Lithographic apparatus and device manufacturing method

Abstract

An immersion lithographic apparatus is disclosed having comprising a pump and buffer volume configured to remove remaining liquid from a substrate, the pump and the buffer volume configured to generate a vacuum cleaning gas flow near the substrate by gas suction into the buffer volume. In an embodiment, since gas flow is needed only a limited amount of time (ordinarily less than 5%), evacuation may be performed using only a moderately powered vacuum pump. In addition or alternatively, the buffer volume may be used as a backup volume buffer configured to provide gas vacuum suction, e.g., in case of a vacuum supply outage.

1 . A lithographic apparatus, comprising:
 a support structure configured to support a substrate;   a projection system configured to project a patterned beam through a liquid onto a target portion of the substrate; and   a pump and a buffer volume configured to remove remaining liquid from the substrate, the pump and the buffer volume configured to generate a vacuum cleaning gas flow near the substrate by gas suction into the buffer volume.   
     
     
         2 . The apparatus according to  claim 1 , wherein the buffer volume is arranged to intermittently generate a gas flow to clean the substrate after an immersion projection exposure. 
     
     
         3 . The apparatus according to  claim 1 , wherein the buffer volume is arranged to generate a backup gas flow for the pump to remove remaining liquid from the substrate during an immersion projection exposure. 
     
     
         4 . The apparatus according to  claim 1 , wherein the pump and buffer volume are connected to a drying station and the support structure is arranged to move the substrate underneath the drying station. 
     
     
         5 . The apparatus according to  claim 4 , wherein the buffer volume is arranged to generate a flow rate of the gas flow greater than about 40 m 3 /h in a gap larger than about 0.3 mm. 
     
     
         6 . The apparatus according to  claim 5 , wherein the flow rate of the gas flow is greater than or equal to 400 m 3 /h and the gap is about 1 mm for ambient pressure and temperature conditions. 
     
     
         7 . The apparatus according to  claim 1 , wherein the buffer volume is dimensioned to generate twice the amount of gas needed, wherein the vacuum pressure varies from 0-0.5 bar. 
     
     
         8 . The apparatus according to  claim 7 , wherein the buffer volume exceeds 100 liters. 
     
     
         9 . The apparatus according to  claim 1 , comprising a liquid confinement structure configured to provide liquid to a space between the substrate and the projection system, the liquid confinement structure comprising a suction inlet coupled to the buffer volume and the buffer volume comprises a backup buffer volume. 
     
     
         10 . The apparatus according to  claim 1 , wherein the buffer volume is configured to generate a cleaning gas flow such that (τ wall ·δt)glass>1.5[Pa·s], wherein τ wall  is a calculated sheer stress at the substrate and δt is a total residual time of a droplet. 
     
     
         11 . A method of intermittently providing vacuum suction in an immersion lithographic apparatus, comprising:
 alternatingly vacuum extracting a buffer volume using a pump; and   generating a cleaning gas flow near the substrate by gas suction into the buffer volume.   
     
     
         12 . The method according to  claim 11 , wherein the cleaning gas flow is generated for up to 1 minute. 
     
     
         13 . The method according to  claim 11 , wherein the buffer volume is configured to generate a cleaning gas flow such that (τ wall ·δt)glass>1.5[Pa·s], wherein τ wall  is a calculated sheer stress at the substrate and δt is a total residual time of a droplet. 
     
     
         14 . The method according to  claim 13 , wherein the calculated sheer stress exceeds 20 N/m 2 . 
     
     
         15 . The method according to  claim 11 , wherein generating the cleaning gas flow comprises intermittently generating the cleaning gas flow to clean the substrate after an immersion projection exposure. 
     
     
         16 . The method according to  claim 11 , wherein generating the cleaning gas flow comprises generating a backup gas flow for the pump to remove remaining liquid from the substrate during an immersion projection exposure. 
     
     
         17 . The method according to  claim 11 , comprising generating a flow rate of the cleaning gas flow greater than about 40 m 3 /h in a gap larger than about 0.3 mm. 
     
     
         18 . A method of providing a backup vacuum suction in an immersion lithographic apparatus, comprising:
 vacuum extracting a backup buffer volume using a pump; and   generating a backup vacuum suction near the substrate by gas suction into the backup buffer volume.   
     
     
         19 . The method according to  claim 18 , comprising providing a liquid to a space between the substrate and a projection system using a liquid confinement structure, the liquid confinement structure comprising a suction inlet by which the backup suction is provided near the substrate. 
     
     
         20 . The method according to  claim 18 , comprising generating a flow rate of gas flow caused by the gas suction greater than about 40 m 3 /h in a gap larger than about 0.3 mm.