JPS61264727A - Exposing device - Google Patents

Abstract

PURPOSE:To perform more accurate positioning by accurately detecting a photomask and a positioning mark on a wafer by a photodetector, detecting the displacement of the wafer, and correcting it. CONSTITUTION:A lattice group K is formed on a reticle 14 surface, and lattice groups Aw, Bw are formed at the positions corresponding to the group K on a wafer W. The luminous fluxes diffracted by the group K on the reticle pass through a space filter 16 as a pair of diffracted lights on the spectral surface of the first lens system 15, the two fluxes are guided to the second lens system 17, an interference moire generated by the two fluxes is projected on a substrate, and the light intensity of the again diffracted light from the groups Aw, Bw provided on the substrate are respectively detected by photodetectors D1, D2. Thus, the positional relationship between the groups K and Aw is detected. Similarly, the positional relationship between the group K on the reticle and the group Bw on the wafer is detected. Thus, an error of the interval between the groups Aw and Bw with respect to the group K is calculated.

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 a semiconductor device or the like having a submicron rule of 1 micron or t<ld or less.

BACKGROUND OF THE INVENTION Semiconductor devices have recently become more and more densely packed, with the dimensions of the fine patterns of each element reaching 1 micron or less. L
Conventionally, alignment between a photomask and an LSI wafer during SI manufacturing was performed by overlapping alignment marks on the photomask and alignment marks on the wafer, but the alignment accuracy was ±0.3. It is on the order of microns, and when forming submicron elements, the alignment accuracy is poor and it is not practical. Furthermore, since the wafer is manufactured through various thermal processes, the alignment marks formed on the wafer W as shown in FIG.
The distance lw between marks changes due to thermal expansion or the like. Therefore, the alignment marks on the reticle and the alignment marks on the wafer do not perfectly match. When forming submicron elements, as described above, it is necessary to minimize alignment errors due to wafer deformation.

Problems to be Solved by the Invention As described above, the conventional alignment methods have poor alignment accuracy and cannot accurately correct alignment errors due to wafer deformation.

The present invention has been made in view of this point, and it detects the photomask and the alignment mark on the wafer with high precision,
Another object of the present invention is to provide an exposure apparatus that incorporates a highly accurate positioning method by also detecting and correcting the amount of deformation of the wafer.

Means for Solving the Problems In order to solve the above problems, the present invention forms a grating group K on the reticle surface, and also forms a grating group AV on the wafer at a position corresponding to the grating group K. and Bw, and the light beam diffracted by the grating group K on the reticle is passed through a pair of diffracted lights at the first lens system's (Subek) tV plane by a spatial filter, and these two light beams are passed through the second lens. system, and project the interference fringes generated by the binary flux onto the substrate.
The light intensity of the diffracted light diffracted again from the grating groups w and 13w provided on the substrate is detected by a photodetector.

According to the above-described configuration, the present invention detects the diffracted light generated by the grating group X on the reticle by the grating group W on the wafer and detects the light intensity of the diffracted light with a photodetector. The positional relationship between the group and the grid group person W is detected. Similarly, the positional relationship between the grating group on the reticle and the grating group By on the wafer is detected. From the above,
It is possible to calculate the error amount between the grating group K and the grating group spacing of the grating groups w and By, and by correcting the error amount, highly accurate alignment is realized.

Example An embodiment of the optical system according to the present invention is shown in FIG.

The light emitted from the light source 11 (in this figure, the configuration is assumed to be a laser beam in order to obtain clearer coherence and deeper depth of focus, but the entire optical system is a white interference optical system. An Az light source (such as a mercury lamp) may also be used. ) is expanded by a beam expander 12 and incident on the entrance pupil of the first lens thread 16 by an illumination optical system 13 composed of a collimator lens or a condenser lens for converting this light into parallel light or convergent light. do.

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, but they are not necessarily Fourier transform lenses. It's okay.

A reticle 14 is arranged between the light source optical system 13 and the first Fourier transform lens 15, and the image emitted from the pattern of the reticle 14 as a secondary light source is once focused by the first Fourier transform lens, and then Fourier transform lens 17
The image of the pattern on the reticle is projected onto the wafer 18 through the reticle. When the focal lengths of the first Fourier transform lens and the second Fourier transform lens are made equal, the pattern on the reticle is projected at the same magnification. By changing the focal lengths of the first and second Fourier transform lenses, reduced projection becomes possible.

The diffracted light (Fourier spectrum) of the pattern on the reticle is spatially distributed on the rear focal plane of the first Fourier transform lens, and in the configuration example of the present invention, a spatial filter The pattern formed on the reticle is filtered by the spectrum plane, and the pattern formed on the reticle is filtered by the spectrum plane.
The light is incident on the W plane.

FIG. 3 shows a reticle used in the exposure apparatus of the present invention. FIG. 3A is a plane view of the reticle fi714, and FIG. 3A is a cross-sectional view thereof. The reticle 14 is a circuit pattern section 4
In the peripheral part 43, a grating group AR1 and a grating group BR whose longitudinal direction of the gratings is parallel to the grating group AH are formed at positions separated by an interval An. Incident light 44 enters the reticle 14, and as shown in FIG. It is diffracted.

FIG. 1 is a diagram further illustrating the positioning principle of the exposure apparatus of the present invention. Light having a wavelength λ emitted from a light source 11 is expanded by a beam expander 12 and further converted into parallel light having a predetermined spread 9 by a collimator lens 21 . Reticle /l/14 having grating groups AR and BR with pitch P1 at position J:1 of front focal point f1 of first Fourier transform lens 51
Place. The pitch P1 of the grating groups AR and BR and the diffraction angle θ of the diffracted light are P 1slRθH=nλ (n=o, ±1
．． There is a relationship of ±2−・−). The light diffracted into a plurality of light beams in this way enters the first Fourier transform lens 51,
Furthermore, the coordinate ξ61 corresponding to the Fourier spectrum μ of the −1st-order diffracted light, which forms the Fourier spectrum image corresponding to each diffracted light on the back focal plane ξ, is ξ61=f1S.
1rIθ1 P1thθ=λ, and a Fourier spectrum image is formed on the Fourier transform plane in a state completely separated from the Fourier spectrum ξ60 ξ6o=f1sIrIθo=0 of the zero-order diffracted light. A spatial filter 16 is arranged near this Fourier transform surface, and only the ±1st-order diffracted light passes through.

This diffracted light passes through the second Fourier transform lens 62, and is further projected onto a grating group W1 and a grating group Bw formed on the wafer W at a distance lw apart. (lattice group At,
Bw is the lattice group a.

It is formed at a position corresponding to Bit. ) wafer W
In the image projected above, interference fringes are generated by the interference of the ±1st-order light components of each of the gratings in grating groups A, BH.

At this time, light intensity information indicating the positional relationship between the interference fringes and the grating groups w, By on the wafer W is obtained. In other words,
The +1st-order diffracted light L1 and the -1st-order diffracted light L2 diffracted by the grating group H generate interference fringes on the grating group W on the wafer W, and also generate interference fringes that are diffracted again by the grating group W. The light intensity of the light L3 is detected by the photodetector D1. FIG. 4 shows the positional relationship with very good resolution between the interference fringes generated by the grating group Mn and the grating group Aw by slightly displacing the wafer W and measuring the change in the light intensity of the diffracted light L3. A sinusoidal light intensity change like this can be obtained. Similarly, the +1st-order diffracted light L4 and -1st-order diffracted light L5 diffracted by the grating group BH on the reticle 14 generate interference fringes on the grating group BY on the wafer W, and are diffracted again by the grating group Bw. By detecting the light intensity of the diffracted light L6 by the photodetector D2, the grating group BR
The positional relationship between and the grating group BR can be detected with high accuracy.

At this time, since the wafer W has undergone various thermal processes,
The wafer W is slightly deformed due to thermal stress, thermal expansion, and the like. Therefore, since the interval between the grating groups Ay and By on the wafer W has slightly changed from the initial interval, the interval lR between the grating groups AR and BR on the reticle does not completely match.

In other words, if the positional relationship between the grating group AR and the grating group lw is the same at the intermediate position S in FIG.
They match at the intermediate position S in FIG. 4, but if there is a slight deformation ΔS, they deviate from the intermediate position S by ΔS. By detecting this ΔS, the minute deformation amount ΔS of the wafer W can be detected with high accuracy.

As a second embodiment, in the first embodiment, for convenience of explanation,
For example, a series of grating groups K and Bw are formed on the reticle at positions separated by an interval IR.
are formed on the wafer, and the lattice groups 5 w,
The same effects as in the first embodiment can be obtained by forming interference fringes on the grating groups w and 3w by the light beams incident on the grating groups.

As a third embodiment, in the first embodiment, photodetectors D1 and D
2 at a distance δ from the spatial filter surface, and each diffracted light L5
and L6 are detected independently, but as shown in Fig. 5, only one photodetector is provided, and the grating group AR on the reticle
, by alternately blocking the light beams incident on the BFI, the positional relationship of each grating group is set near the Fourier transform plane.
It may be detected by the photodetector D1.

As a fourth embodiment, as a method for correcting after detecting the minute deformation amount ΔS of the wafer W, a grating group AR on the reticle 14 is used.
, BR distance # The wafer W is adjusted so that the intermediate position of IR and the center position of the grating group w, Bw on the wafer W coincide.
By moving the position of the reticle 1 or the reticle Iv14, it becomes possible to perform positioning that takes even the minute amount of deformation of the wafer W into account, thereby making it possible to perform highly accurate positioning.

As a sixth embodiment, a distance f between the reticle 14 and the first Fourier transform lens 51 is used as a method for correcting after detecting the minute deformation amount ΔS on the wafer W.

By changing the grating group AR on the reticle 14
, distance from BR! By taking advantage of the fact that R changes on the wafer W, the positional relationship between the reticle /l/14 and the first Fourier transform lens 61 is corrected by an amount corresponding to the minute deformation amount ΔS of the wafer W. , the grating group 71 on the reticle 14, the interval lR between B1 and the grating group A on the wafer W.
The distances between w and 81 can be made equal, allowing for more accurate positioning.

As a sixth embodiment, in FIG. 1, the light beam emitted from the light source 11 is incident on almost the entire area of the reticle 14, but the light beam is incident only on the grating groups AR and BR on the reticle/l/14. Inject the two beams onto the reticle 14 so that
A similar effect can be obtained even if each light beam is made incident only on the grating groups Fl and BR.

As a seventh embodiment, as shown in FIG. 6, grating groups OR and DR whose longitudinal directions of gratings are perpendicular to grating groups AR and BR on the reticle 14 are formed. Also, on the wafer W,
Grating groups Ay, Bw, Gw, and Dw are formed at positions corresponding to the grating groups AR, BR, On, and DR.

As described in the first embodiment, by detecting the positional relationship between each grating group on the reticle 14 and each grating group on the wafer W, alignment in two orthogonal axes, that is, X-Y can be performed with high precision.

Furthermore, as a sixth embodiment, it is possible to accurately align the reticle 1v14 and the wafer W by combining the above alignment method with a conventional alignment method. In other words, by performing rough alignment of 01S μm or less using the conventional alignment method, and then detecting and correcting the positions of each grating group on the reticle 14 and each grating group on the wafer W as described above, More precise positioning becomes possible.

Effects of the Invention According to the present invention, even if the wafer is minutely deformed due to thermal deformation or the like, the positional relationship between each grating group formed on the reticle and each grating group configured on the wafer can be detected, thereby deforming the wafer minutely. The amount of deformation can be detected and alignment can be performed with higher precision.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of positioning of an exposure apparatus in an embodiment of the present invention, Figure 2 is a diagram of the principle of the optical system of the same apparatus, and Figure 3 is e.
) is a plan view of the reticle of the same device, FIG. 3(b) is a cross-sectional view of FIG. 3(!L) showing the alignment grating of the same device, and FIG. A characteristic diagram showing the positioning sensitivity of the left side of the grating, FIG. 6 is a diagram of the positioning principle of the exposure apparatus in the second embodiment of the present invention, FIG. 6 is a plan view of the reticle of the apparatus of the fifth embodiment, and FIG. FIG. 7 is a plan view of a wafer for explaining a conventional exposure apparatus. 11...Light source, 14...Reticle, 1
6...First Fourier transform lens, W...
・Wafer, 'RI BRICR, DB, K-...-
... Lattice group on Retik/L/14, Aw. Bw, (w, Dw... grating group on wafer W, 16... spatial filter, 17...
・Second Fourier transform lens, n, , D2...
...Photodetector. Name of agent: Patent attorney Toshio Nakao and one other prestigious lawyer
Fig. 2 Fig. 3 Fig. 4 Travel distance Fig. 6 R Fig. 7

Claims (7)

[Claims] (1) Light source, illumination optical system, reticle, first lens system,
A grating group K is formed on the reticle surface of an exposure device consisting of a spatial filter, a second lens system, a substrate, and a photodetector, and a grating group K is also formed on the substrate at a position corresponding to the grating group K. Aw and a grating group Bw are formed with a distance lw apart, and the light beam emitted from the light source is made incident on the grating group K, and each diffracted light beam is guided to the first lens system.
A predetermined spectrum is selectively transmitted by a predetermined spatial filter provided near the spectral plane of the lens system, and is guided to a second lens system. is projected onto each grating group on the substrate, and each of the diffracted lights diffracted by the grating groups Aw and Bw formed on the substrate is detected independently by a photodetector, thereby determining the positional relationship with the grating group K. An exposure device characterized by detecting. (2) A grating group A_R on the reticle and the grating group A_R
, and a grating group B_R whose longitudinal direction is parallel to each other at an interval l_
The grating group A is formed at a distance R, and also on the substrate.
A grating group Aw and a grating group B are placed at the positions corresponding to _R and B_R.
2. The exposure apparatus according to claim 1, wherein the exposure apparatus detects the positional relationship of each grating group. (3) The exposure according to claim 1, characterized in that two photodetectors are arranged at positions shifted by a distance δ from the spectral plane, and the diffracted light diffracted from the grating groups Aw and Bw is detected. Device. (4) Lattice groups Aw and Bw for lattice groups A_R and B_R
Claims characterized in that the position of the substrate or reticle is corrected so that the center positions of the grating groups A_R and B_R coincide with the center positions of the grating groups Aw and Bw. Exposure apparatus according to item 2. (5) Lattice groups Aw and Bw for lattice groups A_R and B_R
A patent characterized in that the distance relationship between the reticle and the first lens is corrected so that the positional relationship between the grating groups Aw and Bw is approximately equal to the positional relationship between the grating groups A_R and B_R. An exposure apparatus according to claim 2. (6) The exposure apparatus according to claim 2, characterized in that two beams are provided so that the light flux is incident only on the grating groups A_R and B_R on the reticle. (7) Light source, illumination optical system, reticle, first lens system,
A grating group A_R is formed on the reticle surface of an exposure apparatus consisting of a spatial filter, a second lens system, a substrate, and a photodetector;
A grating group B whose longitudinal direction is parallel to the grating group A_R.
_R are formed at a distance l_R apart from each other, and further, grating groups C_R and D_R whose longitudinal directions of the gratings are orthogonal to the grating groups A_R and B_R are formed at a distance apart, and Also, the lattice groups A_R, B_R, C_R, D
Grating groups Aw, Bw, Cw, and Dw are formed at positions corresponding to _R, and the light beam emitted from the light source is made incident on each grating group on the reticle, and each diffracted light beam is reflected on the spectral surface of the first lens system. A predetermined spatial filter provided nearby selectively transmits a predetermined spectrum and guides it to a second lens system, and the interference fringes generated by the light beam passing through the second lens system are reflected in each grating on the substrate. Projected onto the group, each lattice group A
An exposure apparatus characterized in that the positional relationship of each grating group is detected by independently detecting the diffracted light diffracted by w, Bw, Cw, and Dw with a photodetector.