Substrate Bipolar Transistor and Breakdown Diode for ESD Protection
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Solution Overview
Problem
Integrated circuits (ICs) in electronic systems are vulnerable to transient electrical events, such as electrostatic discharge (ESD), which can cause overvoltage conditions and high power dissipation, leading to damage like gate oxide punch-through, junction damage, and latch-up, necessitating effective protection mechanisms.
Innovation Solution
A substrate-based protection circuit configuration using a bipolar transistor and breakdown diode structure, where a second active area surrounds a first active area to recombine carriers and operate as a breakdown diode, providing protection by maintaining voltage levels within safe ranges and diverting current associated with transient events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional protection circuit is used, then the IC can be protected from transient electrical events, but the circuit occupies more chip area and has higher complexity
Solution Approach 1:
The patent combines the ESD protection function and latch-up prevention function into a single integrated circuit structure. The protection circuit includes a first protection device (such as a diode or transistor) and a second protection device coupled together, where the first device handles ESD protection while the second device prevents latch-up. This merging eliminates the need for separate protection circuits, reducing overall device complexity while maintaining comprehensive protection functionality.
2Reliability
If the breakdown voltage is reduced to protect against transient events, then protection effectiveness improves, but normal operational voltage range is limited
Solution Approach 1:
The patent segments the protection function into two distinct devices with different breakdown voltage characteristics. The first protection device has a lower breakdown voltage optimized for ESD protection, while the second protection device has a higher breakdown voltage that allows normal operational voltages to pass through unaffected. This segmentation enables the circuit to provide effective protection against transient events while maintaining a wide operational voltage range for normal functionality.
3Reliability
If larger protection structures are used, then protection capability increases, but chip area consumption increases
Solution Approach 1:
The patent implements a nested structure where the second protection device is coupled within or alongside the first protection device. The devices share common substrates, wells, or isolation structures, allowing the protection circuit to achieve enhanced protection capability through the combined functionality of multiple devices while minimizing the total chip area required. The nested arrangement ensures that protection capability is multiplied rather than simply added, reducing area consumption.
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 protects ICs from transient electrical events by maintaining voltage levels, reducing power dissipation, and preventing latch-up, thereby enhancing the reliability and longevity of electronic systems.
Implementation Method 1
The second active area, the first well, and the second well are configured to operate as an emitter, a base, and a collector of a bipolar transistor, respectively, and the second active area surrounds at least a portion of the first active area so as to aid in recombining carriers injected into the first well from the second well before the carriers reach the first active area
Implementation Method 2
The first well and the second well are configured to operate as a breakdown diode, and a punch-through induced breakdown voltage between the second well and the first well is lower than or equal to about a direct breakdown voltage between the second well and the first well
Data Source
Figure 1A
Figure 1B
Figure 2A
AI summary
Apparatus and methods for electronic circuit protection are disclosed. In one embodiment, an apparatus (1) comprises a substrate (247) that includes an n-well (251b) and a p-well (254b) adjacent the n-well. An n-type active area (243c) and a p-type active area (242c) are disposed in the n-well. The p-type active area, the n-well, and the p-well are configured to operate as an emitter, a base, and a collector of an PNP bipolar transistor (22), respectively, and the p-type active area surrounds at least a portion of the n-type active area so as to aid in recombining carriers injected into the n-well from the p-well before the carriers reach the n-type active area. The n-well and the p-well are configured to operate as a breakdown diode (27), and a punch-through breakdown voltage between the n-well and the p-well is lower than or equal to about a breakdown voltage between the p-type active area and the n-well.