Off MOS Transistor Gate-Drain Coupling for CDM ESD Protection
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Solution Overview
Problem
Conventional semiconductor devices with off transistors are prone to damage from severe transient potential differences generated during charged device models (CDM), which can lead to gate insulation film damage due to the rapid discharge of small energy in extremely short times.
Innovation Solution
The semiconductor device incorporates an off transistor with a gate electrode extensively covering the drain region, including the channel area, and a capacitance forming region between the gate and drain, ensuring the gate potential follows the drain potential, thereby minimizing potential differences and protecting the gate insulation film. This design includes a gate electrode that covers the drain region and source region, with specific capacitance regions to enhance the potential following capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional off transistor is used with gate and source connected to ground, then ESD protection function is provided, but severe transient potential differences during CDM can damage the gate insulation film
Solution Approach 1:
The gate electrode is extended to cover the drain region, creating a capacitance between gate and drain that couples their potentials. This equipotentializing effect ensures that during CDM events, the gate potential follows the drain potential, minimizing potential differences and protecting the gate insulation film from breakdown.
Solution Approach 2:
The extended gate electrode acts as an intermediary between the drain and the original gate structure. By extending the gate to cover the drain region, it mediates the potential relationship between drain and gate, allowing the gate to track drain potential changes during transient events through capacitive coupling.
2Object-affected harmful factors
If the gate electrode is extended to cover the drain region, then potential difference is minimized and gate insulation film is protected, but device structure becomes more complex
Solution Approach 1:
The gate electrode structure is merged with the drain region by extending the gate to cover the drain. This combining of gate and drain structures creates a capacitive coupling that minimizes potential differences without requiring separate protection components, thus managing complexity through integration.
Solution Approach 2:
The extended gate electrode serves multiple functions: it maintains the original transistor switching function, provides ESD protection, and minimizes potential differences during CDM events. This multi-functionality reduces the need for additional components, managing overall device complexity.
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 solution effectively suppresses potential differences between the gate and drain, reducing the risk of gate insulation film damage and enhancing ESD protection by ensuring the gate potential follows the drain potential, even during transient events like CDM discharges.
Implementation Method 1
a capacitance forming region is provided between the drain region and the gate electrode extensively provided over the drain region
Data Source
AI summary
A semiconductor device has an off transistor (10) in which a gate electrode (3) and a source region (6) of an N-type MOS transistor are connected to a ground terminal and a drain region (5) is connected to an external signal terminal (100b). In the off transistor (10), the gate electrode (3) is extensively provided over a portion or entirety of the drain region (5) in addition to a channel region. A capacitance (C2) formed between the gate electrode (3) and the drain region (5) may be greater than a capacitance (C1) generated between the gate electrode (3) and a ground potential.