Semiconductor Isolation Trench Width Control for Lower Parasitic Capacitance
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Solution Overview
Problem
The use of buried bit lines in semiconductor structures, particularly in DRAMs, leads to increased parasitic capacitance, which is a challenge in deep sub-micron semiconductor processes.
Innovation Solution
A method involving precise control of trench widths through thermal oxidation and oxide etching processes to form isolation structures with precise dimensions, reducing parasitic capacitance by forming bit line and word line isolation trenches using low-K dielectric materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If buried bit lines are used to simplify connection structures, then device complexity is reduced, but parasitic capacitance increases
Solution Approach 1:
The patent divides the continuous buried bit line into segmented structures by introducing isolation trenches between adjacent bit line segments. This segmentation electrically isolates adjacent bit lines, reducing parasitic capacitance while maintaining the simplified buried bit line connection structure.
Solution Approach 2:
The patent extracts and removes portions of the substrate between adjacent buried bit lines to form isolation trenches. By taking out these intermediate regions and filling them with insulating materials, the patent reduces parasitic capacitance between bit lines while preserving the overall buried bit line architecture.
2Manufacturing precision
If feature dimensions are reduced to continue scaling, then device density increases, but manufacturing precision requirements increase
Solution Approach 1:
The patent performs preliminary formation of trench initial structures with predetermined dimensions before final trench formation. This preliminary action establishes a foundation that guides subsequent processing steps, ensuring precise final trench dimensions even as feature sizes scale down to increase device density.
Solution Approach 2:
The patent employs a feedback mechanism through iterative oxidation and etching cycles. The oxidation thickness is controlled based on desired final trench dimensions, and etching is adjusted accordingly, providing feedback control that maintains manufacturing precision during scaling.
3Manufacturing precision
If thermal oxidation and oxide etching are sequentially performed to precisely control trench widths, then manufacturing precision improves, but process complexity increases
Solution Approach 1:
The patent uses thermal oxidation where the silicon substrate itself serves as the source of oxide material. The oxidation process automatically forms oxide layers on exposed silicon surfaces, and subsequent etching removes these oxides to define trench widths. This self-service mechanism simplifies the overall process compared to depositing oxide from external sources.
Solution Approach 2:
The patent controls trench width by adjusting oxidation parameters (temperature, time, atmosphere) and etching parameters. By changing these process parameters, precise trench width control is achieved without fundamentally altering the process flow, balancing manufacturing precision with process simplicity.
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
Effectively reduces parasitic capacitance, improves production yield and electrical properties of semiconductor structures, and enhances manufacturing efficiency.
Implementation Method 1
sequentially performing a thermal oxidation process and an oxide etching process on trench walls of the plurality of first trench initial structures
Implementation Method 2
sequentially performing a thermal oxidation process and an oxide etching process on trench walls of the plurality of first trench initial structures
Data Source
AI summary
Embodiments relate to a semiconductor structure and a method for fabricating the same. The method includes: providing a substrate, where a plurality of first trench initial structures are formed on the substrate, and the first trench initial structures extend along a first direction; and sequentially performing a thermal oxidation process and an oxide etching process on trench walls of the first trench initial structures to form first trenches whose trench widths satisfy a first preset dimension. The semiconductor structure and the method for fabricating the same can precisely control a trench width dimension of a trench, to form an isolation structure having a precise dimension in the trench, thereby effectively reducing parasitic capacitance and improving production yield and electrical properties of the semiconductor structure.