What is magnetic sputtering?

Magnetically controlled sputtering principle

Sputter means (plant) to Sputter.

This so-called splash plating refers to the object to ion impact, by sputtering fly out. A thin film is made by attaching a sputtering object to a target substrate.

In the fluorescent lamp socket near the common blackening phenomenon, which is the most admired example, this is due to the fluorescent lamp electrode is sputtered and attached to the surrounding formation.

Since its discovery in the 19th century, sputtering has been undesirable, especially in discharge tubes.

In recent years, it has been used in thin film production technology with high efficiency and will become available.

The application research of thin film production was mainly conducted by Bell Lab.  And Western Electric Company at the beginning. In 1963, a continuous sputtering device with a total length of about 10m was made.

High frequency sputtering technology was introduced by IBM in 1966, which enables the fabrication of insulating films.

After various researches, we have reached the goal of "no matter what the substrate material is, it can be covered with any material of the film".

To make a film, you need at least a substrate to hold the film and a prop (internal mechanism) to hold the vacuum.

This prop is necessary to make a space and use a vacuum pump to pump out the gas inside.

Sputter(magnetic sputtering) principle

The working principle of magnetron sputtering is shown in the figure below.Under the action of electric field E, electrons collide with argon atoms in the process of flying to the substrate, ionizing Ar+ and a new electron, the electron flies to the substrate, Ar+ accelerates to the cathode target under the action of electric field, and bombards the target surface with high energy, making the target sputtering.In sputtering particles, neutral target atoms or molecules are deposited on the substrate to form a thin film.Once the secondary electron EL leaves the target, it is subjected to both electric and magnetic fields.In order to explain the motion of the electron, it can be approximated that: when the secondary electron is in the dark region of the cathode, it is only affected by the electric field;Once in the negative glow zone, it is only affected by the magnetic field.Thus, the secondary electrons emitted from the target surface are first accelerated by the electric field in the dark region of the cathode and fly to the negative region.The electrons entering the negative glow zone have a certain velocity and are moving perpendicular to the magnetic field lines.In this case, the electron rotates around the magnetic field line due to the B Lorentz force of the magnetic field.After rotating half a circle, the electrons re-enter the dark region of the cathode and are slowed by an electric field.As the electron approaches the target, its velocity drops to zero.Later, under the action of the electric field, the electron flies away from the target again, and begins a new period of motion.The electrons do this over and over again, jumping in the direction indicated by E(electric field)×B(magnetic field) (see picture below).E×B drift for short.

The trajectory of electron motion under orthogonal electromagnetic field is approximate to a cycloid.In the case of a circular magnetic field, the electrons move in an approximate cycloidal circle around the target surface.Under the control of the circular magnetic field, the secondary electrons not only move along a long path, but also are bound to the plasma region near the target surface, in which a large number of Ar+ ions are ionized to bombard the target, thus achieving the characteristics of high deposition rate of magnetron sputtering.As the number of collisions increases, the energy of electron E1 is exhausted and it gradually moves away from the target.And finally deposited on the substrate under the action of electric field E.Because the energy of the electron is very low, the energy transferred to the substrate is very small, resulting in a low temperature rise of the substrate.In addition, for e2 electrons, because the electric field and magnetic field are parallel at the magnetic pole axis, e2 will fly directly to the substrate, but the ion density at the magnetic pole axis is very low, so e2 electrons are few and have a very small effect on the temperature rise of the substrate.

To sum up, the basic principle of magnetron sputtering is to use magnetic field to change the direction of motion of electrons, and bind and extend the trajectory of electrons, so as to improve the ionization probability of electrons to the working gas and effectively use the energy of electrons.Therefore, the target sputtering caused by positive ion bombardment is more effective.Meanwhile, electrons bound by an orthogonal electromagnetic field can only be deposited on the substrate when their energy is exhausted.This is magnetron sputtering with "low temperature", "high speed" two characteristics of the truth.The specific application in Sputter magnetron sputtering is shown in the figure below.