Full-waveband high-reflectivity metal composite film structure and preparation method thereof

Abstract

The invention discloses a full-wave-band high-reflectivity metal composite film structure and a preparation method thereof, and relates to the technical field of semiconductor light-emitting elements. The metal composite film structure is applied to a light-emitting element, light enters from one side of an adhesion layer of the metal composite film structure, and the metal composite film structure at least comprises the adhesion layer with the thickness ranging from 0.5 nm to 2.5 nm; the composite reflecting layer is arranged on the adhesion layer, and the composite reflecting layer is of a stacked structure of a silver layer and an aluminum layer, or is a silver-aluminum alloy layer. The invention further discloses a preparation method of the structure, a vacuum electron beam evaporation process is adopted, when the composite reflecting layer is deposited, the evaporation rate is controlled to be 1-15 angstroms per second, and cavity heating at the temperature of 40-70 DEG C is supplemented. The invention preferably also comprises a double-layer protection structure consisting of atomic layer deposited aluminum oxide and chemical vapor deposited silicon dioxide. According to the invention, the problems of low reflectivity, narrow wave band, contradiction between adhesive force and reflectivity, high-cost sputtering process damage and the like of a traditional reflector are solved, and the advantages of full-wave band high reflectivity, high adhesive force, high reliability, low cost and low damage preparation are realized.

Description

Technical Field

[0001] This invention relates to the field of semiconductor light-emitting element technology, specifically to a full-band high-reflectivity metal composite film structure and its preparation method. Background Technology

[0002] In the structural design of light-emitting components (such as light-emitting diodes, LEDs), metal reflective films are widely used to improve the light extraction efficiency of the device. In the structure of a standard LED chip, the metal reflective film typically functions as both a reflector and an electrode. In the light emitted from the quantum well, the light directed towards the substrate needs to be effectively reflected by the metal reflective electrode, redirecting it towards the light-emitting surface, thereby improving the overall brightness of the LED.

[0003] Traditionally, the electrodes of these reflective mirrors generally employ a "chromium + aluminum + protective layer" structure prepared by vacuum electron beam evaporation. In this structure, metallic chromium (Cr) serves as the electrode adhesion layer, ensuring good ohmic contact between the electrode and the underlying material and providing sufficient adhesion; metallic aluminum (Al) serves as the main reflective layer, utilizing its high reflectivity in the visible light band to enhance brightness.

[0004] However, existing traditional metal reflective film structures have the following significant drawbacks: 1. Lower-than-expected reflectivity and limitations imposed by the adhesive layer: The adhesive layer (such as chromium) itself absorbs light. To ensure adhesion, the adhesive layer needs a certain thickness. When the chromium layer is 2.5 nanometers thick, the reflectivity of the underlying aluminum layer (measured at a wavelength of 460 nanometers) is only about 75%; even if the chromium layer is thinned to 1.5 nanometers, the reflectivity can only be increased by about 5% (i.e., about 80%), which is still far below the theoretical reflectivity of pure aluminum of over 90%.

[0005] 2. Processing Challenges of High-Reflectivity Metals (such as Silver): To further improve reflectivity, the industry has attempted to use silver (Ag), a metal with even higher reflectivity, instead of aluminum. However, this introduces new problems: Interface scattering: The contact smoothness between silver (Ag) and chromium (Cr) and the underlying epitaxial material is poor. If conventional evaporation processes are used, silver tends to grow in island-like patterns on the ultrathin chromium layer, forming a rough interface and resulting in severe light scattering. This reduces the actual reflectivity of silver mirrors to only 68% to 75%.

[0006] The trade-off between adhesion and reflectivity: Studies have shown that only by thinning the chromium layer to below 0.5 nanometers can the smoothness and reflectivity of the silver film be significantly improved. However, chromium layers below 0.5 nanometers cannot provide sufficient electrode adhesion and are not suitable for upright LED structures that require high reliability.

[0007] Reliability issues: Silver (Ag) is a chemically reactive metal that is prone to silver migration and corrosion, which can lead to device failure.

[0008] 3. Inability to achieve full-spectrum reflectivity: Single metal films inherently exhibit a decrease in reflectivity within specific wavelengths. For example, pure aluminum has a characteristic absorption peak near the 860 nm wavelength in the near-infrared region, resulting in low reflectivity in this band; while pure silver's reflectivity drops sharply to below 80% in the ultraviolet band (e.g., 300-400 nm) due to surface plasmon resonance. This makes traditional reflectors unsuitable for applications requiring full-spectrum coverage from ultraviolet to infrared.

[0009] 4. Mass production costs and process damage issues: Although vacuum sputtering can produce silver films with better smoothness, the equipment cost of sputtering equipment and the cost per wafer are more than ten times higher than those of electron beam evaporation, making it unsuitable for traditional standard LED products with low profit margins. Furthermore, the high-energy particles generated during sputtering can cause physical damage to the delicate epitaxial structure of the LED substrate, affecting the device's photoelectric performance.

[0010] To address some of the aforementioned problems, several related technical solutions have emerged. For example, Chinese patent CN114114488B discloses a full-band high-reflectivity mirror employing a composite structure of metallic silver and metallic aluminum. However, this patent applies to external reflectors, where light enters from the reflective layer (silver / aluminum) side, and the thickness of the adhesive layer is set at 1000 nanometers. If this design were applied to the LED built-in reflector described in this invention (where light must pass through the adhesive layer to be reflected), the 1000-nanometer adhesive layer would cause severe light absorption, resulting in a "negative benefit" to LED brightness. Therefore, this patent is not suitable for the built-in electrodes of self-emissive elements.

[0011] For example, Chinese patent CN111736246A discloses the use of metal nitrides or fluorides as a barrier protective layer to protect active metals such as silver and aluminum. However, this solution places the barrier layer between the silver and aluminum stacked structures to prevent film damage and corrosion. These nitrides or fluorides typically have poor conductivity; if used in LED electrode structures, they would significantly increase the device's startup voltage, which is detrimental to electrical performance.

[0012] Therefore, there is an urgent need in this field for a novel metal reflective film structure and its fabrication method, which should be able to solve the following technical problems simultaneously: (1) Overcome the inherent contradiction between ultra-thin adhesive layers and high adhesion and high reflectivity; (2) Achieve high reflectivity across the entire wavelength range from ultraviolet to infrared; (3) Use low-cost, low-damage preparation processes (such as electron beam evaporation); (4) While ensuring electrical performance and long-term reliability (such as suppressing silver migration), the photoextraction efficiency is not compromised. Summary of the Invention

[0013] The purpose of this invention is to provide a full-band high-reflectivity metal composite film structure and its preparation method, so as to solve the contradiction between low reflectivity of LED reflector electrodes, poor full-band performance, insufficient reliability, high cost and high-damage process in the prior art.

[0014] To achieve the above objectives, the first aspect of this invention provides a full-band high-reflectivity metal composite film structure for use in a light-emitting element. The structure is disposed in the light-emitting path of the light-emitting element, with light incident from the adhesion layer side of the structure. For ease of explanation, the term "metal electrode" as used in this specification refers to an integral metal electrode structure formed by sequentially depositing an adhesion layer, a composite reflective layer, and optionally a metal barrier layer and a bonding layer. This term is used to refer to the entire multilayer metal film and does not limit the number of internal layers, material combination, or specific thickness; it aims to describe the overall function and structural position of the metal electrode region in this invention.

[0015] The structure includes at least: An adhesive layer with a thickness ranging from 0.5 nanometers to 2.5 nanometers. This thickness range is one of the key aspects of this invention. 0.5 nanometers is the lower limit to ensure sufficient adhesion to the substrate, while 2.5 nanometers is the upper limit to control light absorption.

[0016] A composite reflective layer is disposed on the adhesive layer.

[0017] The composite reflective layer is a stacked structure of silver (Ag) and aluminum (Al) layers, or a silver-aluminum (AgAl) alloy layer. This is the key to achieving high reflectivity across the entire wavelength range in this invention. Silver alone has poor reflectivity in the ultraviolet band, while aluminum alone has an absorption peak in the infrared band. This invention utilizes the extremely high reflectivity of silver in the visible and infrared bands, and the excellent reflectivity of aluminum in the ultraviolet band, to achieve a balance by combining the strengths of both materials through a "silver + aluminum" composite or "silver-aluminum alloy" approach, maintaining high reflectivity across the entire wavelength range from ultraviolet to infrared.

[0018] Preferably, the material of the adhesive layer is selected from one or more of chromium (Cr), nickel (Ni), or titanium (Ti). These materials all have good ohmic contact and adhesion properties with common semiconductor substrates.

[0019] Preferably, the thickness of the adhesive layer is 1.5 nanometers. At this thickness, an optimal balance is achieved between adhesion, electrical properties, and light absorption.

[0020] Preferably, when the composite reflective layer is a stacked structure of a silver layer and an aluminum layer, the thickness of the silver layer ranges from 100 nanometers to 250 nanometers, and the thickness of the aluminum layer is preferably 100 nanometers.

[0021] Preferably, when the composite reflective layer is a silver-aluminum alloy layer, the thickness of the silver-aluminum alloy layer ranges from 100 nanometers to 250 nanometers.

[0022] More preferably, in the silver-aluminum alloy layer, the weight percentage of silver to aluminum is 80:20. The invention also includes optimizing reflectivity in specific wavelength bands by adjusting the ratio of silver to aluminum: for example, increasing the proportion of aluminum to emphasize the ultraviolet band, and increasing the proportion of silver to emphasize the infrared band.

[0023] Preferably, the structure further includes a metal barrier layer and a bonding layer disposed on the composite reflective layer. The metal barrier layer is used to prevent quality problems such as silver migration and corrosion that may occur in subsequent processes.

[0024] An important technical feature of the present invention is that the structure preferably includes a double-layer protective structure sequentially disposed on the patterned area after the metal composite film structure is prepared.

[0025] The dual-layer protective structure includes: The first protective layer is an alumina (Al2O3) layer prepared by atomic layer deposition (ALD). The Al2O3 film prepared by ALD is highly dense, pinhole-free, and exhibits excellent conformality, serving as a reliable gas and moisture barrier layer. It effectively inhibits the migration or corrosion of the silver (Ag) layer by moisture and ions, significantly improving the long-term reliability of the metal reflective electrode. This first protective layer is deposited only in a patterned manner on the area covered by the metal electrode.

[0026] The second protective layer is a silicon dioxide (SiO2) layer prepared by chemical vapor deposition (CVD, such as PECVD). Due to the overall deposition characteristics of the CVD process, this second protective layer will cover the entire device surface, including: (1) The surface of the first protective layer already formed in the electrode coating area; (2) The transparent conductive film (ITO) surface in the light-emitting area that is not covered by the first protective layer.

[0027] Preferably, the thickness of the first protective layer is in the range of 10 nm to 30 nm; and the thickness of the second protective layer is in the range of 60 nm to 250 nm.

[0028] Therefore, a double-layer structure of "Al2O3 + SiO2" is formed in the electrode coating area to provide highly reliable barrier protection; while in the main light-emitting area, only a single-layer antireflection structure composed of SiO2 exists, thereby maintaining the stepwise transition relationship of refractive index from GaN to ITO to SiO2.

[0029] This dual-layer protective structure of "ALD alumina + CVD silica" has a dual function: 1. Reliability protection: The ALD alumina layer provides a dense physical barrier to prevent silver migration and corrosion.

[0030] 2. Optical Optimization: Although ALD-prepared alumina (Al2O3) possesses extremely high density and barrier properties, its refractive index is approximately 1.6–1.7, which is relatively close to the refractive indices of the underlying ITO (n≈2.0) and GaN (n≈2.4). Covering the entire light-emitting area with Al2O3 would weaken the anti-reflection effect originally provided by SiO2 (n≈1.45). Therefore, this invention employs a partitioned optical design: a "ALD Al2O3 + CVD SiO2" bilayer structure is set in the electrode coating area to provide silver migration suppression and sidewall passivation; in the main light-emitting area, Al2O3 is not introduced, and instead, a GaN→ITO→SiO2 refractive index gradient structure is preferred to ensure optimal light extraction efficiency. This partitioned design ensures that the reliability protection layer does not interfere with the optical path optimization of the light-emitting area, while maintaining the maximum light extraction efficiency of the overall LED chip.

[0031] Preferably, the light-emitting element is a positively mounted light-emitting diode (LED) chip, and the metal composite film structure is disposed on the transparent conductive film of the LED chip as a reflector electrode.

[0032] A second aspect of the present invention provides a method for preparing the above-mentioned metal composite film structure.

[0033] Another important technical feature of this invention is that the method employs a vacuum electron beam evaporation process. This process choice aims to address the problems of high cost and high-energy particle damage to the epitaxial layer in the prior art sputtering process.

[0034] The method includes the following steps: S1: The adhesion layer is deposited using a vacuum electron beam evaporation process to achieve a thickness of 0.5 nanometers to 2.5 nanometers.

[0035] S2: The composite reflective layer is deposited on the adhesion layer using a vacuum electron beam evaporation process.

[0036] The core process improvement of this invention lies in the following: when depositing the composite reflective layer in step S2, or when depositing the composite reflective layer containing a silver component, the evaporation rate is controlled to be 1 Å / s to 15 Å / s, and supplemented by cavity heating at 40 °C to 70 °C.

[0037] Conventional electron beam evaporation for silver deposition on ultrathin adhesion layers suffers from severe scattering due to interface irregularities and island growth. This invention discovers that a specific process combination of "cavity heating (providing thermal energy)" and "controlled evaporation rate (providing migration time)" can significantly increase the surface mobility of silver atoms on the ultrathin adhesion layer. This allows silver atoms sufficient time to migrate to the lowest-energy lattice positions before being "buried" by subsequent atoms, thereby suppressing rough island growth and resulting in a smoother, denser silver film with lower scattering.

[0038] Therefore, the preparation method of the present invention solves the contradiction between the ultrathin adhesion layer and the high reflectivity silver film in the prior art by optimizing the low-cost electron beam evaporation process parameters without using the high-cost and high-damage sputtering process.

[0039] Preferably, in step S1, the evaporation rate of the deposited adhesive layer is preferably 0.1 Å / s. This ultra-low rate helps to form a more uniform and continuous ultra-thin adhesive layer on the substrate.

[0040] Preferably, the method further includes the step of sequentially depositing a metal barrier layer and a bonding layer after depositing the composite reflective layer.

[0041] Preferably, the method further includes the step of sequentially depositing a double-layer protective structure after the metal electrode is fabricated: An alumina layer with a thickness of 10 to 30 nanometers was grown as the first protective layer using an atomic layer deposition (ALD) system. A silicon dioxide layer with a thickness of 60 nm to 250 nm was grown as a second protective layer using a chemical vapor deposition (CVD) system.

[0042] Compared with the prior art, the present invention has the following significant advantages: 1. Balancing High Reflectivity and High Adhesion: By employing an ultrathin adhesion layer of 0.5-2.5 nanometers, the light absorption of the adhesion layer itself is reduced; and by using electron beam evaporation supplemented by a key process of "cavity heating (40-70 ℃) + low speed (1-15 Å / s)," the problems of poor film quality and interface scattering of silver (Ag) on ​​the ultrathin adhesion layer are solved. Ultimately, extremely high reflectivity is achieved while ensuring high adhesion.

[0043] 2. Achieving high reflectivity across the entire wavelength range: By employing a composite reflective layer structure of "silver + aluminum" stacking or "silver-aluminum alloy," the advantages of silver in the visible / infrared range and aluminum in the ultraviolet range are combined, overcoming the problem of reduced reflectivity of a single metal in a specific wavelength range. Test results show significant improvements in both the ultraviolet 300 nm band and the infrared 860 nm band.

[0044] 3. Low-cost, low-damage process: This invention employs a vacuum electron beam evaporation process, rather than the high-cost sputtering process. Furthermore, electron beam evaporation is a low-energy particle process, avoiding the physical damage to the delicate epitaxial structure of the LED substrate caused by sputtering. This invention is suitable for large-scale, low-margin, standard-sized LED products.

[0045] 4. Balancing High Reliability and High Luminous Efficiency: The preferred dual-layer protective structure of "ALD alumina + CVD silicon dioxide" in this invention achieves a precise division of labor between reliability and luminous efficiency: The first protective layer (Al2O3) is patterned and deposited only in the metal electrode coating area. Its high density and excellent barrier properties effectively suppress silver migration, corrosion, and degradation caused by environmental humidity, significantly improving the long-term reliability of the electrode. The second protective layer (SiO2) is deposited through an overall CVD process, covering the entire surface of the device. In the light-emitting area, since the first protective layer is not covered, a single-layer SiO2 antireflection film naturally forms, creating an optimized refractive index ladder from GaN to ITO to SiO2, maintaining the chip's high light extraction efficiency. Through this structural configuration of "Al2O3 only in the electrode area + SiO2 covering the entire area," this invention achieves the dual goals of improved electrode reliability and optimized luminous efficiency without sacrificing optical performance. Attached Figure Description

[0046] Figure 1 This is a schematic diagram of the metal composite film structure of the present invention.

[0047] Figure 2 This is a schematic diagram illustrating the application of the metal composite film structure of the present invention in a standard LED chip.

[0048] Figure 3 This is a comparison chart of reflectance between the embodiments of the present invention and the control group. Detailed Implementation

[0049] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the scope of protection of the invention.

[0050] Example 1

[0051] This embodiment provides a full-band high-reflectivity metal composite film structure for upright LED chips, and its preparation steps are as follows (refer to...). Figure 1 and Figure 2 ): 1. Substrate preparation and pre-processing: This case uses a patterned sapphire substrate on which GaN-based LED epitaxial layer structures, such as NGaN and PGaN, have been grown using methods such as MOCVD. Figure 2 (Not shown in detail in the text).

[0052] MESA (mesa) structures were fabricated using standard photolithography and dry etching techniques.

[0053] A current blocking layer (CBL) with a thickness of 100 nm to 300 nm is deposited at a specific location below the subsequent metal electrode (PAD), preferably made of silicon dioxide (SiO2).

[0054] A transparent conductive film with a thickness of 30 nm to 120 nm is deposited on the MESA mesa (PGaN side), preferably indium tin oxide (ITO).

[0055] 2. Adhesion layer preparation: An adhesion layer 1 is deposited on a pattern (ITO layer) prepared in the previous process using a vacuum electron beam evaporation apparatus.

[0056] In this embodiment, the adhesive layer material is preferably chromium (Cr) (but can also be replaced by nickel (Ni) or titanium (Ti).

[0057] Thickness: preferably controlled at 1.5 nanometers.

[0058] Process parameters: The evaporation rate was controlled at 0.1 Å / s. This ultra-low rate ensured the formation of a uniform and continuous 1.5 nm ultrathin chromium layer on the ITO surface, providing a good adhesion interface for subsequent silver growth.

[0059] 3. Fabrication of the composite reflective layer: On the adhesion layer, a silver layer and an aluminum layer are deposited sequentially using a vacuum electron beam evaporation device to form a silver-aluminum composite reflective layer 2.

[0060] (a) Silver (Ag) layer: Thickness: preferably 100 nanometers.

[0061] Key process parameters: During the deposition of this silver layer, the evaporation rate is controlled between 1 Å / s and 15 Å / s, while chamber heating is used to maintain the substrate stage temperature between 40 °C and 70 °C, and the process is completed under a fixed low vacuum.

[0062] (b) Aluminum (Al) layer: An aluminum layer is then deposited on top of the silver layer.

[0063] Thickness: preferably 100 nanometers.

[0064] Process parameters: Evaporation rate is 10 Å / s.

[0065] Structural function: The silver layer provides ultra-high reflectivity in the visible and infrared bands, while the top aluminum layer is mainly used to compensate for the insufficient reflectivity of silver in the ultraviolet band (300-400 nm).

[0066] 4. Preparation of metal barrier layer and bonding layer: Following the composite reflective layer (aluminum layer), a metal barrier layer 3 and a bonding layer 4 are deposited sequentially.

[0067] The metal barrier layer 3 is preferably a (titanium + platinum) (Ti / Pt) or (nickel + platinum) multilayer structure, for example, depositing 3 pairs of (Ti 50 nm + Pt 100 nm) stacks.

[0068] The bonding layer 4 is preferably gold (Au), with a thickness controlled between 1500 nm and 2500 nm.

[0069] 5. Deposit the first protective layer: After the aforementioned metal electrode structure is fabricated, a pattern is defined only in the metal electrode coverage area using photolithography, and a first protective layer is selectively deposited using atomic layer deposition (ALD). Because the deposition area is defined by photolithography, the first protective layer has a striped pattern that covers only the surface of the metal electrode and its sidewalls, without extending into the surrounding exposed ITO or CBL areas.

[0070] Material: Alumina (Al2O3).

[0071] Thickness: preferably 20 nm.

[0072] Function: The Al2O3 layer prepared by ALD is characterized by its density, absence of pinholes, and high conformality, which can effectively inhibit silver (Ag) migration and corrosion, and improve the long-term reliability of metal electrodes.

[0073] 6. Deposit a second protective layer: After selective ALD (Al2O3) deposition, a second protective layer of silicon dioxide (SiO2) is grown using plasma-enhanced chemical vapor deposition (PECVD). Since PECVD is a monolithic coating process, the second protective layer will simultaneously cover: The surface of the aforementioned first protective layer; The surface of the transparent conductive film (ITO) in the light-emitting area that is not covered by the first protective layer; Other exposed areas (such as CBL areas).

[0074] Material: Silicon dioxide (SiO2).

[0075] Thickness: preferably 90 nm.

[0076] Function: In the electrode region, the second protective layer and the first protective layer together provide robust and reliable protection; while in the light-emitting region, since there is no first protective layer, the formed SiO2 monolayer structure acts as an optical antireflection film, realizing the refractive index ladder structure of GaN→ITO→SiO2→air, thereby ensuring the best light extraction efficiency.

[0077] 7. Subsequent processes: Subsequent photolithography, etching (etching the protective layer to expose the gold bonding layer), substrate thinning, and dicing processes are then performed to ultimately form a complete upright LED chip (such as...). Figure 2 (As shown).

[0078] Example 2

[0079] This embodiment provides another metal composite film structure, whose preparation steps are roughly the same as those in Embodiment 1, with the main difference being the preparation of the composite reflective layer.

[0080] 1. Step 1: Same as Example 1.

[0081] 2. Step 2: Same as Example 1. Vacuum electron beam evaporation was used to deposit 1.5 nm chromium (Cr) as an adhesion layer at a rate of 0.1 Å / s.

[0082] 3. Fabrication of the composite reflective layer: On the adhesion layer, a silver-aluminum alloy layer is deposited using a vacuum electron beam evaporation device as the composite reflective layer 2.

[0083] Material: Silver-aluminum alloy (AgAl).

[0084] The preferred weight percentage of silver to aluminum is 80:20.

[0085] Thickness: preferably 200 nanometers.

[0086] Key process parameters: During the deposition of this alloy layer, the evaporation rate is between 1 Å / s and 15 Å / s, supplemented by chamber heating (temperature: 40 °C to 70 °C), and the process is completed under a fixed low vacuum.

[0087] Process characteristics: Compared with Example 1, the preparation of the reflective layer in this example is more simplified (one-step alloy deposition replaces two-step stacking).

[0088] Adjustability of the solution: The ratio of silver to aluminum in the alloy can be adjusted according to the target wavelength. For example, the 80:20 ratio in this embodiment focuses more on high reflectivity in the visible to infrared wavelength range. If the application product focuses on reflectivity in the ultraviolet wavelength range, the proportion of aluminum can be appropriately increased.

[0089] 4. Step 4: Same as Example 1.

[0090] 5. Step 5: Same as Example 1. Deposit 20 nm of ALD alumina.

[0091] 6. Step 6: Same as Example 1. Deposit 90 nm CVD silicon dioxide.

[0092] 7. Step 7: Same as Example 1.

[0093] To verify the beneficial effects of this invention, the metal composite film structures prepared in Examples 1 and 2 were compared with a control group (using a conventional "Cr 1.5 nm + Al 200 nm" structure, conventional E-beam evaporation) by reflectance spectroscopy testing. The test results are as follows: Figure 3 As shown, and summarized in Table 1 below.

[0094] Table 1: Comparison of Technical Solutions parameter Control group (traditional Cr+Al) Example 1 (Cr / Ag / Al) Example 2 (Cr / AgAl) Adhesion layer (Cr) thickness 1.5 nanometers 1.5 nanometers 1.5 nanometers reflective layer Al (200 nanometers) Ag (100 nm) + Al (100 nm) AgAl (80:20, 200 nm) Reflective layer process E-beam (Standard) E-beam + cavity heating (40-70℃) + low speed (1-15 Å / s) E-beam + cavity heating (40-70℃) + low speed (1-15 Å / s) outer protective layer Conventional protective layer <![CDATA[ALD A2O3 (20 nm) + CVD SiO2 (90 nm)]]> <![CDATA[ALD A2O3 (20 nm) + CVD SiO2 (90 nm)]]> Average reflectivity across the entire band 84% (benchmark) 90% (6% higher) 87% (3% higher) UV (300 nm) reflectivity 79% (benchmark) 83.7% (4.7% higher) 77% (2% lower) IR (860 nm) reflectivity 89% (benchmark) 92% (3% higher) 90.2% (1.2% higher) Results analysis: 1. Example 1 (Cr / Ag / Al): as follows Figure 3 As shown, the curves of Example 1 are significantly superior to the control group across the entire wavelength range from 300 nm to 1000 nm. Its average reflectance across the entire wavelength range reaches 90% (6% higher than the control group). Particularly noteworthy is the near-infrared reflectance at 860 nm, where the control group (pure aluminum) exhibits an absorption peak, reaching as high as 92% (3% higher); and even in the ultraviolet 300 nm band, a weak point for silver (Ag), the reflectance remains as high as 83.7% (4.7% higher) due to compensation from the aluminum (Al) layer. This demonstrates the effectiveness of the structural design and key fabrication process (heating + low-rate E-beam) of this invention.

[0095] 2. Example 2 (Cr / AgAl): as follows Figure 3 As shown, Example 2 (80:20 alloy) achieved an average reflectance of 87% across the entire wavelength range (3% higher). While this 80:20 ratio is geared towards the visible to infrared band (90.2% reflectance at 860 nm), it suffers a slight sacrifice in the ultraviolet 300 nm band (77%). Nevertheless, its process is simpler, and the overall average reflectance is still significantly higher than the conventional control group.

[0096] In summary, the metal composite film structure and its preparation method of the present invention effectively solve many defects of the prior art and have extremely high application value in the field of light-emitting elements such as LED chips.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A full-band high-reflectivity metal composite film structure, applied to light-emitting elements, characterized in that, The structure is disposed on the light emission path of the light-emitting element, and light is incident from the adhesion layer side of the structure. The structure includes at least: An adhesion layer having a thickness ranging from 0.5 nm to 2.5 nm; and A composite reflective layer is disposed on the adhesive layer; The composite reflective layer is a stacked structure of silver and aluminum layers, or a silver-aluminum alloy layer.

2. The metal composite film structure according to claim 1, characterized in that, The material of the adhesive layer is selected from chromium, nickel or titanium.

3. The metal composite film structure according to claim 1 or 2, characterized in that, The thickness of the adhesion layer is 1.5 nanometers.

4. The metal composite film structure according to claim 1, characterized in that, When the composite reflective layer is a stacked structure of a silver layer and an aluminum layer, the thickness of the silver layer ranges from 100 nanometers to 250 nanometers, and the thickness of the aluminum layer is 100 nanometers.

5. The metal composite film structure according to claim 1, characterized in that, When the composite reflective layer is a silver-aluminum alloy layer, the thickness of the silver-aluminum alloy layer ranges from 100 nanometers to 250 nanometers.

6. The metal composite film structure according to claim 5, characterized in that, In the silver-aluminum alloy layer, the weight percentage of silver to aluminum is 80:

20.

7. The metal composite film structure according to claim 1, characterized in that, The structure also includes a metal shielding layer and a bonding layer disposed on the composite reflective layer.

8. The metal composite film structure according to claim 7, characterized in that, The metal protective layer is a multilayer structure of titanium and platinum, or nickel and platinum, and the bonding layer is a gold layer.

9. The metal composite film structure according to any one of claims 1 to 8, characterized in that, The structure further includes a double-layer protective structure sequentially disposed on the patterned area after the metal composite film structure is prepared, the double-layer protective structure comprising: A first protective layer is an alumina layer prepared by atomic layer deposition; and A second protective layer is a silicon dioxide layer prepared by chemical vapor deposition on top of the first protective layer.

10. The metal composite film structure according to claim 9, characterized in that, The thickness of the first protective layer ranges from 10 nanometers to 30 nanometers; the thickness of the second protective layer ranges from 60 nanometers to 250 nanometers.

11. The metal composite film structure according to claim 1, characterized in that, The light-emitting element is a positively mounted light-emitting diode chip, and the metal composite film structure is disposed on the transparent conductive film of the LED chip as a reflector electrode.

12. A method for preparing a metal composite film structure as described in any one of claims 1 to 11, characterized in that, The method employs a vacuum electron beam evaporation process and includes the following steps: S1: Deposit the adhesion layer to a thickness of 0.5 nanometers to 2.5 nanometers; S2: Deposit the composite reflective layer on the adhesion layer; In step S2, when depositing the composite reflective layer or depositing a component containing silver in the composite reflective layer, the evaporation rate is controlled to be between 1 Å / s and 15 Å / s, and supplemented by cavity heating at 40 °C to 70 °C.

13. The preparation method according to claim 12, characterized in that, In step S1, the evaporation rate of the deposited adhesion layer is preferably 0.1 Å / s.

14. The preparation method according to claim 12, characterized in that, The method further includes the steps of sequentially depositing a metal protective layer and a bonding layer after depositing the composite reflective layer.

15. The preparation method according to claim 12, characterized in that, The method further includes the step of sequentially forming a double-layer protective structure after the metal electrode is fabricated, including: An atomic layer deposition (ALD) process is used to deposit an aluminum oxide layer with a thickness of 10 to 30 nanometers in the metal electrode coating region as a first protective layer; and A silicon dioxide layer with a thickness of 60 nanometers to 250 nanometers is grown as a second protective layer using a chemical vapor deposition process. The second protective layer is formed by a monolithic deposition method and covers the first protective layer as well as the device surface area not covered by the first protective layer.

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