In-line deposition for wafer coating like other in-line processing creates a uniform layer via the transfer of the wafer under either a circular target or a rectangular target. Transfer under a circular target requires the use of a uniformity mask to correct the geometrical imbalance and this results in additional particulates and material use inefficiencies. Transfer under a rectangular target however does not require a uniformity mask if the target width to length ratio is correct relative to the wafer size (see e-news for a detailed description). Gencoa offer a number of rectangular cathode solutions targeted at wafer metallizing.

The principle requirement for a rectangular cathode for wafer metallizing is to provide both a highly repeatable uniformity deposit through the target life and minimize defect generation. The uniformity is determined by the accuracy of the magnetic pack incorporated in the cathode. It is critical that magnetic materials are of a constant blend and energy product. Gencoa only uses magnets that have a strict blend and energy product tolerance.

The magnet type of choice in today's market is that of a NdFeB alloy. Gencoa never incorporate any magnet in a water channel to avoid any possibility of corrosion or degradation over time - all the Gencoa arrays are on the atmosphere side of the cathode. The magnetic retaining poles are machined structures onto which the magnets are assembled and accurately aligned. This ensures a uniform magnetic field and uniformity cathode to cathode and batch to batch. Each magnet pack is then subject to a 3D magnetic mapping to provide a QC check (new in 2007).

Defect generation in sputtered films are especially problematic in semi-conductor based products as they will lead to device limitations or failure. Defects in planar magnetrons come either direct from the target after a 'micro-arc' or from the re-deposit either on the target or anodes / shields. Cleanliness around the target area is essential - even micro-arcs are increased with larger re-deposit areas. To optimise the performance Gencoa use a combined magnetic field and anode design that minimises the re-deposit both on the target and anode by promoting sputtering right to the targets edge and moving the anode position to prevent any line-of-sight from the target surface to the anode. Additionally any anode or shield parts that will be subject to coating have a carefully controlled rough surface to retain the coating material.

 The ability of Gencoa to fit and tune 1 of 9 different magnetic arrays means that a wide variety of processes and demands can be met. for example, unique cathodes such as the FFE and MZ in particular can offer a clean target surface or extended up-times. Gencoa also specialise in customising the magnetron designs to fit into existing tools and to meet the customers demands. Going forward we work with the tool maker to continuously improve yields and performance. A good example of this approach is the Nimbus tool illustrated in the case-studies section under Nexx Systems.