What Is a Plasma Etching System?
Plasma etching systems utilize plasma, a state of ionized gas, for microfabrication processes in semiconductor LSI (large-scale integrated circuit) manufacturing, including the creation of photomasks and smartphone displays. These systems enable the removal of materials like silicon, silicon oxide, and metal films beneath developed resist patterns, facilitating the formation of extremely fine patterns crucial for the high integration and resolution of LSIs and displays.
Uses of Plasma Etching Systems
Plasma etching systems are integral in producing semiconductor devices, such as memory chips and CPUs, and flat panel displays for devices like smartphones. They play a key role in the manufacturing cycle, which includes exposure, development, etching, and resist stripping processes, allowing for the precise formation of patterns on substrates.
Compared to wet etching, which uses chemical solutions and can cause undercuts due to solution penetration beneath the resist, dry etching with plasma offers clean, vertical cuts along the resist pattern, making plasma etching the preferred method for achieving precise patterning.
Principle of Plasma Etching Systems
In a plasma etching system, the wafer or substrate is placed in a vacuum chamber with electrode plates positioned above and below it. Etching gases, such as fluorocarbon gases for silicon and silicon oxide films or halogenated gases for metal films, are introduced into the chamber. The application of a high-frequency electric or magnetic field ionizes the gas into plasma, and the generated electric field causes ions to bombard the wafer, selectively removing material from exposed areas.
Types of Plasma Etching Systems
Plasma etching systems can be classified by their plasma generation method into capacitively coupled plasma (CCP), inductively coupled plasma (ICP), and microwave ECR (electron cyclotron resonance) plasma. CCP systems generate plasma between two electrode plates, using the electric field to accelerate ions towards the workpiece for etching, while ICP and ECR systems offer alternative methods for plasma generation, maintaining the principle of ion-accelerated etching.