Buffer Pad Design for Semiconductor Bump Stress Relief
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Solution Overview
Problem
Highly integrated semiconductor chips with low-k material interlayer dielectrics are vulnerable to stress-induced defects like cracking and peeling due to their low elastic modulus and hardness, which limits the use of bump structures in semiconductor packages, especially for high bandwidth memory devices that require larger connection structures.
Innovation Solution
A semiconductor chip design featuring a buffer pad thicker and wider than the electrode pad, surrounded by protection layers with specific openings, relieves stress by forming a bump structure that reduces defects in the interlayer dielectric and enhances electrical characteristics and reliability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a bump structure is used to package highly integrated semiconductor chips, then connection capacity and integration are improved, but stress-induced defects like cracking and peeling occur due to low elastic modulus and hardness of low-k material
Solution Approach 1:
A buffer pad is introduced as an intermediary component between the electrode pad and the bump structure. This buffer pad acts as a stress-absorbing mediator that protects the low-k material interlayer dielectric from stress-induced defects while enabling the bump structure to provide high connection capacity. The buffer pad specifically addresses the contradiction by absorbing mechanical stress during bonding processes, preventing cracking and peeling of the low-k material.
Solution Approach 2:
The buffer pad provides beforehand cushioning by being positioned in advance between the electrode pad and the bump structure. This cushioning layer is designed to absorb and distribute stress before it reaches the low-k material interlayer dielectric, preventing stress-induced defects like cracking and peeling that would otherwise occur during bump structure formation and subsequent bonding processes.
2Reliability
If the buffer pad is made thicker to reduce stress, then stress resistance is improved, but manufacturing complexity increases due to precise thickness and opening width requirements
Solution Approach 1:
The invention specifies precise parameter ranges for the buffer pad thickness (greater than electrode pad thickness) and opening width relationships (first opening width equal to or greater than second opening width). By defining these parameter relationships, the design simplifies manufacturing while ensuring adequate stress resistance. The parameter changes transform a complex design problem into a set of clear dimensional specifications that guide the fabrication process.
3Reliability
If protection layers with specific openings are added to protect the electrode pad and buffer pad, then stress resistance is improved, but manufacturing precision requirements increase
Solution Approach 1:
The invention defines specific parameter relationships for the protection layer openings: the first opening width in the first direction must be equal to or greater than the second opening width. This parameter specification provides clear manufacturing guidance while ensuring adequate stress protection. By establishing these dimensional relationships rather than absolute values, the design balances protection effectiveness with manufacturing feasibility.
Data Source
AI summary
A semiconductor chip includes a substrate having a low-k material layer. An electrode pad is disposed the substrate. A first protection layer at least partially surrounds the electrode pad. The first protection layer includes a first opening at an upper portion thereof. A buffer pad is electrically connected to the electrode pad. A second protection layer at least partially surrounds the buffer pad. The second protection layer includes a second opening at an upper portion thereof. A pillar layer and a solder layer are sequentially stacked on the buffer pad. A thickness of the buffer pad is greater than a thickness of the electrode pad. A width of the first opening in a first direction parallel to an upper surface of the semiconductor substrate is equal to or greater than a width of the second opening in the first direction.