Vertical Schottky Diode Layout for High Current in Small IC Area
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Solution Overview
Problem
Existing Schottky diodes face challenges in achieving a small area while maintaining high forward current, low forward resistance, and high breakdown voltage, particularly in integrated circuit applications, which are exacerbated by the drive towards miniaturization.
Innovation Solution
The Schottky diode design incorporates a vertical depleted region between a deep p-well and an n-type channel region, providing a conductive path for forward current and pinch-off for reverse current, with an annular layout compatible with standard bipolar-CMOS-DMOS fabrication workflows, using ion implantation to form doped regions without additional steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of moving object
If the Schottky diode area is reduced for miniaturization, then the device size decreases, but the forward current decreases and forward resistance increases
Solution Approach 1:
The patent transitions from a planar Schottky diode structure to a vertical three-dimensional structure by introducing a deep p-well extending beneath the n-type region. This vertical configuration allows the current to flow through multiple dimensions (vertical and lateral), effectively increasing the conductive path length and active volume without proportionally increasing the surface area footprint, thereby maintaining high forward current in a miniaturized device.
Solution Approach 2:
The deep p-well is nested within the n-type region, creating a layered vertical structure where the p-well extends downward beneath the n-type region. This nested configuration allows the diode to pack more functional elements into a smaller vertical space, increasing the effective active area for current conduction without increasing the lateral footprint, thus resolving the contradiction between miniaturization and forward current maintenance.
2Strength
If interspersed opposite doping regions are added to increase breakdown voltage, then the breakdown voltage increases, but the effective Schottky barrier diode area decreases
Solution Approach 1:
Instead of distributing opposite doping regions laterally across the Schottky barrier area (which would reduce the effective area), the patent places the p-type doping vertically beneath the n-type region in the form of a deep p-well. This vertical placement provides breakdown voltage enhancement through the vertical field effect while preserving the lateral extent of the Schottky barrier area, thus maintaining both high breakdown voltage and large effective area.
3Productivity
If a vertical depleted region is created with deep p-well, then forward current and breakdown voltage are improved, but device complexity increases
Solution Approach 1:
The deep p-well structure serves multiple functions simultaneously: it creates the vertical depleted region for high breakdown voltage, provides an additional conductive path for high forward current, and enables lateral pinch-off for reverse current suppression. By making this single structural element multi-functional, the patent achieves multiple performance improvements without proportionally increasing device complexity.
Solution Approach 2:
The patent merges the functions of breakdown voltage enhancement and forward current conduction into a single deep p-well structure. Traditionally, these would require separate structural elements, but here the deep p-well simultaneously provides the vertical field for breakdown control and the conductive channel for current flow, simplifying the overall device architecture while achieving multiple performance goals.
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 achieves high forward current and low forward resistance while maintaining high breakdown voltage, suitable for integrated circuits, with efficiency confirmed by TCAD simulations and experimental measurements.
Implementation Method 1
an interface between the anode and the n-type region comprises a Schottky barrier
Implementation Method 2
using ion implantation to form doped regions
Implementation Method 3
providing a conductive path for forward current
Implementation Method 4
providing pinch-off for reverse current
Data Source
AI summary
A Schottky diode includes an n-type region, an anode disposed on the n-type region, a buried p-type region, and a shallow p-type region. An interface between the anode and the n-type region forms a Schottky barrier. An n-type channel portion of the n-type region is disposed between the buried p-type region and the shallow p-type region. The anode may also contact the annular shallow p-type region. In an annular configuration, the buried p-type region and the shallow p-type region are annular regions, and the n-type region includes a central portion encircled by the annular shallow p-type region and an annular peripheral portion of the n-type region which encircles the annular shallow p-type region. In one application, a buck converter includes the Schottky diode.