Semiconductor Pad Metallization for Defect-Free Small-Area Bonding
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Solution Overview
Problem
The existing techniques for forming metal films on semiconductor devices using a plating method result in nickel welling out, gold deposition failures, and excessive zinc deposition on small area pad electrodes, leading to wire bonding defects.
Innovation Solution
A semiconductor device and manufacturing method where a dielectric layer with specific openings exposes different conductive layers, allowing an electroless plating process to form a nickel-aluminum-gold structure without intermediate layers, reducing nickel welling and zinc deposition issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a plating method is used to form metal films on both large area source pad electrode and small area gate pad electrode simultaneously, then both electrodes can be processed in one step, but nickel welling out, gold deposition failure, and excessive zinc deposition occur causing wire bonding defects
Solution Approach 1:
The patent divides the pad electrodes into two groups: source pad electrodes (large area) and gate pad electrodes (small area). Different metal film formation processes are applied to each group - plating method for source pads and sputtering method for gate pads. This segmentation resolves the contradiction by allowing each electrode type to receive optimized processing appropriate to its specific requirements, preventing deposition defects while maintaining overall processing efficiency.
Solution Approach 2:
The patent applies different metal film formation methods tailored to specific locations: plating for large area source pads and sputtering for small area gate pads. This local quality approach ensures that each region receives the treatment best suited to its characteristics, achieving uniform and defect-free metal film deposition across the entire device surface.
2Stability of the object's composition
If a plating method is used to form metal films on pad electrodes, then a continuous metal film can be formed, but nickel welling out from the gold layer surface occurs due to thermal history
Solution Approach 1:
The patent applies sputtering method specifically to gate pad electrodes (small area) where wire bonding is performed, instead of using plating method. This local quality approach prevents nickel welling out and ensures proper metal film composition and structure for reliable wire bonding, while plating method continues to be used for source pad electrodes where it provides adequate performance.
3Productivity
If a plating method is used to form metal films on small area gate pad electrode, then deposition can be completed in one step, but undeposition (deposition failure) of the gold layer on the palladium layer occurs
Solution Approach 1:
The patent applies sputtering method to gate pad electrodes (small area) instead of plating method. This local quality approach ensures complete and uniform gold layer deposition on the small area pads, preventing deposition failures that occur with plating method, while accepting the additional processing time as necessary for achieving defect-free results on critical bonding areas.
4Stability of the object's composition
If a plating method is used to form metal films on pad electrodes, then a laminated structure can be formed, but excessive deposition of zinc occurs leading to wire bonding defects
Solution Approach 1:
The patent applies sputtering method to gate pad electrodes (small area) where wire bonding is performed, instead of plating method. This local quality approach prevents excessive zinc deposition and ensures proper metal film composition for reliable wire bonding. The sputtering process provides better control over film composition and prevents the zinc deposition issues that plague plating processes on small area pads.
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 minimizes wire bonding defects by ensuring proper deposition on both large and small area pad electrodes, enhancing bonding reliability and current flow.
Implementation Method 1
A plating layer is formed on the first pad region of the first layer exposed from the first opening by an electroless plating method
Data Source
AI summary
A dielectric layer has a first opening exposing a surface of a first conductive layer and a second opening exposing a surface of a second conductive layer and having an opening area smaller than an opening area of the first opening. A material of the surface of the second conductive layer exposed from the second opening is different from a material of the surface of the first conductive layer exposed from the first opening, and includes aluminum.