Transient Voltage Absorber Layout for Low Capacitance and Leakage
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Transient voltage absorption elements face a trade-off between reducing parasitic capacitance and suppressing leakage current, as high impurity concentrations in buried layers increase capacitance while low concentrations in substrates lead to increased leakage due to auto-doping.
Innovation Solution
A transient voltage absorption element design featuring a semiconductor substrate with epitaxial layers, p+ and n+ regions, and buried layers with high impurity concentrations, where trenches reach the buried layers from the surface side, separating diodes and avoiding auto-doping, thus reducing parasitic capacitance and leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the impurity concentration of the substrate is reduced to reduce parasitic capacitance, then parasitic capacitance is reduced, but leakage current increases due to auto-doping at the trench portion
Solution Approach 1:
The substrate is divided into a trench portion and non-trench portions, with the trench separating adjacent diodes. The trench reaches from the surface to the buried layer, creating distinct regions that prevent auto-doping between adjacent structures while allowing the substrate to maintain low overall impurity concentration for reduced parasitic capacitance.
Solution Approach 2:
The trench acts as an intermediary barrier between adjacent diodes, preventing the diffusion of impurities that would cause auto-doping. This intermediary structure allows the substrate to have low impurity concentration without causing leakage current, as the trench physically separates the regions that would otherwise interact through diffusion.
2Reliability
If a buried layer with high impurity concentration is formed to suppress leakage current, then leakage current is suppressed, but parasitic capacitance increases
Solution Approach 1:
The buried layer is formed with high impurity concentration only in specific localized regions adjacent to the trenches, rather than uniformly across the entire substrate. This local quality approach allows the buried layer to suppress leakage current at critical interfaces while minimizing the overall parasitic capacitance by limiting the high-concentration region to where it is most needed.
3Loss of energy
If the oxide film thickness is increased to suppress parasitic capacitance with surface electrodes, then parasitic capacitance is reduced, but leakage current increases due to auto-doping in low-concentration substrate
Solution Approach 1:
The trench is formed to reach the buried layer before final device completion, establishing a permanent barrier that prevents auto-doping throughout subsequent processing steps. This preliminary action of creating the deep trench structure ensures that even with thin oxide films, leakage current is suppressed by the physical barrier rather than relying on thick oxide layers.
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 suppresses leakage current and reduces parasitic capacitance, improving frequency characteristics and insertion loss in transmission lines by avoiding the trade-off relationship between impurity concentration and buried layer formation.
Implementation Method 1
a transient voltage absorption element that absorbs a transient abnormal voltage due to electrostatic discharge (ESD) or the like, or a surge such as a lightning surge
Implementation Method 2
a first diode and a second diode that are opposite to each other in polarity and are connected in parallel between the first terminal and the second terminal
Data Source
AI summary
A transient voltage absorption element is provided that includes a semiconductor substrate, an epitaxial layer on a surface of the semiconductor substrate, p+ regions and n+ regions in the epitaxial layer, buried layers in the semiconductor substrate, and trenches. A plurality of diodes each including the epitaxial layer, the p+ region, and the n+ region are formed, the trenches extend to the buried layers from a surface side of the epitaxial layer to separate the diodes. The buried layers have an impurity concentration higher than the semiconductor substrate and are separated between the diodes adjacent to each other.