Conductor Bump Protective Layer for Semiconductor Singulation
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Solution Overview
Problem
The semiconductor industry faces challenges in forming metal bumps on semiconductor dies that are easily removable during the singulation process, leading to difficulties in attaching the dies to external structures.
Innovation Solution
A method involving the formation of conductor bumps with a protective layer etched at a slower rate than the bump material, which minimizes material removal during singulation and facilitates strong mechanical and low resistance electrical connections by using a gold-tin alloy for the bumps and a gold or tin-based protective layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If metal bumps are formed on semiconductor die using conventional methods, then interconnection to external structures is enabled, but portions of the bump material are removed during die singulation making attachment difficult
Solution Approach 1:
The patent applies a protective layer to the bump structure before the singulation process. This preliminary protective action prevents bump material loss during subsequent etching operations, ensuring the bump material remains intact for reliable attachment to external structures.
Solution Approach 2:
The protective layer acts as an intermediary between the bump material and the etchant used during singulation. This intermediary layer is etched at a slower rate than the bump material, providing differential protection that preserves the bump structure while allowing the substrate to be removed.
2Productivity
If bump material is removed during singulation, then die separation is achieved, but attachment to external structures becomes difficult
Solution Approach 1:
The patent creates different etching rates for different regions of the device. The protective layer has a slower etching rate than the bump material, which itself etches slower than the substrate. This local quality differentiation enables selective removal of substrate material during singulation while preserving the bump structures for subsequent attachment operations.
3Device complexity
If conventional bump structures are used, then simple formation process is maintained, but strong mechanical and electrical connections are not achieved
Solution Approach 1:
The patent employs a composite bump structure consisting of multiple materials with different etching rates. The bump material (e.g., gold-tin alloy) is combined with a protective layer (e.g., gold or tin-based) that etches at a different rate. This composite structure provides both mechanical strength for reliable attachment and electrical conductivity, while the differential etching rates enable selective material removal during processing.
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
This approach reduces the amount of bump material removed during singulation, ensuring reliable attachment and electrical connectivity between semiconductor dies and external structures.
Implementation Method 1
forming a protective layer on an outer surface of the conductor bump wherein the protective layer is etched at a slower rate than the bump material by the etchant
Data Source
AI summary
In one embodiment, a conductor bump is formed on an under bump conductor of a semiconductor device to extend a first distance away from a surface of the under bump conductor including forming a protective layer on an outer surface of the conductor bump wherein the plurality of semiconductor dies are subsequently singulated by etching through the semiconductor substrate with an etchant and wherein the protective layer protects the conductor bump from the etchant.