Rapid coating of wafers

摘要

An improved technique achieves a uniform photoresist film on a wafer by controlling the volatility of the solvent in a photoresist solution during the bake process step. Because film formation takes place in the bake rather than the spin steps of the process, the improved technique involves using less viscous and therefore less costly and easier to use resists to cast relatively thick photoresist films. Such control is achieved in an enclosed chamber into which a carrier gas is introduced; the carrier gas mixes with gaseous solvent to create a saturating atmosphere in which the rate of evaporation of solvent decreases. This enables the heating of the wafer without the reduction of solvent in the film so that the photoresist can self-level. When the film has self-leveled, the solvent is then baked off as usual.

主权项

1. 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, andwhen 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, andprior 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.