Sensor Element Array Fabrication on Flexible Substrates
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Solution Overview
Problem
Flexible substrates with higher thermal expansion coefficients pose challenges during the fabrication of flexible electronic devices due to CTE mismatch with rigid substrates, leading to stress and alignment issues, particularly in high-temperature processing environments.
Innovation Solution
A roll-to-roll process is employed to fabricate a sensor element array on a flexible substrate, using a patterned conductive layer with sensing lines, power lines, and channel layers, along with insulating and conductive layers, to create a stress-sensing device that avoids high-temperature processing and aligns layers self-alignedly, ensuring low-cost and large-area production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible substrate with higher thermal expansion coefficient is used, then the device achieves flexibility and lightness, but stress and alignment issues occur during fabrication due to CTE mismatch with rigid substrates
Solution Approach 1:
A buffer layer is introduced between the flexible substrate and the rigid substrate to act as an intermediary that accommodates the thermal expansion coefficient mismatch. This buffer layer absorbs the differential expansion and contraction during temperature changes, preventing stress transmission to the fabricated device layers and maintaining alignment accuracy throughout the fabrication process.
Solution Approach 2:
The thermal expansion coefficient parameter is matched across layers by selecting appropriate materials for the buffer layer and fabrication process conditions. The process temperature is controlled and limited to below 150°C to minimize thermal expansion differences, and the buffer layer material is specifically chosen to have a thermal expansion coefficient that bridges the gap between the flexible substrate and rigid substrate.
2Strength
If high-temperature processing is used for fabricating electronic devices on flexible substrates, then material properties are improved, but the flexible substrate experiences excessive thermal expansion and distortion
Solution Approach 1:
The fabrication process temperature parameter is strictly controlled to remain below 150°C, preventing excessive thermal expansion of the flexible substrate. This temperature limit is maintained throughout all fabrication steps including deposition and annealing processes, ensuring that the substrate dimensions remain stable and alignment accuracy is preserved while still achieving adequate material properties through low-temperature processing techniques.
3Reliability
If conventional fabrication methods are used on flexible substrates, then device functionality is achieved, but the process is complex and costly due to multiple alignment steps
Solution Approach 1:
The buffer layer is pre-formed on the flexible substrate before any device fabrication steps begin. This preliminary action establishes a stable, thermally-matched foundation that simplifies subsequent alignment operations. The buffer layer's stable dimensions at fabrication temperatures eliminate the need for complex real-time alignment compensation procedures, reducing overall process complexity while maintaining device functionality.
Data Source
AI summary
A sensor element array and method of fabricating the same are provided. The sensor element array is disposed on a substrate and includes a first patterned conductive layer, a channel layer, a first insulation layer, a second patterned conductive layer, a second insulation layer, and a third patterned conductive layer. The first patterned conductive layer includes a sensing line, a first power line, a source/drain pattern and a branch pattern. The channel layer includes a first channel and a second channel. Margins of the first insulation layer and the second patterned conductive layer are substantially overlapped. The second patterned conductive layer includes a selecting line, a gate pattern, and a gate connecting pattern. The second insulation layer has a first connecting opening for exposing the gate connecting pattern. The third patterned conductive layer includes a sensing electrode electrically connected to the gate connecting pattern.