Electrostatic Protection Device Vertical Current Path Design
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional electrostatic protection devices for semiconductor integrated circuits have poor protection capability due to reduced breakdown endurance and low holding voltage, primarily because the current path is concentrated near the surface of the semiconductor substrate, leading to increased current density and thermal runaway, making them unsuitable for high breakdown voltage elements.
Innovation Solution
The electrostatic protection device is configured with a diffusion layer of the same conductivity type as the base provided below the base, increasing the vertical current component and reducing the lateral current component near the surface, thereby enhancing breakdown endurance and holding voltage without increasing the device area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the current path is concentrated near the surface of the semiconductor substrate, then the device area can be kept small, but the breakdown endurance decreases due to increased current density and thermal runaway
Solution Approach 1:
The invention introduces a fifth diffusion layer positioned below the emitter in the depth direction, transforming the current path from a primarily lateral (surface-level) configuration to one that extends vertically into the substrate. This dimensional change distributes the current flow across multiple spatial dimensions, reducing current density at the surface while maintaining compact device footprint.
2Volume of moving object
If the base width is narrow to reduce device area, then the current gain (hFE) increases, but the holding voltage decreases significantly
Solution Approach 1:
By positioning the fifth diffusion layer below the emitter at a controlled depth, the invention effectively increases the functional base width in the vertical dimension without expanding the lateral device area. This allows the transistor to maintain narrow base width benefits (high hFE) while achieving adequate holding voltage through the extended vertical current path.
3Reliability
If the emitter area is increased to reduce current density and improve breakdown endurance, then the protection capability improves, but the device area increases
Solution Approach 1:
The invention achieves current density reduction by extending the current path into the vertical dimension through the fifth diffusion layer, rather than increasing the lateral emitter area. This allows the device to handle higher surge currents and improve breakdown endurance while maintaining a compact footprint suitable for high-density integration.
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 configuration increases breakdown endurance and maintains a high holding voltage, improving the protection capabilities of the electrostatic protection device without enlarging the device area, making it suitable for high breakdown voltage elements.
Implementation Method 1
a current produced by avalanche breakdown flows between the collector and the base (a collector-base breakdown voltage: BVCBO)
Implementation Method 2
the npn transistor starts a bipolar operation (a trigger point: a trigger voltage Vt1, a trigger current It1). When the current increases, the number of electrons injected from the n-type high concentration diffusion layer 106 into a region located below the n-type high concentration diffusion layer 106 in the n-type low concentration semiconductor substrate 103 becomes excessive
Data Source
AI summary
A semiconductor circuit includes: a first diffusion layer formed on a substrate; a second diffusion layer formed in an upper part of the first diffusion layer; a third diffusion layer formed in an upper part of the second diffusion layer; a fourth diffusion layer formed in the upper part of the first diffusion layer; and a fifth diffusion formed below the third diffusion layer. A sum of a shortest distance from the third diffusion layer to the fifth diffusion layer and a shortest distance from the fifth diffusion layer or the lower end of the first diffusion layer to the fourth diffusion layer is smaller than a shortest distance from the third diffusion layer to the fourth diffusion layer. The substrate, the second and the fifth diffusion layer are a first conductivity type and the others are a second conductivity type.