Conductive Bump UBM Layer Insulating Barrier
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Solution Overview
Problem
Conventional flip chip packaging processes face challenges in achieving stable conductive bumps due to poor quality control of Under Bump Metal (UBM) layers, leading to instability and increased manufacturing costs, particularly because the insulating layer is unnecessary after bump formation and requires additional steps for removal.
Innovation Solution
A conductive structure for semiconductor chips is developed, featuring a patterned insulating layer that exposes a smaller second opening, allowing the UBM layer to cover the conductive bump and pad, enhancing stability and electrical connection, while the patterned insulating layer is retained as a barrier, reducing manufacturing steps and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the insulating layer is removed after bump formation, then the manufacturing process can proceed to UBM etching, but additional steps and costs are incurred for photoresist removal and surface cleaning
Solution Approach 1:
The patent extracts the insulating layer removal step from the manufacturing process by designing the insulating layer to remain in place. The UBM etching process is modified to selectively remove UBM only in regions where the insulating layer is absent, eliminating the need for separate photoresist removal and surface cleaning steps.
Solution Approach 2:
The insulating layer serves multiple functions: it acts as a barrier during bump formation, defines the bump pattern, and continues to serve as a protective and insulating layer after bump formation. By retaining the insulating layer, the process eliminates additional removal steps while maintaining its functional benefits throughout the manufacturing process.
2Ease of manufacture
If the UBM layer bonds only through surface contact with the pad and bump, then the bonding process is simple, but cracks easily occur leading to unstable conductive effect
Solution Approach 1:
The patent transitions from surface-only bonding to three-dimensional bonding by forming the UBM layer in a recessed region beneath the insulating layer. This allows the UBM to bond to the pad through both surface contact and side wall contact, creating a multi-dimensional bond structure that significantly enhances bonding strength and conductive stability.
Solution Approach 2:
The UBM layer is nested within a recessed region formed in the insulating layer, creating a layered structure where the UBM is surrounded by the insulating layer on multiple sides. This nested configuration provides mechanical support and enhances the bonding interface between the UBM, pad, and bump, preventing crack formation.
3Reliability
If the UBM layer consists of two metal layers for adhesion, then conductivity is achieved, but poor quality control leads to cracks between UBM and bump or pad
Solution Approach 1:
The patent applies different metal layers with specific properties at different locations within the UBM structure. The first and second metal layers are strategically positioned to provide both electrical conductivity and mechanical adhesion, with each layer optimized for its specific function in the bonding interface between pad, UBM, and bump.
Solution Approach 2:
The UBM layer is constructed as a composite structure with multiple metal layers, each providing different functional properties. This composite material approach combines the advantages of different metals to achieve both excellent electrical conductivity and strong mechanical bonding, eliminating the cracks that occur with single-layer or poorly controlled multi-layer structures.
Data Source
AI summary
A conductive structure for a semiconductor chip and a method for forming the conductive structure are provided. The semiconductor chip comprises a semiconductor substrate, a pad, a passivation layer and a patterned insulating layer. The patterned insulating layer is disposed on the passivation layer and partially and directly covers the first opening of the pad to expose a second opening. The conductive structure comprises an under bump metal (UBM) layer and a conductive bump. The UBM layer is disposed in the second opening defined by the patterned insulating layer and is electrically connected to the pad. The conductive bump is disposed on the UBM layer and is electrically connected to the UBM layer. The upper surface of the conductive bump is greater than the upper surface of the patterned insulating layer, while the portion of the conductive bump disposed in the second opening is covered by the UBM layer.