Plasmasyövytys

Plasmasyövytys, also known as plasma etching, is a dry etching process used extensively in microfabrication, particularly in the semiconductor industry. It utilizes a plasma, which is an ionized gas containing free electrons and ions, to remove material from a substrate. The process typically occurs in a vacuum chamber where a gas, such as a halogen-containing gas like chlorine or fluorine, is introduced and subjected to a radio frequency (RF) or microwave field. This energy input ionizes the gas, creating the plasma.

The plasma contains reactive species, including ions and free radicals, that are responsible for the etching. In a typical capacitively coupled plasma etching system, a DC bias is applied to the substrate, which attracts positively charged ions from the plasma. These ions bombard the substrate surface, physically sputtering away material. Simultaneously, neutral free radicals diffuse to the surface and react chemically with the substrate material, forming volatile byproducts that are then pumped away. This combination of physical and chemical interactions leads to anisotropic etching, meaning the etching occurs primarily in the vertical direction, which is crucial for creating fine features in microelectronic devices.

Plasmasyövytys offers several advantages over wet chemical etching, including better control over etch profiles, reduced undercutting, and the ability to etch a wider range of materials. It is a critical step in the manufacturing of integrated circuits, microelectromechanical systems (MEMS), and other microfabricated devices. Different plasma chemistries and process parameters are employed depending on the specific material being etched and the desired etch rate and selectivity.