Schottky Diode Silicon Mesa JBS Wells
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Solution Overview
Problem
Existing power Schottky diodes face a trade-off between high voltage blocking capability and low on-state resistance, with previous solutions either increasing forward voltage drop or compromising on reverse blocking voltage.
Innovation Solution
Incorporating a doped silicon mesa and junction barrier Schottky (JBS) implants within the conductive channel of the diode, rather than just at the edges, to enhance both forward conductivity and reverse voltage blocking ability, while allowing for a thinner substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If JBS implants are positioned within the drift region to increase reverse blocking voltage, then reverse voltage blocking capability is improved, but forward voltage drop increases
Solution Approach 1:
The patent applies local quality by positioning JBS implants specifically within the drift region rather than uniformly across the device. This localized placement creates regions of high doping concentration (p+ and n+) that selectively enhance reverse blocking voltage where needed, while the silicide layer and metal contact provide localized pathways for low-resistance forward conduction. The differential doping creates spatially varying electrical properties that resolve the contradiction between reverse blocking and forward conduction.
Solution Approach 2:
The patent employs composite materials by combining multiple semiconductor layers with different properties: the drift region (n-type), p+ diffusion regions, n+ diffusion regions, silicide layer, and metal contact. This composite structure allows each material to contribute its unique properties - the drift region provides voltage blocking, the doped regions provide carrier generation, and the silicide/metal combination provides low-resistance contact - thereby achieving both high reverse blocking and low forward voltage drop simultaneously.
2Reliability
If JBS implants are used to improve reverse blocking characteristics, then reverse voltage capability is enhanced, but on-state performance deteriorates
Solution Approach 1:
The patent resolves this contradiction by creating local quality variations through selective doping. The p+ and n+ regions are localized within the drift region to provide reverse blocking enhancement only where electric field management is needed. The silicide layer and metal contact create localized low-resistance pathways that maintain high on-state performance. This spatial differentiation allows the device to exhibit both improved reverse blocking and maintained on-state performance.
Solution Approach 2:
The silicide layer acts as an intermediary between the metal contact and the semiconductor drift region. It provides a transition zone that facilitates low-resistance forward conduction while allowing the underlying JBS structures to maintain reverse blocking capability. The silicide layer mediates between the conflicting requirements of low forward resistance and high reverse blocking by providing a conductive pathway that does not interfere with the voltage blocking mechanism.
3Strength
If standard silicon carbide substrate is used, then device robustness is maintained, but on resistance increases
Solution Approach 1:
The patent applies parameter changes by modifying the doping concentration and distribution within the drift region. By introducing p+ and n+ diffusion regions with high doping concentrations, the electrical parameters of the drift region are changed to reduce on-resistance. The substrate thickness and doping profile are optimized to maintain mechanical robustness while achieving lower electrical resistance, thereby resolving the contradiction between strength and on-resistance.
Solution Approach 2:
The patent uses composite materials by combining the silicon carbide substrate with additional doped regions and silicide layers. This composite structure allows the substrate to provide mechanical strength and robustness, while the additional layers contribute to reducing on-resistance through enhanced carrier generation and transport. The composite material approach enables independent optimization of mechanical and electrical properties.
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 diode achieves high forward conductivity and significantly improved reverse voltage blocking, maintaining performance even with a reduced substrate thickness, supporting high reverse voltages and controlling electric fields effectively across the drift region.
Implementation Method 1
Under a forward bias, the silicon mesa provides carriers to achieve desirable forward current characteristics
Implementation Method 2
The diode achieves a considerable reverse blocking voltage by implanting junction barrier Schottky wells within the body of the diode
Implementation Method 3
Hashieh forms an array of PN junctions as adjacent diffusion regions to reduce forward barrier heights while increasing reverse blocking voltages
Data Source
AI summary
A power diode having a silicon mesa atop the drift region includes a first contact positioned on the silicon mesa. The silicon mesa is highly doped p-type or n-type, and the anode may be formed on the mesa. The mesa may include two separate silicon layers, one of which is a Schottky barrier height layer. Under a forward bias, the silicon mesa provides carriers to achieve desirable forward current characteristics. The substrate has a significantly reduced thickness. The diode achieves reverse voltage blocking capability by implanting junction barrier Schottky wells within the body of the diode. The diode utilizes a deeper portion of the drift region to support the reverse bias. The method of forming the diode with a silicon mesa includes forming the mesa within a window on the diode or by thermally or mechanically bonding the silicon layer to the drift region.