ESD Artifact Reduction in Thin Film Transistor Image Sensor Arrays
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Solution Overview
Problem
Image sensor arrays are vulnerable to electrostatic discharge (ESD) during fabrication, particularly during the photolithographic patterning of interlayer dielectric into via contact holes, leading to defects and artifacts due to insufficient protection before the formation of data lines and voltage bias lines.
Innovation Solution
A conductive layer is deposited over the dielectric interlayer in the image sensor array, which spreads out charges induced by tribo-electric events, reducing the risk of localized damage to switching transistors and preventing ESD-induced artifacts during subsequent fabrication steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If guard rings and protection structures are added to protect against ESD, then reliability is improved, but device complexity increases
Solution Approach 1:
A conductive layer is deposited over the dielectric interlayer before subsequent fabrication steps to proactively protect against ESD events during photolithographic patterning and other processing steps, preventing localized charging artifacts before they can occur
Solution Approach 2:
The invention changes the electrical properties of the structure by adding a conductive layer, transforming the insulating dielectric interlayer into a protected configuration that can dissipate electrostatic charges, thereby modifying the electrical parameter state to prevent ESD damage
2Manufacturing precision
If ESD protection structures are added, then manufacturing precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The conductive layer is integrated into the existing fabrication process flow, combining ESD protection functionality with the standard manufacturing sequence without requiring separate dedicated protection steps, thereby maintaining ease of manufacture while improving precision
3Reliability
If the array is protected during fabrication, then reliability is improved, but device complexity increases
Solution Approach 1:
The conductive layer serves a dual purpose: it is part of the functional device structure and simultaneously provides self-service ESD protection during fabrication, eliminating the need for separate protection mechanisms and maintaining process simplicity
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 layer effectively protects the image sensor array from ESD events, reducing the potential for defects and artifacts by distributing electrostatic charges, thus enhancing the robustness and yield of the fabrication process without adding extra process complications.
Implementation Method 1
A conductive layer is deposited over the dielectric interlayer in the image sensor array, which spreads out charges induced by tribo-electric events
Implementation Method 2
spreads out charges induced by tribo-electric events
Data Source
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Figure 3
Figure 4~5
AI summary
A method is provided for fabricating an image sensor array in a manner that reduces the potential for defects resulting from electrostatic discharge events during fabrication of the image sensor array. The method includes: forming at least one pixel over a substrate, the pixel including a switching transistor and a photo-sensitive cell; and forming a dielectric interlayer over the pixel. A key step in the method of the present invention is depositing a first conductive layer over the dielectric interlayer. After the first conductive layer is formed, the image sensor array is well protected from ESD events because the first conductive layer spreads out any charge induced by tribo-electric charging events that may occur during subsequent fabrication processing steps, thereby reducing the potential for localized damage to the switching transistors upon the occurrence of ESD events.