Wafer Cleaning After Etching Using Plasma and HF
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Solution Overview
Problem
Conventional wafer cleaning methods after the etching process are inadequate in removing polymers and metallic fluorides, leading to adverse effects on electrical device performance and increased complexity, which affects productivity.
Innovation Solution
A two-stage cleaning process involving a dry etching step with helium and a mixture of nitrogen and hydrogen, followed by a wet cleaning process using a trace amount of hydrofluoric acid, effectively removes polymers and metallic fluorides from the wafer surface, preventing residual materials from affecting device performance and simplifying the cleaning process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a conventional three-stage cleaning process (wet cleaning, dry cleaning, wet cleaning) is used to remove polymers, then the polymers can be removed from the wafer surface, but the process complexity increases and productivity decreases
Solution Approach 1:
The cleaning process is segmented into two distinct stages: a dry cleaning stage using plasma to remove organic polymers, and a wet cleaning stage using HF-based solution to remove inorganic metallic fluorides. This segmentation allows each stage to target specific contaminant types with optimized chemistry, reducing overall process complexity while maintaining effectiveness.
Solution Approach 2:
The invention changes the chemical parameters of the cleaning process by using a fluorine-based plasma chemistry that generates CF3 and F radicals, which are highly effective at removing organic polymers. The wet cleaning stage uses HF-based solution with controlled concentration and temperature parameters to selectively remove metallic fluorides without damaging the metal interconnection layer.
2Manufacturing precision
If alkaline cleaning solution is used in wet cleaning processes, then polymers can be softened and removed, but damage occurs to the metallic layer in the substrate
Solution Approach 1:
Instead of using alkaline solutions that damage metal layers, the invention inverts the approach by using fluorine-based plasma chemistry that generates CF3 and F radicals. These radicals selectively attack and remove organic polymers through fluorocarbon formation, while the subsequent wet cleaning uses HF-based solution that removes inorganic metallic fluorides without the harmful effects of alkaline chemistry on metallic layers.
3Manufacturing precision
If conventional cleaning methods are used, then polymers can be removed, but metallic fluorides remain on the wafer surface affecting device performance
Solution Approach 1:
The invention uses fluorine-based plasma chemistry that generates highly reactive CF3 and F radicals. These radicals act as strong chemical species that not only remove organic polymers through fluorocarbon formation but also convert metallic residues into inorganic metallic fluorides. The subsequent HF-based wet cleaning solution then effectively removes these metallic fluorides, ensuring complete contamination removal and preserving device performance.
4Manufacturing precision
If a three-stage cleaning process is used to remove polymers, then cleaning effectiveness is improved, but productivity decreases due to process complexity
Solution Approach 1:
The invention merges the polymer removal function and the metallic fluoride removal function into an integrated two-stage process. The dry cleaning stage using fluorine-based plasma simultaneously addresses organic polymer removal, and the wet cleaning stage using HF-based solution addresses inorganic metallic fluoride removal. This merging of functions into fewer stages reduces process complexity and improves wafer processing throughput while maintaining comprehensive cleaning effectiveness.
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
The proposed method effectively removes polymers and metallic fluorides, enhancing device performance by preventing residual material effects and reducing the cleaning process complexity, thereby improving productivity through a simplified dry cleaning/wet cleaning two-stage process.
Implementation Method 1
a dry etching process is performed in the environment of helium to remove the etching stop layer exposed by the opening
Implementation Method 2
a dry cleaning process is performed on the wafer surface using a mixture of nitrogen and hydrogen as the reactive gases
Implementation Method 3
a wet cleaning process is performed on the wafer surface using a cleaning solution containing a trace amount of hydrofluoric acid
Data Source
AI summary
A method of cleaning a wafer after an etching process is provided. A substrate having an etching stop layer, a dielectric layer, a patterned metal hard mask sequentially formed thereon is provided. Using the patterned metal hard mask, an opening is defined in the dielectric layer. The opening exposes a portion of the etching stop layer. A dry etching process is performed in the environment of helium to remove the etching stop layer exposed by the opening. A dry cleaning process is performed on the wafer surface using a mixture of nitrogen and hydrogen as the reactive gases. A wet cleaning process is performed on the wafer surface using a cleaning solution containing a trace amount of hydrofluoric acid.