Flip chip LED with side reflectors and phosphor
An array of light emitting devices is mounted on a support surface with the transparent growth substrate (e.g., sapphire) facing up. A photoresist layer is then deposited over the top surface of the growth substrate, followed by depositing a reflective material over the top and side surfaces of the light emitting devices to encapsulate the light emitting devices. The top surfaces of the light emitting devices are then ground down to remove the reflective material over the top surface of the photoresist. The photoresist is then dissolved to leave a cavity over the growth substrate having reflective walls. The cavity is then filled with a phosphor. The phosphor-converted light emitting devices are then singulated to form packaged light emitting devices. All side light is reflected back into the light emitting device by the reflective material and eventually exits the light emitting device toward the phosphor. The packaged light emitting devices, when energized, appear as a white dot with no side emission (e.g., no blue halo).
1. A method for forming a light emitting device comprising the following ordered steps:
(a) providing a plurality of light emitting devices on a carrier, each of the plurality of light emitting devices comprising a stack of semiconductor layers and a first temporary layer over the stack of semiconductor layers;
(b) depositing a reflective material over the plurality of light emitting devices such that the reflective material conforms to a top surface of the first temporary layer, sides of the stack of semiconductor layers, and the carrier in spaces between the light emitting devices;
(c) removing the reflective material over the top surface of the first temporary layer of each of the light emitting devices to expose the first temporary layer;
(d) removing the first temporary layer to form a reflective cavity over each of the plurality of light emitting devices; and
(e) at least partially filling the reflective cavity with a wavelength-converting material.
2. The method of claim 1 further comprising depositing a protective layer over the reflective material prior to removing the reflective material over the top surface of the first temporary layer.
3. The method of claim 1 wherein the removing the reflective material over the top surface of the first temporary layer to expose the first temporary layer comprises grinding down the reflective material.
4. The method of claim 1 wherein the first temporary layer is a photoresist, and the removing the first temporary layer comprises dissolving the photoresist with a solvent.
5. The method of claim 1 wherein the at least partially filling the reflective cavity with a wavelength-converting material comprises dispensing a phosphor material into the cavity.
6. The method of claim 1 wherein the plurality of light emitting devices are flip-chip light emitting devices with anode and cathode electrodes.
7. The method of claim 1 wherein the stack of semiconductor layers is disposed on a transparent growth substrate for epitaxially growing the semiconductor layers.
8. The method of claim 1 , wherein a thickness of the first temporary layer is selected based on a desired thickness for the wavelength-converting material.
9. The method of claim 1 , further comprising curing the wavelength-converting material using heat or ultraviolet (UV) light after at least partially filling the cavity with the wavelength-converting material.
10. The method of claim 9 , wherein the wavelength-converting material is a phosphor mixture including phosphor particles in a transparent binder.
11. The method of claim 1 , wherein an amount of the wavelength-converting material is pre-measured prior to at least partially filling the cavity with the wavelength-converting material or an optical feedback mechanism is used to fill the cavity to the top with the wavelength-converting material.
12. The method of claim 1 , wherein the reflective material is deposited in direct contact with the top surface of the temporary layer.