TSV with Segmented Side Profile for Thermal Stress Reduction
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Solution Overview
Problem
Through-silicon vias (TSVs) in stacked-die semiconductor devices face challenges in reducing thermal stress and preventing cracking and electromigration failure due to mismatched thermal expansion coefficients between TSVs and surrounding materials, particularly at the interface with pads.
Innovation Solution
The TSVs are designed with a side profile that includes an upper segment forming a first angle and a lower segment forming a second angle, where the lower segment has a height less than 20% of the TSV's total height and a tapered or curvilinear configuration, reducing the horizontal cross-sectional dimension at stress-prone areas to mitigate thermal stress and enhance structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If TSVs are used to interconnect multiple devices vertically, then circuit density and integration are improved, but thermal stress and cracking risk increase due to mismatched thermal expansion coefficients
Solution Approach 1:
The TSV structure implements different geometric characteristics at different locations: the upper segment has a first angle relative to the longitudinal axis while the lower segment has a second angle. This local variation in geometry allows the structure to accommodate thermal expansion differences at the stress-prone lower interface while maintaining vertical connectivity for high density, thereby resolving the contradiction between circuit density and cracking resistance
Solution Approach 2:
The TSV side profile is divided into distinct segments (upper segment and lower segment) with different angular characteristics. This segmentation allows each portion to perform its specific function: the upper segment maintains vertical alignment for dense routing, while the lower segment with its different angle reduces thermal stress at the pad interface, thus improving reliability without sacrificing productivity
2Stress or pressure
If TSV cross-sectional dimension is reduced at certain locations, then thermal stress is reduced, but structural integrity and current carrying capacity may be compromised
Solution Approach 1:
The TSV structure reduces cross-sectional dimension locally at the lower segment where thermal stress is most problematic, while maintaining adequate dimensions in the upper segment for structural integrity. This selective dimensional reduction allows stress mitigation without compromising overall strength
Solution Approach 2:
The lower segment of the TSV features a curvilinear configuration instead of a straight vertical profile. This curved geometry smoothly transitions the cross-sectional dimension, reducing stress concentration points while maintaining sufficient structural integrity and current carrying capacity
3Ease of manufacture
If TSV side profile is made vertical for simplicity, then manufacturing is easier, but thermal stress concentration increases at pad interfaces
Solution Approach 1:
The TSV maintains a simple vertical profile in the upper segment for ease of manufacture, while introducing angular variations only in the lower segment where stress concentration occurs. This localized modification minimizes the impact on manufacturing complexity while effectively reducing stress concentration at the pad interface
Data Source
Figure 1
Figure 2A~3
Figure 4~6
AI summary
A semiconductor device includes a substrate (105) having a top surface (109) and a bottom surface (1 10), and a through-silicon via (TSV) (103) extending from the top surface (109) of the substrate (105) to the bottom surface (1 10) of the substrate (105), the TSV (103) having a height and a side profile extending along a longitudinal axis (200), where the side profile has an upper segment (201, 21 1, 301, 401, 501, 601 ) forming a first angle relative to the longitudinal axis (200), and a lower segment (202, 212, 302, 402, 502, 603) forming a second angle relative to the longitudinal axis (200), where the second angle is different than the first angle, and where the lower segment (202, 212, 302, 402, 502, 603) has a height that is less than 20% of the height of the TSV (103).