Power Schottky Diodes with Closely-Spaced Deep Blocking Junctions
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Solution Overview
Problem
Conventional power Schottky diodes face a tradeoff between forward voltage and reverse leakage current, with increased reverse blocking voltage leading to higher on-state resistance and reverse leakage, and challenges in fabricating devices with small channel widths due to doping variations and ion implantation mask inaccuracies.
Innovation Solution
The design incorporates a highly doped drift region with deeper and more closely spaced blocking junctions, increasing doping concentration and reducing channel widths to enhance electric field blocking while maintaining low forward voltage, achieved through high energy ion implantation and precise depth control of blocking junctions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the reverse blocking voltage rating is increased by reducing the doping concentration and/or increasing the thickness of the drift region, then the reverse blocking voltage is improved, but the on-state resistance increases
Solution Approach 1:
The drift region is segmented into multiple regions with different doping concentrations: a first drift region with higher doping concentration (1×10^16 to 1×10^17 atoms/cm³) and a second drift region with lower doping concentration (1×10^15 to 1×10^16 atoms/cm³). This segmentation allows the device to achieve both low on-state resistance (through the heavily doped first drift region) and high reverse blocking voltage (through the lightly doped second drift region with increased thickness)
Solution Approach 2:
Different regions of the drift region are assigned different doping concentrations to optimize local functions: the first drift region near the Schottky contact is heavily doped to reduce contact resistance and on-state voltage drop, while the second drift region is lightly doped and thicker to provide high reverse blocking voltage capability
2Area of stationary object
If the channel width is reduced to decrease device size, then the device area is improved, but manufacturing precision deteriorates due to doping variations and ion implantation mask inaccuracies
Solution Approach 1:
The channel definition is transitioned from a purely lateral dimension (defined by photolithography mask width) to include a vertical dimension (defined by the depth of the blocking junction). The blocking junction depth of 1-3 microns provides a three-dimensional reference that constrains the electric field and stabilizes channel characteristics, compensating for lateral dimensional variations caused by photolithography tolerances
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 results in a 25% reduction in device size while maintaining desired reverse blocking voltage and forward voltage, with improved high-temperature performance and reduced reverse leakage currents, achieving lower forward voltage drops and smaller chip size compared to conventional Schottky diodes.
Implementation Method 1
achieved through high energy ion implantation and precise depth control of blocking junctions
Data Source
AI summary
A Schottky diode includes a drift region, a channel in an upper portion of the drift region, and first and second adjacent blocking junctions in the upper portion of the drift region that define the channel therebetween. The drift region and channel are doped with dopants having a first conductivity type, and the first and second blocking junctions doped with dopants having a second conductivity type that is opposite the first conductivity type. The blocking junctions extend at least one micron into the upper portion of the drift region and are spaced apart from each other by less than 3.0 microns.