TSV Bump Contact Venting for Thermal Stress Relief
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Solution Overview
Problem
Unfilled through substrate vias (TSVs) in semiconductor devices are prone to damage due to thermal expansion during manufacturing processes, especially reflow soldering, as gas inside the closed TSVs expands, leading to potential fractures and contamination risks.
Innovation Solution
The semiconductor device incorporates a stress relief feature, such as a venting channel or predetermined breaking point in the under-bump metallization, allowing communication between the TSV cavity and the environment, thereby preventing fractures and contamination by enabling gas or liquid escape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stress or pressure
If TSVs are left unfilled to reduce thermal stress, then thermal stress in the semiconductor substrate is reduced, but the TSVs become vulnerable to damage from expanding gas during reflow soldering
Solution Approach 1:
A stress relief feature (venting channel or predetermined breaking point) is created in the under-bump metallization layer before the reflow soldering process. This preliminary structural modification allows gas to escape from the TSV cavity during subsequent heating, preventing the TSV from rupturing while maintaining the unfilled configuration that reduces thermal stress on the substrate.
Solution Approach 2:
The under-bump metallization layer serves as an intermediary structure that contains the stress relief feature. This intermediary element mediates between the TSV cavity (which needs to remain unfilled for thermal stress reduction) and the external environment (which allows gas escape), enabling the TSV to maintain its unfilled state while protecting against gas expansion damage during manufacturing processes.
2Object-affected harmful factors
If TSVs are closed to prevent contamination, then contamination risk is reduced, but gas expansion during heating causes fractures
Solution Approach 1:
The under-bump metallization layer has non-uniform local quality: it is continuous and protective in most areas to prevent contamination, but contains a localized stress relief feature (venting channel or predetermined breaking point) that provides a controlled pathway for gas escape. This localized modification allows the majority of the structure to maintain its protective function while the specific local region accommodates gas expansion to prevent fractures.
3Reliability
If a venting channel is created in under-bump metallization, then gas escape is enabled and thermal stability is improved, but the device structure becomes more complex
Solution Approach 1:
The under-bump metallization layer is segmented by incorporating a venting channel or predetermined breaking point, dividing it into regions that are separated by this stress relief feature. This segmentation creates a controlled pathway for gas escape while maintaining the overall integrity and protective function of the under-bump metallization layer, achieving thermal stability with a relatively simple structural modification.
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 solution provides thermal stability to the bump contacts, reducing the risk of damage and contamination, even under changing ambient temperatures, by allowing gases or liquids to escape, thus maintaining the integrity of the semiconductor device.
Implementation Method 1
gas remaining inside the closed TSV expands. This may especially happen during reflow soldering in the manufacturing process
Data Source
Figure 1~2
Figure 3~5
Figure 6~8
AI summary
The semiconductor device comprises a semiconductor substrate (1) with a main surface (10) and a further main surface (11) opposite the main surface, a TSV (3) penetrating the substrate from the main surface to the further main surface, a cover layer (2) arranged above the TSV at the main surface, a bump contact (6) arranged on the TSV at the further main surface, and a stress relief feature at the main surface or at the further main surface. The stress relief feature is provided to expose the TSV at least partially to the environment, which can be the ambient air, for instance, or any region of the device lying outside the region occupied by the TSV. The stress relief feature can be a channel (8) in an under-bump metallization (5).