JP2018205458A - Defect inspection apparatus for euv blank and euv mask, defect inspection method, and manufacturing method for euv mask - Google Patents

Abstract

To provide a defect inspection apparatus for an EUV blank capable of accurately acquiring a state of defects which occurred in a multilayer film leading to the phase defect in the inside of the multilayer film, in particular, position information in the thickness direction, and to provide a defect inspection apparatus for an EUV mask using the defect inspection apparatus for the EUV blank.SOLUTION: There is provided a defect inspection apparatus for an EUV blank comprising: a light source A3 irradiating a multilayer film of the EUV blank with a plurality of light of different wavelengths; a sensor A2 receiving reflected light of irradiated light; an image forming unit for forming images from the received reflected light; and a defect position determining unit for determining a defect position present in the multilayer film in the thickness direction. In addition, the defect inspection apparatus for the EUV blank comprises; a function of retrieving an absorption film pattern data of the EUV mask; and a phase defect pass/fail determination unit for performing an EUV light exposure simulation.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a defect inspection apparatus, a defect inspection method, and an EUV mask manufacturing method for a reflective EUV blank and EUV mask used in EUV lithography using extreme ultraviolet (EUV) as a light source.

  The circuit pattern of a semiconductor integrated circuit has been miniaturized and highly integrated in order to improve performance and productivity, and the light source of an exposure apparatus used for pattern formation has also been shortened in wavelength. As a next-generation lithography candidate, a pattern transfer process using extreme ultraviolet light (hereinafter referred to as EUV or EUV light) near a wavelength of 13.5 nanometers (nm) has been developed.

  In lithography using EUV, unlike conventional deep ultraviolet light such as 193 nm, the refractive index of all materials is a value close to 1, and the absorption coefficient is large, so that a transmission optical system using refraction cannot be applied. Therefore, an exposure apparatus of a reflective optical system using a multilayer mirror in which materials having a large refractive index difference are alternately stacked is used. Accordingly, a reflection type mask (hereinafter referred to as EUV mask) is used instead of a conventional transmission type.

  An outline of the EUV mask is shown in FIG. The EUV mask has a reflective multilayer film (multilayer film) 30c for reflecting EUV light on the substrate 40, a protective film 20 for the multilayer film 30c, and an absorption film 10 for forming a circuit pattern. A conductive film 50 is formed to use an electric chuck.

As the substrate 40, for example, an ultra-low thermal expansion material (hereinafter, abbreviated as LTEM) made of silicon oxide (SiO ₂ ) added with titanium oxide is used. When the wavelength of light is 13.5 nm, the multilayer film 30c has silicon (Si) and molybdenum (Mo) of about 4.2 nm and 2.8 nm, respectively, as indicated by 30a and 30b. A laminated multilayer film is used (five pairs in FIG. 7 for easy viewing). In many cases, a protective film (capping film) 20 made of Si or ruthenium (Ru) for protecting the surface of the multilayer film is formed on the surface of the multilayer film. The absorption film 10 is a film that absorbs EUV light. For example, a film containing tantalum as a main component is used, and it may have a multilayer structure for the purpose of increasing the sensitivity of pattern defect inspection.

  In general, a photomask blank (blank) refers to a form of a photomask before a circuit pattern is formed. In the present application, a form in which a multilayer film is formed but before an absorption film is formed, or a multilayer is formed. A form in which an absorption film is not formed later in order to dig a film instead of the absorption film pattern, and a state in which an alignment mark, an accessory pattern, etc. are drawn are also called EUV blanks. When producing an EUV mask from an EUV blank, the absorption film 10 is partially removed by electron beam (EB) lithography and etching technology, and an EUV light absorption part (low reflection part) and reflection part (high reflection part). A circuit pattern is formed. The light image reflected by the EUV mask thus manufactured is transferred to a semiconductor substrate (hereinafter referred to as a wafer) through a reflection optical system.

In general, as a method of manufacturing an integrated circuit pattern on a wafer, the circuit pattern is formed on a photomask with a size that is 4 to 10 times larger than the design size on the wafer, and the exposure method of reduced projection is used on the photomask. The circuit pattern is formed on the wafer with a size reduced to 1/4 to 1/10.

  Therefore, in manufacturing an integrated circuit, it is important to determine a defect on a photomask serving as an original. Since the integrated circuit is transferred with the photomask pattern reduced as described above, the defect size on the photomask and the defect size on the integrated circuit do not match. The ease with which defects are transferred varies depending on the density and size of peripheral circuits, the type of defect, the formation position, the defect size, and the like. Therefore, if the defect determination is wrong, the defect on the photomask is transferred to the integrated circuit, resulting in a defect such as a missing pattern or an abnormal dimension.

  In particular, in the EUV mask, there is a possibility that a specific phase defect that cannot be seen in the conventional photomask may occur. The phase defect has a step in a part of the multilayer film, and if there is a phase defect, the reflectance of that part is lowered. The phase defect is caused by foreign matter (particles) on the substrate, pits or scratch-like defects generated when the substrate is polished, or foreign matter or voids mixed during the deposition of the multilayer film.

  FIG. 8 schematically shows phase defects (60a, 60b, 60c, 60d) caused by particles. These are defects generated in the manufacturing process of the EUV blank, 60a being particles adhering to the substrate, and 60b, 60c, and 60d being caused by particles adhering during the formation of the multilayer film. Hereinafter, in the present application, the cause of the phase defect will be described as particles, but the effectiveness of the present invention is the same for the phase defect of other causes.

  When particle adhesion occurs during film formation, a multilayer film is stacked on the particles as shown in FIG. This disturbance of the period is propagated to the upper layer part of the multilayer film, and a phase difference is generated between the normal part and the normal part. For this reason, when there is a circuit pattern in the vicinity of the defect, problems such as missing transferred circuit patterns and abnormal dimensions occur. Thus, the phase defect due to the disturbance of the multilayer film period has a great influence on the formation of the circuit pattern on the wafer.

FIG. 9 shows an example in which the phase difference between the EUV reflected light of the defective portion and the normal portion is calculated due to the difference in the thickness direction position of the defect generated in the multilayer film. FIG. 9A is a model diagram, where E is incident EUV light, Rm is reflected EUV light of a normal part, and Rd is reflected EUV of a defective part. Of course, the reflection is a superposition of the reflections at each interface in the multilayer film, but is represented by the arrow on the outermost surface in FIG. The multilayer film 30c is made of Si and Mo, and the total number of layers is L0 = 40 pairs. Here, the result of calculating the phase difference between Rm and Rd by changing the position (number of layers from the multilayer film surface (Ld: pair)) of the particle defect P (made Si of 2 nm in height) is shown in FIG. ). Thus, it can be seen that even a defect having a height of only 2 nm causes a larger phase difference as Ld is larger, that is, closer to the substrate 40. The optical constants (refractive index and extinction coefficient) of each material shown in Table 1 were used for the calculation. The value of SiO ₂ was substituted for LTEM as the substrate. The extinction coefficient of the substrate is not included in the calculation formula.

  FIG. 10 shows the results of experiments and investigations on the influence on the wafer transfer caused by the difference in the thickness direction position of defects generated in the multilayer film. As an example, the wafer size fluctuation amount (normal part) when a particle defect having a defect width of 40 nm and a height of 2 nm occurs in each thickness from the 0th layer (outermost surface) to the 40th layer (bottom surface, on the substrate) of the multilayer film. Difference). Note that iron (Fe) was used as the material of the particles. When the defect occurs in the uppermost part (FIG. 7-30 directly below the protective film 20) of the multilayer film (FIGS. 7-30c), 0 layer, and when the defect occurs in the position of the bottom part (FIG. 7-above the substrate 40), 40 layers And From this result, it can be seen that the dimension on the wafer varies by 5 to 6% due to the difference in the position of the defect in the thickness direction.

Various methods have been developed for EUV blank defect inspection. For example, a dark-field defect inspection method using EUV light uses EUV light generated from an LPP light source (Laser-Produced Plasma light source) and conversely uses a reduction optical system of an exposure experimental apparatus as an enlargement optical system. Thus, the scattered light from the phase defect is photographed with a CCD camera. This inspection method is a high-sensitivity method that can visually inspect 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. For this reason, the EUV blank is not corrected, and first, the position and number of phase defects on the plane are recorded with reference to the alignment marks prepared on the substrate in advance.

  Next, the position of the phase defect of the EUV blank and the circuit pattern data are compared. If the phase defect is under the absorption film, the phase defect does not affect the exposure transfer onto the wafer. There is no need to fix. Therefore, when the circuit pattern is arranged on the EUV mask, the pattern layout is made so that the position of the phase defect is hidden under the area without the circuit pattern (light-shielding area) or under the absorption film by utilizing the position information of the phase defect. A method of changing is proposed.

  However, it is difficult to avoid all the phase defects even by using the above-described method of changing the pattern layout and hiding the phase defects under the light shielding region or the absorption film. It will be applied to the pattern. As an improvement method in this case, Patent Document 1 discloses that a compensation pattern for performing transformation (change) such as deletion or addition after deletion of the absorption film pattern adjacent to the phase defect is used on the wafer. Describes a method for improving the circuit pattern transferred to the computer. The deletion or addition is performed using a FIB (Focused Ion Beam) or a correction device using an electron beam. Hereinafter, a circuit pattern formed on the absorption film will be referred to as an absorption film pattern as appropriate.

  Patent Document 1 specifically discloses a method of correcting an absorption film pattern adjacent to a phase defect. That is, the exposure state of the phase defect adjacent to the absorption film pattern changes depending on the correction state of the absorption film pattern, and the influence on the wafer transfer changes. Therefore, AIMS (registered trademark, Aerial) which is a transferability evaluation system using EUV light is changed. Image Measurement System (aerial image measurement system) is used, and trial and error of correction and confirmation by AIMS are performed many times.

  AIMS captures an image of a defective portion of a photomask into the apparatus, forms a transfer image on the wafer, and evaluates the degree of influence of the photomask defect on the circuit pattern based on the image and a pattern size measured from the image. (For example, refer to Patent Document 2). Although development of the same device is being promoted for EUV masks, problems such as accuracy and throughput remain for mass production. As described above, the work with the correction device and the confirmation work with the AIMS are repeated many times. Since it needs to be repeated, there is a problem that TAT (Turn Around Time) for EUV mask fabrication becomes very long.

  As a method for evaluating defect transferability of an EUV mask, a method using simulation has also been proposed (see Patent Document 3). That is, this is a method for obtaining an optimal layout and correction amount of the absorption film pattern by performing exposure simulation using phase defect information and pattern data as parameters at the time of layout and before correction of the absorption film pattern.

JP 2012-089580 A JP 2009-92792 A JP 2012-142468 A

  When the influence of phase defects on wafer transfer is evaluated by the method using the simulation, information such as the height, depth, and width of the phase defects cannot be obtained by the dark field type defect inspection apparatus using the EUV light described above. Therefore, it is measured using a technique such as AFM (Atomic Force Microscope). However, in AFM, only the state of the outermost surface of the EUV blank can be grasped, and what is the origin of the phase defect in the multilayer film and what is the shape of the source of the phase defect. Can not know.

  As shown in FIG. 10, since the defect transferability to the wafer varies greatly depending on the position where the defect occurs, in order to optimally lay out and correct the absorption film pattern adjacent to the phase defect, the phase defect inside the multilayer film must be It is necessary to perform exposure simulation using information. That is, it is necessary to consider not only the surface irregularities but also the state inside the multilayer film, and in particular, accurate position information (thickness direction position information) in the multilayer film thickness direction of defects generated in the multilayer film is important. . However, at present, no suitable method has been found for suitably acquiring position information in the thickness direction of defects embedded in the multilayer film.

  The present invention has been made in view of the above problems, and its object is to accurately acquire the state of defects generated in a multilayer film that causes phase defects of the multilayer film, particularly thickness direction position information. It is an object of the present invention to provide an EUV blank defect inspection apparatus that can be used. More preferably, an EUV blank and EUV mask defect inspection apparatus, a defect inspection method, and the defect inspection method capable of accurately performing an accurate exposure simulation using the thickness direction position information accurately obtained are used. Another object of the present invention is to provide a method for manufacturing an EUV mask.

In order to solve the above-described problem, the invention according to claim 1 includes a light source that irradiates a multilayer film of an EUV blank with a plurality of lights having different wavelengths,
A sensor for receiving reflected light of the irradiated light;
An image forming unit that forms an image from the received reflected light;
And a defect position determination unit that determines a position in the thickness direction of a defect present in the multilayer film from the formed image.

  The invention according to claim 2 is the EUV blank defect inspection apparatus according to claim 1, wherein the wavelengths of the plurality of lights are two or more different wavelengths selected from 193 nm to 532 nm. It is.

  The invention according to claim 3 is characterized in that the irradiation of the plurality of lights onto the multilayer film is performed from the front (front) surface, the back surface (substrate side) or both of the multilayer film. The EUV blank defect inspection apparatus according to claim 1.

  According to a fourth aspect of the present invention, the multilayer film is simultaneously irradiated with a plurality of lights having different wavelengths, and an image formed by reflected light of the plurality of lights is simultaneously formed. The EUV blank defect inspection apparatus according to claim 1.

In addition to the function with which the EUV blank defect inspection apparatus as described in any one of Claims 1-4 is equipped, the invention of Claim 5 is provided,
Equipped with a function to capture EUV mask absorption film pattern data,
The present invention provides an EUV blank and EUV mask defect inspection apparatus including a phase defect acceptance / rejection determination unit that performs EUV exposure simulation.

The invention according to claim 6 irradiates a multilayer film of EUV blank with a plurality of lights having different wavelengths,
The reflected light of the irradiated light is received by a sensor,
Forming an image from the received reflected light,
The EUV blank defect inspection method is characterized in that a position in the thickness direction of a defect existing in the multilayer film is determined from the formed image.

  The invention according to claim 7 is the EUV blank defect inspection method according to claim 6, wherein the wavelengths of the plurality of lights are two or more different wavelengths selected from 193 nm to 532 nm. It is.

  The invention according to claim 8 is characterized in that the irradiation of the plurality of lights to the multilayer film is performed from the front (front) surface, the back surface (substrate side) or both of the multilayer film. The EUV blank defect inspection method according to claim 6.

In addition to the EUV blank defect inspection method according to any one of claims 6 to 7, the invention according to claim 9 uses the absorption film pattern data of the EUV mask,
An EUV exposure simulation is performed to determine whether a phase defect is acceptable or not.

  By implementing the present invention, it is possible to accurately acquire position information in the thickness direction of defects that cause phase defects occurring in EUV blanks. Therefore, since an exposure simulation with high accuracy can be performed based on the phase defect information obtained there, an optimum absorption film pattern layout including a compensation pattern can be performed on the EUV blank before patterning, and after patterning. It becomes possible to correct the optimum absorption film pattern including the compensation pattern for the EUV mask. Therefore, it is possible to manufacture an EUV mask that avoids the influence of phase defects on wafer transfer more efficiently than in the past.

(A) Model diagram for calculating reflectance when light is incident on a multilayer film. (B) The characteristic view which calculated the relationship between the number of layers of a multilayer film, and the reflectance of the light of each wavelength which injected from the front (air) side. The characteristic view which calculated the relationship between the number of layers of a multilayer film, and the reflectance with respect to the light of each wavelength which injected from the back (substrate) side. The characteristic view which calculated | required the penetration depth of the light of each wavelength to a multilayer film. 1 is a basic configuration diagram of an EUV blank defect inspection apparatus according to an embodiment of the present invention. The basic block diagram of the EUV blank defect and EUV mask defect inspection apparatus based on another embodiment of this invention. The phase defect inspection flow figure of EUV blank and EUV mask based on embodiment of this invention. The schematic cross section of an EUV mask. FIG. 3 is a schematic cross-sectional view of a particle defect that occurs in a multilayer film formation step. (A) Model diagram for calculating phase difference between reflected light of phase defect portion and normal portion. (B) The characteristic view which shows the example which calculated the phase difference of the reflected light of a phase defect part and a normal part. The characteristic view which illustrates the experimental result which calculates | requires the relationship between the generation | occurrence | production position of a phase defect, and the amount variation on a wafer.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. The same components are denoted by the same reference numerals unless there is a reason for the sake of convenience, and redundant description is omitted. In each drawing, the thicknesses and ratios of the constituent elements may be exaggerated for ease of viewing, and the number of constituent elements may be reduced. Moreover, it is not limited to the following embodiment in the range which does not deviate from the meaning of this invention.

  Since the defect inspection apparatus of the present invention uses light in the wavelength region normally used for optical inspection, it is necessary to grasp the depth (penetration depth) that the light in the wavelength region penetrates into the multilayer film of the EUV mask. . As a clue, first, reflectance was calculated when light of each wavelength of 193, 257, 365, and 488 nm was incident on a multilayer film having a different number of layers. FIG. 1A is a model diagram thereof, and FIG. 1B is a calculation result of the reflectance of light of each wavelength incident from the front (air) side when the number of layers of the multilayer film is changed. According to FIG. 1B, when the wavelengths are 193, 257, 365, and 488 nm, the reflectivity is saturated when the number of layers is about 4, 3, 6, and 12, respectively, and the thickness is thicker. It is expected that light will not penetrate into the number of layers. In addition, since the transparency of the multilayer film increases as the wavelength becomes longer, the influence of interference appears and the change in reflectance is curved.

FIG. 2 is a result of performing the same calculation as FIG. 1B on the light of each wavelength incident from the back side (substrate 40) side. According to this, although the reflectance itself is about 5 to 10% lower than the front side (air) side incidence, the number of layers (pairs) in which the reflectance tends to be saturated is almost the same as the front side (air) side incidence. Therefore, it is expected that the penetration depth of light is equivalent to the case of front side (air) side incidence. The optical constants (refractive index and extinction coefficient) of each material shown in Table 2 were used for the calculations in FIGS. The value of SiO ₂ was substituted for LTEM as the substrate. The extinction coefficient of the substrate is not included in the calculation formula.

  FIG. 3 shows results obtained by irradiating a plurality of light beams having different wavelengths from the surface of the multilayer film and simulating to which thickness of the multilayer film the light of each wavelength penetrates. The penetration depth of light varies depending on the optical characteristics of the material for each wavelength. When the wavelength is 193 nm, 3 layers from the surface of the multilayer film, 257 nm light from the surface is 2 layers, 365 nm is 5 layers, 488 nm is 12 layers It can be seen that light penetrates up to 11 layers at 532 nm. From the above, in the present invention, the position in the thickness direction of the defect is determined by utilizing the fact that the penetration depth of light into the multilayer film differs for each wavelength.

  FIG. 4 is a basic configuration diagram of the EUV blank defect inspection apparatus 100 according to the embodiment of the present invention. A stage A1 on which the EUV blank A4 can be mounted, a light source A3 for irradiating the EUV blank A4 with light, and a light receiving sensor A2 are provided. In addition, an image is formed by an image forming unit (comprising a computer, a display device, etc.) connected to the light receiving sensor A2, and various image processes are performed according to the purpose.

  FIG. 5 is a basic configuration diagram of an EUV blank defect and EUV mask defect inspection apparatus 200 according to another embodiment of the present invention. In addition to the EUV blank defect inspection apparatus 100 of FIG. 4, the EUV blank defect and EUV mask defect inspection apparatus 200 further includes a phase defect acceptance / rejection determination unit (comprising a computer, a display device, etc.) connected to the image forming unit / image processing unit. Is provided. In the phase defect acceptance / rejection determination unit (as will be described later with reference to FIG. 6), in the case of EUV blank defect inspection, the absorption film pattern layout data including the compensation pattern, and in the case of EUV mask defect inspection, the compensation pattern is included. The correction data of the absorption film pattern is taken in, and the EUV exposure simulation is performed together with information from the image forming unit / image processing unit, and the pass / fail judgment of each phase defect is performed by comparing with the standard value of the phase defect.

  The light source A3 can irradiate two or more lights selected from wavelengths of 193 nm to 532 nm, and can divide or continuously irradiate light having a plurality of wavelengths. A plurality of light irradiations of light of a selected wavelength can be obtained by switching a plurality of light sources or by branching broadband light through a wavelength selection filter. The light reception of the plurality of lights may be time division, and a plurality of light receiving sensors may be arranged so as to avoid crossing of the optical paths.

  FIG. 6 is a flowchart showing a phase defect inspection method for EUV blanks and EUV masks according to an embodiment of the present invention. First, in step S0, the penetration depth of light into the multilayer film is obtained by simulation or measurement. The irradiation light is preferably light having a wavelength in the range of 193 to 532 nm, and two or more lights are selected from these, and the penetration depth thereof is acquired. If the multilayer film is the same material / structure, it is not necessary to obtain it every time, so it is desirable to obtain it in advance and make it into a library.

  The step S1 in FIG. 6 is a step for obtaining the plane position information of the phase defect, and a dark field type defect inspection using EUV light and a general blank inspection apparatus using ultraviolet light are used. In the step of FIG. 6-S2, a plurality of lights having different wavelengths are irradiated to the defect portion embedded in the multilayer film, the reflected light of the irradiated light is received by the light receiving sensor, and an image is formed from the received reflected light. It is a process. The sensor image formation for each wavelength may be performed separately using a plurality of devices.

  In the process of FIG. 6-S3, the thickness direction position of each phase defect (defect causing it) is determined from the penetration depth data of the S0 process and the image formed in the S2 process, and the contrast of the image. In this step, the width and shape are ascertained, and phase defect information is accumulated together with the result of AFM measurement as necessary. Note that in the image, information on the width and shape can be obtained because light is reflected in an oblique direction and the contrast changes in a portion where the sectional view profile of the defect is oblique.

  The process of FIG. 6-S5 is a process of performing an EUV exposure simulation in order to investigate the degree of influence of defects on the circuit pattern. In step S5, EUV exposure simulation is performed using the original circuit pattern data (D1), the phase defect information accumulated in step S3, and the result of the layout of the absorption film pattern including the compensation pattern to avoid the phase defect in step S4. Do. At this time, by using the defect thickness direction position information determined in step S3, simulation can be performed with higher accuracy than in the past.

  In the process of FIG. 6-S6, the pass / fail determination of the phase defect of the EUV blank is performed based on the simulation of the S5 process. If it is determined to be within the specification, the process proceeds to the EUV mask manufacturing process in step S7 through the absorption film forming process. Do the following.

  After the EUV mask is manufactured in step S7, the phase defect inspection of the EUV mask is performed. Step S8 is a normal defect inspection and correction of the absorption film pattern.

  As a result of producing the EUV mask, the actual absorption film pattern position may be deviated from the pattern layout set in step S4. In accordance with the result and the correction of the absorption film pattern in step S8, the absorption film pattern including the compensation pattern is corrected in step S9, and EUV exposure simulation is performed in step S10. Also at this time, by using the defect thickness direction position information determined in step S3, it is possible to perform simulation with higher accuracy than in the past.

In the process of FIG. 6-S11, the pass / fail judgment of the phase defect of the EUV mask is performed based on the simulation of the S10 process. If the determination is within the standard, the phase defect inspection of the EUV mask is completed. If the standard is out of specification, the absorption film pattern correction including the compensation pattern is performed again in step S9, and then the simulation process of S10 is performed again.

  The determination method of the thickness direction position in S3 process is demonstrated concretely. As described above, Table 3 shows an example in which the position in the thickness direction of the EUV blank phase defect is determined by using the difference in the penetration depth of light into the multilayer film surface due to the difference in the wavelength of light. Table 3 selects three types of light of 193 nm, 365 nm, and 488 nm, and irradiates light of each wavelength from the front surface (denoted as the table) or the back surface (denoted as the back) of the defective portion of the multilayer film. It is the result which described the presence or absence of the defect detection in. Result 1 is detected at 193 nm, which has the shallowest penetration depth among the three selected wavelengths. Since the penetration depth of the light having a wavelength of 193 nm into the multilayer film is three layers as shown in FIG. 3, defects are generated in the first to third layers which are the range in which the light of 193 nm penetrates.

  Result 2 is undetected at a wavelength of 193 nm (penetration depth 3 layers), so the defect occurrence position is deeper than the fourth layer, and is detected with light of wavelength 365 nm (penetration depth 5 layers). Therefore, the defect occurrence position is considered to be in the first to fifth layers, but it can be understood that the defect is generated in the fourth to fifth layers by combining the results of 193 nm and 365 nm.

  Similarly, since the result 3 is detectable at 488 nm of the penetration depth of 12 layers, the defect is considered to be in the 1 to 12 layers, but is not detected at 365 nm (penetration depth of 5 layers). It can be seen that it occurs between ~ 12 layers.

  Although the result 4 is not detected in any light of 193 nm, 365 nm, and 488 nm irradiated from the table, it can be detected by light with a wavelength of 193 nm irradiated from the back, so the first to third layers from the back, that is, It can be seen that defects have occurred in the 37th to 39th layers from the surface layer.

  When judged by the same method, it can be seen that the result 5 has defects in the 35th to 36th layers, and the result 6 has defects in the 28th to 34th layers. As for result 7, it is difficult to detect any light applied from the front surface and the back surface. If there is a defect within 12 layers from the front surface, it can be detected with light of 488 nm. Therefore, the position where the defect occurs is 13th layer or later, and similarly, from the back surface to the 12th layer (28th layer and beyond from the table) Since there is no defect, it can be seen that the defect occurs between the 13th and 27th layers.

  In this way, by combining detection results at each wavelength, it is possible to narrow down the range of defect occurrence positions. Similarly, the determination can be made with other combinations of wavelengths. For example, the same determination can be made with a combination of wavelengths 257 nm (penetration depth 2 nm) and 532 nm (penetration depth 11 nm). In this evaluation, light having a wavelength generally used in a defect inspection machine is taken as an example, but the same determination can be made by using light other than these wavelengths.

10 .... Absorbing film 20 ... Protective film 30a ... Silicon (Si)
30b Molybdenum (Mo)
30c ... reflective multilayer film (multilayer film)
40 .... Substrate (LTEM)
50... Conductive film 60 a... Foreign matter (particle) defect 60 b generated on the substrate... Foreign matter (particle) defect 60 c generated in the multilayer film manufacturing process. foreign matter (particles) defect 60d · · · multilayer film foreign material generated in the production process (particles) defect I · · · · · inspection light _R I, _{R Ib} ·· reflected inspection light E · · · · · incident EUV light Rm .... Reflected EUV light Rd at normal part ... Reflected EUV light P at phase defect part ... Particle defect A1 ... Stage A1 'on which EUV blank is mounted EUV blank or EUV Stage A2 on which a mask is mounted .... A sensor A3 that receives reflected light .... A light source A4 that emits light of a plurality of wavelengths .... EUV blank A4 '.... EUV blank or EUV mask. Click 100 · · · EUV blank defect inspection apparatus 200 · · · EUV blanks and EUV mask defect inspection device

Claims (9)

A light source that irradiates a multilayer film of an EUV blank with a plurality of lights having different wavelengths;
A sensor for receiving reflected light of the irradiated light;
An image forming unit that forms an image from the received reflected light;
From the formed image, a defect position determination unit that determines the position in the thickness direction of the defects present in the multilayer film,
An EUV blank defect inspection apparatus comprising:   2. The EUV blank defect inspection apparatus according to claim 1, wherein the wavelengths of the plurality of lights are two or more different wavelengths selected from 193 nm to 532 nm.   The irradiation of the plurality of lights onto the multilayer film is performed from the front (front) surface, the back surface (substrate side), or both of the multilayer film. The EUV blank defect inspection apparatus described.   4. The EUV blank defect according to claim 1, wherein the multilayer film is simultaneously irradiated with a plurality of lights having different wavelengths, and an image is formed simultaneously by reflected light of the plurality of lights. Inspection device. In addition to the function of the EUV blank defect inspection apparatus according to any one of claims 1 to 4,
Equipped with a function to capture EUV mask absorption film pattern data,
An EUV blank and EUV mask defect inspection apparatus comprising a phase defect acceptance / rejection determination unit that performs EUV exposure simulation. Irradiate multiple layers of EUV blanks with different wavelengths,
The reflected light of the irradiated light is received by a sensor,
Forming an image from the received reflected light,
An EUV blank defect inspection method, comprising: determining a position in a thickness direction of a defect present in the multilayer film from the formed image.   The EUV blank defect inspection method according to claim 6, wherein the wavelengths of the plurality of lights are two or more different wavelengths selected from 193 nm to 532 nm.   The irradiation of the plurality of lights onto the multilayer film is performed from the front (front) surface, the back surface (substrate side), or both of the multilayer film. The described EUV blank defect inspection method. In addition to the EUV blank defect inspection method according to any one of claims 6 to 7,
Using EUV mask absorption film pattern data,
A method of manufacturing an EUV blank or EUV mask, wherein an EUV exposure simulation is performed to determine whether or not a phase defect is acceptable.