Seal Ring Suppresses Cracks in Low-k Films Around TSVs
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Solution Overview
Problem
The miniaturization of semiconductor devices leads to thermal stress due to the difference in thermal expansion coefficients between copper TSVs and silicon semiconductor elements, causing cracks in low relative permittivity films used to reduce parasitic capacitance, which hinders the improvement in element operation speed.
Innovation Solution
A seal ring is provided from the closest low relative permittivity film to the silicon substrate to the farthest low relative permittivity film surrounding the TSV, formed in the vicinity of the TSV to inhibit crack generation and progression, with an octagonal shape to effectively block crack propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a low relative permittivity film is used as an insulating film to reduce parasitic capacitance between wiring, then the speed of element operation is improved, but the film is prone to cracks due to lower mechanical strength
Solution Approach 1:
A seal ring is formed in advance around the TSV before the low relative permittivity film is deposited. This preliminary structural preparation creates a protective barrier that prevents crack initiation and propagation in the subsequently deposited low relative permittivity film, allowing the film to be used despite its lower mechanical strength
Solution Approach 2:
The seal ring acts as an intermediary protective structure between the TSV and the low relative permittivity film. It absorbs and distributes thermal stress, preventing direct stress transmission to the film and thereby preventing crack formation while allowing the film to maintain its low parasitic capacitance properties
2Loss of energy
If copper TSVs are used to connect semiconductor devices, then electrical resistance is reduced, but thermal stress is generated due to difference in thermal expansion coefficients between copper and silicon
Solution Approach 1:
The seal ring serves as a stress-absorbing intermediary between the copper TSV and the silicon substrate. It accommodates the differential thermal expansion between copper and silicon during temperature cycles, preventing stress concentration and crack formation in the surrounding low relative permittivity film
Solution Approach 2:
The seal ring structure changes its physical parameters (such as volume or shape) in response to thermal stress, allowing it to absorb and dissipate the stress generated by thermal expansion differences between copper TSVs and silicon, thereby protecting the overall structure from damage
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 seal ring effectively suppresses the generation and progression of cracks in low relative permittivity films, enhancing the mechanical strength and reducing thermal stress, thereby improving the reliability and speed of semiconductor device operations.
Implementation Method 1
The coefficient of thermal expansion differs between copper, which is a material of the TSV, and silicon, which is a material of the semiconductor element. Thus, thermal stress is generated due to temperature fluctuations.
Data Source
AI summary
A semiconductor device includes a TSV that penetrates a silicon substrate. A seal ring is provided from a first low relative permittivity film that is closest to the silicon substrate to a second low relative permittivity film that is farthest from the silicon substrate. The seal ring is formed to surround the TSV in bird's eye view on the silicon substrate from a wafer front surface. This achieves suppression of generation or progress of a crack in a low relative permittivity film in a semiconductor device including the low relative permittivity film and a TSV.