Redistribution Layer Protection During Seed Layer Etch Back
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Solution Overview
Problem
Existing redistribution layers in semiconductor integrated circuits face issues with unsatisfactory etching selectivity, leading to damage and loss of conductive features, resulting in increased resistance.
Innovation Solution
A protective structure, which can be single, dual, or tri-layered, is formed over the conductive features before the etch back process, using materials like silicon nitride to prevent damage during etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If etching is performed to remove the seed layer below conductive features, then electrical isolation of conductive features is achieved, but damage to or loss of conductive features occurs due to unsatisfactory etching selectivity
Solution Approach 1:
A protective layer is introduced as an intermediary between the etching process and the conductive features. This protective layer is selectively removed after etching, allowing precise control of the etching process while preventing damage to the conductive features. The protective layer acts as a mediator that enables the etching to proceed without directly exposing the conductive features to harmful etchants.
Solution Approach 2:
The protective layer is formed before the etching process to preemptively protect the conductive features. This preliminary action ensures that when the etching occurs, the conductive features are already shielded, preventing any potential damage before it can happen.
2Reliability
If conductive features are formed by depositing a seed layer and then forming metal features over it, then higher conductivity is achieved, but the seed layer must be etched back which risks damaging the conductive features
Solution Approach 1:
The protective layer serves as an intermediary that allows the seed layer to be etched away while preventing the etchant from reaching and damaging the highly conductive metal features. This enables the necessary removal of the seed layer for electrical isolation without compromising the integrity of the conductive features formed over it.
Solution Approach 2:
The protective layer is deposited before the seed layer etching process to preemptively safeguard the conductive features. This preliminary protective measure ensures that the subsequent etching operation can proceed with confidence that the conductive features will not be damaged, maintaining manufacturing precision.
3Reliability
If the seed layer is etched back to isolate conductive features, then electrical isolation is achieved, but resistance increases due to loss of conductive feature volume
Solution Approach 1:
The protective layer acts as a mediator during the etching process, preventing direct contact between the etchant and the conductive features. This intermediary protection ensures that the conductive feature volume is preserved, maintaining low resistance while still achieving the necessary electrical isolation through selective seed layer removal.
Solution Approach 2:
By forming the protective layer before etching, the conductive features are preemptively protected from volume loss. This preliminary action ensures that when the seed layer is removed for electrical isolation, the conductive features retain their full volume and conductivity, preventing any increase in resistance.
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 structure effectively prevents damage to conductive features during etching, reducing resistance and maintaining feature volume, thereby improving the integrity of the redistribution layer.
Implementation Method 1
A protective structure, which can be single, dual, or tri-layered, is formed over the conductive features before the etch back process, using materials like silicon nitride to prevent damage during etching.
Implementation Method 2
The protective structure effectively prevents damage to conductive features during etching, reducing resistance and maintaining feature volume
Data Source
AI summary
Semiconductor structures and method of forming the same are provided. A semiconductor structure according to the present disclosure includes a contact feature in a dielectric layer, a passivation structure over the dielectric layer, a conductive feature over the passivation structure, a seed layer disposed between the conductive feature and the passivation structure, a protecting layer disposed along sidewalls of the conductive feature, and a passivation layer over the conductive feature and the protecting layer.