Pixelated Conductive Barrier for X-ray Imagers

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Solution Overview

Problem

Direct X-ray imaging detectors face significant corrosion issues due to the corrosive nature of X-ray sensitive materials, which existing protective methods, such as insulating barrier layers, either introduce signal loss or cross-talk, and current solutions are not effective in preventing corrosion throughout the detector array.

Innovation Solution

Implementing a pixelated, electrically conductive barrier layer made from materials like amorphous silicon between the X-ray sensitive material and pixel electrodes, which can be deposited using methods like PECVD, to prevent corrosion while maintaining efficient signal response.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thick insulating barrier layer is used to protect active circuitry from corrosion, then corrosion resistance is improved, but signal response is lost due to electrical insulation

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidsignal loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The barrier layer changes its electrical conductivity parameter based on applied voltage: at low voltages (normal operation) it remains insulating to prevent corrosion, while at high voltages (breakdown voltage) it becomes conductive to allow signal readout. This voltage-dependent parameter change resolves the contradiction between maintaining corrosion protection and enabling signal response.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The barrier layer transitions from a static insulating state to a dynamic state where its electrical properties can change in response to applied voltage. This dynamic behavior allows the same layer to serve dual functions: protecting against corrosion during normal operation and allowing signal passage during readout operations.

Inventive Principle:

Principle #15Dynamics

2Reliability

If an electrically conductive barrier layer is used to prevent corrosion, then signal response is maintained, but cross-talk between pixels is introduced via lateral conduction

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidcross-talk

Core Design Contradiction:

ReliabilityVSLoss of information

Solution Approach 1:

The barrier layer exhibits voltage-dependent conductivity: at low voltages it remains insulating to prevent lateral conduction and cross-talk, while at high voltages it becomes conductive to allow vertical signal readout. This parameter change with voltage resolves the contradiction between corrosion protection and preventing cross-talk.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If corrosion-resistant pixel electrodes like ITO are used, then corrosion resistance is improved, but pinholes can still initiate corrosion that leads to complete destruction of circuitry

Engineering Contradiction:

Improvecorrosion resistanceVSAvoidcorrosion propagation

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

A barrier layer is introduced as an intermediary between the pixel electrode and the corrosive X-ray detector material. This intermediate layer provides an additional protective barrier that prevents corrosion propagation even when pinholes are present in the pixel electrode, thereby resolving the contradiction between using corrosion-resistant electrodes and preventing corrosion initiation.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Reliability

If a multi-layer photoconductor structure is used with less reactive material as barrier, then corrosion resistance is improved, but detection performance is reduced compared to more reactive material

Engineering Contradiction:

Improvecorrosion resistanceVSAvoiddetection performance

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

A separate barrier layer is introduced as an intermediary between the high-performance photoconductor material and the pixel electrode. This allows the use of optimal photoconductor material for detection performance while the barrier layer provides corrosion protection, resolving the contradiction between using reactive high-performance material and preventing corrosion.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 conductive barrier layer effectively reduces corrosion, avoids signal loss and cross-talk, and allows for thin deposition of X-ray sensitive materials, enhancing the overall performance and longevity of direct X-ray imaging detectors.

Implementation Method 1

which can be deposited using methods like PECVD

Methodology Applied

Scientific EffectPlasma Enhanced Chemical Vapour Deposition: Plasma Enhanced Chemical Vapour Deposition

Data Source

PatentUS8232531B2Corrosion barrier layer for photoconductive X-ray imagers

Publication Date: 2012.07.31 VAREX IMAGING CORP

AI summary

Improved corrosion resistance for direct X-ray imaging detectors is obtained by providing a pixelated, electrically conductive barrier layer between the X-ray sensitive material and the pixel electrodes. Each barrier layer can cover part or all of its corresponding pixel electrode. In cases where pixel electrodes makes contact to underlying circuitry through vertical vias, it is preferred for the barrier layers to cover the via sections of the pixel electrodes. The barrier layers for each pixel electrode can be spaced apart from each other, or they can all be included within a continuous film on top of the pixel electrodes. Such a continuous film can be pixelated by spatially modulating its properties (e.g., thickness, doping) to significantly reduce lateral conductivity from pixel to pixel.