THIN-FILM OPTICAL DEVICE WITH VARYING LAYER COMPOSITION
A thin-film optical device is formed on a substrate by atomic layer deposition. A mixing system provides a homogeneous gaseous mixture having a controllable ratio of first and second reactive gaseous materials. The first and second reactive gaseous materials each react with a third reactive gaseous material but do not react with each other. The homogeneous gaseous mixture is provided to a first inlet port, the third reactive gaseous material is provided to a second inlet port, and an inert gaseous material is provided to a third inlet port. The gas flows are directed through corresponding output channels of the delivery head toward the substrate. The mixing system is controlled to change the ratio of the first and second reactive gaseous materials as a function of time as the substrate is moved relative to the delivery head with an oscillating motion such that deposited layers have a varying composition.
1 . A process of making a thin-film optical device comprising:
providing a substrate;
providing a plurality of gaseous material sources including a first gaseous source providing a first reactive gaseous material, a second gaseous source providing a second reactive gaseous material, a third gaseous source providing a third reactive gaseous material, and an inert gaseous material source providing an inert gaseous material, wherein the first reactive gaseous material and the second reactive gaseous material each react with the third reactive gaseous material but do not react with each other under a specified set of operating conditions;
providing a mixing system to mix a controllable ratio of the first and second reactive gaseous materials to provide a homogeneous gaseous mixture;
providing a delivery head in fluid communication with the mixing system, the third gaseous material source and the inert gaseous material source through a plurality of inlet ports, the mixing system being connected to a first inlet port, the third gaseous material source being connected to a second inlet port, and the inert gaseous material source being connected to a third inlet port, the delivery head including an output face having a first plurality of elongated substantially parallel output channels connected in fluid communication with the first inlet port, a second plurality of elongated substantially parallel output channels connected to a second inlet port, and a third plurality of elongated substantially parallel output channels connected to a third inlet port, wherein at least some of the third elongated output channels are positioned to separate at the first elongated output channels and the second elongated output channels;
simultaneously directing the homogeneous gaseous mixture, the third reactive gaseous material, and the inert gaseous material to flow through the first elongated output channels, the second elongated output channels, and the third elongated output channels, respectively, of the delivery head toward the substrate;
causing an oscillating relative motion between the delivery head and the substrate to cause the third reactive gaseous material to react with a portion of the substrate that has been treated with the homogeneous gaseous mixture thereby forming thin film layers of deposited material; and
controlling the mixing system to change the ratio of the first and second reactive gaseous materials as a function of time such that the thin film layers of deposited material have a varying composition.
2 . The process of claim 1 , wherein the thin film layers of deposited material have a varying refractive index.
3 . The process of claim 1 , further including:
receiving a refractive index profile specifying the refractive index as a function of height above the substrate;
receiving a first calibration function relating the refractive index of the deposited thin film layer as a function of the ratio of the first and second reactive gaseous materials;
receiving a second calibration function relating a growth rate of the deposited material as a function of the ratio of the first and second reactive gaseous materials; and
controlling the ratio of the first and second reactive gaseous materials as a function of time responsive to the refractive index profile and the first and second calibration functions.
4 . The process of claim 3 , wherein the thin-film optical device is an optical interference filter, and wherein the refractive index profile is determined to provide a specified reflectance spectrum or transmission spectrum for the optical interference filter.
5 . The process of claim 3 , wherein the thin-film optical device is an optical waveguide.
6 . The process of claim 1 , wherein a pressure generated by the flow of the one or more of the homogeneous gaseous mixture, the third reactive gaseous material, and the inert gaseous material create a gas fluid bearing that maintains a substantially uniform distance between the output face of the delivery head and the substrate.
7 . The process of claim 1 , wherein the first and second reactive gaseous materials are metal-containing precursor materials.
8 . The process of claim 1 , wherein the third reactive gaseous materials is a non-metal precursor material.
9 . The process of claim 1 , wherein the first reactive gaseous material and the third reactive gaseous material react to form a high refractive index material and the second reactive gaseous material and the third reactive gaseous material react to form a low refractive index material, wherein the high refractive index material has a higher refractive index than the low refractive index material.
10 . The process of claim 9 , wherein the high refractive index material is TiO 2 , ZnO, ZrO 2 or HfO 2 .
11 . The process of claim 9 , wherein the low refractive index material is Al 2 O 3 or SiO 2 .
12 . The process of claim 1 , wherein the mixing system mixes the first and second reactive gaseous materials by merging a gas flow of the first reactive gaseous material in a first conduit and a gas flow of the second reactive gaseous material in a second conduit to form a combined gas flow in a third conduit.
13 . The process of claim 1 , wherein the mixing system also mixes a controllable gas flow of the inert gaseous material into the homogeneous gaseous mixture.