JPS6066819A - Position aligning method - Google Patents

Abstract

PURPOSE:To accurately align the position of grating on a wafer and generated interference fringe by reflecting or transmitting the light flux having passed two diffraction gratings on a reticle with the diffraction grating on the wafer. CONSTITUTION:The light fluxes 12, 13 in the same phase are vertically directed to the gratings 14, 15 on a reticle, an interference fringe F is formed by crossing the diffracted lights 16, 17 on a wafer W at a crossing angle 2theta and it is aligned to the grating G provided on the wafer. Rotations PHI, PSI of grating G and fringe F in the afer surface and incident surface are adjusted by reducing a wafer surface and incident surface are adjusted by reducing a number of moire-image interference fringes through fine adjustment of wafer. The diffracted lights 16, 17 sent from the grating G having almost the same pitch as the pitch A of interference fringe determined by the wavelength of light and incident angle theta are collected and interfered again. Light intensity to be observed depends on the angle of detector D and has a peak value. Therefore, a detector is fixed at the peak intensity position and relative position (x) of fringe F and grating G is changed. Since light intensity periodically changes for each pitch of grating G, relative position can be obtained from measurement of light intensity and highly accurate position aligning can be realized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a 41]' high degree alignment device, especially a high degree
, relates to a positioning method that can be used in a positioning apparatus VC4 for a defective semiconductor device (hereinafter referred to as LSI).

Conventional 111 configuration and its problems Figure 1 (r) is an explanatory diagram of the conventional alignment method./:FS1 Figure (a) shows an example of the pattern for alignment by a photomask technician. 0 again this 1st night 1''
Using a pattern with a constant width and a radius of 14, the wafer l
x: j (: Transfer pattern 1 of hanging-layout pattern
4, FIG. 1 Φ) is a diagram when the same pattern is used again on the wafer J: (/C) formed on the alignment pattern 1. Butter 71 is formed on the wafer 2)A
Relative alignment is performed between the shadow 2 of the alignment mark formed on the upper mask and the pattern 1 on the wafer. The alignment accuracy at this time is about ±0.3 μm, which is the best way to align an LSI with a gate length of 1 micron or less.
, is insufficient. In a 0.6 micron Lucy 4 degree LSI, the alignment accuracy is. , 06 l1
m must be 4′i″ degrees, and in the conventional way d, 1
All I can do is work at the temple.

OBJECTS OF THE INVENTION In view of the above-mentioned problems of curvature, it is an object of the present invention to provide a method for highly accurate alignment between a mask pattern such as a reticle and sample t1 of a wafer tongue. do.

Construction of QF4 Present Invention-1 A coherent first beam is incident on the reticle of two substrates to be aligned (i.e., a reticle and a wafer), and a diffraction grating is placed on the reticle for the first beam VC. is provided, and the second beam diffracted by the diffraction grating of this reticle is further incident on the wafer, and at the same time, a third beam coherent with the second beam is directed onto the wafer. In this configuration, the intensity of the light incident on the wafer and reflected or transmitted by a diffraction grating provided on the wafer is measured. Achieves high precision matching of relative positions.

'8k, the present invention provides a method for aligning two substrates.
A coherent first beam is input to the 51 substrates 4! No, a first diffraction grating is provided on the substrate surface 1- of the M1 on which the first light beam is incident, and the second light beam is rotated by the first four-point grating. is incident on the second substrate surface, and the reference brush 3 for interference with the diffracted second light beam
simultaneously incident on the second substrate surface, and the second. A fourth light flux that has been reflected or transmitted by the third light flux is directed to a light detection means, and the light intensity is measured by this means. . . . and detecting the relative position between the interference fringes of the third light beam and the second diffraction grating on the second substrate surface, and adjusting the relative positions of the first substrate and the second substrate. This is what we do.

DESCRIPTION OF EMBODIMENTS FIG. 2 shows the principle of a reduction projection exposure apparatus that implements a positioning method according to an embodiment of the present invention. .

First, arrangement 6 and 9 in the case of normal reduction projection exposure will be explained. The light source, reticle R, lens thread, and conductor wafer W are arranged in this order.Parallel light 11 emitted from Gwangju is deflected by a nokukuon on the reticle R, and the light flux with this shading pattern is transmitted by the lens system. The light is focused.''
Two projections of 1/chiku/l/ [form an image it-'.

The configuration used for alignment is to input coherent light such as a laser into a beam splitter, etc., and generate three beams of light with approximately the same intensity 12. '13 amplitude division. The three beams 12, 13 are respectively incident on the diffraction gratings 14, 15P provided on the reticle R, and the arrangement where the reticle H is placed is expressed by the phase and angle ψ1° ψ2 of the incident light and the diffracted light. The diffracted light 16.1 γ from the reticle R passes through the lens system J7f1, and the three light beams 16.17 interfere with each other at the wafer W.
, W are placed. A diffraction grating G is formed on a part of the wafer W as shown in FIG.
Interference fringes F of 22 beams of light 16.17 are formed. and,
The reflected light 18 diffracted by the grating G is detected by the light zH, >
D gets 47. The grating G on the wafer is shown in Figure 4 (/ζ
- As an example, Vζ is regularly 1/(
A two-form/repeat pattern may be used.

The wavelength of the laser is λ, and the interference fringes F...
If the pitch is 1, it can be expressed as Δ=λ/2sin O.

As shown in FIG. 3, the interference fringes F partially generated by the three-beam interference are obtained at a pitch Δ corresponding to the incident angle θ of the equidistant 1i'* as shown in the above equation. 1. Ru.

The pitch, L, J, is approximately equal to the pitch Δ of this interference fringe.
1.22 beams of light 16.17 interfere from one grating G.
! ! 1.1/d light is obtained, and interference fringes F and grating G of two light beams are obtained.
Light intensity information indicating the relative positional relationship between the two is displayed. Light intensity I observed on the photodetector (rJ, Yonegi - U2 + U2 → U -'U +U -'U... (1
)A B A BAB However, UA and UB are the swings of luminous flux 16.17 ξ
'1゛1d i+H degrees, U, , *, UB* are conjugate complex amplitudes. 1/ko, 5in(lha/2"81nOfi/also ftfl(,, 8, B is a constant, N: number of lattices, 6Al
δB is the optical path difference between the light diffracted by two adjacent gratings, X is the relative position between the interference fringes due to beams 16 and 17 and the grating, θ is
ga(no4: zu angle)

is shown. The actually observed Kogyo Electric Works is shown in Figure 5 as 7J<
It exhibits a wide angular dependence, with four peaks (1:), and the peak at -611,el overlaps with the 0th-order diffracted light of the incident light 16°17. -02,02 peak f (includes 1st-order diffracted light of 1 incident light 16.17, and each diffracted light has interference fringes formed by light beam 16.17) - between earth lattice G Contains location information.

Figure 6 shows the position of the photodetector and the peak in Figure 6.
4' position V(mouth 1)・1 ujl L, relative position X between the interference fringe F created by the luminous flux 16.17 and the grating G on the wafer W
This shows the change in fL Saze/Kotoki's Hikari Electric Works. Changes in the relative position jl''j For example, if the wavelength of the laser beam is 0.4/1 m and the pitch of the interference fringes F is 1 μm, and the pitch of the grating G formed on the wafer is 17 ym, the alignment accuracy will be 100 people. 1) Next, the procedure for homologous [>7 if+'' interposition of the reticle L and wafer W will be explained using FIG. 7.

The three beams 12.13 incident on the reticle H are arranged so that they are perpendicular to the reticle H, and the three beams 12.13 are incident on the grating 14.16 on the reticle.

Transmits grating 14, 11JJ29 bundle, diffracted light 16.1
Shoot 7. Three beams of light 12 incident on the grating 14°16.
Since the optical system is arranged so that the phase (l) of 13 is four, the wavefront of the light diffracted by the grating becomes symmetrical with the light beams 16 and 17 as shown in FIG. The alignment of this phase is 11° bundle 16.17 is sea urchin/%W plane.
If the intersection angle 20 is exceeded, dark and light interference fringes (FIG. 3 F) are produced, and the position of the interference fringes F is fixed at the position where the wavefronts intersect. The diffraction grating (third, /JG) formed on Ueno-W is aligned with this (i>,'il-hair).

Sea urchin... The rotation (azimuth) ψ of the grating G on W and the interference fringes F of the three beams within the wafer plane can be detected by the rotation of the moire fringes that occur between the gratings on the wafer and the interference fringes, and the moire fringes The rotation (tilt) ψ of the interference fringes between the grating on the wafer and the three beams within the plane of incidence of the three beams is the Compared to the grid on the wafer, the pitch is relatively J〈
< ft-1/ This is the same as the easy case.
l-(1', O reflected by the diffraction grating G on the wafer
After the secondary light returns to the photoeclipse, the tilt of the sea urchin V can also be adjusted by learning the change in the position of this reflected light due to the movement of the wafer.

Adjust the azimuth and tilt using eζ as described above.
After C, it is possible to align the pattern position between the reticle and the mirror on the basis of the principle shown in Section 1.2.3.

As a second embodiment, as shown in FIG. By combining the positioning marks M (cross-shaped), positioning can be performed in a shorter time than with Lζ.

As shown in FIG. 8(-), the diffracted light from the grating pattern of the wafer W10 in FIG. 4 is a combination of a dark cross pattern in a bright quadrilateral pattern. The diffracted light of one incident light 12 corresponds to sh of pattern d1, and the diffracted light of the other incident light 13 corresponds to INK of pattern d2. If the alignment is insufficient when 1'M is viewed from the light detection means side, the cross pattern will appear double. If a light detection means is provided in accordance with this cross pattern, and the wafer and reticle are vertically aligned so that the cross patterns overlap, pattern alignment similar to the conventional pattern can be performed. In other words, rough alignment of about 0.3 microns compared to the conventional alignment method can be performed by the J:9 method.

When this alignment is completed, as shown in FIG. 8(b), moiré-like stripes will be visible in the quadrilateral bright pattern, and using these stripes, the alignment method of the present invention High-precision alignment can be performed in a short time using

FIG. 9 shows a third embodiment according to the present invention, and the difference between this embodiment and the second embodiment is that the period of the gratings in the grating patterns 19 and 20 of the reticle R'2 is For example, a linear figure of 5゛4 is formed, and the light 1 diffracted by the gratings 19 and 20 on the wafer W is
8, when the alignment is not sufficient, g1
o As shown in Figure (a), a positional shift occurs in the diffracted light 18,
0.3 μm Q, degree and sales channels can be aligned in the same way as before. In this case, alignment can be done in the same way as in the case of FIG. -C, it is possible to align the reticle Rf with the wafer W while the wafer W is fixed. Complete the approximate alignment of this u; and then proceed as shown in Fig.
Similarly, the fine alignment of the present invention may be performed using the particular moiré-like stripes shown in FIG. 10(b).

FIG. 11, which is a part of the present invention, shows an actual positioning method for f1. Fig. 2 174';
The difference from the example shown in Figure 7 is that in Figures 2 and 7, two diffraction gratings are provided on the reticle, and coherent light is directed to the diffraction gratings in the valleys of the IL. However, in this embodiment, only one diffraction grating 21 is provided on the reticle H, and coherent light 22 is incident on the diffraction grating 21 and the position information of the reticle is expressed by the diffraction angle. It is expressed by the angle of τ diffraction by fit^, and it is a sea urchin...W"
Second, the diffracted light 26 is made incident. The reference beam 23, which is 22 and 2
4 and interferes with the J1 light 26, the positional information is transmitted through interference fringes of the three beams, and the reflected light 26 from the wafer W is discriminated by a light detector. Therefore, at the position of the photodetector that receives the foul light 26 from Ueno W, the illusion 1 and the reference light 23 are detected.
is incident on the lattice and Ueno s'/l is coarsely
j, Ii' can be aligned, and then the light 26 diffracted by the J1 grating on the reticle is incident on the reticle, thereby achieving high precision similar to that shown in Figs. 2 and 7. It is possible to achieve good alignment.

FIG. 12 shows another embodiment according to the present invention. The difference between this embodiment and case I in FIG. On the reticle R, for example, a diffraction grating 3Q formed on the scribe line,
For example, the gate turn 31 of a MOS+- transistor, which is a circuit element, is arranged and formed with high precision. This diffraction grating 30 further includes a cross alignment mark (not shown in FIG. 12) as shown in FIG. 13(a), for example.
or is formed. Reference numeral 32 in FIG. 12 shows interference fringes formed on the wafer. As in the case of FIG. 9, the laser beams 12 and 13 are aligned to the grating 30 so that the alignment notches on the reticle are aligned. 3rd year middle school
This is shown in 3. The grating 34 on the Ueno'-W is superimposed on this turf 33 by λ as a cross-shaped alignment pattern.

Since this grating 34 is formed on the wafer W by the conventional light beam δ light bC, the interference fringe pattern 1 of the interference fringe exposure by laser holography according to the present invention is a very large pattern. is not obtained. Therefore, Ueno W” 2 (6 children 3
If the pitch of 4 is an integral multiple of the pitch of the interference fringes, as shown in FIG. The diffraction r images of the overlapping patterns are subjected to f(J), and precise G and 'im alignment can be performed from the moiré fringes of this diffraction image.

In addition, it is desirable that the wavelength of the laser beam during alignment is a wavelength that does not sensitize the resist i formed on the sea urchin. After alignment, conventional ultraviolet light exposure can be performed to simply align and illuminate the area.

Effects of the Invention According to the present invention, all of the diffracted light emitted from the grating formed on the reticle by the misalignment method is irradiated onto the grating provided on the reticle, and the diffracted light from the grating on the reticle is irradiated. By observing the strength, the putter 7 on the wafer can be aligned with the reticle with high precision. Furthermore, positioning can be performed in a short time using a reticle or a pattern provided on the vine. However, when the grid pitch of Ueno/Soil is 1 μm, alignment accuracy of several 1 Qo is possible. Further, in the embodiment, the first substrate is a reticle and the second substrate is bound with a wafer, but it is also possible to align two ordinary photomasks or other general objects other than a reticle.廿/c1 In the embodiment, the light incident on the reticle is transmitted light, but it is also possible to use reflected light from the reticle.

[Brief explanation of the drawing]

Fig. 1(a) shows the alignment mark on the conventional photomask; Fig. 1(b) shows the alignment mark on the conventional photomask; A block diagram of a 6'L alignment between a wafer and a reticle in one embodiment,
FIG. 3 is an explanatory diagram of the relative positions of the grating according to the present invention and the two-beam interference fringes, FIG. 4 is a plan view of an example of the upper grating according to the present invention, and FIG. 6 is a 1-minute alignment diagram according to the present invention. FIG. 6 is a diagram showing the observation angle dependence of the intensity of the diffraction grating on the wafer used for 11r > t, FIG. Fig. 7 is an explanatory diagram of each component and operation during alignment according to the present invention, Figs. 8 (a) and (b) are explanatory diagrams of the alignment method according to the present invention, and Fig. 9 is an explanatory diagram of the alignment method according to the present invention. Configuration diagram of another embodiment, FIG. 10(a)
, (b) is an explanatory diagram of the positioning method shown in FIG. 9,
FIG. 11 is a schematic configuration diagram of still another embodiment of the (5'/', lI'1' alignment method according to the present invention, FIG. 12 is a plan view of the pattern on the reticle, and FIG. 13 (a) is the present invention. IJJ diagram, Figure 13 (b
) is a plan view of the diffraction image. 11...Parallel light, 12, 13, 16, 17°1
8.23, 25.26... Luminous flux, 14, 15° 19.20.2j, 30... Diffraction grating, 18
......Reflected light, 23...Reference light flux, R
... Reticle, W ... Semiconductor wafer, D.
...photodetector, G...grid. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure (0-)! ('t)) Fig. 2 1 E3 5 Hri1% -θ? -θ, 0 θ, θ2L/zth 6I7
1 O1 ρ 3 躬 21, Fig. 8 (1) (b) 1 2 real 13th N (Su

Claims (5)

[Claims] (1) Two first diffraction gratings are provided on the surface of the first substrate on which the light flux on the first substrate of the two substrates to be aligned is provided. J knee on the diffraction grating
Te times AJ? 1) The second and third light beams described in II are made incident on the second no.1 curve, and are provided on the second substrate surface! ■It is reflected or transmitted by the second diffraction grating and guided to the fourth Kuto gold light detection means (・(
J: -, by dill the light intensity:
(Plate i1U J-: Interference fringes of the three incident beams of light and the second) (Detect the relative position with the second grid on the board 1-1+iiJ A positioning method in which the relative positions of the first substrate and the second substrate are aligned. (2)・', A', 52 Notices 1P' 2 - A part of the revered second diffraction grating J- t (of this grating) c' = i
The shapes that are different from Jυ and r are the shapes J′v, and b)
The positioning method according to claim 1, wherein the rough positioning is performed using this figure. (3) In a part of two regular first diffraction gratings provided on the first substrate, a figure with a period of this grating and lk The first diffraction grating of 1] is diffracted by the first diffraction grating of 8-2. 11-11- The method of claim 1, in which the !R+ feature is to perform approximate positioning using the figures containing 11-. (4) First no +'r1 of two substrates to be aligned
A first diffraction grating is provided on the first substrate surface on which the first light beam is incident, and a first diffraction grating is provided on the surface of the first substrate on which the first light beam is incident on [). The substrate surface of the second beam diffracted by the second beam r-: V
(The third luminous flux is simultaneously incident on the second fast ζ plate surface 1t, the second substrate surface J: 7n, /ζ second time j1 white i'i J- By guiding the reflected fourth light flux of the second and third light fluxes to a light detection means and measuring the light intensity lW by this means, 7i!, the angle between the interference fringes of the second and third light beams incident on the plate surface and the second diffraction grating on the second substrate surface II
41 of the first substrate and the second substrate.
An alignment method characterized by aligning pairs. (5) A pattern different from that of the second diffraction grating is formed in a part of the regular second diffraction grating provided on the second substrate, and rough alignment is performed using this pattern. The positioning method according to claim 4 of the patent claim.