X-ray detector capacitance-optimized light-tight pad structure
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Solution Overview
Problem
Existing X-ray detectors face challenges in achieving minimal input capacitance while maintaining light-tightness, especially in highly integrated pixel electronics with small distances between detector elements, where light can interfere with analog electronics and degrade response.
Innovation Solution
The X-ray detector design includes a substrate with a readout contact and light protection structures that minimize input capacitance and protect the preamplifier input from direct light incidence, using a combination of conductive connections and insulation layers to optimize the pad structure for reduced capacitance and light shielding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a metallization-free zone is set up around the via connection to reduce capacitance, then the capacitance of the via connections is reduced, but the space requirement increases and light can enter the integrated circuit
Solution Approach 1:
The patent transitions from a two-dimensional planar layout to a three-dimensional stacked architecture. The readout contact is positioned above the integrated circuit substrate, with via connections extending vertically through insulation layers. This vertical stacking allows the metallization-free zone to be confined in the vertical dimension rather than occupying lateral space, thereby reducing the horizontal area requirement while maintaining low capacitance.
Solution Approach 2:
The patent divides the connection structure into multiple vertically separated components: the readout contact on the substrate surface, via connections penetrating through insulation layers, and contact pads on the integrated circuit. This segmentation allows each component to be optimized independently - the via connections can have reduced capacitance through controlled geometry while the overall structure maintains compact footprint.
2Shape
If the readout contact is made large to maximize distance from sensor and minimize capacitance, then the capacitance between readout contact and integrated circuit is minimized, but the space requirement increases
Solution Approach 1:
The patent resolves this contradiction by moving the capacitance-reducing mechanism from the lateral dimension to the vertical dimension. Instead of enlarging the readout contact area to increase distance, the design uses vertical via connections that extend downward through insulation layers, achieving capacitance reduction through increased vertical separation while maintaining a compact horizontal footprint.
3Object-affected harmful factors
If light-tight structures are implemented to protect preamplifier input from light, then light interference is prevented, but the input capacitance cannot be minimized simultaneously
Solution Approach 1:
The patent segments the light protection function from the electrical connection function. The metallization-free zone serves as the light-tight structure protecting the preamplifier input, while separate via connections provide the electrical pathway. This segmentation allows the light protection zone to be optimized for light blocking without compromising the electrical connection geometry, thereby achieving both light tightness and minimal capacitance.
Solution Approach 2:
The patent introduces an intermediary insulating layer between the readout contact and the integrated circuit substrate. This insulating layer with its metallization-free zone serves as both an electrical isolation medium and a light-tight barrier, mediating between the electrical connection requirements and the optical protection requirements without compromising either function.
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 design achieves reproducible X-ray exposures with high spatial resolution, independent of light incidence, and minimizes parasitic capacitance, ensuring stable response of sensitive analog circuits.
Implementation Method 1
The input of the preamplifier is protected against direct incidence of light
Implementation Method 2
The electron-hole pairs are separated by an electric field applied to the sensor
Implementation Method 3
The X-rays or the photons can be converted into electrical pulses by a suitable sensor
Data Source
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AI summary
The invention relates to an x-ray detector (1) comprising a substrate (23) which has an electrically conductive connection between a read-out contact (57) in the region of the top side of the substrate (23) and an input of a pre-amplifier (3) in an active layer (5) of an integrated circuit. A first electrically conductive connection (17) is provided between the read-out contact and a second electrically conductive connection (19). A surface of a first light protection (7) on the top side of the substrate (23) is larger than a surface of a light-permeable region (15) in the substrate, laterally delimited by a second light protection (9), so that the surface of the first light protection (7) covers the surface of the light-permeable region (15) in a first projection along the surface normal. The second electrically conductive connection (19) is provided within a second projection of the surface of the light-permeable region (15) along the surface normal and below the second light protection (9). A third electrically conductive connection (21) between the second electrically conductive connection (19) and the pre-amplifier (3) is provided below the second light protection (9). The input of the pre-amplifier (3) is protected against direct incidence of light.