Abstract:
The invention relates to an illuminator for a photolithography device. The invention comprises: a source ( 1 ′) of a light beam ( 10 ) which is used to illuminate a mask ( 8 ) and to expose an area of a wafer (W); at least one main array ( 4 ) of microlenses; and a shutter ( 6 ) consisting of at least one shutter plate ( 61 ) comprising at least one part ( 612 ) that is opaque to the light beam ( 10 ) and a plurality of parts ( 610 ) that are transparent to the beam, whereby said plate ( 61 ) can be moved in relation to the beam ( 10 ) along a direction of movement (X) that is essentially parallel to the plate, such that the opaque part ( 612 ) can at least partially block the light beam or such that the transparent parts can at least partially enable the passage of the light beam ( 10 ). The invention is characterized in that it comprises movement means ( 9 ) which can move the shutter ( 6 ) in synchronism with the movements of the mask ( 8 ) and the wafer (W), said shutter ( 6 ) being located in an area ( 11 ) close to a pupil ( 40, 410 ) of an optical system comprising at least the main array ( 4 ) of microlenses. The invention also relates to a photolithography device comprising one such illuminator.

Description:
GENERAL TECHNICAL FIELD 
     The present invention relates to an illuminator for a photolithography device, as well as such a device. 
     PRIOR ART 
     Photolithography, also called “microlithography”, has been used for many years to produce semiconductor devices, and, for this purpose, uses electromagnetic radiation to generate fine patterns on semiconductor devices. To this end, an illuminator for a photolithography device illuminates a mask, of which the image is projected onto a semiconductor wafer, which provides a circuit after an ad hoc treatment known to a person skilled in the art. 
     As shown in  FIG. 1 , the illumination system, which will be referred to as an “illuminator” in the remainder of the description, for a photolithography device is complex. It must take into account a plurality of parameters simultaneously in order to satisfy the microlithography requirements. The parameters concerned are in particular:
         the illumination profile in the pupil of the device;   the uniformity of illumination on the mask (and therefore the wafer); and   the illumination profile on the mask.       

     To this end, a known illuminator generally comprises a diffractive optical element  1  (DOE), which is illuminated by an illumination source  1 ′. The element  1  can be any element generally used to produce diffraction, such as, for example, a two-dimensional array of spherical microlenses, a Fresnel lens, a diffraction grating, etc. The element  1  acts as an optical diffuser and is intended primarily to produce, at its output, a pupil with a general desired pattern, for example a disk or ring-shaped pattern, or a dipolar or quadripolar pattern. The element  1  is interchangeable, because an element  1  of a given type can generate only a single pattern at a time. 
     The illuminator comprises, at the output of the element  1 , a zoom  2  formed by a plurality of lenses. The function of the zoom  2  is to bring the image of the pupil to a finite distance and to be capable of causing it to vary in dimension. 
     The output of the zoom  2  is directed toward axicons  3  that give its definitive shape to the pupil. For example, in the case of axicons comprised of conical lenses, it is possible to control the internal diameter of a ring-shaped pupil. 
     The assembly formed by the element  1 , the zoom  2  and the axicons  3  therefore makes it possible to obtain a desired illumination profile in the pupil. 
     The light beam leaving the axicons  3  illuminates an optical element  4 . The element is generally constituted by two matrices formed by a two-dimensional array of spherical microlenses, which cuts the pupil obtained at the output of the assembly of the element  1 , the zoom  2  and the axicons  3 . The pupil of the zoom  2  is located at the level of the element  4  of which the output illuminates a condenser  5 . 
     The condenser  5  comprises a plurality of lenses that make it possible to superimpose the sub-beams coming from the diffractive element  4  at the level of the shutter  6 . 
     The assembly of the element  4  and the condenser  5  standardizes the illumination in the plane of a shutter  6 . 
     Indeed, the output of the condenser  5  illuminates a shutter  6  (also called a “slit”). The shutter  6  makes it possible in a known manner to block the light beam coming from the condenser  5 . 
     The shutter  6  makes it possible to control the dose, the image format and the illumination profile on a mask  8  owing in particular to a group  7  of illumination lenses (or “Illumination Lens Group” (ILG)) placed at the output of the shutter  6 . 
     The shutter  6  comprises, as shown in  FIG. 2 , in particular two stationary plates  63  and  64 . The plates  63  and  64  are rectangular, and their length extends substantially in direction X. The plates  63  and  64  are immobile with respect to the illumination, in particular with respect to directions X and Y of  FIG. 2 . The plates  63  and  64  are separated from one another in direction Y and define two edges of an area of exposure  67 . 
     The shutter  6  also comprises two plates  65  and  66  that are mobile with respect to the illumination in direction X. The plates  65  and  66  are rectangular, and their length extends substantially in direction Y. When the plates  65  and  66  are separated from one another in direction X, they define two edges of area  67 . 
     The space between plates  63 ,  64 ,  65  and  66  thus defines the area  67  of exposure to the illumination for the etching of the wafer. 
       FIGS. 3A to 3E  show the operation of the shutter  6  of the prior art. 
     In the known movement of the mask  8  and the wafer W, one with respect to the other, for an exposure for the purpose of etching, it is not necessary for the points outside of the zone W 1  of the wafer to be etched to receive the exposure energy. Thus, in particular the movement of the plates  65  and  66  is synchronized with the movements of the mask  8  and the wafer W. 
     In  FIGS. 3A to 3E , it has been shown for greater clarify that the mask  8  was located on the wafer W. Of course, the mask is optically located to the right of the wafer W.  FIG. 3A  shows that when the wafer W and the mask are moved in direction X but are located outside of the exposure zone  76  defined by the relay  7 , then the plates  66  and  65  are closed. The area  67  is a null and the beam  10  is blocked by the shutter  6 . 
       FIG. 3B  shows that when the left edge of the mask  8  defining the first zone W 1  of the wafer W to be exposed arrives at the level of the right edge of the plate  66 , going beyond the right edge of the zone  76 , then the plate  66  begins a movement in synchrony with and in the same direction as the mask  8  with a speed in synchrony with the speed Vs of the wafer W and the mask  8 . In other words, the speed of the plate  66  is proportional to the speed Vs. The zones of the wafer W located outside of the zone W 1  to be exposed thus are not exposed to the beam  10 . 
       FIG. 3C  shows that the plate  66  follows the mask  8  until the left edge of the mask  8  is located at the level of the left edge of the exposure zone  76 . The area  67  is then maximal and the entire beam  10  exposes the zone W 1  through the zone  76 . 
       FIG. 3D  shows that it is then the plate  65  that follows the mask  8  in the same direction as the mask  8  in direction X when the right edge of the mask goes beyond the right edge of the zone  76 . Again, the movement of the plate  65  is in synchrony with the movements of the wafer W and the mask  8 , namely in the same direction as and with a speed proportional to the speed Vs of the wafer W. In this way, the zones of the wafer W located outside of the zone W 1  are not exposed to the beam  10 . 
       FIG. 3E  corresponds to the closure of the exposure area  67 , in which plates  65  and  66  are then joined. The zone W 1  is outside of the zone  76  and the beam  10  is blocked by the shutter. 
     When the mask moves in the other direction according to X, for example, for an exposure of zones W 2  to W 8 , the plates  65  and  66  of course move in the other direction. The closure can occur at a speed of around 160 mm/s. 
     With this method of opening and closing the plates  65  and  66 , all of the points of the zone to be etched receive the same exposure energy and the zones that should not be exposed are not exposed. 
     Group  7  forms an optical relay that conjugates the plane of the shutter  6  and the mask  8 . In fact, without group  7 , the shutter  6  and the mask  8  should be located in the same plane, which is impossible from a mechanical perspective in the assembly of  FIG. 1 . There would in particular be friction of the plates  65  and  66  against the mask  8 . 
     The illuminators of the prior art have disadvantages. 
     The illuminator according to the prior art is complicated and expensive to produce, in particular due to the presence of a group  7  forming an optical relay for conjugating the plane of the shutter and the mask. The complexity of such a group is both optical and mechanical. 
     In addition, the mechanical elements making it possible to move the mobile plates of the shutter are complex and expensive, due to the large amplitude of the course and the high speed of translation of the plates (around 160 mm/s). 
     DESCRIPTION OF THE INVENTION 
     The invention is intended to overcome at least one of these disadvantages. 
     To this end, the invention proposes an illuminator according to claim  1 . 
     The invention is advantageously complemented with the features presented in the dependent claims. 
     The invention also relates to a device comprising such an illuminator. 
     The invention has numerous advantages. 
     First, an illuminator according to the invention is simpler and therefore less expensive, due to the absence of a group forming an optical relay in order to conjugate the plane of the shutter and the mask. 
     In addition, the mechanical elements enabling the movement of the mobile plates, one with respect to another, are also simpler and therefore less expensive, due to the reduction in amplitude of the course and the speed of translation of the plates. One may expect a reduction by a factor of 10 in the speed of movement of the plates of the shutter, which allows for a reduction in vibrations produced in the photolithography device as well as a simplification of the means for moving the shutter. 
     An illuminator according to the invention makes it possible in particular to correct certain defects of the illumination due to the nature of the illumination source, in particular when the source is a laser. An illuminator according to the invention makes it possible to obtain a trapezoidal illumination profile according to the direction of movement of the mask and the wafer. 
     An illuminator according to the invention also in particular allows for a clean cut of the illumination. 
    
    
     
       DESCRIPTION OF THE FIGURES 
       Other features, objectives and advantages of the invention will become clear from the following description, provided solely for illustrative and non-limiting purposes, which should be read in reference to the appended drawings, in which: 
         FIG. 1 , mentioned above, diagrammatically shows an illuminator known from the prior art; 
         FIG. 2 , also mentioned above, shows a shutter known from the prior art; 
         FIGS. 3A to 3E , mentioned above, diagrammatically show the various phases of movement of plates of the shutter according to  FIG. 2  according to the movement of a mask placed in an illuminator according to  FIG. 1 ; 
         FIGS. 4A and 4B  each diagrammatically show a plate of a shutter according to the invention; 
         FIG. 5  diagrammatically shows a possible arrangement of the two plates of  FIGS. 4A and 4B ; 
         FIG. 6  diagrammatically shows a first position of the shutter in an illuminator according to the invention; 
         FIG. 7  diagrammatically shows a second position of the shutter in an illuminator according to the invention; 
         FIG. 8  diagrammatically shows an alternative of the invention comprising two shutter plates; 
         FIGS. 9A to 9F  diagrammatically show a possible mode of operation of an alternative according to  FIG. 8 ; 
         FIG. 10  diagrammatically shows an alternative of the invention comprising two cross-plates; 
         FIG. 11  diagrammatically shows an alternative of the invention comprising a mobile shutter plate and cross-plate; 
         FIGS. 12 and 13  diagrammatically show an alternative of the invention comprising an array for creating a pupil image of the main pupil array; and 
         FIG. 14  diagrammatically shows an alternative of the invention comprising a mask defocused with respect to a condenser focusing plane. 
     
    
    
     In all of the figures, similar elements have the same numeric references. 
     DETAILED DESCRIPTION 
       FIGS. 4A and 6  diagrammatically show that a shutter  6  of an illuminator according to the invention of a photolithography device comprises primarily at least one shutter plate  61 . 
     Preferably, the shutter plate  61  has a square or rectangular shape. The plate  61  is composed of an opaque portion  612  capable of blocking a photolithography light beam  10 . The plate  61  also comprises a plurality of slots  610  formed in the plate, capable of allowing said light beam to pass through. 
       FIG. 6  also shows that an illuminator of a photolithography device according to the invention comprises a source  1 ′ of the light beam  10  for the illumination of a mask  8  for an exposure of a zone of a wafer W, and at least one main microlens array  4 . It is noted that the illuminator also comprises a condenser  5  that makes it possible to superimpose the sub-beams  100  from the array  4  at the level of the mask  8  (the beam  10  is, at the output of the array  4 , comprised of sub-beams  100  and thus forms an output pupil  40  of the array  4 ). 
     Preferably, the array  4  is constituted by two matrices formed by a two-dimensional array of spherical or cylindrical microlenses. The array  4  cuts the input pupil of the array  4  obtained at the output of an assembly formed by a diffractive element  1  placed at the output of the source  1 ′, a zoom  2  and axicons  3 . The diffractive element  1 , the zoom  2  and the axicons  3  are placed upstream of the array  4  and at the output of the source  1 ′. 
       FIG. 6  shows that the shutter plate  61  is located in a zone  11  upstream or downstream, according to a direction Z of propagation of the light beam  10  in the illuminator, of a focusing plane  11  of the beam  10 —and therefore of the sub-beams  100 . The focusing of the sub-beams  100  is performed by the array  4  formed by microlenses. The shutter plate  61  of the shutter  6  is thus located in the zone  11  near the pupil  40  of the main microlens array  4 . 
     Preferably, the plate  61  is placed on the less bulky side, namely between the focusing plane  111  and the condenser  5 . 
     The depth of the zone  11  in direction Z is dependent on the spatial bulk of the plate with respect to the space between the array  4  and the condenser  5 , but also on the width of the slots. 
     It can easily be seen in  FIG. 6  that the width of each of the slots  610  must be such that it allows a sub-beam  100  to pass entirely in a first exposure position. The slots  610  each allow a sub-beam  100  to pass, so that the entire beam  10  passes through the plate  61  in order to illuminate the mask  8  in the first position of  FIG. 6 . Each sub-beam  100  has the characteristics of the beam  10 , which causes all of the sub-beams  100  to have the same characteristics as one another. Their recombination at the level of the mask  8  in a focusing plane of the condenser  6  makes it possible to obtain the same result as for the illuminators comprising a group forming an optical relay. 
       FIG. 7  shows that the plate  61  is capable of being moved with respect to the beam  10  in a direction X of movement perpendicular to direction Z and parallel to the plate  61  so as to totally block the beam  10  in a second shutter position. In the position of  FIG. 7 , the mask  8  is no longer illuminated. The sub-beams  100  are blocked by the opaque portion  612  of the plate  61  between the slots  610 . The plate  61  makes it possible to block each sub-beam  100  just after the array  4 . 
     Means  9  for moving the shutter  6  are capable of moving the plate  61  in synchrony with the movements of the mask  8  and the wafer W, namely in the same direction, and according to a speed proportional to the movements of the wafer W and the mask  8 , while preventing exposure of the zones that should not be exposed. 
     The plate  61  blocks the beam at least partially between the two positions of  FIG. 6  and  FIG. 7 . 
     The plate  61  is moved between the exposure position of  FIG. 6  and the shutter position of  FIG. 7  in synchrony with the movements of the mask  8  and the wafer W to be exposed. This mode of exposure/blocking of each beam  100  gives the same result as in the prior art shown in  FIGS. 3A to 3E . Each point of the exposure zone of the wafer has the same exposure energy as all of the other points of the exposure zone in the movement of the mask  8 , and in particular the zones of the wafer located outside of the zones to be exposed are not exposed to the beam  10 . 
       FIG. 4A  shows that the slots  610  of the plate  61  have an oblong shape and a longitudinal axis  611 . 
     Preferably, each slot  610  has a substantially rectangular shape. The rectangles of the slots  610  are defined and contained between large sides  613  and small sides  614 . 
     Also preferably, the longitudinal axes  611  of the slots  610  are parallel to one another. 
     The character “a” defines the distance between two longitudinal axes  611  of two successive slots of the plate  61  in the direction of movement X. “a” thus defines the pitch of the slots  610 . It is constant and is dependent on the microlenses of the main array  4 . 
     The character “b” defines the distance between two large sides  613  of two successive slots, with the understanding that said two large sides are the closest and are successive in the direction of movement X. “b” can vary in order to adjust to the illumination conditions of the weather. 
     For successful operation of the device according to the invention, the ratio a/b must be lower than two for the plate  61 . With this ratio value, the beam is not blocked in the first position of  FIG. 6 , and the blocking is complete in the second position of  FIG. 7 . 
     It is noted that, with the mobile plate  61 , the illuminator according to the invention no longer needs a group forming an optical relay in order to conjugate the shutter plane and the mask. The mask  8  is placed directly in the focusing plane of the condenser  5 , and the shutter  6  comprising primarily the mobile shutter plate  61  is located in the zone  11  described above. 
       FIG. 4B  shows that preferably the shutter  6  according to the invention comprises advantageously a cross-plate  62 . The cross-plate  62  comprises at least one alternation of an opaque portion  622  and a slot  620  capable of allowing the light beam  10  to pass through. 
     The cross-plate  62  is located optically to the right of the shutter plate  61 . For the sake of clarity, the cross-plate  62  has been shown near the shutter plate  61  in  FIG. 5 , but it can be at a distance from the shutter plate. Thus, the cross-plate  62  can be placed at the level of the main array  4 , upstream or downstream according to direction Z of a microlens array. Preferably, the cross-plate  62  is located in the zone  11  near the pupil of the microlens array  4 . 
     Other positions are possible for the cross-plate  62  according to the possibilities of mechanical implantation and bulk in the illuminator. 
     Preferably, each slot  620  of the cross-plate  62  has an oblong shape and a longitudinal axis  621 . 
     Also preferably, the cross-plate  62  comprises, like the shutter plate  61 , a plurality of alternations of opaque portions  622  and slots  620 . 
     As shown in  FIG. 5 , the respective longitudinal axes  611  and  621  of the slots of the two plates  61  and  62  are perpendicular to one another. 
     As shown in  FIGS. 4B and 5  also, each slot  620  of the cross-plate  62  has a substantially rectangular slot. Each rectangle is contained between large sides  623  and small sides  624 . The longitudinal axes  621  of the slots are parallel to one another. 
       FIG. 5  shows that, when the cross-plate  62  is located to the right of the shutter plate  61 , and the shutter plate  61  is in the first position—namely the slots of the plate  61  allow the ray  10  to pass through—the slots  610  and  620  define exposure zones  625 . The shape and arrangement of the zones  625  of the shutter formed by the two plates  61  and  62  correspond to the shape and the arrangement of the various illumination zones of the microlenses of the array  4 . The ratio of the small sides  614  and  624  of the respective rectangles of the plates  61  and  62  is equal to a dimensional ratio of a microlens of the array  4 . In other words, the dimensions of the zones  625  are proportional to an illumination surface of a microlens of the array  4 . The fact that the longitudinal axes  611  and  621  of the slots of the plates  61  and  62  are respectively perpendicular causes a plate to define a dimension of the illumination zones  625 , with the other plate defining the other dimension. 
     As shown in  FIGS. 4B and 5 , a distance a′ is defined between the longitudinal axes  621  of two successive slots  620  according to a direction Y perpendicular to the direction of movement X. A distance b′ is also defined between two large sides  623  of said two successive slots, which two large sides  623  are close and successive according to direction Y. 
     The cross-plate  62  is, for the sake of simplicity, immobile with respect to the beam in a plane XY substantially parallel to the cross-plate. The cross-plate plays substantially the role of the plates  63  and  64  of a shutter according to the prior art, and the shutter plate  61  plays the role of the plates  65  and  66  of the shutter of the prior art. 
     By way of a non-limiting example, the plates  61  and  62  have a side of 130 mm and a thickness of several tens of millimeters. The pitch of the slots  610  and  620  is on the order of several millimeters. 
     The course of the plate  61  is on the order of several millimeters, with a speed of around 30 mm/s. 
     The plates can be made of metal or silica or fluorine coated with chromium. 
     We will now describe alternatives of the embodiments of the invention described above. 
       FIG. 11  thus shows that, according to a first alternative, the shutter can advantageously also comprise a shutter plate  61  and a cross-plate, mobile with respect to the illumination and having slots of a different shape. 
     The shutter plate  61  comprises a plurality of slots  610  formed in the plate  61 , and, similarly, the cross-plate  62  comprises a plurality of slots  620  formed in the plate  62 . 
     As shown in  FIG. 11 , the slots  610  and  620  have substantially a square shape. 
     The means  9  for moving the shutter  6  comprise means  91  for moving the shutter plate  61 , and means  92  for moving the cross-plate  62 . Thus, the movements of the shutter plate  61  or of the cross-plate  62  can be performed in synchrony with the movements of the mask  8  and the wafer W. 
     The cross-plate  62  is mobile with respect to the beam in a plane (X, Y) substantially parallel to said cross-plate  62 . 
     The shutter plate  61  is preferably also mobile in two directions (X, Y) substantially parallel to the shutter plate  61 . 
     Thus, for an exposure of a zone of a given wafer, the position of the cross-plate  62  is adjusted with respect to the shutter plate  61 , in particular in position on the Y-axis. Thus, the dimension, according to the Y-axis, of the zones  625  transparent to the illumination beam is adjusted by defining opaque zones  630  where at least one opaque zone of plate  61  and/or plate  62  is present. 
     As before, the ratio of the dimensions of the zones  625  transparent by the combination of slots  610  and  620  of the two plates  61  and  62  is equal to a ratio of the dimensions of a microlens of the main array  4 . 
     The closure is then performed, as above, by moving the shutter plate  61  along the X-axis, for example, but still in synchrony with the movements of the mask  8  and the wafer W. 
       FIGS. 8 and 9A  to  9 F show another alternative according to the invention. 
     According to this alternative shown in  FIG. 8 , the illuminator comprises two shutter plates  61  and  61 ′ optically located one opposite the other and mobile with respect to one another with respect to the beam  10  in a direction X of movement substantially parallel to the shutter plates  61  and  61 ′. 
     The movement means  9  are capable of moving the plates  61  and  61 ′ as indicated in  FIGS. 9A to 9F , in synchrony with the movements of the mask  8  and the wafer W. 
     In the known movement of the mask  8  and the wafer W, one with respect to the other, for an exposure for the purpose of etching, in particular the movement of the plates  61  and  61 ′ is synchronized with the movements of the mask  8  and the wafer W. 
       FIGS. 9A to 9E  show, for greater clarity, that the mask  8  was located on the wafer W. Of course, the mask is optically located to the right of the wafer W. Also for greater clarity, only the combination of a slot  610  and  610 ′ respectively of each plate  61  and  61 ′ has been shown, but the plates  61  and  61 ′ comprise a plurality of slots. 
       FIG. 9A  shows that when the wafer W and the mask  8  move in direction X but are located outside of the exposure zone  56  defined by the condenser  6 , then the slots  610  and  610 ′ of the plates  61  and  61 ′ are positioned one with respect to another so that the area  67  is null. The beam  10  is blocked by the shutter. 
       FIG. 9B  shows that when the left edge of the mask  8  defining the first zone W 1  of the wafer W to be exposed arrives with the speed Vs at the level of the left edge of the slot  610  of the plate  61 , then the latter begins a movement in synchrony with the movements of the mask  8  and the wafer W, namely in the same direction as the mask  8  with a speed proportional to the speed Vs. The zones of the wafer W located outside of the zone W 1  to be exposed are thus not exposed to the beam  10 . 
       FIG. 9C  shows that the plate  61  follows the mask  8  until the left edge of the mask  8  is located at the level of the left edge of the exposure zone  56 . The area  67  is then maximal and the entire beam  10  exposes the zone W 1  through the zone  56 . 
       FIG. 9D  shows that it is then the plate  61 ′ that follows the mask  8  in the same direction as the mask  8  in direction X when the right edge of the mask goes beyond the right edge of the zone  56 . Again, the movement of the plate  61 ′ is in synchrony with the movements of the wafer W and the mask  8 , namely in the same direction as and with a speed proportional to the speed Vs of the wafer W. In this way, the zones of the wafer W located outside of the zone W 1  are not exposed to the beam  10 . 
       FIG. 9E  corresponds to the closure of the exposure area  67 , in which the right edge of the slot  610 ′ of the plate  61 ′ and the left edge of the slot  610  of the plate  61  are joined. The zone W 1  is outside of the zone  56  and the beam  10  is blocked by the shutter. 
     When the mask moves in the other direction according to X, for example, for an exposure of zones W 2  to W 8 , the plates  61  and  61 ′ of course move in the other direction. 
     With this method of opening and closing the plates  61  and  61 ′, all of the points of the zone to be etched receive the same exposure energy and the zones that should not be exposed are not exposed. 
     According to an alternative of the invention, the cross-plate  62  of the embodiment shown in  FIG. 11  acts as the plate  61 ′. 
     According to another alternative shown in  FIG. 10 , the illuminator comprises two cross-plates  62  and  62 ′ located optically one opposite the other and mobile, one with respect to the other, with respect to the beam  10  in a direction Y of movement substantially parallel to the cross-plates  62  and  62 ′. The direction of movement of the cross-plates  62  and  62 ′ is perpendicular to the direction X of movement of at least one shutter plate  61  placed to the right of plates  62  and  62 ′. 
     The movement means  9  are capable of moving the plates  62  and  62 ′. This makes it possible in particular to adjust the dimension of the exposure area according to direction Y. 
       FIGS. 12 and 13  diagrammatically show another alternative according to which the illuminator has at least one array  41  of microlenses for creating a pupil  410 . 
     Reference  111  corresponds to the focusing plane of the main array  4 . 
     The creation array  41  is located in a zone  11 ′ near the plane  111  for focusing the beam  10  through the main microlens array  4 . The creation array  41  is located downstream of the main microlens array  4 , but upstream of the shutter  6 . 
     The array  41  makes it possible to re-image the pupil  40  of the main array  4 . The beam  10  is not perfectly collimated, which can present problems of clean cutting of the illumination at the level of the mask  8 . 
     The shutter  6  is therefore placed in a zone  11  near the pupil  410  of the optical system comprising the main array  4  and the creation array  41 , which enables clean cutting of the beam and clean blocking at the level of the mask  8 . 
     Thus, according to the invention, the shutter is placed in a zone  11  near an optical system pupil comprising only the main array when the main array is not associated with another microlens array, or near an output pupil of the optical system comprising the main array and the creation array located downstream of the main array in order to re-image the pupil of the main array. 
     The shutter  6  is of course placed, as in all of the embodiments described above, in a plane conjugated with the plane of the mask  8  and the plane of the wafer W. 
     Preferably, the illuminator comprises a microlens homogenization array  42  located downstream of the shutter  6  and upstream of a condenser  5 . The array  42  also makes it possible to make the illuminator telecentric. Reference  422  corresponds to the object plane of the condenser. 
     The shutter is placed in a zone near an intermediate pupil  410  of the optical system comprised of the main array  4 , the creation array  41  and the homogenization array  42 . It can also be located in an area near an output pupil of an optical system comprising the main array, the creation array and the homogenization array. 
     In addition, very advantageously, the illumination profile of the mask must be trapezoidal according to the direction of movement of the mask and the wafer. 
     To obtain the desired trapezoidal illumination profile, the mask  8  is defocused with respect to a focusing plane  51  of the condenser  5  in direction Z, perpendicular to the plane of the shutter and the direction X of movement of the mask  8 , as shown in  FIG. 14 . Such a defocusing makes it possible in particular to correct certain illumination defects due to the nature of the illumination source, in particular when the source is a laser. 
     Such a defocusing can however present problems of clean cutting of the illumination at the level of the mask. 
     Thus, advantageously, a pitch of the slots  610  of the shutter plate  61  and the shutter  6  is greater than a pitch of the main microlens array  4  in a direction substantially parallel to a direction of movement of the mask  8 . Such a difference in pitch creates a slight phase shift in the time that each opaque portion cuts the beam from the corresponding array  4 . 
     If the illuminator comprises an array  41  of microlenses for creating a pupil  410  and/or a homogenization array  42 , in order not to lose the benefit of the clean cutting provided by the advantageous presence of the creation array  41 , a pitch of the slots  610  of the shutter plate  61  and the shutter  6  is greater than a pitch of the creation array  41  in a direction substantially parallel to a direction of movement of the mask  8 , and preferably greater than a pitch of the array  42  in the same direction. 
     The alternatives described above can be combined with one another. The shutter can thus comprise two shutter plates and two cross-plates, possibly comprise an array  41  for creating a pupil  410 , and possibly comprise a mask defocused in the plane  51 . 
     In all of the embodiments mentioned above, each cross-plate  62  is preferably located in a zone  11  near a pupil of a system comprising the main microlens array  4 , optically opposite the shutter plate  61 . 
     We have described slots formed in the plates, but any number of portions transparent to the beam obviously have the same function, on the condition that the transparent portions are totally transparent to the beam and the opaque portions completely block the beam. 
     In every case, the movement of the shutter is performed with a precision on the order of the micron, and the fact that the shutter is comprised of plates facilitates such a precise movement.