Semiconductor Electrostatic Protection Circuit Layout
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Solution Overview
Problem
The existing electrostatic protection circuits in semiconductor devices with thyristor elements have limited layout freedom and increased area due to restrictive design constraints, particularly in the aspect ratio and placement of SCR anodes and cathodes, which hampers the effective use of thyristor elements for electrostatic discharge protection.
Innovation Solution
The design introduces a comb-like layout for N-type wells with high-concentration P-type regions as SCR anodes and N-type regions as SCR cathodes, allowing for increased flexibility in the number and placement of SCR elements without compromising performance, including the formation of multiple pairs of SCR anodes and cathodes and a trigger tap that extends perpendicular to the anodes, thereby enhancing the aspect ratio and reducing the layout area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thyristor element effective width is increased to increase ESD breakdown voltage, then the protection performance is improved, but the layout area increases due to restricted aspect ratio freedom
Solution Approach 1:
The N-type well is divided into multiple segments (first N-type well and second N-type well) that are coupled together, allowing the thyristor structure to be distributed across multiple regions. This segmentation enables increased effective width through multiple SCR anode-cathode pairs while managing layout area through modular arrangement
Solution Approach 2:
The trigger tap is extended in a direction perpendicular to the SCR anodes (second direction versus first direction), utilizing a different spatial dimension to provide trigger functionality without increasing the layout area in the plane parallel to the substrate. This dimensional change resolves the conflict between trigger access and compact layout
2Ease of manufacture
If the trigger tap is located in the center for symmetric layout, then the manufacturing is simplified, but the layout freedom is reduced and area increases
Solution Approach 1:
The trigger tap is segmented into multiple portions (first trigger tap portion and second trigger tap portion) that extend in opposite directions from different SCR anodes. This segmentation provides manufacturing simplicity through repeated structures while achieving layout freedom through flexible arrangement of the segmented portions
Solution Approach 2:
The trigger tap structure serves multiple functions: it provides trigger access for multiple SCR elements, extends in perpendicular directions to optimize layout, and can be configured in various patterns. This multi-functionality achieves both manufacturing ease through standardized components and layout freedom through flexible configuration
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
This approach significantly reduces the layout area and increases the freedom in design while maintaining or improving the thyristor element's electrostatic discharge protection performance, allowing for efficient discharge of ESD current with a smaller footprint and higher discharge capacity per unit area.
Implementation Method 1
SCR current ISCR flows from the SCR anodes to the SCR cathodes
Data Source
AI summary
An electrostatic protection circuit in a semiconductor device includes a first first-conductivity type well extending in a first direction over a semiconductor substrate, a second first-conductivity type well extending in a second direction over the semiconductor substrate and perpendicular to the first direction with one end coupled to a first long side of the first first-conductivity type well, and a second-conductivity type well formed around the first first-conductivity type well and the second first-conductivity type well. It also includes a first high-concentration second-conductivity type region extending in the second direction on a surface of the second first-conductivity type well and a first high-concentration first-conductivity type region extending in the second direction on a surface of the second-conductivity type well while facing the first high-concentration second-conductivity type region.