Depletable Cathode Diode for NDMOS Integration
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Solution Overview
Problem
Conventional diodes with a quasi-vertical structure, such as Schottky diodes, require specific epi thickness and resistivity for different voltages and are not compatible with current process flows for lateral drain extension NDMOS structures, limiting their application in high voltage, low charge storage diode circuits.
Innovation Solution
The development of a depletable drain extension diode with a high breakdown voltage, where the anode is formed on a portion of the drain extension, allowing total depletion of the drain extension under the anode before junction breakdown, achieved through punch through or biased isolated islands, enabling the use of the same process steps for both NDMOS and diode fabrication.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Schottky diodes with quasi-vertical structure are used, then high voltage capability is achieved, but compatibility with lateral drain extension NDMOS process flows is lost
Solution Approach 1:
The patent merges the diode structure with the NDMOS drain extension structure, making them compatible through the same fabrication process. The diode anode is formed on the drain extension region, and the cathode is formed on the N-type island, allowing both NDMOS and diode devices to be manufactured using identical process flows without requiring separate fabrication steps.
Solution Approach 2:
The drain extension region serves dual purposes: it functions as part of the NDMOS device structure and simultaneously serves as the anode region for the diode. This multi-functionality allows the same structural elements to fulfill multiple roles, achieving both NDMOS operation and diode functionality within a unified device architecture.
2Reliability
If conventional diodes are used, then diode function is achieved, but additional process steps are required beyond NDMOS fabrication
Solution Approach 1:
The patent combines the diode fabrication steps with the NDMOS fabrication steps. The anode is formed during the drain extension formation process, the cathode is formed during the N-type island processing, and the junction is created as part of the standard NDMOS工艺流程. This merging eliminates the need for separate diode fabrication process steps.
Solution Approach 2:
The same process steps that create the NDMOS device structure also create the diode structure. The lateral drain extension formation process simultaneously forms the diode anode, and the N-type island formation simultaneously forms the diode cathode, making the process universally applicable to both device types.
3Quantity of substance
If depletable drain extension is used, then charge storage is reduced, but turn-off delay increases
Solution Approach 1:
The patent applies local quality by creating a depletable region specifically under the anode contact area while maintaining other regions of the drain extension. This localized depletion reduces charge storage in the critical area under the anode where charge accumulation would most affect diode performance, while the overall drain extension structure remains intact for NDMOS operation.
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 solution allows for the creation of high voltage diodes with low charge storage and reduced turn-off delay, compatible with existing NDMOS processes, enhancing the performance and efficiency of half bridge driver circuits without adding additional process steps.
Implementation Method 1
total depletion of the drain extension occurs under the anode before the anode to drain extension junction reaches breakdown
Implementation Method 2
total depletion of the N drain extension under the anode contact before anode to N extension junction breakdown can be achieved by use of punch through from the anode through the drain extension to an island thereunder
Data Source
AI summary
An integrated circuit device comprising a diode and a method of making an integrated circuit device comprising a diode are provided. The diode can comprise an island of a first conductivity type, a first region of a second conductivity type formed in the island, and a cathode diffusion contact region doped to the second conductivity type disposed in the first region. The diode can also comprise a cathode contact electrically contacting the cathode diffusion contact region, an anode disposed in the island, an anode contact electrically contacting the anode, and a first extension region doped to the first conductivity type disposed at a surface junction between the first region and the island.