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Researchers Submit Patent Application, "Multilayer Substrate, Manufacturing Method for Multilayer Substrate, and Quality Control Method for...

January 29, 2014



Researchers Submit Patent Application, "Multilayer Substrate, Manufacturing Method for Multilayer Substrate, and Quality Control Method for Multilayer Substrate", for Approval

By a News Reporter-Staff News Editor at Electronics Newsweekly -- From Washington, D.C., VerticalNews journalists report that a patent application by the inventors OKAMURA, Yuzo (Tokyo, JP); IKUTA, Yoshiaki (Tokyo, JP), filed on September 9, 2013, was made available online on January 16, 2014.

The patent's assignee is Asahi Glass Company, Limited.

News editors obtained the following quote from the background information supplied by the inventors: "In recent years, following the downsizing of semiconductor devices, the lithography technique (EUVL) using an EUV (Extreme Ultra-Violet) light having a shorter wavelength instead of the conventional ArF laser is considered promising. The EUV light as referred to herein means a light having a wavelength of a soft X-ray region or a vacuum ultraviolet ray region, and specifically, is a light having a wavelength of from about 0.2 to 100 nm. Currently, as a lithography light source, the use of the light having a wavelength in the vicinity of 13.5 nm is mainly investigated.

"In addition, following the downsizing of semiconductor devices, a problem of defects on a photomask which is used in the lithography technique has been actualized, In particular, since the photomask is fabricated by subjecting a mask blank to pattern processing, a problem of defects on the mask blank has been actualized.

"In order to avoid the problem of defects on the mask blank, there has been developed a technique for identifying a defect position on the mask blank and changing a position or direction of the processing pattern in accordance with the defect position. In addition, in order to identify the defect position on the mask blank, there has been proposed a technique for forming a concave fiducial mark that indicates a fiducial position of the mask blank (see, for example, Patent Document 1).

"The mask blank is a multilayer substrate obtained by depositing a multilayer film on a substrate. In the mask blank for EUVL, the multilayer film includes a reflective layer that reflects an EUV light and an absorber layer that absorbs an EUV light in this order from the side of the substrate.

"In the conventional methods, the defect position on the substrate is identified while taking a position of a fiducial mark formed on the substrate as a fiducial position. In addition, since the fiducial mark is transferred to the multilayer film to be deposited on the substrate, the defect position of each of functional layers constituting the multilayer film is identified while taking the position of the transferred fiducial mark as a fiducial position (see, for example, Patent Document 2)."

As a supplement to the background information on this patent application, VerticalNews correspondents also obtained the inventors' summary information for this patent application: "Problems to be Solved by The Invention

"Now, an electron beam lithography system which is used in the manufacturing step of a photomask detects a position of a fiducial mark which has been transferred to the uppermost layer of a multilayer film, by using reflected electron beams. In addition, a mask registration system and a mask inspection system which are used in the manufacturing step of a photomask detect reflected ultraviolet rays having a wavelength of from 190 to 400 nm to detect a position of a fiducial mark which has been transferred to the uppermost layer of a multilayer film.

"However, in the conventional fiducial marks, it was difficult to detect the position of a concave fiducial mark by using reflected electron beams or reflected ultraviolet rays. This is because an edge of the fiducial mark to be transferred to a functional layer becomes round every time when the functional layer is stacked one by one. This is also because the inner bottom surface of the fiducial mark which has been transferred to the uppermost layer of the multilayer film and the uppermost layer of the multilayer film are constituted of the same material, and therefore, a difference in the intensity of reflected electron beams or in the intensity of reflected ultraviolet rays is small between a portion where the fiducial mark is present and a surrounding portion thereof. Patent Document 2 describes a multilayer film mask blank having a fiducial mark provided thereon, which is obtained by providing a concave in a part of the surface of a super-smooth substrate in advance and further accumulating a multilayer film thereon, and also describes that the fiducial mark formed on the substrate can be detected its pattern by electron beams. However, in the case of fabricating a mark on the substrate, there was involved such a problem that a detection signal becomes low, so that the required accuracy of detection position is hardly obtained.

"In view of the foregoing problem, the present invention has been made, and objects thereof are to provide a multilayer substrate capable of detecting a fiducial position with good accuracy by reflected electron beams or reflected ultraviolet rays, a manufacturing method for the multilayer substrate, and a quality control method for the multilayer substrate.

"Means for Solving the Problems

"In order to accomplish the above objects, the present invention provides:

"a multilayer substrate comprising a substrate and a multilayer film provided on the substrate, in which

"a concave or convex fiducial mark that indicates a fiducial position of the multilayer substrate is formed on the surface of the multilayer film on the opposite side to the side of the substrate; and

"a material of at least a part of the surface of the fiducial mark is different from a material of a most superficial layer of the multilayer film on the opposite side to the side of the substrate.

"Further, the present invention provides:

"a manufacturing method for a multilayer substrate comprising a substrate and a multilayer film provided on the substrate, which comprises:

"a step of forming a concave or convex fiducial mark that indicates a fiducial position of the multilayer substrate on the surface of the multilayer film on the opposite side to the side of the substrate, in which

"a material of at least a part of the surface of the fiducial mark is different from a material of a most superficial layer of the multilayer film on the opposite side to the side of the substrate.

"Further, the present invention provides:

"a quality control method for a multilayer substrate comprising a substrate and a multilayer film provided on the substrate, with a concave or convex fiducial mark that indicates a fiducial position of the multilayer substrate being formed on the surface of the multilayer film on the opposite side to the side of the substrate, which comprises:

"an identification step of identifying a defect position existing on the substrate before depositing the multilayer film on the substrate while taking a position of a concave or convex temporary fiducial mark existing on the substrate as a fiducial position, and/or identifying a defect position of at least one layer of the multilayer film on the way of depositing the multilayer film while taking a position of a concave or convex temporary fiducial mark existing on the substrate as a fiducial position;

"a detection step of detecting a positional relation between the temporary fiducial mark and the fiducial mark; and

"a conversion step of converting the defect position identified in the identification step into a position that takes the position of the fiducial mark as the fiducial position on the basis of results of the detection step, in which

"a material of at least a part of the surface of the fiducial mark is different from a material of a most superficial layer of the multilayer film on the opposite side to the side of the substrate.

"Furthermore, the present invention provides:

"a quality control method for a multilayer substrate comprising a substrate and a multilayer film provided on the substrate, with a concave or convex fiducial mark that indicates a fiducial position of the multilayer substrate being formed on the surface of the multilayer film on the opposite side to the side of the substrate, which comprises:

"an identification step of identifying a defect position existing on the substrate before depositing the multilayer film on the substrate while taking a position of a concave or convex temporary fiducial mark existing on the substrate as a fiducial position, and/or identifying a defect position of at least one layer of the multilayer film on the way of depositing the multilayer film while taking a position of a concave or convex temporary fiducial mark existing on the substrate as a fiducial position, in which

"the fiducial mark is formed so as to be superimposed on the temporary fiducial mark in a planar view, and a material of at least a part of the surface of the fiducial mark is different from a material of a most superficial layer of the multilayer film on the opposite side to the side of the substrate,

"Effect of the Invention

"According to the present invention, it is possible to provide a multilayer substrate capable of detecting a fiducial position with good accuracy by reflected electron beams or reflected ultraviolet rays, a manufacturing method for a multilayer substrate, and a quality control method for a multilayer substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIG. 1 is a cross-sectional view of a mask blank for EUVL according to the First embodiment of the present invention.

"FIG. 2 is a cross-sectional view of an example of a photomask obtained by subjecting a mask blank to pattern processing.

"FIG. 3 is a plan view of an example of a substrate and a temporary fiducial mark.

"FIG. 4 is a diagram showing an example of a cross-sectional profile of a concave fiducial mark and a cross-sectional profile of a concave temporary fiducial mark transferred to an uppermost layer of a multilayer

"FIG. 5 is a plan view of an example of a mask blank and a fiducial mark.

"FIG. 6 is an explanatory view of a difference in contrast of a reflected electron image (SEM photograph) due to a difference of material.

"FIG. 7 is an explanatory view of a difference in ultraviolet-region reflectivity spectrum due to a difference of material.

"FIG. 8 is a cross-sectional view of a mask blank for EUVL according to the Second embodiment of the present invention.

"FIG. 9 is a flowchart of a manufacturing method for a mask blank according to the Third embodiment of the present invention.

"FIG. 10 is a flowchart of a quality control method for a mask blank according to the Fourth embodiment of the present invention.

"FIG. 11 is a cross-sectional view of a mask blank for EUVL according to the Fifth embodiment of the present invention."

For additional information on this patent application, see: OKAMURA, Yuzo; IKUTA, Yoshiaki. Multilayer Substrate, Manufacturing Method for Multilayer Substrate, and Quality Control Method for Multilayer Substrate. Filed September 9, 2013 and posted January 16, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=2354&p=48&f=G&l=50&d=PG01&S1=20140109.PD.&OS=PD/20140109&RS=PD/20140109

Keywords for this news article include: Electronics, Semiconductor, Asahi Glass Company Limited.

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Source: Electronics Newsweekly


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