This week marks the beginning of a busy summer of exhibiting, with Gencoa currently promoting products for the thin film industry at the ISSP conference and exhibition in Kyoto, Japan.

In August, Gencoa will be at two further tradeshows, the details of which are as follows:

August 21-23: Guangzhou International Vacuum Industrial Show Guangzhou, China.
August 25-30: AEPSE 2013 Jeju, Korea (in association with KCMC).

This month's technical paper from Gencoa focusses on how system geometry tuning can help to achieve optimum uniformity for your application. A summary of the paper can be read below, with the full PDF document available to download from the Technical Papers section of our website, or by clicking the following link: Gencoa technical paper, July 2013.

For circular magnetrons, the uniformity on a substrate is determined by the coating flux distribution from the target surface. Geometry is also an important factor as the target diameter relative to the substrate size, and target to substrate separation will have major influences.

For target sizes of 6" or smaller, the magnetic system will usually contain one plasma trap, while target sizes of 8" or greater can utilize a multi-ring magnetic design which enhances the uniformity for a given situation (figure 1).

Uniformity from a small target can be improved by moving the substrate to a high separation, but this has an impact on the coating rate, which is reduced as a result.

Figure 1: Multi-ring magnetic design

Due to the modest area of uniformity from small sources, the off-axis and rotation of the substrate method is commonly used to improve uniformity over larger areas.

This involves positioning the magnetron head away from the centre of the substrate and then rotating the substrate.

Uniformity can be improved via the geometry of this arrangement, as the shape of the coating flux works with the rotational effect of the substrate to equalize the rate of material arrival over the whole area.

The success of the off-axis and rotation method will be determined by good lateral positioning of the magnetron head, the angle of the head relative to the substrate, the size of target and substrate, and the vertical separation of the substrate from the magnetron.

Figure 2: Combined action of the vapour flux distribution with the substrate rotation can create high uniformity

To help achieve the correct uniformity, Gencoa have developed a tool that can predict the coating uniformity on a substrate.

The uniformity simulation software calculates the sputtering probability across the substrate and hence a model of the coating flux from the target material can be generated.

Correction factors can be added to the model to account for different target materials, since the angular sputtering dependance varies for each material.

Also taken into account are differing sizes of substrate, and the software allows for changes in magnetron location and tilt.

If the uniformity cannot be achieved, then some manipulation of the magnetic field may be required, and the software can provide a prediction of the corresponding change in uniformity.

The uniformity simulator tool is available to Gencoa circular magnetron customers. Contact your local sales representative to request a copy.

Figure 3: Gencoa uniformity simulator tool

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