JP2014090163A - Defective evaluation method for euv mask and manufacturing method for euv mask - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make UV mask manufacture efficient by acquiring an optimum pattern layout before patterning of an EUV mask and then reducing a correcting operation for a part having a phase defect.SOLUTION: A defective evaluation method for an EUV mask includes the steps of: acquiring position information on a phase defect and luminance profile information for an EUV blank; measuring an outermost surface of the phase defect in three dimensions; estimating an internal state of the phase defect through simulation; temporarily determining a pattern layout in which the phase defect is positioned under an absorption layer pattern; calculating a transfer pattern by carrying out exposure simulation using a three-dimensional shape and a propagation parameter of the phase defect with respect to the temporarily determined pattern layout; determining the pattern layout by evaluating a phase defect part of the transfer pattern calculated through the exposure simulation; and generating the EUV mask.

Description

  In the defect evaluation method of EUV (Extreme Ultra Violet) mask and the manufacturing method of EUV mask, the present invention can more efficiently evaluate the defect of EUV mask by verifying the influence of phase defect on pattern transfer with high accuracy. The present invention relates to a method capable of manufacturing an EUV mask.

  In order to cope with pattern miniaturization of semiconductor devices, the exposure wavelength has been shortened, and an exposure apparatus of 193 nm ArF (argon fluoride) laser is currently used in mass production. In addition, development of an exposure apparatus using 13.5 nm EUV light has been energetically advanced for further shortening of the wavelength.

  EUV light of 13.5 nm is absorbed by all substances. Therefore, the photomask for transferring the device pattern to the wafer is not a conventional transmission type but a reflection type. The light reflection type EUV mask uses a low thermal expansion glass called LTEM as a substrate, and a multilayer film of 40 pairs of molybdenum (Mo) (layer thickness 3 nm) and silicon (Si) (layer thickness 4 nm) is formed thereon. . And the absorption layer which does not reflect EUV light in the uppermost layer is formed by sputtering. A device pattern is formed on the absorption layer in a patterning process by EB drawing (electron beam drawing). In EUV lithography, a desired pattern is transferred onto a wafer due to the contrast of reflectance between the multilayer film and the absorbing layer of the EUV mask.

  It is desirable that the EUV mask is defect-free as in the conventional photomask. However, in the EUV mask, in addition to foreign matters and pattern defects (protrusions, chips, disconnections, shorts, misalignments) in conventional photomasks, phase defects peculiar to EUV masks become a problem. The phase defect is a step in a part of the multilayer film. The phase defect occurs due to foreign matters or irregularities on the LTEM substrate, foreign matters mixed in the formation of the multilayer film, voids, and the like.

  The effects of such phase defects on wafer transfer have been verified by simulations and the like. Currently, even a defect having a width of 20 nm and a height of several nanometers can greatly affect the size of the transferred pattern. I know. For this reason, it is necessary to inspect the EUV blank in advance. An EUV blank is a mask in a state where a multilayer film is formed but before an absorption layer is formed.

  Various methods have been developed for EUV blank inspection. The most promising method is a dark-field type defect inspection method using EUV light. In this inspection method, an LPP light source (Laser-Produced Plasma light source) is used to capture the scattered light from the phase defect with a CCD camera by using the reduction optical system of the exposure experimental apparatus as an enlargement optical system. That's it. This inspection method is the most sensitive method for inspecting minute irregularities on the EUV blank surface that cause phase defects.

  In the conventional photomask, the detected defect is corrected in a correction process. However, it is difficult to correct the phase defect of the EUV blank itself. For this reason, the EUV blank is not corrected, and the position and number of phase defects are recorded on the basis of the alignment marks created in advance on the substrate. Thereafter, an absorption layer is formed on the EUV blank, and the process proceeds to a circuit pattern patterning step.

  Here, when the phase defect of the EUV blank is below the absorption layer, the phase defect does not affect the exposure transfer onto the wafer, so that it is not necessary to take measures such as correcting the phase defect. . For this reason, when the circuit pattern is arranged on the EUV mask, the position of the phase defect and the information on the number of the phase defects are utilized so that the position of the phase defect is an area without the circuit pattern (hereinafter referred to as “light shielding area”) or an absorption layer. A method of changing the pattern layout so as to be hidden under the pattern has been proposed.

  However, even when using the above-described method of changing the pattern layout to hide the phase defects under the light shielding region or the absorption layer pattern, it is difficult to avoid all the phase defects, and some phase defects It will be applied to the reflective layer pattern. As an improvement method in this case, Patent Document 1 discloses that after the patterning and process steps of the EUV mask are completed, the phase defect is moved to a place where the absorption layer pattern adjacent to the phase defect is modified or changed. Describes a method for improving a circuit pattern transferred onto a wafer. The correction is performed using a correction device using FIB (Focused Ion Beam) or an electron beam.

  Patent Document 2 discloses a specific method for correcting an absorption layer pattern adjacent to a phase defect. In this method, the exposure state of the phase defect hidden inside the absorption layer pattern changes depending on the correction state of the absorption layer pattern, and the influence on the wafer transfer changes. Therefore, the exposure transfer system AIMS ( Using the Aerial Image Measurement System), the trial and error of the correction and confirmation by AIMS are performed many times.

Japanese translation of PCT publication No. 2002-532738 JP 2012-895800 A

  The conventional method of changing the pattern layout (circuit pattern position) described above and adjusting the phase defect so that it is under the light shielding region or the absorption layer pattern, simply looks at the two-dimensional positional relationship. is there. However, in EUV lithography, EUV light having an inclination of 6 degrees with respect to the mask surface is incident and the reflected light is exposed on the wafer. Therefore, it is necessary to confirm whether or not the phase defect is at a position where the exposure is not affected by performing an exposure simulation. Further, the range of influence of the phase defect needs to consider not only the irregularities on the surface of the absorption layer but also the state inside the laminated film.

  On the other hand, when the phase defect is applied to the reflective layer pattern, the method for correcting the absorbing layer pattern needs to repeat the correction work by the correction device and the confirmation work by AIMS as described above, and TAT for EUV mask creation. There is a problem that (Turn Around Time) becomes very long.

  One way to solve this problem is to input the correct phase defect information and pattern data into the simulator and perform exposure simulation before correcting the EUV mask pattern. There is a method for determining whether a desired transfer pattern can be obtained. Information such as the width, height, or depth of the phase defect cannot be obtained by the above-described dark field type defect inspection method, and is thus measured using another method such as AFM (Atomic Force Microscope).

  However, in AFM, only the state of the outermost surface of the EUV blank can be grasped. Where the phase defect starts from, the shape of the defect source of the phase defect propagates through the multilayer film. It is unknown whether it is. Naturally, when the assumption is different from the actual one, the degree of influence at the time of transfer is greatly different, so that the influence of the phase defect is likely to remain after the correction.

  Therefore, in order to correct the absorption layer pattern at the phase defect location correctly, it is necessary to perform exposure simulation using accurate information including the state of the phase defect inside the multilayer film to grasp the correct correction amount. is there.

  The present invention has been made to solve these problems, and a first object is to obtain an optimal pattern layout before patterning of an EUV mask, thereby reducing the work of correcting a portion having a phase defect. This is to improve the efficiency of EUV mask manufacturing.

  The second object is to correctly grasp the state of the phase defect in the multilayer film and to accurately calculate the correction amount of the absorption layer pattern by exposure simulation, so that an efficient EUV mask defect evaluation method and EUV mask can be obtained. Is to establish a manufacturing method.

  According to a first aspect of the present invention, in the defect evaluation method for an EUV mask, the step of acquiring phase defect position information and phase defect luminance profile information from the EUV blank on which the multilayer film is formed, and the phase defect position information based on By measuring the three-dimensional shape of the outermost surface of the phase defect and performing simulation, the internal state of the phase defect is estimated from the three-dimensional shape of the outermost surface and the luminance profile information of the phase defect, and the phase defect in the multilayer film A step of extracting a propagation parameter indicating a propagation state of the shape of the defect source to the outermost surface side, a step of tentatively determining a pattern layout in which a phase defect is located under the absorption layer pattern as a layout of the absorption layer pattern, Exposure simulation using the three-dimensional phase defect and propagation parameters for the tentatively determined pattern layout Calculating a transfer pattern in which the absorption layer pattern is transferred to the wafer by performing an application (for example, setting a phase defect state in the multilayer film by a propagation parameter as an input condition of exposure simulation); The method has a step of determining a pattern layout by evaluating a phase defect portion of a transfer pattern calculated by exposure simulation, and a step of creating an EUV mask using the determined pattern layout. In the step of determining the pattern layout, the pattern layout may be determined by repeatedly determining the pattern layout and performing the exposure simulation, and evaluating the phase defect portion of the transfer pattern calculated by the exposure simulation.

  Further, the second aspect is the step of performing the appearance inspection of the created EUV mask after the step of creating the EUV mask, the step of correcting pattern defects detected by the appearance inspection, and the transfer in the first aspect Investigating whether there is a phase defect on the reflective layer of the EUV mask by performing three-dimensional measurement of the outermost surface of the phase defect with the phase defect that affects the phase as a measurement target, and applying to the reflective layer The phase defect includes a step of calculating a corrected shape by performing an exposure simulation and a step of correcting the absorption layer pattern of the EUV mask according to the corrected shape.

  According to a third aspect, in the EUV mask manufacturing method, the step of acquiring phase defect position information and phase defect luminance profile information from the EUV blank on which the multilayer film is formed, and the phase defect position information based on In addition, by measuring the three-dimensional shape of the outermost surface of the phase defect and performing a simulation, the internal state of the phase defect is estimated from the three-dimensional shape of the outermost surface and the luminance profile information of the phase defect. A step of extracting a propagation parameter indicating a propagation state of a defect source shape to the outermost surface side, and a step of tentatively determining a pattern layout in which a phase defect is located under the absorption layer pattern as a layout of the absorption layer pattern; , Exposure simulation using the three-dimensional shape of phase defect and propagation parameters for the tentatively determined pattern layout Calculating a transfer pattern in which the absorption layer pattern is transferred to the wafer by performing a simulation (for example, setting a phase defect state inside the multilayer film by a propagation parameter as an input condition of exposure simulation), and exposure. The method includes a step of determining a pattern layout by evaluating a phase defect portion of a transfer pattern calculated by simulation, and a step of creating an EUV mask using the determined pattern layout. In the step of determining the pattern layout, the pattern layout may be determined by repeatedly determining the pattern layout and performing the exposure simulation, and evaluating the phase defect portion of the transfer pattern calculated by the exposure simulation.

  According to a fourth aspect, in the fourth aspect, after the step of creating the EUV mask, a step of performing an appearance inspection of the created EUV mask, a step of correcting a pattern defect detected by the appearance inspection, and a transfer Investigating whether there is a phase defect on the reflective layer of the EUV mask by performing three-dimensional measurement of the outermost surface of the phase defect with the phase defect that affects the phase as a measurement target, and applying to the reflective layer The phase defect includes a step of calculating a corrected shape by performing an exposure simulation and a step of correcting the absorption layer pattern of the EUV mask according to the corrected shape.

  According to the present invention, it is possible to set an optimal pattern layout in consideration of the influence on the transfer pattern before patterning the EUV mask. In addition, in an area where correction is required in the absorption layer pattern of the EUV mask, an optimal correction shape can be obtained by performing an exposure simulation reflecting the state inside the multilayer film of the phase defect. High quality EUV mask can be manufactured.

Process flow diagram before EUV mask creation in an embodiment of the present invention Process flow diagram after EUV mask creation in an embodiment of the present invention Sectional drawing showing the state of the phase defect in the multilayer film of EUV blank A diagram showing the positional relationship between the mask pattern and phase defects The figure showing the positional relationship of a phase defect different from a mask pattern and FIG. Examples of optimal correction patterns

  An embodiment of the present invention will be described with reference to FIGS. 1 and 2. First, alignment marks are formed on a low thermal expansion glass (LTEM) by etching or the like. This alignment mark serves as a reference for the position coordinates of the phase defect, and is used for adjusting the layout of a circuit pattern (device pattern) formed on the absorption layer. Next, 40 pairs of molybdenum (Mo) and silicon (Si) are alternately laminated on the LTEM substrate, and the EUV blank 1 in which the multilayer film is formed on the LTEM substrate is created. In order to confirm whether or not the EUV blank 1 has a phase defect, an actinic inspection (Actinic inspection) using EUV light is performed (step S1). This inspection is an inspection method that uses the reduction optical system of an exposure experimental apparatus using an LPP light source (Laser-Produced Plasma light source) as an enlargement optical system, and captures scattered light from a phase defect with a CCD camera. Do it. By this inspection, as phase defect information 3, coordinate data (defect position information) representing the position of the phase defect and a luminance profile (luminance distribution on the image) of the phase defect are acquired. In addition, as a method for acquiring the luminance profile of the phase defect, Actinic, which can acquire an image closer to a transfer image in an EUV exposure apparatus, SHARP (SEMATECH High-NA Actinic Reticle review Project) developed by a consortium called SEMATECH in the United States. An inspection device may be used.

  Next, in order to investigate the state of the outermost surface of the phase defect detected in step S1, three-dimensional measurement of the phase defect is performed (step S2). This three-dimensional measurement is performed in order to examine the type of phase defect (Pit or Bump defect) on the EUV blank 1 and the width and height (depth) of the phase defect. In general, the width of the phase defect is several tens to several hundreds nm, and the height (depth) of the phase defect is several nanometers. Therefore, in three-dimensional measurement, an atomic force microscope (AFM) is used. Is used to measure the phase defect dimensions. Note that a CD-SEM capable of three-dimensional measurement having a plurality of detectors described in Japanese Patent Application No. 2013-086422 proposed by the applicants of the present application may be used for three-dimensional measurement.

  The phase defect information obtained by using the three-dimensional measuring means in step S2 is only the outermost surface of the EUV blank 1. Here, when a circuit pattern is actually transferred onto a wafer with EUV light, it is important how the phase defect is formed in the laminated film (a laminated film including a multilayer film). Most of the phase defects are mainly caused by minute irregularities on the LTEM substrate, but in the middle of laminating a thin film of molybdenum (Mo) or silicon (Si), a foreign substance that becomes a defect adheres. There is also. The dimension (width, height, or depth) of the phase defect on the outermost surface may reflect the dimension of the unevenness (hereinafter referred to as “defect source”) that causes the phase defect. There may be no. Depending on how the width and height (depth) of the defect propagates as the film is stacked (that is, how the shape of the defect source propagates to the outermost surface), the effect on the transfer is It will change. That is, the influence on the transfer varies depending on the cross-sectional shape of the phase defect in the multilayer film (the propagation state of the defect source shape to the outermost surface side).

  Therefore, in the present invention, in the step of estimating the internal state of the phase defect by simulation (step S3), the result of step S2, where the phase defect starts from the laminated film, and the width and height (depth) of the phase defect. ) Set the state of the phase defect inside the laminated film in the simulator, such as whether it gradually becomes smaller, does not change, or conversely increases as the film is laminated, and the simulation is performed. The phase defect propagation parameter 6 is extracted by comparing the luminance profile of the phase defect information 3 and the simulation result (luminance profile obtained by the simulation). In other words, the three-dimensional measurement result of the phase defect, the depth position of the defect source in the laminated film, and the assumed parameters (cross-sectional profile) assuming the propagation state of the defect source shape to the outermost surface inside the laminated film are the simulator. Is input. Multiple types of data are prepared as hypothetical profiles. Then, the simulation is performed for each assumption parameter, the simulation result of each assumption parameter is compared with the luminance profile of the phase defect information 3, and the assumption parameter used in the simulation result having the highest degree of coincidence between them is used as the propagation parameter of the phase defect. 6 is extracted.

  Next, an absorption layer is formed on the EUV blank 1 (step S4). For example, a metal film containing tantalum (Ta) as a main component is used for the absorption layer.

  Next, using the mask pattern layout tool, pattern layout (circuit pattern layout in the absorption layer) is arranged so that as many phase defects as possible overlap with the light shielding region or absorption layer pattern. A layout is provisionally determined (step S5). At this time, in the region where the phase defect is hidden under the absorption layer pattern, in order to confirm whether the influence of the phase defect appears on the transfer pattern when the circuit pattern is exposed and transferred onto the wafer, the phase defect exposure simulation ( Transfer simulation) is performed (step S6). In the exposure simulation software, by inputting two-dimensional pattern data of several μm square of the area to be simulated from the design data of the absorption layer pattern and performing simulation calculation, a transfer pattern obtained by exposing and transferring the circuit pattern on the wafer is obtained. calculate. At this time, a more accurate simulation evaluation can be performed by inputting the propagation parameter 6 of the phase defect to the simulator. If the transfer pattern is affected by the assumed phase defect situation, the position of the pattern layout is adjusted again.

  Steps S5 and S6 are performed by the number of phase defects. Then, it is determined whether or not the number of phase defects affecting the transfer pattern is minimum (step S7), and the operations of step S5 and step S6 are performed until the number of phase defects affecting the transfer pattern is minimized. Repeat. Then, the pattern layout that minimizes the number of phase defects that affect the transfer pattern is determined as the pattern layout used to create the EUV mask 5. Since the operations from step S5 to step S7 are all performed on a computer, a pattern layout that minimizes the influence of phase defects can be obtained efficiently. Then, the EUV mask 5 is created using the obtained pattern layout (step S8).

  In step S8, the EUV mask 5 is formed through resist application, drawing, development, etching, and cleaning according to a general process.

  Next, the inspection / correction process of the EUV mask 5 will be described with reference to FIG. First, in order to confirm whether the EUV mask 5 created in step S8 has an appearance defect, an appearance inspection of the EUV mask 5 is performed (step S9). The appearance inspection of the EUV mask 5 is performed using an existing inspection apparatus. In addition to an optical inspection device using DUV light (deep Ultra-Violet light), an EB inspection device using an electron beam may be used.

  Next, the pattern defect (appearance defect) detected in step S9 is corrected using a correction device (step S10). Appearance defects include black defects (absorption layer pattern residue) and white defects (absorption layer pattern defect). The black defect is corrected by a method of removing by irradiating with FIB (Focused Ion Beam) or an electron beam, or a method of mechanically scraping with a fine needle. On the other hand, the white defect is corrected by a method of depositing a substance that absorbs EUV light such as carbon on the defective portion.

  Next, three-dimensional measurement of all phase defects is performed based on the phase defect information 3 (step S11). In this three-dimensional measurement, when an absorption layer pattern (circuit pattern) is drawn on the EUV blank 1, there is a possibility that the actual pattern position is deviated from the adjusted layout position (pattern layout determined in step S7). Therefore, it is performed to confirm whether or not the phase defect that should originally be under the absorbing layer pattern is applied to the reflecting layer pattern (pattern of the exposed portion of the reflecting layer). If the phase defect is under the absorption layer pattern, the irregularities of the phase defect on the Multi Layer will also appear in the absorption layer, so the phase defect is moved to the position of the phase defect coordinates and measured three-dimensionally with AFM etc. Is completely hidden by the absorption layer pattern, or part or all of the reflection layer pattern is not covered. At this time, if a CD-SEM capable of three-dimensional measurement having a plurality of detectors described in Japanese Patent Application No. 2013-086422 proposed by the present applicants is used, it can be confirmed more efficiently.

  As a result of the three-dimensional measurement of the phase defect performed in step S11, it is determined whether or not there is a phase defect related to the reflective layer pattern (step S12). Ends. Conversely, if there is even a phase defect in the reflective layer pattern, correction is necessary. Using the result of 3D measurement in the phase defect area to be corrected, 3D information (absorbing layer pattern 2D shape and absorbing layer pattern) of the absorber pattern (absorbing layer pattern) in that area is used for the simulation. Information on the side wall angle) and the width and height (depth) of the phase defect is input to the simulator, and simulation calculation is performed to obtain an optimal corrected shape (step S13). At this time, how to correct the absorber pattern greatly varies depending on the situation inside the layered film of the phase defect. Therefore, by inputting the phase defect propagation parameter 6 to the simulator, a more optimal correction is possible. The shape can be calculated.

  Then, the absorbent layer pattern is corrected using the correction device in accordance with the optimal correction shape obtained in step S13 (step S14). By performing the correction for the number of phase defects that affect the transfer, the optimum EUV mask 5 can be created.

Hereinafter, specific examples of the method for correcting an EUV mask according to the present invention will be described.
(EUV blank creation and phase defect analysis)
First, a process for producing an EUV blank and analyzing a phase defect will be described.
First, a low thermal expansion glass (LTEM) substrate is prepared, and an alignment mark is added to the LTEM substrate. The specifications of the alignment mark are standardized by the ITRS standard committee. In the examples, marks conforming to standardized specifications were used. Specifically, a resist was applied to the LTEM substrate, an alignment mark was drawn with a drawing apparatus, and an alignment mark was created through development and etching processes. After cleaning the LTEM substrate to which the alignment mark was added, an EUV blank was prepared by forming a multilayer film in which 40 pairs of molybdenum (Mo) and silicon (Si) were alternately laminated by sputtering.

  Next, phase defects were inspected on the entire EUV blank using an inspection apparatus for actinic inspection. As a result, five phase defects that seem to affect the transfer were detected. Then, the position information of each phase defect (XY coordinates relative to the alignment mark) and the luminance profile of the phase defect were acquired and stored as data.

  Next, the position coordinates of each phase defect were input to the AFM, and the observation and three-dimensional measurement of the five phase defects were performed. As a result, it was found that all five phase defects were bump defects, the size was 50 nm to 100 nm, and the height was 2 nm to 5 nm.

Here, using the EUV light exposure simulation (transfer simulation) software, the state inside the laminated film of phase defects was estimated. Specifically, the surface profile data (phase defect three-dimensional measurement result) measured by AFM is input to the exposure simulation software, and the cross-sectional profile of the laminated film (the depth of the defect source inside the laminated film). Set the position and the assumption parameters assuming the propagation state of the defect source shape to the outermost surface inside the laminated film) and perform the simulation calculation, and obtain the defect profile (phase defect of the phase defect) obtained with the inspection device for Actinic inspection (Luminance profile). Here, as an example, a result of inferring a phase defect (width = 100 nm, height = 5 nm) on the outermost surface is shown. Since the cross-sectional shape of the phase defect is not known in the laminated film, several types of data (cross-sectional profiles) are generated in the simulation software, which change the way of propagation of the shape of the defect source. Since the transfer result varies depending on where the defect source of the phase defect is in the laminated film and how the width and height of the phase defect propagate (change) as the film is laminated, the corrected shape of the pattern In order to calculate correctly, information inside the laminated film is important. This time, three cases (Table 1) were prepared by changing the width and height of the defect source on the assumption that the defect source exists on the LTEM substrate.
FIG. 3 is a diagram showing the propagation state of case 1. FIG.

  The above three cases with respect to the state inside the laminated film were respectively input to the simulator, and simulation calculation was performed for each case. As a result of comparison with the actual defect profile, it was found that Case 2 had the highest degree of coincidence. As a result, this phase defect is presumed to be a defect in which a bump defect having a width = 100 nm and a height = 5 nm on the LTEM substrate propagates through the laminated film and protrudes to the outermost surface. The cross-sectional shape was taken as the estimation result (propagation parameter of phase defect). In the same manner for the other four bump defects, the estimation result (phase defect propagation parameter) of the propagation state (cross-sectional shape of the phase defect) of the shape of the defect source inside the laminated film was obtained.

  Thereafter, an absorption layer of TaBN was formed on the outermost surface of the EUV blank.

(Pattern layout adjustment)
Next, a method for adjusting the pattern layout before entering the EUV mask creation process will be specifically described.
Pattern layout placement processing was performed based on EUV mask pattern data and phase defect position coordinate data. As a result, three of the five phase defects were located in the upper right corner of the EUV blank, so by shifting the pattern to the lower left as a whole by about 2 mm, the phase defect is located below the absorption layer outside the main pattern region. I was able to hide. As a result, the phase defects affecting the transfer pattern could be reduced to two.

  Next, for the two phase defects that overlap with the main pattern even after pattern layout adjustment, the coordinate values of the phase defects and the pattern data after the pattern layout change are examined. The positional relationship between each phase defect and the pattern is as follows. 4 and FIG. 5 were found. The phase defect in FIG. 4 has a width of 30 nm and a height of 3 nm. The phase defect in FIG. 5 has a width of 100 nm and a height of 5 nm. In FIG. 4, there is an absorption layer pattern having a width of 300 nm at a distance of 1 μm from the phase defect in the x direction. Therefore, if the pattern layout is further changed so that the phase defect in FIG. 4 is hidden under the absorption layer pattern having a width of 300 nm, the influence on the transfer can be reduced.

  Therefore, in order to investigate the influence of the phase defect on the transfer, an exposure simulation calculation was performed when the phase defect of FIG. 4 was arranged at the center of the absorption layer pattern having a width of 300 nm. In the exposure simulation calculation, the propagation parameter calculated in advance in step S3 is applied to the internal state of the phase defect. For comparison, an exposure simulation calculation was also performed when there was no phase defect in the same pattern area. As a result, it has been found that when the phase defect of FIG. 4 is arranged at the center of the absorption pattern, the same transfer result as that without the phase defect can be obtained. Accordingly, it has been found that the influence of the phase defect in FIG. 4 is eliminated by moving the pattern layout by −1 μm in the x direction.

  On the other hand, the phase defect of FIG. 5 may be as large as 100 nm, and there was no absorption layer pattern for hiding the defect in the periphery.

  The above pattern layout adjustment operation (from the initial pattern layout, the pattern layout is adjusted to a position moved −2 mm in the x direction, −2 mm in the y direction, and further moved by −1 μm in the x direction with respect to the EUV mask. ) To finalize the pattern layout. By adjusting the pattern layout, the phase defects affecting the transfer can be reduced from five to one.

  Subsequently, an EUV mask was created using the adjusted pattern layout. The EUV mask was prepared by sequentially performing resist coating, pattern drawing, development, etching of the absorbing layer, and cleaning in accordance with normal processes.

(Confirmation and correction of EUV mask phase defects)
Next, the defect correction method after creating the EUV mask will be specifically described. First, an appearance inspection using an inspection apparatus was performed on the created EUV mask in order to check for the presence or absence of pattern shape defects. As a result, several defects were detected, and the defect was corrected by the correction device.

  Next, for the five phase defects, coordinate information is input to the AFM in order to confirm whether the phase defect exists at an assumed position with respect to the adjusted pattern layout. Three-dimensional measurement was performed. As a result, for the four phase defects set to be arranged under the absorption layer by pattern layout adjustment, it can be confirmed that the absorption layer is raised according to the width and height of each phase defect, It has been confirmed that an EUV mask made according to the layout assumed by is created.

  If there is no phase defect that affects the transfer, the process ends. However, one phase defect is left on the reflective layer pattern this time. Therefore, the correction pattern for performing the pattern correction of the phase defect area is calculated.

  First, information obtained by measuring the target phase defect and the peripheral pattern is input to the exposure simulation software. At this time, by inputting three-dimensional data such as the phase defect propagation parameter 6 and the side wall angle of the peripheral absorption layer pattern, a more accurate simulation is possible. Next, while changing the absorption layer pattern data of the target region to deform the absorption layer pattern, the process of performing simulation calculation was repeated until a desired transfer pattern was obtained. As a result, an optimum correction pattern in consideration of the internal state of the phase defect was obtained. FIG. 6 shows pattern data to which a correction pattern is added. Finally, pattern correction was performed as shown in FIG. 6 using a correction device using FIB.

  By the above procedure, an optimum EUV mask free from the influence of phase defects could be produced. Therefore, exposure transfer evaluation to a wafer was actually performed and it was confirmed that there was no problem.

  The present invention is useful for EUV mask defect evaluation methods, EUV mask manufacturing methods, and the like.

DESCRIPTION OF SYMBOLS 1 EUV blank 3 Phase defect information 5 EUV mask 6 Phase defect propagation parameter S1 EUV blank Actinic inspection S2 Three-dimensional measurement of phase defect S3 Investigation of phase defect inside by simulation S4 Formation of absorption layer S5 Pattern layout placement process S6 Phase defect exposure simulation S7 Minimum number of phase defects affecting transfer S8 Creation of EUV mask S9 EUV mask appearance inspection S10 Defect correction S11 Three-dimensional measurement of all phase defects S12 Whether there is a phase defect on the reflective layer S13 Simulation Calculate the optimal correction shape with S14 Pattern correction

Claims (4)

In the EUV mask defect evaluation method,
Obtaining phase defect position information and phase defect luminance profile information from an EUV blank having a multilayer film formed thereon;
Based on the position information of the phase defect, measuring the three-dimensional shape of the outermost surface of the phase defect;
By performing simulation, the internal state of the phase defect is estimated from the three-dimensional shape of the outermost surface and the luminance profile information of the phase defect, and the shape of the defect source of the phase defect in the multilayer film is moved to the outermost surface side. Extracting a propagation parameter indicating the propagation state of
Tentatively determining a pattern layout in which the phase defect is located under the absorbing layer pattern as the layout of the absorbing layer pattern;
For the tentatively determined pattern layout, by performing an exposure simulation using the three-dimensional shape of the phase defect and the propagation parameter, calculating a transfer pattern in which the absorption layer pattern is transferred to a wafer;
Confirming the pattern layout by evaluating the phase defect portion of the transfer pattern calculated in the exposure simulation;
EUV mask defect evaluation method comprising: creating an EUV mask using the determined pattern layout. In the EUV mask defect evaluation method according to claim 1,
After the step of creating the EUV mask, performing an appearance inspection of the created EUV mask;
Correcting pattern defects detected by the visual inspection;
By investigating whether or not there is a phase defect on the reflective layer of the EUV mask by performing three-dimensional measurement of the outermost surface of the phase defect with a phase defect that affects transfer as a measurement target;
For the phase defect on the reflective layer, calculating a corrected shape by performing exposure simulation;
And correcting the absorption layer pattern of the EUV mask in accordance with the corrected shape. Obtaining phase defect position information and phase defect luminance profile information from an EUV blank having a multilayer film formed thereon;
Based on the position information of the phase defect, measuring the three-dimensional shape of the outermost surface of the phase defect;
By performing simulation, the internal state of the phase defect is estimated from the three-dimensional shape of the outermost surface and the luminance profile information of the phase defect, and the shape of the defect source of the phase defect in the multilayer film is moved to the outermost surface side. Extracting a propagation parameter indicating the propagation state of
Tentatively determining a pattern layout in which the phase defect is located under the absorbing layer pattern as the layout of the absorbing layer pattern;
For the tentatively determined pattern layout, by performing an exposure simulation using the three-dimensional shape of the phase defect and the propagation parameter, calculating a transfer pattern in which the absorption layer pattern is transferred to a wafer;
Confirming the pattern layout by evaluating the phase defect portion of the transfer pattern calculated in the exposure simulation;
Creating an EUV mask using the determined pattern layout, and a method for manufacturing an EUV mask. In the manufacturing method of the EUV mask of Claim 3,
After the step of creating the EUV mask, performing an appearance inspection of the created EUV mask;
Correcting pattern defects detected by the visual inspection;
By investigating whether or not there is a phase defect on the reflective layer of the EUV mask by performing three-dimensional measurement of the outermost surface of the phase defect with a phase defect that affects transfer as a measurement target;
For the phase defect on the reflective layer, calculating a corrected shape by performing exposure simulation;
Correcting the absorption layer pattern of the EUV mask in accordance with the corrected shape.