JPS61228449A - Exposing device - Google Patents

Abstract

PURPOSE:To perform high-precision positioning operation by detecting the shape of a positioning grating formed on a wafer and correcting the quantity of an occurring error in positioning by using the grating shape. CONSTITUTION:A reticle 14 is arranged between an illumination optical system 13 and the 1st Fourier transform lens 15 and an image emitted as a secondary light source is converged temporarily by the 1st Fourier transform lens 15 and further passed through the 2nd Fourier transform lens 15 to project an image of the pattern of the reticle 14 on the semiconductor wafer. When the 1st Fourier transform lens 15 and the 2nd Fourier transform lens 17 are equalized in focal length, the image of the pattern on the reticle is projected to life size. When the 1st and the 2nd Fourier transform lenses 15 and 17 are made different in focal length, the image is projected while reduced. The diffracted light of the pattern on the reticle is distributed spatially on the rear focal plane of the 1st Fourier transform lens and a spatial filter 16 is arranged to filter the pattern image formed on the reticle in a spectral plane, thereby projecting the light on the surface of the wafer W.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus having a fine pattern, particularly an exposure apparatus for semiconductor devices and the like having a submicron rule of 1 micron or less.

Conventional technology g8 The conventional example (IEEE, trans on
E, DED-26, 4, 1979, 723, Gijs
In Bouwhuis), a laser beam is incident on the 7-Lier transformation plane of a microlens indicated by a lens system Ll and L2, and the beam is incident on a grating formed on a wafer W via a lens L2. Then, the diffracted light diffracted from the grating is returned through the lens system L2, and the spatial filter S
Only the ±1st-order diffracted light passes through the F, and then enters the reticle R through the lens system and the +1st-order diffracted light overlaps in the vicinity of the reticle, creating interference fringes. , a configuration is shown in which light passing through a grating provided on the reticle R is detected by a photodetector to align the wafer W and the reticle Ri. In the configuration of FIG. 8, the wafer W
It has been stated that the position cannot be corrected starting from the asymmetrical grid formed on the alignment mark, but it is impossible to achieve this in all processes and marks in the production of alignment marks, and it is difficult to put it into practical use. Not yet reached.

Problems to be Solved by the Invention It is an object of the present invention to provide an exposure apparatus that has a function of correcting the amount of alignment error caused by the shape of the grid by detecting the shape of the alignment grid formed on the wafer. The purpose is

Means for Solving the Problems In order to solve the above problems, the present invention makes the light beam emitted from the light source incident on a reticle on which a first grating is formed, and the light beam diffracted by the grating is transmitted to the first lens. In an exposure apparatus that has a positioning method in which the light beam passes through a system, a spatial filter, and a second lens system and is incident on a substrate on which a second grating is formed, a light beam emitted from a light source is diffracted by the first grating. A first aperture group for passing only the 11th-order or +1st-order diffracted light, and the light intensity of a plurality of diffracted lights that have passed through the 1st-order aperture group and are diffracted by a second grating. a first photodetector group for respectively detecting 1. and a second aperture group for passing only the +1st order or -1st order diffracted light also diffracted by the first grating; A second photodetector group for detecting the light intensity of each of the plurality of diffracted lights whose diffracted light passing through the aperture group @2 is diffracted by the second grating; and a third aperture group for passing the +1st-order diffracted light, and detecting the light intensity of each of the plurality of diffracted lights in which the diffracted light that has passed through the third aperture group is diffracted by the second grating. A spatial filter equipped with a third photodetector group for the purpose of detecting the lattice shape, and a moving means for moving each aperture group of the spatial filter to the passing position of each diffracted light beam are provided. A configuration is provided that detects the alignment error amount and detects the relative position of the first grating and the fjg2 grating.

According to the above-described configuration, the present invention moves each aperture group of the spatial filter to the passing position of each diffracted light in order, makes each diffracted light incident on the second grating, and is transmitted by the second grating. The diffracted light is detected by each photodetector group. The first aperture group/first photodetector group and the second aperture group/second photodetector group detect the second lattice shape, and estimate the amount of alignment error generated by the lattice shape. In addition, the third aperture group and the third photodetector group detect the amount of positional deviation between the first grating and the second grating for alignment, and also detect the amount of error caused by the aforementioned grating shape. Correct.

Embodiment An embodiment of the optical system according to the present invention is shown in FIG.
The light emitted from A beam expander 12 expands the light (which may be a spectral light source such as incident on the entrance pupil.

In the following description, in order to briefly describe the principle of the present invention, the reticle is illuminated by a parallel light beam, and the first and second lens systems are Fourier transform lenses. However, the illumination optical system 13 does not necessarily have to be Fourier transform lenses. and the first Fourier transform lens 167, the reticle 14 is disposed between the
The image produced by using the pattern of the reticle 14 as a secondary light source is
The light is once condensed by the Fourier transform lens 16, and then subjected to Fourier transform of the electron 2. The image of the pattern on the reticle is projected onto the semiconductor urchin jSVir through the lens 17. When the focal lengths of the first 7-Lier transformation lens 16 and the 7-Lier transformation lens 17 of flX2 are made equal, the pattern on the reticle is projected at the same magnification. By making the focal lengths of the first and second Fourier transform lenses 15, 17 different, reduction projection is possible. The back focal plane of the first 7-Lier conversion lens has the diffracted light (7-Lier) of the pattern on the reticle.
A spatial filter 16 is arranged to filter the pattern formed on the reticle in the spectral plane, and the pattern is incident on the wafer W surface.

FIG. 3 shows a reticle used in the exposure apparatus of the present invention. FIG. 3 is a plan view of the third blurred reticle 14, and FIG. 3 is a sectional view thereof. The reticle 14 includes a circuit pattern section 42
and its peripheral portion 43, and a first grating 41 for positioning is provided in a portion of the peripheral portion 43 corresponding to the scribe line.
．． 41' is formed (the grating 41 is for the X direction,
' is for the y direction).

Incident light 44 is incident on the reticle 14, and as shown in FIG.

A plurality of diffracted lights are diffracted, such as +2nd order. FIG. 4 is a diagram further explaining the principle of the exposure apparatus of the present invention. The light of wavelength λ emitted from the light source 11 is transmitted to the beam expander 1
2, and further converted into parallel light with a predetermined spread by a collimator lens 21. A first grating 41, which is the front focal point f1P of the first Fourier transform lens 61, is arranged. The pitch P1 of the first grating 41 and the diffraction angle θ1 of the diffracted light are P1s+nθn=nλ(n==o, ±1.±
2...) The light diffracted into a plurality of light beams in this way enters the 17th-Lie transformation lens 51, and furthermore, the back focal plane ξ has a light beam corresponding to each diffracted light beam. to do
The coordinate ξ61 corresponding to the Fourier spectrum of the −1st-order diffracted light that forms the Jnis vector image is ξ61; f1Sinθ
1 p1sinθ1=λ, the Fourier spectrum of the 0th order diffracted light ξ6゜ξ
eo=f1sinθ0=.

The Fourier spectrum image is focused on the Fourier transform plane while being completely separated from the

As shown in FIG. 2, a spatial filter 16 is placed on this Fourier transform surface. The spatial filter 16 has three filtering functions: when only the 1st-order diffracted light 61 passes, when only the +1st-order diffracted light 62 passes, and when the ±1st-order diffracted lights 61 and 62 pass simultaneously. . First, a case where only the first-order diffracted light 61 diffracted by the I-direction grating 41 is allowed to pass through will be described with reference to FIG. The first-order diffracted light 61 that has passed through the first aperture 7oξ formed in the spatial filter 16 passes through the 27th-Lie transformation lens 62 having a focal length f2, and is further projected onto the wafer W. On the sea urchin ISW there is a first grid 41
．． A second grating GG' is provided at a position corresponding to 41' (G/ is not shown).

The −1st-order diffracted light 61 is again diffracted by the second grating G into a plurality of diffracted lights such as 0th order, ±1st order, ±2nd order, and so on. The light intensity of each of these diffracted lights is detected by the first photodetector 71ξ. In this example, 0th order, ±1st order, −
It consists of six photodetectors 71ξ for detecting the second, +3rd and +4th order diffracted lights. The intensity of each diffracted light is influenced by the shape of the second grating G, and from the intensity of the diffracted light, the shape of the grating f The shape of is estimated.

Here, regarding the spatial filter 16, the spatial filter 16
This will be explained with reference to FIG. 6, which shows the planar configuration of. As mentioned above, 7
oξ is! The first aperture 71ξ for passing the 1st-order diffracted light 61 of the direction grating 41 is the 0th order, ±1, where the diffracted light passing through the first aperture is diffracted by the second grating on the wafer W.
Next, −2nd order.

A photodetector (indicated by the mouth in FIG. 6) consisting of six photodetecting elements for detecting +3rd-order and +4th-order diffracted light; 7
0v.71 is a first aperture associated with the y-direction grating 41' and a photodetector (70ξ,
70η and the first aperture group 071ξ and 71η together form the first photodetector group). 7oξ and 71ξ are approximately on the same axis, and 70v and 71η are also approximately on the same axis. The intersection angle between 7oξ and 70η is the x-y direction grating 41°. 772ξ and 72η are the second aperture group for passing the +1st-order diffracted light 62 (however, the +1st-order diffracted light in the y direction is not shown), and 73ξ and 73η are the The diffracted light that has passed through the second aperture is diffracted by the second grating on the wafer W, 0th order, ±1st order, +
A second photodetector group (indicated by the mouth in FIG. 6) includes 10 photodetector elements for detecting second-order, -third-order, and -fourth-order diffracted light. 74ξ−1・74ξ−2974 goo 1 is ±
Third aperture group 75ξ/75 for passing the first-order diffracted light 61.62 (however, ±1st-order diffracted light in the y direction is not shown)
17 is the ±1st-order diffracted light 61.62 that passed through the third aperture group
is diffracted by the second grating on the wafer W (+1st order, -1st order) t (+3rd order, +1st order).

(+4th order, +2nd order), (-1st order, -3rd order).

A third photodetector group composed of eight photodetector elements for detecting each diffracted light (-2nd order, -4th order).

The spatial filter 16 configured as described above is equipped with a moving means as shown in FIG. The main part of the moving means is a moving stage 79 that holds the spatial filter 16 fixedly and rotatably. As mentioned above, the zero-order spatial filter 16 is composed of a ball screw 8o, a pulse motor 81, etc. for moving the moving stage 79 (the moving stage 79 may be moved using a linear motor, etc.). It has a street filtering function and a function for pattern exposure. Let's explain its functions.

(1) When only the -1st-order diffracted light 61 is allowed to pass (although not shown, the -1st-order diffracted light for the y direction is also included),
First-order diffracted light 6 diffracted by the first grating 41, 41'
The spatial filter 16 is rotated by the pulse motor 78 so that the first aperture groups 7oξ and 70v are located at the first passing position. The 1st-order diffracted light 61 that has passed through the first aperture group 7oξ/7077 is re-diffracted by the second gratings G, G/ on the wafer W, and the diffracted light is transmitted to the first photodetector group 71ξ/7.
1η, and the grid shape is estimated as described above.

(When only the 21st + 1st order diffracted light 62 is allowed to pass (However,
Although not shown, it also includes the +1st-order diffracted light for the y direction) (1
), a second aperture group 72 is provided at the passage position of the +1st-order diffracted light.
The spatial filter 16 is rotated by the pulse motor 78 so that ξ·72 is located. The diffracted light diffracted again by the second grating G-α is detected by the second photodetector group 73ξ/73? Detect and estimate the grid shape.

(2) When only the ±1st order diffracted light 61.62 is allowed to pass (However, although not shown, the +1st order diffracted light for the y direction is also included) Similarly to (1), the passing position of the ±1st order diffracted light 61°e2 the third aperture group 74ξ-1, 74ξ-2, 74η-1,
The spatial filter 16 is rotated by the pulse motor 78 so that the filter 747-2 is positioned. By detecting the diffracted light diffracted again by the second grating with the third photodetector group 76ξ and 75η, the first gratings 41 and 41' of the reticle 14 and the second grating G on the wafer W are detected. -G' can be obtained. Furthermore, based on the grid shape estimation results in (1) and (2) above, highly accurate alignment is possible by feeding back the alignment error generated by the grid shape to the position information and correcting it. It is. Further, since the distance moved for correction can be detected as position information by detecting the light intensity with the third photodetector group 75ξ and 76η, it can be monitored. Therefore, it is possible to accurately grasp the amount of movement of the Ueno SW.

(4) When exposing the circuit pattern etc. of the reticle 14 When exposing the circuit pattern 42 etc. of the reticle 140, the pulse motor 81 is used to remove the spatial filter 16 from within the aperture of the first Fourier transform lens 16. By moving the stage 79, the circuit pattern 42 is exposed on the wafer W.

In the above explanation, in order to estimate the lattice shape, (1
) − When only the first-order diffracted light is passed, and (2) +
Although the grating shape was estimated based on the case where only the first-order light passes through, it is possible to estimate the grating shape using only one of the diffracted lights, but (1) and Han) are used in this example. ,3
Although the filtering is performed using separate apertures, each aperture may also be used for the same purpose (for example, the first aperture 7
0ξ and second opening 72ξ) 0 In this embodiment, the first, second,
The third aperture groups are arranged concentrically, and the spatial filter 16
By rotating and moving linearly to provide three filtering functions and a pattern exposure function, the spatial filter 16 can be made compact and each filtering function can be selected at high speed. It is.

In this embodiment, in order to perform pattern exposure, the moving stage 7
Although the lens 9 is moved linearly, the moving stage 79 may be moved outside the aperture of the first Fourier transform lens 16 by rotating the moving stage 79 using a motor or the like.

-Also, as an example of fa2, the aperture groups are not arranged concentrically but are arranged as shown in FIG. 7. 80.81st 4th
Opening. 16' is a spatial filter fixed on the moving means. The main part of the moving means is a moving stage 86. which fixes the spatial filter 16'. A ball screw 87 for moving the moving stage 86. It is composed of a pulse motor 88 and the like. By arranging each aperture group in series, the moving means can be constructed using only linear moving means.

Effects of the Invention According to the present invention, it is possible to detect the shape of the alignment grid formed on the wafer, correct the alignment error generated by the grid shape, and perform alignment between the reticle and the wafer. , it is possible to perform highly accurate positioning.

[Brief explanation of drawings]

Fig. 1 is a basic configuration diagram of a spatial filter according to the present invention;
The figure is a basic configuration diagram of an exposure apparatus according to the present invention, and FIG. 3(a)
3(b) is a cross-sectional view of the alignment grating, FIG. 4 is a principle diagram of the re-diffraction optical system according to the present invention, and FIG. 6 is a diagram of the X-direction grating according to the present invention. Figure 6 is a detailed view of the vicinity of the wafer when only the first-order diffracted light is passed through. Figure 6 is a plan configuration diagram of the spatial filter.
This figure is a basic configuration diagram of a spatial filter according to the second embodiment, and FIG. 8 is a diagram showing an example of a conventional alignment method. 11...Light source, 14...Reticle, 1
5...First Fourier transform lens, 16...
... Spatial filter, 17... Second Fourier transform lens, W... Wafer, 41, 41'...
...First lattice, G-α...Second lattice,
7oξ・7oη・・・・・・First aperture group, 71ξ・71
η...First photodetector group, 72ξ・72η...
...Second aperture group, 73ξ・73η...Second photodetector group, 74ξ 74ri...Third aperture group, 7
5ξ・76η...Third photodetector group. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 Figure 3 (a-1st order tj-order missing number 5 Figure 7 Figure 8 XW□

Claims (4)

[Claims] (1) The light flux emitted from the light source passes through the reticle on which the first grating is formed, the first lens system, the spatial filter, and the second lens system, and is incident on the substrate on which the second grating is formed. ,
The spatial filter of the exposure apparatus, which includes a photodetector that detects the diffracted light from the second grating, detects the -1st or +1st order of the light flux emitted from the light source that is diffracted by the first grating. A first aperture group for allowing only the diffracted light to pass through, and a plurality of diffracted light beams that have passed through the first aperture group and are diffracted by the second grating to detect the light intensities of each of them. a third aperture group for passing the ±1st-order diffracted light diffracted by the first grating; a third photodetector group for respectively detecting the light intensity of a plurality of diffracted lights that are diffracted by the second grating, and each diffracted light passes through each aperture of the spatial filter. An exposure apparatus characterized by having a moving means for moving to a certain position. (2) A first aperture group for passing only -1st or +1st order diffracted light, which is the light beam emitted from the light source and is diffracted by the first grating; Apart from the first photodetector group for detecting the light intensity of each of the plurality of diffracted lights whose diffracted lights are diffracted by the second grating, the first photodetector group
a second aperture group for passing only the +1st-order or -1st-order diffracted light diffracted by the grating; and a second aperture group for allowing the diffracted light that has passed through the second aperture group to be diffracted by the second grating. 2. The exposure apparatus according to claim 1, further comprising a spatial filter including a second photodetector group for detecting the light intensity of each of the plurality of diffracted lights. (3) The exposure apparatus according to claim 2, wherein the first, second, and third aperture groups are arranged concentrically. (4) The exposure apparatus according to claim 2, wherein the first, second, and third aperture groups are arranged in series.