MOS Device Isolated Drain Substrate Current Injection
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Solution Overview
Problem
Conventional power MOS devices in battery-operated electronic systems experience undesired substrate current injections due to the action of the substrate diode, leading to potential latch-up and circuit function failures in control circuitry.
Innovation Solution
A metal-oxide-semiconductor (MOS) device with an isolated drain is fabricated using a semiconductor substrate with strategically formed well regions and a gate stack, which prevents the turning on of the substrate diode, thereby isolating the drain and reducing substrate current injections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional power MOS device is used in battery-operated electronic systems, then low on-resistance is achieved for efficient power distribution, but substrate current injections occur due to substrate diode action causing latch-up and circuit function failures
Solution Approach 1:
The device is segmented into multiple well regions (first well region with second conductivity type, second well region with first conductivity type, third well region with second conductivity type, and fourth well region with first conductivity type) that are interleaved and overlie the first well region. This segmentation creates isolated drain structures that prevent substrate current injection while maintaining low on-resistance for efficient power distribution in battery-operated electronic systems
Solution Approach 2:
The fourth well region acts as an intermediary structure between the first and third well regions, providing isolation that prevents substrate current injection. The interleaved well regions create a barrier that blocks the harmful substrate diode action while allowing the MOS device to function as a low on-resistance switch
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 MOS device with an isolated drain effectively prevents substrate current injections, minimizing noise and circuit failures, and is applicable in both low and higher drain voltage applications, offering improved power management in electronic systems.
Implementation Method 1
performing a first ion implant process on the portions of the semiconductor substrate exposed by the first patterned mask layer, forming a plurality of second well regions in the semiconductor substrate and defining a plurality of third well regions in the semiconductor substrate
Data Source
AI summary
A method for fabricating a metal-oxide-semiconductor (MOS) device with isolated drain. The method performing operations of: forming a first well region embedded in a portion of a semiconductor substrate; forming a first patterned mask layer over the semiconductor substrate, exposing portions of the semiconductor substrate; performing a first ion implant process on the portions of the semiconductor substrate exposed by the first patterned mask layer; performing a second ion implant process to a second well region exposed, forming a fourth well region between the first well region and the second well region; performing a third implant process to the second well region, forming a fifth well region overlying the fourth well region; forming a source region in a portion of the third well region; and forming a drain region in a portion of the fifth well region.