Photoresist patterning process supporting two step phosphor-deposition to form an LED matrix array
A method is described for low temperature curing of silicone structures, including the steps of providing patterning photoresist structures on a substrate. The photoresist structures define at least one open region that can be at least partially filled with a condensation cure silicone system. Vapor phase catalyst deposition is used to accelerate the cure of the condensation cure silicone, and the photoresist structure is removed to leave free standing or layered silicone structures. Phosphor containing silicone structures that are coatable with a reflective metal or other material are enabled by the method.
1. A method of fabricating an array of phosphor pixels, the method comprising:
in a first phosphor deposition step depositing a photoresist layer and patterning the photoreist layer to form an array of photoresist blocks separated from each other by gaps, the photoresist blocks and the gaps occupying alternating locations in a matrix array and forming a checkerboard pattern;
depositing a first phosphor composition in the gaps, the first phosphor composition comprising phosphor particles dispersed in a condensation cure silicone system;
after depositing the first phosphor composition, curing the condensation cure silicone system using one or more vapor phase catalysts to form a first plurality of phosphor pixels occupying alternating locations in the matrix array;
after curing the condensation cure silicone system, removing the photoresist blocks;
after removing the photoresist blocks, depositing reflective structures on side walls of the first plurality of phosphor pixels;
after depositing the reflective structures, in a second phosphor deposition step depositing a second phosphor composition at locations in the matrix array formerly occupied by photoresist blocks; and
curing the second phosphor composition deposited in the second phosphor deposition step to form a second plurality of phosphor pixels occupying alternating locations in the matrix array, with adjacent phosphor pixels in the matrix array in contact with and spaced apart by one of the reflective structures.
2. The method of claim 1 , wherein the condensation cure silicone system comprises organosiloxane block copolymers.
3. The method of claim 1 , wherein the one or more vapor phase catalysts comprise superbase catalyzing agents.
4. The method of claim 1 , wherein the one or more vapor phase catalysts comprise 1,8-Diazabicyclo[5.4.0]undec-7-ene (DBU).
5. The method of claim 1 , wherein the second phosphor composition is the same as the first phosphor composition.
6. The method of claim 1 , wherein the second phosphor composition differs from the first phosphor composition.
7. The method of claim 1 , wherein the first phosphor composition emits light of a first color upon excitation, the second phosphor composition emits light of a second color upon excitation, and the second color differs from the first color.
8. The method of claim 1 , wherein:
the second phosphor composition comprises phosphor particles dispersed in a condensation cure silicone system; and
curing the second phosphor composition deposited in the second phosphor deposition step comprises using one or more vapor phase catalysts.
9. The method of claim 1 , in which adjacent phosphor pixels are spaced apart by less than or equal to about 10 microns by the reflective structures.
10. The method of claim 1 , in which adjacent phosphor pixels are spaced apart by less than or equal to about 3 microns by the reflective structures.
11. The method of claim 1 , wherein the reflective structures comprise scattering particles dispersed in a matrix.
12. The method of claim 1 , wherein the reflective structures comprise reflective metal layers.
13. The method of claim 1 , wherein the reflective structures comprise Distributed Bragg Reflector structures.
14. A method of forming an array of phosphor-converted LEDs, comprising attaching the array of phosphor pixels fabricated by the method of claim 1 to a corresponding array of light emitting diodes.