Multilayer Reflector for Pixelated X-ray Scintillators
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Solution Overview
Problem
Current x-ray detectors face a tradeoff between high spatial resolution and high quantum efficiency due to the isotropic emission of secondary visible photons, leading to low light output efficiency and limitations in small structure formation and processing time.
Innovation Solution
A multilayer reflector with alternating high and low refractive index dielectric thin films is integrated into a pixelated mold to enhance light output efficiency, using conformal atomic layer deposition (ALD) for precise coating and compatibility with high temperature melting processes, reducing crosstalk between pixels and improving reflectivity over a wide range of incident angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If pixelated scintillators are fabricated by filling Si micro-well matrix molds with scintillator materials, then spatial resolution is improved, but light output efficiency deteriorates
Solution Approach 1:
The patent applies composite materials by creating a multilayer reflector structure consisting of alternating high refractive index (TiO2) and low refractive index (SiO2) dielectric layers. This composite structure leverages the optical properties of different materials to achieve high reflectivity across a wide angular range, thereby improving light output efficiency while preserving the spatial resolution benefits of the pixelated micro-well structure.
Solution Approach 2:
The patent employs parameter changes by precisely controlling the thickness of each dielectric layer (TiO2 and SiO2 layers with specific thicknesses) to optimize optical reflectivity. By adjusting these physical parameters during conformal ALD deposition, the reflector achieves maximum light reflection efficiency for photons escaping at various angles from the scintillator pixels.
2Measurement precision
If dicing or cutting methods are used to produce structured scintillators, then spatial resolution is improved, but manufacturing complexity and processing time increase
Solution Approach 1:
The patent replaces mechanical dicing or cutting methods with a chemical vapor deposition approach (conformal ALD). Instead of mechanically slicing scintillator materials to create pixelated structures, the invention uses atomic layer deposition to conformally coat dielectric layers onto the micro-well structure, significantly reducing fabrication complexity and processing time while maintaining high spatial resolution.
Solution Approach 2:
The patent applies local quality by using conformal ALD to deposit dielectric layers with precise local thickness control on the complex three-dimensional micro-well structure. This method ensures uniform coating quality on vertical sidewalls and bottom surfaces of each pixel, achieving consistent optical properties throughout the device without the mechanical complexity of dicing.
3Measurement precision
If columnar growth technique is used for scintillators, then spatial resolution is improved, but cross talk between adjacent columns increases
Solution Approach 1:
The patent extracts the light confinement function from the scintillator material itself and places it in a dedicated reflector structure. By depositing alternating high and low refractive index dielectric layers on the micro-well walls, the harmful light scattering and cross-talk between adjacent columns is eliminated, as the reflector actively directs photons within their respective pixel channels.
4Loss of energy
If a multilayer reflector with alternating high and low refractive index dielectric layers is integrated into pixelated mold, then light output efficiency is improved, but device complexity increases
Solution Approach 1:
The patent replaces complex mechanical assembly of multilayer structures with a streamlined conformal ALD deposition process. The alternating high and low refractive index dielectric layers are deposited in sequence through atomic layer deposition, which automatically forms conformal coatings on complex micro-well geometries, reducing fabrication complexity despite the multilayer structure.
Solution Approach 2:
The patent achieves multi-functionality by using the same conformal ALD process for both creating the pixelated micro-well structure and depositing the multilayer reflector. This universal fabrication approach eliminates the need for separate assembly steps, reducing overall device complexity while maintaining the sophisticated multilayer optical structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves simultaneous high spatial resolution and high quantum efficiency, suitable for mass production and compatible with existing semiconductor fabrication instruments, significantly improving light output efficiency by maintaining total reflection at large incident angles and enhancing photon escaping rates.
Implementation Method 1
The reflector consists of multiple layers of dielectric thin films with alternating high and low refractive indices at the emission wavelength of the x-ray scintillator material. The thicknesses of the dielectric layers are designed such that high reflectivity is achieved in a wide range of incident angle.
Implementation Method 2
The reflector consists of multiple layers of dielectric thin films with alternating high and low refractive indices at the emission wavelength of the x-ray scintillator material.
Implementation Method 3
The dielectric layers of desired thicknesses can be accurately coated via conformal atomic layer deposition (ALD).
Implementation Method 4
the first dielectric layer adjacent to the Si micro-well surfaces can be SiO2 and be accurately coated via wet or dry oxidation of Si to the desired thickness.
Data Source
AI summary
Disclosed herein is a pixelated x-ray scintillator with a multilayer reflector for x-ray detectors with simultaneous high spatial resolution and high quantum efficiency and fabrication method to produce the pixelated x-ray scintillator. The multilayer reflector provides high reflectivity for the emitted visible photons over a broad incident angle range, thus boosts the light output efficiency of the pixelated x-ray scintillator. The fabrication process to produce the pixelated scintillator with the multilayer reflector in this disclosure is compatible with standard semiconductor fabrication instrument and suitable for mass production.