JPH0645218A - Method for measuring alignment accuracy of aligner and method for measuring position - Google Patents

Abstract

PURPOSE:To make it possible to use one and the same wafer repeatedly and to eliminate a necessity to newly form a pattern for measurement which is the same one as used in the first exposure when measurements are conducted repeatedly and to make measurements rapidly, in a method for measuring an alignment accuracy of an aligner. CONSTITUTION:On a wafer, a diffraction grating 26 by the wafer itself and a diffraction grating 28 by resist are formed. Minus primary diffracted light of the diffraction grating 26 by the wafer itself and minus primary diffracted light of the diffraction grating 28 by resist are detected and then an alignment accuracy of an aligner is measured from a movement position of the wafer for which the diffracted lights are detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a positioning accuracy measuring method for an exposure apparatus and a position measuring method used for a positioning accuracy measuring method for an exposure apparatus.

[0002]

2. Description of the Related Art Conventionally, a vernier method, a box-in-box method, a resistance measuring method and the like have been known as a method of measuring alignment accuracy of an exposure apparatus. In the following, first, these will be described by dividing them into terms.

Vernier method ... FIGS. 7 and 8 The vernier method utilizes a vernier pattern. When this is executed, for example, as shown in FIG. 7, for the X axis and the Y axis, , prepared as vernier pattern 1 pitch P _1, the pitch P ₂ forms a reticle having a vernier pattern 2 (<P ₁₎ (or mask).

The vernier pattern 1 and the vernier pattern 2 are arranged such that the central portion of the left end tooth portion 1A of the vernier pattern 1 and the central portion of the left end tooth portion 2A of the vernier pattern 2 are separated by a distance L. Let

Then, the exposure is performed for the first time by using an exposure apparatus whose alignment accuracy is to be measured, the vernier patterns corresponding to the vernier patterns 1 and 2 are formed on the wafer itself, and then the position of the wafer is adjusted to the first time. The second exposure is performed by shifting the position by a distance L to the right of the exposure, and a vernier pattern corresponding to the vernier patterns 1 and 2 is formed by a resist.

In this case, for example, as shown in FIG. 8, a vernier pattern 3 formed on the wafer itself corresponding to the vernier pattern 1 and a resist corresponding to the vernier pattern 2 are formed. The vernier patterns 4 can be superposed.

As described above, when the vernier pattern 3 and the vernier pattern 4 are obtained, the alignment accuracy of the exposure apparatus in the X-axis direction can be measured by the same principle as the caliper.

Box-in-box method: FIG.
The box-in-box method uses a box pattern. When this is executed, for example,
As shown in FIG. 9, with respect to the X-axis and the Y-axis, a square box pattern 5 having a length of one side of the inner side is Q ₁ and a length of one side separated by a distance L between the centers is Q ₂ A reticle (or mask) having a square box pattern 6 with (<Q ₁ ) is prepared.

Then, the first exposure is performed by using the exposure apparatus for measuring the alignment accuracy, and after forming the box patterns corresponding to the box patterns 5 and 6 on the wafer itself, the position of the wafer is set to the first time. The box pattern corresponding to the box patterns 5 and 6 is formed by a resist by performing the alignment by shifting the position to the right by a distance L from the case of the exposure.

In this case, for example, as shown in FIG.
As shown in, the box pattern 8 formed of a resist corresponding to the box pattern 6 can be arranged in the box pattern 7 formed on the wafer itself corresponding to the box pattern 5.

By determining the position of the box pattern 8 with respect to the box pattern 7 by performing image processing, the alignment accuracy of the exposure apparatus in the X-axis direction and the Y-axis direction can be measured.

Resistance Measuring Method FIGS. 11 to 13 The resistance measuring method uses a resistor, and when this is performed, for example, as shown in FIG. 11, a resistor forming pattern 9 is used. Reticle (or mask) that formed
And a reticle (or mask) having a line-shaped pattern 10 as shown in FIG. 12 are prepared. The position of the central axis 11 of the resistor forming pattern 9 and the position of the central axis 12 of the linear pattern 10 are formed to coincide with each other.

Then, the reticle on which the resistor forming pattern 9 is formed is used for the first exposure to form a resistor pattern corresponding to the resistor forming pattern 9 on the wafer, and then the linear pattern 10 is formed. A second exposure is performed by using the reticle having the pattern formed therein to divide the resistor formed corresponding to the resistor forming pattern 9 into resistors 14 and 15, as shown in FIG.

Then, the square portion 16 of the resistors 14 and 15
A-16D and 17A-17D are used as electrodes, and the resistance values of the resistors 14 and 15 are measured. Here, the widths W ₁ and W ₂ of the strip portions 18 and 19 of the resistors 14 and 15 can be known from the resistance values of the resistors 14 and 15, and thus the alignment accuracy of the exposure apparatus in the X-axis direction can be obtained. , ΔW =
(W ₁ -W ₂₎ / ₂ can be measured.

[0015]

Although the vernier method is convenient, it has a problem that it is difficult to automate and high-speed measurement cannot be performed. Also,
The box-in-box method has a problem that a large amount of image data must be processed and high-speed measurement cannot be performed.

In the resistance measuring method, the measuring process is complicated, and when the measurement is repeated, the pattern formed by the first exposure is kept as it is as in the case of the vernier method or the box-in-box method. It cannot be used, and there is a problem that the pattern forming process becomes more than that of the vernier method or the box-in-box method.

In view of the above point, the present invention makes it possible to repeatedly use the same wafer when the measurement is repeatedly performed, and it is not necessary to newly form the measurement pattern by the first exposure, and accordingly, it is possible to do so. It is used for the alignment accuracy measurement method of an exposure apparatus, which can reduce the number of measurement pattern forming steps and can measure the alignment accuracy at high speed, and the alignment accuracy measurement method of this exposure apparatus. The purpose of the present invention is to provide a position measuring method.

[0018]

According to a method of measuring alignment accuracy of an exposure apparatus according to the present invention, a first exposure is performed using an exposure apparatus whose alignment accuracy is to be measured, and a diffraction grating formed by the wafer itself on a wafer surface. Then, the second exposure is performed using the exposure apparatus, and a diffraction grating formed on the wafer itself is formed by a resist diffraction grating having the same angle of diffracted light as the diffraction grating formed on the wafer itself. It is formed on the wafer surface so that the grating has the same grating direction and does not overlap with the diffraction grating formed on the wafer itself, and the projection light is applied to the wafer surface, and the projection light is While moving the wafer so as to scan the wafer surface, the diffraction grating formed on the wafer itself causes diffraction of a predetermined order other than the 0th order by the photodetector arranged at a predetermined position. And a moving position of the wafer that detects the predetermined-order diffracted light by the diffraction grating formed by the resist, and detects the predetermined-order diffracted light by the diffraction grating formed on the wafer itself, and the resist. The alignment accuracy of the exposure apparatus is measured from the relationship with the moving position of the wafer where the diffracted light of the predetermined order is detected by the diffraction grating formed by.

[0019]

According to the alignment accuracy measuring method of the exposure apparatus of the present invention, a diffraction grating is formed on a wafer, a projection light is applied to the wafer, and the wafer is moved so that the projection light scans the wafer surface. The position of the diffraction grating formed by the resist is measured by detecting the diffracted light of a predetermined order other than the 0th order by the diffraction grating formed by the resist by the light detection means arranged at the predetermined position. One of the features is that it uses a position measurement method that has not been available in the past.

According to the alignment accuracy measuring method for the exposure apparatus of the present invention, when the measurement is repeated,
The same wafer can be used repeatedly by removing the diffraction grating formed by the resist.

Moreover, in this case, since the diffraction grating formed on the wafer itself can be repeatedly used as the diffraction grating formed by the first exposure, it is not necessary to newly form the diffraction grating by the first exposure. Therefore, the number of measurement pattern forming steps can be reduced accordingly.

Further, according to the alignment accuracy measuring method of the exposure apparatus according to the present invention, the light detecting means detects the diffracted light by the diffraction grating, but the intensity signal of the diffracted light is compared with the image signal. Since the amount of data is very small, the measurement speed can be increased.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A method of measuring alignment accuracy of an exposure apparatus according to the present invention will be described below with reference to FIGS.

In this embodiment, as shown in FIG.
A reticle formed with the diffraction grating forming pattern 20 and a reticle formed with the diffraction grating forming pattern 21 are prepared as shown in FIG.

The diffraction grating forming patterns 20 and 21 are formed.
22 and 23 are rectangular portion forming patterns for forming rectangular portions of the diffraction grating, and these diffraction grating forming patterns 20 and 21 have the same arrangement direction of the rectangular portion forming patterns and are rectangular. The central axes 24 and 25 in the arrangement direction of the portion forming patterns are arranged so as to coincide with each other and not to overlap with each other.

Further, these diffraction grating forming patterns 2
0 and 21 have the same shape. That is, the rectangular portion forming patterns 22 and 23 have the same shape, and the intervals between the rectangular portion forming patterns 22 and the rectangular portion forming patterns 23 are the same.

In other words, the diffraction grating forming pattern 20.
And the angle of the diffracted light with respect to the projected light obtained when the projected light is applied to the diffraction grating formed by, and obtained when the projected light with the same angle is applied to the diffraction grating formed by the diffraction grating forming pattern 21. The diffraction grating forming patterns 20 and 2 so that the angle of the diffracted light with respect to the projected light is the same.
1 is formed.

In this embodiment, the reticle on which the diffraction grating forming pattern 20 is formed is used for the first exposure, and as shown in FIG. 3, it corresponds to the diffraction grating forming pattern 20. The diffraction grating 26 is formed on the wafer itself. In addition, 27 is a rectangular part.

Next, a second exposure is performed using the reticle on which the diffraction grating forming pattern 21 is formed, and as shown in FIG. 3, the diffraction grating 28 corresponding to the diffraction grating forming pattern 21 is resisted. Formed by.

Incidentally, 29 is a rectangular portion, and in this example,
The diffraction grating 26 and the diffraction grating 28 show the case where the central axes 30 and 31 of the rectangular portions 29 in the arrangement direction are displaced by a distance ΔD.

Next, an apparatus whose main part is shown in FIG. 4 is prepared. In the figure, 33 is a wafer stage movable up and down, left and right, and front and back, and 34 is a diffraction grating forming pattern 2.
6 and 28 are formed wafers.

Further, 35 is a laser tube for emitting a laser beam, 36 is a laser beam emitted from the laser tube 35, 37 is a focusing lens for focusing the laser beam 36, 38
Is a mirror, 39 is a linear Fresnel zone plate (LF
ZP: linear fresnel zone plate), 40 is a photodiode, and 41 is an amplifier for amplifying the signal output from the photodiode 40.

Here, the linear Fresnel zone plate 3
As shown in FIG. 5, 9 is arranged so that the extending direction of its central axis 42 and the extending direction of the Y-axis of the wafer 34 coincide with each other.

The photodiode 40 is arranged at a position where only the −1st order light can be detected from the diffracted light emitted from the diffraction gratings 26 and 28 when the laser light 36 is projected onto the diffraction gratings 26 and 28. Has been done.

Therefore, in this embodiment, the laser light 3
6 is generated, and the wafer 34 is moved in the X-axis direction via the wafer stage 33 so that the laser beam 36 including the diffraction grating 26 scans the surface of the wafer 34 in the X-axis direction.

In this way, via the amplifier 41,
For example, the signal 43 as shown in FIG. 6 can be detected. Here, in the signal 43, the convex portion 44 is a signal by the −1st order light of the diffraction grating 26, and the coordinates 46 corresponding to the vertex 45 thereof can be grasped as the coordinates at which the −1st order light is detected. .

Then, next, the wafer 3 is passed through the wafer stage 33 so that the laser beam 36 scans the surface of the wafer 34 including the diffraction grating 28 formed by the resist in the X-axis direction.
Move 4 in the X-axis direction.

In this way, via the amplifier 41,
For example, the signal 47 as shown in FIG. 6 can be detected. Here, the convex portion 48 of the signal 47 is a signal due to the −1st order light of the diffraction grating 28, and the coordinates 50 corresponding to the vertex 49 thereof can be grasped as the coordinates at which the −1st order light is detected. .

In this case, the distance ΔD between the diffraction grating 26 and the diffraction grating 28 can be known from the distance ΔD between the coordinates 46 and the coordinates 50, as shown in FIG. 3, and the alignment accuracy of the exposure apparatus can be obtained. Can be measured.

According to the present embodiment, when the measurement is repeated, the same wafer 34 can be repeatedly used by removing the diffraction grating 28 formed of the resist.

Further, in this case, since the diffraction grating 26 formed on the wafer 34 itself can be continuously used as the diffraction grating formed by the first exposure, it is necessary to newly form the diffraction grating by the first exposure. Without
Therefore, the pattern forming process can be reduced.

Further, according to this embodiment, the photodiode 40 obtains the intensity signal of the diffracted light by the diffraction gratings 26 and 28. However, the intensity signal of the diffracted light has a data amount larger than that of the image signal. Since the number is very small, the measurement speed can be increased.

In the above embodiment, the case where the diffraction grating forming patterns 26 and 28 are formed on two reticles has been described, but the diffraction grating forming patterns 26 and 28 are formed on one reticle. It may be done.

[0044]

According to the alignment accuracy measuring method of the exposure apparatus of the present invention, when the measurement is repeatedly performed, the same wafer can be repeatedly used and the diffraction grating is newly formed by the first exposure. Therefore, the number of steps for forming the measurement pattern can be reduced, and the alignment accuracy can be measured at high speed.

According to the position measuring method of the present invention, when the position measuring method is used in a method requiring the position measuring such as the aligning accuracy measuring method of the exposure apparatus according to the present invention, the position measuring is simple and Can be done quickly.

[Brief description of drawings]

FIG. 1 is a diagram showing a diffraction grating forming pattern formed on a reticle.

FIG. 2 is a diagram showing a diffraction grating forming pattern formed on a reticle.

FIG. 3 is a diagram showing a diffraction grating formed on the wafer itself and a diffraction grating formed by a resist.

FIG. 4 is a view showing an apparatus for carrying out an embodiment of the alignment accuracy measuring method for an exposure apparatus according to the present invention.

FIG. 5 is a diagram for explaining a positional relationship between a linear Fresnel zone plate and a wafer.

FIG. 6 is a diagram showing an output signal of an amplifier.

FIG. 7 is a diagram showing a vernier pattern formed on a reticle (or mask).

FIG. 8 is a diagram showing a vernier pattern formed on a wafer.

FIG. 9 is a diagram showing a box pattern formed on a reticle (or a mask).

FIG. 10 is a diagram showing a box pattern formed on a wafer.

FIG. 11 is a diagram showing a resistor-forming pattern formed on a reticle (or mask).

FIG. 12 is a diagram showing a line-shaped pattern formed on a reticle (or mask).

FIG. 13 is a diagram showing a resistor formed on a wafer.

[Explanation of symbols]

 20, 21 Diffraction grating forming pattern 26 Diffraction grating formed on wafer itself 28 Diffraction grating formed by resist

Claims (2)

[Claims] 1. A first exposure is performed by using an exposure apparatus whose alignment accuracy is to be measured, a diffraction grating is formed on the wafer surface by the wafer itself, and then a second exposure is performed by using the exposure apparatus. A diffraction grating made of a resist having the same angle of diffracted light as the diffraction grating formed on the wafer itself so that the diffraction grating has the same grating direction as the diffraction grating formed on the wafer itself, and Formed on the wafer surface so as not to overlap with the formed diffraction grating, while applying projection light to the wafer surface, while moving the wafer so that the projection light scans the wafer surface,
The light detecting means arranged at a predetermined position separates the diffracted light of a predetermined order other than the 0th order by the diffraction grating formed on the wafer itself and the diffracted light of the predetermined order by the diffraction grating formed by the resist. The moving position of the wafer which is detected and detects the predetermined order diffracted light by the diffraction grating formed on the wafer itself, and the wafer which detects the predetermined order diffracted light by the diffraction grating formed by the resist A method for measuring alignment accuracy of an exposure apparatus, comprising measuring the alignment accuracy of the exposure apparatus from a relationship with a moving position. 2. A resist diffraction grating is formed on a wafer, projected onto the wafer, and moved at a predetermined position while moving the wafer so that the projected light scans the wafer surface. A position measuring method characterized in that the position of the diffraction grating is measured by detecting diffracted light of a predetermined order other than the 0th order by the light detection means.