Merged P-i-N Schottky Diode Shallow Diffusion Array
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Solution Overview
Problem
Semiconductor devices with shallow diffusion wells, such as Fast Recovery Epitaxial Diodes, struggle to absorb reverse avalanche energy effectively due to localized high electric field 'hot spots' near the corners of shallow diffusion wells, resulting in lower breakdown voltages compared to ideal bulk values.
Innovation Solution
The use of an array of P+ diffusion stripes spaced wider apart in a Merged P-i-N Schottky (MPS) device allows for improved absorption of reverse avalanche energy, enabling the device to withstand breakdown voltages comparable to those with deeper diffusion wells, while being manufactured at lower temperatures and costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If shallow diffusion wells are used in FRED devices, then manufacturing complexity and cost are reduced, but the device cannot effectively absorb reverse avalanche energy and breakdown voltage is lowered
Solution Approach 1:
The single deep diffusion well is segmented into multiple shallow diffusion wells arranged in an array. This segmentation allows the device to achieve the required reverse avalanche energy absorption capability through the collective effect of multiple shallower structures, each easier to manufacture, while maintaining the overall performance of a deeper well structure.
Solution Approach 2:
Multiple shallow diffusion wells are merged into a single integrated structure that functions collectively to absorb reverse avalanche energy. The combined effect of the array of shallow wells achieves the energy absorption capability previously requiring a single deep well, resolving the contradiction between manufacturing ease and reliability.
2Reliability
If deep diffusion wells are used to absorb reverse avalanche energy, then breakdown voltage and energy absorption capability are improved, but manufacturing temperature and process complexity increase
Solution Approach 1:
The deep diffusion well structure is segmented into multiple shallow wells that can be manufactured at lower temperatures. Each individual shallow well requires lower manufacturing temperature, but their array configuration collectively achieves the breakdown voltage and energy absorption of a single deep well.
Solution Approach 2:
The diffusion depth parameter is changed from deep to shallow for each individual well, while the number of wells parameter is increased to compensate. This parameter transformation allows manufacturing at lower temperatures while maintaining the required electrical performance through the increased quantity of shallower structures.
3Ease of manufacture
If shallow diffusion wells are used, then manufacturing cost is reduced, but localized high electric field hot spots occur near diffusion well corners
Solution Approach 1:
The single deep diffusion well is segmented into multiple shallow diffusion wells with optimized spacing and geometry. This segmentation distributes the electric field more uniformly across the device structure, eliminating the localized hot spots that occur at the corners of single deep wells while maintaining manufacturing cost advantages.
Solution Approach 2:
The geometry and spacing of each shallow diffusion well in the array is optimized to achieve uniform electric field distribution. By carefully designing the local characteristics of each well and their relative positions, the harmful localized high electric field hot spots are eliminated while maintaining the manufacturing advantages of shallow structures.
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 MPS device with shallower diffusion stripes spaced farther apart demonstrates enhanced capability to absorb reverse avalanche energy, achieving comparable breakdown voltage and avalanche energy to devices with deeper diffusion wells, while reducing manufacturing complexity and cost through lower temperature processing.
Implementation Method 1
improved absorption of reverse avalanche energy, enabling the device to withstand breakdown voltages
Implementation Method 2
Merged P-i-N Schottky (MPS) diode
Data Source
AI summary
A Merged P-i-N Schottky device in which the oppositely doped diffusions extend to a depth and have been spaced apart such that the device is capable of absorbing a reverse avalanche energy comparable to a Fast Recovery Epitaxial Diode having a comparatively deeper oppositely doped diffusion region.