JP2019066207A - Inspection method and inspection device - Google Patents

Abstract

To provide an inspection method and an inspection device, capable of improving an inspection speed without increasing a rotational speed of a rotational phase plate.SOLUTION: An inspection method comprises the steps of: rotating a rotational phase plate crossing a light path of a light source and detecting a rotational direction position of the rotational phase plate; transporting a sample in a column direction of an image pick-up element, irradiating the sample with irradiation light, and imaging an optical image of the sample in an image pick-up element of an i-th column (1≤i≤n) located on an optical path of irradiation light among n-column image pick-up elements; and correcting an amount of light of the optical image of the sample imaged in the image pick-up element of the i-th column on the basis of preliminarily acquired permeability of the rotational phase plate in the rotational direction position detected when the optical image of the sample was imaged in the image pick-up element of the i-th column and preliminarily acquired sensitivity of the image pick-up element of the i-th column.SELECTED DRAWING: Figure 5

Description

  The present invention relates to an inspection method and an inspection apparatus.

  Conventionally, in a pattern inspection apparatus which optically inspects a defect of a pattern provided on a mask used for photolithography, a rotary phase plate is provided in the optical path of laser light between the laser light source and the mask. . The rotational phase plate is disposed substantially perpendicular to the laser light, and is rotated at a predetermined speed in a direction perpendicular to the optical path of the laser light, and the laser light is allowed to pass and change its phase (for example, scattering). It is an optical member that makes the light quantity of laser light uniform. By making the light quantity of the highly coherent laser beam uniform by the rotating phase plate, it is possible to prevent the occurrence of interference fringes in the optical image obtained by imaging the mask illuminated by the laser beam.

  The rotating phase plate is usually made integrally of a transparent or semi-transparent glassy material, but it is difficult to refine it so that the optical characteristics become completely uniform, so the minute transmittance over the entire surface Unevenness occurs. Therefore, the transmittance of the laser beam passing through the rotary phase plate changes minutely by rotating the rotary phase plate, and the light amount of the laser beam reaching the inspection area of the mask is synchronized with the rotation of the rotary phase plate. Increase or decrease. In the high sensitivity defect inspection, there is a possibility that a false defect is detected in the optical image and the inspection accuracy is deteriorated due to the change of the light amount accompanying the rotation of the rotary phase plate.

  Conventionally, in order to suppress the detection of false defects, the amount of light caused by the rotational phase plate is matched by matching the charge accumulation period of the TDI (Time Delay Integration) sensor that captures an optical image with the rotational period of the rotational phase plate. Unevenness was averaged for one cycle at the time of storage of the TDI sensor. In this method, for the optical image captured in any accumulation cycle, the total amount of light used for imaging is made constant to suppress the pseudo defect.

JP, 2009-168524, A

  When matching the accumulation period of the TDI sensor with the rotation period of the rotation phase plate, if the accumulation speed of the TDI sensor is increased to speed up the inspection speed, the rotation speed of the rotation phase plate is increased in proportion to this. There is a need to. However, as described above, since the rotational phase plate is made of a glass-like material, the rotational phase plate is broken by the centrifugal force when the rotational speed is rotated at high speed. For this reason, it is difficult to rotate the rotary phase plate at a speed higher than the present speed in order to increase the inspection speed.

  Therefore, conventionally, there has been a problem that it is difficult to improve the inspection speed without increasing the rotational speed of the rotational phase plate.

  An object of the present invention is to provide an inspection method and an inspection apparatus capable of improving the inspection speed without increasing the rotational speed of the rotary phase plate.

The inspection method which is one aspect of the present invention is
A light source for emitting light toward the sample provided with the pattern;
A plurality of recesses having an irregular depth are disposed between the light source and the sample so as to intersect the light path of the light source, and the plurality of recesses are emitted from the light source while rotating so as to intersect the light path of the light source A rotating phase plate that allows light to pass through the plurality of recesses to substantially equalize the amount of light;
An inspection method for inspecting a pattern defect using an inspection apparatus comprising: an n-row image sensor for capturing an optical image of a sample by irradiation light irradiated onto the sample through the rotary phase plate;
Rotating the rotational phase plate to detect the rotational direction position of the rotational phase plate intersecting the light path of the light source;
The sample is transported in the column direction of the imaging device, and the sample is irradiated with irradiation light, and the imaging device of the i-th row (1 ≦ i ≦ n) positioned on the optical path of the irradiation light among the n imaging devices Capturing an optical image;
The transmittance of the rotational phase plate acquired in advance at the rotational direction position of the rotational phase plate detected when the optical image of the sample is captured by the imaging device in the i-th column, and the imaging element of the i-th row acquired in advance And correcting the amount of light of the optical image of the sample imaged by the imaging element in the i-th column based on the sensitivity of

In the above-mentioned inspection method,
The step of correcting the light amount of the optical image of the sample may be in accordance with the following equation (1).
Ci = Csi / (Ti × Ki) (1)
Where Ci is the amount of light after correction of the optical image of the sample taken by the imaging device in the i-th column, and Csi is the amount of light before correction of the optical image of the sample taken by the imaging device in the i-th column Ti is the transmittance of the rotational phase plate at the rotational position of the rotational phase plate detected when the optical image of the sample is captured by the imaging device in the i-th row, and Ki is the imaging of the i-th row It is a coefficient proportional to the sensitivity of the element (the same applies hereinafter).

In the above-mentioned inspection method,
The step of capturing an optical image of the sample is a step of capturing an optical image of the sample sequentially by the imaging elements of n rows while transporting the sample in the row direction of the imaging element,
The step of correcting the light amount of the optical image of the sample is a step of correcting the light amount of each of the optical images of the sample sequentially imaged by the imaging elements of the n rows,
The inspection method is
The method may further include the step of acquiring the final light amount of the optical image of the sample by adding the corrected light amounts of the optical images of the sample sequentially captured by the imaging elements of the n rows.

In the above-mentioned inspection method,
The step of acquiring the light intensity of the final optical image of the sample may be in accordance with the following equation (2).

The inspection apparatus which is one aspect of the present invention is
A light source for emitting light toward the sample provided with the pattern;
A plurality of recesses having an irregular depth are disposed between the light source and the sample so as to intersect the light path of the light source, and the plurality of recesses are emitted from the light source while rotating so as to intersect the light path of the light source A rotating phase plate that allows light to pass through the plurality of recesses to substantially equalize the amount of light;
An inspection device for inspecting a defect in a pattern, comprising: a sensor having n rows of imaging elements for capturing an optical image of a sample by irradiation light irradiated onto the sample through the rotating phase plate;
A rotational direction position detection unit that detects the rotational direction position of the rotational phase plate that intersects the light path of the light source while the rotational phase plate rotates;
A light quantity correction unit that corrects the light quantity of the optical image of the sample imaged by the sensor;
In the sensor, when the sample is transported in the column direction of the imaging device and the sample is irradiated with the irradiation light through the rotational phase plate, the i-th row (1 ≦ An optical image of the sample is taken by the imaging device of i ≦ n),
The light quantity correction unit includes the transmittance of the rotational phase plate acquired in advance at the rotational direction position of the rotational phase plate detected when the optical image of the sample is captured by the imaging element in the i-th row, and the i acquired in advance The light amount of the optical image of the sample imaged by the i-th imaging device is corrected based on the sensitivity of the imaging device in the i-th column.

  According to the present invention, the inspection speed can be improved without increasing the rotational speed of the rotational phase plate.

It is a figure showing the pattern inspection device by this embodiment. In a pattern inspection device by this embodiment, it is a fragmentary sectional view of a rotation phase plate which met a rotation direction. In the pattern inspection device by this embodiment, it is a schematic diagram showing the 1st sensor. In the pattern inspection device by this embodiment, it is a top view showing a rotation phase plate and a rotation direction position detection part. It is a flowchart which shows the pattern inspection method by this embodiment. It is a perspective view which shows the pattern inspection method by this embodiment. It is an explanatory view for explaining a pattern inspection method by this embodiment. In the pattern inspection method by this embodiment, it is a graph which shows the transmittance | permeability of the rotational phase plate corresponding to the rotation direction position of a rotational phase plate, and the sensitivity of the image pick-up element of each row | line of a 1st sensor.

  Hereinafter, embodiments according to the present invention will be described with reference to the drawings. This embodiment does not limit the present invention.

  FIG. 1 is a view showing a pattern inspection apparatus 1 according to the present embodiment as an example of an inspection apparatus. The pattern inspection apparatus 1 of FIG. 1 can be used to inspect a defect of a pattern provided on a mask 2 which is an example of a sample.

  As shown in FIG. 1, the pattern inspection apparatus 1 includes a light source 3 and a first sensor 5A and a second sensor 5B which are examples of sensors. The light source 3 emits laser light (hereinafter also referred to simply as light) toward the mask 2 provided with a pattern. The first sensor 5A and the second sensor 5B capture an image (hereinafter also referred to as an optical image) of the mask 2 illuminated by the light emitted from the light source 3 to the mask 2. Specifically, the first sensor 5A captures an optical image of the mask 2 illuminated by transmitting the light emitted from the light source 3 to the mask 2 by the mask 2. The second sensor 5 </ b> B captures an optical image of the mask 2 illuminated by causing the mask 2 to reflect the light emitted from the light source 3 to the mask 2.

  The pattern inspection apparatus 1 further includes a condensing lens 41, a collimating lens 42, a rotational phase plate 43, and an optical path on the light path between the light source 3 and the first sensor 5A. A first beam splitter 44, a first mirror 45, a first objective lens 46, an XYθ table 6, a second objective lens 47, a second beam splitter 48, and a first imaging lens 49A.

  The pattern inspection apparatus 1 further includes a condensing lens 41, a collimating lens 42, a rotational phase plate 43, and an optical path on the light path between the light source 3 and the second sensor 5B. The first beam splitter 44, the second mirror 410, the second beam splitter 48, the XYθ table 6, and the second imaging lens 49B are provided.

  The condenser lens 41 condenses the light emitted from the light source 3.

  The collimating lens 42 collimates the light collected by the collecting lens 41.

  The rotary phase plate 43 is disposed substantially perpendicular to the light path on the light path between the light source 3 and the mask 2 so as to partially intersect the light path of the light source 3. In the example of FIG. 1, the rotational phase plate 43 is disposed between the collimating lens 42 and the first beam splitter 44. The rotary phase plate 43 has a disk shape in plan view (see FIG. 4), and is rotationally driven around the central axis by a drive device 7 such as a motor connected on the central axis.

  FIG. 2 is a partial cross-sectional view of the rotational phase plate 43 along the rotational direction d in the pattern inspection apparatus 1 according to the present embodiment. As shown in FIG. 2, the rotary phase plate 43 is provided with a plurality of recesses 431 having irregular depth, width (dimension in the rotational direction d) and depth (dimension in the radial direction) along the rotational direction d. It is done. Each recess 431 changes the phase of the light emitted from the light source 3 according to the depth.

  The rotating phase plate 43 rotates so that the portion intersecting the light path of the light source 3 changes, passes the light emitted from the light source 3 through the recess 431 intersecting the light path, and changes the phase of the light. That is, the rotating phase plate 43 passes the light emitted from the light source 3 to the plurality of recesses 431 while rotating so that the plurality of recesses 431 intersect the optical path of the light source 3 and makes the light quantity uniform.

  The first beam splitter 44 splits the light having passed through the rotary phase plate 43 into the first mirror 45 side and the second mirror 410 side.

  Here, first, an optical system on the transmission side of the first beam splitter 44 will be described in detail. The first mirror 45 reflects the light transmitted through the first beam splitter 44 toward the first objective lens 46.

  The first objective lens 46 condenses the light reflected by the first mirror 45 and irradiates it onto the XYθ table 6. The XYθ table 6 has an XY plane 6 a on which the mask 2 can be placed. The XYθ table 6 is movable in the X and Y directions and rotatable about the Z axis perpendicular to the XY plane 6a. The mask 2 placed on the XYθ table 6 transmits the irradiation light emitted from the first objective lens 46. The transmitted light of the mask 2 illuminates the mask 2. The transmitted light of the mask 2 passes through the second objective lens 47 and the second beam splitter 48, and then enters the first imaging lens 49A.

  The first imaging lens 49A focuses the transmitted light of the mask 2 on the first sensor 5A.

  FIG. 3 is a schematic view showing the first sensor 5A in the pattern inspection apparatus 1 according to the present embodiment. Although not shown, the second sensor 5B also has the same configuration as the first sensor 5A. The first sensor 5A has n imaging elements 51 for capturing an optical image of the mask 2 by the irradiation light emitted from the light source 3 to the mask 2 through the rotary phase plate 43.

  In the example of FIG. 3, the column direction of the imaging element 51 is the X direction. The imaging elements 51 in the same column are disposed in the Y direction. The imaging element 51 receives the light that has illuminated the mask 2 and photoelectrically converts the light, thereby capturing an optical image of the mask 2.

  More specifically, in the first sensor 5A and the second sensor 5B, the mask 2 is transported by the XYθ table 6 in the X direction, which is the column direction of the imaging device 51, and light is transmitted from the light source 3 to the mask 2 through the rotational phase plate 43 When the light is irradiated, the optical image of the mask 2 is picked up by the imaging element 51 of the i-th row (1.ltoreq.i.ltoreq.n) located on the optical path of the irradiation light irradiated to the mask 2 among the imaging elements 51 of n rows Take an image. The first sensor 5A and the second sensor 5B sequentially capture an optical image of the mask 2 with the imaging elements 51 in n rows in accordance with the progress of the transport of the mask 2 in the X direction.

  The imaging device 51 is, for example, a charge coupled device (CCD). The first sensor 5A may be a TDI sensor in which the column direction of the imaging device 51 is the accumulation direction (that is, the transfer direction) of charges obtained by photoelectric conversion of the optical image of the mask 2. The number n of columns of the imaging device 51 may be 1024, for example.

  Next, the optical system on the reflection side of the first beam splitter 44 will be described in detail. The second mirror 410 reflects the light reflected by the first beam splitter 44 toward the second beam splitter 48.

  The second beam splitter 48 reflects the light reflected by the second mirror 410 to the second objective lens 47 side.

  The second objective lens 47 condenses the light reflected by the second beam splitter 48 and irradiates the mask 2 on the XYθ table 6 with the light. The mask 2 reflects the illumination light emitted from the second objective lens 47. The light reflected from the mask 2 illuminates the mask 2. The reflected light of the mask 2 is transmitted through the second objective lens 47 and the second beam splitter 48, and then enters the second imaging lens 49B.

  The second imaging lens 49 </ b> B focuses the reflected light of the mask 2 on the second sensor 5 </ b> B. The second sensor 5B captures an optical image of the mask 2 in the same manner as the first sensor 5A.

  Defects in the pattern of the mask 2 are inspected based on the optical image of the mask 2 captured by the first sensor 5A and the second sensor 5B.

  A light attenuating filter and a wave plate for changing the polarization direction of light may be provided between the light source 3 and the first beam splitter 44.

  Further, as shown in FIG. 1, the pattern inspection apparatus 1 includes a rotational direction position detection unit 8, an autoloader 9, an X axis motor 10A, a Y axis motor 10B and a θ axis motor 10C, and a laser length measuring system 11. A Z sensor 12 and a focusing mechanism 13 are provided.

  FIG. 4 is a plan view showing the rotary phase plate 43 and the rotational direction position detection unit 8 in the pattern inspection apparatus 1 according to the present embodiment. The rotational direction position detection unit 8 detects the rotational direction position of the rotational phase plate 43 intersecting the light path of the light source 3 while the rotational phase plate 43 rotates in the rotational direction d.

  In the example of FIG. 4, the optical axis OA of the light source 3 is representatively shown on the rotary phase plate 43 as an optical path intersecting the rotary phase plate 43. The rotational phase plate 43 may detect, for example, the rotational direction position of the rotational phase plate 43 intersecting the optical axis OA. In the example of FIG. 4, the rotational direction position detection unit 8 optically detects the slit SL formed in the rotational phase plate 43, and the elapsed time after detecting the slit SL, and the rotational phase plate acquired in advance The rotational direction position of the rotational phase plate 43 is detected based on the rotational speed of 43. The rotational direction position detection unit 8 is not limited to the configuration shown in FIG. 4 as long as it can detect the rotational direction position of the rotational phase plate 43 intersecting the light path of the light source 3.

  The rotational direction position detection unit 8 may be an incremental type rotary encoder or an absolute type rotary encoder. The rotational direction position detection unit 8 outputs the detected rotational direction position of the rotational phase plate 43 to a comparison circuit 25 described later.

  The autoloader 9 shown in FIG. 1 automatically conveys the mask 2 onto the XYθ table 6. The X-axis motor 10A, the Y-axis motor 10B, and the θ-axis motor 10C move the XYθ table 6 in the X direction, the Y direction, and the θ direction, respectively. The light of the light source 3 is scanned with respect to the mask 2 on the XYθ table 6 by moving the XYθ table 6. The laser length measuring system 11 detects the position of the XYθ table 6 in the X direction and the Y direction.

  The Z sensor 12 detects the height of the mask surface which is the surface of the mask 2 on the pattern side, that is, the position in the Z direction. The Z sensor 12 may include, for example, a light projector that emits light to the mask surface, and a light receiver that receives the emitted light.

  The focusing mechanism 13 performs focusing to bring the illumination optical system 5 into focus on the mask surface. Focusing is performed, for example, by moving the XYθ table 6 in the Z direction by a movement amount corresponding to the height of the mask surface detected by the Z sensor 12.

  Further, as shown in FIG. 1, the pattern inspection apparatus 1 includes various circuits connected to the bus 14. Specifically, the pattern inspection apparatus 1 includes an autoloader control circuit 15, a table control circuit 17, and an autofocus control circuit 18. The pattern inspection apparatus 1 further includes a position circuit 22, an expansion circuit 23, a reference circuit 24, and a comparison circuit 25 which is an example of a light amount correction unit. The pattern inspection apparatus 1 further includes a sensor circuit 19 which is connected between the first sensor 5 A and the second sensor 5 B and the comparison circuit 25.

  The autoloader control circuit 15 automatically conveys the mask 2 onto the XYθ table 6 by controlling the autoloader 9.

  The table control circuit 17 causes light from the light source 3 to the inspection area 201 along stripes 202 which virtually divide the inspection area 201 (see FIG. 6) of the mask 2 (see FIG. 6) to be inspected for pattern defects. Control to scan. Specifically, the table control circuit 17 drives and controls the motors 10A to 10C to move the XYθ table 6 so that the light from the light source 3 is scanned in the inspection area 201 along the stripe 202.

  The autofocus control circuit 18 automatically focuses the light of the light source 3 on the mask surface by controlling the focusing mechanism 13 in accordance with the height of the mask surface detected by the Z sensor 12.

  The sensor circuit 19 takes in an optical image photoelectrically converted by the first sensor 5A and the second sensor 5B, and A / D converts the taken optical image. Then, the sensor circuit 19 outputs the A / D converted optical image to the comparison circuit 25. The sensor circuit 19 may be, for example, a TDI sensor circuit. The pattern can be imaged with high accuracy by using the TDI sensor.

  The laser length measuring system 11 detects the movement position of the XYθ table 6, and outputs the detected movement position to the position circuit 22. The position circuit 22 detects the position of the mask 2 on the XYθ table 6 based on the movement position input from the laser measurement system 11. Then, the position circuit 22 outputs the detected position of the mask 2 to the comparison circuit 25.

  The expansion circuit 23 reads design data collected by the magnetic disk drive 31 described later from the magnetic disk drive 31, and converts the read design data into binary or multilevel image data. Then, the expansion circuit 23 outputs the converted image data to the reference circuit 24.

  The reference circuit 24 appropriately filters the image data input from the expansion circuit 23 to generate a reference image used for the defect inspection of the mask 2. Then, the reference circuit 24 outputs the generated reference image to the comparison circuit 25.

  The comparison circuit 25 inspects a defect of the pattern formed on the mask 2 based on comparison of the optical image of the mask 2 input from the sensor circuit 19 and the reference image input from the reference circuit 24. For example, the comparison circuit 25 measures the line width of each position of the pattern of the optical image while using the position information input from the position circuit 22, and the pattern of the measured optical image and the pattern input from the reference circuit 24 The line widths and tone values (brightness) of the patterns of the reference image are compared with each other. Then, the comparison circuit 25 detects, for example, an error between the line width of the pattern of the optical image and the line width of the pattern of the reference image as a defect of the pattern.

  In addition, before the comparison circuit 25 compares the optical image of the mask 2 captured by the first sensor 5A and the second sensor 5B with the reference image, the comparison circuit 25 generates the mask 2 caused by the unevenness of the minute transmittance of the rotary phase plate 43. The light amount of the optical image of the mask 2 is corrected so that the unevenness of the light amount of the optical image is not detected as a false defect. Further, the comparison circuit 25 keeps the rotational speed of the rotational phase plate 43 the same as before even if the defect inspection speed, ie, the conveyance speed of the mask 2 in the X direction by the XYθ table 6 is higher than before. The light amount of the optical image of the mask 2 is appropriately corrected.

  Specifically, the comparison circuit 25 acquires in advance the transmittance of the rotary phase plate 43 corresponding to each of the rotational direction positions of the rotary phase plate 43. In addition, the comparison circuit 25 acquires in advance the sensitivities of the imaging elements 51 in n rows of the first sensor 5A and the second sensor 5B. For example, the comparison circuit 25 may store the transmittance and the sensitivity in its own storage area, or can read the transmittance and the sensitivity from an external storage device (for example, a magnetic disk device 31 described later). May be

  Then, the comparison circuit 25 calculates the transmittance of the rotational phase plate 43 at the rotational direction position detected by the rotational direction position detection unit 8 when the optical image of the mask 2 is captured by the imaging device 51 in the i-th row; Based on the sensitivity of the imaging element 51 in the column, the light amount of the optical image of the mask 2 imaged by the imaging element in the i-th column is corrected.

  Note that although the imaging element 51 in the i-th column includes a plurality of imaging elements 51, the correction of the light amount of the optical image of the mask 2 is performed by individual imaging elements 51 (that is, pixels) included in the i-th column It takes place every time.

  Thus, the light amount of the optical image is corrected based on the transmittance of the rotational phase plate 43 when the optical image is captured by the imaging device 51 in the i-th row and the sensitivity of the imaging device 51 in the i-th row. Thus, the amount of light can be properly corrected without rotating the rotational phase plate 43 at a high speed so that the imaging periods of all the imaging elements 51 in n columns and the rotational period of the rotational phase plate 43 are synchronized.

  As a result, it is possible to improve the speed of high-accuracy inspection in which detection of pseudo defects is suppressed without increasing the rotational speed of the rotational phase plate 43.

The comparison circuit 25 may correct the light amount of the optical image of the mask 2 captured by the imaging device 51 in the i-th row according to the following formula (1).
Ci = Csi / (Ti × Ki) (1)
However, Ci is the light quantity after correction of the optical image of the mask 2 imaged by the imaging element 51 in the i-th row. Csi is the light amount before correction of the optical image of the mask 2 captured by the imaging device 51 in the i-th row. Ti is the transmittance of the rotational phase plate 43 at the rotational direction position of the rotational phase plate 43 detected when the optical image of the mask 2 is captured by the imaging device 51 in the i-th row. Ki is a coefficient proportional to the sensitivity of the imaging device 51 in the i-th row (the same applies hereinafter). Ki may be the sensitivity itself of the imaging element 51 in the i-th row.

  By correcting the light amount according to Equation (1), the reduction amount of the light amount due to the correction is obtained by dividing the light amount by the large transmittance or sensitivity for an optical image in which the light amount is large because the transmittance or sensitivity is large. It can be enlarged. On the contrary, for an optical image in which the light amount is small because the transmittance or the sensitivity is small, the reduction amount of the light amount due to the correction can be reduced by dividing the light amount by the small transmittance or the sensitivity. As a result, as long as the optical image does not include a true defect, it is possible to average the corrected light amount of the optical image of the mask 2 captured by the imaging device 51 of each row. As a result, it is possible to suppress the unevenness of the light amount due to the transmittance and the sensitivity, so it is possible to more effectively prevent the pseudo defects and to further enhance the inspection accuracy.

  Further, the comparison circuit 25 obtains the final light amount of the optical image of the mask 2 by adding the corrected light amounts of the optical images of the mask 2 sequentially captured by the imaging elements 51 in n columns.

  Thus, the light amount obtained by adding the light amount corrected for each imaging element 51 of each row is acquired as the light amount of the optical image of the final mask 2 and the optical image of the acquired light amount is compared with the reference image The true defect can be detected with high accuracy while suppressing the detection of the false defect.

The comparison circuit 25 may obtain the final light intensity of the optical image of the mask 2 according to the following equation (2).

  By using Equation (2), the final light quantity of the optical image of the mask 2 can be easily and quickly acquired.

  In addition to the above configuration, as shown in FIG. 1, the pattern inspection apparatus 1 includes a control computer 30, a magnetic disk drive 31, a magnetic tape drive 32, a floppy disk (registered trademark) 33, a CRT 34, and a printer 35. And All of these components 30 to 35 are connected to the bus 14.

  The control computer 30 executes various controls and processes related to defect inspection for each component connected to the bus 14. The magnetic disk drive 31 stores design data of the mask 2. The magnetic tape device 32 and the floppy disk 33 store various types of information related to defect inspection. The CRT 34 displays various images related to defect inspection. The printer 35 prints various information related to defect inspection.

  As described above, according to the pattern inspection apparatus 1 of the present embodiment, the transmission of the rotational phase plate 43 at the rotational direction position detected when the optical image of the mask 2 is captured by the imaging device 51 in the i-th row The light amount of the optical image of the sample imaged by the i-th imaging device can be corrected based on the ratio and the sensitivity of the i-th imaging device 51. As a result, the inspection speed can be improved without increasing the rotational speed of the rotational phase plate 43.

(Pattern inspection method)
Next, a pattern inspection method of the present embodiment to which the pattern inspection apparatus 1 of FIG. 1 is applied will be described. FIG. 5 is a flowchart showing the pattern inspection method according to the present embodiment. The flowchart of FIG. 5 is repeated as necessary. FIG. 6 is a perspective view showing a pattern inspection method according to the present embodiment. As shown in FIG. 6, the inspection area 201 on the mask 2 is virtually divided into a plurality of strip-like stripes 202. The first sensor 5 </ b> A and the second sensor 5 </ b> B image the mask 2 for each stripe 202 as the XYθ table 6 moves. At this time, the table control circuit 17 controls the operation of the XYθ table 6 so that each stripe 202 is scanned continuously in the direction indicated by the broken line arrow in FIG. While moving the XYθ table 6, a defect in the pattern on the stripe 202 is inspected based on the optical image captured by the first sensor 5A and the second sensor 5B.

  In the inspection of the defect, the comparison circuit 25 corrects the light amount of the optical image of the mask 2 according to the flowchart of FIG.

  Specifically, first, the driving device 7 starts rotational driving of the rotational phase plate 43, and the rotational direction position detection unit 8 starts detection of the rotational direction position of the rotational phase plate 43 intersecting the light path of the light source 3. (Step S1).

  After detection of the rotational direction position of the rotational phase plate 43 is started, the mask 2 is transported in the column direction of the imaging device 51 by the XYθ table 6 and light is irradiated from the light source 3 through the rotational phase plate 43 to the mask 2 An optical image of the mask 2 is sequentially captured by the imaging elements 51 in a row.

  Specifically, first, the first sensor 5A and the second sensor 5B capture an optical image of the mask 2 by the imaging element 51 in the i-th row (step S2).

  FIG. 7 is an explanatory view for explaining a pattern inspection method according to the present embodiment. For example, as shown in FIG. 7, the imaging elements 51 of 1024 columns (only 3 columns are representatively shown in FIG. 7) are masks 2 in the column direction (X direction) of the imaging elements 51 by the XYθ table 6. The optical image of the mask 2 is captured sequentially from the imaging device 51 in the first row in accordance with the conveyance of the image.

  In the example of FIG. 7, the mask 2 includes an area A, an area B, and an area C in order from the top side in the transport direction. The imaging element 51 of each column captures an image a of the area A, an image b of the area B, and an image c of the area C sequentially from the first column. Further, as shown in FIG. 7, when the image a is captured by the imaging device 51 in the second row, the image b is captured by the imaging device 51 in the first row. When the image a is captured by the imaging element 51 in the third column, the image b is captured by the imaging element 51 in the second column, and the image c is captured by the imaging element 51 in the first column. When the example of FIG. 7 is applied to FIG. 5, first, the first sensor 5A and the second sensor 5B capture an image a by the imaging element 51 in the first row (step S2).

  As shown in FIG. 5, after the optical image of the mask 2 is captured by the imaging element 51 in the i-th column, the comparison circuit 25 detects the optical image of the mask 2 by the imaging element 51 in the i-th column The transmittance Ti of the rotational phase plate 43 at the rotational direction position detected by the rotational direction position detection unit 8 is acquired (step S3). Further, the comparison circuit 25 obtains a coefficient Ki that is proportional to the sensitivity of the imaging device 51 in the i-th row (step S3).

  FIG. 8 is a graph showing the transmittance of the rotational phase plate 43 corresponding to the position of the rotational phase plate 43 in the rotational direction and the sensitivity of the image sensor 51 of each row of the first sensor 5A in the pattern inspection method according to the present embodiment. It is. The transmittance and sensitivity of the rotary phase plate 43 corresponding to the second sensor 5B are the same as those in FIG. FIG. 8 illustrates the transmittance of the rotational phase plate 43 and the sensitivity of the imaging device 51 stored in advance in the storage area of the comparison circuit 25 or the external storage device. The transmittance of the rotational phase plate 43 is associated with the rotational direction position of the rotational phase plate 43. Further, the sensitivity of the imaging device 51 is associated with the column number (that is, the step number) of the imaging device 51.

  In FIG. 8, the transmittance of the rotational direction position detected at the start of the imaging period and the imaging period for each of the images a, b, and c in order to express the temporal correspondence relationship between the transmittance and the imaging element sensitivity. The sensitivity of the imaging element in the first column that performs imaging at the start of is connected by a broken line. In addition, the transmittance of the rotational direction position detected at the end of the imaging period and the sensitivity of the imaging element of the 1024th column that performs imaging at the end of the imaging period are connected by a broken line.

  When the example of FIG. 8 is applied to FIG. 5, first, the comparison circuit 25 transmits the light corresponding to the rotational direction position (for example, 0 [rad]) when the image a is captured by the imaging device 51 in the first column. The factor T1 and the coefficient K1 proportional to the sensitivity of the imaging device 51 in the first column are acquired (step S3).

After acquiring the transmittance Ti of the rotational phase plate 43 and the coefficient Ki proportional to the sensitivity of the imaging device 51, the comparison circuit 25 performs the following expression on the light intensity of the optical image of the mask 2 captured by the imaging device 51 in the i-th row The correction is made according to (step S4).
Ci = Csi / (Ti × Ki) (1)

  When the example of FIG. 7 is applied to FIG. 5, the comparison circuit 25 corrects the light amount Cs1a of the image a captured by the imaging device 51 in the first column to obtain the corrected light amount Cs1a / (T1 × K1). Do.

  After correcting the light amount of the optical image of the mask 2 imaged by the imaging device 51 in the i-th row, the comparison circuit 25 performs the correction of the optical image of the mask 2 imaged by the imaging device 51 in n-th row (that is, all rows). It is determined whether the correction of the light amount is completed (step S5).

  When the correction of the light amount of the optical image of the mask 2 captured by the imaging elements 51 in n rows is completed (step S5: Yes), the comparison circuit 25 calculates the final light amount of the optical image of the mask 2 according to the following equation. Calculate (step S6).

When the example of FIG. 7 is applied to FIG. 5, the comparison circuit 25 calculates the final light quantity of the image a by the following formula (2a).

Further, the comparison circuit 25 calculates the final light amount of the image b by the following formula (2b).

Further, the comparison circuit 25 calculates the final light amount of the image c by the following formula (2c).

  As long as there is no true defect in the regions A to C, the values of the equations (2a) to (2c) are substantially equal to one another. Therefore, detection of a false defect can be prevented by inspecting the defect using the values of Formula (2a) to Formula (2c).

  On the other hand, when the correction of the light amount of the optical image of the mask 2 imaged by the imaging elements 51 in n rows is not completed (step S5: No), the comparison circuit 25 compares the light amount of the optical image of the mask 2 in the next row. It shifts to calculation (step S7, step S2).

  As described above, according to the present embodiment, the transmittance corresponding to the rotational direction position of the rotational phase plate 43 detected when the optical image of the mask 2 is captured by the imaging device 51 in the i-th row; The amount of light of the optical image of the sample imaged by the i-th imaging device can be corrected based on the sensitivity of the i-th imaging device 51. As a result, the inspection speed can be improved without increasing the rotational speed of the rotational phase plate 43.

  At least a part of the pattern inspection apparatus 1 may be configured by hardware or may be configured by software. When configured by software, a program for realizing at least a part of the function of the pattern inspection apparatus 1 may be stored in a recording medium such as a flexible disk or a CD-ROM, and read by a computer for execution. The recording medium is not limited to a removable medium such as a magnetic disk or an optical disk, and may be a fixed recording medium such as a hard disk drive or a memory.

  The embodiments described above are presented as examples and are not intended to limit the scope of the invention. The embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the invention described in the claims and the equivalents thereof as well as included in the scope and the gist of the invention.

1 pattern inspection device 2 mask 3 light source 43 rotating phase plate

Claims (5)

A light source for emitting light toward the sample provided with the pattern;
A plurality of recesses having an irregular depth are disposed between the light source and the sample so as to intersect the light path of the light source, and the plurality of recesses are rotated so as to intersect the light path of the light source A rotating phase plate that passes the light emitted from the light source to the plurality of concave portions to substantially equalize the light amount of the light;
And a sensor having an n-line image pickup element for capturing an optical image of the sample by the irradiation light irradiated to the sample through the rotary phase plate, and an inspection method for inspecting a defect of the pattern using an inspection apparatus There,
Rotating the rotational phase plate to detect the rotational direction position of the rotational phase plate intersecting the light path of the light source;
The sample is transported in the column direction of the imaging device, the irradiation light is irradiated to the sample, and the i-th row (1 ≦ i ≦ n) positioned on the optical path of the irradiation light among the n rows of imaging devices Imaging an optical image of the sample with the imaging device of
The transmittance of the rotational phase plate acquired in advance at the rotational direction position of the rotational phase plate detected when the optical image of the sample is imaged by the imaging device in the i-th row, and the i acquired in advance Correcting the amount of light of the optical image of the sample imaged by the i-th imaging device based on the sensitivity of the imaging devices in the first column. The inspection method according to claim 1, wherein the step of correcting the light amount of the optical image of the sample follows the following equation (1).
Ci = Csi / (Ti × Ki) (1)
Where Ci is the amount of light after correction of the optical image of the sample taken by the imaging device in the i-th column, and Csi is the amount of light before correction of the optical image of the sample taken by the imaging device in the i-th column Ti is the transmittance of the rotational phase plate at the rotational position of the rotational phase plate detected when the optical image of the sample is captured by the imaging device in the i-th row, and Ki is the imaging of the i-th row It is a coefficient proportional to the sensitivity of the element (the same applies hereinafter). The step of capturing an optical image of the sample is a step of capturing an optical image of the sample sequentially by the imaging elements of the n rows while transporting the sample in the column direction of the imaging element,
The step of correcting the light amount of the optical image of the sample is a step of correcting the light amount of each of the optical image of the sample, which is sequentially imaged by the n rows of imaging elements,
The inspection method is
The method further includes the step of acquiring the final light amount of the optical image of the sample by adding the corrected light amounts of the optical images of the sample sequentially captured by the n rows of imaging elements. Or the inspection method as described in 2. The inspection method according to claim 3, wherein the step of acquiring the final light intensity of the optical image of the sample is performed according to the following equation (2).

A light source for emitting light toward the sample provided with the pattern;
A plurality of recesses having an irregular depth are disposed between the light source and the sample so as to intersect the light path of the light source, and the plurality of recesses are rotated so as to intersect the light path of the light source A rotating phase plate that passes the light emitted from the light source to the plurality of concave portions to substantially equalize the light amount of the light;
A sensor having n rows of imaging elements for capturing an optical image of the sample from the irradiation light irradiated to the sample through the rotating phase plate, the inspection apparatus inspecting a defect in the pattern,
A rotational direction position detection unit that detects the rotational direction position of the rotational phase plate that intersects the light path of the light source while the rotational phase plate rotates;
A light quantity correction unit that corrects the light quantity of the optical image of the sample captured by the sensor;
In the sensor, when the sample is transported in the column direction of the imaging element and the sample is irradiated with the irradiation light through the rotational phase plate, the sensor is placed on the optical path of the irradiation light among the n imaging elements. An optical image of the sample is captured by the imaging element of the i-th row (1 ≦ i ≦ n) located,
The light quantity correction unit is a transmittance of the rotational phase plate obtained in advance in the rotational direction position of the rotational phase plate detected when an optical image of the sample is captured by the imaging device in the i-th row; The inspection apparatus which corrects the light quantity of the optical image of the sample picturized with the imaging device of the i-th row based on the sensitivity of the imaging device of the i-th row acquired beforehand.

Images