Pillar Structure Transistor Preventing Latch-Up
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Solution Overview
Problem
Transistor devices are prone to parasitic bipolar transistor activation due to self-biasing substrate current, leading to undesirable latch-up conditions that prevent proper turn-off.
Innovation Solution
Incorporating a pillar structure within the source region of the transistor, with a conductivity type opposite to the source region, to reduce base resistance and prevent parasitic bipolar device turn-on, while maintaining desirable on-resistance and channel performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional transistor structure is used, then the device can operate, but parasitic bipolar transistor activation occurs due to self-biasing substrate current, leading to latch-up conditions that prevent proper turn-off
Solution Approach 1:
A body contact region is introduced as an intermediary element between the substrate and the parasitic bipolar transistor base region. This body contact provides a low-impedance path to extract substrate current and prevent self-biasing of the parasitic bipolar transistor base, thereby eliminating latch-up conditions while maintaining normal transistor operation.
Solution Approach 2:
The electrical parameters of the transistor structure are modified by introducing the body contact region, which changes the substrate current distribution and potential distribution in the base region. This parameter change reduces the base-emitter voltage of the parasitic bipolar transistor below the turn-on threshold, preventing parasitic activation.
2Reliability
If the base region is reduced to lower base resistance, then parasitic bipolar turn-on is prevented, but on-resistance performance deteriorates
Solution Approach 1:
The base region is segmented into a channel portion and a drift region portion, with the body contact strategically positioned to provide electrical connection without interfering with the channel formation. This segmentation allows the channel region to maintain low resistance for good on-state performance while the overall base structure prevents parasitic bipolar turn-on.
Solution Approach 2:
Different regions of the transistor are assigned different doping concentrations and geometries optimized for their specific functions. The channel region has high mobility and low resistance for conduction, while the drift region has appropriate doping to prevent parasitic activation. The body contact is locally positioned to extract substrate current without affecting channel properties.
Data Source
AI summary
In at least one general aspect, an apparatus can include a first trench disposed in a semiconductor region and including a gate electrode, and a second trench disposed in the semiconductor region. The apparatus can include a mesa region disposed between the first trench and the second trench, and a source region of a first conductivity type disposed in a top portion of the mesa region. The apparatus can include an epitaxial layer of the first conductivity type, and a body region of a second conductivity type disposed in the mesa region and disposed between the source region and the epitaxial layer of the first conductivity type. The apparatus can include a pillar of the second conductivity type disposed in the mesa region such that a first portion of the source region is disposed lateral to the pillar and a second portion of the source region is disposed above the pillar.