Laser Crystallization Method Suppressing Crack Propagation in Display Devices
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Solution Overview
Problem
The existing methods for manufacturing semiconductor devices using a CW laser beam often result in cracks during the cutting process, leading to device failures due to residual stress and crack propagation in the substrate.
Innovation Solution
The method involves irradiating only the peripheral regions of semiconductor devices with a CW or pseudo-CW laser beam to grow crystals laterally, while avoiding irradiation at the cutting positions, and controlling the tensile stress increment to less than 200 N/m by etching the undercoat film and depositing an insulating film, such as silicon oxide, to suppress crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a glass substrate with strain point not higher than 750°C is used to reduce cost and enable large area processing, then productivity and cost-effectiveness are improved, but crack propagation occurs during cutting due to residual stress from laser irradiation
Solution Approach 1:
The substrate is divided into a laser-irradiated region (where semiconductor devices are formed) and a non-irradiated region (peripheral portion where cutting occurs). This segmentation allows the central area to receive full laser treatment for device fabrication while the peripheral area remains stress-free for clean cutting, preventing crack propagation from cut edges into functional regions.
Solution Approach 2:
Different regions of the substrate are given different properties: the central region undergoes laser irradiation to create polycrystalline silicon films for semiconductor devices, while the peripheral region is deliberately left unirradiated to maintain low residual stress. This local differentiation allows simultaneous optimization of device performance in the irradiated zone and cutting reliability in the non-irradiated zone.
2Reliability
If the entire substrate is irradiated with CW laser beam to form polycrystalline silicon film, then semiconductor device performance is improved, but residual stress increases causing crack propagation during cutting
Solution Approach 1:
Instead of irradiating the entire substrate, laser irradiation is applied partially only to the region where semiconductor devices need to be formed. The peripheral portion is intentionally excluded from irradiation, providing a stress-free zone that prevents crack propagation while the irradiated region achieves the necessary polycrystalline silicon formation for high-performance devices.
3Ease of manufacture
If glass substrate with strain point not higher than 750°C is used, then cost is reduced compared to quartz substrate, but heat resistance is limited requiring careful stress control
Solution Approach 1:
The strain point parameter of the substrate is changed from high (quartz, 1000°C) to low (glass, ≤750°C) to reduce cost. To compensate for the reduced heat resistance and prevent crack propagation, the laser irradiation parameters are adjusted to limit residual stress, and a non-irradiated peripheral region is created where cutting occurs, ensuring the glass substrate can be processed without exceeding its thermal limits.
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 approach effectively prevents crack propagation during substrate cutting, ensuring high reliability and performance of semiconductor devices by maintaining the integrity of the semiconductor film and reducing stress-induced failures.
Implementation Method 1
irradiating at least a part of a semiconductor film on the substrate with a CW or pseudo-CW laser beam so as to grow crystals laterally
Implementation Method 2
a laser crystallization method in which an amorphous Si film is formed and then annealed with a laser beam so as to be crystallized
Data Source
AI summary
A method of irradiating at least a part of a semiconductor film on the substrate with a CW or pseudo-CW laser beam so as to grow crystals laterally. A region over the semiconductor film having Si as a chief component is provided with a pixel region, a gate line driving circuit region and a signal line driving circuit region for driving pixels, and a terminal region where connection terminals will be formed. The region not irradiated with the CW laser beam is provided in a peripheral portion of each semiconductor device corresponding to the position where the glass substrate will be cut. Due to this means, it is possible to suppress occurrence of a failure caused by propagation of cracks when the substrate is cut.