ESD Guard Ring Structure for CMOS Transistor Protection
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Solution Overview
Problem
Integrated circuit (IC) devices with advanced sub-quarter-micron CMOS technologies are increasingly susceptible to damage from electrostatic discharge (ESD) due to shallower junction depths, thinner gate oxides, and other design features, which can lead to high transient currents and component damage during ESD events.
Innovation Solution
The implementation of a guard ring structure using heavily doped P-type and N-type diffusion regions around transistors to divert current during ESD events, particularly in the ND strike mode, thereby increasing the breakdown voltage and suppressing failure without increasing device size or cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If advanced sub-quarter-micron CMOS technologies are used to miniaturize IC devices, then device size is reduced, but susceptibility to ESD damage increases
Solution Approach 1:
The patent introduces guard rings as intermediary structures between the miniaturized circuit components and ESD strikes. These guard rings act as mediators that intercept and divert ESD current away from sensitive circuits, resolving the contradiction by adding a protective intermediate layer that enables both miniaturization and ESD protection
Solution Approach 2:
The guard rings are positioned in advance around sensitive circuit regions before ESD events occur. This preliminary placement of protective structures ensures that when ESD strikes happen, the diversion path is already in place, allowing miniaturized devices to maintain reliability without requiring larger protective components
2Reliability
If guard ring structures are added to protect against ESD, then ESD protection is improved, but device area increases
Solution Approach 1:
The patent applies guard ring structures selectively around specific sensitive regions rather than uniformly across the entire device. This localized application provides ESD protection only where needed, maintaining high reliability for critical components while minimizing the additional area consumed by protective structures
Solution Approach 2:
The guard rings are designed with optimized dimensions and spacing that provide sufficient ESD protection through partial coverage of potential strike paths. Rather than creating complete protective barriers around all components, the patent uses strategically placed partial guard rings that divert the majority of ESD current with minimal area overhead
3Reliability
If conventional ESD protection circuits are added at bond pads, then ESD protection is provided, but device complexity increases
Solution Approach 1:
The patent extracts the ESD protection function from complex circuit implementations and implements it through simple guard ring structures. By separating the protection function into dedicated guard ring elements rather than using complex protection circuits, the solution reduces device complexity while maintaining ESD protection capability
Solution Approach 2:
The guard rings are implemented using simple doped region structures that are inexpensive to manufacture compared to complex ESD protection circuits. These simple structures provide effective ESD protection without requiring sophisticated circuit design, reducing overall device complexity
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 proposed solution effectively increases the breakdown voltage during ESD events, specifically in the ND mode, reducing the risk of transistor burnout and maintaining ESD protection without enlarging the device, thus enhancing the reliability of ICs against ESD damage.
Implementation Method 1
electrostatic discharge (ESD) events... high transient currents can damage equipment... ESD protection circuit provides an electrical path to a safe terminal... causes the electrostatic current (called a 'strike') to bypass the susceptible semiconductor devices
Implementation Method 2
heavily doped P-type and N-type diffusion regions... provides an electrical path... current diversion... increasing the breakdown voltage
Data Source
AI summary
An electrostatic discharge (ESD) protection circuit structure includes several diffusion regions and a MOS transistor. The circuit structure includes a first diffusion region of a first type (e.g., P-type or N-type) formed in a first well of the first type, a second diffusion region of the first type formed in the first well of the first type, and a first diffusion region of a second type (e.g., N-type or P-type) formed in a first well of the second type. The first well of the second type is formed in the first well of the first type. The MOS transistor is of the second type and includes a drain formed by a second diffusion region of the second type formed in a second well of the second type bordering the first well of the first type.