CDS liquid supply system process technology

Introduction

Semiconductor manufacturing is highly reliant on chemical processes, with approximately 20% of process steps involving wafer cleaning and surface treatment. The continuous shrinking of integrated circuit linewidths and the rapid development of the photovoltaic industry have placed increasing demands on the precise supply and safe management of chemicals. The Central Chemical Dispense System (CDS) serves as a core support system, using automated control to achieve precise chemical dispensing and recovery, providing reliable assurance for wet processes in semiconductor manufacturing.

Definition and Importance of the CDS System

The CDS system is a critical facility providing a 24-hour continuous supply of chemicals to semiconductor production lines, widely used in the integrated circuit, photovoltaic, LED, and MEMS industries. Its core functions include automatic dispensing, replenishment, and delivery, ensuring that parameters such as chemical concentration, temperature, and flow rate meet stringent process requirements. This system works in conjunction with factory utility systems and waste liquid treatment systems to support efficient semiconductor production, while significantly reducing chemical handling risks and environmental hazards.

Application of the CDS System in Semiconductor Manufacturing

Main Supply Process Steps

1. Photolithography Development: Provides specific chemicals for chip pattern development, ensuring precise removal of photoresist and pattern definition.

2. Wafer Cleaning: Removes particles, metallic contaminants, and organic residues from the wafer surface using chemicals to improve surface cleanliness.

3. Wet Etching: Uses acidic or alkaline solutions to selectively etch materials, forming micro-nano structures.

4. Thin Film Preparation: Delivers precursors required for chemical vapor deposition (CVD) to achieve high-quality thin film growth.

5. Chemical Mechanical Planarization (CMP): Provides polishing slurry to planarize the wafer surface, ensuring the flatness of multi-layer structures.

6. Equipment and Accessory Cleaning: Cleans process equipment and carriers to prevent cross-contamination.

Classification and Uses of Chemicals

Chemicals used in semiconductor processes can be divided into the following four categories:

1. Acids

• Hydrofluoric acid (HF): Used to etch silicon dioxide and clean oxide layers.

• Hydrochloric acid (HCl): Dissolves metallic contaminants, often used to remove ionic residues.

• Sulfuric acid (H₂SO₄): Decomposes organic matter through strong oxidation, suitable for removing photoresist.

2. Bases

• Ammonium hydroxide (NH₄OH): Forms SC-1 solution with hydrogen peroxide, used to remove particles and metallic impurities.

• Potassium hydroxide (KOH): Used in CMP slurries and developer solutions.

3. Organic Solvents

• Isopropyl alcohol (IPA): Acts as a drying agent to accelerate wafer surface dehydration.

• Acetone: Removes photoresist residue, ensuring cleanliness in the yellow light area.

4. Mixed Chemicals

• SC-1/SC-2 solutions: Used for wafer cleaning and surface activation.

• BOE (Buffered Oxide Etch): Precisely controls the silicon dioxide etching rate.

Process Flow and Composition of the Chemical Supply System

CDS systems can be divided into the following two categories based on functional requirements:

1. Basic Supply System

• Function: Directly delivers stored chemicals to process equipment, suitable for single solutions with stable compositions.

• Components: Storage tanks, pumping units, pipelines, and flow control modules.

2. Functional Supply System

• Function: Integrates mixing, heating, or stirring modules to achieve online chemical preparation and parameter optimization.

• Components: Pre-treatment units (such as dilution devices, temperature control modules), mixing reactors, and closed-loop control systems.

Both types of systems must meet the requirements of corrosion resistance, high sealing, and automated monitoring to ensure that the chemical composition and state remain stable during transport.

Conclusion

As a core infrastructure in semiconductor manufacturing, the CDS system significantly improves process stability and production safety through precise control of chemical supply and recovery. In the future, with the increasing complexity of processes, system design will need to further integrate intelligent technologies to achieve real-time monitoring and dynamic adjustments. By optimizing chemical management processes and equipment compatibility, CDS technology will continue to drive the efficient development of the semiconductor industry.

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