Fluoropolymer Products: A Key Material Foundation for Semiconductor Wet Cleaning

Introduction

In the full semiconductor chip manufacturing process, wet cleaning is one of the most frequently used process steps and one of the most directly influential on yield. From RCA standard cleaning to post-etch residue removal, wafers must repeatedly undergo immersion and rinsing in strong acids, strong bases, strong oxidizers, and other chemical solutions. This places extremely stringent requirements on the chemical stability, purity, and temperature resistance of equipment contact materials. Among numerous material options, fluoropolymer products represented by PFA (perfluoroalkoxy) and PTFE (polytetrafluoroethylene) have become core materials for the “media-contact surfaces” of wet cleaning equipment due to their difficult-to-replace comprehensive performance.

Why Wet Cleaning Cannot Do Without Fluoropolymer Products

The core requirements of wet cleaning for materials can be summarized in three aspects: ultra-high purity, extreme corrosion resistance, and wide-range temperature resistance. Semiconductor manufacturing is an industrial process with nanometer-scale precision. Once trace impurities such as metal ions and particles are released from equipment materials and transferred to the wafer surface, they may directly cause device defects and yield loss. The highly corrosive chemicals used in wet cleaning, such as hydrofluoric acid, sulfuric acid, nitric acid, and aqua regia, can corrode almost all metals and high-polymer materials, while cleaning process temperatures range from room temperature up to high-temperature sulfuric acid scenarios above 160°C. Ordinary engineering plastics cannot handle this.

The molecular structure of fluoroplastics is based on a carbon–fluorine bond skeleton. The bond energy is extremely high, and chemical inertness is outstanding, precisely matching the above requirements. Taking PFA as an example, its metal ion leaching can be controlled below ppb levels, and it is resistant to almost all acids, bases, and organic solvents. Its thermal stability is excellent, and it can maintain stable performance over the long term at around 260°C. PTFE also offers near-universal chemical resistance, with a service temperature range from -200°C to 260°C.

In terms of market size, the semiconductor equipment plastic parts industry is growing steadily. According to a YHResearch report, the global market for plastic parts for semiconductor equipment is expected to reach RMB 43.88 billion by 2032, with a compound annual growth rate of 6.8%. Among this, fluoropolymer systems mainly serve as wetted parts and piping systems for wet chemicals and ultrapure water media. Industry assessments generally regard PTFE, PFA, and similar materials as having “hard-to-replace” foundational attributes in the field of semiconductor wet chemistry.

Core Fluoropolymer Components in Wet Cleaning

Fluoropolymer products cover a very wide range of applications in wet cleaning equipment, from chemical storage and delivery to wafer carrying and fluid control, running through almost the entire process chain.

Cleaning tanks and immersion tanks are the most visible fluoropolymer application in wet cleaning equipment. Taking PFA cleaning tanks as an example, they are manufactured using a one-piece molding process with no bonded seams, eliminating the potential leakage risk of traditionally welded tanks. The tank body is semi-transparent, making it easy for operators to observe the reagent status inside. The background level is extremely low, with metal element content less than 0.01 ppb, and there is no dissolution or leaching, so it will not contaminate chips or wafers. These cleaning tanks are designed specifically for semiconductors, photovoltaics, and other industries, and are mainly used for soaking and cleaning wafer cassettes. They have become standard equipment in 12-inch wafer fabs and advanced packaging lines.

Cassettes and wafer carriers are key components that directly contact wafers. PFA and PTFE cassettes need to be immersed for long periods in high-purity, highly corrosive chemical solutions during wet processes. Their low adhesion can effectively prevent silicon wafers from sticking to carrier surfaces, avoiding scratches and contamination. At the same time, fluoroplastic cassettes can provide a stable chemical environment. Whether in the SC-1 and SC-2 sequences of RCA cleaning solutions or in high-temperature hydrofluoric acid or phosphoric acid bath etching scenarios, they can maintain structural integrity.

Piping systems can be called the “blood vessels” of wet cleaning equipment. High-purity PFA tubing has an ultra-smooth inner wall and offers excellent mechanical strength, fatigue resistance, and chemical corrosion resistance. It can control impurity content at the ppb level and avoid secondary contamination during the delivery of high-purity chemicals. In the 5 nm chip etching process, domestically produced high-purity PFA tubing has successfully replaced imported products. Its extremely low fluoride ion leaching (less than 1 ppb) prevents contamination of etching gases, improves etching uniformity by 12%, and increases single-wafer yield from 88% to 93%.

Valves and fluid control components also use large amounts of fluoroplastics. Pneumatic liquid diaphragm valves are one of the core components in wet process equipment. Their wetted parts are made of PFA/PTFE, and the diaphragm and valve body are integrally molded. When closed, they form a physical isolation barrier, eliminating fluid leakage or cross-contamination and meeting SEMI F57 cleanliness standards. PFA needle valves, flow meters, filters, and other components also perform key functions in precise chemical delivery in wet cleaning systems.

Selection Considerations: How to Choose Between PFA and PTFE

In actual engineering, PFA and PTFE each have their own strengths, and selection needs to be combined with specific working conditions. PTFE’s chemical resistance covers almost all known chemical media, and its long-term heat resistance is about 260°C. However, unfilled grades of PTFE have relatively low rigidity and are prone to cold flow, making them suitable for seals, gaskets, isolators, and other locations with relatively less stringent dimensional precision requirements. PFA combines excellent chemical resistance with good processability. It can be melt-welded and injection-molded, making it suitable for precision parts, tubing, fittings, spray arms, and other components with relatively complex structures that require welded assembly. For example, spray arms are often integrated structures of multi-branch manifolds and nozzle arrays, which require materials that can be melt-welded and three-dimensionally formed. This is precisely PFA’s structural advantage over PTFE.

In terms of cleanliness grade, semiconductor wet cleaning should use semiconductor-grade raw materials, requiring metal ion content below 0.1 ppb and extractables below 10 ppb, eliminating the risk of impurity contamination from industrial-grade PFA. At present, the industry generally refers to the SEMI F57 standard for material validation, covering metal ion leaching tests and ultrapure water particle release testing.

Domestic Localization: From Catching Up to Running in Parallel

For a long time, more than 90% of the global market for semiconductor-grade high-purity fluoroplastic products was dominated by international companies such as DuPont and Daikin. Their products can reach 5N grade (99.999%) purity, with surface roughness Ra less than 0.2 μm. Domestic materials still have obvious gaps in impurity content, molecular uniformity, and processing precision. In recent years, this landscape has gradually begun to change.

On the raw material side, Juhua Co., Ltd.’s 10,000-ton/year high-quality melt-processable fluororesin (PFA) facility has been completed and put into operation. Validated by semiconductor customer testing, the product’s metal ion indicators meet SEMI F57 standard requirements and can meet the needs of semiconductor wet processes and chemical storage and transport. On the component side, domestic companies have reduced metal ion content in PTFE raw materials from the conventional 10 ppm level to below 0.1 ppm through “multi-stage purification + composite modification” technology. They have also adopted integrated molding–CNC turning–chemical polishing processing technology to control the wall thickness tolerance of pipe fittings to ±0.02 mm and reduce surface roughness to Ra = 0.15 μm.

In the field of equipment components, companies such as Hualin Kena, leveraging more than 20 years of technical accumulation in semiconductor wet processes, have completed domestic substitution of core components such as diaphragm valves and bellows pumps. The core performance of their full product series has caught up with imported brands, forming significant advantages in cost, delivery, service, and other dimensions. Wote’s precision custom PTFE components, including cups/tanks, integrated corner tanks, cassettes, bellows, spray tubes, and others, have been adopted by leading domestic and international semiconductor cleaning equipment manufacturers.

Conclusion

The role of fluoropolymer products in semiconductor wet cleaning is far more than just that of a “corrosion-resistant material.” From chemical storage and transport to wafer carrying, from piping delivery to fluid control, they form the physical foundation of the entire wet cleaning process. As advanced processes continue to tighten control requirements for particles, metal ions, and total organic carbon, fluoropolymer products are continuing to evolve toward higher purity, lower leaching, and greater traceability. Amid the wave of domestic substitution, from raw material synthesis to precision processing and then to standard certification, China’s fluoropolymer products industry chain is completing a key leap from “being able to make” to “making well,” providing solid material support for the autonomous and controllable development of the semiconductor industry.