Exposure apparatus and method

Abstract

An exposure apparatus for use in a photolithographic process, in which an illumination beam is attenuated, split by a beam splitter, and received by an integrator sensor which produces an illuminance detection signal. The illuminance detection signal and a desired illuminance signal from an exposure control system are supplied to a power supply system which powers a mercury-vapor lamp with a predetermined resolution such that the two signals may be equal to each other. The exposure control system determines any error in the illuminance on the wafer from the illuminance detection signal, and supplies a stage control system with correction values for the velocities at which a reticle stage and a wafer stage is to be moved for scanning. The light source may be powered with a constant input power, and an adjustment rod for adjusting the quantity of light of the illumination beam may be disposed in a light travelling region through which the light of the illumination beam from the light source travels. The adjustment rod serves to shade a portion of the light travelling region. The illuminance of the illumination beam is continuously monitored by the integrator sensor, and the quantity of light passing through the light travelling region is adjusted by controlling the angle of rotation of the adjustment rod such that the actual illuminance may be equal to the desired illuminance. Two mercy-vapor lamps may be used, in which most of the illumination beam from one mercury-vapor lamp and only a small portion of the illumination beam from the other mercury-vapor lamp are combined, and the resulting illumination beam is attenuated, split by the beam splitter and received by the integrator sensor. One mercury-vapor lamp is powered by a constant input power, while the other mercury-vapor lamp is powered in a constant illuminance mode such that the illuminance detection signal from the integrator sensor and the desired illuminance signal from the exposure control system may be equal to each other.

What is claimed is:  
     
         1 . An exposure apparatus for transferring a pattern on a mask onto a photosensitized substrate by exposure, comprising: 
 a light source for generating an illumination beam for exposure;    an illumination optical system for illuminating a predetermined area on said mask with said illumination beam, said predetermined area having said pattern formed thereon;    a mask stage for moving said mask, for scanning, in a predetermined direction with respect to said predetermined area;    a substrate stage for moving said substrate, for scanning, in synchronism with the movement of said mask and in a direction corresponding to said predetermined direction;    an attenuator disposed between said light source and said photosensitized substrate for attenuating said illumination beam with variable attenuation rate;    a sensing system for measuring the exposure energy of said illumination beam;    a controller for controlling the output power of said light source and the attenuation of said illumination beam established by said attenuator such that the exposure energy measured by said sensing system may approach a predetermined desired value; and    a stage controller for controlling the velocities at which said mask stage and said substrate stage are moved for scanning, in accordance with the difference between the exposure energy measured by said sensing system and said predetermined desired value.    
     
     
         2 . An exposure apparatus for transferring a pattern on a mask onto a photosensitized substrate by exposure, comprising: 
 a light source for generating an illumination beam for exposure;    an illumination optical system for illuminating a predetermined area on said mask with said illumination beam, said predetermined area having said pattern formed thereon;    a sensing system for measuring the exposure energy of said illumination beam; and    a fine adjustment device disposed between said light source and said mask for adjusting the quantity of light passing a portion of a region through which the light of said illumination beam travels, in accordance with the exposure energy measured by said sensing system.    
     
     
         3 . An exposure apparatus as claimed in  claim 2 , wherein: 
 said fine adjustment device comprises a shading element which is rotated within or projected into and retracted from said region through which the light of said illumination beam travels.    
     
     
         4 . An exposure apparatus as claimed in  claim 3 , wherein: 
 said shading element is of such a size that may provide a shading area smaller than 10% of the cross-sectional area of said region through which the light of said illumination beam travels.    
     
     
         5 . An exposure apparatus for transferring a pattern on a mask onto a photosensitized substrate by exposure, comprising: 
 a light source for generating an illumination beam for exposure;    an illumination optical system for illuminating said mask with said illumination beam, said mask having said pattern formed thereon;    a first optical integrator;    a second optical integrator receiving said illumination beam from said first optical integrator; and    a quantity-of-light-adjustment element for continuously adjusting the quantity of light of said illumination beam travelling from said first optical integrator to said second optical integrator.    
     
     
         6 . An exposure apparatus for transferring a pattern on a mask onto a photosensitized substrate by exposure, comprising: 
 a light source for generating an illumination beam for exposure;    an illumination optical system for illuminating said mask with said illumination beam, said mask having said pattern formed thereon;    a first optical integrator;    a second optical integrator receiving said illumination beam from said first optical integrator;    a first adjustment mechanism for adjusting at least one of the extent and the shape of a region on an exit surface of said second optical integrator through which region said illumination beam passes;    a second adjustment mechanism, operable in relation to said first adjustment mechanism, for adjusting the extent of an illumination field on an entrance surface of said second optical integrator; and    said second optical integrator having the first group of lens elements defining the entrance side of said second optical integrator and the second group of lens elements defining the exit side of said second optical integrator, each of said first group of lens elements and each of said second group of lens elements having different shapes from each other.    
     
     
         7 . An exposure apparatus of the scanning exposure type for transferring a pattern on a mask onto a photosensitized substrate by exposure, in which said mask is moved for scanning in a predetermined direction with respect to a predetermined area, and in which said substrate is moved for scanning in synchronism with the movement of said mask and in a direction corresponding to said predetermine direction, said exposure apparatus comprising: 
 an illumination optical system for illuminating a predetermined area on said mask with an illumination beam for exposure, said predetermined area having said pattern formed thereon;    said illumination optical system comprising:    a plurality of light sources for generating respective light beams for exposure; and    a light beam combining optical system for combining the light beams from said plurality of light sources into said illumination beam; and    a quantity-of-light-control device for controlling the quantity of light of the light beam from at least one of said plurality of light sources in accordance with the quantity of light of said illumination beam combined by said light beam combining optical system.    
     
     
         8 . An exposure apparatus as claimed in  claim 7 , wherein: 
 said plurality of light sources comprises: 
 a first light source; and  
 a second light source whose output power level is lower than that of said first light source; and  
 said quantity-of-light-control device is so arranged as to control the quantity of light of the light beam from said second light source.  
   
     
     
         9 . An exposure apparatus as claimed in  claim 7 , further comprising: 
 a sensing system for continuously measuring the exposure energy of said illumination beam combined by said light beam combining optical system; and    said quantity-of-light-control device being so arranged as to control the quantity of light of at least one of the light beams from said plurality of light sources such that the exposure energy measured by said sensing system may be maintained at a predetermined desired value.    
     
     
         10 . An exposure apparatus for transferring a pattern on a mask onto a photosensitized substrate by exposure, in which said mask is moved for scanning in a predetermined direction with respect to a predetermined area, and in which said substrate is moved for scanning in synchronism with the movement of said mask and in a direction corresponding to said predetermine direction, said exposure apparatus comprising: 
 an illumination optical system for illuminating a predetermined area on said mask with an illumination beam for exposure, said predetermined area having said pattern formed thereon;    said illumination optical system comprising: 
 a light source for generating a light beam for exposure;  
 a light beam splitting optical system for splitting said light beam from said light source into a plurality of light beams;  
 a light beam combining optical system for combining said plurality of light beams into said illumination beam; and  
 an attenuator for continuously attenuating the quantity of light of at least one of said plurality of light beams within a predetermined attenuation range and at a place between said light beam splitting optical system and said light beam combining optical system; and  
   said attenuator being so arranged as to control the attenuation in accordance with the quantity of light of said illumination beam combined by said light beam combining optical system.    
     
     
         11 . An exposure apparatus for transferring a pattern on a mask onto a photosensitized substrate by exposure, in which said mask is moved for scanning in a predetermined direction with respect to a predetermined area, and in which said substrate is moved for scanning in synchronism with the movement of said mask and in a direction corresponding to said predetermine direction, said exposure apparatus comprising: 
 a light source for generating an illumination beam for exposure;    an illumination optical system for illuminating a predetermined area on said mask with said illumination beam, said predetermined area having said pattern formed thereon;    a sensing system for continuously measuring the exposure energy of said illumination beam and producing an output signal corresponding thereto;    an illumination fluctuation detection system for detecting any fluctuations in the illuminance of said illumination beam generated from said light source;    an illuminance control device for controlling the output power of said light source in accordance with said output signal of said sensing system; and    said illuminance control device being so arranged as to induce variations in the output power of said light source when any fluctuations in the illuminance of said illumination beam are detected by said illuminance fluctuation detection system, said variations induced by said illuminance control device having frequencies higher than a predetermined frequency.    
     
     
         12 . An exposure apparatus as claimed in  claim 11 , wherein: 
 said illuminance fluctuation detection system comprises: 
 a photodetector for detecting the quantity of light of said illumination beam and producing an output signal corresponding thereto; and  
 a comparator for detecting the difference between said output signal of said photodetector and a signal corresponding to electric power supplied to said light source.  
   
     
     
         13 . An exposure apparatus as claimed in  claim 11 , wherein: 
 said illuminance fluctuation detection system comprises: 
 a photodetector for detecting the quantity of light of said illumination beam and producing an output signal corresponding thereto; and  
 a low-pass filter for extracting any low frequency components of said output signal of said photodetector.  
   
     
     
         14 . An exposure apparatus as claimed in  claim 11 , wherein: 
 said illuminance control device comprises: 
 a variable gain device for amplifying any variations in said output signal of said sensing system with a certain gain so as to control the output power of said light source; and  
 the gain of said variable gain device being controlled in accordance with the fluctuations in illuminance detected by said illuminance fluctuation detection system.  
   
     
     
         15 . An exposure apparatus as claimed in  claim 11 , wherein: 
 said light source comprises an electric-discharge lamp; and    the fluctuations in the illuminance of said illumination beam is caused by the fluctuations in the discharge of said electric-discharge lamp.    
     
     
         16 . An exposure apparatus for transferring a pattern on a mask onto a photosensitized substrate by exposure, in which said mask and said substrate are, relatively to each other, moved for scanning in synchronism with each other while an image of a portion of said pattern is projected onto said substrate, said exposure apparatus comprising: 
 a photodetector having a slit-like photosensitive area which is elongate in the scanning direction of said substrate and has a length in the scanning direction smaller than the width of an exposure area in the scanning direction, said exposure area being defined for said pattern formed on said mask;    a relative movement mechanism for generating relative movement between said photodetector and said exposure area in the direction perpendicular to the scanning direction of said substrate; and    a signal processing system for receiving an electrical signal obtained by the photoelectric conversion and produced from said photodetector during the time interval in which said relative movement mechanism generates relative movement between said photodetector and said exposure area.    
     
     
         17 . An exposure apparatus as claimed in  claim 16 , wherein: 
 the length of said slit-like photosensitive area of said photodetector in the scanning direction of said substrate is longer than the width of vignetting periphery of said exposure area.    
     
     
         18 . A method of transferring a pattern on a mask onto a photosensitized substrate by exposure while scanning said mask and said substrate, comprising the steps of: 
 preparing a light source for generating an illumination beam for exposure;    illuminating a predetermined area on said mask with said illumination beam, said predetermined area having said pattern formed thereon;    moving said mask, for scanning, in a predetermined direction with respect to said predetermined area;    moving said substrate, for scanning, in synchronism with the movement of said mask and in a direction corresponding to said predetermined direction;    attenuating said illumination beam with variable attenuation rate;    measuring the exposure energy of said illumination beam on a continuous measurement basis;    controlling the output power of said light source and the attenuation of said illumination beam attenuator such that the measured exposure energy may approach a predetermined desired value; and    controlling the velocities at which said mask and said substrate are moved for scanning, in accordance with the difference between the measured exposure energy and said predetermined desired value.    
     
     
         19 . A method of transferring a pattern on a mask onto a photosensitized substrate by exposure, comprising the steps of: 
 preparing a light source for generating an illumination beam for exposure;    illuminating a predetermined area on said mask with said illumination beam, said predetermined area having said pattern formed thereon;    measuring the exposure energy of said illumination beam; and    adjusting the quantity of light passing a portion of a region through which the light of said illumination beam travels, in accordance with the measured exposure energy.    
     
     
         20 . A method of transferring a pattern on a mask onto a substrate by exposure, comprising the steps of: 
 preparing a first optical integrator;    preparing a second optical integrator;    adjusting a quantity of light of an illumination beam from said first optical integrator on a continuous adjustment basis and then directing said illumination beam to said second optical integrator; and    illuminating said mask with said illumination beam from said second optical integrator.    
     
     
         21 . A method of transferring a pattern on a mask onto a substrate by exposure, comprising the steps of: 
 preparing a first optical integrator;    preparing a second optical integrator receiving an illumination beam from said first optical integrator, a shape of lens elements defining the entrance side of said second optical integrator being different from that of lens elements defining the exit side of said second optical integrator;    adjusting at least one of the extent and the shape of a region on an exit surface of said second optical integrator through which region said illumination beam passes;    adjusting the extent of an illumination field on an entrance surface of said second optical integrator depending on at least one of the extent and the shape of said region.    
     
     
         22 . A method of serially transferring a pattern on a mask onto a photosensitized substrate by exposure, in which said mask is moved for scanning in a predetermined direction with respect to a predetermined area, and in which said substrate is moved for scanning in synchronism with the movement of said mask and in a direction corresponding to said predetermine direction, said method comprising the stops of: 
 illuminating a predetermined area on said mask with an illumination beams for exposure generated from a plurality of light sources, said predetermined area having said pattern formed thereon;    combining the light beams from said plurality of light sources into said illumination beam; and    controlling the quantity of light of the light beam from at least one of said plurality of light sources in accordance with the quantity of light of said illumination beam combined.    
     
     
         23 . A method of serially transferring a pattern on a mask onto a photosensitized substrate by exposure, in which said mask is moved for scanning in a predetermined direction with respect to a predetermined area, and in which said substrate is moved for scanning in synchronism with the movement of said mask and in a direction corresponding to said predetermine direction, said method comprising the steps of: 
 illuminating a predetermined area on said mask with an illumination beam for exposure, said predetermined area having said pattern formed thereon;    splitting a light beam for exposure into a plurality of light beams;    combining said plurality of light beams into said illumination beam;    attenuating the quantity of light of at least one of said plurality of light beams within a predetermined attenuation range between said light beam splitting step and said light beam combining step; and    controlling the attenuation to be established in said attenuating step, in accordance with the quantity of light of said illumination beam combined.    
     
     
         24 . A method of transferring a pattern on a mask onto a photosensitized substrate by exposure, in which said mask is moved for scanning in a predetermined direction with respect to a predetermined area, and in which said substrate is moved for scanning in synchronism with the movement of said mask and in a direction corresponding to said predetermine direction, said method comprising the steps of: 
 providing a light source for generating an illumination beam for exposure;    illuminating a predetermined area on said mask with said illumination beam, said predetermined area having said pattern formed thereon;    measuring the exposure energy of said illumination beam on a continuous measurement basis;    detecting any fluctuations in the illuminance of said illumination beam generated from said light source;    controlling the output power of said light source in accordance with the measured exposure energy of said illumination beam; and    inducing variations in the output power of said light source when any fluctuations in the illuminance of said illumination beam are detected, the induced variations having frequencies higher than a predetermined frequency.    
     
     
         25 . A method of transferring a pattern on a mask onto a photosensitized substrate by exposure, in which said mask and said substrate are, relatively to each other, moved for scanning in synchronism with each other while an image of a portion of said pattern is projected onto said substrate, said method comprising the steps of: 
 providing a photodetector having a slit-like photosensitive area which is elongate in the scanning direction of said substrate and has a length in the scanning direction smaller than the width of an exposure area in the scanning direction, said exposure area being defined for said pattern formed on said mask;    generating relative movement between said photodetector and said exposure area in the direction perpendicular to the scanning direction of said substrate; and    receiving an electrical signal obtained by the photoelectric conversion and produced from said photodetector during the time interval in which relative movement between said photodetector and said exposure area is generated.