JP2786270B2 - Interferometric tilt or height detecting device, reduction projection type exposure device and method thereof - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for optically detecting the tilt or height of an optical multilayer object such as a wafer, and a reduction projection type exposure apparatus and its direction.

[Conventional technology]

2. Description of the Related Art A conventional device for detecting the inclination of an optical multilayer structure object such as a semiconductor wafer detects the inclination and the focus as shown in FIG. 2 of Japanese Patent Application Laid-Open No. 1-46606, which is a first known example. In this known example, light focused on a wafer is irradiated for focus detection, the position of the reflected light is imaged on a position sensor by an imaging lens, and height detection (focus detection) is performed from that position. I have. Regarding the tilt, the wafer is irradiated with parallel light, the reflected light is condensed on a position sensor by a condensing lens, and the tilt is determined from the detected position. In any of these detections, it is difficult to set the incident angle on the wafer to 85 ° or more, and a large amount of light refracts and enters the resist-coated film, making it difficult to truly detect the resist surface. For this reason, the detection position greatly deviates from the true resist surface position due to the reflectance of the base and the thickness of the resist, and it is necessary to set the offset value by performing test exposure for each wafer exposure process.

[Problems to be solved by the invention]

It is difficult to make the incident angle on the wafer 85 ° or more with the above-mentioned conventional technology. This is because in the case of focus detection, sufficient detection sensitivity cannot be obtained unless a certain convergent angle of the converged light to the wafer is set and the beam diameter at the converged position is reduced. Also, in the case of tilt detection, it is impossible to irradiate only the exposure area to be detected unless the beam diameter of the parallel light is reduced. In this case, if the beam diameter is too small, the beam is narrowed down onto the sensor by a condenser lens. The beam spot diameter becomes large and sufficient detection sensitivity cannot be obtained. Therefore, to obtain detection sensitivity, the incident angle was about 80 °. However, when the incident angle is about 80 °, considerable incident light is refracted into the resist, and the light reflected by the wafer pattern under the resist contributes as detection light. As a result, the detected focus position (height) and inclination are greatly changed. For this reason, test exposure is performed for each wafer exposure process,
It was necessary to determine the detection deviation from the resist surface as an offset value and to add a correction. Further, even with the same process wafer, there has been a problem that high-precision detection is hindered, such as a change in the offset value when the resist thickness changes.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problem and to accurately detect the height and inclination of the uppermost surface such as a resist applied on a wafer (substrate) regardless of the wafer (substrate) for each process. SUMMARY OF THE INVENTION It is an object of the present invention to provide an interference type inclination or height detecting device, a reduced projection type exposure device and a method thereof.

[Means for solving the problem]

In order to achieve the above object, in the present invention, a coherent parallel beam such as a laser beam is applied to an object to be measured of an optical multilayer object as shown in Japanese Patent Application Laid-Open No. Hei. Irradiation is performed at an incident angle, interference fringes are generated between the reflected light and the reference light separated from the parallel beam, and the focus (height) is detected from the phase of the interference fringes and the inclination is detected from the pitch. At this time, as described above, when the incident angle is increased, particularly when the incident angle is set to 85 ° or more, the reflection component on the resist surface increases, and high-precision detection becomes possible. However, in this case, if the underlayer has a very large reflectance such as Al, the detection error becomes relatively large. The present invention relates to Japanese Patent Application Laid-Open
It is an object of the present invention to further improve the accuracy of No. 40417 and to provide a means for completely detecting the height and inclination of the resist surface completely without being affected by the material of the base or the thickness of the resist. Therefore, in the present invention, monochromatic light of two or more different wavelengths is used as the wavelength to be detected, and a plurality of wavelengths are selected and used. That is, in the present invention, the occurrence of an error due to components reflected from the base and transmitted through the resist surface,
As will be described in detail later, focusing on the fact that the thickness changes synchronously with the thickness of the resist, the reflection coefficient of the base, and the wavelength,
A plurality of wavelengths of monochromatic light are prepared, and a wavelength to be used for measurement is selected according to the above conditions of the device under test. In the method of selecting the wavelength, if the thickness of the resist is known in advance, the data to be used is used to determine the wavelength to be used based on a theoretical formula described later. However, even when there is no such resist thickness data or the like, the amount of light incident on the wafer at a large angle and reflected, that is, the reflectivity is measured over a plurality of wavelengths, so that the wavelength at which error generation to be adopted can be ignored is negligible. Can be selected.

[Action]

The principle of the present invention will be described. FIG. 2 is a diagram showing the state of reflection and refraction at the boundary of light irradiating the optical multilayer object at an incident angle θ. Medium 1 is usually air and has a refractive index n ₁
The medium 2 is a photoresist in the case of a semiconductor wafer, and the refractive index n ₂ is usually about 1.65. Medium 3 is a pattern of the underlying, vary process also there is a case of a multilayer structure, the refractive index viewed from the boundary surface between the medium 2 and n _b. Amplitude incident on the resist surface as shown in FIG.
A _p, it can be seen that there exists a (p-polarized light) A _s於Ru reflection on the boundary surface 0 point of the linear polarization of the (s-polarized light), focusing on the refraction, four components of light. That is, reflected light R _p , R _s , refracted light D _2p , D _2s
And D _1p and D _1s incident on the zero point from within the resist. As is widely known, p-polarized light has a refraction component larger than that of s-polarized light, and thus is not very suitable for the purpose of detecting the surface of the present invention. Therefore, if s-polarized light is incident light, the second
From the condition regarding the continuity of the electric and magnetic fields at the zero point on the boundary surface in the figure, the amplitude R _{s of the} reflected light is represented by the incident angle θ,
Using the amplitude A _s of the incident light, expressed by the following equation.

Here, α _s is the reflection coefficient γ _{d of the} base (generally γ _d is a complex number), the phase φ that changes during one round trip in the photoresist, and the extinction coefficient if a light absorbing material is contained in the resist. It is given by the following equation using β.

In Equation (3), the first term in {} is the phase difference due to the optical path length difference between the light reflected at 0 and the light reflected at the background, and the second term is the attenuation due to absorption. If base is Al, most gamma _b is increased, gamma _b at the detection wavelength in the visible region is about 0.878. When the base is Al and the second term in {} is 0, that is, when the resist does not absorb the detection light, the error is the largest due to the influence of the base. When the base is made of Al, a light absorbing material may be added because a standing wave is generated when the pattern is exposed. However, this light-absorbing material absorbs g-line (436 nm), i-line (365 nm) and KuF excimer laser light (248 nm), but does not always absorb laser light used for tilt and height detection.
Therefore, in the worst case where the influence of the background reflection is the largest and the error is large, even when Al is the base and the absorption coefficient β = 0, if accurate detection is guaranteed, there is no problem in other cases. The detection can be performed with higher accuracy.

Assuming the above case, description of the operation of the present invention will be continued. Substituting as beta = 0 expression (3) to (2) R _s can be expressed by the following equation becomes complex.

R _s = γeiΨA _s (4) Now, assuming that the background reflection is 0, that is, α _s = 0, from the equation (1), Ψ = 0 as compared with the equation (4). This is the expression for the reflection at the boundary between the refractive indices n ₁ and n ₂ . Β = 0 in equation (3)
Therefore, when α _s is represented by the following equation, From the equations (1), (4), and (5), R _s , Ψ in the equation (4) is obtained as follows. (However, γ _b is assumed to be a real number.) The amplitude A _{S of the} incident light is set to 1, and R _S is obtained from equation (7).
When the thickness changes with the thickness d obtained from the equation (6), the reflectance γ _b = 0.878 and the incident angle θ of the Al base and the φ obtained from the equation (2) and the resist refractive index n ₂ = 1.65 and θ become (8 by substituting), theta = 88 °, 86 °, R _S to 80 ° can be shown on the complex plane, it is obtained first 3-5 FIG. The value shown on the circumference of each graph changes with the resist thickness (6)
Φ obtained from the equation. This graph will be described. The length of the line segment connecting one point on the curve and the coordinate origin is | R _S |
It shows the amplitude reflectance including the influence of the base. The angle between this line segment and the actual coordinates (horizontal axis) represents the phase change of the reflected light. This phase change is not affected by the background, and in the case of surface reflection alone, φ = 0 as described above. Therefore, a phase shift due to the background, that is, an error in height detection due to the background is caused. Examine how much this error is in the interference detection method. The relationship between the interference fringes obtained by the detection optical system shown in FIGS. 1 and 9 and the height ΔZ and the inclination Δθ of the wafer, which will be described in detail later, is given by the following equation.

Here, X is the coordinate in the fringe pitch direction at the position where the two lights overlap and interfere, θ ₀ and θ are the angles Δθ with respect to the perpendicular of the reference light and the measurement light, the inclination of the chip of interest on the wafer from the horizontal, and ΔZ is the focus The change in height in the direction. Also, ₀
Is a phase constant determined by the initial setting conditions of the measuring optical system.
M in the expression (9) is 1 when the object to be measured is irradiated once as shown in FIG. 1, and is 2 when it is irradiated twice in FIG. The vertical movement amount ΔZ _p of the wafer required for the interference fringes represented by the equation (9) to change by one pitch is given by the following equation.

For the case of m = 1 and 2, λ ₁ = 0.6328 μm,
FIG. 6 shows the results obtained for θ = 80 ° to 89 °. When calculating the height ΔZ from the intensity of the expression (9) obtained from the interference measurement, if the phase shift of Ψ given by the expression (8) occurs in the measurement light due to the influence of the reflection from the base, the error ΔZe of the measurement result Is given by the following equation from equation (10).

FIG. 8A shows the values obtained for θ = 88.5 °, 88 °, 86 °, and 80 ° with respect to the Al base. FIG. 8B shows the value of Δ. As is clear from the diagrams of R _S on the complex plane when the incident angles are 88 ° and 86 °, and FIGS. 3 and 4, the maximum angle 込 む max at which the circumference is viewed from the origin is represented by (11) The maximum error of detection is given by putting in Ψ of the equation. Therefore, when θ ≦ 85 ° where the circumference enters the second and third quadrants, Ψ changes from 0 to 360 °, so that the maximum value of the detection error becomes equal to ΔZy and measurement becomes impossible. Therefore, it is indispensable to make the incident angle 85 ° or more in the case of the Al base. FIG. 7 shows the maximum value ΔZemax (maximum value in the graph) of the detection error ΔZe also shown in FIG. 8 (A) with respect to the reflectance γ _{b of the} background and various incident angles as parameters. The material name entrusted to the arrow shown in the graph of FIG. 7 is a substance serving as a base of the semiconductor wafer,
From this figure, it is not a problem for materials other than Al. However, when Al is the base, the maximum detection error is 0.6μ at a specific resist thickness (specific φ) even when the incident angle is 85 ° or more.
m. Although the graph of the phase φ and the detection error ΔZe in FIG.
For 80 to 360 ゜, the curve of the graph from 0 to 180 ゜ (180
(゜, 0 μm) by 180 ° rotation. Looking at this graph, φ = 0 ~ 120 ゜ and 240 ゜ ~
The detection error is less than about 0.1 μm between 360 °. That is, if it can be used in this range, high detection accuracy can be obtained. This method will be described below on the basis of the relational expression (6) between φ, the resist thickness d, the wavelength λ of the measurement light, and the incident angle θ. At the same incident angle, for example, two wavelengths λ ₁ = 0.6328 μ
m and λ ₂ = 0.6119 μm laser light is incident on the object to be measured,
When the measurement is carried out by the interferometry, the phase value φ at which the measurement error shown in FIG. This region exists at a constant resist thickness cycle according to equation (6). FIG. 10 shows a region where the error at these two wavelengths becomes large by a line segment. As is apparent from this figure, when the resist thickness is in the range of about 1.2 to 2.4 μm, 2
If any one of the two laser beams is used, the error becomes sufficiently small and accurate measurement can be performed.

〔Example〕

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

FIG. 1 is a diagram showing one embodiment of the present invention, which is applied to a reduction projection type exposure apparatus. Reference numeral 81 denotes an exposure illumination system. The exposure illumination light emitted from the exposure illumination system irradiates the reticle 9, and the transmitted light is transmitted through the reduction lens 8 in the Z direction and Δθ (2
A reduced image of the original reticle image is formed and exposed on the wafer 4 on the wafer stage 7 having a fine adjustment mechanism (inclination about the orthogonal axis, but only one axis will be described hereinafter). A large number of chips are arranged on a wafer, and one to several chips are printed by one exposure. In each chip, since the wafer is not completely flat, immediately before exposure, the height and inclination of the exposure area are obtained by the following method, corrected by the wafer stage 7, and the wafer surface is set to the highest resolution state. Perform exposure. A photoresist is applied to the surface of the wafer with a thickness of about 1.5 μm. In order to accurately detect the height and inclination of the photoresist surface on the wafer, the interference type detection shown in the embodiment of FIG. 1 is performed. The laser light source 1 has a wavelength λ ₁
It is a He-Ne laser of 0.6328 μm. The laser light source 1 ′ is a He—Ne laser having a wavelength λ ₂ of 0.6119 μm. The beam emitted from each laser light source is turned on and off by optical shutters 111 and 111 '. Each laser, for example, by beam splitter 18, 18 'consisting of Bragg gratings, after being 2 minutes, by the wavelength selective mirror 19, light of the wavelength lambda ₁ is transmitted, light of the wavelength lambda ₂ is reflected at each wavelength The split beams are adjusted to pass on the same optical path. Prism 11
0 functions so that the beams of each wavelength divided into two are approximately parallel. One of the parallel beams 16 (16 ') is reflected by the mirror 13 as measurement light and then enters the wafer at an incident angle of 88 °. The other beam 17 (17 ') does not enter the wafer,
Both lights overlap at point A as reference light. The beam passing through the point A reaches the CCD sensor 3 by the mirror 23 and the lenses 21 and 22. The light receiving surface of the sensor is at a position conjugate to A, and interference fringes between the measurement light and the reference light reflected on the wafer are detected. The detection signal of the interference fringe changes in intensity as shown in the expression (9). However, since the CCD has a large number of elements separated and arranged, each signal is converted by the A / D converter 52 in the processing circuit 5. A / D converted sequentially,
It becomes a digital signal. Measurements for the two wavelengths are made by sequentially opening and closing the shutters 18, 18 '. FIG. 11 is an embodiment showing a flow of data processing executed by the processing circuit 5 of FIG. The interference fringe data Fi (Xj) (i is ₁ for data of wavelength λ ₁ and ₂ for λ ₂ ) A / D converted as indicated by 60 in A / D converter 52 is fast Fourier transform (FF
T) The Fourier transform is performed by the circuit 53 in a time of about 1 ms as shown by 61. The spectrum data Ii (ωj) Fourier-transformed by the fast Fourier transform circuit 53 has peaks at two places, ω = ω ₀ (= 0) and ω = ωi, as shown in FIG. 11 (C). ω ₀ is a DC bias component, and ω i is a spectrum corresponding to the period of the interference fringes. Although ω = ωi has a local maximum, ωi is a discrete sample point, so the true peak position is near the sample point giving this local maximum. The spectrum ωi ′ giving this true maximum
Can be determined by the data processing means 54 from the peripheral data such as ωi and ωi + 1, ωi−1, etc. by various known methods as indicated by 62. The true peak values I ₁ (ω _{1 ′} ) and I ₂ (ω _{2 ′} ) and the spectral values at ω ₀ thus obtained for the two wavelengths as indicated by 62 by the data processing means 54. The respective ratios of I ₁ (ω ₀ ) and I ₂ (ω ₀ ) are compared by comparing means 55 as indicated by 63. That _{γ 1 = I 1 (ω 1} ') / I 1 (ω 0) γ 2 = I 2 (ω 2') / I 2 (ω 0) determine the gamma ₁ and larger gamma ₂ in. For example, if γ ₁ > γ _2, i ₀ = 2, and the wavelength of i ₀ is used for detecting the inclination and the height. Since the data of the FFT has already been obtained at each wavelength, the data processing means 54 uses the data of i = i ₀ obtained at 63 and interpolates the FFT data at ωi _{0 ′} and ωi _{0 ′.} Ii ₀
(Ωi _{0 ′} ) (complex number) is obtained, and this Ii
_The phase Ψ is obtained from the imaginary / real number of ₀ (ωi _{0 ′} ). Then, the data processing means 54 calculates the true peak position ω as indicated by 65.
From i _{0 ′} , the pitch of the interference fringes, that is, the inclination Δ of the wafer surface
The height ΔZ of the wafer surface is determined from θ and the phase Ψ. By feeding back the obtained inclination Δθ and height ΔZ, the partial inclination and height of the wafer 4 are controlled. The reason why accurate measurement can be performed by using the wavelength λi ₀ of i (= i ₀ ), which is the larger of γ ₁ and γ ₂ , will be described with reference to FIG. FIG. 8 (A),
(B) has already been described. FIG. 8 (C) shows Al
The third view graph illustrating the complex plane of the complex amplitude R ₃ of the reflected light in the case of a base, and from Figure 4, in which to determine the amplitude γ of the reflected light R _5. FIG. 3 shows a change in the complex reflection coefficient of a wafer in which a resist is applied to Al with a change in resist thickness (phase φ change). (Incident angle θ = 88
゜, Al amplitude reflectance γ _b = 0.878). The graph of FIG. 8 (A) and the horizontal axis coincide. As described above, φ is 120 ° ~ 240
When the resist thickness reaches 相当, the detection error ΔZe increases. The amplitude γ reflected light R ₃ as shown in FIG. 8 At a φ of this region (C) becomes small. As the amplitude γ of R ₃ decreases, the degree of modulation of the interference fringes decreases, and as a result,
Peak value Ii (ωi ') of the spectrum corresponding to the fringe period
Becomes smaller. To remove the effects of light source fluctuations
Ii (ωi ′) is converted to DC bias component Ii as described above.
By dividing by (ω ₀ ) and normalizing, this value (the aforementioned γ
₁ , γ ₂ ) has a small value when φ is 120 to 240 °. However, for λ ₁ = 0.6328 μm and λ ₂ = 0.6119 μm, φ is 12
The photoresist thickness in the range of 0 to 240 ° is the region shown by the line segment in FIG. 10, but the resist thickness where the line segments at these two wavelengths overlap does not exist between 1.2 μm and 2.4 μm. Slave connexion, processing obtains the gamma ₁ and gamma ₂ of the above two wavelengths as mentioned above by the data processing means 54 in the circuit 5, when measured by using light of a wavelength larger, the range of the resist thickness The measurement error does not exceed 0.1 μm, and the data processing means 54 in the processing circuit 5 can accurately detect the inclination and the height. Figure 10 is acceptable when having conducted a and wavelength selection using the lambda ₁ and lambda ₂ (resist thickness corresponding to the solid line component above) detection resist thickness of occurrence of errors exceeding the allowable value when varying the detection wavelength It shows a resist thickness region (lower line segment) in which a detection accuracy within a value can be obtained.

In this embodiment, the input signal 51 to the processing circuit 5 shown in FIG.
May be input as to whether the base of the current wafer is Al or not. Above processing for Al, for the sample base reflectivity is small than Al, be fixed to one wavelength of lambda ₁ or lambda ₂ becomes possible precise measurement of the inclination and height. The fine movement control of the wafer stage 7 is performed based on the tilt and height information obtained in this manner.

FIG. 9 shows an embodiment of the present invention. 1 denote the same parts. The light source 1 is a semiconductor laser having a wavelength lambda ₁ is 831Nm, the light source 1 'is the wavelength lambda ₂ is a semiconductor laser of 810 nm. Beams emitted from both light sources are lenses 11 and 11 '.
Is converted into parallel light, λ ₁ is transmitted through the wavelength selection mirror 19, and λ _1
2 is reflected and guided to the same optical path. The cylindrical lenses 110 and 120 convert the parallel beam of the semiconductor laser to a desired beam diameter. The beam splitter 10 separates a beam into measurement light and reference light. The measurement light reflected by the half mirror 12 is reflected on the surface of the wafer 4, returned vertically by the turning mirror 14, and reflected again on the surface of the wafer 4.
Through. On the other hand, the reference light is reflected by the half mirror 12,
The light is returned vertically by the direct reflection mirror 14 and passes through the half mirror 12. Both light mirror 210, a lens 21, a mirror 220, passes through a lens 22, both light of wavelength lambda ₁ passes through the wavelength selection mirror 28, the lens 22 ', an interference fringe overlap on the imaging surface of the imager 3 " The wedge glass 24 in the optical path of the reference light is used for refracting the reference light so that the imaging surface and the vicinity of the mirror surface of the return mirror 14 have a co-post relation, and both lights overlap on the imaging surface. and it is. light of the wavelength lambda ₂ in the same manner by the wavelength selective mirror 28, which is generated in the imaging device 3 via the lens 22 "the interference fringes of lambda _2. The interference fringe data of both wavelengths are detected at the same time and input to the processing circuit 5. Processing circuit 5
The information such as the material of the base of the wafer to be exposed and the resist thickness information are input by the input means 51 'such as a key input terminal and a magnetic card. These pieces of information are measured in advance by another device or the like. When information on these wafers is input by the input means 51 ', FIGS.
The wavelength at which the error is smaller is determined by the software in the processing circuit 5 by the method described with reference to the drawings and the like, and the inclination and height are detected based on the measurement data of the wavelength.

FIG. 12 shows an embodiment of the present invention, and the same parts numbers as those in FIGS. 1 and 9 represent the same parts. Semiconductor laser,
'And' have wavelengths of 831 nm, 810 nm and 750 nm, respectively. Each semiconductor laser is provided with a Peltier element 120, 120 'and 120 "for temperature control to maintain a constant temperature and stabilize the oscillation wavelength. I have. The oscillation of each semiconductor laser is controlled by a control circuit 5 ". The beams emitted from each semiconductor laser are collimated lenses 11, 11 ', 1
1 "and the beam splitters 18, 18 ', 19, 19' are guided to the same optical path to generate reference light 17 and object light 16 on the same optical path. An interference image is detected by the sensor 3. The semiconductor lasers 1 and 1 'are oscillated in time series, and an interference pattern at each wavelength is sequentially taken out.
The aforementioned spectral ratios γ ₁ γ ₂ are compared, and the larger wavelength is used. To select this wavelength, a shutter (not shown) for blocking the reference light is inserted behind the prism 110 in FIG.
Only the object light may be detected by the CCD3, and the selection may be made from the level. Since the two wavelengths used for selection are relatively close to each other, a 750 nm semiconductor laser 1 "separated from these wavelengths is used for removing uncertainty in height detection. In particular, the wafer is removed from a wafer cassette (not shown). When mounted on the wafer stage No. 7, the variation in the height of the resist surface on the wafer becomes about 25 μm in width due to the variation in the thickness of the wafer, etc. However, at λ ₂ = 810 μm at 86 ° incidence, from the equation (10) ΔZp = 5.8 μm (m = 1) That is, at one wavelength, when the height change is an integral multiple of 5.8 μm, the height change becomes the same phase value.
When the wafer 4 is mounted on the wafer stage 7, the true height is not known. Then, comparing the phases at the two wavelengths of 750 nm and 831 nm, the height change ΔZ ₃₁ of the wafer at which the phase relationship at the two wavelengths is the same is given by the following equation.

Therefore, when the height is in the range of 55.2 μm, the height is accurately obtained from the relationship between the phases of the two wavelengths. In the embodiment shown in FIG. 12, as described above, the two wavelengths close to each other are used for high-precision detection of the height, and the rough detection is performed at the other wavelength and the one of the wavelengths, so that the influence of the underlayer covers a wide range. Hardly ever
The height and inclination can be obtained with high accuracy. λ ₁ and λ ₂
Is selected as described above, so that φ is 0 to 120 °, 24
Since the angle can be 0 ° to 360 °, as shown in FIG. 8 (A), even with the Al base pattern, the height detection accuracy is within 0.1 μm. However, it is also possible to perform more accurate measurements. If the thickness of the resist has been measured in advance, the value is input from the input terminal 51 "of the control circuit 5" to obtain an error value as shown in FIG. 8 (A). By correcting the height control value,
Very accurate detection and control are possible.

Although λ ₃ is used only for coarse detection in the embodiment of FIG. 12,
It may be used for fine detection, or may have a fourth wavelength. The present invention can also be realized by using a wavelength-variable laser such as a dye laser. In addition, not only laser light but also a light source having a high power such as a mercury lamp may be used to generate collimated light to obtain a narrow band spectrum and obtain interference fringes.

Although the embodiments described with reference to FIGS. 1, 9 and 12 all aim at the exposure focusing of the reduction exposure apparatus, the present invention is not limited to such applications. It goes without saying that the present invention can be widely used to detect the height and inclination of the surface with high accuracy of less than a micron meter, and to use the detection result to control the height and inclination of the detection surface.

〔The invention's effect〕

As described above, according to the present invention, the base of an optical multilayer
Even with a material having a very high reflectivity, such as Al, the height and inclination of the surface can be detected with high accuracy within 0.1 μm. For example, 0.5 μmL & S
When the fine pattern is exposed, the image plane and the resist surface can be completely controlled to coincide with each other, and a pattern with almost no line width variation can be formed. As a result, the yield of pattern exposure is greatly improved, and a great economic effect is exhibited.

[Brief description of the drawings]

1, 9 and 12 show an embodiment of the present invention.
FIG. 2 is a diagram showing reflection and refraction of light on the surface for explaining the principle of the present invention, FIGS. 3 to 5 are complex amplitude diagrams of reflected light when Al is a base, and FIG. FIG. 7 is a graph showing the relationship between the incident angle and the height of the interference fringe pitch in the invention, FIG. 7 is a graph showing the relationship between the reflectance of the base and the maximum error, and FIG. 8 is a detection error due to a phase change accompanying a change in the resist thickness. FIG. 10 is a diagram showing the relationship between the phase of reflected light and the amplitude of reflected light. FIG. 10 is a diagram showing a resist thickness exceeding an allowable detection error when the detection wavelength is changed.
FIG. 5 is a diagram showing an embodiment of the present invention showing a method of processing detected interference fringe information and selecting a wavelength. 1,1 ', 1 "... Interference light source 18,18', 19,19 '... Beam splitter 10,110 ... Prism, 21,22 ... Lens 3 ... CCD sensor, 4 ... Wafer 5,5 "... Processing circuit, 7 ... Wafer stage

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-57107 (JP, A) JP-A-59-178304 (JP, A) JP-B 8-28319 (JP, B2) (58) Field (Int.Cl. ⁶ , DB name) G01B 11/00-11/30 H01L 21/027

Claims (9)

(57) [Claims] 1. A monochromatic light source for emitting beams of a plurality of wavelengths having different wavelengths, collimating means for converting a beam emitted from the monochromatic light source into substantially parallel light, a beam splitter for dividing the beam into a plurality of beams, and the beam Irradiation optical means for irradiating one of the parallel beams split by the splitter to the optical multilayer object, and a detection optical system for guiding the object light irradiated by the irradiation optical means and reflected by the optical multilayer object to the detector, A reference light optical system for directing the other parallel beam split by the beam splitter to the detector directly without passing through the optical multilayer object and superimposing the object light obtained by the detection optical system on the detector; Selecting any one of a plurality of interference fringe information signals detected by the detector corresponding to the plurality of wavelengths of light to detect the inclination or height of the optical multilayer object. Interferometric inclination or height detection device is characterized in that a means out. 2. The interference type inclination or height detection according to claim 1, wherein the selection by said selection detecting means is performed based on optical characteristics of an optical multilayer object and information on a film structure. apparatus. 3. The apparatus according to claim 1, wherein said selection detecting means has a comparing means for comparing object lights at a plurality of wavelengths.
The interferometric tilt or height detection device as described. 4. The selection detecting means performs a Fourier transform on the information of the interference fringes, and calculates a frequency ω of the Fourier transform spectrum.
₀ (= 0), a ratio I (ω ′) between a bias component I (ω ₀ ) and a spectrum component I (ω ′) corresponding to the frequency of the interference fringes.
2. The interference type inclination or height detecting device according to claim 1, further comprising a comparing means for comparing the value of / I (ω ₀ ) at each wavelength. 5. The apparatus according to claim 3, wherein said selection detecting means corrects a measurement result at a selected wavelength by using information on an optical characteristic and a film structure of the optical multilayer object. Or the interference type inclination or height detecting device according to 4. 6. An apparatus according to claim 1, wherein an angle of incidence by said irradiation optical means is 85 ° or more with respect to a normal direction of a surface of said optical multilayer object. Interferometric tilt or height detector. 7. The interference type inclination or height detecting device according to claim 1, wherein the monochromatic light source is configured to emit S-polarized light. 8. A light source for emitting beams of a plurality of wavelengths having different wavelengths in a reduction projection exposure apparatus for reducing and exposing a circuit pattern formed on a mask by a reduction projection lens onto a substrate by step-and-repeat the substrate. When,
Collimating means for converting a beam emitted from the light source into substantially parallel light, a beam splitter for splitting the beam into a plurality of beams, and passing one of the parallel beams split by the beam splitter through a gap between the reduction projection lens and the substrate. An irradiation optical unit for irradiating the substrate, a detection optical system for guiding object light irradiated by the irradiation optical unit and reflected on the substrate to a detector through a gap between the reduction projection lens and the substrate, and the beam splitter. A reference light optical system that guides the other split parallel beam to the detector, and superimposes the object light obtained by the detection optical system on the detector, and corresponds to light of a plurality of wavelengths, is detected by the detector. Selection detecting means for selecting any one of a plurality of information signals of interference fringes and detecting a partial inclination or height of the substrate. Apparatus. 9. A reduction projection exposure method for reducing and exposing a circuit pattern formed on a mask by a reduction projection lens onto a substrate by step-and-repeat the substrate, wherein a plurality of wavelengths having different wavelengths emitted from a light source are provided. The beam is divided into a plurality of beams by converting the beam into substantially parallel light, and one of the divided parallel beams is irradiated onto the substrate through a gap between the reduction projection lens and the substrate, and the object light reflected on the substrate is reflected by the reduction projection lens. To the detector through the gap between the substrate and the substrate, the other split parallel beam is guided to the detector and superimposed on the object light on the detector, and for light of a plurality of wavelengths, a plurality of light beams detected by the detector are detected. A reduction projection type exposure method comprising selecting one of information signals of interference fringes and detecting a partial inclination or height of the substrate.