Bonding Pad Protective Layer for Stacked IC Reliability
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Solution Overview
Problem
Existing bonding methods for integrated circuits in three-dimensional stacked configurations expose bonding pad metal materials to air, leading to reliability concerns due to oxidation and corrosion, especially as inter-wafer bonding pad dimensions decrease and density increases.
Innovation Solution
A protective layer, such as copper silicide, is formed over the exposed portions of bonding pads between stacked dies using a reactive gas process before, during, or after the bonding process, to prevent oxidation and corrosion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If bonding pads are formed with smaller dimensions and higher density to increase integration, then the number of bonding pads per chip increases, but the bonding pads become more susceptible to oxidation and corrosion from environmental exposure
Solution Approach 1:
A protective layer is introduced as an intermediary substance between the bonding pad metal and the environmental atmosphere. This protective layer acts as a mediator that prevents direct contact between the metal bonding pads and oxidizing/corrosive environmental factors, thereby maintaining reliability while allowing high-density integration.
Solution Approach 2:
The patent converts the harmful effect of environmental exposure by applying a protective coating that transforms the vulnerable metal surface into a protected structure. The protective layer absorbs the environmental stress that would otherwise damage the bonding pads, turning the potential harm into an opportunity for enhanced reliability through deliberate protection.
2Ease of manufacture
If bonding pads are exposed to air for bonding process access, then bonding operations can be performed, but oxidation and corrosion occur reducing connection reliability
Solution Approach 1:
The protective layer is applied in advance to the bonding pads before the bonding process. This preliminary action ensures that when the bonding pads are exposed to air during bonding operations, the protective coating is already in place to prevent oxidation and corrosion, allowing easy manufacturing access without compromising reliability.
Solution Approach 2:
The protective layer creates an inert environment around the bonding pad metal, shielding it from reactive atmospheric components. This inert barrier prevents chemical reactions between the metal and environmental factors, allowing the bonding process to proceed with air exposure while maintaining metal integrity.
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 protective layer effectively shields bonding pads from environmental damage, enhancing the reliability and longevity of electrical connections in stacked integrated circuits by preventing metal oxidation and corrosion.
Implementation Method 1
This problem can cause reliability concerns with the metal material bonding pads due to metal oxidation and corrosion in open-air or other harsh environments.
Implementation Method 2
metal oxidation and corrosion in open-air or other harsh environments
Data Source
AI summary
The formation of bonding pad protective layer over exposed bonding pad materials between stacked integrated circuit (IC) dies or wafers is described in preferred embodiments in which the bonding pad protective layer is formed in the integrated process of forming wafer bonding pads. The bonding pad protective layer prevents the exposed bonding pad materials from oxidation and corrosion in open-air or other harsh environments. By providing a bonding pad protective layer on exposed bonding pad materials, significant product reliability improvement is expected on ICs having a three-dimensional “stacked-die” configuration.