Bootstrap Diode Leakage Suppression in High Voltage MOSFET
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-voltage integrated circuit devices face issues with leakage current due to holes flowing to the substrate side during forward biasing of the bootstrap diode, which reduces charging current for the bootstrap capacitor and increases chip area.
Innovation Solution
A semiconductor device with a p-type semiconductor substrate, an n-type buried layer, and a high-voltage n-channel MOSFET, featuring a floating potential region and separation regions to isolate the diode, reducing leakage current and increasing charging efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bootstrap diode is forward biased to charge the bootstrap capacitor, then the charging current increases, but leakage current flows to the substrate side reducing efficiency
Solution Approach 1:
The substrate is divided into multiple regions with different potential levels. A floating potential region is created between the diode formation region and the substrate, separated by insulating films. This segmentation prevents direct current leakage to the substrate while allowing charging current to flow through the isolated path to the bootstrap capacitor.
Solution Approach 2:
An insulating film is introduced as an intermediary between the diode formation region and the substrate. This intermediary layer blocks the leakage current path to the substrate while maintaining electrical isolation, allowing the bootstrap diode to charge the capacitor without losing current to the substrate.
2Loss of energy
If separation regions are added to isolate the diode and reduce leakage current, then leakage current is suppressed, but chip area increases
Solution Approach 1:
Instead of using lateral separation regions that consume chip area, the patent uses vertical isolation through insulating films deposited in trenches. The floating potential region is created by depositing insulating films to a depth that electrically isolates the diode formation region from the substrate, utilizing the third dimension (depth) rather than lateral space.
Solution Approach 2:
The insulating films are nested within trenches formed in the substrate. The first insulating film is deposited to a first depth, then a second insulating film is deposited to a second depth greater than the first, creating a nested structure that provides multiple levels of electrical isolation while minimizing lateral space consumption.
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 enhances charging current for the bootstrap capacitor, while minimizing the chip area, thus improving the performance and efficiency of high-voltage integrated circuit devices.
Implementation Method 1
a p-type first separation region surrounding the part of the semiconductor layer where the floating potential region is provided, the first separation region being in contact with the semiconductor substrate, and spaced apart from the floating potential region to be formed in a ring-like shape; a p-type second separation region spaced apart from the first separation region to surround, in a ring-like shape, a region where the diode is located
Implementation Method 2
an n-type buried layer formed on the semiconductor substrate; an n-type semiconductor layer formed on the buried layer; a diode
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
In a semiconductor device (100) including a bootstrap diode (Db) and a high voltage electric field transistor (62) on a p-type semiconductor substrate (1), a cavity (3) is formed in an n--type buried layer (50) of the semiconductor substrate (1) to use the buried layer (50) beneath the cavity as a drain drift region of the high voltage n-channel MOSFET (62), whereby a leakage current by holes (92) that flows to the semiconductor substrate (1) side in forward biasing of the bootstrap diode (Db) can be suppressed, and charging current for a bootstrap capacitor C1 can be increased, as well as increase in chip area can be suppressed.