Wet Etching of High-Aspect-Ratio Features With Neutral Surface Charge
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Solution Overview
Problem
The challenge of achieving uniform wet etching of materials within high aspect ratio features, such as deep trenches and holes, on patterned substrates, due to variations in etch rate along the depth of these features.
Innovation Solution
Ensuring that the wall surfaces of the material being etched exhibit a neutral surface charge when exposed to the etch solution, which maintains a uniform concentration of reactive species and prevents electrostatic forces that cause non-uniform etching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If wet etching is used to etch material within high aspect ratio features, then material removal is achieved, but non-uniform etch rate along the depth of features occurs
Solution Approach 1:
The patent changes the pH parameter of the etch solution to achieve a neutral surface charge on the feature walls. By adjusting this chemical parameter, the electrostatic interactions are eliminated, resulting in uniform etch rate throughout the high aspect ratio features without requiring complex process control modifications
Solution Approach 2:
The patent introduces an intermediary substance (surfactant or pH adjuster) into the etch solution to modify the surface charge characteristics. This intermediary mediates the interaction between the etch solution and the feature walls, preventing electrostatic attraction or repulsion and enabling uniform material removal
2Reliability
If charged wall surfaces are present in high aspect ratio features, then electrostatic forces affect reactive species distribution, but non-uniform etching results
Solution Approach 1:
The patent converts the harmful electrostatic forces into a beneficial neutral state by adjusting the pH to the isoelectric point. The charged wall surfaces that cause non-uniform etching are transformed into neutral surfaces, eliminating the harmful electrostatic effects while maintaining the structural integrity of the features
Solution Approach 2:
By changing the pH parameter to a specific value (isoelectric point), the surface charge density is transformed from charged to neutral. This parameter change eliminates the electrostatic forces that repel or attract reactive species, ensuring uniform distribution and consistent etch rate throughout the feature 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 approach provides a uniform etch rate along the depth of high aspect ratio features, preventing over/under-etching and reducing critical dimension variations, thereby improving the precision of semiconductor fabrication processes.
Implementation Method 1
The chemical solution (otherwise referred to herein as an etch solution) often contains a solvent and etchant chemical(s) designed to react with materials on the substrate surface and promote dissolution of the reaction products
Implementation Method 2
Wall surfaces exhibiting positive surface charge (e.g., a surface charge substantially greater than 0 mV) in the presence of the etch solution may attract the anions and repel the cations within the etch solution. On the other hand, wall surfaces exhibiting negative surface charge (e.g., a surface charge substantially less than 0 mV) in the presence of the etch solution may attract the cations and repel the anions within the etch solution
Data Source
AI summary
Embodiments of a wet etch process and methods are disclosed herein to provide uniform wet etching of material within high aspect ratio features. In the present disclosure, a wet etch process is used to etch material within high aspect ratio features, such as deep trenches and holes, provided on a patterned substrate. Uniform wet etching is provided in the present disclosure by ensuring that wall surfaces of the material being etched (or wall surfaces adjacent to the material being etched) exhibit a neutral surface charge when exposed to the etch solution used to etch the material.