JP2005150759A - Scanning exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure device which can prevent the positional deviation of a mask. <P>SOLUTION: This scanning exposure device which transfers a pattern formed on a mask 12 to a substrate 16 by relatively moving the mask 12 and the substrate 16 in synchronization comprises a mask hold member 18 for placing the mask 12 thereon, a mask stage 20 for moving the mask hold member 18, and pressing means 72, 88a and 88b for pressing the mask 12 against the mask hold member 18. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a scanning exposure apparatus that relatively moves a mask and a photosensitive substrate synchronously.

  A projection exposure apparatus used for manufacturing a semiconductor integrated circuit or a liquid crystal display substrate irradiates a mask with illumination light emitted from an illumination optical system and applies a pattern image of the mask to the photosensitive substrate via the projection optical system. Image on top. Since this type of apparatus exposes a plurality of patterns superimposed on the same region on the substrate, a high overlay accuracy is required between the layer to be exposed and the layer previously exposed.

  Currently, as a projection exposure apparatus, a step-and-scan exposure apparatus that performs exposure while synchronously scanning a mask and a photosensitive substrate with respect to exposure illumination light has been proposed and put into practical use. . In such a step-and-scan exposure apparatus, a mask held by a mask holder is mounted on a movable mask stage, and a photosensitive substrate is mounted on a movable substrate stage. A part of the outer periphery of the mask on the mask stage is fixed to the mask holder by vacuum suction. Then, the transfer pattern formed on the mask is projected onto the photosensitive substrate by moving the mask stage and the substrate stage synchronously. In such a step-and-scan exposure apparatus, it is necessary to move the mask stage with the mask and the substrate stage with the photosensitive substrate mounted at a high speed and increase the acceleration in order to improve the throughput (throughput). It has become.

  However, if the mask stage is driven at a high speed, the position of the mask may be shifted on the mask holder. That is, the mask may slide on the mask holder due to inertial force when the mask stage is accelerated or decelerated. In particular, in the reduction projection type exposure apparatus, the movement distance of the mask is longer than the photosensitive substrate by the reduction magnification, so that the problem of mask misalignment becomes significant. Here, since the position of the mask is measured by, for example, a moving mirror system using an interferometer moving mirror on the mask stage, if the position of the mask is shifted on the mask holder, the position of the mask with respect to the interferometer moving mirror is changed. It will change. Such misalignment of the mask is not only a problem only on the mask stage, but also eventually deteriorates the overlay accuracy of the mask pattern on the photosensitive substrate.

  The present invention has been made in view of the above situation, and an object of the present invention is to prevent misalignment of a mask.

  In order to solve the above problems, a scanning exposure apparatus according to the present invention is a scanning exposure apparatus that transfers a pattern formed on a mask onto a substrate by synchronously moving the mask and the substrate. And a mask holding member movable in the scanning direction, and pressing means for pressing the mask against the mask holding member.

  In the above configuration, a mask stage provided with a mask holding means and a pressing means, and a driving means for moving the mask stage in the scanning direction may be further provided.

  Further, the pressing means may press the mask from a direction perpendicular to the pattern forming surface of the mask.

  Further, the pressing means may press the mask from a direction perpendicular to the direction in which the mask moves.

  You may use together the adsorption | suction means which adsorb | sucks a mask with respect to a mask holding member.

  Further, a sealing means for forming a sealed space between the upper surface of the mask and the mask holding member may be further provided.

  Further, in order to correct an imaging error of the projection image of the mask pattern caused by the deflection of the mask, an adjusting means for adjusting the projection optical system may be further provided.

  The pressing means may include a pressing member provided so as to be able to contact and detach from the upper surface of the mask.

  The pressing means may use magnetic force.

  When the pressing means uses a magnetic force, the pressing means includes a pressing member provided so as to be able to contact and detach from the mask, an electromagnet fixed to the mask holding member, and fixed to the pressing member so as to face the electromagnet. You may comprise so that the permanent magnet arrange | positioned and the control means which controls the magnetism of an electromagnet may be performed so that the mask may be fixed to the mask holding member and released.

  The pressing means may be configured to control the pressing force for pressing the mask.

  According to the present invention, since the mask is pressed against the mask holding member, no displacement occurs even when the mask is driven at high acceleration by the mask stage.

  Hereinafter, embodiments of the present invention will be described based on the following examples. In each of the embodiments described below, the present invention is applied to a scanning projection exposure apparatus for manufacturing a semiconductor device.

  FIG. 1 shows the overall configuration of the projection exposure apparatus according to the first embodiment of the present invention, and FIG. 2 shows the configuration around the reticle stage of the projection exposure apparatus. The projection exposure apparatus of the present embodiment irradiates the reticle 12 with exposure light emitted from the illumination optical system via the condenser lens 10, and generates an image of a predetermined pattern formed on the reticle 12. 14 is transferred onto the wafer 16 via 14. The projection optical system 14 is fixed to the apparatus by a gantry 17 and projects a pattern image of the reticle 12 onto the wafer 16 at a predetermined reduction magnification (1/4, 1/5, etc.). Yes.

  The reticle 12 is placed on the reticle stage 20 in a state of being fixed to the reticle holder 18 by vacuum suction at four locations on the outer periphery thereof. The reticle stage 20 is movable at a predetermined speed in the scanning direction (Y direction) by the reticle stage drive system 24. A movable mirror 28 that reflects the laser beam output from the reticle interferometer 26 is fixedly disposed on the reticle stage 20 so that the position of the reticle stage 20 can be constantly monitored by the reticle interferometer 26. In FIG. 1, only the reticle interferometer 26 and the movable mirror 28 for measuring the position in the scanning direction (Y direction) are shown, but in reality, the interferometer for measuring the position in the non-scanning direction (X direction). And a moving mirror is also provided.

  An aperture glass 30 is attached to the bottom of the reticle holder 18, and the reticle holder 18, the reticle 12, and the aperture glass 30 form a sealed space 32 that is shielded from the outside air below the reticle 12. . The reason why the aperture glass 30 is used to form the sealed space 32 is to transmit illumination light. A vacuum source 36 is connected to the sealed space 32 via a vacuum pipe 34. The reticle 12 can be strongly held by the reticle holder 18 by making the pressure of the sealed space 32 lower than the external pressure by the vacuum source 36. At this time, the reticle 12 may be deformed due to a pressure difference between the sealed space 32 and the outside air. An imaging error of the projection image of the reticle pattern caused by the deformation is caused by the control unit 38 via the lens controller 40. The image is canceled by adjusting the imaging state of the projection optical system 14.

  The wafer 16 disposed below the projection optical system 14 is placed on the wafer stage 44 while being vacuum-sucked by the wafer holder 42. The wafer stage 44 is configured to be movable in a plane (XY plane) perpendicular to the optical axis of the projection optical system 14 by a wafer stage drive system 46 so that the wafer 16 moves in synchronization with the scanning of the reticle 12. Driven by. A movable mirror 50 that reflects the laser light output from the wafer interferometer 48 is fixed on the wafer stage 44, and the reflected light from the movable mirror 50 and a fixed mirror installed at the lower end of the projection optical system 14. The position of the wafer stage 44 can be constantly monitored by interference light consisting of reflected light from (not shown). In FIG. 1, only the wafer interferometer 48 and the movable mirror 50 for measuring the position in the Y direction are shown, but actually, an interferometer and a movable mirror for measuring the position in the X direction are also provided.

  Next, the operation and principle of the first embodiment having the above configuration will be described. When the reticle 12 is illuminated with uniform illumination light collected through the condenser lens 10, the reticle stage 20 moves in the scanning direction (Y direction) relative to the illumination area on the reticle 12, and synchronizes with this. Then, the wafer stage 44 on which the wafer 16 is mounted moves in the direction opposite to the movement direction of the reticle stage 20. At this time, the relative positions of the reticle 12 and the wafer 16 are monitored by the reticle interferometer 26 and the wafer interferometer 48, respectively.

Here, the inertial force at the time of movement of the reticle 12 is Fk, the holding force to the reticle holder 18 by the friction of the reticle 12 is Fh, the mass of the reticle 12 is m, the normal force acting on the reticle 12 is N, and the reticle 12 is moving Is expressed as a, and the friction coefficient between the reticle 12 and the reticle holder 18 is μ, the following equations (1) and (2) are established.
Fk = ma (1)
Fh = Nμ (2)

Further, in order for the reticle 12 not to move with the inertial force at the time of movement, the following equation (3) must be satisfied.
Fk <Fh (3)

Then, the following expression (4) is derived from the above expressions (1), (2), and (3).
a <Nμ / m (4)

Here, since the mass m of the reticle 12 and the friction coefficient μ between the reticle 12 and the reticle holder 18 are substantially constant values, it can be seen that N can be increased in order to increase the acceleration a. . When the reticle 12 is held on the reticle holder 18 by vacuum suction, the following equation (5) is established, where S is the suction area, Po is the external pressure, and Pv is the vacuum pressure.
N = S (Po−Pv) (5)

  In this embodiment, since the air pressure in the sealed space 32 below the reticle 12 is set lower than the external air pressure, the suction surface of the reticle 12 with respect to the reticle holder 18 extends to a wide range including the region where the transfer pattern is formed. Can be enlarged. That is, it can be regarded as equivalent to expanding the adsorption area S to an area slightly smaller than the area of the reticle 12. As a result, it is possible to increase the acceleration a during movement of the reticle 12 from the equations (4) and (5). In addition, since the pattern surface of the reticle 12 is blocked from the outside air, there is an advantage that contamination of the reticle 12 can be prevented.

  FIG. 3 shows the structure around the reticle stage (20) of the projection exposure apparatus according to the second embodiment of the present invention. The configuration other than the vicinity of the reticle stage of the projection exposure apparatus of the present embodiment is the same as that of the first embodiment shown in FIG. 1, and therefore illustration and description thereof are omitted in this embodiment. In FIG. 3, the same or corresponding components as those in the first embodiment are denoted by the same reference numerals, and redundant description is omitted here. In the figure, an aperture glass 30 is disposed in the vicinity of the bottom surface of the reticle holder 18, and a first sealed space 32 is formed by the reticle 12, the reticle holder 18, and the aperture glass 30 as in the first embodiment. A partition wall 54 is provided on the top of the reticle 12, and an aperture glass 56 is installed on the ceiling portion of the partition wall 54. A second sealed space 58 is formed by the upper surface of the reticle 12, the partition wall 54, and the aperture glass 56.

  A vacuum pipe 60 is connected to the first and second sealed spaces 32 and 58, and the air pressure in the first and second sealed spaces 32 and 58 is adjusted to be lower than the external pressure by the vacuum source 36. As a result, the reticle 12 can be strongly held by the reticle holder 18. In this case, the first sealed space 32 on the lower side of the reticle 12 and the sealed space 58 on the upper side of the reticle 12 are connected to each other by the vacuum pipe 60 so that the pressures of the sealed spaces 32 and 58 are the same. It is possible to prevent the reticle 12 from being deformed by the pressure difference between the upper surface and the lower surface of the reticle.

Also in this embodiment, since the air pressure in the upper and lower sealed spaces 32, 58 of the reticle 12 is set lower than the external air pressure, the suction surface of the reticle 12 with respect to the reticle holder 18 includes a wide range including the region where the transfer pattern is formed. Can be expanded to.
That is, it can be regarded as equivalent to expanding the adsorption area S to an area slightly smaller than the area of the reticle 12. As a result, it is possible to increase the acceleration a during movement of the reticle 12 from the equations (4) and (5).

  FIG. 4 shows the structure around the reticle stage (20) of the projection exposure apparatus according to the third embodiment of the present invention. The configuration other than the vicinity of the reticle stage of the projection exposure apparatus of the present embodiment is the same as that of the first embodiment shown in FIG. 1, and therefore illustration and description thereof are omitted in this embodiment. Also, in FIG. 4, the same or corresponding components as those in the first and second embodiments are denoted by the same reference numerals, and redundant description is omitted here. In the drawing, a suction hole (not shown) is formed on the upper surface of a reticle holder 62 on which the reticle 12 is placed, and the reticle 12 is vacuum-sucked by a vacuum source 66 through a vacuum pipe 64. It is designed to be fixed.

The aperture glass 30 is disposed on the bottom surface of the reticle holder 62, and a first sealed space 67 is formed by the reticle 12, the reticle holder 62, and the aperture glass 30 as in the first and second embodiments. . A partition wall 68 is provided on the top of the reticle 12, and an aperture glass 70 is installed on the ceiling portion of the partition wall 68. A second sealed space 72 is formed by the upper surface of the reticle 12, the partition walls 68, and the aperture glass 70. The second sealed space 72 is connected to the compressor 78 via an air pipe 74 and a regulator 76.
Then, the compressor 78 sets the pressure in the first and second sealed spaces 67 and 72 above and below the reticle 12 to be higher than the atmospheric pressure. Accordingly, the reticle 12 is pressed against the reticle holder 62, and the holding force of the reticle 12 on the reticle holder 62 is increased. In this case, the holding force can be controlled by controlling the pressure in the first and second sealed spaces 67 and 72 above and below the reticle 12 using the regulator 76. For example, the air pressure in the second sealed space 72 on the upper side of the reticle 12 is set to be slightly larger than the pressure in the first sealed space 67 on the lower side.

  In the present embodiment, the pressure difference (Po−Pv) is set by setting the air pressure in the upper and lower sealed spaces 67 and 72 of the reticle 12 higher than the external air pressure, and vacuum adsorbing the contact surface between the reticle 12 and the reticle stage 62. ) Can be increased. As a result, it is possible to increase the acceleration a during movement of the reticle 12 from the equations (4) and (5).

  FIG. 5 shows the structure around the reticle stage (20) of the projection exposure apparatus according to the fourth embodiment of the present invention. Since the configuration other than the periphery of the reticle stage of the projection exposure apparatus of the present embodiment is the same as that of the first embodiment shown in FIG. 1, overlapping illustrations and descriptions thereof are omitted in this embodiment. In FIG. 5, the same or corresponding components as those in the first, second and third embodiments are denoted by the same reference numerals. In the figure, electromagnets 82a and 82b are fixedly arranged on both sides of a reticle holder 80 on which the reticle 12 is placed. Support blocks 84a and 84b are installed on the sides of the electromagnets 82a and 82b, respectively.

  Reticle pressing members 88a and 88b are attached to the support blocks 84a and 84b via hinges 86a and 86b, respectively, and permanent magnets 90a and 90b are attached to the lower surfaces of the reticle pressing members 88a and 88b, respectively. The electromagnets 82a and 82b are connected to current supply portions 92a and 92b for generating magnetic force, respectively. When current is supplied from the current supply units 92a and 92b to the electromagnets 82a and 82b under the control of the current control unit 94, a magnetic field is generated above the electromagnets 82a and 82b.

  In the embodiment as described above, the current control unit 94 generates a magnetic force in a direction repelling the permanent magnets 90a and 90b with respect to the electromagnets 82a and 82b when the reticle 12 is replaced. The current supply units 92a and 92b are controlled. The reticle pressing members 88a and 88b are retracted upward by the repulsive force of the electromagnets 82a and 82b and the permanent magnets 90a and 90b. After the reticle 12 is placed on the reticle holder 80 with the reticle pressing members 88a and 88b opened (withdrawn), the permanent magnets 90a and 90b are applied to the electromagnets 82a and 82b by the current control unit 94. The current supply units 92a and 92b are controlled so as to generate a magnetic force in a direction that attracts them. Then, the reticle pressing members 88a and 88b press the reticle 12 against the reticle holder 80 by the attractive force of the electromagnets 82a and 82b and the permanent magnets 90a and 90b. As a result, the reticle 12 is fixed to the reticle holder 80. In this case, the holding force of the reticle 12 can be controlled by adjusting the current value flowing through the electromagnets 82a and 82b. Further, if the distance between the electromagnets 82a and 82b and the permanent magnets 90a and 90b is reduced, a large holding force can be obtained with a small current value.

  In this embodiment, the vertical drag N can be increased by pressing the reticle 12 against the reticle holder 80 by a magnetic force, and the acceleration a during movement of the reticle can be increased from the equation (4).

  As described above, in the present invention, since the mask is pressed against the mask holding member, no positional deviation occurs even when the mask is driven at a high acceleration by the mask stage.

  In addition, when the mask is fixed to the mask holding member by magnetic force, the mask can be strongly fixed to the mask holding member as compared with the conventional case where only a part of the mask is fixed by vacuum suction. . For example, when replacing the mask, the presser member is retracted upward so that the electromagnet and the permanent magnet repel each other. Then, after placing the mask on the mask holding member, the electromagnet and the permanent magnet are attracted to each other, and the pressing member presses the mask against the mask holding member by the attractive force of the electromagnet and the permanent magnet. At this time, the holding force of the mask can be controlled by adjusting the value of the current flowing through the electromagnet.

  As mentioned above, although the Example of this invention was described, this invention is not limited to these Example, In the range which does not deviate from the summary as a technical idea of this invention shown by the claim Can be changed.

FIG. 1 is a conceptual diagram (front view) showing the configuration of the projection exposure apparatus according to the first embodiment of the present invention. FIG. 2 is a front view with a partial cross section showing the configuration around the reticle stage, which is the main part of the first embodiment. FIG. 3 is a front view with a partial cross section showing the configuration around the reticle stage, which is the main part of the second embodiment of the present invention. FIG. 4 is a front view with a partial cross section showing the structure around the reticle stage, which is the main part of the third embodiment of the present invention. FIG. 5 is a front view with a partial cross section showing the structure around the reticle stage, which is the main part of the fourth embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 ... Reticle 14 ... Projection optical system 16 ... Wafer 18, 62, 80 ... Reticle holder 20 ... Reticle stage 30, 56, 70 ... Aperture glass 32 ... Sealed space 34 , 64 ... Vacuum piping 36, 66 ... Vacuum source 38 ... Control unit 40 ... Lens controller 54, 68 ... Partition wall 56 ... Aperture glass 58 ... Second sealed space 60 ..Vacuum piping 67 ... first sealed space 72 ... second sealed space 74 ... air piping 76 ... regulator 78 ... compressors 82a, 82b ... electromagnets 84a, 84b ... block 86a, 86b ... Hinges 88a, 88b ... Reticle holding members 90a, 90b ... Permanent magnets 92a, 92b ... Current supply unit 94 ... Current Control unit

Claims (11)

A scanning exposure apparatus that transfers a pattern formed on the mask to the substrate by relatively moving the mask and the substrate synchronously,
A mask holding member that mounts the mask and is movable in the scanning direction;
And a pressing unit that presses the mask against the mask holding member.   The scanning exposure apparatus according to claim 1, further comprising: a mask stage provided with the mask holding unit and the pressing unit; and a driving unit that moves the mask stage in the scanning direction.   The scanning exposure apparatus according to claim 1, wherein the pressing unit presses the mask from a direction perpendicular to a pattern forming surface of the mask.   4. The scanning exposure apparatus according to claim 3, wherein the pressing means presses the mask from a direction perpendicular to the scanning direction.   5. The scanning exposure apparatus according to claim 1, further comprising suction means for sucking the mask with respect to the mask holding member. 6.   The scanning exposure apparatus according to claim 1, further comprising a sealing unit that forms a sealed space between an upper surface of the mask and the mask holding member. . A projection optical system for transferring the pattern to the substrate;
7. The apparatus according to claim 1, further comprising an adjusting unit that adjusts the projection optical system to correct an imaging error of a projection image of the pattern caused by the deflection of the mask. The scanning exposure apparatus according to one item.   5. The scanning exposure apparatus according to claim 1, wherein the pressing unit includes a pressing member provided so as to be able to contact and detach from the upper surface of the mask. 6. .   The scanning exposure apparatus according to any one of claims 1 to 4, wherein the pressing means uses a magnetic force. The pressing means is
A pressing member provided so as to be able to contact and detach from the mask;
An electromagnet fixed to the mask holding member;
A permanent magnet fixed to the pressing member and disposed opposite the electromagnet;
The scanning exposure apparatus according to claim 9, further comprising a control unit that controls magnetism of the electromagnet so as to fix and release the mask with respect to the mask holding member.   11. The scanning exposure apparatus according to claim 1, wherein the pressing unit can control a pressing force for pressing the mask. 11.

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