Improvement of uniformity of magnetron sputtering optical film

With the development of optical communication, the performance requirements of optical films are getting higher and higher, which puts higher requirements on the uniformity of the coating machine. In this paper, by designing a new fixture, the uniformity of the coating machine is optimized from 1% to 0.1%.

With the rapid development of optical communications and other industries, various optical films with different functions have emerged, and their spectral performance requirements have become higher and more widely used. There is an increasing demand for difficult films such as 50G and GFF. The requirements for coating machines are getting higher and higher.

At present, the uniformity of mainstream coating machines on the market can only reach 1%, which has little effect when coating ordinary optical films, but when coating difficult films such as 50G and GFF, the coating yield and output are difficult to reach Claim. At present, most measures in the industry are to use shielding plates to optimize uniformity. However, a large number of experiments are required to determine the size of the shielding plate, and different film shielding plates cannot be used universally, which greatly limits the use of the shielding plate. In this paper, the uniformity is improved by directly improving the fixture of the coating machine. There is no relevant report at present.

This article uses OCLI’s J-CLASS magnetron sputtering coating machine, which is mainly composed of vacuum system, sputtering system, and light control system. Because the vacuum system and light control system have little effect on uniformity, this article will not repeat it. Mainly introduce the sputtering system, as shown: The coated substrate is screwed on a high-speed rotating shaft installed on the top of the cavity, as shown:

Improvement of uniformity of magnetron sputtering optical film

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A uniformity experiment was plated with the following design, the first 36 layers were monitored at 1535nm wavelength, and the following 37 layers were monitored at 1565nm wavelength.

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The left and right peaks of the spectrum curve represent the spectral lines of low-refractive-index materials and high-refractive-index materials, respectively. The 0.5dB bandwidth center wavelength of this spectral line is used to calculate the uniformity.

By measuring the spectrum of each point in the radius direction, the 0.5dB bandwidth center wavelength of the high and low refractive index materials at each point can be measured respectively, and the radius-center wavelength curve can be obtained, as follows:

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The uniformity calculation formula is: Uniformity = (Maximum Center Wavelength-Minimum Value)/Monitoring Wavelength*100%. The uniformity of the coating machine is calculated as:

The uniformity of low refractive index materials = (1549.3-1535)/1535=0.9%.

The uniformity of high refractive index materials = (1577.6-1565)/1565=0.8%.

The old fixture uses screws to fix the substrate, the substrate and the rotating shaft are completely locked, and the motor drives the substrate to rotate at high speed. However, various vibrations inevitably exist in the mechanical motion, and the unstable speed caused by power fluctuations will cause the unstable speed of the substrate rotation and the jitter of the substrate, resulting in poor uniformity.

This paper designs a brand-new fixture. The schematic diagram is as follows: a smooth ball is used to reduce the friction and make the rotation more stable under the action of centrifugal force when the substrate rotates at high speed, thereby improving the uniformity of the radial direction. Part of the physical structure is shown in the figure.

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The substrate and the rotating shaft adopt a dynamic connection, relying on friction to drive the substrate to rotate. The flying ball and collar are very smooth, which can effectively shield the speed instability caused by the instability of the motor power and the substrate jitter caused by various vibrations, thereby significantly improving the uniformity of the film.

The same uniformity experiment method as before the improvement of the fixture is adopted, and the uniformity results after the improvement of the fixture are measured as follows:

Through calculation, the uniformity of high and low refractive index materials are as follows:

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The uniformity of low refractive index materials = (1535.2-1533.6)/1535=0.1%.

The uniformity of high refractive index materials = (1567.1-1565.6)/1565=0.1%.

In this paper, a newly designed fixture is used to successfully improve the radial uniformity from about 1% to 0.1%, which provides a new method for coating high-performance films and improving the coating yield, compared with the use of shield There is no need to design a series of shielding plates and frequently replace the shielding plates, which can reduce costs, reduce experiments, and improve production efficiency.

Founded in 2015,Zunhua Baorui Titanium Equipment Co.,Ltd. is a manufacturer specializing in pvd vacuum ion coating equipment. The company’s products mainly include large plate coating machine, large tube collating machine, tool coating machine and LOW-E glass production line. Mr.Wang baijiang ,general manager of the company ,has been engaged in vacuum coating industry for more than 30 years. He continuously improve production technology, improve product performance and devote himself to provide customers with better product experience and higher production efficiency.