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Main factors affecting the voltage of magnetron sputtering

The main factors that affect the sputtering voltage of a magnetron target are: the magnetic field of the target surface, the target material, the gas pressure, the cathode-anode distance, and so on. This article analyzes the influence of these factors on the target sputtering voltage in detail.



The influence of target surface magnetic field on target sputtering voltage

· The cathode working voltage of the magnetron target decreases with the increase of the magnetic field of the target surface, and also decreases with the deepening of the sputtering etching groove of the target surface. The sputtering current also increases with the deepening of the sputtering etch groove on the target surface. This is because the sputter etching groove surface of the target will get closer and closer to the strong magnetic field of the permanent magnet behind the target. Therefore, the thickness of the target material is limited. Thicker non-magnetic targets can be used in stronger magnetic fields. When the magnetic field strength increases above 0.1T, the influence of the magnetic field strength on the sputtering voltage is not obvious.

· The ferromagnetic target material will affect the sputtering of the magnetron target. Since most of the magnetic field lines pass through the ferromagnetic material, the magnetic field on the surface of the target material is reduced, and a very high voltage is required for the target surface to ignite. Unless the magnetic field is very strong, the magnetic target must be thinner than the non-magnetic material in order to shine and operate normally (the typical value of the permanent magnet structure Ni target is <0.16cm, and the non-special design maximum value of the magnetron target should not exceed The maximum value of 3mm, Fe, and co targets does not exceed 2mm; targets with electromagnetic structures can be sputtered with thicker targets, even up to 6mm thick) in order to shine and operate normally. During normal operation, the magnetic field intensity on the surface of the magnetron target is about 0.025T~0.05T; when the target is about to be perforated by sputtering etching, the magnetic field intensity on the target surface is greatly increased, approaching or greater than about 0.1T.

The influence of target material on target sputtering voltage

· Under the condition of constant vacuum conditions, different materials and types of target materials will have a certain impact on the normal sputtering voltage of the magnetron target.


· The normal sputtering voltage of commonly used targets (such as copper Cu, aluminum Altitanium Ti) is generally in the range of 400~600V.


· Some sputtering targets (such as manganese Mn, chromium Cr, etc.) have relatively high sputtering voltages, and generally require more than 700V to complete the normal magnetron sputtering process; while some targets (such as indium tin oxide ITO) sputtering The radio voltage is relatively low, and the normal magnetron sputtering deposition coating can be realized at a voltage of more than 200 volts.


· In the actual coating process, due to changes in the working gas pressure, or the distance between the cathode and the anode is too small (changes the impedance characteristics in the vacuum chamber), or the mechanical dimensions of the vacuum chamber and the magnetron target do not match, the output characteristics are selected at the same time For reasons such as softer target power supply, the sputtering voltage of the magnetron target (that is, the output voltage of the target power supply) is much lower than the normal sputtering value, and it may appear that the front memory of the target shows a very bright aperture, but it is not visible. When the target ion is flooded with the corresponding color, it can not be sputtered to form a film.

The influence of gas pressure on target sputtering voltage

In the process of magnetron sputtering or reactive magnetron sputtering coating process, the pressure of working gas or reactive gas can have a certain influence on the sputtering voltage of magnetron target.


· The influence of working gas pressure on target sputtering voltage
The general rule is: when the environmental conditions of the vacuum equipment are determined and the control panel setting parameters of the target power supply remain unchanged, as the working gas (such as argon) pressure (0.1~10Pa) gradually increases, the density of the gas discharge plasma will also The synchronous increase causes the equivalent plasma impedance to decrease, the sputtering current of the magnetron target will gradually increase, and the sputtering operating voltage will also decrease synchronously.

· The influence of reactive gas pressure on target sputtering voltage
In the process of reactive magnetron sputtering coating, when the environmental conditions of the vacuum equipment are determined and the control panel setting parameters of the target power supply remain unchanged, as the pressure (or flow) of the reactive gas (such as nitrogen and oxygen) gradually increases (generally Be careful not to exceed the upper limit of the process setting value). As the magnetron target surface and the substrate (workpiece) surface are gradually covered by the insulating film, the equivalent impedance of the discharge between the cathode and the anode will also increase simultaneously. The sputtering current of the target will gradually decrease (until "cathode poisoning" and "anode disappear"), and the sputtering working voltage will also increase simultaneously.

The influence of the cathode-anode distance on the target sputtering voltage

The vacuum gas discharge cathode-anode distance can have a certain impact on the target sputtering voltage. When the cathode-anode distance is too large, the internal resistance of the equivalent gas discharge is mainly determined by the plasma equivalent internal resistance. On the contrary, when the cathode-anode distance is too small, the internal resistance of the plasma discharge will show a smaller value. Since the magnetron target enters normal sputtering after it is ignited, if the cathode-anode distance is too small, because the sputtering voltage output by the target power supply has a certain soft load characteristic, it may appear that the sputtering current has reached the process setting. When setting the value, the target sputtering voltage is always low and cannot be adjusted. The "craft-type" target power supply can improve and make up for this situation; while the "economical" target power supply can't do anything about this situation.


· Twin target (or dual magnetron target) cathode-anode spacing symmetrical bipolar pulse intermediate frequency target power supply and sine wave intermediate frequency target power supply when operating with twin target or dual magnetron target, it is recommended that the two alternating cathode-anode minimum poles The spacing should not be less than 2 inches 2 inches;


· Single magnetron target cathode-anode spacing
When the target power supply is operated with a single magnetron target, this problem generally does not exist; however, it is easy to ignore this problem when the small vacuum chamber is equipped with a long rectangular planar magnetron single target. The magnetron target surface and the inner wall of the vacuum chamber metal shell The minimum distance between poles is generally recommended not to be less than 2 inches 2 inches.

Xinkang New Materials is a global supplier of various high-quality sputtering targets such as metals, alloys, oxides, and ceramic materials. All the sputtering targets mentioned above are provided by Xinkang. If you have any questions about the target materials, please consult us.


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