N-EDSCR ESD Protection Circuit Counter Pocket Source Design
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Solution Overview
Problem
Conventional N-type extended drain silicon controlled rectifier (N-EDSCR) devices suffer from latch-up issues and unstable operation in multi-finger structures, leading to inadequate avalanche breakdown voltage and triggering current, which limits their effectiveness in electro-static discharge (ESD) protection circuits.
Innovation Solution
The design incorporates a counter pocket source region and a partial P-type well structure, optimizing the distance between the N-type drift region and diffusion layers to increase triggering voltage and current while reducing leakage current, ensuring stable operation and preventing latch-up in ESD protection circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the distance between the N-type drift region and diffusion layers is reduced to increase triggering current, then the triggering current increases, but the leakage current also increases
Solution Approach 1:
The patent applies local quality by creating a counter pocket source region with specific doping characteristics in a localized area adjacent to the gate electrode. This region has different doping concentration and depth compared to other parts of the device, allowing it to provide localized triggering current enhancement without affecting the overall leakage current characteristics of the drift region.
Solution Approach 2:
The patent changes the doping parameters (concentration, depth, and distribution) of the counter pocket source region to optimize the balance between triggering current and leakage current. By carefully controlling the doping profile in this specific region, the device achieves higher triggering current while maintaining acceptable leakage current levels.
2Reliability
If the avalanche breakdown voltage is increased to improve ESD protection capability, then the ESD tolerance improves, but the triggering voltage becomes too high causing unstable operation
Solution Approach 1:
The patent segments the device into distinct functional regions: the drift region for avalanche breakdown and ESD protection, and the counter pocket source region for triggering control. This segmentation allows independent optimization of each region's parameters, enabling high avalanche breakdown voltage for ESD protection while maintaining appropriate triggering voltage for stable operation.
Solution Approach 2:
The counter pocket source region acts as an intermediary that mediates between the high voltage drift region and the control circuitry. It provides a controlled path for triggering current that is independent of the high voltage avalanche process, ensuring stable triggering operation even when the avalanche breakdown voltage is high for superior ESD protection.
3Quantity of substance
If a multi-finger structure is used to increase current handling capacity, then the ESD current tolerance increases, but latch-up occurs causing irregular operation
Solution Approach 1:
The multi-finger structure is segmented into independent fingers, each with its own counter pocket source region. This segmentation isolates the triggering control in each finger, preventing lateral propagation of triggered states that could lead to latch-up. Each finger can handle ESD current independently while maintaining stable triggering control.
Solution Approach 2:
Each finger in the multi-finger structure is self-sufficient with its own counter pocket source region that provides localized triggering control. This self-service capability ensures that each finger operates independently and reliably, preventing latch-up conditions that could affect the entire device while maintaining high total current handling capacity.
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 modified N-EDSCR device achieves increased triggering current and snapback holding voltage, enabling stable operation of each finger in multi-finger structures and effectively protecting microchips from electrostatic discharge without increasing leakage current.
Implementation Method 1
an avalanche breakdown voltage (Vav) and a triggering voltage (Vtr) of the ESD protection circuit are higher than the operation voltage (Vop) of the micro chip
Implementation Method 2
It is necessary to have a tolerance with respect to a serge voltage and a serge current caused by an electro-static discharge (ESD) given on an input/output pad of a semiconductor chip
Data Source
AI summary
An ESD protection circuit using an N-type extended drain silicon controlled rectifier (N-EDSCR) and a method for fabricating the same are provided. An electro-static discharge (ESD) protection circuit includes a substrate, a well formed in the substrate, a drift region having a predetermined portion overlapped with the well, a plurality of first diffusion layers respectively formed in the well and the drift region, a plurality of second diffusion layers respectively formed in the well and the drift region, wherein corresponding first and second diffusion layers in the well are formed separately from each other and those in the drift region are formed adjacent to each other, a source region formed in a manner of surrounding a second conductive type diffusion layer inside the well, and a gate electrode formed on the well between the source and the drift region.