Engineering the optical properties of an integrated computational element by ion implantation

Abstract

Systems and methods of engineering the optical properties of an optical Integrated Computational Element device using ion implantation during fabrication are provided. A system as disclosed herein includes a chamber, a material source contained within the chamber, an ion source configured to provide a high-energy ion beam, a substrate holder to support a multilayer stack of materials that form the Integrated Computational Element device, a measurement system, and a computational unit. The material source provides a material layer to the multilayer stack, and at least a portion of the ion beam is deposited in the material layer according to an optical value provided by the measurement system.

1 . A system for fabricating an Integrated Computational Element (ICE) device, comprising:
 a chamber;   a material source contained within the chamber;   an ion-beam generator configured to provide an ion beam;   a substrate holder to support a multilayer stack of materials that form the ICE device;   a measurement system; and   a computational unit, wherein the material source provides a material layer to the multilayer stack, and at least a portion of the ion beam is deposited in the material layer according to an optical value provided by the measurement system.   
     
     
         2 . The system of  claim 1 , wherein the ion-beam generator is configured to provide a selected dose of ions at a selected energy and with a selected angle of incidence to the multilayer stack. 
     
     
         3 . The system of  claim 1 , wherein the measurement system comprises:
 an optical system configured to provide broadband electromagnetic radiation to the multilayer stack;   an optical transducer to measure the electromagnetic radiation after it interacts with the ICE device in-situ and provide a signal; and   a recording device to store the signal.   
     
     
         4 . The system of  claim 3 , wherein the signal provided by the measurement system is one of a broadband transmission spectrum, a broadband reflection spectrum, and a combination of a broadband transmission and reflection spectra. 
     
     
         5 . The system of  claim 1 , wherein the ion-beam generator is configured to provide the ion beam to increase a free carrier concentration at a selected layer in the multilayer stack of materials that form the ICE device. 
     
     
         6 . The system of  claim 1 , wherein the ion-beam generator is configured to provide the ion beam formed with ions from the group consisting of Oxygen, Argon, Boron, Phosphorus, Arsenic, Gallium, and Nitrogen. 
     
     
         7 . The system of  claim 1 , wherein the ion-beam generator and the substrate holder are configured to move relative to each other to produce a free carrier density distribution through a single layer of material in the multilayer stack of materials that form the ICE device. 
     
     
         8 . The system of  claim 1 , wherein the material source provides a plurality of layers of material on a substrate to form the multilayer stack, the plurality of layers including alternating layers of a first type of material and a second type of material, the second type of material being different from the first type of material. 
     
     
         9 . The system of  claim 8 , wherein, for each layer of the multilayer stack, the measurement system:
 measures a thickness of the layer with a measurement system;   determines whether the layer includes the first type of material or the second type of material;   determines a complex index of refraction for the layer, the complex index of refraction being determined using a first refraction coefficient and a first extinction coefficient when the layer was determined to include the first type of material, or the complex index of refraction being determined using a second refraction coefficient and a second extinction coefficient when the layer was determined to include the second type of material, the first refraction coefficient being different from the second refraction coefficient and the first extinction coefficient being different from the second extinction coefficient; and   determines a resulting electromagnetic radiation spectrum for the layer based on the thickness and the complex index of refraction of the layer.   
     
     
         10 . The system of  claim 9 , wherein the computational unit determines an optical error value for at least one layer of the multilayer stack based on a comparison of the resulting electromagnetic radiation spectrum of the at least one layer to a desired electromagnetic radiation spectrum of the at least one layer. 
     
     
         11 . The system of  claim 10 , wherein the computational unit determines that the optical error value of the at least one layer exceeds a pre-determined threshold, the at least one layer including a first charge carrier concentration. 
     
     
         12 . The system of  claim 11 , wherein the computational unit determines, in response to the optical error value exceeding the pre-determined threshold, a predetermined charge carrier concentration, the predetermined charge carrier concentration being associated with a first density of charge carriers when the at least one layer includes the first type of material and a second density of charge carriers when the at least one layer includes the second type of material, the second density of charge carriers being different from the first density of charge carriers. 
     
     
         13 . The system of  claim 12 , wherein the computational unit determines a dose and an energy for the ion beam provided by the ion-beam generator based on the predetermined charge carrier concentration. 
     
     
         14 . The system of  claim 13 , wherein the computational unit alters the complex index of refraction of the at least one layer by ion implantation using the ion beam with the determined dose and energy, the at least one layer with the altered complex index of refraction including a second charge carrier concentration, wherein the ion implantation increased the first charge carrier concentration to the second charge carrier concentration by the predetermined charge carrier concentration. 
     
     
         15 . A non-transitory computer readable medium storing commands that, when executed by a processor in a computer unit included in a system for fabricating an integrated computational element (ICE) device, cause the system to perform a method comprising:
 measuring an optical property of a multilayer stack of materials that form the ICE device;   comparing the optical property with a target optical property of the ICE device;   determining a concentration of free carriers in at least one layer of material in the multilayer stack required to reduce a difference between the optical property and the target optical property; and   providing the concentration of free carriers to the at least one layer of material.   
     
     
         16 . The non-transitory computer readable medium of  claim 15 , wherein measuring the optical property of the multilayer stack of materials comprises:
 measuring a thickness of the layer with a measurement system, the multilayer stack comprising a plurality of layers for use as an optical device, the plurality of layers including alternating layers of a first type of material and a second type of material, the second type of material being different from the first type of material;   determining whether the layer includes the first type of material or the second type of material;   determining a complex index of refraction for the layer, the complex index of refraction being determined using a first refraction coefficient and a first extinction coefficient when the layer was determined to include the first type of material, or the complex index of refraction being determined using a second refraction coefficient and a second extinction coefficient when the layer was determined to include the second type of material, the first refraction coefficient being different from the second refraction coefficient and the first extinction coefficient being different from the second extinction coefficient; and   determining a resulting electromagnetic radiation spectrum for the layer based on the thickness and the complex index of refraction of the layer.   
     
     
         17 . The non-transitory computer readable medium of  claim 16 , wherein comparing the optical property with the target optical property comprises:
 comparing the resulting electromagnetic radiation spectrum of the layer of the multilayer stack to a desired electromagnetic radiation spectrum of the at least one layer;   determining an optical error value for at least one layer based on the comparison; and   determining that the optical error value of the at least one layer exceeds a pre-determined threshold, the at least one layer including a first charge carrier concentration.   
     
     
         18 . The non-transitory computer readable medium of  claim 17 , wherein determining the concentration of free carriers comprises:
 determining, in response to the optical error value exceeding the pre-determined threshold, a predetermined charge carrier concentration, the predetermined charge carrier concentration being associated with a first density of charge carriers when the at least one layer includes the first type of material and a second density of charge carriers when the at least one layer includes the second type of material, the second density of charge carriers being different from the first density of charge carriers.   
     
     
         19 . The non-transitory computer readable medium of  claim 18 , wherein providing the concentration of free carriers comprises:
 altering the complex index of refraction of the at least one layer by ion implantation, the at least one layer with the altered complex index of refraction including a second charge carrier concentration, wherein the ion implantation increased the first charge carrier concentration to the second charge carrier concentration by the predetermined charge carrier concentration.   
     
     
         20 . The non-transitory computer readable medium of  claim 19 , wherein determining the concentration of free carriers comprises:
 determining a dose and an energy for an ion beam provided by an ion-beam generator based on the determination that the optical error value of the at least one layer exceeds the pre-determined threshold, the complex index of refraction being altered by the ion implantation, using the determined dose and energy of the ion beam.