JP2005072513A - Aligner and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aligner, capable of realizing projection exposure having high throughput, using a projection optical system having a ring-band shaped optically effective exposure region and keeping the stroke during the period of scan exposure to a small level. <P>SOLUTION: The aligner comprises illumination systems (11 to 19) for illuminating a mask (M), and a projection optical system (PL) for forming the pattern image of the mask on a photosensitive substrate (W). The mask and the photosensitive substrate are moved with respect to the projection optical system to perform projection exposure of the mask pattern onto the photosensitive substrate. The projection optical system has a ring-band shaped optically effective exposure region corrected into a predetermined state of aberration on the photosensitive substrate. The exposure apparatus comprises a definition means (19) for defining a circular actual exposure region in the ring-band shaped optically effective exposure region. When it is defined that the external radius of the ring-band shaped optically effective exposure region is Ro and the inner radius thereof is Ri, the condition (Ro+Ri)/2<Re≤Ro is satisfied, where Re is the radius of the circle of the circular actually exposed region. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an exposure apparatus and an exposure method, and more particularly to an exposure apparatus suitable for manufacturing a microdevice such as a semiconductor element in a photolithography process using EUV light having a wavelength of about 5 to 40 nm.

 In this type of exposure apparatus, further improvement in resolving power is required as the circuit pattern to be transferred becomes finer, and light having a shorter wavelength is used as exposure light. In addition, “light” in this specification means not only “light” in a narrow sense that can be seen with eyes, but also “light” in a broad sense including a so-called infrared ray to X-ray having a wavelength shorter than 1 mm among electromagnetic waves. To do. In recent years, an exposure apparatus using EUV (Extreme UltraViolet) light having a wavelength of about 5 to 40 nm (hereinafter referred to as “EUVL (Extreme UltraViolet Lithography) exposure apparatus”) has been proposed as a next-generation apparatus.

  In such a very short wavelength range of EUV light, there is no substance having a sufficient transmittance as a refractive optical member, so that a reflection type projection optical system composed of only a reflection optical member is used. In general, when a catoptric system or a catadioptric system is used as a projection optical system, the optical axis differs from that of a dioptric system because of the folding of the light beam by the reflecting surface. It is not always possible to ensure a circular effective exposure region (region corrected to a required aberration state) including.

  Rather, when a reflective optical system or a catadioptric optical system is used, it is common for the aperture to be in a ring shape or the effective exposure region to be in an arc shape. Specifically, in the case where the Schwartschild type projection optical system as shown in FIG. 6A is used, only a minute effective exposure region centered on the optical axis can be obtained, as shown in FIG. 6B. In addition, the opening (pupil shape) has a ring shape. On the other hand, when an Offner type projection optical system as shown in FIG. 7A is used, an arc-shaped (optically ring-shaped) effective exposure region is obtained as shown in FIG. 7B.

  In an EUVL exposure apparatus, it is common to use a projection optical system that can obtain an effective exposure area in an arc shape (optically in an annular shape). In this case, an arc-shaped actual exposure area is defined within the arc-shaped effective exposure area, and the mask pattern is scanned onto the photosensitive substrate while moving the mask and the photosensitive substrate (wafer, etc.) relative to the projection optical system. Exposure (scanning exposure) is performed. Therefore, in the EUVL exposure apparatus, it is important to improve the throughput by minimizing the stroke at the time of scan exposure.

  Here, the stroke is a relative movement amount of the mask and the photosensitive substrate with respect to the projection optical system in one scan exposure. Throughput is an index of how many silicon wafers can be baked per unit time, and is an important index that determines the price of semiconductor devices.

  The present invention has been made in view of the above-described problems, and achieves high-throughput projection exposure by using a projection optical system having a ring-shaped optically effective exposure region and suppressing the stroke during scan exposure to be small. An object of the present invention is to provide an exposure apparatus and an exposure method capable of performing the above.

In order to solve the above problems, in the first embodiment of the present invention, an illumination system for illuminating a mask on which a predetermined pattern is formed, and projection optics for forming a pattern image of the mask on a photosensitive substrate. An exposure apparatus for projecting and exposing a pattern of the mask onto the photosensitive substrate by moving the mask and the photosensitive substrate along a predetermined direction with respect to the projection optical system.
The projection optical system has a ring-shaped optically effective exposure area corrected to a required aberration state on the photosensitive substrate,
A defining means for defining an arc-shaped actual exposure area within the annular optically effective exposure area,
An exposure apparatus is provided in which an arc radius Re of the arc-shaped actual exposure region substantially coincides with an outer radius Ro of the annular optically effective exposure region. In this case, it is preferable that the defining means has a field stop for defining an arcuate illumination area corresponding to the arcuate actual exposure area on the mask arranged in the optical path of the illumination system.

In a second aspect of the present invention, the projection optical system includes: an illumination system for illuminating a mask on which a predetermined pattern is formed; and a projection optical system for forming a pattern image of the mask on a photosensitive substrate. In an exposure apparatus for projecting and exposing a pattern of the mask onto the photosensitive substrate by moving the mask and the photosensitive substrate along a predetermined direction with respect to a system,
The projection optical system has a ring-shaped optically effective exposure area corrected to a required aberration state on the photosensitive substrate,
A defining means for defining an arc-shaped actual exposure area within the annular optically effective exposure area,
An arc radius Re of the arc-shaped actual exposure region is defined as follows: Ro is an outer radius of the annular optically effective exposure region, and Ri is an inner radius of the annular optically effective exposure region.
(Ro + Ri) / 2 <Re ≦ Ro
An exposure apparatus is provided that satisfies the following conditions. In this case, it is preferable that the defining means has a field stop for defining an arcuate illumination area corresponding to the arcuate actual exposure area on the mask arranged in the optical path of the illumination system.

In a third aspect of the present invention, an illumination step of illuminating a mask on which a predetermined pattern is formed, and the mask and the photosensitive substrate are moved along a predetermined direction with respect to the projection optical system to change the pattern of the mask In an exposure method including an exposure step of projecting and exposing onto a photosensitive substrate,
The projection optical system has a ring-shaped optically effective exposure area corrected to a required aberration state on the photosensitive substrate,
In the exposure step, an arcuate actual exposure region is defined in the annular optically effective exposure region, and an arc radius Re of the arcuate actual exposure region is set outside the annular optically effective exposure region. The exposure method is characterized in that it substantially matches the radius Ro. In this case, in the illumination step, it is preferable that an arcuate illumination area corresponding to the arcuate actual exposure area is defined on the mask via a field stop arranged in the optical path of the illumination system.

In a fourth embodiment of the present invention, an illumination process for illuminating a mask on which a predetermined pattern is formed, and the mask and the photosensitive substrate are moved along a predetermined direction with respect to the projection optical system to change the pattern of the mask. In an exposure method including an exposure step of projecting and exposing onto a photosensitive substrate,
The projection optical system has a ring-shaped optically effective exposure area corrected to a required aberration state on the photosensitive substrate,
In the exposure step, an arc-shaped actual exposure area is defined within the annular optically effective exposure area,
An arc radius Re of the arc-shaped actual exposure region is defined as follows: Ro is an outer radius of the annular optically effective exposure region, and Ri is an inner radius of the annular optically effective exposure region.
(Ro + Ri) / 2 <Re ≦ Ro
An exposure method characterized by satisfying the above condition is provided. In this case, in the illumination step, it is preferable that an arcuate illumination area corresponding to the arcuate actual exposure area is defined on the mask via a field stop arranged in the optical path of the illumination system.

  In the present invention, when the arc-shaped actual exposure area is defined in the annular optically effective exposure area obtained through the projection optical system, the radius Re of the arc of the actual exposure area is outside the effective exposure area. When the radius and the inner radius are Ro and Ri, they are set so as to satisfy the condition of (Ro + Ri) / 2 <Re ≦ Ro. As a result, in the exposure apparatus and exposure method of the present invention, a projection optical system having a ring-shaped optically effective exposure region can be used, and a high-throughput projection exposure can be realized with a small stroke during scan exposure. As a result, a microdevice can be manufactured with high throughput.

Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a view schematically showing the overall configuration of an exposure apparatus according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing the internal configuration of the light source and illumination optical system of FIG. In FIG. 1, the Z axis along the optical axis direction of the projection optical system, that is, the normal direction of the wafer as the photosensitive substrate, the Y axis in the direction parallel to the paper surface of FIG. The X axis is set in the direction perpendicular to the paper surface of FIG.

  Referring to FIG. 1, the exposure apparatus of this embodiment includes, for example, a laser plasma light source 1 as a light source for supplying exposure light. The light emitted from the light source 1 enters the illumination optical system 2 through a wavelength selection filter (not shown). Here, the wavelength selection filter has a characteristic of selectively transmitting only EUV light having a predetermined wavelength (for example, 13.4 nm or 11.5 nm) from light supplied from the light source 1 and blocking transmission of other wavelength light. . The EUV light 3 that has passed through the wavelength selection filter illuminates a reflective mask (reticle) M on which a pattern to be transferred is formed, via an illumination optical system 2 and a plane reflecting mirror 4 as an optical path deflecting mirror.

  The mask M is held by a mask stage 5 that can move along the Y direction so that its pattern surface extends along the XY plane. The movement of the mask stage 5 is configured to be measured by a laser interferometer 6. The light from the illuminated pattern of the mask M forms an image of the mask pattern on the wafer W, which is a photosensitive substrate, via the reflective projection optical system PL. That is, on the wafer W, as will be described later, for example, an arc-shaped actual exposure region symmetric with respect to the Y axis is formed.

  The wafer W is held by a wafer stage 7 that can move two-dimensionally along the X and Y directions so that the exposure surface extends along the XY plane. The movement of the wafer stage 7 is measured by a laser interferometer 8 as in the mask stage 5. Thus, the scanning exposure (scanning exposure) is performed while moving the mask stage 5 and the wafer stage 7 along the Y direction, that is, while relatively moving the mask M and the wafer W along the Y direction with respect to the projection optical system PL. As a result, the pattern of the mask M is transferred to one rectangular shot area of the wafer W.

  At this time, when the projection magnification (transfer magnification) of the projection optical system PL is, for example, 1/4, the moving speed of the wafer stage 7 is set to 1/4 of the moving speed of the mask stage 5 to perform synchronous scanning. Further, by repeating scanning exposure while moving the wafer stage 7 two-dimensionally along the X direction and the Y direction, the pattern of the mask M is sequentially transferred to each shot area of the wafer W.

  Referring to FIG. 2, in the laser plasma light source 1, light (non-EUV light) emitted from the laser light source 11 is condensed on the gas target 13 via the condenser lens 12. Here, a high-pressure gas made of, for example, xenon (Xe) is supplied from the nozzle 14, and the gas injected from the nozzle 14 forms the gas target 13. The gas target 13 obtains energy from the focused laser beam, turns it into plasma, and emits EUV light. The gas target 13 is positioned at the first focal point of the elliptical reflecting mirror 15. Therefore, the EUV light emitted from the laser plasma light source 1 is collected at the second focal point of the elliptical reflecting mirror 15. On the other hand, the gas that has finished emitting light is sucked through the duct 16 and guided to the outside.

  The EUV light collected at the second focal point of the elliptical reflecting mirror 15 becomes a substantially parallel light beam via the concave reflecting mirror 17 and is guided to an optical integrator 18 including a pair of fly-eye mirrors 18a and 18b. As the pair of fly-eye mirrors 18a and 18b, for example, the fly-eye mirror disclosed by the present applicant in JP-A-11-312638 can be used. For more detailed configuration and operation of the fly-eye mirror, reference can be made to related descriptions in the publication.

  Thus, a substantial surface light source having a predetermined shape is formed in the vicinity of the reflection surface of the second fly's eye mirror 18b, that is, in the vicinity of the exit surface of the optical integrator 18. Here, the substantial surface light source is formed at or near the exit pupil position of the illumination optical system 2, that is, the surface optically conjugate with the entrance pupil of the projection optical system PL or the vicinity thereof. The light from the substantial surface light source is deflected by the plane reflecting mirror 4, and then the arc-shaped illumination area is formed on the mask M through the field stop 19 disposed substantially parallel to and close to the mask M. Form. The light from the illuminated pattern of the mask M forms an image of the mask pattern on the arc-shaped actual exposure region on the wafer W via the projection optical system PL.

  FIG. 3 is a diagram for explaining a wafer stroke necessary for one scan exposure in the present embodiment. Referring to FIG. 3, when the pattern of the mask M is transferred to the rectangular shot area SR of the wafer W by scan exposure, the arc-shaped actual exposure area ER that is symmetrical with respect to the Y axis starts scanning indicated by a solid line in the figure. It moves from the position to the scan end position indicated by the broken line in the figure. Here, the dimension along the scan direction (Y direction) of the shot area SR is L1, and the overall dimension along the scan direction of the actual exposure area ER is L2.

  Therefore, the stroke of the wafer W necessary for one scan exposure with respect to the shot area SR, that is, the movement distance of the actual exposure area ER from the scan start position to the scan end position is represented by L1 + L2. As described above, in order to realize high-throughput projection exposure, the stroke (L1 + L2) at the time of scan exposure needs to be kept small, but since the scan direction dimension L1 of the shot region SR is a predetermined amount, the stroke (L1 + L2) It can be seen that it is necessary to keep the overall dimension L2 along the scanning direction of the actual exposure region ER small so as to keep it small.

  FIG. 4 is a diagram schematically showing a state in which an arcuate actual exposure region is defined in an annular optically effective exposure region obtained through the projection optical system of the present embodiment. As shown by a broken line in FIG. 4, a ring-shaped (annular) optically effective exposure region having an outer radius Ro and an inner radius Ri is obtained through the projection optical system PL of the present embodiment. In practice, however, as described above, an arc-shaped effective exposure region which is a part of the annular optically effective exposure region is obtained due to the folding of the light flux by the reflecting surface.

  In the present embodiment, in order to realize high-throughput projection exposure, a circular arc-shaped actual exposure area ER is defined in an arc-shaped effective exposure area that is a part of an annular optically effective exposure area. It is necessary to keep the overall dimension L2 along the scanning direction of the arcuate actual exposure region ER small. However, the radii of two opposing arcs must be set equal to each other so that the length in the scan direction of the arc-shaped actual exposure region ER is always constant at all positions along the X direction, which is the scan orthogonal direction. I must. The length of the arcuate actual exposure region ER in the scanning direction must be set to the maximum, specifically, (Ro-Ri) within the arcuate effective exposure region.

  In this case, as shown in FIG. 4A, it is common in the prior art that the radius Re of the arc of the actual exposure region ER is set to satisfy Re = (Ro + Ri) / 2. On the other hand, in this embodiment, as shown in FIG. 4B, the radius Re of the arc of the actual exposure region ER is set so as to satisfy Re = Ro. As a result, in the present embodiment, as is apparent from the comparison between FIG. 4A and FIG. 4B, the overall dimension L2 along the scanning direction of the arcuate actual exposure region ER is set to be d compared with the prior art. Can only be kept small.

  As described above, in the present embodiment, when the arc-shaped actual exposure region ER is defined within the arc-shaped (optically annular) effective exposure region obtained via the projection optical system PL, the actual exposure is performed. The radius Re of the arc of the area ER is set to coincide with the radius Ro outside the effective exposure area. As a result, in the exposure apparatus of the present embodiment, high-throughput projection exposure can be realized by using the projection optical system PL having a ring-shaped optically effective exposure region and suppressing the stroke during scan exposure.

  In the present embodiment, the arc-shaped actual exposure region ER on the wafer W can be defined via the field stop 19 that is disposed substantially parallel to and close to the mask M. That is, an arcuate illumination area corresponding to the arcuate actual exposure area ER on the wafer W is formed on the mask M by setting the opening (light transmission part) of the field stop 19 in a predetermined arcuate shape. be able to. Of course, the present invention is not limited to this, and the arc-shaped actual exposure region ER on the wafer W can be defined using other appropriate defining means other than the field stop 19.

  In the above-described embodiment, in order to minimize the stroke during scan exposure, the radius Re of the arc of the actual exposure region ER is set to coincide with the radius Ro outside the effective exposure region. However, the present invention is not limited to this, and by setting the radius Re of the arc of the actual exposure region ER so as to satisfy the condition of (Ro + Ri) / 2 <Re ≦ Ro, the stroke at the time of scan exposure can be kept small. High throughput projection exposure can be realized.

  In the exposure apparatus according to the above-described embodiment, the illumination system illuminates the mask (illumination process), and exposes the transfer pattern formed on the mask using the projection optical system onto the photosensitive substrate (exposure process). Microdevices (semiconductor elements, imaging elements, liquid crystal display elements, thin film magnetic heads, etc.) can be manufactured. Hereinafter, referring to the flowchart of FIG. 5 for an example of a method for obtaining a semiconductor device as a micro device by forming a predetermined circuit pattern on a wafer or the like as a photosensitive substrate using the exposure apparatus of the present embodiment. I will explain.

  First, in step 301 of FIG. 5, a metal film is deposited on one lot of wafers. In the next step 302, a photoresist is applied on the metal film on the lot of wafers. Thereafter, in step 303, using the exposure apparatus of the present embodiment, the pattern image on the mask (reticle) is sequentially exposed and transferred to each shot area on the wafer of one lot via the projection optical system. .

  Thereafter, in step 304, the photoresist on the one lot of wafers is developed, and in step 305, the resist pattern is etched on the one lot of wafers to form a pattern on the mask. Corresponding circuit patterns are formed in each shot area on each wafer. Thereafter, a device pattern such as a semiconductor element is manufactured by forming a circuit pattern of an upper layer. According to the semiconductor device manufacturing method described above, a semiconductor device having an extremely fine circuit pattern can be obtained with high throughput.

  In the above-described embodiment, the present invention is applied to an exposure apparatus and an exposure method that use a laser plasma light source as a light source for supplying EUV light. However, the present invention is not limited to this, and other appropriate light sources. The present invention can also be applied to an exposure apparatus and an exposure method using the above.

It is a figure which shows schematically the structure of the exposure apparatus concerning embodiment of this invention. It is a figure which shows schematically the internal structure of the light source and illumination optical system of FIG. It is a figure explaining the stroke of a wafer required for one scan exposure in this embodiment. It is a figure which shows roughly a mode that an arc-shaped real exposure area | region is prescribed | regulated in the ring-shaped optically effective exposure area | region obtained via the projection optical system of this embodiment. It is a figure which shows the flowchart about an example of the method at the time of obtaining the semiconductor device as a microdevice. It is a figure explaining opening (pupil shape) becoming a ring zone shape when using a Schwartschild type projection optical system. It is a figure explaining that an arc-shaped effective exposure area is obtained when an Offner type projection optical system is used.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser plasma light source 2 Illumination optical system 5 Mask stage 7 Wafer stage 11 Laser light source 13 Gas target 14 Nozzle 15 Elliptical mirror 18 Optical integrator 18a, 18b Fly eye mirror 19 Field stop M Mask PL Projection optical system W Wafer ER Actual exposure area SR shot area

Claims (8)

An illumination system for illuminating a mask on which a predetermined pattern is formed, and a projection optical system for forming a pattern image of the mask on a photosensitive substrate, the mask and the mask with respect to the projection optical system In an exposure apparatus for projecting and exposing the pattern of the mask onto the photosensitive substrate by moving the photosensitive substrate along a predetermined direction,
The projection optical system has a ring-shaped optically effective exposure area corrected to a required aberration state on the photosensitive substrate,
A defining means for defining an arc-shaped actual exposure area within the annular optically effective exposure area,
An exposure apparatus, wherein an arc radius Re of the arc-shaped actual exposure region substantially coincides with an outer radius Ro of the annular optically effective exposure region. 2. The field stop for defining an arcuate illumination area corresponding to the arcuate actual exposure area on the mask disposed in the optical path of the illumination system. 2. The exposure apparatus according to 1. An illumination system for illuminating a mask on which a predetermined pattern is formed, and a projection optical system for forming a pattern image of the mask on a photosensitive substrate, the mask and the mask with respect to the projection optical system In an exposure apparatus for projecting and exposing the pattern of the mask onto the photosensitive substrate by moving the photosensitive substrate along a predetermined direction,
The projection optical system has a ring-shaped optically effective exposure area corrected to a required aberration state on the photosensitive substrate,
A defining means for defining an arc-shaped actual exposure area within the annular optically effective exposure area,
An arc radius Re of the arc-shaped actual exposure region is defined as follows: Ro is an outer radius of the annular optically effective exposure region, and Ri is an inner radius of the annular optically effective exposure region.
(Ro + Ri) / 2 <Re ≦ Ro
An exposure apparatus satisfying the following conditions: 2. The field stop for defining an arcuate illumination area corresponding to the arcuate actual exposure area on the mask disposed in the optical path of the illumination system. 4. The exposure apparatus according to 3. An illumination process for illuminating a mask on which a predetermined pattern is formed, and the mask and the photosensitive substrate are moved along a predetermined direction with respect to the projection optical system to project and expose the mask pattern onto the photosensitive substrate. In an exposure method including an exposure step,
The projection optical system has a ring-shaped optically effective exposure area corrected to a required aberration state on the photosensitive substrate,
In the exposure step, an arcuate actual exposure region is defined in the annular optically effective exposure region, and an arc radius Re of the arcuate actual exposure region is set outside the annular optically effective exposure region. An exposure method characterized by substantially matching the radius Ro. 6. The illumination step includes defining an arcuate illumination area corresponding to the arcuate actual exposure area on the mask via a field stop disposed in an optical path of the illumination system. An exposure method according to 1. An illumination process for illuminating a mask on which a predetermined pattern is formed, and the mask and the photosensitive substrate are moved along a predetermined direction with respect to the projection optical system to project and expose the mask pattern onto the photosensitive substrate. In an exposure method including an exposure step,
The projection optical system has a ring-shaped optically effective exposure area corrected to a required aberration state on the photosensitive substrate,
In the exposure step, an arc-shaped actual exposure area is defined within the annular optically effective exposure area,
An arc radius Re of the arc-shaped actual exposure region is defined as follows: Ro is an outer radius of the annular optically effective exposure region, and Ri is an inner radius of the annular optically effective exposure region.
(Ro + Ri) / 2 <Re ≦ Ro
An exposure method characterized by satisfying the following condition. 8. The illumination step includes defining an arcuate illumination area corresponding to the arcuate actual exposure area on the mask via a field stop disposed in the optical path of the illumination system. An exposure method according to 1.

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