I. Why is Corrosion Protection Critical for Single-Side Polishing Equipment?

Chemical Mechanical Polishing (CMP) is a critical process for achieving global planarization in semiconductor manufacturing. This process utilizes a vast amount of aggressive, corrosive chemicals, including:

Acidic Slurries: Mixtures containing Nitric Acid, Hydrochloric Acid, Hydrofluoric Acid, etc.

Alkaline Slurries: Potassium Hydroxide, Ammonia, etc.

Various Cleaning Agents and Etchants.

These chemicals pose severe challenges to the equipment's chemical delivery systems (CDS), chambers, valves, piping, and waste exhaust systems. Improper corrosion protection design can lead to reduced equipment lifespan, metal ion contamination, and particle shedding, ultimately directly impacting wafer yield.

Key Factors Influencing the Corrosive Environment:

Chemical Type & Concentration: Oxidizing acids (HNO₃), non-oxidizing acids (HCl), mixed acids (DHF), or strong alkalis (KOH) have distinct corrosion mechanisms.

Operating Temperature: Corrosion rates typically double for every 10°C increase in temperature.

Fluid State: Static immersion, low-velocity flow, or high-speed impingement. Gas-liquid two-phase flow can easily cause cavitation erosion.

System Pressure & Stress: Internal pressure in piping, external loads, and assembly stress.

II. Material Selection: Three Core Principles and Mainstream Solutions

Core Selection Principles:

Corrosion Resistance First: Materials must possess excellent chemical stability in specific concentrations and temperatures of acid/alkali media.

Ultra-High Purity:

Low Metal Ion Leaching: Preventing contamination from Cu, Fe, Ni, Na, etc.

Low Particle Shedding: Surfaces must be smooth and dense to withstand fluid impingement.

Low Organic Leaching: No release of monomers, additives, or other molecular pollutants.

Mechanical Performance & Cost-Effectiveness: Sufficient strength, stiffness, and wear resistance, balancing total cost of ownership (TCO).

Comparative Analysis of Mainstream Anti-Corrosion Materials:

1. Engineering Plastics & High-Performance Polymers (Mainstream Choice)

PVDF (Polyvinylidene Fluoride)    Good resistance to acids/alkalis/salts, high strength, high temp resistance (~140°C), high purity.    Average resistance to strong polar solvents.    Chemical lines, valve bodies, pump chambers (especially HF environments).    Use injection-grade high-purity PVDF; avoid extruded sheets.    

PFA (Perfluoroalkoxy)    Strong chemical inertness, resistant to almost all chemicals, non-stick surface, high purity.    Low mechanical strength, prone to creep, high cost.    High-purity chemical delivery pipes, seals, components contacting wafers.    For areas requiring high cleanliness but low mechanical load.    

PTFE (Polytetrafluoroethylene)    Chemical inertness comparable to PFA, high temp resistance (~260°C).    Hard to injection mold, difficult machining, poor mechanical properties, cold flow issues.    Seals, linings, dispersion fillers.    Not suitable for structural parts; watch for purity and particle shedding.    

PP (Polypropylene)    Low cost, resistant to most acids/alkalis.    Not resistant to oxidizing acids, halogens, organic solvents; temp limit <90°C.    Waste drainage pipes for low-concentration alkalis/cleaners (non-core areas).    Prohibited for oxidizing acids and high-temperature environments.    

2. Composite Materials

FRP/PVC (Fiberglass Reinforced Plastic): Cost-effective but carries a high risk of harboring contaminants and loses strength at high temperatures. Typically used for peripheral exhaust and waste drainage pipes, not in core clean zones.

3. Metal Materials (Limited Application) In the core process areas of single-side polishers dealing with strong acids/alkalis, metal application is very limited:

316L Stainless Steel: Only suitable for DI water (UPW) and weak alkaline systems without halogen ions.

Hastelloy C-276: Excellent corrosion resistance but high cost; used for critical small components.

Titanium & Ti Alloys: Suitable for high-concentration nitric acid systems but strictly prohibited in fluoride environments.

III. Teflon Coating Technology: The Key Solution for Metal Protection

When critical equipment parts require both the mechanical strength of metal and resistance to strong acid/alkali corrosion, Teflon coatings become the ideal choice. Teflon coatings form a dense, inert, continuous fluoropolymer film on the surface of metal substrates (e.g., Aluminum alloy, Stainless steel), completely isolating the corrosive medium from the substrate. This "Barrier-Style Protection" is crucial in the harsh environments of semiconductor equipment.

Core Performance Advantages:

Extreme Chemical Inertness: PTFE and PFA possess strong C-F bonds and complete fluorine atom shielding, withstanding almost all strong acids, alkalis, and oxidizers.

Low Surface Energy & Non-Stick: Prevents slurry/chemical buildup, reducing particle generation and cross-contamination.

High Surface Smoothness: Meets SEMI F57 and other particle shedding standards.

Good Thermal Stability: PTFE can operate continuously from -200°C to +260°C.

Coating Types and Applications:

PTFE: Best inertness/non-stick, highest heat resistance. Used for seals, gaskets, chamber linings.

PFA: Inertness comparable to PTFE but melt-processable, forming a denser, tougher coating. Core choice for equipment tanks, wet etch tanks, and inner walls of chemical distribution lines.

FEP: High transparency, melt-processable. Used for sight glasses and low-temp linings.

ETFE: Best mechanical strength, toughness, and abrasion resistance. Used for robot arms, cassettes, and transport tracks.

Quality Control Key Points:

Coating Integrity: Must be 100% pinhole-free; otherwise, the "wicking effect" will cause corrosion more severe than on uncoated parts.

Ultra-High Purity: Low metal ion, particle, and TOC (Total Organic Carbon) leaching.

Process Control: Strict substrate pretreatment, cleanroom spraying, and precise sintering processes.

Certification Standards: Suppliers should provide test reports based on SEMI standards regarding chemical compatibility, ion leaching, and particle levels.

IV. Industry Practice and Selection Recommendations

Current Technology Trends: In the field of semiconductor single-side polishing equipment, High-Purity PVDF and PFA have become the materials of choice for structural parts and piping systems in strong acid/alkali environments, striking the best balance between corrosion resistance, cleanliness, and mechanical performance. For parts that must use metal substrates, PFA Spray Coating is the mature, reliable technology for corrosion protection.

Implementation Recommendations:

Establish Strict Selection Standards: Choose materials based on specific chemical types, concentrations, temperatures, and fluid states.

Focus on Supplier Qualifications: Select suppliers with deep industry experience and strict quality control systems.

Verify Performance Data: Require suppliers to provide complete SEMI standard test reports.

Lifecycle Assessment: Comprehensively consider initial cost, installation convenience, lifespan, and maintenance/replacement costs.

Pro Tip: Considering corrosion protection needs during the design phase is far more cost-effective than retrofitting later. Collaborative planning with material suppliers, equipment OEMs, and Fab process engineers is recommended.

The Strategic Significance of Anti-Corrosion Technology As semiconductor manufacturing advances towards smaller nodes, the corrosion resistance of single-side polishing equipment is no longer just a reliability issue but a key factor influencing Wafer Yield and manufacturing costs. A scientific and rigorous material selection system can significantly extend equipment life, reduce maintenance costs, and ultimately ensure high efficiency and yield in chip manufacturing.