Smart Semiconductor Switch Parasitic Bipolar Prevention
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Solution Overview
Problem
Integrated semiconductor devices face issues with electrical isolation between circuits and the substrate, leading to parasitic diode and bipolar transistor activation, causing undesired current conduction and potential drops that can render circuitry inoperative.
Innovation Solution
A protection circuit is integrated to monitor and manage the current passing between semiconductor regions, charging the gate electrode of a MOS transistor based on detected current thresholds to prevent parasitic bipolar transistor activation, thereby maintaining reverse bias and preventing forward biasing of pn-junction isolations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If pn-junction isolation is used to isolate circuits and substrate, then electrical isolation is achieved, but parasitic bipolar transistors are activated causing undesired current conduction
Solution Approach 1:
The protection circuit proactively counteracts the harmful effect of parasitic bipolar transistor activation by detecting the voltage condition that precedes activation (when anode voltage exceeds cathode voltage by more than 0.6V) and preemptively charging the MOS transistor gate to turn it on, thereby preventing the parasitic transistor from activating and causing harmful current conduction
Solution Approach 2:
The protection circuit continuously monitors the voltage difference between the anode and cathode of the pn-junction isolation and uses this feedback information to control the MOS transistor gate charging state, dynamically adjusting the transistor conduction state based on the detected voltage conditions to prevent parasitic activation
2Reliability
If additional protection circuitry is integrated, then parasitic transistor activation is prevented, but device complexity increases
Solution Approach 1:
The protection circuit is fully integrated with the existing semiconductor device structure, combining the protection function with the MOS transistor and pn-junction isolation already present in the device, thereby preventing parasitic transistor activation without adding separate discrete protection components
Solution Approach 2:
The MOS transistor serves dual functions: as a normal switching element in the circuit and as a protection element when activated by the protection circuit in response to parasitic activation conditions, thereby providing protection without requiring a dedicated separate protection device
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 protection circuit effectively counters parasitic transistor activation, ensuring stable operation of integrated circuitry by maintaining appropriate voltage levels and preventing unintended resets or failures due to parasitic transistor operation.
Implementation Method 1
a protection circuit electrically connected to a portion of the first semiconductor layer and the gate electrode and being configured to charge the gate electrode dependent on a current passing from the first semiconductor layer to a drain electrode of the MOS transistor
Implementation Method 2
The pn-junction may be reverse biased to isolate the n-doped semiconductor layer from the p-doped substrate
Data Source
AI summary
A semiconductor device may comprise a semiconductor substrate, which is doped with dopants of a first doping type and includes a semiconductor layer adjoining a top surface of the semiconductor substrate, the semiconductor layer being doped with dopants of a second doping type; a MOS transistor being integrated in the first semiconductor region; and a protection circuit electrically connected to a portion of the first semiconductor layer and the gate electrode and being configured to charge the gate electrode dependent on a current passing from the first semiconductor layer to a drain electrode of the MOS transistor.