Medium frequency magnetron sputtering coating technology

- Mar 09, 2019-

Medium frequency magnetron sputtering coating technology


Magnetron sputtering includes many types. Each has different working principle and applied object. But they have one thing in common: they use magnetic fields to interact with electrons, causing them to spiral around the target surface, increasing the probability that they will hit argon to produce ions. The generated ions collide with the target surface under the action of electric field and splash out the target material. In recent decades of development, people gradually adopt permanent magnets, rarely coil magnets.


Target source is divided into balanced and non-balanced, balanced target source coating uniform, non-balanced target source coating film layer and matrix binding force is strong. Balanced target sources are mostly used in semiconductor optical films, while non-balanced targets are mostly used in worn decorative films.


No matter the equilibrium or non-equilibrium, if the magnet is stationary, its magnetic field characteristics determine that the general target material utilization rate is less than 30%. In order to increase the utilization rate of the target, the rotating magnetic field can be used. However, rotating magnetic field requires rotating mechanism, and sputtering rate should be reduced. The rotating magnetic field is mostly used for large or valuable targets. Such as semiconductor film sputtering. For small equipment and general industrial equipment, the use of static magnetic field target source.


Sputtering of metals and alloys with a magnetron target source is easy, and ignition and sputtering are easy. This is because the target (cathode), plasma, and splashed parts/vacuum cavity can form a loop. But if the sputtering insulator such as ceramic the circuit is broken. So people use the high frequency power supply, the circuit adds very strong capacitance. Thus the target becomes a capacitor in the insulated circuit. However, the high frequency magnetron sputtering power supply is expensive, the sputtering rate is very small, and the grounding technology is very complex, so it is difficult to be used on a large scale. To solve this problem, magnetron reactive sputtering was invented. This is a metal target with argon and reactive gases such as nitrogen or oxygen added. When a metal target collides with a part, it combines with the reaction gas to form nitrides or oxides due to energy conversion.

Magnetron reactive sputtering insulators seem easy but are difficult to operate. The main problem is that the reaction occurs not only on the surface of the part, but also on the anode, the surface of the vacuum cavity, and the surface of the target source. Thus causes the fire extinguishing, the target source and the workpiece surface arcing and so on. The twin target source technology invented by Germany laibao solves this problem well. The principle is that a pair of target sources are anode and cathode to eliminate anodic surface oxidation or nitriding.


Cooling is necessary for all sources (magnetron, multi-arc, ion) because a large part of the energy is converted to heat, which, if not cooled or not cooled enough, will melt the entire target source at a temperature of more than a thousand degrees.


A magnetic control device is often very expensive, but people tend to spend money on other equipment such as vacuum pump, MFC, film thickness measurement and ignore the target source. A good magnetron sputtering device without a good target source is like drawing a dragon without a point.


The advantages of medium frequency sputtering are smooth and dense, high hardness of film layer, linear growth of film thickness, non-toxic, mild temperature rise, but the requirements of equipment are high, the working pressure range is very narrow, and various control requirements are rapid and accurate.


Multi-arc sputtering applied small voltage and large current on the target material to ionize the material (positively charged particles), thus hitting the substrate (negatively charged) at high speed and depositing, forming a dense film hard film. Mainly used for wear - resistant and corrosion - resistant film. The disadvantage is that the film is not uniform, cavitation and ablation.


The principle of intermediate frequency sputtering with general dc sputtering is the same, the difference is dc sputtering the cylinder when the anode, and the intermediate frequency sputtering is in pairs, barrel whether attend depends on the overall design, and the whole system sputtering process, the arrangement of anode, cathode, there are a lot of ways to participate in the ratio of the cycle, different ways of different sputtering yield can be obtained, are not the same ion density


The main technology of if sputtering lies in the design and application of power supply. Currently, sine wave and pulse square wave are two kinds of output modes, which have their own advantages and disadvantages. First, the types of film layers should be considered to analyze which type of power supply output mode is suitable for which film layer.


Intermediate frequency sputtering is also a kind of magnetron sputtering, general magnetron sputtering target design, the design of the magnetic field is the key of the various technology, the international several famous manufacturers of sputtering target, for the design of target magnetic field is professional, change the magnetic field design can get different plasma evaporation. The path of the electron, the distribution of the plasma, so is the technical secrets of sputtering target magnetic field.

As for cathode arc (i.e., ion plating), magnetron sputtering, and crucible evaporation, all belong to PVD (physical vapor deposition), crucible evaporation is mainly a phase change, and the evaporation target has only a few electron volts of energy. Therefore, the film adhesion is small, but high deposition rate, mostly used for optical coating. In magnetron sputtering, argon ions impingle on the target material to deposit atomic and molecular fragments on the parts, and the kinetic energy of the target material can reach hundreds or even thousands of electron volts. It is a real neutral nano - level coating. After the cathode arc arcing, on the one hand, the metallurgy of the material is melted by the target surface at high temperature, and then the melted material is almost completely ionized by the strong electric field, and the film is formed under the combined action of the target power supply and the partial pressure of the parts. Looks like the cathode arc plating is more advanced, actually is not. First of all, the target surface melting process is random and uncontrollable, and ions are deposited into the parts. Uniformity and smoothness of plating are difficult to guarantee. Generally speaking, cathode arc plating is a welding process under vacuum. The principle of cathode arc power supply and welding power supply is very similar. The cathode arc technology is mainly originated from the former Soviet union. It is popular in China for various reasons. But technology is improving. In recent years, the filtration cathode arc technology has developed rapidly, which avoids the disadvantage of uneven film formation. However, some gains must be lost, and the filtration reduces the deposition rate and increases the equipment cost.


Medium frequency magnetron sputtering requires high target and magnetic field design as well as working pressure. Medium frequency magnetron sputtering is 2 to 3 times of dc magnetron sputtering deposition rate. Medium frequency magnetron sputtering is used for two targets to prepare compound films. Due to its low ionization rate, it is difficult to find an optimal poisoning point, and the flow control of the working gas is very strict. If the control is not good it is difficult to prepare uniform and good adhesion film. And the design is mainly the uniformity of magnetic field distribution of the magnetic field can improve the utilization rate of target material, so in addition to the stability of the best poisoning some work also has a lot to improve the magnetron sputtering ion energy and diffraction are far below the arc target surface, and the distance of the workpiece is important, too close to ion bombardment of artifacts can damage the membrane layer, too far, deviation from the optimal sputtering coating binding force of the preparation of distance is very poor

The target material of if is used for target, some of them are used for three pairs. The target is relatively large, as for if, most of them are used for metal-plated workpieces. Such a vacuum furnace is generally made larger, which can put down a lot of tasks, and the plated film layer is more dense.


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Can if sputtering work at low vacuum? There is no problem. Our current schedule is 8.0* 10-2pa.

What are the influence factors of TiN film color by if sputtering? What is the effect of bias on L, a, and b?

Bias does have a lot to do with color,

Effect of sputtering gas pressure (argon) on L, a and b values?

This problem is complicated, which is related to ionization rate, pressure and target distance interconnection mode. It may take quite a long time to systematize very clear data. Sputtering gas and color should be said to be determined by the sputtering amount produced, which affects the relationship with the reaction gas and has an impact on color

Is it feasible to use ammonia in reactive sputtering? Yes.