In this example, the technique of terracing is employed to improve the thickness uniformity in coating flat substrates of 25 mm in diameter. In the same model planetary-rotation coater as in Case 1, we first level ten such substrates along a radius of a fixture. The overall thickness nonuniformity is 2.0% without correction masks, as shown below.
Next, we terrace the substrates in the "Surface Coated" panel by moving selected substrates in the z-direction and pivoting them for various amounts. After a few numerical trials for each of the substrates we arrived at a terracing arrangement summarized in the following table:
The result of the terracing is a much improved thickness distribution among and in the substrates as shown in the following figures. The overall peak-to-valley nonuniformity is reduced to 0.23% from an otherwise 2.0%.
Please view also 'Get the most out of your coater' for details.