KR20200001491A - Detecting method, lithography method, article manufacturing method, optical apparatus, and exposure apparatus - Google Patents

Abstract

The present invention relates to a detection method which detects the focus position of an optical system forming an image of an imaging target in an imaging surface of an imaging device. The detection method comprises the steps of: obtaining evaluation value groups of a plurality of sets including an evaluation value group C1 of set 1 and an evaluation value group C2 of set 2 based on an output signal output from the imaging device in a state in which the imaging target is located In each of a plurality of positions in the optical-axis direction of the optical system; obtaining an evaluation value group C3 of set 3 based on the evaluation value groups of the plurality of sets; and detecting the focus position based on the evaluation group C3 of the set 3.

Description

Detection methods, lithographic methods, article manufacturing methods, optical devices and exposure devices {DETECTING METHOD, LITHOGRAPHY METHOD, ARTICLE MANUFACTURING METHOD, OPTICAL APPARATUS, AND EXPOSURE APPARATUS}

The present invention relates to a detection method, a lithographic method, an article manufacturing method, an optical device and an exposure device.

In the exposure apparatus which manufactures articles, such as a semiconductor device, position alignment of a shot area and a disc is performed by detecting the position of the alignment mark provided in the shot area of a board | substrate. The exposure apparatus is provided with an alignment detection system which detects the position by imaging an alignment mark. In order to detect the position of the alignment mark with high precision, it is necessary to image the alignment mark in the best focus state. The state in which the alignment mark is arranged on the object plane of the alignment detection system is the best focus state, and if it is shifted from the best focus state, the state is defocused. The focus state of the alignment mark in the alignment detection system is based on a result of positioning the substrate at a plurality of positions in the optical axis direction of the alignment detection system, and imaging the alignment mark by the imaging element of the alignment detection system at each position. Can be detected. More specifically, the curve showing the relationship between the position and the evaluation value in the optical axis direction by calculating an evaluation value (for example, contrast) from an output signal from the imaging element in each of the plurality of positions in the optical axis direction. Is obtained. Then, the peak position of this curve is detected as the best focus position. Such a curve is called a contrast curve when an evaluation value is contrast (refer patent document 1).

Japanese Patent Publication No. 2009-192271

However, when detecting the focus position, the curve of the evaluation value may have a plurality of peaks instead of one peak, depending on the surface state of the substrate on which the alignment mark is formed, the imaging condition by the alignment detection system, and the like. Moreover, the curve of an evaluation value may be flat and the peak position may be unclear. In such a situation, the detected focus position is not stable. If the detected focus position is not stable, the detection result of the position of the alignment mark is also not stable.

It is an object of the present invention to provide an advantageous technique for stably detecting a focus position.

One aspect of the present invention relates to a detection method for detecting a focus position of an optical system that forms an image of an object to be imaged on an imaging surface of an imaging device, wherein the detection method includes a plurality of positions in the optical axis direction of the optical system. Obtaining a plurality of sets of evaluation value groups including the first set of evaluation values and the second set of evaluation values based on an output signal output from the image pickup device in a state where the image capturing target is located in each of the plurality of sets A step of obtaining the evaluation value group of Article 3 based on the evaluation value group, and a step of detecting the focus position based on the evaluation value group of the third article.

According to the present invention, an advantageous technique is provided for stably detecting the focus position.

BRIEF DESCRIPTION OF THE DRAWINGS The figure which shows the structure of the exposure apparatus of embodiment.
2 is a diagram illustrating an image of an alignment mark.
3 illustrates a contrast curve.
4 is a diagram illustrating a focus curve (a), an output signal (b) of an image pickup device that is picked up at ZP1, and an output signal (c) of an image pickup device that is picked up at ZP2;
5 is a diagram illustrating respective curves of contrast (first evaluation value), correlation (second evaluation value), and combination evaluation value (third evaluation value).
6 illustrates an arrangement of shot regions of a substrate.
7 is a diagram illustrating a relationship between a detection range of a focus position and a curve of an evaluation value group.
8 is a diagram illustrating an operation sequence of an exposure apparatus.
9 is a diagram illustrating details of a focus position detection sequence.
10 is a diagram for explaining another correlation diagram.
11 is a view for explaining a method of obtaining a combination evaluation group for focus position detection from a plurality of sets of evaluation value groups.
FIG. 12 is a diagram for explaining a problem (a) that may occur when estimating a focus position based on a contrast curve, and a method (b) for estimating a focus position based on a combination evaluation value group. FIG.
13 is a diagram showing details of another focus position detection sequence.
14 illustrates an example of a flow of an overall manufacturing process of a semiconductor device.
15 is a diagram illustrating an example of a detailed flow of a wafer process.

Hereinafter, the configuration and operation of the detection method, the exposure apparatus and the optical apparatus according to the present invention will be exemplarily described through the description of the configuration and operation of the exposure apparatus of the embodiment to which the detection method, the exposure apparatus, and the optical apparatus according to the present invention are applied. Explain. The detection method according to the present invention can be applied, for example, to detect the focus position of an optical system in an optical device such as an alignment detection system built in the exposure apparatus. In addition to being able to be implemented as an exposure apparatus, the optical device according to the present invention can be implemented, for example, as a microscope device for enlarging and imaging an imaging target. In the following description, a direction is represented by the XYZ coordinate system which makes Z direction the direction parallel to the optical axis of projection optical system PO. The XY direction means a direction parallel to the XY plane.

FIG. 1: is a figure which shows the structure of the exposure apparatus 100 of 1st Embodiment. The exposure apparatus 100 exposes the substrate W after the original plate (reticle) R and the substrate (wafer) W are aligned (aligned) using the alignment detection system OA. Exposure of the board | substrate W is performed by illuminating the original plate R with exposure light with the illumination system IL, and projecting the pattern of the original plate R to the board | substrate W through the projection optical system PO. The board | substrate W has a photosensitive material layer on the surface, the pattern of the original plate R is transferred to the said photosensitive material layer by exposure, and a latent image is formed. This latent image is converted into a physical pattern by going through a developing step. The substrate W is held by the substrate chuck CH. The substrate chuck CH is mounted on the stage STG, and can be driven, for example, in the X, Y, and Z directions by the drive mechanism DM. The position of the stage STG can be measured by a measuring instrument such as an interferometer IF.

The exposure apparatus 100 is equipped with the control part HP. The control part HP positions the stage STG by controlling the drive mechanism DM based on the position measurement result of the stage STG by the interferometer IF. The control unit HP is, for example, a PLD (abbreviation for Programmable Logic Device) such as FPGA (abbreviation for Field Programmable Gate Array), or ASIC (abbreviation for Application Specific Integrated Circuit), or a general-purpose or dedicated computer in which a program is embedded. Or combinations of all or part thereof. On the board | substrate W, in order to perform the position alignment of the board | substrate W and the original plate R, the some mark (alignment mark) MA is provided. The mark MA has positional information in the X direction and the Y direction, for example, as illustrated in FIG. 2A.

The exposure apparatus 100 includes an alignment detection system OA. The alignment detection system OA is a detection apparatus which detects the position (position of XY direction) of the mark MA provided in the board | substrate W. As shown in FIG. When detecting the position of the mark MA using the alignment detection system OA, the stage STG is positioned so that the mark MA may fall within the detection range AR of the alignment detection system OA.

The alignment detection system OA may include the illumination light source LI, the optical system OL, the half mirror M, and the imaging device S, for example. The illumination light emitted from the illumination optical system LI is reflected by the half mirror M, and can illuminate the mark MA through the optical system OL. The reflected light or scattered light from the mark MA forms an image of the mark MA, which is an imaging target, on the imaging surface of the imaging device S through the optical system OL. The imaging element S may include an image sensor such as a CCD image sensor and a CMOS image sensor. The imaging element S generates an electrical image signal corresponding to the mark MA formed on the imaging surface, and supplies it to the control unit HP. The exposure apparatus 100 may be understood as an optical apparatus having an imaging device S and an optical system OL for forming an image of a mark MA, which is an imaging target, on the imaging surface of the imaging device S. FIG.

In the alignment measurement, the control unit HP detects the position (position in the XY direction) of the mark MA on the substrate W by processing the image signal output from the alignment detection system OA. In addition, in alignment measurement, the control part HP can acquire arrangement | sequence information of the some shot area arrange | positioned at the board | substrate W based on the information from the interferometer IF other than the position of the mark MA. have. The control part HP controls the drive mechanism DM so that the pattern of the original plate R may be sequentially transferred to the some shot area | region of the board | substrate W based on this arrangement information.

In the detection of the focus position of the alignment detection system OA (optical system OL), the plurality of the plurality of positions is positioned while positioning the stage STG in a plurality of positions in the Z direction (the optical axis direction of the alignment detection system OA). Imaging is performed by the alignment detection system OA at each of the positions of. By evaluating the plurality of images obtained thereby, the focus position of the alignment detection system OA can be determined. In global alignment measurement, the position of the mark MA of the several shot area | region of the board | substrate W is detected using the alignment detection system OA. In order to increase the detection accuracy of the position of each alignment mark MA, the focus position (mark MA of the stage STG for arranging the mark MA at the focus position of the alignment detection system OA with respect to each mark MA) Position in the Z direction) must be determined.

As an evaluation value used for determining the focus position of the alignment detection system OA, contrast is mentioned, for example. This is because, when the contrast is high, the influence of the random noise component represented by the electrical noise is relatively low, and improvement in measurement reproducibility is expected. 2A shows a mark MA observed in a focused state (best focus state), and FIG. 2B shows a mark MA observed in an out of focus state (defocused state). ) Is shown. In the defocused state, the difference between the maximum value and the minimum value of the luminance of the mark MA is small, that is, the contrast is low. As a calculation method of contrast, (Formula 1) or (Formula 2) is typical, for example.

Here, Lmax is the maximum value of the luminance in the detection range AR of the alignment detection system OA, and Lmin is the minimum value of the luminance in the detection range AR of the alignment detection system OA.

In the detection of the focus position, first, the stage STG is driven by the drive mechanism DM so that the mark MA to be detected falls within the detection range AR of the alignment detection system OA. Then, while the stage STG is positioned at a plurality of positions in the Z direction by the drive mechanism DM, the mark (by the imaging element S of the alignment detection system OA at each of the plurality of positions) MA) imaging is performed. Thereby, the some image of mark MA corresponding to the some position in a Z direction is obtained, respectively. And the contrast as an evaluation value can be calculated from each of the plurality of images of the mark MA. Thereby, the correlation between the position in the Z direction of the stage STG (mark MA) and the contrast of the picked-up image is obtained.

FIG. 3A shows an example of the correlation obtained in this way visually, and the curve in FIG. 3A is called a contrast curve. Ideally, the contrast curve is a convex curve. The position in the Z direction at the peak (peak) of the contrast curve is the focus position of the alignment detection system OA (optical system OL) (the position in the Z direction of the stage STG from which the best focus state is obtained). The position in the Z direction at the vertex of the contrast curve can be accurately calculated by performing the center of gravity calculation using a few points near the vertex, for example.

When the number of peaks of the contrast curve is one, even if there is a process variation, the position of the peak (position in the Z direction) and the contrast value only slightly change. Therefore, stable focus position detection with less influence on overlay accuracy can be performed. However, in the case where the contrast curve has a plurality of peaks, if there is a process variation, the detected focus position may change greatly. For example, the contrast curve when the illumination sigma of the alignment detection system OA is reduced can be as shown in FIG. Referring to FIG. 3B, the contrast curve has two peaks. In this case, the state of the mark changes for each shot region or for each substrate due to process variation, whereby the peak representing the maximum value can be replaced between two peaks. Therefore, which peak position is detected as the focus position for each shot region or for each substrate, may change, and a variation may occur in the focus position at the time of detection of the mark position.

In the alignment detection system OA, there may exist a problem that the position of the detected mark (position in the XY direction) is shifted in accordance with the position in the Z direction of the substrate W due to an error in assembling and adjusting the optical system. have. Therefore, if the focus position is changed at the time of detecting the position of the mark, the detected value of the mark position also fluctuates, causing a great influence on the alignment accuracy of the substrate W (shot area) and the original plate R. Done. In consideration of this variation, the focus position may be detected under illumination conditions and detection conditions in which the contrast curve has only one peak. However, the contrast of the output signal (image signal) from the imaging element S may be low depending on the process. In this case, the focus position cannot be detected with high precision unless the illumination σ is reduced and the method of increasing the contrast is not adopted. However, when the illumination σ is reduced, there is a possibility that a plurality of peaks occur.

Therefore, thereafter, even when a plurality of peaks occur in a curve indicating a relationship between the focus position and the evaluation value (for example, contrast) group of the output signal of the imaging element S for imaging the mark MA, stable focus is achieved. A method for enabling the detection of the position will be described.

Hereinafter, the method of detecting the focus position of the alignment detection system OA (optical system OL) in an exposure apparatus is demonstrated. 4A illustrates a contrast curve having a plurality of peaks. In FIG. 4A, the horizontal axis represents the position in the Z direction of the stage STG, and the vertical axis represents contrast as an evaluation value. In addition, although the position of the Z direction of the stage STG, the position of the Z direction of the chuck CH, and the position of the Z direction of the board | substrate W (mark MA) have a fixed difference mutually, except this difference, Equivalent information. Therefore, the position in the Z direction of the stage STG may be read in place of the position in the Z direction of the chuck CH or the position in the Z direction of the substrate W (mark MA).

In FIG. 4A, the first peak position (the position in the Z direction when the contrast curve indicates the first peak) is represented by ZP1 and the second peak position (the Z direction when the contrast curve indicates the second peak). Position) is called ZP2. FIG. 4B is an output signal WZP1 of the image pickup device S that has been imaged at the first peak position ZP1, and the horizontal axis is perpendicular to the Z direction, that is, the planar direction of the mark MA (FIG. In b), X direction) is shown. FIG. 4C is an output signal WZP2 of the image pickup device S that is picked up at the second peak position ZP2, and the horizontal axis is perpendicular to the Z direction, that is, the planar direction of the mark MA (FIG. c) shows the X direction).

The contrast at the first peak position ZP1 and the contrast at the second peak position ZP2 are almost the same. Therefore, if there is a process variation, there may occur a case where the first peak position ZP1 is determined as the focus position and the second peak position ZP2 is determined as the focus position.

On the other hand, it can be seen that the shape of the output signal WZP1 and the shape of the output signal WZP2 are different from each other. Therefore, the 1st peak position ZP1 and the 2nd peak position ZP2 can be distinguished by devising the method of obtaining an evaluation value from the output signal of the imaging element S. FIG. In this embodiment, the control part HP is the evaluation value group of Article 2 evaluated by the evaluation method different from the evaluation value group of Article 1 and the evaluation value group of Article 1 based on the output signal of the imaging element S. FIG. Is generated, and an evaluation value group of Article 3 is generated based on the evaluation value group of Article 1 and the evaluation value group of Article 2. And the control part HP detects the focus position of the alignment detection system OA (optical system OL) based on the evaluation value group of 3 sets.

Here, the evaluation value group of the first set includes a plurality of output signals that are picked up by the imaging device S and output from the imaging device S while the mark MA is located at each of a plurality of positions in the Z direction. It is an aggregate of a plurality of first evaluation values, respectively. In this example, each of the plurality of first evaluation values constituting the first set of evaluation values is picked up by the imaging element S when the mark MA is located at one position in the Z direction, and the imaging element ( Contrast obtained from the output signal output from S). The evaluation value group in the second set corresponds to a plurality of output signals respectively picked up by the imaging device S and output from the imaging device S in a state where the mark MA is located at each of a plurality of positions in the Z direction. It is an aggregate of a plurality of second evaluation values. The evaluation value group of Article 3 is a collection of a plurality of third evaluation values generated from the evaluation value group of Article 1 and the evaluation value group of Article 2.

In this embodiment, the control part HP determines the 1st peak position ZP1 as a reference peak position used for determining a focus position as preparation for generating | generating a 2nd set of evaluation value group. And the control part HP calculates a group of evaluation values of Article 2 based on the output signal (henceforth a "reference peak output signal") WZP1 from the imaging element S in a reference peak position.

In this example, the evaluation value group of Article 2 is picked up by the imaging device S in a state where the reference peak output signal WZP1 and the mark MA are located at each of a plurality of positions in the Z direction, and the imaging device S Is a correlation diagram of a plurality of output signals output from That is, in this example, each of the plurality of evaluation values constituting the evaluation group of the second set is the imaging element S when the reference peak output signal WZP1 and the mark MA are located at one position in the Z direction. It is a correlation diagram of the output signal picked up by the image and output from the imaging element S. In this example, the first peak position ZP1 is used as the reference peak position, but the second peak position ZP2 may be used as the reference peak position. For a plurality of shot regions and a plurality of substrates, a common reference peak output signal is used to measure the same peak among the plurality of peaks in the set of evaluation values in the first set. The reference peak output signal can be understood as a reference signal for calculating the correlation.

As a method of calculating the correlation, there is a method of calculating the absolute value sum of the difference between the reference peak output signal and the output signal (output signal of the imaging element S) to which the correlation is to be calculated. For example, it is represented by (Equation 3). Another method for calculating the degree of correlation is a method for calculating normalized cross correlation, which is represented by, for example, (Formula 4). Here, the number of output values (pixel number) in the plane direction (for example, X direction) of the output signal of the imaging element S is called N. Further, the output value of the reference peak output signal is WZP (n), the output value of the output signal (image signal) at the nth position in the Z direction is ZPA (n), 1≤n≤N, the maximum value of the output value is Omax, The correlation is called Corr.

Correlation Corr is 0≤Corr≤1 when ZPA (n) and WZP (n) are 0 or more, and the closer to 1, the higher the correlation.

In FIG. 5, the evaluation value group of Article 1, the evaluation value group of Article 2, and the evaluation value group of Article 3 are illustrated. The evaluation value group of Article 1 is the same as that of FIG. The evaluation value group of Article 1 provides the curve C1 of contrast which changes according to the position of the mark MA in the Z direction. The evaluation value group of Article 2 provides the curve C2 of the correlation which changes according to the position of the mark MA in the Z direction. In contrast to the curve C1 having a plurality of peaks, the curve C2 has a peak only at the first peak position ZP1.

In the present embodiment, the control unit HP combines the contrasts of the plurality of evaluation value soldiers of the first article and the correlations of the plurality of evaluation value soldiers of the second article, and the evaluation value military combination evaluation value group of the third article (plural combination evaluation values). ) Is calculated. Here, combining a plurality of sets of evaluation value groups means obtaining a value of a function using a plurality of sets of evaluation values as a variable. As a specific method of combination, the method of obtaining the evaluation value group of Article 3 is multiplied by multiplying the evaluation value (contrast) of Article 1 and the evaluation value (correlation) of Article 2 in each position in the Z direction. Curve C3 is a curve comprised by the evaluation value group of Article 3 by multiplying the evaluation value (contrast) of Article 1 and the evaluation value (correlation) of Article 2 at each position in the Z direction. In the focus position detection in the present embodiment, the control unit HP determines the focus position based on the curve C3 of the group of evaluation values in the third set.

The difference between the maximum value and the minimum value in the evaluation value group (curve C3) of Article 3 is the difference between the maximum value and the minimum value in the evaluation value group (curve C1) of Article 1 and the evaluation value group (curve C2) of Article 2 It is preferable that it is larger than at least one of the difference of the maximum value and minimum value in. In another aspect, the difference between the maximum value and the minimum value in the curve C3 in the section between ZP1 and ZP2 is at least one of the difference between the maximum value and the minimum value in the curve C1 and the maximum value and the minimum value in the curve C2. Larger is preferred. In another aspect, the difference in the value of the curve C3 in ZP1 and ZP2 is larger than at least one of the difference in the value of the curve C1 in ZP1 and ZP2 and the value of the curve C2 in ZP1 and ZP2. It is preferable.

From the viewpoint of stabilization of detection of the focus position, the number of peaks in the evaluation value group in Article 3 is preferably smaller than the number of peaks in the evaluation value group in Article 1. In addition to this, it is more preferable that the number of peaks in the evaluation value group of Article 3 is smaller than the number of peaks in the evaluation value group of Article 2. Or it is most preferable that the number of peaks in the evaluation value group of Article 3 is one. The peak in the evaluation value group of Article 1 is a first curve (more succinctly, the evaluation value group of Article 1) indicating the relationship between the position of the mark MA in the Z direction and the evaluation value group of the first article. Peak in the curve). The peak in the evaluation value group of Article 2 is a second curve (more succinctly, of the evaluation value group of Article 2) showing the relationship between the position of mark MA in the Z direction and the evaluation value group of Article 2. Peak in the curve). The peak in the evaluation value group of Article 3 is the third curve (more succinctly of the evaluation value group of Article 3) indicating the relationship between the position of the mark MA in the Z direction and the evaluation value group of the Article 3. Peak in the curve).

The evaluation value group (third curve) of Article 3 may have a plurality of peak values, and the evaluation value group (first curve) of Article 1 may have a plurality of peak values. In such a case, the difference between the largest peak value and the second largest peak value among the plurality of peak values in the evaluation value group (third curve) of the third article is the evaluation value group (first curve) of the first article. It is preferable that it is larger than the difference between the largest peak value and the 2nd largest peak value among the some peak value of. In addition to this, the group of evaluation values (second curve) in Article 2 may also have a plurality of peak values. In this case, the difference between the largest peak value and the second largest peak value among the plurality of peak values in the evaluation value group (third curve) of the third set is the evaluation value group (second curve) of the second set. It is preferable that it is larger than the difference of the largest peak value and the 2nd largest peak value among several peak values.

In alignment measurement in the exposure apparatus 100, the mark MA disposed in each of the plurality of shot regions of the substrate W is measured. Therefore, focus position detection is also performed on the mark MA disposed in each of the plurality of shot regions. 6, the plurality of shot regions S1 to S4 for alignment measurement set on the substrate W are illustrated.

An example of detecting the focus position in the shot region S1 and the shot region S2 will be described with reference to FIG. 7. First, the control part HP drives the stage STG by the drive mechanism DM so that the mark MA of the shot area S1 may fall within the detection range AR of the alignment detection system OA. Thereafter, the control unit HP controls the drive mechanism DM so that the stage STG is positioned at a plurality of positions within the drive range W1 in the Z direction illustrated in FIG. 7A. Moreover, the control part HP image | photographs the mark MA on the imaging element S in each of the some position in the drive range W1, and acquires the output signal from the imaging element S. FIG. Then, the control part HP calculates contrast as a 1st evaluation value from the output signal of the imaging element S about each position in the drive range W1. Thereby, the evaluation value group of a set of 1 which is an aggregate of the some 1st evaluation value corresponding to each of the some position in the drive range W1 is calculated. In FIG.7 (b), the curve C4 of contrast as an evaluation value group of a set 1 is illustrated. Curve C4 has a first peak ZP3 and a second peak ZP4. In this example, the control unit HP sets the first peak ZP3 as the reference peak position.

The control unit HP calculates a correlation between the output signal of the imaging device S at the reference peak position ZP3 and the output signal of the imaging device S at each position within the drive range W1 as a second evaluation value. . Thereby, the evaluation value group of 2 sets which is an aggregate of the some 2nd evaluation value corresponding to each of the some position in the drive range W1 is calculated. Then, the control part HP combines the evaluation value group of Article 1 and the evaluation value group of Article 2, and calculates the evaluation value soldier combination evaluation value group (plural combination evaluation values) of Article 3. Curve C5 of the combination evaluation value group is illustrated in FIG.7 (b). Based on the curve C5 of the combination evaluation value group in the drive range W1, the control part HP determines the 1st peak ZP3 as a focus position.

Subsequently, the control unit HP drives the stage STG by the drive mechanism DM so that the mark MA of the shot region S2 falls within the detection range AR of the alignment detection system OA. The surface of the board | substrate W has an unevenness, and the position of the Z direction of the shot area S2 may shift | deviate with respect to the position of the Z direction of the shot area S1. When the driving range W2 in the Z direction of the stage STG at the time of focus measurement is determined based on the position of the Z direction of the shot area S1, the contrast curve obtained from the mark MA of the shot area S2 is shown in FIG. It may be as shown in the curve C6 of 7 (d). The curve C6 whose range is limited within the drive range W2 has only one peak at the second peak position ZP6. In this case, when the focus position is detected using the curve C6, the second peak position ZP6 is determined as the focus position, so the determination criteria of the focus position differ in the shot region S1 and the shot region S2.

On the other hand, the curve of the combination evaluation value group with respect to the mark MA of the shot area S2 becomes like curve C7 of FIG.7 (d). In the drive range W2, the curve C7 monotonously increases and does not have a peak. Therefore, the focus position cannot be detected from the curve C7 in the drive range W2. Thus, the control unit HP changes the driving range and redo the detection of the focus position. As a result of the re-execution, the control unit HP can detect the first peak position ZP5 as the focus position from the curve C7 of the combination evaluation value group for the new drive range W3.

Hereinafter, the operation sequence of the exposure apparatus will be described with reference to FIG. 8. This operation sequence is controlled by the control unit HP. In step S001, the substrate (wafer) W is loaded into the exposure apparatus. In step S002, the alignment of the substrate W is performed. The prealignment is, for example, a process of detecting two marks of the substrate W at a position of a low magnification alignment scope not shown, and determining the shift, magnification, and rotation of the substrate W based on the detection result. .

In step S003, it is determined whether or not the current processing target substrate W is a first sheet of a lot including a plurality of substrates. In the case of the first substrate W, the focus position detection is performed in step S004. After step S005 is executed. On the other hand, when the board | substrate W currently processing object is 2 or more sheets after a lot, process S004 is not performed and process S005 is performed. In step S005, global alignment is executed. Global alignment detects the position (position in XY direction) of the some mark MA of the board | substrate W using the high magnification alignment detection system OA, and based on this detection result, the angle on the board | substrate W This is the process of determining the position of the shot region. When detecting the position of the mark MA, the control part HP performs the process S004 so that the mark MA may match the height of the mark MA to the object surface of the optical system OL of the alignment detection system OA. The stage STG is driven by the drive mechanism DM in accordance with the detected focus position. This operation is called a focus operation. That is, in step S005, after performing the focus operation for positioning the mark MA at the focus position, the position (marking position in the XY direction) of the mark MA is detected using the alignment detection system OA.

In step S006, an exposure process is performed sequentially on the plurality of shot regions of the substrate W, and in step S007, the substrate W is carried out. In step S008, it is determined whether or not the exposure process for all the substrates W in the lot has ended, and when the exposure process for all the substrates W in the lot is finished, a series of operation sequences ends. On the other hand, when the unprocessed board | substrate W remains, the process S001-S007 is performed with respect to the board | substrate W. As shown to FIG.

In FIG. 9, the detailed sequence of process S004 (focus position detection) of FIG. 8 is shown. Hereinafter, focus position detection will be described with reference to FIG. 9. In step S101, the control unit HP drives the stage STG by the drive mechanism DM so that the mark MA of the detection target of the focus position falls within the detection range AR of the alignment detection system OA. Let's do it. In step S102, the control unit HP controls the drive mechanism DM so that the stage STG is positioned at a plurality of positions within the drive range in the Z direction. In the step S102, the control unit HP captures the mark MA on the imaging element S at each of a plurality of positions within the driving range in the Z direction, and outputs an output signal from the imaging element S. Acquire. In step S103, the control unit HP calculates the contrast as the first evaluation value from the output signal of the imaging device S at each position within the driving range in the Z direction. That is, in step S103, the control unit HP calculates a plurality of contrasts (a group of evaluation values of the first set) corresponding to the plurality of positions in the Z direction, respectively. As a result, a contrast curve is obtained.

In step S104, the control unit HP determines whether or not the reference peak output signal has already been acquired for the current processing target substrate W, and proceeds to step S107 when the acquisition is completed. Proceed to step S105. Since the reference peak output signal depends on the process conditions of the substrate, the type of the mark MA, and the illumination conditions of the alignment detection system OA, the reference peak output signal is preferably acquired for each condition.

In step S105, the control unit HP determines the focus position based on the contrast curve obtained in step S103. In step S106, the control unit HP stores the output signal from the imaging element S at the focus position determined in step S105 as a reference peak output signal. In step S107, the control unit HP calculates the correlation between the reference peak output signal and the output signal from the imaging element S as the second evaluation value for each position in the Z direction. That is, in step S107, the control unit HP calculates a plurality of correlation degrees (assembly group of the second set) corresponding to the plurality of positions in the Z direction, respectively. In step S108, the control unit HP performs a combination evaluation value group (multiple combination evaluations) that combines the contrast of the plurality of evaluation value soldiers of the first set and the plurality of evaluation value soldiers of the second set for each position in the Z direction. Value) is computed as an evaluation value group of Article 3. In step S109, the control unit HP determines (detects) the focus position based on the combination evaluation value group as the evaluation value group in the third set. In step S110, the control unit HP determines whether or not the detection of the focus position has ended for all marks to be detected in the focus position, and executes steps S101 to S109 for the undetected mark. On the other hand, when detection of a focus position is complete | finished for all the marks to be detected of a focus position, it progresses to step S005 of FIG.

In the above embodiment, in order to detect the focus position, a correlation between the output signal at the reference peak position and the output signal at each position in the Z direction has been described as an example as the first evaluation value and the second evaluation value. As it is not limited to these. Since more reflected light is incident on the imaging device S at the focus position, the maximum light amount or the accumulated light amount in the imaging area can be used as the evaluation value. In addition, the symmetry of the marks, the degree of irregularities of the marks, and the like can also be evaluated values. For each of the evaluation values exemplified here, the correlation between the evaluation value of the reference peak position and the evaluation value of each position in the Z direction may be obtained, and this may be used as an evaluation value relating to the correlation.

As an example of the evaluation value regarding the correlation degree other than the correlation degree of contrast and the output signal of the imaging element S, the method of calculating the unevenness degree of the unevenness | corrugation of a mark is demonstrated using FIG. With respect to the output signal SIG of the imaging element S at the time of imaging the mark, the measurement window Wl is set from the center of the mark to the left side and the measurement window Wr is arranged to be symmetrical with each other. At this time, if the value at the left end of the left window Wl is L1, the value at the right end is L2, the value at the left end of the right window Wr is L3, and the value at the right end is L4. Is displayed.

When Unevenness> 0, it means convex shape, when Unevenness <0 it is concave shape, and when Unevenness = 0, it means flat shape. The correlation between Unevenness of the reference peak position and Unevenness of each position in the Z direction is calculated so that the correlation between the output signal of the reference peak position and the output signal of each position in the Z direction is the same, and this is an evaluation value with respect to the correlation You can do

The evaluation value to combine is not limited to two, The combination evaluation value which combines two or more evaluation values and obtains the evaluation value curve from which a peak is determined uniquely is employable. The method of combining evaluation values increases with the increase of the number of evaluation values. So, after this, the method of deriving the combination of evaluation values is demonstrated. The method described here can be executed by the control unit HP.

N evaluation values D1-DN are illustrated in FIG. First, evaluation value group D1 (for example, contrast) is selected as an evaluation value group of Article 1. Evaluation value group D1 has a 1st peak and a 2nd peak, and each peak position (position in a Z direction) is 1st peak position ZP7 and 2nd peak position ZP8. For example, the first peak position ZP7 may be the reference peak position.

The combined evaluation value group of the (N-1) group can be generated by combining the evaluation value military evaluation value group D1 of Article 1 and one of the other evaluation value groups D2 to DN of the (N-1) group. Then, the amount of change (difference between the maximum value and the minimum value) of the combination evaluation value group of (N-1) sets in the section between the first peak position ZP7 and the second peak position ZP8 can be calculated. At this time, it is assumed that the combined evaluation value at the first peak position ZP7 is larger than the combined evaluation value at the second peak position ZP8. A change amount is calculated for the group of combination evaluation values in group (N-1), and the group of combination evaluation values (two evaluation values for obtaining the combination evaluation value) having the largest change amount can be selected. In addition, a combination evaluation value group may be obtained by combining three or more sets of evaluation value groups. Also in this case, the combination evaluation value group with the largest change amount of the combination evaluation value group in the section between the first peak position ZP7 and the second peak position ZP8 (three or more evaluation values for obtaining the combination evaluation value). Can be selected.

Summarizing the above, the detection method of this embodiment is a detection method which detects the focus position of the optical system OL which forms the image of the mark MA as an imaging object in the imaging surface of the imaging element S, and is a 1st process And a second step and a third step. In this 1st process, based on the output signal output from the imaging element S in the state in which the mark MA is located in each of the several position in the Z direction which is the optical-axis direction of the optical system OL, A plurality of sets of evaluation value groups including the evaluation value group and the evaluation value group in Article 2 are obtained. In the said 2nd process, the evaluation value group of Article 3 is obtained based on the said evaluation value group of several sets. In this 3rd process, the focus position (object surface position) of the optical system OL is detected based on the evaluation value group of this 3rd article.

In the above description, the curve of the evaluation value group of the first set has a plurality of peaks. However, although only one peak is present, even when the difference between the peak of the curve and the other region is small and a flat shape is obtained, the evaluation by the combination evaluation value group is useful. Also in such a case, by using the combination evaluation value group, the difference between the peak and the other region is increased, and the focus position detection can be stably performed. The selection method of the combination evaluation value group can be based on the above-mentioned example in which the evaluation value group of Article 1 has several peak. However, instead of the second peak position, for example, a position away from the first peak position by a certain amount may be used.

According to the present embodiment, even when the curve of the set of evaluation values in the first set has a plurality of peaks or when the peaks are not clear, the variation in the detected focus position can be suppressed.

Hereinafter, the method of estimating a focus position based on the evaluation value group of Article 3 obtained by the combination of the evaluation value group of Article 1 and the evaluation value group of Article 2 is demonstrated. First, a problem that may occur when estimating the focus position based on the contrast curve will be described with reference to FIG. 12A. FIG. 12A illustrates a curve C8 of the evaluation group of the first set (plural contrasts). Curve C8 has a first peak and a second peak as a plurality of peaks. The position of each Z direction of a 1st peak and a 2nd peak is a 1st peak position ZP9 and a 2nd peak position ZP10. In this case, the contrast P1 at the first Z position (position in the Z direction) z1 and the contrast P2 at the second Z position z2 are the contrast P3 and fourth at the third Z position z3. The value equivalent to contrast P4 in the Z position z4 can be taken. Therefore, even if the regression curve is calculated from curve C8 and the focus position is estimated on the basis of the regression curve, since the same contrast exists in a plurality of places, the peak position cannot be uniquely estimated from the contrast of two points. . In such a case, it is necessary to estimate the peak position using the evaluation values in at least three Z positions.

Next, the method of estimating a focus position based on a combination evaluation value group is demonstrated, referring FIG. 12B. In FIG. 12B, a combination evaluation value group as the evaluation value group in Article 3 obtained by combining a plurality of contrasts as the evaluation value group in Article 1 and a plurality of correlations as the evaluation value group in Article 2 (plural combination evaluations) Value) curve C9 is illustrated. Curve C9 is an example of the combined evaluation value group obtained by combining a plurality of sets of evaluation value groups so as to have only one peak. Whether or not the curve of the combination evaluation value group has only one peak can be determined based on the number of local maxima of the curve of the combination evaluation value group, for example. By determining the method of generating the combined evaluation value group so that only one peak has the curve of the combined evaluation value group, the peak position, that is, the focus position can be estimated (determined) based on the two Z positions.

In the example of FIG. 12B, the regression curve C9 'of the combination evaluation value group C9 is calculated, and the combination evaluation value P5 of two combination evaluation values, namely, the first Z position z5, is calculated using the regression curve C9'. Focus position ZP11 can be estimated from the combined evaluation value P6 of and 2nd Z position z6. The regression curve (approximation formula) which approximated secondly the combination evaluation value group C9 is represented, for example by (equation 6).

Here, P is a combination evaluation value and z is a Z position (in Z direction). The coefficients a ₁ to a ₃ are known values calculated beforehand. When the combined evaluation value P5 of the first Z position z5 and the combined evaluation value P6 of the second Z position z6 are applied to (Expression 6),

Becomes In this step, since it is impossible to specify which position on the regression curve the first Z position z5 and the second Z position z6 are, the respective positions are specified from (Equations 7) and (8). If z6 is a position spaced apart from z5 by d,

Can be displayed as If you apply this to (Eq. 8),

Becomes If you solve equation (7) and equation (10),

It is possible to specify the position of z5 on the regression curve. Since the focus position ZP11 becomes the maximum value of the regression curve of (Equation 6), it is given to the position where P 'of (Equation 12) which differentiates (Equation 6) becomes 0, namely (Equation 13).

Finally, the difference Zm between (Equation 11) and (Equation 13) is the distance between the first Z position z5 and the focus position ZP11 (Equation 14).

In FIG. 13, the modification of the focus position detection (process S004 (focus position detection) of FIG. 8) shown in FIG. 9 is shown. Hereinafter, focus position detection in a modification will be described with reference to FIG. 13. In step S201, the control unit HP drives the stage STG by the drive mechanism DM so that the mark MA to be detected at the focus position falls within the detection range AR of the alignment detection system OA. Let's do it. In step S202, the control unit HP determines whether or not the regression curve of the curve of the combined evaluation value is calculated, proceeds to step S203 if not calculated, and proceeds to step S213 if calculated.

In step S203, the control unit HP captures the mark MA on the imaging device S at each of a plurality of positions within the driving range in the Z direction, and acquires an output signal from the imaging device S. . In step S204, the control unit HP calculates the contrast as the first evaluation value from the output signal of the imaging element S at each position within the drive range in the Z direction. That is, in step S204, the control unit HP calculates a plurality of contrasts (a group of evaluation values of the first set) corresponding to the plurality of positions in the Z direction, respectively. As a result, a contrast curve is obtained.

In step S205, the control unit HP determines the focus position based on the contrast curve obtained in step S204. In step S206, the control unit HP stores the output signal from the imaging element S at the focus position determined in step S205 as the reference peak output signal. In step S207, the control unit HP calculates the correlation between the reference peak output signal and the output signal from the imaging element S as the second evaluation value for each position in the Z direction. That is, in step S207, the control unit HP calculates a plurality of correlation degrees (assembly group of the second set) corresponding to the plurality of positions in the Z direction, respectively. In step S208, the control unit HP performs a combination evaluation value group (multiple combination evaluations) that combines the contrast of the plurality of evaluation value soldiers of the first set and the plurality of evaluation value soldiers of the second set for each position in the Z direction. Value) is computed as an evaluation value group of Article 3.

In step S209, the control unit HP calculates a regression curve (coefficients a ₁ to a ₃ ) for estimating the focus position based on the combination evaluation value group as the evaluation value group in the _{third set} . This regression curve is an approximation formula which shows the relationship between the position of the imaging object (mark MA) in a Z direction (optical axis direction), and the value which a set of evaluation values of Article 3 should have.

In step S202, when the control unit HP determines that the regression curve has been calculated, steps S213 to S217 are executed. In step S213, the control unit HP captures the mark MA on the imaging element S at each of the two positions in the Z direction, and acquires an output signal from the imaging element S. The two positions in the Z direction can set, for example, the focus position of the mark previously measured or the position spaced apart by a constant distance therefrom. When driving the stage STG by the drive mechanism DM so that the mark MA of the detection target of the focus position in the step S201 falls within the detection range AR of the alignment detection system OA, the stage STG The position in the Z direction may be positioned in one of the two positions.

In step S214, the control unit HP calculates the contrast as the set of evaluation values of the first set from the output signal of the imaging device S for each of the two positions in the Z direction. In step S215, the control unit HP calculates the correlation between the reference peak output signal and the output signal from the imaging element S at two positions in the Z direction as an evaluation value group of the second set. In step S216, the control unit HP combines the two combination evaluation values in which the contrast of two evaluation value soldiers of Article 1 and two evaluation value soldiers of Article 2 is combined with respect to two positions in the Z direction. Value group) is computed as an evaluation value group of Article 3. In step S217, the control unit HP calculates the focus position based on the two sets of evaluation values calculated in step S216 and the regression curves (coefficients a ₁ to a ₃ ) calculated in step S209. .

In step S210, the control unit HP determines whether or not the detection of the focus position has ended for all marks to be detected in the focus position, and returns to step S201 to detect the focus position for the undetected mark. On the other hand, when detection of a focus position is complete | finished for all the marks to be detected of a focus position, it progresses to step S005 of FIG.

Since the focus position calculated based on the regression curve may contain an error, the focus position measurement may be performed again in the vicinity of the calculated focus position after step S217. In this way, a more accurate focus position can be calculated.

As described above, by calculating a combination evaluation value group having one peak and estimating the focus position by a regression curve, the focus position is smaller from the evaluation value group than in the first set of evaluation value groups in which a plurality of peaks exist. Can be estimated.

The lithographic method according to one embodiment of the present invention includes a position alignment step of positioning the substrate S and the original plate R based on the position of the mark MA provided on the substrate W, and after the position alignment step. An exposure step of exposing the substrate W and a step of developing the substrate W after the exposure step may be included. In this position alignment process, the focus position of the optical system OL of the alignment detection system OA is detected by the said detection method, the mark MA as imaging object is located at the said focus position, and the position of the mark MA is adjusted. Detect.

An article manufacturing method according to an embodiment of the present invention comprises a step of forming a pattern on a substrate W by the lithography method, and processing the substrate W on which the pattern is formed (for example, etching and ion implantation). It includes a process to make.

Hereinafter, the device manufacturing method using the said exposure apparatus is demonstrated. 14 is a diagram illustrating a flow of an article manufacturing method or an entire manufacturing method of a device. In circuit design S301, the circuit design of a semiconductor device is performed. In reticle production (S302), a reticle (also called a disc or a mask) is produced based on the designed circuit pattern. On the other hand, in wafer fabrication (S303), a wafer (also referred to as a substrate) is manufactured using a material such as silicon. The wafer process S304 is called a preprocess, and uses the reticle and the wafer to form the actual circuit on the wafer by lithography technique. The following assembly (S305) is called a subsequent step, and is a step of semiconductor chip formation using a wafer manufactured by S304, and includes an assembly step such as an assembly step (dicing and bonding) and a packaging step (chip encapsulation). In the inspection S306, inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in S305 are performed. Through this process, a semiconductor device is completed and shipped (S307).

15 is a diagram illustrating a detailed flow of the wafer process. In oxidation (S401), the surface of the wafer is oxidized. In CVD (S402), an insulating film is formed on the wafer surface. In electrode formation S403, an electrode is formed on the wafer by vapor deposition. In ion implantation (S404), ions are implanted into the wafer. In the CMP S405, the insulating film is planarized by the CMP process. In the resist process (S406), a photosensitive agent is applied to the wafer. In exposure S407, the exposure apparatus is used to expose a wafer coated with a photosensitive agent through a mask on which a circuit pattern is formed to form a latent image pattern in the resist. In the development S408, a latent image pattern formed in the resist on the wafer is developed to form a resist pattern. In etching S409, the layer or wafer under the resist pattern is etched through the portion where the resist pattern is opened. In resist peeling (S410), the resist which became unnecessary after etching is removed. By repeating these steps, a circuit pattern is formed multiplely on a wafer.

Although the above is an example of typical embodiment of this invention, this invention is not limited to embodiment shown to the above and drawing, It can change suitably and can implement in the range which does not change the summary.

S: imaging device
OL: optical system
LI: light source
OA: alignment detector
STG: XYZ Stage
W: Substrate
MA: Mark
HP: Control
100: exposure apparatus

Claims (17)

It is a detection method which detects the focus position of the optical system which forms the image of an imaging target in the imaging surface of an imaging element,
A plurality of evaluation value groups of the first set and the evaluation value group of the second set based on an output signal output from the imaging element in a state where the imaging target is located at each of a plurality of positions in the optical axis direction of the optical system; Obtaining a group of evaluation values of the group;
Obtaining an evaluation value group of Article 3 based on the plurality of evaluation value groups;
Detecting the focus position based on the evaluation value group of the third article;
Detection method comprising a. The method of claim 1,
The difference between the maximum value and the minimum value in the evaluation value group of the third article is at least the difference between the maximum value and the minimum value in the evaluation value group of the first article, and the difference between the maximum value and the minimum value in the evaluation value group of the second article. The detection method characterized by larger than one side. The method of claim 1,
The number of peaks in the curve which shows the relationship between the position in the said optical axis direction and the evaluation value group of the said 3rd group is smaller than the number of peaks in the evaluation value group of the said 1st group. The method of claim 3,
The number of peaks in the curve which shows the relationship between the position in the said optical axis direction and the said evaluation set of 3 groups is smaller than the number of peaks in the evaluation set of 2nd group. The method of claim 1,
The number of peaks in the curve which shows the relationship between the position in the said optical axis direction and the said 3rd group of evaluation values is 1, The detection method characterized by the above-mentioned. The method of claim 1,
The third curve showing the relationship between the position in the optical axis direction and the evaluation group of the third set has a plurality of peak values,
The first curve showing the relationship between the position in the optical axis direction and the evaluation group of the first set has a plurality of peak values,
The difference between the largest peak value and the second largest peak value among the plurality of peak values in the third curve is the largest peak value and the second largest peak among the plurality of peak values in the first curve. A detection method, characterized in that it is greater than the difference in value. The method of claim 6,
The second curve showing the relationship between the position in the optical axis direction and the evaluation group of the second set has a plurality of peak values,
The difference between the largest peak value and the second largest peak value among the plurality of peak values in the third curve is the largest peak value and the second largest peak among the plurality of peak values in the second curve. A detection method, characterized in that it is greater than the difference in value. The method of claim 1,
The said 2nd evaluation value group shows the correlation degree of a reference signal and the output signal from the said image pick-up element, The detection method characterized by the above-mentioned. The method of claim 8,
And the reference signal is a signal selected from an output signal output from the imaging element in a state where the imaging target is located at each of the plurality of positions in the optical axis direction of the optical system. The method of claim 8,
And detecting the reference signal. The method of claim 1,
The said evaluation value group of a said 1st group shows the contrast of the output signal from the said imaging element, The detection method characterized by the above-mentioned. The method according to any one of claims 1 to 11,
In the step of detecting the focus position based on the evaluation value group of the third set, an approximation equation indicating the relationship between the position of the imaging target in the optical axis direction and the value that the third evaluation group should have; Detecting the focus position based on at least two evaluation value groups of the third set. A position aligning step of aligning the substrate and the disc based on the position of the mark provided on the substrate;
An exposure step of exposing the substrate after the alignment step;
Including developing the substrate after the exposure process;
In the said alignment process, the alignment detection system which has an imaging element and the optical system which forms the image of the said mark in the imaging surface of the said imaging element is used,
The position alignment process,
A plurality of sets of evaluation values including the first set of evaluation values and the second set of evaluation values based on an output signal output from the imaging device in a state where the mark is located at each of a plurality of positions in the optical axis direction of the optical system. Process of obtaining,
Obtaining an evaluation value of Article 3 based on the plurality of evaluation values;
Detecting a focus position of the optical system based on the evaluation value of the third set;
And positioning the mark at the focus position to detect the position of the mark. Forming a pattern on the substrate by the lithographic method according to claim 13,
Process of processing the substrate on which the pattern is formed
Article manufacturing method comprising a. It is an optical device which has an image pick-up element and the optical system which forms the image of an imaging target in the imaging surface of the said image pick-up element,
Evaluation of a plurality of sets including an evaluation value of a first set and an evaluation value of a second set based on an output signal output from said imaging element in a state where said imaging target is located at each of a plurality of positions in the optical axis direction of said optical system And a controller for generating a value, generating a third set of evaluation values based on the plurality of sets of evaluation values, and detecting a focus position of the optical system based on the third set of evaluation values. It is an exposure apparatus which exposes a board | substrate,
A detection device for detecting the position of the mark provided on the substrate;
A projection optical system for projecting a pattern of the original plate onto the substrate to expose the substrate,
The detection apparatus includes an imaging device, an optical system for forming an image of an imaging target on an imaging surface of the imaging device, and a control unit,
The control unit includes an evaluation value of the first set and an evaluation value of the second set based on an output signal output from the imaging element in a state where the imaging target is located at each of a plurality of positions in the optical axis direction of the optical system. Generate a plurality of sets of evaluation values, generate a third set of evaluation values based on the plurality of sets of evaluation values, detect a focus position of the optical system based on the third set of evaluation values, and mark the mark at the focus position. The focusing apparatus controls the focusing operation so that the apparatus is arranged. Forming a pattern on a substrate using the exposure apparatus according to claim 16,
Process of processing the substrate on which the pattern is formed
Article manufacturing method comprising a.

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