Plasma analysis of magnetron sputter

What is Plasma?

Matter is often divided into solid, liquid, and gas, but plasma can be created by further heating gas.

For this reason, plasma is often described as the “fourth state” of matter.

Plasma is the ionized state of matter.

Ionization is a phenomenon in which a molecule or atom breaks apart and separates into electrons and ions.

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Plasma is created when particles (ions, electrons, and atoms) collide with each other.

What kind of environment creates plasma?

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Plasma is mainly generated in ultra-high temperature regions such as the sun or when high voltages are applied to gases.

In this article, we will analyze magnetron sputtering equipment, an industrial product that uses plasma.

A magnet that generates a magnetic field is placed behind the target to confine electrons within the magnetic field, producing a high-density plasma.

This increases the frequency with which ions strike the target compared to a two-pole sputtering system, thereby increasing the deposition rate.

Magnetron sputtering equipment is,

Semiconductor manufacturing
Display manufacturing
Medical equipment
Electronic component manufacturing
Optical component manufacturing

It is used in various research and industrial fields such as those listed above.

Fig.1: Conceptual diagram of magnetron sputtering equipment

The figure above shows a conceptual diagram of the magnetron sputtering system.

The deposition process of magnetron sputtering equipment is as follows

Electrons are emitted from the cathode.
Electrons are trapped around the target by a magnet.
The trapped electrons collide with the gas near the target, generating plasma.
Ions in the generated plasma are attracted to the cathode and collide with the target.
Target atoms are ejected, deposited on the substrate, and deposited.

Analysis of magnetron sputtering equipment

Use our PIC PLASMA3D to simulate plasma in magnetron sputtering equipment.

The analytical model is as follows (Created with FreeCAD)

Analysis Model

We created an analytical model for magnetron sputtering as described above and performed orbital analysis of free electrons (particles that are the origin of plasma generation) emitted from the cathode.

In the case of this magnetron sputtering system, electrons emitted from the cathode are affected by the magnetic field, and electrons are trapped around the cathode.

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Compared to the two-pole sputtering method, the use of magnets increases the number of electrons in the vicinity of the target.

Therefore, it can achieve more efficient sputtering than electrode-only sputtering equipment.

The mechanism of plasma generation is as follows.

図２：プラズマの生成過程

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This time, we simulate electrons emitted from the cathode, which is the origin of plasma generation!

In the diagram above, you mean the first electron?

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Yes! PIC-PLASMA3D can also calculate ionized plasma (both ions and electrons), so if you can afford it, try it.

I understand!

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Analysis conditions

The analysis conditions are as follows

Table 1: Analysis conditions

Analysis Software	PIC PLASMA3D(Standard) or PIC PLASMA3D(Pro)
Analysis type	Orbital analysis of plasma in electrostatic and static magnetic fields
Initial electron density	1.0×10¹¹[pcs/m³]
Newly generated particles	electron
Initial velocity of generated electrons	70[m/s]
Average density of generated electrons	1.0×10¹⁷[pcs/m³]
Voltage	Cathode voltage:0[V] Anode voltage:400[V]
residual flux density	Cylinder magnet:1.2[T] (upward) Ring magnet:1.2[T] (downward)
time step width	1.0×10^-11[s]
Total simulation time	1.0×10^-8[s]

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This time, we will set more electrons coming out of the cathode for verification and do an orbital analysis.

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These initial conditions can be set in the software (PIC-PLASMA3D).

Analysis Results

図3：陰極から放出される自由電子の解析結果

The above video is a visualization of the actual results calculated by PIC-PLASMA3D (regular version).

We simulate the trajectories of free electrons emitted from the cathode, which is the origin of plasma generation.

The “data” in the movie indicates the number density of electrons [pcs/m3].

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You can see that the electrons emitted from the cathode are trapped in a ring along the magnet.

Are you saying that these electrons are the origin of the plasma?

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That's right! Electrons captured near the target collide with argon gas in the sputtering equipment to produce plasma.

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The inert ions in the plasma hit the target to form the film.

Since the cad model used in this study was created in a simplified manner, the number of electrons and other condition settings have been simplified.

In addition to the above calculation results, PIC-PLASMA3D can also output various data.

Electrostatic potential
Magnetic field distribution
Electron density
Current density
Charge density

※The above is an example.

We hope you will utilize the PIC-PLASMA3D, which we have analyzed in this study, to improve the performance of your plasma products.