LED chip and preparation method thereof

Abstract

The invention relates to the technical field of semiconductor materials, and discloses an LED chip and a preparation method thereof, and the preparation method comprises the steps: (1) providing a substrate, growing an epitaxial layer on the substrate, and then depositing a current blocking layer on the surface of the epitaxial layer; (2) coating photoresist on the surface, patterning the photoresist through a yellow light process, sequentially depositing a light reflecting material and a first metal material, removing the photoresist, and cleaning to form a light reflecting layer with a preset shape and a first metal electrode layer with a preset shape; (3) an ITO material is deposited on the surface, and then an ITO current expansion layer in a preset shape is formed through yellow light and etching; (4) coating photoresist on the surface, patterning the photoresist through a yellow light process, then depositing a second metal material, and performing photoresist removal treatment to form a second metal electrode layer with a preset shape; and (5) depositing a passivation protection layer on the surface. Through the preparation method provided by the invention, the luminance of the LED chip can be improved, and the problems that the LED chip is easy to fall off, the process yield is low and the like are solved.

Description

Technical Field

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

[0002] After about 20 years of development, LED chip technology has reached a relatively mature stage. However, it is becoming increasingly difficult to further improve LED chips in terms of both process and performance.

[0003] Traditional upright LED chips will inevitably lose a part of the luminous area due to the presence of metal electrodes. This part of the lost luminous area is usually more than 8%. Reducing this part of the luminous area as much as possible and improving the brightness of the LED chip is one of the core difficulties in the LED chip manufacturing process. Generally speaking, there are two main ways to solve the above problems: the first is to reduce the area of ​​the metal electrode as much as possible, thereby increasing the luminous area of ​​the chip; the second is to increase the reflectivity of the bottom of the metal electrode and increase the light extraction efficiency. Such methods include: using high-reflectivity metal Al to replace low-reflectivity metals such as Cr, Ti, Ni as an adhesion layer; adding a light reflection layer to the bottom of the metal, etc.

[0004] However, the metal electrode area of ​​LED chips has usually been optimized to the best under the current manufacturing process, and it is difficult to further reduce it. If it is further reduced, it may cause problems such as reduced reliability and poor electrical properties. After the metal of the LED chip electrode adhesion layer is changed to Al, although the chip brightness has increased, the electrode is generally prone to easy detachment and high voltage. If a light reflection layer is prepared at the bottom of the metal, the metal electrode will also be easy to detach, and in actual mass production, it will also cause problems such as a significant reduction in chip yield. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a high-brightness LED chip and a preparation method thereof, which can improve the luminous brightness of the LED chip and solve the problems of easy falling off of the LED chip and low process yield.

[0006] In order to solve the above technical problems, the present invention provides a method for preparing an LED chip in a first aspect, comprising:

[0007] (1) providing a substrate, growing an epitaxial layer on the substrate, and then depositing a current blocking layer on the surface of the epitaxial layer;

[0008] (2) coating a photoresist on the surface of the LED wafer obtained in (1), patterning the photoresist by a yellow light process, and then sequentially depositing a light reflecting material and a first metal material, and removing and cleaning the photoresist to form a light reflecting layer of a preset shape and a first metal electrode layer of a preset shape;

[0009] (3) depositing an ITO material on the surface of the LED wafer obtained in (2), and then forming an ITO current spreading layer of a preset shape by yellow light and etching;

[0010] (4) coating a photoresist on the surface of the LED wafer obtained in (3), patterning the photoresist by a yellow light process, then depositing a second metal material, and performing a desmearing process to form a second metal electrode layer of a preset shape;

[0011] (5) Depositing a passivation protective layer on the surface of the LED wafer obtained in (4).

[0012] As an improvement of the above solution, the first metal electrode layer includes an interdigitated portion of the P electrode;

[0013] The second metal electrode layer includes a metal electrode layer on the surface of the N-type layer and a metal pad layer on the surface of the P-type layer.

[0014] As an improvement of the above solution, the first metal electrode layer includes a first metal sublayer, a second metal sublayer and a third metal sublayer stacked in sequence from bottom to top;

[0015] The thickness of the first metal sublayer is 5nm to 100nm;

[0016] The thickness of the second metal sublayer is 50nm to 600nm;

[0017] The thickness of the third metal sublayer is 5nm-100nm.

[0018] As an improvement of the above solution, the thickness of the second metal electrode layer is 1 μm to 3 μm.

[0019] As an improvement of the above solution, the metal material in the first metal sublayer is one of Al, Cr, Ti, and Ni;

[0020] The metal material in the second metal sub-layer is Au;

[0021] The metal material in the third metal sublayer is one of Cr, Ti and Ni.

[0022] The metal material of the second metal electrode layer is at least two of Cr, Al, Ti, Ni, Au, and Pt.

[0023] As an improvement to the above solution, the time interval between forming the light reflecting layer and starting to deposit the material of the first metal electrode layer is less than or equal to 6 hours.

[0024] As an improvement of the above solution, an edge angle between the light reflecting layer and the first metal electrode layer is less than 40°.

[0025] As an improvement of the above scheme, the light reflecting layer includes SiO2 layers and TiO2 layers periodically stacked from bottom to top, and the number of periods is 2 to 40;

[0026] In each period, the thickness of the SiO2 layer is 10nm-300nm, and the thickness of the TiO2 layer is 10nm-200nm.

[0027] As an improvement of the above solution, the material of the current blocking layer is SiO2, and the thickness of the current blocking layer is 50nm to 600nm;

[0028] The thickness of the ITO current spreading layer is 15nm to 120nm;

[0029] The material of the passivation protection layer is SiO2 or Al2O3, and the thickness of the passivation protection layer is 30nm-200nm.

[0030] Correspondingly, the second aspect of the present invention also provides an LED chip prepared according to the preparation method.

[0031] The implementation of the present invention has the following beneficial effects:

[0032] In the present invention, the metal electrode layer is divided into a first metal electrode layer and a second metal electrode layer, and the first metal electrode on the surface of the P electrode is prepared before the ITO current spreading layer, and then the second metal electrode layer on the surface of the N electrode and the surface of the P electrode metal pad is prepared on the ITO current spreading layer, which is conducive to increasing the surface area of ​​the ITO current spreading layer in contact with the metal electrode, reducing the contact resistance, and improving the luminous efficiency. At the same time, the ITO current spreading layer is coated, and the adhesion effect between the light reflection layer and the metal electrode layer is improved, thereby improving the chip reliability. In addition, the preparation method of the present invention also helps to improve the brightness and manufacturing yield of the LED chip. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 : A schematic diagram of the structure of the mask in step (11) of the present invention (the black area is the opaque area, and the white area is the translucent area);

[0034] Figure 2 : Schematic diagram of the structure obtained after step (11) in the present invention is completed;

[0035] Figure 3 : A schematic diagram of the structure of the mask in step (12) of the present invention (the black area is the opaque area, and the white area is the translucent area);

[0036] Figure 4 : Schematic diagram of the structure obtained after step (12) in the present invention is completed;

[0037] Figure 5 : A schematic diagram of the structure of the mask in step (21) of the present invention (the black area is the opaque area, and the white area is the translucent area);

[0038] Figure 6 : A schematic diagram of the structure after the light reflecting layer of a preset shape is obtained in step (23) of the present invention;

[0039] Figure 7 : A schematic diagram of the structure of the first metal electrode layer of a preset shape obtained in step (23) of the present invention;

[0040] Figure 8 : A schematic diagram of the structure of the mask in step (3) of the present invention (the black area is the opaque area, and the white area is the translucent area);

[0041] Fig. 9 : Schematic diagram of the structure obtained after step (3) in the present invention is completed;

[0042] Fig.10 : A schematic diagram of the structure of the mask in step (4) of the present invention (the black area is the opaque area, and the white area is the translucent area);

[0043] Fig.11 : A schematic diagram of the structure of the mask in step (5) of the present invention (the black area is the opaque area, and the white area is the translucent area);

[0044] Fig.12 : Schematic diagram of the structure obtained after step (5) in the present invention is completed;

[0045] Fig.13 : A cross-sectional view of an LED chip in the present invention ( Figure 4 Cross-sectional view at position A in the middle);

[0046] Reference numerals:

[0047] 10-substrate; 11-N-GaN layer; 12-multi-quantum well layer; 13-P-GaN layer; 14-current blocking layer; 15-light reflecting layer; 16-first metal electrode layer; 17-ITO current spreading layer; 18-second metal electrode layer; 19-passivation protection layer. DETAILED DESCRIPTION

[0048] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail with specific embodiments below.

[0049] To solve the above problems, the present invention provides a method for preparing an LED chip in a first aspect, comprising:

[0050] (1) providing a substrate 10, growing an epitaxial layer on the substrate 10, and then depositing a current blocking layer 14 on the surface of the epitaxial layer;

[0051] (2) coating a photoresist on the surface of the LED wafer obtained in (1), patterning the photoresist by a yellow light process, and then sequentially depositing a light reflecting material and a first metal material, and removing and cleaning the photoresist to form a light reflecting layer 15 of a preset shape and a first metal electrode layer 16 of a preset shape;

[0052] (3) depositing an ITO material on the surface of the LED wafer obtained in (2), and then performing yellow light etching to form an ITO current spreading layer 17 of a preset shape;

[0053] (4) coating a photoresist on the surface of the LED wafer obtained in (3), patterning the photoresist by a yellow light process, then depositing a second metal material, and performing a debonding process to form a second metal electrode layer 18 of a preset shape;

[0054] (5) Depositing a passivation protection layer 19 on the surface of the LED wafer obtained in (4).

[0055] In the present invention, the metal electrode layer is divided into a first metal electrode layer 16 and a second metal electrode layer 18, and the first metal electrode on the surface of the P electrode is prepared before the ITO current spreading layer 17, and then the second metal electrode layer 18 on the surface of the N electrode and the metal pad surface of the P electrode is prepared on the ITO current spreading layer 17, which is conducive to increasing the surface area of ​​the ITO current spreading layer 17 in contact with the metal electrode, reducing the contact resistance, and improving the luminous efficiency. At the same time, the ITO current spreading layer 17 is coated, and the adhesion effect between the light reflection layer 15 and the metal electrode layer is improved, thereby improving the chip reliability. In addition, the preparation method of the present invention also helps to improve the brightness and manufacturing yield of the LED chip.

[0056] Each step is described in detail below:

[0057] Regarding step (1), a substrate 10 is provided, an epitaxial layer is grown on the substrate 10, and then a current blocking layer 14 is deposited on the surface of the epitaxial layer; specifically, the step includes:

[0058] (11) providing a substrate 10 and growing an epitaxial layer on the substrate 10;

[0059] Preferably, the substrate 10 may be a sapphire substrate, or a substrate of other materials such as a silicon substrate, a silicon carbide substrate, a gallium nitride substrate, etc., which is not specifically limited in the present invention.

[0060] Preferably, the epitaxial layer comprises an N-GaN layer 11, a multi-quantum well layer 12 and a P-GaN layer 13 stacked in sequence from bottom to top. Further, the N-GaN layer 11 is a Si-doped N-GaN layer, the multi-quantum well layer 12 is an InGaN / GaN multi-quantum well layer, the P-GaN layer 13 is a Mg-doped P-GaN layer, and the thickness of the epitaxial layer is 3 μm to 7 μm.

[0061] Furthermore, before depositing the current blocking layer 14, the epitaxial layer is subjected to MSA treatment to form an etching step, and the specific operation is as follows:

[0062] A photoresist is coated on the surface of the epitaxial layer, and then Figure 1 The mask is exposed and developed to obtain a patterned photoresist, and finally the epitaxial layer is etched using an etching technique to expose the N-type layer in the epitaxial layer, and the etching step is obtained after the resist is removed and cleaned. Figure 2 shown.

[0063] In this step, the photoresist is a positive photoresist. The positive photoresist in the exposed area is easily removed by the developer in the development process, leaving the negative photoresist in the unexposed area to form a patterned positive photoresist to protect the bottom material. During the etching process, the material without photoresist protection is etched away, and the part protected by the photoresist is retained. The etching technology uses dry etching, specifically ICP etching.

[0064] (12) depositing a current blocking layer 14 on the surface of the epitaxial layer;

[0065] The specific operations are:

[0066] A current blocking material is deposited on the surface of the epitaxial layer to form a current blocking film layer, and then a photoresist is coated on the surface of the current blocking film layer. Figure 3 The mask is exposed and developed to obtain a patterned photoresist, and finally the current blocking film layer is etched using an etching technique, and then the resist is removed and cleaned to form a current blocking layer 14 of a preset shape, such as Figure 4 shown.

[0067] The current blocking material in the present invention is SiO2, the deposition method of the current blocking material is PECVD, the photoresist is positive photoresist, and the etching technology is wet etching. Specifically, the SiO2 film layer can be etched with an etching solution, and the etching solution includes but is not limited to BOE etching solution.

[0068] Furthermore, the thickness of the current blocking layer 14 is 50 nm to 600 nm.

[0069] Regarding step (2), coating a photoresist on the surface of the LED wafer obtained in (1), patterning the photoresist by a yellow light process, and depositing a light reflective material to form a light reflective film layer; specifically comprising:

[0070] (21) coating a photoresist on the surface of the LED wafer obtained in (1), and then Figure 5 The mask is exposed and developed to obtain a patterned photoresist;

[0071] In this step, the photoresist is a negative photoresist. The negative photoresist portion in the unexposed area is easily removed by the developer during the development operation, leaving the negative photoresist in the exposed area to form a patterned negative photoresist to protect the bottom material, and then the light reflective material is deposited by electron beam evaporation.

[0072] (22) depositing a light reflective material by electron beam evaporation to form a light reflective film layer;

[0073] In the present invention, the material of the light reflective film layer is SiO2 and TiO2, thereby ensuring that the light reflective layer 15 of the preset shape formed after debonding contains SiO2 and TiO2. Specifically, the light reflective layer 15 of the preset shape includes a SiO2 layer and a TiO2 layer, and further, the light reflective layer 15 includes SiO2 layers and TiO2 layers periodically stacked from bottom to top, and the number of periods is 2 to 40, and exemplary ones are 2, 5, 10, 15, 20, 25, 30, 35, 40, but not limited thereto.

[0074] Further, in each period, the thickness of the SiO2 layer is 10nm to 300nm, exemplarily 10nm, 50nm, 100nm, 150nm, 200nm, 250nm, and 300nm, but not limited thereto; the thickness of the TiO2 layer is 10nm to 200nm, exemplarily 10nm, 50nm, 100nm, 150nm, and 200nm, but not limited thereto.

[0075] (23) Continue to deposit the first metal material by electron beam evaporation to form a first metal film layer, and then remove the glue and clean it to form a light reflection layer 15 (such as Figure 6 ) and a first metal electrode layer 16 of a preset shape (as shown Figure 7 shown).

[0076] The first metal electrode layer 16 in the present invention corresponds to the interdigital part in the P electrode. The light reflecting layer 15 is designed under the metal electrode and deposited and prepared after the same yellow light process. This not only improves the brightness of the chip, but also avoids the exposure alignment accuracy problem between different process flows, thereby effectively improving the chip manufacturing yield.

[0077] Furthermore, in order to prevent the light reflection layer 15 from absorbing too much impurities and water vapor on its surface, which would affect the adhesion of the first metal electrode layer 16, the time interval from forming the light reflection layer 15 to starting to deposit the material of the first metal electrode layer 16 is controlled to be less than or equal to 6 hours, thereby further improving the manufacturing yield of the LED chip. The upper and lower contact surfaces of the first metal electrode layer 16 are the ITO current spreading layer 17 and the light reflection layer 15, respectively. In order to ensure the coating effect of the ITO current spreading layer 17 in the present invention, the edge angles of the light reflection layer 15 and the first metal electrode layer 16 need to be controlled to be lower than 40°, preferably 30 to 40°. If the edge angle is too high, the subsequently evaporated ITO film layer and the passivation protective layer 19 will break at the edge, resulting in reduced yield and reliability. If the edge angle is too small, the film thickness cannot be accurately controlled. The edge angle here specifically refers to the angle of the slope of the edge of the film layer.

[0078] The first metal material includes but is not limited to Al, Cr, Ti, Ni, and Au, and the first metal film layer has a stacked structure of three metal layers, thereby ensuring that a metal electrode layer of a preset shape formed after degumming and cleaning has a stacked structure of three metal layers. Specifically, the metal electrode layer of the preset shape includes a first metal sublayer, a second metal sublayer, and a third metal sublayer stacked in sequence from bottom to top, wherein the thickness of the first metal sublayer is 5nm to 100nm, and the metal material in the first metal sublayer is one of Al, Cr, Ti, and Ni; the thickness of the second metal sublayer is 50nm to 600nm, and the metal material in the second metal sublayer is Au; the thickness of the third metal sublayer is 5nm to 100nm, and the metal material in the third metal sublayer is one of Cr, Ti, and Ni. In the present invention, by setting the first metal electrode layer 16 of the three-layer structure, not only can the current be expanded more effectively, thereby improving the luminous efficiency and uniformity of the LED chip, but also a better heat dissipation path can be provided, and the structural stability of the LED chip can be enhanced, thereby extending the service life of the chip and maintaining stable performance. At the same time, in cooperation with the light reflection layer 15, the reflection of the unextracted light can be improved, thereby improving the light output efficiency. In addition, compared with a single thick metal film layer, the stress in the metal can also be reduced and the reliability can be enhanced; compared with a metal structure with more layers, the film layer is simple, easy to prepare and low in cost.

[0079] Regarding step (3), an ITO material is deposited on the surface of the LED wafer obtained in (2), and then an ITO current spreading layer 17 of a preset shape is formed by yellow light and etching;

[0080] The specific operations are:

[0081] ITO material is deposited on the surface of the LED wafer obtained in (2) to form an ITO film layer, and then a photoresist is coated on the surface, and then the ITO film layer is formed. Figure 8 The mask is exposed and developed to obtain a patterned photoresist; finally, the ITO film layer is etched using an etching technique, and the ITO film layer is removed and cleaned to form an ITO current spreading layer 17 of a preset shape, such as Fig. 9 shown.

[0082] In this step, the photoresist is positive photoresist, and the etching technology is wet etching.

[0083] Furthermore, the thickness of the ITO current spreading layer 17 is 15nm to 120nm, and the ITO current spreading layer 17 is deposited by magnetron sputtering. The film layer obtained by magnetron sputtering deposition has high density and good adhesion effect, so that the obtained ITO current spreading layer 17 can not only play a good current spreading role, but also can well coat the light reflecting layer 15 and the first metal electrode layer 16, and have good ohmic contact with the first metal electrode layer 16, thereby reducing the contact resistance.

[0084] Regarding step (4), a photoresist is coated on the surface of the LED wafer obtained in (3), the photoresist is patterned by a yellow light process, and then a second metal material is deposited and stripped to form a second metal electrode layer 18 of a preset shape;

[0085] The specific operations are:

[0086] The surface of the LED wafer obtained in (3) is coated with photoresist, and then Fig.10 The mask is exposed and developed to obtain a patterned photoresist; finally, the second metal material is deposited by electron beam evaporation to form a second metal film layer, and then the second metal electrode layer 18 of a preset shape is formed by de-bonding and cleaning.

[0087] The second metal electrode layer 18 includes a metal electrode layer on the surface of the N-type layer and a metal pad layer on the surface of the P-type layer. By combining the second metal electrode layer 18 with the first metal electrode layer 16, a complete N-electrode metal layer and a P-electrode metal layer can be obtained.

[0088] In this step, the photoresist is a negative photoresist.

[0089] Furthermore, the metal material of the second metal electrode layer 18 is at least two of Cr, Al, Ti, Ni, Au, and Pt. The second metal electrode layer 18 is a stacked structure, which can be a stacked structure of two or more metal layers, or three or more layers. The second metal electrode layer 18 does not need to be consistent with the first metal electrode layer 16, and can be matched according to actual mass production.

[0090] Furthermore, the thickness of the second metal electrode layer 18 is 1 μm to 3 μm. More preferably, the second metal electrode layer 18 is a Cr layer, an Al layer, a Ti layer and an Au layer stacked from bottom to top, wherein the thickness of Cr is 2 nm to 7 nm, the thickness of Al is 100 nm to 200 nm, the thickness of Ti is 150 nm to 300 nm, and the thickness of Au is 1000 nm to 2000 nm.

[0091] (5) Depositing a passivation protection layer 19 on the surface of the LED wafer obtained in (4).

[0092] The specific operations are:

[0093] A passivation protection material is deposited on the surface of the LED wafer obtained in (4) to form a passivation protection film layer, and then a photoresist is coated on the surface of the passivation protection film layer. Fig.11 The mask is exposed and developed to obtain a patterned photoresist; finally, the passivation protective film layer is etched using an etching technique to expose the metal pad below, and the resist is removed and cleaned to form a passivation protective layer 19 of a preset shape, such as Fig.12 shown.

[0094] In this step, the photoresist is a positive photoresist, the etching technology adopts ICP etching, and the deposition method of the passivation protection layer 19 includes but is not limited to PECVD and ALD.

[0095] Furthermore, the thickness of the passivation protection layer 19 is 30-200 nm, and the material of the passivation protection layer 19 is SiO2 or Al2O3.

[0096] In the present invention, the coating method of the photoresist can be spin coating, which is not specifically limited.

[0097] Accordingly, the present invention also provides an LED, which is prepared by the above preparation method and has a structure as shown in FIG. Fig.13 shown.

[0098] The present invention will be further described below with specific embodiments:

[0099] Example 1

[0100] This embodiment provides an LED chip, which is prepared by the following method:

[0101] (1) providing a substrate, growing an epitaxial layer on the substrate, and then coating a positive photoresist on the surface of the epitaxial layer, using a method such as Figure 1 The mask is exposed and developed to obtain a patterned positive photoresist, and the epitaxial layer is etched using an ICP machine to expose the N-type layer in the epitaxial layer, and the etching step is obtained after the resist is removed and cleaned;

[0102] The epitaxial layer includes a Si-doped N-GaN layer, an InGaN / GaN multi-quantum well layer, and a Mg-doped P-GaN layer, and the thickness of the epitaxial layer is 4 μm.

[0103] (2) SiO2 is deposited on the surface of the epitaxial layer by PECVD to form a SiO2 film layer, and a positive photoresist is coated on the surface of the SiO2 film layer. Figure 3 The mask is exposed and developed to obtain a patterned photoresist, and finally the SiO2 film is etched by BOE etching solution, and then the film is stripped and cleaned to form a SiO2 current blocking layer of a preset shape with a thickness of 200nm.

[0104] (3) coating a negative photoresist on the surface of the LED wafer obtained in (2), and then using Figure 5 The mask is exposed and developed to obtain a patterned photoresist negative resist, and then placed in an electron beam evaporation machine to deposit a SiO2 layer and a TiO2 layer in sequence as a cycle to repeat the cycle to form a light reflective film layer; then an Al layer, an Au layer and a Ni layer are sequentially deposited in the electron beam evaporation machine to form a first metal electrode layer, and the resist is removed and cleaned to form a light reflective layer and a first metal electrode layer of a preset shape, and the edge angle of the light reflective layer and the first metal electrode layer is 35°;

[0105] Among them, the number of periods of the light reflection film layer is 6, the thickness of the SiO2 layer in each period is 60nm, the thickness of the TiO2 layer is 30nm, the thickness of the Cr layer in the first metal electrode layer is 3nm, the thickness of the Au layer is 50nm, and the thickness of the Ni layer is 30nm.

[0106] (4) depositing ITO material on the surface of the LED wafer obtained in (3) by magnetron sputtering to form an ITO film layer, and then coating the surface with a photoresist, using a method such as Figure 8 The mask is exposed and developed to obtain a patterned photoresist. Finally, the ITO film is etched by wet etching, and then the film is stripped and cleaned to form an ITO current spreading layer of a preset shape with a thickness of 70 nm.

[0107] (5) coating a negative photoresist on the surface of the LED wafer obtained in (4), and then using Fig.10 The mask is exposed and developed to obtain a patterned negative photoresist; finally, it is placed in an electron beam evaporation machine to sequentially deposit a Cr layer, an Al layer, a Ti layer, and an Au layer to form a second metal electrode layer of a preset shape, wherein the thickness of Cr is 3 nm, the thickness of Al is 120 nm, the thickness of Ti is 200 nm, and the thickness of Au is 1200 nm;

[0108] (6) SiO2 is deposited on the surface of the LED wafer obtained in (5) by PECVD to form a SiO2 film layer, and then a photoresist is coated on the surface of the SiO2 film layer, and a Fig.11 The mask is exposed and developed to obtain a patterned photoresist. Finally, the SiO2 film is etched by an ICP machine to expose the metal pad below, and the resist is removed and cleaned to form a passivation protection layer of a preset shape with a thickness of 80nm.

[0109] Comparative Example 1

[0110] This comparative example provides an LED chip, and the preparation method is basically the same as that of Example 1, except that:

[0111] (3) coating a negative photoresist on the surface of the LED wafer obtained in (2), and then using Figure 5 The mask is exposed and developed to obtain a patterned photoresist negative resist, which is then placed in an electron beam evaporation machine to deposit a SiO2 layer and a TiO2 layer in sequence as a cycle and repeated to form a light reflective film layer, and then the resist is removed and cleaned to form a light reflective layer of a preset shape;

[0112] (5) coating a photoresist negative resist on the surface of the LED wafer obtained in (4), followed by exposure and development to obtain a patterned photoresist negative resist; finally placing the wafer in an electron beam evaporation machine to sequentially deposit an Al layer and an Au layer, and then removing the resist and cleaning the wafer to form a metal electrode layer of a preset shape, wherein the metal electrode layer includes a metal electrode layer on the surface of the N-type layer, a metal pad layer on the surface of the P-type layer, and a finger portion of the P electrode.

[0113] Comparative Example 2

[0114] This comparative example provides an LED chip, and the preparation method is basically the same as that of Example 1, except that:

[0115] (1) providing a substrate, growing an epitaxial layer on the substrate, and then coating a positive photoresist on the surface of the epitaxial layer, using a method such as Figure 1 The mask is exposed and developed to obtain a patterned positive photoresist, and the epitaxial layer is etched using an ICP machine to expose the N-type layer in the epitaxial layer, and the etching step is obtained after the resist is removed and cleaned;

[0116] (2) SiO2 is deposited on the surface of the epitaxial layer by PECVD to form a SiO2 film layer, and a positive photoresist is coated on the surface of the SiO2 film layer. Figure 3 The mask is exposed and developed to obtain a patterned photoresist, and finally the SiO2 film is etched by a BOE etching solution, and then the SiO2 film is removed and cleaned to form a SiO2 current blocking layer of a preset shape;

[0117] (3) depositing ITO material on the surface of the LED wafer obtained in (2) by magnetron sputtering to form an ITO film layer, and then coating the surface with a photoresist, using a method such as Figure 8 The mask is exposed and developed to obtain a patterned photoresist, and finally the ITO film is etched by wet etching, and the resist is removed and cleaned to form an ITO current spreading layer of a preset shape;

[0118] (4) coating a negative photoresist on the surface of the LED wafer obtained in (2), and then using Figure 5 The mask is exposed and developed to obtain a patterned photoresist negative resist, which is then placed in an electron beam evaporation machine to sequentially deposit a Cr layer, an Al layer, a Ti layer, and an Au layer to form a first metal electrode layer, and then the mask is removed and cleaned to form a first metal electrode layer of a preset shape;

[0119] (5) coating a negative photoresist on the surface of the LED wafer obtained in (4), and then using Fig.10 The mask is exposed and developed to obtain a patterned photoresist negative resist; finally, it is placed in an electron beam evaporation machine to sequentially deposit a Cr layer, an Al layer, a Ti layer, and an Au layer to form a second metal electrode layer of a preset shape;

[0120] (6) SiO2 is deposited on the surface of the LED wafer obtained in (5) by PECVD to form a SiO2 film layer, and then a photoresist is coated on the surface of the SiO2 film layer, and a Fig.11 The mask is exposed and developed to obtain a patterned photoresist. Finally, the ICP machine etches the SiO2 film layer to expose the metal pad underneath, and removes the resist to form a passivation protective layer of a preset shape.

[0121] Performance Testing

[0122] The LED chips obtained in the embodiment and the comparative example were cut into 10 mil*24 mil, and 1000 chips were respectively selected to test their luminous brightness, luminous efficiency and manufacturing yield under 120 mA.

[0123] The test results are shown in Table 1 below.

[0124] Table 1 Performance test results of LED chips obtained in the embodiments and comparative examples

[0125] Luminous brightness (mW) Luminous efficiency (%) Yield (%) Example 1 220.1 59.17 96.3 Comparative Example 1 219.4 58.98 92.7 Comparative Example 2 210.2 56.45 95.2

[0126] From the above results, it can be seen that the metal electrode layer is divided into a first metal electrode layer and a second metal electrode layer, and the first metal electrode on the surface of the P electrode is deposited before the ITO current spreading layer, and then the second metal electrode layer on the surface of the N electrode and the metal pad surface of the P electrode is prepared on the ITO current spreading layer, and the light reflecting layer and the first metal electrode layer are prepared in the same yellow light process, which can improve the luminous brightness, improve the light extraction efficiency, achieve the coating effect of the ITO current spreading layer, improve adhesion, and increase the manufacturing yield of the LED chip. At the same time, the material of the first metal electrode layer and the thickness of the light reflecting layer can be adjusted to achieve better results.

[0127] The above disclosure is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing an LED chip, characterized in that: include: (1) providing a substrate, growing an epitaxial layer on the substrate, and then depositing a current blocking layer on the surface of the epitaxial layer; (2) coating a photoresist on the surface of the LED wafer obtained in (1), patterning the photoresist by a yellow light process, then sequentially depositing a light reflecting material and a first metal material, and removing and cleaning the photoresist to form a light reflecting layer of a preset shape and a first metal electrode layer of a preset shape; (3) depositing an ITO material on the surface of the LED wafer obtained in (2), and then forming an ITO current spreading layer of a preset shape by yellow light and etching; (4) coating a photoresist on the surface of the LED wafer obtained in (3), patterning the photoresist by a yellow light process, then depositing a second metal material, and performing a desmearing process to form a second metal electrode layer of a preset shape; (5) Depositing a passivation protective layer on the surface of the LED wafer obtained in (4).

2. The method for preparing an LED chip according to claim 1, wherein: The first metal electrode layer includes an interdigitated portion of a P electrode; The second metal electrode layer includes a metal electrode layer on the surface of the N-type layer and a metal pad layer on the surface of the P-type layer.

3. The method for preparing an LED chip according to claim 1, wherein: The first metal electrode layer includes a first metal sublayer, a second metal sublayer and a third metal sublayer stacked in sequence from bottom to top; The thickness of the first metal sublayer is 5nm to 100nm; The thickness of the second metal sublayer is 50nm to 600nm; The thickness of the third metal sublayer is 5nm-100nm.

4. The method for preparing an LED chip according to claim 1 or 2, characterized in that: The thickness of the second metal electrode layer is 1 μm to 3 μm.

5. The method for preparing an LED chip according to claim 1, wherein: The metal material in the first metal sublayer is one of Al, Cr, Ti and Ni; The metal material in the second metal sub-layer is Au; The metal material in the third metal sublayer is one of Cr, Ti and Ni. The metal material of the second metal electrode layer is at least two of Cr, Al, Ti, Ni, Au, and Pt.

6. The method for preparing an LED chip according to claim 1, wherein: The time interval between forming the light reflection layer and starting to deposit the material of the first metal electrode layer is less than or equal to 6 hours.

7. The method for preparing an LED chip according to claim 1, wherein: An edge angle between the light reflecting layer and the first metal electrode layer is less than 40°.

8. The method for preparing an LED chip according to claim 1, wherein: The light reflection layer includes SiO2 layers and TiO2 layers periodically stacked from bottom to top, with the number of periods being 2 to 40; In each period, the thickness of the SiO2 layer is 10nm-300nm; the thickness of the TiO2 layer is 10nm-200nm.

9. The method for preparing an LED chip according to claim 1, wherein: The material of the current blocking layer is SiO2, and the thickness of the current blocking layer is 50nm to 600nm; The thickness of the ITO current spreading layer is 15nm to 120nm; The material of the passivation protection layer is SiO2 or Al2O3, and the thickness of the passivation protection layer is 30nm-200nm.

10. An LED chip prepared according to the preparation method according to any one of claims 1 to 9.

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