Illumination system optimized for throughput and manufacturability

Abstract

An optimized illumination system that efficiently produces uniform illumination for exposure, photoablation, and laser crystallization systems. The illumination system includes a homogenizer that uniformizes and shapes a light beam, which is directed onto a mask by condenser optics. The illumination system recycles radiation by directing light reflected by the mask back into the illumination system, where an apertured mirror situated at the input end re-directs it back toward the mask. The relative mirror and aperture sizes affect recycling efficiency and system throughput, so the system features a wide recycling segment enabling greater mirror-to-aperture area ratios. An added segment at the output end of the homogenizer matches the homogenizer diameter to the projection imaging system object field size. This standardizes the homogenizer and condenser lens construction system, reducing the need for customized parts and thus reducing manufacturing time and expense.

1 . A homogenizing illumination subsystem, for accepting radiation from a radiation source, performing homogenization by repeated reflections, and delivering a self-luminous radiation beam having a set of specifications including image size and numerical aperture appropriate for a selected collection means, 
 characterized by:    a) first-size section means of finite length with a primary function of input acceptance, having inward reflectivity for homogenization;    b) second-size section means of finite length with a primary function of output delivery, having inward reflectivity for homogenization, said first-size section and said second-size section being of similar cross-sectional configurations but different sizes so as to achieve longitudinal fit with at least one step when configured together as a longitudinal composite; and    c) a reflective-back-surface input aperture plate having an input aperture for acceptance of a beam of input radiation of significant power, said input aperture plate reflective back surface serving to recycle radiation reflected back toward it by re-reflecting such radiation forward again toward such second-size section.    
   
   
       2 . An illumination subsystem according to  claim 1 , 
 further characterized in that:    said first-size section means and said second-size section means are slidable to a plurality of aggregate length settings.    
   
   
       3 . An illumination subsystem according to  claim 1 , 
 further characterized in that:    at least one of said section means includes at least one extension segment.    
   
   
       4 . An illumination subsystem according to  claim 2 , 
 further characterized in that:    the illumination subsystem is step-down, with said first-size section being of sufficiently greater cross-sectional area than said second-size section to allow for sliding assembly; and    said input aperture plate encompasses an area completing an internally-reflective entry-chamber for radiation, permitting the entering radiation to disperse and homogenize somewhat before being introduced into further elements of the subsystem, so as to avoid damaging such further elements.    
   
   
       5 . An illumination subsystem according to  claim 4 , 
 further characterized in that:    said second-size section is solid, with total internal reflection for homogenization.    
   
   
       6 . An illumination subsystem according to  claim 4 , 
 further characterized in that:    said step tapers between said first-size section means and said second-size section means.    
   
   
       7 . An illumination subsystem according to  claim 1 , 
 further characterized by:    d) an internally-reflective apertured exit gap plate which, with said input aperture plate and said first-size section means, encloses a recycling entry chamber;    further characterized in that:    the subsystem is in a step-down configuration; and    said first-size section has reflective internal surfaces for a recycling entry chamber, having a small entry aperture and a larger exit gap each with internally mirrored surround, for recycling of homogenized radiation beams which are reflected back through such exit gap;    whereby such illumination subsystem serves as an easy-to-assemble recycling homogenizer.    
   
   
       8 . An illumination subsystem according to  claim 7 , 
 further characterized in that:    said first-size section means has both input acceptance and recycling responsibilities;    further characterized by:    e) a reflective back surface input aperture plate, mounted at a radiation entry plane on said first-size section means, having an input aperture for acceptance of a beam of input radiation of significant power, said input aperture plate reflective back surface serving to recycle radiation reflected back toward it by re-reflecting such radiation forward again toward such second-size section means through said exit gap and also toward said exit gap surround mirror for additional recycling.    
   
   
       9 . An illumination subsystem according to  claim 7 , 
 further characterized in that:    said exit gap surround plate and said first-size section are significantly larger in area and cross-sectional area, respectively, than is the second-size section, with a large exit gap and forward-reflecting exit gap surround providing connection of first-size section and second-size section for exit of the radiation beam from said recycling chamber toward further elements of the system, at least one of which has homogenization responsibilities, with sufficient homogenization and dispersion of such radiation as to avoid damaging further elements.    
   
   
       10 . An illumination subsystem according to  claim 9 , 
 further characterized in that:    said exit gap surround is slidable longitudinally within said recycling chamber to provide for easy longitudinal placement of first-size section and second-size section.    
   
   
       11 . An illumination subsystem according to  claim 8 , 
 further characterized in that:    said first-size section means is hollow, with internal reflectivity for homogenization and recycling.    
   
   
       12 . An illumination subsystem according to  claim 7 , 
 further characterized in that:    the subsystem comprises homogenizing section and condensing section articulated together.    
   
   
       13 . An illumination subsystem according to  claim 7 , 
 further characterized in that:    the subsystem comprises recycling section, homogenizing section, and condensing section articulated together.    
   
   
       14 . An illumination subsystem according to  claim 3 , 
 further characterized in that:    said first-size section means and said second-size section means are hexagonal in cross-section.    
   
   
       15 . An illumination subsystem according to  claim 3 , 
 further characterized in that:    said first-size section means and said second-size section means in the aggregate have homogenization capability plus magnification/condensation optical capability.    
   
   
       16 . A standardized assembly kit for making a recycling homogenizer illumination system with parameters selected from a set of standardized parameters, 
 characterized by:    a) a set of interchangeable homogenizer segments matched for longitudinally-aligned assembly to achieve a composite homogenizer section, with a selected number of reflections as a function of aggregate dimensions of segments aligned; and    b) a set of differentiated recycling sections, each with an internally-reflecting recycling chamber, and a set of means providing internally-reflecting exit gaps/surrounds, each appropriately dimensioned for accepting one of said set of interchangeable homogenizer segments.    
   
   
       17 . A standardized recycling segment for assembly with a homogenizing section in a recycling homogenizer illumination system, having standardized dimensions, such recycling segment having a mirrorized-back entry aperture plate with a small entry aperture and having a recycling mirrorized-front exit gap surround for making sliding sealing contact with a standardized homogenizer segment.  
   
   
       18 . A standardized homogenizer extension segment for use in augmenting homogenization reflections, said segment having standardized dimensions and a standard butt-joint for making contact to a previous homogenizer element.  
   
   
       19 . An illumination subsystem according to  claim 6 , 
 further characterized in that:    said first-size section means is larger than said second-size section means, and said second-size section means comprises a solid homogenizer section having an entry face, said first-size section means being capable of accepting a more highly concentrated radiation beam than is acceptable by said entry face of said second-size section means, and said first-size section means having the characteristic of diminishing the fluence applied to said entry face of said second-size section means.    
   
   
       22 . An illumination system, 
 characterized by:    a) a radiation source providing a radiation beam;    b) beam shaping means for receiving and shaping such radiation beam;    c) a homogenizer subassembly for accepting such a radiation beam from said radiation source via said beam shaping means and for providing plural reflective redirections of such radiation beam for homogenization, such homogenizer subassembly comprising:    recycling section means having a reflective-back-surface input aperture plate for acceptance of a shaped beam of input radiation focused into a small input aperture at a significant power level and for expanding and forwarding such shaped beam at a lesser average power level per area over a greater area than the area of such small aperture;    homogenizer section means for accepting the forwarded shaped greater-area beam and with homogenization due to plural reflections and in turn forwarding such greater-area beam to a patterning means having means to reflect unwanted areas of radiation back through said homogenizer section and back into said recycling section for re-reflection by the mirrored surround about its entry aperture into said homogenizer section and re-use;    whereby high-fluence radiation is accepted through said small entry aperture, expanded in beam size with reduction of fluence, and forwarded with homogenization for patterning, with non-pattern areas re-reflected for recycling by re-reflection from the entry aperture mirrored surround.