Chamfered Conductor Corners for Thermal Stress Reduction
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Solution Overview
Problem
Integrated circuit chip structures face cracking and delamination issues due to thermal expansion mismatches between different materials in the back-end-of-line (BEOL) structures, particularly at the interfaces between underfill and passivation layers, which can lead to microcracks and delamination.
Innovation Solution
The introduction of chamfered corners on patterned conductors and through conductors, which reduce stress concentrations by eliminating right-angled corners and distributing thermal stress more evenly, thereby reducing the likelihood of cracking and delamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If right-angled corners are used in patterned conductors and through conductors, then manufacturing is simpler, but stress concentration occurs leading to cracking and delamination
Solution Approach 1:
The patent applies curvature by replacing right-angled corners with chamfered corners (45-degree angled corners) in patterned conductors and through conductors. This geometric modification eliminates stress concentration points while maintaining manufacturing feasibility through standard photolithography and etching processes. The chamfered corners distribute thermal stress more evenly, preventing cracking and delamination at conductor intersections.
2Adaptability or versatility
If different materials with different CTE are used in BEOL structures, then functional requirements are met, but thermal expansion mismatch causes delamination and microcracks
Solution Approach 1:
The patent applies local quality by modifying the geometry of conductors specifically at corner locations where stress concentration occurs, while leaving the rest of the conductor structure unchanged. The chamfered corners are strategically placed at intersections and bends to locally manage stress, allowing the use of different CTE materials in BEOL structures without compromising overall interface stability.
3Reliability
If chamfered corners are introduced in conductors, then stress distribution is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies parameter changes by specifying the chamfer angle (45 degrees) and providing guidance on chamfer dimensions relative to conductor width. These standardized parameters enable manufacturers to achieve the required stress distribution benefits using conventional fabrication processes without requiring ultra-precise manufacturing capabilities. The 45-degree angle is particularly advantageous as it can be achieved through standard diagonal etching techniques.
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 enhances the reliability of chip packages by minimizing cracking defects and improving interaction between chip components, effectively addressing the thermal expansion mismatch issues.
Implementation Method 1
These different materials in BEOL structures can have different coefficients of thermal expansion (CTE) relative to other layers internal to the IC chips. CTE mismatch is amplified at different material interfaces... The introduction of chamfered corners on patterned conductors and through conductors, which reduce stress concentrations by eliminating right-angled corners and distributing thermal stress more evenly
Data Source
AI summary
Devices are formed to have inner layers that have electronic devices, and an outer passivation layer. A patterned conductor is formed on a first surface of the inner layers, and through conductors (that extend through interior insulator layers) are positioned to electrically connect the patterned conductor to the electronic devices. The patterned conductor includes a pattern of connected linear sections that are parallel to the first surface of the inner layers. The linear sections of the patterned conductor meet at conductor corners, and at least one of the conductor corners of the patterned conductor includes a chamfer side that terminates at the linear sections. Further, the chamfer side is not perfectly diagonal, but instead forms unequal angles with the linear sections that intersect to form the corner.