MPS Diode Graded Doping Layout for Lower Voltage Drop
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Solution Overview
Problem
Merged-PiN Schottky (MPS) diodes face challenges with high on-state voltage drop and limited forward surge current capability due to non-uniform current distribution, leading to local heating and premature breakdown.
Innovation Solution
Incorporating a doped region with a decreasing dopant concentration from the center to the edge of the active area, forming PN junctions with wells, to enhance current uniformity and reduce voltage drop, thereby improving on-state voltage and forward surge current capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a uniform doping concentration is used in the drift region, then the manufacturing process is simple, but the current distribution is non-uniform leading to high on-state voltage drop
Solution Approach 1:
The drift region is divided into multiple zones with different doping concentrations: a first doped region with higher concentration and a second doped region with lower concentration. This local quality variation optimizes current distribution across the active area, reducing on-state voltage drop while maintaining manufacturing feasibility through selective doping processes.
Solution Approach 2:
The doping concentration parameter is changed spatially within the drift region, transitioning from a uniform concentration to a graded concentration profile. The first doped region has a higher dopant concentration than the second doped region, creating optimal electric field distribution and current flow characteristics that reduce voltage drop.
2Device complexity
If a uniform doping concentration is used in the drift region, then the device structure is simple, but the forward surge current capability is limited due to local heating
Solution Approach 1:
Different regions of the drift region are assigned different doping concentrations to address local heating issues. The first doped region with higher concentration handles high current density areas, while the second doped region with lower concentration manages areas prone to heating, thereby improving forward surge current capability and reliability.
Solution Approach 2:
The dopant concentration parameter is varied across the drift region to optimize thermal and electrical performance under surge conditions. This parameter change enables better heat dissipation and current distribution, enhancing the device's ability to handle forward surge currents reliably.
3Loss of energy
If the dopant concentration is increased uniformly in the drift region, then the voltage drop is reduced, but the breakdown voltage decreases due to premature breakdown
Solution Approach 1:
The drift region employs non-uniform doping with a first doped region having higher concentration and a second doped region having lower concentration. This local differentiation allows voltage drop reduction in high-current areas while maintaining adequate breakdown voltage in regions where high doping would cause premature breakdown.
Solution Approach 2:
The dopant concentration parameter is optimized locally rather than uniformly across the entire drift region. By implementing a graded doping profile with varying concentrations, the patent achieves reduced voltage drop without compromising breakdown voltage, as each region's doping level is tailored to its specific electrical and thermal conditions.
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 solution increases current uniformity across the active area, reducing voltage drop and enhancing the MPS diode's power handling capabilities by optimizing the dopant concentration profile and well arrangement.
Implementation Method 1
The drift region comprises a doped region surrounding each of the plurality of wells, the doped region having a higher dopant concentration than a remainder of the drift region, wherein, in a first direction from a center of the doped region to an edge of the doped region, the dopant concentration in the doped region decreases
Implementation Method 2
each well forming a respective PN-junction with the drift region. Depending on a forward voltage applied to the first and second terminal, MPS diode 100 may be operable in several modes. At lower voltages, MPS diode 100 may operate in a first mode, a depletion region of said PN junctions extends between adjacent wells
Data Source
Figure 1
Figure 2A~2B
Figure 3~4
AI summary
Aspects of the present disclosure generally relate to an MPS diode and a manufacturing method therefor. The MPS diode comprises a semiconductor body including an active area, wherein the active area comprises a drift region of a first conductivity type, and a plurality of wells of a second conductivity type different from the first conductivity type, the plurality of wells being mutually spaced apart, each well forming a respective PN-junction with the drift region. The MPS diode further comprises a metal layer assembly arranged on a surface of the semiconductor body and comprising at least one metal layer, the metal layer assembly forming a plurality of Schottky contacts together with the drift region and a plurality of respective Ohmic contacts with the plurality of wells. The drift region comprises a doped region surrounding each of the plurality of wells, the doped region having a higher dopant concentration than a remainder of the drift region. The dopant concentration in the doped region decreases in a first direction from a center of the doped region to an edge of the doped region.