Applications of power supplies of different frequencies in dry etching

What frequencies of power supplies does dry etching have?

Common power supply frequencies
DC power supply: DC

Low Band (LP): 40kHz, 400kHz, 2 MHz, etc.

High Band (HF): 13.56 MHz, 27.12 MHz, 40.68 MHz, etc.

Very High Band (VHF): 60 MHz, 100 MHz / 162 MHz, etc.

Microwave band: 2.45GHz, etc.
The relationship between power supply frequency and ion kinetic energy

Frequency directly determines the two core parameters of a plasma: ionic energy (physical impact force) and ion density (amount of chemical reaction). Namely: the higher the frequency, the lower the ionic energy, but the higher the ionic density.

0021-35922 Chamber Body, Txz Mcvd

Applications of power supplies of different frequencies

40 - 100 kHz

The ion energy is still very high, it can generate high self-bias, and heavier ions can keep up with the changes in the electric field, so they can obtain greater acceleration kinetic energy.

Suitable for plasma cleaning and etching.

400 kHz

It is commonly used in early PECVD (plasma-enhanced chemical vapor deposition) equipment to improve the stress control of the film and make the deposited film denser by bombardment.

2 MHz

The "bombardment workhorse" of modern etching machines usually uses high frequencies (such as 60MHz) to generate plasma density, while 2MHz is applied to the lower electrode to independently control the bombardment energy of the ions. It's easier to match than 400kHz, but still bombards a lot.

13.56 MHz – Industry standard frequency

This is the most commonly used frequency in semiconductor devices. At this frequency, the ions can no longer keep up with the change in the electric field (energy decreases), but the electrons can, resulting in a stable plasma.

100 MHz / 162 MHz

The higher the frequency, the higher the electron density, and the high frequency helps improve center and edge uniformity when processing large wafers (300mm). It is mainly used for extremely delicate etching processes.

2.45 GHz

The frequency is extremely high, and electrons undergo cyclotronic resonance with the assistance of the magnetic field, greatly increasing the probability of collision and generating a large number of ions and active radicals.

Suitable for processes that require extremely fast chemical reaction rates (e.g., degumming ashing). Because of its low ionic energy, it mainly "eats" the material through chemical reactions, causing minimal physical impact damage to the chip surface, making it ideal for handling sensitive devices.

Summary

Lower frequency (towards DC): More like a "physical hammer", using high-energy impacts for sputtering or hard etching. Higher frequency (towards 2.45GHz): The more like a "chemical solvent", utilizing high-density chemical reactions for high-speed, low-damage etching.