JP2007073546A - Exposure method and equipment, and method for manufacturing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure technology capable of forming a fine pattern on the level of the wavelength of illumination light or less inexpensively. <P>SOLUTION: An interference pattern is formed by irradiating two transparent plates P1 and P2, each having a grating formed thereon, with illumination light and a wafer W is exposed by that interference pattern. Holders 36A and 36B are supported movably in a plane parallel with the surface of the wafer W and in the direction perpendicular to that surface, the transparent plate P1 is suction held through air pads 100A and 100B secured to the bottom face of the upper holder 36A, and the transparent plate P2 is suction held through air pads 102A and 102B secured to the bottom face of the lower holder 37A. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an exposure technique used in a fine pattern forming process in an electronic device manufacturing process such as a semiconductor integrated circuit, a flat panel display device, a thin film magnetic head, and a micromachine, and an electronic device manufacturing technique using the exposure technique.

  In forming a fine pattern in a manufacturing process of an electronic device such as a semiconductor integrated circuit, a photolithography technique is generally used. This is a coating process in which a photoresist (photosensitive thin film) is applied to the surface of a processed substrate such as a wafer, and illumination light for exposure having a light amount distribution corresponding to the shape of a pattern to be formed is irradiated onto the processed substrate. A desired pattern is formed on the substrate to be processed by an exposure process, a development process, an etching process, and the like.

  In an exposure process for manufacturing a state-of-the-art electronic device at present, a projection exposure method is mainly used as an exposure method. In this method, a pattern to be formed on a mask such as a reticle is enlarged by 4 times or 5 times, irradiated with illumination light for exposure, and the transmitted light is reduced using a reduction projection optical system. By exposing the substrate to be processed, the pattern is transferred onto the substrate to be processed.

The fineness of the pattern that can be formed by the projection exposure method is determined by the resolution of the reduction projection optical system, which is approximately equal to the value obtained by dividing the exposure wavelength by the numerical aperture (NA) of the projection optical system. Therefore, in order to form a finer circuit pattern, it is necessary to shorten the exposure wavelength or increase the NA of the projection optical system.
On the other hand, for example, as disclosed in Non-Patent Document 1 and Non-Patent Document 2, a plurality of diffracted lights generated by disposing a diffraction grating between a light source and a substrate to be processed and irradiating illumination light on the diffraction grating. Has also been proposed (hereinafter referred to as an interference exposure method) in which a fine pattern is formed on a substrate using a light / dark pattern formed by the interference fringes.
JM Carter et al: "Interference Lithography" http://snl.mit.edu/project_document/SNL-8.pdf Mark L. Schattenburg et al: "Grating Production Methods" http://snl.mit.edu/papers/presentations/2002/MLS-Con-X-2002-07-03.pdf

Of the conventional exposure methods described above, the projection exposure method requires a shorter wavelength exposure light source or a higher NA projection optical system in order to obtain higher resolution.
However, in the current state-of-the-art exposure apparatus, the exposure wavelength is shortened to 193 nm, and further shortening in the future is difficult from the viewpoint of usable lens materials. Further, the NA of the most advanced projection optical system has reached about 0.92, and it is difficult to increase the NA further, and this causes a significant increase in the manufacturing cost of the exposure apparatus.

On the other hand, in the interference exposure method of the conventional exposure methods, in principle, it is possible to realize exposure of a fine pattern having an exposure wavelength or less. However, the conventional method requires a laser light source having high coherence, and has a problem that the holding mechanism of the diffraction grating for forming interference fringes is complicated and the manufacturing cost is increased.
The present invention has been made in view of such a problem, and an object of the present invention is to provide an exposure technique that can form a fine pattern, for example, a pattern having a line width less than or equal to the wavelength of illumination light at low cost.

  Another object of the present invention is to provide a device manufacturing technique using the exposure technique.

The following reference numerals with parentheses attached to some elements of the present invention correspond to the configuration of the embodiment of the present invention. However, each symbol is merely an example of the element, and the element of the present invention is not limited to the configuration of the embodiment.
An exposure method according to the present invention is an exposure method in which a pattern is exposed on a photosensitive object (W) by illumination light from a light source (1), and the light source is included in an illumination optical path of the illumination light from the light source. The first diffraction grating (G11) and the second diffraction grating (G21) are arranged in series from the side, and the object is irradiated with diffracted light from the second diffraction grating, and an interference fringe pattern is exposed on the object. In addition, the substrate (P1, P2) on which at least one of the first diffraction grating and the second diffraction grating is formed is sucked and held from the light source side.

  According to the present invention, when a projection optical system or a light source having high spatial coherence is used by exposing a pattern of interference fringes on the object (substrate to be processed) through two diffraction gratings. Compared to the illumination light wavelength, it is possible to form a fine pattern with a line width equal to or less than the wavelength of the illumination light. In addition, the holding mechanism of the diffraction grating can be simplified by attracting and holding at least one of the substrates on which the diffraction grating is formed from the light source side.

In the present invention, as an example, the first and second diffraction gratings are formed on different surfaces of the same substrate.
As another example, at least one of the different substrates on which the first and second diffraction gratings are respectively formed is sucked and held from the light source side.
Further, a movement limiting member (101A, 103A) may be arranged on the object side of the substrate held by suction. In this case, a notch may be formed at a position corresponding to at least a part of the movement restricting member in the object-side surface of the substrate held by suction.

Further, as an example, the substrate is sucked and held from the light source side at least during its transportation. As another example, the substrate is held by suction from the light source side at least during the exposure of the object.
The device manufacturing method according to the present invention uses the exposure method of the present invention in at least a part of the process of forming a circuit pattern constituting an electronic device.

  Next, the exposure apparatus of the present invention arranges the first diffraction grating (G11) and the second diffraction grating (G21) in series in the illumination light path of the illumination light from the light source (1) in order from the light source side. An exposure apparatus that irradiates a photosensitive object (W) with diffracted light from the second diffraction grating and exposes an interference fringe pattern on the object, at least of the first diffraction grating and the second diffraction grating. One is provided with a suction holding mechanism (100A, 102A) for sucking and holding the substrate on which one is formed from the light source side. According to the present invention, the exposure method of the present invention can be used.

In the present invention, as an example, the suction holding mechanism holds the substrate by vacuum suction.
Further, as an example, a transport mechanism (104, 106) for transporting the substrate into the illumination optical path of illumination light from the light source is further provided, and the suction holding mechanism is included in at least the transport mechanism.

  As another example, the suction holding mechanism is included in a mechanism (36A, 37A) that holds at least the substrate disposed in the illumination optical path.

  According to the present invention, an object is exposed with an interference fringe pattern formed through two diffraction gratings, and at least one of the substrates on which the diffraction gratings are formed is held by suction from the light source side. A fine pattern such as a pattern having a line width less than or equal to the wavelength of illumination light can be formed at low cost.

Hereinafter, an example of a preferred embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a view showing the schematic arrangement of the exposure apparatus of this example. Note that the XYZ coordinate system shown in FIG. 1 is the same as the coordinate systems shown in the following drawings. In FIG. 1, an ArF (argon / fluorine) excimer laser that outputs illumination light IL <b> 1 composed of a pulsed laser beam having a wavelength of 193 nm is used as the light source 1. As the light source 1, a KrF (krypton / fluorine) excimer laser with an oscillation wavelength of 248 nm, an F ₂ (fluorine dimer) laser with an oscillation wavelength of 157 nm, a harmonic laser using a wavelength conversion element, or the like can also be used.

The illumination light IL1 emitted from the light source 1 is converted into a parallel light beam (having a predetermined beam size) by the lenses 2, 3, 4, and 6 constituting the first lens group arranged along the first optical axis AX1. The illumination light IL2 is a parallel beam.
The illumination light IL2 becomes illumination light IL3 set in a predetermined polarization state by the polarization control element 9, and enters the condensing optical system 10 constituting a part of the illumination light uniformizing means. The illumination light IL5 emitted from the condensing optical system 10 is incident on a fly-eye lens 13 as an optical integrator (a homogenizer or a homogenizer) that constitutes a part of the illumination light uniformizing means. An aperture stop 17 is disposed near the exit side surface of the fly-eye lens 13 as necessary.

The details of the illumination light uniformizing means including the condensing optical system 10, the fly-eye lens 13, the aperture stop 17 and the like will be described later.
The illumination light IL7 emitted from the fly-eye lens 13 is incident on the lenses 19, 20, and 21 constituting the second lens group arranged along the second optical axis AX2, and is refracted by these lenses to illuminate. It becomes the light IL8 and reaches the field stop 22 (details will be described later).

  The illumination light transmitted through the field stop 22 is further refracted by the lenses 25, 26, and 27 constituting the third lens group disposed along the second optical axis AX2, and reaches the condensing point. The condensing point 28 is conjugated with one point on the exit-side surface of the fly-eye lens 13 via the second lens group (19, 20, 21) and the third lens group (25, 26, 27). (Imaging relationship).

  The illumination light IL9 that has passed through the condensing point 28 is further refracted by the lenses 29, 30, 32, and 35 constituting the fourth lens group to become the illumination light IL10 and is incident on the first translucent flat plate P1. . In addition, the optical member on the optical path of illumination light IL1-IL10 from the above 1st lens group (2,3,4,5) to 4th lens group (29,30,32,35) is included. The optical system is hereinafter referred to as illumination optical system IS. This illumination optical system IS can also be regarded as an illumination optical device in which the surface on which the first translucent flat plate P1 is disposed is a predetermined irradiation surface.

Hereinafter, the Z-axis is taken along the optical axis AX2 on the emission side of the illumination optical system IS so that the light source 1 side is in the + direction, and the X-axis is set in a direction parallel to the paper surface of FIG. A description will be given taking the Y axis in a direction perpendicular to the paper surface of FIG. In this example, the XY plane including the X axis and the Y axis is substantially parallel to the horizontal plane.
A second translucent flat plate P2 is provided below the first translucent flat plate P1 (−Z direction). The second translucent flat plate P2 is disposed to face a substrate W (hereinafter also referred to as a wafer as appropriate) as an object such as a semiconductor wafer to be processed on which a pattern is to be formed. A first diffraction grating G11 shown in FIG. 2A is formed on the first translucent flat plate P1, and the diffracted light generated when the illumination light IL10 is irradiated onto the first diffraction grating G11. Is irradiated to the second translucent flat plate P2. A second diffraction grating G21 shown in FIG. 2B is formed on the second translucent flat plate P2, and the diffracted light is applied to the second diffraction grating G21. Then, the diffracted light generated by the second diffraction grating G21 is applied to the wafer W, and a light / dark pattern is formed on the wafer W by interference fringes composed of a plurality of diffracted lights. The translucent flat plates P1 and P2 can be regarded as substrates, respectively, and a configuration in which the translucent flat plates P1 and P2 are also used as one substrate is possible (details will be described later).

  In FIG. 1, a photosensitive member PR such as a photoresist for exposing and recording the light and dark pattern is formed on the surface of a wafer W. That is, the wafer W can be regarded as a photosensitive substrate. The wafer W has a disk shape with a diameter of 300 mm as an example, and the first light transmitting flat plate P1 has a disk shape with a diameter that covers the entire surface of the wafer W as an example. Similarly, the second light-transmitting flat plate P2 has a disk shape with a diameter that covers the entire surface of the first light-transmitting flat plate P1 as an example. However, the diameter of the first translucent flat plate P1 is desirably about 30 mm or more larger than the diameter of the wafer W. In this example, the light-transmitting flat plates P1 and P2 are disk-shaped, but the light-transmitting flat plates P1 and P2 may be rectangular flat plates that are large enough to cover the surface of the wafer W.

  The wafer W is held on a wafer stage 38 which is a substrate holding mechanism movable on the wafer base 50 in the X direction and the Y direction, and is movable in the X direction and the Y direction. A wafer stage system is configured to include a drive mechanism such as a wafer stage 38 and a linear motor (not shown). Further, the positions of the wafer W in the X direction and the Y direction are measured by the laser interferometer 40 through the position of the movable mirror 39 provided on the wafer stage 38. That is, the laser beam from the laser interferometer 40 is divided into a measurement beam and a reference beam by a beam splitter (for example, a polarization beam splitter) 90, the measurement beam is irradiated to the movable mirror 39, and the reference beam is column-structured via the mirror. The reference mirror 91 fixed to the body 75 (a reference frame serving as a position reference) is irradiated. Then, the interference light between the measurement beam from the movable mirror 39 and the reference beam from the reference mirror 91 is detected by the laser interferometer 40, so that the position of the wafer stage 38 in the X direction and Y direction with respect to the column structure 75. Can be measured with a resolution of about 1 to 0.1 nm, for example. The laser interferometer 40 actually represents two-axis X-axis laser interferometers 40X1, 40X2 and three-axis Y-axis laser interferometers 40Y1, 40Y2, 40Y3, as shown in FIG. The movable mirror 39 also represents an X-axis movable mirror 39X and a Y-axis movable mirror 39Y.

  In FIG. 1, a wafer mark detection mechanism 43 is disposed above the wafer base 50 in the + X direction. The wafer mark detection mechanism 43 is formed of, for example, an optical microscope and detects the position of an existing circuit pattern or alignment mark formed on the wafer W. The wafer W held on the wafer stage 38 is moved immediately below the wafer mark detection mechanism 43 before exposure as necessary, and the position of the pattern or mark on the wafer W is detected. The measurement beam of the Y-axis laser interferometer 40Y3 in FIG. 6 is set so as to pass through the detection center of the wafer mark detection mechanism 43 in parallel with the Y-axis. It is used to measure the Y coordinate of the wafer stage 38.

  In order to measure the height distribution of the surface of the wafer W, for example, a projection optical system that projects a slit image obliquely to a plurality of measurement points on the surface of the wafer W, and reflected light from the surface of the wafer W are received. And a light receiving optical system that re-images the plurality of slit images, and a predetermined reference plane (hereinafter referred to as a first reference surface) of the plurality of measurement points based on the lateral shift amount of the re-imaged slit images. An oblique incidence type wafer surface position detection system (not shown) that measures the amount of positional deviation in the Z direction from the surface) is disposed in the vicinity of the wafer mark detection mechanism 43, for example. A specific configuration of the oblique incidence type multi-point wafer surface position detection system is disclosed in, for example, Japanese Patent Application Laid-Open No. 05-129182. In the present example, the first reference plane is parallel to the XY plane.

  The wafer stage 38 of this example also incorporates a Z leveling mechanism 38Z that controls the position of the wafer W in the Z direction and the tilt angles (rotation angles) around the X and Y axes. Based on the measurement result, the Z leveling mechanism 38Z causes the average surface of the surface of the wafer W to coincide with the first reference surface when the wafer W is exposed. The Z leveling mechanism 38Z has, for example, a table portion for holding the wafer W, and the height of the table portion in the Z direction with respect to the base portion of the wafer stage 38 at three locations arranged near the apex of the regular triangle. And a drive member to be controlled.

  Further, the translucent flat plate P1 has a substantially U-shaped cross section when viewed in the Y direction and is substantially equal to the bottom surface of the first holder 36A in which a rectangular or circular opening through which illumination light passes is formed in the central portion. It is held by vacuum suction from the light source 1 side through three air pads 100A, 100B, 100C (see FIG. 2A) arranged at angular intervals. Similarly, the translucent flat plate P2 also has three air pads 102A, 102B, and 102C (see FIG. 2B) arranged at substantially equal angular intervals on the bottom surface of the second holder 37A similar to the holder 36A. And is held by vacuum suction from the light source 1 side. Air pads 100A to 100C and 102A to 102C as suction holding mechanisms are each connected to a vacuum pump via a flexible pipe (not shown), and the suction on / off is a main control system for controlling the operation of the entire apparatus. (Not shown). Thus, by holding the translucent flat plates P1 and P2 from the light source 1 side, the mechanism for holding the translucent flat plates P1 and P2 between the illumination optical system IS and the wafer stage 38 can be simplified. .

  2A is a plan view showing the translucent flat plate P1, and FIG. 2B is a plan view showing the translucent flat plate P2. In this example, the air pads 100A to 100C on the translucent flat plate P1 side are shown. The air pads 102A to 102C on the translucent flat plate P2 side are arranged at the same angular positions. However, the air pads 102A to 102C may be arranged so as to be shifted from the air pads 100A to 100C, for example, at approximately the middle position. The translucent flat plates P1 and P2 may be held by electromagnetic adsorption. Further, one of the translucent flat plates P1 and P2 may be placed and held on a holding member arranged on the wafer stage 38 side instead of being attracted from the light source 1 side. Furthermore, the number of the air pads holding the translucent flat plates P1 and P2 is not limited to three, and may be arbitrary, or may be, for example, a ring-shaped air pad facing the entire outer periphery.

  Further, as shown in an enlarged view in FIG. 8, when the suction is turned off on the opposite side of the air pads 100A and 102A holding the translucent flat plates P1 and P2, the translucent flat plates P1 and P2 are in the −Z direction. Covers 101A and 103A as movement restriction members may be provided so as not to move significantly. At this time, in order to make it easier to dispose the covers 101A and 103A, cutout portions P1E and P2E may be provided in regions facing the covers 101A and 103A on the bottom surfaces of the translucent flat plates P1 and P2. The same applies to the other air pads 100B and 100C and 102B and 102C in FIGS. The light-transmitting flat plates P1 and P2 are provided with notches (P1E and P2E) only at a part of the outer periphery (three places in this example). For example, the notches are provided over the entire outer periphery. It may be formed. Further, for example, at least a part of the movement restricting member such as the covers 101A and 103A may be an impact absorbing member, which reliably prevents damage or breakage when the translucent substrates P1 and P2 are dropped due to suction off or the like. You may do it.

  In the case where the light transmitting plate P1 is sucked by the air pads 100A to 100C when the cover 101A or the like is provided, for example, in a method in which the light transmitting flat plate P1 is simply raised from the −Z direction by an arm (not shown), the cover There is a possibility that 101A and the like and the translucent flat plate P1 may interfere mechanically. In order to avoid this, one air pad 100C shown in FIG. 2A is configured to be retracted to the outside by a drive mechanism (not shown) with respect to the holder 36A. With the air pad 100C retracted in this way, the translucent flat plate P1 is raised by the arm, and then the arm is moved in the + Y direction so that the end of the translucent flat plate P1 is the bottom surface of the air pads 100A and 100B. After moving to, the light pad 100A can be adsorbed by the air pads 100A to 100C by moving the air pad 100C in the + Y direction. In order to perform the same operation on the translucent flat plate P2 side, one air pad 102C in FIG. 2B is also configured to be retracted outward with respect to the holder 37A.

  In FIG. 1, the translucent flat plate P2 is arranged in parallel to the XY plane and facing the wafer W at a predetermined interval by a second holding drive mechanism including a holder 37A. Further, the translucent flat plate P1 is arranged in parallel to the XY plane and facing the second translucent flat plate P2 with a predetermined interval by the first holding drive mechanism including the holder 36A. Further, in this example, the portion of the first holder 36A that holds the translucent flat plate P1 via the air pads 100A to 100C is transparent in the X direction via the air pads 102A to 102C of the second holder 37A. It arrange | positions so that it may accommodate in the part holding P2. For this reason, for example, when it is necessary to replace the translucent flat plates P1 and P2, the holders 36A and 37A can be pulled out in the Y direction independently of each other. Accordingly, the holders 36A and 37A in this example include the translucent flat plates P1 and P2 in the illumination light path, the mechanism for holding the translucent flat plates P1 and P2 during exposure, and the mechanism for holding the translucent flat plates P1 and P2 during exposure. It also serves as a holding mechanism.

  In FIG. 1, on the + X direction side of the optical axis AX2, a pair of elongated flat plate-like base members 75A and 75B that are parallel to the XY plane, parallel to the Y axis, and at a predetermined interval in the Z direction are disposed, and the optical axis AX2 A pair of base members 75C and 75D are arranged symmetrically with respect to the base members 75A and 75B and parallel to the Y axis. The upper surfaces of the base members 75A to 75D are each processed into a guide surface with good flatness. The column structure 75 is configured by fixing the ends in the + Y direction and the −Y direction of the base members 75A to 75D with connecting members (not shown).

  Further, both end portions in the X direction of the holder 36A for holding the first light transmitting flat plate P1 are movably mounted on the base members 75A and 75C via flat sliders 36B and 36C, respectively. The holder 36A and the sliders 36B and 36C are connected via three Z-axis actuators 81A capable of controlling the position of the holder 36A in the Z direction and two pins (not shown) for preventing relative rotation. . Accordingly, the holder 36A and the sliders 36B and 36C can be moved integrally in the X direction, the Y direction, and the rotational direction around the Z axis on the upper surfaces of the base members 75A and 75C, and the three Z-axis actuators 81A can By controlling the height, the position in the Z direction of the holder 36A (first translucent flat plate P1) with respect to the base members 75A and 75C and the rotation angles around the X axis and the Y axis can be adjusted.

  Further, the + X direction slider 36B is connected to the slider 77A via two X axis actuators 80A separated in the Y direction, and the slider 77A is driven along a Y axis guide fixed on the base member 75A. It is driven in the Y direction by a motor. By adjusting the drive amount of the two X-axis actuators 80A, the position in the X direction of the holder 36A (first translucent flat plate P1) relative to the base member 75A and the rotation angle around the Z axis are adjusted. Can do. Further, by driving the slider 77A in the Y direction, the holder 36A (first translucent flat plate P1) can be moved greatly in the Y direction in conjunction with it, and the position in the Y direction can be adjusted. .

As a result, the position of the holder 36 </ b> A (first translucent flat plate P <b> 1) in the X direction, Y direction, and Z direction with respect to the column structure 75, and the rotation angle of 6 around the X axis, Y axis, and Z axis are 6. The displacement of the degree of freedom can be adjusted, and the holder 36A (first translucent flat plate P1) is pulled out from the lower side of the illumination optical system IS in the + Y direction as necessary to replace the translucent flat plate P1. Can do.
Further, the position of the holder 36A (first translucent flat plate P1) in the X direction and the Y direction, and the rotation angle around the Z axis are determined by laser interference via the position of the movable mirror 84 provided on the holder 36A. It is measured by a total 82.

  That is, the laser beam from the laser interferometer 82 is split into a measurement beam and a reference beam by the beam splitter 83, the measurement beam is irradiated to the movable mirror 84, and the reference beam is passed through the mirror to the base 75C (column structure 75). The reference mirror 85 fixed to the beam is irradiated. Then, the interference light between the measurement beam from the movable mirror 84 and the reference beam from the reference mirror 85 is detected by the laser interferometer 82, whereby the positions of the holder 36A in the X direction and the Y direction are determined with the column structure 75 as a reference. For example, the measurement can be performed with a resolution of about 1 to 0.1 nm, and the rotation angle around the Z axis of the holder 36A can be measured from the difference between the positions in two Y directions (or in the X direction). For this reason, the laser interferometer 82 is actually composed of one axis in the X direction and two axes in the Y direction, and the movable mirror 84 is also one axis in the X direction and two axes in the Y direction. It is composed of The moving mirror in the Y direction is not limited to two axes. For example, one moving mirror (or a reflecting surface processed on the holder 36A itself) reflects the laser beam from the two-axis laser interferometer. Also good. Alternatively, the X-axis laser interferometer may be two axes and the Y-axis laser interferometer may be one axis.

  Further, if necessary, a plurality of, for example, three laser beams are irradiated obliquely on the upper surface of the translucent flat plate P1 from a laser light source of the first Z position detection system (not shown) and reflected by the upper surface. By detecting the position of the laser beam with a photoelectric detector, the position of the upper surface of the translucent flat plate P1 in the Z direction with respect to a predetermined reference plane (hereinafter referred to as a second reference plane), The rotation angle around the X axis and the Y axis is measured. The second reference plane is parallel to the XY plane.

  As a result, the displacement of the holder 36A (first translucent flat plate P1) in the X direction, the Y direction, and the Z direction, and the six-degree-of-freedom displacement of the rotation angle around the X axis, the Y axis, and the Z axis are measured. By driving the three Z-axis actuators 81A, the two X-axis actuators 80A, and the Y-axis drive motor for the slider 77A based on the measured values, the holder 36A (first translucent flat plate P1) is driven. ) Is controlled to a target state.

  In FIG. 1, as in the case of the first holder 36A, both end portions in the X direction of the second holder 37A that holds the second translucent flat plate P2 are respectively base members via flat sliders 37B and 37C. It is movably mounted on 75B and 75D. The holder 37A and the sliders 37B and 37C are connected via three Z-axis actuators 81B that can control the position of the holder 37A in the Z direction and two pins (not shown) for preventing relative rotation. . The + X direction slider 37B is connected to the slider 77B via two X axis actuators 80B separated in the Y direction, and the slider 77B is driven along a Y axis guide fixed on the base member 75B. It is driven in the Y direction by a motor.

As a result, the position of the holder 37 </ b> A (second translucent flat plate P <b> 2) in the X direction, the Y direction, and the Z direction with respect to the column structure 75 and the rotation angle of 6 around the X axis, Y axis, and Z axis are 6. The displacement of the degree of freedom can be adjusted, and the holder 37A (second translucent flat plate P2) is pulled out from the lower side of the illumination optical system IS in the + Y direction as necessary to replace the translucent flat plate P2. Can do.
Further, the position of the holder 37A (second translucent flat plate P2) in the X and Y directions and the rotation angle around the Z axis are fixed to the base 75D (column structure 75) in the same manner as the holder 36A. The measurement is performed by the laser interferometer 86 through the position of the movable mirror 88 provided on the holder 37A with the reference mirror 89 as a reference.

  In addition to this configuration, for example, by fixing the reference mirror 89 of the laser interferometer 86 to the holder 36A, the X direction between the holder 36A and the holder 37A can be directly adjusted by the laser interferometer 86 without using the laser interferometer 82. The relative positional relationship in the Y direction may be measured. Further, for example, by fixing the reference mirror 91 of the laser interferometer 40 to the holder 37A, the X- and Y-direction relative of the wafer stage 38 and the holder 37A can be directly adjusted by the laser interferometer 86 without using the laser interferometer 86. A general positional relationship may be measured.

  Further, if necessary, a plurality of, for example, three laser beams are obliquely applied to the upper surface of the translucent flat plate P2 from a laser light source of a second Z position detection system (not shown) and reflected by the upper surface. By detecting the position of the laser beam with a photoelectric detector, the position of the upper surface of the translucent flat plate P2 in the Z direction with respect to a predetermined reference surface (hereinafter referred to as a third reference surface), The rotation angle around the X axis and the Y axis is measured. The third reference plane is parallel to the XY plane. In place of the first and second Z position detection systems, a detection system having the same configuration as the oblique incidence type multi-point wafer surface position detection system for measuring the Z position of the wafer W, or Z It is also possible to use a laser interferometer that measures the position in the direction.

  As a result, the displacement of the holder 37A (second translucent flat plate P2) in the X direction, the Y direction, and the Z direction, and the six-degree-of-freedom displacement of the rotation angles around the X, Y, and Z axes are measured. The Then, based on the measured values, the holder 37A (second translucent flat plate) is driven by driving the three Z-axis actuators 81B, the two X-axis actuators 80B, and the Y-axis drive motor for the slider 77B. The displacement of 6 degrees of freedom of P2) is controlled to a target state.

  In this example, each of the first, second, and third reference planes is parallel to the XY plane, and the interval between the first and second reference planes in the Z direction, and the third and first reference planes. The distance between the reference planes in the Z direction is stored in advance in a main control system that controls the operation of the entire apparatus. In this example, the surface of the wafer W is controlled to be parallel to the first reference plane at the time of exposure, and the position of the surface of the wafer W and the second translucent flat plate P2 (second diffraction grating). The relationship and the positional relationship between the first translucent flat plate P1 (first diffraction grating) and the second translucent flat plate P2 are controlled to be a predetermined relationship. Furthermore, as necessary, the surface of the wafer W is controlled so as to be shifted from the first reference plane by a predetermined distance in the Z direction.

Next, a bright and dark pattern of interference fringes formed on the wafer W by the exposure apparatus of this example will be described with reference to FIGS.
A one-dimensional phase modulation type diffraction grating G11 having periodicity in the X direction is formed on the + Z side of the first translucent flat plate P1 in FIG. A one-dimensional phase modulation type diffraction grating G21 having periodicity in the X direction is also formed on the surface of the second translucent flat plate P2 on the + Z side, that is, the first translucent flat plate P1 side. Yes.

First, these diffraction gratings G11 and G21 will be described with reference to FIG.
FIG. 2A is a view of the first light-transmitting flat plate P1 of FIG. 1 as viewed from the + Z side. The surface has a longitudinal direction in the Y direction and is one-dimensional in the X direction perpendicular thereto. A phase-modulation type first diffraction grating G11 having a long period T1 is formed.
The first diffraction grating G11 includes a surface portion of the first light-transmitting flat plate P1 and a dug portion in which the flat plate surface is dug by etching or the like as in a so-called chromeless phase shift reticle (in FIG. 2A). (Shaded part). The depth of the digging portion is set so that a phase difference of approximately 180 degrees is formed between the illumination light transmitted through the surface portion and the illumination light transmitted through the digging portion. When a phase difference of 180 degrees is formed in both illumination lights, the digging depth is set for the wavelength λ of the exposure light, the refractive index n of the first light-transmissive plate P1, and an arbitrary natural number m.
(2m−1) λ / (2 (n−1)) (1)
And it is sufficient.

Moreover, it is preferable that the ratio (duty ratio) of the width between the surface portion and the dug portion is approximately 1: 1. However, values different from 180 degrees and 1: 1 can be adopted for both the phase difference and the duty ratio.
FIG. 2B is a view of the second light-transmitting flat plate P2 of FIG. 1 viewed from the + Z side, and the surface (the surface on the first light-transmitting flat plate P1 side) is long in the Y direction. A second diffraction grating G21 having a direction and a one-dimensional period T2 in the X direction is formed. The structure of the second diffraction grating G21 is the same as that of the first diffraction grating G11 described above.

The first light-transmitting flat plate P1 and the second light-transmitting flat plate P2 are made of synthetic quartz or the like and have a high transmittance (translucency) to ultraviolet rays and a small thermal expansion coefficient (linear expansion coefficient). It is made of a material that has a small thermal deformation accompanying absorption. The thickness is preferably 5 mm or more, for example, in order to prevent deformation such as self-weight deformation. However, in order to further prevent the self-weight deformation and the like, the thickness may be 10 mm or more. In particular, when an F ₂ laser is used as the light source 1, it is preferable to use synthetic quartz to which fluorine is added.

  2A and 2B, for convenience of explanation, the period T1 is represented as about 10% of the diameter (for example, 300 mm or more) of the first translucent flat plate P1. T1 is about 240 nm, for example, and the period T2 is about 120 nm, for example, which is overwhelmingly smaller than the diameter of the first translucent flat plate P1. The same applies to each figure other than FIGS. 2 (A) and 2 (B).

Hereinafter, the principle of forming a bright / dark pattern of interference fringes on the wafer W by irradiating the first diffraction grating G11 and the second diffraction grating G21 with the illumination light IL10 will be described with reference to FIG.
FIG. 3 is a cross-sectional view of the first translucent flat plate P1, the second translucent flat plate P2, and the wafer W arranged to face each other. In FIG. 3, when the illumination light IL10 is irradiated. From the first diffraction grating G11, diffracted light corresponding to the period T1 is generated. If the first diffraction grating G11 is a phase modulation type grating having a duty ratio of 1: 1 and a phase difference of 180 degrees, the generated diffracted light is mainly + 1st order diffracted light LP and −1st order diffracted light LM. However, other orders of diffracted light may be generated.

The diffraction angle θ of the ± first-order diffracted light LP and LM is relative to the wavelength λ of the exposure light (illumination light IL10).
sin θ = λ / T1 (2)
Is the angle represented by
However, this is because ± 1st-order diffracted light LP, LM passes through the first light-transmitting flat plate P1 and is in the air (it may be nitrogen or a rare gas instead. The same applies hereinafter). It is the diffraction angle after ejection. That is, the diffraction angle θ ′ of the ± first-order diffracted light LP, LM in the first light-transmitting flat plate P1 is obtained by using the refractive index n of the first light-transmitting flat plate P1.
sin θ ′ = λ / (n × T1) (3)
Is the angle represented by

Subsequently, the ± first-order diffracted lights LP and LM are incident on the second diffraction grating G21 on the second translucent flat plate P2. Here, since the second diffraction grating G21 is also a phase modulation type diffraction grating as described above, ± first-order diffracted light is mainly generated from the second diffraction grating G21.
In this example, the period T2 of the second diffraction grating G21 satisfies the condition of half the period T1 of the first diffraction grating G11, that is, T1 = 2 × T2. In this case, the −1st order diffracted light LP1 generated by irradiating the second diffraction grating G21 with the + 1st order diffracted light LP is generated with an inclination angle θ with respect to the Z direction and tilted in the −X direction. Further, the + 1st order diffracted light LM1 generated by irradiating the second diffraction grating G21 with the −1st order diffracted light LM is generated tilted in the + X direction with an inclination angle θ with respect to the Z direction. Note that the second diffraction grating T2 = Q × T1 / 2 is used on the assumption that second-order or higher-order (Q order using natural number Q) generated by the second diffraction grating G21 is used. You can also The above equation is generally established when Q is a natural number, and the period of the interference fringes formed has a period of 1 / Q (1 / Q) of the period of the second diffraction grating G21. It will be.

As shown in FIG. 4, the two diffracted lights are irradiated onto the wafer W while maintaining the tilt angle θ with respect to the vertical direction (normal direction) VW of the wafer W, and the wafer W is subjected to light and dark as interference fringes. A pattern IF is formed. At this time, the period (intensity distribution period) T3 of the light / dark pattern IF of the interference fringes formed on the wafer W is:
T3 = λ / (2 × sin θ) (4)
It becomes. This is half of the period T1 of the first diffraction grating G11 and is equal to 1 / Q times the period T2 of the second diffraction grating G21.

The light / dark pattern IF exposes a photosensitive member such as a photoresist PR formed on the surface of the wafer W according to the light / dark, and the light / dark pattern IF is exposed and transferred onto the wafer W.
Accordingly, a bright and dark pattern parallel to the Y direction having a period T3 in the X direction is formed on the entire surface of the wafer W. The light and dark pattern is irradiated and exposed on the photoresist PR formed on the wafer W.

  By the way, when the period T2 of the second diffraction grating G21 is larger than a predetermined value, the + 1st order diffracted light (not shown) is generated by irradiating the second diffraction grating G21 with the + 1st order diffracted light LP, and the −1st order diffracted light. Irradiation to the second diffraction grating G21 of the LM generates −1st order diffracted light (not shown). Such diffracted light reduces the contrast of the light / dark pattern IF as unnecessary diffracted light.

  In this example, in FIG. 3, the first distance L1 between the first diffraction grating G11 and the second diffraction grating G21, and the second distance L2 between the second diffraction grating G21 and the wafer W. As an example, the first-order diffracted light LP, LM emitted from an arbitrary point on the first diffraction grating G11 is set so as to irradiate substantially the same point on the wafer W. As a result, the diffracted light irradiated to each point on the wafer W is ± 1st order diffracted light LP and LM emitted from substantially the same point on the first diffraction grating G11. Interference is high, and interference fringes can be formed with good contrast.

Even in this case, the interference fringes formed via the diffraction gratings G11 and G21 are formed in the vicinity of the second diffraction grating G21 on the opposite side to the first diffraction grating G11, for example, about several mm apart. I can say.
When the distance L2 from the second diffraction grating G21 of the wafer W is set so as to deviate from the reference position as described above, the deviation amount in the Z direction and the incident angle in the X direction of the illumination light IL10. In general, the contrast of the interference fringes IF formed on the wafer W decreases in proportion to the product of the range. Accordingly, in order to form high-contrast interference fringes over the entire surface of the wafer W even if the wafer W has surface irregularities or setting errors, the incident angle range in the X direction of the illumination light IL10 is smaller than a predetermined value. It is desirable.

Next, an example of the illumination light uniformizing means of this example will be described with reference to FIG. The illumination light uniformizing means of this example comprises the condensing optical system 10 and the fly eye lens 13 in FIG.
FIG. 5A shows a fly-eye lens 13, an illumination system rear group lens 35 a that collectively represents the lens system from the lens 19 to the lens 35 in FIG. 1, and translucent plates P 1 and P 2. It is the figure seen from the direction, FIG.5 (B) is the figure seen from the -Y direction. 5A, the fly-eye lens 13 is configured by arranging lens elements F1, F2, F3, F4, F5, F6, F7, and F8 in a line along the Y direction on a light-shielding member. ing. Illumination light IL5 from the condensing optical system 10 of FIG. 1 is applied to the fly-eye lens 13, and the illumination light IL7 emitted from the fly-eye lens 13 is refracted by the illumination system rear group lens 35a and becomes the illumination light IL10. 1 is incident on a translucent flat plate P1.

In this case, you may provide the input optical system which condenses a light beam to several lens element F1-F8 arrange | positioned at the line of the fly eye lens 13. FIG.
At this time, since the fly-eye lens 13 is composed of a plurality of lens elements F1 to F8 arranged in a line along the Y direction, the incident angle characteristic of the illumination light IL10 to the first translucent flat plate P1 is as follows. The X direction and the Y direction are different.

The illumination system rear group lens 35a has an incident-side focal plane that coincides with the exit surface of the fly-eye lens 13, and an exit-side focal plane that coincides with the upper surface (the surface in the + Z direction) of the first translucent flat plate P1. Arranged. Accordingly, the illumination system rear group lens 35a constitutes a so-called Fourier transform lens.
The illumination light IL7 emitted from each lens element of the fly-eye lens 13 is refracted by the illumination system rear group lens 35a, and is irradiated with the illumination light IL10 superimposed on the first translucent flat plate P1. Therefore, the intensity distribution of the illumination light on the first translucent flat plate P1 is made uniform by the averaging effect due to the superposition.

An incident angle range φ in the Y direction of the illumination light IL10 to an arbitrary point IP on the first translucent flat plate P1 is shown in FIG. 5A according to the arrangement of the fly-eye lenses 13 in the Y direction. It becomes such a predetermined value.
On the other hand, since the fly-eye lens 13 has only one row in the X direction, the incident angle range in the X direction can be set to a predetermined value or less. Therefore, the incident angle distribution of the illumination light IL10 at one point IP can be set such that the incident angle range in the X direction is smaller than the incident angle range in the Y direction. The incident angle range in the X direction can be set to a predetermined value or less, and the incident angle range in the Y direction can be set to a predetermined value or more.

  Further, if necessary, the illumination light is provided by providing an aperture stop 17 having a slit-shaped opening 18 that is long in the Y direction and narrow in the X direction as shown in FIG. The incident angle range of the IL 10 in the X direction can be further limited. Note that, by adjusting the length of the opening 18 in the longitudinal direction (Y direction), the incident angle range in the Y direction of the illumination light IL10 to the one point IP on the first translucent flat plate P1 can be made variable. it can. Further, the aperture stop 17 can be provided at the position of the condensing point 28 in FIG. 1 which is conjugate with the exit surface of the fly-eye lens 13.

  By the way, when the interference fringe light / dark pattern IF having a one-dimensional period is formed, the polarization direction (electric field direction) of the illumination light IL10 used for the formation is parallel to the longitudinal direction of the light / dark pattern IF. The linearly polarized light is preferably parallel to the longitudinal direction of the diffraction grating G11 and the second diffraction grating G21. This is because the contrast of the interference fringe IF can be maximized in this case.

However, even if the illumination light IL10 is not perfect linearly polarized light, it may be illumination light in which the electric field component in the longitudinal direction (Y direction) of the first diffraction grating G11 is larger than the electric field component in the periodic direction (X direction). Thus, the above-described contrast improvement effect can be obtained.
Such polarization characteristics of the illumination light IL10 are realized by the polarization control element 9 provided in the illumination optical system of FIG. The polarization control element 9 is, for example, a polarization filter (polaroid plate) or a polarization beam splitter that is rotatably provided with the optical axis AX1 as the rotation axis direction, and the polarization direction of the illumination light IL3 is changed to a predetermined linear polarization by the rotation. be able to.

  When the light source 1 is a light source that emits illumination light IL1 polarized in substantially linear polarization, such as a laser, a half-wave plate that is also rotatably provided can be used as the polarization control element 9. It is also possible to employ two quarter-wave plates provided in series so as to be independently rotatable. In this case, the polarization states of the illumination lights IL3 to IL10 can be not only substantially linearly polarized light but also circularly polarized light and elliptically polarized light.

Note that a pattern has already been formed in the previous exposure process (photolithography process) on the wafer W to be exposed by the exposure apparatus. In the new exposure process, the pattern is kept in a predetermined positional relationship. Generally, it is necessary to form.
In many cases, the existing pattern on the wafer W has a certain degree of expansion and contraction compared to the design value due to thermal deformation and stress deformation accompanying the film forming process and etching process on the wafer W. Therefore, the exposure apparatus is required to be applied to such expansion / contraction of the wafer W to form a new pattern on the wafer W by correcting the expansion / contraction to some extent.

In the exposure apparatus of this example, the wafer W is changed by changing either the Z position of the wafer W set by the Z leveling mechanism 38Z (height control apparatus), the convergence / divergence state of the illumination light IL10, or both. Expansion / contraction correction of the light / dark pattern formed on W can be performed.
In the exposure apparatus of the present example, as shown in FIG. 1, among the lenses 29, 30, 32, and 35 constituting the fourth lens group in the illumination optical system IS, the negative lens 30 has a lens driving mechanism. Reference numerals 31a and 31b are attached, and lens drive mechanisms 33a and 33b are attached to the positive lens 32. These lens driving mechanisms 31a, 31b, 33a, and 33b are movable in the Z direction on the fixed shafts 34a and 34b, whereby the lens 30 and the lens 32 are also independently movable in the Z direction.

  That is, the fourth lens group 29, 30, 32, 35 constitutes a so-called inner focus lens as a whole, and its focal length or focal position is variable. By controlling the focal lengths or focal positions of the fourth lens groups 29, 30, 32, and 35 with the lens driving mechanisms 31a, 31b, 33a, and 33b, the convergence / divergence state of the illumination light IL10 can be made variable. it can. In addition to this, a Z position adjusting mechanism is also provided for the first lens groups 2, 3, 4, and 6 of the illumination optical system IS, and together with the fourth lens groups 29, 30, 32, and 35, The convergence / divergence state of the illumination light IL10 may be variable.

  For this purpose, as shown in FIG. 1, lens driving mechanisms 5a and 5b are attached to the negative lens 4 in the first lens group 2, 3, 4 and 6, and the lens driving mechanisms 7a and 5a are attached to the positive lens 6. 7b is attached. These lens driving mechanisms 5a, 5b, 7a and 7b are movable in the Z direction on the fixed shafts 8a and 8b, whereby the lens 4 and the lens 6 can be independently moved in the Z direction. it can.

  These expansion / contraction corrections are performed in advance by measuring the positions of existing circuit patterns or alignment marks formed at a plurality of locations on the wafer W by the wafer mark detection mechanism 43 prior to exposure of the wafer W. It is desirable to carry out based on the amount of expansion / contraction. The exposure apparatus also includes a Y-axis laser interference that is a detection mechanism that enables the position measurement of the wafer stage 38 at the position of the wafer mark detection mechanism 43 in order to improve the position measurement accuracy by the wafer mark detection mechanism 43. It is desirable to provide a total of 40Y3 (see FIG. 6).

  Next, an example of the exposure method of this example will be described. In this example, the area of the illumination light IL10 irradiated to the first translucent flat plate P1 in FIG. 1 is a circular area covering the wafer W or an illumination area 42 smaller than the wafer W as shown in FIG. Either is possible. The width of the latter illumination area 42 in the X direction is larger than the diameter of the wafer W. When such a small illumination area 42 is used, exposure is performed by scanning the wafer W in the longitudinal direction of the interference fringes, that is, in a direction substantially parallel to the Y direction, with respect to the illumination areas 42 where the interference fringes are formed. There is a need.

  6 is a view of the wafer stage 38 of FIG. 1 as viewed from the lens 35 side, and the exposure to the wafer W is performed by the light source 1, the illumination optical system IS, the first light-transmitting flat plate P1, FIG. As shown in FIG. 6, the wafer W is scanned by the wafer stage 38 in a direction substantially parallel to the Y direction with respect to the second translucent flat plate P2. As described above, the illumination light IL10, the first diffraction grating G11 on the first translucent flat plate P1, and the second diffraction grating G21 on the second translucent flat plate P2 are placed on the wafer W in the X direction. Since the bright and dark pattern of the interference fringes having the periodic direction in the longitudinal direction and the longitudinal direction in the Y direction is formed, the scanning in the Y direction is performed along the longitudinal direction of the bright and dark pattern of the interference fringes.

  In the scanning exposure, the position of the wafer W (wafer stage 38) in the X direction and the Y direction and the rotation angle about the Z axis as the rotation center are set on the X axis movable mirror 39X and the Y axis provided on the wafer stage 38. It is measured using the X-axis laser interferometers 40X1 and 40X2 and the Y-axis laser interferometers 40Y1 and 40Y2 via the movable mirror 39Y, and the measured position and rotation angle are measured by a stage control mechanism (not shown). Be controlled.

By such scanning exposure, the wafer W is exposed by integrating the bright and dark patterns of interference fringes formed by the first diffraction grating G11 and the second diffraction grating G21 in a stage running direction substantially parallel to the Y direction. As a result, the effects of these diffraction grating defects and foreign matter are alleviated, and a good pattern without defects is exposed on the wafer W.
Note that the positional deviation and rotational deviation in the X and Y directions between the bright and dark patterns of interference fringes and the wafer W generated during scanning exposure are measured by the laser interferometers at the positions of the transmissive plates P1, P2 and the wafer stage 38 described above. Based on the result, correction is made by the movement of at least one of the first and second transparent flat plates P1 and P2 and the wafer W.

  In addition, the illuminance non-uniformity that may remain in the illumination region 42 is also accumulated and averaged substantially in the Y direction, so that substantially higher uniformity can be realized. Further, the shape of the illumination area 42 may be such that the width in the Y direction changes depending on the position in the X direction. This is because, by changing the shape of the illumination area 42 itself, the integrated value in the generally Y direction of the illumination light illuminance distribution in the illumination area 42 can be made more uniform.

The shape of the illumination area 42 can be determined by the shape of the opening provided in the field stop 22 in the illumination optical system IS of FIG. The field stop 22 may be disposed in the vicinity of the light source side of the first light-transmitting substrate P1.
Further, as shown in FIG. 7, it is also possible to use an illumination area 42a that is smaller in both the X direction and the Y direction with respect to the size of the wafer W. In FIG. 7, the illumination area 42 a is an elongated area in the X direction, and the width in the Y direction at both ends in the X direction is narrowed outward in a substantially linear manner. In this case, in order to expose the entire surface of the wafer W in the illumination area 42a, as shown by the locus 45 of the center of the illumination area 42a in FIG. 7, as an example, the wafer W and the illumination area 42a are relatively moved in the Y direction. It is necessary to repeat an operation of moving and exposing (scanning exposure) and an operation of moving the wafer W and the illumination area 42a relative to each other in the X direction (step moving operation). At that time, in the adjacent rows, the relative movement direction between the wafer W and the illumination region 42a is reversed, and in order to reduce the joint error between the adjacent rows, the end portions of the illumination regions 42a in a certain row Then, exposure is performed so that the end of the illumination area 42a in the adjacent row overlaps.

  Actually, the illumination area 42a is fixed, and the wafer W moves in the X direction and the Y direction with respect to the illumination area 42a by driving the wafer stage 38. In FIG. It represents that the illumination area | region 42a moves with respect to. It is to be noted that the illumination area 42 can be set to a large field of view that covers the entire surface of the wafer W by enlarging the lenses constituting the illumination optical system IS as necessary and widening the opening of the field stop 22. In this case, the light and dark patterns of the interference fringes can be collectively exposed on the entire surface of the wafer W without performing the scanning exposure.

  If the exposure on the wafer W is a superposition exposure, it is necessary to previously align the bright and dark pattern of the interference fringes with the circuit pattern formed on the wafer W in the steps so far. Therefore, an interference fringe measurement system 41 for measuring the position of the interference fringes formed by the diffraction gratings G11 and G21 in FIG. 2 is also provided on the wafer stage 38 in FIG.

In the above embodiment, as shown in FIG. 2, the light-transmitting flat plates P1 and P2 on which the diffraction gratings G11 and G21 are formed are held by the air pads at three locations. As shown in the example, the number and arrangement of the air pads are arbitrary.
FIG. 9A shows a configuration in which the translucent flat plate P1 is sucked and held via the four air pads 100A, 100B, 100C, and 100D arranged on the bottom surface of the holder 36A at intervals of about 90 degrees. In (A), one air pad 100C is configured to be retracted to the outside. In this case, it goes without saying that the number of air pads holding the translucent flat plate P1 may be different from the number of air pads holding the translucent flat plate P2.

Moreover, in said embodiment, although the conveyance mechanism of translucent flat plate P1, P2 and the holding mechanism at the time of exposure were common, you may isolate | separate them.
FIG. 10 is a diagram showing a main part of the structure in which the transport mechanism and the holding mechanism at the time of exposure are separated as described above. In FIG. 10 in which parts corresponding to those in FIG. A translucent flat plate P1 is adsorbed and held thereon, and a transport arm 106 (transport mechanism) having air pads 107B and 107D (which are a part of four air pads) fixed to the upper surface of the end of the translucent flat plate P1. They are arranged so as to be movable within a predetermined range in the Y direction and the Z direction. Similarly, the translucent flat plate P2 is sucked and held on the holder 37A, and the air arms 105B and 105D (which are a part of four air pads) are fixed to the upper surface of the end of the translucent flat plate P2. The (conveyance mechanism) is arranged in a state where it can move within a predetermined range in the Y direction and the Z direction. Diffraction gratings G11 and G21 shown in FIGS. 2A and 2B are formed on the translucent flat plates P1 and P2, respectively.

  The holders 36A and 37A of this example are formed with circular openings smaller than the diameters of the light-transmitting flat plates P1 and P2, and a suction part for vacuum suction or electromagnetic suction is formed in the vicinity of the openings. The translucent flat plates P1 and P2 are adsorbed and held by the adsorbing portion during exposure. Further, since the holders 36A and 37A can be pulled out in the + Y direction, the transfer arms 104 and 106 are actually arranged at positions deviated in the + Y direction with respect to the optical path of the illumination light IL10.

  In this example, when the translucent flat plate P1 sucked and held by the transport arm 106 via the air pads 107B and 107D is passed to the holder 36A, the holder 36A is pulled out to the bottom surface side of the transport arm 106 in the + Y direction. In this state, the transfer arm 106 is gradually lowered. Then, after the translucent flat plate P1 is placed on the holder 36A (the state shown in FIG. 10), the suction of the air pads 107B, 107D, etc. is turned off and the transfer arm 106 is raised to turn on the suction on the holder 36A side. By doing so, the translucent flat plate P1 is delivered to the holder 36A side. Then, the translucent flat plate P1 is disposed on the optical path of the illumination light IL10 by moving the holder 36A to the front. When passing the translucent flat plate P1 from the holder 36A to the transfer arm 106, the reverse operation may be performed. Similarly, the translucent flat plate P2 can be transferred between the transfer arm 104 and the holder 37A.

  As described above, in the example of FIG. 10, the transport mechanism and the mechanism for holding the light-transmitting flat plates P1 and P2 at the time of exposure are separated, so that the light-transmitting flat plates P1 and P2 (diffraction gratings G11 and G21) are disposed at the time of exposure. The holding mechanism can be downsized. Further, since the translucent flat plates P1 and P2 are attracted and held downward (from the light source 1 side in FIG. 1) in the transport mechanism, the structure of the transport mechanism can be simplified and miniaturized, and the entire exposure apparatus. The manufacturing cost can be reduced.

In addition, although translucent flat plate P1 and P2 of said embodiment were circular, those shapes may be any shapes, such as a rectangle, as shown in the example of FIG. 9 (B).
FIG. 9B shows a second translucent flat plate P2A placed on the second holder 37A of FIG. 1, and in FIG. 9B, there is no figure on the rectangular translucent flat plate P2A. The same diffraction grating G21 as 2 (B) is formed. In this example, both end portions of the translucent flat plate P2A in the Y direction are positioned above the side portions 37Ac and 37Ab sandwiching the opening 37Aa of the holder 37A in the Y direction. A suction part of a vacuum suction or electromagnetic suction method for sucking and holding the substrate from the bottom side is formed. Further, a transfer arm 104 (transfer mechanism) is disposed above the holder 37A, and the translucent flat plate P2A is attached by air pads 105A, 105B and 105C, 105D fixed to the bottom surfaces of the two arm portions 104Aa and 104Aa of the transfer arm 104. Adsorption can be held. In other words, in this example, the suction part (air pads 105A to 105D) of the transfer arm 104 and the suction part of the holder 37A are arranged so as to be orthogonal to each other.

  In the example of FIG. 9B, the transfer arm 104 is movable in a predetermined range in the Y direction and the Z direction. When transferring the translucent flat plate P2A from the holder 37A to the transfer arm 104, the transfer arm 104 is moved. Moving from the + Y direction to above the holder 37A, the suction on the holder 37A side is turned off. Then, after the transport arm 104 is gradually lowered and the air pads 105A to 105D come into contact with the translucent flat plate P2A, the transport arm 104 is stopped and suction is turned on, and then the transport arm 104 is raised and then the + Y direction What is necessary is just to move to the storage (not shown) side. When transferring the translucent flat plate P2A from the transfer arm 104 to the holder 37A, the reverse operation may be performed.

In this way, in the example of FIG. 9B as well, the transport mechanism and the mechanism that holds the translucent flat plate P2A at the time of exposure are separated, so the mechanism that holds the translucent flat plate P2A (diffraction grating G21) at the time of exposure. Can be miniaturized, and the structure of the transport mechanism that holds the translucent flat plate P2A by suction can be simplified and miniaturized.
In the example of FIG. 1, the first diffraction grating G11 and the second diffraction grating G21 are each a phase modulation type diffraction grating, but the configuration of both diffraction gratings is not limited to this. For example, any of the diffraction gratings may be a diffraction grating that modulates both the phase and intensity of transmitted light, such as a halftone phase shift reticle. Further, the first diffraction grating may be a phase modulation type diffraction grating, and the second diffraction grating may be an intensity modulation type diffraction grating.

  FIG. 11 is a diagram illustrating the first light-transmitting flat plate P1 on the surface on the + Z direction side (light source side) formed with phase modulation type first diffraction gratings G11 and G12 having a period T1 in the X direction. This shows a case where an intensity-modulated second diffraction grating G21A having a period T2 (here, equal to T1 / 2) is formed on the −Z direction side (wafer W side) of the second translucent flat plate P2. Also in the example of FIG. 11, the translucent flat plates P1 and P2 are sucked and held from the light source 1 side through the air pads 100A to 100C and 102A to 102C, respectively, as in the example of FIG.

Hereinafter, the principle that the bright and dark patterns of interference fringes are formed on the wafer W by irradiating the first diffraction gratings G11 and G12 and the second diffraction grating G21A with the illumination light IL10 will be described with reference to FIG.
In FIG. 11, when the illumination light IL10 is irradiated, diffracted light corresponding to the period T1 is generated from the first diffraction gratings G11 and G12. If the first diffraction gratings G11 and G12 are phase modulation type gratings having a duty ratio of 1: 1 and a phase difference of 180 degrees, the 0th-order diffracted light disappears and does not occur. In this case, two diffracted lights of ± 1st order light are mainly generated, but there is a possibility that higher order diffracted lights such as ± 2nd order light are also generated.

  However, when the period T1 is shorter than three times the effective wavelength λ of the illumination light, the third-order or higher-order diffracted light cannot be generated. Further, if the phase modulation type grating has a duty ratio of 1: 1 and a phase difference of 180 degrees as described above, no second-order diffracted light can be generated. Therefore, in this case, only two of the + 1st order diffracted light LP and the −1st order diffracted light LM are generated from the first diffraction gratings G11 and G12, and pass through the first translucent flat plate P1 to obtain the second. 2 is incident on the translucent flat plate P2. Subsequently, the + 1st order diffracted light LP and the −1st order diffracted light LM are applied to the second diffraction grating G21A provided on the wafer W side surface of the second translucent flat plate P2. Since both diffracted lights are symmetrical, only the + 1st order diffracted light LP will be described below.

  The + 1st-order diffracted light LP is inclined by a predetermined angle from a direction perpendicular to the second diffraction grating G21A (normal direction) by the period T1 of the first diffraction gratings G11 and G12, and enters the second diffraction grating G21A. Incident. When the + 1st order diffracted light LP is irradiated onto the second diffraction grating G21A, diffracted light is also generated from the second diffraction grating G21A. Since the second diffraction grating G21A is an intensity modulation type diffraction grating, the diffracted light is diffracted light including zeroth-order light.

Here, the angle direction in which each diffracted light is generated is inclined according to the inclination of the incident angle of the illuminating illumination light (+ 1st order diffracted light LP). That is, the second diffraction grating G21A is diffracted according to the zero-order diffracted light LP0 traveling in the direction parallel to the irradiated + 1st-order diffracted light LP and the X-direction period T2 of the second diffraction grating G21A. First-order diffracted light LP1 is generated.
If the period T2 of the second diffraction grating G21A is larger than a predetermined value determined by the relationship between the period T1 and the effective wavelength, + 1st order diffracted light (not shown) may also be generated. However, by setting the period T2 to be equal to or less than the effective wavelength of the illumination light, it is possible to substantially prevent the generation of + 1st order diffracted light (not shown).

As a result, two diffracted lights of 0th-order diffracted light LP0 and −1st-order diffracted light LP1 are irradiated on the wafer W, and a light / dark pattern of interference fringes is formed by interference of these diffracted lights.
In the configuration of FIG. 11, as an example, the distance D2 between the second diffraction grating G21A and the surface of the wafer W is set to the distance D1 between the first diffraction grating G11, G12 and the second diffraction grating G21A. Set small.

In the above example, the first diffraction grating G11 (or G11, G12) and the second diffraction grating G21 (or G21A) are formed on different translucent flat plates, respectively. Both diffraction gratings can also be formed on the same translucent flat plate.
FIG. 12 is a diagram showing an example in which the first diffraction grating G13 and the second diffraction grating G14 are formed on the light source side and the wafer W side of one translucent flat plate P3, respectively. Also in this example, the structure and manufacturing method of each diffraction grating are the same as those in the above example. The lens 35 and the illumination optical system upstream thereof are the same as in the example of FIG. 1, and the translucent flat plate P3 is air pads 100A and 100B fixed to the holder 36A in the same manner as the translucent flat plate P1 of FIG. Is held by suction from the light source 1 side and held during conveyance and exposure by the holder 36A.

  Note that the translucent flat plate P4 in FIG. 12 is provided to prevent contamination of the second diffraction grating G14 and to make the first distance L1 and the second distance L2 substantially equal. Further, as an example, it is possible to hold the translucent flat plate P4 together with the translucent flat plate P3 by the holder 36A of FIG. 1, and in this case, the holder 37A and the holding drive mechanism of FIG. Is possible. It is also possible to form a light / dark pattern of interference fringes of higher-order diffracted light of ± 2nd order or higher and 0th-order light.

Further, the first diffraction grating and the second diffraction grating are not limited to those provided only on the surface of the translucent flat plate.
In the above example, air is present between the second translucent flat plate P2 and the wafer W, but instead, a predetermined dielectric may be filled. Thereby, the substantial wavelength of the illumination light (diffracted light) irradiated to the wafer W can be reduced by the refractive index of the dielectric, and the period of the bright and dark pattern of the interference fringes formed on the wafer W. It becomes possible to further reduce T3. For this purpose, it goes without saying that the period T2 of the second diffraction grating G21 and the period T1 of the first diffraction grating G11 also need to be reduced in proportion thereto.

  FIG. 13A is a diagram showing an example of a wafer stage 38a and the like suitable for this. Continuous side walls 38b and 38c are provided around the wafer stage 38a, and a liquid 56 such as water can be held in a portion surrounded by the side walls 38b and 38c. As a result, the space between the wafer W and the second translucent flat plate P2 held on the holder 37A via the air pads 102A, 102B and the like is filled with water, and the wavelength of the illumination light is the refractive index of water (wavelength 193 nm). Is reduced by 1.46).

A water supply mechanism 54 and a drainage mechanism 55 are also provided so that a clean liquid without contamination is supplied to and discharged from a portion surrounded by the side walls 38b and 38c.
Further, as shown in FIG. 13B, the uppermost surfaces of the side walls 38d and 38e of the wafer stage 38a are made higher than the lower surface of the first translucent flat plate P1, and are held by the holder 36A via the air pads 100A and 100B. The space between the first translucent flat plate P1 and the second translucent flat plate P2 held by the holder 37A via the air pads 102A, 102B, etc. can be filled with liquid. The functions of the liquid supply mechanism 54a and the drainage mechanism 55b are the same as described above.

As a result, the entire optical path from the first diffraction grating G11 to the wafer W can be covered with a dielectric other than air, and the effective wavelength λ of the illumination light can be reduced by the amount of refraction of the liquid. It becomes. As a result, a pattern having a finer period can be exposed.
Needless to say, the dielectric filled between the second translucent flat plate P2 and the wafer W is not limited to water but may be another dielectric liquid. In that case, the refractive index of the dielectric liquid is preferably 1.2 or more from the viewpoint of reducing the period of the bright and dark pattern of interference fringes.

  13A and 13B, the wafer W is disposed in the liquid, but includes at least an interference fringe pattern formation region between the second transparent flat plate P2 and the wafer W. The supply and discharge may be performed so that the predetermined area is filled with the liquid. At this time, particularly in the scanning exposure apparatus, the liquid may flow along the scanning direction at the time of scanning exposure, and the height of the surface of a predetermined region surrounding the wafer W on the wafer stage 38 is set to the surface of the wafer W. It is preferable to make them substantially coincide. Further, a predetermined area including at least the passage area of the illumination light IL10 may be filled with the liquid between the first and second transmissive flat plates P1 and P2, and in the scanning exposure apparatus, in particular, along the scanning direction. The liquid may flow. At this time, the liquid may be supplied and discharged between the first and second permeable flat plates P1 and P2 independently of the space between the second permeable flat plate P2 and the wafer W.

  In the exposure apparatus of this example, various translucent flat plates are arranged close to each other along the optical path, and there is a risk of adverse effects due to multiple interference accompanying surface reflection on each surface. Therefore, in this example, as the illumination lights IL1 to IL10 from the light source 1 in FIG. 1, light whose temporal coherence distance (coherence distance in the light traveling direction) is 100 [μm] or less is used. It is preferable to do. Thereby, it is possible to avoid generation of unnecessary interference fringes due to multiple interference.

The temporal coherence distance of light is a distance approximately represented by λ ² / Δλ, where λ is the wavelength of the light and Δλ is the half-value width of the wavelength distribution of the light. Therefore, when the exposure wavelength λ is 193 nm from the ArF laser, it is desirable to use the illumination light IL1 to IL10 whose wavelength half width Δλ is about 370 pm or more.
Moreover, it is desirable to use illumination light of 200 [nm] or less as the wavelengths of the illumination lights IL1 to IL10 in order to obtain a finer interference fringe pattern IF.

  In the above embodiment, for example, the movable mirrors 39, 89, 84 such as the laser interferometers 40, 86, 82 in FIG. 1 are fixed to the wafer stage 38 and the holders 36A, 37A as independent members. Instead of using the movable mirror, the side surface of the upper end portion of the wafer stage 38 and the side surfaces of the holders 36A and 37A themselves may be mirror-finished, and these mirror-finished reflecting surfaces may be used as the movable mirror. The same applies to the reference mirrors 91, 89, and 85.

In addition, the configuration of the exposure apparatus (in particular, the illumination optical system IS and the transmissive flat plates P1 and P2) for forming the interference fringe pattern is not limited to the above embodiment, and the exposure apparatus of the interference exposure system for forming the interference fringe pattern. Then, the present invention can be applied.
The wafer W having the light and dark pattern exposed by the interference fringes as described above is transferred to the outside of the exposure apparatus by a wafer loader (not shown) and is transferred to the developing apparatus. By development, a resist pattern corresponding to the exposed light and dark pattern is formed on the photoresist on the wafer W. In the etching apparatus, a predetermined pattern is formed on the wafer W by etching the wafer W or a predetermined film formed on the wafer W using the resist pattern as an etching mask.

A manufacturing process of an electronic device such as a semiconductor integrated circuit, a flat panel display, a thin film magnetic head, or a micromachine includes a process of forming the fine pattern as described above over a plurality of layers. An electronic device can be manufactured by using the above-described exposure method by the exposure apparatus of the present invention in at least one of such multiple pattern forming steps.
In addition, in the at least one step, a pattern having a predetermined shape is formed by a general projection exposure apparatus on the photoresist PR on the wafer W that has been exposed to the bright and dark pattern by the interference fringes using the exposure method by the exposure apparatus of the present invention. And the pattern formation can be performed by developing the photoresist PR subjected to the synthetic exposure.

  In addition, this invention is not limited to the above-mentioned embodiment, Of course, a various structure can be taken in the range which does not deviate from the summary of this invention.

  The exposure method and apparatus of the present invention can be used in the manufacturing process of electronic devices such as semiconductor integrated circuits, flat panel displays, thin film magnetic heads, and micromachines.

1 is a partially cutaway view showing a schematic configuration of an exposure apparatus as an example of an embodiment of the present invention. (A) shows the first diffraction grating G11 formed on the first translucent flat plate P1, and (B) shows the second diffraction grating G21 formed on the second translucent flat plate P2. FIG. It is sectional drawing which shows the positional relationship of the 1st diffraction grating G11, the 2nd diffraction grating G21, and the wafer W, and the diffracted light LP, LM, LM1, LP1. 3 is a cross-sectional view showing an intensity distribution of interference fringes formed on a wafer W. FIG. (A) is a side view of the incident angle range of illumination light on the first light-transmitting flat plate as viewed from the + X direction, (B) is a side view of the incident angle range from the -Y direction, and (C) is the aperture stop 17. FIG. It is a top view which shows an example of the illumination area of the interference fringe in embodiment of this invention. It is a top view which shows another example of the illumination area of the interference fringe in embodiment of this invention. It is an enlarged view of the principal part which shows the structural example which provides a cover in the bottom face side of the translucent flat plates P1 and P2 of FIG. (A) is a top view which shows another arrangement | positioning of the several air pad which adsorbs and holds the translucent flat plate P1, (B) is a top view which shows the principal part of the conveyance mechanism and holding mechanism of a rectangular translucent flat plate P2A. is there. It is the figure which notched the part which shows the principal part of the conveyance mechanism and holding mechanism of the translucent flat plates P1 and P2 of the other example of embodiment of this invention. It is sectional drawing which shows the positional relationship of 1st diffraction grating G11, G12, 2nd diffraction grating G21A, and wafer W in the other example of embodiment of this invention. It is a figure which shows the state which provided the 1st diffraction grating G13 and the 2nd diffraction grating G14 on each of both surfaces of the translucent flat plate P3. (A) is explanatory drawing of the mechanism with which a liquid is filled only between the wafer W and the 2nd translucent flat plate P2, (B) is also liquid also between the translucent flat plate P2 and the translucent flat plate P1. It is explanatory drawing of the mechanism to satisfy | fill.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Light source, IS ... Illumination optical system, P1 ... 1st translucent flat plate, P2 ... 2nd translucent flat plate, 36A ... 1st holder, 37A ... 2nd holder, W ... Wafer, 38 ... Wafer stage , 40 ... laser interferometer, G11 ... first diffraction grating, G21 ... second diffraction grating, IL1 to IL10 ... illumination light, 100A to 100C, 102A to 102C ... air pad

Claims (17)

An exposure method for exposing a pattern on a photosensitive object with illumination light from a light source,
In the illumination light path of the illumination light from the light source, a first diffraction grating and a second diffraction grating are arranged in series from the light source side, and the object is irradiated with the diffraction light from the second diffraction grating, Exposing an interference fringe pattern on the object;
An exposure method comprising sucking and holding a substrate on which at least one of the first diffraction grating and the second diffraction grating is formed from the light source side.   2. The exposure method according to claim 1, wherein the first and second diffraction gratings are formed on different surfaces of the same substrate.   2. The exposure method according to claim 1, wherein at least one of different substrates on which the first and second diffraction gratings are respectively formed is sucked and held from the light source side.   4. The exposure method according to claim 1, wherein a member for restricting movement is disposed on the object side of the substrate held by suction.   5. The exposure method according to claim 4, wherein a notch is formed at a position corresponding to at least a part of the movement restricting member in the object side surface of the substrate held by suction.   6. The exposure method according to claim 1, wherein the substrate is sucked and held from at least the light source side during transport.   The exposure method according to claim 1, wherein the substrate is sucked and held from the light source side at least during exposure of the object. In at least a part of the process of forming the circuit pattern constituting the electronic device,
A device manufacturing method using the exposure method according to claim 1. A first diffraction grating and a second diffraction grating are arranged in order from the light source side in the illumination optical path of the illumination light from the light source, and the photosensitive object is irradiated with the diffracted light from the second diffraction grating, An exposure apparatus that exposes an interference fringe pattern on an object,
An exposure apparatus comprising: a suction holding mechanism for sucking and holding a substrate on which at least one of the first diffraction grating and the second diffraction grating is formed from the light source side.   The exposure apparatus according to claim 9, wherein the suction holding mechanism holds the substrate by vacuum suction.   The exposure apparatus according to claim 9 or 10, wherein the suction holding mechanism holds the same substrate on which the first and second diffraction gratings are formed on different surfaces.   The exposure apparatus according to claim 9, wherein the suction holding mechanism holds at least one of different substrates on which the first and second diffraction gratings are respectively formed.   13. The exposure apparatus according to claim 9, wherein the suction holding mechanism includes a movement limiting member disposed on the object side of the suction held substrate.   14. The exposure apparatus according to claim 13, wherein a notch is formed at a position corresponding to at least a part of the movement restricting member in the object side surface of the substrate held by suction. . A transport mechanism for transporting the substrate into an illumination light path of illumination light from the light source;
The exposure apparatus according to claim 9, wherein the suction holding mechanism is included in at least the transport mechanism.   The exposure apparatus according to claim 15, wherein the transport mechanism holds the substrate even when the object is exposed.   The exposure apparatus according to claim 9, wherein the suction holding mechanism is included in a mechanism that holds at least the substrate disposed in the illumination optical path.

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