Metal Etch in High Aspect-Ratio Features via Fluorine Gas Control
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Solution Overview
Problem
Conventional etching processes face challenges in achieving uniformity and control when processing high-aspect ratio features in 3D NAND structures, leading to issues like top-to-bottom loading imbalances and deformation due to wet etching, and plasma damage from dry etching.
Innovation Solution
A dry etching method involving a fluorine-containing precursor and a secondary gas, such as oxygen or nitrogen, is used to control the etch process, maintaining a flow rate ratio greater than 1:1, with a substrate temperature below 500°C and chamber pressure between 1 Torr and 50 Torr, allowing for plasma-free operation and scavenging of residual fluorine with a chlorine-containing precursor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etching is used to remove exposed material, then etching speed and selectivity are improved, but deformation of remaining material and inability to penetrate constrained trenches occur
Solution Approach 1:
The patent replaces wet chemical etching with a dry plasma-based etching process using fluorine-containing precursors. This substitution eliminates liquid contact that causes deformation while maintaining etching capability through chemical reactions in the gas phase, resolving the contradiction between etching effectiveness and material shape preservation.
Solution Approach 2:
The patent changes the physical state of the etching medium from liquid (wet etch) to gas (dry plasma etch), and controls plasma parameters such as power, pressure, and gas flow ratios to achieve uniform etching without deformation. This parameter transformation allows penetration of constrained trenches while preserving material integrity.
2Shape
If dry plasma etching is used to penetrate constrained trenches, then etching uniformity and lack of deformation are improved, but substrate damage from electric arcs occurs
Solution Approach 1:
The patent optimizes plasma process parameters including maintaining specific flow rate ratios of fluorine-containing precursor to secondary gas (greater than 1:1), controlling chamber pressure between 1-50 Torr, and limiting substrate temperature below 500°C. These parameter controls suppress harmful arc discharge while preserving the benefits of uniform dry etching.
Solution Approach 2:
The patent introduces a secondary gas (oxygen or nitrogen) as an intermediary component in the plasma process. This secondary gas acts as a buffer that moderates plasma reactivity, reducing direct ion bombardment damage to the substrate while allowing controlled fluorine-based etching to proceed uniformly through constrained trenches.
3Productivity
If high fluorine precursor flow is used to etch metal in high aspect-ratio features, then etching rate is improved, but top-to-bottom loading imbalance increases
Solution Approach 1:
The patent uses secondary gas (oxygen or nitrogen) as a mediator to modulate the distribution of fluorine radicals throughout the high aspect-ratio structure. The secondary gas helps transport and distribute etching species more uniformly from top to bottom, enabling high etching rates while maintaining loading uniformity through controlled gas phase chemistry.
Solution Approach 2:
The patent maintains a flow rate ratio of fluorine-containing precursor to secondary gas greater than 1:1, which optimizes the concentration and distribution of reactive fluorine species. This parameter control ensures sufficient etching rate for productivity while the secondary gas prevents excessive accumulation at the top, maintaining uniformity throughout the high aspect-ratio feature.
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 precise control over the etch profile, reducing top-to-bottom loading imbalances and minimizing substrate damage, resulting in uniform metal removal within high-aspect ratio structures.
Implementation Method 1
forming a plasma of the fluorine-containing precursor and the secondary gas
Implementation Method 2
etching the exposed metal within the high aspect-ratio structure
Implementation Method 3
contacting the exposed metal with plasma effluents of the oxygen-containing precursor to produce oxidized metal
Implementation Method 4
contacting the oxidized metal with the second fluorine-containing precursor
Implementation Method 5
The chlorine-containing precursor may scavenge residual fluorine
Data Source
AI summary
Exemplary methods of etching may include flowing a fluorine-containing precursor and a secondary gas into a processing region of a semiconductor processing chamber. The secondary gas may be or include oxygen or nitrogen. A flow rate ratio of the fluorine-containing precursor to the secondary gas may be greater than or about 1:1. The methods may include contacting a substrate with the fluorine-containing precursor and the secondary gas. The substrate may include an exposed metal. The substrate may define a high aspect-ratio structure. The methods may include etching the exposed metal within the high aspect-ratio structure.