Layered Etching Sequence for Uniform High-Aspect-Ratio Recesses
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Solution Overview
Problem
Existing semiconductor fabrication processes face challenges in uniformly etching recessed features with high aspect ratios, particularly in structures like 3D NAND, due to the difficulty in processing narrow widths and deep depths.
Innovation Solution
A method involving alternating exposure to etching and oxidizing gases, with controlled bias powers, is used to sequentially remove and convert layers in a stacked structure, allowing precise formation of recessed features through a mask.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used on high aspect ratio structures, then the etching process can be completed, but the uniformity of etching across narrow widths and deep depths deteriorates
Solution Approach 1:
The etching process is segmented into multiple alternating steps: etching the second layer, oxidizing the first layer, etching the converted first layer, and repeating this cycle. This segmentation allows the deep etching to be performed in controlled increments, maintaining uniformity throughout the high aspect ratio structure by periodically converting and re-etching layers rather than attempting to etch the full depth in a single continuous process
Solution Approach 2:
The patent employs periodic alternation between etching gas exposure and oxidizing gas exposure. The first gas (etching) is applied to remove portions of the second layer, then the second gas (oxidizing) converts portions of the first layer, followed by another etching step. This periodic action sequence is repeated multiple times to progressively form the recessed feature while maintaining etching uniformity throughout the deep structure
2Shape
If the structure has narrow widths and deep depths, then high aspect ratio features can be formed, but the difficulty of etching uniformly increases
Solution Approach 1:
Before attempting to etch deep into the structure, the patent first forms a mask with the desired pattern on the top surface. The etching process then proceeds by alternately etching and oxidizing layers in a controlled sequence, with each cycle removing a controlled amount of material. This preliminary mask formation combined with iterative layer processing allows the narrow width and deep depth geometry to be achieved while maintaining etching uniformity through the high aspect ratio structure
Solution Approach 2:
The patent changes the chemical state of materials through periodic oxidation and etching cycles. The first layer is converted from its original state to an oxidized state, which is then etched differently than the unoxidized material. This parameter change in material state allows for controlled removal of material at different depths, maintaining uniformity throughout the high aspect ratio feature by adapting the etching process to the local material state rather than attempting uniform etching through the entire depth
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 enables the efficient and uniform etching of high aspect ratio recessed features by iteratively applying etching and oxidizing gases, ensuring precise pattern transfer and depth control.
Implementation Method 1
exposing the structure to a first gas, thereby removing one or more portions of a topmost one of the plurality of second layers that was intact through a mask
Implementation Method 2
exposing the structure to a second gas, thereby converting one or more portions of a topmost one of the plurality of first layers that was intact
Data Source
AI summary
A method includes providing a structure in a chamber, wherein the structure comprising a plurality of first layers and a plurality of second layers alternately stacked on top of one another; exposing the structure to a first gas, thereby removing one or more portions of a topmost one of the plurality of second layers that was intact through a mask; exposing the structure to a second gas, thereby converting one or more portions of a topmost one of the plurality of first layers that was intact; and exposing the structure to the first gas, thereby removing the one or more converted portions of the topmost first layer.