High-Voltage Semiconductor Doping Layout to Suppress Parasitic BJT Turn-On
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Solution Overview
Problem
High voltage devices face the issue of parasitic transistors being turned ON due to hot carriers, leading to increased voltage drop and potential damage, which limits their safe operation area.
Innovation Solution
The design includes a semiconductor layer with a well and bulk region of different conductivity types, where the bulk region has higher impurity concentrations in specific peak regions, preventing the parasitic transistor from turning ON by reducing the voltage drop through a 'hot carriers absorption channel'.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the high voltage device operates with conventional structure, then the device can conduct current, but the parasitic transistor turns ON due to hot carriers, causing high ON current and potential damage
Solution Approach 1:
The patent applies local quality by creating a concentration peak region with higher impurity concentration specifically at the interface between the bulk region and well, rather than uniform doping throughout. This localized high concentration zone suppresses parasitic transistor activation at the critical interface where hot carriers are generated, while maintaining lower impurity concentrations in other regions to preserve device performance.
Solution Approach 2:
The patent changes the impurity concentration parameter by introducing a concentration peak region with higher dopant concentration at the bulk region-well interface. This parameter change increases the activation energy for parasitic transistor formation, preventing hot carriers from turning on the parasitic transistor while maintaining normal device operation.
2Loss of energy
If the impurity concentration in the bulk region is increased uniformly, then the voltage drop is reduced, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
Instead of uniform impurity distribution, the patent implements local quality by concentrating impurities in a specific peak region at the bulk region-well interface. This localized approach reduces voltage drop where it matters most (at the interface) without requiring high impurity concentrations throughout the entire bulk region, thereby simplifying manufacturing compared to uniform high-doping approaches.
3Reliability
If the drift region length is increased to withstand higher voltage, then the breakdown voltage increases, but the device area and manufacturing complexity increase
Solution Approach 1:
The patent changes the impurity concentration parameter at the bulk region-well interface to suppress parasitic transistor activation. This allows the device to maintain compact dimensions while achieving reliable high voltage operation by preventing the parasitic transistor effect that would otherwise limit the safe operation area, rather than relying solely on increased drift region length.
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 effectively inhibits the parasitic bipolar junction transistor from being activated, thereby increasing the safe operation area of high voltage devices by minimizing voltage drop within the bulk region.
Implementation Method 1
preventing the parasitic transistor from turning ON by reducing the voltage drop through a 'hot carriers absorption channel'
Data Source
AI summary
A high voltage device includes: a semiconductor layer, a well, a bulk region, a gate, a source, and a drain. The bulk region is formed in the semiconductor layer and contacts the well region along a channel direction. A portion of the bulk region is vertically below and in contact with the gate, to provide an inversion region of the high voltage device when the high voltage device is in conductive operation. A portion of the well lies between the bulk region and the drain, to separate the bulk region from the drain. A first concentration peak region of an impurities doping profile of the bulk region is vertically below and in contact with the source. A concentration of a second conductivity type impurities of the first concentration peak region is higher than that of other regions in the bulk region.