JPH0274805A - Alignment apparatus - Google Patents

Abstract

PURPOSE:To make it possible to perform highly accurate position alignment when the relative position alignment of a first body and a second body is performed by constituting a convex and concave system and a concave and convex system by the combination of the different orders with diffracted light beams for first and second physical optic elements. CONSTITUTION:A first physical optic element 3 is formed with a first alignment mark which diffracts first and second signal luminous fluxes at the different orders. A second physical optic element 4 is formed with a second alignment mark which diffracts the first and second signal luminous fluxes at the different orders. The first and second alignment marks 3 and 4 are provided on the surfaces of first and second bodies 1 and 2. The arrangements of the diffraction forces in two systems having the different orders are set. The luminous fluxes through the alignment marks 3 and 4 are utilized, and the magnification factors of the deviations of the first body 1 and the second body 2 are detected in reverse signs to each other. In this way, the position deviation can be accurately detected regardless of the inclination of the surface of a wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an alignment device, and for example, in an exposure device for manufacturing semiconductor elements, the first object surface of a mask, reticle (hereinafter referred to as "mask"), etc. This relates to an alignment device suitable for performing relative positioning (alignment) between a mask and a wafer when exposing and transferring a fine electronic circuit pattern formed thereon onto a second object surface such as a wafer. be.

(Prior Art) Conventionally, in exposure apparatuses for semiconductor manufacturing, relative alignment between a mask and a wafer has been an important element for improving performance. Particularly in alignment in recent exposure apparatuses, alignment accuracy of, for example, submicron or less is required due to the high integration of semiconductor devices.

In many alignment apparatuses, so-called alignment patterns for alignment are provided on the mask and the wafer 1, and positional information obtained from these patterns is used to align both. As an alignment method at this time, for example, the amount of deviation between both alignment patterns is detected by performing image processing, or alignment method as proposed in U.S. Pat. This is carried out by, for example, using a zone plate as a pattern, irradiating the zone plate with a light beam, and detecting the focal point position of the light beam emitted from the zone plate on a predetermined surface.

In general, an alignment method using a zone plate has the advantage of being able to perform alignment with relatively high precision without being affected by defects in the alignment pattern, compared to a method using a simple alignment pattern.

FIG. 11 is a schematic diagram of a conventional alignment device using a zone plate.

In the same figure, the parallel light beam emitted from the light source 72 passes through a half mirror 74 and is condensed at a condensing point 78 by a condensing lens 76, and then passes through a mask alignment pattern 68a on the surface of the mask 68 and a support base 62. The wafer alignment pattern 60a on the surface of the wafer 60 placed a is irradiated. These alignment patterns 68a and 60a are composed of reflective zone plates, and each form a focal point on a plane perpendicular to the optical axis including the focal point 78. At this time, the amount of deviation of the focal point position on the plane is detected by guiding the light onto the detection surface 82 using the condensing lens 76 and the lens 80.

Based on the output signal from the detector 82, the control circuit 8
4 drives the drive circuit 64 to position the mask 68 relative to the wafer 60.

FIG. 12 is an explanatory diagram showing the imaging relationship between the light beams from the mask alignment pattern 68a and the wafer alignment pattern 60a shown in FIG. 11.

In the figure, a part of the light beam diverging from the condensing point 78 is diffracted by the mask alignment pattern 68a,
A focal point 78a indicating the mask position is formed near the focal point 78. The other part of the light flux passes through the mask 68 as zero-order transmitted light, and enters the wafer alignment pattern 60a on the wafer 60 without changing its wavefront. At this time, the light beam is diffracted by the wafer alignment pattern 60a, and then passes through the mask 68 again as zero-order transmitted light, condensing near the converging point 78 and focusing on the wafer position.
form. In the figure, when the light beam diffracted by the wafer 60 forms a condensing point, the mask 68 simply acts as a transparent state.

The position of the focal point 78b due to the wafer alignment pattern 60a formed in this way is determined according to the displacement amount Δσ of the wafer 60 with respect to the mask 68 along a plane perpendicular to the optical axis including the focal point 78. It is formed as a deviation amount Δσ' corresponding to Δσ.

In this method, if the wafer surface is inclined with respect to the mask surface, the reference plane such as the mask holder in the semiconductor exposure equipment, or the ground plane of the exposure equipment, the center of gravity of the light beam incident on the sensor This will cause an alignment error.

In general, establishing an absolute coordinate system on the sensor and setting its reference origin is difficult to avoid due to other alignment error factors, such as tilting of the wafer surface due to warpage or deflection, fluctuations in the center of gravity of the light beam due to uneven resist coating, and alignment. Fluctuations in the oscillation wavelength of the light source, oscillation output, luminous flux output angle, fluctuations in sensor characteristics,
There is also a problem in that it is very difficult to set the origin with high precision due to fluctuations in the position of the alignment head due to repeated changes.

(Problems to be Solved by the Invention) The present invention provides a means for eliminating error factors in detecting the amount of deviation when aligning a first object such as a mask and a second object such as a wafer. In addition to the alignment light beam as the second signal light, an alignment light beam as the second signal light is formed by diffracted light of a different order from the first signal light. In particular, the present invention is characterized by providing a positioning device that enables highly accurate positioning by using a second signal light beam. It is set so that the action of the second signal light flux is exactly equal to that of the first signal light flux, and the center of gravity is moved in the same way as that of the second signal light flux or the first signal light flux with respect to changes in the position of the alignment head. This makes it possible to make highly accurate alignment possible by making the fluctuation in the relative positions of the second signal beam and the first signal beam sensor 2 in principle dependent only on the misalignment between the mask and the wafer. The purpose is to provide a matching device.

(Means for solving the problem) When relative positioning is performed by making a first object and a second object face each other, a first physical optical element is formed on the first object surface,
A second physical optical element is also formed on the second object surface, and diffracted light generated when light is incident on the first physical optical element is made to enter the second physical optical element, and the second physical optical element is made to enter the second physical optical element. By detecting the light intensity distribution of the diffraction pattern generated by the element on a predetermined surface by the detection means, the first object and the second object are detected.
When positioning relative to an object, the first. The second physical optical element f is set to simultaneously form a convex-concave system and a concave-convex system for the diffracted light by combining different orders.

That is, in the present invention, the first physical optical element is formed by a first alignment mark that diffracts the 1° and second signal light beams in different orders, and the second physical optical element is formed by the first alignment mark. A second alignment mark is formed to diffract a second signal light beam in a different order, the light beam is made incident on the first alignment mark, the diffracted light generated at this time is made incident on the second alignment mark, and the second signal light beam is made incident on the second alignment mark. 1st from alignment mark
．． The light beam gravity centers of the two diffracted lights of the second signal light beam are respectively detected by the first. The second detection section detects the first. When positioning the first object and the second object using the output signal from the second detection section, the center of gravity of the light flux incident on the first detection section and the center of gravity of the light flux incident on the second detection section are displaced in directions opposite to each other with respect to the direction of positional deviation between the first object and the second object. It is characterized by setting a second alignment mark.

(Embodiment) FIG. 1 is a schematic diagram of the main parts of an embodiment showing the optical principle of the alignment device of the present invention. In the figure, 1 and 2 are a first object and a second object for detecting relative positional deviation, respectively, and 3 and 4 are a first physical optical element and a first physical optical element provided on the first object 1 and second object 2, respectively. 2 physical optical element.

In this embodiment, the light beam from the light source 8 is converted into a parallel light beam by the projecting lens system 9 and is converted into a parallel light beam by the first physical optical element 3 (hereinafter also referred to as "first alignment mark") provided on the first object 1. It is input to. The first physical optical element 3 is a Fresnel zone plate, a grating lens, or the like, which functions as a physical optical element having a one-dimensional or two-dimensional lens function. The first . The two diffracted lights of different orders, which serve as the second signal beam, are incident on the second physical optical element 4 (hereinafter also referred to as "second alignment mark") as the second alignment mark provided on the second object 2. are doing.

Note that the second physical optical element 4 has optical properties similar to those of the first physical optical element 3. The first beam emitted from the second physical optical element 4. The two diffracted lights 6.7 of different orders, which become the second signal beam, are the first and second signal beams. The light is guided to a detection means 5 having second detection sections 5a and 5b.

Now, the optical distance from the second object 2 to the detection means 5 is L
, the distance (gap) between the first object 1 and the second object 2 is g,
1st. The focal lengths of the second alignment marks 3.4 are assumed to be ±fM and ±fw, respectively. Let ε be the amount of relative positional deviation between the first object 1 and the second object 2, and the first object 1 at this time. The first signal beam center of gravity of the second signal beam 6.7. The amount of displacement of the second object from the matching state is defined as St and S2, respectively. Also, for convenience, the light flux incident on the first object l is assumed to be a plane wave, and the symbols are used as shown in the figure.

1st. Displacement amount Sl, S of the center of gravity of the second signal beam 6.7
l can be determined geometrically by connecting the focal points FM, F'M of the first alignment mark 3 and the center of the optical axis of the second alignment mark 4, and using the detection means 5 as the intersection of the straight line and the surface of the detection means 5.

Therefore, in order to set the displacement 1ls1°82 of the center of gravity of each signal beam to be in opposite directions with respect to the relative positional deviation between the first object 1 and the second object 2, the first. The refractive power arrangement of the second alignment mark can be achieved by combining a so-called concave-convex system consisting of convergence and divergence, and a so-called concave-convex system consisting of divergence and condensation.

Next, the two systems, the uneven system and the uneven system, will be explained using equations.

Now, if the refractive power arrangement in the first alignment mark 3 and the second alignment mark 4 is uneven, the displacement amount S1
In the case of an uneven system, the displacement amount S2 is as follows. Here, f M The position moves.

In general, the magnification is slightly different between the concave and convex systems and the concave and convex systems, but in order to align
5=32-3l should be evaluated. The difference in movement amount ΔS at that time is expressed as follows.

bl − −g + iM −fW Here, under the condition of f M << b 1, fM>>g, ΔS 2 □ ・ε 1M, and 2 when using either the uneven or uneven brown. You can get double the sensitivity.

Furthermore, it can be similarly determined when the second alignment mark 4 is of a reflective type. That is, the second alignment mark 4 and subsequent parts in FIG. 1 may be considered by folding back symmetrically with respect to the second alignment mark 4.

Next, a case will be described in which the second object 2 is tilted by a slight amount β, for example.

All the light beams emitted from the second alignment mark 4 are tilted at an angle of 2β according to the law of reflection. The movement of the spot due to this inclination lSβ is Sβ;2 if the distance is sufficiently large.
βL roars. The spot position on the detection means surface changes in both the concave-convex system and the concave-convex system, and the displacement amount Sl'', S2' becomes Sl''=51+2βL Sl''=S2+2βL.The difference in the amount of movement ΔS' at this time is ΔS'= S2”
-5l = S2-31 = ΔS, and the difference in movement amount Δ
S' remains constant regardless of the slope.

': jrJ2 Figure is a perspective view of essential parts of the first embodiment of the present invention. In the figure, the first alignment mark 3 on the first object 1 and the second alignment mark 4 on the second object -F are both made of two-dimensional Fresnel zone plates.

The light beam from the light source 8 is made into parallel light by the projection lens 9,
The first alignment mark 3 is irradiated. The light beam diffracted by the first alignment mark 3 is further diffracted by the second alignment mark 4, and the light beam corresponding to the uneven system becomes the light beam 6 as the first signal light, and the light beam corresponding to the uneven system becomes the second signal light. The light becomes a light beam 7 and is incident on the detection means 5. A positional deviation signal based on the light beams 6 and 7 on the detection means 5 is input to the controller 11 via the processing circuit 10, and the stage 12 is moved so that the first object 1 and the second object 2 are in predetermined positions, thereby aligning the position. It constitutes a system that performs

In this example, the optical system is developed along the incident light flux, the O-order transmitted light flux, and the 0-order reflected light flux of each alignment mark, and the optical path in the plane perpendicular to the incident plane constitutes the same system as in FIG. 1 above. The displacement 1ist, S2 of the spot position of the light beam on the surface of the detection means 5 is expressed by equations (1) and (2).

Now, number one. If the focal lengths ±fM and ±fw of the ±1st-order diffracted light of the Fresnel zone plate, which is the second alignment mark, are ±400 μm, the gap g = 30 μm, and the distance L from the second object 2 to the detection means 5 = 40000 μm, then , 1st. The positional deviation ε of the second object is detected with a sensitivity 185 times higher.

That is, when the resolution of the detection means 5 is 1 μm, 0.00
A positional deviation of 54 μm will be detected.

Also, the spot diameter of the light beam 6.7 at this time is as follows. The spread diameter of the point image of the light beam 6.7 due to geometrical optical defocus is φ1. φ2 and the spread diameter due to diffraction are φ1' and φ2', respectively, and when evaluated for each prefecture, it becomes x 40000 ε 匈 −926.

Therefore, the movement amount difference signal ΔS is ΔS = 52-5l = (93-(-92))ε-
1856-30 ÷ 400 - 400 -658 [μm co-597 [μm] φI -2X122X λXFN.

-876 [μm] φ2 ・2x1.22X λx FN.

810 [μm] becomes.

From the above, the spot diameter is about 90 in the uneven system as the first system.
0 μm, and in the uneven system as the second system, it is about 850 μm.

Although the spot diameters of the two are somewhat different, there will be no problem if a detection system for determining the center of gravity of the light amount is set up for each independently. For example, the pitch of the CCD array sensor may be made sufficiently fine, and each evaluation area may be divided to determine the center of gravity of the light amount.

FIG. 3 is a perspective view of essential parts of a second embodiment of the present invention. In this embodiment, the first object on the first object 1 and the second object 2. When the centers of the second alignment marks 3 and 4 coincide in the alignment direction, the spot position Sol of the light beam on the surface of the detection means 5
, S02 or uneven system and uneven system, constant amount S. , as long as the offset is the first. 2nd alignment mark 3.4
is being designed.

Figure 4 is a schematic diagram of the optical path expanded in Figure 3;
5(A) is an explanatory diagram of the first alignment mark in FIG. 3, and FIG. 5(B) is an explanatory diagram of the second alignment mark in FIG. 3.

The first alignment mark 3 on the first object 1 in the second embodiment is the same as that in the first embodiment as shown in FIG. 5(A), but the second alignment mark 4 on the second object 2 is
As shown in Figure (B), it is eccentric in accordance with the offset amount. When the alignment mark 4 acts as a convex lens and when it acts as a concave lens, the direction in which the light beam is deflected is reversed as shown in FIG. 4.

Detection - The spot position on the 5th surface F of the L stage and the positional deviation 1iε between the first object 1 and the second object 2 are expressed by the following formula.The difference ΔS in the spot position is Δ5=S2−5l, and the signal obtained from this is Offset S from ΔS
. By subtracting f, a signal proportional to the positional deviation ε can be obtained.

By providing such an offset, the 0th-order transmitted light, 0th-order reflected light, and measurement light flux can be separated by the detection means 5,
Signal processing becomes easier.

FIG. 6 is a perspective view of essential parts of a third embodiment of the present invention. This embodiment shows a case where the present invention is applied to a semiconductor printing apparatus. In the figure, a first alignment mark 3 for input and an alignment mark 13 for ejection are provided on a mask 1 as a first object, and a second alignment mark 4 is provided on a sea urchin as a second object. ing. The light beam from the second alignment mark 4 is returned substantially in the direction of the contact point, so that light can be projected and received by one pickup head.

This embodiment has exactly the same configuration as the second embodiment described in 11η up to the second alignment mark 4 on the wafer. The difference is that the optical system is configured so that the formed linear grating is bent in the direction of the detection means 5.

The sensitivity with respect to the positional deviation of the mask 1 and the wafer 2 and the influence with respect to the tilt of the wafer 2 are approximately the same.

FIG. 7 is a perspective view of essential parts of a fourth embodiment of the present invention. In this embodiment, the first. The second alignment mark 3.4 constitutes a system in which a concave-convex system and an alignment light beam 6.7 due to the concave-convex system are separately received by two detection means 51 and 52 shifted in a direction orthogonal to the X direction, which is the alignment direction. ing.

This embodiment is the same as the second and third embodiments in terms of alignment direction, but the two systems differ in the direction orthogonal to the alignment due to the difference in the light receiving sections. That is, the sensitivity of the positional deviation of the mask 1 as the first object and the wafer 2 as the second object is the same, and the influence on the tilt of the wafer 2 is also the same if the deviation of the two systems is small.

Figure 8 (A), CB) shows the first. As an example of the second alignment mark, FIG. 9 shows the distribution state of the light flux on the detection means 51 and 52 surfaces. As shown in FIG. 9, in this embodiment, only the luminous flux due to the focused order combination is detected by the detection means 5.
1.52, which facilitates sensor processing.

FIG. 10 is a schematic view of the main parts when the alignment apparatus of the fourth embodiment shown in FIG. 7 is applied to a proxy mirror type exposure apparatus for semiconductor manufacturing. In the figure, the entire configuration is shown with the light projecting system and the light receiving system shown in a central cross section. These light projection/reception systems include an alignment light source 8, a projection lens 9, and a projection mirror 1.
7, detection means 51, 52, and processing circuits 101, 1
02 is housed in a pickup head 16, and the entire structure is movable to the alignment mark position by a stage (not shown). The alignment light beam projected from the pickup head 16 is diffracted by the first alignment mark 3 on the mask 1 supported by the mask holder 15, diffracted by the second alignment mark 4 on the wafer 2 supported by the wafer stage 12, Furthermore, it is diffracted by the alignment mark 13 for emission on the mask 1 surface, and enters the pickup head 16 again, and the detection means 51
．． The light is received at 52. The spot information received by the detection means 51 and 52 passes through processing circuits 101 and 102 and is recognized by the exposure system controller 14 as alignment information between the mask 1 and the wafer 2. Here, in order to move the wafer stage to the optimum position and perform exposure, a movement signal is sent to the stage controller 11, and the wafer stage 12 is moved.

When the alignment is completed, an exposure beam is projected onto the exposure area indicated by E, and printing is completed. At this time, the alignment light constitutes an oblique light and an oblique light receiving system, and no evacuation operation is required.

(Effects of the Invention) According to the present invention, the first. The second alignment marks are respectively aligned with the first alignment marks. provided on the second object plane 1],
Two systems of refractive power arrangement with different orders are set, and the light beams passing through each alignment mark are used to detect the first object and the second object.
By detecting the mutual shift magnification of objects with opposite signs, the following effects can be obtained when aligning a mask as a first object and a wafer as a second object.

(b) Even if the center of gravity of the alignment light changes due to an inclination of the wafer surface, uneven resist coating, or local inclination such as warping that occurs during the exposure process, the position of the center of gravity of the alignment light relative to the two alignment signal lights will change. By detecting the position of the center of gravity, it is possible to accurately detect positional deviation without being affected by the inclination of the wafer surface.

(b) Even if the position of the center of gravity of sensor 7 of the alignment signal light changes because the position of the alignment head changes relative to the mask, the relative center of gravity position of the two alignment signal lights can be detected. , it is possible to accurately detect the positional deviation between the mask and the wafer without being affected by the positional deviation of the alignment head.

(A) By constructing two systems using the same alignment mark, a total magnification can be effectively obtained, and an alignment signal with approximately twice the sensitivity can be obtained.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram of the optical principle of the alignment device of the present invention, and FIG. Third. 6th. FIG. 7 shows the first embodiment of the present invention in order. Second
．． Third. A perspective view of the main parts of the fourth embodiment, FIG. 4 is a developed view of the optical system in FIG. 3, and FIGS. Explanatory diagram of the second alignment mark, Fig. 8 (A)
, (B) is an explanatory diagram of the first and second alignment marks in FIG. 7, FIG. 9 is an explanatory diagram of the luminous flux distribution on the detection means surface of FIG. 7, and FIG. 10 is an explanatory diagram of the fourth implementation of FIG. 7. 11. Schematic diagram when the example is applied to a proximity type exposure apparatus for semiconductor manufacturing. FIG. 12 is an explanatory diagram of a positioning device using conventional zone plates. In the figure, 1 is the first object, 2 is the second object, 3 is the first physical optical element, 4 is the second physical optical element, 5°51.52 is the detection means, 6 is the first signal light, and 7 is the first physical optical element. 2 signal light, 8 is a light source, 9 is a projection lens, 10° 10a, 10b, 101, 102 are processing circuits, 1st is a controller, 12 is a stage, 3rd is a stage
14 is an exposure system controller 14, 15 is a mask chuck, and 16 is a pickup head. Condolence? figure

Claims (2)

[Claims] (1) When relative positioning is performed by making a first object and a second object face each other, a first physical optical element is formed on the first object surface, and a second physical optical element is also formed on the second object surface. forming an optical element, making diffracted light generated when light is incident on the first physical optical element enter the second physical optical element, and producing a light amount of a diffraction pattern on a predetermined surface by the second physical optical element; By detecting the distribution with the detection means, when relative positioning of the first object and the second object is performed, the first and second objects are detected.
A positioning device characterized in that the physical optical element is set to simultaneously form a convex-concave system and a concavo-convex system for the diffracted light by combining different orders. (2) A computing means for computing a difference in spot position of diffracted light on a predetermined surface formed by the convex-concave system and the concave-convex system formed by the first and second physical optical elements. 1. The alignment device according to 1.