Through Wiring Surface Irregularities for Thermal Stress Reduction
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Solution Overview
Problem
Through wirings in electronic devices experience thermal expansion issues, leading to stress and deformation of thin films and elements due to differences in thermal expansion coefficients between the substrate and the through wirings, which can result in performance deficiencies and reduced integration density.
Innovation Solution
The method involves forming through holes with varying surface irregularities on the inner walls, where the degree of surface irregularities is greater on the side where the element is disposed, to restrain the through wiring and reduce relative movement, allowing for closer integration of elements without damaging the thin films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If through wirings are formed of metal (e.g., Cu) to reduce resistivity, then electrical conductivity is improved, but thermal expansion difference causes relative movement and stress on thin films
Solution Approach 1:
The patent applies local quality by creating surface irregularities (scallops) at specific locations on the inner wall of the through hole, specifically on the side where the element is disposed. This localized modification provides differential restraint: the irregularities create engagement structures that suppress thermal expansion movement at the element side while allowing the other side to move more freely, thus resolving the thermal expansion stress problem while maintaining the electrical conductivity benefit of metal wirings
2Reliability
If elements are disposed far from through wirings to avoid stress and deformation, then thin film quality is improved, but integration density decreases
Solution Approach 1:
The patent applies preliminary anti-action by pre-forming surface irregularities (scallops) on the inner wall of the through hole before element formation. These irregularities create a restraining structure that counteracts the thermal expansion forces that would otherwise damage thin films. This preliminary protective structure enables elements to be disposed close to through wirings without risking thin film damage, thus improving integration density while maintaining thin film quality
3Object-affected harmful factors
If scallops are formed entirely in the through hole to restrain through wiring, then relative movement is reduced, but stress on scallops and thin film increases causing deformation or damage
Solution Approach 1:
The patent applies local quality by forming surface irregularities (scallops) selectively only on the side of the through hole where the element is disposed, rather than uniformly throughout the entire through hole. This localized approach creates restraint where needed (at the element side) while leaving the opposite side more compliant, thus distributing and reducing stress concentrations that would otherwise cause deformation or damage to the scallops and thin film
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 reduces permanent deformation and stress on thin films, enhances the reliability of the device by allowing elements to be placed closer to through wirings, and improves the integration density while maintaining the quality of thin films formed on the through hole surfaces.
Implementation Method 1
the thermal expansion coefficient of Cu is six times larger than that of silicon. Accordingly, when the temperature increases and decreases to form the elements, the through wirings contract and expand or slide relative to the inner wall of the through hole
Data Source
AI summary
In a method of producing a device in which an element structure is provided on a substrate including a through wiring, a through hole is formed so as to extend from a first surface of the substrate to a second surface of the substrate disposed on an opposite side of the substrate to the first surface, the through wiring is formed by filling the through hole with an electrically conductive material, and the element structure is formed on a first surface side. In the step of forming the through hole, a degree of surface irregularities of an inner wall of the through hole is larger on the first surface side than on a second surface side.