JP2007294550A - Exposure method and apparatus, and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely transfer a pattern onto a substrate using a progressive focus exposure method even if the spectrum width of an exposure beam varies. <P>SOLUTION: In the exposure method, exposure light EL is irradiated on a pattern of a reticle R to transfer the pattern onto a wafer W by the exposure light EL via a projection optical system PL. The method includes a process wherein the spectrum width of the exposure light EL is measured using a spectrum monitor 15; and an exposure process wherein the pattern is transferred onto the wafer W via the projection optical system PL, while continuously or intermittently changing a relative positional relationship in the optical axis AX direction, between the surface of the wafer W and a field of the projection optical system PL within a range of a predetermined swing width set up according to the measured value of the spectrum width of the exposure light EL. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exposure technique for transferring a predetermined pattern onto an exposure substrate via a projection optical system and a device manufacturing technique using this exposure technique. For example, a semiconductor element, a liquid crystal display element, an imaging element (CCD, etc.) Or, it is suitable for use in transferring a device pattern onto a substrate such as a wafer in a lithography process for manufacturing a device such as a thin film magnetic head.

  Conventionally, in a lithography process for manufacturing a semiconductor element or the like, a pattern formed on a reticle (or a photomask) as a mask is illuminated with exposure light from an exposure light source, and the pattern is generated under the exposure light. Is transferred onto a wafer (or glass plate or the like) as a substrate via a projection optical system, so that a static exposure type (collective exposure type) projection exposure apparatus such as a stepper or a scanning exposure type such as a scanning stepper is used. An exposure apparatus such as a projection exposure apparatus is used.

The resolving power (resolution) R of the projection optical system provided in this type of exposure apparatus is represented by a relational expression of R = k ₁ × λ / NA, as is well known from the Rayleigh equation. . Here, λ is the wavelength of the exposure light, NA is the numerical aperture of the projection optical system, and k ₁ is a constant determined by the characteristics of the photoresist coated on the wafer, process conditions, and the like. Therefore, in order to improve the resolving power, it is conceivable to shorten the wavelength λ of the exposure light and increase the numerical aperture NA. Therefore, as the exposure light, recently, excimer laser light with a narrower spectral width such as KrF excimer laser (wavelength 248 nm) or ArF excimer laser (wavelength 193 nm) is mainly used.

On the other hand, the projection optical system of depth of focus (DOF) using a predetermined constant k _2, so represented a _{DOF = k 2 × λ / NA} 2, simply by shortening the wavelength lambda, increase the numerical aperture NA As a result, the depth of focus may become too shallow. In this regard, when the pattern to be exposed is a periodic grid pattern like a memory circuit, the resolution is improved by a so-called modified illumination method that tilts the principal ray of exposure light on the pattern. In addition, it is known that the depth of focus can be substantially increased.

On the other hand, when the pattern to be exposed is an isolated pattern, for example, a contact hole pattern, the irradiation area of the wafer surface irradiated with the exposure light via the projection optical system is the image plane of the projection optical system. Between the image plane and the wafer so that the distribution of the exposure dose given on the wafer according to the relative position between the image plane and the wafer surface is a predetermined distribution. The depth of focus of the projection optical system is substantially increased by the progressive focus exposure method in which exposure is performed while changing the relative positional relationship in the optical axis direction of the projection optical system continuously or intermittently in a predetermined procedure (apparent focus). It is known that the depth can be increased). The progressive focus exposure method is sometimes called a flex method or a DP (CDP) exposure method. Further, the progressive focus exposure method in the static exposure type projection exposure apparatus is disclosed in, for example, Patent Document 1 and Patent Document 2, and the progressive focus exposure method in the scanning exposure type projection exposure apparatus is disclosed in, for example, Patent Document 3, It is disclosed in Patent Document 4 and the like.
JP 63-42122 A JP-A-5-13305 JP-A-4-277612 JP-A-6-314646

In the conventional progressive focus exposure method described above, for example, the exposure conditions such as the relative movement range in the optical axis direction of the projection optical system on the wafer surface relative to the image plane and the exposure amount distribution are the center wavelength of the exposure light and It was determined according to the depth of focus obtained from the numerical aperture of the projection optical system.
In this regard, the excimer laser light mainly used as exposure light should have a narrower spectral width from the viewpoint of reducing chromatic aberration, but from the viewpoint of maintaining high power and reducing the manufacturing cost of the light source. It is desirable that the spectrum width is wider. Therefore, for an excimer laser light source, for example, when used in an exposure apparatus for a critical layer, the requirement for the spectral width is tightened, and when used for an exposure apparatus for other purposes, the requirement for the spectral width is relaxed. Thus, changing the specification of the spectrum width according to the application is also being studied. However, when the spectral width of the exposure light changes in this way, there is a possibility that the optimum exposure condition also changes when the progressive focus exposure method is applied.

In addition, even if the specification of the spectral width of the exposure light is determined, depending on whether the spectral width is actually near the upper limit value of the specification or the intermediate value of the specification, etc. The optimum exposure condition when applying the progressive focus exposure method may change.
In view of such circumstances, the present invention aims to provide an exposure technique and a device manufacturing technique that can transfer a pattern with high precision onto a substrate using a progressive focus exposure method even when the spectral width of exposure light changes. And

  An exposure method according to the present invention includes an exposure method in which an exposure beam is irradiated onto a transfer pattern (R) and the substrate (W) is exposed with the exposure beam through the pattern and a projection optical system (PL). The relative positional relationship in the optical axis direction of the projection optical system between the exposure area of the projection optical system and the image plane of the projection optical system is within a predetermined swing width (ΔZ) set in accordance with the spectral width of the exposure beam. And an exposure process in which the pattern is transferred to the exposed area of the substrate through the projection optical system by changing the pattern continuously or intermittently.

According to the present invention, in view of the fact that the focal depth of the projection optical system changes depending on the spectral width of the exposure beam, as an example, after obtaining the focal depth according to the spectral width, Determine the width. As a result, the image of the pattern can be transferred with high accuracy onto the substrate using the progressive focus exposure method.
In the present invention, it is possible to have a measurement process for measuring the spectral width of the exposure beam before the exposure process. Thereby, the swing width can be determined more accurately.

  An exposure apparatus according to the present invention is an exposure apparatus that irradiates a transfer pattern (R) with an exposure beam and exposes the substrate (W) with the exposure beam via the pattern and the projection optical system (PL). A relative drive device (27) for controlling the relative positional relationship between the substrate and the image plane of the projection optical system in the optical axis direction of the projection optical system, the range of change in the relative positional relationship, and the exposure beam A storage device (51) for storing a predetermined amplitude (ΔZ) set in accordance with the spectral width of the substrate, and an exposure region of the substrate irradiated with the exposure beam via the pattern and the projection optical system. The relative drive device is driven and the relative positional relationship between the exposed area of the substrate and the image plane of the projection optical system is within the range of the swing width stored in the storage device. Continuous or It is obtained and a control device for intermittently changed (50).

Further, as an example, the apparatus further includes a measurement device that measures spectral width information of the exposure beam, and the control device obtains the amplitude based on the measurement result of the measurement device and stores the amplitude in the storage device. You may let them. The exposure method of the present invention can be carried out by the exposure apparatus of the present invention.
The device manufacturing method according to the present invention is a device manufacturing method including a lithography process, and uses the exposure method or the exposure apparatus of the present invention in the lithography process.

  In addition, although the reference numerals in parentheses attached to the predetermined elements of the present invention correspond to members in the drawings showing an embodiment of the present invention, each reference numeral of the present invention is provided for easy understanding of the present invention. The elements are merely illustrative, and the present invention is not limited to the configuration of the embodiment.

<< First Embodiment >>
A first embodiment of the present invention will be described below with reference to FIGS.
FIG. 1 schematically shows a configuration of an exposure apparatus 10 including a scanning stepper type scanning exposure type projection exposure apparatus of the present embodiment. In FIG. 1, the exposure apparatus 10 includes a laser light source 16 as an exposure light source. , A spectrum monitor 15 for monitoring the spectral width of the laser beam emitted from the laser light source 16, the illumination optical system 12, a reticle stage RST for driving the reticle R illuminated by the illumination optical system 12, and a pattern of the reticle R A projection optical system PL for projecting onto the wafer W, a wafer stage WST having a Z tilt stage 58 for driving the wafer W and an XY stage 14 on which the Z tilt stage 58 is mounted, a control system for these, and the like are provided. . Hereinafter, the Z-axis is taken in parallel to the optical axis AX of the projection optical system PL, the X-axis is perpendicular to the plane of FIG. 1 in the plane perpendicular to the Z-axis, and the Y-axis is parallel to the plane of FIG. Take and explain. In this example, the scanning direction of the reticle R and the wafer W during scanning exposure is the Y direction (a direction parallel to the Y axis).

In this example, a KrF excimer laser (oscillation wavelength 248 nm) is used as the laser light source 16, and the laser light source 16 includes an excimer laser tube, two resonator mirrors arranged so as to sandwich the excimer laser tube, and the laser tube. And a narrow-band module disposed between the resonator mirror and one of the resonator mirrors. The laser controller 14 controls the start and end of pulse emission of the laser light source 16, the pulse emission frequency, the pulse energy, etc. under the control of the main controller 50 comprising a computer that controls the overall operation of the exposure apparatus. To control. As the laser light source 16, another excimer laser light source such as an ArF excimer laser (oscillation wavelength 193 nm) can also be used. Further, an F ₂ laser (oscillation wavelength 157 nm) can be used as the laser light source 16, and a harmonic generator such as a metal vapor laser, a YAG laser, or a semiconductor laser can also be used.

The laser beam LB as the exposure beam emitted from the laser light source 16 passes through the beam splitter 17 having a high transmittance, and then enters the illumination optical system 12 through a beam matching unit (not shown).
The laser beam reflected by the beam splitter 17 enters the spectrum monitor 15 for measuring the center wavelength and spectrum width of the incident light. In the spectrum monitor 15, the laser beam from the beam splitter 17 passes through the half mirror 15c and enters the beam monitor mechanism 15d. In addition, a reference light source 15a is disposed in the spectrum monitor 15, and the light emitted from the reference light source 15a in a state where the laser light source 16 is not emitting light and the shutter 15b is opened is half The light is reflected by the mirror 15c and enters the beam monitor mechanism 15d. Therefore, the laser beam branched from the laser beam LB by the beam splitter 17 or the light from the reference light source 15a can selectively enter the beam monitor mechanism 15d. Normally, the shutter 15b is closed, and the laser beam branched from the laser beam LB enters the beam monitor mechanism 15d.

  The beam monitor mechanism 15d is a Fabry composed of a condensing lens, a collimator lens, an etalon, a telemeter lens, a line sensor, and the like sequentially arranged on the optical path of a laser beam (or light from the reference light source 15a) branched from the laser beam LB. Includes a Perot interferometer. In this configuration, a fringe pattern (interference fringes) is formed on the focal plane of the telemeter lens, and this fringe pattern is detected by a line sensor arranged on the focal plane. The light intensity distribution detected by the line sensor is a number of mountain-shaped spectra that appear at predetermined intervals in the longitudinal direction of the line sensor corresponding to the fringe pattern.

  2A and 2B (the horizontal axis indicates the wavelength λ and the vertical axis indicates the light intensity I) each show an example of the spectrum. In this example, based on the detection result of the beam monitor mechanism 15d, The spectral width corresponding to the width when the intensity decreases to a predetermined ratio with respect to the peak value is measured. As this spectrum width, as shown in FIG. 2A, the full width at half maximum (FWHM: Full) which is the width of the wavelengths λ1 and λ2 when the intensity is reduced to ½ with respect to the peak value IP of the spectrum. Width Half Maximum) (hereinafter referred to as spectrum width FWHM) is detected.

  Instead of the spectrum width FWHM, a spectrum width determined based on the integral value of the spectrum intensity distribution can be used. As an example of this spectrum width, as shown in FIG. 2B, the integral value of the portion where the wavelength is λ3 or less is 2.5% with respect to the total integral value of the spectral intensity distribution, and the portion where the wavelength is λ4 or more. 95% energy purity width (hereinafter referred to as the integrated value of the intensity distribution within this width is 95% of the total integrated value) when the integrated value of 2.5% is 2.5%. It is also possible to use a spectrum width E95%).

  In FIG. 1, the position in the longitudinal direction of the line sensor corresponding to the peak of the peak of the light intensity distribution of the fringe pattern formed in the beam monitor mechanism 15d is determined according to the center wavelength. That is, the fringe pattern corresponds to the center wavelength λc of the incident light and the spectral width FWHM (or E95%), and the image signal of the fringe pattern from the line sensor inside the beam monitor mechanism 15d. Is output to the laser controller 14. As the center wavelength λc, the peak wavelength λp of the spectrum is used, but the wavelength (centroid wavelength) λg at the center of gravity of the intensity distribution can also be used.

Next, the reference light source 15a is a light source of reference wavelength light (reference light) when performing absolute wavelength measurement by the beam monitoring mechanism 15d, and a solid narrow-band laser is used. In the present embodiment, an Ar harmonic laser light source (argon ion second harmonic laser light source) is used as the reference light source 15a. The center wavelength of this Ar harmonic laser light source is 248.253 nm, which is very close to the center wavelength λ ₀ = 248.385 nm of a KrF excimer laser light source, and is suitable as a reference. When the laser light source 16 is an ArF excimer laser light source or the like, a light source having a narrow spectral width and a center wavelength close to the wavelength of the laser light source 16 may be employed as the reference light source 15a.

  Here, the absolute wavelength measurement of the beam monitor mechanism 15d performed by the laser controller 14 will be briefly described. At this time, the laser controller 14 first stops the light emission of the laser light source 16, opens the shutter 15b, and causes the light from the reference light source 15a to enter the beam monitor mechanism 15d. At this time, information on the fringe pattern obtained from the beam monitor mechanism 15 d is stored in the image memory in the laser control device 14. Subsequently, the laser control device 14 closes the shutter 15b, starts the light emission of the laser light source 16, makes the laser beam branched from the laser beam LB enter the beam monitor mechanism 15d, and obtains the laser obtained from the beam monitor mechanism 15d. The measured spectrum (measured apparent spectral characteristic) s (λ) of the laser beam LB is obtained by comparing the fringe pattern corresponding to the beam LB with the fringe pattern in the image memory (the fringe pattern of the reference light). . However, since this measured spectrum s (λ) includes the influence of the spectral characteristics of the reference light, the laser control device 14 eliminates the influence and performs the actual spectrum (true) of the laser beam LB as follows. The spectral characteristic) f (λ) is obtained. Note that s (λ) and f (λ) represent light intensity distributions with respect to the wavelength λ, respectively.

  In this case, in this embodiment, an Ar harmonic laser is used as a reference light source, and the spectral width (FWHM) of the Ar harmonic laser is very narrow, 0.01 pm or less, and the spectral width of the laser beam LB ( FWHM) is about 0.1 to 0.2 pm, so the Ar harmonic laser is regarded as light with an infinitely narrow bandwidth, and the measured spectrum s (λ) is regarded as the actual spectrum f (λ). Is also possible.

  However, more precisely, using the device function mi (λ), which is a single measured spectrum of the Ar harmonic laser, and the Fourier transform M (ω), the actual spectrum f (λ) of the laser beam LB as follows: Is desirable. That is, since the actually measured spectrum s (λ) of the laser beam LB is considered to be a convolution (represented by the symbol *) of the actual spectrum f (λ) and the device function mi (λ), the following equation (1) is established.

s (λ) = f (λ) * mi (λ) (1)
Therefore, in order to perform the deconvolution of Expression (1), when Expression (1) is Fourier-transformed, Fourier transforms S (ω) and F (ω) of the spectra s (λ), f (λ), and mi (λ) are performed. , M (ω) is as follows.
S (ω) = F (ω) · M (ω) (2)
Therefore, if the function S (ω) / M (ω) is subjected to inverse Fourier transform (F ⁻¹ ), the actual spectrum f (λ) of the laser beam LB can be obtained as follows.

F ⁻¹ [S (ω) / M (ω)] = F ⁻¹ [F (ω)] = f (λ) (3)
In this way, in the present embodiment, the laser control device 14 can perform deconvolution to obtain the actual spectrum f (λ), and based on the actual spectrum f (λ), the accurate laser beam LB can be obtained. Information on spectral characteristics, that is, information on the center wavelength λc (λp or λg) and the spectral width FWHM (or E95%) can be obtained. It is possible to provide the main controller 50 with all or part of the function for obtaining information on the spectral characteristics. Further, at least a part of the spectrum monitor 15 may be provided inside the laser light source 16.

  The laser control device 14 transmits information on the center wavelength λc and the spectral width FWHM (or E95%) of the laser beam LB to the main control device 50, and the main control device 50 stores the information in the storage device 51. Then, as necessary, the main controller 50 transmits information on the target value of the wavelength of the laser beam LB to the laser controller 14. The laser control device 14 controls the band narrowing module in the laser light source 16 so that the shift amount Δλ of the center wavelength λc with respect to the target value set by the main control device 50 becomes small.

  Thus, the measurement of the spectral characteristics of the laser beam LB using the spectrum monitor 15 may be executed every day, for example, at the start of operation of the exposure apparatus 10. Since the change in the spectrum width is small, the spectrum width may be measured every predetermined number of days, for example, after the maintenance of the laser light source 16 or the like. Further, a predetermined specification (upper limit value) is determined for the spectral width of the laser beam output from the laser light source 16, and the spectral width is usually close to the value of the specification. Therefore, it is possible to approximate the spectrum width of the laser beam LB with the value of the specification of the spectrum width. The value of the spectrum width (FWHM or E95%) in this case is also stored in the storage device 51.

  Next, the illumination optical system 12 includes a beam shaping optical system 18, an energy coarse adjuster 20, a fly-eye lens 22 as an optical integrator (homogenizer), an illumination system aperture stop plate 24, a beam splitter 26, a first relay lens 28A, A fixed blind 30A, a movable blind 30B, a second relay lens 28B, an optical path bending mirror M, a condenser lens 32, and the like are provided.

  In the illumination optical system 12, the beam shaping optical system 18 efficiently enters the cross-sectional shape of the laser beam LB pulsed from the laser light source 16 into the fly-eye lens 22 provided behind the optical path of the laser beam LB. For example, a cylinder lens or a beam expander is used. The energy coarse adjuster 20 is disposed on the optical path of the laser beam LB that has passed through the beam shaping optical system 18, and here, a plurality of ND filters (having different transmittances around one or a plurality of rotating plates 34). (Attenuation filter) 36A, 36D, etc. are arranged, and the rotating plate 34 is rotated by a drive motor 38 controlled by the main controller 50, whereby the transmittance for the incident laser beam LB is switched from 100% in a plurality of stages. be able to. The energy coarse adjuster 20 may be one that continuously changes the intensity of the laser beam LB.

  The fly-eye lens 22 is arranged on the optical path of the laser beam LB emitted from the energy coarse adjuster 20, and in order to illuminate the reticle R with a uniform illuminance distribution, a surface light source composed of a number of secondary light sources is provided at the exit end. Form. Hereinafter, the laser beam emitted from the surface light source is referred to as exposure light EL. Instead of the fly-eye lens 22, a rod lens (an internal reflection type integrator) or a diffractive optical element may be used.

  A disc-shaped illumination system aperture stop plate 24 is disposed in the vicinity of the exit surface of the fly-eye lens 22. The illumination system aperture stop plate 24 includes, for example, an aperture stop for normal illumination, an aperture stop for illumination with a small coherence factor (σ value), an annular aperture stop for annular illumination, and substantially equal angular intervals. An aperture stop composed of a plurality of eccentric apertures for the modified illumination method is disposed. The illumination system aperture stop plate 24 is rotated by a driving device 40 such as a motor controlled by the main controller 50, whereby any aperture stop is selectively set on the optical path of the exposure light EL. Instead of the illumination system aperture stop plate 24, an optical system in which a diffractive optical element, a pair of prisms (for example, a conical axicon system) at least one of which is movable, and a zoom lens system can be used. .

  A beam splitter 26 having a high transmittance is disposed on the optical path of the exposure light EL emitted from the illumination system aperture stop plate 24, and further, the first and second blinds 30A and 30B are interposed on the rear optical path. A relay optical system including the relay lens 28A and the second relay lens 28B is disposed. The fixed blind 30A is disposed on a surface slightly defocused from the conjugate surface with respect to the pattern surface of the reticle R, and a rectangular opening that defines the illumination area IAR on the reticle R is formed. In addition, a movable blind 30B having an opening having a variable position and width in the direction corresponding to the scanning direction (and the direction corresponding to the non-scanning direction) is disposed in the vicinity of the fixed blind 30A. Sometimes further limiting the illumination area IAR via the movable blind 30B prevents exposure of unwanted portions.

  FIG. 3A conceptually shows how the illumination area IAR (shaded portion) on the reticle R is defined by the fixed blind 30A. FIG. 3A is a view of the fixed blind 30A viewed from the −Y direction. The Z direction in FIG. 3A corresponds to the Y direction which is the scanning direction on the reticle R, and the Y direction in FIG. 3A corresponds to the Z direction parallel to the optical axis AX on the reticle R. As is apparent from FIG. 3A, an image of the rectangular slit-shaped opening of the fixed blind 30A is formed on the pattern surface of the reticle R, and the rectangular slit-shaped illumination area IAR is defined. In this case, the illumination area IAR extends in the X direction, which is the non-scanning direction, at the center of the circular field IF of the projection optical system PL, and the width in the scanning direction (Y direction) is equal to that at the start of one scanning exposure. It is fixed except at the end.

Returning to FIG. 1, the exposure light EL that has passed through the openings of the blinds 30 </ b> A and 30 </ b> B illuminates the pattern surface of the reticle R via the second relay lens 28 </ b> B, the mirror M, and the condenser lens 32.
On the other hand, the exposure light EL reflected by the beam splitter 26 is received by an integrator sensor 46 including a light receiving element via a condenser lens 44, and the detection signal DS of the integrator sensor 46 is an exposure amount control unit in the main controller 50. Has been supplied to. The exposure amount control unit indirectly obtains the exposure amount (exposure energy) for each pulse of the exposure light EL on the wafer W from the detection signal of the integrator sensor 46, integrates this exposure amount, and calculates each point on the wafer W. Based on this result, for example, the laser controller 14 is instructed about the energy at the time of the next pulse emission of the laser light source 16.

  The reticle R is held by suction on the reticle stage RST. Reticle stage RST can be finely driven in an XY plane (here, a horizontal plane) and is scanned on a reticle base (not shown) in a scanning direction (Y direction) within a predetermined stroke range by reticle stage driving unit 56R. The position of the reticle stage RST during the scanning is measured by an external laser interferometer 54R via a movable mirror 52R fixed on the reticle stage RST, and the measured value of the laser interferometer 54R is supplied to the main controller 50. Is done. Instead of providing the movable mirror 52R, for example, the side surface of the reticle stage RST may be mirror-finished to form a reflecting surface.

The projection optical system PL is a double-sided telecentric reduction system and a refraction system including a plurality of lens elements 61 ₁ , 61 ₂ ,. The projection magnification β of the projection optical system PL is, for example, 1/4, 1/5, or the like. As described above, when the illumination area IAR on the reticle R is illuminated by the exposure light EL, an image (partial inverted image) obtained by reducing the circuit pattern in the illumination area with the projection magnification β by the projection optical system PL is applied to the surface of the photoresist. It is projected onto a slit-like exposure area IA (an area optically conjugate with the illumination area IAR) on the wafer W coated with (photosensitive agent).

In the present embodiment, a mechanism for moving the position of the image plane of the projection optical system PL in the direction of the optical axis AX is incorporated in the projection optical system PL. Specifically, it is supported by three different points by an actuator 62 in which the lens holder is made of a piezoelectric element for holding the lens element 61 ₁ located closest to the reticle R in the projection optical system PL. Then, the main controller 50 by driving the actuator 62 via the lens controller (not shown), the lens elements 61 ₁ located closest to the reticle R, the lens element 61 ₂ in the position closer to the second The interval is adjusted, and the position of the image plane of the projection optical system PL can be adjusted within a predetermined range in the Z direction.

  The wafer stage WST that moves while attracting and holding the wafer W is, for example, driven on a wafer base (not shown) by a drive system composed of a linear motor or the like in a scanning direction (Y direction) and a non-scanning direction (X direction) orthogonal thereto. XY stage 14 that is two-dimensionally driven and also driven minutely in the rotation direction around the Z axis, and is mounted on XY stage 14 and holds wafer W by vacuum suction or the like via a wafer holder (not shown). And a tilt stage 58.

  The Z tilt stage 58 is mounted on the XY stage 14 in a state in which movement in the Z direction and tilting around the X axis and the Y axis are allowed. The Z tilt stage 58 is supported at three different support points by three shafts 27 (however, the shaft on the back side of the drawing is not shown in FIG. 1), and these three shafts 27 are driven. It is driven independently in the Z-axis direction by the system. As a result, the position (plane position) of the surface of the wafer W held on the Z tilt stage 58, the position in the Z direction and the tilt angle with respect to the XY plane are set to a desired state.

In FIG. 1, the drive system of the XY stage 14 and the drive system of the Z tilt stage 58 are typically shown as a wafer stage drive unit 56W. Measure the position of the movable mirror 52W fixed on the Z tilt stage 58 (actually, two axes are arranged so as to be orthogonal) with a multi-axis laser interferometer 54W arranged to face the outside. Thus, the position and rotation amount of the Z tilt stage 58 (XY stage 14) in the X and Y directions (including the rotation amount (yaw amount) at least around the Z axis in this embodiment) is, for example, about 0.1 nm. Always detected with resolution. The measured values of the laser interferometer 54W are sent to the main controller 50, and the main controller 50 determines the X and Y positions of the XY stage 14 and the Z direction via the wafer stage drive unit 56W based on these measured values. Controls the angle of rotation around the axis.
Instead of providing the movable mirror 52W, for example, the side surface of the wafer stage WST (such as the Z tilt stage 58) may be mirror-finished to form a reflecting surface. Wafer stage WST may have a coarse / fine movement configuration in which, for example, Z tilt stage 58 can be finely moved in the XY plane.

  Further, in the present embodiment, oblique incident light type autofocus detection systems 19A and 19B are provided for detecting the position (focus position) in the Z direction of the exposure area IA on the surface of the wafer W and the vicinity thereof. Yes. The autofocus detection systems 19A and 19B are composed of an irradiation optical system 19A and a light receiving optical system 19B. As this focus detection system 19, for example, a multipoint focal position detection system disclosed in Japanese Patent Laid-Open No. 6-283403 is used. The output of the focus detection system 19 is supplied to the main controller 50. In the main controller 50, the Z-direction on the optical axis AX of the surface (average surface) of the wafer W is based on the output of the light receiving optical system 19B. The position (Z position) and inclination angles around the X axis and Y axis are obtained, and the Z tilt stage 58 is controlled by the autofocus method so that the Z position and inclination angle coincide with a predetermined target value.

  Instead of or in combination with autofocus detection systems 19A and 19B, a movable mirror (reflecting member) provided on the side surface of wafer stage WST is irradiated with a plurality of laser beams, and Z-axis of wafer stage WST. A laser interferometer (Z interferometer) that measures the position in the direction and the rotation angle about the X axis and the Y axis is provided, and the Z tilt stage 58 is controlled based on the measured value of the Z interferometer during the exposure operation. It is good. Details of the exposure apparatus provided with the Z interferometer are disclosed in, for example, Japanese Patent Application Publication No. 2001-510577 (and the corresponding pamphlet of International Publication No. 1999/28790).

  The main controller 50, which is the main part of the control system of the exposure apparatus of this example, is configured to include a computer comprising a CPU (Central Processing Unit), a semiconductor memory, a magnetic disk device, a communication unit, etc. For example, in addition to the above-described autofocus control of the wafer W, the synchronous scanning of the reticle R and the wafer W, the stepping of the wafer W, the exposure timing, and the like are controlled in an integrated manner. Further, another storage device 51 such as a magnetic disk device is connected to the main controller 50, and various exposure data and the like are stored in the storage device 51.

Specifically, in the exposure process, main controller 50 aligns each shot area (partition area) of reticle R and wafer W using an alignment system (not shown). Next, the illumination condition is set by controlling the illumination system aperture stop plate 24, and an oscillation frequency (light emission timing) and light emission of the laser light source 16 are applied to the wafer W to provide an integrated exposure amount determined according to the photoresist sensitivity and the like. Control information such as power is sent to the laser control device 14, and the transmittance of the energy coarse adjuster 20 is controlled as necessary. Then, at the time of scanning exposure, main controller 50 synchronizes with scanning of reticle R through illumination stage IAR at a speed V _R in the Y direction through reticle stage RST, and wafer through wafer stage WST. The positions and speeds of reticle stage RST and wafer stage WST are controlled so that W is scanned at a speed β · V _R (β is the projection magnification) in a direction corresponding to exposure area IA. At this time, for example, the opening / closing operation of the movable blind 30B is controlled in synchronization with the operation of the reticle stage RST. When stepping the wafer W, the main controller 50 controls the position of the wafer stage WST via the wafer stage driving unit 56W based on the measurement value of the laser interferometer 54W. As a result, the image of the pattern of the reticle R is sequentially exposed to each shot area (partition area) on the wafer W.

Here, the progressive focus exposure method by the exposure apparatus 10 according to the present embodiment will be described with reference to FIGS. In this case, the circuit pattern formed on the reticle R of FIG. 1 includes a large number of contact hole patterns which are isolated patterns as an example.
FIGS. 4A to 4C show a circuit pattern IR formed on the reticle R in FIG. 1 and a part of the surface of the wafer W in order to visually understand the progressive focus exposure method according to this embodiment. A region (region in a certain shot region) is schematically shown. In these figures, for convenience of explanation, the projection magnification β of the projection optical system PL is set to 1 (upright image). In addition, position numbers 1 to 9 for explanation are set in the circuit pattern IR, and position numbers 1 to 9 are respectively provided at positions on the wafer W where the images of the portions of the position numbers 1 to 9 on the circuit pattern IR are exposed. Is set. Further, as described above, the wafer W is held on the Z tilt stage 58 of FIG. 1, and in this embodiment, the upper surface of the Z tilt stage 58 (and thus the surface of the wafer W) is a plane perpendicular to the optical axis AX (here, , Which is parallel to the best imaging plane BF, which is the image plane of the projection optical system PL, indicated by a two-dot chain line) around the axis parallel to the non-scanning direction (axis parallel to the X axis) Is inclined by a predetermined angle θ.

  The exposure light in the illumination area IAR defined by the fixed blind 30A in FIG. 1 (the movable blind 30B is fully opened) is a width in the scanning direction on the wafer W in FIG. 4A via the projection optical system PL. Are projected onto the exposure area IA of D, and three typical light beams LR, LC, and LL are shown in FIGS. 4A to 4C. The light beam LC passes through substantially the center of the exposure area IA (on the optical axis AX), and the light beams LR and LL pass through both ends of the exposure area IA in the scanning direction.

  At the time of scanning exposure, the main controller 50 in FIG. 1 drives the XY stage 14 in the Y direction, and at the same time the surface of the wafer W is inclined by the angle θ with respect to the best imaging plane BF of the projection optical system PL. In addition, the Z tilt stage 58 is moved in the optical axis AX direction (Z) so that the surface of the wafer W always coincides with the best imaging plane BF at the approximate center (optical axis AX position) of the exposure area IA with respect to the scanning direction (Y axis direction). Direction). At this time, each point on the wafer W (for example, a point of position number 1) changes its position in the Z direction by ΔZ while traversing the exposure area IA in the scanning direction. This is referred to as the swing width in the optical axis AX direction). Assuming that the tilt angle θ is a minute amount, the Z swing width ΔZ is approximately as follows using the width D in the scanning direction of the exposure area IA and the tilt angle θ [rad].

ΔZ = D · θ (4)
In the main controller 50, the value of the depth of focus (DOF) of the projection optical system PL, that is, the width in the optical axis direction of the projection optical system PL at the position of the exposure surface where an acceptable resolution is obtained is defined as DF and the depth of focus DF. The Z swing width ΔZ is set to kf times the focal depth DF as follows using a coefficient kf larger than a predetermined 1 that changes accordingly. The value of the coefficient kf is about 3 to 4 as an example.

ΔZ = D · θ = kf · DF (5)
In this case, the depth of focus DF of the projection optical system PL changes according to the spectral width FWHM (or E95%, the same applies hereinafter) of the exposure light EL (laser beam LB). Normally, when the spectral width of the laser beam LB becomes narrower, the depth of focus becomes shallower (value DF becomes smaller), and the change in the coefficient kf is small, so that each point (exposed region) on the surface of the wafer W is expressed by Equation (5). The Z swing width ΔZ is also reduced. That is, when the spectral width of the laser beam LB is narrowed and the depth of focus of the projection optical system PL is shallower than DF1 (<DF), the inclination angle θ is reduced to θ1 (= kf · DF1 / D) from Equation (5). Thus, the Z swing width is also reduced to ΔZ1 (= D · θ1).

In other words, as in this example, the projection accompanying the change in the spectral width of the laser light source 16 is optimized by optimizing the Z swing width ΔZ when the progressive focus exposure method is applied according to the spectral width FWHM of the laser beam LB. It is possible to reduce the influence of changes in the imaging characteristics (here, the depth of focus) of the optical system PL.
In order to more accurately determine the Z oscillation width ΔZ according to the spectral width FWHM of the laser beam LB, the spectral width FWHM is changed by a predetermined step amount from FWHM1 to FWHMm (m is an integer of 2 or more) The respective focal depths DF1 to DFm of the projection optical system PL are obtained, and for each of these focal depths DF1 to DFm, by calculation or by test prints at various inclination angles θ, for example, a contact hole pattern of a predetermined shape has a high resolution. What is necessary is just to obtain | require Z swing width (DELTA) Z1- (DELTA) Zm at the time of exposure. In this case, in the storage device 51 of FIG. 1, for example, the optimum Z swing widths ΔZ1 to ΔZm obtained in this manner are set in a table corresponding to the focal depths DF1 to DFm (or spectrum widths FWHM1 to FWHMm themselves). You can remember as.

  Thereafter, when information on the spectrum width FWHM of the laser beam LB measured by the spectrum monitor 15 is transmitted from the laser control device 14 to the main control device 50, the main control device 50 obtains the focal depth DF from the spectrum width FWHM. By interpolating the values of the Z swing widths ΔZi, ΔZ (i + 1) (i = 1 to (m−1)) corresponding to the values before and after the depth of focus DF from the table in the storage device 51, the optimum value is obtained. The Z swing width ΔZ can be obtained. When the optimum Z swing widths ΔZ1 to ΔZm are stored in the table so as to correspond to the spectral widths FWHM1 to FWHMm, the main controller 50 causes the Z swing corresponding to the values before and after the spectral width FWHM. The optimum Z swing width ΔZ may be obtained by interpolating the values of the widths ΔZi and ΔZ (i + 1). Further, instead of using the table, an optimum Z swing width ΔZ may be calculated as a predetermined function (for example, a linear function or an exponential function) of the focal depth DF (or spectral width FWHM).

  As an example, when the spectral width FWHM of the laser beam LB in FIG. 1 is 0.20 pm, the focal depth DF of the projection optical system PL is 50 nm, and the optimum value of the Z swing width ΔZ corresponding to it is 190 nm (formula The coefficient kf of (5) is 3.80). Further, when the spectral width FWHM of the laser beam LB is narrowed to 0.12 pm, the focal depth DF of the projection optical system PL is as shallow as 30 nm, and the optimum value of the Z swing width ΔZ corresponding thereto is 110 nm (formula (5) coefficient kf = 3.67), which is 80 nm narrower than the former case.

  In addition to the spectral width of the laser beam LB (exposure light EL) (and hence the depth of focus of the projection optical system PL) as parameters for determining the optimum Z swing width ΔZ, Resist sensitivity, scanning speed of the wafer W, and the like may be used. Even when the number of parameters increases in this way, the optimum Z swing width ΔZ may be obtained by calculation or test printing for each combination of the parameters for each predetermined step.

  Hereinafter, the scanning exposure method (progressive focus exposure method) according to the present embodiment will be described in order, assuming that the optimum Z swing width ΔZ is determined according to the spectral width FWHM of the laser beam LB in FIG. The positional relationship with respect to the exposure light flux between the wafer W and the circuit pattern IR immediately after the scanning exposure is started is as shown in FIG. When attention is paid to position 2 in the circuit pattern IR, this position 2 has entered the exposure area IA and is in a state of being irradiated with the light beam LR. In this state, the image at position 2 on the wafer W is in a defocused state, and the intensity distribution of the projected image has a gentle peak. Further, when the scanning exposure proceeds, the state shown in FIG. 4B is reached, and the position 2 on the wafer W is located on the best imaging plane BF. In this state, the image at position 2 is in the best focus state, and the peak of the intensity distribution of the image is sharp. When the reticle R and the wafer W are moved to the position shown in FIG. 4C, the position 2 is in a defocus state opposite to the state shown in FIG. 4A, and the peak of the intensity distribution of the image due to the light beam LL is It becomes a gradual state.

  As shown in FIG. 5A, the distribution of the exposure amount (exposure energy amount) irradiated to the position 2 on the wafer W in the optical axis AX direction (Z-axis direction) by the above scanning exposure is the best result. It is almost uniform in the range of the Z swing width ΔZ centered on the image plane (range of the focal depth DF or more). This means that when the wafer surface moves within the range of the Z swing width ΔZ, the exposure amount of an isolated pattern, for example, a contact hole image applied to the resist layer on the wafer W is substantially constant within the range of ΔZ. To do. The fact that a substantially constant exposure amount (contact hole image) is obtained over a wide range in the optical axis direction in this way means that the depth of focus is substantially (apparently) widened accordingly.

Further, the intensity distribution of the image given to the position 2 by the above scanning exposure is as shown in FIG. 5B and FIG. 5C. Here, the intensity distributions ER, EC, and EL in FIG. 5B represent the image intensities obtained by the light beams LR, LC, and LL in FIG. 4A, respectively. The intensity distribution E represents the integrated value of the image intensity obtained by the exposure light including the light beams LR, LC, and LL. In this case, since the position 2 is irradiated with the light beam while it is in the exposure area IA, the integrated image intensity distribution E has a gentle peak distribution. In this case, the width having the intensity equal to or higher than the threshold value P _{0 of the} accumulated energy for exposing the resist layer on the wafer W (completely removed in the case of the positive type) is the width G shown in FIG. Since the width G is substantially constant regardless of the height on the resist layer on the wafer W, a resist image is stably formed after development of the resist layer.

  Also in this case, when the spectral width of the laser beam LB in FIG. 1 becomes narrow and the depth of focus of the projection optical system PL becomes shallow to the value DF1 in FIG. By narrowing from (5) to ΔZ1, the exposure amount distribution in the Z direction becomes substantially constant in the range of the width ΔZ1 as shown in FIG. 5A, so that the resist image is stable after development of the resist layer. Formed.

  In order to narrow the width G of the pattern image in FIG. 5C, the light amount distribution in the exposure area IA on the wafer W may be maximized at least at two locations in the scanning direction. For this purpose, instead of the fixed blind 30A of FIG. 3 (A), for example, a fixed blind 30A ′ having a double slit-shaped opening shielded from the center as shown in FIG. 3 (B) may be used. . When such a fixed blind 30A ′ is used, the distribution in the optical axis AX direction of the exposure amount irradiated to an arbitrary position (for example, position 2 described above) on the wafer W by scanning exposure is shown in FIG. As shown in the figure, the two parts near both ends of the range of the Z swing width ΔZ (ΔZ1 when the spectrum width is narrow) have the same level of intensity (peak). Thereby, it becomes possible to give intensity | strength only to the part corresponded to the light beams LL and LR of both ends among the exposure light shown in FIG. 4 (A)-(C).

Further, when scanning exposure similar to the above is performed using the fixed blind 30A ′, the intensity distribution of the image obtained at an arbitrary position on the wafer W (for example, the position 2 described above) is shown in FIG. B) and as shown in FIG. Here, the intensity distributions ER ′ and EL ′ in FIG. 6B represent the image intensities obtained by the light beams LR and LL, respectively, and the intensity distribution E ′ in FIG. It represents the integrated value of image intensity obtained by exposure light including LL. As is apparent from a comparison between FIG. 6C and FIG. 5C, the intensity distribution E ′ has a sharper peak than the intensity distribution E, and the resist on the wafer W is exposed (completely removed). It can be seen that the width G ′ having an intensity equal to or greater than the threshold value P _{0 of the} integrated energy is narrower than the width G. Therefore, by adopting the fixed blind 30A ′ having a double slit-shaped opening, exposure with high resolution capable of forming an isolated pattern with little image blur, for example, an image of a contact hole, while substantially increasing the depth of focus. It becomes possible.

In addition, by adopting the above progressive focus exposure method, it is a matter of course that even if there are irregularities on the wafer W, the pattern is transferred with the same accuracy in both the concave and convex portions. As is clear from the above description, according to the progressive focus exposure method according to the present embodiment, it is possible to realize highly accurate transfer of an isolated pattern by substantially increasing the depth of focus.
In the above embodiment, the case where a double-slit fixed blind is employed in order to improve the resolution of an image formed on the wafer W has been described. However, the present invention is not limited to this, and there are three or more openings. Such fixed blinds can also be employed. In this case, the scanning speed of the XY stage 14 can be increased as compared with the case where a double slit-shaped fixed blind is employed.

Further, when a fixed blind having a rectangular opening as shown in FIG. 3A is used, a size corresponding to a region to be shielded, which is disposed at a position almost conjugate with the circuit pattern IR in the optical path, and By providing the light shielding member having the shape, the same effect as that in the case of using the double-slit fixed blind or the fixed blind having three or more openings can be obtained.
In the above embodiment, the wafer stage WST is driven with the surface of the wafer W tilted by a variable angle θ. However, the present invention is not limited to this, and for example, the optical element (lens element) of the projection optical system PL. ) And reticle R may be used to drive wafer stage WST parallel to the XY plane while tilting the image plane of projection optical system PL by the variable angle θ.

<< Second Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIGS. Here, the same reference numerals are used for the same or equivalent components as those in the first embodiment described above, and descriptions thereof are omitted or simplified.
The configuration of the exposure apparatus of this example is the same as that of the first embodiment of FIG. 1 described above, and exposure is performed by the step-and-scan method, as in the first embodiment described above. The pattern of the reticle R is transferred to each shot area on the wafer W. At that time, similarly to the first embodiment, the projection optical system when applying the progressive focus exposure method according to the spectrum width FWHM (or E95%, etc.) of the laser beam LB by the main controller 50 of FIG. A Z swing width ΔZ that is a relative fluctuation width in the Z direction between the image plane of PL and an exposed area (shot area) on the surface of the wafer W is set.

However, in the exposure apparatus of this example, the control method of the Z tilt stage 58 at the time of scanning exposure (when the progressive focus exposure method is applied) by the main controller 50 is different from the first embodiment described above. The explanation will be focused on the point.
FIG. 7A shows how the shot area SA on the wafer W is scanned in the + Y direction with respect to the exposure area IA by the projection optical system PL during the scanning exposure of this example. As shown in FIG. 7A, when the scanning speed of the wafer W during scanning exposure is V _W , and the width of the exposure area IA in the scanning direction is D, the wafer W has a width in the Y direction (scanning direction). The time to move by D (the time to move one point Q in the shot area of the wafer W by the distance D) T ₀ is expressed by the following equation (6).

T ₀ = D / V _W (6)
Further, the main controller 50, when scanning the shot area SA on the wafer W with respect to exposure area IA, during the time T ₀ to a point Q in the shot area SA on the wafer W passes through the exposure area IA The exposure surface (front surface) of the wafer W is periodically oscillated in the Z direction with respect to the image surface of the projection optical system PL via the Z tilt stage 58. FIG. 7B shows how the position in the Z direction (Z position) of the exposure surface of the wafer W at that time changes with time t. In this FIG. 7 (B), the position Z ₀ is Z position of the image plane of the projection optical system PL (the best focus plane). As indicated by a solid curve A in FIG. 7B, the Z position of the exposure surface of the wafer W is between the position (Z ₀ + b) and the position (Z ₀ -b) with a constant period T ₀ . It changes in a sine wave shape. The Z swing width ΔZ (= 2b) is set based on the original focal depth DF (see FIG. 4A) of the projection optical system PL and the spectral width FWHM of the laser beam LB (exposure light EL). In this case, the initial position of the exposure surface of the wafer W in the Z direction, that is, the Z position when the movement in the Z direction is started is an arbitrary position between the position (Z ₀ + b) and the position (Z ₀ -b). Good.

In this case, when the exposure surface of the wafer W moves from the position (Z ₀ -b) to the position (Z ₀ + b), and conversely, the exposure surface of the wafer W moves from the position (Z ₀ + b) to the position (Z ₀ when moving to the -b), the speed V _Z in the Z direction of the Z tilt stage 58, characteristic curve a obtained by differentiating at the time t in FIG. 7 (B), i.e. such that the cosine wave, the main controller 50 Controlled by. In this example, the pulse oscillation of the laser light source 16 needs to be performed in synchronization with the scanning of the wafer W and the reticle R. However, the movement of the Z tilt stage 58 in the Z-axis direction is speed-controlled using the speed characteristics as described above. Just do it.

In this case, while a certain exposure point Q in the shot area SA on the wafer W in FIG. 7A crosses the exposure area IA having the width D, the Z position of the exposure point Q is the position (Z 1 round trip is made between ₀ + b) and the position (Z ₀ -b). Further, while the exposure point Q crosses the exposure area IA having the width D, the laser light source 16 in FIG. 1 emits M (M is an integer equal to or larger than the minimum exposure pulse) ultraviolet pulsed light at a substantially constant period. At the same time, an image of the same pattern on the reticle R in FIG. Accordingly, the distribution of the exposure energy E (Z) with respect to the Z position at the exposure point Q is as shown by a distribution curve M1 indicated by a solid line in FIG. 8, and the position (Z ₀ −b) and the position (Z ₀ + b) The exposure energy at is increased.

In the same manner as described above, while any exposure point other than the exposure point Q in the shot area SA of the wafer W crosses the exposure area IA having the width D in the X direction, the Z position of the exposure point is the position (Z ₀ + b) and 1 reciprocates between the position (Z ₀ -b). Therefore, the distribution of exposure energy at an arbitrary exposure point increases at the position (Z ₀ −b) and the position (Z ₀ + b), and the depth of focus of the projection optical system PL substantially increases. Therefore, even if there are irregularities on the wafer W, the pattern is transferred with the same accuracy in both the concave and convex portions. Also in this case, particularly when an isolated pattern such as a contact hole is projected and exposed on the wafer W, the effect of increasing the depth of focus is increased.

In the present embodiment, generally, _assuming that the period of vibration in the Z direction of the exposure surface of the wafer W is T _n (n is an integer of 1 or more), the period T _n is an arbitrary point on the wafer W. The width D of the exposure area IA may be set to 1 / n of the time T ₀ that crosses in the Y direction. That is, using the width D of the scan velocity V _W and the exposure area IA of the wafer W, the period T _n is expressed by the following equation (7).
T _n = T ₀ / n = D / (n · V _W ) (7)
A curve B in FIG. 7C shows, as another example when the condition of the above formula (7) is satisfied, how the Z position of the exposure surface of the wafer W changes with time t when n = 2. It is shown. In this case, any exposure point in the shot area SA on the wafer W, while traversing the exposure area IA of the width D in the Y-direction, Z position is the position (Z ₀ + b) and position (Z ₀ -b) 2 round trips. Therefore, also in this case, the distribution of the exposure energy at an arbitrary exposure point is as shown by the distribution curve M1 in FIG.

Although not within the condition of Expression (7), as shown by a dotted curve A2 in FIG. 7B, the time at which an arbitrary point on the wafer W crosses the width D of the exposure area IA in the X-axis direction. The exposure surface of the wafer W may be periodically oscillated in the Z direction with respect to the image plane of the projection optical system PL at a period twice as long as T ₀ . Even in this case, an arbitrary exposure point in the shot area of the wafer W moves between the position (Z ₀ + b) and the position (Z ₀ -b) while crossing the exposure area IA having the width D. To do. Therefore, the effect of increasing the depth of focus can be obtained.

Further, when the spectral width FWHM of the laser beam LB (exposure light EL) in FIG. 1 becomes narrow and the depth of focus of the projection optical system PL becomes shallow to the value DF1 in FIG. 4A, FIGS. The Z swing width ΔZ in C) is also an interval between the position (Z ₀ + c) and the position (Z ₀ -c) as indicated by the curves A1 and B1. In this case, the width 2c corresponds to the Z swing width ΔZ1 in FIG. In response to this, the exposure energy for Z position for each point on the wafer W E (Z), as indicated by the curve M3 in FIG. 8, greatly and position (Z ₀ + c) and the position (Z ₀ -c) Become. Thereby, the Z oscillation width is optimized according to the spectrum width of the laser beam LB.

Note that the distribution of the exposure energy E- (Z) with respect to the Z position has a substantially uniform value from the position (Z ₀ -b) to the position (Z ₀ + b), as shown by the dotted straight line M2 in FIG. May be.
As described above, in the second embodiment, the progressive focus exposure method is executed for each shot area SA on the wafer W during scanning exposure.

As described above, according to the exposure apparatus and the exposure method according to the second embodiment, the same effects as those of the first embodiment described above can be obtained.
In the second embodiment, the case where the surface of the wafer W is driven sinusoidally (continuously) in the optical axis direction with respect to the image plane of the projection optical system PL has been described. However, the present invention is limited to this. For example, it may be vibrated in a triangular wave shape or the like. Further, the surface of the wafer W may be driven intermittently in the optical axis direction with respect to the image plane of the projection optical system PL so that the Z position of the surface of the wafer W changes stepwise or trapezoidally with respect to time t, for example. . Even in these cases, the distribution of the energy amount at an arbitrary point on the wafer becomes a distribution close to the curve M1 in FIG. 8, so that the effect of a substantial increase in the depth of focus can be obtained.

In the first and second embodiments, when the progressive focus exposure method is performed, the wafer W is moved in the optical axis direction (Z direction) of the projection optical system PL, so that the image plane of the projection optical system PL Although the case where the relative positional relationship with the surface of the wafer W is changed has been described, the present invention is not limited to this. For example, the position of the exposure surface of the wafer W is fixed and the image plane of the projection optical system PL is fixed. The position itself may be changed. In this case, the relative drive device for relatively driving the surface of the image plane and the wafer W in the Z direction, for example, the moving mechanism of the lens elements 61 _1, associated with the projection optical system PL in FIG. 1 It may be used. Even in this case, it is possible to obtain the same effect as the above embodiment.

  In addition, when the double-sided telecentric projection optical system PL as in each of the above embodiments is used, the image plane of the projection optical system PL, the surface of the wafer W, and the surface of the wafer W are driven by slightly driving the reticle R in the optical axis AX direction. It is also possible to change the relative positional relationship. Further, the relative positional relationship between the image plane and the surface of the wafer W may be changed by shifting the center wavelength of the exposure light EL, or by using at least two of these methods in combination. Note that when the center wavelength of the exposure light EL is shifted, the imaging characteristics (projection magnification, focal position, aberration, etc.) of the projection optical system PL change. It is desirable to correct the variation in imaging characteristics by moving at least one optical element of the projection optical system PL (if the value is exceeded).

  In each of the above embodiments, the progressive focus exposure method is applied when an isolated pattern (contact hole or the like) is transferred. However, the present invention is not limited to this. For example, the reticle is a dense pattern (line and space pattern or the like). ), The progressive focus exposure method may be applied. Further, in each of the above embodiments, the position information of the reticle stage RST and the wafer stage WST is measured using the interferometer system (54R, 54W). However, the present invention is not limited to this, and is provided in each stage, for example. An encoder system that detects the scale (diffraction grating) to be used may be used. In this case, it is preferable that a hybrid system including both the interferometer system and the encoder system is used, and the measurement result of the encoder system is calibrated using the measurement result of the interferometer system. Further, the position of the stage may be controlled by switching between the interferometer system and the encoder system or using both.

  In each of the above embodiments, the case where the present invention is applied to a scanning stepper has been described. However, the scope of the present invention is not limited to this, and the present invention is also applied to a stationary exposure apparatus such as a stepper. Can be suitably applied. When applied to such a stepper or the like, for example, the progressive focus exposure method disclosed in Japanese Patent Laid-Open No. 5-13305 is used, and the energy amount distribution in the optical axis AX direction (Z swing width, The movement speed in the Z direction, etc.) may be changed.

  In the exposure apparatus of the above-described embodiment, after installing a column mechanism (not shown), an illumination optical system composed of a plurality of lenses and a projection optical system composed of a catadioptric system are incorporated in the exposure apparatus body and optical adjustment is performed. Then, a reticle stage or wafer stage made up of a large number of mechanical parts can be attached to the exposure apparatus body, wiring and piping are connected, and overall adjustment (electrical adjustment, operation check, etc.) can be made. The exposure apparatus is preferably manufactured in a clean room where the temperature, cleanliness, etc. are controlled.

  Further, when a semiconductor device is manufactured using the exposure apparatus of the above-described embodiment, the semiconductor device includes a step of designing a function and performance of the device, a step of manufacturing a reticle based on this step, and a wafer from a silicon material. Forming, aligning with the projection exposure apparatus of the above embodiment to expose the pattern of the reticle onto the wafer, forming a circuit pattern such as etching, device assembly step (dicing process, bonding process, packaging process) Including) and an inspection step.

  The present invention is applicable not only to so-called dry exposure but also to exposure using an immersion type exposure apparatus disclosed in, for example, International Publication No. 99/49504 and International Publication No. 2004/019128. it can. In addition, as disclosed in, for example, Japanese translations of PCT publication No. 2004-51850 (and corresponding US Pat. No. 6,611,316), two reticle patterns are synthesized on a substrate via a projection optical system, The present invention can also be applied to an exposure apparatus that performs double exposure of one shot area on a substrate almost simultaneously by one scanning exposure. Furthermore, the present invention can also be applied to the case where exposure is performed with a projection exposure apparatus that uses extreme ultraviolet light (EUV light) having a wavelength of about several nm to 100 nm as an exposure beam.

  In the above-described embodiment, a reticle (mask) on which a transfer pattern is formed is used. Instead of this reticle, for example, as disclosed in US Pat. No. 6,778,257. In addition, an electronic mask that forms a transmission pattern or a reflection pattern based on electronic data of a pattern to be exposed may be used. This electronic mask is also called a variable shaping mask, and includes, for example, a DMD (Digital Micro-mirror Device) which is a kind of non-light emitting image display element (spatial light modulator).

  In addition, the present invention is not limited to application to an exposure apparatus for manufacturing a semiconductor device, for example, an exposure apparatus for a display device such as a liquid crystal display element formed on a square glass plate or a plasma display, It can also be widely applied to an exposure apparatus for manufacturing various devices such as an image sensor (CCD or the like), a micromachine, a MEMS (Microelectromechanical Systems), a thin film magnetic head, and a DNA chip. Furthermore, the present invention can also be applied to an exposure process (exposure apparatus) when manufacturing a mask (photomask, reticle, etc.) on which mask patterns of various devices are formed using a photolithography process. As described above, the present invention is not limited to the above-described embodiment, and it is needless to say that various configurations can be taken without departing from the gist of the present invention.

  According to the present invention, even when the spectral width of the exposure beam changes, a progressive focus exposure method can be applied to manufacture a device with high accuracy.

1 is a drawing schematically showing an overall configuration of an exposure apparatus according to a first embodiment of the present invention. (A) is a diagram showing the full width at half maximum FWHM of the spectrum width, and (B) is a diagram showing a 95% energy purity range E95% of the spectrum width. (A) is a figure which shows the exposure area | region prescribed | regulated by the blind mechanism of FIG. 1, (B) is a figure which shows the modification of a fixed blind. It is a figure for demonstrating the exposure method which concerns on 1st Embodiment. (A) is a figure which shows distribution of the optical axis direction of the exposure amount irradiated to the arbitrary positions on a wafer with the exposure method which concerns on 1st Embodiment, (B) is the exposure which concerns on 1st Embodiment. The figure which shows intensity distribution of the image given to the arbitrary positions on a wafer by a method, (C) is a figure which shows distribution of the integrated image intensity of all the light beams in an exposure area | region. It is a figure for demonstrating the effect at the time of employ | adopting the blind mechanism of FIG. 3 (B) corresponding to FIG. It is a figure for demonstrating the exposure method which concerns on 2nd Embodiment. It is a figure which shows distribution of the optical axis direction of the exposure amount irradiated to the arbitrary positions on a wafer with the exposure method which concerns on 2nd Embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Exposure apparatus, 12 ... Illumination system, 14 ... Laser control apparatus, 15 ... Spectrum monitor, 16 ... Laser light source, 50 ... Main control apparatus, 56W ... Wafer stage drive part, 58 ... Z tilt stage, PL ... Projection optical system , R ... reticle, W ... wafer

Claims (15)

In an exposure method of irradiating a transfer pattern with an exposure beam and exposing the substrate with the exposure beam through the pattern and a projection optical system,
The relative positional relationship in the optical axis direction of the projection optical system between the exposure area of the substrate and the image plane of the projection optical system is continuously within a range of an amplitude set according to the spectrum width of the exposure beam. Alternatively, an exposure method comprising an exposure step of intermittently changing and transferring the pattern to the exposed region of the substrate through the projection optical system.   The exposure method according to claim 1, further comprising a measurement step of measuring a spectral width of the exposure beam before the exposure step.   The exposure method according to claim 1, wherein the swing width is set to be narrower as the spectrum width of the exposure beam is narrower.   4. The exposure according to claim 1, wherein the swing width is set so as to include a case where the exposed area of the substrate coincides with an image plane of the projection optical system. 5. Method.   The exposing step includes a step of periodically changing a relative positional relationship in the optical axis direction of the projection optical system between the exposed area of the substrate and the image plane within a range of the swing width. The exposure method according to any one of claims 1 to 4. The exposure step includes
When exposing the exposed area of the substrate through the pattern and the projection optical system by relatively moving the pattern and the substrate synchronously,
5. The method according to claim 1, further comprising: moving the exposed area of the substrate in an oblique direction with respect to the image plane at an inclination angle determined according to the swing width. 6. Exposure method.   The spectral width of the exposure beam is a value determined based on a width when the intensity decreases to a predetermined ratio with respect to a peak value of the spectrum of the exposure beam, or an integral value of an intensity distribution of the spectrum of the exposure beam. The exposure method according to claim 1, wherein: A device manufacturing method including a lithography process,
A device manufacturing method using the exposure method according to claim 1 in the lithography process. In an exposure apparatus that irradiates a transfer pattern with an exposure beam and exposes the substrate with the exposure beam through the pattern and a projection optical system,
A relative driving device that controls a relative positional relationship in the optical axis direction of the projection optical system between the substrate and the image plane of the projection optical system;
A storage device for indicating a range of change in the relative positional relationship and storing a predetermined amplitude set according to a spectrum width of the exposure beam;
Within the range of the swing width stored in the storage device by driving the relative driving device during the period in which the exposure beam through the pattern and the projection optical system is irradiated onto the exposed region of the substrate An exposure apparatus comprising: a control device that continuously or intermittently changes the relative positional relationship between the exposure area of the substrate and the image plane of the projection optical system. A measuring device for measuring spectral width information of the exposure beam;
The exposure apparatus according to claim 9, wherein the control apparatus obtains the swing width based on a measurement result of the measurement apparatus and stores the swing width in the storage device.   11. The exposure apparatus according to claim 9, wherein the control device sets the swing width to be narrower as a spectrum width measured by the measurement device is narrower.   12. The stage according to claim 9, wherein the relative driving device includes a stage mechanism that drives at least one of the member on which the pattern is formed and the substrate in the optical axis direction of the projection optical system. The exposure apparatus according to item.   The relative drive device includes a drive mechanism for driving a predetermined optical member constituting the projection optical system in the optical axis direction in order to control the position of the image plane of the projection optical system in the optical axis direction. The exposure apparatus according to any one of claims 9 to 12, wherein The exposure apparatus is a scanning exposure type in which the pattern and the substrate are relatively moved synchronously during exposure of the substrate,
The relative drive device moves the substrate at an inclination angle corresponding to the swing width in order to move the exposed area of the substrate in an oblique direction with respect to the image plane of the projection optical system during the movement of the substrate. The exposure apparatus according to claim 9, further comprising a stage mechanism that gradually changes a position of the projection optical system of the substrate in an optical axis direction in an inclined state. A device manufacturing method including a lithography process,
15. A device manufacturing method using the exposure apparatus according to claim 9 in the lithography process.

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