Calibration substrate for charged particle beam device and charged particle beam device

Abstract

To provide a calibration substrate suitable for use in charged particle beam devices for fabricating or analyzing photomasks.SOLUTION: It is characterized that a calibration substrate for a charged particle beam device has a substrate and a pattern provided on the substrate, and the pattern comprises an upper layer and a lower layer containing a transition metal, which is provided under the upper layer.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a calibration substrate for a charged particle beam device, and to a charged particle beam device. [Background technology]

[0002] Devices using charged particle beams, such as electron microscopes and electron beam lithography devices, use calibration substrates with patterns for dimensional calibration in order to calibrate the beam diameter and measure images accurately. Regarding such calibration substrates, Patent Document 1 listed below describes a method in which rectangular patterns are formed using a lithography technique, and the pattern pitch is calibrated with a standard microscale using a critical dimension scanning electron microscope (CDM), to which a standard value is assigned and uncertainty is also noted.

[0003] However, in the above-mentioned charged particle beam device, if the sample surface is insulating, the sample surface becomes charged, which causes a problem that accurate image measurement and drawing cannot be performed. Therefore, when the sample surface is insulating, charging by the charged particle beam is prevented by coating the sample surface with a conductive vapor deposition material (see Patent Document 2 below).

[0004] Furthermore, in the above-mentioned charged particle beam device, there is a retarding technique in which a negative voltage is applied to the sample to form a decelerating electric field, as a technique that enables high-resolution observation with increased electron beam acceleration energy while preventing the sample from charging or being damaged. In implementing the retarding technique, when the sample surface is insulating, a potential difference is generated between the internal electrodes of an electrostatic chuck that serves as the sample support base, thereby establishing electrical continuity between the sample and contact terminals provided on the sample support base, thereby preventing charging of the sample surface (see Patent Document 3 below). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-279321 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-197272 [Patent Document 3] WO2010 / 097858A1 Summary of the Invention [Problem to be solved by the invention]

[0006] Here, the calibration substrate of the charged particle beam device is treated in the same way as the sample to be processed or observed with the charged particle beam. For this reason, the calibration substrate of the charged particle beam device used to fabricate an exposure mask, for example, is preferably made of the same material as the exposure mask corresponding to the sample, and in many cases, a non-conductive substrate is used.

[0007] However, as shown in Patent Document 2, when a calibration substrate is coated with a conductive vapor deposition material to prevent static buildup, not only does this change the pattern dimensions, but the vapor deposition film thickness becomes thicker at the corners of the convex portions of the pattern than in other areas. Therefore, it is not possible to perform accurate image measurement or beam diameter calibration using such a calibration substrate. Furthermore, as shown in Patent Document 3, the technology of generating a potential difference in the electrostatic chuck of the sample support table requires modifications to the device configuration, which results in a lack of versatility.

[0008] Therefore, an object of the present invention is to provide a calibration substrate suitable for use in a charged particle beam device for fabricating or analyzing exposure masks, and a charged particle beam device capable of highly accurate analysis of exposure masks based on accurate calibration or fabricating exposure masks with high pattern accuracy. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention has the following configuration.

[0010] (Configuration 1) A substrate; a pattern provided on the substrate, The pattern includes an upper layer, a lower layer provided below the upper layer and containing a transition metal, A calibration substrate for a charged particle beam device, comprising:

[0011] (Configuration 2) the substrate has a first main surface, a second main surface opposite to the first main surface, and a side surface in contact with the first main surface and the second main surface; The lower layer is provided only on the first main surface. 2. A calibration substrate for a charged particle beam device according to configuration 1.

[0012] (Configuration 3) The upper layer and the lower layer have etching selectivity with respect to each other. 3. A calibration substrate for a charged particle beam device according to configuration 1 or 2.

[0013] (Configuration 4) The underlayer includes at least one of chromium, tantalum, and molybdenum. 4. A calibration substrate for a charged particle beam device according to any one of configurations 1 to 3.

[0014] (Configuration 5) The upper layer contains at least one of a transition metal and silicon. 5. A calibration substrate for a charged particle beam device according to any one of configurations 1 to 4.

[0015] (Configuration 6) The upper layer contains molybdenum. 6. A calibration substrate for a charged particle beam device according to any one of configurations 1 to 5.

[0016] (Configuration 7) When the upper layer is etched, the etching selectivity of the upper layer to the lower layer is 2 or more. 7. A calibration substrate for a charged particle beam device according to any one of configurations 1 to 6.

[0017] (Configuration 8) The pattern has a recess, and the surface of the underlying layer is exposed at the bottom of the recess. 8. A calibration substrate for a charged particle beam device according to any one of configurations 1 to 7.

[0018] (Configuration 9) The pattern has a protrusion, The protrusion has a lower surface in contact with the lower layer, an upper surface opposite to the lower surface, and a side surface in contact with the upper surface and the lower surface. The upper surface and the side surface are formed by exposing the upper layer. 9. A calibration substrate for a charged particle beam device according to any one of configurations 1 to 8.

[0019] (Configuration 10) A charged particle beam device comprising a calibration substrate according to any one of configurations 1 to 9. Charged particle beam device. [Effects of the Invention]

[0020] The present invention provides a calibration substrate suitable for use in a charged particle beam device for fabricating or analyzing exposure masks, and a charged particle beam device that is capable of highly accurate analysis of exposure masks based on accurate calibration or fabricating exposure masks with high pattern accuracy. [Brief explanation of the drawings]

[0021] [Figure 1] 2 is a schematic cross-sectional view of a calibration substrate of the charged particle beam device according to the first embodiment. FIG. [Figure 2] FIG. 10 is a schematic cross-sectional view of a calibration substrate according to a modified example of the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the embodiments described below, the same components are designated by the same reference numerals, and redundant description will be omitted.

[0023] First Embodiment FIG. 1 is a schematic cross-sectional view of a calibration substrate 1 of a charged particle beam device according to a first embodiment. The calibration substrate 1 shown in FIG. 1 is installed in a charged particle beam device that uses a charged particle beam, particularly an electron beam. Charged particle beam devices include scanning secondary electron microscopes, transmission electron microscopes, electron beam lithography systems, electron beam analysis systems, and even ion beam analysis systems and ion beam processing systems equipped with electron microscopes. In particular, the charged particle beam device on which the calibration substrate 1 is installed is preferably a length measurement device (e.g., a length measurement scanning electron microscope) used for measuring the dimensions of an exposure mask or a fine pattern formed on a semiconductor device during the fabrication of the exposure mask. The calibration substrate 1 is used in these charged particle beam devices for calibrating the beam diameter of the electron beam, for accurate image measurement, or for calibration for accurate length measurement.

[0024] Such a calibration substrate 1 has a substrate 10 and a pattern 20 provided on the substrate 10. The pattern 20 is composed of a lower layer 201 and an upper layer 202 provided on top of the lower layer 201, and the lower layer 201 contains a transition metal. These components will be described in detail below.

[0025] <Substrate 10> The substrate 10 is a flat plate having a first main surface 11, a second main surface 12 opposite to the first main surface 11, and side surfaces 13 in contact with the first main surface 11 and the second main surface 12. The planar shape of the substrate 10, i.e., the shapes of the first main surface 11 and the second main surface 12, is not limited, but is typically circular, rectangular, or square.

[0026] Such a substrate 10 is preferably made of the same material as the substrate of the exposure mask, and is made of single crystal silicon or glass. As the glass, synthetic quartz glass is preferably used, but other glass substrates such as aluminosilicate glass, soda-lime glass, low thermal expansion glass (SiO2-TiO2 glass, etc.), multi-component glass ceramics, and various other glass substrates can also be used.

[0027] <Lower layer 201> The lower layer 201 is provided on the first main surface 11 of the substrate 10. The lower layer 201 may be provided on the entire first main surface 11 of the substrate 10. Preferably, the lower layer 201 is provided only on the first main surface 11, and not on the side surface 13 or the second main surface 12 of the substrate 10. This prevents the lower layer 201 from peeling off from the substrate 10. The lower layer 201 is formed in contact with the first main surface 11 of the substrate 10 without any other film interposed therebetween. This makes it possible to effectively suppress charge-up of the calibration substrate 1.

[0028] The lower layer 201 contains a transition metal and is conductive. Transition metals have high melting points and are therefore less susceptible to damage when irradiated with a charged particle beam, making them preferable. Among transition metals, the lower layer 201 preferably contains at least one of chromium (Cr), tantalum (Ta), and molybdenum (Mo). These metals have high chemical resistance and sufficient hardness. By forming the lower layer 201 from these materials, a highly durable lower layer 201 can be formed at relatively low cost, making it preferable. Furthermore, the lower layer 201 is particularly preferable as a layer containing chromium (Cr), because it facilitates processing. For example, when the pattern 20 formed on the substrate 10 of the calibration substrate 1 is removed to reuse the substrate 10, the lower layer 201 containing chromium (Cr) can be removed relatively easily.

[0029] Furthermore, the metal content of the lower layer 201 is preferably 30 atomic % or more, more preferably 40 atomic % or more. This ensures the conductivity of the lower layer 201 and prevents charging of the calibration substrate 1 due to electron beam irradiation. The lower layer 201 may be opaque to visible light, thereby broadening the options for materials constituting the lower layer 201. For example, when the lower layer 201 contains at least one of chromium (Cr), tantalum (Ta), and molybdenum (Mo) as a metal, the thickness of the lower layer 201 can be reduced while ensuring conductivity by including enough metal to make the lower layer 201 opaque to visible light. Reducing the thickness of the lower layer 201 reduces unwanted peeling of the lower layer 201, makes it easier to achieve a uniform thickness within the surface, and enables the calibration substrate 1 to be manufactured at lower cost. Furthermore, the calibration substrate 1 does not require the ability to transmit exposure light, such as that of an ArF excimer laser with a wavelength of 193 nm, which is required for an exposure mask (photomask). Therefore, the lower layer 201 can have an optical density (OD) of 1.5 or more for light with a wavelength of 193 nm, for example.

[0030] Furthermore, the difference in reflectance between the lower layer 201 and the upper layer 202 constituting the convex portions 20a of the pattern 20 (described below) is preferably 8% or more, more preferably 10% or more, at the inspection wavelength (e.g., 193 nm) of the pattern 20. This allows the pattern 20 to be inspected with high precision.

[0031] The film thickness of the lower layer 201 is preferably 3 nm or more, more preferably 5 nm or more. This allows sufficient suppression of charge-up on the calibration substrate 1. The film thickness of the lower layer 201 is preferably 100 nm or less, more preferably 80 nm or less. By making the lower layer 201 have such a film thickness, it is possible to suppress unnecessary peeling of the lower layer 201. It is also possible to make the film thickness of the lower layer 201 uniform within the plane. The lower layer 201 may have a structure consisting of a single film, or may have a layered structure including multiple films. In order to simplify the film formation process of the lower layer 201 and obtain a uniform film thickness, it is preferable that the lower layer 201 be made of a single film.

[0032] An example of a material for the lower layer 201 is a chromium compound containing chromium (Cr) and one or more elements selected from boron (B), carbon (C), nitrogen (N), and oxygen (O). Specific examples include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. Furthermore, as a material containing tantalum (Ta), it is preferable to use Ta (tantalum), an alloy containing Ta, or a Ta compound containing any of these and at least one of boron (B), carbon (C), nitrogen (N), and oxygen (O). Furthermore, as a material containing molybdenum (Mo), it is preferable to use a tantalum (Ta)-molybdenum (Mo) alloy, TaMoN containing tantalum (Ta), molybdenum (Mo), and nitrogen (N), and MoSi, MoSiN, MoSiON, and MoSiO containing molybdenum (Mo) and silicon (Si).

[0033] <Upper layer 202> The upper layer 202 is a layer patterned on top of the lower layer 201, and constitutes the convex portions 20a of the pattern 20 provided on the substrate 10. The spaces between the convex portions 20a of the pattern 20 are the concave portions 20b of the pattern 20, and the lower layer 201 is exposed at the bottom surfaces 20c of the concave portions 20b. The upper layer 202 can be formed in contact with the lower layer 201 without any other film interposed therebetween.

[0034] The convex portions 20a of the pattern 20 are formed by the upper layer 202, and each convex portion 20a has a lower surface in contact with the lower layer 201, an upper surface opposite the lower surface, and side surfaces in contact with the upper and lower surfaces, the upper and side surfaces being formed by the exposed upper layer 202. That is, the convex portions 20a of the pattern 20 are formed only by the upper layer 202, and the convex portions 20a (i.e., the upper layer 202) are exposed without being covered by any other film. Therefore, the convex portions 20a retain the edge shape obtained when the upper layer 202 was patterned by etching.

[0035] The material for the upper layer 202 is not particularly limited, but preferably has etching selectivity with respect to the lower layer 201. An example of the material for the upper layer 202 is a chromium compound containing chromium (Cr) and one or more elements selected from boron (B), carbon (C), nitrogen (N), and oxygen (O). Specific examples include CrN, CrON, CrCN, CrCON, CrBN, CrBON, CrBCN, and CrBOCN. Furthermore, the material containing tantalum (Ta) is preferably Ta (tantalum), an alloy containing Ta, or a Ta compound containing any of these and at least one of boron (B), carbon (C), nitrogen (N), and oxygen (O). Furthermore, examples of materials containing molybdenum (Mo) include tantalum (Ta)-molybdenum (Mo) alloys, TaMoN containing tantalum (Ta), molybdenum (Mo), and nitrogen (N), and MoSi, MoSiN, MoSiON, and MoSiO containing molybdenum (Mo) and silicon (Si).

[0036] The upper layer 202 preferably contains at least one of a transition metal and silicon (Si) and is preferably conductive, but not necessarily conductive. Among transition metals, the upper layer 202 more preferably contains molybdenum (Mo). Molybdenum (Mo) can be easily processed with a fluorine-based gas capable of anisotropic etching, resulting in a favorable cross-sectional shape of the pattern 20. Therefore, molybdenum (Mo) is particularly preferred as a material for the upper layer 202. Examples of fluorine-based gases include F2 gas, perfluorocarbon gases such as CF4, hydrofluorocarbon gases such as CFH3, SF6 gas, NF3 gas, SiF4 gas, and HF gas. These fluorine-based gases may further contain noble gases and / or oxygen. The upper layer 202 containing molybdenum (Mo) is suitable for use in a calibration substrate 1 for a charged particle beam device used in the fabrication or analysis of an exposure mask.

[0037] The upper layer 202 is made of a material that has etching selectivity with respect to the lower layer 201, and is a layer that can be selectively etched with respect to the lower layer 201. When etching the upper layer 202, the etching selectivity ratio of the upper layer 202 to the lower layer 201 is preferably 2 or more. This makes it possible to etch the upper layer 202 without damaging the lower layer 201, and to form the convex portions 20a with high film thickness accuracy.

[0038] As an example of the above-described configuration, for example, when the lower layer 201 is made of a material containing chromium (Cr), the upper layer 202 is made of molybdenum silicide (Mo-Si). In such a configuration, when the upper layer 202 is patterned to form the protrusions 20a, dry etching is performed using the above-described fluorine-based gas as an etchant. This allows the upper layer 202 made of molybdenum silicide (Mo-Si) to be etched away with a high selectivity of 2 or more relative to the lower layer 201 made of a material containing chromium (Cr).

[0039] As another example of the above configuration, for example, when the lower layer 201 is made of a material containing molybdenum silicide (Mo—Si), the upper layer 202 contains chromium (Cr). In this configuration, dry etching using a chlorine-based gas as an etchant is performed to pattern the upper layer 202 and form the protrusions 20a. Examples of chlorine-based gases include Cl2, SiCl2, CHCl3, CH2Cl2, CCl4, and BCl3. This chlorine-based gas may further contain a noble gas and / or oxygen. This allows the upper layer 202 made of a material containing chromium (Cr) to be etched away with a high selectivity of 2 or more relative to the lower layer 201 made of a material containing molybdenum silicide (Mo—Si).

[0040] The planar shape of the convex portion 20a of the pattern 20 formed by the upper layer 202 has a shape for adjusting the beam diameter of the electron beam used in the charged particle beam device, for image measurement using the electron beam, or for calibration for accurate dimensional measurement.

[0041] <Effects of the first embodiment> According to the calibration substrate 1 of the first embodiment described above, charge caused by electron beam irradiation can be released from the lower layer 201 containing a transition metal provided on the substrate 10. This makes it possible to perform highly accurate image measurement, dimensional measurement, and calibration of the electron beam diameter while preventing charge-up caused by electron beam irradiation. Moreover, since the calibration substrate 1 is configured such that the upper layer 202 constituting the convex portions 20a is provided on the substrate 10 via the lower layer 201 containing a transition metal, calibration can be performed using the same material as an exposure mask.

[0042] As a result, it is possible to create a calibration substrate 1 that is suitable for use in a charged particle beam device for fabricating exposure masks, while also allowing for accurate calibration of the beam diameter to prevent charge-up and calibration for highly accurate image measurement and dimensional measurement.A charged particle beam device equipped with this calibration substrate 1 makes it possible to fabricate exposure masks with high pattern accuracy based on accurate calibration, and to analyze exposure masks with high accuracy.

[0043] Second Embodiment 2 is a schematic cross-sectional view of a calibration substrate 2 according to a modified example of the second embodiment. The calibration substrate 2 of the second embodiment shown in this figure differs from the calibration substrate 1 of the first embodiment described with reference to FIG. 1 in that the lower layer 201′ and the upper layer 202′ are made of the same material film 200; otherwise, the configuration is the same. If the lower layer 201′ and the upper layer 202′ are made of the same material film 200, peeling of the upper layer 202′ from the lower layer 201′ can be further suppressed, which is preferable.

[0044] That is, the calibration substrate 2 has a substrate 10 and a pattern 20' provided on the substrate 10. The pattern 20' is composed of a lower layer 201' formed by the lower part of a material film 200 provided on the substrate 10, and an upper layer 202' formed by the upper part of the material film 200, and has convex portions 20a of the pattern 20' formed by patterning the upper layer 202'.

[0045] Between the convex portions 20a of the pattern 20 are concave portions 20b of the pattern 20, and a lower layer 201′ is exposed at the bottom surface 20c′ of the concave portion 20b. This lower layer 201′ is made of the same material film 200 as the upper layer 202′. The material film 200 constituting the lower layer 201′ is not provided on the side surface 13 or the second main surface 12 of the substrate 10, but is provided only on the first main surface 11. This prevents the lower layer 201′ (i.e., the material film 200) from peeling off from the substrate 10. The lower layer 201′ may be provided over the entire first main surface 11 of the substrate 10. The lower layer 201′ is formed in contact with the first main surface 11 of the substrate 10 without any other film interposed therebetween. This effectively suppresses charge-up of the calibration substrate 1. The film thickness of the lower layer 201′ may be the same as that of the lower layer 201 of the first embodiment.

[0046] In such a calibration substrate 2, the material film 200 constituting the pattern 20′ may be the same as the lower layer 201 (see FIG. 1) of the calibration substrate 1 of the first embodiment. A specific example of such a material film 200 is a chromium compound containing chromium (Cr) and one or more elements selected from boron (B), carbon (C), nitrogen (N), and oxygen (O). Chromium compounds are preferred because they can be easily processed by dry etching using a chlorine-based gas as an etchant. Chromium compounds are also preferred because they can be easily processed by wet etching.

[0047] In addition, in the preparation of the calibration substrate 2, after forming the material film 200 on the substrate 10, the upper layer 202′ of the material film 200 is etched and patterned to form the convex portions 20a of the pattern 20. At this time, dry etching is performed with the etching time controlled, so that the lower layer 201′ is formed on the substrate 10 with the above-mentioned predetermined film thickness, leaving the material film 200.

[0048] <Effects of the second embodiment> Even with the calibration substrate 2 of the second embodiment described above, the charge caused by irradiation with an electron beam can be released from the lower layer 201' of the pattern 20 containing a transition metal provided on the substrate 10, so that the same effect as in the first embodiment can be obtained. [Explanation of symbols]

[0049] 1,2...Calibration board 10 Substrate 11 First main surface 12 Second main surface 13 Side 20,20'...Pattern 20a...Convex part 20b...recess 20c,20c'...bottom 200...Material film 201,201'...lower layer 202,202'...upper layer

Claims

1. A substrate; a pattern provided on the substrate, The pattern includes an upper layer, a lower layer provided below the upper layer and containing a transition metal, A calibration substrate for a charged particle beam device, comprising:

2. the substrate has a first main surface, a second main surface opposite to the first main surface, and a side surface in contact with the first main surface and the second main surface; The lower layer is provided only on the first main surface.

2. The calibration substrate for a charged particle beam device according to claim 1.

3. The upper layer and the lower layer have etching selectivity with respect to each other.

3. The calibration substrate for a charged particle beam device according to claim 1 or 2.

4. The underlayer includes at least one of chromium, tantalum, and molybdenum.

3. The calibration substrate for a charged particle beam device according to claim 1 or 2.

5. The upper layer contains at least one of a transition metal and silicon.

3. The calibration substrate for a charged particle beam device according to claim 1 or 2.

6. The upper layer contains molybdenum.

3. The calibration substrate for a charged particle beam device according to claim 1 or 2.

7. When the upper layer is etched, the etching selectivity of the upper layer to the lower layer is 2 or more.

3. The calibration substrate for a charged particle beam device according to claim 1 or 2.

8. The pattern has a recess, and the surface of the underlying layer is exposed at the bottom of the recess.

3. The calibration substrate for a charged particle beam device according to claim 1 or 2.

9. The pattern has a protrusion, The protrusion has a lower surface in contact with the lower layer, an upper surface opposite to the lower surface, and a side surface in contact with the upper surface and the lower surface. The upper surface and the side surface are formed by exposing the upper layer.

3. The calibration substrate for a charged particle beam device according to claim 1 or 2.

10. A charged particle beam device comprising the calibration substrate according to claim 1 or 2. Charged particle beam device.

Images