JP3089798B2 - Positioning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detecting device for detecting the position and the amount of rotation of an object to be inspected. The present invention is suitable for a position detection device of a step-and-repeat type exposure apparatus that superimposes and exposes a circuit pattern of a mask (or a reticle) on a plurality of circuit patterns formed on a substrate to be exposed by a step-and-repeat method.

[0002]

2. Description of the Related Art In recent years, an apparatus for repeatedly exposing a circuit pattern of a mask or a reticle (hereinafter, referred to as a reticle) on a semiconductor wafer or a glass substrate (hereinafter, referred to as a wafer) for manufacturing a semiconductor device and a liquid crystal display, a so-called step. A large number of AND repeat exposure apparatuses are used in production sites, and a great effect is obtained. In particular, a reduction projection type exposure apparatus that transfers a reticle circuit pattern onto a wafer through a reduction projection lens projects a small reticle circuit pattern, so that minute foreign matter adhering to the reticle is transferred by the resolution power of the reduction projection lens. In addition, the circuit pattern of the reticle is overlaid on each of a plurality of circuit patterns formed on the wafer for exposure, so that accurate overlay can be always performed even when the wafer is expanded or contracted by various processes. Therefore, it can be said that the exposure apparatus has extremely high productivity.

[0003]

An exposure apparatus of this type has a two-dimensional moving stage on which a wafer is placed, and moves this stage at a constant pitch in accordance with a predetermined coordinate system with respect to a circuit pattern image of a reticle. And repeating the exposure. For this reason, circuit patterns are arranged in a matrix on the wafer. The arrangement coordinates of the circuit pattern on the wafer follow the coordinate system of the stage being exposed. However, when the wafer is replaced, the arrangement coordinates on the wafer and the coordinate system of the stage are rotationally displaced.

[0004] Although this rotational deviation can be corrected by rotating the wafer, a rotational deviation of a small angle still remains. This minute rotational deviation between the arrangement coordinates on the wafer and the coordinate system of the stage is what is called wafer rotation. In order to achieve higher-accuracy overlay exposure, Japanese Patent Application Laid-Open No. Sho 56-102823 discloses a method for correcting wafer rotation. In the reduction projection type exposure apparatus disclosed in these publications, exposure is performed by a step-and-repeat method using a reticle on which an enlarged pattern 5 times (or an arbitrary fixed magnification) of a circuit pattern on a wafer is drawn.
At that time, the reticle was assumed to be mounted without rotational displacement with respect to the coordinate system of the stage.

However, when the size of the circuit pattern to be transferred onto the wafer is reduced and the line width is reduced to about 1 μm, a slight rotation deviation of the reticle cannot be ignored. When the reticle is slightly rotated, not only does the overlay accuracy with each circuit pattern on the wafer deteriorate, but also the first
When the circuit pattern of the layer is transferred, the transferred circuit pattern slightly rotates with respect to the arrangement coordinates of the wafer, and the superimposition of the second and subsequent layers becomes insufficient,
A semiconductor element and a liquid crystal substrate satisfying expected characteristics cannot be obtained with high productivity. For this reason, Japanese Unexamined Patent Publication No.
No. 5 discloses a method for correcting a minute rotation deviation of a reticle, a so-called reticle rotation, and the like.

However, in addition to a mark for performing two-dimensional alignment, a mark for detecting a minute rotation of the reticle is required on the reticle, so that the size of the circuit pattern to be transferred onto the wafer is small. This was one of the factors that reduced productivity. In the case where exposure is performed using a reticle having a size different from the normal size, the position of a mark formed on the reticle varies with the size of the reticle. For this reason, each mark on the reticle must be accurately detected by moving the alignment optical system, which has been a factor of reducing the throughput.

The present invention solves the above-mentioned drawbacks. Even when the reticle has a rotational deviation with respect to the wafer, and when aligning a reticle having a size different from the normal size, the positioning device can be used for each mark of the reticle. It is an object of the present invention to provide a position detecting device capable of quickly detecting a reticle and a wafer with high accuracy using two reticle marks in principle, even if they are not strictly aligned.

[0008]

According to the present invention, as shown in FIGS. 1 and 2, a wafer W held on an XY stage 1 which moves along predetermined XY orthogonal coordinates is provided. When exposing a reticle R on which a predetermined pattern Pr is formed, a first reticle provided on the reticle R in a positioning apparatus for adjusting the relative position between the reticle R and the wafer W. A first detection system 10 for detecting the position of a mark Rxy and a first wafer mark WM1 provided on a wafer W, and a second detection system 10 provided at a predetermined position on a reticle R different from the first reticle mark Rxy. Reticle mark Rθx and first wafer mark WM1
And a second detection system 20 for detecting the position of the second wafer mark WM2 provided at a predetermined position on the wafer different from the above.

Based on this basic configuration, the first detection system 10 includes a first objective lens 11 and an image of the first reticle mark Rxy and the first wafer mark WM1 via the first objective lens 11. A first image detecting means 14 for detecting an image, a first reticle-side light splitting member 15 and a first detecting side which are sequentially arranged between the optical paths of the first objective lens 11 and the first image detecting means 14 The first reticle mark Rxy and the first wafer mark WM are provided in the light dividing direction of the light dividing member 17 and the first reticle side light dividing member 15.
A first X direction detecting means 13 for detecting the first X direction, and a Y direction of the first reticle mark Rxy and the first wafer mark WM1 provided in the light dividing direction of the first detecting side light dividing member 17. And a first Y-direction detecting means 12 that performs
The second detection system 20 is configured to detect a second objective lens 21 and an image of the second reticle mark Rθx and an image of the second wafer mark WM2 via the second objective lens 21.
An image detecting means 24, a second reticle-side light splitting member 25 and a second detection-side light splitting member 27 which are sequentially arranged between the optical paths of the second objective lens 21 and the second image detecting means 24; The second reticle mark Rθx and the second wafer mark W are provided in the light splitting direction of the second reticle side light splitting member 25.
Second X direction detecting means 22 for detecting the X direction of M2,
First Y-direction detecting means 23 provided in the light dividing direction of the second detection-side light dividing member 27 to detect the Y direction of the second reticle mark Rθx and the second wafer mark WM2.
And a first correction member 16 for displacing the optical axis of the first detection system 10 in the X direction is disposed between the first reticle-side light splitting member 15 and the first detection-side light splitting member 17. And a second correction member 26 for displacing the optical axis of the second detection system 20 in the Y direction between the second reticle-side light splitting member 25 and the second detection-side light splitting member 27. It is.

As a preferred configuration of the present invention, the first correction member 16 is a parallel flat plate having a variable tilt angle and having a rotation axis S ₁ in the Y direction perpendicular to the optical axis Ax ₁ of the first detection system 10. The second correction member 26 is connected to the optical axis Ax ₂ of the second optical system 20.
It is good to tilt variable plane parallel plate in the X direction perpendicular with the rotation axis S ₂ in.

[0011]

In the apparatus according to the present invention, the reticle R has a rotation error Δθ.
Even if the respective reticle marks are detected in the state where the reticle R is included and the rotation error Δθ of the reticle R is corrected, the field of view of the first and second detection systems is shifted with respect to the reticle R, 1st and 2nd by 1st and 2nd correction member
Each reticle mark can be accurately detected without moving the detection system.

In addition, even if the position of the reticle mark differs due to the fact that the reticle is different from the normal size, the reticle mark can be accurately detected even if each detection system is not strictly aligned with the reticle mark. be able to. Therefore, even when the reticle R includes the rotation error Δθ and when the reticle mark is detected including the lateral displacement even when the first and second detection systems are moved with the difference in the reticle size, the first and second reticle marks are detected. Without strictly aligning the detection system with the detection marks, quick and highly accurate alignment is possible on the reticle even with two detection marks in principle.

[0013]

FIG. 1 shows an example in which a position detecting apparatus according to the present invention is applied to a reduction projection exposure apparatus, which will be described with reference to FIG. A reticle (mask) R on which a predetermined pattern is formed is uniformly illuminated by an illumination optical system (not shown), and an image of a pattern region Pr of the reticle R is transferred onto the wafer W by the projection lens 2. Reticle R
Are mounted on a reticle stage 3, and a driving unit 4 is provided in the X direction of the reticle stage 3, and a driving unit 5 is provided in the Y direction. The driving unit 4 moves the reticle stage 3 in the X direction.
Moves the reticle stage 3 in the Y direction to perform two-dimensional positioning including a rotation error of the reticle R.

On the other hand, a wafer W is mounted on a wafer stage 1. One end of the stage 8 is provided with an alignment optical system 10, 2
A reference mark plate (cross-shaped mark) 30 for determining a reference position of 0 or detecting a rotation error or the like of the reticle R.
(Hereinafter referred to as reference marks). The wafer stage 1 is moved in the X direction by the drive unit 6 and is moved in the Y direction by the drive unit 7. Below the wafer stage 1, there is provided a Z stage 8 for moving the wafer stage 1 in the Z direction (vertical direction in FIG. 1). Although not shown, an interference system for detecting the position of the wafer stage 1 in the XY coordinates is provided.

The apparatus of the present invention is provided with an optical system for alignment (alignment) and a detection system. FIG.
2 for aligning the reticle R with respect to the apparatus main body (for example, the optical axis Ax ₀ of the projection reticle R).
Alignment systems 10 and 20. The two alignment systems 10 and 20 are provided so as to be movable in the X direction so as to be compatible with reticles having different sizes. Alignment system 10 is a reticle predetermined pattern (hereinafter referred to as pattern region) drawn area on R reticle marks provided on the periphery of the P _r (cross-shaped mark) Rx
observing the y, alignment system 20 for observing the reticle mark Rθx provided at a position different from the reticle mark (cross-shaped mark) Rxy around the pattern area P _r. That is, alignment systems 10 and 20 function as a reticle alignment microscope.

The reticle R is positioned in the X and Y directions by operating the driving units 4 and 5 so as to align the reticle mark Rxy with an index (a sandwiched cross-shaped mark) in the reticle alignment system 10. By operating the driving units 4 and 5 so that the mark Rθx matches the index in the reticle alignment system 20, positioning in the rotation direction of the reticle R is achieved. These reticle alignment systems 10 and 20 may be used for visual alignment (alignment).
The monitor image may be processed using a D camera or the like, or the observed image of the reticle marks Rxy and Rθx may be photoelectrically detected and used for automatic alignment.

Now, as another use of the alignment systems 10 and 20, a die-by-die (a die-by-die) in which the mark Rxy or Rθx on the reticle R and the mark on the wafer W are superimposed via the projection lens 2 and observed. Die by Die) It can also be used as an alignment system (hereinafter referred to as DDA system). DDA system marks provided on the periphery of the pattern region P _r of the reticle R Rxy, irradiates illumination light of the exposure light in the same wavelength Arushitax. This illumination light illuminates the marks Rxy and Rθx and also passes through the projection lens 2 to illuminate a minute area including the marks WM1 and WM2 on the wafer W. Then, the mark WM on the wafer W back-projected by the projection lens 2
1, WM2 image and the reticle R of the mark Rxy, the image of Rθx is formed by DDA system, the alignment state of the reticle R in the pattern area P _r and one local area to be exposed on the wafer W is detected You. In the alignment method of the die-by-die, when one of the local area on the projection image and the wafer W of the pattern region P _r of the reticle R are superimposed exactly, the mark of the mark and the reticle R on the wafer W Rxy and Rθx are aligned in a predetermined positional relationship and observed by the DDA system. Therefore, after the wafer stage 8 and the reticle stage 3 are finely moved so as to be aligned by the DDA system, the exposure operation can be immediately started.

Although not shown, each of the alignment systems 10 and 20 and the driving units 4 to 7 are generally controlled by a main controller. Next, a specific configuration of the alignment systems 10 and 20 shown in FIG. 1 will be described with reference to FIG. Light source 19 (2) in alignment system 10 (20)
The alignment light from 9) is the half mirror 18 (28)
And the reticle mark R via the objective lens 11 (21)
xy (Rθx), and illuminates the wafer mark WM1 (WM2) or the reference mark 30 via the projection lens 2.

The reflected light (detection light) from each mark passes through the half mirror 18 (28) via the objective lens 11 (21) again along the reverse optical path. After that, the detection light
The light is split into two optical paths by the half mirror 18 (28), one of which is reflected, and the Y direction detection system 12 (in the alignment system 20, the X direction of each mark is photoelectrically detected) for photoelectrically detecting the Y direction of each mark. X-direction detection system 22)
, Where the Y direction of each mark (X direction detection system 22
X direction) is photoelectrically detected.

On the other hand, the other detection light transmitted by the half mirror 18 (28) is split into two optical paths by the half mirror 17 (27) via the plane parallel plate 16 (26). One of the detection lights reflected by the half mirror 17 (27) is used to photoelectrically detect the X direction of each mark.
And reaches a direction detection system 13 (in the alignment system 20, a Y direction detection system 23 that photoelectrically detects the Y direction of each mark).
Here, the X direction (Y direction in the Y direction detection system 23) of each mark is photoelectrically detected.

The other detection light transmitted through the half mirror 17 (27) reaches the image detection system 14 (24), where the image is detected. Here, the image detection system 14 (2
4) includes an index plate having an index mark (an interposing cross-shaped mark), a CCD, and the like. At the time of image alignment, alignment is performed so that each alignment mark matches this index mark. .

[0022] Here, the plane-parallel plate 16 in the alignment system 10 has a rotary shaft S ₁ in the direction (Y-direction) perpendicular to the paper surface direction, is provided on the inclination angle vary within the paper.
Therefore, when the inclination angle is changed, as shown in FIG.
The optical axis Ax ₁ of the alignment system 10 is displaced in the X direction, X
The direction detection system 13 and the image detection system 14 can displace the detection area of the reticle R in the X direction.

On the other hand, the plane-parallel plate 26 in the alignment system 20 has a rotation axis S ₂ in the direction of the paper (X direction) and is provided with a variable tilt angle in the plane of the paper. The axis S ₂ is provided orthogonal to the rotation axis S ₁ of the plane-parallel plate 16. Thus, changing this inclination angle, as shown in FIG. 4, the optical axis Ax ₂ of the alignment system 20 is displaced in the Y-direction, Y-direction detecting system 23 and the image detection system 24 detects the Y direction of the reticle R region Can be displaced.

As described above, since the photoelectric detection systems in the X direction and the Y direction in the alignment system 10 are arranged in the opposite relationship to the photoelectric detection systems in the X direction and the Y direction in the alignment system 20, In the apparatus according to the embodiment, adjustment of the optical axis in each direction with respect to the two detection systems in each alignment system is possible in principle with one parallel flat plate. Now, an example of a reticle alignment operation using the parallel plane plates 16 and 26 will be described.

First, it is assumed that the respective optical axis positions with the alignment systems 10 and 20 are adjusted so as to have a predetermined positional relationship with respect to the orthogonal coordinates of the wafer stage 1. Next, when the reticle R is mounted on the reticle stage 3, the reticle marks Rxy and Rθx are aligned with the alignment systems 10 and 20.
The alignment is performed by the driving systems 4 and 5 so as to match the indices of the image detection systems 14 and 24 in the image forming apparatus, and the alignment is performed so as to match at least the indices in the image detection system 14 of the alignment system 10. . Here, a reticle having a normal size is not always mounted on the reticle stage 3. Therefore, when a reticle R having a size different from the normal size is mounted on the reticle stage 3, the inside of the alignment systems 10 and 20 is removed. Move the reticle mark R in the X direction.
The positioning is performed by the driving systems 4 and 5 so that xy and Rθx fall within each field of view of each of the alignment systems 10 and 20. Then, as shown in FIG. 3, the parallel plane plate 16 in the alignment system 10 is tilted via a driving unit (not shown) controlled by the main control system, and the optical axis Ax of the alignment system 10 is tilted.
₁ is displaced by X in the X direction, and the reticle mark Rxy
Of the reticle mark Rxy,
The X direction is matched with Rθx, and the alignment is performed so as to match at least the index in the image detection system 14 of the alignment system 10.

Next, the rotation amount as of the reticle R in FIG. 5 Θ _R
Reticle rotation may occur due to reticle rotation (reticle rotation)
Is detected. First, the reference mark 30 on the wafer stage 1 is moved into each field of view of the alignment systems 10 and 20,
The X direction detection system 13 and the Y direction detection system 12 determine an X coordinate value and a Y coordinate value at which the intensity of the reflected light from the reference mark 30 is maximum from an interference system (not shown).

Similarly, the X-direction detection system 22
The Y-coordinate value and the Y-coordinate value at which the intensity of the reflected light from the reference mark 30 is maximized are obtained from an interference system (not shown) by the Y-direction detection system 23. The XY coordinate value of each mark is
It is input to a reticle rotation error detection unit (not shown). Here, since each mark on the reticle is provided with a predetermined distance relationship, a reticle rotation error detecting unit previously stores information on the distance between the marks.

Accordingly, when the XY coordinate values of each mark are input to the reticle rotation error detection unit,
The reticle rotation is calculated from the Y coordinate value. Note that in this case, the X in the state where the indices inside these and the reference mark 30 match each other by the image detection systems 14 and 24.
The coordinate value and the Y coordinate value may be obtained from an interference system (not shown), and thereafter, the reticle rotation error may be calculated by a reticle rotation error detection unit.

The reticle rotation is corrected by rotating the reticle stage 3 by a very small amount by the control units 4 and 5 by the reticle rotation based on the reticle rotation calculation result obtained as described above.
If the reticle rotation is within the allowable range, each photoelectric detection system (1
2,13,22,23) to the reticle mark (Rx
(y, Rθx) and the wafer mark (WM1, WM2) are aligned, and the process proceeds to the exposure operation.

However, if there is an unacceptable reticle rotation, the reference mark 30 is moved to the center of the index in the image detection system 24 of the alignment system 20, and then the reference mark 30 is further rotated in the Y direction. the amount Θ is divided by fine movement of the shift amount ΔY corresponding to _R, alignment system to the reference mark 30 at that time 20
4 so that the center of the index in the image detection system 24 of FIG.
As shown in the figure, the parallel flat plate 26 is inclined. Thereby, the reticle rotation is corrected. Then, if this reticle rotation is corrected, each of the photoelectric detection systems (12, 13, 22, 23) of each of the alignment systems 10, 20 will be described.
Then, the reticle mark (Rxy, Rθx) is aligned with the wafer mark (WM1, WM2), and the operation shifts to the exposure operation.

The reticle rotation may be corrected by rotating the wafer stage 1. As described above, the present invention is not applied only to the reduction projection type exposure apparatus. For example, even in the case of an X-ray exposure apparatus that performs exposure using a soft X-ray in a proximity method, the same applies to a step-and-repeat method. The effect of is obtained.

In the present embodiment, an example is shown in which an image processing system and a photoelectric detection system are combined in the alignment system. However, the alignment system may be appropriately combined with a detection system of another system.

[0033]

As described above, according to the present invention, 1
When repeatedly exposing a pattern of a mask (reticle) onto a plurality of substrates (wafers) to be exposed, when reticle rotation is present, or when aligning a reticle having an unusual size, the alignment apparatus can be used. Even if the marks are not exactly aligned with each other, two reticle marks can quickly detect the reticle and the wafer with high accuracy in principle. As a result, it is possible to obtain an effect that the yield rate of the manufactured semiconductor element or liquid crystal substrate is increased and the yield is remarkably improved.

Further, an exposure apparatus having a high positioning accuracy and a high reproducibility accuracy by merely increasing the positioning accuracy of the wafer stage and the reticle stage with respect to the orthogonal coordinates (coordinate system XY) without pursuing the positioning accuracy with respect to the rotational deviation of the reticle or wafer. There is also an advantage that can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of two alignment systems.

FIG. 3 is a diagram illustrating a state where an optical axis of one alignment system is displaced in an X direction.

FIG. 4 is a diagram illustrating a state where the optical axis of the other alignment system is displaced in the Y direction.

FIG. 5 is a diagram illustrating a state of a reticle when a reticle rotation exists.

[Description of Signs of Main Parts]

 DESCRIPTION OF SYMBOLS 1 ... Wafer stage 2 ... Projection lens 3 ... Reticle stage 4, 5, 6, 7 ... Driving part 8 ... Z stage 10, 20 ... Alignment system 11, 21 ... Objective lenses 13, 22 ... X-direction detection system 12, 23 ... Y-direction detection system 14, 24 ... Image detection system 16, 26 ... Parallel plane plate 15, 17, 18, 25, 27, 28 Half mirror 30 Reference mark plate R Reticle W Wafer

Claims (2)

(57) [Claims] 1. XY moving along predetermined XY rectangular coordinates
When exposing a reticle on which a predetermined pattern is formed on a wafer held on a stage, a positioning apparatus for adjusting a relative position between the reticle and the wafer is provided on the reticle. A first detection system for detecting the positions of the first reticle mark and the first wafer mark provided on the wafer, and a second reticle provided at a predetermined position on the reticle different from the first reticle mark A second detection system for detecting a position of a mark and a second wafer mark provided at a predetermined position on the wafer different from the first wafer mark, wherein the first detection system comprises a first objective. A lens, first image detecting means for detecting the first reticle mark image and the first wafer mark image via the first objective lens, the first objective lens and the first image detecting means, A first reticle-side light splitting member and a first detection-side light splitting member sequentially arranged between optical paths, and the first reticle mark and the first reticle mark provided in the light splitting direction of the first reticle-side light splitting member. First X direction detecting means for detecting the X direction of the first wafer mark;
The first reticle mark and the first wafer mark are provided in the light dividing direction of the first detection side light dividing member.
A first Y-direction detecting means for detecting a direction, wherein the second detection system includes a second objective lens, and the second reticle mark image and the second wafer mark image via the second objective lens. A second reticle-side light splitting member and a second detection-side light splitting member sequentially arranged between the optical paths of the second objective lens and the second image detecting means, Second X-direction detecting means provided in the light dividing direction of the second reticle-side light dividing member to detect the X direction of the second reticle mark and the second wafer mark;
The second reticle mark and the Y mark of the second wafer mark are provided in the light dividing direction of the second detection side light dividing member.
A first Y-direction detecting means for detecting a direction, wherein an optical axis of the first detection system is X between the first reticle-side light splitting member and the first detection-side light splitting member. A first correction member for displacing in the direction is disposed, and an optical axis of the second detection system is displaced in the Y direction between the second reticle-side light dividing member and the second detection-side light dividing member. Second
An alignment device comprising a correction member. 2. The first correction member comprises a plane parallel to the optical axis of the first detection system and having a variable tilt angle and having a rotation axis in the Y direction, and the second correction member comprises a second detection system. 2. The alignment device according to claim 1, wherein the alignment device is constituted by a parallel flat plate having a variable tilt angle and a rotation axis in the X direction perpendicular to the optical axis.