Lateral Schottky Diode High Breakdown Voltage
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Solution Overview
Problem
Conventional vertical Schottky diodes face limitations in achieving high breakdown voltage without increasing epitaxial layer thickness, which raises costs, and low doping concentration in guard rings compromises forward current performance.
Innovation Solution
A lateral Schottky diode design featuring a substrate with a first conductivity type, an epitaxial layer of a second conductivity type, a current region, buried layers, well structures, and a guard ring with specific doping concentrations to manage reverse voltage and reduce leakage current, allowing for higher breakdown voltage without excessive epitaxial thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of the epitaxial layer is increased to improve breakdown voltage, then the breakdown voltage is improved, but the manufacturing cost increases and the thickness cannot be increased infinitely
Solution Approach 1:
The patent transitions from a vertical Schottky diode structure to a lateral Schottky diode structure. In the lateral structure, the current flows horizontally through the epitaxial layer rather than vertically through its thickness. This dimensional change allows the breakdown voltage to be determined by the lateral distance between the anode and cathode regions rather than by the epitaxial layer thickness, enabling high breakdown voltage without increasing epitaxial thickness and thus avoiding increased manufacturing cost.
Solution Approach 2:
The patent introduces a guard ring structure with specific doping concentration positioned at the edge of the cathode region. This local modification creates a field effect that extends the depletion region laterally, enhancing the breakdown voltage at critical edge regions without requiring uniform increase of epitaxial thickness across the entire device, thereby improving breakdown voltage while controlling manufacturing cost.
2Reliability
If the doping concentration of the P-type guard ring structure is decreased to improve breakdown voltage, then the breakdown voltage is improved, but the forward current performance deteriorates
Solution Approach 1:
The patent applies different doping concentrations to different regions: the guard ring structure uses low doping concentration (1E16 to 1E18 atoms/cm³) to enhance breakdown voltage at edge regions, while the main current path regions (anode and cathode regions) maintain higher doping concentrations to ensure good forward current performance. This spatial differentiation of doping concentrations allows simultaneous optimization of both breakdown voltage and forward current characteristics.
Solution Approach 2:
The patent segments the doping structure into distinct regions with different doping concentrations: the guard ring region with low doping for high breakdown voltage, and the current path regions with higher doping for low forward resistance. This segmentation allows each region to be optimized independently for its specific function, resolving the contradiction between breakdown voltage and forward current performance.
Data Source
AI summary
A lateral diode with high breakdown voltage capability and a method for forming the lateral diode. The lateral diode has an anode, a cathode, a substrate having a first conductivity type, an epitaxial layer having formed on the substrate, a current region formed in the epitaxial layer and on the substrate, a first well coupled to the anode, a second well coupled to the cathode, a third well with light doping concentration formed beside the first well, and a guard ring with heavy doping concentration formed in the first well and beside the third well, and between the third well and the second well is a drift region, a lateral breakdown occurs in the third well, the drift region and the second well when a reverse voltage added on the lateral diode is equal to or higher than a breakdown voltage.