JPH06265480A - Pattern defect inspection method and device - Google Patents

Abstract

PURPOSE:To provide a pattern defect inspection method and device, capable of performing a stringent inspection easily without entailing any complication to its constitution even in the case of such a sample as a phase shift mask. CONSTITUTION:In a pattern defect inspection method which detects the defect of an inspected pattern by way of comparing (16, 17) both of measuring data (S) obtained after optically scanning a sample formed with the inspected pattern and designed data (Q) used in time of forming the inspected pattern to the sample successively, such a inspecting method as securing defect information on the inspected pattern upon comparing (19, 20, 21, 22 and 23) measured data themselves at each constant range portion to be obtainable in consecutive order by at least scanning in an area where a constant-form pattern is repeatedly formed, is adopted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern defect inspecting method and an inspecting apparatus used for, for example, inspecting a pattern of a mask used in a manufacturing process of semiconductor integrated circuits and liquid crystal display devices.

[0002]

2. Description of the Related Art The manufacturing yield of a large scale integrated circuit (LSI) is greatly influenced by the quality of a photomask used in an exposure process. That is, if the photomask used in the exposure process has a pattern defect, a high yield cannot be expected. Therefore, usually, the mask pattern is inspected by using the pattern defect inspection apparatus after the photomask is manufactured, and only the passed photomask is used.

The pattern defect inspection apparatus is the same as the one that employs a method of detecting defects by comparing measured data obtained by observing a sample on which a pattern is drawn with design data used when the pattern is created. It is considered that a method of detecting a defect by comparing measurement data obtained by observing two samples on which patterns are drawn by different observing means is considered.

In the former case, since it is compared with the design data, it is possible to perform a strict inspection, and it is possible to perform an inspection even when one pattern is formed on one sample. . In the latter case, two samples with the same pattern are required, but there is an advantage that the device configuration is simple because no design data is required.

By the way, recently, in order to further improve the degree of integration, an attempt has been made to use a phase shift mask in which a chrome pattern and a phase shifter are mixed as a photomask used in an exposure process. The technical contents of this phase shift mask are, for example,
NIKKEI MICRODEVICE, P108 in July 1990 and August 1991
It is described in detail in the monthly issue of NIKKEI MICRO DEVICE, P52.

When inspecting such a phase shift mask, the former defect inspection apparatus for comparing design data with measured data requires a dedicated bit expansion circuit for reading the design data twice. However, there is a problem that the device configuration becomes more complicated. Further, as described above, the latter defect inspection apparatus requires two samples in which the same pattern is drawn, so that it is difficult to apply it to a sample such as a phase shift mask.

[0007]

As described above, the conventional pattern defect inspection apparatus has a problem that it is difficult to apply it to a sample such as a phase shift mask and the apparatus cannot be complicated. there were.

Therefore, the present invention provides a pattern defect inspecting method and an inspecting apparatus which can easily and strictly inspect even in the case of a sample such as a phase shift mask without complicating the structure. It is an object.

[0009]

In order to achieve the above object, the present invention focuses on the following points. That is, in a sample such as a phase shift mask, generally, a phase shifter is applied to a region where a pattern of a constant shape is repeatedly arranged, such as a memory cell formation location. Therefore, in such an area, a defect can be detected by comparing the measurement data for every certain area.

Based on such an idea, in the pattern inspection method according to the present invention, the measurement data obtained by optically scanning the sample on which the pattern to be inspected is formed and the pattern to be inspected on the sample. In the pattern defect inspection method for detecting defects of the pattern to be inspected by sequentially comparing the design data used at the time of creation, in a region where a pattern of a constant shape is repeatedly formed, at least a constant region obtained sequentially by the scanning. An inspection method for obtaining defect information of the pattern to be inspected by comparing the measured data for each fixed area, which is sequentially obtained by the above scanning, or the measured data for each fixed area, which is a reference, is incorporated.

Further, in the pattern defect inspection apparatus according to the present invention, a measurement data acquisition means for optically scanning the sample on which the pattern to be inspected is formed to obtain the actual measurement data of the pattern to be inspected, and to the sample. A storage unit that stores the design data used when the pattern to be inspected is stored, and the design data read from this storage unit and the measurement data obtained by the measurement data acquisition unit are compared to determine the pattern to be inspected. First defect information acquisition means for obtaining defect information, means for outputting area information indicating an area in which a pattern of a constant shape is repeatedly formed based on the design data read from the storage means, and the means for outputting the area information. When the area information is being output, the measurement data for a certain area sequentially obtained by the scanning or the area for a certain area sequentially obtained by the scanning Obtained by the second defect information acquisition means for obtaining the defect information of the pattern to be inspected by comparing the measured data of 1) with the data for the certain area serving as the reference, and the first and second defect information acquisition means. And a means for judging the defect information based on a predetermined judgment standard.

[0012]

In the defect inspection method and the defect inspection apparatus according to the present invention, the defect information is obtained by comparing the design data and the measured data in the region where the pattern of the constant shape is not repeatedly formed. . Further, in a region where a pattern of a constant shape is repeatedly formed, defect information is obtained by two types of data comparison, for example, comparison between design data and measurement data and comparison between measurement data and measurement data. By utilizing the advantages of each comparison method, highly reliable inspection results can be obtained. Further, even in the case of a sample such as a phase shift mask, in the area where the pattern of a constant shape is repeatedly formed (the area where the phase shifter is provided), the inspection by comparing the measurement data with the measurement data can be performed. Since it is executed, it is possible to perform the inspection without the design data of the phase shifter.

[0013]

Embodiments will be described below with reference to the drawings. FIG. 1 shows a schematic structure of a pattern defect inspection apparatus according to an embodiment of the present invention, which is a fully automatic mask inspection apparatus.

In the figure, 1 indicates an XYθ table. A mask 2 to be inspected, which is a sample, is placed on the XYθ table 1, and a light source 3 is used to illuminate a pattern on the mask from above the mask 2 to be inspected. Then, the pattern image drawn on the mask 2 to be inspected is formed on the light receiving surface of the CCD line sensor 5 by using the magnifying optical system 4, and the output obtained from the CCD line sensor 5 at this time is output by the sensor circuit 6. Measurement data S is obtained by A / D conversion. This measurement data S is sent to the data comparison circuit 7. Further, a laser length measurement system 9 for detecting the position of the XYθ table 1 is provided, and the position information P obtained by this laser length measurement system 9 is sent to the data comparison circuit 7 via the position circuit 10.

Here, a method of scanning the entire mask 2 to be inspected by the CCD line sensor 5 to obtain pattern information will be described. FIG. 2 shows the driving mode of the mask 2 to be inspected and the imaging width of the CCD line sensor 5. FIG. 3 is an enlarged view of a part of FIG. 2 and shows a state of measurement scanning of the CCD line sensor 5. That is, since the width that can be measured by the CCD line sensor 5 is limited, the XYθ table 1 is continuously moved in the Y-axis direction to reach the end in the Y-axis direction, as indicated by the broken line arrow in FIG. XYθ table 1 at time
Is stepwise moved in the X-axis direction by the measurement width of the CCD line sensor 5, and the same operation is repeated thereafter to perform measurement scanning of the entire surface of the mask.

Returning to FIG. 1 again. The magnetic desk device 11 stores design data used when forming a pattern on the mask 2 to be inspected. This design data is read out under the control of the control computer 12, sent to the bit pattern generation circuit 13 to be converted into binarized graphic data, and then sent to the data comparison circuit 7.

The data comparison circuit 7 is specifically constructed as shown in FIG. That is, the design data Q binarized by the bit pattern generating circuit 13 is introduced into the multi-valued circuit 14, and the multi-valued circuit 14 performs appropriate filtering to multi-value the data. This is based on the following reasons. The measurement data S is in a state in which a filter acts due to the resolution characteristic of the magnifying optical system 4 and the aperture effect of the CCD line sensor 5. Therefore, the design data Q is filtered in order to match the measurement data S.

Multivalued design data Q and measurement data S
And are introduced into the pre-alignment circuit 15. The pre-alignment circuit 15 aligns the design data Q and the measurement data S with reference to the position information P. And
The aligned design data Q and measurement data S are introduced into the comparison circuit 16. The comparison circuit 16 compares both data according to a predetermined algorithm. The comparison result is stored in the memory 17 together with the position information.

On the other hand, the measured data S is the changeover 1
Via the first memory 19 or the second memory 20
Stored in. The switch 18 is normally held in a neutral position as shown in the figure, and operates by a switch signal R given from the control computer 12 to alternately store the measurement data S in the first memory 19 and the second memory 20. To do.

The switching signal R is given in the following cases. That is, as shown in FIG. 5, on the mask 2 to be inspected, for example, memory cell formation locations are A1, A2, A3.
, ..., these areas A1,
In A2, A3, ..., Usually, patterns having a constant shape are repeatedly arranged. Therefore, when the repeating pattern is accurately formed, the areas A1, A2,
A3, ..., for example, measurement data S1, S1
′, S1 ″ should match.

Therefore, in areas such as areas A1, A2, A3, ... In which patterns of a constant shape are repeatedly arranged, a flag is set so that a start point and an end point of each area arrive in the process of supplying design data. A flag signal is stored in the magnetic disk device 11 in advance, and this flag signal is used as the switching signal R. That is, when the start point of the area A1 arrives, the switch 18 is switched to the first memory 19 side, and the measurement data S1, S2, ...
It is stored in the memory 19 of. Then, when the end point of the area A1 arrives, it is switched to the neutral position. Next, when the start point of the area A2 arrives, the switch 18 is switched to the side of the second memory 20, and the measurement data S1 ', S2', ... Sn of the area A2.
′ Is stored in the second memory 20. The first memory 19 and the second memory 20 actually include two independent storage units A, B and a, b, and the storage units alternately store the measurement data. There is.

In this way, the measurement data S stored in the first memory 19 and the second memory 20 are read out, aligned in the pre-alignment circuit 21, and then compared in the comparison circuit 22. It Then, the comparison result is stored in the memory 23. On the other hand, a determination circuit 24 for determining the presence or absence of a defect using the comparison result stored in the memory 17 and the comparison result stored in the memory 23 is provided. In the case of this example, the determination circuit 24 respects the content of the memory 17 in the area where the pattern of the constant shape is not repeatedly formed, and the content of the memory 23 in the area where the pattern of the constant shape is repeatedly formed, A portion where the deviation of the comparison result is a certain value or more is determined as a defect. The defect information is stored together with the position information in the defect storage device 25 shown in FIG.
Stored in.

Reference numeral 26 in the figure denotes a monitor for displaying the defect data and the design data stored in the defect storage device 25 in different colors, and 27 is for loading the mask to be inspected on the XYθ table 1. An autoloader control circuit is shown, 28 is a table control circuit, and 29 is an autofocus control circuit. Next, the operation of the fully automatic mask inspection device configured as described above will be described.

First, in a region where a pattern of a constant shape is not repeatedly formed, the switch 18 is held at the neutral position, and therefore, the same operation as that of the conventional device is performed. That is, the design data is expanded by the bit pattern generation circuit 13 and enters the multilevel conversion circuit 14. Then, the multi-valued design data Q and the measurement data S actually obtained by measurement enter the pre-alignment circuit 15, and the positional deviation amount is corrected with reference to the position information P, and then the comparison circuit. Sent to 16. The comparison result is stored in the memory 17 together with the position information.

On the other hand, areas A1, A2, A3, shown in FIG.
When the inspection of the repeated portion is started as shown in the drawing, the design data Q and the measurement data S are compared in the same manner as above. In addition, since the switch 18 performs the switching operation each time the start point of each area arrives, the measurement data S1, ...
Of the area A2, the measurement data S1 '... Sn' of the area A2 are stored in the section a of the second memory 20, and the measurement data S1 ", ... Sn" of the area A3 are stored next. The measurement data S is stored in the B section of the memory 19 of No. 1 and thereafter in the same order.

During this period, the measurement data stored in the section A of the first memory 19 and the measurement data stored in the section a of the second memory 20 are read out, and the prealignment circuit 21 positions them. After being matched, the comparison circuit 22 compares them. Then, the comparison result is stored in the memory 23.
It should be noted that when the comparison operation is finished, A of the first memory 19
The measurement data stored in the section is cleared. Then, the measurement data stored in the B section of the first memory 19 and the measurement data stored in the a section of the second memory 20 are read out and aligned by the pre-alignment circuit 21 and then the comparison circuit. 22. Then, the comparison result is stored in the memory 23. At the time when the comparison operation is completed, the measurement data stored in the part a of the second memory 20 is cleared. Hereinafter, similarly, the measurement data of the regions adjacent to each other in the scanning direction are compared with each other.

In this example, the determination circuit 24 uses the memory 17 in the area where the pattern of the constant shape is not repeatedly formed.
The content of the memory 23 is respected in the area where the pattern of the constant shape is repeatedly formed, and the portion where the deviation of the comparison result is equal to or more than the constant value is determined as a defect. Then, the defect information is stored in the defect storage device 25 together with the position information.

The pre-alignment circuit 21 is provided for the following reason. That is, when comparing the measurement data in the area where the pattern of a constant shape is repeatedly formed, as shown in FIG. 5, the coordinate positions corresponding to the individual measurement data when measuring the areas S1, ... Strictly speaking, it is different from the coordinate position corresponding to each measurement data when measuring the area of S1 '... Sn'. In order to correct this discrepancy, the pre-alignment circuit 21 sets the first and second memories 1 before the respective data are compared.
The data of 9 and 20 are taken in, and as an example, pattern matching is performed between a part of the data in the first memory 19 and a part of the data in the second memory 20. (Possible) is calculated, and the positional deviation amount that minimizes the degree of disagreement is calculated to correct the position. It is also possible to input the position data to the pre-alignment circuit 18 as needed.

As described above, in the region where the pattern of the constant shape is not repeatedly formed, the defect information is obtained by comparing the design data and the measurement data as in the conventional device. Further, in a region where a pattern of a constant shape is repeatedly formed, defect information is obtained by comparing the measured data with the measured data. Therefore, even in the case of a sample such as a phase shift mask, in the region where the pattern of a constant shape is repeatedly formed (the region where the phase shifter is provided), the inspection by comparing the measured data with the measured data is required. It can be executed, and the inspection can be performed without the design data of the phase shifter. Similarly, the contact hole portion of the IC element (this portion is repeatedly present) and the like can be satisfactorily inspected. That is, in the case of the contact hole portion, even if there is a slight change in the amount of transmitted light, it is difficult to detect the defect by comparing the design data with the measurement data. However, the comparison inspection of the measurement data can relatively easily detect the difference and can identify the defect.

In the above-described embodiment, the defect determination is performed by using the comparison information between the design data and the measurement data in the area where the pattern of the constant shape is not repeatedly formed, and the pattern of the constant shape is repeatedly formed. In the area, the defect judgment is performed by using the comparison information of the measurement data, but in the area where the pattern of the constant shape is repeatedly formed, the comparison information of the design data and the measurement data and the measurement data A comprehensive defect determination may be performed using the comparison information. In this case, the logical sum of the defects, the logical product, or an appropriate weighting operation (this may be performed by hardware or software)
The defect may be determined depending on whether or not. These selections may be performed by the operator before the inspection or based on preset conditions.

By doing so, the defect detection rate can be further improved. For example, the comparison of the design data with the measurement data reduces the defect detection rate at the corners of the pattern. That is, taking a photomask as an example, the corners of the pattern are already rounded when the mask is manufactured, and this is not a defect in IC manufacturing. Therefore, when comparing the design data and the measurement data, it is necessary to consciously reduce the detection sensitivity of the above portion. However, when comparing the measurement data, it is easy to increase the detection sensitivity because the corners are already rounded.
In this way, it is possible to detect a defect in a pattern by drawing out a method that is good at each defect detection.

In the above-described embodiment, the measurement data of the first repeated portion and the measurement data of the second repeated portion (that is, the nth and the (n + 1) th measurement are performed in the region where the pattern of the constant shape is repeatedly formed. data)
However, for example, the measurement data of the first repeated portion may be fixed as reference data, and this may be compared with the measured data of the repeated portion that is sequentially measured. Further, as the reference data of the repeated portion, the measurement data of the portion where no defect is generated by comparison with the design data may be used as the reference data.

Further, in order to inform the operator that the defect is recognized, the condition and the inspection result may be indicated by a color difference or the like at the time of review, and the difference may be displayed.

[0034]

As described above, according to the present invention, a defect can be detected in a portion where a repetitive pattern does not exist by the same method as in the conventional apparatus, and there is no design data in a portion where the repetitive pattern exists. However, the defect can be detected. Therefore, even in the case of a sample such as a phase shift mask, it is possible to perform a simple and strict inspection without complicating the apparatus.

[Brief description of drawings]

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

FIG. 2 is a diagram for explaining optical scanning of a sample in the same apparatus.

FIG. 3 is a diagram for explaining optical scanning of a sample in the same device.

FIG. 4 is a block diagram of a data comparison circuit in the device.

FIG. 5 is a diagram for explaining a pattern layout example of a sample having a repeating pattern.

[Explanation of symbols]

1 ... XYθ table 2 ... Mask to be inspected 3 ... Light source 4 ... Enlarging optical system 5 ... CCD line sensor 6 ... Sensor circuit 7 ... Data comparison circuit 9 ... Laser length measurement system 10 ... Position circuit 11 ... Magnetic disk device 12 ... Control computer 13 ... Bit pattern generation circuit 14 ... Multi-valued circuit 15, 21 ... Pre-alignment circuit 16, 22 ... Comparison circuit 17, 23 ... Memory 18 ... Switching device 19 ... First memory 20 ... Second memory 24 ... Judgment circuit 25 ... Defect storage device 26 ... Monitor

Claims (3)

[Claims] 1. A measurement data obtained by optically scanning a sample on which an inspection pattern is formed and design data used at the time of forming the inspection pattern on the sample are sequentially compared, and the measurement data is compared. In a pattern defect inspection method for detecting defects in an inspection pattern, in a region where a pattern of a constant shape is repeatedly formed, at least measurement data for each constant region sequentially obtained by the scan or a constant region sequentially obtained by the scan. A pattern defect inspection method, characterized in that an inspection method for obtaining defect information of the pattern to be inspected by comparing the measured data for each minute with the data for the above-mentioned fixed area as a reference. 2. A first inspection for obtaining defect information of the pattern to be inspected by sequentially comparing the measurement data obtained by the scanning and the design data in the region where the pattern of a constant shape is repeatedly formed. The pattern to be inspected by comparing the method and the measured data for each constant area sequentially obtained by the scanning or the measured data for each constant area sequentially obtained by the scanning and the data for the certain area as a reference And a second inspection method for obtaining the defect information, the defect information obtained by the first and second inspection methods is determined based on a predetermined determination criterion. Item 2. The pattern defect inspection method according to Item 1. 3. A measurement data acquisition means for optically scanning a sample on which a pattern to be inspected is formed to obtain actual measurement data of the pattern to be inspected, and a design used when the pattern to be inspected is formed on the sample. Storage means for storing data,
A first defect information acquisition unit that obtains defect information of the pattern to be inspected by comparing the design data read from the storage unit with the measurement data obtained by the measurement data acquisition unit; Means for outputting area information indicating an area in which a pattern of a constant shape is repeatedly formed based on the design data, and when the area information is being output from this means, a fixed area portion obtained sequentially by the scanning Second defect information acquisition means for obtaining defect information of the pattern to be inspected by comparing the measured data for each fixed area obtained sequentially by the above scanning data or the data for each fixed area as a reference with each other. And a means for judging the defect information obtained by the first and second defect information acquisition means based on a predetermined judgment standard. The pattern defect inspection apparatus.