Device for machining a substrate and a method for this purpose

A method for machining a substrate comprising the steps of:

• providing a turntable comprising a dish-shaped bottom plate;
• locating a diffuser in the dish-shaped bottom plate wherein a Venturi gap is formed by an inner rim of the dish-shaped bottom plate and a circumferential edge of the diffuser;
• providing a chamfer on a circumferential surface of the bottom plate proximate to the Venturi gap,
• whereby a pressure medium emerging from the Venturi gap is directed along the chamfer and under an upper surface of the turntable;
• placing a substrate on the upper surface of the turntable;
• supplying the Venturi gap with a pressure medium;
• rotating the substrate on the turntable;
• applying a machining medium to the substrate;
• and
• removing the substrate from the turntable.