I/O Circuit Layout Using Transistor Secondary Clamps for ESD
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Solution Overview
Problem
Conventional I/O circuits for semiconductor devices face challenges in providing adequate electrostatic discharge (ESD) protection without increasing the circuit area, particularly due to the need for additional secondary clamps which require extra components.
Innovation Solution
The proposed I/O circuit configuration effectively utilizes the third element forming region to integrate transistors as secondary clamps, enhancing ESD immunity and reducing area by eliminating the need for separate secondary clamp components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If separate secondary clamp components are added to protect protection target elements from electrostatic breakdown, then ESD immunity is improved, but circuit area increases
Solution Approach 1:
The patent merges the secondary clamp function with existing transistors in the circuit. Specifically, transistors that are already present for circuit operation are configured to also serve as secondary clamps during ESD events, eliminating the need for separate dedicated secondary clamp components and thus reducing circuit area while maintaining ESD protection capability
Solution Approach 2:
The patent makes existing transistors multi-functional by configuring them to perform both their primary circuit function and secondary clamp function for ESD protection. This is achieved through specific circuit configuration where the transistors can operate normally during regular operation and automatically function as clamps during electrostatic discharge events, thereby providing universal protection without adding dedicated components
Data Source
AI summary
An I/O circuit is formed by combining plural types of standard cells contained in a cell library. For example, the standard cell includes a first element forming region having, formed therein, protection target elements each having a gate electrically connected to an external terminal, a second element forming region arranged in immediate proximity to the external terminal and having first protection elements formed therein, and a third element forming region arranged between the first and second element forming regions and having transistors formed therein. The transistors each have a drain connected to gates of the protection target elements and a source, gate, and back gate all connected to a power supply or ground terminal, thus functioning as a second protection element.