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The influence factors of plasma cleaning effect

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Published on:

08 Oct,2020

The influence factors of plasma cleaning effect:

1. Principle and Implementation Method:

Plasma cleaning can remove surface stains by means of physical shock (such as argon plasma) or chemical reaction (oxygen plasma) caused by the impact of high-energy particles in a specific material plasma on the surface of the object that needs cleaning. At present, most plasma cleaning systems obtain the plasma by lowering the reaction chamber pressure to 100Pa, then pumping in the appropriate gas at a certain speed and powering up.

2. Main factors affecting the cleaning effect:

(1) Influence of electrode on plasma cleaning effect:

The design of the electrode has a significant influence on the plasma cleaning effect, mainly including the material, layout and size of the electrode. For inner electrode plasma cleaning system, because the electrode exposed in plasma, some materials of electrode are some plasma etching or sputtering phenomenon occurs, causing unnecessary pollution and lead to changes in the size of the electrode, which affect plasma cleaning has a great influence on the speed and uniformity, the small electrode spacing can limit plasma in a small area to get a high density plasma, achieve faster to clean. With the increase of spacing, the cleaning speed decreases gradually but the uniformity increases gradually.

The size of the electrode usually determines the overall capacity of the plasma system. In the plasma cleaning system with parallel electrode distribution, the electrode is usually used as a tray. The larger electrode can clean more components at one time to improve the operating efficiency of the equipment.

(2) Influence of working pressure on plasma cleaning effect:

Work pressure is one of the important parameters of plasma cleaning, the increase of the pressure means the increase of plasma density and the average energy of the particles is reduced, the plasma chemical reaction as the leading, enhanced density plasma system can obviously improve the cleaning speed, and physical bombardment dominate the effect of plasma cleaning system is not obvious. In addition, changes in pressure may cause changes in plasma cleaning reaction mechanism. For example, the CF4/O2 plasma used in silicon wafer etching process plays a dominant role when the pressure is low, while with the increase of pressure, the chemical etching is constantly strengthened and gradually plays a dominant role.

(3) Influence of power and frequency on plasma cleaning effect:

The power of the power source influences all plasma parameters, such as the temperature of the electrode, the self-bias generated by the plasma and the cleaning efficiency. With the increase of the output power, the plasma cleaning speed gradually strengthened and stabilized at a peak value, while the self-bias voltage increased with the increase of the output power. Since the power range is basically constant, frequency is the key parameter that affects the plasma self-bias. With the increase of frequency, the self-bias decreases gradually. In addition, with the increase of frequency, the density of electrons in the plasma increases gradually, while the average energy of particles decreases gradually.

(4) Influence of working gas selection on plasma cleaning effect:

The selection of process gas is a key step in the design of plasma cleaning process. Although most of the gas or gas mixture can remove pollutants in many cases, the cleaning speed can vary several times or even dozens of times. For example, adding different proportions of sulfur fluoride (SF6) in oxygen (O2) to clean plexiglass as a process gas can greatly improve the cleaning speed.

The influence factors of plasma cleaning effect

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