JP3360321B2 - Surface position detecting apparatus and method, and exposure apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface position detecting device, and more particularly, to a surface position detecting device for detecting a position of a wafer in a semiconductor manufacturing apparatus.

[0002]

2. Description of the Related Art In a semiconductor exposure apparatus for transferring a circuit pattern formed on a reticle onto a wafer via a projection lens, the depth of focus of the projection lens is relatively shallow, and the wafer has partial irregularities. Because
It is necessary to correct the defocus of the projection lens in each exposure area of the wafer.

At this time, as a device for detecting a wafer position in the optical axis direction of a projection lens, for example, an image of a slit is projected from an oblique direction to a surface to be inspected such as a wafer, and the image of the slit is projected from an oblique direction. An oblique incidence type autofocus sensor for detecting is known. In this oblique incidence type autofocus sensor, the surface to be inspected (wafer)
Is moved up and down along the optical axis direction of the projection lens, the position of the image of the slit on the surface to be measured is shifted in a direction orthogonal to the oblique direction. Then, by measuring the amount of the shift, the position in the vertical direction (normal direction of the test surface) of the test surface can be detected.

[0004]

However, the above-described conventional detection apparatus cannot simultaneously detect the position in the vertical direction in a wide area on the surface to be detected. In recent years, with the increasing integration of LSIs, it has been desired to transfer a finer pattern to each exposure area (shot area) on a wafer. The numerical aperture (NA) of the projection lens that forms an image thereon is increased. When the numerical aperture of the projection lens increases, the depth of focus of the projection lens decreases. Therefore, it is desired to position each exposure area more accurately and reliably within the depth of focus of the projection lens.

Further, when exposing a plurality of LSI chips collectively, and when changing the size of the LSI chips to be exposed (the size of the exposure area), the position of the LSI chip at an appropriate position on the surface to be detected is to be detected as it is. Irradiation light for detection is not applied, and to perform accurate position detection, it is necessary to change the position of the irradiation light. At this time, it is conceivable to project a slit-like luminous flux at a necessary location and to sequentially move the stage on which the wafer is mounted to a required detection location, but the time required for position detection becomes longer and throughput is reduced. There is a problem that decreases.

Therefore, the present invention can simultaneously and accurately detect the vertical position (normal direction of the test surface) at a plurality of positions on the test surface without lowering the throughput. An object is to simplify an optical system.

[0007]

In order to achieve the above object, the present invention relates to a surface position detecting device for detecting a surface position of a surface to be inspected as shown in FIG. A predetermined pattern formed on the target surface, a projection optical system that projects an image of the predetermined pattern from an oblique direction to the test surface, and a light beam reflected on the test surface to condense the predetermined A condensing optical system that forms an image of a pattern on a second surface, and a relay that is disposed in an optical path between the second surface and the third surface and conjugates the second surface and the third surface. An optical system, a deflecting optical system provided on the second surface for deflecting a light beam emitted from the condensing optical system, and arranged on the third surface to photoelectrically detect an image of the predetermined pattern. A detector, wherein the first surface and the surface to be detected are symmetrical with respect to a main plane of the projection optical system. And the test surface and the second surface satisfy the Scheimpflug condition with respect to the main plane of the light-collecting optical system, and the second surface and the third surface meet the relay optical system. Satisfies the Scheimpflug condition with respect to the main plane, the condensing optical system is a double-sided telecentric optical system arranged on one optical axis, and the relay optical system is arranged on the one optical axis It is configured as follows.

In this case, as shown in FIG. 9, for an optical system that forms a pattern on the surface A on the surface B, it is more accurate that the surfaces A and B satisfy the Scheimpflug condition. In the meridional section of this optical system, the intersection of the extension line on plane A with the object-side principal plane of the optical system is H, the extension line of plane B and the image-side principal plane of the optical system. When the intersection with H is defined as H ′, it means that the distance L from the intersection H to the optical axis is equal to the distance L ′ from the intersection H ′ to the optical axis. When the Scheimpflug condition is satisfied, a so-called tilt image relationship is established,
Light beams emitted from arbitrary points on the plane converge on corresponding points on the plane B, respectively. Therefore, an image of the entire point on the surface A is formed on the surface B.

According to another aspect of the present invention, there is provided a surface position detecting method for detecting a surface position of a surface to be inspected, as shown in FIG. Projecting an image of a predetermined pattern formed on the surface from an oblique direction with respect to the surface to be inspected, and condensing a light beam reflected by the surface to be inspected through a condensing optical system, and Forming an image of the pattern on the second surface, deflecting a light beam emitted from the condensing optical system, and forming the predetermined pattern formed on the second surface via a relay optical system. Re-imaging the image on the third surface, and photoelectrically detecting the image of the predetermined pattern using a detector arranged on the third surface, wherein the first surface The surface to be measured satisfies the Scheimpflug condition with respect to the main plane of the projection optical system, The test surface and the second surface satisfy the Scheimpflug condition with respect to the main plane of the condensing optical system, and the second surface and the third surface satisfy the Scheimpflug condition with respect to the main plane of the relay optical system. Are satisfied, a plurality of light beams are emitted from a predetermined pattern on the first surface, the plurality of light beams reach the surface to be inspected, and the plurality of light beams reflected by the surface to be inspected are 1 The condensing optical system, which is a double-sided telecentric optical system arranged on two optical axes,
And reaching the detector via a relay optical system arranged on the one optical axis.

[0010]

As described above, according to the surface position detecting device of the present invention, the first surface and the test surface satisfy the so-called tilt image forming relationship, and the test surface and the second surface are tilted. Since the imaging relationship is satisfied, each point on the entire surface of the test surface forms an image on the second surface. In this case, since the projection optical system projects an image of a predetermined pattern from an oblique direction with respect to the surface to be inspected, if the surface to be inspected partially has irregularities, the image on the second surface is A distortion (displacement) corresponding to the unevenness occurs. If this displacement is detected by, for example, the principle of the photoelectric microscope disclosed in Japanese Patent Application Laid-Open No. 56-42205, it is possible to obtain vertical position information of the surface to be inspected. The principle of the photoelectric microscope will be briefly described. First, the light receiving surface and the second
The image on the surface is relatively scanned, and the light modulation at this time is detected on the light receiving surface. Then, when the optical modulation detected based on the scanning cycle is synchronously detected, a detection output corresponding to the positional deviation amount of the surface to be detected can be obtained.

Further, since the surface to be inspected and the second surface are in a tilted image forming relationship, the amount of lateral displacement on the second surface due to the vertical fluctuation of the surface to be inspected is smaller than the magnification relationship between the surfaces. growing. This will be described quantitatively. For example, as shown in FIG. 1, the incident angle of the projection optical system with respect to the test surface is θ, the vertical displacement of the test surface is z, and the tilt of the test surface to the second surface is along the imaging plane. Assuming that the imaging magnification is β ′, the lateral shift amount y ₁ on the second surface can be expressed by the following equation.

[0012]

Y ₁ = 2 · β ′ · tan θ · z (1) By the way, if the lateral magnification, which is the magnification in the direction perpendicular to the optical axis between the test surface and the second surface, is β, Scheimpflug The following relationship is established from the condition (1).

[0013]

Β ′ = (β ² cos ² θ + β ⁴ sin ² θ) ^1/2 ‥‥ (2) On the other hand, in the prior art disclosed in Japanese Patent Application Laid-Open No. 56-42205, for example, since the detection in a direction perpendicular to the optical axis, the lateral shift amount y ₂ to be detected is as follows.

[0014]

Y ₂ = 2 · β · sin θ · z ‥‥ (3) Here, when the expressions (1) and (2) are compared, the incident angle θ
Is the greater, the equation (1) is larger in the lateral deviation y ₁ in the case that satisfies the imaging relationship of the tilt. For simplicity, β
If = 1, β ′ = 1 from the equation (2), and the lateral displacement amounts y ₁ and y ₂ are proportional to tan θ and sin θ, respectively. For example, when θ = 80 °, according to equation (1), y
₁ = _11.3z, and becomes a y ₂ = 2.0z According to (3) below. Therefore, when the tilt image formation relationship is satisfied, the lateral shift is increased by 5.7 times, and the detection sensitivity and the detection accuracy with respect to the upper and lower sides of the test surface are improved.

In the present invention, when the angle of incidence θ on the surface to be inspected by the projection optical system is increased, the degree of change in the amount of lateral shift with respect to vertical displacement of the surface to be inspected increases.
Further detection accuracy can be improved. However, when the incident angle θ is large, the incident angle of the light beam incident on the second surface also becomes large. This means that, for example, when the light receiving surface of the detecting means is arranged on the second surface, surface reflection on the light receiving surface, blurring of the light beam, etc. occur, and the amount of light received on the light receiving surface is significantly reduced. is there. Therefore, by disposing a deflecting optical system such as a prism on the second surface, the optical axis of the condensing optical system is deflected. Accordingly, the incident angle of the light beam reaching the light receiving surface is reduced, and there is no possibility that the light receiving amount is reduced.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a surface position detecting device according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an example in which a surface position detecting device according to the present invention is applied to a projection exposure apparatus. In FIG. 1, the main illumination light from the main illumination light source 40 is:
A predetermined circuit pattern illuminates a reticle R provided on the surface. Then, the image of the reticle R is projected on the exposed surface 1a of the wafer 1 by the projection lens 5. This wafer 1
The holder 2 on which the wafer 1 is placed
In a plane perpendicular to the optical axis AX1, a slight rotation, and a movement in the direction (focusing direction) along the optical axis AX1. The holder 2 is supported by a holding mechanism 3 that supports the holder 2 at three support points that can move in the vertical direction. Then, the drive unit 4 causes the support point of the holding mechanism 3 to move in the vertical direction, and performs leveling (leveling) of the holder 2.

Here, a reticle is placed on the test surface 1a of the wafer 1.
In order to satisfactorily transfer the circuit pattern provided on R, for each exposure shot, the current exposure area of the test surface 1a is set within the range of the depth of focus of the projection lens 5 with respect to the imaging plane. There is a need. For this purpose, after accurately detecting the position of each point on the current exposure area of the test surface 1a in the direction of the optical axis AX1 of the projection lens 5, the test surface 1a is adjusted to the width of the depth of focus of the projection lens 5. The leveling of the holder 2 and the movement of the wafer 1 in the focusing direction may be performed so as to fall within the range.

An optical system and a processing system for detecting the current position of the exposure area on the surface 1a to be inspected will be described below. In FIG. 1, illumination light from a light source 6 that supplies white light having a wide wavelength width is converted into a substantially parallel light beam by a condenser lens 7 and enters a deflection prism 26. The deflection prism 26 deflects the substantially parallel light beam from the condenser lens 7 by refracting it. And this deflection prism
On the emission side 26, there is provided a transmission type lattice pattern plate 8 composed of a stripe pattern extending in the direction perpendicular to the plane of the drawing. The transmission type lattice pattern plate 8 is arranged such that the lattice pattern forming surface 8a provided with the transmission portions and the light shielding portions alternately is on the wafer 1a side. In addition, instead of the transmission type grating pattern, a reflection type diffraction grating having an uneven shape may be applied, and further, a reflection grating pattern in which reflection portions and non-reflection portions are alternately formed may be applied.

Here, the surface of the wafer 1 (the surface 1a to be inspected) is
Generally, the light source 6 is covered with a thin film such as a resist, so that the light source 6 is desirably a white light source having a wide wavelength width in order to reduce the influence of interference by the thin film. The light source
6 may be a light-emitting diode or the like that supplies light in a wavelength band where the photosensitivity to the resist is weak. The illumination light that has reached the grating pattern forming surface 8a passes through the grating pattern forming surface 8a and then is projected along an optical axis AX2 that intersects the optical axis AX1 of the projection lens 5 at an angle θ. The light enters the optical systems 9 and 10. These projection optical systems 9 and 10 are condensing lenses
9 and a projection objective lens 10, and the lattice pattern forming surface 8a and the test surface 1a are conjugated to each other. The grating pattern forming surface 8a and the test surface 1a are
Since the grid pattern 10 is arranged so as to satisfy the Scheimpflug condition, the grid pattern on the grid pattern forming surface 8a accurately forms an image over the entire surface to be measured 1a.

As shown by a dotted line in FIG. 2, the projection optical systems 9 and 10 composed of a condenser lens 9 and a projection objective lens 10 are so-called double-sided telecentric optical systems, The conjugate point on the forming surface 8a and the test surface 1a is
The magnification is the same over the entire surface. Therefore, since the lattice pattern forming surface 8a has an equidistant lattice pattern with the longitudinal direction in FIG. 1 as the longitudinal direction, the image formed on the test surface 1a is Is a grid-like pattern at equal intervals with the longitudinal direction as.

Returning to FIG. 1, the light projected on the test surface 1a is reflected by the test surface 1a and enters the light condensing optical systems 11 and 12. The condensing optical systems 11 and 12 are
It is composed of a preparative condenser lens 12, the optical axis AX3 ₁ on the incident side of the converging optical system 11, 12 with respect to the optical axis AX1 of the projection lens 5, the optical axis AX2 axisymmetrical projection optical system 9, 10 It is provided to be. In the optical path between the test surface 1a and the second surface 25a, there is provided a vibrating mirror 30 as a scanning means.
The light reaches the condenser lens 12 via 30. In this embodiment, the oscillating mirror 30 is disposed substantially on the pupil plane of the condenser optical systems 11 and 12.
It suffices if it is in the optical path between a.

When the test surface 1a coincides with the image forming surface of the projection lens 5, the incident surface 25a of the tilt correction prism 25 is placed on a conjugate surface of the test surface 1a by the condenser optical systems 11 and 12.
Are arranged to be located. At this time, the test surface 1a
Is reflected on the incident surface 25a of the tilt correction prism 25. A light receiving slit S as light blocking means is provided on the incident surface 25a. This receiving slit S
As shown in FIG. 3, for example, five openings Sa ₁ , Sa ₂ ,
_{Sa 3, Sa 4, Sa 5} ( hereinafter, Sa ₁ -SA ₅ abbreviated) is configured to have, the test surface through the focusing optical system 11 and 12
The reflected light from 1a, an opening Sa ₁ -SA ₅ of the receiving slit S
, And enters the tilt correction prism 25.

The number of openings Sa of the light receiving slit S corresponds to a detection point on the surface 1a to be detected. For example, the test surface in FIG.
As shown in the figure showing a state where the image 80a of the lattice pattern forming surface 8a is projected on 1a, a detection point (detection area) on the surface 1a to be detected
_{Da 1, Da 2, Da 3} , ( hereinafter abbreviated as _{Da 1 ~Da 5) Da 4,} Da 5 is
As shown in FIG. 3, five openings Sa ₁ to Sa of the light receiving slit S are formed.
Corresponds to Sa ₅ . Here, when it is desired to increase the number of detection points on the surface 1a to be inspected, it is only necessary to increase the number of the openings Sa. Therefore, even if the number of detection points is increased, the configuration does not become complicated. .

Further, the image forming surface of the projection lens 5 and the incident surface 25a of the tilt correction prism 25 are connected to the focusing optical systems 11 and 12 respectively.
Is configured to satisfy the Scheimpflug condition. Therefore, when the test surface 1a and the image forming surface coincide with each other, the image 80a of the lattice pattern on the test surface 1a is accurately re-imaged over the entire incident surface 25a. Also, as shown by the dotted line in FIG.
Is composed of a bilateral telecentric optical system,
Each point on the test surface 1a and the conjugate point on the prism entrance surface 25a have the same magnification over the entire surface. Therefore, when the surface 1a to be inspected coincides with the image plane of the projection lens 5, the light receiving slit S
The image projected on the upper side also becomes a grid-like pattern at regular intervals with the longitudinal direction perpendicular to the paper surface of FIG.

That is, in this embodiment, when the surface 1a to be inspected and the image forming surface of the projection lens 5 coincide with each other, the lattice pattern forming surface 8a, the surface 1a to be inspected, and the tilt correction prism
The 25 incident surfaces 25a are in a relationship satisfying the Scheimpflug condition, and each surface has the same magnification over the entire surface. Next, the lateral displacement y of the image of the lattice pattern on the entrance surface 25a of the tilt correction prism 25 when the displacement of the surface 1a in the direction of the optical axis AX1 is z is determined. Here, the incident angle of the principal ray of the incident light to the surface 1a to be inspected is θ, the lateral magnification of the condensing optical systems 11 and 12 is β, and the tilt of the tilt from the surface 1a to the incident surface 25a of the tilt correction prism 25. Assuming that the magnification along the image plane is β ′, from the above-described equations (1) and (2), the lateral shift amount y is

[0026]

Y = 2 · β ′ · tan θ · z = 2 (β ² sin ² θ + β ⁴ sin ⁴ θ / cos ² θ) ^1/2 · z ‥‥ (4) That is, if the incident angle θ of the lattice pattern projected on the surface 1a to be inspected is increased, the lateral shift amount y is also increased, and the surface position can be detected with higher accuracy.

Incidentally, the projection optical systems 9 and 10 and the condensing optical systems 11 and 12 respectively satisfy the Scheimpflug condition. Therefore, the angle between the normal line of the transmission grating pattern plate 8 and the reflected light is γ, and the angle between the incident light on the tilt correction prism 25 and its normal is α (this angle α is the incident angle of the tilt correction prism 25 The angle of incidence of the principal ray on the surface 25a), the lateral magnification of the projection optical systems 9 and 10 is β ₄ , and the condensing optical system 1
If the lateral magnification of 1,12 is β, the following relationship holds.

[0028]

Tanγ = β ₄ · tanθθ (5)

[0029]

Tanα = β · tanθ ‥‥ (6) By the way, when the light receiving surface 17a is arranged on the second surface,
When the incident angle θ with respect to the surface 1a is large, the incident angle of the light beam on the light receiving surface 17a is also large. For example, when a silicon photodiode SPD is arranged on the light receiving surface 17a, if the incident angle of the light beam on the silicon photodiode SPD is large, the silicon photodiode SPD
In addition to the above, the surface reflection becomes large, and the luminous flux is blurred, so that the amount of received light may be significantly reduced.

In this embodiment, in order to avoid such a decrease in the amount of received light, as shown in FIG. 1, a tilt correction prism 25 is disposed on the second surface as a deflecting optical system, and a condensing optical system is used. Light beams emitted from 11,12 are deflected. This tilt correction prism 25 is, as shown in the sectional view of FIG.
Has a predetermined apex angle ξ, and the apex angle ξ is determined such that the exit light beam L2 refracted by the tilt correction prism 25 is substantially parallel to the normal to the exit surface 25b of the tilt correction prism 25. . At this time, the angle formed by the outgoing light beam L2 with respect to the incident light beam L1 incident on the tilt correction prism 25 is ₂₅ / n ₂₅ when the refractive index of the tilt correction prism 25 is n ₂₅ . This angle is considerably smaller than the angle α formed between the incident light beam L1 incident on the tilt correction prism 25 via the condenser optical systems 11 and 12 and the incident surface 25a.

On the exit side of the tilt correction prism 25, there are arranged relay optical systems 14 to 16 composed of a relay lens 14, a plane mirror 15, and a relay lens 16. This relay optical system is a double-sided telecentric optical system as shown in FIG. Returning to FIG. 1, the light beam incident on the tilt correction prism 25 is guided to the plane mirror 15 after being refracted by the tilt correction prism 25. This plane mirror
The light beam reflected by 15 is focused on light receiving surface 17a by relay optical systems 14-16. That is, this relay optical system
14 to 16 form a further conjugate image of the image formed on the incident surface 25a of the tilt correction prism 25 on the light receiving surface 17a.

Here, the operation of the tilt correction prism 25 will be described with reference to FIG. 5, when the L1 parallel beam to the optical axis AX3 ₂ on the exit side of the converging optical system 11, the incident angle of the beam L1 relative tilt correction prism 25 from FIG. 1, the alpha. In FIG. 5, if the refractive index of the tilt correction prism 25 is n and the refraction angle is ξ, the following equation is established.

[0033]

７ = sin ⁻¹ (sin α / n) ‥‥ (7) In the present embodiment, the apex angle of the tilt correction prism 25 is set to ξ similarly to its refraction angle. Accordingly, the beam L2 emitted from the emission surface 25b of the tilt correction prism 25 becomes perpendicular to the emission surface 25b.

Therefore, considering the floating of the image by the glass of the tilt correction prism 25, the tilt angle ρ, which is the inclination of the relayed image plane of the test surface 1a with respect to the plane perpendicular to the emitted beam L2, is It is shown by the formula.

[0035]

Ρ = tan ⁻¹ (tan ξ / n) ‥‥ (8) Now, assuming that the magnification of the relay optical systems 14 to 16 is 1, the tilt angle ρ is not changed and the light receiving surface 17a of the light receiving unit 17 is an angle between a plane perpendicular to the optical axis AX4 ₂ on the exit side of the relay optical system 14 to 16, that is, the angle of incidence of the chief ray with respect to the light-receiving surface 17a.

For example, a refractive index n = 1.8, an incident angle α = 80.1
°, the tilt angle ρ = 20.0 °, and the tilt angle is 0
° is approaching. Here, the angle of incidence on the light receiving surface 17a is also 2
0.0 °
Can be regarded as almost none. As described above, in the present embodiment, the tilt correction prism is used as the deflection optical system.
Since the light receiving surface 25a is used, the incident angle of the light beam incident on the light receiving surface 17a is reduced, so that a decrease in the amount of light received by the silicon photodiode SPD disposed on the light receiving surface 17a can be prevented.

The incident surface 25a of the tilt correction prism 25
It is desirable that the light receiving surface 17a of the light receiving section 17 satisfy the Scheimpflug condition with respect to the relay optical systems 14 to 16. Incidentally, when the wavelength band of the light source is wide, it is desirable to use a prism, for example, the tilt correction prism 25 as the deflection optical system. Here, for example, when a diffraction grating is used as the deflecting optical system, the dispersion of the deflected light beam becomes larger than when using a prism, and the relay optical system 14
Since it is necessary to increase the numerical aperture of ~ 16, it is not preferable.

The incident angle α of the light beam incident on the surface 1a to be measured
Is large, the transmittance of the light beam passing through the tilt correction prism 25 is greatly different between the P-polarized light and the S-polarized light. For example, when the incident angle α = 80 ° and the refractive index n = 1.8, the transmittance of P-polarized light is 0.79, and the transmittance of S-polarized light is 0.
It becomes 37. As described above, since the transmittance of the tilt correction prism 25 varies depending on the polarization state of the light beam, the weight of information for each polarization varies, and there is a possibility that the position detection of the test surface 1a may not be accurate. However, in the present embodiment, as shown in FIG. 1, a half-wave plate 24 is arranged in the optical path between the condensing optical systems 11 and 12 and the tilt correction prism 25, and this half-wave plate
The configuration is such that a light beam whose polarization direction is rotated by 45 ° by 24 is incident on the tilt correction prism 25. Therefore, the light beam incident on the tilt correction prism 25 is in a state where the P-polarized light and the S-polarized light are mixed, and the position of the surface 1a to be detected is correctly detected.

Note that, instead of the half-wave plate 24, a quarter-wave plate 24 is used.
A wave plate may be used. When a quarter wave plate is used, the light beam incident on the tilt correction prism 25 becomes circularly polarized light, and the position of the surface 1a to be detected is detected using a half wave plate. Is done exactly as if it had been. In addition, tilt correction prism
25 exit surface 25b and a light beam L2 emitted from the exit surface 25b
Is preferably substantially vertical. In this embodiment, the apex angle of the tilt correction prism 25 is made equal to the refraction angle の of the light beam L2 with respect to the light beam L1 incident on the tilt correction prism 25, so that the exit surface 25b and the light beam L2 are substantially perpendicular. Here, if the exit surface 25b and the light beam L2 do not become substantially perpendicular, aberrations such as astigmatism occur when relaying the image on the incident surface 25a by the relay optical systems 14 to 16, Not desirable.

Now, the incident surface 25a of the tilt correction prism 25
As shown in FIG. 3, a light receiving slit S having _five openings Sa _{1 to} Sa ₅ is provided on the upper surface, so
The image of the lattice pattern re-imaged on a is partially shielded. That is, the openings Sa _{1 to} Sa _{5 of} the light receiving slit S
Only the light flux from the image of the lattice pattern formed in the region is emitted from the tilt correction prism 25.

The images of the openings Sa _{1 to} Sa ₅ of the light receiving slit S formed on the incident surface 25 a are
By 16, it is relayed to the light receiving section 17. This light receiving section 17
As shown in the plan view of FIG. 6, for example the opening Sa ₁ -SA ₅ corresponding to the five silicon photodiode SPD ₁ light receiving slit S, SPD _2, SPD _3, SPD _4, SPD ₅ (hereinafter, SPD _{1 to} SPD ₅
(Abbreviated as) is provided on the light receiving surface 17a. These silicon photodiodes SPD ₁ -SP
D on _5, opening Sa ₁ -SA image is slit image SL ₁ of _5, SL _{2,
SL 3, SL 4, SL 5} ( hereinafter, abbreviated as SL ₁ to SL ₅₎ to form an image as. The slit image SL ₁ to SL ₅ is imaged so as to be smaller than the size of the silicon photodiode SPD ₁ ~SPD _5.

In this embodiment, a plurality of silicon photodiodes are provided on the light receiving surface.
A two-dimensional charge-coupled imaging device) or a photomultiplier may be used. When the surface 1a moves up and down along the optical axis of the projection lens 5, the pattern projected on the incident surface 25a of the tilt correction prism 25 has a pattern pitch corresponding to the top and bottom of the surface 1a. Cause lateral displacement in the direction. The amount of this lateral displacement is determined by using the vibrating mirror 30 and the light receiving unit 17, for example, as disclosed in
If the detection is performed based on the principle of the photoelectric microscope disclosed in Japanese Patent No. 2205, the surface position in the direction of the optical axis AX1 with respect to the direction of the optical axis AX1 on the test surface 1a can be detected.

Returning to FIG. 1, the surface position detection based on the principle of the photoelectric microscope will be described in detail. In FIG. 1, a vibrating mirror 30 is provided in the optical path of the condensing optical systems 11 and 12. Then, the mirror drive unit 31 causes the vibrating mirror 30 to vibrate in a direction indicated by an arrow in the figure at a predetermined cycle T based on a signal from an internal oscillator. With the vibration of the vibration mirror 30, the image of the lattice pattern formed on the incident surface 25a of the tilt correction prism 25 also vibrates. At this time, the incident surface 25a
The amplitude of the vibration of the grid-shaped pattern imaged above is defined below half the pitch of the grid-like pattern, and the width of the opening Sa ₁ -SA ₅ slit S also of grid-like pattern image Specified below 1/2 of the pitch. With the vibration of the image of the grid pattern, on the entrance surface 25a, i.e., the amount of light transmitted through the region of the opening portion Sa ₁ -SA ₅ of the light receiving slit S is changed.
Then, this transmitted light is transmitted by the relay optical systems 14 to 16,
Silicon photodiodes SPD _{1 to} SPD ₅ on light receiving section 17
Reach the area.

[0044] In the following, in order to simplify the explanation, only for one of the silicon photodiode SPD _1. Light transmitted through the region of the opening portion Sa ₁ of the light receiving slit S, a slit image on a silicon photodiode SPD ₁
Reach inside the SL ₁ area. The brightness of the slit image SL ₁ varies with the vibration of the vibrating mirror 30. Next, FIG.
Reference to be described in detail changes in the brightness of the slit image SL _1. Figure 7 is an enlarged view of the opening Sa ₁ near the light reception slit S. In FIG. 7, the lattice pattern ST is formed on the light receiving slit S at a pitch _PST , and the lattice pattern ST vibrates in the direction of the arrow in FIG.

[0045] Here, the width WSa ₁ of the opening Sa ₁ is the pitch of the grid-like pattern ST is formed on the opening portions Sa ₁ P _ST
And when

[0046]

Equation 9] It is desirable to satisfy the _{WSa 1 ≦ P ST / 2 ‥‥} (9). The amplitude A _ST of the lattice pattern ST vibrated by the vibrating mirror 30 is

[0047]

It is desirable that A _ST ≦ P _ST / 2 ‥‥ (10) is satisfied. Here, the width WS of the opening Sa ₁
If a ₁ does not satisfy the above equation (9), or if the amplitude A _ST of the lattice pattern does not satisfy the above equation (10), the amplitude at the opening Sa ₁ due to the vibration of the vibrating mirror 30 is increased. This is not preferable because the change in light amount is small and the detection accuracy is reduced. In this embodiment, it is defined as the width WSa ₁ of the opening is less than half of the pitch P _ST of the grating pattern ST, further the grid pattern ST amplitude A _ST pitch
Due to the defined to be 1/2 or less of P _ST, there is no risk of change in light amount due to the vibration of the vibration mirror 30 is reduced.

[0048] The position of the openings Sa _1, when the test surface 1a and the image plane of the projection lens are the same, the openings Sa ₁
Is provided so that the center of the pattern coincides with the vibration center of the lattice pattern ST. The width of the opening Sa ₁ is 1/2 or less of the pitch of the grid pattern, and the amplitude of the grid pattern is also at 1/2 of the pitch, this grid-like pattern ST vibrates, silicon Photodiode SPD ₁
The amount of light received above changes. And silicon photo
Diode SPD _1, the output change of the light intensity, that is, the detection output SD ₁ according to the light modulation detection unit 18.

Similarly, another silicon photo downloader
Iod SPD_Two, SPD_Three, SPD_Four, SPD_Five Also in the slit image
SL_Two, SL_Three, SL_Four, SL_FiveDetection output SD according to the light modulation of_Two, SD_Three, SD
_Four, SD _FiveIs output to the detection unit 18. Also, the mirror drive unit 31
Also, an AC signal having the same phase as the oscillation cycle T of the oscillation mirror 30 is generated.
Output to the detection unit 18. Here, in the detection unit 18,
The detection output SD is based on the phase of the AC signal having a period T.₁, SD
_Two, SD_Three, SD_Four, SD_Five(Hereinafter SD₁~ SD_Five Abbreviated as)
Current, that is, synchronous detection is performed, and the detection output signal FS₁, FS_Two,
FS_Three, FS_Four, FS_Five(Hereinafter FS₁~ FS_Five Abbreviated as)
Output to the output unit 19. This detection output signal FS₁~ FS_Five Is
A so-called S-curve signal, which is a detection area on the surface 1a to be inspected.
Da₁, Da_Two, Da_Three, Da_Four, Da_Five(Hereafter, Da₁~ Da_Five (Abbreviated as)
When it is positioned on the image plane of the projection lens 5,
Output SD₁~ SD_Five Is 1/2 of the oscillation period T of the oscillation mirror 30
When they change in a cycle, they each become zero level. Ma
The detection area Da of the test surface 1a₁~ Da_FiveIs the connection of the projection lens 5.
Positive level when the sensor is displaced above the image plane.
Detection area Da of surface 1a₁~ Da_Five Is from the image plane of the projection lens 5.
When it is displaced downward, it indicates a negative level. This
The detection output signal FS₁~ FS_FiveCorresponds to the displacement of the test surface 1a.
The corresponding output value is shown.

After that, the correction amount calculating section 19 to which the detection output signals FS _{1 to} FS ₅ have been output, outputs the detection output signals FS _{1 to} FS ₅ .
₅ of positive and negative levels, the detection areas Da ₁ to DA on the test surface 1a
₅ are calculated in the focusing direction, and the average inclination of the test surface 1a and the position of the test surface 1a in the focusing direction are calculated. Then, the correction amount of the tilt such that the surface to be measured 1a is located within the range of the depth of focus of the projection lens 5 and the correction amount in the focusing direction are calculated. After that, the correction amount calculation unit 19 transmits these correction amounts to the drive unit 4.

Then, the drive section 4 drives the holding mechanism 3 based on the correction amount of the inclination to level the holder 2 and drives the wafer holder 2 based on the correction amount in the focusing direction. To move the wafer 1 in the focusing direction. With such a configuration, a plurality of detection points on the test surface 1a can be simultaneously detected, and the test surface can be positioned at a predetermined position based on the detection output.

[0052] Further, as shown in FIG. 8, on one silicon photodiode SPD _6, a plurality of slit images (e.g., three slit images _{SL 6a, SL 6b, SL 6C} ) may be formed . At this time, the interval between the slit images SL _6a, SL _{6b, and} SL _6C
P _SPD is

[0053]

It is desirable to satisfy P _SPD = m · P _ST ‥‥ (11). Here, m is an integer. Also, the slit images SL _6a, SL _6b, SL _6C width W _SPD6 are

[0054]

It is desirable that W _SPD6 ≦ P _ST / 2 ‥‥ (12) be satisfied. Here, the slit image SL _6a,
When the distance P _SPD between SL _{6b and} SL _6C deviates from the above equation (11), a vibrating mirror is provided for each slit image SL _6a, SL _{6b and} SL _6C.
Since the change in the amount of light due to the vibration of 30 becomes different, the detection value becomes inaccurate, which is not preferable. Also, slit image
When the width W _{SPD6 of the} SL _6a, SL _6b, SL _6C is out of the range of the above-described expression (12), the change in the amount of light due to the vibration of the vibrating mirror 30 becomes small, which is not preferable.

According to the above-described configuration, in addition to the advantage that the amount of light received on the silicon photodiode SPD ₆ increases, the corresponding area on the surface 1a to be measured is widened and an averaging effect is obtained. There are advantages. In the present embodiment, the silicon photo provided on the light receiving surface 17a is used.
Although light through the light receiving slit S is made incident on the diode SPD, it is not always necessary to pass through the light receiving slit S. When not passing through the light receiving slit S, the area of the silicon photodiode SPD becomes the light receiving area on the test surface 1a. That is, the silicon photodiode SPD may be arranged at a position corresponding to the detection area on the surface 1a to be detected.

In this embodiment, the light receiving slit is used.
S is disposed on the second surface (the incident surface 25a of the tilt correction prism 25), but may be on the light receiving surface 17a of the light receiving unit 17. At this time, it is desirable that the size of the opening Sa of the light receiving slit S be smaller than the size of the light receiving surface 17a. In this embodiment, a plurality of silicon photodiodes are connected to the light receiving surface 17a.
It may be provided thereon by a photo etching method. In this case, there is an advantage that even if the number of openings Sa of the light receiving slit S is greatly increased, it can be dealt with.

The surface of the wafer as the test surface 1a is
Depending on the convenience of the process, it is not always flat. In such a case, the number of detection areas (detection points) on the test surface 1a may be increased. Here, to increase the number of detection points on the test surface 1a, the number of openings of the light receiving slit S corresponding to this detection area may be increased.
As described above, the surface position detecting device according to the present invention can increase the number of detection points on the test surface 1a with a simple configuration, and thus can detect a surface position over a wide range on the test surface 1a. can do. Moreover, even if the number of detection points increases, they can be detected at the same time, so that the throughput does not decrease.

As described above, according to the present invention, the first surface and the test surface are configured to satisfy the Scheimpflug condition with respect to the projection optical system, and the test surface and the second
The surface is configured to meet the conditions of Scheimpflug,
Further, since the second and third surfaces of the relay optical system are configured to satisfy the Scheimpflug condition, and the condensing optical system and the relay optical system are arranged along one optical axis, With a simple optical system, it is possible to simultaneously and accurately detect the distribution of positions in the vertical direction in a wide area of the surface to be measured.

Since the deflecting optical system for deflecting the direction of the optical axis of the condensing optical system is provided on the second surface, the incident angle of the light beam incident on the light receiving surface on the third surface is reduced to approximately 0 °. You can get closer. Therefore, it is possible to increase the angle of incidence of the pattern projected on the surface to be detected and to perform more accurate position detection without causing a decrease in the amount of light received on the light receiving surface.

[Brief description of the drawings]

FIG. 1 is a diagram schematically showing an embodiment of a surface position detecting device according to the present invention.

FIG. 2 is an optical path diagram showing that the optical system shown in FIG. 1 is telecentric on both sides.

FIG. 3 is a plan view of a light receiving slit.

FIG. 4 is a diagram showing a relationship between a lattice pattern projected on a test surface and a detection area.

FIG. 5 is a view showing a tilt correction prism shown in FIG. 1;

FIG. 6 is a plan view showing a relationship between an arrangement of silicon photodiodes on a light receiving surface and a slit image.

FIG. 7 is an enlarged plan view showing an opening on a light receiving slit.

FIG. 8 is a plan view showing an example in which a plurality of slit images are formed on one silicon photodiode.

FIG. 9 is an explanatory diagram for explaining conditions of Scheimpflug.

[Explanation of symbols]

 1a 面 Test surface 5 ‥‥ Projection lens 8 透過 Transmission grating pattern plate 8a 格子 Grating pattern forming surface (first surface) 9 ‥‥ Condensing lens 10 ‥‥ Projection objective lens 11 ‥‥ Light receiving objective Lens 12 ‥‥ Condenser lens 14 ‥‥ Relay lens 16 ‥‥ Relay lens 17 ‥‥ Light receiving section 17a 受 光 Light receiving surface 25 ‥‥ Tilt correction prism 25a ‥‥ Incident surface (second surface) 30 ‥‥ Vibrating mirror 31振動 Vibrating mirror drive S ‥‥ Light receiving slit

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/027 G03F 7/20

Claims (6)

(57) [Claims] 1. A surface position detecting device for detecting a surface position of a surface to be detected, wherein a predetermined pattern formed on a first surface and an image of the predetermined pattern from an oblique direction with respect to the surface to be detected. A projection optical system for projecting, a condensing optical system for condensing a light beam reflected on the test surface to form an image of the predetermined pattern on a second surface, and the second surface and the third surface. A relay optical system disposed in an optical path between the first and second surfaces to conjugate the second surface and the third surface; and a deflection device provided on the second surface and deflecting a light beam emitted from the condensing optical system. An optical system; and a detector disposed on the third surface for photoelectrically detecting the image of the predetermined pattern, wherein the first surface and the surface to be detected are relative to a main plane of the projection optical system. The condition of Scheimpflug is satisfied, and the test surface and the second surface are a main plane of the light-converging optical system. The second surface and the third surface satisfy the Scheimpflug condition with respect to the main plane of the relay optical system, and the light-collecting optical system is arranged on one optical axis. A surface position detecting device, wherein the relay optical system is disposed on the one optical axis. 2. The surface position detecting device according to claim 1, wherein said projection optical system is a double-sided telecentric optical system. 3. A projection exposure apparatus for transferring a pattern on a reticle onto a wafer via a projection optical system, comprising the surface position detection apparatus according to claim 1 or 2 for detecting the position of the wafer. A projection exposure apparatus. 4. A projection exposure method for transferring a pattern on a reticle onto a wafer via a projection optical system, comprising a step of aligning the wafer using the surface position detection device according to claim 1. A projection exposure method. 5. A surface position detecting method for detecting a surface position of a surface to be inspected, wherein an image of a predetermined pattern formed on the first surface is projected from a direction oblique to the surface to be inspected via a projection optical system. Projecting; condensing a light beam reflected on the surface to be inspected via a condensing optical system to form an image of the predetermined pattern on a second surface; Deflecting a light beam to be applied, re-imaging an image of the predetermined pattern formed on the second surface on a third surface via a relay optical system, and disposing the image on the third surface. Detecting the image of the predetermined pattern photoelectrically using the detector, wherein the first surface and the test surface satisfy a Scheimpflug condition with respect to a main plane of the projection optical system. The test surface and the second surface are shy with respect to a main plane of the condensing optical system. The second surface and the third surface satisfy the condition of Scheimpflug with respect to the main plane of the relay optical system, and a plurality of light beams are emitted from a predetermined pattern on the first surface. The plurality of light beams reach the surface to be inspected, and the plurality of light beams reflected by the surface to be inspected are the two-sided telecentric optical system arranged on one optical axis, and the light-collecting optical system. And a relay optical system disposed on the one optical axis to reach the detector. 6. A projection exposure method for transferring a pattern on a reticle onto a wafer via a projection optical system, wherein: the step of aligning the wafer using the surface position detection method according to claim 5; Forming an image of the pattern on the reticle on a wafer via an optical system.