Semiconductor Trench Etching via Multi-Layer Insulator Segmentation
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Solution Overview
Problem
Variations in insulating film thickness during the anisotropic etching process for semiconductor device manufacturing lead to layer-to-layer variations and transistor characteristic fluctuations.
Innovation Solution
A method involving the sequential formation of multiple insulating films with different materials, where a photosensitive pattern is used to etch through these films, and the exposed third insulating film is used as a mask to extend trenches into the semiconductor substrate, allowing for the removal of varying film portions and subsequent formation of a hollow space, thereby stabilizing the film thickness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If anisotropic etching is performed to form a trench using an oxide film as a mask, then the trench can be formed with vertical walls, but the oxide film thickness varies in the wafer plane causing film thickness variations
Solution Approach 1:
The patent segments the insulating film structure into multiple layers (first insulating film, second insulating film, third insulating film) with different materials. This segmentation allows each layer to serve different functions: the first layer provides the initial mask, while the second and third layers compensate for thickness variations, thereby resolving the contradiction between achieving vertical trench walls and maintaining film thickness uniformity.
Solution Approach 2:
The patent changes the material parameters of the insulating films by using different materials for the first, second, and third insulating films. This parameter change enables selective etching and allows the structure to compensate for thickness variations, maintaining both vertical trench walls and uniform final film thickness.
2Manufacturing precision
If multiple insulating films with different materials are formed sequentially, then film thickness variations can be suppressed, but the device structure becomes more complex
Solution Approach 1:
The patent applies multi-functionality to the insulating film structure where the first insulating film serves as both a structural layer and an initial etch mask, while the second and third insulating films serve as both structural layers and thickness compensation layers. This multi-functionality reduces the need for additional separate components, thereby managing complexity while achieving thickness uniformity.
Solution Approach 2:
The patent uses a nested structure where the first insulating film is embedded within the second insulating film, which is in turn embedded within the third insulating film. This nesting arrangement allows multiple functional layers to be integrated in a compact manner, suppressing thickness variations without proportionally increasing overall structural complexity.
3Manufacturing precision
If the third insulating film is used as a mask to extend the trench, then the varying portions of the insulating film can be removed, but additional etching steps are required
Solution Approach 1:
The patent performs preliminary action by forming the second and third insulating films before the trench etching process. These pre-formed layers serve as thickness compensation structures that will be removed later, allowing the etching process to proceed with consistent reference surfaces, thereby improving transistor characteristic consistency despite requiring additional steps.
Solution Approach 2:
The patent converts the harmful effect of thickness variations into a benefit by using the third insulating film as a sacrificial mask. The varying portions of the insulating film that would normally cause problems are instead utilized as part of the masking structure, which is then selectively removed to achieve uniform final dimensions, thereby improving precision despite additional process steps.
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 effectively suppresses film thickness variations and transistor characteristic fluctuations, enhancing the consistency and performance of semiconductor devices.
Implementation Method 1
performing etching using the photosensitive pattern as a mask to form a trench extending through the first to third insulating films and reaching the semiconductor substrate
Implementation Method 2
performing etching using the exposed third insulating film as a mask to extend the trench in the semiconductor substrate
Implementation Method 3
the trench is formed by anisotropic etching using the oxide film as a mask. During the anisotropic etching, the oxide film corresponding to a predetermined film thickness is also removed by etching
Data Source
AI summary
A method of manufacturing a semiconductor device includes the steps of forming a plurality of gate electrodes, forming a first insulating film over the plurality of gate electrodes such that the first insulating film is embedded in a space between the plurality of gate electrodes, forming a second insulating film over the first insulating film, forming a third insulating film over the second insulating film, forming a photosensitive pattern over the third insulating film, performing etching using the photosensitive pattern as a mask to form a trench extending through the first to third insulating films and reaching a semiconductor substrate, removing the photosensitive pattern, performing etching using the exposed third insulating film as a mask to extend the trench in the semiconductor substrate, removing the third and second insulating films, and forming a fourth insulating film in the trench and over the first insulating film.