Abstract:
A self-damping shutter apparatus for use in an exposure system of a photolithography machine, comprising: at least two pieces of shutter blades ( 1 ) for cutting off light source to an exposure area when the shutter is closed; a shutter driving arm ( 2 ), for driving the shutter blades ( 1 ) to synchronically open or close; a magnetic damping brake motor ( 3 ), for driving or braking the shutter driving arm ( 2 ), and the magnetic damping brake motor ( 3 ) drives and brakes, via the shutter driving arm ( 2 ), the shutter blades ( 1 ). The self-damping shutter apparatus for use in the exposure system of the photolithography machine increases consistency of opening or closing the shutter blades, improves a light shading effect of the shutter apparatus in an exposure, and improves stability in the process of opening or closuring the shutter blades. When the shutter blades complete actions of opening or closing, current is not needed, the magnetic damping braking motor enables the shutter blades to maintain the state of opening or closing, shortens duration of control current, reduces heat dissipation, and saves energy.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to the manufacturing of photolithography equipment and, more particular, to a self-damping shutter device for use in an exposure sub-system of a photolithography tool. 
       BACKGROUND 
       [0002]    Photolithography is a technique for printing a pattern with features onto the surface of a substrate. A commonly-used substrate is a semiconductor wafer or a glass substrate which is surface-coated with a light-sensitive material. During a photolithography process, a wafer is placed on a wafer stage and the pattern with features is projected onto the surface thereof through an exposure device incorporated in the photolithography equipment. 
         [0003]    Referring to  FIG. 1 , a conventional damping-free shutter device used in an exposure sub-system of a photolithography tool includes: at least two shutter blades  100  provided with respective voice coil motors  200  for driving the shutter blades  100  into an open or closed configuration. Motions of the shutter blades  100  toward the open or closed configuration as well as an extent to which they are opened or closed are controlled through adjusting currents flowing in mover coils of the voice coil motors  200 . Referring to  FIG. 4 a   , during operation of the damping-free shutter device, the mover coils in the voice coil motor  200  first accelerate for t/ 2  (i.e., 0-t 1 ) under the effect of forward currents and then decelerate for t/ 2  (i.e., t 1 -t 2 ) under the effect of reverse currents until their speeds decrease to zero. After the shutter blades  100  reach the open configuration, currents are further provided in order to keep them in the open configuration. In  FIG. 4 a   , t 1  denotes an instant of time when the conventional damping-free shutter device starts to be braked under the action of the reverse currents, t 1 -t 2  indicates a period of time required for breaking of the conventional damping-free shutter device, Q represents a curve showing dependence of a Lorentz force acting on the mover coil in each of the conventional voice coil motors on time, and W indicates a curve illustrating evolution of an angle of deflection of each shutter blade  100  during its movement over time. 
         [0004]    Therefore, the motions of the shutter blades  100  toward the open or closed configuration as well as the extent to which they are opened or closed are subject to an open-loop current control. The control side may interfere with the exposure process, and the open-loop current control may affect the stability of the shutter blades  100  during their acceleration and braking. Additionally, as the shutter blades  100  are separately controlled by the respective voice coil motors  200 , there is a lack of consistency between their opening or closing processes, leading to insufficient repeatability of the shutter blade  100  and impaired exposure performance. 
       SUMMARY OF THE INVENTION 
       [0005]    It is an object of the present invention to provide a self-damping shutter device for use in an exposure sub-system of a photolithography tool, which has improved opening or closing consistency between the shutter blades, reduced interference with the exposure process by the control side and enhanced exposure performance. 
         [0006]    In order to achieve the above goal, the present invention provides a self-damping shutter device for use in an exposure system of a photolithography tool, comprising: at least two shutter blades, configured to shade a light for an exposure area when the at least two shutter blades are in a closed configuration; a shutter actuation arm, configured to drive the at least two shutter blades simultaneously into the closed configuration or an open configuration; and a magnetic damping braking motor, configured to drive or brake the shutter actuation arm such that the at least two shutter blades enter the open or the closed configuration simultaneously. 
         [0007]    Preferably, the magnetic damping braking motor comprises a stator, a mover and a magnetic damping braking module. The mover is movable relative to the stator and the magnetic damping braking module. The mover is coupled to the shutter actuation arm via an actuation frame. 
         [0008]    Preferably, the stator comprises a magnet, an iron core cap and an iron core. The magnet is coupled to both the iron core cap and the iron core. 
         [0009]    Preferably, the mover comprises a coil bobbin on which a mover coil is wound. The coil bobbin has an axisymmetric structure. A first axially-magnetized damping magnet ( 3 - 71 ) and a second axially-magnetized damping magnet ( 3 - 72 ) are fixedly provided on each of an upper side and a lower side of a horizontal symmetric axis of the coil bobbin, the first axially-magnetized damping magnet and the second axially-magnetized damping magnet have a first normally-magnetized damping magnet and a second normally-magnetized damping magnet disposed therebetween. 
         [0010]    Preferably, the first axially-magnetized damping magnets arranged on the upper and lower sides of the horizontal symmetric axis of the coil bobbin are magnetized in a same direction. The second axially-magnetized damping magnets arranged on the upper and lower sides of the horizontal symmetric axis of the coil bobbin are also magnetized in a same direction. The first axially-magnetized damping magnets and the second axially-magnetized damping magnets are magnetized in opposite directions. 
         [0011]    Preferably, the magnetic damping braking module has an upper half and a lower half in symmetry with each other and comprises a first damping magnet and a second damping magnet that are oppositely magnetized. The first damping magnet is fixedly connected to the iron core via a first damping leaf spring. The second damping magnet is fixedly connected to a fixed frame disposed on the magnetic damping braking motor via a second damping leaf spring. 
         [0012]    Preferably, the shutter actuation arm is a symmetric four-bar linkage mechanism having a first end hinged to the at least two shutter blades and a second end, which is symmetric to the first end hinged to an actuation frame, and the actuation frame is connected to the magnetic damping braking motor. 
         [0013]    Preferably, the at least two shutter blades are of a sluice type. 
         [0014]    Preferably, the at least two shutter blades are fabricated from hardened aluminum or ceramic sheets. 
         [0015]    Preferably, the at least two shutter blades are surface-coated with a reflective material. 
         [0016]    Compared to the prior art, the self-damping shutter device according to the present invention incorporates the shutter actuation arm and the magnetic damping braking motor which drives the shutter actuation arm such that the shutter blades are opened or closed at the same time. This results in improved opening or closing consistency between the shutter blades, good exposure repeatability and better shading of the exposure light. Additionally, the opening or closing process of the shutter blades is made not subject to an open-loop current control, immunizing motions of the shutter blades from an adverse impact by the control side and enhancing the stability of the opening or closing process of the shutter blades. Further, once the shutter blades have reached the completely open or closed configuration, the magnetic damping braking motor can keep them in the configuration by means of the shutter actuation arm without needing a current supply any more. This shortens the period of time required for current control, reduces dissipated heat and saves energy. Furthermore, the magnetic damping braking module brakes the opening or closing of the shutter blades by itself, with reduced consumption of time, stable motions of the shutter blades, no need for rubber damping rods and capabilities of excellent non-linear damping and rapid braking of the mover moving at a high speed, thus improving the braking of the shutter blades. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIG. 1  is a structural schematic of a conventional shutter device. 
           [0018]      FIG. 2 a    is a structural schematic of shutter blades in an open configuration according to a specific embodiment of the present invention. 
           [0019]      FIG. 2 b    is a structural schematic of shutter blades in a closed configuration according to a specific embodiment of the present invention. 
           [0020]      FIG. 3 a    is a structural schematic of a magnetic damping-braking motor according to a specific embodiment of the present invention. 
           [0021]      FIG. 3 b    is a structural schematic of open shutter blades in a self-damping shutter device according to a specific embodiment of the present invention. 
           [0022]      FIG. 3 c    is a structural schematic of closed shutter blades in a self-damping shutter device according to a specific embodiment of the present invention. 
           [0023]      FIG. 4 a    is a diagram showing the evolution of an angle of deflection of conventional shutter blades over time during their movement. 
           [0024]      FIG. 4 b    is a diagram showing the evolution of an angle of deflection of shutter blades according to a specific embodiment of the present invention over time during their movement. 
       
    
    
       [0025]    In the figures showing the prior art,  100  denotes shutter blades; and  200 , a voice coil motor. 
         [0026]    In the figures illustrating the present invention,  1  denotes shutter blades;  2 , a shutter actuation arm;  3 , a magnetic damping-braking motor;  301 , a stator;  302 , a mover;  303 , a magnetic damping braking module;  3 - 2 , a magnet;  3 - 3 , an iron core cap;  3 - 4 , an iron core;  3 - 5 , a coil bobbin;  3 - 6 , a mover coil;  3 - 71 , a first axially-magnetized damping magnet;  3 - 72 , a second axially-magnetized damping magnet;  3 - 81 , a first normally-magnetized damping magnet;  3 - 82 , a second normally-magnetized damping magnet;  3 - 9 , a fixed frame;  3 - 101 , a first damping magnet;  3 - 102 , a second damping magnet;  3 - 111 , a first damping leaf spring;  3 - 112 , a second damping leaf spring;  4 , an actuation frame; 
         [0027]    M, first magnetic circuits; and N, second magnetic circuits. 
       DETAILED DESCRIPTION 
       [0028]    The present invention will be described below in detail with reference to the accompanying drawings. 
         [0029]    Referring to  FIGS. 2 a  and 2 b   , a self-damping shutter device for use in an exposure sub-system of a photolithography tool comprises: at least two shutter blades  1 , configured to shade light bound to an exposure area when they are in a closed configuration; a shutter actuation arm  2 , adapted to drive the shutter blades  1  into the closed configuration or an open configuration in a synchronized manner; and a magnetic damping braking motor  3 , configured to drive or brake the shutter actuation arm  2 . The magnetic damping braking motor  3  drives and brakes the shutter blades  1  through the shutter actuation arm  2 . Although two shutter blades  1  are depicted in  FIGS. 2 a  and 2 b   , those skilled in the art will appreciate that three, four or more shutter blades  1  may also be used as long as they can shade the light bound to the exposure area when in the closed configuration. 
         [0030]    Referring to  FIGS. 2 a , 2 b  and 3 a   , the magnetic damping braking motor  3  includes a stator  301 , a mover  302  and a magnetic damping braking module  303 . The mover  302  is movable relative to the stator  301  and to the magnetic damping braking module  303 . The mover  302  is connected to the shutter actuation arm  2  via an actuation frame  4 . The mover  302  drives the actuation frame  4  so that the moving actuation frame  4  in turn drives the shutter actuation arm  2  to make the shutter blades  1  move toward the open or closed configuration in a synchronized and braked manner. 
         [0031]    Referring to  FIGS. 2 a , 2 b  and 3 a   , the stator  301  includes a magnet  3 - 2  that is connected, at one end, to an iron core cap  3 - 3  and, at the other end, to an iron core  3 - 4 . 
         [0032]    The magnet  3 - 2  is so assembled with the iron core  3 - 4  as to overall appear like a letter “E”. 
         [0033]    Referring to  FIGS. 2 a , 2 b  and 3 a   , the mover  302  includes a coil bobbin  3 - 5  over which a mover coil  3 - 6  is wound. The coil bobbin  3 - 5  is an axisymmetric structure. A first axially-magnetized damping magnet  3 - 71  and a second axially-magnetized damping magnet  3 - 72  are fixedly provided on each of an upper side and a lower side of a horizontal symmetric axis of the coil bobbin ( 3 - 5 ), between which a first normally-magnetized damping magnet  3 - 81  and a second normally-magnetized damping magnet  3 - 82  are disposed. 
         [0034]    The first axially-magnetized damping magnets  3 - 71  arranged on the opposing sides of a horizontal axis of symmetry of the coil bobbin  3 - 5  are magnetized in the same direction. Similarly, the second magnetized damping magnets  3 - 72  on the opposing sides of the horizontal axis of symmetry of the coil bobbin  3 - 5  are also magnetized in the same direction. In addition, on each side of the horizontal axis of symmetry, the magnetization direction of the first axially-magnetized damping magnet  3 - 71  is opposite to that of the second axially-magnetized damping magnet  3 - 72 . 
         [0035]    Referring to  FIGS. 2 a  and 3 c   , an initial standby position of the mover  302  corresponds to the closed configuration of the shutter blades  1 . At this position, the first normally-magnetized damping magnets  3 - 81 , the iron core  3 - 4 , the magnet  3 - 2  and the iron core cap  3 - 3  form two complete first magnetic circuits M which exert a magnetic force on the mover  302  and keep it stationary. In addition, the mover  302  pulls the shutter blades  1  via the shutter actuation arm  2  so that the shutter blades  1  are maintained in the closed configuration. 
         [0036]    Referring to  FIGS. 2 b  and 3 b   , an end point of movement of the mover  302  corresponds to the open configuration of the shutter blades  1 . When a current is introduced into the mover coil  3 - 6 , a Lorentz force is produced therefrom to drive the mover  302  to move axially relative to the stator  301 . Consequently, the shutter blades  1  are opened with the aid of the shutter actuation arm  2 . Upon the second normally-magnetized damping magnets  3 - 82  reaching locations above the iron core cap  3 - 3 , the second normally-magnetized damping magnets  3 - 82 , the iron core  3 - 4 , the magnet  3 - 2  and the iron core cap  3 - 3  form two complete second magnetic circuits N which exert a capture force on the mover  302  so that the mover  302  is gradually braked. The braking process is described in detail below. 
         [0037]    The coil bobbin  3 - 5  is disposed outside of the magnet  3 - 2  and within the iron core  3 - 4 . 
         [0038]    Referring to  FIGS. 2 a , 2 b  and 3 a   , the magnetic damping braking module  303  has an upper half and a lower half in symmetry with each other and includes a first damping magnet  3 - 101  and a second damping magnet  3 - 102  that are oppositely magnetized. The first damping magnet  3 - 101  is fixedly connected to the iron core  4  via a first damping leaf spring  3 - 111 , and the second damping magnet  3 - 102  is fixedly connected to a fixed frame  3 - 9  disposed on the magnetic damping braking motor  3  via a second damping leaf spring  3 - 112 . 
         [0039]    Referring to  FIGS. 2 a  and 2 b   , the shutter actuation arm  2  is a symmetric four-bar linkage mechanism having an end hinged to the shutter blades  1  and another end symmetric thereto hinged to the actuation frame  4 . The actuation frame  4  is connected to the magnetic damping braking motor  3 . 
         [0040]    Use of the four-bar linkage mechanism enables synchronized actuation of the two shutter blades  1  with the single magnetic damping braking motor  3 , enhancing movement consistency between the two shutter blades  1  and increasing exposure repeatability. 
         [0041]    The shutter blades  1  are of the sluice type in order to facilitate synchronized actuation of the two shutter blades  1  through the magnetic damping braking motor  3 . 
         [0042]    Actuation of both the two shutter blades  1  with the single magnetic damping braking motor  3  with the aid of the shutter actuation arm  2  improves the opening and closing consistency between these two shutter blades  1 , in particular a sluice-type shutter blades  1 , while achieving good exposure repeatability and enhancing shading of the exposure light by the shutter device. 
         [0043]    The shutter blades  1  are fabricated from hardened aluminum or ceramic sheets and can withstand a maximum operating temperature of 300° C. 
         [0044]    The shutter blades  1  are surface-coated with a reflective material. In the closed configuration of the shutter blades  1 , the reflective material can reflect away most of incident light from an exposure light source. As a result, heat absorbance of the shutter blades  1  is reduced, which is conducive to the normal operation of the shutter blades  1 . 
         [0045]    Referring to  FIGS. 2 a , 2 b  and 3 a  to 3 c   , when the shutter blades  1  are in the closed configuration, the mover  302  is at the initial position, and the first normally-magnetized damping magnets  3 - 81 , the iron core  3 - 4 , the magnet  3 - 2  and the iron core cap  3 - 3  form two complete first magnetic circuits M which exert a magnetic force on the mover  302  and keep it stationary. The mover  302  pulls the shutter blades  1  via the shutter actuation arm  2  so that the shutter blades  1  are maintained in the closed configuration. At this point, there is a repulsive force between the first axially-magnetized damping magnet  3 - 71  and the first damping magnet  3 - 101 , so that the first damping leaf spring  3 - 111  is compressed and stores elastic potential energy. While the repulsive force has a certain urging effect on the mover  302 , as it is less than the magnetic force exerted thereon by the first magnetic circuits M, the mover  302  remains stationary. 
         [0046]    Upon application of a current into the mover coil  3 - 6 , a Lorentz force is generated therefrom which drives the mover  302  to axially move relative to the stator  301 . As a result, the mover  302  gradually goes away from the iron core  3 - 4 , and the distance between the first axially-magnetized damping magnet  3 - 71  and the first damping magnet  3 - 101  gradually increases. This results in a reduction in the repulsive force as well as release of magnetic energy. In addition, the first damping leaf spring  3 - 111  is gradually decompressed, releasing the elastic potential energy. The released magnetic energy and elastic potential energy together power the mover  302  to accelerate axially, which in turn drives, via the shutter actuation arm  2 , the two shutter blades  1  to gradually move toward the open configuration simultaneously. 
         [0047]    When the mover  302  is accelerated by the Lorentz force to an intermediate position, referring to  FIG. 4 b   , at the instant t 1 , the mover coil  3 - 6  is controlled to be short-circuited or disconnected, leaving the mover coil  3 - 6  subject to a damping force generated from its own reverse holding current or not subject to any force. Consequently, the mover  302  starts to be braked and decelerated. 
         [0048]    Upon the mover  302  decelerating to a position where the second normally-magnetized damping magnet  3 - 8  is located above the iron core cap  3 - 3 , the second normally-magnetized damping magnet  3 - 82 , the iron core  3 - 4 , the magnet  3 - 2  and the iron core cap  3 - 3  form two complete second magnetic circuits N which exert a magnetic force on the mover  302 , making the mover  302  continue the axial movement. With this axial movement proceeding, the second normally-magnetized damping magnet  3 - 82  gradually goes away from the magnet  3 - 2  and the magnetic force exerted on the mover  302  by the second magnetic circuits N decreases. 
         [0049]    With the mover  302  further moving axially, a magnetic force is created between the second damping magnet  3 - 102  and the second axially-magnetized damping magnet  3 - 72  and increases with the second damping magnet  3 - 102  approaching the second axially-magnetized damping magnet  3 - 72 . This magnetic force has a braking effect on the mover  302  and may be referred to as a damping braking force. The damping braking force gradually neutralizes the magnetic force exerted by the second magnetic circuits N on the mover  302 . As a result, after slight vibration of the mover  302 , part of energy of the mover  302  is rapidly converted through the short-circuited mover coil  3 - 6  into heat that is subsequently dissipated, another part thereof is converted into magnetic energy between the second damping magnet  3 - 102  and the second axially-magnetized damping magnet  3 - 72 , and still another part thereof is converted into elastic potential energy of the second damping leaf spring  3 - 112 . Under the action of the damping braking force, the mover  302  is gradually stopped and drives, with the aid of the shutter actuation arm  2 , the shutter blades  1  simultaneously into the completely open configuration. As such, the braking of the shutter actuation arm  2  by the magnetic damping braking motor is accomplished. The magnetic energy between the second damping magnet  3 - 102  and the second axially-magnetized damping magnet  3 - 72  and the elastic potential energy of the second damping leaf spring  3 - 112  enable the shutter blades  1  to be kept in the open configuration and can serve as an energy source for initializing the closing of the shutter blades  1 . 
         [0050]    Referring to  FIG. 4 b   , t 1  denotes the instant when the magnetically damped shutter device of the present invention starts the braking through short-circuiting, t 1 -t 3  indicates a period of time required for breaking of the magnetically damped shutter device, P represents a curve showing dependence of a magnetic damping force acting on the mover  302  on time, and Z indicates a curve illustrating evolution of an angle of deflection of the shutter blades  1  during their movement over time. In the magnetically damped shutter device of the present invention, during the process of the shutter blades  1  shifting from the closed configuration to the completely open configuration, the angular position of the shutter blades  1  during their opening or closing is dependent on a combination of the Lorentz force from the mover coil  3 - 6  and the magnetic damping forces exerted by the first magnetic circuits M and the second magnetic circuits N. During operation, a current is first applied to drive the mover  302  to accelerate to a maximum speed and then cut off at the instant t 1  when the mover  302  is approaching the end point of its movement. Therefore, the magnetic damping braking motor  3  can accomplish the braking of the mover  302  without requiring a reverse current to decelerate the mover  302 . Compared to the conventional damping-free shutter device, this theoretically allows a 20% reduction in the movement time of the mover  302  at the same acceleration and driving force conditions. From a comparison between the curves W and Z, it can be found that the opening or closing speed of the shutter blades  1  is increased according to the present invention because they manage the completely open configuration early at the instant t 2  and then maintain the configuration. In contrast, according to the curve Z of the conventional device, the shutter blades are completely open at the instant t 3 . Therefore, the magnetic damping braking motor  3  increases the opening or closing speed of the shutter blades  1 . Additionally, the opening or closing process of the shutter blades  1  is made not subject to an open-loop current control. This immunizes motions of the shutter blades  1  from an adverse impact by the control side and enhances the stability of the opening or closing process of the shutter blades  1 . Further, the magnetic damping braking module  303  brakes the opening or closing of the shutter blades  1  by itself, with reduced consumption of time, stable motions of the shutter blades, stable position limitations during the movement, no need for rubber damping rods and capabilities of excellent non-linear damping and rapid braking of the mover  302  moving at a high speed. Furthermore, once the shutter blades  1  have reached the completely open or closed configuration, the magnetic damping braking motor  3  can keep them in the configuration without needing a current supply any more. This shortens the period of time required for current control, reduces dissipated heat, saves energy, mitigates the adverse influence of the control side on motions of the shutter blades  1  and enhances the braking of the shutter blades  1 . 
         [0051]    Various modifications and variations can be made to the present invention by those skilled in the art without departing from the spirit and scope thereof. Accordingly, it is intended that the present invention also includes such modifications and variations if they fall within the scope of the appended claims and the equivalents thereof.