Two step phosphor deposition to make a matrix array
A method of fabricating closely spaced pcLEDs arranged in a matrix array of perpendicular rows and columns comprises an initial phosphor deposition step in which phosphor is deposited at alternating locations (pixels) in the matrix array in a checkerboard pattern, so that the locations in the array at which phosphor is deposited are not adjacent to each other. In a subsequent phosphor deposition step phosphor is deposited at the alternating locations at which phosphor was not deposited in the first deposition step. In between the two phosphor deposition steps, reflective or scattering structures may be fabricated on sidewalls of the phosphor pixels to optically isolate pcLEDs in the resulting array from each other.
1. A method of fabricating a matrix array of phosphor-converted LEDs, the method comprising:
in a first phosphor deposition step depositing a phosphor material at alternating locations in a matrix array to form a checkerboard pattern of phosphor pixels in which locations in the matrix array at which phosphor pixels are deposited alternate with locations in the array at which phosphor pixels are not deposited, the phosphor pixels comprising side walls adjacent to and facing the locations in the array at which phosphor pixels are not deposited;
depositing reflective structures on the side walls of the phosphor pixels deposited in the first phosphor deposition step; and
in a second phosphor deposition step, after depositing the reflective structures, depositing a phosphor material to form phosphor pixels at the alternating locations in the matrix array at which phosphor pixels were not deposited in the first phosphor deposition step, such that after the first and second phosphor deposition steps adjacent phosphor pixels in the resulting matrix array of phosphor pixels are in contact with and spaced apart by one of the reflective structures.
2. The method of claim 1 , in which the phosphor pixels are spaced apart by less than or equal to about 10 microns by the reflective structures.
3. The method of claim 1 , in which the phosphor pixels are spaced apart by less than or equal to about 3 microns by the reflective structures.
4. The method of claim 1 , wherein depositing reflective structures on the side walls of the phosphor pixels deposited in the first phosphor deposition step comprises also depositing reflective structures on other surfaces of the matrix array of phosphor-converted LEDs, comprising removing reflective structures from at least some of those other surfaces after the second phosphor deposition step.
5. The method of claim 1 , wherein the phosphor material deposited in the second phosphor deposition step is the same as the phosphor material deposited in the first phosphor deposition step.
6. The method of claim 1 , wherein the phosphor material deposited in the second phosphor deposition step differs from the phosphor material deposited in the first phosphor deposition step.
7. The method of claim 1 , comprising forming the matrix array of phosphor pixels on a carrier, and transferring the matrix array of phosphor pixels from the carrier to a matrix array of LEDs to form the matrix array of phosphor-converted LEDs.
8. The method of claim 1 , comprising forming the matrix array of phosphor pixels directly on a matrix array of LEDs to form the matrix array of phosphor-converted LEDs.
9. The method of claim 1 , comprising in the first phosphor deposition step depositing the phosphor material in openings in a photoresist structure to form the checkerboard pattern of phosphor pixels.
10. The method of claim 9 , comprising removing the photoresist structure before depositing the reflective structures.
11. The method of claim 10 , comprising:
forming the photoresist structure on a carrier; and
subsequently transferring the matrix array of phosphor pixels from the carrier to a matrix array of LEDs to form the matrix array of phosphor-converted LEDs.
12. The method of claim 10 , comprising forming the photoresist structure on an array of LEDs.
13. The method of claim 1 , comprising in the first phosphor deposition step depositing the phosphor material in openings in a mold to form the checkerboard pattern of phosphor pixels.
14. The method of claim 13 , wherein the phosphor material deposited in the first phosphor deposition step comprises a phosphor in a glass matrix.
15. The method of claim 14 , wherein the mold is formed from boron nitride.
16. The method of claim 13 , comprising;
transferring the checkerboard pattern of phosphor pixels from the mold to a carrier before depositing the reflective structures; and
subsequently transferring the matrix array of phosphor pixels from the carrier to a matrix array of LEDs to form the matrix array of phosphor-converted LEDs.
17. The method of claim 1 , wherein the reflective structures comprise scattering particles dispersed in a matrix.
18. The method of claim 1 , wherein the reflective structures comprise reflective metal layers.
19. The method of claim 1 , wherein the reflective structures comprise Distributed Bragg Reflector structures.
20. The method of claim 1 , wherein, in the second phosphor deposition step, depositing a phosphor material to form phosphor pixels comprises depositing a phosphor material to form phosphor pixels each having a width matching a distance between adjacent reflective structures on the side walls of the phosphor pixel deposited in the first phosphor deposition step.