JP3200874B2 - Projection exposure equipment - Google Patents

Projection exposure equipment

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Publication number
JP3200874B2
JP3200874B2 JP16978191A JP16978191A JP3200874B2 JP 3200874 B2 JP3200874 B2 JP 3200874B2 JP 16978191 A JP16978191 A JP 16978191A JP 16978191 A JP16978191 A JP 16978191A JP 3200874 B2 JP3200874 B2 JP 3200874B2
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Japan
Prior art keywords
mark
projection
system
reference
detection
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JP16978191A
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Japanese (ja)
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JPH0521314A (en
Inventor
健爾 西
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株式会社ニコン
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Priority to JP16978191A priority Critical patent/JP3200874B2/en
Priority claimed from US07/998,642 external-priority patent/US5243195A/en
Publication of JPH0521314A publication Critical patent/JPH0521314A/en
Priority claimed from US09/002,884 external-priority patent/USRE36730E/en
Application granted granted Critical
Publication of JP3200874B2 publication Critical patent/JP3200874B2/en
Anticipated expiration legal-status Critical
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Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus for exposing a photosensitive layer applied to a substrate such as a semiconductor wafer or a glass plate for a liquid crystal, and more particularly, to accurately control a baseline of an off-axis type alignment system. The present invention relates to a projection exposure apparatus having a function of performing

[0002]

2. Description of the Related Art Conventionally, a projection exposure apparatus having an off-axis alignment system (hereinafter referred to as a stepper for convenience) has been disclosed in Japanese Patent Application Laid-Open Nos. 53-56975 and 56-56975.
As disclosed in JP-A-134737, a reference mark plate is fixed on a wafer stage that holds a photosensitive substrate (hereinafter, referred to as a wafer) and moves two-dimensionally by a step-and-repeat method. The reference mark plate is used to manage the distance between the off-axis alignment system and the projection optical system, that is, the so-called baseline amount. FIG. 1 is a diagram schematically illustrating the principle of baseline measurement disclosed in each of the above publications. In FIG. 1, a main condenser lens ICL illuminates a reticle (mask) R uniformly during exposure. Reticle R is held by reticle stage RST, and reticle stage RST is moved so that center CC of reticle R coincides with optical axis AX of projection lens PL. On the other hand, wafer stage WST
A reference mark FM equivalent to an alignment mark formed on the wafer surface is provided on the upper side.
Is positioned at a predetermined position in the projection field of view of the projection lens PL, the mark RM of the reticle R and the reference mark are aligned by a TTL (through-the-lens) type alignment system DDA provided above the reticle R. FM are detected at the same time. The distance La between the mark RM and the center CC of the reticle R is a predetermined value in design, and the distance between the projection point of the mark RM and the projection point of the center CC on the image plane side (wafer side) of the projection lens PL is: La /
It becomes M. Here, M is the magnification of the projection lens PL when viewing the reticle side from the wafer side, and M = 5 in the case of a 1/5 reduction projection lens.

[0003] Outside the projection lens PL (outside the projection field of view)
Has an off-axis wafer alignment system O
The WA is fixed. The optical axis of the wafer alignment system OWA is parallel to the optical axis AX of the projection lens PL on the projection image plane side. In the inside of the wafer alignment system OWA, a target mark TM serving as a reference for aligning a mark on the wafer or the reference mark FM is provided on a glass plate, and a projection image plane (the wafer surface or the reference mark FM) is provided. Plane).

The baseline amount BL is shown in FIG.
Reticle mark RM and reference mark FM
Stage WST position X when1And the indicator
Mark TM and fiducial mark FM are aligned
Stage WST Position X TwoWith a laser interferometer, etc.
Measure the difference (X1-XTwo) Is calculated by
You. This baseline amount BL will be referred to later as a mark on the wafer.
Is aligned with wafer alignment system OWA
The reference amount when sending the image directly below the shadow lens PL
It is. That is, one shot on the wafer
XP is the distance between the center of the area) and the mark on the wafer.
Wafer stay when the mark matches the index mark TM
X position of WSTThreeThen, the shot center and reticle
To match the center CC, the wafer stage W
ST may be moved to the position of the following equation.

X 3 -BL-XP or X 3 -BL + XP Note that this formula only represents the one-dimensional direction in principle, and it is actually necessary to consider it in two dimensions. The calculation method differs depending on the arrangement of the mark (ie, the mark RM), the arrangement of the wafer alignment system OWA, and the like.

In any case, after the mark position on the wafer is detected using the off-axis type wafer alignment system OWA, the wafer stage WST is fed by a fixed amount, and the pattern of the reticle R is immediately transferred onto the wafer. Exposure can be performed so as to be accurately superimposed on the shot area.

[0007]

In the prior art as described above, the detection center point of the off-axis type alignment system OWA (the center of the index mark TM) and the projection point of the mark RM of the reticle R by the projection lens PL. When measuring the positional relationship (baseline amount BL) with respect to the above, the relative distance is obtained by moving the wafer stage WST and using a laser interferometer. For this reason, there is a natural limitation in improving the accuracy of the baseline measurement due to inevitable factors such as the running accuracy of the wafer stage WST and air fluctuation in the laser beam optical path of the laser interferometer. In addition, movement of wafer stage WST for positioning reference mark FM in the detection area of TTL alignment system DDA, and off-axis alignment system OWA of reference mark FM.
Stage WS for positioning at the detection center point
It is necessary to move T, and there is naturally a limit in increasing the speed of the baseline measurement processing.

Further, in the conventional stepper, the extension line of the measurement axis (beam optical axis) of the laser interferometer for measuring the position of the wafer stage WST is set so as to intersect the optical axis of the projection lens in both the X and Y directions. It is only set,
When various marks are detected by the axis alignment system OWA, it may be difficult to always realize a mark detection direction in which Abbe error (sine error) becomes zero. Therefore, a set of laser interferometers in which the Abbe error is zero with respect to the optical axis of the projection lens, and a laser interferometer in which the Abbe error is zero with respect to the detection center point of the off-axis alignment system OWA It is also conceivable to provide a set of In this case, the two sets of laser interferometers
Switching between stage position measurement during wafer alignment using the Axis / Alignment System OWA and stage position measurement during projection exposure will be used. Otherwise, it naturally becomes an error factor.

The present invention has been made in view of such conventional problems, and has as its object to provide a projection exposure apparatus which improves the baseline measurement accuracy and the processing speed.

[0010]

In the present invention, in order to solve the problem], on the wafer stage WST, the reference mark FM 2 to match the mark RM on the reticle R, the off-axis alignment system O
Providing a reference plate FP of the reference mark FM 1 was formed together to match the detected center point of the WA. At the time of the baseline measurement, the amount of positional deviation between the reticle R and the reference plate FP is obtained with the wafer stage WST stationary, and at the same time, the positional deviation between the detection center point of the off-axis alignment system OWA and the reference plate FP. The amount was determined.

Further, a pair of interferometers (IF) satisfying Abbe error with respect to the off-axis alignment system OWA
X, IFY 1 ) and a pair of interferometers (IFX, IFY 2 ) satisfying the Abbe error with respect to the projection optical system. The internal counters were configured to be mutually preset so that the interferometer measurements would be equal.

[0012]

When the position of the reticle R is measured using the reference plate FP at the time of the baseline measurement, if two interferometers are preset so that the measured values become equal, two positions for the same direction, for example, the Y direction are measured. The virtual line connecting the reference points of the interferometer is precisely parallel to the reflecting surface of the Y-direction moving mirror (IMy) on the wafer stage.

Therefore, after the presetting, no error occurs even if one of the two sets of interferometers is selected and used as it is for the position control of the wafer stage.

[0014]

FIG. 2 is a perspective view showing the configuration of a projection exposure apparatus according to an embodiment of the present invention, and the same members as those of the conventional apparatus of FIG. In FIG. 2, on a reticle R, a pattern area PA in which a circuit pattern to be exposed on a wafer and the like are formed, and reticle marks RM 1 and RM 2 for alignment are provided. These reticle marks RM 1 and RM 2 are photoelectrically detected via objective lenses 1A and 1B of a TTL alignment system, respectively.
The reticle stage RST can be moved two-dimensionally (X, Y, θ directions) by a drive system such as a motor not shown in FIG. 2, and the amount of movement or the position of movement is three laser interferometers IRX. , IRY, and IRθ. The amount of rotation of the reticle stage RST about the Z axis (coordinate axis parallel to the optical axis AX) is obtained by the difference between the measured values of the interferometers IRY and IRθ, and the amount of parallel movement in the Y axis direction is determined by the interference system IR.
It is obtained by the average of the measured values of Y and IRθ, and the amount of parallel movement in the X-axis direction is obtained by the interferometer IRX.

In the present embodiment, a second TTL alignment system for detecting a mark on the wafer W via only the projection lens PL is provided separately for the X direction and for the Y direction. The second TTL alignment system for the X direction includes a mirror 2X and an objective lens 3X fixed between the reticle stage RST and the projection lens PL, and the second TTL alignment system for the Y direction is similarly configured. And the objective lens 3Y and the like.

In this embodiment, the first TTL alignment system including the objective lenses 1A and 1B is hereinafter referred to as a TTR (through-the-reticle) alignment system, and the objective lens 3X,
The second TTL alignment system including 3Y will be simply referred to as a TTL alignment system. Now, on two sides of the wafer stage WST on which the wafer W is mounted, a moving mirror IMx that reflects a beam from the laser interferometer IFX and a beam from each of the laser interferometers IFY 1 and IFY 2 are reflected. The movable mirror IMy is fixed. The beam from the interferometer IFX is perpendicular to the reflecting surface of the moving mirror IMx extending in the Y direction, and the extension of the beam is orthogonal to the extension of the optical axis AX of the projection lens PL. Beam from the interferometer IFY 2 is perpendicular to the reflecting surface of the movable mirror IMy extending in the X direction, also perpendicular to the extension of the optical axis AX extension line of the beam. Beam from another interferometer IFY 1 is perpendicular and the reflecting surface of the movable mirror IMy, is parallel to the beam of the interferometer IFY 2.

The off-axis type wafer alignment system includes a reflecting prism (or mirror) 4A fixed to the lower end of the projection lens PL and an objective lens 4A.
B or the like. Light receiving system 4 for wafer alignment system
C includes a conjugate target mark TM inside, and captures a mark or the like on the wafer formed on the target mark plate via the prism 4A and the objective lens 4B with a CCD camera. In this embodiment, the optical axis of the objective lens 4B that falls on the wafer stage WST via the prism 4A and the optical axis A of the projection lens PL
It is set so that X and X are separated by a certain distance only in the X direction, and there is almost no positional difference in the Y direction.

Further, the wafer stage W of the objective lens 4B
Extension of the optical axis falling on ST is orthogonal to each of the extension line of the interferometer IFX extension line interferometer IFY 1 beam beam. The arrangement of such an interferometer is described in detail in
No. 309324. On wafer stage WST, a reference plate FP provided with two reference marks FM1 and FM2 for baseline measurement is fixed. The reference plate FP is disposed at a corner surrounded by the two movable mirrors IMx and IMy on the wafer stage WST, and forms a light-shielding layer such as chromium on the surface of a low expansion coefficient transparent material such as a quartz plate. A part is etched in the shape of the reference marks FM1 and FM2. The fiducial mark FM1 is an off-axis type wafer alignment system (4A, 4A,
B, 4C), and the reference mark FM2 is TT
It can be detected by an R alignment system (1A, 1B) or a TTL alignment system (2X, 3X; 2Y, 3Y).

The intervals between the fiducial marks FM1 and FM2 in the X direction are accurately formed with submicron precision. If there is a residual placement error amount, the value is precisely measured in advance and set as a device constant. Shall be sought. FIG. 3 is a plan view showing the arrangement of each member on wafer stage WST. Wafer W is mounted on wafer holder WH which can be microrotated on wafer stage WST, and is vacuum-sucked.
In this embodiment, the wafer W is placed on the wafer holder WH after being mechanically pre-aligned so that the linear cutout OF of the wafer W is parallel to the X axis.

As shown in FIG. 3, the center of the diameter (optical axis AX) of the lower end of the lens barrel of the projection lens PL and the field of view of the objective lens 4B are arranged as close as possible. Thus, when the projection lens PL and the reference plate FP are arranged, the wafer W
Is moved from the position immediately below the projection lens PL to the diagonally lower right in the figure, and the loading and unloading of the wafer W can be performed in this state. This arrangement is disclosed in, for example, JP-A-63-224326.

FIG. 4 shows a reference mark FM on a reference plate FP.
1 is a plan view showing a detailed mark arrangement of FM2. 4, a central intersection of the reference mark FM 2 of the X axis and parallel to line LX and parallel to the Y axis linear LY 2, at the time of baseline measurement, approximately the intersection with the optical axis AX of the projection lens PL Matches. In this embodiment, a light-emitting cross-shaped slit mark IFS is arranged on the intersection, and illumination light having the same wavelength as the exposure light illuminates only the local area ISa including the light-emitting slit mark IFS from the back side of the reference plate FP. Reference marks FM2A and FM2B corresponding to the respective arrangements of the reticle marks RM 1 and RM 2 are provided at two symmetrical positions sandwiching the light emitting slit mark IFS on the straight line LX. The marks FM2A and FM2B are the reference plate FP
Obtained by etching the chromium layer above the cross-shaped slit, marked FM2A is reticle mark RM 1 and the alignment mark FM2B is aligned with the reticle mark RM 2.

The center (intersection) of the emission slit mark IFS
Is the projection field of view of the projection lens PL. In the case of this embodiment, the mark LIMx detectable by the TTL alignment system (2X, 3X) for the X direction shown in FIG. disposed on a straight line LY 2 in PIF, TTL alignment system for the Y direction (2Y,
3Y), two marks LIMy and LS detectable by
My is arranged on the straight line LX of the visual field region PIF. Although the detailed arrangement relationship of each mark will be described later, in this embodiment, two TTL alignment systems 1A,
1B simultaneously detects the reticle marks RM 1 and RM 2 and the reference marks FM2A and FM2B, respectively, the TTL alignment system (2X, 3X) for the X direction detects the mark LIMx, and detects the mark LIMx. Each mark FM2 is set so that a TTL alignment system (2Y, 3Y) can be created.
A, FM2B, LIMx and LIMy were arranged.

On the other hand, a straight line LY 1 which is set apart by a predetermined distance from the straight line LY 2 in the X direction is parallel to the Y axis, on the intersection of the straight line LY 1 and the straight line LX, the off-axis alignment system The reference mark FM1 having a size that can be included in the field of view MIF of the objective lens 4B is formed. The mark FM1 has an X so that two-dimensional alignment is possible.
It is an aggregate of a plurality of line patterns provided in parallel with each other in the direction and the Y direction. As is apparent from the above description, the reference plate FP is a straight line LY 1 is in the X-Y plane, as much as possible consistent with interferometer IFY 1 of the beam center line (measurement axis),
The straight line LY 2 is fixed on the wafer stage WST so as to coincide as much as possible with the center line (measuring axis) of the beam of the interferometer IFY 2 (ie, so as not to cause rotational displacement as much as possible).

Further, two reference marks FM are provided at symmetric positions on the straight line LX with respect to the intersection of the straight lines LX and LY 1.
2C and FM2D are provided. Fiducial mark FM2
C and FM2D are cross-shaped slit patterns of exactly the same shape and size as the reference marks FM2A and FM2B, and the interval in the X direction is exactly the same as the interval between the marks FM2A and FM2B. The mark LSMx in FIG. 4 is detected by the TTL alignment system (2X, 3X) for the X direction, and is provided at the same position as the X coordinate value of the reference mark FM2B.

FIG. 5 shows a reference mark FM2 on the reference plate FP.
Only the arrangement of each mark on the side is enlarged, and the projection lens P
The center of the projection field area PIF of L is the emission slit mark I
The state where it matched with the intersection of FS is shown. FIG. 5 further shows the positional relationship between the outer shape of the reticle R and the outer shape of the pattern area PA, which are ideally positioned in this state, by a two-dot chain line. TTL alignment mark LIMx,
LIMy is located at the outermost periphery of the projection field of view PIF, because the mirrors 2X and 2Y at the tip of the TTL alignment system are arranged so as not to shield the projection area of the pattern area PA. In this state, the reference mark FM2A is may be aligned with the reticle mark RM 1, the reticle mark R
M 1 (RM 2 same), as shown in FIG. 6, is composed of a double slit mark RM 1 x extending in the double slit mark RM 1 y and Y-direction extending in the X direction, these marks RM 1 y and RM 1 x are formed as dark portions in a transparent portion surrounded by a rectangular light shield SB. Of the cross-shaped slits of the reference mark FM2A, the slit extending in the X direction is sandwiched between the double slit marks RM 1 y, and the slit extending in the Y direction is sandwiched between the double slit marks RM 1 x. The ideal alignment has been achieved.

Here, the distance K 1 in the X direction between the center of the reference mark FM2A and the center of the mark LIMy and the distance K 2 in the X direction between the center of the light emitting slit mark IFS and the center of the mark LSMy are shown in FIG. Emitting slit mark I shown in
X when FS is Y direction scanning the reticle mark RM 1
It is set so as to have a difference by a direction offset amount ΔXk (wafer-side conversion value). That is, K 1 = K 2 + Δ
Xk or K 1 = K 2 −ΔXk.

Further, the center position in the X direction of the mark LSMx detectable by the TTL alignment system for the X direction coincides with the center position in the X direction of the reference mark FM2B. This is the distance K in the X direction between the center point of each of the two reference marks FM2A and FM2B and the center of the light emitting slit mark IFS.
3 is a condition that holds when both are equal. The position of the mark LSMx in the Y direction is substantially equal to the position of the mark LIMx in the Y direction.
When the distance in the Y direction between the center of the mark LIMx and the center of the mark LIMx is K 4 , and the distance in the Y direction between the center of the light emitting mark IFS and the center of the mark LSMx is K 5 , K 4 = K 5 + ΔY
k or K 4 = K 5 −ΔYk.
(Note that K 4 and K 5 are not shown). Here, ΔYk is shown in FIG.
As shown in the figure, the emission slit mark IFS is the offset amount in the Y direction when scanning the double slit mark RM 1 x of the reticle mark RM 1 in the X direction.

Next, the detailed configuration of the TTR alignment system (1A) will be described with reference to FIG. Reticle mark R
Above M 1, a total reflection mirror 100 is inclined at 45 ° to make the optical axis of the horizontally arranged objective lens 101 perpendicular to the reticle R. The TTR alignment system switches between a beam splitter 102, a light source 103 that generates light of an exposure wavelength, and blocking and passing of illumination light for coaxial epi-illumination. A shutter 104, an optical fiber 105 for guiding illumination light, a condenser lens 106 for condensing illumination light from an exit end of the optical fiber 105 to uniformly illuminate an illumination field stop 107, and a Koehler for applying illumination light from the field stop 107. It has a self-illumination system composed of a lens system 109 for transmitting light to the objective lens 101 under illumination conditions. Thus,
Objective lens 101 illuminates only the inner shielding band SB mark RM 1 of the reticle R is formed. As a result, the reflected light from the mark RM 1 is reflected by the mirror 100 and the objective lens 1
The light is reflected by the beam splitter 102 via the optical system 01 and enters the imaging lens 110. The image light flux of the mark RM 1 is split into two by the half mirror 111,
As a result, an enlarged image is formed on each imaging surface of the CCD camera 112X for detecting the X direction and the CCD camera 112Y for detecting the Y direction. The CCD camera 112X and 112Y, the direction of the horizontal scanning lines are arranged perpendicular to each other with respect to the enlarged image of the mark RM 1.

At this time, the mark RM1Of the light-shielding band SB including
The reference mark FM2A on the reference plate FP is located immediately below the inner area.
Is positioned, the CCD 112X and 112Y
The cross-shaped slit of the FM2A is imaged as a black line. Picture
The image processing circuit 113X receives an image from the CCD camera 112X.
The image signal is subjected to digital waveform processing, and Y of the reference mark FM2A is processed.
Slit extending in the direction, and reticle mark RM1Dub of
Luslit mark RM 1X direction with x (horizontal scanning line direction
Direction) is obtained. The image processing circuit 113Y is C
Digital waveform processing of image signal from CD camera 112Y
And a slit extending in the X direction of the reference mark FM2A.
And reticle mark RM1Double slit mark RM
1Calculates the amount of positional deviation from y in the Y direction (horizontal scanning line direction)
You. The main control system 114 includes processing circuits 113X and 113Y.
The determined reference mark FM2A and reticle mark RM1
Is out of the allowable range set in advance in the X and Y directions.
, Drive system 115 of reticle stage RST is
By controlling, the position of the reticle R is corrected.

The drive system 115 is driven by the three interferometers IRX, IRY and IRθ shown in FIG.
The position (X, Y, θ) before the correction of ST is detected, and the measurement values to be detected by the three interferometers IRX, IRY, and IRθ after the correction are calculated. Therefore, the driving system 11
5 is such that the measured values of the three interferometers IRX, IRY, IRθ are the measured values to be detected after the correction.
Reticle stage RST is positioned by position servo control. The main control system 114 includes a wafer stage WS
The drive system 116 that performs position servo control of the movement of T based on the measurement value of the interferometer IFX, IFY 1 , or IFY 2 is also controlled.

Now, the TTL alignment system 1A shown in FIG. 7 applies illumination light from the light emitting mark IFS on the reference plate FP to the projection lens PL, the transparent portion inside the light shielding band SB of the reticle R, the mirror 100, A light emitting mark light receiving system for detection via the objective lens 101, the beam splitter 102, the lens system 109, and the beam splitter 108 is provided. This light emitting mark light receiving system is composed of a lens system 120 and a photoelectric sensor (photomultiplier) 121 and the like.
The light receiving surface of the photoelectric sensor 121 is the pupil E of the projection lens PL.
P and a pupil plane between the objective lens 101 and the lens system 109 are conjugated with each other. The photoelectric sensor 121 photoelectrically detects the amount of transmitted light that changes when the light emitting mark IFS scans the reticle mark RM 1 (or RM 2 ), and outputs a photoelectric signal SSD corresponding to the change. This photoelectric signal S
In the SD processing, the signal waveform is digitally sampled in response to an up / down pulse (for example, one pulse for every movement of 0.02 μm) output from the interferometers IFX and IFY 2 following the scanning of the wafer stage WST, This is performed by storing it in a memory.

Next, an example of the configuration of the TTL alignment system (2Y, 3Y) in FIG. 2 will be described with reference to FIG. The TTL alignment system used in this embodiment is He-Ne
The red light from the laser light source 130 is used as mark illumination light, thereby preventing the influence of the resist layer of the wafer W when detecting the mark reflected light and preventing the resist layer from being exposed to light. Further, the TTL alignment system incorporates two alignment sensors having different mark detection principles, and uses the objective lens 3Y in common to selectively use the two alignment sensors. Such a configuration is disclosed in JP-A-2-272305 or JP-A-2-2-2305.
Since this is disclosed in detail in Japanese Patent Publication No. 83011, a brief description will be given here.

The He-Ne laser light from the laser light source 130 is split by the beam splitter 131 and reaches shutters 132A and 132B which are opened and closed complementarily. In FIG. 8, the shutter 132A is open and the shutter 132B is closed, and the laser beam is subjected to two-beam interference alignment (L
The light enters the light transmission system 133A of the IA) system. This light transmission system 1
33A divides an incident beam into two laser beams, and outputs the two laser beams by giving a certain frequency difference using an acousto-optic modulator. In the case of FIG. 8, two laser beams output from the light transmission A133A are arranged in parallel in a direction perpendicular to the paper surface of FIG. This 2
This laser beam is reflected by the half mirror 134 and further split into two by the beam splitter 135. The two laser beams reflected by the beam splitter 135 intersect on the aperture APA on the wafer conjugate plane by the objective lens 3Y. The two parallel laser beams that have passed through the stop APA are reflected by the mirror 2Y, enter the projection lens PL, and intersect again on the wafer W or the reference plate FP. One-dimensional interference fringes are formed in the region where the two laser beams intersect, and the interference fringes flow in the pitch direction of the interference fringes at a speed corresponding to the frequency difference between the two beams.

Therefore, the mark LIM shown in FIGS.
Assuming that y and LIMx are diffraction gratings parallel to the interference fringes, interference beat light whose intensity changes at a beat frequency corresponding to the frequency difference is generated from the diffraction grating marks LIMx and LIMy. Assuming that the pitch of the diffraction grating of the marks LIMx and LIMy and the pitch of the interference fringes have a certain relationship, the interference beat light is generated perpendicularly from the wafer W or the reference plate FP, and is transmitted through the projection lens PL. Along the optical path of the transmitted light beam, the mirror 2Y, the aperture APA, and the objective lens 3Y return in this order. The interference beat light partially passes through the beam splitter 135 and reaches the photoelectric detector 139.
The light receiving surface of the photoelectric detector 139 is the pupil plane EP of the projection lens PL.
And are arranged approximately conjugate. In addition, a plurality of photoelectric elements (photodiodes, phototransistors, etc.) are separately arranged on the light receiving surface of the photoelectric detector 139, and the interference beat light is generated at the center of the photoelectric detector 139 (the center of the pupil plane). The light is received by the element. The photoelectric signal becomes a sine wave AC signal having a frequency equal to the beat frequency, and is input to the phase difference measurement circuit 140.

The two transmitted light beams transmitted through the beam splitter 135 cross each other as parallel light beams on a transmission type reference grating plate 137 by an inverse Fourier transform lens 136. Therefore, one-dimensional interference fringes are formed on the reference grating plate 137, and the interference fringes flow in one direction at a speed corresponding to the beat frequency. The photoelectric element 138 includes a reference grid plate 137.
One of the interference light of the ± 1st-order diffracted light and the interference light of the 0th-order light and the 2nd-order diffracted light generated coaxially from the light source is received. These interference lights also change in intensity in a sinusoidal manner at a frequency equal to the beat frequency, and the photoelectric element 138 uses an AC signal having a frequency equal to the beat frequency as a reference signal to generate the phase difference measurement circuit 1.
Output to 40.

The phase difference measuring circuit 140 includes a photoelectric element 138
, The phase difference Δφ (within ± 180 °) of the AC signal from the photoelectric detector 139 is determined based on the reference signal from
The information SSB of the displacement amount in the Y direction (or equivalent mark on the wafer), that is, in the lattice pitch direction, is output to the main control system 114 in FIG. The resolution of the displacement detection is determined by the relationship between the pitch of the mark LIMy and the pitch of the interference fringes irradiated on the mark, and the resolution of the phase difference detection circuit. If the phase difference detection resolution is ± 1 °. Then, assuming that the grid pitch Pg of the mark LIMy is 8 μm and the pitch Pf of the interference fringes is Pg / 2, the displacement detection resolution is represented by ± (1 ° / 180 °) × (Pg / 4), ± 0.01 μm.

The main control system 114 shown in FIG. 7 servo-controls the drive system 116 of the wafer stage WST on the basis of the positional deviation information SSB from the TTL alignment system of the high resolution LIA method, Mark LIM
Wafer stage WST can be servo-locked so that y is always driven into a fixed positional relationship with reference lattice plate 137.

However, when performing servo lock, it is sufficient that the phase difference between the signals from the photoelectric element 138 and the photoelectric detector 139 is stable to a predetermined value.
It is not necessary to convert the phase difference into the amount of positional deviation, and servo lock can be performed only by detecting the amount of change in the phase difference.
As another detection method of the TTL alignment system, as disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2-233011, a slit laser spot light extending in a direction orthogonal to the mark detection direction is used. A mark is scanned, and a signal level obtained by photoelectrically detecting diffraction and scattered light generated from the mark is converted to a wafer stage W for mark scanning.
Interferometer IFX occurring with the movement of the ST, a method of digitally sampled in response to the up-down pulses from IFY 2.

The laser step alignment (L
The SA) type light transmission system 133B includes a shutter 132A.
Is closed and the laser beam enters when the shutter 132B is open. The incident beam is shaped by a beam expander and a cylindrical lens into a slit shape in which the beam cross section at the focal point extends in one direction, and the beam splitters 134 and 135, the lens system 3Y, and the mirror 2
The light enters the projection lens PL via Y. At this time, aperture AP
A is conjugated to the wafer surface (the surface of the reference plate FP) under the wavelength of the He-Ne laser beam, and the beam is focused here in a slit shape. In the case of the TTL alignment system shown in FIG. 8, the beam spot created by the LSA method is
It is formed in a slit shape extending in the X direction at a stationary position in the projection field of view PIF. When the mark LSMy on the reference plate FP crosses the beam spot by scanning the wafer stage WST in the Y direction, the diffracted light or the scattered light generated from the mark LSMy causes the projection lens PL, the mirror 2Y, the objective lens 3Y, and The light reaches the photoelectric detector 139 via the beam splitter 135 and is received by peripheral photoelectric elements other than the central photoelectric element. The photoelectric signal from this photoelectric element is LS
The signal is input to the A processing circuit 142 and is digitally sampled in response to an up / down pulse signal UDP from the interferometer IFY 2 (or IFY 1 ) for the wafer stage WST. The processing circuit 142 stores the digitally sampled signal waveform in a memory, and performs high-speed waveform processing using digital calculation to determine the center point in the Y direction of the LSA type slit spot light and the Y of the mark LSMy from the waveform on the memory.
The Y coordinate value of wafer stage WST when the center point in the direction precisely matches is calculated and output as mark position information SSA. This information SSA is stored in the main control system 114 in FIG.
And is used for drive control of the drive system 116 of the wafer stage WST.

In the LSA processing circuit 142, a memory for digitally sampling the photoelectric signal SSD from the photoelectric sensor 121 shown in FIG. and a circuit, the projection lens PL the reticle mark RM 1
The coordinate value of the wafer stage WST when the projected image by the light emitting mark IFS matches the reticle mark RM 1
Is output to the main control system 114 as the projection position information SSC.

Next, a detailed configuration of the off-axis alignment system OWA will be described with reference to FIGS.
FIG. 10 shows the configuration of the off-axis alignment system OWA, IMP represents the surface of the wafer or the surface of the reference plate FP, and the image of the surface region located within the field of view MIF of the objective lens 4B is the prism mirror 4A and the objective lens. An image is formed on the index plate 4F via the lens 4B, the mirror 4C, the lens system 4D, and the half mirror 4E. Light for illuminating the surface IMP is transmitted through a half mirror 4E to a lens system 4D and a mirror 4D.
C, the surface I through the objective lens 4B and the prism 4A
Proceed to MP. The illumination light has a bandwidth of about 300 nm in a wavelength region where the sensitivity to the resist layer of the wafer is extremely low.

As shown in FIG. 9, the index plate 4F has index marks TMX 1 , TMX 2 , TM composed of a plurality (for example, 4) of line patterns formed by a light shielding portion on a transparent glass.
Y 1 and TMY 2 are formed. Figure 10 represents a state in which the center of the intersection and the index plate 4F the line LX and LY 1 set on the reference plate FP are matched. Index mark TM
X 1 and TMX 2 indicate the reference mark FM 1 on the reference plate FP.
The index marks TMY 1 ,
TMY 2 is provided so as to interleave the reference mark FM 1 in the Y direction.

Now, each index mark on the optotype plate 4F and the base
Quasi-mark FM1(Or the mark on the wafer)
Two via an image forming lens 4G and a half mirror 4H
Is enlarged and formed on the CCD cameras 4X and 4Y. CCD
The imaging area of the camera 4X is the area shown in FIG.
The area is set to 40X, and the imaging area of the CCD camera 4Y is
It is set in the area 40Y. And the water of CCD camera 4X
The flat scan line is the index mark TMX1, TMXTwoLine pa
The CCD camera 4Y is defined in the X direction orthogonal to the turn.
Horizontal scanning line is the index mark TMY 1, TMYTwoLine of
It is determined in the Y direction orthogonal to the pattern. CCD camera
The image signal from each of 4X and 4Y is signal level by pixel.
Digital sampling circuit, multiple horizontal scanning lines
Times to convert and average the image signal (digital value) obtained for each
Road, index mark TM and reference mark FM1X direction with Y
Waveform processing such as a circuit that calculates the amount of misalignment in each direction at high speed
The information on the amount of displacement is processed by the main control shown in FIG.
It is sent to the system 114 as information SSE.

In the case of the present embodiment, the detection center point of the off-axis alignment system OWA is, for example, the X of two index marks TMX 1 and TMX 2 in the X direction.
In the Y direction, the two index marks TMY 1 and TMY 2 are bisected in the Y direction. However, in some cases, two index marks TMX 1 , TM
Of X 2 , for example, the center of the mark TMX 2 only in the X direction may be the detection center.

[0045] Figure 11 is an enlarged view of the reference mark FM 1 which are formed on the reference plate FP, while a plurality of arranged at a constant pitch line pattern extending in the Y direction in the X direction,
It is formed as a two-dimensional pattern in which a plurality of line patterns extending in the X direction are arranged at a constant pitch in the Y direction. When the position detection in the X-direction of the reference mark FM 1, C
The image signal from the CD camera 4X is analyzed by a waveform processing circuit, and the average position of each detection position (pixel position) of a plurality of line patterns arranged in the X direction is set as the X direction position of the reference mark FM1, and the index mark TMX 1 , TMX 2 may be obtained from the center position. Reference mark F for Y direction
Detection of M 1, carried out in the same manner by the CCD camera 4Y also the detection of the positional deviation amount.

As described above with reference to FIG.
The arrangement of various marks on the reference plate FP detected by the TR alignment system and the TTL alignment system is determined in a fixed positional relationship.
This will be described with reference to FIG. FIG. 12 is an enlarged view of each mark positioned on the straight line LX. The mark LIMy is a diffraction grating in which grating elements are arranged at a constant pitch (for example, 8 μm) in the Y direction, and the mark LSMy is shown enlarged in a circle. Pitch dot pattern in X direction
This is a two-dimensional lattice pattern arranged in x and arranged in the Y direction at a pitch PSy. Mark LSMy is LS for Y direction
The beam spot is detected by a beam spot of the TTL alignment system of the A type, and the beam spot extends in a slit shape in the X direction, and the beam width in the Y direction is substantially equal to the dimension of the dot pattern in the Y direction. The pitch PSx in the X direction contributes to the generation of diffracted light at the time of mark detection, and the pitch PSy in the Y direction is for arranging a plurality of grid marks in the Y direction to form a multi-mark. Therefore, when it is not necessary to perform multi-marking, only an example of a dot pattern group arranged on the straight line LX is required.

Although the pitch PSx in the X direction is uniquely determined by the wavelength of the beam spot and the required diffraction angle of the first-order diffracted light, the pitch PSy in the Y direction is PSx
It is better if it is equal to or larger than. Now, as described in FIG. 5, marked distance K 1 between the center point of the X-direction in the X direction of the center point and the reference mark FM2A of Limy, emission mark IFS in the X direction of the center point and mark L
The distance K 2 between the center point of SMy and the X direction is K 1 = K 2
There is a relationship of ± ΔXk. This condition is such that the center of the mark detection area (irradiation area of interference fringes) of the LIA TTL alignment system in this embodiment substantially coincides with the mark detection center point (beam spot) of the LSA TTL alignment system. This is necessary for the above, and is not necessarily limited to the above conditions.

The TTL alignment system described with reference to FIG. 8 is configured in exactly the same manner for the X direction, and the position information of each mark in the X direction is sent to the main control system 114. Next, the baseline measurement and various alignment operations performed by the apparatus (stepper) of this embodiment will be described.
Before that, the correction for the mounting error of the reference plate FP to the wafer stage WST will be described. Among the mounting errors of the reference plate FP, those that affect the final accuracy are residual rotation errors in the coordinate system XY of the reference plate FP.

Conventionally, when this type of reference plate is mounted on a wafer stage, it has been proposed to fix the reference plate via a metal which can be finely adjusted with a set screw or the like (for example, Japanese Patent Application Laid-Open No. 55-55).
-135831). However, considering the change over time, the method of fixing the reference plate via the fine adjustment mechanism would be extremely disadvantageous in terms of stabilization of accuracy. For this reason, it is desirable that the reference plate FP be fixed on the wafer stage so as not to be able to move even slightly (on the order of nm).

Regardless of the fixing method, in this embodiment,
Is to determine the residual rotation error amount of the reference plate FP in advance.
I made it. The residual rotation error referred to here is, for example, as shown in FIG.
A straight line LX set on the reference plate FP, and FIG.
Means the parallelism with the reflecting surface of the movable mirror IMy. Wafer
All coordinate position management of stage WST is performed by interferometer IF
X, IFY1(Or IFY Two),
Each reflecting surface of the movable mirrors IMx and IMy is the reference for coordinate position measurement
It can be said that it is. Therefore, the reflecting surface of the movable mirror IMy
The degree of parallelism with the straight line LX on the reference plate FP becomes a problem. Also
As an attachment error, it is orthogonal to the reflecting surface of the movable mirror IMy
Between the Y direction and the X direction orthogonal to the reflecting surface of the movable mirror IMx
Regarding the parallel displacement in each direction, the wafer stage WST
Since it can be dealt with by positioning, there is almost no problem.

Now, the residual rotation error of the reference plate FP is shown in FIG.
May be obtained by self-measurement by a stepper
Alternatively, it may be obtained by trial printing using a wafer. This
Here, a method based on self-measurement will be described as an example. Figure
Of the alignment sensors of the stepper shown, Y
Direction mark detection direction and two interferometers IFY
1, IFYTwoSatisfies Abbe condition for any one of
What is needed is an off-axis wafer alignment
In this embodiment, the interferometer IFY
1With respect to the alignment system OWA in the Y direction.
The mark detection function shall be used. First, on the reference plate FP
The two reference marks FM2A and FM2D
Coordinate position is measured by off-axis alignment OWA
Measure. Therefore, as shown in FIG.
The bar mark extending in the X direction of the mark FM2D is
View of the objective lens 4B of the Axis / Alignment System OWA
The index mark TMY shown in FIG.1, T
MYTwoAnd the amount of positional deviation in the Y direction is obtained. that time,
Index mark TMY1, TMYTwoOnly one of
The bar mark extending in the X direction of the reference mark FM2D is
You may make a comment. In FIG. 13,
The moving mirror IMy and the straight line LX on the reference plate FP are rotated by θf.
It has been turned over and is exaggerated.

In any case, the index marks TMY 1 , TM
Displacement amount in the Y direction of the reference mark FM2D relative to the Y 2 is ΔYFd is detected based on the image signal from the CCD camera 4Y of FIG. The displacement amount is obtained as information SSE input to the main control system 114 in FIG. At the same time, the measured values YA1 and YA2 of the interferometers IFY 1 and IFY 2 when the reference mark FM2D is detected by the objective lens 4B are stored in the main control system 114.

Next, the wafer stage WST is moved in the X direction by a fixed amount Lfp, and the bar mark extending in the X direction of the reference mark FM2A is moved relative to the index marks TMY 1 , TMY 2 of the off-axis alignment system OWA. Position. The state at this time is shown in FIG. The certain amount Lfp at that time is determined to be equal to the design interval in the X direction between the reference marks FM2A and FM2D.

Then, similarly, the amount of deviation ΔYFa of the reference mark FM2A in the Y direction and the measured values YB 1 and YB 2 of the interferometers IFY 1 and IFY 2 are obtained. The measurement operation is completed by the above operation, and thereafter, the residual rotation error θf is obtained by calculation. First, the wafer stage WST is moved by a certain amount L in the X direction.
Assuming that yawing does not occur when moving by fp, the rotation error θf ′ can be approximately obtained by the following equation.

Θf ′ = (YA 1 −ΔYFd) − (YB 1 −ΔYFa) / Lfp = (YA 1 −YB 1 ) + (ΔYFa−ΔYFd) / Lfp (1) However, when yawing has occurred Is a minute rotation error Δ of wafer stage WST due to the yawing.
θy is included in equation (1). Therefore, the true residual rotation error θf is given by the following equation.

Θf = θf′−Δθy (2) The rotation error Δθy due to yawing is obtained by Δθy ≒ (YA 1 −YA 2 ) / LB− (YB 1 −YB 2 ) / LB (3) Here, LB is two interferometers IFY 1 , I
FY is an X-direction distance of each measurement axes of two.

Therefore, assuming that the same measurement is performed using the reference mark FM2C instead of the reference mark FM2D, the design distance in the X direction between the reference marks FM2A and FM2C is the distance LB in the X direction between the interferometers IFY 1 and IFY 2. Therefore, the movement of the fixed amount Lfp of the wafer stage WST also becomes Lfp = LB. Therefore, the reference mark FM2
When using A and FM2C (or FM2B and FM2D), equation (3) becomes as follows.

Δθy ≒ (YA 1 −YB 1 ) + (YB 2 −YA 2 ) / Lfp (4) Thus, from the equations (1), (2) and (4), the residual rotation error θf is θf ≒ θf′−Δθy = (ΔYFa−ΔYFd) − (YB 2 −YA 2 ) / Lfp (5)

That is, two reference marks used for measurement
When the interval in the X direction is two interferometers IFY1, IFYTwoX
When the distance in the direction is equal, the interferometer I considered as a reference
FY 1Measurement value (YA1, YB1) Without monitoring
Will also be good. As described above, the reference plate FP is moved.
The residual rotation error θf with respect to the moving mirror IMy is obtained.
Then, this value is stored in the main control system 114. The reference plate F
There are four reference marks along the straight line LX on P
The remaining rotation using any two of the reference marks
An error may be obtained and its average value may be taken. example
The rotation obtained by the reference marks FM2A and FM2C
Error θf1And reference marks FM2B and FM2D
Rotation error θfTwoAnd the average value (θf1+ Θf
 Two) / 2 is the residual rotation error of the reference plate FP. Further
On the straight line LX, marks LIMy, LSMy, IF
S, FM1Is provided, so any of these
One or two detected by off-axis alignment OWA
Then, the mark position measurement in the Y direction may be performed. In any
However, the distance between the two marks to be measured in the X direction is
It is desirable that the size be as large as possible to secure the degree.

The method of measuring the residual rotation error by the self-measurement described above is an example, and other methods by the self-measurement can be considered. This will be described in a later operation sequence. Further, the above-described measurement method is for obtaining θf. However, since θf is detected as an offset during wafer alignment by the off-axis alignment system OWA, a method for obtaining θf by examining a vernier after exposure may be considered. That is,
By performing overlay exposure on the test wafer using the off-axis alignment system OWA and reading the vernier in the X and Y directions of the developed resist pattern for checking the overlay accuracy, the residual mounting error θ
f can be obtained.

Next, the operation of the baseline measurement by the apparatus of this embodiment will be described. The operation described here is typical, and some modified operations will be described later. FIGS. 14 and 15 are flowcharts for explaining a typical sequence. The sequence is mainly controlled by the main control system 114.

First, the reticle R stored in the case of predetermined storage is automatically or manually conveyed and loaded on the reticle stage RST depending only on mechanical positioning accuracy and delivery accuracy (step 500). In this case, loading accuracy of reticle R, double slit mark RM 1 x and the size of the window region of the reticle mark shown in FIG. 6 (inner light-shielding band SB) of about 5mm square, R
Assuming that the length of M 2 y is about 4 mm, it is desirable that the length be ± 2 mm or less.

Next, the main control system 114 performs preliminary rough alignment of the position of the reticle R so that the marks RM 1 and RM 2 of the reticle R are normally detected by the TTL alignment systems 1A and 1B. Perform reticle search. In this reticle search, step 5 in FIG.
04, 506, the SRA system and the IFS system
In step 502, which mode is selected. The pre-alignment by the IFS method in step 504 means that the reticle stage R
While the position of ST is fixed, the wafer stage WST is moved in the X and Y directions by a large stroke (for example, several mm) so that the emission mark IFS searches for a position where the reticle mark RM 1 or RM 2 is likely to exist. The positions of the reticle marks RM 1 , RM 2 using the interferometers IFX, IF
This is a method in which the reticle stage RST is finely moved on the basis of a rough detection based on Y 2 , a deviation amount of the detected position from a designed position is obtained, and the reticle stage RST is relied on interferometers IRX, IRY, and IRθ for the reticle stage RST. .

On the other hand, the pre-alignment by the SRA method in step 506 is executed as follows.
The plain surface of the reference plate FP is placed immediately below the position where the reticle marks RM 1 and RM 2 are likely to exist, and the TTR is
Using the alignment systems 1A and 1B, the CCD camera 11
The pattern on the reticle R is imaged by 2X and 112Y (FIG. 7), and the image signal waveform corresponding to the horizontal scanning line in one screen is taken into the memory. Next, the reticle stage RST is moved by a fixed amount in the X or Y direction by the drive system 115 based on the measured values of the interferometers IRX, IRY, and IRθ, and then the image signal waveform of the second screen is captured from the CCD camera. 1. Connect with the signal waveform of the first screen. After that, the connected image signal waveforms are analyzed, then the respective positions of the reticle marks RM 1 and RM 2 are obtained, the amount of deviation from the designed position is obtained, and then the position of the reticle stage RST is moved.

In any of the search modes, the reticle
Mark RM of Le R1, RMTwoEach center of the two TTR
CCD cameras provided for each of alignment systems 1A and 1B
A few μm at the center of the camera 112X, 112Y in the imaging area
Pre-alignment can be performed with accuracy of degree. Next, the main control system 11
4 is the reticle alignment operation from step 508
Before entering, two reference marks FM2A, FM2
2B are designed in the field of view PIF of the projection lens PL.
Drive system 116 is set to interferometer IFX, IFY Two
(Or IFY1) Is controlled according to the measured value of
Position WST. Wafer stage WST
Once positioned, fiducial marks FM2A, (FM2B)
Reticle mark RM1(RMTwo) And roughly aligned
In this state, images are taken by the CCD cameras 112X and 112Y.
At this stage, the processing circuits 113X and 113Y in FIG. 7 are operated.
Then, the reticle mark R with respect to the reference mark FM2A
M1In the X and Y directions (ΔXR1, ΔYR1)
And reticle mark RM for reference mark FM2BTwo
In the X and Y directions (ΔXRTwo, ΔYRTwo) And
measure.

Next, at step 510, each displacement amount is allowed.
It is judged whether it is within the tolerance or not.
If yes, go to step 512. At this time, two reticks
Lemark RM1, RMTwoAs apparent from the shape and arrangement of
The alignment of the reticle R in the X direction is
Each reticle mer for each center point of FM2A and FM2B
KRM1, RMTwoOf each center point of the reticle center CC
When it is displaced toward normal, when it is displaced in the opposite direction
If it is negative, the amount of deviation ΔXR in the X direction1And ΔXR TwoPolarity
And the absolute value are made equal.

Similarly, the reticle R in the Y direction and the θ direction
The remarks are for each reticle mark RM1, RMTwoCenter of
Positive when the point is shifted in the positive direction of the Y axis of the stationary coordinate system
And the deviation amount ΔYR in the Y direction1And ΔYRTwoPolarity and absolute value
This is achieved by making Θ direction of reticle R
(Rotational direction) deviation amount ΔθR is equal to the reticle mark R
M 1, RMTwoLet Lrm be the interval in the X direction of
Deviation ΔYR1, ΔYRTwo(Actual size on reticle)
It is obtained by the following equation.

ΔθR = sin −1 ((ΔYR 1 −ΔYR 2 ) / Lrm) ≒ (ΔYR 1 −ΔYR 2 ) / Lrm (6) However, since the distance Lrm is constant for any reticle, the distance Lrm is constant in the θ direction. Evaluation of the displacement amount of the reticle R is simply Δ
It is only necessary to determine the magnitude of the absolute value of YR 1 −ΔYR 2 .
From the above, when the deviation amount of the reticle R in the X, Y, and θ directions is larger than the allowable value, the reticle stage RST is finely moved in step 512. At this time, X direction, Y
Reticle stage RS
The amount of deviation (ΔXR 1 , ΔYR
1 ) and (ΔXR 2 , ΔYR 2 ), the position of the reticle stage RST is determined by three interferometers IR.
While monitoring with X, IRY, and IRθ, finely move to the position to be corrected. This driving method is called a so-called open control method. If the control accuracy of the drive system 115 and the positioning accuracy of the reticle stage RST are sufficiently high and stable, one displacement measurement (step 508) and one The reticle R can be accurately aligned with the target position only by performing the position correction (step 512). However, since it is necessary to confirm whether or not the target position is correctly aligned by the position correction, the main control system 114
Repeats the operation from step 508 again.

By the above steps 508 to 510,
Reticle R has two reference marks FM2 on reference plate FP.
A, alignment with respect to the designed coordinate position of FM2B. Now, the reticle R is thus aligned with the reference marks FM2A and FM2B, but the reference plate FP has a constant residual rotation error θf with respect to the reflecting surface of the movable mirror as described above with reference to FIG. Therefore, the reticle R after the alignment is strictly rotated by θf with respect to the reflecting surface of the movable mirror.

Therefore, at step 512, the reticle stage
When finely moving RST, reticle mark RM1The standard of
In addition, the alignment position with respect to the
Ox 1, ΔOy1) With offset
Kulmark RMTwoAlignment with reference mark FM2B
The position of theTwo, ΔOyTwo) Offset
Set to have Where the offset Δ in the X direction
Ox1, ΔOxTwoMay be zero, and the offset in the Y direction
G ΔOy1, ΔOyTwoIs defined as follows.

ΔOy 1 = Lrm · θf / 2 ΔOy 2 = −Lrm · θf / 2 Therefore, when aligning the reticle R with the reference plate FP as a reference, the final condition in consideration of the mounting error (θf) of the reference plate FP is as follows. , The amount of displacement when each mark is detected by the TTR alignment system is as follows.

X direction: ΔXR 1 = ΔXR 2 → 0 Y direction: ΔYR 1 → ΔORy 1 , ΔYR 2 → ΔORy 2 The final alignment position with these offsets is set by the interferometers IRX, IRY for the reticle. An open control method using IRθ may be used, or a position shift amount obtained from each of the processing circuits 113X and 113Y of the TTR alignment system may be used as a deviation signal, and the reticle stage RST may be closed-loop controlled using the final position shift amount as a target value. May be driven.

Incidentally, the residual rotation error θf of the reference plate FP
In addition to the method described with reference to FIG. 13, there is a method using reticle marks RM 1 and RM 2 and a TTR alignment system. Before the step 508 in the flow chart of FIG. 14, the reticle marks RM 1 and RM 2 and the reference marks FM2C and FM2D are used in the TTR method.
Can be performed by adding a step of aligning

That is, when the pre-alignment of the reticle R is completed in step 504 or 506, the reticle R is set with an accuracy within ± several μm, so that the reticle marks RM 1 and RM 2 are used as temporary reference points. , The coordinate positions of the reference marks FM2C and FM2D are measured. At this time, since the reticle marks RM 1 and RM 2 are located substantially symmetrically with respect to the X direction from the optical axis AX of the projection lens PL, the Y of the reticle mark RM 1 detected by the TTR alignment system 1A and the reference mark FM2C
Direction deviation amount ΔY2C and TTL alignment system 1
They are respectively the Y-direction position deviation amount ΔY2D the reticle mark RM 2 and the reference mark FM2D are detectable by B, strictly includes Abbe error. However, the averaging value ΔYRC [(ΔY2C +
[ΔY2D) / 2], the Abbe error is canceled by the averaging. Therefore, stored TTR alignment system 1A, displacement in 1B amount Derutawai2C, the measured value Yfm 1 interferometer IFY 2 when detects the Derutawai2D, be determined a value of YF 1 = Yfm 1 -ΔYRC, the reticle R Y coordinate value YF 1 of the center point of the reference marks FM1 relative to the center point (X direction midpoint of the reference mark FM2C and FM2D) is obtained.

With respect to the X direction, based on the deviation ΔX2C detected by the TTR alignment system 1A and the deviation ΔX2D detected by the TTR alignment system 1B, the direction (positive or negative) of the deviation is considered. What is necessary is just to obtain the amount of deviation ΔXRC [(ΔX2C−ΔX2D) / 2] in the X direction between the center point of the reticle R and the center point of the reference mark FM1. At this time, the X coordinate position of wafer stage WST is detected as Yfm 1 by interferometer IFX, and XF
By calculating 1 = Yfm 1 −ΔXRC, X of the center point of the reference mark FM1 with respect to the center point of the reticle R is calculated.
Coordinates XF 1 is obtained.

The coordinate values (XF
1 , XF 2 ) is a reference mark FM1 from each reflection surface of the movable mirrors IMy, IMx based on the interferometers IFX 2 , IFX.
Is a value that includes the distance to the center point. Next, wafer stage WST is moved to step 508 in FIG.
Execute As described above, in step 508,
First, reticle marks RM 1 , RM 2 and reference marks FM 2 A , FM 2 B are provided by TTR alignment systems 1 A, 1 B.
Are determined. Reticle mark R
Positional displacement amount of the reference mark FM2A for M 1 is ([Delta] X
R 1 , ΔYR 1 ), and the amount of displacement of the reference mark FM2B with respect to the reticle mark RM 2 is (ΔXR 2 , ΔY
R 2 ). At this time, although the reference marks FM2A and FM2B are not necessary in step 508 in FIG.
The coordinate values (Xfm 2 , Yfm 2 ) of the wafer stage WST detected by the R alignment system are calculated using the interferometers IFX, IFX.
And stores from FY 2.

From the above measurement results, the main control system 114 determines that the coordinate values (XF 2 , YF 2 ) of the center point of the reference mark FM2 (the midpoint in the X direction between the marks FM2A and FM2B) with respect to the center point of the reticle R. ) Is determined as follows. XF 2 = Xfm 2 − (ΔXR 1 −ΔXR 2 ) / 2 YF 2 = Yfm 2 − (ΔYR 1 −ΔYR 2 ) / 2 These coordinate values (XF 2 , YF 2 ) are interferometers IFY 2 , IF
From each reflecting surface of the moving mirrors IMy and IMx based on X,
The value includes the distance to the center point of the reference mark FM2.

Therefore, the wafer stage WST is moved from the detected position of the reference marks FM2C and FM2D to the reference mark FM2.
A, the mounting error θf ′ of the reference plate FP including the yawing amount Δθy when moved to the detection position of the FM2B is:
It is calculated by the following equation. θf ′ ≒ YF 1 −YF 2 / XF 1 −XF 2 (7) In this case, the measured value of IFY 1 of the two interferometers and the interferometer I
Since the variation of the difference between the measured value of the FY 2 corresponds to yawing amount [Delta] [theta] y, determined true mounting error θf by correcting as in the previous equation (2).

While the above operations are being performed, the main control system 114 executes the following steps 510 and 512.
That is, as described above, obtaining the mounting error θf of the reference plate FP in the sequence of FIG. 14 is based on the positional deviation amounts (ΔXR 1 , ΔY
R 1 ) and (ΔXR 2 , ΔYR 2 ) are only required. Next, main control system 114 executes the operation from step 516 shown in FIG. Step 516 sets the position of the reference plate FP to the interferometers IFX and IFY for the wafer stage WST.
2 (or IFY 1 ) to select whether to perform servo lock or to perform servo lock using the TTL alignment system LIA method. If the servo lock using the interferometer has been selected, the process proceeds to step 518, where the coordinate values of the wafer stage WST at the time when the reticle alignment is achieved are stored, and the interferometers IFX, IFX
Driving system 116 of wafer stage WST so that the measured value of FY 2 (or IFY 1 ) always matches the stored value.
Servo control. If the LIA servo lock has been selected, the process proceeds to step 520, where the shutters 132A and 132B shown in FIG.
Each of the marks LIMx and LIMy on the reference plate FP is irradiated with interference fringes. Then, the wafer stage WST is servo-controlled by the phase difference measurement circuit 140 such that the phase difference between the reference signal and the reference signal always becomes a predetermined value in each of the X direction and the Y direction. In the case of the LIA method, the two marks LIMx and LIMy on the reference plate FP are aligned with the reference grating plate 138 fixed inside the TTL alignment system.

The servo lock of wafer stage WST is
Interferometer IFX, IFYTwo(Or IFY1)
Mode based on TTL alignment system
LIA mode is possible with almost the same accuracy.
And simulations show that LIA mode interferes better
It is confirmed that it is more stable than the meter mode. one
Generally, moving straws in the X and Y directions of wafer stage WST
The diameter is larger than the diameter of the wafer, for example, 30 cm or more
Is necessary. Therefore, interferometers IFX, IFY Twofrom
The optical path length of the laser beam exposed to the atmosphere is several + cm or less
Local refractive index fluctuations in the air above and above
When the wafer stage WST is strictly stationary
Regardless, the counter value inside the interferometer is 1 / 100μ
It varies on the order of m to 1/10 μm. Therefore the interferometer
Servo lock so that the count value is constant
The position of the wafer stage WST is
For example, fine movement may occur within the range of ± 0.08 μm.
You. Fluctuations in the refractive index are caused by the light of the laser beam from the interferometer.
A lump of air with a temperature difference slowly passes through the road.
It occurs when it happens. This type of interferometer for wafer stage
Environmental disadvantages, more stable than LIA
Sometimes lacks gender. The beam used in the LIA method is
Covers should be barely exposed to the atmosphere
Can be provided, further exposure of the beam is not avoided
The space between the reticle and the projection lens, and the projection lens and the wafer
The space with c is only a few cm at most, so the refractive index
Fluctuation is unlikely to occur.

As described above, when the position servo of the reference plate FB (wafer stage WST) can be performed using the TTL alignment system while the reference marks FM2A and FM2B are being detected by the TTR alignment system, It is preferable to do so. Next, the main control system 114
Performs reference mark detection using the TTR alignment system and the off-axis alignment system simultaneously in step 522. In general, when the reticle stage RST is finely moved to the target position in the previous step 510 and the alignment is achieved, the reticle stage RST is fixed by vacuum suction or the like on the column side serving as the base. During this suction, the reticle stage RST may be laterally shifted by a small amount. Although this lateral displacement is minute, it is one of the error factors in the baseline management and needs to be sufficiently recognized. The recognition is based on the CC of the TTR alignment system.
Step 5 is performed again using the D cameras 112X and 112Y.
08 measurement operation or interferometer IRX, I
For example, it is possible to monitor the amount of change in the measured values of RY and IRθ from the time when the reticle alignment is achieved. However, in this embodiment, since the lateral shift is managed as the baseline amount, it is not necessary to individually determine only the lateral shift amount.

By the way, at the stage of step 522, already
Off-axis alignment system within the detection area of OWA
The reference mark FM1 on the reference plate FP is located. There
In the main control system 114, the off-axis control shown in FIG.
Target using CCD camera 4X, 4Y of alignment system
X between the target mark TM and the reference mark FM1 in the plate 4F,
The amount of displacement in the Y direction (ΔXF, ΔYF) is
Calculate as dimensions. At the same time, TTR alignment CCD
Reticle mark R using cameras 112X and 112Y
M1Between the reference mark FM2A and the reference mark FM2A (ΔXR1,
ΔYR1) And reticle mark RMTwoAnd fiducial mark FM
2B (ΔXR Two, ΔYRTwo) And the wafer
Measure as the actual size of the side. At this time, the TTR method is also off.
・ Each Axis system uses a CCD camera as a photoelectric sensor
Image signal corresponding to the captured mark image
Import waveforms into memory Match timing as closely as possible
Thus, the processing circuits 113X and 113Y are controlled. Was
However, a CCD camera generally generates an image signal for one frame.
Since it is output every 1/30 second, the TTR method and the
Strict capture of image signals with the cis system in frame units
There is no need to synchronize. That is, the signals are almost simultaneously
You only need to capture it, for example, within a few seconds (preferably
Or less than one second). The reference plate FP
If the position is servo-locked by the interferometer, TTR
Signal waveform capture and off-axis method
The capture of the image signal waveform at
More than the time required to change the wafer stage position due to
Short intervals are required.

Next, main control system 114 releases the servo lock of wafer stage WST in step 524 and shifts to the operation of step 526, and detects each mark on reference plate FP by simultaneously using the LSA method and the IFS method. Therefore, movement (scanning) of wafer stage WST is started. The step 526 above 6, as described with reference to FIG. 5, in which light emission slit mark IFS moves the wafer stage WST to scan the reticle mark RM 1 in a two-dimensional, the wafer stage WST, first The light emitting slit mark IFS is positioned so as to have the positional relationship shown in FIG. At this time, the slit-shaped beam spot extending in the X direction by the LSA method of the TTL alignment system is shifted in the Y direction with respect to the mark LSMy on the reference plate FP. When the wafer stage WST is scanned in the Y direction from that state, the photoelectric signal from the LSA type photoelectric detector 139 and the photoelectric signal SS from the IFS type photoelectric element 121 are read.
Both waveforms with D are as shown in FIG. FIG.
(A) is a detection waveform of the mark LSMy captured on the memory by the LSA method.
Since My has five diffraction grating patterns, five peaks occur on the signal waveform. The processing circuit 142 shown in FIG. 8 obtains the position of the center of gravity of each of the five peak waveforms, and calculates the average value as the Y coordinate position YLs of the mark LSMy.

On the other hand, the signal SSD obtained by the IFS method
Is the reticle mark RM 1 as shown in FIG.
Include two bottom waveform portions for the double slit mark RM 1 y. The processing circuit 142 obtains the center point of each of the two bottom waveforms in the signal waveform of FIG. 16B, and calculates the center point as the center coordinate position YIf in the Y direction of the projected image of the double slit mark RM 1 y. .

Similarly, the light emitting slit mark IFS is moved as indicated by the arrow in the X direction in FIG. 6 to scan the double slit mark RM 1 x of the reticle mark RM 1 . At this time, the slit-shaped spot by the LSA method of the TTL alignment system for the X direction is formed by the mark LS on the reference plate FP.
Scanning is performed simultaneously by Mx, and a waveform similar to that in FIG. 16 is obtained. At this time, the X coordinate value of the mark LSMx detected by the LSA method for the X direction is XLs, and LFS
Double slit mark RM 1 x detected by the method
Is XIf.

As shown in FIG. 16, the coordinate positions TLs and X
The difference from If is the base line amount in the Y direction between the detection center point of the TTL alignment system by the LSA method for the Y direction and the projection point of the center CC of the reticle R. Next, the main control system 1
14 performs an operation for obtaining a baseline amount in step 528. The parameters required for this calculation are shown in FIG.
As shown in the table in FIG. 7, the measured values are divided into measured values and constant values predetermined in design. In the measured values in the table of FIG. 17, “TTR-A” indicates the TTR alignment system 1A in FIG. 2, and “TTR-B” indicates the TTR alignment system 1B. In addition, the measured values obtained by the respective alignment systems are displayed with the amount of displacement or the mark position in the X direction and the Y direction separately. On the other hand, the constant value in the design includes the center point of the reference mark FM1 and the reference mark FM1.
Each distance (ΔXfa, ΔYfa) in the X and Y directions with respect to 2A, X and Y between the center point of the reference mark FM1 and the reference mark FM2B.
Each distance in the direction (ΔXfb, ΔYfb) is precisely measured and stored in advance with reference to the straight line LX.

The main control system 114 has constant values ΔXfa, ΔXfa
, The X-direction distance LF between the bisecting point of the line connecting the center points of the reference marks FM2A and FM2B and the center point of the reference mark FM1 is calculated. LF = (ΔXfa, ΔXfb) / 2 ... (8) The main control system 114, X-direction displacement amount ΔX calculated in X direction displacement amount? XR 1 and TTR-B obtained in TTR-A
One half of the difference ΔXcc from R 2 is obtained as the dimension on the wafer side.

ΔXcc = (ΔXR 1 −ΔXR 2 ) / 2 (9) where ΔXR 1 and ΔXR 2 are reticle marks RM 1 and R
M 2 is the reference mark FM2A, when you are displaced in the direction of the reticle center for each of FM2B positive, it is shifted in the opposite direction is assumed to have a negative value. When the value ΔXcc obtained by the equation (2) is zero, the projected point of the center CC of the reticle R exactly matches the bisecting point in the X direction of each of the center points of the two reference marks FM2A and FM2B. Will be.

Next, the main control system 114 determines the center CC of the reticle R based on the measured value ΔXF and the calculated values LF and ΔXcc.
Of the projection point of the XY coordinate plane, in XY coordinate plane in the X direction of the center point of the index plate 4F of the off-axis alignment system OWA (2 bisector point between the index marks TMX 1 and TMX 2) The distance BLOx in the X direction from the projection point is calculated as an X-direction base line amount related to the off-axis alignment system OWA. BLOx = LF−ΔXcc−ΔXF (10) where ΔXF is a distance between the reference mark FM1 and the projection lens P with respect to the bisecting point of the index marks TMX 1 and TMX 2 in the X direction.
It is assumed that a positive value is detected when the light is detected in the direction of L (reference marks FM2A, FM2B), and a negative value is detected when the light is detected in the reverse direction.

Next, the main control system 114 determines a line segment connecting the projection point of the center point CC of the reticle R, the center point of the reference mark FM2A, and the center point of FM2B based on the measured values ΔYR 1 and ΔYR 2 . bisector point seek Y direction deviation amount ΔYcc with (approximately linear LY is on 2). ΔYcc = (ΔYR 1 −ΔYR 2 ) / 2 (11) where ΔYR 1 and ΔYR 2 are reticle marks R
M 1, the reference mark FM2A that each of RM 2 is a corresponding, F
With respect to M2B, the value is positive when shifted in the positive Y direction (upward in the plane of FIG. 4) in FIG. 4, and negative when shifted in the reverse direction. The shift amount Ycc is determined by comparing the projected point of the center CC of the reticle R with the reference marks FM2A and FM2.
It becomes zero when the bisector of the line connecting the center points of 2B exactly matches.

The main control system 114 further includes a constant value ΔYfa,
Based on DerutaYfb, reference marks FM2A, obtains the Y-direction displacement amount DerutaYf 2 between the center point of the bisector point and the reference mark FM1 of the line segment connecting the center points of FM2B. ΔYf 2 = (ΔYfa-ΔYfb) / 2 ... (12) or more calculated values DerutaYcc, based on the DerutaYf 2 and Found DerutaYF, the main control system 114 includes a projection point of the center CC of the reticle R, the off-axis alignment system OWA index plate 4F in the Y direction of the center point of the (index marks TMX 1 and TMX 2
Distance in the Y direction from the projection point of (a bisecting point between the two points)
Is calculated as the Y-direction baseline amount of the off-axis alignment system OWA.

BLOy = ΔYcc−ΔYf 2 −ΔYF (13) By the above calculation, the off-axis alignment system O
The baseline amount (BLOx, BLOy) of the WA is determined, and then the main control system 114 determines the baseline amount (BLTx, BLTy) of the TTL alignment system of the LSA system. The baseline amount BLTy of the LSA TTL alignment system for the Y direction is a shift amount in the Y direction between the center point of the slit beam spot in the Y direction, the center point of the reticle R, and the projection point of the center CC of the reticle R. Yes, and is determined by the following equation:

BLTy = YIf−YLs (14) Similarly, the base line amount BLTx of the LSA TTL alignment system for the X direction is the center point of the slit beam spot in the X direction and the center CC of the reticle R. And the amount of deviation in the X direction from the projection point, and is obtained by the following equation. BLTx = YIf−YLs (15) However, the values obtained by Expressions (14) and (15) include an arrangement error ΔYsm in the Y direction between the center of the light emitting mark IFS and the mark LSMy on the reference plate FP, and light emission. Since the placement error ΔXsm in the X direction between the mark IFS and the mark LSMx is included, if these errors cannot be ignored, they are stored in advance as constant values, and the equations (14) and (15) are respectively expressed by the equations (14) and (15). What is necessary is just to change it like (14 ') and (15').

BLTy = YIf−YLs−ΔYsm (14 ′) BLTx = XIf−XLs−ΔXsm (15 ′) By the above sequence, the baseline measurement is completed and the pre-aligned wafer is placed on wafer stage WST. W is placed. A plurality of exposure areas, that is, shot areas on which the pattern area PA of the reticle R is projected are two-dimensionally arranged on the wafer W. Each shot area has an off-axis alignment system OW
A or TTL alignment system (2X, 3X; 2Y, 3
The alignment mark detected by Y) is formed in a fixed relation to the center point of the shot area.
In many cases, the alignment marks on those wafers are provided in the street lines. Since various methods or sequences are conventionally known as actual wafer alignment methods, descriptions of these methods and sequences are omitted here, and only basic wafer alignment will be described.

FIG. 18 shows the arrangement of shot areas and marks on the wafer W. The distance between the center SCn of the shot area SAn and the mark WMx in the X direction in the X direction is ΔXwm, and the center SCn and the Y mark in the Y direction are shown. The width between Y and WMy in the Y direction is determined by design as ΔYwm. First, when the off-axis alignment system OWA is used, the mark WMx of an arbitrary shot area SAn is set to the index mark TMX 1 , within the detection area of the off-axis alignment system OWA.
Positioning the wafer stage WST as sandwiched in TMX 2. Here, it is assumed that the marks WMx and WMy are multi-line patterns similarly to the reference mark FM1.

Then, main control system 114 reads coordinate position Xm of wafer stage WST in the X direction positioned from interferometer IFX. Further, an image signal from the CCD camera 4X in the off-axis alignment system OWA is processed to detect a deviation amount ΔXp in the X direction between the center point of the index plate 4F and the center point of the mark WMx. Next, wafer stage WST is moved so that wafer mark WMy is sandwiched between index marks TMX 1 and TMX 2 of the off-axis alignment system.
Position. Reading the coordinate position Ym of Y direction at this time from the interferometer IF 1. Then, the amount of displacement ΔYp in the Y direction between the center point of the index plate 4F and the center point of the mark WMy is obtained by imaging with the CCD camera 4Y.

After the above-described mark position detection is completed, the coordinate position of the wafer stage WST for aligning the center SCn of the shot area SAn with the projection point of the center CC of the reticle R during exposure is calculated only by the following equation. Xe, Y
e) is required. Xe = Xm-.DELTA.Xp + (BLOx-.DELTA.Xwm) (16) Ye = Ym-.DELTA.Yp + (BLOy-.DELTA.Ywm) (17) The mark WM in the TTL alignment system of the LSA method.
When detecting x and WMy, the mark W by the LSA method is used.
With the respective detection positions of Mx and WMy being Xm and Ym, the stage coordinate position at the time of exposure is obtained by the following equation.

Xe = Xm + BLTx−ΔXwm (18) Ye = Ym + BLTy−ΔYwm (19) In the above description, the off-axis alignment system OWA
Even at the detection center point in the stationary coordinate system, the interferometers IFX, I
Since both the measured value of FY 1 is are set to be orthogonal, the two-dimensional mark position detection using the off-axis alignment system OWA, 2 two interferometers IFX, With a measurement of IFY 1, mark Coordinate of wafer stage WST at detection, position Xm, Ym, and deviation amount ΔX of mark position
p and ΔYp do not include Abbe error.

Therefore, the off-axis alignment system
When detecting a wafer mark or fiducial mark using OWA
The interference that satisfies the Abbe condition with the projection lens PL
Total IFYTwoBut not alignment system OWA.
Interferometer IFY that satisfies the Abbe condition 1It is important to use
You. However, the Abbe condition for the projection lens PL
Interferometer IFX, IFYTwoAnd off-axis
Interferometer I that satisfies Abbe conditions for liment type OWA
FX, IFY1To switch and use as is,
Interferometer IFX for two Y directions1, IFYTwoEach internal power
Reset (or preset) the counter to a specific state
Must be done with In conclusion, the projection lens P
At the same time as detecting the fiducial mark FM2 via L,
Reference Axis via Axis Alignment System OWA
When FM1 is detected and baseline measurement is performed.
Two interferometer IFs at the stop position of the stage WST
Y1, IFYTwoValue of each internal counter
Preset equal to the value. Therefore, the earlier mentioned
In the sequence of FIGS. 14 and 15, two interferometers
IFY1, IFYTwoThat the preset operation of
This is caused by the mounting error θf of the reference plate FP described above.
It is necessary to perform a calculation for correcting the calculated baseline amount. Then
A specific example will be described below.

First, steps 508 and 51 in FIG.
Reticle alignment is performed by 0 and 512. At this time, in consideration of the mounting error θf of the reference plate FP, as described above, the X of the reticle marks RM 1 , RM 2
Direction alignment position is a ΔXR 1 = ΔXR 2, and set to be forced to zero, Y direction alignment position within ΔYR 1 → ΔOy 1, ΔYR 2 → ΔO
Set to be driven by y 2 respectively. That is, the reticle R is aligned so that a line connecting the two reticle marks RM 1 and RM 2 is parallel to the reflection surface of the movable mirror IMy.

Thereafter, the measurement of the baseline error is started. After the reticle alignment is achieved, the servo lock operates so that the wafer stage WST does not move. Considering the servo locked state, at that time, the interferometer I that satisfies the Abbe condition with respect to the projection lens
The measured value Le of FY 2, between the measured value Lf of the interferometer IFY 1 satisfying the Abbe condition for off-axis alignment system, the error of the Ly (Δθa + Δθr) is present. Where Ly is the two interferometers IFY 1 , IFY 2
Is the interval in the X direction of each measurement axis, and the rotation error Δθa is
Ideal position (ideal X) of the reflecting surface of movable mirror KMy generated at the position of wafer stage WST during baseline measurement
Axis). The rotation error Δθr
Is the ideal position (X-axis) of the reflecting surface of movable mirror IMy generated when wafer stage WST comes to the predetermined origin position
This is a small rotation error from. These errors Δθa, Δθ
r cannot be measured directly by itself, but usually, when the wafer stage WST comes to the home position, the interferometers IFY 1 , IFY 1
By simultaneously keep reset (or preset) an internal counter of Y 2, it can be measured as a change from the reset position of the combined value of Δθa and Derutashitaaru. That is, the change of Δθa + Δθr can be measured as the yaw amount with reference to the reset position.

[0102] Thus, the state being monitored, or controls the position of wafer stage WST in the interferometer IFY 2 satisfying the Abbe condition with respect to the projection lens, the measurement value Lf of the other interferometer IFY 1 course Lf-
Le = Ly becomes what is included an error of (Δθa + Δθr), can not be incorporated into the baseline amount measured directly as the true value measurements Lf of the interferometer IFY 1.
Or not can also be transferred under the control of it interferometer IFY 1 the control of wafer stage WST.

Therefore, when measuring the baseline, the reference plate FP
And the measured value Lf of the interferometer IFY 1 when the wafer stage WST is servo-locked and the interferometer IFY
The difference from the measured value Le of 2 is ΔLyw [Ly (Δθa + Δθ
After storing as r)], it changes the internal counter of the interferometer IFY 1 from the measured value Lf to measure Le (preset). By doing so, in the subsequent control, the interferometer IFY 2 used for positioning the wafer stage WST during exposure
The control based on, be switched to a control based on the interferometer IFY 1 to be used at the off-axis alignment, not any trouble occurs.

The state at this time is exaggeratedly shown in FIG.
In FIG. 19, two reference marks FM2A and FM2B
LX is rotated by an error θf with respect to a line Lrc parallel to the reflection surface of the movable mirror IMy. When the reticle R is aligned, the reticle mark RM 1 the reference mark F
DerutaOy 1 only located offset relative to M2A, the reticle mark RM 2 is ΔO the reference mark FM2B
To position offset by y 2, after all, the line segment connecting the reticle mark RM 1, RM 2 is parallel to a line Lrc. In FIG. 19, since line Lrc is set to pass through reticle center CC, reticle marks RM 1 , RM 2 and center CC are located on line Lrc.

Now, in this state, two interferometers IFY 1 ,
IFY 2 is preset to the same count value Le, but as shown in FIG. 19, the reference of the two interferometers IFY 1 and IFY 2 after the preset changes to the reference line Lir ′. In FIG. 19, a line Lir represents, for example, the interferometers IFY 1 and IFY 1 when the wafer stage WST comes to the origin position.
The reference is shown with 2 preset to the same value. That is, it can be considered that the interferometers IFY 1 and IFY 2 measure the distance from these virtual reference lines Lir or Lir ′ to the movable mirror IMy. Therefore, immediately after the preset, the reference line Lir ', the reflecting surface of the movable mirror IMy, and the line Lrc
Are parallel to each other. Incidentally, when the yawing of the wafer stage WST is obtained from the difference between the measured values of the two interferometers IFY 1 and IFY 2 after the presetting, the reference of the yawing amount has been changed to the line Lir ′ in FIG. That is, a line parallel to the reflection surface of the movable mirror IMy when the reference plate FP is positioned immediately below the projection lens PL and the off-axis alignment system during baseline measurement,
It becomes the reference for subsequent yawing amount measurement.

Further, in the baseline measurement, the amount of displacement (ΔXF, ΔYF) between the reference mark FM1 and the index mark TM is obtained by the off-axis alignment system as shown in FIG. In FIG. 19, Of is a detection center point defined by the index mark TM of the off-axis alignment system. Here, the true baseline amount is determined by the positional relationship between the center point CC of the reticle R and the detection center point Of. If the mounting error θf of the reference plate FP is extremely small, the baseline amount in the X direction is Figure 17 of
FaXfa (the distance between FM1 and FM2A) and the constant value XXfb (the distance between FM1 and FM2B), the amount of deviation of the center point CC in the X direction during reticle alignment, and the amount of deviation detected by the off-axis alignment system shown in FIG. It is determined by ΔXF.

That is, two reference marks FM2A, F
Assuming that the distance on the line LX between the midpoint of the X direction of M2B in the X direction and the center point of the reference mark FM1 is LF, LF is given by the above equation (8).
LF = (ΔXfa + ΔXfb) / 2 in the same manner as Also, the X-axis deviation amount ΔXcc of the center point CC from the center point of the reference mark LM2 remaining during the reticle alignment is measured values ΔXR 1 and ΔXR 2 in FIG.
Thus, as in the above equation (9), ΔXcc = (ΔXR 1 −ΔXR 2 ) / 2.

Therefore, the true baseline amount BL in the X direction
Ox is obtained by the following equation in the same manner as in the equation (10): BLOx = LF−ΔXcc−ΔXF. On the other hand, as for the baseline amount BLOy in the Y direction, a sign error (a shift amount in the Y direction) due to the attachment error θf occurs, and therefore, the accuracy is not guaranteed by using the above-described equation (13).

Here, consider again with reference to FIG. First, as long as the two interferometers IFY 1 and IFY 2 are preset, there is no problem in controlling the position of the wafer stage using either of the interferometers. For example, reticle R
From a state of being positioned a certain point on the wafer directly below the center point CC of, so as not to change the measured values of the interferometer IFY 1, the distance of the wafer stage WST in the X-direction LF, only (strictly LF-ΔXcc) If moved, the specific point on the wafer will be located at point Pc in FIG.
Therefore, the true baseline amount BLOy in the Y direction to be managed
Is the distance in the Y direction between the detection center point Of and the point Pc of the off-axis alignment system.

Since the mounting error θf of the reference plate FP has been determined, the deviation ΔTfc between the point Pc and the reference mark FM1 in the Y direction is ΔYfc ≒ (LF− ΔXcc) · θf (20) Therefore, by changing the above equation (13), the base line amount BLOy in the Y direction in consideration of the mounting error θf is as follows.

[0111] BLOy = ΔYcc-ΔYf 2 -ΔYfc- ΔYF ... (21) Note that, ΔYcc, ΔYf 2 each destination of formula (11), (1
It is obtained from 2). As described above, the two interferometers IFY 1 and IFY 2 are preset to the same value at the time of baseline measurement by the reference plate FP, and the calculation of the baseline amount is corrected according to the mounting error θf. By performing the alignment of the reticle R with respect to the reference mark on the reference plate FP in the line measurement state, all error factors are canceled out, and the accuracy becomes much higher than the conventional baseline measurement. .

[0112] Incidentally, when the baseline measurement operation, even when reading the stop position of the wafer stage WST in the interferometer IFY 1, about several tens of times during about one second, samples the measured value of the internal counter, their By averaging,
The error due to fluctuation was experimentally 0.03 μm to 0.01.
Reduce to about 2 μm. Also, as shown in FIG.
When the off-axis alignment system OWA detects the alignment marks WMx, WMy, and the like, the positioning of the wafer stage WST is controlled by the interferometers IFY 1 and IFX. There is. However, the occurrence of yawing at this time does not affect the final alignment accuracy (the overlay accuracy of the reticle and the shot on the wafer) after presetting the two interferometers IFY 1 and IFY 2 .

FIG. 20 shows an example of realizing the mutual presetting of the two interferometers IFY 1 and IFY 2 described with reference to FIG. 19. Here, it is assumed that the interferometers are realized on hardware. Can be realized in exactly the same way. In Figure 20, the up-down counter (UDC) 200 is an internal counter of the interferometer IFY 1, reversibly counts an up pulse UP1 and the down pulse DP1 generated due to movement of the Y direction of the wafer stage WST. Up / down counter (UDC) 20
Reference numeral 2 denotes an internal counter of the interferometer IFY2, which similarly counts up pulses UP2 and down pulses DP2 reversibly. The count values of the UDCs 200 and 202 are output to the main control system 114 as, for example, parallel 24-bit Y coordinate values DY 1 and DY 2 . Latch circuits (LT) 204, 20
6 receives the count values DY 1 and DY 2 , respectively, and latch pulses S 1 a and S 1 b from the main control system 114.
, The count values DY 1 and DY 2 are kept held. Here, the output value of LT 204 is UDC 202
, And the output value of the LT 206 is applied as a preset value to the UDC 200. U
DCs 200 and 202 are set to preset values in response to load pulses S 1 b and S 2 b from main control system 114, respectively.

[0114] As mentioned earlier, if the preset interferometer IFY 2 measurements Le a (DY 2) to the interferometer IFY 1, is output latch pulse S 2 a relative LT206, predetermined time (uSec order The load pulse S 1 b is output to the UDC 200 with a delay. Of course, FIG.
The circuit of 0, the inverse of the preset is possible, it is also possible to preset measured value Lf of the interferometer IFY 1 a (DY 1) to the interferometer IFY 2. Since the coordinate measurement using the interferometer is relative, the interferometers IFY 1 , IFY 2
, The UDCs 200 and 202 may be reset to zero at the same time, or may be simultaneously reset to a fixed value irrelevant to the measured values Le and Lf.

By the way, as shown in FIGS. 14 and 15, the baseline measurement operation exemplified above is performed after the precise reticle alignment is completed.
Baseline measurement may be performed when the reticle is roughly aligned. For example, at step 504 or 506 in FIG.
Until M 1 and RM 2 reach positions that can be detected by the TTR alignment systems 1A and 1B,
The reticle is roughly aligned by the method. Then run the step 522 in step 508 and FIG. 15 in FIG. 14 at the same time, the reference mark FM2A and positional deviation between the reticle mark RM 1 (ΔXR 1, ΔYR 1 ), the reference mark FM2B the reticle mark RM 2 (ΔXR 2 , ΔYR 2 ) and the positional deviation (ΔXF, ΔYF) between the reference mark FM1 and the index mark of the off-axis alignment system.

At this time, the reference plate FP is servo-locked in the interferometer mode or the LIA mode. Repeat several times to find the average. This averaging reduces the amount of error that occurs randomly. When the respective positional deviation amounts are obtained in this manner, the center CC of the reticle R (or the marks RM 1 ,
RM 2 ) projection point and off-axis alignment system O
The relative positional relationship with the detection center point of the WA can be understood. further,
The position (rough alignment position) of reticle stage RST in this state is determined by interferometers IRX, IRY, IR
Read from the measured value of θ and store it. It is desirable to perform averaging also for this reading.

Then, the previously measured displacement (ΔXR
1 , ΔYR 1 ), (ΔXR 2 , ΔYR 2 ), (ΔXF,
Based on (ΔYF) and a preset constant value, the detection center point of the off-axis alignment system OWA matches the center of the reference mark FM1 (ΔXF = 0, ΔYF =
0), the projected point of the center CC of the reticle and the center point of the reference mark FM2 (the marks FM2A and FM2).
The position shift amount (in the X, Y, and θ directions) with respect to a bisecting point with the position 2B is calculated. After that, the reticle stage RST is finely moved by the positional deviation amount from the stored rough alignment position by using the interferometers IRX, IRY, and IRθ. Thus, reticle R is precisely aligned with the detection center of off-axis alignment system OWA, and thereafter main control system 114 continues the sequence from step 524 in FIG.

As described above, when there is a sensor (interferometer or alignment system) that can measure the position change amount of reticle stage RST (that is, reticle R) with high accuracy over a relatively long range (for example, ± several mm). Can store the rough alignment position, perform the operation of detecting each fiducial mark for baseline measurement, and then perform fine alignment of the reticle R.
Throughput can be improved as compared with the sequences 4 and 15.

In the embodiment of the present invention, the TTL of the LIA system is used.
Although the alignment system is used for servo locking of the reference plate FP, it is necessary to manage the baseline of the LIA TTL alignment system itself with the center CC of the reticle R. Assuming that a TTL alignment system of the LIA system is used to detect a mark on the wafer W, the reticle marks RM 1 and RM 2 detected by the TTR alignment systems 1A and 1B and the reference mark FM2A,
The phase errors Δφx and Δφy of the marks LIMx and LIMy detected by the TTL alignment systems 3X and 3Y of the LIA when the FM2B precisely matches each other.
May be stored as a considerable amount of the baseline error amount with respect to the center CC of the reticle R.

Next, a modification of this embodiment will be described.
Step 50 in the sequence described with reference to FIGS.
In Steps 8 to 512, the reticle alignment is completely achieved using the TTR alignment systems 1A and 1B, but the operation can be omitted to some extent.
As shown in FIG. 2, in the apparatus of the present embodiment, the displacement of the reticle R in the X, Y, and θ directions is determined by the interferometers IRX and IR.
Since Y and IRθ are continuously monitored, step 50
When the coordinates of the projection points of the reticle marks RM 1 and RM 2 are detected by the interferometer on the wafer stage side by the IFS type search operation of No. 4 , the X, Y, and θ directions of the reticle R are calculated based on the coordinate values. The reticle stage RST may be finely moved by relying on the reticle-side interferometer so that the amount of deviation from the designed arrangement is calculated. In this case, the reticle-side interferometers IRX and IR
The measurement resolution of Y and IRθ is sufficiently high (for example, 0.005
.mu.m), the reticle R can be positioned very accurately.

The off axis used in this embodiment is
Alignment system OWA is a static alignment system that performs mark detection while wafer stage WST is stationary. However, as in TTL alignment system of LSA system or 1FS system, mark detection is performed by moving wafer stage WST. The same effect can be obtained by a scanning alignment method that performs the above. For example, in a case where the off-axis alignment system OWA is configured to project the laser beam spot into a slit shape on the wafer W and detect the mark on the wafer by scanning the stage WST,
When the wafer stage WST is moved so that the reference mark FM1 on the reference plate FP crosses the beam spot, at the same time, the emission mark IFS is changed to the reticle mark RM 1 ,
Or to scan the RM 2, it may be determined the placement of each mark on the fiducial plate FP.

Further, off-axis alignment system O
When the LIA system is incorporated in the WA and the reference mark FM1 on the reference plate FP is set to the same diffraction grating as the marks LIMx and LIMy, the reference mark FM1 detected by the off-axis alignment system OWA becomes off-axis alignment The wafer stage WST can be servo-locked based on the detection result of the phase difference measurement circuit so that the wafer stage WST is always aligned with the LIA reference grating in the system. In this case, with the detection center of the off-axis alignment system OWA precisely aligned with the center of the fiducial mark FM1, the TTR alignment systems 1A and 1B
By just finding the reference mark FM2A, each positional displacement amount between FM2B and the reticle mark RM 1, RM 2, it is possible to calculate the baseline amount.

Further, as a TTL alignment system, CC
The D camera 4 is used to image both the mark image on the wafer or the reference plate FP and the image of the index mark provided in the optical path of the TTL alignment system, and by detecting the amount of displacement, the mark is obtained. May be used. In the case of this method, the projection point of the center point (detection center point) of the index mark in the optical path of the TTL alignment system on the wafer side and the projection of the center of the reticle marks RM 1 and RM 2 (or the center CC of the reticle). What is necessary is just to manage the baseline amount between the points.

Incidentally, although the IFS system shown in this embodiment has been described exclusively as a stage scan, that is, a scanning alignment system, a static alignment system can also be used. For that purpose, the light emitting mark IFS on the reference plate FP is changed from a slit shape to a rectangular light emitting surface,
Double slit RM 1 y of reticle mark shown in FIG.
(Or RM 1 x), a rectangular light emitting surface sufficiently larger than the width of the double slit is positioned, and a mark RM 1 y is positioned from above the reticle R using a TTR alignment system or the like.
If an image of (or RM 1 x) is taken by a CCD camera or the like, an image signal having the same waveform as the waveform shown in FIG. 16B can be obtained. At this time, if the mark serving as the index is not in the TTR alignment system, the CCD
Specific pixel position of the camera can be determined amount of deviation of the double slit mark RM 1 y (or RM 1 x) as a reference. Further, in this method, the projected point at the center of reticle mark RM 1 (or RM 2 ) is calculated based on the shift amount and the coordinate value of wafer stage WST when positioning the rectangular light emitting surface. As shown in FIG. 21, a light-shielding slit pattern SSP for measuring the amount of deviation from the double slit mark RM 1 y (RM 1 x) is provided on a part of the rectangular light emitting surface PIF. , TTR
The light emitting surface PIF may be imaged by an alignment-based CCD camera, and the positional deviation between the dark line based on the double slit mark RM 1 y and the dark line based on the slit pattern SSP may be obtained.

FIG. 22 shows a reference on wafer stage WST.
Layout of board FP and layout of off-axis alignment system
And a modification of the off-axis alignment system.
When the position of the objective lens 4B is within the plane of the paper in FIG.
L is below. This position is on the front side of the main unit.
In the loading direction of the wafer. The mark in FIG. 22
Of interferometer I for position measurement of wafer stage WST
FY, IFX1, IFX TwoExcept for Figure 3
Is the same as In the case of FIG. 22, the optical axis position of the projection lens PL
And the off-axis alignment OWA are being detected.
The line connecting the center (almost the optical axis position of the objective lens 4B) is
Because it is parallel to the Y axis, there is only one interferometer IFY in the Y direction.
X-direction interferometer IFX1, IFXTwoWere two.
According to this, change the arrangement of each mark on the reference plate FP
Then, each center point of the reference mark FM1 and the reference mark FM2 is
The connecting line segment is parallel to the Y axis.

Also in the case shown in FIG. 22, marks on the wafer are formed by off-axis alignment system OWA.
Or when detecting the reference mark FM1, etc., using an interferometer IFX 1 and IFY which satisfies the Abbe condition, the wafer stage positioning during exposure, the interferometer IFX 2, 1F
Y is used. That is, when a mark is detected by the off-axis alignment system OWA, the interferometer I
Position coordinate value in the X direction measured by the FX 1 is the interferometer IF
Associated with the position coordinate values measured by X 2. This association is made by interferometer IFY 1 ,
Completely carried out in the same manner as each other presets between IFY 2.

The exposure apparatus described in the above embodiments is a stepper for exposing the projection image of the pattern area PA on the reticle R onto the wafer W by a step-and-repeat method. The present invention is similarly applicable to a step-scan type exposure apparatus that simultaneously scans a wafer in a direction perpendicular to the optical axis of a projection optical system. Also S
A similar alignment system can be applied to an X-ray aligner, an X-ray stepper, or the like using an X-ray source such as an OR.

[0128]

As described above, according to the present invention, since the baseline measurement is performed without being affected by the various precisions of the substrate stage, an improvement in the accuracy of the baseline measurement can be expected. In addition, the alignment of the reticle (mask) and the baseline measurement can be performed almost simultaneously, the stage is moved to check the rotation error of the mask (error in the θ direction), or the stage is moved for the baseline measurement. Since there is no need to perform such operations, the effect of improving the total processing speed can be obtained.

Furthermore, according to the present invention, since reticle alignment and baseline measurement can be performed almost simultaneously, even if a sequence for performing baseline measurement every time a wafer is replaced is set, the throughput is not deteriorated. In addition, a long-term drift of the baseline and a position drift of the reticle holder due to irradiation of the reticle with the exposure light can be confirmed and corrected at high speed.

According to the embodiment, a TTL alignment system or a TTR alignment system (second mark detecting means)
With the position of the reference plate servo-locked using, the mark on the reference plate is set to off-axis alignment system (1st
The mark is detected by the mark detection means) and baseline measurement is performed, so that the measurement caused by the influence of air fluctuation (refractive index fluctuation) on the optical path of the interferometer without using an interferometer for measuring the position of the substrate stage as in the related art. Errors can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a state of baseline measurement in a conventional projection exposure apparatus.

FIG. 2 is a perspective view showing a configuration of a projection exposure apparatus according to an embodiment of the present invention.

FIG. 3 is a plan view showing an arrangement of a reference mark plate on a wafer stage.

FIG. 4 is a plan view showing an arrangement of various marks on a reference mark plate.

FIG. 5 is a plan view showing an arrangement relationship between an image field, a reticle pattern, and a reference mark of a projection lens.

FIG. 6 is a diagram showing an example of the shape of a reticle alignment mark.

FIG. 7 is a diagram showing a configuration of a TTR alignment system.

FIG. 8 is a diagram showing a configuration of a TTL alignment system.

FIG. 9 is a diagram showing a pattern arrangement of an index plate of an off-axis alignment system.

FIG. 10 is a diagram showing a configuration of an off-axis alignment system;

FIG. 11 is an enlarged view showing a reference mark FM1 on a reference mark plate.

FIG. 12 shows reference marks FM2 and LI on a reference mark plate.
The figure which expands and shows M and LSM

FIG. 13 is a view for explaining an error in mounting a reference mark plate on a wafer stage and a measuring method thereof.

FIG. 14 is a view for explaining a typical sequence of the present apparatus.

FIG. 15 is a view for explaining a typical sequence of the present apparatus.

FIG. 16 is a diagram showing an example of a waveform of a photoelectric signal detected by an LSA system and an ISS system.

FIG. 17 is a diagram summarizing constant values and measured values required for baseline management.

FIG. 18 is a plan view showing the arrangement of shot arrays and wafer marks on a wafer.

FIG. 19 illustrates the principle of mutual presetting of two Y-direction interferometers.

FIG. 20 is a circuit block diagram showing an example for presetting an interferometer.

FIG. 21 is a diagram showing another pattern example of the light emitting mark on the reference mark plate.

FIG. 22 is a plan view showing another arrangement of the off-axis alignment system.

[Description of Signs of Main Parts]

R Reticle W Wafer PL Projection lens RST Reticle stage WST Wafer stage 1A, 1B TTR alignment system 2X, 3X TTL alignment system for X direction 2Y, 3Y TTL alignment system for Y direction OWA Off-axis alignment system FP Reference plate FM1 Off- reference marks for the axis alignment system FM2 TTR reference mark IFX for alignment systems, laser interferometer RM 1, RM 2 reticle mark 200, 202 up-down counter for IFY wafer stage

Claims (23)

(57) [Claims]
1. A mask stage for holding a mask, a projection system for projecting a pattern image of the mask onto a photosensitive substrate, a substrate stage for holding the photosensitive substrate and moving two-dimensionally, and an optical axis of the projection system Has a detection center point at a fixed distance from the alignment system for detecting the mark on the photosensitive substrate, and is orthogonal to the detection center point of the alignment system for measuring the coordinate position of the substrate stage. The projection system, comprising: a pair of first interferometers having two measurement axes; and a pair of second interferometers having two measurement axes orthogonal to each other at the optical axis position of the projection system. After measuring the relative positional relationship between the coordinates of the specific point on the mask that can be projected and the coordinates of the detection center point of the alignment system to determine the baseline amount, aligning the photosensitive substrate with the alignment system, In an apparatus for exposing the pattern image of the mask on the photosensitive substrate by moving the substrate stage based on the alignment result and the baseline amount, the apparatus is fixed on the substrate stage and detected by the alignment system. A first fiducial mark to be obtained and a second fiducial mark that can be set to a unique positional relationship with a specific point of the mask when the first fiducial mark is positioned at the detection center point.
A reference plate on which a reference mark is formed; and a stop of the substrate stage which is positioned when measuring the baseline amount with reference to an arrangement of the first reference mark and the second reference mark on the reference plate. A projection exposure apparatus, comprising: setting means for setting a measurement value of the first interferometer and a measurement value of the second interferometer to be equal at a position.
2. A projection system for projecting a pattern image of a mask onto a photosensitive substrate, a substrate stage holding the photosensitive substrate and moving two-dimensionally, and the projection system for detecting a mark on the photosensitive substrate. A first mark detection system in which a detection center point is set at a predetermined position outside the projection field of view, and a mark on the mask at a predetermined position within the projection field of view or a mark located within a projection image plane of the projection system. A second mark detection system for detecting, and a coordinate position of the substrate stage,
One set of first interferometers having two measurement axes orthogonal to each other at the detection center point of the first mark detection system, and one set of two measurement axes orthogonal to each other at the optical axis position of the projection system In the projection exposure apparatus provided with the second interferometer, a design arrangement of a projection point of the mask mark by the projection system and a detection center point of the first mark detection system provided on the substrate stage A reference plate on which a first reference mark and a second reference mark are formed at positions corresponding to the relationship; and a position where the first reference mark is located near a detection center of the first mark detection system for baseline measurement. And control means for positioning the substrate stage such that the second reference mark is located near the projection point of the mark on the mask; and wherein the positioning is performed by the first interferometer when the positioning is performed. Substrate stage present Correction means for correcting coordinate measurement values of at least one of the first interferometer and the second interferometer such that the position and the current position of the substrate stage measured by the second interferometer are recognized as the same position. And a projection exposure apparatus.
3. A projection optical system for projecting a pattern image of a mask onto a photosensitive substrate, a substrate stage for holding the photosensitive substrate, and an off-axis first mark detection system for detecting a mark on the photosensitive substrate. A second mark detection system for detecting a mark arranged on the image plane side via the projection optical system, a first interferometer having a measurement axis passing through a detection center of the first mark detection system, A projection exposure apparatus comprising: a second interferometer having a measurement axis that intersects an optical axis of an optical system. The projection exposure apparatus is provided on the substrate stage, and has a positional relationship according to an arrangement of the first and second mark detection systems. A reference plate on which first and second marks are formed; detection of the first mark by the first mark detection system;
Setting means for arranging the substrate stage at a predetermined position where the detection of the second mark by the second mark detection system can be performed simultaneously, and associating each measurement value of the first and second interferometers with A projection exposure apparatus comprising:
4. When associating each measurement value of the first and second interferometers, a baseline amount of the first mark detection system is determined based on a detection result of the first and second mark detection systems. 4. The projection exposure apparatus according to claim 3, further comprising a measuring unit for determining.
5. A projection optical system for projecting a pattern image of a mask onto a photosensitive substrate, a substrate stage for holding the photosensitive substrate, and first and second measuring axes having mutually parallel measurement axes orthogonal to a reflection surface of the substrate stage. In a projection exposure apparatus having a second interferometer, a plurality of reference marks provided on the substrate stage and at least one of the plurality of reference marks are provided.
A first mark detection system for detecting a mark, and detection of the first mark detection system on an image plane side of the projection optical system.
A detection center at a position different from the center;
At least one fiducial mark of the projection light
A second mark detection system for detecting the first mark and the second mark detection system through the first and second mark detection systems.
The reference marks to be detected by the respective mark detection systems are located within the area.
Position the substrate stage at a predetermined position where
Stage control means for determining, and a state in which the substrate stage is positioned at the predetermined position
In a projection exposure apparatus characterized by comprising a setting means for associating each measurement value of the first and second interferometers.
6. The reference mark detection system according to claim 1 , wherein
Phrases and projection exposure apparatus according to claim 5, wherein the this <br/> detecting a mark formed on the mask.
7. The method according to claim 7, wherein the plurality of fiducial marks include the first mark.
A first mark that is detected by the click detection system, and a second mark detected by said second mark detection <br/> out system, the first and the second mark, the first mark detection system
And a positional relationship according to the arrangement of the second mark detection system ,
The projection exposure apparatus according to claim 5 or claim 6, characterized in that it is formed on the same of the reference plate on the substrate stage.
8. A detection center of the first mark detection system is arranged on a measurement axis of the first interferometer, and a measurement axis of the second interferometer intersects an optical axis of the projection optical system. The projection exposure apparatus according to claim 5, wherein:
9. The projection exposure apparatus according to claim 5, wherein a detection center of the first mark detection system is disposed within a projection field of view of the projection optical system.
10. The projection exposure apparatus according to claim 5, wherein a detection center of the first mark detection system is disposed outside a projection visual field of the projection optical system.
11. The first mark detection system has an objective optical system provided separately from the projection optical system, and detects a mark on the photosensitive substrate via the objective optical system. The projection exposure apparatus according to claim 10.
12. A projection optical system for projecting a mask pattern image onto a photosensitive substrate, a substrate stage for holding the photosensitive substrate, an interferometer for detecting positional information of the substrate stage, and a mark on the photosensitive substrate. A first mark detection system for detecting a mark, and a second mark detection system for detecting a mark arranged on the image plane side via the projection optical system, provided on the substrate stage, A reference mark plate detected by the first and second mark detection systems; and a position information of the substrate stage detected by the interferometer a plurality of times when the first and second mark detection systems detect the reference mark plate. The plurality of location information and the first and second
A projection exposure apparatus comprising: a measuring unit that determines a baseline amount of the first mark detection system based on detection information of a mark detection system.
13. The fiducial mark plate is configured to place a first mark detected by the first mark detection system and a second mark detected by the second mark detection system on the same plate in a predetermined positional relationship. 13. The projection exposure apparatus according to claim 12, wherein the projection exposure apparatus is formed.
14. The first and second marks are formed in a positional relationship according to the arrangement of the first and second mark detection systems, and the measuring means is configured to detect the first mark by the first mark detection system. 14. The projection exposure apparatus according to claim 13, wherein detection of the second mark and detection of the second mark by the second mark detection system are performed substantially simultaneously.
15. The arrangement of the first and second marks is such that detection of the first mark by the first mark detection system and detection of the second mark by the second mark detection system are performed on the substrate stage. 15. The projection exposure apparatus according to claim 13, wherein the projection exposure apparatus is set so as to be performed without movement.
16. The second mark detection system detects the reference mark and the mark of the mask via the projection optical system, and the first mark detection system detects the mark of the mask by the projection optical system. The projection exposure apparatus according to any one of claims 12 to 15, wherein the projection exposure apparatus has a detection center at a position different from the projection point.
17. The projection exposure apparatus according to claim 16, wherein a detection center of the first mark detection system is disposed in a projection field of the projection optical system.
18. The first mark detection system has an objective optical system provided separately from the projection optical system, and detects a mark on the photosensitive substrate via the objective optical system. The projection exposure apparatus according to any one of claims 12 to 16.
19. The method according to claim 19, wherein the measuring unit is provided on the substrate stage.
Information on the mounting error of the reference mark plate
Correcting the baseline amount based on the
The projection exposure according to any one of claims 12 to 18,
apparatus.
20. The first and second mark detection systems
Obtain the detection information and the substrate stage
Based on the information on the mounting error of the reference plate,
Measuring means for determining a baseline amount of the first mark detection system
8. The projection dew according to claim 7, further comprising:
Light device.
21. The first mark detection system has a detection center.
Are arranged outside the projection field of view of the projection optical system.
The projection exposure apparatus according to claim 20, wherein
22. The setting means, comprising:
By making each measurement value of the interferometer equal,
2. The method according to claim 1, wherein the measurement values are associated with each other.
A projection exposure apparatus according to claim 3 or claim 5.
23. The setting means, comprising: the first interferometer;
The measured value of one of the second interferometers is
3. The method according to claim 2, wherein the interferometer is preset.
3. The projection exposure apparatus according to 2.
JP16978191A 1991-07-10 1991-07-10 Projection exposure equipment Expired - Fee Related JP3200874B2 (en)

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JP16978191A JP3200874B2 (en) 1991-07-10 1991-07-10 Projection exposure equipment
US07/998,642 US5243195A (en) 1991-04-25 1992-12-29 Projection exposure apparatus having an off-axis alignment system and method of alignment therefor
US09/002,884 USRE36730E (en) 1991-04-25 1998-01-05 Projection exposure apparatus having an off-axis alignment system and method of alignment therefor

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JP3200874B2 true JP3200874B2 (en) 2001-08-20

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