Lithographic apparatus and device manufacturing method using dose control

Abstract

A system and method are used to manufacture a device using at least one exposure step. Each exposure step projects a patterned beam of radiation onto a substrate. The patterned beam includes a plurality of pixels. Each pixel delivers a radiation dose no greater than a predetermined normal maximum dose to the target portion in the exposure step and/or at least one selected pixel delivers an increased radiation dose, greater than the normal maximum dose. The increased dose may be delivered to compensate for the effect of a defective element at a known position in the array on a pixel adjacent a selected pixel or compensate for underexposure of the target portion at the location of a selected pixel resulting from exposure of that location to a pixel affected by a known defective element in another exposure step.

1 . A device manufacturing method, comprising: 
 (a) patterning a beam of radiation with a patterning device to form a plurality of pixels;    (b) projecting the patterned beam onto a target portion of a substrate;    (c) controlling the patterning device, such that each pixel in the plurality of pixels delivers a first radiation dose to the target portion that is below or equal to a first value; and    (d) controlling the patterning device, such that at least one selected pixel in the plurality of pixels delivers a second radiation dose to the target that is greater than the first value to compensate at least partially for: 
 (1) an effect of a defective area in the patterning device on a pixel in the plurality of pixels adjacent the selected pixel, or  
 (2) an underexposure of the target portion at a location corresponding to the selected pixel resulting from exposure of the location to a pixel in the plurality of pixels affected by a known defective area of the patterning device.  
   
   
   
       2 . The method of  claim 1 , wherein step (c) comprises using a value for the second radiation dose that is a factor of about 1.1 to 2.0 of the first value.  
   
   
       3 . The method of  claim 1 , further comprising: 
 delivering a dosage pattern onto the substrate, the dosage pattern comprising, 
 white regions onto which a radiation dosage at least equal to a threshold value is delivered, and  
 black regions onto which a radiation dosage less than the threshold value is delivered,  
   wherein step (c) comprises controlling the patterning device such that each pixel in the plurality of pixels projected onto one of the white regions delivers a radiation dose no greater than the threshold value; and    wherein step (d) comprises controlling the patterning device such that the selected pixel is projected onto a white region and delivers an increased radiation dose to the white region to compensate at least partially for at least one of: 
 an effect of a defective area of the patterning device on a pixel adjacent the selected pixel on the same white region, and  
 an underexposure of the white region at the location of the selected pixel resulting from exposure of the location to a pixel affected by a defective area in the patterning device in another exposure step.  
   
   
   
       4 . The method of  claim 3 , wherein: 
 the substrate comprises a layer of radiation sensitive material having an activation threshold;    the threshold value is substantially equal to the activation threshold; and    the target surface is a surface of the layer.    
   
   
       5 . The method of  claim 1 , further comprising: 
 performing steps (c) and (d) first and second times to deliver a radiation dosage pattern to a target area of the substrate, wherein, 
 during performing of steps (c) and (d) the first time, the target area is exposed to a first plurality of the pixels corresponding to a first portion of the patterning device, and  
 during performing of steps (c) and (d) the second time, the target area is exposed to a second plurality of the pixels corresponding to a second, different portion of the patterning device.  
   
   
   
       6 . The method of  claim 5 , further comprising: 
 controlling the first portion of the patterning device such that the first plurality of pixels includes at least one selected pixel arranged to deliver an increased radiation dose to compensate at least partially for an underexposure effect of a defective element of the first or second portions of the patterning device.    
   
   
       7 . The method of  claim 5 , further comprising: 
 controlling the second portion of the patterning device such that the second plurality of pixels includes at least one selected pixel arranged to deliver an increased radiation dose to compensate at least partially for an underexposure effect of a defective element of the first or second portions of the patterning device.    
   
   
       8 . The method of  claim 1 , wherein each pixel corresponds to an area of the patterning device.  
   
   
       9 . The method of  claim 1 , wherein step (d) comprises controlling at least one area immediately adjacent the defective area, such that at least one corresponding pixel, immediately adjacent the pixel corresponding to the defective area, delivers an increased radiation dose to compensate at least partially for the effect of the defective area.  
   
   
       10 . The method of  claim 1 , further comprising: 
 controlling each non-defective area to selectively adopt one of at least three states, the states comprising, 
 a nominal black state, in which the area interacts with the beam so as to make a minimum contribution to the radiation dose delivered by a corresponding pixel;  
 at least one nominal grey state, in which the area interacts with the beam so as to make an increased contribution to the radiation dose delivered by the corresponding pixel; and  
 at least one nominal white state, in which the area interacts with the beam so as to make a contribution to the radiation dose delivered to the corresponding pixel greater than that in any grey state,  
   wherein step (c) comprises controlling each area to adopt one of the black or grey states,    wherein step (d) comprises controlling at least one selected area to adopt a white state.    
   
   
       11 . The method of  claim 1 , further comprising performing an exposure step using steps (c) and (d).  
   
   
       12 . A lithographic apparatus comprising: 
 an illumination system configured to process a beam of radiation;    a patterning device configured to pattern the beam;    a projection system configured to project the patterned beam onto a target portion of a substrate, the patterned beam comprising a plurality of pixels, each pixel delivering a respective radiation dose to the target portion; and    a controller configured to control at least one area of the patterning device to selectively adopt one of at least three states, the states comprising: 
 a nominal black state, in which the at least one area interacts with the beam to make a minimum contribution to the radiation dose delivered by a corresponding pixel in the plurality of pixels;  
 at least one nominal grey state, in which the at least one area interacts with the beam as to make an increased contribution, compared to the nominal black state, to the radiation dose delivered by the corresponding pixel in the plurality of pixels; and  
 at least one nominal white state, in which the at least one area interacts with the beam to make a contribution to the radiation dose delivered to the corresponding pixel in the plurality of pixels greater than that in the at least one nominal grey state,  
 wherein the controller controls the patterning device, such that multiple ones of the at least one area adopts one of the nominal black state or the at least one nominal grey state,  
 wherein the controller selectively controls the area to adopt the at least one nominal white state to provide compensation for effects of one or more pixels of the plurality of pixels when the one or more pixels are defective.  
   
   
   
       13 . The lithographic apparatus of  claim 12 , wherein the at least one area, when operating normally, is controllable to selectively adopt one of a series of grey states or white states.  
   
   
       14 . The lithographic apparatus of  claim 13 , wherein: 
 the substrate has a target surface to which a dosage pattern is to be delivered, the dosage pattern comprising nominal white regions, to which a radiation dosage at least equal to a threshold value is to be delivered, and nominal black regions, to which a radiation dosage less than the threshold value is to be delivered;    the series of grey states includes a maximum grey state, in which the increased contribution is a maximum for the grey states;    the illumination system and the controller are used to expose the target portion to each pixel for a common exposure time; and    the illumination system and the at least one area is used to expose the target portion for the common exposure time to a pixel whose corresponding element is in the maximum gray state delivers a dose at least equal to the threshold value.    
   
   
       15 . The lithographic apparatus of  claim 13 , wherein: 
 the substrate has a target surface to which a dosage pattern is to be delivered, the dosage pattern comprising nominal white regions, to which a radiation dosage at least equal to a threshold value is to be delivered, and nominal black regions, to which a radiation dosage less than the threshold value is to be delivered;    the series of grey states includes a maximum grey state in which the increased contribution is a maximum for the grey states;    the illumination system and the controller are used to expose the target portion to each pixel for a common exposure time;    the illumination system and the at least one area expose the target portion for the common exposure time to a pixel whose corresponding element is in the maximum gray state delivers a dose less than the threshold value, but greater than half the threshold value.    
   
   
       16 . The lithographic apparatus of  claim 12 , wherein the patterning device comprises an array of individually programmable elements or a programmable mirror array.