Electrostatic Protection Element With Segmented Well Contact
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Solution Overview
Problem
Semiconductor devices with insulating trenches face challenges in electrostatic discharge (ESD) protection, as external disturbances can cause unstable substrate potentials, leading to latch-up and erroneous circuit operations due to current flow through the substrate.
Innovation Solution
An electrostatic protection element is designed with a substrate of a first conductivity type, an epitaxial layer of a second conductivity type, a well of the first conductivity type, and a transistor with a drain, source, and gate, along with a well contact region that forms an opposing region with the drain, effectively isolating the substrate and stabilizing its potential.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If DTI is formed to reach the P-type substrate to improve ESD protection capability, then the parasitic BJT operates more effectively, but the substrate potential becomes unstable and latch-up or erroneous operation occurs
Solution Approach 1:
The invention divides the substrate interaction into two separate paths: one for ESD current (through the well contact region) and one for substrate potential stabilization (through the isolated substrate contact). This segmentation prevents the ESD current from destabilizing the substrate potential while maintaining effective ESD protection.
Solution Approach 2:
The well contact region acts as an intermediary structure that provides a dedicated path for ESD current to reach the substrate without affecting the substrate potential. By mediating the current flow through this intermediate structure, the patent prevents direct coupling between ESD events and substrate potential instability.
2Strength
If the insulating trench is used to isolate the drain from the substrate to improve breakdown voltage, then element isolation is achieved, but the ESD protection function is reduced due to current flow restriction
Solution Approach 1:
The invention applies different properties to different regions: the insulating trench provides high resistance for normal operation (maintaining breakdown voltage), while the well contact region provides a low-resistance path specifically for ESD events. This local differentiation allows both functions to coexist without compromising either.
Solution Approach 2:
The structure dynamically switches between isolation mode (during normal operation) and conduction mode (during ESD events). The well contact region remains electrically isolated during normal operation to maintain breakdown voltage, but becomes conductive during ESD events to provide protection.
3Ease of manufacture
If the substrate contact is placed outside the DTI to simplify structure, then manufacturing is easier, but the isolation function is not fully utilized and substrate potential becomes unstable
Solution Approach 1:
The invention segments the contact structure into two distinct components: the well contact region (for ESD current) and the substrate contact (for potential stabilization). This segmentation maintains structural simplicity while achieving both isolation and stability functions that a single contact structure cannot provide.
Data Source
AI summary
An electrostatic protection element includes a substrate of a first conductivity type, an epitaxial layer formed on the substrate, the epitaxial layer being of a second conductivity type; a well formed on the epitaxial layer, the well being of the first conductivity type; a transistor formed inside of the well, the transistor including a drain region, a source region formed to face the drain region across a channel region, and a gate formed above the channel region so as to be insulated; and a well contact region of the first conductivity type disposed so as to form an opposing region where the drain region and the well contact region face each other while being separated by a prescribed distance in a direction parallel to at least an extension direction of the gate.