Trench-Gate MOSFET Stacked Insulating Films for Breakdown Voltage
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Solution Overview
Problem
Existing semiconductor devices face challenges in achieving high breakdown voltage and low ON-resistance due to impurities in insulating films, which affect device characteristics and switching performance.
Innovation Solution
The semiconductor device incorporates a trench-gate MOSFET structure with a field plate positioned closer to the drain electrode than the gate electrode, using a stacked insulating film structure including silicon oxide and silicon nitride films to reduce internal stress and prevent impurity movement, thereby stabilizing device characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick insulating film is formed inside the gate trench by CVD to reduce internal stress, then the breakdown voltage is improved, but impurities are introduced that affect device characteristics
Solution Approach 1:
The thick insulating film is divided into multiple thin insulating films (first insulating film 21, second insulating film 23, third insulating film 25) deposited in sequence. Each thin film has lower internal stress and fewer impurities compared to a single thick film, while the combined structure provides the necessary total thickness for breakdown voltage protection.
Solution Approach 2:
The patent uses a composite insulating film structure with different materials (silicon oxide for films 21 and 23, silicon nitride for film 25) to achieve both mechanical stress reduction and electrical insulation. The different materials have different stress characteristics, allowing the overall structure to maintain adhesion while providing sufficient insulation thickness.
2Ease of manufacture
If a single thick insulating film is used, then the manufacturing process is simple, but impurity contamination occurs that degrades switching characteristics
Solution Approach 1:
The insulating film formation process is segmented into multiple deposition steps, where each step deposits a thin film with controlled thickness and composition. This segmentation allows better control over impurity introduction in each step compared to forming a single thick film, while the cumulative effect achieves the required total insulation.
Solution Approach 2:
The patent changes the deposition parameters by performing multiple CVD processes with different gas compositions and conditions for each thin film layer. This allows optimization of each layer's properties to minimize impurity incorporation while maintaining the overall film thickness needed for device performance.
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 enhances breakdown voltage and maintains low ON-resistance while preventing impurity-induced degradation of switching characteristics, ensuring stable device performance.
Implementation Method 1
a stacked insulating film structure including silicon oxide and silicon nitride films to reduce internal stress
Data Source
AI summary
A semiconductor device includes first and second electrodes; a semiconductor part between the first and second electrodes; a control electrode and a third electrode in a trench between the semiconductor part and the second electrode. The device further includes a first insulating part insulating the control electrode from the semiconductor part; a second insulating part insulating the third electrode from the semiconductor part; and a third insulating part insulating the third electrode from the control electrode. The second insulating part includes first and second insulating films and a portion of a third insulating film. The first insulating film is provided between the semiconductor part and the third electrode. The second insulating film is provided between the first insulating film and the third electrode. The third insulating film includes the portion between the first insulating film and the second insulating film, and another portion inside the third insulating part.