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CFUBMSIP - Closed Field Unbalanced Magnetron Sputter Ion Plating

The Closed Field Unbalanced Magnetron Sputter Ion Plating system, developed by Teer Coatings Ltd, produces optimised deposition conditions allowing deposition of dense, hard coatings with excellent adhesion. The CFUBMSIP arrangement is covered by patents granted to Teer Coatings Ltd.

• UK Patent No 2 258 343,
• USA Patent No 5 556 519,
• European Patent No 0 521 045

Development Of The CFUBMSIP System

Development of the CFUBMSIP system at Teer Coatings began in 1986, when a long term development programme, intended to increase the ion current density in magnetron sputter ion plating, was started. This work led to the development of the closed field system.

The major stage in the development of the system was the idea of using unbalanced magnetrons in an arrangement whereby neighbouring magnetrons are of opposite magnetic polarity. Using this arrangement, the deposition zone in which the substrates are located is surrounded by linking magnetic field lines. This traps the plasma region, prevents losses of ionising electrons and results in significant plasma enhancement.

The use and design of the closed field unbalanced system is covered by patents granted to Teer Coatings Ltd. The patented closed field system covers any magnetron deposition system containing more than one magnetron where the linking of magnetic field lines from neighbouring magnetrons causes plasma enhancement. This includes twin magnetron systems with facing magnetrons of opposing magnetic polarity and four magnetron systems where the arrangement of the polarity of the magnetrons is closed to enhance the plasma.

ION Current Density

Figure 1 shows ion current against substrate bias voltage for different system configurations. The increase in ion current density obtained by using the closed field unbalanced system can be clearly seen.

Figure 1. Ion current against substrate bias

Coating Structure

From the graph of ion current against bias voltage it can be seen that the maximum ion current is achieved at a bias voltage of around 50V. Therefore deposition can be carried out using a high density of low energy bombarding ions. This results in deposition of very dense, non columnar coating structures with low internal stresses. The use of a low bias voltage during deposition also allows deposition of coatings with dense structures at low temperature.

Coating Adhesion

Figure 2 shows ion current against bias voltage for two different levels of current applied to the magnetrons. Here it can be seen that as the current to the magnetrons is increased there is a corresponding increase in ion bombardment, hence the ratio of ions to neutrals within the system is kept approximately constant. This ensures that the quality of the coatings produced by the system is independent of the deposition rate.

Figure 2. Bias voltage for 0.5A (lower line) and 10A (upper line)

In the CFUBMSIP system ion cleaning prior to deposition is carried out with the magnetrons switched on at low power. The use of magnetrons at this stage allows a plasma to strike to the substrates at low Argon pressure (around 1×10-3Torr) which is much more effective than a high pressure plasma. Ion cleaning is carried out at point B on the graph with deposition at point A. The ion current at point B is approximately 100 times greater than in a conventional system without the closed field arrangement.

Therefore in the CFUBMSIP system the efficiency of ion cleaning is significantly increased, resulting in coatings with very high levels of adhesion.

Systems Covered By The Patents

Any magnetron sputter deposition system containing more than one magnetron where the linking of magnetic field lines from neighbouring magnetrons causes plasma enhancement is covered by the above patents.

This includes twin magnetron systems with facing magnetrons of opposing magnetic polarity. It includes four magnetron systems where the arrangement of the polarity of the magnetrons is closed to enhance the plasma.
The magnetrons may be round or rectangular. They may be oriented with their long axis vertical or horizontal. If linking magnetic field lines enhance the plasma then the above patents are infringed.

Teer Coatings invite applications from manufacturers and users of Magnetron Sputter Ion Plating Systems for licences to cover the use of the Closed Field System.

Technical Poster To Download

Variations on the closed field unbalanced magnetron sputter ion plating configuration