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Original Publication Date: 2000-Apr-01
Included in the Prior Art Database: 2003-Jun-20

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Described is a method to better control the composition of the alloy films deposited using ion beam sputtering technique. The composition of different alloy films can change across the 5 inch wafers which presents a problem for the production of spin valve devices. Specifically, the composition of the PtMn films change by up to 0.5% from center to edge of the wafers in standard deposition condition (both target and substrate are vertical ie. 90 degrees). The new method improves the composition uniformity to about 0.2 at.% which is within the x-ray fluorescence measurement error. The composition of the alloy films can show different uniformity behaviour when deposited on large substrates. For example, NiFe films which have atoms with similar atomic mass show an excellent uniformity (0.2 at.%) across the 5 inch wafer while PtMn films with large atomic mass mismatch shows up to 0.5 at.% variation in film composition. The composition of the PtMn films can be controlled by tilting the stage during the film deposition. The results in the Figure below show that the wafer edge (sample #1) has less Mn compare to wafer center (sample #3) when the films are deposited with the stage at 90 degrees. When the stage is at 80 degrees, the PtMn composition uniformity is within 0.2 at.% therefore giving the best composition uniformity. At 70 degrees stage angle, the Mn composition is higher at the wafer edge which is opposite to the 90 degree deposition condition. For different alloys and system geometries, the film composition at the substrate can be improved by adjusting the stage tilt to different angles. Mn PERCENTAGE IN ION BEAM PtMn FILMS ACROSS 5 INCH WAFER 52