JPH10260021A - Pattern inspecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pattern inspecting device which inspects a pattern correcting position off-set, expansion amount, and rotation amount without requiring a specific alignment mark and a complex and large electric control system. SOLUTION: By comparing sensor data which is provided by reading a pattern on a sample 1 with a line sensor 5 with reference data which is output from a reference data generator 13 using a comparing device 6 in the comparing method in which inconsistent number is used, and by correcting position information of an XY stage 2 on the basis of the comparison result, positioning is performed so that the reference pattern region fits to the sensor pattern region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern inspection apparatus, and more particularly to a pattern inspection apparatus using sensor data and image pattern data obtained by imaging a pattern drawn on a photomask, reticle, wafer, or the like. The present invention relates to a pattern inspection apparatus used for performing an inspection or the like.

[0002]

2. Description of the Related Art As is well known, semiconductor integrated circuits are becoming more and more highly integrated with improvements in exposure technology and process technology.
Miniaturization is in progress. Along with this, even more positional accuracy,
Improvements in dimensional accuracy and reduction of minute defects and foreign matter are required. For example, it is said that it is necessary to detect a defect having a size of 0.15 μm with a quadruple mask for a circuit pattern having a width of 0.25 μm on a wafer.

[0003] Incidentally, in a pattern defect inspection apparatus for a photomask, a reticle or the like, a die-to-database is usually used.
(die-to-database) An inspection method called comparison is adopted. In this method, sensor data obtained by imaging a circuit pattern to be inspected by a line sensor is compared with reference data created from CAD data used for designing the pattern, and a mismatch point between the two is detected as a defect.

As described above, in the pattern defect inspection apparatus,
Since a mismatch point between the sensor data and the reference data is detected as a defect, it is particularly important to align the two. Factors that impair the alignment between the two include yaw and speed unevenness of the XY axis stage, mask position offset, amount of expansion / contraction, amount of rotation, and the like. Therefore, it is necessary to correct these with an electric control system or computer software.

With respect to yaw and speed unevenness of the XY-axis stage, reference data is generated by feeding back the position of the XY-axis stage measured by a laser interferometer or the like.

On the other hand, the amount of expansion and contraction and the amount of rotation of the mask are corrected by dynamically aligning the sensor data with the reference data by pattern matching, or by using a specific method provided around the main pattern area. A method of reading an alignment mark and correcting a position offset, an amount of expansion / contraction, and an amount of rotation has been adopted.

However, in the former method, it is not necessary to create a specific alignment mark, but on the other hand, there is an electric control system that corrects the variation in the position of the mask loaded on the stage in order to match the sensor data with the reference data. There is a problem that the circuit becomes complicated and the circuit scale becomes large.

In the latter method, first, one of the four alignment marks provided around the main pattern area is almost aligned with the sensor, and the stage is moved at a low speed in the X-axis direction. The edge position of the alignment mark is obtained from the change in the output. Next, the scanning direction of the stage is reversed, and it is obtained again, and the average value of both positions is set as the alignment mark position in the X-axis direction. next,
The stage scanning is changed in the Y-axis direction, and the same operation as in the X-axis direction is repeated. Thus, the position offset, the amount of expansion / contraction correction from the alignment mark position read by the four marks,
The rotation amount correction value is obtained. According to this method, since the sensor data and the reference data can be matched with sufficient accuracy, the former pattern matching is not required.

However, to read the alignment mark position, at least four stage scans are required for each mark.
It is necessary to perform the stage scan 16 times in total at four positions of the alignment mark, so it takes a long time until the inspection, and it requires complicated calculation for calculating the XY position offset, the amount of expansion and contraction, and the amount of rotation. There was a problem.

[0010]

As described above, in the pattern inspection, a conventional pattern inspection in which the position of the sensor data and the reference data is dynamically adjusted by pattern matching to correct the amount of expansion and contraction and the amount of rotation. In the device, the electric control system becomes complicated, and the circuit scale may be increased. Further, in a conventional pattern inspection apparatus which reads a specific alignment mark provided around the main pattern area and corrects the position offset, the amount of expansion / contraction, and the amount of rotation from the position data, there are four alignment marks. It is necessary to perform stage scanning a total of 16 times, so that this stage scanning takes time,
Further, there is a drawback that complicated calculations for obtaining the position offset, the amount of expansion and contraction, and the amount of rotation are required.

Therefore, the present invention does not require a specific alignment mark, does not require a complicated and large-scale electric control system, and can inspect a pattern while correcting a position offset, an expansion / contraction amount, and a rotation amount. An object of the present invention is to provide a pattern inspection apparatus.

[0012]

In order to achieve the above object, the present invention provides a pattern inspection apparatus for inspecting a pattern formed on a sample, wherein the sample is held on a stage, and the stage is mounted on an X-axis. First means for continuously moving in the direction and step-moving in the Y-axis direction orthogonal to the X axis, second means for reading a pattern on the sample with a line sensor and outputting sensor data, Third means for obtaining an X-axis position and a Y-axis position of the stage in synchronization with the output of the sensor data; and a first bias applied to the X-axis position of the stage obtained by the third means. A fourth means for accumulating a second bias value at regular intervals in the X-axis direction to obtain a corrected X-axis direction correction stage position with respect to the added value;
A third position in the Y-axis direction position of the stage obtained by
Fifth means for obtaining a corrected Y-axis direction correction stage position by accumulating a fourth bias value at regular intervals in the X-axis direction with respect to the sum of the bias values, and inputting the pattern design data. A sixth means for generating reference data based on the design data inputted by the sixth means and the correction stage position obtained by the fourth and fifth means; Eighth means for comparing the reference data obtained by the seventh means with the sensor data obtained by the second means to detect a mismatch, and based on the mismatch data obtained by the eighth means. The first
And ninth means for comparing and analyzing the results obtained by adjusting the fourth bias value to obtain a position offset in the X-axis direction and the Y-axis direction and a magnification correction value. .

In the pattern inspection apparatus configured as described above, a specific alignment mark is not required, and the electric control system can be suppressed from becoming complicated or large.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a pattern inspection apparatus according to an embodiment of the present invention, which is an apparatus for inspecting a defect of a circuit pattern drawn on an exposure mask. In FIG. 1, reference numeral 1 denotes a mask to be inspected, and the mask 1 to be inspected is held on an XY stage 2. The XY stage 2 is continuously moved in the X-axis direction by the stage controller 3, and is subjected to step movement control in the Y-axis direction.

A light source 4 is disposed above the mask 1 to be inspected held by the XY stage 2, and the light emitted from the light source 4 is irradiated on the mask 1 as illumination light. A line sensor 5 for imaging a circuit pattern drawn on the inspection target mask 1 is disposed below the inspection target mask 1, and sensor data output from the line sensor 5 is provided to a comparison device 6 described later. Can be

On the other hand, in synchronization with the transmission of sensor data from the line sensor 5, the position of the XY stage 2 in the X-axis direction and the position of Y
A stage position measuring device 7 for detecting an axial position with a laser interferometer, a linear encoder, or the like is provided. Position data measured by the stage position measuring device 7 is introduced to a stage position correcting device 8.

The stage position correcting device 8 includes bias values Xi and Yi given from a bias value adjusting device 9 described later.
The stage position is corrected based on (position offset in the X and Y axis directions), εi (expansion and contraction correction value), and θi (mask rotation correction value).

That is, the stage position correcting device 8
Is the stage position Xpos in the X-axis direction as shown in FIG.
, A bias value εi per unit length is accumulated at regular intervals in the X-axis direction to obtain a corrected stage position Xpos1 in the X-axis direction, and further, a stage position Ypos in the Y-axis direction. Then, the bias value θi per unit length is accumulated at regular intervals in the X-axis direction to obtain a corrected stage position Ypos1 in the Y-axis direction.

In this device 8, a synchronization generator 10 is provided which receives a stage position Xpos in the X-axis direction and generates a synchronization signal.
At regular intervals, the registers 11 and 12 store the expansion / contraction correction values εi,
The mask rotation correction value θi is accumulated.

The information on the correction stage positions Xpos1 and Ypos1 output from the stage position correction device 9 is supplied to a reference data generator 13 as a control signal for generating reference data. The reference data generator 13 is provided with the design pattern data used when the circuit pattern is formed on the inspection target mask 1 from the database 14, and when position information as a read signal is provided from the stage position corrector 8, The design pattern data at that position is output as reference data.

The design pattern data output from the reference data generator 10, that is, the reference data, is introduced into the comparator 6 and compared with the sensor data described above. As will be described later, the comparison device 6 stores the number of mismatches at regular intervals in the X-axis direction. Then, the comparison result is analyzed by the analysis device 15. In this example, the magnitude of the displacement between the sensor data and the reference data is estimated from the distribution of the number of mismatches, and the position offset and magnification correction value in the X-axis direction and the position offset and magnification correction value in the Y-axis direction are obtained.
The bias value of the bias value adjusting device 9 is changed according to the analysis result.

Next, a description will be given of a positioning operation of the pattern inspection apparatus having the above-described configuration, in particular. First, the circuit pattern drawn on the inspection target mask 1 is inspected in a strip-like unit having a certain width in the Y-axis direction, as shown in FIG. That is, the XY stage 2 is continuously moved in the X-axis direction, and the XY stage 2 is step-moved in the Y-axis direction by the width of a strip to inspect the entire surface of the inspection target mask.

FIG. 3B shows a range scanned by the line sensor 5 at the start of the inspection, that is, the sensor pattern area 21 and a range of the reference data, that is, the reference pattern area 2.
3 is shown.

Originally, these two areas must match. However, if the positioning is not performed, the position is shifted as shown in FIG. Where Δx, Δ
y is the sensor pattern area 21 at the inspection start position
, Ε is a magnification error in the X-axis direction, and θ is a rotation error in the Y-axis direction. As shown in FIG. 3B, the displacement (Δx, Δy) between the sensor pattern area 21 and the reference pattern area 22 and the rotation error θ
Is caused by positioning when the inspection target mask 1 is loaded on the XY stage 2, and the magnification error ε is caused by a fluctuation factor such as temperature and pressure of the length measuring system and a mask position error. Therefore, the magnification error ε is usually sufficiently smaller than the position offset (Δx, Δy) and the rotation error θ. At this time, the sensor pattern area 21 and the reference pattern area 2
2 from the inspection start position in the X-axis direction.
At the position advanced by i, (Δx + ε · Li, Δy +
θ · Li).

As described above, when the sensor pattern area 21 and the reference pattern area 22 are greatly displaced, even if the reference data and the sensor data are compared, a highly accurate inspection result cannot be obtained. Therefore, in order to obtain a correct inspection result, the pattern inspection apparatus according to this example corrects the reference pattern region 22 using the bias value as shown in FIG. The pattern area 21 is made to match. Accordingly, the displacement between the sensor pattern area 21 and the reference pattern area 22 is (Δx−xi + (ε−εi) · L
i, Δy−yi + (θ−θi) · Li). Here, (xi, yi), εi, and θi correspond to given bias values, respectively.

Next, a procedure for actually correcting the positional deviation will be described with reference to FIG. FIG. 4A shows a sensor pattern area 21 serving as a reference, and a reference pattern area 22 when a bias value is set to 0.

In the first step, a pattern matching is performed using the sensor data and reference data taken in at the inspection start position, so that the sensor pattern area 2
1 (sensor data) and (Δx, Δy), which is the displacement between the reference pattern area 22 (reference data), are obtained as initial values. The positional deviation amount obtained here is sufficient with coarse accuracy. The displacement can be obtained with high accuracy by the subsequent steps.

In the second step, FIG. 4 (b-1) and FIG.
As shown in (b-2), the bias values xi = Δx and εi = 0
Then, by appropriately selecting yi and θi, Li that minimizes the number of mismatches between the sensor pattern area 21 and the reference pattern area 22 is obtained for at least two parameter combinations. As a result, L ₁ and L ₂ are obtained as shown in FIGS. 5 (b-1) and 5 (b-2). Using these L ₁ and L ₂ , equations (2) and (3) are obtained from equation (1), and rotation errors θ and Δy in the Y-axis direction are obtained.

−Δy = −y ₁ + (θ−θ ₁ ) L ₁ = −y ₂ + (θ−θ ₂ ) L ₂ (1) θ = (y ₁ −y ₂ + θ ₁ · L ₁ −θ ₂ · L ₂ ) / (L ₁ −L ₂ ) (2) Δy = {y ₂ · L ₁ −y ₁ · L ₂ −L ₁ · L ₂ (θ ₁ −θ ₂ )} / (L ₁ − L ₂ ) (3) In the third step, as shown in FIG. 4 (c-1) and FIG. 4 (c-2), as the bias values yi, θi, Δy obtained in the second step, θ is set, xi and εi are appropriately selected in the same manner as in the second step, and Li that minimizes the number of mismatches between the sensor pattern area 21 and the reference pattern area 22 is obtained for at least two combinations of parameters. . As a result, L ₃ and L ₄ are obtained as shown in FIGS. 5 (c-1) and 5 (c-2). This L ₃ , L ₄
Using Equation (4), Equations (5) and (6) hold from Equation (4), and the magnification errors ε and Δx in the Y-axis direction are obtained.

−Δx = −x ₁ + (ε−ε ₁ ) · L ₃ = −x ₂ + (ε−ε ₂ ) L ₄ (4) ε = (x ₁ −x ₂ + ε ₁ · L ₃ − ε ₂ · L ₄ ) / (L ₃ -L ₄ ) (5) Δx = {x ₂ · L ₃ -x ₁ · L ₄ -L ₃ · L ₄ (ε ₁ -ε ₂ )} / (L ₃ −L ₄ ) (6) The Δx, Δy, θ, and ε thus obtained are given to the stage position correcting device 8 via the bias value adjusting device 9. Therefore, the circuit pattern of the inspection target mask 1 can be inspected in a state where the reference pattern region 22 is matched with the sensor pattern region 21, and highly accurate inspection can be performed.

The accuracy of the bias value may be improved by repeating the second and third steps described above.
In this case, in the above description, in the second step, the bias value x
While i = Δx and εi = 0, xi and εi obtained in the third step are set.

[0032]

As described above, according to the present invention, the inspection accuracy can be improved without requiring a specific alignment mark and without complicating or enlarging the electric control system. .

[Brief description of the drawings]

FIG. 1 is a block diagram of a pattern inspection apparatus according to an embodiment of the present invention.

FIG. 2 is a configuration diagram of a stage position correcting device in the device.

FIG. 3 is a diagram for explaining the reason why alignment between a sensor pattern area and a reference pattern area is required;

FIG. 4 is a diagram for explaining a positioning operation in the apparatus of the present invention.

FIG. 5 is a diagram for explaining a positioning operation in the apparatus of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 mask to be inspected 2 XY stage 3 stage control device 4 light source for illumination 5 line sensor 6 comparison device 7 stage position measurement device 8 stage correction device 9 bias value adjustment device 13 reference data Generator 14 ... Database 15 ... Analyzer

Claims (1)

[Claims] 1. A pattern inspection apparatus for inspecting a pattern formed on a sample, wherein the sample is held by a stage, the stage is continuously moved in an X-axis direction, and a Y-axis orthogonal to the X-axis is provided. First means for step-moving in the direction, second means for reading a pattern on the sample with a line sensor and outputting sensor data, and X-axis position of the stage in synchronization with the output of the sensor data And a third means for obtaining a position in the Y-axis direction, and a value obtained by adding a first bias value to the position in the X-axis direction of the stage obtained by the third means. X corrected by accumulating the second bias value
A fourth means for obtaining an axial correction stage position; and a result obtained by adding a third bias value to the Y-axis direction position of the stage obtained by the third means, at regular intervals in the X-axis direction. Y corrected by accumulating the fourth bias value
Fifth means for obtaining an axial direction correction stage position, sixth means for inputting the design data of the pattern, design data inputted by the sixth means, and the design data obtained by the fourth and fifth means. Means for generating reference data based on the corrected stage position, and comparing the reference data obtained by the seventh means with the sensor data obtained by the second means to detect a mismatch. And an X-axis direction and a Y-axis direction by comparing and analyzing the results obtained by adjusting the first to fourth bias values based on the inconsistency data obtained by the eighth means. And a ninth means for calculating a magnification correction value.