.3eV, the transmittance in the visible light range is greater than 90%; it has good conductivity, and its resistivity reaches 10 -4 Ω·cm order of magnitude. Because it has a low resistivity, the current can be more uniformly distributed on the P-GaN through the ITO layer, so ITO is often used as a current spreading layer in the preparation of LED chips. At the same time, the refractive index value of ITO is between GaN and encapsulation resin, and the visible light transmittance is high, which can increase the light efficiency.

[0004] In the existing Mesa etching process, wet etching is often used to obtain the required pattern of ITO layer, which will cause the etching morphology of ITO film layer to be uneven due to the differences in effective reactant concentration, reaction temperature and ITO deposition thickness in different areas, and further cause the performance of devices in different batches to be different. SUMMARY

[0005] The purpose of the present application is to provide a manufacturing method of a light emitting device, which realizes the improvement of the surface roughness of the etching morphology of the transparent conductive layer and ensures the consistency of the etching morphology of the transparent conductive layer.

[0006] In order to achieve the above purpose, the present application provides a manufacturing method of a light emitting device, comprising:

[0007] Depositing a transparent conductive layer on the surface of a semiconductor epitaxial wafer;

[0008] Etching the transparent conductive layer by using a first etching gas to form a predetermined pattern, wherein the first etching gas comprises a bromine-containing gas;

[0009] Etching the semiconductor epitaxial wafer by using a second etching gas.

[0010] Optionally, before etching the transparent conductive layer by using the first etching gas, the method further comprises:

[0011] forming a patterned photoresist mask layer on the transparent conductive layer.

[0012] Optionally, the bromine-containing gas comprises HBr, and the first etching gas further comprises Cl2 and BCl3.

[0013] Optionally, the total flow rate of the first etching gas ranges from 100 to 200 sccm, and the volume ratio of Cl2 in the first etching gas ranges from 20 to 50%.

[0014] Optionally, during the etching of the transparent conductive layer by the first etching gas, the inductively coupled power ranges from 200 to 300 W, and the radio frequency bias power ranges from 100 to 200 W.

[0015] Optionally, during the etching of the transparent conductive layer by the first etching gas, the chamber pressure ranges from 3 to 10 mTorr.

[0016] Optionally, the etching of the transparent conductive layer by the first etching gas and the etching of the semiconductor epitaxial wafer by the second etching gas are two steps of etching continuously completed in the same process chamber.

[0017] Optionally, the second etching gas comprises Cl2 and BCl3, and the chamber pressure used in the etching of the semiconductor epitaxial wafer by the second etching gas is the same as the chamber pressure used in the etching of the transparent conductive layer by the first etching gas.

[0018] Optionally, during the etching of the semiconductor epitaxial wafer by the second etching gas, the inductively coupled power ranges from 300 to 500 W, and the radio frequency bias power ranges from 50 to 200 W.

[0019] Optionally, before the etching of the semiconductor epitaxial wafer by the second etching gas, the method further comprises:

[0020] The ICP-OES detection system is used to determine whether the transparent conductive layer at the bottom of the microstructure is completely removed, and if so, the step of etching the semiconductor epitaxial wafer by the second etching gas is performed.

[0021] The present application has the following beneficial effects:

[0022] In the process of etching the transparent conductive layer, the transparent conductive layer is dry etched by using the etching gas containing bromine, the reaction byproduct of the etching gas containing bromine and the transparent conductive layer has a lower boiling point, the byproduct is easy to remove, and the byproduct does not need to be removed by increasing the bombardment strength, the radio frequency bias power (lower electrode power) can be reduced, the degree of plasma bombardment of the transparent conductive layer is weakened, the byproduct of the oxide generated by the strong bombardment of the transparent conductive layer can be avoided, the oxide byproduct does not need to be removed by wet cleaning in the whole etching process, the continuity of the etching process environment can be realized, thereby avoiding the problem that the etching environment needs to be switched by equipment or process between ITO and GaN etching in the traditional method, the etching continuity in the same etching environment cannot be realized, and the etching result drift problem exists due to the change of the etching gas environment.

[0023] Further, since the reaction byproduct of the etching gas containing bromine and the transparent conductive layer has a lower boiling point, a lower inductance coupling power (upper electrode power) can be used when etching the transparent conductive layer, thereby avoiding the problem that the photoresist layer is difficult to remove due to high temperature paste or other hard masks are used, and then the etching morphology of the ITO film layer after etching can be obtained, the consistency of the ITO film layer etching morphology is ensured, and the paste needs to be replaced by other hard masks due to the temperature rise caused by the high inductance coupling power in the traditional method, which is avoided in the present application, the photoresist can be directly used as a mask in the present application, and the process cost is lower.

[0024] Further, the etching of the transparent conductive layer and the etching of the semiconductor epitaxial wafer are two continuous etchings completed in the same process chamber, and the chamber pressures of the two etchings are the same, the etching continuity in the same etching environment is realized, and the etching result drift problem caused by the change of the etching gas environment is avoided.

[0025] The system of the present application has other characteristics and advantages, which will be apparent from or set forth in the accompanying drawings and the detailed description that follows, which together serve to explain certain principles of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0026] The above and other objects, features and advantages of the present application will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings in which like reference characters refer to like parts throughout and in which:

[0027] Figure 1 A step diagram of a manufacturing method of a light emitting device according to an embodiment of the present application is shown.

[0028] Figure 2Etching byproducts commonly encountered are shown in a boiling point diagram.

[0029] Figure 3 GaN epitaxial wafer surface after etching ITO film layer using Cl2+BCl3+Ar under low power conditions.

[0030] Figure 4 GaN epitaxial wafer surface after etching ITO film layer using Cl2+BCl3+Ar under high power conditions.

[0031] Figure 5 GaN epitaxial wafer surface after etching ITO film layer using Cl2+BCl3+HBr under low power conditions. DETAILED DESCRIPTION

[0032] Prior art one uses ITO film layer with thickness of 600-1000A as current spreading layer, under photoresist as mask, ITO is wet etched in acidic solution to obtain the required pattern, then ICP dry etching P-GaN to N-GaN is used to complete Mesa process. Mainly includes the following steps:

[0033] (1) Sputter process is used to deposit ITO film layer with thickness of 600-1000A on sapphire-based GaN epitaxial wafer surface.

[0034] (2) Photoresist is applied on the sapphire-based GaN epitaxial wafer after deposition of ITO and solidification heat treatment is performed to form photoresist mask.

[0035] (3) ITO is wet etched in acidic solution (commonly used acidic solution such as HCl / FeCl3 solution) to obtain the required pattern.

[0036] (4) GaN etching is performed using inductively coupled plasma dry etching machine to complete Mesa process. Dry etching process parameters are as follows: reaction gas Cl2 / BCl3, wherein the volume percentage of Cl2 is 20-80%, gas pressure: 3-10 mTorr, total flow of reaction gas: 100-200 sccm, inductively coupled power: 300-500 W, radio frequency bias power: 50-200 W.

[0037] Prior art one obtains the required pattern by wet etching ITO in acidic solution (commonly used acidic solution such as HCl / FeCl3 solution), but wet etching ITO will cause differences in etching rate due to different effective reactant concentrations, reaction temperatures, etc. in different regions, and differences in wafer morphology after ITO wet etching in different regions due to different ITO deposition thicknesses, which will affect the effect of ITO as current spreading layer and cause differences in performance of devices in different regions or batches.

[0038] The prior art two discloses a method for improving the electrical characteristics of a P-type gallium nitride film. A layer of indium tin oxide is deposited on the P-GaN film of the epitaxial layer of the conventional structure LED, and the ITO film is bombarded by inductively coupled plasma, so that the hole concentration of the bombarded P-GaN film is improved, the resistivity is reduced, and the electrical characteristics of the film are improved.

[0039] In the prior art two, the ITO film layer is etched by the ICP method using Cl2 and He gas, and the process gas needs to be switched for subsequent GaN film etching. This process method is complex, and in order to improve the etching surface roughness, the ICP bombardment effect (increase the radio frequency bias power) is increased to remove byproducts, but at the same time, the surface oxides (such as In2O3) are also bombarded, and subsequent wet etching is required to remove the oxides generated due to the bombardment. The sample after ICP bombardment needs to be soaked in a buffer oxide etchant (BOE) solution to remove the oxides (indium oxide) generated due to high-power ICP bombardment of the ITO film layer. The ITO and GaN etching need to be switched between devices or processes, and there is no etching continuity in the same etching environment. Due to the change of etching gas environment, there is a problem of etching result drift.

[0040] In addition, improving the surface roughness can also use high temperature (such as increasing the inductance coupling power, increasing the etching heat production), which is beneficial to the volatilization of byproducts. However, the above two methods will cause the photoresist to be pasty, and it is difficult to remove the photoresist or other hard mask problems are formed.

[0041] The present application can reduce the degree of ICP bombardment, avoid the generation of indium oxide during the etching of the transparent conductive layer, and thus does not need additional process switching to clean the oxide, so that continuous etching of the transparent conductive layer and the semiconductor epitaxial wafer can be realized, thereby ensuring the consistency of the device and simplifying the process.

[0042] The present application will be described in more detail below with reference to the accompanying drawings. Although the preferred embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0043] Embodiment

[0044] As Figure 1 shown, the present embodiment provides a method for manufacturing a light emitting device, comprising:

[0045] S1: depositing a transparent conductive layer on the surface of a semiconductor epitaxial wafer;

[0046] The semiconductor epitaxial wafer in the embodiment is a GaN epitaxial wafer, and the transparent conductive layer is an ITO film layer. The GaN epitaxial wafer includes, from bottom to top, a sapphire substrate, a U-GaN layer, an N-GaN layer, an MQW layer, and a P-GaN layer. The GaN epitaxial wafer is prepared by providing a sapphire substrate, and epitaxially growing the U-GaN layer, the N-GaN layer, the multi-quantum well layer, and the P-GaN layer on the surface of the sapphire substrate in sequence by using an epitaxial process to form a GaN epitaxial layer.

[0047] In this step, the ITO film layer is formed on the surface of the GaN epitaxial layer of the GaN epitaxial wafer by using a sputter process. Preferably, the thickness of the ITO film layer is 100-200 nm.

[0048] S2: etching the transparent conductive layer to form a predetermined pattern by using a first etching gas, wherein the first etching gas includes a bromine-containing gas.

[0049] In this embodiment, before step S2 is performed, a patterned photoresist mask layer is formed on the transparent conductive layer.

[0050] Specifically, the patterned photoresist mask layer is formed on the ITO film layer by spin-coating photoresist and performing a curing heat treatment, and then by exposure and development.

[0051] In step S2, the bromine-containing gas in the first etching gas is preferably HBr.

[0052] Meanwhile, the first etching gas in this embodiment also includes Cl2 and BCl3.

[0053] Preferably, the total flow rate of the first etching gas ranges from 100 to 200 sccm, and the volume ratio of Cl2 in the first etching gas ranges from 20 to 50%. In the etching of the transparent conductive layer by using the first etching gas, the inductively coupled power ranges from 200 to 300 W, the radio frequency bias power ranges from 100 to 200 W, and the chamber pressure ranges from 3 to 10 mTorr.

[0054] In this step, the ITO film layer is etched by using an inductively coupled plasma dry etching machine, and HBr gas is used to etch the ITO film layer. The by-products generated by the etching are InBrx and InClx, etc., wherein the volatilization temperature of InBrx is lower than that of InCl2x (for example, the volatilization temperature of InBr3 is 600°C, and the volatilization temperature of InCl3 is 800°C). Figure 2As shown, the boiling point of InBrx is 371℃ and that of InCl2x is 600℃ at atmospheric pressure. Therefore, byproducts generated during the etching of the ITO film are more easily removed from the etched surface. Consequently, the etching power can be reduced during ITO etching (both inductive coupling power and RF bias power are relatively low), thus lowering the etching temperature and preventing photoresist smearing, which can lead to difficulties in resist removal or the formation of other hard masks on the epitaxial wafer surface. Therefore, this embodiment uses a gas containing HBr as the etching gas to etch the ITO film at low power and low temperature, resulting in a smooth morphology without byproduct residue. Furthermore, since there is no smearing problem, this application can use a lower-cost photoresist directly as the mask, thereby reducing process costs.

[0055] Surface roughness can also be improved by increasing the temperature (e.g., using power to increase etching heat), which facilitates the volatilization of byproducts. In contrast, Figure 3 When Cl2 / BCl3 / Ar is used as the process gas under low power conditions (inductive coupling power: 200-300W, RF bias power: 100-200W), the volatilization of In-containing byproducts after etching is difficult, resulting in a rough surface morphology of the GaN epitaxial wafer. Figure 4 For high-power conditions (inductive coupling power: 400-600W, RF bias power: 200-300W), Cl2 / BCl3 / Ar is used as the process gas. Increasing the inductive coupling power can increase the etching temperature, promote the volatilization of In-containing byproducts, and improve the surface roughness of the etched surface. However, the increase in etching temperature leads to photoresist paste formation. Figure 5 In this embodiment, Cl2 / BCl3 / HBr is used as the process gas under low power conditions (inductive coupling power: 200-300W, RF bias power: 100-200W). The In-containing byproducts are more volatile, the etched surface is rough and smooth, and the etching temperature does not cause photoresist to stick.

[0056] S3: The semiconductor epitaxial wafer is etched using a second etching gas.

[0057] In this embodiment, before executing step S3, the method further includes: using an ICP-OES detection system to determine whether the ITO film layer at the bottom of the etched microstructure has been completely removed; if so, then executing step S3.

[0058] Specifically, after completing step S2 to etch the transparent conductive film layer, the endpoint determination of ITO dry etching (EPD final inspection) can be performed using an ICP-OES inspection system, which can avoid differences in the performance of different batches of devices due to different ITO deposition thickness.

[0059] Preferably, the etching of the transparent conductive layer by the first etching gas and the etching of the semiconductor epitaxial wafer by the second etching gas in step S3 are two-step etching continuously completed in the same process chamber.

[0060] Since the surface topography after the etching of the transparent conductive layer in step S2 is free of residue of by-products, and the by-products do not need to be soaked and cleaned, after the ITO post-etching is completely judged by the EPD, the dry etching of the GaN epitaxial wafer can be continuously performed in the same process chamber, so as to complete the Mesa process.

[0061] In step S3, the second etching gas preferably comprises Cl2 and BCl3, and the chamber pressure used in the etching of the semiconductor epitaxial wafer by the second etching gas is the same as that used in the etching of the transparent conductive layer by the first etching gas. Alternatively, the second etching gas comprises Cl2 and BCl3, and the use of the etching gas can achieve a relatively inclined sidewall angle (30-60°). It should be noted that the use of the second etching gas lacks HBr gas compared with the first etching gas in step S2, and therefore the gas flow of Cl2 or BCl3 can be appropriately increased to ensure that the chamber pressure in the process chamber is consistent with that in step S2, so as to reduce the change of the process gas environment. Preferably, the total flow of the second etching gas (Cl2 and BCl3) ranges from 100 to 200 sccm, the volume percentage of Cl2 in the second etching gas ranges from 20 to 80%, the chamber pressure ranges from 3 to 10 mTorr, the inductively coupled power ranges from 300 to 500 W, and the radio frequency bias power ranges from 50 to 200 W.

[0062] Preferably, the second etching gas in step S3 also comprises HBr, i.e., the second etching gas comprises Cl2, BCl3 and HBr. The use of the same reaction gas as the first etching gas can etch an etching topography with a sidewall angle (70-90°). The chamber pressure used in the etching is the same as that in step S2, and the chamber pressure ranges from 3 to 10 mTorr.

[0063] The use of the same etching gas and the same chamber pressure in the two-step etching in steps S2 and S3 can effectively reduce the fluctuation of the process gas environment in the etching chamber, so as to realize the etching continuity of the etching of the transparent conductive layer and the etching of the GaN epitaxial layer in the same etching environment.

[0064] Further, in the etching of the semiconductor epitaxial wafer by the second etching gas, a larger etching power can be used to increase the etching rate. Preferably, the inductively coupled power used in the etching of the GaN epitaxial wafer ranges from 300 to 500 W, and the radio frequency bias power ranges from 50 to 200 W.

[0065] The embodiment can reduce etching power, avoid paste glue leading to difficultly removing glue or using other hard mask by using process gas including HBr for ITO dry etching. After judging ITO after etching is completed, continue to perform GaN dry etching in the same process cavity and process gas environment to complete Mesa process.

[0066] In summary, the method of the embodiment can reduce etching power by using Cl2 / BCl3 / HBr as process gas for etching transparent conductive layer (ITO film layer), avoid paste glue or using other hard mask due to In by-product volatilization requiring temperature rising. Use OES to judge end point of ITO dry etching, avoid different batches of devices from showing difference due to different deposition thickness of ITO film layer. For GaN epitaxial layer etching after ITO etching, realize various process angle requirements in as small process gas change environment as possible. Simplify production process under the premise of guaranteeing product performance.

[0067] The above has described the embodiments of the present application, the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A method for manufacturing a light-emitting device, characterized in that, include: A transparent conductive layer is deposited on the surface of a semiconductor epitaxial wafer, wherein the semiconductor epitaxial wafer is a GaN epitaxial wafer and the transparent conductive layer is an ITO film layer; A patterned photoresist mask layer is formed on the transparent conductive layer; The transparent conductive layer is etched using a first etching gas to form a predetermined pattern. The first etching gas includes a bromine-containing gas, Cl2, and BCl3, and the bromine-containing gas includes HBr. The semiconductor epitaxial wafer is etched using a second etching gas, which includes Cl2, BCl3, and HBr. The etching of the transparent conductive layer using a first etching gas and the etching of the semiconductor epitaxial wafer using a second etching gas are two etching steps that are completed continuously in the same process chamber. The chamber pressure used when etching the semiconductor epitaxial wafer with the second etching gas is the same as the chamber pressure used when etching the transparent conductive layer with the first etching gas.

2. The method for manufacturing a light-emitting device according to claim 1, characterized in that, The total flow rate of the first etching gas is 100~200 sccm; the volume percentage of Cl2 in the first etching gas is 20~50%.

3. The method for manufacturing a light-emitting device according to claim 1, characterized in that, During the etching process of the transparent conductive layer using the first etching gas, the inductive coupling power ranges from 200 to 300 W, and the radio frequency bias power ranges from 100 to 200 W.

4. The method for manufacturing a light-emitting device according to claim 1, characterized in that, During the etching process of the transparent conductive layer using the first etching gas, the chamber pressure ranges from 3 to 10 mTorr.

5. The method for manufacturing a light-emitting device according to claim 1, characterized in that, During the etching process of the semiconductor epitaxial wafer using the second etching gas, the inductive coupling power range is 300~500W, and the radio frequency bias power range is 50~200W.

6. The method for manufacturing a light-emitting device according to claim 1, characterized in that, Before etching the semiconductor epitaxial wafer using the second etching gas, the process further includes: The ICP-OES detection system is used to determine whether the transparent conductive layer at the bottom of the etched microstructure has been completely removed. If so, the step of etching the semiconductor epitaxial wafer using a second etching gas is performed.

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