Integrated Diode Simulation Accuracy During ESD Events
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Solution Overview
Problem
Existing compact models of integrated diodes fail to accurately simulate their behavior during electrostatic discharges (ESD), particularly in the disabled mode and reverse-recovery phase, leading to erroneous simulation results due to abrupt voltage decreases and overvoltages.
Innovation Solution
A novel compact diode model that includes a conductivity modulation model for well resistance, with a curve that increases steeply from an initial resistance value to a plateau for negative current values, accurately reproducing the reverse-recovery effect and disabled mode behavior, avoiding simulation artifacts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing compact models are used to simulate integrated diode behavior, then the simulation process is simple, but the accuracy of ESD behavior simulation is poor
Solution Approach 1:
The diode model is segmented into multiple independent components: a PN junction model, a series resistance model, and a well resistance model. Each component is modeled separately with specific mathematical relationships, allowing the complex ESD behavior to be broken down into manageable segments that can be simulated independently and then combined.
Solution Approach 2:
The model uses parameter changes to accurately represent different operational states. The well resistance is modeled as a function of current using exponential relationships (Rwell = R0 * exp(α * I) for negative current), and the series resistance includes conductivity modulation effects. These parameter transformations enable the model to capture the nonlinear ESD behavior accurately.
2Reliability
If conventional well resistance modeling is used, then the model is simple, but it cannot accurately represent reverse-recovery behavior
Solution Approach 1:
The well resistance model is made dynamic by making it current-dependent rather than constant. For negative current values (reverse-recovery phase), the resistance follows an exponential relationship that dynamically adapts to the instantaneous current, allowing the model to accurately capture the transient reverse-recovery behavior without requiring complex time-dependent differential equations.
Solution Approach 2:
The well resistance parameter changes based on the operating condition: for negative current, Rwell = R0 * exp(α * I) where the resistance increases exponentially as current becomes more negative, and for positive current, a different relationship applies. This parameter transformation accurately represents the physical behavior during reverse-recovery.
3Measurement precision
If abrupt voltage decrease is simulated, then the computation is fast, but simulation artifacts and overvoltages occur
Solution Approach 1:
The model incorporates beforehand cushioning by including series resistance and conductivity modulation effects that naturally limit voltage spikes before they occur. The exponential well resistance model acts as a cushion during reverse-recovery, preventing abrupt voltage decreases by providing a continuous, smooth resistance transition that dampens voltage artifacts.
Solution Approach 2:
The well resistance model serves as an intermediary element between the PN junction and the external circuit. It mediates the voltage and current transitions during reverse-recovery, providing a continuous resistance value that smooths out abrupt changes and prevents simulation artifacts while maintaining computational efficiency.
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 model effectively simulates the electrical behavior of integrated diodes during ESD events, providing a faithful representation of both forward-recovery and reverse-recovery phenomena, thus improving the accuracy of ESD protection simulations and preventing overvoltages.
Implementation Method 1
modelling a well resistance for positive values of a current passing through the diode involving a conductivity modulation model
Data Source
AI summary
A method for simulating, in an electrical device simulator, electrical behavior of an integrated diode is described. The diode is modelled using a compact model in the electrical device simulator to determine the electrical behavior of the diode in a given situation. The modelling includes modelling a series resistance relating to the active regions and to the connections, modelling a PN junction of the diode, and modelling a well resistance for positive values of a current passing through the diode involving a conductivity modulation model. The method further includes modelling of the well resistance for negative values of the current by a curve which increases steeply from an initial resistance value corresponding to a zero value of current up to a plateau.