What is the polymer in the silicon etching process

The formation of polymer is an important physicochemical phenomenon in the process of silicon wafer etching, which has a significant impact on the final result of etching. Polymers are mainly formed during plasma etching, especially when fluorinated gases (such as CF4 or C2F6) are used. These polymers are formed by the deposition of carbides and fluorides produced during the etching process on the surface or side wall of the silicon wafer.

The formation of polymer has a two-sided effect on the etching process. On the one hand, they can act as a protective layer to reduce the etching of the side walls, thus improving the anisotropy of the etching, which is very important for the manufacture of aspect ratio structures and fine patterns. By controlling the formation of the polymer, precise control of the etched profile can be achieved, which is essential for the manufacture of high-performance semiconductor devices.

On the other hand, if the polymer is over-formed or unevenly distributed, it can lead to uneven etching, increased side wall roughness, or residue problems, which can affect the performance of the device. For example, when making an etched grating wave divider, the formation of polymer may cause the rounded edge of the grating groove surface to increase, affecting the optical performance of the device.

To control polymer formation, process engineers need to carefully select etching parameters such as gas type, flow, pressure, power, and temperature. In addition, post-etching treatment steps, such as cavity cleaning, oxidation polishing, etc., are also crucial for polymer removal and control.