Multi-Layer Mask Etching for High Aspect Ratio Semiconductor Holes
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Solution Overview
Problem
The challenge in fabricating semiconductor devices lies in forming high aspect ratio features, such as capacitors in DRAM and vertical NAND structures, where existing methods struggle to achieve the necessary etching depth and uniformity due to limitations in etch selectivity and mask thickness, leading to defects and non-uniform critical dimensions.
Innovation Solution
A method involving the use of multiple mask films with different etch selectivities and thicknesses is employed, where a first mask film with a silicon material and a second mask film with a metal material are sequentially used to etch an oxide film, allowing for the formation of high aspect ratio holes and capacitors by controlling the etching process to achieve the desired depth and uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single mask film is used for etching the oxide film, then the process is simple, but the etching depth and uniformity are insufficient to form high aspect ratio features
Solution Approach 1:
The mask film is segmented into multiple layers (first mask film with semiconductor material and second mask film with metal material) that have different etch selectivities. This segmentation allows each layer to contribute differently to the etching process, enabling precise control over etching depth and uniformity to achieve high aspect ratio features.
Solution Approach 2:
The mask film structure uses composite materials with different etch selectivities - a semiconductor material (such as silicon) for the first mask film and a metal material (such as tungsten or molybdenum) for the second mask film. This composite structure enables differential etching rates that facilitate the formation of high aspect ratio holes with improved precision.
2Manufacturing precision
If the mask film thickness is increased to achieve greater etching depth, then etching depth improves, but tilting and unevenness increase
Solution Approach 1:
Different regions of the mask film structure have different etch selectivities - the first mask film region and second mask film region are designed with distinct material properties. This local quality differentiation allows the etching process to proceed at different rates through different mask layers, maintaining hole verticality and uniformity while achieving the required etching depth for high aspect ratio features.
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 holes and capacitors with improved etching depth and uniformity, enhancing the capacitance and reliability of semiconductor devices by mitigating tilting and unevenness issues associated with single-mask etching processes.
Implementation Method 1
etching first portions of the oxide film by using the second mask film pattern as a first etch mask film; and etching second portions of the oxide film by using the first mask film pattern as a second etch mask film
Data Source
AI summary
Provided is a method of fabricating a semiconductor device. The method includes forming an oxide film on a target layer, forming a first mask film on the oxide film, wherein the first mask film contains a semiconductor material and has a first thickness and a first etch selectivity with respect to the oxide film, forming a second mask film on the first mask film, wherein the second mask film contains a metal and has a second thickness smaller than the first thickness and a second etch selectivity larger than the first etch selectivity with respect to the oxide film, forming a second mask film pattern by patterning the second mask film, forming a first mask film pattern by patterning the first mask film, etching some portions of the oxide film by using the second mask film pattern as an etch mask film, and etching the rest of the oxide film by using the first mask film pattern as an etch mask film to form a hole, wherein the target layer is exposed via the hole.