JPS6066431A - Method and apparatus for detecting position - Google Patents

Abstract

PURPOSE:To position a fine pattern by simple constitution in atmospheric air by projecting beams having coherency from two directions, measuring the light intensity of beams reflected or diffracted by obtained interference fringes and a lattice arranged in an optical path and detecting the relative positions of the interference fringes and the lattice. CONSTITUTION:A tattice 18 is formed to a wafer 17, and reflected beams 19 and 20 diffracted by the lattice 18 are projected to photodetectors 23 and 24 through slits 21 and 22 disposed in approximately parallel with the longitudinal direction (a) to interference fringes of two luminous flux. Beams diffracted by a lattice wavefront-splitting interfering beams of two luminous flux 15, 16 are obtained from the lattice 18 having pitches approximately equal to the pitches of interference fringes formed on the lattice 18 on the wafer 17, and parallelism between interference fringes of two luminous flux and the lattice 18 and light intensity information displaying the relationship of relative positions in the direction of pitches are acquired by the beams. The wafer 17 is turned minutely around the normal of a surface with the lattice 18, and introduced to the photodetectors 23, 24 through the slits 21, 22 thus obtaining the change of light intensity I.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a highly accurate alignment device, and particularly to a method and device for aligning a high-density semiconductor device (hereinafter referred to as LSI).

Conventional configurations and their problems Recently, semiconductor devices have become more and more densely packed, and each element f-
The dimensions of the fine patterns range from 1 micron or less. Conventional LS I%! Photomask and LSI during manufacturing
The wafer is aligned using alignment marks provided on the wafer, by rotating and moving the stage on which the wafer is mounted upward on two axes, and aligning the mark on the photomask I and the mark on the wafer. However, the alignment accuracy is about ±0.3 microns, and when forming submicron elements, the alignment accuracy is poor and it is not practical. Also, S. Austin (Applie
dPhysics Letters, Vol. 31 N
In the positioning method using the 1" traversal method, which was presented by J. O., 7 P., 428, 1977, the configuration is as shown in FIG. 1. The incident laser beam l is incident on the photomask 2, and The diffracted light is diffracted by the grating 3 formed on the mask 2, and the diffracted light is again diffracted by the grating 5 formed on the wafer 4 to obtain diffracted lights 6, 7, 8, etc. , the diffracted light 6 is expressed as (0
, l), the diffracted light 7 is (1, l), and the diffracted light 8 is (-1
, 2)... This diffracted light is
The light intensity is determined by focusing the light on one point. The diffracted light has a light intensity at a position symmetrical with respect to the incident laser beam l, and in order to align the mask 2 and the wafer 4,
11 by matching the intensities of the diffracted lights observed on the left and right sides. In this method, the accuracy of place matching is several 10
It is said to be 0A. However, in this method, the alignment between the photomask 2 and the wafer 4 is largely dependent on the spacing between the photomask 2 and the wafer 4, and therefore requires precision in spacing. Also, photomask 2 and wafer 4
It is necessary to bring the two parts close to each other and perform alignment while maintaining the accuracy of the spacing, which complicates the apparatus and poses a problem in practical use.

In addition, for alignment of elements with submicron line width,
There is a method of observing secondary electron emission from element E, but since it cannot be handled in the atmosphere, the throughput in manufacturing LSI becomes small, which poses a practical problem.

Purpose of the Invention The purpose of the present invention is to provide an alignment method and apparatus that can eliminate the conventional problems as described in (h) and perform alignment of fine patterns in the atmosphere with a simple configuration. It is said that

Structure of the Invention The first aspect of the present invention is that light for observing coherency is incident from two directions, and reflected or Guide the diffracted light to the light detection means through the slit,
By measuring the light intensity, the relative position between the interference fringes of the two light beams and the grating is detected.

Further, the second invention is an apparatus for implementing the 1-power distribution method, and its configuration includes a beat splitter that splits coherency light into two beams, and reflected light and transmitted light from this beam splitter. Two reflecting mirrors are arranged so that the light is incident on the wafer grating at approximately the same angle θ, and two light detectors are arranged so that the reflected light diffracted by the wafer grating is incident through a slit. device and the output of these photodetectors! This is a position detection device comprising a light intensity measuring circuit that indicates the parallelism between the I2 light terminal and the grating and the relative positional relationship in the pitch direction. , 1-, the parallelism between the interference fringes of the two light beams and the grating and the relative positional relationship in the pitch direction can be measured, and it is possible to align the semiconductor elements with high precision.

DESCRIPTION OF THE EMBODIMENTS FIG. 2 shows a position sensing device equipped with a holographic haze stirrup and a photodetector that can implement the position sensing method according to the present invention.

Coherent light 9 is incident on the beam splitter 0 from a laser generator (not shown), and the beam 4 is divided into reflected light 11 and transmitted light 12, each having approximately the same intensity and intensity.
and 14, so that both reflected light beams 15.16 enter the surface of the wafer 7 at an approximately equal angle 1λ0,
Place each one.

A grating f-18 is formed on the wafer 17J-, and the reflected lights 19 and 20 diffracted by the grating 18 are reflected by the tfS3.
As shown in the figure, the interference fringes of the two beams are incident on photodetectors 23 and 24 through slits 21 and 22 arranged substantially parallel in the long direction a.
If P is the pitch of the F-fringe formed by the reflected light 15.16 from the reflecting mirror 13.14, then the grating 18 of the wafer 17 is
The interference fringes that can be formed are expressed as .

This [grating 1 with a pitch approximately equal to the pinch P of the interference fringes
From 8, light is obtained which is diffracted by a grating that splits the wavefront of the F-crossed light of 2-light East 15.18, and this light gives
Light intensity information indicating the relative positional relationship between the interference fringes of the two-light east and the grating 18 in the W row degree and pitch direction is obtained. 4 and 5 show the interference fringes of two light beams and the grating 18.
Relative (Q positional relationship is shown before alignment. K is interference fringe, α
The angle formed between the interference fringes and the grating 18, χ, indicates the pitch deviation between the interference fringes and the grating 18.

The wafer 17 is slightly rotated around the normal to the surface having the grating 18, and the photodetector 23.2 is detected through the slit 22.22.
4, a change in the light intensity I can be obtained as shown in FIG. The vertical axis is light intensity 1. The horizontal axis indicates the amount of rotation α. At this time, the peak value of the light intensity differs depending on the shape of the slits 21 and 22. Figure 56 shows the change in light intensity when the slits 21 and 22 are arranged with the longitudinal direction a substantially parallel to the interference fringes of the two light beams as shown in Figure 3. FIG. 7 shows changes in light intensity when the longitudinal direction a of the slit is arranged substantially perpendicular to the interference fringes of the two light beams. Note that b indicates the lateral-r direction of the slit. Figure 6,
From FIG. 7, it is possible to detect more changes in light intensity information due to rotation when the slits 21 and 22 are arranged so that the longitudinal direction a is substantially parallel to the two light beams. That is, in the case of the configuration of this embodiment, as the angle α between the interference fringes of the two light beams and the case J'-18 approaches α=0, the change in light intensity increases, and Intensity changes appear in a direction parallel to the interference fringes. Therefore, slit 21.22
(longitudinal direction a and transverse direction b0') where a>b, and the longer a is, the more remarkable the change in light intensity becomes.

At the peak value of the light intensity, the angle α formed by the case f-18 on the interference fringe becomes α==0. In other words, interference h + K and case f
-18 becomes parallel 6 In addition, as shown in Figure 9, as 1 A slit 26 inclined by a certain angle βl and a slit 27 inclined by a certain angle β2 are arranged with respect to the slit 25, and photodetectors 28, 29, 30 are placed at positions corresponding to each slit. By comparing the values of the three photodetectors, it is possible to
It is possible to detect the direction of rotation in which the angle with 8 is set to α=0.

Although the wafer 17 was rotated in this embodiment, similar positioning can be achieved by rotating the two light beams. Further, the wafer 17 is slightly moved in the pitch direction of the interference fringes of the two beams, and the light intensity I
By detecting this, a change in the light intensity (■) can be obtained as shown in FIG. The vertical axis shows the light intensity I, and the horizontal axis shows the movement amount χ.

The light intensity I changes periodically for each P and P of the grating-18. Moreover, the minute fluctuations in the light intensity I are caused by fine pitch-to-socket feeding at certain intervals. At the peak value of the light intensity I, the pitch deviation χ between the interference fringes and the grating 18 is χ-
It becomes 〇.

In this embodiment, the wafer 17 is moved, but the same positioning can be achieved even if the two light beams are moved. Either alignment in the rotational direction α or alignment in the pinch direction χ may be performed first.

Finally, the alignment in both directions is completed at the peak value of the light intensity I, and the peak value of the light intensity I is reached.
The closer it is to i, the more the alignment accuracy becomes rη accuracy.

In another embodiment, as shown in FIG. 10, a grating 32 is provided at the intersection of each scribe line 31 of the wafer 17 at an angle of 45 with respect to the scribe line 3I. Diffraction images of the provided patterns can be avoided, and highly accurate positioning can be achieved.

According to the method of the present invention as described in 1-Effect of Emission IJII, the light that has been refracted or diffracted by the interference fringes and grating produced by the interference of the two light beams is reflected against the interference fringes of the two light beams, Slit length
By guiding the light to a photodetector through a slit arranged approximately parallel to the L direction and detecting the light intensity, the relative position of the interference fringes of the two light east and the grating and the relative position of the 11 rows and the lattice are detected. It was possible to achieve high alignment of the melon at least 0.05 lm or less. In addition, the device of the present invention has 1
- This is a method that implements the power distribution method, and can be installed during popular use, and the light intensity detected by the photodetector IJi is used to create an IJi inside the cylinder.
I.

We can provide a device that can perform accurate measurements.

[Brief explanation of drawings]

Fig. 1 is a principle diagram of a conventional positioning device, Fig. 2 is a block diagram of a device for realizing an embodiment of the positioning method according to the present invention, and Fig. 3 shows an embodiment of a slit according to the present invention. Enlarged floor plan! Figures 84 and 5 are plan views showing the relative positional relationship between the interference fringes of the two beams and the grating before alignment, and Figure 6 is a plan view showing the interference fringes of the two beams with slits arranged approximately parallel in the longitudinal direction to the interference fringes of the two beams. Figure 7 is a graph showing the dependence of the interference fringes of two light beams on the light intensity in the rotation direction of the grating when
Graph showing the light intensity dependence of the interference fringes of two light beams in the rotational direction of the grating when a slit arranged approximately perpendicular to the long-L direction is provided for the interference fringes of the two light beams, fj', 8 The figure is a graph showing the light intensity dependence in the pitch direction obtained by the alignment method of the present invention. FIG. 3 is a plan view showing an example of the arrangement of case-f. 9...Light 10...Beam splitter 11...Reflected light 12...Transmitted light 13.14...Reflector 15
, lEi...Reflected light I7...Wafer I8...
Case f・19.20...Reflected light 21.22...Slit 23.24...Photodetector 25.28.27...
・Slit 28.211.30...Photodetector 31・
... Scribbler in 32... Lattice agent Patent attorney Person Island - Public Fig. 1 Fig. 4 and Fig. 6 Rotation amount Fig. 7 X

Claims (1)

[Claims] (+) Light having coherency is transmitted from person Q(
Then, the light reflected or diffracted by the I-# fringe obtained by the interference of these two light beams and the grating arranged in the optical path of the two light beams is guided to the light detection means via the slund,
By measuring the light intensity, the interference fringes of the two light beams described above and the phase *J (:t8R) of the grating are detected. (2) The position detection method according to claim 1, wherein a slit is used as the slit, the longitudinal direction of the slit being substantially parallel to the interference fringes of the two light beams. . (3) As a slit, a slit is arranged approximately parallel to the longitudinal direction of the slit with respect to the -'crossing fringe number of the two light beams;
A slit tilted by a certain angle βl with respect to this slit, a slit tilted by a certain angle β2 with respect to the slit, and a luminous flux passing through each of the three slits,
The position according to claim 1, wherein the inclination direction of the grating with respect to the interference fringes of the two light beams is detected by guiding each light beam to a light detection means and measuring the intensity of light obtained from each light detection means. Detection method. (4) The position detection method according to claim 1, wherein the grid is a grid tilted at 45 degrees with respect to the scribe lines in the vicinity of the intersecting position of each scribe line on the IC wafer. (5) Split the light with coherency into 2 beams 1rtl
A beam splitter is used, and the reflected light and transmitted light from this beam splitter are set at an angle θ approximately equal to the height of the wafer.
Two reflecting mirrors are arranged so that the light is incident on the wafer, and two photodetectors are arranged so that the reflected light diffracted by the wafer grating is received through a slit. 1. A position detection device comprising a light intensity measuring circuit that indicates the relative positional relationship in the pitch direction and the degree of deviation between the beam w4- of two light beams and the grating.