Manufacturing method of LED mounting substrate, cleaning liquid and cleaning method

Abstract

The present invention is a method for manufacturing an LED mounting substrate, comprising a step for cleaning an LED chip, which is transferred from a sapphire substrate to a receptor substrate by laser lift-off, with an alkaline cleaning solution. As a result, provided is a method for manufacturing an LED mounting substrate, whereby it is possible to selectively remove metal Ga adhering to an LED chip transferred from a sapphire substrate to a receptor substrate by laser lift-off without dissolving or modifying other metals, thereby manufacturing the LED mounting substrate. A cleaning liquid that can be used therein; according to the cleaning method, gallium attached to the LED chip is selectively removed under the condition that other metal is not dissolved or modified. And a cleaning method for selectively removing gallium from a component having gallium and a metal other than gallium on the surface without dissolving or modifying the metal other than gallium.

Description

Technical Field

[0001] The invention relates to a manufacturing method, a cleaning liquid and a cleaning method of an LED mounting substrate. Background Art

[0002] In recent years, optical elements using nitride semiconductors have been used as backlights of liquid crystal displays or signage displays.

[0003] Optical elements are mass-produced on sapphire substrates, for example, through semiconductor processes. When a 4-inch display substrate is produced using LEDs called micro-light emitting diodes (LEDs) that are 100 μm square or less, millions of micro-LEDs are required. Micro-LEDs, which are tiny elements of tens of μm, are separated from the sapphire substrate used as a substrate for epitaxial growth and used.

[0004] In the manufacturing process of micro LED display, laser lift-off (LLO) is performed to peel the micro LED chip from the sapphire substrate. The LLO process is, for example, the following process: irradiating the GaN layer of the LED chip with an excimer laser to decompose the GaN layer into gaseous N 2 The LED chip is separated from the sapphire substrate by adding metal Ga. Thus, a receptor substrate having a plurality of optical elements arranged on the surface can be obtained.

[0005] This method is not limited to those related to optical devices, but can also be applied to the manufacture of a receptor substrate on which a plurality of transfer objects such as fine semiconductor devices are arranged.

[0006] For example, Patent Document 1 proposes a method of transferring a transfer object on a donor substrate to an acceptor substrate with high accuracy using laser irradiation.

[0007] Prior art literature

[0008] Patent Literature

[0009] Patent Document 1: Japanese Patent Application Publication No. 2020-4478 Summary of the invention

[0010] Problems to be solved by the invention

[0011] During the LLO process, opaque metal Ga will precipitate on the surface of the peeled micro LED chip. The metal Ga precipitated on the LED chip is removed by an acidic cleaning solution, and the cleaned LED chip is installed on the substrate, resulting in poor connection. The inventors and others studied various possibilities for the cause of the poor connection and found that the shape of the bump before connection also changed compared to the original shape. It was also found that the reason for the change was that the bump was dissolved and modified by the acidic cleaning solution in the cleaning process.

[0012] Here, when the LED chip is subjected to LLO from the sapphire substrate to the acceptor substrate, although the surface provided with the bumps is attached to the acceptor substrate to protect it from the influence of the cleaning liquid, it is still dissolved and modified during the cleaning process. That is, it is believed that there is a gap formed by the step difference of the bumps between the LED chip and the acceptor substrate, and the cleaning liquid invades from the gap and dissolves and modifies the bumps.

[0013] like Figure 5 As shown in FIG. 1 , most metals used in the bumps (In or SnAgCu alloy (SAC)) are close to Ga (gallium) in the periodic table, and it is considered difficult to selectively remove gallium when the bumps and gallium are in contact with the cleaning solution. Therefore, the inventors first studied how to protect the bumps from the cleaning solution by deeply burying the bumps in the adhesive layer of the acceptor substrate. However, it is known that in the method, although the bumps can be protected from the cleaning solution, it becomes difficult to peel the adhesive layer from the bumps in the subsequent process.

[0014] Here, the so-called close to gallium in the periodic table refers to a position close to the position of gallium in the periodic table, i.e., the fourth period and the thirteenth group. For example, it can be a position in the range of the third period to the sixth period and the eleventh group to the fifteenth group, or it can be a position in the range of the third period to the fifth period and the eleventh group to the fourteenth group.

[0015] As can be seen from the above, there is a need for a cleaning method or a cleaning liquid that can selectively remove metal Ga from a component such as an LED chip having metal Ga and metal other than metal Ga on the surface without affecting the metal other than metal Ga.

[0016] The present invention is made to solve the above-mentioned problems, and its purpose is to provide a method for manufacturing an LED mounting substrate that can selectively remove metal Ga (hereinafter sometimes referred to as "Ga", "gallium", etc.) attached to an LED chip transferred from a sapphire substrate to a receptor substrate by laser stripping without dissolving or modifying other metals to manufacture the LED mounting substrate; a cleaning liquid that can be used therefor; a cleaning method that selectively removes gallium attached to the LED chip without dissolving or modifying other metals; and a cleaning method that selectively removes gallium from a part having gallium and a metal other than gallium on its surface without dissolving or modifying a metal other than gallium.

[0017] Technical means of solving problems

[0018] The present invention is made to achieve the above-mentioned purpose and provides a method for manufacturing an LED mounting substrate, which has a step of using an alkaline cleaning solution to clean the LED chip transferred from a sapphire substrate to a receptor substrate by laser stripping.

[0019] According to this method for manufacturing an LED mounting substrate, unnecessary gallium can be removed without dissolving or modifying metals such as bumps of an LED chip, thereby manufacturing a high-quality LED mounting substrate.

[0020] At this time, gallium is present on the surface of the LED chip transferred onto the acceptor substrate, which is opposite to the acceptor substrate. The gallium can be removed by the cleaning step.

[0021] The step of performing cleaning in the method for manufacturing an LED mounting substrate of the present invention is particularly effective in removing gallium from such an LED chip.

[0022] At this time, the alkali concentration of the alkaline cleaning solution can be set to 0.5 mass % or more and below the saturation concentration. In addition, the temperature of the alkaline cleaning solution can be set to 5° C. or more and 80° C. or less. In addition, the cleaning time using the alkaline cleaning solution can be set to 10 seconds or more and 1 hour or less.

[0023] Under such conditions, gallium can be removed more stably, reliably and selectively.

[0024] In this case, a bump may be provided on the surface of the LED chip on the side in contact with the acceptor substrate.

[0025] The method for manufacturing an LED mounting substrate of the present invention is particularly effective when manufacturing an LED mounting substrate having bumps using such an LED chip.

[0026] In this case, the bump may be formed of lead-free solder. In addition, the bump may have at least one selected from SnAgCu alloy, SnZnBi alloy, SnCu alloy, SnAgInBi alloy, SnZnAl alloy and indium as a main component.

[0027] The method for manufacturing an LED mounting substrate of the present invention is particularly effective when targeting an LED chip having such bumps.

[0028] At this time, the LED chip transferred onto the acceptor substrate may be cleaned by immersing the acceptor substrate together with the LED chip in the alkaline cleaning solution.

[0029] This makes it possible to more easily manufacture the LED mounting substrate.

[0030] In addition, the present invention provides a cleaning liquid for cleaning an LED chip disposed on a sapphire substrate after the LED chip is transferred to a receptor substrate by laser lift-off, wherein the cleaning liquid is alkaline.

[0031] This cleaning solution can selectively remove unnecessary gallium without dissolving or modifying metals such as the bumps of the LED chip.

[0032] At this time, the pH of the cleaning solution may be set to 9.5 to 14.0. In addition, the cleaning solution may contain at least one aqueous solution selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide, magnesium hydroxide, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, sodium carbonate, sodium bicarbonate, and potassium acetate.

[0033] This makes it possible to perform cleaning more easily and more stably.

[0034] In addition, the present invention provides a cleaning method for cleaning an LED chip separated from a sapphire substrate by laser lift-off, wherein the cleaning method uses an alkaline cleaning solution for cleaning.

[0035] By using this cleaning method for cleaning LED chips, unnecessary gallium can be selectively removed without dissolving or modifying metals such as bumps of the LED chip.

[0036] At this time, the LED chip may be transferred onto a receptor substrate.

[0037] The cleaning method of the present invention is particularly effective when cleaning such LED chips.

[0038] In addition, the present invention provides a cleaning method for selectively removing gallium from a part having gallium and a metal other than gallium on its surface, wherein the cleaning method uses an alkaline cleaning solution to clean the part.

[0039] According to this cleaning method for selectively removing gallium, gallium can be selectively removed in a simple manner without dissolving or modifying metals other than gallium.

[0040] In this case, during the cleaning, the alkaline cleaning solution may be brought into contact with the gallium and the metal other than gallium.

[0041] This makes it possible to selectively remove gallium in a simpler manner without dissolving or modifying metals other than gallium.

[0042] At this time, it can be set as follows: the part is in a substrate shape and is fixed to another substrate during the cleaning, the gallium exists on the surface of the part opposite to the other substrate side, and the metal other than gallium exists on the other substrate side of the part.

[0043] The cleaning method of the present invention is particularly effective when cleaning such parts.

[0044] In this case, the metal other than gallium may include at least one metal selected from the group consisting of aluminum, copper, zinc, silver, indium, tin, and bismuth. In addition, the metal other than gallium may include at least one metal selected from the group consisting of copper, silver, indium, and tin. In addition, the metal other than gallium may include copper, silver, and tin.

[0045] If it is a metal other than gallium, it is more stable and will not dissolve or change.

[0046] Effects of the Invention

[0047] As described above, the method for manufacturing an LED mounting substrate of the present invention can selectively remove unnecessary gallium without dissolving or modifying metals such as bumps of LED chips to manufacture a high-quality LED mounting substrate, thereby reducing poor connection of LED chips.

[0048] Furthermore, the cleaning liquid of the present invention can selectively remove unnecessary gallium without dissolving or modifying metals such as bumps of LED chips, thereby reducing poor connection of LED chips.

[0049] In addition, according to the cleaning method of the present invention for cleaning the LED chip separated from the sapphire substrate by laser lift-off, unnecessary gallium can be selectively removed without dissolving or modifying metals such as bumps of the LED chip, thereby reducing poor connection of the LED chip.

[0050] In addition, the cleaning method for selectively removing gallium of the present invention can selectively remove unnecessary gallium from a part having gallium and a metal other than gallium on its surface without dissolving or modifying the metal other than gallium by a simple method.

[0051] In addition, in the present invention, it is preferred that the metal such as the bump or the metal other than gallium does not dissolve at all. However, if the amount of gallium removed is greater than the amount of metal such as the bump or the metal other than gallium removed and gallium can be selectively removed, the metal such as the bump or the metal other than gallium may also dissolve within a practical range. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] [ Figure 1 ] is a diagram illustrating an example of the cleaning process of the present invention.

[0053] [ Figure 2 ] represents the conditions and evaluation results of Examples 1 to 3, Comparative Example 1, and Comparative Example 2.

[0054] [ Figure 3 ] represents the evaluation results of Example 4.

[0055] [ Figure 4 ] shows the evaluation results of Comparative Example 3.

[0056] [ Figure 5 ] is a diagram (periodic table) used to explain examples of metal elements that are to be removed / not to be removed during cleaning.

[0057] [ Figure 6 ] is a schematic diagram illustrating gap-laser lift-off (Gap-LLO).

[0058] [ Figure 7 ] is a schematic diagram illustrating contact-laser lift-off (Contact-LLO). DETAILED DESCRIPTION

[0059] Hereinafter, the present invention will be described in detail, but the present invention is not limited thereto.

[0060] As described above, a method for manufacturing an LED mounting substrate is required, which can selectively remove the metal Ga attached to the LED chip transferred from the sapphire substrate to the acceptor substrate by laser stripping without dissolving or modifying other metals; a cleaning liquid that can be used therefor; and a cleaning method that selectively removes the gallium attached to the LED chip without dissolving or modifying other metals; and a cleaning method that selectively removes gallium from a part having gallium and a metal other than gallium on the surface without dissolving or modifying the metal other than gallium.

[0061] The inventors of the present invention have repeatedly conducted diligent research on the above-mentioned subject and have found that, by using an alkaline cleaning solution to clean the LED chip that has been transferred from the sapphire substrate to the acceptor substrate by laser stripping, it is possible to selectively remove unnecessary gallium without dissolving or modifying the metal such as the bumps of the LED chip to manufacture a high-quality LED mounting substrate, thereby reducing poor connection of the LED chip, thereby completing the present invention.

[0062] In addition, the inventors of the present invention have discovered that by using an alkaline cleaning solution to clean the LED chips disposed on a sapphire substrate after they are transferred to a receptor substrate by laser stripping, it is possible to selectively remove unnecessary gallium without dissolving or modifying metals such as the bumps of the LED chip, thereby reducing poor connection of the LED chip, thereby completing the present invention.

[0063] In addition, the inventors of the present invention discovered that by using a cleaning method for cleaning LED chips separated from a sapphire substrate by laser stripping and using an alkaline cleaning solution, it is possible to selectively remove unnecessary gallium without dissolving or modifying metals such as the bumps of the LED chip, thereby completing the present invention.

[0064] In addition, the inventors of the present invention have discovered that a cleaning method that selectively removes gallium from parts having gallium and metals other than gallium on their surfaces and cleans the parts using an alkaline cleaning solution can selectively remove unnecessary gallium in a simple manner without dissolving or modifying metals other than gallium, thereby completing the present invention.

[0065] Hereinafter, description will be given with reference to the drawings.

[0066] As described above, the inventors and others have made great efforts to solve the above-mentioned problems, and surprisingly found that by using an alkaline aqueous solution as a cleaning liquid, gallium can be selectively removed without affecting metals other than gallium, even if the bumps are not physically protected. The fact that gallium can be selectively removed by using an alkaline aqueous solution as a cleaning liquid in this way can help simplify the production process or improve the yield, which is a very big step towards reducing the cost of a micro-LED display of tens of millions of yen. The present invention is described in more detail below.

[0067] [Cleaning fluid]

[0068] The cleaning liquid of the present invention is an alkaline cleaning liquid used for cleaning the LED chip disposed on the sapphire substrate after being transferred to the acceptor substrate by laser stripping. The cleaning liquid of the present invention can selectively remove unnecessary gallium without dissolving or modifying the metal such as the bump of the LED chip, thereby reducing poor connection of the LED chip.

[0069] The cleaning liquid is not particularly limited as long as it is alkaline, but preferably has a pH of 9.5 to 14.0. Ga can be removed stably, reliably, and selectively without dissolving or modifying metals such as bumps of the LED chip.

[0070] In addition, the cleaning solution of the present invention can be an aqueous solution containing at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide, magnesium hydroxide, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, sodium carbonate, sodium bicarbonate and potassium acetate. Such an aqueous solution is relatively easy to obtain or process and has low cost.

[0071] Preferred conditions and the like when cleaning using the cleaning solution of the present invention will be described later.

[0072] [Method for manufacturing LED mounting substrate]

[0073] The method for manufacturing an LED mounting substrate of the present invention includes a step of cleaning the LED chip transferred from the sapphire substrate to the acceptor substrate by laser lift-off using an alkaline cleaning solution. The laser lift-off method is not particularly limited, and gap-laser lift-off (Gap-LLO), contact-laser lift-off (Contact-LLO), etc. can be applied. Figure 6 and Figure 7 These methods are briefly described.

[0074] In gap-laser lift-off, first, as Figure 6 As shown in (a) in the figure, a sapphire substrate 1 including, for example, an LED chip 5 as a transfer object and a receptor substrate 2 such as a quartz substrate including an adhesive layer 3 such as silicone on the surface are placed facing each other with a space, that is, a gap, between the LED chip 5 and the adhesive layer 3. In the above state, a laser oscillator 110 irradiates the interface 11 between the plurality of LED chips 5 and the sapphire substrate 1 through the surface of the sapphire substrate 1 opposite to the LED chip 5. Generally, the entire surface of the interface 11 between each LED chip 5 and the sapphire substrate 1 is irradiated with the laser 20 one by one in sequence.

[0075] For example, in the case of a sapphire substrate 1 including a plurality of LED chips 5 including a gallium nitride semiconductor layer such as a GaN layer at the interface 11, the GaN layer is decomposed (ablated) by irradiation with the laser 20. When the bonding force (adhesion force, joining force, etc.) between the LED chip 5 and the sapphire substrate 1 is weakened due to the ablation, the LED chip 5 is peeled off from the sapphire substrate 1. In addition, gas (such as nitrogen) is generated by the decomposition of the GaN layer. Due to the pressure of the gas, the peeled LED chip 5 obtains a propulsion force toward the acceptor substrate 2, moves in the space between the sapphire substrate 1 and the acceptor substrate 2, and reaches the adhesive layer 3 on the acceptor substrate 2. In this way, the LED chip 5 is transferred to the acceptor substrate 2. Then, as Figure 6 As shown in (b) in FIG. 1 , the sapphire substrate 1 is removed. Thus, the transfer of the LED chip 5 from the sapphire substrate 1 to the acceptor substrate 2 is completed.

[0076] Regarding contact laser lift-off, when the laser 20 is irradiated, Figure 7 As shown in (a) of FIG. 1 , a sapphire substrate 1 including an LED chip 5 as a transfer object and a receptor substrate 2 including an adhesive layer 3 on the surface are placed facing each other in a state where the LED chip 5 and the adhesive layer 3 are in contact with each other. The same as the gap-laser lift-off is performed except that. After irradiation with the laser 20, as shown in FIG. Figure 7 As shown in (b) , the sapphire substrate 1 is removed, thereby completing the transfer of the LED chip 5 from the sapphire substrate 1 to the acceptor substrate 2 .

[0077] In this LLO process, due to the decomposition of the GaN layer and other gallium nitride semiconductor layers, metal Ga will remain on the parts such as the LED chip 5. In order to remove the metal Ga, the LED chip 5 is cleaned using an alkaline cleaning solution in the present invention. In this way, unnecessary gallium can be selectively removed without dissolving or modifying the metal such as the bump of the LED chip, and as a result, poor connection of the LED chip can be reduced.

[0078] As the alkaline cleaning solution used here, the above-mentioned alkaline cleaning solutions can be used.

[0079] The alkali concentration of the alkaline cleaning solution is preferably set to be greater than 0.5 mass % and less than the saturation concentration. In addition, the temperature of the alkaline cleaning solution is preferably set to be greater than 5°C and less than 80°C. The temperature of the cleaning solution is preferably set to a temperature that will not freeze, that is, greater than 5°C. In addition, even if the temperature is too high, the gallium removal effect no longer changes, so it can be less than 80°C. Furthermore, the time for cleaning with an alkaline cleaning solution is preferably set to be greater than 10 seconds and less than 1 hour. By setting the cleaning time to more than 10 seconds, Ga can be removed more stably, reliably and selectively. Even if the cleaning time is too long, the gallium removal effect no longer changes, so it can be less than 1 hour. In addition, by appropriately combining the alkali concentration, the temperature of the alkaline cleaning solution, and the time for cleaning, gallium can be further stably, reliably and selectively removed.

[0080] The LED chip transferred onto the acceptor substrate as described above has gallium on the surface opposite to the acceptor substrate. In addition, the LED chip has a bump on the side in contact with the acceptor substrate. Gallium on the surface opposite to the acceptor substrate can be easily removed by cleaning with an alkaline cleaning solution.

[0081] In the method for manufacturing an LED mounting substrate of the present invention, the bump is preferably formed of a lead-free solder, and more preferably has at least one selected from SnAgCu (SAC) alloy, SnZnBi alloy, SnCu alloy, SnAgInBi alloy, SnZnAl alloy and indium as a main component. In particular, when such a bump is used, even when cleaning is performed using an alkaline cleaning solution, dissolution or modification (damage) of the bump can be stably and reliably prevented.

[0082] Figure 1 An example of a process for cleaning an LED chip using an alkaline cleaning solution is shown in FIG. Figure 1 As shown, in the step of cleaning the LED chip with an alkaline cleaning solution in the method for manufacturing an LED mounting substrate of the present invention, it is preferred to clean the LED chip 5 transferred to the acceptor substrate 2 together with the acceptor substrate 2 by immersing the LED chip 5 in an alkaline cleaning solution 6. Gallium 4 can be removed more simply, reliably, stably and selectively. More specifically, as Figure 1 As shown, the acceptor substrate 2 with the LED chip 5 transferred thereon may be immersed in a cleaning container filled with an alkaline cleaning solution 6, and then cleaned a suitable number of times with pure water or the like, and then dried (air-dried).

[0083] [LED chip cleaning method]

[0084] In addition, the present invention provides a cleaning method for cleaning an LED chip separated from a sapphire substrate by laser stripping as described above, using an alkaline cleaning solution. With this cleaning method, only gallium can be selectively removed by cleaning without dissolving or modifying metals other than gallium, and as a result, poor connection of the LED chip can be reduced. In addition, in this cleaning method of the present invention, the LED chip is preferably transferred to a receptor substrate. A specific example of the cleaning method of the LED chip is similar to the above-mentioned method of using Figure 1 The method described is the same.

[0085] [Cleaning method for selectively removing gallium from parts]

[0086] The inventors and others have found that by cleaning the LED chip separated from the sapphire substrate by laser lift-off using an alkaline cleaning solution as described above, only gallium can be selectively removed without dissolving or modifying metals other than gallium. Furthermore, further repeated studies have been conducted, and as a result, it has been found that, not only in the case of selectively removing gallium from parts having gallium and metals other than gallium on the surface, it is also possible to selectively remove gallium without dissolving or modifying metals other than gallium by using an extremely simple method of cleaning the parts using an alkaline cleaning solution, not only in the case of LED chips, but also in the case of selectively removing gallium from parts having gallium and metals other than gallium on the surface.

[0087] In such a cleaning method, it is particularly preferred to clean by bringing gallium and a metal other than gallium into contact with an alkaline cleaning solution. Gallium can be selectively removed in a simpler method without dissolving or modifying metals other than gallium.

[0088] In addition, the part to be cleaned is preferably in the form of a substrate and fixed to another substrate during cleaning. Gallium is preferably present on the surface of the part opposite to the other substrate side, and metals other than gallium are present on the other substrate side of the part.

[0089] As the metal other than gallium, it is preferred to have at least one metal selected from the group consisting of aluminum, copper, zinc, silver, indium, tin and bismuth, more preferably at least one metal selected from the group consisting of copper, silver, indium and tin, and even more preferably copper, silver and tin. The reason for this is that if the metal other than gallium is such a metal, dissolution or modification during cleaning can be more stably suppressed.

[0090] In addition, in the present invention, gallium as the object to be removed may exist in a state of 100% purity, or in a state of oxide or nitride, etc. In addition, these states may also exist in a mixed state. It is effective when the proportion of gallium in the object to be removed is 50% by volume or more, preferably 70% by volume or more, and more preferably 90% by volume or more.

[0091] In addition, in the present invention, it is effective that the ratio of the dissolution rate of gallium to the dissolution rate of other metals, that is, the selectivity is large. The selectivity may be greater than 1, greater than 5, or greater than 10. From the perspective of the working environment or workability, the upper limit of the selectivity may be about 100, about 50, or about 20.

[0092] Here, the dissolution rate (μm / minute) can be measured by, for example, the methods shown in the following (A) to (G).

[0093] (A) Prepare 1 liter of an alkaline cleaning liquid for cleaning, for example, a 5 mass % potassium hydroxide (KOH) aqueous solution.

[0094] (B) A gallium substrate and a metal substrate other than gallium were prepared in the form of a plate with a length of 1 cm, a width of 1 cm, and a thickness of 1 mm, and their masses W0 were measured. If a natural oxide film or the like existed on the surface of the substrate, it was removed in advance.

[0095] (C) The alkaline aqueous solution is divided into two containers, each containing 500 ml, and the gallium substrate and the metal substrate other than gallium are immersed in the alkaline aqueous solution adjusted to 25° C. for 3 minutes under predetermined cleaning conditions. The posture of each substrate in each container is adjusted during the immersion process to avoid the two substrates being extremely different and affecting the dissolution amount. In addition, when the substrate is completely dissolved, the thickness of the substrate to be prepared in (B) is thickened.

[0096] (D) Each substrate is taken out from the alkaline aqueous solution and cleaned at room temperature.

[0097] (E) The mass W1 of each substrate after cleaning is measured.

[0098] (F) The dissolution rate (μm / minute) is calculated based on the difference between the mass W0 and the mass W1 and the specific gravity of each substrate. At this time, the calculation is performed assuming that dissolution occurs only in the thickness direction of the substrate.

[0099] (G) The selectivity ratio is calculated according to the following formula based on the obtained dissolution rate value.

[0100] Selectivity = gallium dissolution rate (μm / min) / other metal dissolution rate (μm / min)

[0101] In addition, when the contact area between the metal other than gallium and the cleaning liquid is sufficiently smaller than the contact area between gallium and the cleaning liquid, the selection ratio may be less than 1.

[0102] The above description is about the cleaning method of an object containing gallium and metals other than gallium, but as long as the technical concept of the present invention is used, it can also be applied to the cleaning method of an object containing a combination of metals other than gallium. For example, it is a cleaning method of an object containing a combination of a specific metal and a metal close to the metal in the periodic table (for example, a metal in the range of period ±2 and group ±2 of the specific metal).

[0103] Example

[0104] Hereinafter, the present invention will be specifically described with reference to Examples, but the present invention is not limited thereto.

[0105] LED chips with bumps formed on one surface were prepared and transferred to an acceptor substrate by laser lift-off, and then cleaned. LED chips using indium (In) bumps and SAC bumps were prepared.

[0106] (Evaluation before cleaning)

[0107] First, the LED chip was observed using an optical microscope before cleaning, and it was confirmed that gallium was attached to the surface of the LED chip opposite to the surface where the bumps were formed. In addition, the presence or absence of gallium adhesion after cleaning and whether the bumps were dissolved due to cleaning can be distinguished by the difference in color. Figure 2 The observation results are shown in the "Before Cleaning Photo".

[0108] (Example 1)

[0109] The cleaning was performed using a 5 mass % potassium hydroxide (KOH) aqueous solution as an alkaline cleaning solution. The LED chip was immersed in the cleaning solution together with the receptor substrate on which the LED chip was transferred, and the cleaning time was set to 3 minutes and the cleaning temperature was set to 25°C (room temperature). The LED chip was observed using an optical microscope in the same manner as the evaluation before cleaning, and the presence or absence of gallium adhesion and the dissolution of the bumps were evaluated.

[0110] (Example 2)

[0111] Cleaning and evaluation were performed in the same manner as in Example 1, except that a 2.34 mass % tetramethylammonium hydroxide (TMAH) aqueous solution was used as the cleaning liquid, which is an alkaline cleaning liquid.

[0112] (Example 3)

[0113] In addition to using 10 mass % sodium carbonate (Na 2 CO 3 ) aqueous solution as the cleaning solution, cleaning and evaluation were carried out in the same manner as in Example 1.

[0114] (Comparative Example 1)

[0115] Cleaning and evaluation were performed in the same manner as in Example 1 except that a 12.3 mass % HCl aqueous solution (hydrochloric acid) was used as the cleaning liquid.

[0116] (Comparative Example 2)

[0117] In addition to using 6 mass% H 2 SO 4 Cleaning and evaluation were carried out in the same manner as in Example 1 except that an aqueous solution (sulfuric acid) was used as the cleaning liquid.

[0118] exist Figure 2 The evaluation results are shown in . In Examples 1 to 3, it was confirmed that the metal Ga attached to the LED chip was removed regardless of the type of cleaning solution. On the other hand, neither the In bump nor the SAC bump was dissolved by cleaning. It can be seen that as long as an alkaline cleaning solution is used for cleaning, only the metal Ga can be selectively dissolved and removed. On the other hand, in Comparative Examples 1 and 2, which were cleaned with an acidic cleaning solution, it was confirmed that the In bump was dissolved. However, the dissolution of the SAC bump was not confirmed.

[0119] (Example 4)

[0120] After being immersed in the same alkaline cleaning solution (5 mass % potassium hydroxide (KOH) aqueous solution) as in Example 1, an isopropanol (IPA) solution of abietic acid as a component of flux was applied to the SAC bumps, which were dried at 40° C. and then heated to 250° C. on a hot plate. Figure 3 The evaluation results obtained using an optical microscope are shown in FIG. Figure 3 As shown, after heating at 250°C, the color of the bump changes, indicating that the SAC bump is dissolved. The flux is used to improve the solubility or wettability of the solder and ensure electrical connection by reducing the oxide film on the surface of the bump. Therefore, the melting of the SAC bump after the treatment as in Example 4 means that the SAC bump is not modified due to the cleaning treatment of Example 4. In addition, the composition of the SAC bump used is Sn = 96.5 mass%, Ag = 3.0 mass%, and Cu = 0.5 mass%.

[0121] (Comparative Example 3)

[0122] After being immersed in the same acid cleaning solution as in Comparative Example 1 (12.3 mass % HCl aqueous solution (hydrochloric acid)), an IPA solution of rosinic acid as a flux component was applied to the SAC bumps, and dried at 40° C. Thereafter, the bumps were heated to 250° C. on a hot plate. Figure 4 The evaluation results obtained using an optical microscope are shown in FIG. Figure 4 As shown in the figure, the color of the bumps did not change before and after heating at 250°C, indicating that the SAC bumps did not dissolve. It is believed that the reason is that the alloy composition of Sn / Ag / Cu changes due to cleaning with an acidic cleaning solution, the melting point rises, and it is believed that the state of the bumps used in normal use has been modified. In other words, it can be seen that although the SAC bumps themselves will not be dissolved by the acidic cleaning solution, the composition will be modified, so the electrical characteristics of the LED chip will change. This suggests the occurrence of poor connection.

[0123] As described above, it is understood that according to the embodiments of the present invention, only gallium can be removed by cleaning without dissolving or modifying metals other than gallium.

[0124] This specification includes the following aspects.

[0125] [1]: A method for manufacturing an LED mounting substrate, comprising the step of cleaning an LED chip transferred from a sapphire substrate to an acceptor substrate by laser lift-off using an alkaline cleaning solution.

[0126] [2]: The method for manufacturing an LED mounting substrate according to [1], wherein the surface of the LED chip transferred onto the acceptor substrate that is opposite to the acceptor substrate has gallium, and the gallium is removed by the cleaning step.

[0127] [3]: The method for manufacturing an LED mounting substrate according to [1] or [2], wherein the alkali concentration of the alkaline cleaning solution is set to be greater than or equal to 0.5 mass % and less than or equal to a saturation concentration.

[0128] [4]: The method for manufacturing an LED mounting substrate according to [1], [2] or [3], wherein the temperature of the alkaline cleaning solution is set to 5° C. or higher and 80° C. or lower.

[0129] [5]: The method for manufacturing an LED mounting substrate according to [1], [2], [3] or [4], wherein the cleaning time using the alkaline cleaning solution is set to be greater than 10 seconds and less than 1 hour.

[0130] [6]: A method for manufacturing an LED mounting substrate according to [1], [2], [3], [4] or [5], wherein a bump is provided on the surface of the LED chip on the side in contact with the receptor substrate.

[0131] [7]: The method for manufacturing an LED mounting substrate according to [6], wherein the bump is formed of lead-free solder.

[0132] [8]: A method for manufacturing an LED mounting substrate according to [6] or [7], wherein the bump has at least one selected from SnAgCu alloy, SnZnBi alloy, SnCu alloy, SnAgInBi alloy, SnZnAl alloy and indium as a main component.

[0133] [9]: A method for manufacturing an LED mounting substrate according to [1], [2], [3], [4], [5], [6], [7] or [8], wherein the LED chip transferred to the acceptor substrate is cleaned by immersing the acceptor substrate together with the acceptor substrate in the alkaline cleaning solution.

[0134]

[10] : A cleaning liquid used to clean an LED chip disposed on a sapphire substrate after the LED chip is transferred to a receptor substrate by laser lift-off, wherein the cleaning liquid is alkaline.

[0135]

[11] : The cleaning solution according to

[10] , wherein the pH of the cleaning solution is 9.5 to 14.0.

[0136]

[12] : The cleaning solution according to

[10] or

[11] , wherein the cleaning solution is an aqueous solution containing at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide, magnesium hydroxide, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, sodium carbonate, sodium bicarbonate and potassium acetate.

[0137]

[13] : A cleaning method for cleaning an LED chip separated from a sapphire substrate by laser lift-off, the cleaning method using an alkaline cleaning solution for cleaning.

[0138]

[14] : According to the cleaning method of

[13] , the LED chip is transferred to a receptor substrate.

[0139]

[15] : A cleaning method for selectively removing gallium from a part having gallium and a metal other than gallium on its surface, wherein the part is cleaned using an alkaline cleaning solution.

[0140]

[16] : The cleaning method according to

[15] , wherein the alkaline cleaning solution is brought into contact with the gallium and the metal other than gallium during the cleaning.

[0141]

[17] : A cleaning method according to

[15] or

[16] , wherein the part is in the form of a substrate and is fixed to another substrate during cleaning, the gallium is present on a surface of the part opposite to the other substrate side, and the metal other than gallium is present on the other substrate side of the part.

[0142]

[18] : The cleaning method according to

[15] ,

[16] or

[17] , wherein the metal other than gallium is at least one metal selected from the group consisting of aluminum, copper, zinc, silver, indium, tin and bismuth.

[0143]

[19] : The cleaning method according to

[15] ,

[16] ,

[17] or

[18] , wherein the metal other than gallium is at least one metal selected from the group consisting of copper, silver, indium and tin.

[0144]

[20] : The cleaning method according to

[15] ,

[16] ,

[17] ,

[18] or

[19] , wherein the metal other than gallium includes copper, silver and tin.

[0145] The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and any device having substantially the same structure as the technical concept described in the claims of the present invention and exhibiting the same function and effect is within the technical scope of the present invention.

Claims

1. A method for manufacturing a light emitting diode mounting substrate, comprising the step of cleaning a light emitting diode chip transferred from a sapphire substrate to an acceptor substrate by laser lift-off using an alkaline cleaning solution.

2. The method for manufacturing a light emitting diode mounting substrate according to claim 1, wherein: The light emitting diode chip transferred onto the acceptor substrate has gallium on its surface opposite to the acceptor substrate, and the gallium is removed by the cleaning step.

3. The method for manufacturing a light emitting diode mounting substrate according to claim 1, wherein: The alkali concentration of the alkaline cleaning solution is set to 0.5 mass % or more and not more than the saturation concentration.

4. The method for manufacturing a light emitting diode mounting substrate according to claim 1, wherein: The temperature of the alkaline cleaning solution is set to 5° C. or higher and 80° C. or lower.

5. The method for manufacturing a light emitting diode mounting substrate according to claim 1, wherein: The cleaning time using the alkaline cleaning solution is set to 10 seconds to 1 hour.

6. The method for manufacturing a light emitting diode mounting substrate according to claim 1, wherein: The surface of the light emitting diode chip on the side in contact with the acceptor substrate has bumps.

7. The method for manufacturing a light emitting diode mounting substrate according to claim 6, wherein: The bumps are formed of lead-free solder.

8. The method for manufacturing a light emitting diode mounting substrate according to claim 6, wherein: The bump includes at least one selected from SnAgCu alloy, SnZnBi alloy, SnCu alloy, SnAgInBi alloy, SnZnAl alloy and indium as a main component.

9. The method for manufacturing a light emitting diode mounting substrate according to any one of claims 1 to 8, wherein: The light emitting diode chip transferred onto the acceptor substrate is cleaned by immersing the acceptor substrate together with the acceptor substrate in the alkaline cleaning solution.

10. A cleaning liquid for cleaning a light emitting diode chip disposed on a sapphire substrate after being transferred to a receptor substrate by laser lift-off, wherein the cleaning liquid is alkaline.

11. The cleaning solution according to claim 10, wherein The pH of the cleaning solution is 9.5-14.

0.

12. The cleaning solution according to claim 10 or 11, wherein The cleaning solution is an aqueous solution containing at least one selected from the group consisting of sodium hydroxide, potassium hydroxide, ammonium hydroxide, magnesium hydroxide, tetramethylammonium hydroxide, tetrabutylammonium hydroxide, sodium carbonate, sodium bicarbonate and potassium acetate.

13. A cleaning method for cleaning a light emitting diode chip separated from a sapphire substrate by laser lift-off, the cleaning method using an alkaline cleaning solution for cleaning.

14. The cleaning method according to claim 13, wherein: The light emitting diode chip is transferred to a receptor substrate.

15. A cleaning method for selectively removing gallium from a part having gallium and a metal other than gallium on its surface, wherein the cleaning method uses an alkaline cleaning solution to clean the part.

16. The cleaning method according to claim 15, wherein: During the cleaning, the alkaline cleaning solution is brought into contact with the gallium and the metal other than gallium.

17. The cleaning method according to claim 15, wherein: The part is in the form of a substrate and is fixed to another substrate during the cleaning. The gallium is present on a surface of the component that is opposite to the other substrate side, The metal other than gallium exists on the other substrate side in the component.

18. The cleaning method according to claim 15, wherein: The metal other than gallium includes at least one metal selected from the group consisting of aluminum, copper, zinc, silver, indium, tin, and bismuth.

19. The cleaning method according to claim 15, wherein: The metal other than gallium includes at least one metal selected from the group consisting of copper, silver, indium, and tin.

20. The cleaning method according to any one of claims 15 to 19, wherein: The metals other than gallium include copper, silver and tin.

Images