Method of fabricating light emitting diode using laser lift-off technique and laser lift-off apparatus having heater
View Patent ↗Disclosed is a method of fabricating a light emitting diode using a laser lift-off apparatus. The method includes growing an epitaxial layer including a first conductive-type compound semiconductor layer, an active layer and a second conductive-type compound semiconductor layer on a first substrate, bonding a second substrate, having a different thermal expansion coefficient from that of the first substrate, to the epitaxial layers at a first temperature of the first substrate higher than a room temperature, and separating the first substrate from the epitaxial layer by irradiating a laser beam through the first substrate at a second temperature of the first substrate higher than the room temperature but not more than the first temperature. Thus, during a laser lift-off process, focusing of the laser beam can be easily achieved and the epitaxial layers are prevented from cracking or fracture. The laser lift-off process is performed by a laser lift-off apparatus including a heater.
1. A method for making a light emitting diode, comprising:
growing an epitaxial layer on a first substrate, the epitaxial layer comprising a first conductive-type compound semiconductor layer, an active layer, and a second conductive-type compound semiconductor layer;
bonding a second substrate, having a different thermal expansion coefficient from that of the first substrate, to the epitaxial layer at a first temperature of the first substrate higher than a room temperature, wherein the second substrate is bonded to the epitaxial layer by metal eutectic bonding; and
separating the first substrate from the epitaxial layer by irradiating a laser beam through the first substrate at a second temperature of the first substrate higher than the room temperature but not more than the first temperature.
2. The method according to claim 1 , further comprising:
heating the first substrate to the second temperature prior to irradiating the laser beam.
3. The method according to claim 2 , wherein the first substrate is heated to maintain the second temperature during irradiation of the laser beam.
4. The method according to claim 2 , wherein the heating of the first substrate is performed using a heater provided in a laser lift-off apparatus.
5. The method according to claim 1 , wherein the first substrate is approximately 2-inch sapphire substrate and the second temperature is an average temperature to cause bowing of the first substrate in the range of about 3 mm or less.
6. The method according to claim 1 , wherein the first substrate is approximately 2-inch sapphire substrate and the second temperature is an average temperature to cause bowing of the first substrate in the range of about 1.5 mm or less.
7. The method according to claim 1 , wherein the metal eutectic bonding is AuSn.
8. The method according to claim 1 , wherein the second temperature is in the range of about 200˜300° C.
9. The method according to claim 1 , wherein irradiation of the laser beam is performed during the first substrate cooling subsequent to the second substrate bonding to the epitaxial layers.
10. The method according to claim 1 , wherein a total thickness of the epitaxial layers is less than approximately 10 μm.