Surface preparation: Clean and dry the wafer. Dehydration is carried out in an oven.

Spin coat: The wafer is held to the spindle using vacuum. Dispense about 5 ml of photo resist on to the wafer. Start with slow spin (~500 rpm) and then ramp up ~ 3000 to 5000 rpm. The excess resist fly off during the spinning.

Where is the thickness of the photo resist after spinning, is viscosity of the resist, is the angular velocity and is radius of the wafer.

Fig. 3.53 : Schematic of a photo resist spinner