Display Test Pattern with Contact Holes for Uniform Insulating Film Evaluation
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Solution Overview
Problem
Existing methods for evaluating the characteristics of insulating films in display devices face challenges such as non-uniform current application, electrode damage, and difficulty in distinguishing between intrinsic and extrinsic defects, leading to inaccurate breakdown voltage measurements.
Innovation Solution
A test pattern design with a first and second electrode layer, separated by insulating layers, connected via contact holes, ensuring uniform current application and preventing electrode damage, allowing for precise evaluation of insulating film characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage stress is applied for breakdown voltage measurement, then insulating film characteristics can be evaluated, but foreign substances are produced due to breakdown, making defect detection difficult
Solution Approach 1:
The patent changes the evaluation parameter from voltage stress (breakdown voltage measurement) to current stress (time dependent dielectric breakdown evaluation). By applying a constant current density instead of increasing voltage, the method avoids sudden breakdown that produces foreign substances, while still evaluating insulating film characteristics through the time-to-breakdown measurement under controlled current stress.
2Ease of operation
If the upper electrode extends beyond the lower electrode to connect to test pad, then current can be applied to the test pattern, but a step occurs due to lower electrode thickness, causing resistance increase and electrode tearing
Solution Approach 1:
The patent introduces a third layer (third electrode layer) above the second electrode layer to serve as the upper electrode. This upper electrode has a smaller area than the second electrode layer below it, avoiding the need for the electrode to extend beyond the layer beneath. The dimensional arrangement (upper electrode smaller than lower electrode) eliminates the step formation that causes resistance increase and tearing, while still maintaining electrical connection capability through the insulating film.
3Measurement precision
If a flat test pattern with uniform electrodes is used, then insulating film intrinsic characteristics can be evaluated, but non-uniform current application occurs, reducing evaluation consistency
Solution Approach 1:
The patent applies different qualities to different parts of the electrode structure. The third electrode layer (upper electrode) has a smaller area than the second electrode layer (lower electrode), creating a localized quality difference. This design ensures that current is concentrated in the overlapping region where the insulating film is evaluated, improving current uniformity in the measurement area while maintaining overall system functionality. The local quality variation in electrode areas resolves the contradiction between intrinsic characteristics evaluation and evaluation consistency.
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 test pattern enables accurate and consistent evaluation of insulating film characteristics, distinguishing between intrinsic and extrinsic defects, thereby improving the reliability and lifespan of display devices.
Implementation Method 1
One of the evaluation schemes including applying the current stress may be time dependent dielectric breakdown (TDDB) evaluation under current stress application. The TDDB evaluation under current stress application is a scheme of evaluating progressive insulation breakdown characteristics over time under application of a certain current stress to the insulation film.
Data Source
AI summary
Disclosed are a test pattern and a display device including the same. A first test wiring and a second test wiring are connected to a first electrode layer and a second electrode layer constituting the test pattern via a plurality of contact holes, respectively. Thus, current is applied to the first electrode layer and the second electrode layer via the first test wiring and the second test wiring, respectively. Thus, the current may be applied as uniformly as possible to an entire area of each of the first electrode layer and the second electrode layer.