JPS6227613A - Position detector - Google Patents

Abstract

PURPOSE:To detect the position of a surface to be measured accurately, by the constitution, in which two luminous fluxes are projected on the surface to be measured through symmetrical light paths with respect to a specified plane and the reflected light beams of the two luminous fluxes from the surface to be measured are received. CONSTITUTION:Two luminous fluxes 1r and 1l intersect at the same point in a specified plane, which is approximately parallel with a surface to be measured 3. The luminous fluxes pass symmetrical light paths with respect to a line AX, which includes the same point and is vertical to the specified plane. One of the reflected light beams of the luminous fluxes 1r and 1l from the surface to be measured 3 is received by a first photoelectric detector 5r. The other reflected light beam from the surface to be measured 3 is received by a second photoelectric detector 5l. Based on the photoelectric outputs of both detectors 5r and 5l, the position signals of the surface to be measured 3 are outputted from position detecting circuits. The luminous fluxes 1r and 1l are projected in the slant directions on the surface to be measured 3. Therefore, the same effect is received from the surface to be measured 3. Thus the position can be accurately detected without the effect of the state of the surface to be measured 3 by using the position signals from the position detecting circuits.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention obliquely irradiates a surface to be measured with a light beam, receives reflected light from the surface to be measured, and detects the difference from the change in the receiving position of the reflected light. The present invention relates to a position detection device that detects the position of a surface to be measured in a direction substantially perpendicular to the surface, and is used for detecting the position of a surface to be measured in a microscope or the like.

(Background of the Invention) Conventionally, as this type of position detection device, there is one shown in FIG. 11, for example.

The conventional position detection device shown in FIG. The light is focused on the two-split photoelectric element 5 by the two-split photoelectric element 5, and each photoelectric element 5a of the two-split photoelectric element 5 is focused.

5b is input to the differential amplifier 6, and when the surface to be measured 3 is moved in the direction of the optical axis Ax of the objective lens 2, the focal point P moves along the straight line Lll. The device is configured to detect the matching/non-matching position of the surface to be measured 3 based on the movement of P.

In this position detection device, when the surface to be measured 3 is moved in the direction of the optical axis Ax of the objective lens 2 and the surface to be measured 3 is at the in-focus position shown by the solid line in the figure, the focal point P is located at the center of the two-divided photoelectric element f5, that is, at the boundary between the photoelectric elements 5a and 5b, and when the surface to be measured 3 is at the dotted line position 3', the condensing point P is located at the point P', so the Depending on the position of the surface 3, an output signal as shown in FIG. 12 is obtained from the differential amplifier 6. Here, in FIG. 12, the horizontal axis represents the position Z of the surface to be measured 3, and the vertical axis represents the differential amplifier 6.
represents the output signal V of .

Therefore, when the output signal of the differential amplifier 6 is zero, it can be determined that the surface to be measured 3 is in the focused position as shown by the solid line in FIG. The direction in which the measurement surface 3 is deviated from the in-focus position can be determined.

However, in such conventional position detection devices, (
1) As shown in FIG. 13(a), when the light beam l hits the edge of the pattern PT formed on the surface to be measured 3, the pattern FT surface and the surface to be measured 3 have different reflectances. Therefore, even if the surface to be measured 3 is at the focus position indicated by L,
As shown in FIG. 14(a), even when the focal point P is located at the center of the two-split photoelectric element f5, the output signal from the differential amplifier 6 does not become zero, and a large position detection (2) As shown in FIG. 13(b), if a thin resist R is applied to the surface to be measured 3I, and the light beam 1 hits the lens )R, the error will occur.
In this case, even if the surface to be measured 3 is at the focal position indicated by L, the focal point P as shown in FIG. is located at the center of the two-divided photoelement f5, the differential amplifier 6
(3) At a position where the surface to be measured 3 is deviated from the focus of the objective lens 2, as shown in FIG. 13(C), and the angle formed with the optical axis Ax of the objective lens 2 is a right angle (
If it is slightly tilted from the solid line (IE), the first
As shown in Fig. 4 (C), the position of the condensing point P in the two-split photoelectric element 5l shifts from the position of the solid line to the position of the broken line, so the correct output signal cannot be obtained from the differential amplifier 6. However, there is a problem in that position detection errors occur.

(Object of the Invention) The present invention has been made by focusing on such conventional problems, and provides a position detection device that can accurately detect the position of a surface to be measured without being affected by the state of the surface to be measured. is intended to provide.

(Summary of the Invention) The gist of the present invention for achieving the above object is to irradiate a surface to be measured with a light beam obliquely, receive reflected light from the surface to be measured, and detect changes in the receiving position of the reflected light. In a position detection device that detects the position of the surface to be measured in a direction substantially perpendicular to the surface to be measured, the surface of the surface to be measured intersects with the surface to be measured at the same point within a predetermined plane that is substantially parallel to the surface to be measured, and includes the same point and lies within the predetermined plane. an irradiation optical system that irradiates the surface to be measured from two directions with two light beams passing through symmetrical optical paths with respect to a perpendicular line;
a first photoelectric detector, one of which receives the reflected light reflected by the surface to be measured; a second photoelectric detector, the other of the two light fluxes receives the reflected light reflected by the surface to be measured; and a position detection circuit that outputs a position signal of the surface to be measured with respect to the predetermined plane based on the photoelectric outputs of the first and second photodetectors.

In the L position detection device, the two light beams obliquely enter the surface to be measured E through optical paths that are symmetrical with respect to a line perpendicular to the predetermined plane, and are subject to the same influence on the surface to be measured. According to the position signal from the position detection circuit, the position of the surface to be measured can be accurately detected without being affected by the state of the surface to be measured.

(Example) Hereinafter, each example of the present invention will be described based on the drawings. In addition, in the description of each embodiment, similar parts are given the same reference numerals, redundant descriptions are omitted.

1 to 7 show a first embodiment of the present invention,
FIG. 1 is a schematic layout diagram of an optical system showing a position detection device according to a first embodiment.

As shown in Figure i1, the half mirror 7 is placed at a symmetrical position with respect to the optical axis Ax of the objective lens 2! ; L, 7r are arranged, and the parallel incident light 1 is placed on the half mirrors 7fL, 7r.
1 and lr are respectively incident. Therefore, these two
Once the two incident lights are reflected, lr is reflected by the half mirrors 7fL and 7r so as to be parallel to the optical axis Ax, and the spot size is the same at the same point within a predetermined plane perpendicular to the optical axis Ax that includes the focal position of the objective lens 2. It is designed to focus light.

A surface to be measured 3 is arranged perpendicularly to the optical axis Ax, and the surface to be measured 3 is movable parallel to the optical axis Ax.

Here, an irradiation optical system that irradiates the measured surface 3 from two directions with two light beams passing through optical paths symmetrical with respect to the optical axis Ax (a line perpendicular to the predetermined plane) includes an objective lens 2, half mirrors 7g, 7r. It is made up of.

A diaphragm 8r is arranged at the pupil position of the objective lens 2 in order to block the scattered light from the surface to be measured 3 and to reduce the adverse effects of the scattered light on position detection. The aperture 8r,
The size of the 8th lens is set to just barely allow the regular reflection of the incident light IJ1.1r from three surfaces to be measured to pass through.

Behind the apertures 8 and 8r, there is a condenser lens 4J1.4 that condenses the reflected light from the surface to be measured 3 that has passed through the half mirrors 7 and 7r onto a two-split photoelement 7-51.5rL.
r is placed.

2-split photoelectric barley 7/5r has two photoelectric elements %50r, 51r
It consists of 2 photoelectric elements, and the 5 parts are also composed of 2 photoelectric elements.''
:f50fL, 51! It consists of l.

Each photoelectric output S1. S2 and each photoelectric output S4 from the 5-cross light 'rri of the 2-split photoelectric element, 50 elements, and 51 sentences
．． S3 is processed by the position detection circuit 20 shown in FIG.

The positive terminal of the subtracter 21 of the position detection circuit 20 shown in FIG. The photoelectric output S4 is input to - respectively. The photoelectric outputs S1 and S2 are input to an adder 23, and the photoelectric outputs S3 and S4 are input to an adder 24, respectively.

The output terminal T of the subtracter 21 is connected to the numerator side terminal of the divider 25, the output terminal of the adder 23 is connected to the denominator side terminal of the divider 25, and the output terminal of the subtractor 22 is connected to the numerator side terminal of the divider 26. The output terminal f of the adder 24 is connected to the denominator side terminal of the divider 26, respectively.

The output terminal of the divider 25 and the output terminal of the divider 26 are connected to the input terminal of an adder 27, and the adder 27 outputs a position signal S representing the position of the surface to be measured 3. It is made up like this.

In the position detection device of the first embodiment having the above configuration, the incident light 1! ; L and 1r are reflected by the half mirrors 7fL and 7r, then focused by the objective lens 2, and irradiated onto the surface 3 to be measured.

After the incident light IJJ is reflected by the surface to be measured 3, it passes through the objective lens 2, the half mirror 7r, and the diaphragm 8, and is condensed onto two divided lights 1 and 5 by the single-step light lens 4.

In addition, most of the scattered light is eclipsed by the aperture 8, and is 2 minutes;
I haven't reached the 5th sentence of Koden Soryo (t/).

On the other hand, the incident light 1r is reflected by the surface to be measured 3 and then passes through the objective lens 2 and the half mirror 7.
r for 2 minutes; the light is focused on one photoelement 'f-5r. Note that most of the scattered light is filtered out by the aperture 8r and does not reach the two-split photoelectric element T-5r, so that the influence of the scattered light on position detection is reduced.

As shown by the solid line in FIG. 1, when the surface to be measured 3 is located on the predetermined plane (when the surface to be measured 3 is in the in-focus position), the incident light ti passes through the two-split photoelectric element 5. At the center of the intersection, the incident light 1r is focused on the center of the two-split photoelectric element 5r. The condensing positions of each of the incident lights 1 and 1r at this time are shown as condensing points P and Pr, respectively.

When the surface to be measured 3 is moved parallel to the optical axis Ax, the incident light I
L: Each condensing point of L and 1r is viewed in a straight line and moves on Lr. For example, as shown by the broken line in FIG. When the incident light 19,,lr+7) is located at P
l', Pr'.

In this way, depending on the position of the surface to be measured 3, the incident light 1M, 1r
The position of each condensing point of this incident light moves, and the way of photoelectric output according to the position of each condensing point of this incident light is divided into two photoelectric elements 5! ;
It is output from each photoelectric element of L and two-split photoelectric element 5r.

Each photoelectric output S1. from the photoelectric elements 50r, 51r of the two-divided photoelectric element 5r. S2 is sent to the subtracter 21 and adder 23 of the position detection circuit 2°, and the subtracter 21 receives the photoelectric output Sl
The adder 23 subtracts the photoelectric output s2 from the photoelectric output s1 to output a signal of (Sl-52), and the adder 23 adds the photoelectric output S2 to the photoelectric output Sl and outputs a signal of (St+52).

Each output signal from the subtracter 21 and adder 23 is sent to the divider 25.
The divider 25 converts the signal (Sl-32) into (S1
+52) signal, (Sl-32)/(S1+S
2) Outputs the signal.

On the other hand, photoelectric element 7-stx of 2-split photoelectric element 5fL, 50
Light from text'+t=outputs S3 and S4 are position detection circuit 20
The subtracter 22 subtracts the photoelectric output S3 from the photoelectric output S4 to obtain (S4-S3).
), and the adder 24 adds the photoelectric output s3 to the photoelectric output S4 to output a signal (S4+33).

Subtractor 22. Each output from the adder 24 is sent to the divider 26, and the divider 26 converts the signal (S4-53) into (S4+3
3) (7) Divide by the signal, (s4-S3)/(S4+5
Output the signal of 3).

Each output signal from the divider 25 and the divider 26 is sent to the adder 27.
The adder 27 adds the signals of both people and obtains the first l signal S (S= (Sl-52)/(S1+S2)+
(S4-S3)/(S4+83)) is output.

The output waveform of this position signal S is L as shown in FIG.
This is similar to the conventional example described above, and the position of the surface to be measured 3 can be detected using this position signal S. That is, when the surface to be measured 3 is at the focal position, the position signal S becomes zero, so the surface to be measured 3 is adjusted so that the position signal S becomes zero.
What is necessary is to move it toward the optical axis Ax.

Note that this position signal S is the sum of the output signals from the divider 25 and the divider 26, as described above.
This position signal S has better sensitivity than that of the conventional example.

Furthermore, the divider 25 converts (Sl-32) into (S1+
32) and normalize it by dividing (S4-53) by (S4+33) in the divider 26, so even if the reflectance of the surface to be measured 3 differs, the position detection accuracy will vary. There isn't.

Furthermore, even if the intensities of the two incident lights 11 and lr are different, and even if the sensitivity characteristics of the two-split photoelectric element 5r and the five-crossing are different, the position detection accuracy will not vary. As shown in FIG. 3, when the surface to be measured 3 on which the pattern FT is formed is moved in the direction of the arrow in the figure, the surface to be measured 3 at one focal position moves in the direction of the arrow in the figure, so that the incident light 11, lr is focused on the edge of the pattern FT. Part 1 of G.
The operation of the embodiment will be explained. Here, it is assumed that the reflectance of the pattern FT surface and the surface to be measured 3 are different, and the thickness of the pattern FT is smaller by F than the depth of focus of the incident lights 1M and 1r.

FIG. 3 shows a case where the focal point of the incident light IJIL, lr hits the edge portion of the pattern FT, and the incident light IJIL, lr has a large spot size which is also the focal point. Therefore, when the incident light beam 11.1r hits the edge portion of the pattern FT at its focal position as shown in FIG. 3, the focal point Pr of the incident light beams 1r and 11.

As shown in FIGS. 4(a) and 4(b), Pl is located in the center of the 2-split photoelectric element 5r and the 2-split photoelectric element 5, but the photoelectric element 7-5 Or of the 2-split photoelectric element 5r The photoelectric element T-51 of the two-split photoelectric element 'f51 receives the reflected light from the pattern FT, and the photoelectric element 51r of the two-split photoelectric element 5r and the photoelectric element 50fL of the two-split photoelectric element f5 receive the reflected light from the pattern FT. The reflected light from the surface to be measured 3 itself, which is on the r ground, is received.

Therefore, even though the surface to be measured 3 is in the focused position and the condensing points Pr and PR are located at the center of the two-split beam 'iTi, element') 5r and the two-split photoelectric element) 51, , due to the difference in reflectance between the pattern FT and the surface to be measured 3, the photoelectric output S
1 and the photoelectric output S2 are different, and the photoelectric output S3 and the photoelectric output S4 are different.

Therefore, the output signals from the divider 251 and the divider 26 when the surface to be measured 3 moves in the X direction shown by the arrow in FIG.
3)/(S4+53) changes as shown in FIGS. 5(a) and (b). Here, the horizontal axis represents the position of the Δ14 constant surface 3, and when the edge portion of the pattern PT on the surface to be measured 3L hits the focal point of the incident light 1r, the divider 25, In each output signal of the divider 26, angular disturbances protruding in mutually opposite directions occur. FIGS. 4(a) and (b) are similar to those in FIGS. 5(a) and (b), respectively. This corresponds to the apex portion (edge position Xi) of the angular disturbance.

However, since the respective output signals of the divider 25 and the divider 26 are added by the adder 27, the device signal S composed of the adder 27 is generated in such a way that the disturbances in the color scheme cancel each other out. As shown in Figure 5 (C), a stable signal with no disturbances is obtained.

The level difference (deviation voltage Vp) of the output signal S in the figure corresponds to the thickness of the putter 7FT on the surface to be measured 37.

Therefore, in the position detection device having the configuration L, the incident light 1! Even if the focus of L and lr hits the edge portion of pattern FT, the position of 1 m3 to be measured can be detected without error.

In addition, as shown in FIG. 13(b), using the surface to be measured 3 coated with a thin resist R, the focus of the incident light 1, 1r was on the resist R, as in the case shown in FIG. In this case, there is a risk that the unevenness of the thickness of the lens (R) may cause a wavy stitch.

In this case as well, for the same reason as when the focal points of the incident light beams 1u and 1r hit the edge portion of the pattern FT, the device signal S composed of the adder 27 is stable without disturbance in the form of a diagonal. This becomes a signal, and the position of the surface to be measured 3 can be detected without error.

Next, as shown in FIG. 6, the surface to be measured 3 is at a position shifted from the focal position of the objective lens 2, and the angle formed with the optical axis Ax of the objective lens 2 is a right angle (a state shown by a solid line 8). ) at a position indicated by a dashed line that is slightly inclined.

In this case, as shown in FIG. 7(a), the focal point of the incident light 1r formed on the two-split photoelectric elements 5r and 31 is shifted from the actual position Pr shown by the solid line to the dotted line position Pr''. As shown in FIG. 7(b), the convergence point of one incident light formed when looking at the two-split photoelectric element 5 is also shifted from the actual position PM shown by the solid line to the dotted line. It shifts upward to position PM''.

Here, the condensing point Pr of the incident light 1r and the condensing point PH of the incident light 1 are both shifted upward, and the displacement amount Δr of the condensing point Pr and the displacement amount Δ of the condensing point 2 are The intersections are almost equal.

Therefore, the output signal from the divider 25 (Sl-S
2) the maximum deviation Δr included in /(S1+S2);
Output signal from the divider 26 (S4-53)/(S
4+53), the signs are opposite to each other, so the adder 27 is connected to the divider 2.
By adding the output signals from the 51 divider 26, the deviation ¥-Δr and the deviation amount Δ are canceled out, and the position signal S from the adder 27 includes an error component due to the tilt of the surface to be measured 3. This does not cause a large error in detecting the position of the +1+11 target 3. In addition, since the reflected light flux passing through the pupil plane changes its position on the pupil plane depending on the inclination of the surface to be measured 3, the apertures 8r and 81 are opened in accordance with the change so as not to receive the reflected light flux. , with a slightly larger diameter.

Note that in the first embodiment, the Jllll constant surface 3 is aligned with the optical axis A.
The surface to be measured 3 is positioned at the in-focus position by moving the object surface 3 downward to It may be configured so that the surface 3 is positioned at the in-focus position, and this also applies to each actual flow side described later.

Furthermore, in this first embodiment, the incident light 1r.

It is preferable that the amount of light (light intensity) in one sentence is the same.
Even if there is a difference in the amount of incident light 1r and IJl, it does not pose a problem because AGC is applied by the divider of the circuit shown in FIG.

Next, a second embodiment of the present invention will be described based on FIG. FIG. 8 is a schematic layout diagram of an optical system showing a position detection device according to a second embodiment.

The position detection device shown in FIG. 8 uses a laser beam 90 from a laser light source 9 as the incident light irradiated onto the surface to be measured 3, and the laser beam 90 is divided into two laser beams 9041 by a half mirror 10. It is separated into .9Or. Note that for convenience of drawing, all beams in the figure show only principal rays.

In the reflected optical path of the half mirror 1O, a laser beam 9
A mirror 11 that reflects the light 0r toward the objective lens 2 is arranged parallel to the optical axis Ax. Half mirror 10
Mirrors 12 and 13 are arranged in the transmission optical path of the mirror 12 and 13 to reflect the laser beam 90 symmetrically with the laser beam 90r with respect to the optical axis Ax and toward the objective lens 2 .

Therefore, this two-tree laser beam 90 sentences, 90r
The two incident lights are condensed at the same point within a predetermined plane perpendicular to the optical axis Ax including the focal position of the objective lens 2, as in the case of the two incident lights, lr, in the first embodiment. There is.

Here, the surface to be measured 3 is 2
An irradiation optical system that emits light from a direction includes an objective lens 2. Racer light source9. It is composed of a half mirror 10 and mirrors 11-13.

The laser beams 90 and 90r reflected by the surface to be measured 3 are reflected by the half mirrors 7 and 7r, and then split into two photoelectric elements 5 and 5r by condenser lenses 4fL and 4r. It is designed so that the light is focused on the

As in the case of the first embodiment, the two-split photoelectric element f5
Each photoelectric output S1.r from the photoelectric elements 50r, 51r. S
2 and 2 split photoelectric elements 5 standing photoelectric elements 50 sentences, 519
．． The photoelectric outputs S4 and S3 are processed by a position detection circuit 20 shown in FIG.

In the position detection device having the above configuration, a laser beam 9 is emitted from the laser light source 9 parallel to the optical axis Ax as shown by the solid line.
When 0 is emitted, the laser beam 90 is separated by the half mirror 10 into a laser beam 90r and a laser beam 90fL. After being reflected by the mirror 11, the laser beam 90r travels parallel to the optical axis Ax, passes through the half mirror 7, and is focused by the objective lens 2 onto the surface to be measured 3F. On the other hand, a laser beam of 909° is
After being reflected by the mirrors 12 and 13, the beam proceeds symmetrically with the laser beam 90r with respect to the optical axis Ax, passes through the half mirror 7r, and is focused onto the surface to be measured 3 by the objective lens 2.

In FIG. 8, the surface to be measured 3 is at the focused position, so the laser beam 90r and the laser beam 90 are focused on the same point on the surface to be measured 3.

Each laser beam 90 r reflected by the surface to be measured 3,
90M passes through objective lens 2 and half mirrors 7r, 7
The light is reflected by the light beam, and is focused by the condensing lens 4r, 4 onto the two-split photoelectric elements 5r, 5. In the case shown in FIG. 8, since the surface to be measured 3 is in the focused position, each laser beam 90r.

90! 1 is condensed at the center of the two-split photoelectric element 'f5r, 5a, and each condensing point at this time is indicated by Pr and Pl.

Then, the photoelectric elements 50r, 5 of the two-split photoelectric element r5r
Each photoelectric output S1. S2 and each photoelectric output from the photoelectric element 50 and 51 of the two-split photoelectric element 5 S4.
S3 is processed by the position detection circuit 20 shown in FIG. 2, and the adder 27 outputs the position signal S.

Therefore, in this embodiment, as in the case of the first embodiment, even if the laser beams 90r and 90 cross each other and hit the edge portion of the pattern FT or the resist, or the surface to be measured 3 is in focus. Even if the measured surface 3 is deviated from the position and tilted from the position perpendicular to the optical axis Ax, the position of the measured surface 3 can be accurately determined without any error without being affected by the state of the measured surface 3. Can be detected.

Furthermore, when the emission angle of the laser beam 90 from the laser light source 9 changes slightly as shown by the broken line in the state shown in FIG. 8, the focal point Pr of the laser beam 90r on the two-split photoelectric element 5r The two-split photoelectric element'T
deviated by Δr' from the center of -5r, two-split photoelectric element 5
11. The condensing point 2 of the laser beam 90 in is also shifted by Δt' from the center of the two-divided photoelectric element 7-51.

These deviations Δr' and Δcross' are equal to the amount of deviation when the surface to be measured 3 moves in the direction of the optical axis Ax by fXO/2tanφ, and the former (Δr') means that the surface to be measured 3 is The latter direction (Δtext') corresponds to the case of movement toward the objective lens 2. Here, f is the focal length of the objective lens 2, θ is the change in the emission angle of the laser beam 90 by -1, and φ is the inclination of the laser beam 90r at the end of the surface 3 to be measured.

However, since the deviations Δr' and Δsentence' are equal, the adder 27 adds the output signals from the divider 255 and the divider 26, so that the difference gBΔr'2Δsentence' cancel each other out. , the position signal S from the adder 27 does not include error components attributable to the deviation amounts Δr' and Δr', and the position of the surface to be measured 3 can be detected without error.

Next, a third embodiment of the present invention will be described based on FIG.

In the position detection device shown in FIG.
The light enters the objective lens 2 in a direction along the optical axis Ax via the half mirrors 15 and 16, is condensed by the objective lens 2, and enters the surface to be measured 3. The half mirror
Between the condenser lens 16 and the condenser lens 4r, the condenser lens 17
．． 18 are arranged. A diaphragm 19 is arranged at a position conjugate with the pupil position of the objective lens 2 with respect to the condenser lens 17 .

The diaphragm 19 has apertures 19r and 19vertical openings located at symmetrical positions with respect to the optical axis Ax.

An irradiation optical system that irradiates the surface to be measured 3 from two directions with two light beams passing through optical paths symmetrical with respect to the optical axis Ax (a line perpendicular to the predetermined plane) includes an objective lens 2, parallel light 14, and a half mirror 16. It is configured.

In the position detection device of the third embodiment having the above configuration, the diaphragm 19 is arranged at a position conjugate with the pupil position of the objective lens 2, and the diaphragm 19 is located at the pupil position of the objective lens 2 with a diaphragm 19' indicated by a broken line. This is equivalent to placing 2. Openings 19r, 19 of the diaphragm 19 via the half mirror 16
The peripheral luminous flux that passed through fL is 3Or, only 30 parts are 5r, 5
The other light beams are rejected by the aperture 19. At this time, the openings 19r and 1941 are opened at symmetrical positions with respect to the optical axis Ax.

The peripheral light beams 30r and 301 pass through optical paths that are symmetrical with respect to the optical axis Ax.

Therefore, when the surface to be measured 3 is at the in-focus position shown by the solid line in FIG. 9, the surface to be measured 3 is 2 It is irradiated obliquely from the direction, and the peripheral luminous flux 3O
The reflected light of r, 301 is focused on the two-split photoelectric element 75r, 5.

The optical path when the surface 3 to be measured is at the dotted line position 3' in the figure is shown by the dotted line.

In this way, the position detection device of this embodiment irradiates the surface to be measured 3 from two directions with two light beams passing through symmetrical optical paths with respect to the optical axis Ax, as in the case of 51 and the second embodiment above. It is designed to do this.

Therefore, in this third embodiment, even if the peripheral light beams 30r, 301 hit the edge portions of the pattern FT or the resist, as in each of the above embodiments, even if the peripheral light beams 30r, 301 hit the edge portion of the pattern FT or the resist, The position of the surface to be measured 3 can be detected accurately without any error without being affected by the state of the surface. Also, even if the light beam 14 is slightly tilted as in the case of Fig. 8,
The effects of that slope cancel out.

It goes without saying that the aperture 19 removes the scattered light.

Further, in this embodiment, the light beam transmitted through the half mirror 16 is used as a signal for detecting the position of the surface to be measured 3.
The reflected light beam can be used for other signal processing purposes.

Next, a fourth embodiment of the present invention will be described based on FIG. This embodiment is applied to a reduction projection type exposure apparatus.

As shown in FIG. 1O, a surface to be measured 3 is arranged perpendicularly to the optical axis Ax of a reduction projection lens 31 of a reduction projection type exposure apparatus, and a position detection device for detecting the position of the surface to be measured 3 is as follows:
It consists of a pair of optical systems arranged symmetrically with respect to the optical axis Ax.

Each of the pairs of optical systems is a light source 32r.

32 sentences, lens 33r, 33 sentences, beam splitter 34
r, 34 views, objective lens 2r, 2g,, condensing lens 4r
, 4! j, and two-split photoelectric elements 5r and 5, respectively, and the light rays 4 from each of the pair of optical systems
Or, 40 yen is configured to pass through a symmetrical optical path with respect to the optical axis Ax.

The light beam 4Or from the light source 32r is reflected by the surface to be measured 3, and then condensed onto the two-split photoelectric element 5 through the objective lens 2, the beam splitter 34, and the condenser lens 4L; The light beam 40fL from 32fL is on the surface to be measured 3.
After being reflected by the objective lens 2r, the beam splitter 3
4r, 2-split photoelectric element 7-5r via condensing lens 4r
It is designed so that the light is focused on the

Here, an irradiation optical system that irradiates the surface to be measured 3 from two directions with two light beams passing through optical paths symmetrical with respect to the optical axis Ax (a line perpendicular to the predetermined plane) includes objective lenses 2r and 2.
It is composed of a light source 32r, a lens 33r, a lens 33r, a beam lens 34r, and a beam lens 34r.

In this fourth embodiment, as in the above-mentioned embodiments, even if the light beams 4Or, 40 hit the edge portion of the pattern FT or the resist, or the surface to be measured 3 is at the focused position. The position of the surface to be measured 3 can be accurately detected without error even if the surface to be measured 3 is tilted from a position perpendicular to the optical axis Ax, without being affected by the state of the surface to be measured 3. .

Furthermore, in each of the above embodiments, one of the two light beams receives the reflected light reflected by the surface to be measured 3: the tSl photoelectric detector, and the other one receives the reflected light reflected by the surface to be measured 3. The second photoelectric detector is divided into two photoelectric elements-5r and 5.
However, as the first and second photoelectric detectors, linear sensors with continuous light receiving parts are used, and when each linear sensor receives reflected light at the center of its light receiving part, When zero photoelectric output is received at a position shifted to one side from the center, a positive photoelectric output corresponding to that position is received, and when light is received at a position shifted to the other side from the center, a positive photoelectric output corresponding to that position is received. It may be configured to emit negative photoelectric outputs, respectively, and further configured to add or subtract the photoelectric outputs from both linear sensors.

(Effects of the Invention) According to the position detection device according to the present invention, the two light beams obliquely enter the surface to be measured through optical paths that are symmetrical with respect to a line perpendicular to the predetermined plane. A position detection circuit outputs a position signal based on each light output from the first and second photoelectric detectors, which are subjected to the same influence on the surface and receive respective reflected lights of the two light beams from the surface to be measured. So,
The position signal allows the position of the surface to be measured to be accurately detected without being affected by the state of the surface to be measured.

[Brief explanation of drawings]

1 to 7 show a first embodiment of the present invention,
Figure 1 is a schematic layout diagram of the optical system showing the position detection device;
Figure 2 is a block diagram showing the position detection circuit, Figure 3 is an explanatory diagram showing a state in which two light beams hit the edge of a pattern, and Figure 4 (a) shows that one of the two light beams is
Explanatory diagram showing how light is focused on the split photoelectric element, 4th
Figure (b) is an explanatory diagram showing how the other of the two light beams is focused on the other two-split photoelectric element, and Figure 5 (a) is an explanatory diagram showing how the other of the two light beams is focused on the other two-split photoelectric element.
Figure 5(b) is a signal waveform diagram of the standardized signal from one of the two-split photoelectric elements when the surface to be measured is moved in the direction of the arrow in Figure 3. The signal waveform diagram of the standardized signal from the other two-split photoelectric element, FIG. 5(c), is shown in FIG.
A signal waveform diagram of the signal obtained by adding the signal in a) and the signal in FIG. Figure 7 (a) and (b) are explanatory diagrams of the optical path when the angle formed by the angle is slightly tilted from a right angle. FIG. 8 is a schematic layout diagram of the optical system showing the second embodiment of the present invention, and FIG. 9 is an explanatory diagram showing how the light is focused.
FIG. 10 is a schematic layout diagram of the optical system showing the S3 embodiment, and FIG. 10 is a schematic layout diagram of the optical system showing the :54 embodiment of the present invention.
11 to 14 show a conventional example, in which FIG. 11 is a schematic layout diagram of an optical system showing a position detection device, and FIG.
The figure is a waveform diagram of the output signal, FIG. 13(a) is an explanatory diagram showing how the light beam hits the edge part of the pattern,
Figure 3 (b) is an explanatory diagram showing how the light beam is reflected on a thin resist, and Figure 13 (c) shows that the surface to be measured is at a position shifted from the focal position of the objective lens, and the optical axis of the objective lens is 14 (a), (b), (c)
) are shown in Figures 13(a) and (b). (c), respectively, and is an explanatory diagram showing Y- in which the light beam is focused on the two-split charging element. lr, LfL...Two incident lights (two luminous fluxes) 90r
, 90! Q.--2 (7) L/- laser beam (2 luminous fluxes) 3Or, 301...2 peripheral luminous fluxes (2 luminous fluxes)
40r, 40fL-・Two rays (two luminous fluxes) Ax・
... Optical axis (line perpendicular to a predetermined plane) 3 ... Surface to be measured 5r ... Two-split photoelectric element (first photoelectric detector) Fig. 1 Fig. Nz Fig. δ Fig. C Fig. N7 Fig. 3 Figure 11V Figure 1Z Figure 13 Figure 14

Claims (1)

[Scope of Claims] A light beam is irradiated obliquely onto the surface to be measured, the reflected light from the surface is received, and from a change in the receiving position of the reflected light, the surface of the measured surface is irradiated with a light beam in a direction substantially perpendicular to the surface to be measured. In a position detection device that detects the position of a measurement surface, two light beams intersect at the same point in a predetermined plane substantially parallel to the surface to be measured, and pass through optical paths that are symmetrical with respect to a line that includes the same point and is perpendicular to the predetermined plane. an irradiation optical system that irradiates the surface to be measured from two directions, a first photoelectric detector that receives reflected light in which one of the two light beams is reflected by the surface to be measured, and the other of the two light beams a second photoelectric detector that receives reflected light reflected by the surface to be measured; and outputting a position signal of the surface to be measured with respect to the predetermined plane based on each photoelectric output of the first and second photoelectric detectors. A position detection device comprising: a position detection circuit.