MICRO-LED PICK AND PLACE USING METALLIC GALLIUM

• US 20190109027A1
• Filed: 06/07/2018
• Published: 04/11/2019
• Est. Priority Date: 10/09/2017
• Status: Active Grant

• Current Assignee: META Platforms Technologies LLC (Meta Platforms, Inc. (f/k/a Facebook, Inc.))
• Original Assignee: Facebook Technologies, LLC (Meta Platforms, Inc. (f/k/a Facebook, Inc.))
• Inventors: Pourchet, Allan, Saketi, Pooya
• Granted Patent: US 10,304,706 B2
• Time in Patent Office: Days
• CPC Class Codes: H01L 21/67144 Apparatus for mounting on conductive members, e.g. leadframes or conductors on insulating substrates
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 25/167 comprising optoelectronic devices, e.g. LED, photodiodes
• CPC Class Codes: H01L 33/0093 Wafer bonding; Removal of the growth substrate
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination
• CPC Class Codes: H01L 33/20 with a particular shape, e.g. curved or truncated substrate
• CPC Class Codes: H01L 33/30 containing only elements of Group III and Group V of the Periodic Table
• CPC Class Codes: H01L 33/32 containing nitrogen

Abstract

An LED die containing a gallium semiconductor layer is placed on a target substrate using a pick-up tool (PUT) attached to the LED die using metallic gallium. As a result of a laser lift-of (LLO) process to separate the gallium semiconductor layer from a substrate layer on which the gallium semiconductor layer is formed, a layer of gallium metal is formed on a surface of the LED die. The gallium layer is melted to form liquid gallium. A head of the PUT is contacted with the liquid gallium, whereupon the LED die is cooled such that the liquid gallium solidifies, attaching the LED die to the PUT. The PUT picks up and places the LED die at a desired location on a target substrate. The LED die can be heated to melt the gallium layer, allowing the PUT to be detached.

Claims

1. A method, comprising:

forming an array of light emitting diode (LED) dies, each of the LED dies including a gallium semiconductor layer;

forming, for each of the LED dies, a gallium material converted from a portion of the gallium semiconductor layer; and

attaching a pick-up-tool (PUT) to the gallium material of one or more LED dies of the array of LED dies to pick up the one or more LED dies, wherein the PUT directly contacts the gallium material.

2. The method of claim 1, wherein attaching the PUT to the gallium material of the one or more LED dies to pick up the LED dies includes:

heating the one or more LED dies to form liquid gallium from the gallium material of the one or more LED dies;

contacting the liquid gallium of the one or more LED dies with the PUT;

cooling the liquid gallium into solid gallium to attach the PUT with the one or more LED dies via the solid gallium;

picking up the one or more LED dies using the PUT.

3. The method of claim 1, further comprising exposing the gallium semiconductor layer to a laser, the laser being absorbed by a portion of the gallium semiconductor layer to form the gallium material on a surface of the gallium semiconductor layer for each of the array of LED dies.

4. The method of claim 3, wherein the array of LED dies is formed on a substrate layer, and wherein exposing the gallium semiconductor layer to the laser detaches the gallium semiconductor layer of the LED dies from the substrate layer.

5. The method of claim 4, wherein the gallium material is formed at an interface between the gallium semiconductor layer of the LED dies and the substrate layer.

6. The method of claim 4, wherein exposing the gallium semiconductor layer to the laser comprises projecting the laser through the substrate layer to the gallium semiconductor layer, wherein the laser is a pulsed ultraviolet laser, and the substrate layer comprises a sapphire substrate that is substantially transparent to the pulsed ultraviolet laser.

7. The method of claim 4, wherein the gallium semiconductor layer includes gallium nitride (GaN), and wherein the laser being absorbed by the portion of the gallium semiconductor layer to form gallium material separates the portion of the gallium semiconductor layer into the gallium material and nitrogen gas.

8. The method of claim 4, wherein the gallium semiconductor layer includes gallium arsenide (GaAs), and wherein the laser being absorbed by the portion of the gallium semiconductor layer to form gallium material separates the portion of the gallium semiconductor layer into the gallium material and an arsenic compound.

9. The method of claim 4, wherein the laser being absorbed by a portion of the gallium semiconductor layer weakens bonding between the gallium semiconductor layer and the substrate layer to detach the substrate layer and the gallium semiconductor layer.

10. The method of claim 4, further comprising:

prior to exposing the gallium semiconductor layer to the laser to detach the gallium semiconductor layer from the substrate layer, attaching the array of LEDS to a carrier substrate, the gallium semiconductor layer being positioned between the substrate layer and the carrier substrate; and

wherein attaching a pick-up-tool (PUT) to the gallium material of one or more LED dies of the array of LED dies to pick up the one or more LED dies comprises picking up the one or more LED dies from the carrier substrate.

11. The method of claim 2, further comprising:

placing the one or more LED dies on a target substrate using the PUT;

heating the solid gallium attaching the PUT with the one or more LED dies to detach the PUT from the one or more LED dies.

12. The method of claim 11, wherein the target substrate comprises a device substrate including control circuits for the LED dies.

13. The method of claim 11, further comprising removing gallium material remaining on the one or more LED dies subsequent to detaching the PUT from the one or more LED dies.

14. The method of claim 13, wherein removing the gallium material remaining on the one or more LED dies includes etching the gallium material with an etchant.