Exposure method and apparatus, method of making exposure apparatus, device and device manufacturing method

Abstract

When a mask is irradiated obliquely with light from a lighting system, the light reflected from the mask is projected onto a wafer through a projection optical system, and the pattern of the mask is transferred to the wafer. If the magnification of the projection optical system changes because of a vertical movement of the mask, a control unit detects the projection position of the mask pattern image on a stage by an aerial image sensor and also detects a mark on the aerial image sensor by a mark detector so as to determine the baseline of the mark detector. Thus, the positional shift of the projection position of the mask pattern image on the wafer due to the change in magnification is corrected to sufficiently restrict or prevent alignment inaccuracy associated with the change in magnification.

What is claimed is:  
     
         1 . An exposure apparatus which transfers a pattern of a mask onto a substrate, comprising: 
 an illumination system including a light source and which irradiates said mask with an illumination light for exposure;    a projection optical system arranged between said mask and said substrate and which projects said illumination light from said mask onto said substrate;    a magnification changing unit which changes a projection magnification of said projection optical system;    a substrate stage which holds said substrate;    a mark detection system including a photoelectric device and which detects a mark located on said substrate stage; and    a correction unit electrically connected to said magnification changing unit and said mark detection system and which corrects a shift of a projection position of a pattern on said mask after a magnification change using a baseline of said mark detection system on transferring said pattern of said mask onto said substrate, said baseline being obtained in consideration of said shift when said magnification change is made by said magnification changing unit.    
     
     
         2 . An exposure apparatus according to  claim 1 , further comprising: 
 at least one reference mark including a specific reference mark provided on said substrate stage; and    wherein: 
 said exposure apparatus further comprises a position detection system including a photoelectric device and which detects a positional relationship between said specific reference mark and a projection position of a pattern image of said mask on said substrate stage; and  
 said correction unit including a control unit electrically connected to said mark detection system and said position detection system and which calculates the baseline which corresponds to said magnification change based on a first result obtained using said position detection system to detect said positional relationship and a second result obtained using said mark detection system to detect one of said specific reference mark on said substrate stage and a different reference mark that has a predetermined positional relationship with the specific reference mark.  
   
     
     
         3 . An exposure apparatus according to  claim 2 , wherein: 
 said mark detection system including a focus detection system; and    said exposure apparatus further comprises an adjustment unit which adjusts a position of said substrate stage in an optical axis direction to position a mark at a focal position of said mark detection system based on a detection result obtained by said focus detection system upon detection of said mark included on said substrate stage using said mark detection system.    
     
     
         4 . An exposure apparatus according to  claim 2 , wherein: 
 said illumination light comprises light in a soft X-ray region, and    said position detection system comprises an aerial image sensor formed on said substrate stage, said aerial image sensor including    a fluorescent material,    a thin film made on a surface of said fluorescent material, said thin film structured of one of a reflecting layer and an absorbing layer of said illumination light, said thin film having an opening which also serves as said specific reference mark, and    a photoelectric conversion device which photoelectrically converts light generated by said fluorescent material, wherein said illumination light reaches said fluorescent material via said opening on conversion.    
     
     
         5 . An exposure apparatus according to  claim 2 , further comprising: 
 a focal position detection system which detects a position of said substrate on said substrate stage in an optical axis direction of said projection optical system; and    a stage control unit electrically connected to said focal position detection system which offsets said focal position detection system which corresponds to a driving amount of said mask in said optical axis direction by said magnification changing unit and which feedback-controls said position of said substrate stage in said optical axis direction based on a detection result obtained by said focal position detection system.    
     
     
         6 . An exposure apparatus according to  claim 1 , further comprising: 
 at least one reference mark including a specific reference mark provided on said substrate stage; and    wherein: 
 said exposure apparatus further comprises a position detection system including a photoelectric device and which detects a positional relationship between said specific reference mark and a projection position of a pattern image of said mask on said substrate stage; and  
 said correction unit includes 
 a memory unit which stores a baseline of said mark detection system, said baseline calculated using a detection result of said position detection system and using a result obtained by detection of one said specific reference mark on said substrate stage and a different reference mark with a predetermined relationship to said specific reference mark, and  
 a calculation unit electrically connected to said memory unit and said magnification changing unit and which calculates a correction to said baseline stored in said memory unit in accordance with said magnification change.  
 
   
     
     
         7 . An exposure apparatus according to  claim 6 , wherein: 
 said illumination light comprises light in a soft X-ray region, and    said position detection system comprises an aerial image sensor provided on said substrate stage, said aerial image sensor including    a fluorescent material,    a thin film made on a surface of said fluorescent material, said thin film formed from one of a reflecting layer and an absorbing layer of said illumination light for exposure, said thin film having an opening which also serves as said specific reference mark, and    a photoelectric conversion device which photoelectrically converts light generated from said fluorescent material, said illumination light for exposure reaches said fluorescent material via said opening on conversion.    
     
     
         8 . An exposure apparatus according to  claim 6 , further comprising: 
 a focal position detection system which detects a position of said substrate on said substrate stage in an optical axis direction of said projection optical system; and    a stage control unit electrically connected to said focal position detection system and which offsets said focal position detection system which corresponds to a driving amount of said mask in said optical axis direction by said magnification changing unit and feedback-controls said position of said substrate stage in said optical axis direction based on a detection result obtained by said focal position detection system.    
     
     
         9 . An exposure apparatus according to  claim 1 , wherein said magnification changing unit comprises a unit which drives said mask in an optical axis direction of said projection optical system.  
     
     
         10 . An exposure apparatus according to  claim 1 , wherein: 
 said projection optical system comprises a reflection optical element, and    said magnification changing unit comprises an optical characteristic changing unit which changes optical characteristics of said projection optical system.    
     
     
         11 . An exposure apparatus according to  claim 10 , wherein said optical characteristic changing unit changes a curvature of said reflection optical element.  
     
     
         12 . An exposure apparatus according to  claim 1 , wherein: 
 said projection optical system comprises a reflection optical element;    said exposure apparatus further comprises a mask stage which holds said mask and a driving unit which is connected to said mask stage and which synchronously moves said mask stage and said substrate stage in a first direction perpendicular to an optical axis direction of said projection optical system; and    said magnification changing unit comprises a unit which changes said magnification of said projection optical system in a second direction perpendicular to said optical axis direction and said first direction by driving said mask in said optical axis direction of said projection optical system via said mask stage.    
     
     
         13 . An exposure apparatus according to  claim 12 , wherein said illumination light comprises light in the vacuum ultraviolet range.  
     
     
         14 . An exposure apparatus according to  claim 12 , wherein: 
 said projection optical system comprises a reflection optical system formed by reflection optical elements; and    said mask comprises a reflection type mask.    
     
     
         15 . An exposure apparatus according to  claim 14 , wherein said illumination light comprises light in the soft X-ray region.  
     
     
         16 . An exposure apparatus according to  claim 1 , wherein: 
 said apparatus further comprises a detection unit which detects a plurality of alignment marks on said substrate using said mark detection system prior to transfer of said pattern of said mask onto said substrate; and    said magnification changing unit changes said magnification based on position detection results of said plurality of alignment marks of said detection unit.    
     
     
         17 . An exposure apparatus according to  claim 1 , wherein said projection optical system is non-telecentric on said mask side.  
     
     
         18 . An exposure apparatus which repeatedly transfers a pattern of a mask onto a substrate, comprising: 
 an illumination system including a light source and which irradiates said mask with an illumination light for exposure;    a projection optical system arranged between said mask and said substrate and which projects said illumination light from said mask onto said substrate;    a substrate stage which holds said substrate;    a mark detection system including a photoelectric device and which detects a mark located on said substrate stage;    a judgement unit which judges whether it is necessary to update a baseline of said mark detection system based on a predetermined judgement condition;    a baseline updating unit electrically connected to the judgement unit and which calculates a new baseline when a result of said judgement unit is affirmative; and    a stage control unit electrically connected to the judgement unit and the baseline updating unit and which controls a position of said substrate stage using, when said result of said judgement unit is negative, said baseline of said mark detection system obtained prior to transfer of said pattern of said mask onto said substrate, and, when said result of said judgement unit is affirmative, said new baseline to transfer said pattern of said mask onto said substrate.    
     
     
         19 . An exposure apparatus according to  claim 18 , wherein said judgement unit determines whether it is necessary to update said baseline of said mark detection system based on whether said substrate comprises a first substrate of a lot.  
     
     
         20 . An exposure apparatus according to  claim 18 , wherein said judgement unit determines whether it is necessary to update said baseline based at least in part on a magnification change of said projection optical system.  
     
     
         21 . An exposure apparatus according to  claim 20 , wherein said judgement unit determines whether it is necessary to update said baseline based at least in part on an occurrence of said magnification change.  
     
     
         22 . An exposure apparatus according to  claim 20 , wherein said judgement unit decides that update of said baseline is necessary based on said magnification change being greater than an acceptable amount.  
     
     
         23 . An exposure method for transferring a pattern formed on a mask onto a substrate through a projection optical system while synchronously moving said mask and said substrate, comprising steps of: 
 irradiating a pattern surface of said mask with said illumination light for exposure at a predetermined incident angle; and    setting a desired projection magnification of said projection optical system in a direction perpendicular to said synchronously moving direction, and    controlling a position of said substrate using a baseline of a mark detection system, said baseline obtained by consideration of a shift of a projection that occurs when said desired projection magnification is set, wherein said baseline being used to detect an alignment mark on said substrate.    
     
     
         24 . An exposure method according to  claim 23 , further comprising a step of detecting said baseline corresponding to said desired projection magnification after said desired projection magnification is set.  
     
     
         25 . An exposure method according to  claim 23 , further comprising a step of calculating said baseline corresponding to said desired projection based at least in part on said projection magnification.  
     
     
         26 . An exposure method according to  claim 23 , wherein said mask comprises a reflection type mask and said projection optical system comprises a reflection optical system.  
     
     
         27 . An exposure method for transferring a pattern formed on a reflection mask onto a substrate through a projection optical system which is configured only of a plurality of reflection optical elements, comprising steps of: 
 moving synchronously said reflection mask and said substrate;    adjusting optical characteristics of said projection optical system prior to transfer; and    adjusting a positional relationship between a projection area of a pattern image and said substrate during said synchronous movement so as to compensate a shift of said projection area in an image field of said projection optical system.    
     
     
         28 . An exposure method according to  claim 27 , further comprising a step of: 
 determining an exposure position using positional information obtained by detection of a mark on said substrate using a mark detecting system,    wherein:    said step of adjusting said positional relationship between said projection area and said substrate is performed by synchronous movement of said substrate with respect to said reflection type mask;    said substrate being controlled based at least in part on said predetermined exposure position information and a baseline of said mark detection system after adjustment of said optical characteristics.    
     
     
         29 . An exposure method according to  claim 28 , wherein said baseline comprises: 
 a measured baseline of said mark detection system, said measured baseline being measured after adjustment of said optical characteristics.    
     
     
         30 . An exposure method according to  claim 27 , wherein: 
 said step of adjusting optical characteristics comprises a step of adjusting a projection magnification of said pattern image in a direction perpendicular to said synchronous moving direction of said substrate,    said step of adjusting a projection magnification comprises a step of moving said reflection mask in a direction along an optical axis of said projection optical system based on at least one of substrate positional information obtained by detection of a plurality of marks on said substrate using said mark detection system and mask positional information obtained by detection of a plurality of marks on said reflection mask using the projection optical system.    
     
     
         31 . An exposure method according to  claim 27 , further comprising a step of irradiating said reflection mask with an illumination light for exposure, said illumination light having a principal ray that tilts with respect to a pattern surface of said mask, 
 wherein: 
 said illumination light being one of light in a soft X-ray region and a vacuum ultraviolet light; and  
 said projection optical system being non-telecentric on said mask side.  
   
     
     
         32 . An exposure method which repeatedly transfers a pattern of a mask onto a substrate through a projection optical system, comprising steps of: 
 monitoring a change in a physical quantity that changes a baseline of a mark detection system configured to detect a mark on the substrate;    judging whether it is necessary to update said baseline of said mark detection system based at least in part on whether said physical quantity exceeds a predetermined value;    obtaining, when a judgement result is affirmative, a new baseline;    controlling, when a judgement result is affirmative, a position of said substrate using said new baseline;    controlling, when the judgement result is negative, said position of said substrate using said baseline of said mark detection system; and    performing exposure.    
     
     
         33 . An exposure method according to  claim 32 , wherein said change in said physical quantity comprises a change in a size of said mask due to thermal expansion.  
     
     
         34 . An exposure method according to  claim 33 , wherein said change in said size of said mask due to thermal expansion is estimated based on a measurement of a temperature distribution of said mask.  
     
     
         35 . An exposure method according to  claim 32 , wherein said change in said physical quantity comprises a change in an image forming characteristic of said projection optical system.  
     
     
         36 . An exposure method according to  claim 32 , wherein: 
 said projection optical system comprises an optic system including a mirror; and    said change in said physical quantity comprises a deformation amount of said mirror.    
     
     
         37 . An exposure method which repeatedly transfers a pattern of a mask onto a substrate through a projection optical system, said method comprising steps of: 
 judging whether it is necessary to update a baseline of a mark detection system based on a predetermined judgement condition, said mark detection system detecting a mark located on a substrate stage;    controlling a position of said substrate stage using, when a result of said judgement is negative, said baseline of said mark detection system, said baseline obtained prior to transfer of said pattern of said mask onto said substrate; and    controlling a position of said substrate stage using, when said result of said judgement is affirmative, a new baseline to transfer said pattern of said mask onto said substrate.    
     
     
         38 . An exposure method according to  claim 37 , wherein said step of judging whether it is necessary to update said baseline of said mark detection system is based at least in part on whether said substrate is a first substrate of a lot.  
     
     
         39 . An exposure method according to  claim 37 , wherein said step of judging whether it is necessary to update said baseline is based at least in part on a magnification change of said projection optical system.  
     
     
         40 . An exposure method according to  claim 39  wherein said step of judging whether it is necessary to update said baseline is based at least in part on whether said magnification change has occurred.  
     
     
         41 . An exposure method according to  claim 39 , further comprising a step of updating said baseline after said judgement when said magnification change has been performed and an amount of said change is greater than an acceptable amount.  
     
     
         42 . A method of making an exposure apparatus which transfers a pattern of a mask onto a substrate, comprising steps of: 
 irradiating said mask with an illumination light for exposure using an illumination system which has a light source;    projecting said illumination light from said mask onto said substrate using a projection optical system arranged between said mask and said substrate;    changing a projection magnification of said projection optical system using a magnification changing unit;    holding said substrate using a substrate stage;    detecting a mark located on said substrate stage using a mark detection system which has a photoelectric device; and    correcting a shift of a projection position of said pattern of said mask after a magnification change using a baseline of said mark detection system on transferring said pattern of said mask onto said substrate using a correction unit,    wherein: 
 said correction unit electrically connected to said magnification changing unit and said mark detection system, and  
 said baseline is obtained through consideration of said shift at said magnification change made by said magnification changing unit.  
   
     
     
         43 . A method of making an exposure apparatus according to  claim 42 , further comprising steps of: 
 holding said mask using a mask stage; and    moving synchronously said mask stage and said substrate stage in a first direction perpendicular to an optical axis direction of said projection optical system using a driving unit.    
     
     
         44 . A method of making an exposure apparatus which repeatedly transfers a pattern of a mask onto a substrate, comprising steps of: 
 irradiating said mask with an illumination light for exposure using an illumination system which has a light source;    projecting said illumination light for exposure outgoing from said mask onto said substrate using a projection optical system arranged between said mask and said substrate;    holding said substrate using a substrate stage;    detecting a mark located on said substrate stage using a mark detection system including a photoelectric device;    judging using a judgement unit whether it is necessary to update a baseline of said mark detection system based on a predetermined judgement condition;    calculating a new baseline, when a result of said judgement unit is affirmative, using a baseline updating unit electrically connected to said judgement unit; and    controlling a position of said substrate stage using a stage control unit electrically connected to said judgement unit and said baseline updating unit, said step of controlling said position including;    employing, when said result of said judgement unit is negative, said baseline of said mark detection system, said baseline obtained prior to transfer of said pattern of said mask onto said substrate; and    employing, when said result of said judgement unit is affirmative, said new baseline.    
     
     
         45 . A device manufacturing method including a lithography process, wherein said lithography process comprises a step of using said exposure apparatus in  claim 1 .  
     
     
         46 . A device manufacturing method including a lithography process, wherein said lithography process comprises a step of using said exposure apparatus in  claim 18 .  
     
     
         47 . A device manufacturing method including a lithography process, wherein said lithography process comprises a step of exposing a substrate using said exposure method in  claim 23 .  
     
     
         48 . A device manufacturing method including a lithography process, wherein said lithography process comprises a step of exposing a substrate using said exposure method in  claim 27 .  
     
     
         49 . A device manufacturing method including a lithography process, wherein said lithography process comprises a step of exposing a substrate using said exposure method in  claim 32 .  
     
     
         50 . A device manufacturing method including a lithography process, wherein said lithography process comprises a step of exposing a substrate using said exposure method in  claim 37 .  
     
     
         51 . A device manufactured using said exposure method in  claim 23 .  
     
     
         52 . A device manufactured using said exposure method in  claim 27 .  
     
     
         53 . A device manufactured using said exposure method in  claim 32 .  
     
     
         54 . A device manufactured using said exposure method in  claim 37 .  
     
     
         55 . An exposure method according to  claim 28 , wherein said baseline comprises: 
 a calculated baseline of said mark detection system, wherein said calculated baseline is calculated from the adjusted optical characteristics.    
     
     
         56 . A device, comprising: 
 means for irradiating a mask with an illumination light;    means for projecting said illumination light from said mask onto a substrate, said means for projecting arranged between said mask and said substrate;    means for changing a projection magnification of said means for projecting;    means for holding said substrate;    means for detecting a position mark, said means for detecting including a photoelectric device; and    means for correcting a shift of a projection position after a magnification change using a baseline obtained by said means for detecting when transferring said pattern of said mask onto said substrate, said means for correcting electrically connected to said means for changing said projection magnification and said means for detecting said position mark.