Split-Gate Trench Structure for Void-Free Field Plate Filling
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Solution Overview
Problem
In semiconductor devices with a split gate structure, voids in the conductive film for the field plate electrode can lead to filling failures, abnormal shape formation, stress concentration, and crystal defects, resulting in decreased withstand voltage and reliability.
Innovation Solution
A method involving ion implantation into the insulating film at an inclined angle to control the etching rate and reduce the thickness of the insulating film, ensuring the conductive film fills the trench without voids, and forming the field plate electrode with a wider upper contact portion to prevent stress concentration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the insulating film is formed by CVD method, then the insulating film can be formed in the trench, but the thickness of the insulating film becomes large at the uppermost portion and overhang occurs
Solution Approach 1:
The patent performs preliminary etching of the insulating film at the uppermost portion of the trench before forming the conductive film. This preliminary action removes the overhanging part of the insulating film, creating a more uniform thickness profile that prevents filling failure and void formation in subsequent conductive film deposition.
Solution Approach 2:
The patent changes the thickness parameter of the insulating film by selectively removing material from the uppermost portion. This parameter change creates a thickness gradient where the upper portion is thinner than the lower portion, preventing overhang and ensuring complete filling of the conductive film without voids.
2Ease of manufacture
If the conductive film is deposited by CVD method, then the conductive film can be formed, but voids occur in the conductive film due to insulating film overhang
Solution Approach 1:
The patent performs preliminary etching of the insulating film before depositing the conductive film. This preliminary action eliminates the overhanging insulating film that would otherwise cause filling failure, ensuring that the conductive film can be completely and uniformly deposited without forming voids.
Solution Approach 2:
The patent applies preliminary anti-action by removing the problematic overhanging insulating film portion before conductive film deposition. This prevents the harmful effect of void formation in advance, ensuring reliable conductive film integrity.
3Manufacturing precision
If the field plate electrode is formed with narrow upper portion, then the trench can be filled, but stress concentration and crystal defects occur
Solution Approach 1:
The patent creates an asymmetric field plate electrode shape where the upper portion is wider than the lower portion. This asymmetric geometry prevents stress concentration and crystal defects by distributing mechanical stress more evenly, while still maintaining proper trench filling and electrical functionality.
Solution Approach 2:
The patent changes the dimensional parameters of the field plate electrode by forming it with a wider upper portion. This parameter change from a uniform or narrow-top geometry to a tapered geometry with wider top prevents stress concentration and improves device reliability.
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 enhances the reliability of semiconductor devices by preventing void formation, reducing crystal defects, and maintaining high withstand voltage, thus improving the manufacturing process and device performance.
Implementation Method 1
performing a first ion implantation to the first insulating film... in the (d), the first ion implantation is performed from a direction inclined by a first angle from a normal direction with respect to the upper surface of the semiconductor substrate
Implementation Method 2
The insulating film IF1 is a silicon oxide film formed by the CVD (Chemical Vapor Deposition) method... the conductive film CF1 for the field plate electrode is deposited in the trench TR1 by the CVD method
Implementation Method 3
by a thermal oxidation method, a gate insulating film GI is formed in the trench TR1 on the insulating film IF1
Data Source
AI summary
A trench is formed in a semiconductor substrate. An insulating film is formed in the trench and on an upper surface of the semiconductor substrate. An ion implantation is performed to the insulating film. An etching treatment is performed to the insulating film, thereby a thickness of the insulating film is reduced. A conductive film is formed in the trench via the insulating film. In plan view, the trench extends in a Y-direction. The above-described ion implantation is performed from a direction inclined by a predetermined angle from an extending direction of a normal line with respect to the upper surface of the semiconductor substrate.