1. Radio frequency (RF) – the energy source for PECVD
Simply put, radio frequency (RF) is the driving force of PECVD; it determines whether plasma can be generated, how strong the generation is, and how high the deposition efficiency is.
2. Glow discharge-the "expression" of plasma
Glow discharge is a visible light phenomenon that occurs naturally after plasma is excited.
When a gas is ionized into plasma by a radio frequency electric field, the electrons inside will continuously jump between high and low energy levels. This process releases photons. When a large number of photons combine together, they form the light we see through the observation window, which is called glow.
The glow is neither decoration nor a byproduct; it directly reflects the true state of the plasma.
Different gases, parameters, and chamber conditions will result in variations in the color, brightness, and uniformity of the plasma glow. A stable glow indicates a healthy plasma, while flickering or abnormal glow indicates a problem with the equipment or process.
In short, glow discharge is the expression and language of plasma, which engineers use to judge whether the equipment is healthy and the process is stable.
Glow can be of different colors.
The color of glow varies depending on the gas.
Neon (Ne): Emits classic red-orange light (neon light)
Argon (Ar): emits a bluish-violet light.
Nitrogen (N2): emits a pinkish-purple light.
Oxygen (O2): emits a pale yellow or white light.
Sodium vapor (Na): emits a very bright yellow light.
2. Relationship between radio frequency and glow discharge
Radio frequency and glow discharge are not two independent things, but rather have a causal relationship, a symbiotic relationship, and a monitoring relationship.
Radio frequency provides energy and is the cause of plasma formation.
Glow discharge accompanies the appearance of plasma and is an external manifestation of plasma.
Without radio frequency, there is no plasma, and therefore no glow.
The absence of a stable and uniform glow indicates poor radio frequency energy transmission, uneven electric field distribution, and abnormal chamber condition.
3. The simplest summary
Radio frequency (RF) is the energy core of PECVD, responsible for generating and controlling plasma.
Glow discharge is a state expression of plasma and is responsible for reflecting whether the process is stable.
If the radio frequency is stable, the glow discharge will be stable.
Stable glow discharge ensures stable film quality.
