High-Aspect-Ratio Trench Gap Fill for GAA Transistor Isolation
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Solution Overview
Problem
The semiconductor industry faces challenges in scaling down integrated circuit (IC) manufacturing due to increased complexity and processing difficulties as geometry sizes decrease, requiring innovative methods for forming efficient semiconductor device structures.
Innovation Solution
The implementation of a bottom-up deposition process and advanced patterning techniques, such as double-patterning or multi-patterning processes, to form gate all around (GAA) transistor structures with void-free and seam-free gap-fill materials like silicon nitride, which improve insulation and device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional deposition processes are used to fill trenches in transistor layers, then the deposition process is simpler and faster, but voids and seams form in the filled material reducing device reliability
Solution Approach 1:
The deposition process is divided into multiple sequential stages: initial deposition to form a bottom layer, removal of sacrificial material, and second deposition to form the final gap-fill material. This segmentation allows each stage to be optimized independently, ensuring void-free filling while maintaining process control
Solution Approach 2:
Sacrificial material is deposited and patterned in advance to define the trench geometry before the final gap-fill material is deposited. This preliminary structuring enables precise control over the final material placement, preventing void formation while simplifying the main deposition step
2Productivity
If geometry size is scaled down to increase functional density, then production efficiency increases and costs decrease, but processing complexity and manufacturing difficulty increase
Solution Approach 1:
The sacrificial material is designed to be automatically removed through selective etching processes, creating self-aligned trenches without requiring additional alignment steps. This self-service approach maintains precision at scaled dimensions while reducing process complexity
Solution Approach 2:
The process utilizes changes in material properties (etch selectivity, deposition temperature) to enable scaling. By adjusting these parameters, the same deposition process can effectively fill trenches at different size scales, maintaining productivity while adapting to reduced geometry dimensions
3Reliability
If high-aspect ratio trenches are formed to improve transistor performance, then device performance improves, but filling these trenches without voids becomes more difficult
Solution Approach 1:
Sacrificial material acts as an intermediary structure that defines the high-aspect ratio trench geometry. The gap-fill material is deposited conformally around this intermediary, ensuring complete filling even in high-aspect ratio structures. The intermediary is then removed, leaving a perfectly filled trench without voids
Solution Approach 2:
The problem of filling high-aspect ratio trenches is approached by adding the time dimension through sequential deposition steps. Rather than attempting to fill in a single step, the process evolves through multiple temporal stages, allowing material to progressively fill the trench from different directions, ensuring complete penetration without void formation
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 enables the formation of high-aspect ratio trenches and isolation structures without voids or seams, enhancing the performance and yield of semiconductor devices by providing better insulation and preventing metal penetration or diffusion, thus addressing the complexity and efficiency issues in IC manufacturing.
Implementation Method 1
The trench is then filled with a gap-fill material using a flowable chemical vapor deposition process
Data Source
AI summary
A method for forming a semiconductor device structure is provided. The method includes forming a transistor layer over a substrate and forming a trench in the transistor layer. A depth to width ratio of the trench is greater than or equal to 3. The method further includes filling the trench with a gap-fill material using a flowable chemical vapor deposition process, wherein a precursor and a reactant are used in the flowable chemical vapor deposition process, and a ratio of the precursor to the reactant is about 1.