Semiconductor Protection Element with Lower Breakdown Voltage
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Solution Overview
Problem
Conventional semiconductor devices face issues with breakdown due to high surge currents, as surge protection elements around pads cannot cope with large surge currents, leading to potential internal circuit breakdown, and avalanche breakdown in internal cells when ESD surge is applied.
Innovation Solution
A semiconductor device structure featuring a bipolar transistor with a protection element having a second junction region with a lower breakdown voltage than the first junction region, surrounded by an isolation region that disperses current generated by overvoltage into the substrate, preventing concentration and protecting the transistor from overvoltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If avalanche breakdown occurs evenly in the entirety of the chip, then current concentration is prevented, but the internal cell may be broken down by large ESD surge
Solution Approach 1:
The invention applies local quality by creating a specific protection element with lower breakdown voltage in the vicinity of the bipolar transistor, while maintaining the overall even avalanche breakdown structure in the chip. This localized modification ensures that excessive current is diverted away from the internal cell without compromising the uniform current distribution achieved by the overall chip structure.
Solution Approach 2:
The invention implements preliminary anti-action by positioning a protection element with lower breakdown voltage before the ESD surge can reach the internal cell. This protection element breaks down first, creating a preferential current path that prevents the internal cell from experiencing damaging current levels, thereby preemptively protecting against potential breakdown.
2Reliability
If a protection element with lower breakdown voltage is introduced, then overvoltage protection is improved, but device complexity increases
Solution Approach 1:
The invention merges the protection element with existing chip structures such as isolation regions or field plates, combining multiple functions into a single structure. This merging approach provides effective overvoltage protection through the lower breakdown voltage element while avoiding significant increases in device complexity by reusing existing structural elements for dual purposes.
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 bipolar transistors from overvoltage by allowing the protection element to break down first, dispersing current through the substrate, thereby preventing internal circuit breakdown and enhancing current capacity.
Implementation Method 1
the protection element has a second junction region having a junction breakdown voltage lower than that of the first junction region. Accordingly, in the present invention, the second junction region of the protection element breaks down before the first junction region of the bipolar transistor
Implementation Method 2
an isolation region which divides the semiconductor layer. Moreover, the protection element is formed by utilizing the isolation region surrounding the formation region of the bipolar transistor. By use of this structure, a current generated by the overvoltage is caused to flow into a substrate through the isolation region, and then dispersed
Data Source
AI summary
In a semiconductor device of the present invention, an N type epitaxial layer is divided into a plurality of element formation regions by an isolation region. In one of the element formation regions, an NPN transistor is formed. Around the NPN transistor, a protection element having a PN junction region is formed. The PN junction region has a junction breakdown voltage lower than that of a PN junction region of the NPN transistor. By use of this structure, when negative ESD surge is applied to a pad for a base electrode, the PN junction region of the protection element breaks down. Accordingly, the NPN transistor can be protected.