Patterned sapphire composite substrate and preparation method thereof

Abstract

The invention discloses a patterned sapphire composite substrate and a preparation method, and relates to the field of LED epitaxial patterned substrate materials, and the patterned sapphire composite substrate comprises a substrate material layer which is made of sapphire, aluminum nitride or gallium nitride; a low refractive index layer material layer; the low-refractive-index material layer is attached to the periphery of the substrate material layer to form a conical inner and outer two-layer type composite pattern structure, and the density of the low-refractive-index material layer is in a gradient increase trend of 1.42-1.52 from a position close to the substrate to a position far away from the substrate. The method has the advantages that the light extraction efficiency is improved, the dislocation density is reduced, the crystal quality is enhanced, the etching process is optimized, the light extraction efficiency is improved, the process compatibility is high, and the cost effectiveness is high.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of LED epitaxial patterning substrate material, in particular to a patterned sapphire composite substrate and a preparation method thereof. BACKGROUND

[0002] With the rapid development of the LED industry, the patterning technology is widely used in the field of LED chips, and the designed and manufactured pattern structure can effectively reduce the dislocation density of GaN epitaxial material, improve the electrical-optical conversion rate and the life of the LED, and change the exit angle of the totally reflected light by multiple refractions of the light emitted by the active region through the GaN and sapphire substrate interface, increase the emission ratio of the light from the sapphire substrate, and further improve the light extraction efficiency of the epitaxial layer.

[0003] Therefore, it is necessary to provide a patterned sapphire composite substrate and a preparation method thereof to solve the above problems. SUMMARY

[0004] The present application aims to provide a patterned sapphire composite substrate and a preparation method thereof to solve the problems raised in the background.

[0005] To achieve the above-mentioned purpose, the present application provides the following technical scheme: a patterned sapphire composite substrate, comprising:

[0006] a substrate material layer, which is sapphire, aluminum nitride or gallium nitride;

[0007] a low refractive index layer material layer, which is silicon nitride or silicon dioxide, and the refractive index of the low refractive index layer material layer is lower than that of the substrate material layer;

[0008] The low refractive index layer material layer is attached around the substrate material layer to form a conical inner-outer two-layer composite pattern structure, and the density of the low refractive index layer material layer gradually increases from 1.42 to 1.52 from the vicinity of the substrate to the position far away from the substrate.

[0009] Preferably, the lateral bottom width of the composite pattern structure gradually increases from top to bottom.

[0010] Preferably, the height and bottom width of the low refractive index layer material layer are positively correlated with the substrate material layer.

[0011] The present application also discloses a preparation method of a patterned sapphire composite substrate for preparing the patterned sapphire composite substrate, further comprising the following steps:

[0012] S101, surface cleaning of the substrate flat sheet to remove impurities and foreign matters;

[0013] S102, according to the uniform glue, exposure, development process to clean the substrate flat piece processing, preparation of the size of the mask pattern;

[0014] S103, the mask pattern substrate is inductively coupled plasma dry etching, to prepare the required conical pattern;

[0015] S104, the etched pattern substrate is atomic force microscopy, scanning electron microscopy, automatic optical detection test rule;

[0016] S105, the substrate after the rule is surface cleaning, remove impurities and foreign matter;

[0017] S106, the substrate is used for plasma assisted vapor deposition of SiO2 film with gradient change in density, the film thickness is 1.2-1.7 microns;

[0018] S107, using three step etching method for dry etching of the substrate, to remove the low refractive index material between the base pattern bottom surface, so that the base pattern bottom surface completely leak out, while the low refractive index material deposition layer of the sidewall is retained.

[0019] Preferably, in the S101, the substrate flat piece is ultrasonically cleaned with SMP solution, the formula of the SMP solution is deionized water and surfactant mixed in a ratio of 3:1, the ultrasonic cleaning time is 10 minutes.

[0020] Preferably, in the S102, the photoresist is uniformly coated on the substrate surface by using spin coater, the rotation speed is 3000-5000 revolutions per minute, the time is 25-35 seconds;

[0021] In the S102 exposure step, the photoresist is exposed by using the photoetching machine, the exposure dose is 100-300 millijoule per square centimeter;

[0022] In the S102 development step, the development liquid is used for development, the development time is 20-30 seconds.

[0023] Preferably, in the S103 dry etching step, ICP dry etching equipment is used, the power is 1000-2000 watts, the BCl3 flow is 80-150 standard cubic centimeter per minute, the CHF3 flow is 10-24 sccm, the etching time is 30-40 minutes, the chamber pressure is 2-15 millitorr.

[0024] Preferably, in the S106 step, the substrate is coated by a PECVD coating device to form a film layer, and the PECVD coating device is set with the following parameters during coating: SiH4 flow rate is 200-400 sccm, N2O flow rate is 10000-15000 sccm, N2 flow rate is 10-30 sccm, chamber pressure is 100-300 mTorr, RF power is 800-2000 W, deposition temperature is 300-400 DEG C, and deposition time is 15-25 min.

[0025] Preferably, in the three-step etching of S107:

[0026] The first step: pure BCl3 is used as the main etching gas, BCl3 flow rate is 80-150 sccm, chamber pressure is 2-15 mTorr, RF power is 1200-1800 W, back RF frequency is 500-600 Hz, He gas pressure is 4-6.5 Torr, temperature is 10-30 DEG C, and etching time is 5-15 min.

[0027] The second step: CHF3, SF6 and O2 are used as the etching gas, CHF3 flow rate is 10-24 sccm, SF6 flow rate is 20-40 sccm, O2 flow rate is 10-20 sccm, chamber pressure is 5-15 mTorr, RF power is 1000-1500 W, back RF frequency is 500-600 Hz, He gas pressure is 4-6 Torr, temperature is 10-30 DEG C, and etching time is 8-18 min.

[0028] The third step: pure CHF3 is used as the etching gas, CHF3 flow rate is 10-30 sccm, chamber pressure is 5-15 mTorr, RF power is 1100-1700 W, back RF frequency is 500-600 Hz, He gas pressure is 4.5-6.5 Torr, temperature is 15-25 DEG C, and etching time is 10-20 min.

[0029] The technical effects and advantages of the present application are as follows:

[0030] 1. Improve light extraction efficiency: by designing the refractive index gradient change (1.42→1.52) of the low refractive index layer material layer, the total reflection angle of light in the propagation process can be effectively reduced, thereby increasing the ratio of light emitted from the sapphire substrate and significantly improving the light extraction efficiency of the epitaxial layer.

[0031] 2. Reduce dislocation density: the conical inner and outer two-layer composite pattern structure can effectively reduce the dislocation density of GaN epitaxial material, thereby improving the electrical-optical conversion rate and service life of the LED.

[0032] 3. Enhanced crystal quality: The gradient density design of the low-refractive layer material layer can reduce the stress during the initial multi-directional growth of GaN, thereby improving the crystal quality.

[0033] 4. Optimized etching process: Through a two-step etching process and a three-step etching method, the formation of the pattern structure is precisely controlled to ensure uniform transition at the junction of the substrate pattern and the low-refractive material, improving the controllability and repeatability of the process.

[0034] 5. Improved light extraction efficiency: The low-refractive material layer effectively confines the light entering the substrate layer, reducing the escape of sidewall light, thereby improving the normal light extraction efficiency of the epitaxial back substrate.

[0035] 6. Strong process compatibility: The preparation method of the present application is compatible with existing LED manufacturing processes and can be easily integrated into existing production processes, having good industrial application prospects.

[0036] 7. High cost-effectiveness: By optimizing process parameters, material waste and process steps are reduced, production costs are lowered, and economic benefits are improved. BRIEF DESCRIPTION OF DRAWINGS

[0037] Fig. 1 is a cross-sectional view of the composite pattern structure of the present application.

[0038] Fig. 2 is a schematic diagram of the composite pattern transfer process of the present application.

[0039] Fig. 3 is a process flow diagram of the preparation method of the patterned sapphire composite substrate of the present application. DETAILED DESCRIPTION

[0040] The present application provides a patterned sapphire composite substrate and a preparation method as shown in Figs. 1-3 , which realizes a conical inner-outer two-layer composite pattern structure through a two-step etching process. The specific steps are as follows:

[0041] 1. Two-step etching process The present application adopts a two-step etching process to obtain a conical inner-outer two-layer composite pattern structure, and the specific steps are as follows:

[0042] 1.1 Two-layer composite pattern structure

[0043] Substrate material: Sapphire (Al2O3), aluminum nitride (AlN), or gallium nitride (GaN) is used as the substrate material.

[0044] Low-refractive layer material: Silicon nitride (Si3N4) or silicon dioxide (SiO2) is used as the low-refractive layer material.

[0045] The refractive index of the deposited material is lower than that of the base material, and the low refractive index layer is attached to the periphery of the base material, and the lateral bottom width gradually increases from top to bottom.

[0046] 1.2 Conical composite structure

[0047] The base material conical pattern: with the base material conical pattern vertex as the center, the low refractive index layer is attached to the periphery of the base material conical pattern, and its height and bottom width are positively correlated with the base layer.

[0048] The density of the low refractive index material layer: the density of the low refractive index material layer shows a gradient increase trend of 1.42→1.52 (the density refers to the value of the refractive index, which is dimensionless itself, so here "density" refers to the change trend of the refractive index). From close to the base to far from the base, the density gradually increases, and the etch resistance of the deposited layer material gradually strengthens, which is beneficial to etching the deposited material close to the base first and retaining the deposited material of the pattern side wall in the etching process 2; at the same time, the gradient change of the refractive index is beneficial to enhance the light extraction rate of the device.

[0049] 2. Etching process

[0050] 2.1 Etching 1 process: using inductively coupled plasma (ICP) dry etching process.

[0051] Parameter adjustment: by adjusting the power, gas flow, etching time and other parameters, the required conical pattern is realized.

[0052] Specific steps:

[0053] (1). Use SMP solution to clean the surface of the substrate flat sheet and remove impurities.

[0054] (2). According to the uniform glue, exposure, development process, process the cleaned substrate flat sheet to prepare the required size mask pattern.

[0055] (3). ICP dry etching (etching 1) is carried out on the mask pattern substrate to prepare the required conical pattern.

[0056] (4). The pattern substrate obtained by etching 1 is tested by atomic force microscope (AFM), scanning electron microscope (SEM), and automatic optical detection (AOI).

[0057] (5). Use SMP solution to clean the surface of the substrate flat sheet and remove impurities.

[0058] It should be noted that in the cleaning step, the substrate flat sheet is ultrasonically cleaned using SMP solution, the formula of the SMP solution is deionized water (DI Water) mixed with surfactant at a ratio of 3:1, and the ultrasonic cleaning time is 10 minutes;

[0059] In the uniform coating step, a spin coater is used to uniformly coat photoresist on the substrate surface at a rotation speed of 3000-5000 rpm for 25-35 seconds;

[0060] In the exposure step, a photoetching machine is used for exposure at an exposure dose of 100-300 mJ / cm2.

[0061] In the development step, a developing solution is used for development for 20-30 seconds.

[0062] 2.2 Etching 2 process: using inductively coupled plasma (ICP) dry etching process.

[0063] Parameter adjustment: by adjusting the formula parameters, the interface transition problem between the deposited material and the substrate material in the etching process is solved to ensure uniform transition of the substrate pattern and the low refractive index material connection.

[0064] Specific steps:

[0065] (1). The above substrate is coated with a SiO2 film with a gradient change in density by plasma-enhanced chemical vapor deposition (PECVD film coating equipment), and the film thickness is 1.2-1.7 microns; it is realized by adjusting the flow rate settings of SiH4, N2O, N2, combined with different chamber pressures, radio frequency power, deposition temperature.

[0066] (2). A three-step etching method is used to dry etch the substrate: first step: using pure BCl3 as the main etching gas, by adjusting the chamber pressure, radio frequency power (SRF), back radio frequency (BRF), BCl3 flow rate, He gas pressure, temperature, etching time, to quickly consume the deposited surface layer material and form a basic outline. Second step: using CHF3+SF6+O2 as the etching gas, combined with adjusting the chamber pressure, CHF3 flow rate, SF6 flow rate, O2 flow rate, SRF, BRF, He gas pressure, temperature, etching time, to form a fluorocarbon film on the surface of the low refractive index material. Third step: using pure CHF3 as the etching gas, combined with adjusting the chamber pressure, CHF3 flow rate, SRF, BRF, He gas pressure, temperature, etching time, to remove the residual low refractive index material between the substrate patterns, so that the bottom surface of the substrate pattern is completely exposed, while the low refractive index material deposition layer on the sidewall is retained.

[0067] Detailed explanation of etching parameters

[0068] I. Etching 1 parameters:

[0069] The power is 1000-2000 watts;

[0070] The gas is BCl3, and the flow rate is 80-150 standard cubic centimeters per minute (sccm);

[0071] CHF3 flow rate: 10-24 seem;

[0072] Etching time: 30-40 minutes;

[0073] Chamber pressure: 2-15 mTorr

[0074] II. Etching 2 parameters:

[0075] First step:

[0076] Gas: BCl3, flow rate: 80-150 seem;

[0077] Chamber pressure: 2-15 mTorr;

[0078] RF power: 1200-1800 watts;

[0079] Backside RF frequency: 500-600 Hz;

[0080] He gas pressure: 4-6.5 Torr;

[0081] Temperature: 10-30 degrees Celsius;

[0082] Etching time: 5-15 minutes.

[0083] Second step:

[0084] Gas: CHF3, flow rate: 10-24 seem;

[0085] SF6 flow rate: 20-40 seem;

[0086] O2 flow rate: 10-20 seem;

[0087] Chamber pressure: 5-15 mTorr;

[0088] RF power: 1000-1500 watts;

[0089] Backside RF frequency: 500-600 Hz;

[0090] He gas pressure: 4-6 Torr;

[0091] Temperature: 10-30 degrees Celsius;

[0092] Etching time: 8-18 minutes.

[0093] Third step:

[0094] Gas: CHF3, flow rate: 10-30 seem;

[0095] Chamber pressure: 5-15 mTorr;

[0096] RF power: 1100-1700 watts;

[0097] Back RF frequency: 500-600 Hz;

[0098] He gas pressure: 4.5-6.5 Torr;

[0099] Temperature: 15-25 degrees Celsius;

[0100] Etching time: 10-20 minutes

[0101] Other process parameters are described as follows:

[0102] I. PECVD film plating parameters:

[0103] Gas SiH4, flow rate of 200-400 sccm;

[0104] N2O flow rate of 10000-15000 sccm;

[0105] N2 flow rate of 10-30 sccm;

[0106] Chamber pressure: 100-300 mTorr;

[0107] RF power: 800-2000 watts;

[0108] Deposition temperature: 300-400 degrees Celsius;

[0109] Deposition time: 15-25 minutes

[0110] Finally, testing and verification are performed:

[0111] (1) AFM test: used to detect surface roughness and nano-scale structure.

[0112] (2) SEM test: used to observe the micro-morphology of the pattern structure.

[0113] It should be noted that the AFM test and the SEM test are prior art, which are common techniques for detecting or observing the surface roughness, nano-scale structure and micro-morphology of the pattern structure, and will not be described here.

Claims

1. A patterned sapphire composite substrate, characterized in that, The patterned sapphire composite substrate includes: A substrate material layer, wherein the substrate material layer is sapphire, aluminum nitride, or gallium nitride; A low refractive index layer material layer, wherein the low refractive index layer material layer is silicon nitride or silicon dioxide, and the refractive index of the low refractive index layer material layer is lower than the refractive index of the substrate material layer; The low refractive index layer material layer is attached to the substrate material layer to form a conical two-layer composite pattern structure, and the density of the low refractive index layer material layer increases in a gradient trend from 1.42 to 1.52 from near the substrate to far from the substrate.

2. The patterned sapphire composite substrate according to claim 1, characterized in that: The horizontal bottom width of the composite graphic structure gradually increases from top to bottom.

3. The patterned sapphire composite substrate according to claim 1, characterized in that: The height and bottom width of the low refractive index layer are positively correlated with those of the substrate layer.

4. A method for preparing a patterned sapphire composite substrate, characterized in that: The method for preparing the patterned sapphire composite substrate according to any one of claims 1-3 further includes the following steps: S101, perform surface cleaning on the substrate flat sheet to remove impurities and foreign matter; S102, the cleaned substrate flat sheet is processed according to the process of spin coating, exposure and development to prepare a mask pattern of the required size; S103, Inductively coupled plasma dry etching is performed on the mask pattern substrate to prepare the desired conical pattern; S104, the etched patterned substrate is subjected to atomic force microscopy, scanning electron microscopy and automatic optical inspection and testing for grading. S105, perform surface cleaning on the sized substrate to remove impurities and foreign matter; S106 is a SiO2 thin film with a gradient density on a substrate, deposited by plasma-assisted vapor deposition, with a film thickness of 1.2-1.7 micrometers. S107, a three-step etching method is used to perform dry etching on the substrate to remove the low refractive index material remaining on the bottom surface between the substrate patterns, so that the bottom surface of the substrate patterns is completely exposed, while the low refractive index material deposition layer on the sidewalls is retained.

5. The method for preparing a patterned sapphire composite substrate according to claim 4, characterized in that: In step S101, an SMP solution is used to ultrasonically clean the substrate flat sheet. The SMP solution is formulated by mixing deionized water and surfactant in a 3:1 ratio, and the ultrasonic cleaning time is 10 minutes.

6. The method for preparing a patterned sapphire composite substrate according to claim 4, characterized in that: In the S102 spin coating step, a spin coater is used to uniformly coat the photoresist onto the substrate surface at a speed of 3000-5000 rpm for 25-35 seconds. In the S102 exposure step, a lithography machine is used for exposure, and the exposure dose is 100-300 millijoules / square centimeter; In the S102 developing step, developing solution is used for developing, and the developing time is 20-30 seconds.

7. The method for preparing a patterned sapphire composite substrate according to claim 4, characterized in that: The S103 dry etching step uses an ICP dry etching device with a power of 1000-2000 watts, a BCl3 flow rate of 80-150 standard cubic centimeters / minute, a CHF3 flow rate of 10-24 sccm, an etching time of 30-40 minutes, and a chamber pressure of 2-15 millitor.

8. The method for preparing a patterned sapphire composite substrate according to claim 4, characterized in that: In step S106, a PECVD coating equipment is used to coat the substrate to form a film layer. During coating, the PECVD coating equipment is set with the following parameters: SiH4 flow rate of 200-400 sccm, N2O flow rate of 10000-15000 sccm, N2 flow rate of 10-30 sccm, chamber pressure of 100-300 millitor, RF power of 800-2000 watts, deposition temperature of 300-400 degrees Celsius, and deposition time of 15-25 minutes.

9. The method for preparing a patterned sapphire composite substrate according to claim 4, characterized in that: In the three-step etching process of S107: Step 1: Use pure BCl3 as the main etching gas, with a BCl3 flow rate of 80-150 sccm, a chamber pressure of 2-15 mTorr, an RF power of 1200-1800 watts, a back RF frequency of 500-600 Hz, a He gas pressure of 4-6.5 Torr, a temperature of 10-30 degrees Celsius, and an etching time of 5-15 minutes; Step 2: CHF3, SF6 and O2 are used as etching gases. The flow rate of CHF3 is 10-24 sccm, the flow rate of SF6 is 20-40 sccm, the flow rate of O2 is 10-20 sccm, the chamber pressure is 5-15 mTorr, the RF power is 1000-1500 watts, the back RF frequency is 500-600 Hz, the He gas pressure is 4-6 Torr, the temperature is 10-30 degrees Celsius, and the etching time is 8-18 minutes. Step 3: Use pure CHF3 as the etching gas, with a CHF3 flow rate of 10-30 sccm, a chamber pressure of 5-15 mTorr, an RF power of 1100-1700 watts, a back RF frequency of 500-600 Hz, a He gas pressure of 4.5-6.5 Torr, a temperature of 15-25 degrees Celsius, and an etching time of 10-20 minutes.

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