JP2867597B2 - Position detection method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a position detecting method, for example, in an exposure apparatus for manufacturing a semiconductor element, on a first object surface such as a mask or a reticle (hereinafter, referred to as “mask”). When exposing and transferring a fine electronic circuit pattern formed on a second object surface such as a wafer by exposure, a relative positional shift amount between the mask and the wafer is obtained, and it is suitable for performing both positioning (alignment). The present invention relates to a simple position detection method.

2. Description of the Related Art Conventionally, in an exposure apparatus for manufacturing a semiconductor, relative positioning between a mask and a wafer has been an important factor for improving performance. In particular, in recent aligners in an exposure apparatus, for high integration of semiconductor elements,
For example, one having a positioning accuracy of sub-micron or less is required.

In many position detecting devices, so-called alignment marks for positioning are provided on a mask and a wafer surface, and both alignments are performed using position information obtained from the alignment marks. As the alignment method at this time, for example, the amount of deviation between both alignment marks is detected by performing image processing, or US Pat.
No. 9, US Pat. No. 4,514,858 and Japanese Patent Application Laid-Open No. 56-157030, use a zone plate as an alignment mark, irradiate the zone plate with a light beam, and at this time, a light beam emitted from the zone plate. This is performed by detecting the position of the condensing point on a predetermined surface.

Generally, an alignment method using a zone plate has a feature that relatively high-precision alignment can be performed without being affected by a defect of an alignment mark, as compared with a method using a simple alignment mark.

FIG. 4 is a schematic view of a conventional position detecting device using a zone plate.

In the figure, a mask M is attached to a membrane 117, which is supported on an aligner body 115 via a mask chuck 116. An alignment head 114 is arranged above the main body 115. To align the mask M and the wafer W, a mask alignment mark MM and a wafer alignment mark WM are printed on the mask M and the wafer W, respectively.

The light beam emitted from the light source 110 becomes parallel light by the light projecting lens system 111, passes through the half mirror 112, and enters the mask alignment mark MM. Mask alignment mark
The MM is formed of a transmission type zone plate, and the incident light beam is diffracted, and the + 1st-order diffracted light is subjected to a convex lens function of converging to a point Q.

The wafer alignment mark WM is formed of a reflection type zone plate and reflects and diffracts the light condensed on the point Q, thereby detecting the light on the detection surface.
It has the action of a convex mirror (divergent action) that forms an image on 119.

At this time, the signal light beam subjected to the -1st-order reflection and diffraction action at the wafer alignment mark WM is the mask alignment mark.
When passing through the MM, the light is transmitted as zero-order light without being affected by a lens and is condensed on the detection surface 119.

Here, a light beam that has undergone an m-order diffraction effect on the alignment mark MM of the mask M, an n-order reflection diffraction effect on the alignment mark WM of the wafer W, and an l-order diffraction effect on the alignment mark MM of the mask M again. Below for convenience (m,
n, l) is called the next light. Therefore, the above-mentioned light beam becomes a signal light beam of the (1, −1,0) order light.

In the position detecting device shown in FIG. 3, when the wafer W is displaced relative to the mask M by a predetermined amount, the incident position of the light beam incident on the detection surface 119 (the amount of light The position of the center of gravity) shifts. At this time, the shift amount Δδw on the detection surface 119 and the positional shift amount Δσw have a fixed relationship. By detecting the shift amount Δδw on the detection surface 119 at this time, the relative position between the mask M and the wafer W is determined. The position shift amount Δσw is detected.

As shown in the figure, when the distance from the condensing position Q of the signal light beam emitted from the mask M to the wafer 2 is aw and the distance bw from the wafer W to the detection surface 119 is bw, the positional deviation amount Δδw on the detection surface 119 is Becomes As is clear from the equation (a), the displacement amount is enlarged by (bw / aw-1) times. This (bw / aw-1) is the displacement detection magnification.

In the apparatus shown in FIG. 1, generally, the mask M is fixed, and the printing is performed, and the position of the signal light flux when there is no displacement between the mask and the wafer (reference position) is used as a reference. The amount of deviation from the incident position is detected by the detection surface 119, and the amount of deviation Δσ is obtained from the expression (a) using the value Δδw at this time.

(Problems to be Solved by the Invention) Generally, in the position detecting device shown in FIG. 4, on the detection surface 119, in addition to the (1, −1,0) order light, the diffraction order (0, −1,1) is different. )
The next light may be substantially condensed.

For example, after being incident on the alignment mark MM on the mask M, this is transmitted by the 0th-order diffracted light, first reflected and diffracted by the alignment mark WM on the wafer W in the -1st order, and is subjected to the action of concave power (divergence). In some cases, the (0, -1, 1) -order light transmitted and diffracted in the + 1st order by the alignment mark MM on the mask M and subjected to the action of convex power (convergence) is substantially converged on the detection surface 119.

FIG. 5 is an explanatory diagram schematically showing the state of propagation of the (1, −1,0) order light and the (0, −1,1) order light at this time.

Here, in general, the (1, -1,0) order light and the (0, -1,1) order light have different detection magnifications of the incident position movement amount with respect to the relative position shift amount between the mask and the wafer. Therefore, as the incident position of the light beam, when the value obtained by multiplying the position vector from each point on the detection surface by the light intensity at that point in the detection surface 119 is integrated over the entire detection surface, the integrated value becomes 0. If a point that becomes a vector (hereinafter referred to as the (center of gravity of the light beam)) is detected, it will be affected by the (0, -1,1,1) -order light in addition to the (1, -1,0) -order light as the signal light beam. Or the S / N ratio deteriorates (a)
In some cases, it was not possible to correctly detect the amount of misalignment even by using the equation.

If the light intensity ratio relationship between the (1, −1,0) -order light and the (0, −1,1) -order light is always maintained to a certain value, the light on the detection surface formed by these two light beams Relative positional deviation Δσw between the mask and the wafer of the deviation of the center of gravity position due to the entire intensity distribution
There is also a method in which a detection magnification for the position is calculated, and this is used as a new position deviation detection magnification to perform position deviation detection.

In this case, the light intensity ratio of each light beam changes with a wafer process factor such as a change in the resist film thickness or a position change between the positioning objects in a direction orthogonal to the position shift detection direction. As a result, there has been a problem that the total displacement detection magnification of the combined (1, −1,0) -order light and (0, −1,1) -order light fluctuates, resulting in a displacement detection error.

The present invention relates to such a target signal beam (m, n,
l) A detection error factor for the next light (m ', n', l ')
It is an object of the present invention to provide a position detection method capable of effectively preventing an adverse effect of the next light (however, m ′ ≠ m or n ′ ≠ n or l ′ ≠ l) and detecting a position shift amount with high accuracy. .

(Means for Solving the Problems) According to the position detection method of the present invention, a first alignment mark having a diffractive action on a first object plane and a second alignment mark having a diffractive action on a second object plane are respectively provided. When m, n, and l of the light flux from the light projecting means are integers, the first alignment mark is subjected to an m-th order diffraction action, and
The converging position on the predetermined plane of the first light beam, which has been subjected to the nth-order reflection / diffraction effect at the alignment mark and again subjected to the lth-order diffraction effect at the first alignment mark, is a relative position between the first object and the second object. The relative position between the first object and the second object is determined by changing the position shift amount at a predetermined magnification and detecting a condensing position of the first light beam on a predetermined plane by a detecting unit. When detecting the shift amount, m ′, n ′, l ′ are calculated as m ′ ≠
When m or n ′ ≠ n or l ′ ≠ l, the first alignment mark is subjected to the m′-order diffraction effect, and the second alignment mark is subjected to the n′-order reflection diffraction effect,
Again, the condensing position on the predetermined plane of the second light beam subjected to the l′-order diffraction action by the first alignment mark is separated from the first condensing position by a predetermined amount on the predetermined plane. A distance between a first object and the second object, focal lengths of the first and second alignment marks, and an incident angle when a light beam from the light projecting means enters the first alignment mark are set. I have.

That is, according to the present invention, the first and second signal alignment marks having a function as a physical optical element on the object plane A when the object plane A and the object plane B are to be positioned as a first object and a second object. A1 and A2 are formed, and first and second signal alignment marks B1 and B2 having the same function as a physical optical element are also formed on the object plane B, and a light beam is incident on the alignment mark A1. The diffracted light generated at this time is incident on the alignment mark B1, and the first detection unit detects the center of the light flux on the incident surface of the diffracted light from the alignment mark B1 as the incident position of the first signal light flux.

Here, the center of gravity of the light beam is defined as the point at which the integral value becomes a zero vector when the value obtained by multiplying the position vector from each point in the light reception within the light beam reception by the light intensity at that point is integrated over the entire light receiving surface. However, for convenience, a point at which the light intensity reaches a peak may be used as the luminous flux center of gravity. Similarly, a light beam is made incident on the alignment mark A2, and the diffracted light generated at this time is made incident on the alignment mark B2, and the alignment mark B2
The second detection unit detects the barycenter of the light beam on the incident surface of the diffracted light from the light source as the incident position of the second signal light beam. And the first
Then, the object plane A and the object plane B are positioned using two pieces of position information from the second detection unit. At this time, each element is set so that the incident position of the (m ′, n ′, l ′)-order light, which is a detection error factor for the (m, n, l) -order light, has the above-described positional relationship. .

In addition, in the present invention, the position of the center of gravity of the light beam incident on the first detection unit and the position of the center of gravity of the light beam incident on the second detection unit are displaced in directions opposite to each other with respect to the displacement between the object plane A and the object plane B. Each alignment mark A1, A2, B1, B2 is set.

(Embodiment) FIG. 1 is an explanatory diagram showing the principle and configuration requirements of the present invention in an expanded manner, and FIG. 2 is a first embodiment of the present invention based on the configuration of FIG.
It is a principal part perspective view of an Example.

In the drawing, reference numeral 1 denotes a first object corresponding to the object plane A, 2 denotes a second object corresponding to the object plane B, and a first object 1 and a second object 2
5 shows a case where a relative displacement amount with respect to is detected.

In FIG. 1, two first objects 1 are shown because light passing through the first object 1 and reflected by the second object 2 passes through the first object 1 again. Reference numeral 5 denotes an alignment mark provided on the first object 1 and reference numeral 3 denotes an alignment mark provided on the second object 2 for obtaining a first signal. Similarly, reference numeral 6 denotes an alignment mark provided on the first object 1 and reference numeral 4 denotes an alignment mark provided on the second object 2 for obtaining a second signal light. In FIG. 1, alignment marks 3 and 4
Is replaced by an optical path replaced with an equivalent transmissive alignment mark.

Each of the alignment marks 3, 4, 5, and 6 has a function of a physical optical element such as a grating lens having a one-dimensional or two-dimensional lens function or a diffraction grating having no lens function.
9 is a wafer scribe line, 10 is a mask scribe line, and each alignment mark is formed on its surface. Reference numerals 7 and 8 denote the first and second signal beams for the first and second alignments, respectively. 7 'and 8' are the first and second
This is a diffracted light beam of a predetermined order corresponding to the signal light beams 7, 8.

In this embodiment, the first signal light beam 7 is the (1, -1,0) -order light, the second signal light beam 8 is the (-1,1,0) -order light, and the light beam 7 'is (0, -1,0).
1) The next-order light beam 8 'is (0,1, -1) -order light.

Reference numerals 11 and 12 denote first and second detectors for detecting the first and second signal light beams 7 and 8, respectively. The first and second detectors 11 and 12 are made of, for example, a one-dimensional CCD or the like, and the arrangement direction of the elements coincides with the x-axis direction.

The optical distance from the second object 2 to the first or second detection unit 11, 12 is L for convenience of explanation. Object 1 and second object 2
Is the distance g, the focal lengths of the alignment marks 5 and 6 are f _a1 and f _a2 , respectively, and the relative displacement between the first object 1 and the second object 2 is Δσ. The displacement amounts of the first and second signal light flux centroids 11 and 12 from the coincidence state are defined as S ₁ and S ₂ , respectively. The alignment light beam incident on the first object 1 is a plane wave for convenience, and the reference numerals are as shown in the figure.

Displacement S ₁ and S ₂ of the signal light beam centroid to the straight line L1, L2 connecting the center of the optical axis of the focus F _1, F ₂ and the alignment marks 3 and 4 of the alignment marks 5 and 6, the light receiving surface of the detector 11 and 12 Geometrically as the intersection with Therefore, in order to obtain the displacement amounts S ₁ and S ₂ of the center of gravity of each signal light beam in directions opposite to each other with respect to the relative positional deviation between the first object 1 and the second object 2,
This is achieved by reversing the signs of the optical imaging magnifications of 3 and 4.

In the present embodiment, the type of the light source a semiconductor laser, H _e -N _e laser light source and which emits coherent light beam A _r laser or the like using a light source such as that emits non-coherent light beam such as a light emitting diode I have.

As shown in FIG. 2, in this embodiment, the light flux 7 as the (1, -1,0) -order light and the light flux 8 as the (-1,1,0) -order light are respectively aligned marks 5 on the mask 1 surface. , 6 at a predetermined angle, then transmitted and diffracted, further reflected and diffracted by the alignment marks 3 and 4 on the surface of the wafer 2, and incident on the detection units 11 and 12.
The light beam 7 'as the (0, -1,1) -order light and the light beam 8' as the (0,1, -1) -order light pass through the alignment marks 5,6 on the mask 1 surface at the 0th order. The light is reflected and diffracted by the alignment marks 3 and 4 on the surface of the wafer 2 and then transmitted and diffracted by the alignment marks 5 and 6 on the surface of the mask 1 and is incident on the detection units 11 and 12.

Of these light beams, the positions of the centers of gravity of the alignment light beams 7 and 8 incident on the surfaces of the detection units 11 and 12 are detected, and the displacement signals of the mask 1 and the wafer 2 are detected using the output signals from the detection units 11 and 12. It is carried out.

 Next, the alignment marks 3, 4, 5, and 6 will be described.

Each of the alignment marks 3, 4, 5, and 6 is composed of a Fresnel zone plate (or grating lens) having a different value of focal length. The dimensions of these alignment marks are 50 in the direction of scribe lines 9 and 10, respectively.
~ 300μm, 20 ~ 1 in the scribe line width direction (y direction)
00 μm is a practically suitable size.

In this embodiment, each of the light beams 7, 7 'and 8, 8' has an incident angle of about 17.5 ° with respect to the mask 1, and the projected component on the mask 1 surface is orthogonal to the scribe line direction (x direction). Injecting.

The distance between the mask 1 and the wafer 2 is 30 μm. (1, −
1,0) The light beam 7 of the next light is transmitted and diffracted in the first order by the alignment mark 5 and is subjected to a convex lens action, and then is subjected to a concave lens action by the alignment mark 3 on the surface of the wafer 2 to be on the first detecting unit 11 surface. Focusing.

The light beam 7 'of the (0, -1,1) order light is transmitted through the mask 1 surface by the 0 order (diffraction), then is reflected and diffracted by the alignment mark 3 on the surface of the wafer 2 first order, and receives a concave lens effect. Further, first-order transmission diffraction occurs at the alignment mark 5 on the mask surface 1, and
After receiving the convex lens action, the light reaches the surface of the detection unit 11.

The amount of change in the incident position of the light beam corresponds to the amount of displacement of the alignment marks 5 and 3 in the x direction, that is, the amount of axial displacement, and is incident on the detection unit 11 in a state where the amount is enlarged. As a result, a change in the position of the center of gravity of the incident light beam is detected by the detection unit 11.

In this embodiment, when the positional deviation between the mask 1 and the wafer 2 is 0, that is, when the alignment mark 5 on the mask 1 is
When the alignment mark 3 and the upper alignment mark 3 form a coaxial system, the exit angle of the principal ray of the light beam 7 from the wafer 2 is 13 degrees, and the projected component of the emitted light on the surface of the wafer 2 at this time is the scribe line width. The light is focused on a predetermined position orthogonal to the direction (y direction), for example, on the surface of the detection unit 11 located at a height of 18.657 mm from the surface of the wafer 2.

Also, the light beam 8 is transmitted and diffracted by the alignment mark 6, and the alignment mark 4 on the surface of the wafer 2 moves the spot position at the image forming point in a direction different from that of the light beam 7, and the position shift is also caused by the emission angle of 7 degrees. When the value is 0, unlike the light beam 8, the projected component on the surface of the wafer 2 is emitted so as to be orthogonal to the scribe line width direction, and is condensed on the surface of the second detection unit 12.

After setting the lens parameters of the alignment mark as described above, in the present embodiment, the x-direction component of the distance between the position of the center of gravity of the light beam 7 on the surface of the detection unit 11 and the position of the light beam 8 and the center of gravity on the surface of the detection unit 12 (Interval along the x direction) is detected. If the wafer is displaced by Δσ with respect to the mask, the displacements S ₁ and S ₂ of the respective centers of gravity of the light beams are determined quantitatively by setting the distance between the mask and the wafer to g and the distance between the wafer and the light receiving surface to L. Β ₁ = S ₁ / Δσ, β ₂ = S ₂ / Δ
can be defined as σ.

As described above, since the signal light beam is displaced in the opposite direction with respect to the same positional deviation amount Δσ, the light beam with respect to the positional deviation amount Δδ
The change amount ΔD of the interval along the x direction of 7, 8 is expressed by the following equation.

ΔD = (β ₁ −β ₂ ) · Δσ The detection of the amount of displacement is performed as follows.

When the amount of displacement between the mask and the wafer in the x direction is 0, the distance D between the positions of both centers of gravity along the x direction is calculated in advance from design values or by trial printing. When the relative displacement between the mask and the wafer in the x direction is detected, the displacement ΔD from the distance D along the x direction between the two centers of gravity is detected, and the relative displacement between the mask and the wafer in the x direction is determined from the displacement ΔD. Calculate the quantity Δσ.

Next, as shown in FIG. 1, a description will be given of a projection angle of a light beam projected on the alignment mark with respect to a normal line of the alignment mark surface, and a light beam incident position on the detection surface corresponding to a positional shift amount Δσ between the first and second objects. I do.

Now, _assume that the center position (optical axis position) of the first alignment mark 5 on the first object is (x _MO1 , y _MO1,0 ), and that the parallel light flux incident on the alignment mark 5 at an angle θ in the xz plane is obtained. When placing the image point position as _{(x M1, y M1, z} M1) becomes Z _M1 = -f _1.

On the other hand, the center position (optical axis position) when the displacement amount of the alignment mark 3 on the second object is 0 is (x _W1 , y _W1 , −
g), and the alignment mark 3 is located at (x _M1 , y _M1 , −f ₁ ).

It is assumed that the point light source is designed to form an image at the position ( _xS1 , _yS1 , _zS1 ) when the displacement amount is zero. Similarly, the center position (optical axis position) of the alignment mark 6 on the first object plane is set to ( _xMO2 , _yMO2 , 0), and the imaging point position is set to ( _xM2 , _yM2 , −f ₃ ). Further to the center position when the positional deviation amount of the alignment mark 4 is 0 (optical axis position) and _{(x W2, y W2, -g} ), the alignment mark 4 is in the _{(x M2, y M2, -f} 3) It is assumed that the point light source is designed to form an image at the position (x _S2 , y _S2 , z _S2 ) when the displacement amount is zero. The distance from the mask surface to the detection surface is L '.

The first object of the (1, −1,0) order light beam 7 and the other (0, −1,1) order light beam 7 ′ that forms the first signal light under the above parameter settings Displacement amount Δ of the second object with respect to
Let S ₁₁ and S ₁₂ be the amounts of change in the center of gravity of the light beam on the detector surface corresponding to σ, respectively. Becomes

Similarly, the amount of change of the center of gravity of the light beam 8 of the (−1,1,0) -order light beam and the other light beam 8 ′ of the (0,1, −1) -order light beam on the detection unit surface is represented by S _12. , and the S ₂₂ Further, from the general relation of the imaging characteristics of the lens, x _MOi = x _Mi + f _2i-1 tan θ (i = 1,2) (5) Further, x _Mi and x _Wi are respectively the alignment marks on the first object plane. The deflection angle of the alignment mark on the second object plane with respect to the principal ray, and the amount determined by the respective focal lengths It is. Here, _{ｊ j} = θ-φ _j (j = 1,4) is a deflection angle with respect to the incident angle θ of each alignment mark.

Now, with the origin at the center of the alignment mark setting area on the first object plane, the direction of detecting the amount of displacement within the alignment mark plane is defined as the x-axis, the orthogonal direction is defined as the y-axis, and the z-axis is defined as the normal to the alignment mark plane. Take.

Detector the center of the light receiving area in the xyz orthogonal coordinate system _{(x S, y S, z} S) d 1 is represented by, and whose size in the x-direction light-receiving region is rectangular, d ₂ in a direction perpendicular thereto And

Now, focusing on the luminous flux 7 'of the (0, -1,1) -order light and the luminous flux 8' of the (0,1, -1) -order light, and substituting equation (5) into equations (2) and (4), At this time, S ₂₁ and S ₂₂ are the detection ranges of the displacement amount ∈ ₁ ≦ Δσ ≦
In ∈ ₂ (∈ ₁ and ∈ ₂ are the upper and lower limit of the amount of displacement that can be detected by the detector with the length of d ₁ ) If the parameters are set so that と₁ ≦ Δσ ≦ ∈ ₂ , the (0, -1,1) -order light beam 7 ′ and the (0,1, −1) -order light beam 8 ′ are placed on the light receiving region. Not reach in the range.

In this embodiment, the above problems are solved by setting the values of ∈ ₁ and ∈ _{2 to} the values described above.

In this embodiment, the projection angle θ of the light beam to the alignment mark and the light beam deflection angles ζ ₁ , ζ ₂ , ζ of each alignment mark are set so as to satisfy the expression (7) without changing the position detection magnification by setting X _S = 0. ₃ , _{４ 4} (ie, x _M1 , x _M2 , x _W1 , x _W2 ) are set appropriately.

Here, the distance L from the center of the alignment mark on the second object plane to the center of the light receiving area of the detection unit is 18.657 mm,
The distance L 'from the center of the alignment mark on the object plane to the center of the light receiving area of the detection unit is 18.628 mm, the distance g between the first and second objects is 30.0 μm, and further given by the equations (1) and (3). The alignment marks 5 on the mask surface are set so that the position shift detection sensitivities β ₁ and β _{2 of the} (1, −1,0) order light and the (−1,1,0) order light become +200 times and −200 times, respectively. , setting the focal length f _1, f ₃ of 6, f ₁ = 122.8209μm, the f ₃ = -63.7538μm.

Conditional expressions for (1, -1,0) order light and (-1,1,0) order light to form an image on the detector surface Thus, f ₂ and f ₄ are f ₂ = −92.361 μm and f ₄ = 94.2273 μ, respectively.
m.

Substituting the above numerical values into the equations (2) 'and (4)', S ₂₁ = −152.23 (x _W1 −x _M1 +30.46 tan θ + Δσ) + x _M1 +122.82 tan θ S ₂₂ = 149.94 (x _W2 −x _M2 +30. 47tanθ + Δσ) + x _M2 -63.75tanθ now, positional deviation measurement range (the range from ∈ ₁ to _{∈ 2) -3.0 <Δσ <3.0} (μm), the detector size d ₁ =
40 mm, d ₂ = 0.48 mm. In the present embodiment, the equation (7) is considered. And At this time, S ₁₁ and S ₁₂ are S ₁₁ = −200.0 (x _W1 −x _M1 + ∈) + x _M1 S ₁₂ = 200.0 (x _W2 −x _M2 + ∈) + x _M2 (1, −1,0) -3.0 ≦ Δσ ≦ 3.0 as the condition that the light and the (−1,1,0) order light are received by the detector. X _M1 , x _M2 , x _W1 , x _W2 are set so as to satisfy

In this embodiment, the expression (7) ′ or the expression (7) ″ and the expression (8)
Θ = 30 °, x _W1 = 10.0 μm, x _M1 = 5.0
μm, x _W2 = 0.0 μm, x _M2 = −5.0 μm.

At this time, S ₂₁ and S ₂₂ are S ₂₁ (∈) = − 152.23∈−2601.22 (μm) (9-1) S ₂₂ (∈) = 149.94∈ + 2595.92 (μm) (9-2) −3.0 <Δσ At> 3.0, −3067.91 <S ₂₁ <−2154.53, 2146.1 <S ₂₂ <3045.74, which satisfies the expression (7) ′.

At this time, S ₁₁ and S ₁₂ are respectively S ₁₁ (∈) = − 200.0∈−995 (μm) (9-3) S ₁₂ (∈) = 200.0∈ + 995 (μm) (9-4), and (8) Satisfy the formula.

As described above, in this embodiment, the (0, -1,1) -order light or the (0.1, -1) -order light is prevented from entering the light beam detection area. (0, −1,1) order light, (−1,1,
0) and the next light (0,1, -1) is also within the positional deviation detection range on the next light detection portion plane be relatively spaced position of the center of gravity always over a certain distance, as described above theta, x _W1, it is possible by making appropriate settings, such as x _M1.

That is, for the first signal light, the luminous flux 7 of the (1, −1,0) order light
And the relative center-of-gravity distance l ₁ of the light beam 7 ′ of the (0, −1,1) order light on the detection unit surface is Next, the l ₁ is always l ₁ ≧ l _min The displacement measurement range of _{∈ 1 ≦ Δσ ≦ ∈ 2 (} > 0) Parameter f ₁ so as to satisfy the _{(9-7), f 2, L} , L ', x _MO1, x _M1, to set the θ. l _min is the permissible minimum value of the relative center of gravity distance at which the two light beams 7, 7 'can approach on the detection unit surface, and the 1 / e ² light beam system (spot diameter) of each light beam on the detection unit surface α ₁ , α
_If α is ₂ , α ₁ and α ₂ are determined from L and the mark size in the x direction, and the separation condition of the two light fluxes is l _min = γ (α ₁ + α ₂ ) (9-8). It is desirable that γ ≧ 2.0. That is, it is desirable that the distance is at least four times the spot diameter. It is necessary to set the second signal light similarly as described above.

By setting as above, for example, (1, −1,
0) Only the center of gravity of the light intensity distribution of the next light can be detected.

That is, the charge accumulation type sensor (CCD) is designed to detect the center of gravity of the light intensity distribution in the range of, for example, 1 / e ^{2 of the} peak intensity around the peak intensity point of the (1, −1,0) -order light. , Etc.) to perform signal processing.

As a more specific parameter setting method, for example, the (1, -1,0) -order light and (-1,, 0) -th light of the first signal light and the second signal light, respectively,
1,0) When only the next light is subjected to the center of gravity detection processing, the displacement amount Δ
The relative center-of-gravity distance l of the two light beams of interest on the detection unit surface corresponding to σ is And the overall detection sensitivity β for the displacement amount Δσ is Becomes

Therefore, first, the total detection sensitivity is a predetermined value (for example, 200 times) β
Conditional expression for parameter setting so as to be ₀ , that is, Then, under the condition of the expression (9-12), the first signal light satisfies the expressions (9-5) to (9-8), and the second signal light similarly has the value (−1). , 1,0) next light beam 8
And (0,1, -1) detection portion plane on the relative center of gravity distance l ₂ are conditions to be satisfied for the light flux 8 of the next light ', i.e. (9-13) - below (9-
15) Expression Set the parameters to satisfy

As described above, (9-5) to (9-8), (9-12) to
The parameters f ₁ , f ₂ ,
_{f 3, f 4, L,} L ', x MO1, x M1, x MO2, x M2, set the theta. Unknown
Since the number of simultaneous conditional expressions (including inequalities) is 8 for 11, the solution is not uniquely determined. For example, a procedure of obtaining a numerical solution by giving f ₁ , f ₃ , L ′ is used.

FIG. 3 (A) shows a configuration diagram of a peripheral portion of the first embodiment of FIG. 2 when the first embodiment is applied to a proximity type semiconductor manufacturing apparatus. Elements not shown in FIG. 2 include a light source 13, a collimator lens system (or beam diameter conversion lens) 14, a projection light beam bending mirror 15, a pickup housing (alignment head housing) 16, a wafer stage 17, and a displacement signal processing unit 18. , A wafer stage drive control unit 19 and the like. E indicates the exposure light beam width.

Also in the present embodiment, the mask 1 as the first object and the second
The relative displacement of the wafer 2 as an object is detected in the same manner as described in the first embodiment.

In this embodiment, as a procedure for performing the alignment, for example, the following method can be adopted.

As a first method, a signal of the amount of displacement of the center of gravity of light flux Δδ on the detection surfaces 11a and 12b of the detection units 11 and 12 with respect to the amount of displacement of two objects Δσ is obtained. The amount of positional deviation Δσ between the objects is determined, and the stage drive control unit 19 moves the wafer stage 17 by an amount corresponding to the amount of positional deviation Δσ at that time.

As a second method, a direction in which the displacement amount Δσ is canceled out from the signals from the detection units 11 and 12 is obtained by the signal processing unit 18, and the stage drive control unit 19 moves the wafer stage 17 in that direction to obtain the displacement amount Δσ. Is repeated until the value falls within the allowable range.

FIGS. 3 (B) and 3 (C) show flowcharts of the above alignment procedure, respectively.

In this embodiment, as can be seen from FIG. 3A, the light beam from the light source 13 is aligned with the alignment marks 5 and 6 from the outside of the exposure light beam.
Into the detectors 11 and 1 provided outside the exposure light beam.
The light is received at 2 and the position of the incident light beam is detected.

With such a configuration, the pickup housing 16 can also realize a system that does not require a retreat operation during exposure.

As a second embodiment of the present invention, for example, (1),
(1, -1,0) shown by the equations (2) ', (3), and (4)'
Order light, (−1,1,0) order light, (0, −1,1) order light, (0,1, −
1) From the expression of the incident position of the next light on the detection unit surface, the (0, -1,1) order light or (0,1, -1) as the alignment signal light
Each element such as the arrangement and size of the detection unit is determined so that only the next light is received by the detection unit.

In the above description, the configuration relating to the device is basically the same as in FIG.

In this embodiment, the xz
The incident angle θ of the light beam in the plane and the values of the eccentricity parameters x _M1 , x _M2 , x _W1 , x _W2, etc. of each alignment mark are the same as those in the first embodiment, and the arrangement and size of the detection units are different. .

At this time, from the expressions (9-1) to (9-4), (0, -1,
1) In order to receive only the next light or only the (0,1, -1) th light, the detection unit center coordinates (x _S , y _S , z _S ) are set as X _S = ｛S ₂₁ (O) + S ₂₂ (O) ｝ / 2, and y _S and z _S were the same as in the first embodiment.

The size of the light receiving region is set to 1.88 mm in the x direction in consideration of the possible values of S ₂₁ and S ₂₂ in the displacement detection range of −3.0 <Δσ <3.0 (μm).

Under the above conditions, the detector receives only the (0, -1,1) -order light or (0,1, -1) -order light and the (1, -1,0) -order light or (-1,1,1) -order light. , 0) It has become possible to detect the amount of displacement stably without being affected by the next light.

According to a third embodiment of the present invention, a light beam that has undergone m-th order transmission diffraction at an alignment mark on a mask surface, further has n-order reflection diffraction at an alignment mark on a wafer surface, and again has an l-order transmission diffraction at an alignment mark on a mask surface. , That is, a configuration in which the (m, n, l) -order light is used as the displacement signal light can be applied.

A one-dimensional or two-dimensional grating lens that generates cylindrical power is considered as the alignment mark, and the direction in which the lens power is generated is set to the x-axis. An axis orthogonal to the x-axis in the plane of the alignment mark and passing through the center of the alignment mark is defined as the y-axis. The z axis is an axis orthogonal to the x axis and the y axis.

Now, when a light beam is incident at an angle θ in the yz plane (m, n,
l) the next light is finally emitted to angle zeta _l from the mask surface angle zeta _l is Given by Here, P _M and P _W represent the pitch of the alignment mark on the mask and wafer surfaces, respectively, in the yz plane having no condensing and diverging effect, and λ represents the wavelength.

From equation (10), the luminous flux that is simultaneously incident on the detection unit that becomes the displacement signal is A light beam corresponding to a combination of diffraction orders that satisfies the following condition, that is, a light beam that transmits the m-th order through the grating lens on the mask surface and undergoes the l-th order transmission diffraction that takes l again to satisfy the expression (10) ′. The light flux serving as the displacement signal is n
こ と が 0 and at least one of m and l is not 0, which is a necessary condition for detecting the enlargement of the displacement using the grating lens.

Now, let f _i ^{M be} the focal length of the alignment mark on the mask corresponding to the i-th order diffracted light, and f _j ^{W be} the focal length of the alignment mark on the wafer surface corresponding to the j-th order diffracted light.
In other words, the position shift detection magnification β of the (m, n, l) -order light on the detection unit surface is calculated from the effective center of gravity of the (m, n, l) -order light. Where L ₁ is Given by, L ₂ is the distance from the center of the alignment mark on the mask surface to the center of the detector.

At this time, the incident position S of the (m, n, l) order light on the detection unit surface is the incident angle θ of the light beam in the xz plane and the x-direction center position x _{MO of} each grating lens, as in the first embodiment. using x _W represented as the following equation.

Now (m, n, l) L 2 when the next light is imaged on the detection portion plane is Given by

Further, f _l ^M and (f _m ^M ) are generally expressed as f _l ^M = f ₁ ^M / l (13), where f ₁ ^M is the focal length corresponding to the + _1st- order diffracted light of the alignment mark on the mask surface. . On the other hand, assuming that the image plane position of the (m ', n', l ')-order light that satisfies m' ≠ m or n '≠ n or l' ≠ l is located at a distance of L ₂ 'from the final mask plane. In the embodiment, the following conditions (1
4) Satisfy the equation.

(M ', n', l ') next light, that is, (m, n, l)
The optical arrangement including the detection unit is determined so that the light beam having the same intensity as the next light does not reach the light receiving area on the detection unit surface.

(14) Equation (m, n, l) the distance to the focal point position of the next light (distance measured from the final pupil center) with respect to L ₂ (m ',
(n ', l') indicates that the distance L ₂ ′ to the position of the condensing point of the next light is substantially the same as L _2, and that the intensity concentration is also substantially the same. Where L ₂ ′ is Given by Using equation (13), the above equation becomes Next, the distance L ₂ ′ given by equation (15-1) ′ and (m, n,
l) and a distance L ₂ to the image plane from the final surface of the next light (14)
A diffraction order (m ′, n ′, l ′) that satisfies the expression is obtained based on the expression (10) ′.

That is, substituting n '= n and m + 1 = m' + l 'into (15-1)' and rearranging m ' Given f ₁ ^M in this embodiment, f ₁ ^W, g and diffraction order (m, n, l) with respect to (m, n, l) and the image plane position L ₂ of the diffracted light (m ', n (M ′, l ′) such that the ratio (difference d = | L ₂ −L ₂ ′ |) of the (′, l ′) order diffracted light to the image plane position L ₂ ′ satisfies equation (14).
n ′, l ′), the two light flux incident positions are calculated based on equation (11). Then, the interval between the incident positions of the two light beams on the detection unit surface satisfies at least the expression (9-8) or, similarly to the expression (7), the (m ′, n ′, l ′)-order light is received on the detection unit surface. The condition that does not reach the area, ie, The projection angle θ, each focal length, and the detection unit setting position may be determined so as to satisfy the following.

That is, the incident position S in the x direction on the detection unit surface of the (m, n, l) order light
Is from equation (1) Similarly, the incident position S ′ of the (m ′, n ′, l ′)-order light on the detector surface is Therefore, the (m, n, l) order light and (m ', n',
l ′) Relative center-of-gravity distance l = | S−
The parameters are set such that S ′ | always satisfies the relationship of l ≧ l _{min, where} l _min satisfies the expression (9-8).
The specific procedure is the same as that of the first embodiment.

As a result, the position of the center of gravity of the light beam can be detected for only one of the position shift signal light beams, and the amount of position shift can be measured, and the effective position shift due to the change in the light amount ratio between the plurality of light beams reaching the detection unit surface. Error factors such as fluctuations in detection sensitivity can be eliminated.

In each of the above-described embodiments, the fact that the amount of change in the distance between the center of gravity of the two detectors along the x direction is proportional to the amount of relative displacement between the mask and the wafer in the x direction is used. Although the method of detecting the amount of change was used, the present invention is not limited to this. For example, as in the conventional example, the amount of deviation of the center of gravity position from the reference position in one detecting unit is x Utilizing the fact that it is proportional to the relative positional deviation amount in the direction, the present invention can be similarly applied to a method of detecting this deviation amount.

(Effects of the Invention) According to the present invention, by setting each element as described above, m ′ ≠ m or n ′ ≠ n for the (m, n, l) -order light which is the target signal light. Alternatively, the influence of the (m ′, n ′, l ′)-order light, which becomes a detection error factor when l ′ ≠ l, is eliminated, and the first
It is possible to achieve a position detection method capable of detecting the relative displacement between the object and the second object with high accuracy.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing the principle and configuration requirements of the present invention, FIG. 2 is a perspective view of a main part of a first embodiment of the present invention based on the configuration of FIG. 1, and FIG. 3 (B) and 3 (C) are flow charts of the measurement control in FIG. 3 (A), and FIG. 4 is a conventional diagram in which the first embodiment of the figure is applied to a proximity type semiconductor manufacturing apparatus. FIG. 5 is an explanatory diagram of the (1, −1,0) -order light and the (0, −1,1) -order light. In the figure, 1 is a first object (mask), 2 is a second object (wafer), 3, 4, 5, and 6 are alignment marks, and 7, 8 are each a mark.
1, a second signal light beam, 9 is a wafer scribe line, 10 is a mask scribe line, 11 and 12 are detectors, 13 is a light source, 14
Denotes a collimator lens system, 15 denotes a half mirror, 16 denotes an alignment head housing, 18 denotes a signal processing unit, and 19 denotes a wafer stage drive control unit.

Continuation of the front page (56) References JP-A-2-74808 (JP, A) JP-A-57-157033 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01B 11 / 00-11/30 H01L 21/30

Claims (2)

(57) [Claims] 1. A first alignment mark having a diffractive action on a first object plane and a second alignment mark having a diffractive action on a second object plane are formed. When n and l are integers, the first alignment mark receives an m-th order diffraction action, the second alignment mark receives an n-th order reflection diffraction action, and the first alignment mark again receives an l-order diffraction action. The condensing position of the received first light beam on a predetermined plane is changed at a predetermined magnification with respect to the relative displacement between the first object and the second object, and the first light beam is focused on a predetermined plane. When detecting the relative position shift amount between the first object and the second object by detecting the condensing position by the detecting means, m ′, n ′, l ′ is changed to m ′ ≠ m or n ′ ≠ n
Or when an integer of l ′ ≠ l is satisfied, the first alignment mark receives an m′-th order diffraction effect, the second alignment mark receives an n′-th order reflection diffraction effect, and the first alignment mark again receives l ′. 'The first object and the second object so that the converging position of the second light beam subjected to the next diffraction action on the predetermined plane is separated from the first converging position by a predetermined amount on the predetermined plane. And a focal length of the first and second alignment marks, and an incident angle when a light beam from the light projecting means enters the first alignment mark. 2. The method according to claim 1, wherein the predetermined amount is the first amount on the predetermined plane.
2. The position detecting method according to claim 1, wherein the diameter is at least four times the diameter of the light beam or the light beam diameter of the second light beam.