DRAM Capacitor Hole Hard Mask Etching With Sacrificial Trenches
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Solution Overview
Problem
The increasing aspect ratio of capacitors in Dynamic Random-Access Memory (DRAM) storage units due to shrinking geometric sizes leads to etching defects, such as non-perpendicular sidewalls and unintended etching of the medium layer, causing performance issues and potential damage to electronic components.
Innovation Solution
A manufacturing method for semiconductor structures involves forming a sacrificial layer with a high etch selectivity ratio and a barrier layer as an etch stop, controlling the topography of trenches and the hard mask layer to prevent etching defects, and using a photolithography process to ensure accurate formation of capacitor holes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the geometric size of the storage unit decreases according to Moore's Law, then the integration density increases, but the aspect ratio of the capacitor increases leading to etching defects
Solution Approach 1:
The patent introduces a multi-layer mask structure consisting of a first mask layer and a second mask layer, dividing the etching process into multiple stages. The first mask layer is used for initial etching to form capacitor holes, while the second mask layer is used for subsequent etching to form transistor structures. This segmentation allows precise control of each etching step independently, preventing etching defects even as device dimensions shrink and aspect ratios increase.
2Reliability
If the aspect ratio of the capacitor increases, then the storage capacity is maintained in smaller devices, but etching defects such as non-perpendicular sidewalls occur
Solution Approach 1:
The patent applies a planarization process before the etching step to create a flat surface for photolithography patterning. This preliminary action ensures that the mask layers are deposited on a uniform surface, enabling precise pattern transfer during etching. The planarization compensates for the challenging high aspect ratio conditions, maintaining sidewall perpendicularity and preventing etching defects while preserving capacitor performance.
3Ease of manufacture
If the etching process is performed without sufficient selectivity, then the manufacturing process is simplified, but unintended etching of the medium layer occurs causing performance issues
Solution Approach 1:
The patent employs a multi-layer mask structure with different materials and thicknesses to achieve high etch selectivity. The first mask layer has specific material properties that provide high selectivity against the medium layer during capacitor hole etching, while the second mask layer provides selectivity during transistor structure etching. By carefully controlling the material composition, thickness, and deposition conditions of each mask layer, the patent achieves sufficient etch selectivity to protect the medium layer while maintaining a manageable manufacturing process.
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 method ensures precise formation of capacitor holes with improved etching selectivity, reducing etching defects and maintaining the performance of the medium layer, thereby enhancing the structural integrity and functionality of DRAM storage units.
Implementation Method 1
An opening pattern is formed over the sacrificial layer by utilizing a photolithography process
Implementation Method 2
The sacrificial layer is etched according to the opening pattern by taking the barrier layer as an etch stop layer to form first trenches
Data Source
AI summary
A manufacturing method of a semiconductor structure includes the following steps. A substrate is provided. A barrier layer is formed on the substrate. A sacrificial layer is formed on the barrier layer. An opening pattern is formed over the sacrificial layer by utilizing a photolithography process. The sacrificial layer is etched according to the opening pattern to form first trenches by using the barrier layer as an etch stop layer. A medium layer material is filled in the first trenches. The sacrificial layer is etched to form second trenches by using the barrier layer as the etch stop layer. A hard mask layer material is filled in the second trenches. The medium layer material is etched to form a hard mask layer by using the barrier layer as the etch stop layer.