Lithographic apparatus, device manufacturing methods, mask and method of characterizing a mask and/or pellicle

Abstract

A thick pellicle is allowed to have a non-flat shape and its shape is characterized to calculate corrections to be applied in exposures to compensate for the optical effects of the pellicle. The pellicle may be mounted so as to adopt a one-dimensional shape under the influence of gravity to make the compensation easier.

1 . A lithographic projection apparatus comprising:
 an illumination system configured to supply a beam of radiation;   a support structure configured to support a patterning device, the patterning device serving to pattern the beam of radiation according to a desired pattern to form a patterned beam of radiation;   a substrate table configured to hold a substrate;   a projection system configured to project the patterned beam of radiation onto a target portion of the substrate;   a layer, substantially transparent to the beam of radiation but having a refractive index different than the surrounding medium, in the optical path of the beam of radiation between the patterning device and the substrate;   a storage device adapted to store information relating to the physical and/or optical characteristics of the layer; and   a controller adapted to control at least one of the projection system, the illumination system, the substrate table and the support structure in response to information stored in the storage device to compensate for imaging aberrations caused by the layer other than a displacement of an apparent patterning device position along an optical axis of the apparatus.   
   
   
       2 . An apparatus according to  claim 1 , wherein the patterning device is a mask, the support structure is a mask table and the layer is a pellicle mounted in spaced relation thereto. 
   
   
       3 . An apparatus according to  claim 2 , further comprising an interface configured to receive the information in conjunction with the loading of a mask into the apparatus. 
   
   
       4 . An apparatus according to  claim 2 , further comprising a sensor configured to measure one or more characteristics selected for the group consisting of physical and optical characteristics of a pellicle fixed to the mask supported by the mask table and wherein the controller is further adapted to control at least one of the sensor and the mask table to characterize the pellicle to generate the information to be stored in the storage device. 
   
   
       5 . An apparatus according to  claim 4 , wherein the sensor is a transmission image sensor. 
   
   
       6 . An apparatus according to  claim 4 , wherein the sensor is a white light interferometer. 
   
   
       7 . An apparatus according to  claim 2 , further comprising a spoiler attached to one of the mask stage, the mask, the pellicle and a frame, mounting the pellicle to the mask, wherein the spoiler is shaped to reduce Bernoulli effects that would otherwise distort the pellicle when the mask moves during an exposure. 
   
   
       8 . An apparatus according to  claim 2 , further comprising a purge gas supply system adapted to supply purge gas to a vicinity of the mask such that the flow of purge gas is parallel to and in the same sense as movement of the mask during a scanned exposure. 
   
   
       9 . An apparatus according to  claim 2 , wherein the storage device is configured to store information relating to the dependency of image aberration on the velocity of movement of the mask during a scanned exposure. 
   
   
       10 . An apparatus according to  claim 1  wherein the patterning device is a programmable patterning device and the layer is a window in a box containing the programmable patterning device. 
   
   
       11 . An apparatus according to  claim 1 , wherein the layer is a liquid film between the projection system and the substrate. 
   
   
       12 . A method of attaching a pellicle to a mask, comprising:
 measuring the shape of the pellicle;   determining an optimum position of the pellicle relative to the mask; and   attaching the pellicle to the mask substantially at the optimum position.   
   
   
       13 . The method according to  claim 12 , wherein the shape of the pellicle is measured before attaching the pellicle to the mask, or during determining an optimum position of the pellicle relative to the mask, or both before attaching the pellicle to the mask and during determining an optimum position of the pellicle relative to the mask. 
   
   
       14 . The method according to  claim 12 , wherein the measuring includes aligning an alignment mark on the pellicle with an alignment mark on the mask. 
   
   
       15 . A method comprising:
 loading a mask into a lithographic projection apparatus;   illuminating the mask with exposure radiation;   projecting an aerial image of the illuminated mask; and   measuring a plane of best focus of images of a plurality of alignment marks using an image sensor;   wherein the plurality of alignment marks are spaced apart in a scanning direction or a direction of an illumination field of the lithographic apparatus.   
   
   
       16 . A method according to  claim 15 , wherein the mask further has a pellicle fixed in spaced rotation thereto. 
   
   
       17 . A device manufacturing method comprising:
 patterning a beam of radiation with a pattern in its cross-section using a mask having a pellicle or fixed relation thereto;   projecting the patterned beam of radiation onto a target portion of a layer of radiation-sensitive material on a substrate; and   prior to an exposure, characterizing a shape of the mask by:
 measuring a shape of the pellicle; 
 determining an optimum position of the pellicle relative to the mask; 
 attaching the pellicle to the mask substantially at the optimum position; and 
 correcting exposure parameters based on the characterizing. 
   
   
   
       18 . The method according to  claim 17 , wherein the shape of the pellicle is measured before attaching the pellicle to the mask, or during determining an optimum position of the pellicle relative to the mask, or both before attaching the pellicle to the mask and during determining an optimum position of the pellicle relative to the mask. 
   
   
       19 . The method according to  claim 17 , wherein the measuring includes aligning an alignment mark on the pellicle with an alignment mark on the mask. 
   
   
       20 . A device manufacturing method comprising:
 patterning a beam of radiation with a pattern in its cross-section using a mask having a pellicle or fixed relation thereto;   projecting the patterned beam of radiation onto a target portion of a layer of radiation-sensitive material on a substrate; and   prior to an exposure, characterizing a shape of the mask by:
 measuring a shape of the pellicle; 
 determining an optimum position of the pellicle relative to the mask; 
 attaching the pellicle to the mask substantially at the optimum position; and 
 correcting parameters pertaining to at least one of a radiation system, a projection system, a position of the mask and a position of the substrate to compensate for aberrations other than a shift in apparent position of the mask in the direction of the optical axis of the projection system caused by the pellicle, the corrections having been determined from information relating to physical and/or optical characteristics of the pellicle. 
   
   
   
       21 . The method according to  claim 20 , wherein the shape of the pellicle is measured before attaching the pellicle to the mask, or during determining an optimum position of the pellicle relative to the mask, or both before attaching the pellicle to the mask and during determining an optimum position of the pellicle relative to the mask. 
   
   
       22 . The method according to  claim 20 , wherein the measuring includes aligning an alignment mark on the pellicle with an alignment mark on the mask.