JP2010181457A - Reflective photomask blank, reflective photomask, inspection device for reflective photomask, and method of inspecting the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide: a reflective photomask blank in which the accuracy of pattern inspection on a reflective photomask is improved and the time required for the inspection can be reduced; a reflective photomask; an inspection device for a reflective photomask; and a method of inspecting the mask. <P>SOLUTION: The reflective photomask includes: a substrate; a reflective film reflecting exposure light emitted to the substrate; an absorber absorbing the exposure light, the absorber being formed by patterning on the reflective film; and a polarizer formed by patterning on the absorber. The inspection device includes an analyzer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a reflection type photomask blank applicable to photolithography, a reflection type photomask, an inspection apparatus for a reflection type photomask, and an inspection method thereof, which are used in a manufacturing process of a semiconductor device or the like.

  Photolithography using visible light (g-line, h-line) or ultraviolet light (i-line, KrF, ArF) is widely used for patterning of wiring and semiconductors such as semiconductor integrated circuits and display devices. In recent years, along with miniaturization of semiconductor integrated circuits, research and development relating to immersion ArF, EUV lithography, nanoimprint lithography, and the like have been actively conducted in addition to electron beam lithography.

  There are two types of photomasks that serve as the originals of these lithography types: transmission type and reflection type. In the transmissive type, a light shielding film for shielding exposure light is formed on a substrate transparent to the exposure light, and this light shielding film is shaped, that is, patterned into a semiconductor circuit pattern shape.

  On the other hand, a reflective structure is shown in FIG. FIG. 3 is a schematic cross-sectional view showing the structure of a conventional reflective photomask 300. As shown in FIG. 3, the conventional reflective photomask 300 includes a substrate 301, a reflective film 302, a reflective film protective layer 303, an absorber 304, an antireflection film 305, and a back conductive film 312.

  A conventional reflective photomask 300 has a reflective film 302 composed of at least one layer that reflects exposure light on a substrate 301, and an absorber 304 that absorbs exposure light is disposed on the reflective film 302. 304 is patterned into the shape of a semiconductor circuit pattern. In some cases, a back surface conductive film 312 for an electrostatic chuck may be provided below the substrate 301. A reflective film protective layer 303 may be provided between the reflective film 302 and the absorber 304.

  In the inspection of the pattern formed on the conventional reflective photomask 300, the reflective photomask 300 is irradiated with inspection light, the light reflected on the reflective photomask 300 is analyzed, and the design data or the non-defective reflective photo is analyzed. It is a common method to compare with the actual mask. For this reason, in the reflection type photomask 300 to be inspected, as shown in FIG. 3, a patterned portion where the absorber 304 does not exist, a portion where the absorber 304 exists, that is, a pattern opening 310, and a pattern non-opening. A high contrast is required with the unit 311. In order to cope with this, Patent Document 1 devises a method of providing an antireflection film 305 for inspection light on an absorber 304 that absorbs exposure light that becomes a pattern non-opening 311 (for example, Patent Reference 1).

  However, when the circuit pattern is further miniaturized and the area of the pattern opening 310 is reduced, the inspection light reflection intensity from the pattern opening 310 is reduced. Depending on the shape of the pattern, the pattern opening 310 and the pattern non-opening In many cases, the contrast with 311 could not be sufficiently obtained. This is because the absolute amount of light reflected by the pattern opening 310 decreases as the area of the pattern opening 310 decreases. When the luminance of the inspection light is increased in order to increase the luminance from the pattern opening 310, the luminance of the light reflected by the pattern non-opening 311 also increases, so that the contrast cannot be improved.

  Further, the pattern of the conventional reflective photomask 300 has a taper shape or rough side surfaces due to various uncertain factors during manufacture. For this reason, in order to perform inspection accurately, not only the bright part is extremely bright and the dark part is extremely dark and the contrast is increased as in the case of the conventional reflective photomask 300, but the dark part is also brightened to a certain degree. In some cases, the pattern can be clearly observed by observing the difference between the dark portion and the dark portion. For this purpose, it is required to individually control the brightness of the bright part and the dark part. In the conventional inspection method of irradiating the reflection type photomask 300 with inspection light and observing only the light reflected on the reflection type photomask 300, a bright portion and a dark portion, that is, a pattern opening portion and a pattern non-opening portion. The brightness could not be changed individually.

JP 2004-39884 A

  The present invention provides a reflection type photomask blank, a reflection type photomask, a reflection type photomask inspection apparatus and an inspection method capable of improving the accuracy of inspection of a reflection type photomask and reducing the time required for the inspection. The purpose is to provide.

  The invention according to claim 1 of the present invention includes a substrate, a reflection film that reflects the exposure light formed on the substrate, an absorber that absorbs the exposure light and is formed on the reflection film, and an absorber. The reflective photomask blank is characterized by comprising a polarizer formed in the above.

  The invention according to claim 2 of the present invention is a reflective photomask blank according to claim 1, further comprising a reflective film protective layer formed between the reflective film and the absorber. It is.

  The invention according to claim 3 of the present invention is the reflective photomask blank according to claim 1 or 2, wherein the polarizer is an absorptive polarizer.

  In the invention according to claim 4 of the present invention, the polarizer is a wire grid polarizer, and the portion where the polarizer is in contact has an electrical insulation property where polarization separation by the wire grid polarizer is observed. The reflective photomask blank according to claim 3, wherein a layer is included.

  The invention according to claim 5 of the present invention is the reflective photomask blank according to claim 4, wherein the electrically insulating layer is an absorber.

  The invention according to claim 6 of the present invention is characterized in that the electrically insulating layer has a function of rotating the polarization plane of one light beam with respect to the inspection light. The reflective photomask blank described in 5 is used.

  The invention according to claim 7 of the present invention is the reflective photomask blank according to claim 6, wherein a λ / 4 wavelength plate is used as a function of rotating the polarization plane.

  According to an eighth aspect of the present invention, there is provided a substrate, a reflection film that reflects exposure light irradiated on the substrate, an absorber that absorbs exposure light and is patterned on the reflection film, and absorption. A reflective photomask comprising a polarizer formed by patterning on a body.

  The invention according to claim 9 of the present invention is a reflective photomask according to claim 8, further comprising a reflective film protective layer formed between the reflective film and the absorber. is there.

  The invention according to claim 10 of the present invention is the reflective photomask according to claim 8, wherein the polarizer is an absorptive polarizer.

  According to an eleventh aspect of the present invention, the polarizer is a wire grid polarizer, and the portion where the polarizer is in contact has an electrical insulation property where polarization separation by the wire grid polarizer is observed. The reflective photomask according to claim 8, further comprising a layer.

  The invention according to claim 12 of the present invention is the reflective photomask according to claim 11, wherein the electrically insulating layer is an absorber.

  The invention according to claim 13 of the present invention is characterized in that the electrically insulating layer has a function of rotating the polarization plane of one light beam with respect to the inspection light. 12. A reflection type photomask as described in item 12 above.

  The invention according to claim 14 of the present invention is the reflective photomask according to claim 13, wherein a λ / 4 wavelength plate is used as a function of rotating the polarization plane.

  According to the fifteenth aspect of the present invention, a reflective photomask including a substrate, a reflective film, a patterned absorber, and a polarizer is prepared in order, and the reflective photomask is irradiated with inspection light. A reflection photomask inspection method characterized by detecting the contrast between a pattern opening and a non-pattern opening of a reflection photomask using an analyzer that can be rotated in a direction perpendicular to the optical axis. Is.

  According to a sixteenth aspect of the present invention, there is provided a reflection type photomask inspection apparatus that inspects a reflection type photomask using the reflection type photomask inspection method according to the fifteenth aspect. is there.

  ADVANTAGE OF THE INVENTION According to this invention, while improving the precision of a test | inspection of a reflection type photomask, the reflection type photomask blanks, a reflection type photomask, the inspection apparatus of a reflection type photomask which can shorten the time required for an inspection, and its inspection A method can be provided.

It is a schematic sectional drawing which shows an example of the reflection type photomask which concerns on embodiment of this invention. It is the schematic which shows an example of the inspection apparatus which implement | achieves the inspection method of the reflection type photomask which concerns on embodiment of this invention. It is a schematic sectional drawing which shows the structure of the conventional reflection type photomask.

  Hereinafter, embodiments of the present invention will be described in more detail with reference to the drawings. The present invention is not limited to the following embodiment.

  FIG. 1 is a schematic cross-sectional view showing an example of a reflective photomask 100 according to an embodiment of the present invention. As shown in FIG. 1, a reflective photomask 100 according to an embodiment of the present invention is patterned on a substrate 101, a reflective film 102 that reflects exposure light formed on the substrate 101, and the reflective film 102. The absorber 104 that absorbs the exposure light formed in this way, and the polarizer 106 that is formed by patterning on the absorber 104 are provided.

  The reflective photomask 100 according to the embodiment of the present invention is formed by patterning the absorber 104 and the polarizer 106 of a reflective photomask blank. Therefore, first, the reflective photomask blank will be described, and then the reflective photomask 100 will be described.

  It is preferable to use a flat substrate 101 having a very low thermal expansion coefficient as the substrate 101 of the reflective photomask blank according to the embodiment of the present invention. When the substrate 101 needs to be electrostatically chucked in the course of exposure or inspection, a back conductive film 112 is preferably provided on the back surface of the substrate 101.

  The reflective film 102 that reflects the exposure light of the reflective photomask blank according to the embodiment of the present invention may be a single layer, but may be a multilayer film depending on the wavelength of the exposure light. can do. For the reflective film 102, it is preferable to select a material and a layer structure that make the reflectance of the exposure light used as high as possible. In order to protect the reflective film 102 or to form an upper etching stopper layer, a reflective film protective layer 103 may be provided between the reflective film 102 and the absorber 104 (described later).

  The absorber 104 of the reflective photomask blank according to the embodiment of the present invention requires a material having a large extinction coefficient with respect to the wavelength of the exposure light in order to absorb the exposure light. Further, from the necessity of patterning the absorber 104, it is preferable to select a material having good processing characteristics by dry etching or other methods.

  For the polarizer 106 of the reflective photomask blank according to the embodiment of the present invention, a material or a structure capable of extracting linearly polarized light with respect to the inspection light is used. The polarizer 106 is preferably made of a material and a structure that have as high an extinction ratio as possible.

  The polarizer 106 according to the embodiment of the present invention can be an absorption type or a wire grid type. The absorptive polarizer 106 can be used to increase the contrast of the reflected light from the pattern opening 110 with respect to the inspection light.

  The wire grid polarizer 106 is a polarizer 106 in which metal wires (wires) are arranged in parallel to each other at equal intervals, and the metal line width and the metal line interval are incident on the wavelength of light incident thereon. When the length is sufficiently short, it means that the polarized light component having an electric field vector perpendicular to the metal line is transmitted and the polarized light component having an electric field vector parallel to the metal line is reflected.

  When the wire grid type polarizer 106 is used for the polarizer 106, if there is a layer having free carriers in a portion in contact with the polarizer 106, it does not function sufficiently. For this reason, a layer 105 having an electrical insulating property that allows at least polarization separation by the wire grid polarizer 106 to be observed is provided in a portion in contact with the polarizer 106. In the case where the absorber 104 has such characteristics, the absorber 104 can also serve as the layer 105 having electrical insulation. The layer 105 having electrical insulation is preferably higher in insulation. However, this portion is a portion patterned into the shape of a circuit pattern like the lower absorber 104. Therefore, the patterning is performed by electron beam lithography. If done, insulation may be a problem. Therefore, the degree of insulation is determined by the balance between the required drawing accuracy and the contrast required at the time of inspection.

  In the polarization of a component having an electric field vector parallel to the metal line, the vibration direction of light coincides with the direction of the metal line, so the electrons in the metal move due to the electric field parallel to the metal line, causing Joule heating. Part of the light is absorbed by the metal. Light that is not absorbed by the metal is reflected by exciting an induced current in the wire (interference effect of scattered waves).

  Light of a component having an electric field vector perpendicular to the metal line is transmitted with almost no effect because the distance that electrons can move in the line width direction is limited. The transmitted light is reflected by the surface of the absorber 104, passes through the polarizer 106 again, and is emitted as reflected light from the reflective photomask 100 together with the component light reflected without passing through the polarizer 106 described above. Therefore, although there is a limit to the improvement in contrast as compared with the absorption polarizer 106, the thickness of the polarizer 106 can be reduced, which is suitable for application to the reflective photomask 100. Moreover, by adjusting the metal line width and the metal line interval, it is possible to cope with inspection light in the ultraviolet region, and it can be easily formed using nanoimprint technology with a small number of processes in addition to photolithography.

  When the electrically insulating layer 105 of the reflective photomask blank according to the embodiment of the present invention has a function of rotating the polarization plane of one light beam with respect to the inspection light, it is reflected by the absorber 104. When the emitted light is incident on the polarizer 106 again, the component that passes through the polarizer 106 can be reduced. As a function of rotating the polarization plane, a λ / 4 wavelength plate can be used. When a λ / 4 wavelength plate is used, the polarization plane rotates 90 ° in a reciprocating manner and cannot pass through the polarizer 106. As a result, when inspecting as a reflective photomask as will be described later, the reflected light observed from the pattern non-opening 111 when irradiated with inspection light is an electric field vector horizontal to the metal line first reflected by the polarizer 106. Since the intensity of the light can be arbitrarily controlled in the range of 0% to 100% by using an analyzer 201 described later, the contrast between the pattern opening 110 and the pattern non-opening 111 Can be adjusted freely. Here, λ represents the wavelength of the inspection light.

  In forming the thin film (the reflective film 102, the reflective film protective layer 103, and the absorber 104) having the above-described configuration, various known film formation techniques can be used. Among these, a sputtering method or pulse laser deposition (PLD) is preferable because a high-quality film can be formed. The absorption polarizer 106 includes, for example, a method in which organic molecules are aligned to adsorb an iodine-based compound, but is not necessarily limited thereto. The wire grid polarizer 106 can use various known techniques such as nanoimprint and ink jet in addition to normal photolithography. For forming a layer (λ / 4 wavelength plate) having a function of rotating the polarization plane, for example, oblique deposition is known.

  By using the materials and methods described above, the reflective photomask blank according to the embodiment of the present invention is completed.

  Next, the reflective photomask 100 according to the embodiment of the present invention will be described. For patterning of the absorber 104, the electrically insulating layer 105, the polarizer 106, etc. of the reflective photomask 100, in addition to photolithography, charged particle beam lithography, nanoimprint, etc., etching using a stencil mask, etc. The method can be used, and can be used as needed, but is not limited. The absorber 104, the electrically insulating layer 105, and the polarizer 106 are patterned to complete the reflective photomask 100 according to the embodiment of the present invention.

  In the embodiment of the present invention, the brightness of the dark part of the reflective photomask 100, that is, the non-defective part or the pattern non-opening part 111 can be adjusted only by changing the direction of the analyzer 201 described later. On the other hand, since the luminance of the pattern opening 110 can be adjusted by changing the luminance of the inspection light to be irradiated as in the conventional case, the defect portion and the non-defective portion, or the pattern opening portion 110 and the pattern non-opening portion 111 can thereby be adjusted. Can be easily polarized and can create the most observable environment for defects or patterns, improving inspection accuracy and reducing inspection time.

  Next, a reflection photomask inspection apparatus and inspection method according to an embodiment of the present invention will be described.

  First, a reflection type photomask inspection apparatus according to an embodiment of the present invention will be described. FIG. 2 is a schematic cross-sectional view showing an example of an inspection apparatus that realizes the reflective photomask inspection method according to the embodiment of the present invention. In order to facilitate the inspection of the reflective photomask 100 according to the embodiment of the present invention, the analyzer 201 is incorporated in a general photomask inspection apparatus. The analyzer 201 is a polarizing element having the same function as the polarizer 106, but is called differently because its role is different. The analyzer 201 is placed in front of the photodetector 202. The analyzer 201 is designed so that it can be rotated in the plane direction, that is, in the direction perpendicular to the optical axis. Depending on the wavelength of the inspection light, it may be preferable to work in a vacuum or in a nitrogen gas atmosphere.

  Next, a reflection photomask inspection method according to an embodiment of the present invention will be described. The reflection type photomask 100 according to the embodiment of the present invention is irradiated with inspection light, the reflected light from the reflection type photomask 100 is incident on the inspection apparatus having the analyzer 201, and the rotation angle of the analyzer 201 is changed. The desired contrast can be obtained by adjusting. By using such a reflection type photomask 100, an inspection apparatus for the reflection type photomask 100, and an inspection method thereof, pattern defects can be easily evaluated.

  As described above in detail, according to the embodiment of the present invention, it is possible to create an environment that is most easily observed by adjusting the rotation angle of the analyzer 201, so that the accuracy of the inspection is improved and the inspection is improved. It is possible to provide a reflection type photomask blank, a reflection type photomask, a reflection type photomask inspection apparatus and an inspection method thereof that can shorten the time required for the above.

DESCRIPTION OF SYMBOLS 100 ... Reflective type photomask 101 ... Substrate 102 ... Reflective film 103 ... Reflective film protective layer 104 ... Absorber 105 ... Electrically insulating layer 106 ... Polarized light Element 110 ... Pattern opening 111 ... Pattern non-opening 112 ... Back conductive film 201 ... Analyzer 202 ... Photo detector 203 ... Analyzer rotating device 204 ... X- Y stage 205 ... control computer 206 ... inspection light source 207 ... contrast adjustment control device 208 ... partition wall 300 ... conventional reflective photomask 301 ... substrate 302 ... reflection Film 303 ... Reflective film protective layer 304 ... Absorber 305 ... Antireflection film 310 ... Pattern opening 311 ... Pattern non-opening 312 ... Back conductive film

Claims (16)

A substrate,
A reflective film that reflects exposure light formed on the substrate;
An absorber that absorbs the exposure light and is formed on the reflective film;
A polarizer formed on the absorber;
A reflective photomask blank, comprising: A reflective film protective layer formed between the reflective film and the absorber;
The reflective photomask blank according to claim 1, comprising:   The reflective photomask blank according to claim 1, wherein the polarizer is an absorptive polarizer.   The polarizer is a wire grid type polarizer, and an electrically insulating layer where polarization separation by the wire grid type polarizer is observed is included in a portion where the polarizer is in contact with the polarizer. The reflective photomask blank according to claim 3.   The reflective photomask blank according to claim 4, wherein the electrically insulating layer is the absorber.   6. The reflective photomask blank according to claim 4, wherein the electrically insulating layer has a function of rotating a polarization plane of one light beam with respect to the inspection light. .   The reflective photomask blank according to claim 6, wherein a λ / 4 wavelength plate is used as a function of rotating the polarization plane. A substrate,
A reflective film that reflects exposure light irradiated on the substrate;
An absorber that absorbs the exposure light and is patterned on the reflective film;
A polarizer formed by patterning on the absorber;
A reflective photomask comprising: A reflective film protective layer formed between the reflective film and the absorber;
The reflective photomask according to claim 8, further comprising:   The reflective photomask according to claim 8, wherein the polarizer is an absorptive polarizer.   The polarizer is a wire grid type polarizer, and an electrically insulating layer where polarization separation by the wire grid type polarizer is observed is included in a portion where the polarizer is in contact with the polarizer. The reflective photomask according to claim 8.   The reflective photomask according to claim 11, wherein the electrically insulating layer is the absorber.   The reflective photomask according to claim 11 or 12, wherein the electrically insulating layer has a function of rotating the polarization plane of one light beam with respect to the inspection light.   The reflective photomask according to claim 13, wherein a λ / 4 wave plate is used as a function of rotating the polarization plane. In order, a reflective photomask including a substrate, a reflective film, a patterned absorber and a polarizer is prepared,
Irradiating the reflective photomask with inspection light,
A reflective photomask for detecting a contrast between a pattern opening and a non-pattern opening of the reflective photomask using an analyzer that can be rotated in a direction perpendicular to the optical axis of the inspection light Inspection method.   An inspection apparatus for a reflective photomask, wherein the reflective photomask is inspected by using the reflective photomask inspection method according to claim 15.

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