Semiconductor Transformer Windings for Thermal Stress Reduction
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Solution Overview
Problem
Traditional transformers with metallic windings face challenges in integration with semiconductor circuits due to thermal expansion mismatches and costly metal-semiconductor interfaces, limiting their integration into semiconductor-based integrated circuits.
Innovation Solution
The use of highly doped semiconductor materials for primary and secondary windings, integrated into a silicon-on-insulator structure with silicides or salicides to enhance conductivity while minimizing thermal expansion issues, allowing for full integration into semiconductor circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If metallic conductors (aluminum or copper) are used for spiral windings on semiconductor surface, then electrical conductivity is improved, but thermal expansion mismatch causes high mechanical stress and track breakage
Solution Approach 1:
The patent changes the material parameter from metal to highly doped semiconductor, fundamentally altering the thermal expansion coefficient to match the silicon substrate. This parameter change eliminates the thermal expansion mismatch problem while maintaining adequate electrical conductivity through heavy doping
Solution Approach 2:
The patent uses homogeneous semiconductor material (highly doped silicon) for both the windings and substrate, ensuring uniform thermal expansion characteristics throughout the structure. This homogeneity prevents mechanical stress and delamination that occur with heterogeneous metal-semiconductor interfaces
2Ease of manufacture
If metallic materials are deposited on semiconductor to form transformer windings, then transformer functionality is achieved, but manufacturing complexity and cost increase due to metal-semiconductor interface requirements
Solution Approach 1:
The patent makes the semiconductor material serve multiple functions: as the substrate, as the winding conductor, and as the structural medium. This eliminates the need for separate metal deposition and interface management processes, simplifying manufacturing while achieving transformer functionality
Solution Approach 2:
The patent extracts the metal layer from the transformer structure, removing the complex metal-semiconductor interface process entirely. The transformer windings are formed directly in the semiconductor material through doping, eliminating the need for metal deposition, patterning, and interface management steps
3Power
If planar transformer structure with long spiral windings is used, then voltage transformation is achieved, but current path length increases causing higher resistance and power loss
Solution Approach 1:
The patent changes the electrical conductivity parameter of the winding material through heavy doping, increasing carrier concentration by several orders of magnitude. This parameter change compensates for the long current path length, reducing resistive power loss while maintaining the planar transformer structure and voltage transformation capability
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 enables the fabrication of semiconductor transformers that can be fully integrated into electronic circuits, reducing manufacturing costs, stray components, and circuit noise, while improving power density and compactness, and minimizing mechanical stress.
Implementation Method 1
the primary and secondary windings comprise highly doped conducting paths in a semiconductor material
Implementation Method 2
The highly doped conducting paths may include silicides or salicides in order to increase the conductivity of the tracks without substantially increasing the thermal expansion coefficients
Implementation Method 3
Traditional transformers are 'electromagnetic devices' because each of them consists of a magnetic core and copper windings
Data Source
AI summary
A planar transformer structure, which can be constructed in an integrated semiconductor circuit without using traditional metallic windings. To avoid large thermal expansion of metallic spiral windings and associated mechanical stress on a metal-semiconductor interface, it is suggested that highly doped semiconductor materials with or without silicides and salicides can be used to form windings or conducting paths because their thermal expansion coefficients are similar to that of semiconductor material. The planar semiconductor transformer may find application for low-power and signal transfer that needs electrical isolation.