Bidirectional ESD Transistor with Silicide-Blocked Base Diffusion
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Solution Overview
Problem
Conventional electrostatic discharge (ESD) protection circuits for integrated circuits are inefficient in handling bidirectional ESD events and consume significant silicon area, leading to potential damage from high current ESD strikes due to current crowding and the need for large diodes.
Innovation Solution
A bidirectional ESD transistor design with a base diffusion that separates emitter and collector diffusions, blocking silicide to prevent shorting and adding series resistance, allowing for reduced area usage and improved current uniformity, and optionally incorporating base biasing diodes for enhanced protection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ESD protection circuits use large diodes to handle high current ESD strikes, then ESD protection capability is improved, but silicon area consumption increases
Solution Approach 1:
The patent merges the ESD protection function with the existing transistor structure by configuring the transistor to operate in the forward active region during ESD events. The transistor's collector and emitter are repurposed to handle bidirectional ESD currents, eliminating the need for separate large diodes and reducing silicon area while maintaining protection capability.
Solution Approach 2:
The transistor is designed to serve dual functions: normal circuit operation and ESD protection. By configuring the transistor with appropriate doping concentrations and geometric ratios (W/L ≥ 1), it can handle both positive and negative ESD pulses effectively, making the protection circuit more area-efficient by using the same structure for multiple purposes.
2Reliability
If conventional ESD circuits use series diodes to handle ESD currents, then ESD protection is provided, but device complexity increases
Solution Approach 1:
The patent combines the ESD protection function into the transistor structure itself, eliminating the need for separate series diodes. The transistor's inherent structure is configured to provide bidirectional ESD protection, reducing the number of discrete components and simplifying the overall circuit design.
Solution Approach 2:
The patent extracts the ESD protection function from the traditional diode-based approach and integrates it into the transistor structure. By removing the separate diode components and using the transistor's collector-emitter path for ESD current handling, the circuit complexity is reduced while maintaining protection functionality.
3Reliability
If conventional ESD circuits use NPN transistors with series diodes, then ESD current discharge is achieved, but current crowding occurs leading to potential damage
Solution Approach 1:
The patent applies local quality by creating non-uniform doping concentrations within the transistor structure. The collector region has a doping concentration (1e18 to 1e20 atoms/cm³) that is higher than the emitter region (1e16 to 1e18 atoms/cm³), which helps distribute the ESD current more uniformly across the device structure, preventing current crowding at specific locations.
Solution Approach 2:
The patent changes the electrical parameters of the transistor by configuring the W/L ratio to be greater than or equal to 1 and setting specific doping concentrations for the collector and emitter regions. These parameter changes enable the transistor to handle bidirectional ESD currents effectively while distributing the current density more evenly, preventing the current crowding effect that occurs in conventional designs.
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 bidirectional ESD transistor design effectively handles both positive and negative ESD pulses with reduced silicon area consumption and eliminates the need for additional diodes, providing enhanced protection against ESD events by controlling the ESD voltage and improving current distribution.
Implementation Method 1
blocking silicide to prevent shorting and adding series resistance
Implementation Method 2
Electrostatic discharge (ESD) is a continuing problem in the design, manufacture, and utilization of integrated circuits (ICs)
Data Source
AI summary
An integrated circuit and method with a bidirectional ESD transistor. A base diffusion separates an emitter diffusion and a collector diffusion. Silicide is blocked from the base diffusion, the emitter-base junction, the collector-base junction, and from equal portions of the emitter diffusion and the collector diffusions.