JP-2026076237-A - Damage reduction methods

Abstract

[Problem] To provide a method for transferring pixels from a display to a carrier substrate when the pixel pitch of the display is not an integer multiple of the pitch of the optical devices arranged on the sapphire substrate. [Solution] The ratio of the moving speeds of the donor substrate and the receptor substrate is determined from the array pitch (3, 4) of the optical devices (2) formed on the sapphire substrate and the array pitch (5, 7) of the optical devices to be transferred onto the carrier substrate (6). By lifting (laser transfer) in synchronization with the movement of the donor substrate, the optical devices on the sapphire substrate are transferred to the carrier substrate with the same array pitch as the pixel pitch of the display. [Selection Diagram] Figure 4

Inventors

• 山岡 裕
• 野口 毅
• 宇佐美 健人
• 植森 信隆
• 仲田 悟基
• 齋藤 剛
• 小沢 周作
• 佐藤 伸一
• 倉田 昌実
• 佐藤 正彦
• 阿部 司

Assignees

• 信越化学工業株式会社

Dates

Publication Date

20260511

Application Date

20260120

Priority Date

20200930

Claims (7)

1. A damage suppression method for suppressing damage to the adhesive layer when laser lift-off is performed on a sapphire substrate, where gallium nitride semiconductor light-emitting diodes formed at predetermined intervals on the substrate are converted to intervals different from the predetermined intervals, and the adhesive layer is subjected to irradiation with laser light used for the laser lift-off, wherein the damage to the adhesive layer is suppressed when laser lift-off is performed. The light-emitting diode is formed in a matrix on the sapphire substrate, The irradiation of the laser light is a reduced projection using a photomask, The photomask has a light-shielding portion and an aperture group, and the aperture group has an aperture group in which apertures corresponding to individual light-emitting diodes are arranged in a single row. The light-shielding portion is a damage suppression method that shields the laser light from irradiating the adhesive layer.
2. The damage suppression method according to claim 1, wherein the conversion interval is in the X direction (the short axis direction of the light-emitting diode).
3. The damage suppression method according to claim 1, wherein the conversion interval is in the Y direction (the long axis direction of the light-emitting diode).
4. A damage suppression method according to any one of claims 1 to 3, wherein a gap is provided between the light-emitting diode and the adhesive layer before laser lift-off.
5. The damage suppression method according to claim 4, wherein the gap is 10 to 200 μm.
6. A damage suppression method according to any one of claims 1 to 5, wherein the sapphire substrate or the receptor substrate is scanned while the laser is lifted off.
7. The damage suppression method according to any one of claims 1 to 6, wherein the light-emitting diode is a microLED.

Description

Regarding the mounting process for micro-LEDs. In recent years, nitride semiconductor optical devices have come into use as backlights for liquid crystal displays and for signage displays. These applications require the simultaneous use of a large number of optical devices, thus demanding high-speed transfer technology. Generally, stamp-type batch transfer is used as the high-speed transfer technology, enabling the transfer of 1,000 to tens of thousands of devices at once. Optical devices are mass-produced on sapphire substrates using semiconductor processes. Micro-LEDs, which are LEDs smaller than 100 μm square, can number in the millions on a 4-inch substrate. These micro-LEDs, being tiny devices measuring tens of micrometers, are separated from the sapphire substrate (an epitaxial substrate) for use. It is common practice to attach support substrates to the optical devices arranged on the sapphire substrate and then separate them from the substrate using laser lift-off. A support board or a board on which optical devices have been transferred from a support board is used as the carrier board. Using a special stamp, the optical devices are picked up from the carrier board at intervals corresponding to the display's pixel pitch and mounted onto the backplane board. Therefore, the pitch of the optical devices on the sapphire substrate must be 1/N times the display's pixel pitch, where N is a positive integer. Patent Document 1 describes laser lift-off of nitride semiconductors from sapphire substrates. Patent Documents 2 and 3 propose high-speed mounting using different stamping methods. Patent Document 4 describes a lifting device for lifting from a donor substrate to a receptor substrate. Special Publication No. 2007-534164Japanese Patent Publication No. 2020-129638Japanese Patent Publication No. 2018-163900Japanese Patent Publication No. 2020-004478 This is a diagram showing the arrangement of micro-LEDs on a sapphire substrate, which is the donor substrate.This is an example of a photomask pattern.This is an example of laser irradiation on a 4-inch diameter sapphire substrate.This is a diagram showing the arrangement of micro-LEDs after lifting in the Y direction.This diagram shows the arrangement of micro-LEDs before and after the lift in the X direction.This is a diagram of the second carrier board with RGB implemented. The following describes embodiments of the present invention, but the present invention is not limited to these embodiments. Furthermore, in all the following drawings, the dimensions and proportions of each component have been appropriately altered from those of the actual components in order to facilitate their recognition in the drawings. In this embodiment, the optical device is described as a GaN (gallium nitride) semiconductor LED (light-emitting diode). LED manufacturers form numerous LEDs on sapphire substrates, and in the case of micro-LEDs of 100 μm or less, they supply the sapphire substrate as is, or carrier substrates transferred by laser lift-off, to companies that manufacture displays using LEDs (hereinafter referred to as LED display manufacturers). This section describes the processing of sapphire substrates. In the case of a 4-inch sapphire substrate, millions of micro-LEDs are formed on the substrate. Figure 1 shows the arrangement of micro-LEDs (2) formed on a sapphire substrate (1). The LED size is 20 × 40 μm (X × Y), the arrangement pitch in the X direction (3) is 30 μm, and the arrangement pitch in the Y direction (4) is 60 μm. This sapphire substrate is an example of a substrate on which the target optical device is formed using the lift method according to this embodiment. The back surface of the sapphire substrate is polished to allow laser light to pass through, and the surface on which the LED is formed is textured to increase brightness. Table 1 below shows the relationship between display type and pixel pitch. In the case of a 21-inch display, the pixel pitch is a positive integer multiple of the array pitch of the sapphire substrate. Therefore, a carrier substrate suitable for stamping can be fabricated simply by performing a normal laser lift-off, enabling high-speed mounting using stamping. This section explains how to manufacture carrier boards for 100-inch displays (4K, 8K). As shown in Table 1, the pixel pitch of a 100-inch display is 0.577 mm for 4K (3840 x 2160 pixels) and 0.288 mm for 8K (7680 x 4320 pixels), which are not integer multiples of the aforementioned array pitches of 30 μm and 60 μm. Therefore, 72.1 μm is selected as the target array pitch to obtain an integer. The resulting pixel pitch is 8 times the target array pitch for 4K and 4 times the target array pitch for 8K. Next, we will describe the fabrication of carrier substrates with a target array pitch using a lift device. The lift device used is the one described in Patent Document 4. The sapphire substrate is adsorbed onto the donor stage of the lift device with the side where the