CMOS Protection Circuit Layout for Latch-Up Immunity
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Solution Overview
Problem
CMOS integrated circuits face latch-up issues due to parasitic P/N/P/N structures, which can lead to undesirable conduction and destruction of the circuits, and existing guard ring and pick-up structures consume significant layout area.
Innovation Solution
Incorporating a shunt path with resistive loads to discharge minority carriers, increasing the voltage required to turn on the silicon controlled rectifier (SCR), thereby preventing undesired conduction and improving latch-up immunity without the need for large layout areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If guard ring structure and/or pick-up structure are applied to prevent latch-up, then latch-up immunity is improved, but layout area is significantly consumed
Solution Approach 1:
The patent changes the electrical parameters of the CMOS circuit by introducing resistive loads that modify the voltage thresholds and carrier concentrations. By adjusting these electrical parameters, the circuit achieves improved latch-up immunity without requiring additional physical structures that would consume layout area.
Solution Approach 2:
The patent extracts the latch-up prevention function from traditional physical structures (guard rings and pick-up structures) and implements it through electrical parameter modification using resistive loads. This removes the need for large-area physical structures while maintaining the protective function.
2Reliability
If shunt path with resistive loads is incorporated to discharge minority carriers, then voltage required to turn on SCR is increased, but circuit complexity increases
Solution Approach 1:
The resistive loads introduced in the patent serve multiple functions: they discharge minority carriers through the shunt path, increase the voltage threshold for SCR activation, and maintain normal circuit operation. This multi-functionality reduces the need for separate dedicated latch-up prevention circuits, thereby limiting the increase in overall circuit complexity.
3Reliability
If conventional guard ring structure is used to prevent latch-up, then latch-up immunity is improved, but manufacturing cost increases due to larger layout area
Solution Approach 1:
The patent achieves latch-up prevention through electrical parameter modification rather than physical structure expansion. By changing the electrical characteristics using resistive loads, the method maintains compact layout area, which directly reduces manufacturing costs associated with larger chip areas.
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 prevents latch-up in CMOS integrated circuits by increasing the holding voltage required for SCR activation, thus preventing undesired operation and circuit destruction while conserving layout space.
Implementation Method 1
Incorporating a shunt path with resistive loads to discharge minority carriers
Implementation Method 2
shunt path with resistive loads to discharge minority carriers
Data Source
AI summary
A semiconductor device includes first to fifth regions, first and second resistive loads. The first region is coupled to a first reference voltage terminal. The first to third regions operate as a first transistor. The fourth region is coupled to a second reference voltage terminal. The fourth to fifth regions operate as a second transistor. The first resistive load couples the second region to the second reference voltage terminal. The second resistive load couples the fifth region to the first reference voltage terminal. The first, third, second, fifth and fourth regions are arranged in order, each of the first, second and third regions corresponds to a first conductive type, and each of the fourth and fifth regions corresponds to a second conductive type.