LDMOS Diode Circuit for Substrate Injection Control
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Solution Overview
Problem
In system-on-a-chip (SOC) applications with inductive loads, negative potential during switching leads to significant injection current into the substrate, disturbing adjacent circuits and affecting their operation, necessitating improved device structures and fabrication methods that are compatible with current manufacturing capabilities and do not increase costs substantially.
Innovation Solution
The implementation of diode circuits, including Schottky diodes and PN junction diodes, coupled between the drain/source regions and isolation structures of laterally diffused metal oxide semiconductor field effect transistors (LDMOSFETs) to reduce or eliminate current injection into the substrate, using diode circuits with breakdown voltages tailored to the operating conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If inductive loads are used in SOC applications, then system functionality is improved, but negative potential during switching causes significant injection current into the substrate that disturbs adjacent circuits
Solution Approach 1:
A diode circuit is introduced as an intermediary component between the inductive load and the substrate. The diode circuit includes a first diode with anode connected to a first node and cathode connected to a first region of the substrate, and a second diode with anode connected to a second node and cathode connected to a second region of the substrate. This intermediary structure prevents negative potential from directly injecting current into the substrate while maintaining system functionality.
Solution Approach 2:
The diode circuit is configured to preemptively counteract the harmful effect of negative potential before it can cause significant injection current. By positioning the diodes with their cathodes connected to substrate regions, the circuit creates a preliminary protective barrier that blocks reverse current flow into the substrate during switching transients.
2Reliability
If diode circuits are added to reduce current injection, then substrate integrity is improved, but device complexity increases
Solution Approach 1:
The diode circuit is merged with the existing circuit nodes and substrate regions. The first diode's anode is connected to a first node that already exists in the circuit, and the second diode's anode is connected to a second node. This merging approach integrates the protective function into the existing circuit architecture rather than adding completely separate components.
Solution Approach 2:
The diode circuit serves multiple functions: it protects against injection current into the substrate, maintains voltage references through connections to existing nodes, and works with both positive and negative potential conditions. This multi-functionality reduces the need for additional separate protective circuits.
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 diode circuits effectively limit current injection into the substrate, reducing disruption to adjacent circuits and maintaining the integrity of the SOC substrate, thereby enhancing the performance and reliability of SOC devices.
Implementation Method 1
using diode circuits with breakdown voltages tailored to the operating conditions
Data Source
AI summary
Embodiments of semiconductor devices and driver circuits include a semiconductor substrate having a first conductivity type, an isolation structure (including a sinker region and a buried layer), an active device within area of the substrate contained by the isolation structure, and a diode circuit. The buried layer is positioned below the top substrate surface, and has a second conductivity type. The sinker region extends between the top substrate surface and the buried layer, and has the second conductivity type. The active device includes a body region of the second conductivity type, and the diode circuit is connected between the isolation structure and the body region. The diode circuit may include one or more Schottky diodes and/or PN junction diodes. In further embodiments, the diode circuit may include one or more resistive networks in series and/or parallel with the Schottky and/or PN diode(s).