The etching process is divided into two major categories: dry etching (DryEtching) and wet etching (WetEtching). Dry etching primarily relies on plasma technology to etch thin film materials and is one of the important processes widely used in micro-nano processing. During dry etching, specific gases are excited into a plasma state, greatly enhancing their chemical activity. By selecting appropriate gases based on the characteristics of the material being etched, rapid reactions can occur between the gases and the material surface, enabling selective removal of the material.

Reactive ion etching (RIE) is an etching process that combines plasma chemical reactions (chemical etching) with high-energy ion bombardment (physical etching). During the RIE process, under the influence of an electric field, gas is excited into high-energy ions that directly bombard the material surface, producing a physical etching effect. Simultaneously, specific reactive gases are introduced, which undergo chemical reactions with the material surface, generating volatile reaction products, thereby accelerating the material removal process.

Main adjustment parameters of reactive ion etching machine

The adjustment parameters of a reactive ion etching machine mainly include discharge power, reaction chamber pressure, etching gas flow rate, etc.

Discharge Power

The parameter that has the greatest impact on the etching rate is the etching power. As the power increases, both the ionization probability of the reaction gas and the energy of the electrons increase, thereby enhancing the bombardment effect of ions on the sample surface and the chemical reaction rate. However, when the power increases to a certain value, the number of ionized molecules in the chamber reaches saturation, and further increasing the power does not significantly enhance the etching rate. In addition, as the ion bombardment effect gradually increases with higher power, this effect has the same removal effect on the etched sample and the mask material, thereby increasing the removal rate of the mask and reducing the etching selectivity ratio. Therefore, the power should be adjusted within a certain range.

Reaction chamber pressure

The parameter that has the greatest impact on the etching rate is the etching power. As the power increases, both the ionization probability of the reaction gas and the energy of the electrons increase, thereby enhancing the bombardment effect of ions on the sample surface and the chemical reaction rate. However, when the power increases to a certain value, the number of ionized molecules in the chamber reaches saturation, and further increasing the power does not significantly improve the etching rate. In addition, as the ion bombardment effect gradually increases with higher power, this effect has the same removal effect on both the etched sample and the mask material, thereby increasing the removal rate of the mask and reducing the etching selectivity ratio. Therefore, the power should be adjusted within a certain range.

Etching gas flow rate

The flow rate of the reaction gas is another parameter that affects the etching rate. Since the basic principle of reactive ion etching is to generate volatile products through the reaction of reaction gas ions with atoms on the surface of the etched sample, thereby removing material from the sample surface, the flow rate of the gas has a significant impact on the etching process. Under the condition that other etching parameters remain unchanged, if the gas flow rate is too fast, the reaction gas may be pumped out of the reaction chamber before it is ionized, reducing the number of activated ions of the reaction gas that actually play a role, and thus inhibiting the etching rate; whereas if the gas flow rate is too low, due to insufficient supply of reaction gas in the chamber, it will also affect the etching rate.