Case 4: Terraced Flats in Planetary Coater
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.
