A method for preventing scratches during the production of non-conforming electrodes on GaAs-based LED tube cores

Abstract

The present invention relates to a method for preventing scratches during the production of electrodes on opposite sides of a gallium arsenide-based LED tube core. The method comprises the following steps: (1) production of the P side; (2) pre-treatment of the N side production: first attaching an adhesive film to a carrier plate, then placing a pressing sheet on the adhesive film for heating, and after the heating is completed, removing the pressing sheet to obtain a treated carrier plate; (3) production of the N side; (4) production of the tube core. The adhesive film used in the present invention is easy to replace, and can be replaced in time according to the degree of scratches produced. However, the carrier plate is generally not replaced for a single small scratch due to inconvenience and cost reasons, so that small scratches will continue to occur, which has a greater impact on the overall product qualification rate. Compared with the technology of adding a protective layer and replacing the carrier plate, the present invention is low-cost and easier to operate.

Description

Technical Field

[0001] The invention relates to a method for preventing scratches during the manufacturing process of electrodes on different surfaces of a gallium arsenide-based LED tube core, and belongs to the technical field of semiconductor processing. Background Art

[0002] LED is the abbreviation of light-emitting diode. It is currently one of the most commonly used semiconductor components. It is a semiconductor that can convert electrical energy into light energy. It is mainly made of III-IV group compounds such as GaAs (gallium arsenide), GaP (gallium phosphide), GaAsP (gallium arsenide phosphide) and other semiconductors, and its core is the PN junction.

[0003] Gallium arsenide-based LEDs first require the production of an epitaxial layer on the substrate surface; the wafer with the epitaxial layer is then fabricated into individual die through a die-forming process; and finally, individual LEDs are produced through a packaging process. The die-forming process typically involves the following: epitaxial wafer cleaning, current spreading layer fabrication, P-side electrode fabrication, substrate thinning, N-side electrode fabrication, die cutting, photoelectric parameter testing, and binning for storage. However, after thinning, the chip is relatively thin, with a thickness controlled between 100-200 microns. Such chips typically experience significant warpage, typically exceeding 10μm, with warpage reaching as high as 50μm. Consequently, the chip warps significantly when the N-side electrode is evaporated. Conventional N-side metallization processes typically utilize full-surface evaporation or sputtering.

[0004] Typically, during the vapor deposition process, the wafer directly contacts the surface of the carrier plate. Due to the need for uniform metal deposition, the deposition process requires the rotation of the coating pot, resulting in slight displacement between the wafer and the carrier plate. Furthermore, friction between the wafer and the carrier plate occurs during wafer loading and unloading. Consequently, as the frequency of wafer deposition increases, the carrier plate surface quickly becomes rough, inevitably causing scratches on the chip's P-side, particularly the electrodes. Furthermore, as the amount of metal deposited increases, the entire coating pot needs to be re-cleaned. Current cleaning methods typically involve sandblasting or etching. Regardless of the method, the surface of the carrier plate remains rough after cleaning, leading to further scratches on the contact surface of the wafer during subsequent metal deposition. To address this widespread scratching problem, one approach is to promptly replace the carrier plate based on the severity of the scratches. Typically, a new carrier plate needs to be replaced after approximately 100-150 runs. However, carrier plates are very expensive, significantly increasing the cost of die production, making them unprofitable. Another method is to make a protective layer on the side of the chip in contact with the carrier plate, using a passivation layer or photoresist for protection. However, this method makes the production process more complicated, while increasing the production cost and increasing the production cycle.

[0005] Chinese patent document CN105914280 A proposes a method for preparing a protective layer for an LED chip and an LED chip. The method for preparing the protective layer is to place an LED chip that has completed mesa etching, transparent conductive layer preparation, and PN electrode evaporation into a PECVD deposition chamber and perform n-step deposition of a silicon dioxide film on its surface. The corresponding thin films obtained by the n-step deposition form a silicon dioxide protective layer. The thickness of the thin films deposited in each step is equal, and 2≤n≤4. The present invention deposits a silicon dioxide film on the outer surface of the LED chip in multiple steps. In the steps of repeatedly depositing the silicon dioxide film, the density of the silicon dioxide protective layer is improved by appropriately increasing the SiH4 flow rate and radio frequency power, thereby increasing the resistance of the LED chip to external mechanical scratches and acid and alkali corrosion; at the same time, the total reflection phenomenon of the LED chip is improved, and the light output is increased. By preparing a high-density protective layer with protective properties to protect the surface of the chip, the growth of multiple protective layers prolongs the entire process cycle, makes the process more complicated, and increases the product cost.

[0006] Chinese patent document CN107221584A proposes a method for fabricating a GaAs-based LED chip with damage-free electrodes and easy wire bonding. The method includes the following steps: a) growing an epitaxial layer on a GaAs substrate; b) photolithographically etching a SiO2 film to form an electrode pattern; c) depositing an Au film; d) growing an Au film to serve as the N electrode; and e) etching the SiO2 film to form a P electrode. The P electrode is formed by first preparing and etching a SiO2 film with an electrode pattern on the epitaxial wafer surface, and then depositing an Au film on the SiO2 film. This patent also uses a protective film process, which increases the instability and cost of the entire process.

[0007] In summary, it is necessary to study a process method for preventing scratches during the production of non-uniform electrodes of GaAs-based LED tube cores, which does not increase the cost or add additional production steps and can effectively prevent scratches. Summary of the Invention

[0008] In view of the shortcomings of the existing technology, a method for preventing scratches during the manufacturing process of non-surface electrodes of GaAs-based LED tube cores is proposed.

[0009] Terminology Notes:

[0010] N side: The semiconductor laser die needs to be connected to the negative side of the detection power supply;

[0011] P side: The semiconductor laser die needs to be connected to the positive side of the detection power supply;

[0012] The technical solutions of the present invention are as follows:

[0013] A method for preventing scratches on GaAs-based LED die electrodes during the manufacturing process includes the following steps:

[0014] (1) P-face fabrication: A transparent conductive layer is fabricated on the surface of a GaAs-based epitaxial wafer. A photoresist mask pattern is then formed on the surface of the wafer with the transparent conductive layer, and a P-face metal electrode is fabricated. The wafer after electrode fabrication is thinned to obtain a P-face fabricated wafer.

[0015] (2) N-side pre-processing: first, attach an adhesive film to the carrier disc, then place a pressing sheet on the adhesive film and heat it. After heating, remove the pressing sheet to obtain the processed carrier disc;

[0016] (3) N-side fabrication: The wafer in step (1) is placed with its P side facing downward on the carrier plate processed in step (2), and N-side evaporation is performed to obtain a wafer with the N-side fabricated;

[0017] (4) Die production: The wafers in step (3) are cut, tested for photoelectric parameters, and sorted and stored in order to complete the preparation of GaAs-based LED die.

[0018] Preferably, according to the present invention, in step (1), an epitaxial buffer layer, an N-type gallium arsenide layer, an MQW quantum well layer, a P-type AlGaInP layer and a P-type gallium arsenide layer are sequentially grown on the surface of the gallium arsenide-based epitaxial wafer.

[0019] According to a preferred embodiment of the present invention, in step (1), the transparent conductive layer is prepared by electron beam evaporation or sputtering evaporation.

[0020] According to the preferred embodiment of the present invention, in step (1), the P-side metal electrode is a metal electrode structure made with Cr, Ni, Ge, Ti, Pt or Au metal as the bottom layer and transition layer, and metal Al, Au, etc. as the top main electrode.

[0021] According to a preferred embodiment of the present invention, in step (1), the P-side metal electrode is corroded by a stripping method or by photoresist protection to obtain a patterned P-side metal electrode.

[0022] According to a preferred embodiment of the present invention, in step (2), the adhesive film is a high-temperature resistant tape, one side of which is smooth and the other side of which is adhesive, and the material is polyimide silicone, and the temperature resistance is above 150°C. It has the advantages of demagnetization, anti-static, high temperature resistance, no adhesive peeling, and no residue left on the adhered surface after being torn off.

[0023] Preferably, according to the present invention, in step (2), the thickness of the pressed sheet is greater than or equal to 300 μm, the weight is 8 to 10 g, and the shape matches the carrier plate.

[0024] Preferably, according to the present invention, in step (2), the heating is carried out in a plating pot, the heating temperature is 100-150°C, the heating time is 6-8 hours, and the plating pot equipped with the carrier plate is kept rotating at a speed of 5-10 rpm during the heating process.

[0025] Preferably, according to the present invention, in step (3), the N-side metal electrode covers the entire back side of the wafer, and the N-side electrode is an electrode structure made of Ni, Ge, Au or Pt metal.

[0026] According to the present invention, the purity of the evaporated metal materials involved in the above steps is all 5N level or above, and the preparation of the photoresist mask pattern, thinning and cutting are all processed according to the existing technology.

[0027] The present invention has the following beneficial effects:

[0028] 1. The present invention is a targeted study based on the problem of easy scratches during the production of non-uniform electrodes of GaAs-based LED cores. One side of the adhesive film is attached to the carrier plate, and the other smooth side is in direct contact with the chip. The smooth surface of the high-temperature resistant tape is used to prevent the chip from being scratched during the placement and N-side evaporation process. Although the friction between the chip and the high-temperature resistant tape increases with the frequency of use, the adhesive film used in the present invention is easy to replace and can be replaced in time according to the degree of scratches. The carrier plate is generally not replaced for a single small scratch due to inconvenience and cost reasons. This will cause continuous small scratches, which has a greater impact on the overall product qualification rate. Compared with the technology of adding a protective layer and replacing the carrier plate, the present invention is low-cost and easier to operate.

[0029] 2. In this invention, post-application processing of the adhesive film is crucial. Due to the rough surface of the carrier disc, the adhesive film immediately after application will produce numerous bubbles and protrusions. After wafer loading, baking at a specific temperature for a specified time gradually releases these bubbles, smoothing the film's surface. This prevents scratches after wafer loading. The heating temperature is crucial: too high a temperature will exceed the film's tolerance, resulting in wrinkles. Too low a temperature will prevent bubbles from being released, and protrusions will remain.

[0030] 3. The process method designed in this invention is simple and easy to operate, and the thinning step is placed as far back as possible. Due to the need for cutting the die, the thinned wafers are extremely prone to cracking during handling. This method can minimize the occurrence of cracking, and can maximize the product qualification rate and output rate. At the same time, it does not require the introduction of special equipment, and at a low cost, it solves the problem of easy scratching during the production of LED chip electrodes on different surfaces. It is applicable to the production process of all LED chip electrodes on different surfaces. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the die structure after the N-side fabrication is completed in Example 1;

[0032] Figure 2 Schematic diagram of a wafer loaded on a carrier plate during N-side evaporation in Example 1;

[0033] Among them: 1 is the substrate; 2 is the epitaxial layer; 3 is the current spreading layer; 4 is the P-side electrode; 5 is the N-side electrode; 6 is the carrier plate; 7 is the adhesive film; and 8 is the wafer. DETAILED DESCRIPTION

[0034] The present invention will be further described below with reference to the embodiments and drawings, but is not limited thereto.

[0035] Example 1

[0036] A method for preventing scratches on GaAs-based LED die electrodes during the manufacturing process includes the following steps:

[0037] (1) P-face fabrication: A transparent conductive layer is prepared on the surface of a GaAs-based epitaxial wafer by electron beam evaporation. A photoresist mask pattern is then formed on the surface of the wafer with the transparent conductive layer grown thereon to prepare a P-face metal electrode. The wafer after electrode fabrication is thinned to obtain a wafer with a completed P-face.

[0038] (2) N-side pre-treatment: First, attach a high-temperature resistant tape to the carrier plate, then place a pressed sheet on the high-temperature resistant tape, and heat it in a plating pot at 120°C for 7 h. During the heating process, the plating pot with the carrier plate is kept rotating at a speed of 8 rpm. After the heating is completed, the pressed sheet is removed to obtain the treated carrier plate;

[0039] (3) N-side fabrication: The wafer in step (1) is placed with its P side facing downward on the carrier plate processed in step (2), and N-side evaporation is performed to obtain a wafer with the N-side fabricated;

[0040] (4) Die production: The wafers in step (3) are cut, tested, and sorted into grades for storage in sequence to complete the preparation of GaAs-based LED die.

[0041] In step (1), an epitaxial buffer layer, an N-type gallium arsenide layer, an MQW quantum well layer, a P-type AlGaInP layer and a P-type gallium arsenide layer are sequentially grown on the surface of the gallium arsenide-based epitaxial wafer; the P-side metal electrode is a metal electrode structure made with Cr, Ni, Ge, Ti, Pt or Au metal as the bottom layer and transition layer, and metal Al, Au, etc. as the top main electrode.

[0042] In step (2), the high-temperature resistant tape is smooth on one side and sticky on the other. It is made of polyimide silicone and has a temperature resistance of above 150°C. It has the advantages of demagnetization, anti-static properties, high temperature resistance, and resistance to adhesive loss. It also leaves no residue on the adhered surface after removal. The pressed sheet has a thickness of 300 μm, a weight of 8 g, and a shape that matches the carrier plate.

[0043] The schematic diagram of the die structure after the N side is completed in this embodiment is as follows: Figure 1 As shown; Schematic diagram of the carrier plate loading the wafer during N-side evaporation, as shown Figure 2 shown.

[0044] Example 2

[0045] A method for preventing scratches on GaAs-based LED die electrodes during the manufacturing process includes the following steps:

[0046] (1) P-face fabrication: A transparent conductive layer is prepared on the surface of a GaAs-based epitaxial wafer by electron beam evaporation. A photoresist mask pattern is then formed on the surface of the wafer with the transparent conductive layer grown thereon to prepare a P-face metal electrode. The wafer after electrode fabrication is thinned to obtain a wafer with a completed P-face.

[0047] (2) N-side pre-treatment: First, attach a high-temperature resistant tape to the carrier plate, then place a pressed sheet on the high-temperature resistant tape, and heat it in a plating pot at 100°C for 8 h. During the heating process, the plating pot with the carrier plate is kept rotating at a speed of 5 rpm. After the heating is completed, the pressed sheet is removed to obtain the treated carrier plate;

[0048] (3) N-side fabrication: The wafer in step (1) is placed with its P side facing downward on the carrier plate processed in step (2), and N-side evaporation is performed to obtain a wafer with the N-side fabricated;

[0049] (4) Die production: The wafers in step (3) are cut, tested, and sorted into grades for storage in sequence to complete the preparation of GaAs-based LED die.

[0050] In step (1), an epitaxial buffer layer, an N-type gallium arsenide layer, an MQW quantum well layer, a P-type AlGaInP layer and a P-type gallium arsenide layer are sequentially grown on the surface of the gallium arsenide-based epitaxial wafer; the P-side metal electrode is a metal electrode structure made with Cr, Ni, Ge, Ti, Pt or Au metal as the bottom layer and transition layer, and metal Al, Au, etc. as the top main electrode.

[0051] In step (2), the high-temperature resistant tape is smooth on one side and sticky on the other. It is made of polyimide silicone and has a temperature resistance of above 150°C. It has the advantages of demagnetization, anti-static properties, high temperature resistance, and resistance to adhesive loss. It also leaves no residue on the adhered surface after removal. The pressed sheet has a thickness of 400 μm, a weight of 10 g, and a shape that matches the carrier plate.

[0052] Example 3

[0053] A method for preventing scratches on GaAs-based LED die electrodes during the manufacturing process includes the following steps:

[0054] (1) P-face fabrication: A transparent conductive layer is prepared on the surface of a GaAs-based epitaxial wafer by electron beam evaporation. A photoresist mask pattern is then formed on the surface of the wafer with the transparent conductive layer grown thereon to prepare a P-face metal electrode. The wafer after electrode fabrication is thinned to obtain a wafer with a completed P-face.

[0055] (2) N-side pre-treatment: First, attach a high-temperature resistant tape to the carrier plate, then place a pressed sheet on the high-temperature resistant tape, and heat it in a plating pot at 150°C for 6 h. During the heating process, the plating pot with the carrier plate is kept rotating at a speed of 10 rpm. After the heating is completed, the pressed sheet is removed to obtain the treated carrier plate;

[0056] (3) N-side fabrication: The wafer in step (1) is placed with its P side facing downward on the carrier plate processed in step (2), and N-side evaporation is performed to obtain a wafer with the N-side fabricated;

[0057] (4) Die production: The wafers in step (3) are cut, tested, and sorted into grades for storage in sequence to complete the preparation of GaAs-based LED die.

[0058] In step (1), an epitaxial buffer layer, an N-type gallium arsenide layer, an MQW quantum well layer, a P-type AlGaInP layer and a P-type gallium arsenide layer are sequentially grown on the surface of the gallium arsenide-based epitaxial wafer; the P-side metal electrode is a metal electrode structure made with Cr, Ni, Ge, Ti, Pt or Au metal as the bottom layer and transition layer, and metal Al, Au, etc. as the top main electrode.

[0059] In step (2), the high-temperature resistant tape is smooth on one side and sticky on the other. It is made of polyimide silicone and has a temperature resistance of above 150°C. It has the advantages of demagnetization, anti-static properties, high temperature resistance, and resistance to adhesive loss. It also leaves no residue on the adhered surface after removal. The pressed sheet has a thickness of 350 μm, a weight of 9 g, and a shape that matches the carrier plate.

[0060] Comparative Example 1

[0061] A method for preventing scratches during the production of electrodes on different surfaces of a gallium arsenide-based LED die, comprising the same steps as described in Example 1, except that in step (2), the electrodes are heated in a plating pot at 70° C. for 7 hours.

[0062] The method of this comparative example will not completely eliminate the bubbles in the high-temperature resistant tape on the carrier plate, and bulges will still exist, which cannot effectively prevent scratches during the subsequent production process of the non-uniform electrodes.

[0063] Comparative Example 2

[0064] A method for preventing scratches during the production of electrodes on different surfaces of a gallium arsenide-based LED die, comprising the same steps as described in Example 1, except that in step (2), the electrodes are heated in a plating pot at 200° C. for 7 hours.

[0065] The method of this comparative example will cause wrinkles on the high-temperature resistant tape on the carrier plate, which will not remain smooth, and cannot effectively prevent scratches during the subsequent production process of the non-uniform electrodes.

[0066] Comparative Example 3

[0067] The gallium arsenide-based LED die is processed according to the method described in Example 1, except that the carrier plate is not processed, and the wafer is directly placed with the P surface facing downward to produce the N-side electrode.

[0068] Test example

[0069] The gallium arsenide-based LED dies were processed using Example 1 and Comparative Example 3, respectively. When the method described in Example 1 was used, the high-temperature resistant tape was replaced according to the situation. The qualified rate was calculated when 3600 wafers were processed in 200 hours and 7200 wafers were processed in 400 hours.

[0070] Qualified rate = qualified wafers / total number of wafers × 100%

[0071] Qualified wafers are those without scratches.

[0072] Table 1 Qualification rate of the method of Example 1 and Comparative Example 3

[0073] Example 1 Comparative Example 3 Wafer qualification rate at 200h (%) 100.00％ 83.03％ Wafer qualification rate at 400h (%) 99.97％ 61.90％

[0074] As shown in Table 1, when processing gallium arsenide-based LED die using the method of Example 1, by promptly replacing the high-temperature resistant tape according to the situation, the pass rate was 100% after processing 3,600 wafers in 200 hours, and the pass rate reached over 99% after processing 7,200 wafers in 400 hours. However, when processing gallium arsenide-based LED die using the method of Comparative Example 3, the pass rate was 83.03% after processing 3,600 wafers in 200 hours, indicating that small scratches had gradually occurred due to the roughening of the carrier plate during processing. After processing 7,200 wafers in 400 hours, the pass rate was 61.90%, approaching 60%. Considering the overall cost, the carrier plate must be replaced, and the price of the high-temperature resistant tape is essentially negligible compared to the carrier plate. Thus, the method of the present invention significantly reduces production costs while ensuring the pass rate of wafer processing.

Claims

1. A method for preventing scratches on GaAs-based LED die during the fabrication of electrodes on opposite sides of the die, comprising the following steps: (1) P-face fabrication: A transparent conductive layer is fabricated on the surface of a GaAs-based epitaxial wafer. A photoresist mask pattern is then formed on the surface of the wafer with the transparent conductive layer, and a P-face metal electrode is fabricated. The wafer after electrode fabrication is thinned to obtain a P-face fabricated wafer. (2) N-side pre-processing: first, attach an adhesive film to the carrier disc, then place a pressing sheet on the adhesive film and heat it. After heating, remove the pressing sheet to obtain the processed carrier disc; The adhesive film is a high-temperature resistant tape with one side smooth and the other side sticky, made of polyimide silicone and heat-resistant at a temperature of 150°C or above. The thickness of the pressed sheet is greater than or equal to 300 μm, the weight is 8 to 10 g, and the shape matches the carrier plate. The heating is carried out in a plating pot at a temperature of 100 to 150°C for 6 to 8 hours, and the plating pot with the carrier plate is kept rotating at a speed of 5 to 10 rpm during the heating process. (3) N-side fabrication: The wafer prepared in step (1) is placed with its P side facing downward on the carrier plate processed in step (2), and N-side evaporation is performed to obtain a wafer with the N-side fabricated; (4) Die production: The wafers in step (3) are cut, tested for photoelectric parameters, and sorted and stored in order to complete the preparation of GaAs-based LED die.

2. The method for preventing scratches during the manufacturing process of electrodes on different surfaces of GaAs-based LED dies according to claim 1, characterized in that: In step (1), an epitaxial buffer layer, an N-type gallium arsenide layer, an MQW quantum well layer, a P-type AlGaInP layer and a P-type gallium arsenide layer are sequentially grown on the surface of the gallium arsenide-based epitaxial wafer.

3. The method for preventing scratches during the manufacturing process of electrodes on different surfaces of GaAs-based LED dies according to claim 1, characterized in that: In step (1), the transparent conductive layer is prepared by electron beam evaporation or sputtering evaporation.

4. The method for preventing scratches during the production of electrodes on different surfaces of a GaAs-based LED die according to claim 1, wherein: In step (1), the P-side metal electrode is a metal electrode structure made with Cr, Ni, Ge, Ti, Pt or Au metal as the bottom layer and transition layer, and metal Al, Au, etc. as the top main electrode.

5. The method for preventing scratches during the manufacturing process of electrodes on different surfaces of GaAs-based LED dies according to claim 1, characterized in that: In step (1), the P-side metal electrode is corroded by a stripping method or by photoresist protection to obtain a patterned P-side metal electrode.

6. The method for preventing scratches during the manufacturing process of electrodes on different surfaces of GaAs-based LED dies according to claim 1, characterized in that: In step (3), the N-side metal electrode covers the entire back side of the wafer, and the N-side electrode is an electrode structure made of Ni, Ge, Au or Pt metal.

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