Boron Micro-Structured Neutron Detector With Conformal Doping
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Solution Overview
Problem
Existing semiconductor neutron detectors face limitations in detection efficiency, particularly thin-film-coated planar detectors, which are limited to 5% efficiency compared to 70% for helium-based gas detectors, and scaling other materials for commercial applications is difficult due to availability, environmental hazards, and production techniques.
Innovation Solution
A thermal neutron detector using isotopically enriched boron in both the neutron conversion layer and as a source for conformal doping, with micro-structured diodes having cavities filled with boron-containing materials, enabling a continuous conductive layer through solid-state diffusion, enhancing detection efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If thin-film-coated planar detectors are used, then the device structure is simple, but the detection efficiency is limited to 5%
Solution Approach 1:
The detector is segmented into micro-structured cavities etched in the semiconductor substrate, with each cavity filled with boron-containing material. This segmentation increases the total surface area for neutron conversion while maintaining a planar overall structure, resolving the contradiction between structural simplicity and detection efficiency.
Solution Approach 2:
The invention transitions from a two-dimensional planar surface to a three-dimensional micro-structured surface with cavities. This dimensional change increases the effective area for neutron interaction without significantly complicating the manufacturing process, as the cavities can be formed using standard semiconductor fabrication techniques.
2Reliability
If other semiconductor materials are used, then detection efficiency may be improved, but availability, environmental hazards, and production techniques become problematic
Solution Approach 1:
The invention uses boron-containing materials that serve dual functions: as a neutron conversion layer and as a p-type dopant source for conformal doping of the semiconductor substrate. This multi-functionality eliminates the need for separate doping materials, simplifying manufacturing while maintaining high detection efficiency through enhanced carrier collection.
3Reliability
If conformal doping is performed using boron as dopant source, then carrier collection is improved, but additional fabrication steps are required
Solution Approach 1:
The invention merges the neutron conversion function and the doping function into a single material (boron-containing material). The same material that converts neutrons also serves as the dopant source, combining two previously separate functions into one, thereby reducing overall device complexity despite adding conformal doping capability.
Solution Approach 2:
The boron-containing material in the cavities serves itself by providing boron atoms that diffuse into the semiconductor substrate during thermal processing, creating the conformal doping layer. This self-service mechanism eliminates the need for separate doping steps and materials, reducing fabrication complexity while improving carrier collection.
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 method achieves high detection efficiency, up to 37% in simulations, by utilizing boron as both a neutron conversion layer and conformal doping source, significantly improving performance over conventional detectors.
Implementation Method 1
The most common reactions used to create a charged particle from neutron interaction is 10B(n,α)7Li and 6Li(n,α)3H reactions
Implementation Method 2
As these charged reaction products travel through the detection media, they generate secondary reaction products by ionization, which will eventually contribute to an electrical signal
Implementation Method 3
These generated charges are separated by the applied electric field and collected at the contacts
Implementation Method 4
The substrate with the filled cavities can then be thermally treated for the solid-state diffusion of boron into the semiconductor (e.g., silicon or germanium) substrate, giving a continuous, conformal conductive layer
Data Source
AI summary
Thermal neutron detectors and methods of fabricating the same are provided. A thermal neutron detector can use boron in both the neutron conversion layer and as a source for conformal doping in a semiconductor substrate. The neutron detector can be a micro-structured diode with cavities having a depth of 60 microns or less. The boron can be filled in the cavities and diffused into the semiconductor substrate via a diffusion annealing process.