Report written by: K.Y. Fan, Research Manager
Section 1. Research Motivation:
Application validation of perfluoroelastomers (FFKMs) filled with the new KATON polymer filler and of silane coupling agents (O-Si-O)

Section 2. Research Purpose:
Will a silane coupling agent (O-Si-O) affect the strength of an FFKM?

Section 3. Research Scope:
1. The traditional carbon black filling technique (C-F-C)
History of development: From 1965 to the present
Carbon black N990 is conventionally used as a reinforcing filler in the FFKM industry. From the perspective of materials science, carbon black N990, which is obtained by cracking natural gas, has a high affinity for FFKMs and can therefore easily bridge with an FFKM without having to be modified, thereby enhancing the physical strength (including mechanical properties such as hardness, tensile strength, elongation, and modulus), wear resistance, oil resistance, and processability of, as well as filler dispersion in, the FFKM effectively.

In recent years, however, the carbon black filling technique has been gradually phased out because carbon black-filled FFKMs used in the equipment in the semiconductor industry tend to release the black-color filler carbon black while the equipment is in use, leading to contamination of the associated manufacturing processes and products.

2. The silane coupling technique (C-F-O-Si-O)
History of development: From 1990 to the present

Around 1990, most of the FFKM sealer manufacturers began their endeavor to replace the traditional black filler with white polymer fillers. For example, a white or colored compound would generally use clay, calcium hydroxide, talc, silica, or other light-color powder as its filler. Such an inorganic filler, however, does not have a satisfactory affinity for FFKMs, so it is necessary to add a silane coupling agent (O-Si-O) to a composite material composed of such a filler material and an FFKM, the objective being to form bridges between the white mineral filler and the FFKM through physical and chemical reactions.

Generally, the use of a silane coupling agent (O-Si-O) can increase the affinity of a filler for an FFKM, thereby increasing the added value of the resulting FFKM product, for example by enhancing the mechanical properties (hardness, tensile strength, elongation, modulus), wear resistance, oil resistance, and processability of, as well as filler dispersion in, the product. Test results have shown that a silicon binding agent is indeed capable of enhancing the mechanical strength, wear resistance, and processability of, as well as powder dispersion in, an FFKM.

This filling technique, however, has its advantages and disadvantages. The technique is advantageous in that it can be widely used in various industries, is low-cost, enables high FFKM processability, and works well in an environment where an organic solvent or other chemical is used.

The technique is nevertheless disadvantageous in that when an FFKM is filled with carbon, barium, titanium, aluminum, magnesium, calcium, zinc, or another similar filler, the filler may outgas when coming in contact with plasma, ozone, or a chemical solvent when it is subjected to ionizing radiation at the same time. The outgassing could cause the associated manufacturing equipment and products to adsorb the volatile matter existing in the FFKM and/or the metal filler to be released and then degraded into small molecules that may contaminate the associated manufacturing process.
When a sealer filled with a traditional metal filler is corroded by plasma or a chemical, the filler may outgas and be released as a result, with the remaining filler particles becoming a source of contamination. One major factor contributing to the outgassing is that the sealer is in a high-vacuum environment where a certain pressure, temperature, plasma, or chemical vapor is introduced. Relatively speaking, therefore, the traditional metal fillers are not suitable for use in manufacturing processes that allow only a low degree of contamination.

Test results have shown that a silane coupling agent does provide significant improvement in mechanical properties, wear resistance, filler dispersion, and processability. This is why KATON rolled out a series of white filler products intended for FFKMs over the course of ten years. However, as their shortcomings have begun to show in the last couple of years, those white fillers have been unable to satisfy the requirements of advanced semiconductor manufacturing processes.

3. The polymer filling technique (C-F)
History of development: From 2021 to the present

The last two years saw the semiconductor industry evolve into the 2-nm generation, and, as a result, more and more attention has been paid to low-release materials, giving rise to the KATON® polymer filler technique.

The new, special formula of the KATON® polymer filler includes a highly dispersed liquid fluoropolymer serving as the polymer filler. The polymer filler provides material enhancement without using traditional contaminating fillers (such as carbon black or minerals). Basically, the polymer filler includes only carbon and fluorine and therefore does not require a silane coupling agent (O-Si-O) used in conjunction with a dedicated curing system for cross-linking. The polymer filler is designed specifically for use with etching processes and chemical vapor deposition (CVD), features lower release than a metal filler, and can reduce contamination by particles generated by sealer degradation and allow a sealer to maintain outstanding sealing functionality even in a corrosive plasma environment.
The polymer filler is intended for high-purity elastomer sealers for use in highly clean environments, in particular high-temperature environments with high-intensity plasma attack. In addition, the polymer filler allows a sealer filled with it to have an extremely low corrosion rate and weight loss when subjected to destructive fluorine and oxygen plasmas. It exhibits high chemical resistance to ammonia, ozone, and water vapor, high resilience to compression, and a super low degree of outgassing.

The greatest advantage of such a fluoroelastomer/fluoropolymer filler is that when the filler is degraded by plasma, harmless volatile matter is formed that can safely be discharged to reduce the chance of contamination by particles or metal, and to prevent a sealer filled with it from becoming sticky.

Section 4. Conclusion of the research project:
Can a silane coupling agent (O-Si-O) be added to an FFKM filled by the new polymer filling technique (C-F)? Technically speaking, the answer is affirmative. However, it can currently be known that such an addition will be false filling and provide no help to the new polymer filling technique, either physically or chemically. In short, the addition of a silane coupling agent (O-Si-O) will not have any substantial technical meaning.

R&D Department, Maxmold Polymer Co., Ltd.
Title of research: Research on the Interaction Between KATON FFKMs and Silane Coupling Agents (O-Si-O)
Report publication date: November 29, 2022
Report written by: K.Y. Fan, Research Manager