Power FinFET Trench Layout With Shielding for Lower On-Resistance
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Solution Overview
Problem
Existing power MOSFETs with vertical channel regions require wide trenches, leading to large pitch dimensions and on-resistance, and the method for producing two-part control electrodes is laborious, while process fluctuations affect short-circuit current limitation.
Innovation Solution
The method involves creating power FinFETs with alternating shielding regions and one-piece control electrodes, using a structured mask to form trenches and shielding regions, and applying an isotropic oxide layer to optimize trench width and spacing, thereby reducing on-resistance and enhancing short-circuit current limitation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If two-part control electrodes are used with wide trenches, then breakdown voltage is improved, but pitch dimension and on-resistance increase
Solution Approach 1:
The patent segments the control electrode into two separate parts: a first control electrode in the first trench and a second control electrode in the second trench. This segmentation allows each trench to be narrower while maintaining the overall breakdown voltage performance, thereby reducing the total pitch dimension without sacrificing strength.
Solution Approach 2:
The patent introduces an intermediary insulated bridge structure that electrically connects the first and second control electrodes while providing electrical insulation. This mediator enables the two-part electrode configuration to function as a unified control system with improved breakdown voltage, while the physical separation allows for reduced trench width and pitch.
2Strength
If two-part control electrodes are used, then breakdown voltage is improved, but manufacturing complexity increases
Solution Approach 1:
The patent performs preliminary actions by forming both trenches and implanting both shielding regions before forming the insulated bridge and control electrodes. This sequential preliminary structuring simplifies the overall manufacturing process by establishing the trench and shielding framework first, then adding the control electrode components in a systematic manner.
Solution Approach 2:
The insulated bridge acts as an intermediary element that simplifies the connection between the two control electrodes. Rather than requiring complex three-dimensional interconnections, the bridge provides a straightforward planar connection structure that reduces manufacturing complexity while achieving the desired electrical connectivity and insulation.
3Object-affected harmful factors
If p-doped shielding regions are implanted with lithographically structured mask, then short-circuit current limitation is achieved, but process fluctuations affect the limitation
Solution Approach 1:
The patent employs self-aligned fabrication techniques where the shielding regions are automatically positioned relative to the trenches through the etching and implantation sequence. The shielding regions are formed by implanting through the trench openings, which self-align to the trench positions, eliminating the need for separate lithographic alignment steps and reducing sensitivity to process fluctuations.
Solution Approach 2:
The patent performs preliminary trench formation and shielding region implantation before final control electrode fabrication. This preliminary structuring establishes precise geometric relationships between trenches and shielding regions that are less sensitive to subsequent process variations, improving the consistency of short-circuit current limitation.
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 approach reduces the distance between shielding regions, tolerates process fluctuations, and decreases on-resistance, effectively limiting short-circuit current and improving the overall performance of power FinFETs.
Implementation Method 1
creating a first structured mask on the front side of the semiconductor body by means of a lithography step
Implementation Method 2
creating first trenches below the first open regions by means of a first etching process
Implementation Method 3
creating shielding regions below the first trenches by means of a first implantation process
Implementation Method 4
applying an isotropic oxide layer to the front side of the semiconductor body
Implementation Method 5
activating the shielding regions by means of annealing
Data Source
AI summary
A method for producing power FinFETs with one-piece control electrodes. The method includes: creating a first structured mask; creating first trenches below first open regions by a first etching process starting from the front side of the semiconductor body and extending into the drift layer; creating shielding regions below the first trenches by a first implantation process; applying an isotropic oxide layer to the front side of the semiconductor body; creating a second structured mask; creating second trenches below second open regions by a third etching process; oxidizing the front side such that a further oxide layer is disposed on the front side; widening the first trenches and the second trenches by a fourth etching process; applying a polysilicon layer to the front side of the semiconductor body such that the first trenches and the second trenches are completely filled; and activating the shielding regions by means of annealing.