Titanium-Copper Seed Layer for Thick NiFe Plating on Silicon
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Solution Overview
Problem
Current seed layers for electroplating nickel-iron layers on silicon-based substrates fail to provide sufficient adhesion and homogeneous growth, limiting the thickness of the nickel-iron layer to less than 5 micrometers due to high tensile stress, which restricts practical applications.
Innovation Solution
A layered structure comprising a titanium-copper seed layer on a silicon-based substrate, with a nickel-iron plating layer directly on the copper layer, facilitated by covalent bonds between the titanium layer and silicon, enabling thick nickel-iron layers up to 20 micrometers without adhesion compromise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of stationary object
If a conventional seed layer is used for electroplating nickel-iron layers, then the plating process can be performed, but the nickel-iron layer thickness is limited to less than 5 micrometers due to high tensile stress and adhesion failure
Solution Approach 1:
The seed layer is segmented into multiple functional layers: a titanium layer (5-20 nm) directly on the silicon substrate to form strong covalent bonds, a copper layer (50-200 nm) on top for electroplating, and optionally an intermediate layer. This segmentation allows each layer to perform its specific function optimally, enabling thick nickel-iron layers up to 20 micrometers without adhesion failure.
Solution Approach 2:
The invention uses a composite seed layer structure combining titanium and copper materials. Titanium provides strong covalent bonding to silicon substrate, while copper provides excellent electrical conductivity for electroplating. This composite approach resolves the contradiction between adhesion strength and plating functionality, enabling both thick layers and reliable attachment.
2Reliability
If the nickel-iron layer is made thicker to reduce tensile stress, then adhesion improves, but the layer becomes too thick for practical applications requiring precise magnetic field control
Solution Approach 1:
By segmenting the seed layer into titanium and copper layers with specific thicknesses, the invention enables nickel-iron layers of optimal thickness (up to 20 micrometers) that provide both sufficient adhesion strength and appropriate magnetic field control for various practical applications.
Solution Approach 2:
The invention changes the parameters of the seed layer (material composition, layer thicknesses) to achieve the optimal nickel-iron layer thickness. The titanium layer (5-20 nm) and copper layer (50-200 nm) parameters are specifically optimized to enable thick nickel-iron plating while maintaining adhesion and application suitability.
3Ease of manufacture
If a single-layer seed layer is used to simplify the structure, then manufacturing is easier, but homogeneous current distribution and lattice structure control are insufficient
Solution Approach 1:
The seed layer is segmented into titanium and copper layers, where titanium ensures strong substrate bonding and copper provides homogeneous current distribution. This segmentation achieves superior manufacturing precision in current distribution and lattice structure control while remaining manufacturable through standard thin-film deposition techniques.
Solution Approach 2:
The composite titanium-copper seed layer combines the advantages of both materials: titanium's strong bonding capability and copper's excellent electrical conductivity. This composite structure achieves homogeneous current distribution and correct lattice structure during electroplating, while the overall process remains compatible with standard manufacturing techniques.
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 solution achieves strong adhesion and homogeneous growth, allowing thicker nickel-iron layers, enhancing product lifetime and enabling applications that were previously impractical with thinner layers.
Implementation Method 1
the titanium layer is arranged on the substrate surface such that covalent bonds are formed between the titanium layer and silicon of the silicon-based substrate
Implementation Method 2
the seed layer should have suitable conductivity to enable homogeneous distribution of current in the seed layer during an electro-galvanic deposition process
Implementation Method 3
forming, by electro-galvanic deposition, a nickel-iron plating layer directly on the copper layer
Data Source
AI summary
A layered structure includes a silicon-based substrate comprising a substrate surface; a titanium-copper seed layer arranged on the substrate surface, wherein the titanium-copper seed layer comprises a titanium layer and a copper layer, wherein the titanium layer is arranged on the substrate surface such that covalent bonds are formed between the titanium layer and silicon of the silicon-based substrate, and wherein the copper layer is arranged directly on the titanium layer, such that the titanium layer is arranged between the substrate surface and the copper layer; and a nickel-iron plating layer arranged directly on the copper layer of the titanium-copper seed layer such that the titanium-copper seed layer is arranged between the silicon-based substrate and the nickel-iron plating layer.