Carbon tetrafluoride plasma

CF4 gas is a relatively common fluorine-containing gas. Under the action of a high-frequency electric field, glow discharge produces plasma. After carbon tetrafluoride is ionized by electron impact, it is mainly composed of carbon fluoride cations (CF3+, CF2+, CF+, F+, C+, etc.) and electrons (e−). In addition, there are unionized carbon fluoride free radicals with high activity in the fluorine plasma.

On the one hand, CF4 plasma is often used to achieve fluorination modification of material surfaces. Plasma fluorination technology is a method of using fluorine or fluorine compounds in a plasma state to efficiently change the properties of a material surface. This technology can be used to generate nano-scale materials with specific functions. On the other hand, CF4 gas is a fluorine-containing gas that is mainly used in the plasma etching process for manufacturing semiconductor devices and various integrated circuits, and is used to etch silicon-based materials.

Etching silicon-based materials

High-purity CF4 is widely used in etching Si, SiO2, Si3N4 and phosphorus silicon glass, and is currently the most widely used plasma etching gas in chip manufacturing. The active fluorine ions or atomic groups generated by CF4 in the active atmosphere of plasma react chemically with the silicon-based material to be processed to generate a highly volatile gaseous product SiF4, thereby achieving etching and removal of the material. The chemical reaction equation is as follows: SiO2+CF4→SiF4↑+CO2↑.

Surface fluorination - using CF4 to increase hydrophobicity

Fluorine atoms incorporated into polymer surfaces

Unlike other plasma gases that enhance surface hydrophilicity by introducing oxygen-containing functional groups, fluorine-containing gases such as CF4 are often used for hydrophobic treatment of polymer materials. This method uses F-containing free radicals generated by plasma technology to adsorb on carbon source materials during plasma fluorination to form different types of C-F bonds, thereby generating fluorinated carbon materials. Fluorine is a low surface energy material, so CF4 plasma modification reduces the overall polarity and surface energy of the material by introducing a large number of fluorine-containing groups, while increasing the hydrophobicity of the material surface and increasing the surface contact angle.

Effect of polymer plasma hydrophobic treatment