JPH0436604A - position detection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

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

(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 devices, a so-called alignment pattern for alignment is provided on the mask and the eight faces of the sea urchin.
Alignment of both is performed using the position information obtained from them. As an alignment method at this time, for example, the amount of deviation between both alignment patterns may be detected by performing image processing, or U.S. Pat.
As proposed in No. 037969 and JP-A-56-157033, a zone plate is used as an alignment pattern and a light beam is irradiated onto the zone plate, and at this time, the light beam emitted from the zone plate is focused at a focal point on a predetermined surface. This is done by detecting the position.

In general, alignment methods using zone plates are
Compared to a method using a simple alignment pattern, this method has the advantage of being able to perform alignment with relatively high precision without being affected by defects in the alignment pattern.

FIG. 6 is a schematic diagram of a conventional alignment device using zone plates.

In the same figure, a parallel light beam emitted from a light source 72 passes through a half mirror 74 and is condensed at a condensing point 78 by a condensing lens 76, after which it is placed on a mask alignment pattern 68a on the surface of a mask 68 and on a support base 62. The wafer alignment pattern 60a on the surface of the wafer 60 is irradiated. These alignment butters: z68a, 60a are composed of reflective zone plates, each forming 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 calculated between the focusing lens 76 and the lens 80.
The light is guided onto the detection surface 82 and detected.

Based on the output signal from the detector 82, a control circuit 84 drives the drive circuit 64 to perform relative positioning of the mask 68 and the wafer 60.

Figure 7 shows mask alignment pattern 6 shown in Figure 6.
8a and an explanatory diagram showing the imaging relationship between the light beams from the wafer alignment pattern 60a and the wafer alignment pattern 60a.

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. Further, the other part of the light beam passes through the mask 68 as zero-order transmitted light and enters the wafer alignment pattern 60a on the surface of 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 changing the wafer position.Concentrating point 78b
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 by the shift 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 the amount Δσ.

Conventionally, the amount of deviation Δσ' at this time was detected to align the mask 68 and the wafer 60.

(Problems to be Solved by the Invention) In the alignment apparatus shown in FIG. 6, there is an uncertain amount of the distance g between the mask and the wafer, which causes the following problems, for example.

Since the amount of deviation Δσ' is dependent on both the amount of deviation Δ0 and the interval g, many sets of the amount of deviation Δσ and the interval g correspond to one amount of deviation Δσ'. Therefore, when trying to detect a matching state at the position of the focal point 78a, if the light beam is focused at the position of the focal point 78b when out of focus, the value of the deviation amount Δσ' cannot be accurately determined. Even if measured, the amount of deviation Δσ cannot be accurately determined. For this reason, although it would be sufficient to perform the alignment operation once, it becomes necessary to perform the alignment operation two or three times, resulting in a decrease in throughput.

The present invention solves the error factors that occur when detecting the position of a first object such as a mask and a second object such as a wafer, and provides position detection with a simple configuration that allows for highly accurate and easy alignment. The purpose is to provide equipment.

(Means for Solving the Problems) The present invention calculates the amount of relative in-plane positional deviation between the first object and the second object (hereinafter also simply referred to as "the amount of deviation"), and at the same time calculates the interval. It is characterized in that the positions of the first object and the second object are determined with high precision.

In particular, in the present invention, physical optical elements are provided on each of the first object plane and the second object plane, and a detection means detects a diffracted light beam of a predetermined order generated on a predetermined plane of the light beam incident on these physical optical elements. When detecting the relative positions of the first object and the second object by doing so, the detecting means detects the position between the first object and the second object among the at least three diffracted beams generated on a predetermined surface. Detect at least two values between the diffracted light beams that are related to both the relative deviation amount W and the relative distance g between the two objects, and use the output signal from the detection means to calculate the deviation amount W and the calculation means using the output signal from the detection means. It is characterized by determining the interval g.

(Embodiment) FIG. 1 is a schematic diagram of the main part of a first embodiment of the present invention, and FIG. 2 is a schematic diagram of the main part when the optical path of each light beam in FIG. 1 is expanded.

1st. On the right side of FIG. 2, ILl is a light flux from a semiconductor laser, LED, or X-ray source (not shown), which is incident at an angle θ to physical optical elements zl and z3, which will be described later, on the surface of a first object such as a mask. ing. Reference numeral 2 denotes a second object such as a wafer, which is placed opposite to the first object 1 at a distance g. W is first
It shows the relative shift amount between the object 1 and the second object 2.

zl and z3 are the transmission-type first
．． The third physical optical element, the luminous flux! 1 is a physical optical element z
It is incident on l and z3. z2゜Z4 is a reflection type (transmission type in FIG. 2) second . The fourth physical optical elements 21 to Z4 are composed of, for example, a diffraction grating or a zone plate.

FIG. 3 shows an example of the pattern of the physical optical elements on the surfaces of the first object 1 and the second object 2 according to this embodiment.

The physical optical elements 21 to Z4 have a lens function, and their focal points are F1 to F4, respectively, and focal paths 11fl to f4.

! 12 to L9 are diffracted lights of predetermined orders from the physical optical elements, and 3 is a detection means such as a line sensor or an area sensor, which is disposed at a distance M from the first object 1. al and a2 are physical optical elements zl and z, respectively
3, of which the optical axis a1 and the optical axis a2 are separated by a distance.

Points C1 to C4 are each diffracted light beam 13. fi5゜17, I
This is the position of the center of gravity of the light beam on the three surfaces of the sensor No. 19. Among these points, points CI and C2 are located at a distance of yx and 3/2 from the optical axis a1, respectively, and points C3 and C4 are located at a distance of y3 and 3/2 from the optical axis a2, respectively. y4M1 indicates the position.

For convenience, the center of gravity of the luminous flux is the point within the cross-section of the luminous flux where, when the product of the position vector from each point of the cross-sectional circle multiplied by the light intensity at that point is integrated over the entire cross-section, the integral value becomes 0 vector. It shows.

4 is a signal processing circuit as a calculating means, which uses information from the sensor 3 to convert the luminous flux 13. Il, 5°117, j
29, and the distances y1 to y4. The amount of positional deviation W and the distance g between the first object 1 and the second object 2 are determined from D and the like using equations to be described later. Reference numeral 5 denotes a control circuit, which controls the amount of positional deviation W and the distance g between the first object 1 and the second object 2 in accordance with information regarding the amount of positional deviation W and the distance g from the signal processing circuit 4.

A stage controller 6 drives a stage (not shown) on which the second object 2 is mounted in accordance with instructions from the control circuit 5.

In this embodiment, the light flux ili from the light source is incident on the physical optical elements zl and z3 on the first surface of the first object, respectively. Among these, the first-order diffracted light I12 generated in the physical optical element z1 of the light beam 11 that has entered the physical optical element z1 enters the physical optical element z2. Then, first-order diffracted light 13 having different diffraction directions depending on the positional deviation amount W is generated. The diffracted light 23 passes through the physical optical element z1 as it is as 0th-order diffracted light. The diffracted light 13 forms an image on the surface of the sensor 3 at a position a distance ylll from the optical axis a1. Since the distance between the sensor 3 and the first object 1 is a constant value, the value of the distance y1 depends on the distance g and the positional deviation amount W.

On the other hand, the luminous flux I11, which has passed through the physical optical element z1 as a 0th order diffracted light without undergoing any diffraction effect, is incident on the physical optical element z2. The first-order diffracted light 14 that has undergone first-order diffraction in the physical optical element Z2 enters the physical optical element z1 again. The first-order diffracted light 1 has different diffraction directions depending on the positional deviation amount W.
5 will occur. The first-order diffracted light I15 forms an image on the surface of the sensor 3 at a distance y2 from the optical axis a1.

From the light beam j21 incident on the physical optical element 23, diffracted lights 16 to β9 similar to the light beam 11 incident on the physical optical element z1 are generated.
is generated, and among these, the diffracted lights 1719 are each detected by the sensor 3.
Distance y3 from the optical axis a2 on the surface. The images are respectively formed at positions y4 apart. 4 is a signal processing circuit as a calculation means, and from the information read from the sensor 3, the luminous flux IL3. Il
5,17°ρ9 luminous flux gravity center position CI, C2, C3, C4
After determining, the distance D14 between the point C1 and the point 04 and the distance D23 between the point C2 and the point C3 are calculated. Interval D14 and interval D
The amount of positional deviation W and the distance g between the first object 1 and the second object 2 are determined by using the values of 23 and the relationship of each equation described later.

The control circuit 5 drives the stage controller 6 in accordance with information regarding the positional deviation amount W and the interval g from the signal processing circuit 4, and moves the second object 2 to a predetermined position.

In this embodiment, the diffracted light is not limited to the first-order diffracted light, but the same effect can be obtained by using second-order or higher-order diffracted light.

In this embodiment, the light source, sensor, etc. can be assembled in one place, so the optical probe can be miniaturized, and since the optical probe does not need to be moved during exposure, the throughput is further improved. have.

Next, a method of determining the amount of positional deviation W and the distance g between the first object 1 and the second object 2 in this embodiment will be explained with reference to FIG. 2.

In the lens system that generates the diffracted light J23 in FIG.
2 and enters point C1. At this time, the distance y1 of the diffracted light 13 to the center of gravity C1 of the light flux is determined by the deviation MW and the distance g between the first object 1 and the second object 2, and generally, yl=F1 (W, g)...・・・・−
It is expressed as (]).

Similarly for the other three lens systems, the distance y2. y3.
y4 is an amount determined by the amount of deviation W and the interval g, and y2=F2 (W, g) −−−−−−・−−
---(2) y3 = F 3 (W, g')
""""...-(3), y4=F4 (W,
g> . . . It is expressed as (4).

When the distances y1 to y4 are expressed as above, the distance D13 between points C1 and C3 and the distance D24 between points C2 and C4
By using , it is possible to express the quantities Yl and Y2 that depend on the shift amount W and the interval g as follows.

Yl-yl+y3-DI3-D-FI+F3-F5 (
g, W) Y2-y2+y4~D24-D-F2◆F4-
F6 (g, i.e., Y 1 = F 5 (g, W) ---
...---(5) Y 2 = F 6 (g,
W) -・・・・・・・・・-(6) Generally, when there are two unknowns, the solution to the unknowns can be found if there are two equations that include the unknowns.

That is, A = a 1 (w, g) −
−−−−−−−−−(7) B = G 2 (W,
g) ...= 2 like (8)
If these two relational expressions are prepared, the values of the two unknowns W9g can be determined by determining the quantities A and B by measurement or the like.

When the above-mentioned formula (1) is specifically expressed by w and g, it becomes as follows.

yl : W=L+2g-f 1 : f 1-g From this. The other equations (2), (3), and (4) are similarly obtained. Based on the above relational expressions, (5), (6)
The formula can be expressed concretely as follows. In equations (13) and (14), the distance between the optical axis a1 and the optical axis a2 is known, and the values of the distance D13 and the distance D24 can be specifically determined by measurement, so (+3) The values of the deviation amount W and the interval g can be obtained from equation (+4). By eliminating the deviation iW from equations (13) and (14), a cubic equation with interval g is obtained,
The amount of deviation W and the interval g can be easily determined using a personal computer or the like.

In this example, the first to fourth physical optical elements 21 to z
The focal lengths 11fl to f4 of No. 4 are set to satisfy the following equation.

Figure 4 shows that in this example, the diffracted light beam is 13°15, +1
7, 19 luminous flux gravity center CI, C2, C3 ° C4 is the deviation amount W
FIG. 3 is an explanatory diagram showing how the sensor changes on the surface of the sensor 3 in response to the change in temperature. Diffraction beam ji43,15. IL7.1
9 has a certain width on the sensor surface, so if there is a portion where the 3 overlap each other, it becomes difficult to accurately determine the points C1 to C4.

Therefore, in this embodiment, if you want to measure within the deviation amount W = ±3 μm, for example, the distance range of each luminous flux is set to the same point WO.
The characteristics between -3 and point WO+3 are determined in advance through simulation, etc., and are used.

That is, in this embodiment, the first. The first . The barycenter position of the second two diffracted light beams and the third. A third . The positions of the centers of gravity of the fourth two diffracted light beams are detected in a state where they are separated from each other by at least the width of the diffracted light beams.

In this embodiment, when the amount of positional deviation W between the first object and the second object is 0, the physical optical element (for example, zl
) and the physical optical element (for example, z2) on the second object.
) by keeping the optical axis a2 at a distance Wo,
Point C when the amount of positional deviation W between the first object and the second object is 0
1 and point C2, and point C3 and point C4 can be kept separate.

The pattern arrangement of the first to fourth physical optical elements 21 to Z4 shown in FIG. element z1
and 22, and the third and fourth physical optical elements z3 and 24
The optical axes of each are set to be shifted by a distance WO.

When using the secondary lever pattern, if the first object and second object are deviated by a distance Wx, replace the value of the amount of deviation W in equations (9) to (12) with W = W o + W x All you have to do is calculate it.

Note that in this embodiment, the first. Instead of providing two physical optical elements on each second object plane, four physical optical elements are provided to provide the above-mentioned diffracted light beam 13. A similar effect can be obtained by obtaining four diffracted lights corresponding to LL5°17 and I19.

However, the method of providing two physical optical F-elements as in this example requires less area than the method of providing four physical optical elements, and when comparing the same area, the amount of diffracted light is smaller. There is a double advantage.

Next, other embodiments of the present invention will be described in order.

(A) Second Embodiment In the first embodiment, the amount of deviation W and the distance g were calculated from the combination of the distances 11yl and y3, and the distances y2 and y4, or the distances yx and y4, the distances My2 and y3, or the distance 1! lyl and y2, distance Hy3 and y4
The deviation amount W and the interval g can be similarly determined from the combination of .

When the distances y1 and y4 are combined with the distance 11 [y2 and y3, the distance between points C1 and C4 is D14, and the distance between points C2 and C3 is D23, this corresponds to equations (7) and (8). The formula is expressed as follows.

・・・・・・・・・(16) Similarly, when the distances y1 and y2 and the distances Hy3 and y4 are combined, the distance between points C1 and C2 is D12, and the distance between points C3 and C4 is D34. Then, it becomes...(18). From these equations, the amount of deviation W and the distance g can be determined.

(b) Third embodiment 1. In the second embodiment, the light beam gravity center position CI of the four light beams,
Using C2, C3, and C4, formulas corresponding to formulas (7) and (8) were derived to obtain the shift amount W and the interval g, but three of the four luminous flux centers CI, C2, C3, and C4 Using this, we can similarly derive equations equivalent to equations (7) and (8).

That is, as above, the interval Dij (the interval between point i and point j)
When expressed using , the following combinations are applicable.

Among these combinations, (I), (IV), (
V).

In the case of (■), (n)', (III), (Vl)
, The width of the sensor is D1 compared to (■) and Example 1.2.
It has the advantage that it only needs to be shorter by 2 or D34.

Next, specific numerical examples will be shown for the case (I) of the above-mentioned equations (19) and (20). All units are μm.
It is.

g=30, Wo=IO, L=18627f
1 = 150.000, f2 = 1
20.768f 3 = 115.000, f
4 = 143.885y 1 = 154.47
5・W , ,y 2 = 124.547・Wy
3 = 129.669・W, 3/4 =
162.560・W=7 (Wo -3) Distance between luminous flux centroid CI and 02: 209 Distance between luminous flux centroids C3 and C4 = 230 (Note: Width of luminous flux: approx. 210) W=13 (Wo+3) Distance of the center of gravity CI of the luminous flux from the optical axis a1 when Two physical optical elements zl and z3 provided on the first object plane and two physical optical elements z2 provided on the second object plane. z4
Instead of being provided independently, each pattern is constructed from one overlapping pattern, as shown in FIG. 5, and the same effect as described above is obtained.

In this embodiment, D corresponds to the distance between optical axes a1 and C2.
The value of is zero, and if D=0 as in the first to third embodiments, this embodiment can be applied.

A feature of the pattern in this embodiment is that it is less affected by the tilting of the second object in the alignment direction than in the pattern shown in FIG.

That is, when using the pattern shown in FIG. 3, when the second object tilts, the first object tilts. The lens system of the second physical optical elements zl, z2 and the third.
Fourth physical optical element z3. Since the influence of the lens system of z4 is different, a detection error occurs. In contrast, in this embodiment, the effects are the same, so even if a detection error occurs, the third
It has the advantage of being extremely small compared to the case shown in the figure.

(d) Fifth Embodiment In this embodiment, a plurality of combinations of two values between the diffracted light beams regarding both the deviation amount W and the interval g are detected, and the plurality of combinations are detected. The deviation amount W and the interval g obtained from the above are evaluated by an evaluation means to improve the detection accuracy. As an evaluation means at this time, for example, averaging a plurality of values of the deviation amount W and the interval g obtained from a plurality of combinations may be considered.

(E) Sixth Embodiment When actually implementing the first to fourth embodiments, pre-alignment is performed in advance. However, as is clear from FIG. 4, on the right and left sides of the deviation amount W=0, the positions of the luminous flux gravity centers C1 to C4 are reversed depending on the direction of deviation, but the states of the luminous flux at positions C1 to C4 are reversed. It is not clear to which side the second object is shifted relative to the first object just by looking at it.

For this reason, in this embodiment, the first. Second two diffracted beams 13.
The distance D12 between the center of gravity positions C1 and C2 of I15 and the third
．． Fourth two diffracted light beams 17. J19 center of gravity position C3
Each element is set so that the interval D34 between and C4 is different.

As a result, after measuring the positions of the light flux gravity centers ff1c1 to C4 on the sensor 3 surface, positions C1 and C2, positions C3 and C4
If you calculate the difference between the two, it becomes clear.

Also, near the deviation amount W = 0, the light beams overlap,
If the combinations of positions C1 and C2 and positions C3 and C4 are far apart, the state can be determined by determining the half-width of the luminous flux, for example.

Further, in this embodiment, if the four light beams overlap on the sensor surface, the discrimination can be performed after changing the amount of rubbing between the first object and the second object to make the discrimination possible.

(Effects of the Invention) According to the present invention, by determining the amount of positional deviation W between the first object and the second object and the distance g between the first object and the second object, there is no misidentification of the matching state, and the high It is possible to achieve a position detection device that can perform accurate positioning and has a high throughput.

For example, position information CI, C in the position detection device of the present invention
When aligning only from the relationship between 3 and the amount of slippage W, the number of chambers described above is g = 30 μm, fl = 150 μm, L = 1
When 8627μm, yl=1544.75μm, the interval g
If there is an error of 0.06 μm in , the amount of deviation W is 0.00
An error of 5 μm occurs. Therefore, when trying to align with an accuracy of 0.01 μm, the error in the interval g is 0.06 μm.
It is necessary to keep it below about m. Therefore, in some way 0
．． The interval g must be set in advance with an accuracy of 0.6 μm or less.

On the other hand, according to the present invention, if the interval g is set with a certain degree of accuracy in pre-alignment, the deviation amount W can be accurately determined no matter what value the interval g is.

For example, in the method of determining the center of gravity of the two diffracted light beams by measuring the overlapping diffracted light beams whose centers of gravity are at positions C1 and 02, if the light intensity changes due to fluctuations in diffraction efficiency, the center of gravity will shift and cause errors. In the present invention, since the diffracted light beams are measured at a sufficient distance, the occurrence of such detection errors can be prevented.

Furthermore, in the present invention, the physical optical element is commonly used for detecting both the positional deviation amount W and the distance g, thereby reducing the luminous flux and the number of physical optical elements, simplifying the detection system and downsizing the entire device. We are trying to make this happen.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the main part of the first embodiment of the present invention, FIG. 2 is a schematic diagram of the main part when the optical path of each light beam in FIG. 1 is schematically developed, and FIGS. 3 and 5 are The first object 1 and the second object in Fig. 1
An explanatory diagram of the physical optical element provided on the surface of the object 2, Fig. 4 is an explanatory diagram showing the positional relationship between the amount of deviation W and the center of gravity position of the light beam (1, C2, C3, C4 on the sensor surface, Figs. 6 and 7). The figure is a schematic diagram of a conventional alignment device. In the figure, 1 is a first object, 2 is a second object, 3 is a sensor, 4 is a signal processing circuit, 5 is a control circuit, 6 is a stage controller, and f11 to 19 is a luminous flux, 21 to Z4 are physical optical elements,
al and a2 are the optical axes of the physical optical element, W is the amount of positional deviation, and g
is the interval. Figure Figure

Claims (7)

[Claims] (1) A physical optical element is provided on each of the first object plane and the second object plane, and a detection means detects a diffracted light beam of a predetermined order generated on a predetermined plane of the light beam incident on these physical optical elements. When detecting the relative positions of the first object and the second object, the first object and the second object are detected between the at least three diffracted beams generated on a predetermined surface by the detection means. Detect at least two values between the diffracted light beams that are related to both the relative deviation amount W and the relative spacing g, and calculate the deviation amount W and the spacing g by a calculation means using the output signal from the detection means. A position detection device characterized by determining the following. (2) two physical optical elements, first and third, are provided on the first object plane, and two physical optical elements, second and fourth, are provided on the second object plane, The diffracted light beam generated on the predetermined surface is connected to one physical optical element on the first object surface,
2. The position detection device according to claim 1, wherein the light beams are each diffracted by one physical optical element on the second object plane. (3) The two physical optical elements on the first object plane and the two physical optical elements on the second object plane each overlap each other to form one pattern. The position detection device described. (4) The positions of the first and second two diffracted light beams generated on a predetermined surface via the first and second two physical optical elements and the third and fourth two physical optical elements. 3. The position detection device according to claim 2, wherein the positions of the third and fourth two diffracted light beams generated on the predetermined surface are detected at positions separated by at least the width of the diffracted light beams. (5) The detection means detects each of a plurality of combinations of two values between the diffracted light beams regarding both the deviation amount W and the interval g, and detects the deviation obtained from the plurality of combinations. 5. The position detection device according to claim 1, wherein the amount W and the distance g are evaluated by evaluation means. (6) The position detection device according to claim 5, wherein the evaluation means averages a plurality of values of the deviation amount W and the interval g obtained from a plurality of combinations. (7) Each element is set so that the positional interval D12 of the first and second two diffracted light beams on the predetermined plane and the positional interval D34 of the third and fourth two diffracted light beams on the predetermined plane are different. 5. The position detection device according to claim 4, wherein: