Trench Gate Insulating Film Structure to Prevent MOSFET Seam Gaps
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Solution Overview
Problem
The manufacturing of semiconductor devices with trench gate structures faces issues such as warpage of semiconductor substrates due to stress from insulating films, leading to gaps in conductive films and subsequent crystalline defects and reduced dielectric strength, which affect the breakdown voltage and reliability of MOSFETs.
Innovation Solution
A method involving the formation of a first silicon oxide film by thermal oxidation and a second silicon oxide film by poly-crystalline silicon oxidation, with a conductive film embedded through a thinner insulating film to reduce stress and prevent gap formation, thereby improving the interface state and reliability of the semiconductor device.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a thick insulating film is formed by CVD method to cover the semiconductor substrate surface, then the coverage is improved, but the film thickness becomes excessively large causing overhang shape and gap formation
Solution Approach 1:
The insulating film is segmented into two distinct layers: a first insulating film formed by thermal oxidation and a second insulating film formed by CVD method. This segmentation allows each layer to serve different functions - the first layer provides good interface contact and the second layer provides thick coverage, resolving the contradiction between coverage area and thickness uniformity
Solution Approach 2:
Different regions of the insulating film structure have different properties: the first insulating film (thermal oxidation) provides excellent interface quality with the semiconductor substrate, while the second insulating film (CVD) provides thick coverage. This local differentiation of film properties solves the contradiction between interface quality and coverage thickness
2Ease of manufacture
If a conductive film is deposited in the trench, then the field plate electrode is formed, but gaps (seams) occur in the conductive film reducing reliability
Solution Approach 1:
The first insulating film is formed by thermal oxidation before forming the second insulating film by CVD. This preliminary formation of a high-quality interface layer prevents gap formation in subsequent conductive film deposition, ensuring both ease of manufacture and reliability
3Manufacturing precision
If thermal oxidation treatment is used to form insulating film, then interface state is improved, but semiconductor substrate warpage occurs due to stress
Solution Approach 1:
The insulating film structure is segmented into a first layer (thermal oxidation) and a second layer (CVD). The thin first layer provides good interface state while the thicker second layer provides coverage. The segmentation allows the stress from thermal oxidation to be limited to a thin layer, reducing overall substrate warpage while maintaining interface quality
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 minimizing gap formation and stress-induced defects, improving the dielectric strength and breakdown voltage of MOSFETs.
Implementation Method 1
forming a first silicon oxide film by thermal oxidation
Implementation Method 2
forming a second silicon oxide film by poly-crystalline silicon oxidation
Data Source
AI summary
A trench is formed in a semiconductor substrate. A first silicon oxide film is formed in an inside of the trench. A poly-crystalline silicon film is formed on the first silicon oxide film. A second silicon oxide film is formed from the poly-crystalline silicon film by performing a thermal oxidation treatment to the poly-crystalline silicon film. Thus, an insulating film including the first silicon oxide film and the second silicon oxide film is formed. A first conductive film is formed so as to embed the inside of the trench via the insulating film.