Back-Illuminated Image Sensor With Thermal Conduction Layer
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Solution Overview
Problem
Thinned transmission silicon active pixel sensors in electron imaging detectors face challenges with electron backscatter due to thick substrate layers, which reduce imaging quality and heat removal efficiency as pixel density increases.
Innovation Solution
A back-illuminated configuration with a thermal conduction layer (TCL) is introduced, where the TCL is applied to the BEOL layer to minimize electron backscatter and support heat removal, using materials with high thermal conductivity and low atomic number to replace the original silicon substrate, allowing for the complete removal of the substrate layer and direct exposure of the epitaxial detection layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the substrate layer is thinned to reduce electron backscatter, then imaging quality is improved, but heat removal capability is reduced
Solution Approach 1:
A dedicated thermal conduction layer is introduced as an intermediary component between the substrate and the detection layer. This layer specifically handles heat conduction functions, allowing the substrate to be thinned for improved electron transmission and imaging quality without compromising heat removal capability.
Solution Approach 2:
The device is segmented into functionally distinct layers: a thinned substrate layer optimized for electron transmission and imaging quality, and a separate thermal conduction layer optimized for heat removal. This segmentation allows each layer to be optimized for its specific function without compromise.
2Object-generated harmful factors
If the substrate layer is thinned to minimize electron backscatter, then backscatter is reduced, but structural support is reduced
Solution Approach 1:
A support layer is introduced as an intermediary between the thinned substrate and the detection layer. This support layer provides the necessary mechanical strength and structural support that would be lost by thinning the substrate, while allowing the substrate to be sufficiently thin to minimize electron backscatter.
Solution Approach 2:
The device structure is segmented into a thinned substrate layer for minimizing electron backscatter and a separate support layer for providing mechanical strength. This functional segmentation resolves the contradiction between reducing backscatter and maintaining structural integrity.
3Measurement precision
If pixel density is increased to improve resolution, then imaging resolution is improved, but heat removal becomes more difficult
Solution Approach 1:
A dedicated thermal conduction layer serves as an intermediary heat pathway, efficiently conducting heat away from high-density pixel regions. This allows pixel density to be increased for improved resolution without compromising heat removal efficiency.
Solution Approach 2:
The thermal conduction layer uses materials with high thermal conductivity parameters to efficiently conduct heat away from high-density pixel regions, enabling increased pixel density for improved resolution while maintaining effective heat removal.
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
This configuration significantly reduces electron backscatter and enhances imaging resolution while maintaining effective heat dissipation, as demonstrated by improved detective quantum efficiency (DQE) and spatial frequency performance, allowing for higher-resolution imaging without aliasing errors.
Implementation Method 1
thermal conduction layer (TCL) is introduced, where the TCL is applied to the BEOL layer to minimize electron backscatter and support heat removal
Implementation Method 2
EPI layer 14 includes a material that generates sensor electrons in response to incoming electron microscope electrons
Implementation Method 3
Because these are transmission devices, electrons which have interacted with the detection layer ideally exit the sensor without being scattered back into the detection layer
Data Source
AI summary
A solid state active pixel image sensor for back illumination by an electron beam is described. The image sensor comprises a thermal conduction layer for heat removal. The image sensor may also comprise a thinned silicon substrate on which an epitaxial layer is formed. The substrate may also be completely removed before or after application of the thermal conduction layer. The thermal conduction layer may comprise a metal, a metal compound, silicon, diamond or graphite.