Flexible Substrate Semiconductor Device Crack Prevention
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Solution Overview
Problem
Flexible semiconductor devices face defects due to cracking during the peeling and substrate division processes, which are exacerbated by high bending stress, leading to broken semiconductor and light-emitting elements.
Innovation Solution
A semiconductor device structure with a semiconductor layer surrounding the display portion and an insulating layer positioned over the semiconductor layer, along with a conductive layer, is implemented. This structure aligns the end portion of the substrate with the semiconductor layer and insulating layer, preventing crack development by creating a step that stops crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If peeling is performed between the peeling layer and the layer to be peeled, then the layer can be separated from the substrate, but high bending stress is applied to the end portion of the layer causing breaking or cracking
Solution Approach 1:
A buffer layer is introduced between the layer to be peeled and the peeling layer. This buffer layer acts as a mediator that absorbs and distributes the bending stress during peeling, preventing stress concentration at the end portions of the layer. The buffer layer has specific mechanical properties that allow it to withstand the peeling stress without transmitting it directly to the fragile layer, thereby enabling successful separation without cracking.
2Productivity
If a plurality of devices are manufactured at a time over a large substrate and the substrate is divided with a scriber, then productivity is improved, but a crack occurs in or develops from an end portion of the substrate due to stress applied when the substrate is divided
Solution Approach 1:
The buffer layer is formed in advance over the entire substrate before the substrate division step. This preliminary action ensures that when the substrate is later divided with a scriber, the buffer layer is already in place to protect the end portions of the substrate from stress-induced cracking. The buffer layer's presence before division allows for high-productivity batch manufacturing while maintaining substrate integrity.
3Adaptability or versatility
If the stack of thin films is made thin to achieve flexibility, then flexibility is improved, but the stack becomes very fragile and more susceptible to cracking
Solution Approach 1:
The structure employs a composite material system consisting of multiple layers with different mechanical properties: the thin film stack for flexibility, the buffer layer for stress absorption, and the peeling layer for separation. This composite structure allows the overall assembly to be flexible while the buffer layer provides the necessary strength and crack resistance. The combination of materials with complementary properties resolves the contradiction between thinness/flexibility and strength/durability.
Data Source
AI summary
Provided is a flexible device with fewer defects caused by a crack or a flexible device having high productivity. A semiconductor device including: a display portion over a flexible substrate, including a transistor and a display element; a semiconductor layer surrounding the display portion; and an insulating layer over the transistor and the semiconductor layer. When seen in a direction perpendicular to a surface of the flexible substrate, an end portion of the substrate is substantially aligned with an end portion of the semiconductor layer, and an end portion of the insulating layer is positioned over the semiconductor layer.