Lateral Bipolar Diode Reduces Parasitic Leakage Current
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Solution Overview
Problem
Conventional diode elements on semiconductor substrates experience leakage currents due to parasitic bipolar transistors, which hinder low current consumption and desired integrated circuit performance.
Innovation Solution
A semiconductor device with a diode element featuring a retrograde type well layer and lateral bipolar transistor structure, including a first and second conductive type impurity layer, and an electrode layer separated by an insulation film, reduces leakage currents by forming a lateral bipolar transistor that redirects parasitic current to the cathode side.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional diode element structure is used, then the device is simple and easy to manufacture, but leakage current flows into the semiconductor substrate due to parasitic bipolar transistor activation
Solution Approach 1:
The patent transforms the conventional vertical parasitic bipolar transistor structure into a lateral bipolar transistor configuration. By arranging the first and second impurity layers horizontally within the well layer rather than vertically, the design redirects the parasitic current path from flowing into the substrate to flowing laterally to the cathode, thereby eliminating leakage while maintaining structural simplicity
Solution Approach 2:
The patent converts the harmful parasitic bipolar transistor effect into a beneficial lateral bipolar transistor. Instead of trying to eliminate the parasitic transistor, the design harnesses its current amplification effect to redirect leakage current through the lateral structure to the cathode, transforming the harmful substrate leakage into useful current flow that contributes to the diode's forward current
2Productivity
If a lateral bipolar transistor structure is added to redirect parasitic current, then current efficiency improves to nearly 100%, but device structure and manufacturing complexity increase
Solution Approach 1:
The patent merges the lateral bipolar transistor structure directly into the diode element fabrication process. The first and second impurity layers are formed as part of the standard diode manufacturing sequence, using the same well layer and following similar processing steps, thereby achieving high current efficiency without requiring separate fabrication stages or additional complex structures
Data Source
AI summary
The invention is directed to a semiconductor device having a diode element which prevents a leakage current due to a vertical parasitic bipolar transistor and enhances current efficiency. An element isolation insulation film is provided on an N well layer, and a first P+ layer and a second P+ layer are formed on the N well layer surrounded by the element isolation insulation film, the second P+ layer being formed at a distance from the first P+ layer. An electrode layer is formed on the N well layer between the first P+ layer and the second P+ layer. An N+ layer for a contact is formed on the N well layer between the element isolation insulation film and other element isolation insulation film. The first P+ layer is connected with an anode wiring, and the electrode layer, the second P+ layer, and the N+ layer are connected with a cathode wiring. A diode element utilizing a lateral PNP bipolar transistor is thus formed on the semiconductor substrate.