JP2892747B2 - Tilt or height detection method and device, and projection exposure method and device - Google Patents

Description

The present invention relates to a projection exposure apparatus for fine circuit patterns such as semiconductor circuit patterns, display device patterns such as liquid crystals, and in particular,
The present invention relates to a projection exposure apparatus provided with means for detecting a tilt and a height of an object to be exposed, which makes it possible to expose the entire exposure area with high resolution.

[Conventional technology]

Exposure of fine patterns of semiconductor integrated circuits or TFT (T
When exposing a drive circuit pattern in a large-field pattern of a display device typified by a liquid crystal television or the like, it is necessary to expose a pattern faithful to the original image with a small line width variation over the entire exposure area. In the field of semiconductor integrated circuits, in particular, it is necessary to expose a line width pattern of 0.5 μm or less over the entire area close to 15 mm in the future, but as the pattern becomes finer, the imaging range (depth of focus) is ± 1 μm or less. Become. For this reason, it is essential to make the photoresist surface on the wafer exactly coincide with the pattern image plane. In order to realize this, it is necessary to accurately detect the inclination and the height in the exposure area of the wafer surface (photoresist surface).

In the first known example shown in Japanese Patent Application Laid-Open No. 63-7626, a semiconductor laser is focused on a wafer surface in an oblique direction, and the height is detected by detecting the focused position. . In this known example, the multiple reflections associated with the multilayer structure of the wafer are dealt with using a three-wavelength semiconductor laser, and the condensing position is changed to the oblique incidence direction and the direction perpendicular to the wafer, and the heights of different places on the wafer are obtained. ing. In this known example, the height is mainly detected, it is possible to measure by changing the location in the oblique incident direction and the direction perpendicular to the direction, and it is also possible to detect the inclination, but two places in a narrow area of about 20 mm in diameter are measured. However, it is difficult to obtain an accurate value of the inclination. In this known example, in order to realize height detection with high accuracy, it is necessary to sufficiently condense light on the wafer, that is, it is necessary to make the converging diameter as small as possible. It is necessary to increase the converging angle (the angle of the outermost ray of the converging beam with respect to the principal ray). As a result, the incident angle of the principal ray has to be reduced. When this angle is reduced (the angle from a line perpendicular to the wafer surface is reduced), the influence of multiple interference accompanying the multilayer structure of the wafer increases. In this known example, three wavelengths are used for this problem. However, each wavelength is affected by interference and does not solve the fundamental problem.

In a second known example of a conventional tilt detection method disclosed in JP-A-63-199420, a tilt detection light having a wavelength different from the exposure wavelength is irradiated through a projection lens, and reflected light is collected. Although the inclination is detected from the position, the light is incident on the wafer at a substantially perpendicular or shallow angle, so that the influence of interference with the reflected light from the base cannot be ignored for the reasons described below, and accurate detection becomes difficult.

Further, as a conventional method for detecting a height of a multi-layer structure object, in a third known example disclosed in Japanese Patent Application Laid-Open No. 63-247741, light reflected from a base film is separated separately. It is difficult to perform on thin films that appear in the process of making semiconductor circuits.

Also, in the later stage of the LSI exposure process, for example, in the exposure process of the wiring pattern, the unevenness of the wafer surface becomes large, and the photoresist applied thereon has considerable unevenness, although not as large as the original wafer surface. Become like
When the above-described conventional method is applied to such a structure, it is difficult to know which part of the photoresist having irregularities is measuring the inclination and height, and thus the accuracy is deteriorated.

[Problems to be solved by the invention]

The above prior art does not consider that information on the inclination and height in the exposure area is accurately obtained for a multilayer structure such as a wafer having a semiconductor circuit pattern.
There is a problem with the high-precision tilt and height control required for circuit pattern exposure of 5 μm or less.

An object of the present invention is to solve the above-mentioned conventional problems, accurately detect the inclination and height of a photoresist surface in an exposure region for any wafer in a semiconductor process, and always provide an image-forming surface with a resist surface or a vicinity thereof. An object of the present invention is to provide a projection exposure apparatus that exposes a high-resolution pattern with a small line width variation in accordance with an optimum position.

[Means for solving the problem]

In order to achieve the above object, in the present invention, the light emitted from the coherent light source is made into parallel illumination light, and the light is irradiated from an oblique angle to the exposure area of the projection optical system on the photoresist surface on the wafer. Then, the reflected light and the reference light generated by separating the light emitted from the light source are incident on the pattern detector at a desired angle to each other, and the interference fringes obtained are detected. From the change in the interference fringe pitch and phase, it is possible to determine the change in the inclination and height of the photoresist surface on the wafer. In addition, it is easy to make the incident angle 85 ° or more in the present invention using a parallel light beam.Because the incident angle is large, the reflection on the photoresist surface becomes the majority, and the reflection on each layer of the underlying layer structure is Accordingly, the influence of the generated interference can be almost ignored. If the photoresist incident light is S-polarized light, the reflection on the surface is further increased, and the accuracy is improved.

Also, the light reflected on the photoresist surface is vertically incident on the plane mirror, and the reflected light is again incident on the photoresist surface. If the reflected light is used as the object light to obtain information on the interference pattern, the tilt and height of the wafer are obtained. Can be performed with twice the sensitivity, and more accurate detection can be performed.

Further, by configuring the reference light so as to effectively travel in substantially the same direction as the irradiation light of the photoresist and the object light (reflected light) and pass through the substantially same area, each optical path is affected by disturbance such as air fluctuation. In the same manner, it is possible to detect a tilt and a height that are not easily affected by changes in the surrounding environment.

Further, if the obtained information on the interference fringes is subjected to a fast Fourier transform, and the slope Δθ and the height ΔZ are obtained from the information near the spectrum of the resulting fringes, the ΔΔ can be determined as fast as real time.
θ and ΔZ are obtained. At this time, if the photoresist irradiation position is in an optically conjugate (image-forming) relationship with the array sensor light-receiving surface as the pattern detecting means, information of only a desired region on the wafer is selected, and the inclination and height of that portion are selected. Can be obtained.

In the present invention, for a relatively large unevenness of the photoresist surface generated in the later stage of the exposure step, by increasing the incident angle, by irradiating a high portion of the resist with light,
By making the concave portion a shadow of the convex portion, the contribution to interference fringe detection is reduced. As a result, in the present invention, the upper surface of the convex portion is detected, and the detection surface which is uncertain in the conventional method is clarified. Therefore, the position of the resist surface can be correctly detected. Further, in the case of an object to be measured having large irregularities, the area of the upper surface of the convex surface affects the intensity of the reflected light. As a result, when the area ratio of the upper surface of the convex surface is large depending on the location of the surface to be measured, the amount of reflected light increases macroscopically, so that the distribution of interference fringes generated with the reference light on the light receiving surface of the array sensor is uniform. Disappears. That is, as described above,
When the object to be measured and the array sensor have a substantially conjugated positional relationship, the amplitude of the interference fringes is large where the area ratio of the upper surface of the convex surface of the surface to be measured is large, and the amplitude is small where the area ratio is small. Become. As a result, if the interference fringes having different amplitudes at different locations are subjected to Fourier transform, and the slope and height are obtained from the spectral information corresponding to the fringe pitch, the accuracy will decrease. With respect to such an object, in the present invention, the reference light is not superimposed, the intensity distribution of the pattern of only the reflected light from the object to be measured is detected by the above-described array sensor, and the interference is determined using this information. The stripe pattern information is corrected, and then Fourier transform is performed. In this way, the corrected interference fringe pattern has the same amplitude at almost any location regardless of the location, and the slope and height can be accurately obtained from the spectrum information.

[Action]

Since the information of the interference fringes obtained by the above pattern detector has the information of the pitch and the phase, the information of the inclination and the height can be obtained at the same time, and when the incident angle is set to 85 ° or more, the reflection on the photoresist surface becomes large. That is, the inclination and height of the photoresist surface can be accurately and simultaneously determined.

Further, as described above, in the latter stage of the exposure step, only the reflected light from the object to be measured is detected on the wafer having large unevenness of the photoresist, and the data of the detected intensity distribution is used as a correction value, so that the convex portion on the resist surface is obtained. The height and inclination of the upper surface of the surface are accurately determined. This operation will be described in detail below. Now, if the cross-sectional structure of the wafer 4 is
When a layer of unevenness 42 having a relatively large step overlaps the Si substrate 43, the photoresist 41
Is smaller than the step of the 42 uneven layer, but the uneven step remains. When a parallel laser beam having an incident angle of 85 ° or more (for example, 88 °) with respect to a vertical line is irradiated on the photoresist surface having such irregularities, only the hatched portions in FIG. 10 are specularly reflected. As shown in the enlarged view of FIG. 10 in FIG. 11, the beam which is a part is scatteredly reflected in a direction different from the direction of the specularly reflected light as shown by the rays of A ₁ , B ₁ , C ₁ . As a result, as will be described later, light hitting other than the upper surface of the convex portion, such as the light beams A ₁ , B ₁ , and C ₁ , does not reach the detection system that extracts only regular reflection light. As described above, in the case of the cross-sectional structure including the concave and convex portions, light having an intensity substantially proportional to the area of the upper surface of the convex portion reaches the detector.

In addition, since the wafer surface and the light receiving surface of the array sensor are in a substantially conjugate relationship, the cross-sectional structure eventually corresponds to a portion that is almost flat or has a large area ratio of the convex upper surface even if it has irregularities. The strength is high and vice versa. As a result, the level of the intensity distribution Ox of the reflected light from the measured object on the array sensor varies depending on the location as shown in FIG. 5, for example. When the light having such a distribution interferes with the reference light Rx at a fixed level as shown in FIG. 6, the amplitude of the interference fringe intensity Ix varies from place to place as shown in FIG. The phenomenon described above will be further described theoretically and quantitatively. The intensity of the reflected light from the object to be measured incident on the array sensor is Ox, the incident angle is α ₁ , and the intensity of the reference light is Rx, and the incident angle is −α _1. (Indicates that it is tilted to the opposite side of the reflected light from the object)
If these two lights are inclined in the X direction, a stripe that changes in the X direction is detected. The obtained interference fringe intensity Ix (X) is Here, λ is the wavelength of the detection light, Δθ is the inclination of the object, n is the number of reflections on the object to be described later,
m is the imaging magnification of the detection optical system. φ (Z) is a phase change accompanying a change in height. Equation (1) is Δθ << α ₁ <<
<1 When n = 1, the following is obtained.

If Ox and Rx take constant values irrespective of X, the spectral peak position corresponding to the fringe period of the Fourier spectrum obtained by Fourier transforming the detection signal given by equation (1) 'and data in the vicinity thereof Using,
The values of Δθ and φ (Z) can be obtained. However, in general, Ox and Rx are not constant. In particular, as described above, when the unevenness of the resist surface of the wafer differs depending on the location, Ox changes as shown in FIG. Assuming that the reference light distribution Rx is a constant value Rc as shown in FIG.
However, the interference fringe intensity given by the expression (1) 'has a different fringe amplitude depending on the location as shown in FIG. With such an amplitude change, the Fourier transform of Ix has a spread around the peak value as shown by | F [Ix] | in FIG. 9, and the original fringe period (slope) and phase (height) Information is hidden and accuracy is reduced.

Therefore, prior to the detection of interference fringes, the reference light is shielded, and only the reflected light from the measured object is detected by the same detection system. This value is naturally Ox. When Rx is not equal to Rc as in the example of FIG. 6, for example, when Rx is as shown in FIG. 14, the intensity distribution Rx of only the reference light is measured. These two measured values (Ox, Rx) or, if Rx = Rc, one measured value (Ox, Rx)
x) is used as a correction value, and the following correction operation is performed to obtain a correction signal I
Derive cx.

Since Ix is given by equation (1) Is found. If the correction signal Icx is Fourier-transformed, as shown in | F [Icx] | in FIG. 9, the spread around the peak value is eliminated, and a sharp spectrum of a pure trigonometric function is obtained, and the slope and the height are accurately determined. Is found.

〔Example〕

 Hereinafter, the present invention will be described specifically with reference to examples.

FIG. 1 shows an embodiment of the present invention. In this embodiment, the tilt and height detection of the present invention is applied to an exposure chip of a semiconductor exposure apparatus. Reference numeral 9 denotes a reticle on which a pattern original used for exposing a circuit pattern on the wafer 4 is drawn. The reticle 9 is irradiated with g-rays or i-rays emitted from a mercury lamp (not shown) from the exposure illumination system 81 or far ultraviolet light emitted from an excimer laser. The light transmitted through the reticle is transmitted as a reticle image onto the surface of the resist applied to the wafer 4 fixed on the wafer stage 7 by transmitting through the reduction lens 8. The depth of focus becomes shallower as the pattern drawn on the wafer 4 becomes submicron, half micron, and further around 0.3 μm. When the line width becomes 0.5 μm or less, the inclination and height are respectively ± 10 ^−. Detection with accuracy within ⁵ rad, ± 0.1μm
If not controlled, product yield will decrease. Reference numeral 100X in FIG. 1 is a detection system for obtaining the horizontality of the resist surface on the wafer in the x direction, that is, the inclination and the height accompanying the rotation around the y axis. In FIG. 1, the horizontality in the y direction is detected similarly to 100X.
100Y is omitted. Reference numeral 1 denotes a light source having a high directivity such as a semiconductor laser or a gas laser. The light emitted from the light source is split into two by a beam splitter 10 in a state of being substantially parallel and having a desired spread. One of the two split lights 16 is applied to the resist surface of the wafer 4 through the beam splitter 12 and the mirror 13 at an incident angle of 85 ° or more with respect to a vertical line and with S-polarized light. Although the resist is transparent to this irradiation light, the incident angle is large and the light is S-polarized, so that nearly 90% of the light is directly reflected without entering the inside of the resist, and is incident on the turning mirror 14 almost perpendicularly. The folded light 26 'follows the same optical path as the outward path and travels in the opposite direction, and becomes light 26 "reflected by the beam splitter and directed to the detection optical path. On the other hand, the other beam 17 separated by the beam splitter 10 is used as reference light. Used.
The beam 17 is turned on and off by desired shuttering by a shutter (light blocking means) 330. When the shutter 330 is turned on, the reference light passes through the beam splitter 12 and the mirror 13 and directly enters the turning mirror 14 vertically. Folded beam
27 'follows the same optical path as the outward path but in the opposite direction, and becomes light 27 "reflected by the beam splitter 12 and directed to the detection optical path. The two beams 26" and 27 "directed to the detection optical path are formed by the lenses 21, 22 and noise. The light passes through a light-shielding plate 23 having a pinhole or a small rectangular opening for removal and is superimposed on the array sensor 3 in a substantially parallel state, as shown by solid lines in FIGS. Such an interference fringe is generated, and this intensity distribution Ix is detected by the array sensor 3. If the parallelism of the wafer 4 is poor or the wafer warps as it goes through various processes, the wafer 4 is step-and-repeat. Is exposed in units of chips or a plurality of chips, since the image plane of the reduction lens and the resist surface do not coincide with each other in terms of inclination and height, the following method is used based on the detection information of the array sensor 3 described above. , The inclination and height are detected by the processing circuit 5, and based on the detected information, a stage control mechanism (for example, a piezo or mechanical fine movement mechanism) provided on the wafer stage 7 is controlled to obtain an image and an image. After aligning the resist surface, exposure is performed, and in FIG.
Is an alignment system used for overlay exposure.

2 and 3 show signals detected by the array sensor 3 in the embodiment of FIG. 1. In each drawing, a signal Ix indicated by a solid line is a signal whose inclination and height are optimally exposed. It is. When the wafer 4 is deviated and tilted from the optimum exposure state, the pitch of the stripe changes from P to P 'as shown by the dotted line in FIG. When the wafer is shifted from the optimum exposure position in the height direction, the phase φz changes as shown by the dotted line in FIG. If the pitch P and the phase φz of the interference fringes accompanying the change in the inclination and the height are n = 2 in the equation (1), then cos α ₁ Holds. However theta ₁ is an incident angle to the wafer, .phi.s is the initial constant phase.

FIG. 4 shows a part 51 of the processing circuit 5 of FIG. 1 of the present invention, showing one embodiment of the present invention. The digital information Ix of the interference fringes detected by the array sensor 3 in FIG. 1 and A / D converted by the A / D conversion circuit 31 is temporarily stored in the memory 1 501 shown in FIG. Prior to the detection of the interference fringes, before the wafer 4 is carried into the stage 7 and exposure is started, the shutter (light shielding means) 330 shown in FIG. 1 is closed, the reference light 17 is shielded, and the reflected light from the wafer 4 is reflected. Array sensor 3 for 26 only
Detect in advance. This signal Ox is A / A
The data is A / D converted by the D conversion circuit 31 and stored in the memory 2 of 502 shown in FIG. 4 in the form of digital information. As described above, if the enlarged view of the surface of the resist on the wafer 4 has a concavo-convex shape as shown in FIG. 10, the incident angle θ ₁ (for example, 88
Among the light incident in (i), the light contributing to the specularly reflected light is the upper surface of the convex portion, and the beam hatched with oblique lines in the enlarged view of FIG. 10 is the specularly reflected light. When the area of the upper surface of the convex portion is reduced, the image on the array sensor 3 due to the reflected light from the concave-convex structure portion becomes dark. On the other hand, an image on the array sensor 3 corresponding to a portion having a small unevenness or a large area of the upper surface of the convex portion of the unevenness becomes bright.
A reflected light image Ox from the wafer 4 as shown in the figure is formed on the array sensor 3. As described above, this Ox can be detected by closing the shutter 330 shown in FIG. 1, and this information is stored in the memory 502. When the wafer 4 is moved in a step-and-repeat manner and the exposure is repeated, interference fringes are detected by the array sensor 3 prior to the exposure. If the distribution of the reference light 17 is uniform as shown in FIG. An interference fringe Ix as shown in the figure is detected, and 501 in the memory 1 in FIG.
Is stored in Therefore, these two information Ix and Ox are stored in each memory
The following calculation is performed by the 503 of the calculation means 1 taking out from 501 and 502 to derive a corrected interference waveform Icx.

However, the intensity of the reference light has a substantially constant value Rc. In the Icx obtained in this manner, components other than the fundamental frequency are greatly reduced as shown in FIG. As a result, this signal is subjected to fast Fourier transform (FFT) by the fast Fourier transform means 504.
As shown by the solid line in FIG. 9, the signal | F [Icx] | obtained as a result has a pure spectrum of the fundamental frequency compared to the FFT | F [Ix] | of the signal before correction. From the information, a very accurate slope and height information (Δ
θ, ΔZ) are obtained.

FIG. 12 shows an embodiment of the present invention. 1 denote the same parts. Fig. 12 shows a transmission grating
The laser beam irradiated to the wafer 18 with a substantially parallel light beam is separated into a light 16 'to be irradiated on the wafer 4 and a reference light 17'. Each light is blocked by the optical shutter 330 '. That the state shown in FIG. 12 the shutter 330 'when it is but the interference fringes are detected by the array sensor 3, the shutter 330' is moved to the right, the position of A _R of the opening A _o is Figure 12 Overlap and wafer illumination light
16 'is shielded, and only the reference beam 17' is detected by the array sensor 3. When the reference light 17 'is detected, a signal Rx having a slightly uneven distribution is detected as shown in FIG. The shutter 330 is light-shielded 'moves to the left, opening A _R overlaps the reference beam 17 to the position of A _o of Figure 12', only the wafer reflected light is detected by the array sensor 3. This wafer reflected light has a distribution Ox as shown in FIG. 13 similarly to the embodiment of FIG. These distributions
Rx and Ox are output from the A / D conversion circuit 31 as 502 'of the memory 2' of the inclination and height detection circuit 51 'of FIG. 17, which is a part of the processing circuit 5' of FIG. 502 respectively. Prior to exposure, 502 'of memory 2' and 502 of memory 2
Using the above Rx and Ox stored in
According to 3 ', the following calculation is performed before exposure by step and repeat. Ix is stored in 501 of the memory 1 as in the case shown in FIG.

This Icx is the interference detection waveform Ix (5 in the memory 1) shown in FIG.
01 is stored. 16), the fundamental frequency component is dominant as shown in FIG. 16, and therefore, as described above, the signal Icx is accurately corrected by the fast Fourier transform means 504 and the arithmetic means 2 '505 for the slope and height (Δθ , ΔZ) can be obtained. In the present embodiment, as compared with the embodiment of FIG. 1, accurate detection is possible even if a small amount of unevenness remains in the distribution of the reference light 17 '. Not only a system such as a pinhole can be omitted, but also the light use efficiency is increased, and it is possible to detect with a light source having a small output.

FIG. 18 is a diagram showing a specific configuration of 505 of the high-accuracy calculating means 2 'of the pitch (slope) and phase (height) of interference fringes by the spectrum information processing shown in FIGS. 4 and 17. Since the detected and corrected signal Ixc contains almost no signal other than the fundamental frequency component, the pitch and phase can be accurately obtained by performing the following calculation. Ixc is a real number, and when this is subjected to complex Fourier transform by complex Fourier transform means 504, F [I] of the following equation is obtained.

Assuming that this spectrum is Aj, | Aj | has a sharp peak value at a spectrum position j = jo corresponding to the fundamental frequency component.
Calculation step of discretely obtained spectrum Ajo calculated in 5051 jo and _{j o + 1, j o-} 1 position in於Ru value A _{j + 1,} A precise pitch by the following method from _jo-1 P and the phase θ _z are obtained. Rewrite the complex values of Ajo, Ajo _{+ 1} and Ajo _-1 into the real and imaginary parts as follows.

Ajo = Ro + i Io ... ( 8) A jo + 1 = R + + i I + ... (9) A jo-1 = R - + i I - ... (10) Next the inner product calculation step 5052 from the value obtained in these FFT (The inner product value of a complex vector).

Using this value, the next Δ is obtained.

Using the Δ thus obtained, the true spectrum peak j _R is obtained by the following equation by the true peak position step 5055.

j _R = jo + Δ (14) Next, the phase value φz is given by the following formula by the phase step 5056 at the true peak position using the above Δ.

Here, the following expression is obtained from the expression φjo (6).

Using Δ given in equation (14), an initial phase value φz is obtained from equation (15).

As in the case of obtaining the equation (1) ′, the pitch P of the interference fringes is determined by the equation (1) with respect to the number of reflections n on the measured object (wafer 4). (Equation (3) is for the case of n = 2).

The pitch P (1 of the interference fringe signal input to the FFT)
The number of sample points per pitch, where a real number, is given by P = N / j _R (17). From equation (3) ′ and equation (14), Δθ = C _θ × (j _R −j _S ) / n ( 18) However, C _θ = λm / (2N) (constant) j _S = 2N sin α ₁ / λ (constant) The stage tilt control amount Δθ is obtained by the stage tilt control amount calculating step 5057. This Δθ is the tilt control amount of the stage.

On the other hand, from the true phase value φz, the initial phase φ which is a constant
_S ([Delta] Z = 0, i.e. initial phase in focus) with (4) a was determined in the same manner as _{ΔZ = λ (φ Z -φ S} ) / (4nπcosθ 1) and since ((4 In equation (3), n = 2) ΔZ = C _Z (φ _Z −φ _S ) / n where C _Z = λ / (4πcos θ ₁ ) (constant) The stage vertical control amount ΔZ is obtained by the stage vertical control amount calculation step 5058. This ΔZ is a stage height control amount. As with the detection of the X axis at 100X,
The stage tilt control amount Δθ and the stage height control amount ΔZ are obtained from 100Y. Δθ, Δ of the X axis and Y axis
Let Z be Δθx, ΔZx, Δθy, ΔZy, respectively. Since two values can be obtained for ΔZ, only one of them is used, or the average ΔZ = (ΔZx + ΔZy) / 2 is used, and Δθx, Δθy,
By controlling two directions perpendicular to the optical axis of the wafer stage 7 and the optical axis direction by three values of ΔZ (or ΔZx or ΔZy), the wafer 4 is positioned on the focal plane (the inclination and height are constant) of the exposure optical system. And the circuit pattern formed on the reticle 9 can be exposed on the wafer 4 by the exposure reduction lens 8 as a high-resolution circuit pattern. Moreover, since this detection operation can be performed at a high speed (several ms), every time a chip on the wafer 4 is step-moved and exposed, the entire surface of the wafer 4 can be obtained with high resolution.
Exposure can be performed at high throughput.

In the above embodiment, the Fourier transform is used as a method of calculating the pitch and the inclination from the corrected interference fringes.However, for example, the pitch and the phase are obtained by a method of obtaining the pitch and the phase from the position cut off at the center of the sine wave and the amplitude. It is also possible to obtain the inclination, and the present invention is not limited to the Fourier transform.
Further, the tilt and height detection method of the present invention is not limited to the semiconductor exposure apparatus of the above-described embodiment, and can be particularly effectively applied to a target that causes uneven distribution of reflected light from the detection target. It is.

〔The invention's effect〕

According to the present invention, it is possible to accurately detect the inclination and height of the surface of an object such as a semiconductor wafer which is an optical multi-layer object and whose surface shape is uneven. As a result, it is possible to expose the LSI pattern with a high yield in all processes having different wafer surface conditions, even if a reduction exposure apparatus having a relatively shallow depth of focus is used, especially for future LSI miniaturization. .

Further, according to the present invention, the inclination and height of the surface can be obtained with high accuracy over a wide range of objects without being limited to the above-mentioned object and regardless of the state of the surface layer structure or pattern.

Further, according to the present invention, generally, the period or pitch and the initial phase of a signal from which a periodic waveform is obtained can be detected very accurately, and the above-described measurement can be performed with high accuracy over a wide range of application.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIGS. 2 and 3 are diagrams for explaining the principle of the present invention, and FIG.
5 to 9 each show the effect of the present invention, and FIG. 10 shows reflected light of irradiation light at a high incident angle on the concavo-convex pattern. FIG. 11, FIG. 11 is a partially enlarged view of FIG. 10, FIG. 12 is a block diagram showing another embodiment of the present invention different from FIG. 1, and FIGS. 13 to 16 are effects of the present invention. 17, FIG. 17 is a schematic configuration diagram showing a part of the processing circuit shown in FIG. 12, and FIG. 18 is a diagram showing the operation flow of the operation means 2, 2 'shown in FIG. 4 and FIG. It is. 1 ... laser light source, 10,12 ... beam splitter, 3 ...
... array sensor, 4 ... wafer, 5 ... processing circuit, 7 ...
... Stage, 8 ... Reduction lens, 9 ... Reticle, 81 ...
… Lighting system, 800 …… Alignment system

Claims (15)

(57) [Claims] An object is irradiated with coherent light, and interference fringe information generated by reflected light from the object and reference light interfering with the coherent light is detected. The information obtained by only the reflected light from the object to be measured is collected, and the detected interference fringe information is corrected using the collected information, and the pitch of the interference fringes or the pitch is calculated from the corrected interference fringe information. A tilt or height detection method comprising calculating phase information and detecting the pitch or the calculated pitch of the interference fringes or the tilt or height of the measured object based on the pitch and phase information. 2. The tilt or height detecting method according to claim 1, wherein information based on only the reference light is collected, and the correction is performed using the collected information. 3. The method according to claim 1, wherein the calculation of the information on the pitch and phase of the interference fringes is performed based on spectrum information obtained by performing Fourier transform on the corrected interference fringe information.
Or the tilt or height detection method according to any of 2. 4. A first irradiating means for irradiating an object to be measured with coherent light, a second irradiating means for irradiating reference light interfering with the coherent light, and the first irradiating means. The reflected light obtained from the object to be measured by the light
Interference fringe information detecting means for detecting interference fringe information generated by the reference light emitted from the irradiating means, collecting means for collecting information only by reflected light from the object to be measured, and collecting means for collecting information from the collecting means. Correction means for correcting the interference fringe information detected by the interference fringe information detection means using the obtained information, and calculating the pitch of the interference fringes or information on the pitch and phase from the interference fringe information corrected by the correction means. ,
A tilt or height detecting device comprising: a tilt or height detecting means for detecting a tilt or a height of the measured object based on the calculated pitch of the interference fringes or information on the pitch and the phase. . 5. The method according to claim 1, wherein the collecting means further includes means for collecting information using only the reference light, and the correcting means further includes means for performing the correction using information based on only the reference light collected by the means. The inclination or height detecting device according to claim 4, characterized in that: 6. The tilt or height according to claim 4, wherein said first irradiating means is configured so that an incident angle of coherent light to the object to be measured is 85 ° or more. Detection device. 7. The method for calculating the pitch of interference fringes or the information on the pitch and phase in the inclination or height detecting means,
7. The tilt or height detecting device according to claim 4, wherein the correction is performed based on spectral information obtained by Fourier-transforming the corrected interference fringe information. 8. A projection exposure method for projecting and exposing a circuit pattern formed on a mask onto a substrate by a projection optical system, irradiating the substrate with coherent light, and reflecting light from the substrate and the coherent light. The interference fringe information generated by the neutral light and the interfering reference light is detected, information is collected only by the reflected light from the substrate, and the detected interference fringe information is corrected using the collected information. Calculating the pitch of the interference fringes or the information of the pitch and phase from the corrected interference fringe information, and detecting the inclination or height of the substrate based on the calculated pitch of the interference fringes or the information of the pitch and phase. Then, at least one of the mask and the substrate is finely moved around two axes orthogonal to the optical axis of the projection optical system and along the optical axis based on the detected information on the inclination or height of the substrate, and the circuit of the mask is provided. Patter Projection exposure method characterized by the imaging surface and the substrate surface of the emissions are leveling control as match. 9. The projection exposure method according to claim 8, wherein information based on only the reference light is collected, and the correction is performed using the collected information. 10. The method according to claim 8, wherein the calculation of the information on the pitch and phase of the interference fringes is performed based on spectrum information obtained by performing Fourier transform on the corrected interference fringe information. Or a projection exposure method. 11. A projection exposure apparatus for projecting and exposing a circuit pattern formed on a mask onto a substrate by a projection optical system, wherein at least one of the mask and the substrate is rotated about two axes orthogonal to the optical axis of the projection optical system. Moving means for tilting and moving along the optical axis; first irradiating means for irradiating the substrate with coherent light; and second means for irradiating reference light interfering with the coherent light. Irradiating means; and interference fringe information detecting means for detecting interference fringe information generated by reflected light obtained from the substrate by the light radiated from the first irradiating means and reference light radiated from the second irradiating means. A collecting unit that collects information based only on light reflected from the substrate; a correcting unit that corrects interference fringe information detected by the interference fringe information detecting unit using information collected from the collecting unit; Based on the interference fringe information corrected by the corrector, information on the pitch of the interference fringes or information on the pitch and phase is calculated, and the inclination or height of the substrate is calculated based on the calculated pitch of the interference fringes or the information on the pitch and phase. The tilt or height detecting means to be detected and the moving means are controlled based on the tilt or height information detected by the tilt or height detecting means so that the image plane of the circuit pattern of the mask coincides with the substrate surface. A projection exposure apparatus comprising: 12. The projection exposure apparatus according to claim 11, further comprising a light shielding means as said collection means. 13. The apparatus according to claim 1, wherein said collection means further includes means for collecting information using only reference light, and said correction means further includes means for performing said correction using information only using reference light collected by said means. 12. The projection exposure apparatus according to claim 11, wherein: 14. The projection exposure apparatus according to claim 11, wherein said first irradiating means is configured so that an incident angle of coherent light to the object to be measured is 85 ° or more. 15. A configuration in which the inclination or height detecting means calculates the pitch of the interference fringes or the information of the pitch and phase based on the spectrum information obtained by performing the Fourier transform on the corrected interference fringe information. 15. The projection exposure apparatus according to claim 11, wherein: