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JP-2026076179-A - Cleaning method

JP2026076179AJP 2026076179 AJP2026076179 AJP 2026076179AJP-2026076179-A

Abstract

[Problem] A cleaning method to prevent connection failures when mounting micro LED chips onto a substrate. [Solution] The present invention is a method for manufacturing an LED mounting substrate, comprising the step of cleaning an LED chip 5, which has been transferred from a sapphire substrate to a receptor substrate 2 by laser lift-off, with an alkaline cleaning solution 6. This provides a method for manufacturing an LED mounting substrate that can selectively remove the metal Ga adhering to the LED chip transferred from the sapphire substrate to the receptor substrate by laser lift-off without dissolving or altering other metals, a cleaning solution that can be used therefor, a cleaning method for selectively removing gallium 4 adhering to an LED chip without dissolving or altering other metals, and a cleaning method for selectively removing gallium from a component having gallium and other metals on its surface without dissolving or altering the other metals. [Selection Diagram] Figure 1

Inventors

  • 松本 展明
  • 北川 太一
  • 小川 敬典
  • 近藤 和紀

Assignees

  • 信越化学工業株式会社

Dates

Publication Date
20260511
Application Date
20251225
Priority Date
20220706

Claims (10)

  1. A cleaning method for selectively removing gallium from a part having gallium and a metal other than gallium on its surface, The metals other than gallium are metals in the period 3 to 5 and groups 11 to 14 of the periodic table. The aforementioned component is in the form of a substrate, and the cleaning is performed while it is fixed to another substrate. The gallium is present on the side of the component opposite to the other substrate side. The metals other than gallium are present on the other substrate side of the component. A cleaning method for the aforementioned parts, wherein an alkaline cleaning solution comes into contact with the gallium and other metals, and selectively removes the gallium.
  2. A cleaning method for selectively removing gallium from a part having gallium and a metal other than gallium on its surface, The metal other than gallium is at least one metal selected from the group consisting of aluminum, copper, zinc, silver, indium, tin, and bismuth. The aforementioned component is in the form of a substrate, and the cleaning is performed while it is fixed to another substrate. The gallium is present on the side of the component opposite to the other substrate side. The metals other than gallium are present on the other substrate side of the component. A cleaning method for the aforementioned parts, wherein an alkaline cleaning solution comes into contact with the gallium and other metals, and selectively removes the gallium.
  3. A cleaning method for selectively removing gallium from a part having gallium and bumps on its surface, The bump is formed with lead-free solder. The aforementioned component is in the form of a substrate, and the cleaning is performed while it is fixed to another substrate. The gallium is present on the side of the component opposite to the other substrate side. The bump is located on the other substrate side of the component, A cleaning method for the aforementioned parts, wherein an alkaline cleaning solution comes into contact with the gallium and the bumps, and selectively removes the gallium.
  4. The cleaning method according to claim 1 or 2, wherein the metal is at least one metal selected from the group consisting of copper, silver, indium, and tin.
  5. The cleaning method according to claim 1 or 2, wherein the metal is copper, silver, and tin.
  6. The cleaning method according to any one of claims 1 to 3, wherein the alkaline concentration of the alkaline cleaning solution is 0.5% by mass or more and less than or equal to the saturation concentration.
  7. The cleaning method according to any one of claims 1 to 3, wherein the temperature of the alkaline cleaning solution is 5°C or higher and 80°C or lower.
  8. The cleaning method according to any one of claims 1 to 3, wherein the cleaning time with the alkaline cleaning solution is 10 seconds or more and 1 hour or less.
  9. The cleaning method according to any one of claims 1 to 3, wherein the alkaline cleaning solution has a pH of 9.5 to 14.0.
  10. The cleaning method according to any one of claims 1 to 3, wherein the alkaline 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.

Description

This invention relates to a method for manufacturing an LED mounting substrate, a cleaning solution, and a cleaning method. In recent years, nitride semiconductor optical devices have come into use as backlights for liquid crystal displays and as displays for digital signage. Optical devices are fabricated in large quantities, for example, on sapphire substrates using semiconductor processes. To fabricate a 4-inch display substrate using micro-LEDs (LEDs smaller than 100 μm square), millions of micro-LEDs are required. These micro-LEDs, being tiny devices measuring tens of micrometers, are separated from the sapphire substrate used for epitaxial growth and then utilized. In the manufacturing process of micro-LED displays, laser lift-off (LLO) is performed to detach the micro-LED chip from the sapphire substrate. The LLO process involves, for example, irradiating the GaN layer of the LED chip with an excimer laser to decompose the GaN layer into gaseous N2 and metallic Ga, thereby detaching the LED chip from the sapphire substrate. This allows for the creation of a receptor substrate on which numerous optical devices are arranged on the surface. This method is not limited to optical devices; it can also be applied to the manufacturing of receptor substrates in which multiple transfer targets, such as miniature semiconductor devices, are arranged on a surface. For example, Patent Document 1 proposes a method for accurately transferring an object to be transferred from a donor substrate to a receptor substrate using laser irradiation. Japanese Patent Publication No. 2020-4478 This is a diagram illustrating an example of a cleaning process according to the present invention.The conditions and evaluation results for Examples 1-3 and Comparative Examples 1 and 2 are shown below.The evaluation results for Example 4 are shown below.The evaluation results for Comparative Example 3 are shown below.This is a diagram (periodic table) illustrating examples of metal elements that are removed or not removed by cleaning.This is a schematic diagram illustrating gap-laser lift-off (Gap-LLO).This is a schematic diagram illustrating Contact-Laser Lift-Off (LLO). The present invention will be described in detail below, but the present invention is not limited to these descriptions. As described above, there was a need for a method for manufacturing an LED mounting substrate that can selectively remove metallic Ga attached to an LED chip transferred from a sapphire substrate to a receptor substrate by laser lift-off, without dissolving or altering other metals; a cleaning solution that can be used in this method; a cleaning method that selectively removes gallium attached to an LED chip without dissolving or altering other metals; and a cleaning method that selectively removes gallium from a component having gallium and other metals on its surface without dissolving or altering the other metals. As a result of diligent research into the above-mentioned problems, the inventors of the present invention have discovered that a method for manufacturing an LED mounting substrate, which includes a step of cleaning the LED chips transferred from the sapphire substrate to the receptor substrate by laser lift-off with an alkaline cleaning solution, can selectively remove unwanted gallium without dissolving or altering metals such as bumps on the LED chips, thereby enabling the manufacture of high-quality LED mounting substrates and reducing LED chip connection failures. This has led to the completion of the present invention. The inventors have also discovered that a cleaning solution for cleaning LED chips placed on a sapphire substrate after they have been transferred to a receptor substrate by laser lift-off, provided the cleaning solution is alkaline, can selectively remove unwanted gallium without dissolving or altering metals such as bumps on the LED chip, thereby reducing connection failures of the LED chip. This discovery has thus completed the present invention. The inventors have also discovered a cleaning method for cleaning LED chips separated from a sapphire substrate by laser lift-off, which uses an alkaline cleaning solution. This method allows for the selective removal of unwanted gallium without dissolving or altering metals such as bumps on the LED chip, thus completing the present invention. The inventors have also discovered a cleaning method for selectively removing gallium from parts having gallium and other metals on their surfaces, wherein the cleaning method involves cleaning the parts with an alkaline cleaning solution. This method allows for the selective removal of unwanted gallium without dissolving or altering the other metals, thus completing the present invention. The following explanation will refer to the diagrams. As described above, the inventors, through diligent research to solve the aforementioned problems, surprisingly discovered that by using an alkaline aqueous solution as a cleaning solution, gal