Contact Pad Passivation Stack for IC Reliability
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Solution Overview
Problem
Existing methods for processing contact pads on integrated circuit elements do not effectively protect the pads from aggressive processing steps and ensure reliable bonding, as they lack a robust protective and reinforcement strategy.
Innovation Solution
A method involving the formation of a passivation layer stack with multiple layers, followed by selective removal and patterning, and the deposition of a reinforcement layer stack, which includes layers like nickel, palladium, and gold, to protect and reinforce the contact pads, preventing material diffusion and ensuring stable bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a single-layer passivation structure is used, then the manufacturing process is simple, but the contact pad is not adequately protected from aggressive processing steps and material diffusion
Solution Approach 1:
The passivation structure is divided into multiple layers (first passivation layer, second passivation layer, third passivation layer) with different functions. The first layer provides diffusion barrier, the second layer provides mechanical protection and planarization, and the third layer provides chemical resistance. This segmentation allows each layer to be optimized for its specific protective function while maintaining overall manufacturing feasibility.
2Ease of manufacture
If the passivation layer is completely removed from the contact pad region, then subsequent bonding layers can be formed directly, but the contact pad becomes vulnerable to damage and contamination during processing
Solution Approach 1:
The method performs preliminary protective actions by forming the multi-layer passivation structure before any aggressive processing steps. The passivation layers are prepared in advance to prevent contamination and damage to the contact pad during subsequent adhesion layer formation, patterning, and other processing steps, eliminating the need to completely remove passivation material.
3Manufacturing precision
If aggressive etching is used to remove passivation material, then the passivation can be effectively removed, but the contact pad metal may be damaged or dissolved
Solution Approach 1:
The adhesion layer serves as an intermediary between the passivation structure and the bonding layers. It is formed on the passivation layers rather than directly on the contact pad metal, allowing aggressive processing steps to be performed on the adhesion and passivation layers without exposing the contact pad metal to damaging conditions. This intermediary layer protects the metal while enabling effective passivation removal.
4Adaptability or versatility
If incompatible materials like polyimides are used for adhesion layers, then versatile bonding options are available, but the materials may react with or contaminate the contact pad metal
Solution Approach 1:
The passivation layers act as intermediaries that allow incompatible materials like polyimides to be used in the adhesion layer without direct contact with the contact pad metal. The passivation layers provide a barrier that prevents harmful reactions and contamination, enabling the use of versatile bonding materials that would otherwise be incompatible with the metal contact pad.
Data Source
AI summary
An integrated circuit includes a substrate. A surface region of the substrate includes a contact pad region. A passivation layer stack includes at least one passivation layer. The passivation layer stack is formed over the surface region and adjacent to the contact pad region. An upper portion of the passivation layer stack is removed in, in a portion of the passivation layer stack proximate the contact pad region.