Lithographic apparatus and device manufacturing method

Abstract

In a lithographic projection apparatus, a liquid supply system maintains liquid in a space between the projection system and the substrate. The liquid supply system may further include a de-mineralizing unit, a distillation unit, a de-hydrocarbonating unit, a UV radiation source, and/or a filter configured to purify the liquid. A gas content reduction device may be provided to reduce a gas content of the liquid. A chemical may be added to the liquid using an adding device to inhibit lifeform growth and components of the liquid supply system may be made of a material which is non-transparent to visible light such that growth of lifeforms may be reduced.

1 .- 20 . (canceled) 
     
     
         21 . A lithographic projection apparatus, comprising:
 a projection system configured to project a radiation beam onto a target portion of a substrate;   a liquid supply system configured to at least partly fill a space between the projection system and the substrate with a liquid; and   a measurement device configured to measure a property of the liquid indicative of contamination.   
     
     
         22 . The apparatus of  claim 21 , wherein the property is one or more properties selected from the group consisting of: electrical conductivity, pH, TOC, particles, oxygen, total silica, and bubbles. 
     
     
         23 . The apparatus of  claim 21 , wherein the property is particles. 
     
     
         24 . The apparatus of  claim 23 , further comprising a liquid purifier configured to purify the liquid such that it has a particle content of no more than 2 particles having a dimension of 50 nm or greater per ml of liquid. 
     
     
         25 . The apparatus of  claim 21 , wherein the measurement device is one or more measurement devices selected from the group consisting of: an electrical conductivity measurement device, a pH sensor, a TOC analyzer, a particle counter, an oxygen sensor, a total silica measurement device, and a bubble measurement device. 
     
     
         26 . The apparatus of  claim 21 , wherein the liquid supply system comprises a liquid confinement structure configured to at least partly confine the liquid within the space and the measurement device is configured to measure the property of the liquid in a flow path between the liquid confinement structure and a gas content reduction device configured to reduce the gas content of the liquid. 
     
     
         27 . The apparatus of  claim 21 , wherein the measurement device is located downstream in a flow path of the liquid from (i) a demineralizer, or (ii) a distillation unit, or (iii) a de-hydrocarbonating unit, or (iv) a source configured to provide UV radiation to the liquid, or (v) any combination selected from (i)-(iv). 
     
     
         28 . The apparatus of  claim 21 , wherein the measurement device is configured to measure the property of the liquid off-line from the flow of the liquid to the space. 
     
     
         29 . The apparatus of  claim 21 , further comprising a liquid purifier configured to purify the liquid such that it has one or more selected from:
 (a) a content of organic compounds of 5 ppb or less;   (b) a particle content of no more than 2 particles having a dimension of 50 nm or greater per ml of liquid;   (c) a dissolved oxygen concentration of 15 ppb or less; and/or   (d) a silica content of 500 ppt or less.   
     
     
         30 . The apparatus of  claim 21 , further comprising a liquid purifier configured to purify the liquid such that it has an electrical conductivity of from 0.055 microSiemens/cm to 0.5 microsiemens/cm. 
     
     
         31 . A lithographic projection apparatus, comprising:
 a projection system configured to project a radiation beam onto a target portion of a radiation-sensitive substrate;   a liquid supply system configured to at least partly fill a space between the projection system and the substrate with a liquid;   a liquid purifier configured to purify the liquid;   a gas content reduction device configured to reduce the gas content of the liquid; and   a measurement device configured to measure the presence of particles in the liquid.   
     
     
         32 . The apparatus of  claim 31 , wherein the liquid purifier is configured to purify the liquid such that it has a particle content of no more than 2 particles having a dimension of 50 nm or greater per ml of liquid. 
     
     
         33 . The apparatus of  claim 31 , wherein the liquid purifier is configured to purify the liquid such that it has a particle content of no more than 0.5 particles having a dimension of 50 nm or greater per ml of liquid. 
     
     
         34 . The apparatus of  claim 31 , wherein the measurement device is located downstream in a flow path of the liquid from the gas content reduction device. 
     
     
         35 . The apparatus of  claim 31 , wherein the gas content reduction device comprises a membrane configured to be in contact with the liquid to separate gas from the liquid, the membrane not in contact with the space. 
     
     
         36 . The apparatus of  claim 31 , wherein the liquid purifier comprises a distillation unit, or a de-hydrocarbonating unit configured to reduce the hydrocarbon content of the liquid, or a demineralizer, or any combination selected from the foregoing. 
     
     
         37 . The apparatus of  claim 31 , wherein the liquid supply system includes a re-circulation mechanism configured to re-use liquid in the space without purifying the liquid for a re-use. 
     
     
         38 . The apparatus of  claim 31 , wherein the liquid supply system includes a re-circulation mechanism configured to re-use liquid in the space and the liquid is partly or fully purified for a re-use. 
     
     
         39 . A lithographic projection apparatus, comprising;
 a projection system configured to project a radiation beam onto a target portion of a radiation-sensitive substrate;   a liquid supply system configured to at least partly fill a space between the projection system and the substrate with a liquid; and   a particle counter configured to count particles in the liquid.   
     
     
         40 . The apparatus of  claim 39 , further comprising a liquid purifier configured to purify the liquid such that it has a particle content of no more than 2 particles having a dimension of 50 nm or greater per ml of liquid. 
     
     
         41 . The apparatus of  claim 39 , further comprising a liquid purifier configured to purify the liquid such that it has a particle content of no more than 0.5 particles having a dimension of 50 nm or greater per ml of liquid. 
     
     
         42 . A lithographic projection apparatus comprising:
 a projection system configured to project a radiation beam onto a target portion of a radiation-sensitive substrate;   a liquid supply system configured to at least partly fill a space between the projection system and the substrate with a liquid; and   an adding device configured to add ozone, a halogen containing compound, an alcohol, an aldehyde, or a heavy metal, to the liquid.   
     
     
         43 . The lithographic apparatus of  claim 42 , wherein the adding device is configured to add ozone to the liquid. 
     
     
         44 . Immersion liquid for use in a space between a projection system of an immersion lithographic projection apparatus and a substrate to be imaged, the immersion liquid including ozone. 
     
     
         45 . A lithographic projection apparatus comprising:
 a projection system configured to project a radiation beam onto a target portion of a radiation-sensitive substrate;   a liquid supply system configured to at least partly fill a space between the projection system and the substrate with an immersion liquid; and   a degasser configured to separate gas and liquid, the degasser being upstream from the liquid supply system in a flow path of the immersion liquid to degas the immersion liquid before introduction into the space and comprising a membrane configured to contact the immersion liquid to separate gas and liquid of the immersion liquid.