Schottky Diode Guard Ring Overlap Reduces Stress
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Solution Overview
Problem
Schottky diodes face challenges in controlling high currents and voltages due to stress concentration between the isolation layer and guard ring, leading to leakage current variations and reduced breakdown voltage, affecting uniform characteristics across dies/wafers.
Innovation Solution
A Schottky diode design with a guard ring that overlaps the isolation layer and impurity regions with graded doping concentrations, minimizing stress concentration and impurity differences, and a well structure that enhances current path efficiency, ensuring uniform forward, leakage, and breakdown voltage characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the guard ring is spaced apart from the isolation layer by a predetermined interval, then the fabrication process is simplified, but stress is concentrated between the isolation layer and the guard ring leading to leakage current
Solution Approach 1:
The guard ring structure is merged with the isolation layer by eliminating the spacing interval between them. The guard ring is positioned to be in direct contact with or overlapping the isolation layer, which distributes the stress uniformly across the interface rather than concentrating it at a specific point, thereby preventing leakage current while maintaining fabrication simplicity
2Reliability
If the impurity doping concentration difference between the deep well and the first impurity region is increased, then the guard ring control capability is improved, but the breakdown voltage is reduced
Solution Approach 1:
The patent optimizes the impurity doping concentration parameter by applying a graded profile rather than a uniform high concentration. The doping concentration is increased locally where needed for guard ring control capability while maintaining a gradual transition to prevent abrupt junction effects that would reduce breakdown voltage, achieving a balance between control capability and voltage withstand
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 design improves forward characteristics by 40% and maintains low leakage currents and high breakdown voltage, achieving uniform performance across dies/wafers by reducing stress concentration and impurity differences, thereby controlling high currents effectively.
Implementation Method 1
The guard ring 20 includes a P-type first impurity region 19 formed on the surface of the substrate 11, and a P-type second impurity region 18 formed under the P-type first impurity region 19
Data Source
AI summary
A Schottky diode includes a deep well formed in a substrate, an isolation layer formed in the substrate, a first conductive type guard ring formed in the deep well along an outer sidewall of the isolation layer and located at a left side of the isolation layer, a second conductive type well formed in the deep well along the outer sidewall of the isolation layer and located at a right side of the isolation layer, an anode electrode formed over the substrate and coupled to the deep well and the guard ring, and a cathode electrode formed over the substrate and coupled to the well. A part of the guard ring overlaps the isolation layer.