Significantly Reduce Costs by Eliminating Solvents
Polymer residues from dry etching are a common challenge in semiconductor manufacturing. While this critical method offers precision and efficiency, it can leave behind contaminants that may disrupt subsequent processes. However, it also presents significant opportunities for resource and cost savings. In this article, discover how to cut costs by eliminating solvents in your cleaning process, while still achieving a 100% polymer removal success rate.
Dry etching removes materials from semiconductor thin films using plasma in a vacuum. This method offers several advantages, such as high accuracy and fewer defects in the final product compared to wet etching.
Engineers use dry etching for small geometry devices to gain better control when shaping vertical walls. They mainly apply it during the front-end of line (FEOL) to define transistor structures and during the back-end of line (BEOL) to create complex metal connections between transistors in semiconductor fabrication.
Residues after dry etch process
Dry etching often causes surface contamination and leaves behind residues, requiring an extra cleaning step. This is especially true for plasma etching, where complex chemicals create polymer-like films. These residues can interfere with later stages, such as material deposition or lithography, making additional cleaning necessary and complicating the process.
Solvents are widely used for removing residues but come with significant limitations. They can effectively remove many organic residues, but they often struggle with inorganic materials like stubborn polymers from dry etching. Solvents also find it hard to reach deep or narrow features, which can leave residues behind. Additionally, they may react with or damage sensitive materials, such as certain metals and insulators. That can potentially harm device quality. Many of the solvent based chemical used today are carcinogenic, mutagenic or reprotoxic substances, flammable, and harmful to the environment, which necessitates careful handling and disposal.
Game changer of polymer removal
perc™, the innovative process by Siconnex, offers a sustainable and cost-saving method for removing all types of polymers after dry etching processes, such as metal, oxide, silicon, or VIA etching. This technology eliminates the need for solvents in polymer removal while still achieving a 100% success rate. It helps the environment by reducing chemical use by up to 79.8% compared to traditional cleaning methods. Additionally, it boosts competitiveness by increasing wafer production by 140% and reducing processing costs per wafer by 58.3%.
Dr. Julien Ladroue, STMicroelectronics
„My experience with perc™ is that after sending wafers through several dry etch steps, we successfully found a recipe to remove all polymers and achieve better sidewall roughness. After conducting electrical checks, we even discovered improved performance compared to the existing process. I genuinely appreciate the excellent cooperation and collaborative work with Siconnex to find solutions for both new and existing processes.“
Savings & benefits
Compared to conventional cleaning systems
How the perc™ process works
You can efficiently remove post-etch polymers and residues using diluted sulfuric peroxide mixtures, which provide thorough cleaning and consistent results in a one-time chemical process. The mixing ratios are freely adjustable to fit any type of polymer, and the process is solvent-free, offering a clean and effective solution.
This process removes polymers from metal lines without causing corrosion and with very little metal loss. It keeps the metal surfaces intact while effectively getting rid of unwanted residues. In detail, this means that the metal line loss per run is less than 20 Å for Aluminum-Copper and less than 15 Å for Titanium-Nitride, with no measurable loss of Silicon-Oxide.
The procedure involves three main steps: 5 minutes for Polymer Etch Residue Clean (perc™), 6 minutes for Rinse & Purge, and 10 minutes for Drying, resulting in a total process duration of 21 minutes. With a 4x Chamber Clean configuration, the process achieves a throughput of 544 wafers per hour, maintaining high productivity and consistent results.
The process is designed for optimal efficiency with precise chemical mixtures for each run. For instance, during the removal of polymers from metal dry etch, 110 liters of deionized water (DIW), 100 milliliters of sulfuric acid (H₂SO₄), and 700 milliliters of hydrogen peroxide (H₂O₂) are utilized. For added flexibility, small amounts of hydrofluoric acid (HF) can be introduced. This careful allocation of chemicals ensures thorough cleaning, minimizes waste, and maintains cost-effectiveness.
Summary of the most important features:
- Removes various polymers with 100% success.
- Suitable for Multiple Dry Etch Processes
- Accurate Concentration Control
- Adjustable for each polymer
- Flexible parameter adjustment
- Point-of-use media usage
- Stable media concentration
- Recontamination avoided
- No solvents needed
- Easy waste treatment
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