Patent ID: 8906452

Claim:
A method of coating a wafer with a film of photoresist having a uniform thickness profile across the wafer, the method comprising: depositing a photoresist solution on a top surface of a wafer, the photoresist solution including a photoresist and a solvent, the photoresist solution configured to provide a particular thickness of photoresist on the wafer upon evaporation of the solvent; and controlling the volatility of the photoresist solution to allow the solvent of the photoresist solution to evaporate at a specified rate concurrently with the photoresist of the photoresist solution forming a film having a uniform thickness profile at the particular thickness on the wafer; wherein depositing the photoresist solution on the top surface of the wafer includes: spinning the wafer on a spinning device about an axis normal to the top surface of the wafer, and when the photoresist solution reaches the edge of the wafer, removing the wafer from the spinning device; wherein removing the wafer from the spinning device when the photoresist solution reaches the edge of the wafer includes: performing a detection operation at the edge of the wafer, the detection operation being configured to detect the presence of photoresist solution, and prior to controlling the volatility of the photoresist solution, stopping the wafer from spinning on the spinning device in response to the detection operation detecting the presence of photoresist solution at the edge of the wafer.