JPH02272305A - Aligning device for exposing device - Google Patents

Abstract

PURPOSE:To miniaturize a device and to eliminate offset between two kinds of optical systems by sharing an optical system member other than two sets of beam forming optical systems to the maximum and switching and using the beam forming optical systems in accordance with the shape of an alignment mark. CONSTITUTION:An illuminating light beam for alignment is emitted from a laser beam source 20 and reaches a polarized beam splitter 22, then the wave surface thereof is splitted to be two light beams, which enter a 1st beam forming optical system 26 and a 2nd beam forming optical system 27 through shutters 24 and 25, pass a beam splitter 29, and enter position detection systems 33X and 33Y through lenses 31X and 31Y and mirrors 32X and 32Y. Then, they enter the entrance pupil PLa of a projecting lens PL through mirrors 33g' and 33g to be projected to wafer W surface as spot light. The beams are switched and used by the shutters 24 and 25 in accordance with the shape of the alignment mark.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an exposure apparatus used for manufacturing semiconductor elements, liquid crystal display elements, etc., and particularly relates to a reticle (synonymous with a mask) on which a circuit pattern is formed, This invention relates to a device that relatively aligns a photosensitive substrate (wafer) onto which a circuit pattern is transferred.

[Conventional technology]

In recent years, step-and-repeat reduction projection exposure apparatuses, or so-called steppers, have come into widespread use in semiconductor device manufacturing processes to transfer reticle patterns onto wafers with high resolution. This type of stepper is equipped with a TTL (Through The Lens) as an alignment optical system that accurately overlaps the projected image of the reticle pattern with the circuit pattern (chip) formed in a matrix on the wafer.
) type laser step alignment (LSA) system is provided.

Regarding the configuration of the LSA system, for example, see
Since it is disclosed in Publication No. 742, the explanation will be omitted, but
A wafer mark (diffraction grating mark) is irradiated with elongated strip-shaped spot light through a projection lens, and diffracted light (or scattered light) generated from the mark is photoelectrically detected. Therefore, the LSA system has a wide mark detectable range (search range) and can perform high-speed alignment measurement.
At present, enhancement global alignment (EGA) using the LSA system is the mainstream alignment method for steppers. EGA is disclosed in Japanese Patent Application Laid-Open No. 61-44429, which measures the coordinate values of multiple chips located near the center of the wafer and its outer periphery, and calculates the chip arrangement using a statistical method from these measured values. Step the wafer stage according to
The projected image of the reticle pattern and the chip are accurately superimposed. However, in the LSA system, the S/N ratio of the photoelectric signal deteriorates due to factors such as uneven resist coating, wafer surface roughness due to sputtering of the aluminum layer, and edge destruction of the diffraction grating due to various processing processes.
The alignment measurement accuracy may deteriorate due to the occurrence of random errors.

Therefore, as disclosed in Japanese Patent Application Laid-open No. 61-215905, for example, a one-dimensional diffraction grating mark formed on a wafer is optically detected, and the position of the wafer is detected with high resolution from the pitch information. A method has been proposed. This disclosed method simultaneously irradiates a diffraction grating mark with parallel laser beams from two directions to create one-dimensional interference fringes, and uses these interference fringes to identify the mark position. It is also called interference fringe alignment method because of its use. This interference fringe alignment method also has two
There are two methods: the heterodyne method, which provides a fixed frequency difference between laser beams irradiated from two directions, and the homodyne method, which does not have a frequency difference. In the homodyne method, stationary interference fringes are created parallel to the diffraction grating mark, and in order to detect the position, it is necessary to move the diffraction grating mark (object) slightly in the pitch direction, and the mark position is determined using the interference fringes as a reference. On the other hand, in the heterodyne method, due to the frequency difference (beat frequency) of the laser beams, the interference fringes flow at high speed in the line direction (pitch direction) at the beat frequency, and the mark position is determined based on the interference fringes. figure,
It is determined based exclusively on the temporal element (phase difference) accompanying the high-speed movement of the interference fringes. An alignment optical system (hereinafter referred to as
La5er Interferometric Ali
gnment (referred to as LIA system) uses a diffraction grating mark (duty is 1:1) in which multiple long grating elements (bar patterns) are arranged in parallel, so it is resistant to wafer surface roughness and various processing processes. Moreover, the phase (sine wave) of the photoelectric signal corresponding to the intensity of the diffracted light from the mark is 36° for a positional shift of 1/2 of the grating pitch P.
Since the angle changes by 0 degrees, it is possible to perform high-resolution measurements.

[Problem to be solved by the invention]

However, although the LIA system as described above has high resolution, the phase difference rotates by 2π and returns to the original state every time the positional shift amount shifts by P/2. Therefore, for the interference fringes created by the two laser beams, at least ±P/
Positioning the diffraction grating mark within 4 (pre-alignment)
If this is not done, there is a problem that an alignment error of an integral multiple of P/2 will occur. Therefore, in addition to the LIA system, which has a narrow mark detectable range (±P/4), it is recommended to provide an alignment optical system, such as an LSA system, to pre-align the mark within ±P/4 with respect to the interference fringes. Conceivable. As mentioned above, the LSA system has a wide search range and is capable of high-speed measurement, so it is an alignment optical system suitable for pre-alignment. It is extremely disadvantageous in terms of space, cost, optical adjustment, etc. Particularly in space, concentration of the alignment optical system around the narrow reticle is disadvantageous in all designs including the alignment optical system. Also,
There is also the problem that diffraction grating marks for both alignment optical systems must be separately provided on the wafer for one chip (shot area), which increases the mark area.

The present invention has been made in consideration of the above points, and is an alignment device that minimizes the space around the reticle, prevents deterioration of alignment accuracy due to wafer surface roughness, etc., and enables high-speed, high-precision alignment. The purpose is to obtain.

[Means to solve problems]

In order to solve this problem, the present invention provides an illumination system that uses a laser light source 20 as a light source, which is installed in an apparatus that exposes a circuit pattern formed on a reticle R onto a wafer W, and generates a coherent light beam of a predetermined wavelength. an irradiation optical system that includes a projection lens PL [objective optical system] that is telecentric at least on the wafer side and irradiates a light beam onto the wafer W; and an LSA mark WM formed on the wafer W.
Wafer mark WMx, WMy including xs, WMys [
The optical information generated from the alignment mark] is projected onto the projection lens P.
A photoelectric detector 33i that receives light via L, and a photoelectric signal SDi from the photoelectric detector 33i.

According to SDr and optical beam signal SDw (detection signal),
In an apparatus for relatively aligning a reticle R and a wafer W, a spot light SP is provided in an illumination system and passes through approximately the center of an entrance pupil PLa of a projection lens PL as a light beam.
[First luminous flux] and a beam LB1p that passes through the entrance pupil PLa so as to be approximately point symmetrical with respect to the center of the spot light SP.
, LB2p [second light beam].
and an LIA optical system 27 [multi-beam unit]; and a shutter 24 that switches so that only one of the spot light SP and the beams LB1p and LB2p passes through the entrance pupil PLa.
, 25 [switching means], and is configured to switch between the spot light SP and the beams LB1p and LB2p according to the shape of the alignment mark.

[For production]

In the present invention, a first beam of light passing through approximately the center of the pupil plane of the objective optical system as illumination light, and two second beams of light passing through the pupil plane so as to be approximately point symmetrical with respect to the center of the first beam are emitted. A multi-beam forming means (two sets of beam shaping optical systems) and a switching means for switching so that only one of the first light beam and the two second light beams passes through the pupil plane of the objective optical system are provided. The configuration is such that the first light beam and the two second light beams are switched depending on the shape of the alignment mark formed on the substrate.

At this time, the present invention focuses on the fact that the alignment optical system has a light splitter that splits the illumination light into two and makes them respectively enter two sets of position detection systems (including an irradiation optical system and a photoelectric detector). By arranging the light splitter so that the first light beam and the two second light beams are incident approximately perpendicular to each other, the optical members (two sets of position detection systems) after the light splitter are shared. It is configured to allow Therefore, the space around the reticle can be minimized, and offsets between the two sets of beam shaping optical systems, that is, the two types of alignment optical systems can be prevented from occurring. In addition, if the optical path of the illumination light is adjusted in one of the two position detection systems so that the optical axes of the two types of alignment optical systems match accurately, the alignment optical system of the other position detection system can be adjusted. Since the optical axes of the two lenses also match accurately, the time required for adjustment can be shortened.

〔Example〕

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a schematic configuration of a stepper equipped with a TTL type alignment optical system according to an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 6.

In Fig. 2, an illumination light source l such as an ultra-high pressure mercury lamp or an excimer laser device generates illumination light IL of a wavelength (exposure wavelength) that sensitizes the resist layer, such as g-line, i-line, or KrF excimer laser light. However, this illumination light IL enters an illumination optical system 2 having an optical integrator (fly's eye lens) and the like. The illumination light IL, which has been uniformized in luminous flux and reduced in speckle by the illumination optical system 2, reaches the main condenser lens CL via the beam splitter 3 and mirror 4, and is placed on the reticle stage R8. The pattern area PA of the reticle R is illuminated with uniform illuminance. The reticle R is moved two-dimensionally (including rotationally) within a horizontal plane by the drive unit 5, and its position is determined by the laser interferometer 6.
For example, it is constantly detected with a resolution of about 0.02 μm. Incidentally, the reticle R has reticle marks RMx, RMy (rectangular transparent windows,
RMy (only RMy shown) is formed. Now, the illumination light IL that has passed through the pattern area PA is
The projected image of the circuit pattern formed in the pattern area PA is projected onto the telecentric projection lens PL, and the projection lens PL receives the projected image of the circuit pattern formed in the pattern area PA, the surface of which is coated with a resist layer.
The image is projected onto the wafer W held so as to substantially coincide with M. The wafer W is a wafer holder (θ table) not shown.
The wafer stage WS is placed on a wafer stage WS via a drive unit 7, and the wafer stage WS is configured to move two-dimensionally in the X and Y directions in a step-and-repeat manner and to move slightly in the Z direction. Further, the position of the wafer stage WS in the X and Y directions is determined by a laser interferometer 8, for example, 0.
．． A movable mirror 8m that reflects the laser beam from the laser interferometer 8 is fixed at the end of the wafer stage WS, which is constantly detected with a resolution of about 0.02 μm.

Further, a reference member (glass substrate) 10 provided with a fiducial mark used in baseline measurement etc. is provided on the wafer stage WS so as to substantially coincide with the surface position of the wafer W.

This reference member 10 has fiducial marks including a cross pattern 10a, which is a light-transmissive slit pattern as shown in FIG. 1 : 1
) 10x and 10y are provided. Here, the third B
The figure shows a schematic configuration of the reference mark 10y. The reference mark 10y has a diffraction grating mark (hereinafter referred to as LSA mark) 10ys in which a plurality of dot marks are arranged in the X direction, and a bar pattern of a plurality of bars (12 in the figure) extending in the X direction, For example, the LSA mark 10y is formed so that a line and space pattern of 4 μm is formed.
They are arranged in the Y direction with s as the center. Also,
The light-transmissive cross pattern 10a is configured to be illuminated from below (inside the wafer stage WS) by illumination light (exposure light) transmitted below the reference member IO using an optical fiber (not shown). . This cross pattern lO
The illumination light that has passed through a forms a projected image of the cross pattern 10a on the back surface (pattern surface) of the reticle R via the projection lens PL. Reticle mark RMy (or RMx
), the illumination light passes through a condenser lens CL and a mirror 4, is reflected by a beam splitter 3, and is then received by a light amount detection system 9 including a photoelectric detector arranged on the pupil conjugate plane of the projection lens PL. is configured to be

Furthermore, FIG. 2 shows an irradiation optical system 11a that supplies an imaging light beam 11 for forming a pinhole or slit image toward the imaging surface IM of the projection lens PL from an oblique direction with respect to the optical axis AX. A focus detection system 11 of an oblique incidence type is provided, which includes a light receiving optical system 11b that receives a reflected light flux 12 of the imaging light flux 11 on the surface of the wafer W. Regarding the configuration of this focus detection system 11, for example,
168112, detects the position of the wafer surface in the vertical direction (Z direction) with respect to the imaging plane IM,
This is to detect the in-focus state between the wafer W and the projection lens PL. Further, off-axis wafer alignment (WGA) systems 12 and 13, which are fixed at a constant interval from the projection lens PL and exclusively detect wafer marks, are provided at a prescribed interval in the X direction. Regarding the configuration of WGA system 12.13, etc., see, for example, Japanese Patent Application Laid-open No. 60-1
30742, so the explanation will be omitted, but a long and thin strip-shaped spot light is minutely vibrated on a wafer mark (diffraction grating mark) using a vibrating mirror such as a galvano mirror, and diffracted light or scattered light from the mark is generated. It performs synchronous detection of photoelectric signals corresponding to light, similar to a photoelectric microscope. In this example, the spotlight extending in the X direction is
The position of the wafer mark in the Y direction is detected by making small vibrations in the Y direction.

Next, using FIG. 1 and FIG.
An alignment optical system (hereinafter referred to as 5) consisting of an LSA system and an LSA system
ite by 5ite Alignment; SS
The configuration of the system (referred to as A system) will be explained in detail. Figure 1 shows SSA
FIG. 4 is a perspective view showing a schematic configuration of the system, and is a diagram illustrating the main parts of the SSA system shown in FIG. 1 in more detail.

In FIG. 4, light having a plane of polarization parallel to the plane of the paper in the figure with respect to the shutter 24° 25 is defined as P-polarized light, and light having a plane of polarization perpendicular thereto is defined as S-polarized light. In addition, the mirrors 28, 32y shown in FIG. 1 or 2 for ease of explanation,
33d, 33f and 33g are omitted. Incidentally, on the wafer W, an LSA mark WMxs having the same shape as the reference marks lox and 10y shown in FIG. 3B is attached to the chip C.
, WMys is formed as a wafer mark WMxSWMy.

In FIG. 1, alignment illumination light (beam) AL of orthogonal linearly polarized light having a predetermined wavelength is emitted from a laser light source 20, and is passed through a polarization plane rotation member (hereinafter simply referred to as a wavefront rotation plate) 21 that changes the polarization state. The light then reaches the polarizing beam splitter 22, where the wavefront is split into a beam ALp consisting of a P-polarized component and a beam ALs consisting of an S-polarized component. still,
The laser light source 20 emits a wavelength that has almost no sensitivity to the resist layer (non-exposure wavelength), for example, H with a wavelength of 633 nm.
It is desirable to use an e-Ne laser as the light source. Now, the beam ALp that has passed through the polarizing beam splitter 22 is
A first beam shaping optical system (hereinafter referred to as LSA optical system) 2 including a cylindrical lens etc. via a shutter 24
6.

On the other hand, the beam ALs reflected by the polarizing beam splitter 22 enters a second beam shaping optical system (hereinafter referred to as an LIA optical system) 27 including a two-beam frequency shifter and the like via a mirror 23 and a shutter 25. Shutter 2
4. ．． Reference numeral 25 is a rotary shutter with, for example, four blades, which closes and opens the optical paths of the beams ALp and ALs, respectively, and is controlled to rotate at the same time so that only one of the optical paths is always open. In addition, shutter 24.2
5 may be provided anywhere between the polarizing beam splitter 22 and a beam splitter 29, which will be described later. Therefore, the LS as the multi-luminous flux means of the present invention
The illumination systems (20 to 27) including the A optical system 26, the LIA optical system 27, and the shutter 24.25 as a switching means switchably generate illumination light emitted from the LSA optical system 26 and the LIA optical system 27, respectively. This allows only one of the illumination lights to pass through the entrance pupil PLa of the projection lens PL as will be described later, and the shape of the wafer mark (in this embodiment, the LSA mark WMxs).

The illumination light can be switched depending on the wafer mark (WMys, wafer mark WMx, WMy).

Here, if a 1/2 wavelength plate is rotatably provided as the wavefront rotating plate 21, the beam AL is wavefront split at a light intensity (light I) ratio according to the rotation angle of the 1/2 wavelength plate, and the LSA optical system 26
and the required light amount of the LIA optical system 27, the beam ALp
, the light amount ratio of ALs can be adjusted to the optimum one. Moreover, this means that the wavefront rotation plate 21 and the polarizing beam splitter 22 have a shutter function.
In particular, it is also possible to omit the shutters 24,25. In addition, the beam ALp (or ALs) between the beam AL and the beam amount is the LSA optical system 26 (or LIA optical system 27).
), which has the advantage that there is no loss in the amount of light of the beam AL. However, in consideration of the thickness accuracy of the 1/2 wavelength plate (light shielding accuracy as a shutter) and the ease of adjusting the light amount, in this embodiment, the above (shutter 24.
5 is provided separately, and the wavefront rotating plate (1/2 wavelength plate) 21 is fixed at a predetermined rotation angle. In addition, the wave front rotating plate 2
Both the polarizing beam splitter 1 and the polarizing beam splitter 22 are arranged so as to be inclined by a small angle (for example, about 1°) in the XY plane in FIG. 1 with respect to the optical axis of the laser light source 20. For this reason, reflected light from optical members such as the wavefront rotating plate 21 placed in the optical path of the beam AL (ALp, ALs) returns to the laser light source 20, resulting in a so-called phenomenon that destabilizes the oscillation of the beam AL. Backtalk is prevented from occurring.

Next, the configuration of the LSA optical system 26 will be briefly described. Fourth
The beam ALp passing through the shutter 24 as shown in the figure
is expanded to a predetermined beam diameter by the beam expander 26a, shaped into an elongated elliptical beam SP by the cylindrical lens 26b, and then passed through the first relay lens 26c1.
It reaches the parallel plane plate 26f via the parallel plane plate 26d and the second relay lens 26e. The parallel plane plates 26d and 26f are both provided to be two-dimensionally tiltable with respect to the optical axis AXa of the LSA optical system 26, and the rear focal position of the second relay lens 26e is the same as the front focal position of lenses 31x and 31y, which will be described later. arranged to match.

The elliptical beam SP as the first light flux that passes through the parallel plane plate 26f, that is, exits the LSA optical system 26, is reflected by the mirror 28, and then split into the same amount of light by the beam splitter 29 as the light splitting means of the present invention. It is divided into two (amplitude division) so that

Elliptical beam SP divided into two by beam splitter 29
are converged into a slit shape by the field stops 30x and 30y, which are placed at the rear focal position of the second relay lens 26e, respectively, and then the lenses 31x and 31y as shown in FIG.
and a position detection system 33x via mirrors 32x and 32y,
It reaches 33y.

Further, the elliptical beam SP that has passed through the position detection systems 33x and 33y reaches the entrance pupil PLa of the projection lens PL via deflection mirrors 33g and 33g, and passes through the approximate center of the entrance pupil PLa within the exposure field. They are formed on the wafer W as elongated strip-shaped spot lights (sheet beams) SP extending in the Y and X directions and toward the optical axis AX, respectively. In addition, in the entrance pupil PLa, the longitudinal direction of the elliptical beam approximately coincides with the X and Y directions, respectively, and this entrance pupil PLa
The longitudinal direction of the elliptical beam at a and the longitudinal direction of the spot light irradiated onto the wafer W are substantially orthogonal to each other.

Furthermore, since the position detection systems 33x and 33y have the same configuration, only the position detection system 33y is shown in FIGS. 2 and 4.

Here, in the position detection system 33y shown in FIG.
After passing through the 3a11/4 wavelength plate 33b1 and the two-dimensional tiltable parallel palm plate 33c as a deflection member of the present invention,
The light reaches the objective lens 33e via the mirror 33d. 1/
The elliptical beam SP, which has become circularly polarized by the four-wavelength plate 33b, is reflected by a mirror 33f, and once converged into a slit shape by an objective lens 33e at a spatial focal point 33α (wafer conjugate plane) within the position detection system 33y, A spot light SP (circularly polarized light) is formed on the wafer W via the mirror 33g and the projection lens PL. Next, the spot light SP is LS
A? - When WMys is relatively scanned in the Y direction, diffracted light (first order or higher order light) 35 and scattered light 36 (not shown) are generated from the LSA mark WMys in addition to specularly reflected light (0th order light) 34.

This optical information (circularly polarized light) passes through the projection lens PL, etc. again, becomes S-polarized light by the quarter-wave plate 33b, is reflected by the polarizing beam splitter 33a, and is reflected by the pupil relay system 33.
The light is received by a photoelectric detector (light receiving element) 331 arranged on the pupil conjugate plane via h. The photoelectric detector 33i photoelectrically detects the higher-order diffracted light of the optical information, for example, the ±1st to third-order diffracted light 35 and the scattered light 36, and generates photoelectric signals according to the respective intensities of the diffracted light 35 and the scattered light 36. Signal SDi.

The SDr is output to an alignment signal processing circuit (hereinafter referred to as AsC) 14.

Next, the configuration of the LIA optical system 27 will be explained. Fourth
In the figure, the beam ALs that has passed through the shutter 25 is incident on a two-beam frequency shifter 27a consisting of two acousto-optic modulators, etc., and two beams LBI and LB2 containing linearly polarized light having different frequencies and orthogonal to each other are generated. is converted to Here, the configuration of the two-beam frequency shifter 27a is shown in FIG. In FIG. 5, the beam ALs (S
The polarized light is reflected by a mirror 40, passes through a quarter-wave plate 41 and a lens 42, and then is wavefront-split by a polarizing beam splitter 43 into a P-polarized beam and an S-polarized beam so that the amount of light is the same. Polarizing beam splitter-43
The P-polarized beam that has passed through passes through a mirror 44 to a first acousto-optic modulator 45a (hereinafter simply referred to as AOM 45a).
S incident on the polarizing beam splitter 43 and reflected by the polarizing beam splitter 43
The polarized beam enters a second acousto-optic modulator 45b (hereinafter simply referred to as AOM 45b). The AOM 45a is driven by a high frequency signal SF1 having a frequency fl, and although not shown in FIG. 5, it outputs as a beam LB1 primary light that is deflected by a diffraction angle determined by the frequency f1. on the other hand,
The AOM45b has a frequency f2 (f2=fl−Δ
f) is driven by the high frequency signal SF2, and outputs the primary light as a beam LB2, which is similarly deflected by the diffraction angle determined by the frequency f2. In addition, AOM45 a.

The zero-order light of the beam incident on the beam 45b is blocked by a slit (not shown) placed at an appropriate position. Further, it is desirable that the relationship between the drive frequencies f1, f2 and the difference frequency Δf is fl>Δf, f2>Δf, and Δf
The upper limit of is determined by the responsiveness of the photoelectric detector 331 and the like.

In this embodiment, the drive frequency f of AOM45a and 45b is
Lf2 is, for example, 80.025 MHz and 80°000 MHz, respectively, and the frequency difference Δf is set as low as 25 KH2, so two AOM45 a.

The diffraction angles of the first-order diffracted lights at 45b are the same. Now, the beam LBI modulated to the frequency fl by the AOM 45a enters the deflection beam splitter 49 arranged on the pupil plane of the SSA system via the parallel plane plate 46, while the beam LB2 modulated to the frequency f2 by the AOM 45b. is incident on a deflection beam splitter 49 via a parallel plane plate 47 and a mirror 48. The polarizing beam splitter 49 does not combine the beams LBI and LB2 completely coaxially, but combines the beams LBI and LB2 parallel to each other so as to be spaced apart by a predetermined amount. Therefore, the parallel plane plates 46, 47 are arranged to be inclined by a predetermined angle in the traveling direction of the beams LBl and LB2, and are set so that the two-dimensional angle of inclination can be arbitrarily adjusted. As a result, the beams LBI and LB2 emitted from the polarizing beam splitter 49, that is, the two-beam frequency shifter 27a, are emitted symmetrically across the optical axis AXb of the LIA optical system 27, as shown in FIG. .

The two parallel beams LBI (P polarized light, frequency fl) and LB2 (S polarized light, frequency f2) emitted from the two-beam frequency shifter 27a have their polarization directions rotated by 45 degrees by a 1/2 wavelength plate 27b. After that, it enters the polarizing beam splitter 27c. From this, beam LBI is P polarized beam LBlp with frequency fl and S polarized beam LB.
The wavefront of beam LB2 is divided into P and Is of frequency f2.
The wavefront is split into a polarized beam LB2p and an S-polarized beam LB2s. Now, the two S-polarized beams LBIs (frequency f l) reflected by the polarized beam splitter 27c,
LB2s (f2) is a reference diffraction grating 27e fixed on the device through a lens system (inverse Fourier transform lens) 27d that converts the pupil into an image plane at a predetermined intersection angle θ from two different directions. The light enters at the center and forms an image (intersects). The photoelectric detector (light receiving element) 27f receives the diffracted light (interference light) other than the zero-order light transmitted through the reference diffraction grating 27e, and outputs a sinusoidal photoelectric signal SR according to the intensity of the diffracted light. This photoelectric signal SR has a difference frequency Δ between the beams LBIs and LB2s.
The frequency becomes proportional to f, and becomes an optical beat signal.

On the other hand, two P-polarized beams LB1p (frequency f1) pass through the polarized beam splitter 27c.

LB2p (same f2) becomes a parallel light flux inside the pupil relay system 27g, and is emitted after intersecting by − degrees, and each principal ray becomes parallel to the optical axis AXb of the LIA optical system 27, and the pupil plane An imaging light beam is condensed as a spot at two symmetrical points with the optical axis AXb in between. Beam LB1p,
After passing through the plane-parallel plate 27h disposed in or near the pupil plane, the LB2p becomes a parallel light flux tilted by a predetermined angle by the lens 27i and enters the plane-parallel plate 27j. The parallel plane plates 27h and 27j are both provided so as to be two-dimensionally tiltable with respect to the optical axis AXb of the LIA optical system 27,
The rear focal position of the lens 27i is the lens 31x, 31
It is arranged to coincide with the front focus position of y. 2 that passed through the parallel plane plate 27j, that is, exited the LIA optical system 27.
Beams LB1p and LB2p as the second light flux of the book are transmitted to the beam splitter 2 as well as the spot light SP mentioned above.
9 to have the same amount of light (amplitude division), and after crossing each other once at field apertures 30x and 30y,
Position detection systems 33x, 3 via lenses 31x, 317, etc.
:Injects at 3y. The beams LBIp and LB2p intersect once at the focal point 33α in the position detection system 33y, and the entrance pupil PLa
After condensing into a -degree spot shape and passing through the entrance pupil PLa so that the spot light (elliptical beam) SP is approximately point symmetrical with respect to the center, the beams are symmetrical with respect to the pitch direction of the wafer mark across the optical axis AX. The light beam becomes a parallel light beam tilted at an angle of , and is incident on the wafer mark from two different directions at an intersection angle θ to form an image (intersect). Here, each spot of the beams LB1p and LB2p in the entrance pupil PLa is on a straight line passing through the center of the spot light SP and extending in the longitudinal direction (Y direction) of the spot light SP, as described above. It is formed so as to be approximately point symmetrical with respect to.

Furthermore, even if the intersection angle θ of the beams LB1p and LB2p is large, the numerical aperture (N
, A, ) will not be exceeded. Furthermore, field stops 30x and 30y are placed conjugate (image conjugate) with the wafer surface.
is for arbitrarily setting the shape (irradiation area) of the alignment illumination light on the wafer W, and the shape is determined to be shared by the spot light SP and the beams LB1p and LB2p. . In addition, in FIG. 4, the pitch direction of the wafer mark WMy is the left-right direction in the plane of the paper,
The direction of inclination of each of the beams LB1p and LB2p from the optical axis AX is also determined within the paper plane of FIG.

Now, when the beams LB1p and LB2p are incident on the wafer mark WMy at the intersection angle θ, the beams LBlp and LB2p
In the spatial region where the lattice pitch intersects, in any plane (wafer surface) perpendicular to the optical axis AX, a one-dimensional interference fringes will be created. This interference fringe moves (flows) in the pitch direction (Y direction) of the wafer mark WMY in response to the difference frequency Δf between the beams LB1p and LB2p, and its velocity V is calculated by the relational expression ■=Δf−P'. It is expressed as As a result, ±1st-order diffracted light (interference light) 37 is generated from the wafer mark WMY, which travels along the optical axis AX and becomes a beat wavefront that periodically repeats changes in brightness and darkness due to the movement of the interference fringes. This diffracted light 37 passes through the projection lens PL, the 1/4 wavelength plate 33b, etc., is reflected by the polarizing beam splitter 33a, and then passes through the pupil relay system 33h to the photoelectric detector 3.
3i. The photoelectric signal SDw output from the photoelectric detector 33i is output to the ASCI 4 as a sinusoidal alternating current signal (beat frequency, hereinafter referred to as optical beat signal) SDw according to the period of brightness change of the interference fringes.

Here, FIG. 6 shows a schematic configuration of the photoelectric detector 33i described above. As shown in FIG. 6, the photoelectric detector 33i is
The light-receiving surface 38a is adapted to the distribution of, for example, the ±1st to third-order diffracted light 35 generated from the LSA mark WMys by irradiation with the spot light SP.

38b, light-receiving surfaces 39a and 39b that match the distribution of scattered light 36 generated from the edge thereof, and beam LB1p,
A light receiving surface 37D arranged to receive diffracted light 37 generated from the wafer mark WMV by irradiation with LB2p.
It is a split light receiving element having Furthermore, when the spot light SP is irradiated on the LSA mark WMys as described above, the LSA
Along with the diffracted light 35, specularly reflected light 34 and scattered light 36 are also generated from the mark WMys, and the specularly reflected light 34 and scattered light 36 are focused on the light receiving surface 37D. However, in this embodiment, the rotation of the shutters 24 and 25 is controlled so that the spot light SP and the beams LBlp and LB2p are not irradiated onto the wafer W at the same time.
This prevents crosstalk in which the specularly reflected light 34, the scattered light 36, and the diffracted light 37 coexist.

Next, when the ASC 14 uses the LSA system (spot light SP), the photoelectric signal 5 output from the photoelectric detector 33i is
Di (or 5Dr) and the position signal from the laser interferometer 8 are input, and the unit movement amount (0,0
The photoelectric signal 5Di (or 5Dr) is sampled in synchronization with up/down pulse signals generated every 2 μm). After each sampling value is converted into a digital value and stored in the memory in address order, the position of the wafer mark WMy in the Y direction is detected by a predetermined calculation process. Furthermore, A
It is desirable that the SC 14 process the waveforms of the photoelectric signals SDi and SDr in parallel, and determine the position of the wafer mark WMY from the detection results of both. In addition, LIA system (beam L
B1p, LB2p), the optical beat signal SDw output from the photoelectric detector 33i and the optical beat signal SR output from the photoelectric detector 27f are input as a reference signal, and the optical beat signal SR is used as a reference signal. optical beat signal SR,
Detect the phase difference on the SDw waveform.

This phase difference (±180°) is the P of wafer mark WMy.
It uniquely corresponds to the relative positional deviation amount within /2. Here, the pitch P of the wafer marks WMx and WMy is 8 μm, and the phase detection resolution of the ASC 14 is 0. Assuming that it is 2°, the measurement resolution of positional deviation is 0.0044μ
It also becomes m. In reality, since it is affected by noise and the like, the practical measurement resolution is about 0.01 μm (0.4° in phase). This detection method is a so-called heterodyne method, and as long as the wafer W is within a positional error range of P/2, positional deviation can be detected with high resolution even in a stationary state. The main controller I5 controls the drive of the shutters 24 and 25 simultaneously, and controls the drive unit based on the mark position and phase difference (positional deviation amount) information from the ASC 14, position information from the laser interferometers 6 and 8, etc. In addition to outputting predetermined drive commands to 5 and 7 to perform alignment between the reticle R and the wafer W, the control unit 5 and 7 also collectively control the entire apparatus including the focus detection system I L WG Al 2.13 and the like.

[Margin below]

Now, the beam splitter 29 as the light splitting means of the present invention shown in FIGS. In the systems 33x, 337, etc., the optical axis AXa of the LSA optical system 26 and the LIA optical system 27
The spot light SP and the beams LBlp and LB2p are used to accurately match the optical axis AXb of the position detection system 33x, 337.
etc., the spot light SP and the beam LBlp
, LB2p are on the same plane (plane parallel to reticle R)
They are arranged so as to be substantially orthogonal to each other and incident on the dividing surface 29a. At this time, it is difficult to align the optical axes AXa and AXb with high precision just by adjusting the position of the beam splitter 29. Therefore, in this embodiment, the inclination angles of the parallel plane plates 26f and 27j provided inside the LSA optical system 26 and the LIA optical system 27 are adjusted at the time of manufacturing or initializing the stepper. That is, by shifting the spot light SP and the beams LBIp, LB2p by minute amounts, the positions of incidence of the spot light SP and the beams LBIp, LB2p on the beam splitter 29 are finely adjusted.

Furthermore, when the parallel plane plates 46 and 47 shown in FIG.
The spots B2 each move two-dimensionally depending on the inclination angle. This means that the beam LB1p at the entrance pupil PLa,
Spot spacing of LB2p, i.e. wafer marks WMx, W
This means that the intersection angle θ on My is defined by the inclination angle of the parallel plane plates 46 and 47. Therefore, in this embodiment, the parallel plane plates 46 and 47 are tilted in advance according to the wavelength of the beam ALs (AL), and the beams LBlp and LB2p are
It is assumed that the intersection angle θ is adjusted in advance. At this time, at the same time, the pitch direction of the interference fringes created by the beams LB1p and LB2p and the beams LB1p and LB2 at the entrance pupil PLa
The parallel plane plate 46. 47 is tilted.

As a result, the pitch direction of the interference fringes and the pitch direction of the wafer marks accurately match on the wafer W, and the optical beat signal SDw can be obtained with high contrast.

Further, the above-mentioned parallel plane plates 26d and 27h are both SS
It is arranged within the pupil plane of the A system, its conjugate plane, or any plane near them. For this reason, the parallel plane plate 26d
. It is possible to adjust the inclination of the principal ray of SP and the principal ray of two beams that bisect the beams LB1p and LB2p with respect to the optical axis AX (hereinafter simply referred to as telecentric inclination). Therefore, in this embodiment, for example, when initializing the stepper, the parallel plane plate 26d, The tilt angle of 27h is adjusted.

In addition, as mentioned above, the parallel plane plates 46, 47 and 26d, 2
When the adjustment of the inclination angle in 7h is completed, the center of the spot light SP in the entrance pupil PLa and the beams LB1p and LB2p are
The direction of the straight line connecting each spot (center) is approximately parallel to the pitch direction (periodic direction) of the wafer marks.

Here, if the above-mentioned parallel plane plates 46 and 47 are respectively tilted in the same direction and at the same angle, the respective spots of the beams LBIp and LB2p at the entrance pupil PLa will be two-dimensional depending on the inclination angle while keeping the interval constant. It will be moved. Therefore, the parallel plane plates 46 and 47 also have the function of correcting the telecentric inclination, and there is no need to separately provide the parallel plane plate 27h. However, in this embodiment, from the viewpoint of adjustment time and ease of adjustment, the parallel plane plates 46 and 47 are used to adjust the intersection angle θ of the beams LBlp and LB2p, that is, the pitch of the interference fringes, and correct the telecenter tilt. shall be performed using the parallel plane plate 27h. Furthermore, beam LB
The wavelengths of the beams LB1p and LB2p are λ, the pitch of the wafer mark WMy is P1, the incident angles of the beams LB1p and LB2p to the wafer 1W are θa and θb across the optical axis AX, respectively (however,
If the intersection angle θ = θa + θb), then the parallel plane plate 46°4
The inclination angles of 7 and 27h are adjusted so as to satisfy the relationship of formula (1) shown below.

sinθa=sinθb=nλ/P (n=1.2.-
) ” (1) As a result, the symmetry of the incident angles θa and θb of the beams LB1p and LB2p is maintained, the telecentric tilt, etc. are corrected, and the diffracted light 3 generated from the wafer mark is
7 will always travel along the optical axis AX.

In addition, the parallel plane plate 33c shown in FIGS. 2 and 4 (
The deflection member of the present invention) is also arranged near the pupil conjugate plane of the SSA system, and is a parallel plane plate 26d.

It has exactly the same function as 27h, that is, a telecenter tilt correction function. In particular, the parallel plane plate 33c is the position detection system 33y.
The light spot SP and each spot of the beams LB1p and LB2p at the entrance pupil PLa are moved by the same amount at the same time. Therefore, since the telecentric inclinations of the projection lens PL on the wafer W side are considered to be equal, if the inclination angle of the parallel plane plate 33c is adjusted according to the telecentric inclination of either one, the spot light SP
And the telecentric inclinations of beams LB1p and LB2p are corrected at the same time. In this embodiment, the inclination angle of the parallel plane plate 33c is not adjusted at the time of initializing the stepper, and for example, the parallel plane plate 33c is aligned with the optical axis (AX) of the SSA system.
a, AXb), and adjust only the inclination angle of the parallel plane plates 26d and 27h to correct the telecentric inclination of the spot light SP and the beams LB1p and LB2p. shall be.

Next, the adjustment operation and mark detection operation of the apparatus according to this embodiment will be explained with reference to FIGS. 7 to 11. FIG. 7 is a schematic flowchart showing an example of the operation of this embodiment.

In step 100, the main controller 15 moves the wafer stage WS by the drive unit 7, and as shown in FIG.
p, set to the irradiation position of LB2p. Next, with the reference mark 10y irradiated with the beams LBlp and LB2p emitted from the position detection system 33y, the distance between the projection lens PL and the reference member 10 in the Z direction is monitored using the focus detection system 11, and the wafer is A Z stage (not shown) constituting the stage WS is moved up and down in the 2 (optical axis AX) direction within a predetermined range so that no lateral deviation occurs in the X and Y directions. The ASC 14 receives the optical beat signal SR from the photoelectric detector 27f and the optical beat signal SDw from the photoelectric detector 33i.
The change in the phase difference φW between the two is detected. The main controller 15 is
Based on the phase difference information (changes in the phase difference φW) and the position information from the focus detection system 11, the change in the phase difference φW is sampled for each minute displacement of the Z stage in the Z direction. The characteristic VT as shown in the figure is calculated. In FIG. 9, the horizontal axis represents the position of the reference member 10 in the Z direction, and the vertical axis represents the phase difference φW. It is assumed that the reference member IO is closest to the projection lens PL at position Z4. Therefore, the main control device 15
is the beam LB1p based on the characteristic VT shown in FIG.
, the telecentric slope of LB2p (i.e., the characteristic V in Fig. 9)
The slope of T) ΔM is obtained from the following equation (2).

ΔM=ΔL/IZl-Z41...(2) However, Δ
It is assumed that L is the amount of lateral shift in the Y direction corresponding to the phase difference 1φl−φ41.

Next, the main controller 15 determines whether the telecenter slope ΔM calculated from the above equation (2) is within a predetermined allowable range.

As a result of this determination, only if the telecentering inclination ΔM exceeds the allowable range, the main controller 15 calculates the inclination angle of the parallel plane plate 33c based on the telecentering inclination ΔM. and,
The parallel plane plate 33c is tilted according to this inclination angle, and the beam L
B1p.

Correct the telecenter tilt of LB2p. Similarly, the telecentric inclinations of the beams LB1p and LB2p emitted from the position detection system 33x are also measured, and correction is performed in the same manner as described above only when the telecentric inclinations exceed the allowable range. As a result,
The symmetry of the incident angles θa and θb of the beams LB1p and LB2p irradiated onto the wafer W is maintained with high precision, and
At the same time as the telecentric tilt of the beams LBlp and LB2p is corrected, the telecentric tilt of the spot light SP is also automatically corrected. Note that in this step 100, the depth of focus is 2.
Beams LBlp, LB2p (
Since the reference member IO is simply moved up and down in the Z direction using a focal depth of about 300 μm, the telecenter tilt can be measured and corrected with high accuracy and high speed. This completes the SSA system telecenter tilt check and executes the next step lO1.

In step 101, the shutters 24 and 25 are simultaneously controlled to rotate, and the beam AL incident on the LSA optical system 26 is
The optical path of the beam ALs entering the LIA optical system 27 is closed while the optical path of the beam ALs entering the LIA optical system 27 is opened. As a result, beam AL
Only the beam p enters the LSA optical system 26, and a beam LB1p is placed on the wafer W.

Spot light SP is irradiated instead of LB2p. This completes the switching from the LIA system to the LSA system, and the next step 102 is executed.

In step 102, the position of the reticle mark RMy in the Y direction, the mark detection reference position of the SSA system in the Y direction,
That is, the optical axis position of the spot light SP emitted from the position detection system 33y is detected, and the baseline ΔBY in the Y direction is calculated. Therefore, as shown in FIG. 10, the reference member 10 is illuminated from below with exposure light, and a projected image of the cross pattern 10a is formed on the reticle R via the projection lens PL. The projected image is the reticle mark RMy (rectangular transparent window)
Wafer stage WS is slightly moved in the Y direction so as to perform relative scanning, and light amount detection system 9 receives illumination light that has passed through reticle mark RMy. At this time, the maximum amount of light passes when the projected image and the reticle mark RMy match, and the amount of light sequentially decreases in accordance with the deviation. From this, ASC, 14
calculates the position of the reticle mark RMy in the Y direction based on the photoelectric signal from the light amount detection system 9 and the position signal from the laser interferometer 8. Next, the optical axis position of the spot light SP in the Y direction is measured using the reference mark lOy formed on the reference member IO. Therefore, the spot light SP is
After forming the mark l Oys on the reference member 10 in parallel, the main controller 15 moves the wafer stage WS slightly in the Y direction to transmit the diffracted light 35 and scattered light 36 generated from the LSA mark 10ys to the photoelectric detector 331 (light receiving Surface 38a, 3
8b and 39a, 39b). And A
SC14 is a photoelectric signal SDi from the photoelectric detector 33i.

The position of the LSA mark 10ys is calculated based on the SDr and the position signal from the laser interferometer 8.

From the above detection results, the main controller 15 calculates the baseline ΔBy of the SSA system in the Y direction, and further calculates the baseline ΔBX in the X direction in exactly the same manner as described above. At this time, in order to improve accuracy, it is preferable to perform similar measurements multiple times and store the averaged values as the baselines ΔBx and ΔBY.

In the next step 103, the main controller 15
Pre-alignment of the wafer W is performed using the system 12.13 and the SSA system. Therefore, the WGA system 12.13 detects the Y-direction positions of two chips formed near the outer periphery of the wafer W and at positions symmetrical to the left and right (Y-axis) with respect to the wafer center, and the SSA system In a similar operation, the position of a chip near the outer periphery of the wafer W and at the same distance from the above two chips in the X direction is detected. Then, the main controller 15 calculates the amount of positional deviation (including rotation error) of the wafer W with respect to the coordinate system XY based on the positional information of the three chips, and performs pre-alignment of the wafer W according to this amount of positional deviation. conduct.

In the next step 104, the main controller 15 performs the same operation as in steps 102 and 103, and uses the SSA system to calculate the coordinate values (X, Y
position).

At this time, if the chip C cannot be measured or the measurement result is questionable due to random errors due to surface roughness of the wafer W, the measurement is performed again, or the chip C in the vicinity thereof is measured again. Then, in order to remove scaling errors caused by expansion and contraction (runout) of the wafer W, the chip position information (design value) is corrected based on these measurement results and the baselines ΔBx and ΔBY measured in step 102, and a new This position information is stored as an array map. From this, if the wafer stage WS is stepped according to the array map, the wafer marks WMx and WMy will always be set to the beams LB1p and LB2.
It will be positioned within ±P/4 with respect to p.

Incidentally, the array map may be calculated using the measurement results in step 103. In this case, it is possible to improve the calculation accuracy of the array map or reduce the number of chips C to be measured. be able to.

In the next step 105, step 101 described above
Similarly, the shutters 24 and 25 are rotated and the beam LBlp is generated instead of the spot light SP.

LB2p is irradiated onto the wafer W. This completes the switching from the LSA system to the LIA system, and the next step 106
Execute.

In step 106, the main controller 15 uses the SSA system to measure the coordinate values of a plurality of chips C (approximately 5 to 10) located near the center of the wafer W and its outer periphery.

Therefore, based on the array map obtained in step 104, the wafer stage WS is stepped, and the wafer mark WMy of the chip C whose coordinate values are to be measured is set to the beam LB.
lp.

Position within ±P/4 with respect to LB2p. Next, the beams LB1p and LB2p are irradiated onto the wafer mark WMY, and the diffracted light 37 generated from the wafer mark WMy is received by the photoelectric detector 331 (light receiving surface 37D). ASC
14 is an optical beat signal SDw from the photoelectric detector 331 and an optical beat signal (reference signal) SR from the photoelectric detector 27f.
Based on, the phase difference φW between the optical beat signals SDw and SR
(±180°) and calculates the position of the wafer mark WMY in the Y direction from this phase difference φW within P/2. Hereafter, by repeatedly performing the above operations, the main controller 1
5 calculates the chip arrangement by a statistical method. From this point, the EGA measurement using the LIA system is completed, and the next step 1 is
Execute 07.

In step 107, the main controller 15
Based on the baselines ΔBx and ΔBy measured in step 02 and the chip arrangement calculated in step 106, the wafer stage WS is stepped, and the projected image of the reticle pattern and the chip C are controlled while rotating the reticle R for each chip. Exposure is performed by accurately overlapping the images.

In the next step 108, the main controller 15 determines whether or not the reticle R is to be replaced. Here, it is assumed that unprocessed wafers stored in the same lot are continuously exposed using the same reticle R, and step 103 is performed again.
Execute. Thereafter, steps 103 to 1 are repeated until the exposure of all wafers W in the same lot is completed.
08 is executed repeatedly. This makes it possible to perform overlay exposure with high precision and high speed without reducing throughput, alignment measurement accuracy, etc.

In addition, due to factors such as mechanical vibration, the baseline ΔBx,
When ΔBy can vary, the baseline drifts particularly in a short time.In a stepper using an excimer laser device as the exposure illumination light source, for example, as shown by the dotted line in FIG. 10 wafers W
When the exposure is completed, it is preferable to adopt a sequence in which step 102 is executed instead of step 1.3 after step 108 is completed.

Further, in this embodiment, the reference mark 10y shown in FIG. 3B is
The same shape as the LSA diffraction grating mark (LS
Av-ri WMys) and the LIA system diffraction grating mark (
Wafer mark WMY integrated with bar pattern)
is used. Therefore, the LSA mark WMys is hardly affected by various processing processes such as development, and edge breakage and the like are greatly reduced. Therefore, step 10 mentioned above
4, when measuring the coordinate values of the chip C, the main controller 15 determines whether the surface condition of the wafer W (resist layer) is good or not based on the measurement result (for example, the waveform of the photoelectric signal SDi, etc.) . If the judgment result is bad, step 105 is executed in the same way as in this embodiment, but if the judgment result is good, the LSA system is used as it is to perform EG.
A sequence may be adopted in which the A measurement is performed, step 105 (switching from the LSA system to the LIA system) and step 106 (EGA measurement using the LIA system) are not performed, and step 107 is subsequently performed.

In addition, in this example, a He-Ne laser (wavelength 633 nm) is used.
) was used as the laser light source 20, but
As described above, in the case of a laser beam of a single wavelength, the alignment accuracy may deteriorate due to the influence of thin film interference caused by the resist layer due to the relationship with the film thickness of the resist layer. Next, a modification of this embodiment that can eliminate the effects of thin film interference and the like will be briefly described with reference to FIG. 11. Furthermore, the 11th A
11B, only members having different configurations from this embodiment are shown, and the same members as in this embodiment are given the same reference numerals.

As shown in FIG. 11A, the laser light source 20 described above as an SSA-based illumination light source and a laser light source 50 whose light source is, for example, a He-Cd laser (wavelength 538 nm) are provided,
Beam AL emitted from each laser light source 20.50
, ALc are coaxially incident on the wavefront rotating plate 21. Furthermore, the 11th B
As shown in the figure, in the position detection system 33y, a gicroic mirror 52 is obliquely installed in front of the photoelectric detector 33i, and a photoelectric detector 53 having the same configuration as the photoelectric detector 33i shown in FIG. A photoelectric detector 33 is installed separately on the surface and detects the diffracted light 37 generated from the wafer mark WMY according to the wavelength.
i, 53 are configured to be detected independently. Furthermore, it is desirable that each optical member such as the objective lens 33e constituting the SSA system be achromatic with respect to two wavelengths. If each optical member is not achromatized, use the reference member IO to measure the amount of deviation in the irradiation position of the spot light SP and beams LB1p and LB2p according to the wavelength on the wafer W in advance. It is preferable that the control device 15 has these deviation amounts as an offset.

Now, when using spot light SP in the SSA system configured as described above, beams AL and ALc are simultaneously emitted from the laser light source 20.50, and two spot lights SP having different wavelengths are generated by the LSA optical system 26. Formed on wafer W. Then, optical information (diffraction light) generated from the wafer mark WMy is received by a photoelectric detector 331.53 according to its wavelength. The ASC 14 detects the position of the wafer mark WMY in the Y direction based on the photoelectric signals from the photoelectric detectors 33i and 53 and the position signal from the laser interferometer 8. At this time, since two positional information of the wafer mark WMy are detected simultaneously by the photoelectric detectors 33i and 53, even if the spot light SP of either wavelength is affected by thin film interference etc., the accuracy is always high. The position of wafer mark WMy can be detected well.

On the other hand, when using the beams LB1p and LB2p, the beams AL and ALc are not emitted simultaneously from the laser light source 20.50, and only when they are affected by thin film interference, for example, from the laser light source 20 to the laser light source 50. Perform switching. Then, using the beam ALc1 emitted from the laser light source 50, that is, the beams LB1p and LB2p with a wavelength of 538 nm, the wafer mark WMY is detected in the same operation as step 106. Therefore, deterioration in alignment accuracy due to thin film interference etc. is also prevented for the beams LB1p and LB2p. Furthermore, when the wavelengths of beams LB1p and LB2p change,
The diffracted light 37 generated from the wafer mark WMy does not travel along the optical axis AX of the projection lens PL;
cannot be detected by the photoelectric detectors 33i and 53. Therefore, at the same time as the laser light source 20.50 is switched so that the diffracted light 37 always travels on the optical axis AX, the equation (1
), adjust the inclination angle of the parallel plane plates 46 and 47,
The intersection angle θ of the beams LB1p and LB2p is set to an optimum value. In addition, the two-beam frequency shifter 2 shown in FIG.
7a, AOM45 a.

45b outputs primary light that is deflected by a diffraction angle determined by frequencies fl and f2 as beams LBI and LB2.

Therefore, depending on the wavelength change of the beam ALs, the AOM45
The diffraction angle of the primary light by a, 45b also changes, and it becomes impossible to detect the diffracted light 37 by the photoelectric detectors 33i, 53 as well. Therefore, AOM45 a, 45
2 so that the diffraction angle of the first-order light due to b is always constant.
The beam frequency shifter 27a also changes the drive signals SFI and SF of the AOMs 45a and 45b according to the wavelength of the beam ALs.
2 frequencies fl and f2 are finely adjusted.

As described above, in one embodiment of the present invention, the two beams LB1p and LB2p have a predetermined frequency difference Δf.
The LIA system that adopted the so-called heterodyne method was used, but the interference was eliminated by moving the diffraction grating mark (wafer mark) in the pitch direction with respect to the stationary interference fringes without giving a frequency difference to the beams LB1p and LB2p. It is clear that the same effect can be obtained by using an LIA system that employs the so-called homodyne method, which detects the position of the diffraction grating mark using the fringe as a reference.

In addition, in this embodiment, the LIA system is combined with the LSA system, but for example, illumination light (exposure light, He-Cd laser, etc.) is irradiated onto a predetermined area on the wafer W through the projection lens PL, and from the wafer mark. The light of It may be combined with an alignment optical system (TTL method) that processes image signals. Note that when using light of a non-exposure wavelength such as a He-Cd laser as the illumination light, an aberration correction optical system is provided within the alignment optical system. Furthermore, WGA systems 12 and 13 using a spot scan method using a vibrating mirror as shown in Fig. 2, a stage scan method such as the LSA system, or an off-axis method using the image signal processing method described above It may also be combined with a wafer alignment system.

Furthermore, in this embodiment, the LSA diffraction grating mark (dot mark) and the LIA diffraction grating mark (bar pattern) were integrally formed as wafer marks WMx and WMy, but both diffraction grating marks The same effect can be obtained even if both diffraction grating marks are formed separately on the wafer W by setting the designed interval as an offset. Further, although a mark in which a plurality of dot marks are arranged in the longitudinal direction of the spot light SP is used as the LSA-based diffraction grating mark, a bar pattern simply extending in the longitudinal direction may be used instead. Also, wafer W
Since the wafer is subjected to various substrate processing such as development processing, even if a reticle mark with a duty ratio of 1:1 is transferred, a wafer mark like the one in this example will not always be formed with a duty ratio of 1:1. do not have. Therefore, it is preferable to predict the amount of change in the duty of the wafer mark due to various substrate processes in advance, and form the reticle mark with a duty ratio calculated from this predicted value so that the duty of the wafer mark becomes 1:. Furthermore, even if a wafer mark formed with a duty ratio of 1:1 is used, the intensity of the diffracted light 37 generated from the wafer mark becomes weak in relation to the thickness of the resist layer, making it difficult to obtain the optical beat signal SDw with high contrast. become unable to do so. In such a case, the duty ratio of the wafer mark is determined in advance so that the intensity of the diffracted light becomes the strongest depending on the thickness of the resist layer, and various methods are used so that the wafer mark is formed with this optimal duty ratio. It is preferable to form a reticle mark in consideration of the amount of change in duty due to substrate processing, etc.

Furthermore, the exposure apparatus suitable for applying the alignment optical system according to the present invention is not limited to a stepper; for example, it may be applied to a contact type or proximity type exposure apparatus, an X-ray exposure apparatus, etc. Exactly the same effects as in the embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, when combining two different types of alignment optical systems, the use of optical members other than the two sets of beam shaping optical systems, including the light splitting means (beam splitter) of the present invention, is maximized. I'm sharing it. Therefore, the space within the exposure apparatus, especially around the reticle, can be minimized, and offset between the two types of alignment optical systems can be prevented. Furthermore, it is possible to prevent loss of the amount of alignment light and instability of the illumination optical path due to sharing of optical members. In addition, when aligning the optical axes of two types of alignment optical systems accurately in each of the two sets of optical members (position detection systems, etc.) placed behind the light splitting means, the optical axis of one of the If the optical adjustment is performed so that they match accurately, the other optical axis will also match exactly, so the time required for the optical adjustment can be shortened. Furthermore, when combining an alignment system (LIA system) employing the heterodyne method or homodyne method with an LSA system (or WGA system), both alignment marks (diffraction grating marks) can be formed integrally on the photosensitive substrate. Therefore, the LSA-based diffraction grating mark is less affected by the substrate processing process, the occurrence of edge breakage of the diffraction grating mark, etc. is significantly reduced, and the accuracy of LSA-based alignment measurement can be improved. Also, LIA series and L
The deflection member (parallel plane plate 33C) that simultaneously deflects the angles of the principal rays of the illumination light from the SA system is placed at least on the photosensitive substrate side at the pupil plane of the telecentric objective optical system, its conjugate plane, or any one of the conjugate planes thereof. It is placed within the plane. Therefore, by simply measuring the telecentric tilt on the photosensitive substrate side of the objective optical system using the LIA system and adjusting the tilt angle of the deflection member according to this telecentric tilt, the LIA system and LS
The telecenter tilt of the A system can be corrected simultaneously (at high speed) and with high precision. As a result, it is possible to realize an exposure apparatus equipped with an alignment optical system that can perform alignment and telecenter tilt correction with high precision and high speed.

[Brief explanation of drawings]

FIG. 1 is a perspective view showing a schematic configuration of a TTL type alignment optical system according to the present invention, FIG. 2 is a plan view showing a schematic configuration of a stepper equipped with an alignment optical system according to the present invention, and FIG. 3A , FIG. 3B is a plan view showing a schematic configuration of the fiducial mark provided on the reference member, and FIG. 4 is a plan view illustrating the main parts of the alignment optical system shown in FIG. 1 in more detail. , FIG. 5 is a diagram showing the detailed configuration of the two-beam frequency shifter, FIG. 6 is a diagram showing the schematic configuration of the photoelectric detector of the alignment optical system according to the present invention, and FIG. 7 is a diagram showing the schematic configuration of the photoelectric detector of the alignment optical system according to the present invention. A schematic flowchart diagram showing an example of the operation, Fig. 8 is a plan view for explaining the telefocusing tilt, Fig. 9 is a graph showing measurement data of the telefocusing property for explaining the telefocusing tilt correction, and Fig. 10 is a reticle mark. Figure 11 for explaining the position measurement operation of
Figures A and 11B are plan views for explaining the present invention in detail. IM...imaging surface, W...wafer, WS...sea urchin/
)stage.

Claims (5)

[Claims] (1) A device that exposes a pattern formed on a mask onto a photosensitive substrate includes an illumination system that generates a coherent light beam of a predetermined wavelength, and an objective optical system that is telecentric at least on the photosensitive substrate side; comprising an irradiation optical system that irradiates a beam onto the photosensitive substrate, and a photoelectric detector that receives optical information generated from an alignment mark of a predetermined shape formed on the photosensitive substrate via the objective optical system; A device for relatively aligning the mask and the photosensitive substrate according to a detection signal from the photoelectric detector, the device being provided within the illumination system and configured to direct the light beam approximately at the center of the pupil plane of the objective optical system. A first light beam passing through the pupil plane and a second light beam passing through the pupil plane so as to be approximately point symmetrical with respect to the center of the first light beam.
a multi-beam converting means for emitting a second light beam from the book; and a switching means for switching so that only one of the first light beam and the two second light beams passes through the pupil plane of the objective optical system. . A positioning device, characterized in that the first light beam and two second light beams are switched according to the shape of the positioning mark. (2) After the two second light beams are condensed into a substantially spot shape on the pupil plane of the objective optical system, each of the two second light beams becomes a substantially parallel light beam, and the objective optical system 2. The alignment device according to claim 1, wherein the alignment device is ejected so as to intersect at a predetermined angle. (3) The alignment mark is formed in a predetermined periodic structure, and the direction of the straight line connecting the center of the first light beam and each center of the two second light beams on the pupil plane of the objective optical system is 3. The first light beam and the two second light beams are made to enter the pupil plane so as to be substantially parallel to the periodic direction of the alignment marks. Alignment device. (4) The irradiation optical system is configured to adjust the angle of the principal ray of the first light beam on the photosensitive substrate side of the objective optical system to the angle of the principal ray of the two second beams.
It has a deflection means for simultaneously deflecting each principal ray angle of the light beam, and the deflection means is disposed within the pupil plane of the objective optical system, its conjugate plane, or any plane in the vicinity thereof. 4. A positioning device according to claim 1, characterized in that: (5) The irradiation optical system is arranged so that the first light beam and the two second light beams are incident approximately orthogonally to each other, and each of the first light beam and the two second light beams is It is characterized by having a light splitting means for splitting, and irradiating the first light beam and two second light fluxes, which are split into two by the light splitting means, onto the photosensitive substrate via the objective optical system, respectively. The alignment device according to any one of claims 1 to 4.