Thin Film uniformity is influenced by viscosity, process temperature, rotational speed, acceleration and time.
The film thickness d corresponds directly to the rotational speed ω. Thickness , where ɑ contains photoresist specific parameters alike angular viscosity. Every vendor of a photoresist publishes curves for d vs. w (normally specified by the resist vendor at 3,000 or 4,000 rpm). For typical photoresists and film thicknesses we achieve a uniformity of better than 5%. The speed can be set from 1-12,000 rpm, time 0.1-99999 sec/step. Vacuum can also affect film uniformity in some processes. Vacuum can be set on or off. We offer mechanical chucks for non-vacuum applications.
Our low-cost FR-portable thickness film measurement tool is recommended for quick scan of the layer thickness.
Accurate acceleration and stable RPM are critical factors for Coating Uniformity. Our digital motor speed controller, with incremental speed signal feed back, guarantees acceleration / deceleration of 1-30,000 rpm/sec and a spin speed accuracy within 0.1 rpm, no overshoot, no stutter. With programmable clockwise and counter-clockwise rotation and puddle function, our spin coaters provide all the necessary precision for critical spincoating processes. For typical photoresists and film thicknesses we achieve a uniformity of better than 5%.