Parasitic Bipolar Transistor Snapback for Surge Protection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Semiconductor devices face challenges in protecting against surge voltages, particularly in scaled-down IC processes with lower operating voltages, as existing ESD protection diodes have high operating resistance and increased chip area, making it difficult to effectively clamp surge voltages and prevent damage to internal circuits.
Innovation Solution
A semiconductor device configuration is developed with a parasitic bipolar transistor and diode structure, where the impurity concentration in the base of the parasitic bipolar transistor is lowered to induce a snapback phenomenon, and the anode of the parasitic diode has increased impurity concentration to lower the breakdown voltage, along with a configuration of alternately arranged parasitic diodes and transistors to reduce operating resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the size of ESD protection diode is decreased to reduce chip area, then chip area is reduced, but operating resistance increases making it difficult to protect internal circuits against surge voltage
Solution Approach 1:
The patent introduces a parasitic bipolar transistor structure with specifically designed impurity concentrations (lower in the base region compared to the anode region) to modify the electrical characteristics. This parameter change enables the protection device to achieve low operating resistance and effective surge voltage clamping while maintaining a compact size beneath the pad electrode, thus resolving the contradiction between chip area reduction and protection capability.
2Use of energy by moving object
If impurity concentration in the base of parasitic bipolar transistor is lowered to induce snapback phenomenon, then operating voltage is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies local quality by creating different impurity concentration regions within the semiconductor structure. The base region of the parasitic bipolar transistor has a lower impurity concentration than the anode region, and this local differentiation is achieved through selective doping processes. This local quality approach enables snapback phenomenon and low operating voltage while using standard semiconductor manufacturing techniques, thus balancing manufacturing precision requirements.
3Reliability
If anode of parasitic diode has increased impurity concentration to lower breakdown voltage, then breakdown voltage is reduced for better protection, but leakage current increases
Solution Approach 1:
The patent carefully controls the impurity concentration parameter in the anode region of the parasitic diode, increasing it to lower the breakdown voltage for effective surge voltage clamping. However, this parameter change is optimized to achieve the desired breakdown voltage while minimizing leakage current through precise doping concentration selection, thus resolving the contradiction between protection capability and leakage current.
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 allows for a semiconductor device with a low operating voltage and improved overvoltage blocking capability, effectively protecting internal circuits from surge voltages while minimizing chip area.
Implementation Method 1
the parasitic diode, the parasitic bipolar transistor and the parasitic resistances form a protection device, in which a reverse current of the parasitic diode, having a breakdown voltage lower than the breakdown voltage of the parasitic bipolar transistor, brings the parasitic bipolar transistor into conduction by the occurrence of a snapback
Implementation Method 2
the anode of the parasitic diode has increased impurity concentration to lower the breakdown voltage
Data Source
AI summary
A semiconductor device is disclosed with a protection device formed of a parasitic bipolar transistor, a parasitic diode and a parasitic resistance and operated at a lowered operating voltage to be capable of improving a blocking capability against an over voltage. The impurity concentration in a semiconductor layer as the base of a parasitic bipolar transistor is lower compared with the impurity concentration of a semiconductor layer of the same conduction type arranged adjacently to the semiconductor layer as the base and to be the anode of a parasitic diode. The lowered impurity concentration is determined to be the concentration for making the parasitic bipolar transistor have a snapback phenomenon occur.