JP7797007B2 - Reflective mask blank manufacturing method, reflective mask blank, and focused ion beam processing apparatus - Google Patents

Description

The present invention relates to a method for manufacturing a reflective mask blank, a reflective mask blank, and a focused ion beam processing apparatus used in the semiconductor manufacturing field.

In recent years, exposure technology using extreme ultraviolet (EUV) light has been seen as a promising option in photolithography. EUV light is light in the wavelength range of the soft X-ray or vacuum ultraviolet region, with wavelengths of approximately 0.2 to 100 nm. Light in this short wavelength range cannot pass through optical components, so the transmissive masks used up until now have prevented the EUV light from reaching the photoresist. Therefore, reflective masks, which do not allow light to pass through the mask, are used for exposure using EUV light.

This reflective mask has a reflective multilayer film (e.g., a Mo/Si multilayer film) formed on the entire surface of the substrate, which has the function of reflecting exposure light, and an absorbing layer that absorbs the exposure light is formed on top of that in accordance with the circuit pattern. EUV light that enters this reflective mask is absorbed by the absorbing layer, and in areas where there is no absorbing layer, it is reflected by the reflective multilayer film and formed into an image on the surface of the exposure material, thereby transferring the pattern of the absorbing layer to the exposure material.

Such a reflective mask is produced from a reflective mask blank serving as an original having a reflective multilayer film formed over the entire surface of the substrate, and an absorbing layer further formed over the entire surface of the reflective multilayer film. This reflective mask blank has a fiducial mark with a groove-shaped cross section formed on the surface of the reflective multilayer film in a region (peripheral region) outside the mask region where the exposure light is incident (see, for example, Patent Document 1). As will be described later, this fiducial mark defines a reference position when determining the coordinates of defect positions in the reflective multilayer film.

In reflective mask blanks, slight irregularities on the surface of the reflective multilayer or distortions within the reflective multilayer scatter light, resulting in defects in the form of non-specularly reflected components. Because light is scattered at the location of these defects, the defects can be detected by collecting this light using an optical system located above and forming an image on an imaging element. In recent years, major challenges in photolithography technology using EUV light have been improving the yield of defect-free reflective masks and establishing a defect detection infrastructure. In reality, it is extremely difficult to create a mask blank that is completely defect-free. Therefore, defect mitigation technology has been developed that controls the circuit pattern so that the absorption layer corresponding to the circuit pattern is positioned above the defect, hiding it and making it equivalent to the defect never having existed in the first place.

Japanese Patent Application Laid-Open No. 2017-58666

In technologies to mitigate the defects described above, improving the accuracy of detecting defect positions in reflective mask blanks is a key challenge. Possible methods for processing fiducial marks in reflective multilayer films include laser processing, dry etching, and FIB (Focused Ion Beam) using a focused ion beam. With laser processing, ablation, such as thermal evaporation of metal, occurs, which can easily result in rough structures such as irregularities at the edges of the fiducial mark, resulting in large errors in the fiducial mark. Furthermore, with dry etching, the surface of the reflective multilayer film in the mask area is exposed to plasma, which disrupts the reflectivity, making it unsuitable for processing fiducial marks.

When fiducial marks are processed using the FIB method, a focused ion beam is irradiated onto the sample surface, enabling fine processing. However, there is a problem with poor fiducial mark detectability. The planar shape of the fiducial mark is a cross to facilitate edge detection, but the mark size required for reliable detection is on the order of several hundred microns to several millimeters, necessitating a very long processing time. For this reason, the current practice is to set the fiducial mark depth shallow (on the order of several tens of nanometers). At this depth, the beam diameter and divergence angle of the focused ion beam result in the rise angle of the sidewalls of the processed groove (the angle between the substrate surface and the inclined surface of the sidewall) being only a few degrees to 10 degrees, resulting in a problem of reduced fiducial mark edge detection accuracy.

The present invention has been made in consideration of the above-mentioned problems, and aims to provide a reflective mask blank manufacturing method, a reflective mask blank, and a focused ion beam processing apparatus that can shorten the processing time for fiducial marks and improve the accuracy of fiducial mark edge detection.

In order to solve the above-mentioned problems and achieve the objectives, one aspect of the present invention is a method for manufacturing a reflective mask blank having a substrate and a reflective film that reflects exposure light and is laminated on the surface of the substrate, with a fiducial mark having a cross-sectional groove shape formed on the reflective film, characterized in that it comprises a contour processing step in which the reflective film is processed using a small-current focused ion beam along the contour of an area where the fiducial mark is to be formed, and an entire area processing step in which the reflective film over the entire area where the fiducial mark is to be formed is processed using a large-current focused ion beam.

In the above embodiment, it is preferable that the full area processing step is performed after the contour processing step.

In the above embodiment, it is preferable to perform the contour machining process after the full-area machining process.

In the above aspect, it is preferable that the contour processing step irradiates the small-current focused ion beam along the contour of the intended formation region until a contour groove recessed toward the substrate is formed along the periphery of the groove bottom region formed in the entire area processing step.

In the above aspect, it is preferable that the small-current focused ion beam is irradiated onto the reflective film from a direction inclined toward the inside of the planned formation region.

Another aspect of the present invention is a reflective mask blank comprising a substrate and a reflective film laminated on the surface of the substrate for reflecting exposure light, wherein a fiducial mark having a cross-sectional groove shape is formed on the reflective film, and wherein a contour groove portion recessed toward the substrate is formed along the periphery of the groove bottom region of the fiducial mark.

Another aspect of the present invention is a focused ion beam processing apparatus including a focused ion beam column that emits an ion beam, and that uses the ion beam to form a reference mark having a cross-sectional groove shape in a region where a reference mark is to be formed on a reflective film laminated on the surface of a substrate, the apparatus including: a transfer stage that is set up to support the substrate and move in X and Y directions; an elevation drive unit that drives the transfer stage up and down in a Z direction; and a control unit that controls the focused ion beam column, the transfer stage, and the elevation drive unit, the control unit controlling the focused ion beam column to switch the ion beam between a small-current focused ion beam and a large-current focused ion beam, and processing the reflective film along the contour of the region where the reference mark is to be formed with the small-current focused ion beam, and processing the reflective film over the entire region where the reference mark is to be formed with the large-current focused ion beam .

In the above aspect, it is preferable to include an inclination angle adjustment unit that changes the inclination angle of the substrate relative to the small-current focused ion beam so that the small-current focused ion beam is irradiated from a direction that is inclined toward the inside of the planned formation region relative to the reflective film.

The present invention provides a reflective mask blank manufacturing method, a reflective mask blank, and a focused ion beam processing apparatus that can shorten the processing time for fiducial marks and improve the accuracy of fiducial mark edge detection.

FIG. 1 is an explanatory diagram showing a schematic configuration of a focused ion beam processing apparatus according to an embodiment of the present invention. FIG. 2 is a plan view showing a state before an absorbing layer is formed in a reflective mask blank according to an embodiment of the present invention. FIG. 3 is a plan view showing a state after an absorbing layer has been formed in the reflective mask blank according to the embodiment of the present invention. FIG. 4A shows a method for manufacturing a reflective mask blank according to a first embodiment of the present invention, and is a diagram illustrating a cross-sectional profile after a contour processing step is performed along the contour of an area in a reflective film where a fiducial mark is to be formed. FIG. 4B shows the method for manufacturing a reflective mask blank according to the first embodiment of the present invention, and is a diagram showing a cross-sectional profile after the contour processing step and the full area processing step. FIG. 5 is a cross-sectional view taken along line VV in FIG. FIG. 6 is an explanatory plan view showing a contour processing step in the method for manufacturing a reflective mask blank according to the first embodiment of the present invention. FIG. 7 is an explanatory plan view showing the entire area processing step in the method for manufacturing a reflective mask blank according to the first embodiment of the present invention. FIG. 8 is a flowchart of a method for manufacturing a reflective mask blank according to the first embodiment of the present invention. FIG. 9A is a diagram showing the beam profile of a high-current focused ion beam used in the full-area processing step in the reflective mask blank manufacturing method according to the second embodiment of the present invention. FIG. 9B is a diagram showing a cross-sectional profile after processing the entire area of the reflective film in the method for manufacturing a reflective mask blank according to the second embodiment of the present invention. FIG. 10A is a diagram showing the beam profile of a small current focused ion beam used in the contour processing step in the method for manufacturing a reflective mask blank according to the second embodiment of the present invention. FIG. 10B is a diagram showing a cross-sectional profile after contour processing is performed after processing the entire area of the reflective film in the method for manufacturing a reflective mask blank according to the second embodiment of the present invention. FIG. 11 is a flowchart of a method for manufacturing a reflective mask blank according to the second embodiment of the present invention. FIG. 12A is a diagram showing the beam profile of a high-current focused ion beam used in the full area processing step in Examples 1 and 2 of the reflective mask blank manufacturing method according to the second embodiment of the present invention. FIG. 12B is a diagram showing a cross-sectional profile after processing the entire area of the reflective film in Examples 1 and 2 of the reflective mask blank manufacturing method according to the second embodiment of the present invention. FIG. 13A is a diagram showing the beam profile of a small current focused ion beam used in the contour processing step in Example 1 of the reflective mask blank manufacturing method according to the second embodiment of the present invention. FIG. 13B is a diagram showing a cross-sectional profile after contour processing in Example 1 of the reflective mask blank manufacturing method according to the second embodiment of the present invention. FIG. 14A is a diagram showing the beam profile of a small current focused ion beam used in the contour processing step in Example 2 of the reflective mask blank manufacturing method according to the second embodiment of the present invention. FIG. 14B is a diagram showing a cross-sectional profile after contour processing in Example 2 of the reflective mask blank manufacturing method according to the second embodiment of the present invention. FIG. 15A is a diagram showing a cross-sectional profile after the full area processing step in Example 3 of the reflective mask blank manufacturing method according to the second embodiment of the present invention. Figure 15-2 is a diagram showing a cross-sectional profile after contour processing is performed along the contour portion (left edge) of the area where the reference mark is to be formed in Example 3 of the reflective mask blank manufacturing method related to the second embodiment of the present invention. Figure 15-3 is a diagram showing a cross-sectional profile after contour processing is performed by shifting the contour (left edge) of the region where the reference mark is to be formed by +0.1 μm in Example 4 of the reflective mask blank manufacturing method related to the second embodiment of the present invention. Figure 15-4 is a diagram showing a cross-sectional profile after contour processing is performed by shifting the contour (left edge) of the region where the reference mark is to be formed by -0.1 μm in Example 5 of the reflective mask blank manufacturing method related to the second embodiment of the present invention. FIG. 16 is a perspective view showing a reflective mask blank manufacturing method according to the third embodiment of the present invention, in which the substrate is tilted at an angle θ with respect to the horizontal plane. FIG. 17 is an explanatory cross-sectional view showing a contour processing step in a method for manufacturing a reflective mask blank according to the third embodiment of the present invention.

The following describes in detail a reflective mask blank, a method for manufacturing a reflective mask blank, and a focused ion beam processing apparatus according to embodiments of the present invention, with reference to the drawings. However, it should be noted that the drawings are schematic, and the number of components, dimensions of each component, dimensional ratios, shapes, etc. may differ from the actual components. Furthermore, the drawings also include portions where the dimensional relationships, ratios, and shapes differ. First, before describing the reflective mask blank and the method for manufacturing a reflective mask blank, we will explain the focused ion beam processing apparatus used to manufacture the reflective mask blank.

[Focused ion beam processing equipment]
1, a focused ion beam processing apparatus 1 according to this embodiment includes a focused ion beam column (hereinafter referred to as an FIB column) 2, a transfer stage 3, an elevation drive unit 4, a tilt angle adjustment unit 5, and a control unit 6. The focused ion beam processing apparatus 1 also includes an exhaust unit (not shown) for discharging particles removed by beam processing using an ion beam to the outside of the apparatus.

The transfer stage 3 is designed to support the reflective film laminated substrate 7A placed thereon. As shown in FIG. 1, the reflective film laminated substrate 7A has a reflective film 9 formed on the surface of a glass substrate 8, which serves as the substrate in this invention. The reflective film 9 has a multilayer structure in which Mo layers serving as low refractive index layers and Si layers serving as high refractive index layers, both not shown, are alternately stacked. This reflective film 9 reflects the EUV light, which is the exposure light.

The transfer stage 3 is configured so that the reflective film laminated substrate 7A can be moved in the X and Y directions by an XY transfer mechanism (not shown) controlled by the control unit 6. The tilt angle adjustment unit 5 can freely change and adjust the tilt of the transfer stage 3 based on control signals from the control unit 6. The lifting and lowering driver 4 is provided on the transfer stage 3 side and is located, for example, below the tilt angle adjustment unit 5. This lifting and lowering driver 4 is connected to the control unit 6 and drives the transfer stage 3 to move up and down (in the Z direction) based on control signals from the control unit 6.

The FIB column 2 comprises a lens barrel 10 with an opening 10A formed at its lower end, and a focused ion beam optical system 11 housed within the lens barrel 10. An ion beam Ib is emitted from the lower end of the FIB column 2 through the opening 10A toward the reflective film laminate substrate 7A.

The focused ion beam optical system 11 includes an ion source 12 that generates an ion beam Ib, a condenser lens 13 that focuses the generated ion beam Ib, a deflector 14 that scans the ion beam Ib, an electrostatic objective lens 15 that focuses the ion beam Ib, and an aperture 16. A gallium (Ga) ion source is typically used as the ion source 12, but it is also possible to use an inductively coupled plasma (ICP) of a rare gas such as argon (Ar), gas field ionization, or a rare gas ion source. An electric field lens is preferably used as the lens for the ion beam Ib.

The control unit 6 includes a microcomputer and performs control based on pre-stored programs and operation signals from an operation unit (not shown). In addition to controlling the elevation drive unit 4 and tilt angle adjustment unit 5, the control unit 6 also outputs control signals to the ion source 12, condenser lens 13, deflector 14, objective electrostatic lens 15, and aperture 16. As a result, the control unit 6 adjusts the output and beam diameter of the ion beam Ib and switches between a small-current focused ion beam Ib1 and a large-current focused ion beam Ib2. The "current" in the small-current focused ion beam Ib1 and large-current focused ion beam Ib2 refers to the probe current used in FIB, and has the same meaning as the probe current. A current value of 10 to 30 pA can be applied to the small-current focused ion beam Ib1, and a current value of 100 to 1000 pA can be applied to the large-current focused ion beam Ib2.

The focused ion beam processing apparatus 1 according to this embodiment can form reference marks 20 that are cross-shaped in plan and groove-shaped in cross section, for example, on the reflective films 9 at the four corners of a reflective film-laminated substrate 7A, as shown in Figure 2.

(Operation of focused ion beam processing device)
In this focused ion beam processing apparatus 1, the small-current focused ion beam Ib1 is set to be irradiated intermittently or continuously along a trajectory 20B (see FIG. 6) that is set along the contour of the reference mark 20. The beam intensity of this small-current focused ion beam Ib1 is set appropriately depending on the constituent material of the reflective film 9, but is set smaller than that of the large-current focused ion beam Ib2. The beam diameter of the small-current focused ion beam Ib1 is set smaller than that of the large-current focused ion beam Ib2. The beam diameter of the small-current focused ion beam Ib1 is determined depending on the size of the reference mark 20.

In this focused ion beam processing apparatus 1, the high-current focused ion beam Ib2 is set to be irradiated intermittently or continuously over the entire formation region 20A (see FIG. 7) that determines the reference mark 20. This high-current focused ion beam Ib2 has a faster speed at which it removes the reflective film 9 than the low-current focused ion beam Ib1. The beam diameter of this high-current focused ion beam Ib2 is set to a diameter dimension that provides good processing efficiency, depending on the size of the reference mark 20. The beam diameters of the low-current focused ion beam Ib1 and the high-current focused ion beam Ib2 are determined by controlling the deflector 14, electrostatic objective lens 15, aperture 16, etc. with the control unit 6.

(Actions and Effects of Focused Ion Beam Processing Equipment)
By using the focused ion beam processing apparatus 1 according to this embodiment to perform the above-described beam processing using the small-current focused ion beam Ib1 and the large-current focused ion beam Ib2, it is possible to form, for example, a reference mark 20 having a cross-sectional groove shape as shown in FIG. 5.

As shown in FIG. 5, a contour groove 22 is formed along a trajectory 20B (see FIG. 6) that follows the contour of the fiducial mark 20, recessing toward the glass substrate 8. The cross-sectional shape of this contour groove 22 is affected by the action of the low-current focused ion beam Ib1, and results in a different shape depending on whether the contour processing step involving irradiation with the low-current focused ion beam Ib1 or the full-area processing step involving irradiation with the high-current focused ion beam Ib2 is performed first. Furthermore, the shape of the groove bottom region 21 is determined by irradiating the entire fiducial mark 20 formation region 20A (see FIG. 7) with the high-current focused ion beam Ib2. Because this groove bottom region 21 is processed to have a shape that rises above the contour groove 22, the boundary between the groove bottom region 21 and the sidewall 23 located outside the contour groove 22 and formed around the periphery of the groove bottom region 21 is clearly defined. Therefore, the focused ion beam processing apparatus 1 according to this embodiment can improve the accuracy of detecting the position of the fiducial mark 20.

Furthermore, by irradiating the small-current focused ion beam Ib1 on a trajectory 20B that follows the contour, the rising angle of the sidewall 23 shown in FIG. 5 can be increased, making it easier to detect the reference mark 20 even if the entire depth of the reference mark 20 is shallow. Therefore, with the focused ion beam processing apparatus 1 according to this embodiment, the processing time for the reference mark 20 can be shortened and the edge detection accuracy of the reference mark 20 can be improved.

Figure 3 shows the state in which an absorption layer 17 has been formed on a reflective mask blank 7, which is made by processing a fiducial mark 20 into a reflective film laminated substrate 7A using this focused ion beam processing device 1. The absorption layer 17 is made of a material film that absorbs EUV light as exposure light, and can be made of, for example, Ta oxide/Ta nitride.

In this embodiment, the absorption layer 17 is formed so as not to cover the peripheral edge of the reflective film laminated substrate 7A so that the fiducial mark 20 is exposed. However, the absorption layer 17 may be configured to cover the entire surface of the reflective film laminated substrate 7A. In that case, when patterning the absorption layer 17, the absorption layer 17 above the fiducial mark 20 can be removed to expose it for use.

Even if the absorbing layer 17 is configured to cover the entire surface of the reflective film laminated substrate 7A, if a reference mark 20 has been transferred onto the absorbing layer 17, the transferred mark may be used as a reference for positioning.

As described above, by improving the edge detection accuracy of the fiducial mark 20, the position coordinates of the defect position can be determined with high precision in the defect detection process for the reflective film 9. This allows for accurate correction (defect mitigation) in which the defective portion is covered with the pattern of the absorbing layer 17 in the patterning process for the absorbing layer 17. Therefore, the focused ion beam processing apparatus 1 according to this embodiment has the effect of increasing the yield of the reflective mask blank 7.

[Method of manufacturing a reflective mask blank]
In the following description of the manufacturing method of a reflective mask blank, the above-described focused ion beam processing apparatus 1 will be used, but the focused ion beam irradiation means is not limited to the configuration of this focused ion beam processing apparatus 1.

(First embodiment)
A method for manufacturing a reflective mask blank according to the first embodiment of the present invention will be described below with reference to the flow chart shown in FIG.

First, in the manufacturing method of the reflective mask blank of this embodiment, as shown in FIG. 1, a reflective film laminated substrate 7A having a reflective film 9 formed on the entire surface is placed on a transfer stage 3 (step S1).

Next, the reflective film laminated substrate 7A is moved and adjusted so that the irradiation position of the planned formation area 20A of the fiducial mark 20 (see FIG. 7) on the periphery of the reflective film 9 is located below the FIB column 2 (step S2). Note that in this embodiment, the irradiation start position below the FIB column 2 is positioned on a track 20B (see FIG. 6) set on or near the outline of the fiducial mark 20 so as to follow the outline.

Then, a contour machining process is performed in which the small-current focused ion beam Ib1 is irradiated intermittently or continuously along the trajectory 20B (step S3). In this embodiment, the small-current focused ion beam Ib1 is irradiated 10 times at each position spaced apart by a predetermined distance along the trajectory 20B, thereby performing contour machining that completes one revolution around the trajectory 20B.

Figure 4-1 shows the cross-sectional profile of the reflective film 9 after the above-mentioned contouring process, with the horizontal axis representing the coordinate X (μm) and the vertical axis representing the depth. Figure 4-1 shows the state where the vertical axis is 0.0 (the state before processing) and the state where the contouring process has been performed and the contour portion has been removed.

Next, as shown in FIG. 7, a full-area processing step is performed in which the high-current focused ion beam Ib2 is irradiated eight times at predetermined intervals across the entire area 20A where the fiducial mark 20 is to be formed, thereby forming the fiducial mark 20 having the cross-sectional profile shown in FIG. 4-2 (step S4). The cross-sectional profile shown in FIG. 4-2 is the same as or similar to the cross-sectional shape shown in FIG. 5, for example. In FIG. 4-2, the same reference numerals are used to designate the same parts as in FIG. 5. That is, in this embodiment as well, the groove bottom region 21, contour groove portion 22, and sidewall 23 of the fiducial mark 20 are formed.

In the manufacturing method of a reflective mask blank according to this embodiment, a contour groove portion 22 is formed that is recessed toward the glass substrate 8. The cross-sectional shape of this contour groove portion 22 is determined by the action of the contour processing performed first using the small-current focused ion beam Ib1. In this way, the cross-sectional shape from the first contour processing step affects the cross-sectional shape resulting from the entire-area processing step using the large-current focused ion beam Ib2, resulting in the contour groove portion 22 being dug deeper than the groove bottom region 21 and having a pointed shape.

As a result, the boundary between the groove bottom region 21 and the sidewall 23 located outside the contour groove portion 22 formed around the periphery of the groove bottom region 21 becomes clear. Therefore, the method for manufacturing a reflective mask blank according to this embodiment makes it possible to realize a reflective film laminated substrate 7A having a fiducial mark 20 with high edge detection accuracy.

In the manufacturing method of a reflective mask blank according to this embodiment, the coordinate position where the contour groove portion 22 is to be formed can be determined by first performing a contour processing step. Furthermore, in the manufacturing method of a reflective mask blank according to this embodiment, the rising angle of the sidewall 23 can be increased by irradiating the small-current focused ion beam Ib1 on a trajectory 20B that follows the contour. This makes it easy to detect the fiducial mark 20 even if the overall depth of the fiducial mark 20 is shallow.

Therefore, the reflective mask blank manufacturing method according to this embodiment can shorten the processing time for the fiducial marks 20 and provide a reflective film laminated substrate 7A with high fiducial mark 20 edge detection accuracy.

As shown in Figure 3, like the reflective film laminated substrate 7A produced using the focused ion beam processing apparatus 1 described above, the absorbing layer 17 may be formed so that it does not cover the peripheral edge of the reflective film laminated substrate 7A, so that the reference mark 20 is exposed, or the absorbing layer 17 may be configured to cover the entire surface of the reflective film laminated substrate 7A.

In the first embodiment described above, the number of times focused ion beams Ib1 and Ib2 are irradiated in the contour processing process and the full area processing process can be changed as needed, and tens of thousands of irradiations can be performed in an extremely short time, resulting in the rapid formation of a fiducial mark 20 with a large rise angle of the sidewall 23 and high edge accuracy.

Second Embodiment
Next, a method for manufacturing a reflective mask blank according to a second embodiment of the present invention will be described with reference to the flow chart shown in FIG.

First, in the manufacturing method of the reflective mask blank of this embodiment, as shown in FIG. 1, a reflective film laminated substrate 7A having a reflective film 9 formed on the entire surface is placed on the transfer stage 3 (step S11).

Next, the reflective film laminate substrate 7A is moved and adjusted so that the region 20A (see Figure 7) where the reference mark 20 is to be formed on the periphery of the reflective film 9 is positioned below the irradiation position of the FIB column 2 (step S12).

Next, as shown in FIG. 7, a full-area processing step is performed in which the high-current focused ion beam Ib2 is irradiated eight times at predetermined intervals across the entire area of the planned formation region 20A of the fiducial mark 20 (step S13). FIG. 9-1 is a diagram showing the beam profile of the high-current focused ion beam Ib2, with the horizontal axis representing the coordinate X (μm) and the vertical axis representing the beam intensity (arbitrary units). FIG. 9-2 shows the state in which the planned formation region 20A of the fiducial mark 20 has been entirely removed by full-area processing. As shown in FIG. 9-2, the rise angle θ1 of the sidewall at this time was 11.8 degrees.

The sidewall rise angle θ1 can be determined by cutting the reflective film laminated substrate 7A in a direction perpendicular to the sidewall at the location where the reference mark 20 is formed, and analyzing the cross-sectional image taken with a scanning electron microscope (SEM).

Then, a contour processing step is performed (step S14) in which a small-current focused ion beam Ib1 is intermittently or continuously irradiated along a trajectory 20B (see FIG. 6) set on or near the contour of the region 20A where the fiducial mark 20 is to be formed. In this embodiment, as shown in FIG. 10-2, the region irradiated with the small-current focused ion beam Ib1 is a range having a width indicated by m, and this range is irradiated intermittently or continuously with the small-current focused ion beam Ib1. In this embodiment, the small-current focused ion beam Ib1 is irradiated 10 times at each irradiation position. FIG. 10-1 shows the beam profile of this small-current focused ion beam Ib1. The beam intensity of this small-current focused ion beam Ib1 is approximately half that of the large-current focused ion beam Ib2, and its beam diameter is also approximately half that of the large-current focused ion beam Ib2. The beam profiles of the small-current focused ion beam Ib1 and the large-current focused ion beam Ib2 are adjusted appropriately depending on the size and depth of the reference mark 20 to be formed, the material and film structure of the reflective film 9, etc.

Figure 10-2 shows the cross-sectional profile of the reflective film 9 after the above-described contour processing has been performed. The cross-sectional profile shown in Figure 10-2 has a shape that is the same as or similar to the cross-sectional shape shown in Figure 5, for example. That is, in this embodiment, shapes similar to the groove bottom region 21, contour groove portion 22, and sidewall 23 of the reference mark 20 shown in Figure 5 are also formed.

In this embodiment, the sidewall rise angle θ2 shown in FIG. 10-2 is 19.15 degrees, which is larger than the sidewall rise angle θ1 when the entire area is simply processed with the high-current focused ion beam Ib2. Therefore, the reflective mask blank manufacturing method according to this embodiment also makes it possible to form a recess that is dug deep and pointed along the contour, thereby achieving a reflective film laminated substrate 7A having a fiducial mark 20 with high position detection accuracy. By performing step S14 described above, the manufacture of a reflective film laminated substrate 7A on which a fiducial mark 20 is formed is completed.

In the manufacturing method of a reflective mask blank according to this embodiment, a contour processing step is performed after the full area processing step, thereby increasing the rise angle of the sidewalls 23. In particular, even if the overall depth of the fiducial mark 20 is shallow, the contour processing step makes it easier to detect the fiducial mark 20. Therefore, according to the manufacturing method of a reflective mask blank according to this embodiment, it is possible to shorten the processing time for the fiducial mark 20 and provide a reflective film laminated substrate 7A with high fiducial mark 20 edge detection accuracy.

In this embodiment, as shown in Figure 3, the absorption layer 17 may be formed so that it does not cover the peripheral edge of the reflective film laminated substrate 7A so that the reference mark 20 is exposed, or the absorption layer 17 may be configured to cover the entire surface of the reflective film laminated substrate 7A.

Example 1
Next, Example 1 of the method for manufacturing a reflective mask blank according to the second embodiment of the present invention will be described with reference to FIGS. 12-1, 12-2, 13-1, and 13-2. First, in Example 1, a full-area processing step is performed on the reflective film 9. Here, the beam profile of the high-current focused ion beam is shown in FIG. 12-1. As shown in FIG. 7, a full-area processing step was performed in which the high-current focused ion beam Ib2 was irradiated twice at predetermined intervals over the entire area of the region 20A where the fiducial mark 20 is to be formed. FIG. 12-2 shows the state in which the region 20A where the fiducial mark 20 is to be formed has been entirely removed by the full-area processing. The sidewall rise angle θ3 shown in FIG. 12-2 at this time was only 2.85 degrees.

Next, a contouring process was performed using a small-current focused ion beam Ib1 with the beam profile shown in FIG. 13-1. In this example, as shown in FIG. 13-2, contouring was performed 30 times to engrave the area from the surface of the reflective film 9 on one end side of the recess formed in the full-area processing process (coordinate 10 μm) to near one end of the recess (coordinate 18 μm). As a result, as shown in FIG. 13-2, the area affected by contouring was from the position indicated by P1 (coordinate 8 μm) to coordinate 21 μm. The rise angle θ4 of the sidewall on one end side shown in FIG. 13-2 was 18.84 degrees. Note that when contouring was performed 20 times, the rise angle was 12.86 degrees, and when contouring was performed 10 times, the rise angle was 6.54 degrees.

Example 2
Next, Example 2 of the method for manufacturing a reflective mask blank according to the second embodiment of the present invention will be described with reference to Figures 12-1, 12-2, 14-1, and 14-2. First, in Example 2, a full-area processing step is performed on the reflective film 9, as in Example 1. The beam profile of the high-current focused ion beam and the cross-sectional profile after full-area processing are as shown in Figures 12-1 and 12-2.

Next, a contouring process was performed using a small-current focused ion beam Ib1 with the beam profile shown in Figure 14-1. In this example, as shown in Figure 14-2, contouring was performed 30 times to engrave the area from the sidewall of the recess formed in the full-area processing process (coordinate 10 μm, near one end) to the interior of the recess (coordinate 18 μm). As a result, as shown in Figure 14-2, the area affected by contouring was from the position indicated by P2 (coordinate 7 μm) to coordinate 21 μm. The rise angle θ5 of the sidewall on the one end side shown in Figure 14-2 was 21.31 degrees. Note that when contouring was performed 20 times, the rise angle was 15.51 degrees, and when contouring was performed 10 times, the rise angle was 9.32 degrees.

Example 3
Next, Example 3 of the method for manufacturing a reflective mask blank according to the second embodiment of the present invention will be described with reference to FIGS. 15-1 and 15-2. In Example 3, as shown in FIG. 15-1, first, the entire area processing step was performed with eight irradiations. Then, as shown in FIG. 15-2, the contour processing step was performed with ten irradiations. In this contour processing step, a small-current focused ion beam Ib1 was irradiated from one end of the formed recess to the area covered by the contour processing (coordinates 7 to 13 μm). In this way, by performing the contour processing step with ten irradiations, it was possible to form sidewalls that rose steeply.

Example 4
15-3 shows Example 4 of the method for manufacturing a reflective mask blank according to the second embodiment of the present invention. In this example, contour processing was performed by irradiating the small-current focused ion beam Ib1 ten times, with a deviation of +0.1 μm from the left-hand contour (edge) of the region 20A where the fiducial mark 20 is to be formed. The full-area processing step in Example 4 is the same as in Example 3 above. As a result, as shown in FIG. 15-3, it was possible to increase the rising angle of the sidewall processed in the contour portion.

Example 5
15-4 shows Example 5 of the method for manufacturing a reflective mask blank according to the second embodiment of the present invention. In this example, contour processing was performed by irradiating the small-current focused ion beam Ib1 ten times, with a shift of −0.1 μm from the left-side contour (edge) of the region 20A where the fiducial mark 20 is to be formed. The entire area processing process in Example 5 is the same as that in Example 3 above.

As a result, as shown in Figure 15-4, the rising angle of the sidewall machined into the contour portion was increased, but a cross-sectional shape like the contour groove portion 22 shown in Figure 5 was not obtained. For this reason, in this Example 5, it is believed that a cross-sectional shape like the contour groove portion 22 can be obtained by increasing the number of times the small-current focused ion beam Ib1 is irradiated during contour machining.

In the second embodiment described above, the number of times focused ion beams Ib1 and Ib2 are irradiated in the full area processing process and the contour processing process can be changed as needed, and tens of thousands of irradiations can be performed in an extremely short time, resulting in the rapid formation of a fiducial mark 20 with a large rise angle of the sidewall 23 and high edge detection accuracy.

(Third embodiment)
16 and 17 show a method for manufacturing a reflective mask blank according to a third embodiment of the present invention. In this embodiment, as shown in Fig. 16, the contour processing step is performed in a state where the reflective film laminated substrate 7A is tilted with respect to the small-current focused ion beam Ib1.

First, in this embodiment, the reflective film laminated substrate 7A is placed horizontally, and a high-current focused ion beam Ib2 is irradiated vertically to machine a recess in the entire region 20A where the reference mark 20 is to be formed.

Next, the control unit 6 drives and controls the tilt angle adjustment unit 5 to adjust the tilt of the transfer stage so that the surface 9A of the reflective film 9, which is the surface of the reflective film laminated substrate 7A, is tilted by θ with respect to the horizontal plane. As a result, as shown in FIG. 17, the small-current focused ion beam Ib1 is irradiated onto the reflective film 9 from a direction tilted toward the inside of the planned formation region 20A.

By performing contour processing in this manner with the low-current focused ion beam Ib1 and the reflective film 9 tilted relative to each other, it is possible to make the rise angle of the sidewall of the reference mark 20 closer to a right angle. Therefore, even if the time for the full-area processing process is shortened and the depth of the recess is shallower, the rise angle of the sidewall can be increased, thereby improving the detection accuracy of the reference mark 20.

In the manufacturing method of a reflective mask blank according to this embodiment, irradiation with a small-current focused ion beam Ib1 from an oblique direction is performed only in the contour processing step, but as shown in FIG. 16, irradiation from an oblique direction may also be performed in the full-area processing step using a large-current focused ion beam Ib2.

(Other embodiments)
Although the embodiments of the present invention have been described above, the descriptions and drawings that form part of the disclosure of the embodiments should not be understood to limit the present invention. The present invention encompasses various accompanying examples and alternative means.

For example, in the above embodiments and examples, an absorption layer 17 is formed on a reflective film laminated substrate 7A as a reflective mask blank, but a protective film may also be formed on the reflective film 9. In this case, the present invention may be applied to form a fiducial mark 20 on the protective film and reflective film 9.

In addition, in the above embodiments and examples, the reference marks 20 are formed at the four corners of the reflective film laminated substrate 7A, but this is not limited to this, and the shape of the reference marks 20 is not limited to a cross shape.

1. Focused ion beam processing equipment 2. Focused ion beam column (FIB column)
3 Transfer stage 4 Elevation drive unit 5 Tilt angle adjustment unit 6 Control unit 7 Reflective mask blank 7A Reflective film laminated substrate 8 Glass substrate 9 Reflective film 10 Lens barrel 10A Opening 11 Focused ion beam optical system 12 Ion source 13 Condenser lens 14 Deflector 15 Electrostatic objective lens 16 Aperture 17 Absorbing layer 20 Reference mark 20A Planned formation region 20B Track 21 Groove bottom region 22 Contour groove portion 23 Side wall

Claims (8)

A method for manufacturing a reflective mask blank, comprising: a substrate; and a reflective film that reflects exposure light and is laminated on a surface of the substrate, wherein a fiducial mark having a cross-sectional groove shape is formed on the reflective film, the method comprising:
a contour processing step of processing the reflective film along the contour of the region where the reference mark is to be formed using a small current focused ion beam;
an entire area processing step of processing the reflective film over the entire area of the intended formation region using a high-current focused ion beam;
A method for manufacturing a reflective mask blank, comprising: The method for manufacturing a reflective mask blank according to claim 1, wherein the full area processing step is performed after the contour processing step. The method for manufacturing a reflective mask blank according to claim 1, wherein the contour processing step is performed after the full area processing step. The method for manufacturing a reflective mask blank according to claim 3, wherein the contour processing step irradiates the small-current focused ion beam along the contour of the region to be formed until a contour groove recessed toward the substrate is formed along the periphery of the groove bottom region formed in the entire area processing step. The method for manufacturing a reflective mask blank according to claim 1, wherein the low-current focused ion beam is irradiated onto the reflective film from a direction tilted toward the inside of the planned formation region. A reflective mask blank comprising: a substrate; and a reflective film laminated on a surface of the substrate and reflecting exposure light, wherein a fiducial mark having a cross-sectional groove shape is formed on the reflective film,
A reflective mask blank, characterized in that a contour groove recessed toward the substrate is formed along the periphery of the groove bottom region of the fiducial mark. a focused ion beam column that emits an ion beam,
a focused ion beam processing apparatus for forming a reference mark having a cross-sectional groove shape in a region where the reference mark is to be formed on a reflective film laminated on a surface of a substrate by using the ion beam,
a transfer stage configured to support the substrate and move in the XY directions;
an elevation drive unit that drives the transfer stage up and down in the Z direction;
a control unit that controls the focused ion beam column, the transfer stage, and the lifting/lowering drive unit,
the control unit controls the focused ion beam column to switch the ion beam between a small-current focused ion beam and a large-current focused ion beam, processes the reflective film along the contour of the planned formation region with the small-current focused ion beam, and processes the reflective film over the entire planned formation region with the large-current focused ion beam . The focused ion beam processing apparatus of claim 7, further comprising an inclination angle adjustment unit that changes the inclination angle of the substrate relative to the small-current focused ion beam so that the small-current focused ion beam is irradiated onto the reflective film from a direction inclined toward the inside of the planned formation region.