Semiconductor Wire with Nanograin Cladding for Strength and Conductivity
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Solution Overview
Problem
Conventional wire structures for semiconductor devices face challenges in achieving a balance between strength and conductivity, as the process of drawing wires increases mechanical strength but also resistivity, and annealing to recover conductivity weakens the material, leading to reliability issues during wire bond operations.
Innovation Solution
A wire structure comprising an elongate flexible core with a cladding layer of conducting material, where the core has a significantly larger grain size than the cladding layer, and the cladding layer is formed of nanograin materials to enhance mechanical strength and conductivity while maintaining the core's native resistivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If wire drawing operation is performed to increase mechanical strength, then the grain size is reduced and strength is improved, but the resistivity increases due to grain alignment
Solution Approach 1:
The wire is divided into two distinct layers: a core layer that has been drawn to achieve high strength, and a cladding layer that restores conductivity. The cladding layer segments the harmful effect of grain alignment by providing a separate conductive pathway with randomized grain structure.
Solution Approach 2:
The wire employs a composite structure combining two materials with different properties: the core material provides mechanical strength while the cladding material provides electrical conductivity. This composite approach allows both strength and conductivity requirements to be satisfied simultaneously.
2Reliability
If annealing is performed to recover conductivity by enlarging grains, then the resistivity decreases, but the mechanical strength is weakened making the wire prone to breaking
Solution Approach 1:
The wire structure separates the functions of strength and conductivity into different layers. The core layer maintains the drawn, high-strength microstructure while the cladding layer provides the annealed, high-conductivity microstructure, eliminating the need to anneal the entire wire.
Solution Approach 2:
Different regions of the wire have different microstructural qualities optimized for their specific functions. The core has a fine-grained drawn structure for strength, while the cladding has a coarse-grained annealed structure for conductivity. Each layer's properties are locally optimized without compromising the other.
3Strength
If dopants are introduced to strengthen the wire, then the mechanical strength is improved, but the wire becomes brittle and excess dopants may further harden the wire
Solution Approach 1:
The need for dopant strengthening is extracted from the core material and replaced by the cladding layer structure. The core can remain pure or lightly doped, maintaining ductility, while the cladding layer provides the necessary strength through its microstructure rather than heavy doping.
Solution Approach 2:
Instead of changing the chemical composition through dopant addition, the strength is achieved by changing the physical microstructure parameters - specifically the grain size and layer configuration. The cladding layer's fine-grained structure provides strength without the brittleness associated with heavy doping.
4Strength
If wire diameter is increased to meet strength requirements, then the mechanical strength is sufficient, but the wire dimension is larger than necessary for signal carrying
Solution Approach 1:
The wire cross-section is segmented into functional zones: the core provides strength with a smaller diameter than conventional wires, while the cladding adds minimal thickness to restore conductivity. This segmentation allows the wire to be thinner overall while meeting both strength and conductivity requirements.
Solution Approach 2:
The composite structure allows optimization of each layer's thickness for its specific function. The core can be thin since it only needs to provide structural integrity, while the cladding adds minimal thickness to provide the conductive pathway, resulting in an overall thinner wire than conventional solid-wire designs.
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 proposed wire structure achieves improved mechanical strength and reliability with minimal impact on conductivity, allowing for thinner wires that can carry high-frequency signals without compromising strength or performance.
Implementation Method 1
The annealed wire can break easily by grain boundary sliding
Implementation Method 2
The alignment of the grains detrimentally increases the resistivity of the drawn material from its native value
Data Source
AI summary
A wire structure, which may be configured for a semiconductor device, is disclosed. The wire may include an elongate flexible core formed of a conductor material and a cladding layer covering an outer surface of the core. The cladding layer may be a conductor. In various aspects the cladding layer and core have different grain sizes. An average grain size of the core material may be several orders of magnitude greater than an average grain size of the cladding layer material. The cladding layer may be an alloy having a varying concentration of a minor component across its thickness. Methods of forming a wire structure are also disclosed.