The principle of sputter coating is based on the following aspects:
Sputtering refers to that when charged particles or neutral particles with sufficient energy collide with the surface of the body, energy can be transferred to the atoms on the surface. As long as the energy obtained by the surface atoms is greater than its own ionization energy, it can get rid of the shackles of surrounding atoms and leave On the surface of an object, this phenomenon is called sputtering.
Glow discharge is a discharge phenomenon that occurs when a high voltage is applied between two electrodes in a vacuum with a pressure of several hundred Pa.
When the vacuum degree in the vacuum chamber is 13Pa, a certain voltage is applied between the cathode and anode electrodes, and the gas undergoes a self-excited discharge, and the atoms or atomic groups emitted from the cathode can be deposited on the anode plate or the wall of the vacuum chamber. cathode sputtering
shoot.
The cathode sputtering discharge circuit is formed by the movement of positive ions generated by gas discharge to the cathode and the movement of primary electrons to the anode. Discharge is generated by the impact of positive ions on the cathode to generate secondary electrons. It is accelerated through the Crooks dark zone to supplement the consumption of primary electrons to maintain, therefore, the discharge current measured in the external circuit is the sum of the positive ion current bombarding the target and the secondary electron current emitted by the cathode.
The main disadvantage of cathode sputtering is the low deposition rate and the temperature rise of the plated parts.
Magnetron sputtering is a kind of abnormal cathode glow low-pressure plasma discharge. The magnetron sputtering source is a sputtering source made by using the principle of magnetron (that is, the magnetic field is perpendicular to the electric field, and the direction of the magnetic field is parallel to the surface of the cathode).
The discharge of the magnetron sputtering source is that the positive ions generated by gas ionization are attracted by the cathode potential, are accelerated in the Crooks dark area, and hit the cathode with an energy of several hundred electron volts to obtain electrons from the anode and become neutral atoms. At the same time, the cathode target atoms are sputtered and fly to the plated parts to form a film. The secondary electrons shot out from the cathode pass through the Crooks dark area, are accelerated by the electric field to obtain energy, and enter the plasma to become primary electrons. In the orthogonal electromagnetic field, the movement direction of the electron is perpendicular to the electric field and the magnetic field, and it is a circular rolling trajectory, which increases the collision with the gas molecules and increases the probability of ionization. After repeated collisions, the once energy is exhausted. Electrons become "final electrons" and enter the anode to form a discharge current. Therefore, magnetron sputtering and cathode sputtering have basically the same discharge mechanism except that the trajectory of primary electrons is different.
