JP2007234717A - Exposure equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an exposure apparatus capable of improving illuminance uniformity in an illumination area.
An illumination optical system 33 that illuminates a light beam 32 that has been wavefront-divided on an illumination region M by using a wavefront splitting element 35 that includes a plurality of reflection optical elements that wavefront-divide the light beam emitted from a light source. In the exposure apparatus provided, the wavefront dividing element 35 includes an incident side optical system including a plurality of incident side element mirrors 35aa and an emission side optical system including a plurality of emission side element mirrors 35bb, and the plurality of emission sides Changing means 25 is provided for changing the traveling direction of the light beam 32 reflected by at least one of the element mirrors 35bb.
[Selection] Figure 1

Description

  The present invention relates to an exposure apparatus for manufacturing microdevices such as semiconductor elements and liquid crystal display elements in a lithography process.

  In recent years, along with miniaturization of semiconductor element circuits, projection lithography technology using EUV (Extreme Ultra Violet) light with a short wavelength (11 to 14 nm) has been developed in order to further improve the resolution. In this wavelength range, a transmission / refraction type optical element such as a conventional lens cannot be used, a reflection type optical element such as a mirror is used, and a reflection type mask is also used (for example, see Patent Document 1).

The illumination optical system provided in the exposure apparatus using the reflective mask is for uniformly illuminating the illumination area on the reflective mask with EUV light emitted from the light source, and uniformly illuminates the reflective mask. A fly-eye mirror, which is a wavefront splitting element, is provided as means for performing this. The fly-eye mirror includes an incident-side fly-eye mirror disposed at a position optically conjugate with the reflective mask surface, and an exit-side fly-eye mirror disposed on the pupil plane of the illumination optical system. The fly-eye mirror and the exit-side fly-eye mirror include a large number of element mirrors. Therefore, even when the EUV light incident on the incident side fly-eye mirror has uneven illuminance, the images formed by the light incident on each of the many element mirrors are projected on the reflective mask in an overlapping manner. The illuminance unevenness of the EUV light is averaged on the reflective mask.
JP 2003-224053 A

  By the way, in the above-described exposure apparatus, when large illuminance unevenness exists in the light incident on the incident side fly-eye mirror, even if the uneven illuminance of light is averaged using the fly-eye mirror, It was difficult to obtain illuminance uniformity within the illumination area. In addition, when the number of element mirrors constituting the entrance-side fly-eye mirror and the exit-side fly-eye mirror is not sufficiently small, the illumination area on the reflective mask is affected by the pupil stop provided in the vicinity of the exit-side fly-eye mirror. There was a problem that the illuminance uniformity in the inside deteriorated. That is, if there is an element mirror located at the boundary between the aperture of the pupil stop and the light shielding part among the element mirrors of the exit side fly-eye mirror, a part of the light reflected by this element mirror is part of the pupil diaphragm light shielding part. As a result, only light that has been shielded by the light and passed through the opening of the pupil stop reaches the reflective mask, resulting in uneven illuminance.

  The subject of this invention is providing the exposure apparatus which can improve the illumination intensity uniformity in an illumination area | region.

  The exposure apparatus according to the present invention uses a wavefront splitting element (35a, 35bb) composed of a plurality of reflective optical elements (35aa, 35bb) that splits a wavefront of a light beam (32) emitted from a light source (31), and the wavefront on the illumination area. In the exposure apparatus provided with an illumination optical system (33) that illuminates the divided light flux (32) in an overlapping manner, the wavefront splitting element (35a, 35b) includes an incident side element mirror (35aa). A traveling direction of the light beam (32) that is reflected by at least one of the plurality of exit-side element mirrors (35bb), including a side optical system and an exit-side optical system including a plurality of exit-side element mirrors (35bb) It is characterized by comprising changing means (25) for changing.

  According to the exposure apparatus of the present invention, the exposure apparatus includes a changing unit that changes the traveling direction of the light beam reflected by at least one of the plurality of exit-side element mirrors constituting the wavefront splitting element that splits the light beam emitted from the light source. Therefore, it is possible to prevent the luminous flux that causes deterioration of the illuminance uniformity of the area illuminated by the illumination optical system (illumination area) from reaching the illumination area, and to improve the illuminance uniformity of the illumination area Can do. Therefore, the pattern illuminated by the illumination optical system can be satisfactorily exposed on the substrate.

  An exposure apparatus according to an embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a schematic configuration of an exposure apparatus according to the embodiment. In the following description, the XYZ orthogonal coordinate system shown in FIG. 1 is set, and the positional relationship of each member will be described with reference to this XYZ orthogonal coordinate system. The XYZ orthogonal coordinate system is set so that the X axis and the Y axis are parallel to the wafer W as the photosensitive substrate, and the Z axis is set in a direction orthogonal to the wafer W. In the XYZ coordinate system in the figure, the XY plane is actually set to a plane parallel to the horizontal plane, and the Z axis is set to the vertical direction. In this embodiment, the direction in which the wafer W is moved (scanning direction) is set to the X direction.

  The EUV light 32 emitted from the EUV light source 31 constitutes an illumination optical system 33, becomes a substantially parallel light beam via a concave reflecting mirror 34 that acts as a collimator mirror, and enters an optical integrator (wavefront dividing element) 35.

  The optical integrator 35 includes an incident side fly-eye mirror (incident side optical system) 35a and an exit side fly-eye mirror (exit side optical system) 35b. FIG. 2 is a diagram illustrating a configuration of the incident-side fly-eye mirror 35a. As shown in FIG. 2, the incident-side fly-eye mirror 35 a includes a plurality of element mirrors (incident-side elements) that are arranged in parallel and have an arc shape that is substantially similar to an illumination area that illuminates a mask M described later. Mirror) 35aa, and is disposed at a position optically conjugate with the mask M surface or wafer W surface or in the vicinity thereof. The light beam incident on the incident side fly-eye mirror 35a is divided into wavefronts by the respective element mirrors 35aa of the incident side fly-eye mirror 35a.

  The EUV light incident on the incident-side fly-eye mirror 35a is reflected by the incident-side fly-eye mirror 35a and enters the emission-side fly-eye mirror 35b. FIG. 3 is a diagram showing the configuration of the exit-side fly-eye mirror 35b. As shown in FIG. 3, the exit-side fly-eye mirror 35b is composed of a large number of element mirrors (optical elements, exit-side element mirrors) 35bb arranged in parallel and having a rectangular shape, and a projection optical system PL described later. It is arranged at a position optically conjugate with or near the pupil position. As shown in FIG. 4, the element mirrors 35bb are arranged in a one-to-one correspondence with the element mirrors 35aa constituting the incident side fly-eye mirror 35a, and a number of wavefront divisions are made by entering each element mirror 35aa. Are incident on each element mirror 35bb. Accordingly, on the exit side of the exit side fly-eye mirror 35b or in the vicinity thereof, a large number of condensing points corresponding to the number of element mirrors 35bb constituting the exit side fly-eye mirror 35b are formed, and a secondary light source is formed. .

  In addition, a drive unit (changing means) 25 such as a piezo actuator is connected to each element mirror 35bb constituting the emission side fly-eye mirror 35b. The drive unit 25 is provided corresponding to each element mirror 35bb, but only one drive unit 25 is shown in FIGS. By driving the drive unit 25, the element mirror 35bb tilts, and the angle of the EUV light reflected by the element mirror 35bb changes. FIG. 5 is a diagram showing the configuration of the tilted element mirror 35bb ′ and the non-tilted element mirror 35bb. The luminous flux A incident on the non-tilted element mirror 35bb and the tilted element mirror 35bb 'is reflected by the non-tilted element mirror 35bb and travels in the direction of arrow B in the figure, and the tilted element mirror 35bb' And travels in the direction of arrow B ′ in the figure. That is, by tilting the element mirror 35bb ′, the traveling direction of the light beam reflected by the element mirror 35bb ′ changes, and the light beam B ′ reflected by the element mirror 35bb ′ does not reach the mask M.

  By controlling the drive of each element mirror 35bb, EUV light that causes uneven illuminance in the illumination area on the mask M out of the EUV light reflected by each element mirror 35bb does not reach the mask M. Can be. For example, when the EUV light reflected by the element mirror 35bb ′ shown in FIG. 5 is a cause of illuminance unevenness in the illumination area on the mask M, the EUV light reflected by the element mirror 35bb ′ is on the mask M. Therefore, it is possible to prevent illuminance unevenness caused by EUV light reflected by the element mirror 35bb ′, and to improve the illuminance uniformity in the illumination area on the mask M. Note that the drive of the drive unit 25 is controlled by the control device 51.

  A pupil stop 24 as illumination condition changing means is provided in the vicinity of the exit surface of the exit-side fly-eye mirror 35b. FIG. 6 is a diagram showing the configuration of the pupil stop 24. As shown in FIG. 6, on the pupil diaphragm 24, diaphragms 24a and 24b having circular openings, a diaphragm 24c having a ring-shaped opening, and a diaphragm 24d having a bipolar opening are provided. The apertures 24a and 24b having circular openings have different aperture diameters. A desired value such as a σ value (ratio of the aperture diameter of the secondary light source image on the pupil plane to the aperture diameter of the pupil plane of the projection optical system PL) for determining the illumination condition by appropriately selecting the diaphragms 24a to 24d Set to. Further, as shown in FIG. 1, a rotation driving unit 26 is connected to the pupil diaphragm 24, and the pupil diaphragm 24 rotates about the center C by driving the rotation driving unit 26.

  The drive of the rotation drive unit 26 is controlled by the control device 51, and the control device 51 selects any one of the diaphragms 24a to 24d based on the illumination condition for illuminating the illumination area on the mask M. The control device 51 outputs a drive signal to the rotation drive unit 26 in order to place the selected diaphragm in the optical path of the EUV light. The rotation drive unit 26 outputs the pupil diaphragm 24 based on the drive signal from the control device 51. Rotate.

  The EUV light reflected by the exit-side fly-eye mirror 35b and passing through one of the stops 24a to 24d of the pupil stop 24 is polarized by the plane reflecting mirror 36 to form an arcuate illumination area. The mask M is mounted on the mask stage 55, and the mask stage 55 is configured to be movable in the X, Y, and Z axial directions and the rotational directions around the respective axes. The EUV light reflected by the mask M forms an image of the pattern of the mask M on the wafer W via the projection optical system PL composed of a plurality of reflecting mirrors (six exemplary reflecting mirrors M1 to M6 in FIG. 1). Form. The wafer W is mounted on the wafer stage 56, and the wafer stage 56 is configured to be movable in the X, Y, and Z axial directions and the rotational directions around the respective axes.

  The positions of the mask stage 55 and the wafer stage 56 in the X and Y directions are measured by interferometers (not shown). The measurement result by the interferometer is output to the control device 51, and the control device 51 outputs drive signals 57 and 58 to the mask stage 55 and the wafer stage 56. Based on drive signals 57 and 58 from the control device 51, the mask stage 55 and the wafer stage 56 are moved by an actuator (not shown) such as a linear motor or an air actuator.

  In this embodiment, an illuminance sensor 29 for measuring the illuminance of EUV light irradiated on the wafer W via the projection optical system PL is provided on the wafer stage 56. When measuring the illuminance of EUV light using the illuminance sensor 29, first, a reference mask having a known reflectance is mounted on the mask stage 55 instead of the mask M. The illuminance sensor 29 measures the illuminance of light reflected by the reference mask and passing through the projection optical system PL. The illuminance sensor 29 outputs the illuminance measurement result to the control device 51, and the control device 51 detects the illuminance distribution in the exposure area on the wafer W based on the illuminance measurement result of the illuminance sensor 29.

  By the way, when there is a large illuminance unevenness in the EUV light incident on the incident side fly-eye mirror 35a, the illuminance unevenness occurs in the illumination area on the mask M. In addition, when the number of element mirrors 35aa and 35bb constituting the entrance-side fly-eye mirror 35a and the exit-side fly-eye mirror 35b is not sufficiently small, the illuminance uniformity in the illumination area on the mask M is affected by the influence of the pupil diaphragm 24. Getting worse.

  FIG. 7 is a diagram showing the positional relationship between the circular aperture stop 24a and the exit-side fly-eye mirror 35b when, for example, the circular aperture stop 24a is selected and arranged in the optical path of EUV light. . As shown in FIG. 7, among the light beams reflected by each of the multiple element mirrors 35bb of the exit-side fly-eye mirror 35b, there are light beams that pass through the opening of the diaphragm 24a and light beams that are shielded by the light shielding unit. . Further, among the many element mirrors 35bb, a part of the light beam reflected by the element mirror (element mirror D shown in FIG. 7) existing at the boundary between the opening of the diaphragm 24a and the light shielding part is partially reflected by the light shielding part of the diaphragm 24a. Is shielded, and the remaining part passes through the opening of the diaphragm 24a. The remaining part of the light beam that has passed through the opening of the diaphragm 24a becomes a cause of illuminance unevenness in the illumination area on the mask M.

  Therefore, in the exposure apparatus according to this embodiment, the illuminance unevenness generated in the illumination area on the mask M is controlled by controlling the traveling direction of the light beam reflected by each element mirror 35bb of the exit side fly-eye mirror 35b. Perform the correction. Specifically, the control device 51 arranges any one of the diaphragms 24 a to 24 d selected based on the illumination condition in the optical path of the EUV light via the rotation driving unit 36. Then, a reference mask having a known reflectance is mounted on the mask stage 55, and the illuminance of the EUV light irradiated on the wafer W using the illuminance sensor 29 (as a result, the illuminance of the EUV light irradiated on the mask M). ). When illuminance unevenness is detected from the illuminance measurement result by the illuminance sensor 29, the control device 51 determines which element mirror 35bb reflects the EUV light that is the cause of the illuminance unevenness.

  That is, when the EUV light incident on the incident side fly-eye mirror 35a has an illuminance distribution having a dark part, the element mirror 35bb corresponding to the element mirror 35aa on which the dark part of the EUV light is incident is selected. In addition, the element mirror 35bb existing at the boundary between the aperture of the diaphragm and the light shielding portion is selected.

  The control device 51 outputs a drive signal to the drive unit 25 provided corresponding to the selected element mirror 35bb, and the drive unit 25 selects the element mirror 35bb selected based on the drive signal from the control device 51. Tilt. By tilting the element mirror 35bb, the traveling direction of the light beam reflected by the selected element mirror 35bb is changed so that the light beam reflected by the selected element mirror 35bb does not reach the mask M. Since the EUV light reflected by the selected element mirror 35bb does not reach the mask M, it is possible to prevent the occurrence of uneven illuminance, and the illuminance in the illumination area on the mask M (in the exposure area on the wafer W). Uniformity can be improved. It should be noted that the correction of the illuminance unevenness in the illumination area on the mask M may be performed every time the illumination condition is changed, or may be performed every predetermined period.

  According to the exposure apparatus of this embodiment, since the reflecting surface of the element mirror 25bb can be tilted by individually driving each of the element mirrors 35bb constituting the exit side fly-eye mirror 35b, the element mirror 35bb The traveling direction of the EUV light reflected by can be changed. Therefore, it is possible to prevent the EUV light that causes the illuminance uniformity on the mask M from deteriorating on the mask M, so that the illuminance uniformity on the mask M can be improved and good exposure can be achieved. Can be done.

  In this embodiment, the EUV exposure apparatus constituted by the reflective optical element has been described as an example. However, the present invention can be applied to an exposure apparatus constituted by the transmissive optical element. Good.

  In this embodiment, the illuminance sensor 29 for measuring the illuminance of the EUV light is provided on the wafer stage 56. However, the EUV light irradiated on the mask M on or near the mask stage 55 is provided. An illuminance sensor for measuring illuminance may be provided.

  In this embodiment, the illuminance unevenness is corrected based on the illuminance measurement result by the illuminance sensor 29. However, the element mirror 35bb to be driven for each of the diaphragms 24a to 24d of the pupil diaphragm 24 is determined in advance. Alternatively (for example, stored in a storage unit (not shown)), illuminance unevenness may be corrected based on this. That is, when any of the diaphragms 24a to 24d is newly selected in accordance with the change of the illumination condition, the illuminance due to the influence of the pupil diaphragm 24 is driven by driving the element mirror 35bb to be driven with respect to the selected diaphragm. Perform unevenness correction.

It is a figure which shows the structure of the exposure apparatus concerning embodiment. It is a figure which shows the structure of the entrance side fly eye mirror concerning embodiment. It is a figure which shows the structure of the radiation | emission side fly eye mirror concerning Embodiment. It is a figure for demonstrating the correspondence of many element mirrors which comprise the entrance side fly eye mirror and the exit side fly eye mirror. It is a figure which shows the structure of the radiation | emission side fly eye mirror concerning Embodiment. It is a figure which shows the structure of the pupil stop concerning Embodiment. It is a figure which shows the positional relationship of the injection | emission side fly eye mirror and a stop.

Explanation of symbols

24 ... pupil stop, 25 ... drive unit, 26 ... rotational drive unit, 29 ... illuminance sensor, 31 ... light source, 33 ... illumination optical system, 35 ... optical integrator, 35a ... incident side fly-eye mirror, 35b ... exit side fly eye Mirror, 51 ... Control device, 55 ... Mask stage, 56 ... Wafer stage, M ... Mask, PL ... Projection optical system, W ... Wafer.

Claims (3)

In an exposure apparatus provided with an illumination optical system that illuminates the light flux that has been wavefront divided on the illumination area using a wavefront splitting element that includes a plurality of reflective optical elements that wavefront split the light flux emitted from the light source.
The wavefront splitting element includes an incident side optical system including a plurality of incident side element mirrors, and an exit side optical system including a plurality of exit side element mirrors,
An exposure apparatus comprising: changing means for changing a traveling direction of the light beam reflected by at least one of the plurality of exit-side element mirrors. Illumination condition changing means for changing the illumination condition for illuminating the illumination area,
The changing means changes a traveling direction of the light beam incident on at least one of the plurality of exit-side element mirrors based on the illumination condition changed by the illumination condition changing means. 1. The exposure apparatus according to 1. The changing means changes a traveling direction of the light beam incident on at least one of the plurality of exit-side element mirrors so as to correct illuminance unevenness in the illumination area illuminated by the light beam. The exposure apparatus according to claim 1 or 2.

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