JPH01240802A - Detecting apparatus for horizontal position - Google Patents

Abstract

PURPOSE:To increase detective sensitivity by a method wherein slope angles in the directions of an X-axis and a Y-axis in an exposure area are detected in the directions along the crosslines of the respective photodetectors of two sets of horizontal position detecting systems. CONSTITUTION:Two sets of horizontal position detecting systems composed of irradiation optical systems 10X, 10Y and convergence optical systems 20X, 20Y are provided along the directions of an X-axis and a Y-axis of a coordinate system X-Y. By photodetectors in the convergence optical systems 20X, 20Y of these horizontal position detecting systems, slope angles in the directions of the X-axis and the Y-axis in an exposure area are detected invariably in the directions along the crosslines of the photodetectors, and outputs of these elements are computed by an arithmetic means for calculation of the inclination of the exposure area.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a reference position detection device for accurately positioning a semiconductor wafer surface or a test object surface in a perpendicular position with respect to the optical axis of an objective lens. This invention relates to a horizontal position detection device. It is something.

[Conventional technology]

In the lithography process in the manufacture of semiconductor integrated circuits, a step-and-repeat reduction projection exposure device (so-called stepper) is mainly used to project a circuit pattern formed on a mask or reticle (hereinafter referred to as a reticle). A wafer, which is a work piece, is sequentially exposed to light through an objective lens (hereinafter referred to as a projection lens). Since a projection lens with a large numerical aperture (N, A,) is generally used in this stepper, the permissible focal range is very small. Therefore, in order to expose a clear pattern over the entire exposure area on the wafer, an autofocus mechanism is usually used to detect the center or peripheral points of each exposure area, and align them with respect to the optical axis of the projection lens. The exposure area is moved vertically in the optical axis direction of the projection lens. However, recently, the numerical aperture (N) of the projection lens has increased in response to the minimum line width of circuits formed on the order of sub-microns.

A) further increases, and the projection lens is tilted with respect to the imaging plane in areas other than the detection point on the exposure area by the autofocus mechanism, and this tilt causes local defocus within the exposure area. This has become a problem. Therefore, it is necessary to accurately maintain the exposure area plane in a vertical position, that is, in a horizontal position, with respect to the optical axis of the projection lens. As a device for detecting the horizontal position of the exposure area, there is a collimator-type horizontal position detecting device as disclosed in, for example, Japanese Patent Laid-Open No. 113706/1983, previously filed by the applicant of the present invention. FIG. 6 shows a schematic layout of this horizontal position detection device when viewed from the optical axis direction of the projection lens. This type of apparatus includes an irradiation optical system 10 that supplies a parallel light beam from a direction oblique to the optical axis of a projection lens, and a light receiving objective lens 21 that receives a light beam that is supplied from the irradiation optical system 10 and reflected on an exposure area on a wafer W. The condensing optical system 20 that condenses light onto the four-part light receiving element 22 via the four-part light receiving element 22 is arranged so that the optical axes 10a and 20a of both optical systems are symmetrical with respect to the optical axis of the projection lens.

Here, it is assumed that the horizontal position detection system consisting of the irradiation optical system 10 and the condensing optical system 20 is provided at a position rotated by ψp from the X axis with respect to the optical axis of the projection lens in the orthogonal coordinate system XY. Note that the optical axis 10a of the irradiation optical system 10
, the plane containing the optical axis 20a of the condensing optical system 20 and the optical axis of the projection lens is called the incident plane, and in the coordinate system xy, the direction along the incident plane is the P-axis direction, and the direction perpendicular to the incident plane is the R-axis direction. In addition, in the light receiving surface of the four-part light receiving element 22, the direction along the intersection line between the light receiving surface and the incident surface is defined as the p direction, and the direction perpendicular to this intersection line (p direction) is defined as the r direction. Now, if the exposure area is kept perpendicular to the optical axis of the projection lens, the light beam reflected from the exposure area will be focused at the center of the four-divided light receiving element 22 (the intersection of the p direction and the r direction). If the exposure area is tilted by α from the vertical, the reflected light beam is tilted by 2α with respect to the optical axis 20a of the condensing optical system 20, so it is condensed at a position off the center on the 4-split light receiving element 22. be done. Therefore,
In order to accurately set the exposure area perpendicular to the optical axis of the projection lens, first, the light convergence point is set at the center on the 4-split light receiving element 22 according to the inclination of the exposure area in the P-axis and R-axis directions. Since the position changes from , the displacement amounts ΔP and ΔR of this focal point in the p direction and the r direction are detected. Next, the displacement amount ΔP of the focal point,
From ΔR, use the following equations (1) and (2) to calculate the tilt angle θp of the exposure area in the P-axis and R-axis directions with respect to the imaging plane of the projection lens.
, θr is calculated. However, the focal length of the condensing optical system 20, that is, the light-receiving objective lens 21 is assumed to be ``, and the angle formed by the parallel light beam supplied onto the exposure area by the irradiation optical system 10 onto the exposure area surface is θS.

ΔP=f-jan(2θp) ・------(
1) ΔR=f-tan(2θr)・cos(90'-
θS)...(2) Here, the detection direction on the 4-split light receiving element 22 surface, that is, the p direction, the numerical aperture NAp, NAr, and the depth of focus FD in the direction.
p, FDr can be calculated using the following equations (3) to (6), and under this condition, the displacement amount ΔP of the focal point,
ΔR is detected. However, the radius of the circular detection area Da of the parallel light beam supplied by the irradiation optical system 10 is a, and the center wavelength is λ.

NAl)=2 ・s iHθS/f ・・・・・・(3
) NAr=a/f −(4)2
(NAp)" 1 λ 2 (NAr)" Tilt angle θp, θ calculated from the above equations (1) and (2)
Based on r, the control means generates control signals according to the inclination angles θp and θr, and the stage on which the wafer is placed is moved by the drive device so as to correct the inclination of the surface of the exposure area of the wafer. is automatically set to an averagely accurate vertical position with respect to the optical axis of the projection lens.

The direction of inclination of the exposure area is uniquely determined by the inclination angle θ from the Z axis shown in FIG. 7 and the angle ψ from the X axis of the image projected onto the XY plane (hereinafter referred to as azimuth angle). It is expressed as a normal unit vector 5. Therefore, if the inclination angles in the X-axis and Y-axis directions of the coordinate system xy of the exposure area with respect to the imaging plane of the projection lens are θX and θy, respectively, then the inclination angle θ and the azimuth angle ψ are θ
It is expressed by the following relational expressions: X=θ·cos ψ, θy=−θ·sin ψ.

Therefore, the tilt angle θp calculated by (1) and (2)
, θr, use the following equations (7) and (8) to calculate the tilt angle θX
, θy, the azimuth angle ψ and the inclination angle θ can be determined.

As a result, it is possible to detect the normal unit vector value, that is, the direction of inclination of the exposure area with respect to the imaging plane of the projection lens.

[Problem to be solved by the invention]

However, this type of horizontal position detection device uses a pair of irradiation optical system 10 and condensing optical system 20 to detect the inclination angles θp and θr of the exposure area in two directions (P-axis and R-axis directions).
The inclination of the exposure area with respect to the imaging plane of the projection lens is determined. Therefore, as is clear from the above equations (3) to (6), the numerical aperture NAp in the p direction in the four-division light receiving element 22 is
The numerical aperture NAr in the r direction increases with respect to 0, and the depth of focus FDr becomes shallower than the depth of focus FDp.
For example, the general design value of such a device, the detection area D
Radius of a = 7.5 mm, focal length f of condensing optical system 20
= 100 mm, center wavelength λ = 800 nm, and angle θ5 = 20° between the parallel light flux and the exposure area surface, and the numerical aperture NAp, N
When calculating Ar, -NAp=0.026, NAr=0
．． It becomes 075.

Similarly, depth of focus FDp, FDr is FDI) = ±608
μm5FDr'=−±71 μm. From this result, the depth of focus FD in the r direction is smaller than the depth of focus FDp in the p direction.
It can be seen that r becomes very shallow.

As a result, it becomes difficult to focus the four-divided light receiving element 22 in the r direction, and it takes time to focus the light receiving element when starting up the apparatus. Furthermore, when detecting the inclination of the exposure area where the reflectance distribution is caused by the circuit pattern formed on the exposure area, that is, the inclination angles θp and θr of the exposure area in the P and R axis directions, the 4-split light receiving element 22 If defocus remains, the light amount distribution at the four-part light receiving element 22 fluctuates, resulting in a detection error, which poses a problem in that the tilt of the exposure area cannot be detected with high precision.

In addition, when detecting the inclination of an exposure area with equal inclination angles in the P-axis and R-axis directions, if the angle θS formed by the parallel light beam with the exposure area surface is θ5=20° in equations (1) and (2), then ,
The ratio of the displacement amount of the focal point in the p direction and the r direction in the four-division light receiving element 22 is ΔP:ΔR=1:0.34. In other words, the amount of displacement ΔR of the focal point in the r direction is the displacement ΔR in the p direction.
There was also a problem that it was smaller than P and had low detection sensitivity in the r direction.

The present invention has been made in consideration of the above points, and it is possible to easily focus the light receiving element of the condensing optical system, have good detection sensitivity, and accurately position the horizontal position of a test object such as a wafer. The objective is to obtain a horizontal position detection device that can detect

Means for Solving Problem C] In order to solve this problem, in the present invention, the leveling stage 2 is arranged perpendicularly to the optical axis AX of the projection lens 1.
The parallel light beam emitted from the diaphragm 13x as the first micro-aperture is transmitted to the exposure area Ea on the wafer W to be iii The first irradiation optical system 1 supplied from
0x and the exposure area E supplied from the first irradiation optical system 10x.
It has a first condensing optical system 20x that condenses the parallel light beam reflected by a onto a two-split light receiving element 22x as a first light receiving element, and the optical axis 10xa of the first irradiation optical system 10x and the first condensing optical system The optical axis 20xa of the light optical system 20x is the optical axis A of the projection lens 1.
a first horizontal position detection system 100x that is arranged symmetrically with respect to X and detects the inclination angle θX of the exposure area Ea in the X-axis direction (first direction) with respect to the reference plane F; A second irradiation optical system toy supplies the parallel light beam emitted from the second irradiation optical system toy from a direction oblique to the optical axis AX of the projection lens 1 via a field diaphragm 16y as a second field diaphragm, and a second irradiation optical system LOy. It has a second focusing optical system 20y that focuses the parallel light flux reflected by the exposure area Ea onto a two-split light receiving element 22y as a second light receiving element, and has an optical axis 10ya of the second irradiation optical system 10y and a second focusing optical system 20y. 2. A second horizontal position where the optical axis 20ya of the condensing optical system 20y is arranged symmetrically with respect to the optical axis AX of the projection lens 1, and the inclination angle θy of the exposure area EaOY axis direction (second direction) with respect to the reference plane F is detected. The detection system 100y; the reference plane is determined based on the inclination angle θX in the X-axis direction detected by the first horizontal position detection system 100x and the inclination angle θy in the Y-axis direction detected by the second horizontal position detection system 100y. F, that is, a control device 31 as a calculation means for calculating the inclination of the exposure area Ea with respect to the imaging plane IM of the projection lens 1 is provided.

[Operation] In the present invention, in the light-receiving surface of the light-receiving element constituting the condensing optical system, the direction along the line of intersection between this light-receiving surface and the incident surface of the horizontal position detection system is the direction perpendicular to this line of intersection. By using the fact that the numerical aperture is smaller and the displacement of the focusing point is larger, in other words, the depth of focus is deeper and the detection sensitivity is higher, two sets of horizontal position detection systems consisting of an irradiation optical system and a focusing optical system are used. A coordinate system is provided along the XYOX and Y axes, and the inclination angle of the exposure area in the X and Y axes is always detected in the direction along the intersection line of each light receiving element. Therefore, the light-receiving element can be easily focused in the direction with a large numerical aperture (direction perpendicular to the intersection line), and the tilt angle of the exposure area can be detected in the light-receiving element in the direction perpendicular to the intersection line. Therefore, the detection sensitivity of the light-receiving element can be substantially increased, and detection errors due to defocus can be prevented.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings. 1st
1 is a diagram showing a schematic configuration of a stepper equipped with a horizontal position detecting device according to a first embodiment of the present invention, and FIG. 2 is a diagram showing a schematic arrangement of a horizontal position detecting device provided in a stepper. be. Regarding the configuration of this stepper, for example, the applicant of the present application has previously applied for Japanese Patent Application Laid-Open No. 60-130742.
Since it is disclosed in the publication, it will be briefly explained here.

Incidentally, members having the same functions and actions as those of the conventional device are given the same reference numerals.

In FIGS. 1 and 2, illumination light of a wavelength (exposure wavelength) that exposes the resist, which is generated by an illumination optical system (not shown), illuminates the pattern area Pa of the reticle R with uniform illuminance. A projection lens 1 having an optical axis AX perpendicular to the XY movement plane (coordinate system XY) of the wafer W and having a telescopic link on both sides or on one side reduces the image of the pattern formed on the reticle R by 115 or 1/10. , this projected image is formed on the imaging plane IM of the projection lens 1. This imaging plane IM is different from a predetermined reference plane F (parallel to the coordinate system XY). Note that the projection lens 1 used in this example
Both the reticle R1 and the wafer W side are telescend link optical systems. Now, the wafer W to be exposed is held on a tilting stage (hereinafter referred to as a leveling stage) 2 which can be tilted in any direction with respect to a reference plane F via a wafer holder (θ table) not shown. . Here, the structure of the leveling stage 2 is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 62-274201, which was previously filed by the applicant of the present application, so the explanation will be omitted. The leveling stage is tilted in an arbitrary direction with respect to the reference plane F by means of driving each of the operating points ) in the Z direction. When the driving point of this driving means is in a predetermined neutral state (for example, a state in which the three operating points are at the center of the movement stroke in the X direction), the operating point is configured to be located approximately within the reference plane F. , the amount of lateral shift of the wafer W when the wafer W is tilted can be reduced to a practically negligible extent. In addition, FIG. 2 shows driving parts 32 a, 32 b, and 32 c arranged on the Z stage 3 at an angle of about 120° with respect to the wafer mounting center of the leveling stage 2, and a circle at a certain distance from the wafer mounting center. Only the operating points OA, OB, and Oc of each drive unit 32a, 32b, and 32c located on the circumference CC are shown. In addition, drive parts 32a, 32b, 32C
are hereinafter collectively referred to as the drive device, and in Fig. 1, the drive device 3
It is shown as 2. This leveling stage 2 is provided on a Z stage 3, and the Z stage 3 is provided on an XY stage 4 that moves in the X and Y directions along a reference plane F. Z stage 3 is X-Y stage 4
It is configured to move only in the direction (optical axis AX direction),
At the end of this Z stage 3, a plane mirror 6X is provided for a light wave interference length measuring device (hereinafter referred to as a laser interferometer) 5 that detects the position (X coordinate value) of the X-Y stage 4 in the X direction. ing. Similarly, the position of the X-Y stage 4 in the Y direction (
Although a laser interferometer and a plane mirror for detecting the Y coordinate value) are also provided, only the plane mirror 6y is shown in FIG.
X-Y stage 4 measured by this laser interferometer
The X and Y coordinate values of are sent to the central processing unit 7. Necessary data such as the diameter of the wafer W and the arrangement map of the exposure area Ea on the wafer W are set in advance in the central processing unit 7, and an appropriate field of view is set based on the position of the exposure area Ea on the wafer W. The aperture is selected and the information is output to the control device 8.

Now, a collimator type first horizontal position detection system 10 consisting of an irradiation optical system 10x and a condensing optical system 20x shown in FIG.
0x is such that the optical axes 10xa and 20xa of both optical systems are arranged symmetrically with respect to the optical axis AX of the projection lens l, and the entrance plane Px of the horizontal position detection system 100x (optical axes 10xa and zoXa
, AX) is provided so that it is parallel to the XYOX axis of the coordinate system. As shown in Figure 1, the irradiation optical system 1
0X indicates a light source 11x, a condenser lens 12x1, an aperture 13x having a minute circular aperture, a mirror 14x, a first relay lens 15x, a field diaphragm 16x1 for arbitrarily setting the shape of the detection area Da, a second relay lens 17x, and an irradiation objective lens 18x. It consists of This irradiation optical system fo
At x, the image of the light source 11x is the condenser lens 12
x is formed on the aperture 13X, and a parallel light beam is supplied to the field aperture 16x by the first relay lens 15x having a focal point on the aperture 13x. Here, mirror 14
x plays the role of changing the optical path direction and is provided to reduce the lateral size of the optical system. Further, as the field diaphragm 16x, a temporary field diaphragm having a plurality of field diaphragms with different shapes or a variable diaphragm that applies the principle of a liquid crystal shutter is used, and the field diaphragm 16x can be changed depending on the shape of the exposure area Ea, etc. Change the shape and detect area D
The configuration is such that the shape of a can be arbitrarily set. In this embodiment, the driving means rotates the field diaphragm plate (not shown) based on the control signal from the control device 8, and sets the field diaphragm 1 to an optimum value according to the shape of the exposure area Ea.
6x is rotationally positioned at the aperture position. The second relay lens 17X and the irradiation objective lens 18x are arranged at positions such that the rear focus of the second relay lens 17x and the front focus of the irradiation objective lens 18x match, and a parallel light beam is also supplied onto the wafer W. It is now possible to do so.

Here, the imaging plane IM of the projection lens 1 and the field aperture 16x are in a conjugate position, and specifically, the field aperture 16x is located at the second
The irradiation objective lens 18x is arranged at the front focal position of the relay lens 17x, and the rear focal position of the irradiation objective lens 18x is located at the imaging plane I.
It is arranged to match M. In this case, if the second relay lens 17x and the irradiation objective lens 18x have the same focal length, the image of the field stop 16x will be formed on the imaging plane 1M at a ratio of 1:1. In addition, the irradiation optical system 10x
The light supplied from the wafer W has a wavelength distribution different from that of the exposure light in order not to expose the resist on the wafer W, and in this embodiment, polychromatic light is used to particularly reduce thin film interference caused by the resist. The condensing optical system 20x includes a light-receiving objective lens 21x and a light-receiving element 22x such as a two-part light-receiving element or a one-dimensional position detection element (PSD). The light flux supplied from the irradiation optical system 10x is applied to the wafer W.
The light is reflected by the upper exposure area Ea, and is focused by the light-receiving objective lens 21x onto a two-split light-receiving element 22x provided on the focal plane of the light-receiving objective lens 21x. When the inclination of the imaging plane TM of the reticle R formed by the projection lens 1 and the inclination of the upper surface of the wafer W match, the light beam from the irradiation optical system 10x is focused on the center position of the two-divided light-receiving element 22x. It is set in advance at a position where it will be illuminated.

Note that since the circuit pattern formed on the wafer W includes fine rectangular patterns formed with a certain degree of regularity, diffracted light may be generated in addition to the directly reflected light of the irradiation light beam. Therefore, although not particularly shown in this embodiment, in order to remove the diffracted light and reduce noise generation in the two-split light receiving element 22x, an opening is provided between the light receiving objective lens 21x and the two-split light receiving element 22X. An aperture and a condenser lens may be provided.

In addition, as shown in FIG. 2, a second horizontal position detection system 100y
consists of an irradiation optical system 10y and a condensing optical system 20y, and the optical axes 10ya and 20ya of both optical systems are the optical axis A of the projection lens 1.
This horizontal position detection system 100 is arranged symmetrically with respect to X.
The y-incident plane Py (a plane including the optical axes 10ya, 20ya, and AX) is provided so as to be parallel to the Y-axis of the coordinate system XY.

Note that the irradiation optical system toy and the condensing optical system 20y have the same configuration as the above-described irradiation optical system 10x and condensing optical system 20x, respectively, so the explanation thereof will be omitted.

Next, the operation of the apparatus configured as in this embodiment will be explained. In FIG. 1, first, the central processing unit 7 uses the laser interferometer 5 to detect the position of the exposure area Ea to be exposed on the wafer W in the X direction. Similarly, the position in the Y direction is also detected from a laser interferometer (not shown), and the shape of the exposure area Ea is determined based on the X and Y coordinate values and information such as the array map of the exposure area Ea that has been input in advance. , a second horizontal position detection system 100x according to the shape of the exposure area Ea.
, 100y, and select the optimum field apertures 16x, 16y. Next, the central processing unit 7 outputs this information to the control device B, and the control device 8 outputs a control signal to the drive device 9x. The drive device 9x rotates a field diaphragm plate (not shown) based on the control signal, and rotationally positions the selected field diaphragm 16x at the aperture position. Similarly, the second horizontal position detection system 10
Even at 0y, based on the control signal from the control device 8,
The selected field stop 16y is rotationally positioned at the aperture position. After setting the optimal field apertures of 16x and 16y,
The first and second horizontal position detection systems 100x and 100y each irradiate a parallel light beam onto the exposure area Ea, and
The parallel light beam reflected from a is divided into two light receiving elements 22x, 22
Receive light at y. Then, the two-split light receiving elements 22X, 22y
is a two-divided light receiving element 22x according to the inclination of the exposure area Ea,
Information on the displacement direction and amount of the focal point on 22y is output to the control device 31, respectively. Based on this information, the control device 31 adjusts the X-axis direction and Y-axis direction of the exposure area Ea with respect to the imaging plane IM.
The axial tilt angles θX and θy are detected. That is, the control device 31 calculates the tilt angles θX and θy using the above-mentioned 2(1) from the displacement position X and ΔY of the focal point detected by the two-split light receiving elements 22x and 22y. Next, the control device 3
1 generates control signals corresponding to the tilt angles θX and θy and outputs them to the drive device 32. The drive device 32 is connected to this control device 3.
The leveling stage 2 is moved in the X direction (optical axis AX direction) according to the control signal from 1, that is, the drive amount in the X direction of each drive unit 5.6.7 of the leveling stage 2 constituting the drive device 32. , the inclination of the exposure area Ea on the wafer W placed on the leveling stage 2 with respect to the back surface imaging plane IM is corrected. As a result, the exposure area Ea accurately matches the imaging plane IM (reference plane F) of the back surface projection lens 1, preventing defocus, etc., and achieving high precision throughout the entire exposure area Ea ((
high resolution) exposure can be performed.

Here, in the above embodiment, the tilt of the exposure area Ea is corrected using control signals corresponding to the tilt angles θX and θy of the exposure area Ea with respect to the imaging plane IM.

However, the tilt angles θχ, θy calculated from the displacements ΔX, ΔY of the focal point using 2(1), and θX−θ' cos
If the azimuth angle ψ and the angle θ are determined from the relational expression ψ, θy=θ・sin ψ, the normal unit vector 5 representing the inclination direction of the exposure area Ea as shown in FIG. 7, that is, the exposure area Ea
The direction of inclination can be detected.

Thus, according to this embodiment, both the first and second horizontal position detection systems 100x and 1003' include the two-split light receiving element 22x,
22y, the amount of displacement of the focal point is detected only in the direction along the intersection line of the light receiving surface and the incident surface, and the exposure area EaOX axis, Y
Since it is configured to calculate the tilt angles θX and θy in the axial direction, it is possible to easily focus the two-split light-receiving elements 22x and 22y, preventing detection errors due to defocus, and increasing the It is possible to accurately correct the inclination of the exposure area Ba with respect to the imaging plane IM (reference element plane F).

As described above, in one embodiment of the present invention, the first horizontal position detection system 100x and the second horizontal position detection system 100y are provided along the coordinate system XYOX axis and Y axis direction, respectively, and the inclination angle θX of the exposure area Ea, Although the horizontal position detecting device used in this embodiment is configured to calculate θy, the horizontal position detecting device used in this embodiment is not limited to the above-described structure. 2 horizontal position detection system 100y
Two sets of horizontal position detection systems may be arranged so that the directions along the entrance plane py are different from each other and the optical axis AX of the projection lens 1 passes through the intersection thereof. For example, as shown in FIG. 3, it is assumed that the first horizontal position detection system 100x and the second horizontal position detection system 100y are arranged at positions rotated by ψ and ψ from the X axis, respectively. In addition, here the coordinate system XY
The direction along the incident plane Px is called the P axis direction, and the direction along the incident plane Py direction is called the P2 axis direction. in this case,
The light condensing points on the two-divided light receiving elements 22x and 22y are shifted from the center depending on the inclination of the exposure area Ea in the P, axial direction, and P2 axial direction. First, in the same operation as described above, the two-split light receiving elements 22x and 22y detect P1 and 8P2 as the displacement amount of the light converging point in the direction along the intersection line between the light receiving surface and the incident surface.

Then, the inclination angle θ of the exposure area Ea in the P1 axis and P2 axis directions
I, θ2 are calculated, and the inclination angles θX, θy in the X-axis and Y-axis directions of the exposure area Ea are calculated from the inclination angles θ1, θ2 using the following formula (9).
, (10).

Next, if the leveling stage 2 is driven in the direction of the optical axis AX of the projection lens 1 based on this tilt angle θx1θy,
Similarly to the embodiments described above, the inclination of the exposure area Ea with respect to the imaging plane IM of the projection lens 1 can be corrected. Alternatively, the inclination angles θX, θy and θ obtained from equations (9) and (10)
From the relational expression: By calculating θ, the direction of inclination of the exposure area Ea can be detected. Therefore, the 2m horizontal position detection system is
It is clear that the same effect as described above can be obtained without arranging them along the axis or perpendicularly to each other.

Furthermore, the first and second horizontal position detection systems 100x, 100y
When placing the
was calculated from the inclination angles θ1 and θ2 using equations (9) and (10). However, for example, as shown in Figure 3, the first
The light receiving surface 2 of the two-split light receiving element 22x shown in FIG.
The relative positional relationship between the dividing direction (S direction) of 2x' and the direction (T direction) along the line of intersection between the light receiving surface 22x' and the incident surface Px is changed (rotated). In this way, by adjusting the relative positional relationship between the S direction and the T direction according to the angle βX, the output information of the two-split light receiving element can be directly obtained without calculating the tilt angle θX in the X-axis direction from the tilt angle θ1. It is also possible to detect the tilt angle θX from . Similarly, in the second horizontal position detection system 100y, the dividing direction on the light receiving surface of the two-split light receiving element and the light receiving surface Change the relative positional relationship (rotation) with the direction along the intersection line between and the plane of incidence py
By doing so, the tilt angle θy can be detected without calculating the tilt angle θ2.

In addition, in this embodiment, a two-split light receiving element was used as the light receiving element of the condensing optical system, but by using a four-split light receiving element instead of this two-split light receiving element, the focusing of the light receiving element is performed. It is possible to prevent the focus shift in the exposure area Ea and improve the detection accuracy of the inclination of the exposure area Ea, that is, the inclination angles θX and θy of the exposure area Ea. Therefore, Figure 5 (
4 of the first horizontal position detection system 100x using a) and (b)
Focusing of the divided light receiving elements 22x1 will be briefly described. For example, as shown in FIG. 5(a), Y
A test object 40 is provided which includes a high reflectance region 40a and a low reflectance region 40b in the direction.

Then, the wafer W is moved in a direction perpendicular to the incident plane Px, that is, in the direction of the arrow in the figure (Y direction ). If there is a focus shift, the light receiving surface from the 4-split light receiving element 22x1 and the incident surface P
The output signal S1 in the direction perpendicular to the line of intersection with
) will result in a waveform with changes as shown in the figure. Therefore, until this output signal S1 becomes a waveform (output signal S2) with a change as shown in FIG.
By adjusting the position of 1, it becomes possible to focus the 4-split light receiving element 22x1 with high precision. still,
In the direction along the intersection line between the light receiving surface of the 4-divided light receiving element 22x1 and the incident surface Px, the exposure area Ea is similar to the above embodiment.
The tilt angle θX in the OX axis direction is detected. Also, the second
In the horizontal position detection system 100y, there is also a high reflectivity area 4 in the direction (X direction) perpendicular to the incident plane py on the wafer W.
0a and the low reflectance area 40b is moved, and the position of the four-division light-receiving element is adjusted based on the output signal in the direction perpendicular to the line of intersection on the four-division light-receiving element surface.
Similarly, it is possible to focus the four-split light receiving element with high precision. Here, focusing was carried out using a test object 40 having two regions 40a and 40b with different reflectances as shown in FIG. 5(a), but this type of test object For example, a wafer W can be used without using the object 40.
It is clear that if there is a region with a -like reflectance above, this region and its vicinity can be used to focus the four-division light-receiving element in a similar manner.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to easily focus the light-receiving element of the light-condensing optical system, thereby shortening the adjustment time of the light-collecting optical system. Without detecting the tilt of the exposure area in the direction perpendicular to the intersection line,
Since detection is always performed in the direction along the intersection line, the detection sensitivity of the light receiving element can be substantially increased, and detection errors due to focal points can be prevented. Furthermore, even if two sets of horizontal position detection systems are arranged in an arbitrary positional relationship depending on the space around the projection lens, the tilt of the exposure area can be detected without reducing detection accuracy, resulting in high precision. A horizontal position detection device capable of detecting the horizontal position of a test object such as a wafer can be realized.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a schematic configuration of a stepper equipped with a horizontal position detecting device according to a first embodiment of the present invention, FIG. 2 is a diagram showing a schematic arrangement of the horizontal position detecting device, and FIG. 4 is a diagram illustrating the horizontal position detection operation by two sets of horizontal position detection systems arranged in an arbitrary positional relationship, FIG. 4 is a diagram showing a schematic configuration of a two-split light receiving element, and FIG. 5 is a diagram used to explain the focusing operation of the horizontal position detection device.
Figure 5 (b) is a diagram showing the waveform of the output signal obtained from the light receiving element when focusing is performed, Figure 5 (C) is a diagram showing the waveform of the output signal obtained from the light receiving element when the focus is adjusted, Figure 6 is a schematic diagram for explaining the conventional horizontal position detection bag holder.
FIG. 7 is a diagram for explaining the operation of detecting the inclination direction of the exposure area. 1... Projection lens, 2... Leveling stage, 3
...Z stage, 4...x-y stage, 10x,
10y...Irradiation optical system, 20x, 20y...Condensing optical system, 31...Control device, 32...Drive device Applicant: Nippon Kogaku Kogyo Co., Ltd. Agent, Patent Attorney Takao Watanabe Figure 1 5°Y Figure 2 Figure 3 (L ×

Claims (1)

[Scope of Claims] A substantially parallel beam of light emitted from a first micro-aperture is directed to a predetermined area on a workpiece disposed substantially perpendicularly to the optical axis of the main objective lens through a first field stop. a first irradiation optical system that supplies light from an oblique direction with respect to the optical axis; and a first condensing optical system that focuses a parallel light beam supplied from the first irradiation optical system and reflected at the predetermined area onto a first light receiving element. system,
The optical axis of the first irradiation optical system and the optical axis of the first condensing optical system are arranged symmetrically with respect to the optical axis of the main objective lens,
a first horizontal position detection system that detects an inclination of the predetermined area with respect to a reference plane in a predetermined first direction; and a substantially parallel light beam emitted from a second minute aperture to the predetermined area through a second field diaphragm to the main objective lens. a second irradiation optical system that supplies the light from an oblique direction with respect to the optical axis of the second irradiation optical system; and a second condenser that condenses a parallel light beam supplied from the second irradiation optical system and reflected at the predetermined area onto a second light receiving element. an optical system, the optical axis of the second irradiation optical system and the optical axis of the second condensing optical system are arranged symmetrically with respect to the optical axis of the main objective lens, and a second horizontal position detection system that detects an inclination in a predetermined second direction different from the first direction; based on the inclination in the first direction and the inclination in the second direction; 1. A horizontal position detection device, comprising: arithmetic means for calculating the horizontal position of the