Glass substrate for mask blank, mask blank and photomask

{
  "publication_number": "US10599031B2",
  "country": "US",
  "kind": "B2",
  "title": "Glass substrate for mask blank, mask blank and photomask",
  "abstract": "A glass substrate for a mask blank includes a first surface and a second surface. The first surface and second surface face each other. Each of the first surface and the second surface is approximately square having a vertical length and a horizontal length being equal to the vertical length. The first surface of the glass substrate has specific profile properties.",
  "claims": [
    "1. A glass substrate for a mask blank, comprising a first surface and a second surface, which face each other and each of which is approximately square having a vertical length (P) and a horizontal length (P) being equal to the vertical length (P), wherein: in the first surface, a first square having a center coinciding with a center of the first surface and sides which are parallel with respective sides of the first surface and have a length P 1 of 104 mm, a second square having a center coinciding with the center of the first surface and sides which are parallel with the respective sides of the first surface and have a length P 2 of 132 mm, and a third square having a center coinciding with the center of the first surface and sides which are parallel with the respective sides of the first surface and have a length P 3 of 142 mm, are assumed; a region inside the first square, the region including the first square, is referred to as a central region, a region enclosed by the second square and the first square, the region including the second square but not including the first square, is referred to as a peripheral region, a region enclosed by the third square and the second square, the region including the third square but not including the second square, is referred to as an edge region, a region inside the second square, the region including the second square, is referred to as a non-edge region, and a region inside the third square, the region including the third square, is referred to as an effective region; in the effective region of the first surface, 100 or more vertical lines are drawn in the vertical direction at same interval d and 100 or more horizontal lines are drawn in the horizontal direction at same interval d, and a profile is recognized by measuring relative heights at respective measurement positions in a cross section taken along each of the vertical lines and the horizontal lines; the profile of the first surface is judged as a convex profile if an average value of heights at measurement positions on all of the vertical lines and the horizontal lines in the central region is higher than an average value of heights at measurement positions on all of the vertical lines and the horizontal lines in the peripheral region, whereas the profile of the first surface is judged as a concave profile if the average value of heights at the measurement positions on all of the vertical lines and the horizontal lines in the central region is lower than the average value of heights at the measurement positions on all of the vertical lines and the horizontal lines in the peripheral region; among the vertical lines, a vertical line that crosses, in the following order, the edge region which is referred to as a first section of the edge region, the peripheral region which is referred to as a first section of the peripheral region, the central region, the peripheral region which is referred to as a second section of the peripheral region, and the edge region which is referred to as a second section of the edge region, is referred to as a particular vertical line; among the horizontal lines, a horizontal line that crosses, in the following order, the edge region which is referred to as a third section of the edge region, the peripheral region which is referred to as a third section of the peripheral region, the central region, the peripheral region which is referred to as a fourth section of the peripheral region, and the edge region which is referred to as a fourth section of the edge region, is referred to as a particular horizontal line; a peak-to-valley (PV) value in the effective region is 70 nm or less; (i) in a case where the profile of the first surface is the convex profile, when a profile curve is drawn by a curve fitting based on each measurement point in the non-edge region in a profile in a cross section taken along each of the particular vertical line and the particular horizontal line, an extrapolation curve having a first portion ϕ 1 in the first section or third section of the edge region and a second portion ϕ 2 in the second section or fourth section of the edge region is drawn by extrapolating the profile curve to the ends of the effective region, and a first reference curve R 1 and a second reference curve R 2 are drawn by adding 3 nm to heights of the first portion ϕ 1 and the second portion ϕ 2, respectively, a mode which a first straight line obtained by straight-line-approximating measurement points of the profile in the first section or third section of the edge region is located under the first reference curve R 1 and a second straight line obtained by straight-line-approximating measurement points of the profile in the second section or fourth section of the edge region is located under the second reference curve R 2 holds in 75% or more of the cross sections taken along all of the particular vertical lines and the particular horizontal lines; and (ii) in a case where the profile of the first surface is the concave profile, when a profile curve is drawn by a curve fitting based on each measurement point in the non-edge region in a profile in a cross section taken along each of the particular vertical lines and the particular horizontal lines, an extrapolation curve having a first portion ϕ 1 in the first section or third section of the edge region and a second portion ϕ 2 in the second section or fourth section of the edge region is drawn by extrapolating the profile curve to the ends of the effective region, and a first reference curve R 1 and a second reference curve R 2 are drawn by subtracting 3 nm from heights of the first portion ϕ 1 and the second portion ϕ 2, respectively, a mode which a first straight line obtained by straight-line-approximating measurement points of the profile in the first section or third section of the edge region is located over the first reference curve R 1 and a second straight line obtained by straight-line-approximating measurement points of the profile in the second section or fourth section of the edge region is located over the second reference curve R 2 holds in 75% or more of the cross sections taken along all of the particular vertical lines and the particular horizontal lines.",
    "2. A mask blank comprising: the glass substrate according to claim 1; and a film formed on the first surface of the glass substrate.",
    "3. The mask blank according to claim 2, wherein the film is a light shield film that interrupts light in a particular wavelength range.",
    "4. The glass substrate according to claim 1, wherein: in the second surface, a fourth square having a center coinciding with a center of the second surface and sides which are parallel with respective sides of the second surface and have a length P 1 of 104 mm, a fifth square having a center coinciding with the center of the second surface and sides which are parallel with the respective sides of the second surface and have a length P 2 of 132 mm, and a sixth square having a center coinciding with the center of the second surface and sides which are parallel with the respective sides of the second surface and have a length P 3 of 142 mm, are assumed; a region inside the fourth square, the region including the fourth square, is referred to as a second central region, a region enclosed by the fifth square and the fourth square, the region including the fifth square but not including the fourth square, is referred to as a second peripheral region, a region enclosed by the sixth square and the fifth square, the region including the sixth square but not including the fifth square, is referred to as a second edge region, a region inside the fifth square, the region including the fifth square, is referred to as a second non-edge region, and a region inside the sixth square, the region including the sixth square, is referred to as a second effective region; a profile of the second surface is judged as a convex profile or a concave profile in the same manner as in the case of the first surface; a peak-to-valley (PV) value in the second effective region is 70 nm or less; in a case where the profile of the second surface is the convex profile, when the same manipulations as performed in the case of the first surface are performed, a mode which a first straight line obtained by straight-line-approximating measurement points of the profile in the first section or third section of the second edge region is located under the first reference curve R 1 and a second straight line obtained by straight-line-approximating measurement points of the profile in the second section or fourth section of the second edge region is located under the second reference curve R 2 holds in 75% or more of the cross sections taken along all of the particular vertical lines and the particular horizontal lines; in a case where the profile of the second surface is the convex profile, when the same manipulations as performed in the case of the first surface are performed, a mode which a first straight line obtained by straight-line-approximating measurement points of the profile in the first section or third section of the second edge region is located over the first reference curve R 1 and a second straight line obtained by straight-line-approximating measurement points of the profile in the second section or fourth section of the second edge region is located over the second reference curve R 2 holds in 75% or more of the cross sections taken along all of the particular vertical lines and the particular horizontal lines; in a case where the profile of the first surface is the convex profile, when the central region of the first surface and the second central region of the second surface are integrally observed from a direction perpendicular to a thickness direction of the glass substrate, the central region of the first surface relatively projects to the side opposite to the second central region and the second central region relatively projects to the side of the central region of the first surface; and in a case where the profile of the first surface is the concave profile, when the central region of the first surface and the second central region of the second surface are integrally observed from a direction perpendicular to a thickness direction of the glass substrate, the central region of the first surface relatively projects to the side of the second central region and the second central region relatively projects to the side opposite to the central region of the first surface.",
    "5. A mask blank comprising: the glass substrate according to claim 4; and a film formed on the first surface of the glass substrate.",
    "6. The mask blank according to claim 5, wherein the film comprises an absorption film that absorbs light in a particular wavelength range and a reflection film that reflects the light.",
    "7. A mask blank comprising: a glass substrate; and a film formed on a surface of the glass substrate, wherein: the glass substrate comprises a first surface and a second surface, which face each other and each of which is approximately square having a vertical length (P) and a horizontal length (P) being equal to the vertical length (P); in the first surface, a first square having a center coinciding with a center of the first surface and sides which are parallel with respective sides of the first surface and have a length P 1 of 104 mm, a second square having a center coinciding with the center of the first surface and sides which are parallel with the respective sides of the first surface and have a length P 2 of 132 mm, and a third square having a center coinciding with the center of the first surface and sides which are parallel with the respective sides of the first surface and have a length P 3 of 142 mm, are assumed; a region inside the first square, the region including the first square, is referred to as a central region, a region enclosed by the second square and the first square, the region including the second square but not including the first square, is referred to as a peripheral region, a region enclosed by the third square and the second square, the region including the third square but not including the second square, is referred to as an edge region, a region inside the second square, the region including the second square, is referred to as a non-edge region, and a region inside the third square, the region including the third square, is referred to as an effective region; in the effective region of the first surface, 100 or more vertical lines are drawn in the vertical direction at same interval d and 100 or more horizontal lines are drawn in the horizontal direction at same interval d, and a profile is recognized by measuring relative heights at respective measurement positions in a cross section taken along each of the vertical lines and the horizontal lines; the profile of the first surface is judged as a convex profile if an average value of heights at measurement positions on all of the vertical lines and the horizontal lines in the central region is higher than an average value of heights at measurement positions on all of the vertical lines and the horizontal lines in the peripheral region, whereas the profile of the first surface is judged as a concave profile if the average value of heights at the measurement positions on all of the vertical lines and the horizontal lines in the central region is lower than the average value of heights at the measurement positions on all of the vertical lines and the horizontal lines in the peripheral region; among the vertical lines, a vertical line that crosses, in the following order, the edge region which is referred to as a first section of the edge region, the peripheral region which is referred to as a first section of the peripheral region, the central region, the peripheral region which is referred to as a second section of the peripheral region, and the edge region which is referred to as a second section of the edge region, is referred to as a particular vertical line; among the horizontal lines, a horizontal line that crosses, in the following order, the edge region which is referred to as a third section of the edge region, the peripheral region which is referred to as a third section of the peripheral region, the central region, the peripheral region which is referred to as a fourth section of the peripheral region, and the edge region which is referred to as a fourth section of the edge region, is referred to as a particular horizontal line; a peak-to-valley (PV) value in the effective region is 70 nm or less; (i) in a case where the profile of the first surface is the convex profile, when a profile curve is drawn by a curve fitting based on each measurement point in the non-edge region in a profile in a cross section taken along each of the particular vertical line and the particular horizontal line, an extrapolation curve having a first portion ϕ 1 in the first section or third section of the edge region and a second portion ϕ 2 in the second section or fourth section of the edge region is drawn by extrapolating the profile curve to the ends of the effective region, and a first reference curve R 1 and a second reference curve R 2 are drawn by adding 3 nm to heights of the first portion ϕ 1 and the second portion ϕ 2, respectively, a mode which a first straight line obtained by straight-line-approximating measurement points of the profile in the first section or third section of the edge region is located under the first reference curve R 1 and a second straight line obtained by straight-line-approximating measurement points of the profile in the second section or fourth section of the edge region is located under the second reference curve R 2 holds in 75% or more of the cross sections taken along all of the particular vertical lines and the particular horizontal lines; and (ii) in a case where the profile of the first surface is the concave profile, when a profile curve is drawn by a curve fitting based on each measurement point in the non-edge region in a profile in a cross section taken along each of the particular vertical lines and the particular horizontal lines, an extrapolation curve having a first portion ϕ 1 in the first section or third section of the edge region and a second portion ϕ 2 in the second section or fourth section of the edge region is drawn by extrapolating the profile curve to the ends of the effective region, and a first reference curve R 1 and a second reference curve R 2 are drawn by subtracting 3 nm from heights of the first portion ϕ 1 and the second portion ϕ 2, respectively, a mode which a first straight line obtained by straight-line-approximating measurement points of the profile in the first section or third section of the edge region is located over the first reference curve R 1 and a second straight line obtained by straight-line-approximating measurement points of the profile in the second section or fourth section of the edge region is located over the second reference curve R 2 holds in 75% or more of the cross sections taken along all of the particular vertical lines and the particular horizontal lines.",
    "8. The mask blank according to claim 7, wherein the film is a light shield film that interrupts light in a particular wavelength range and is formed on the side of the first surface.",
    "9. The mask blank according to claim 7, wherein: in the second surface, a fourth square having a center coinciding with a center of the second surface and sides which are parallel with respective sides of the second surface and have a length P 1 of 104 mm, a fifth square having a center coinciding with the center of the second surface and sides which are parallel with the respective sides of the second surface and have a length P 2 of 132 mm, and a sixth square having a center coinciding with the center of the second surface and sides which are parallel with the respective sides of the second surface and have a length P 3 of 142 mm, are assumed; a region inside the fourth square, the region including the fourth square, is referred to as a second central region, a region enclosed by the fifth square and the fourth square, the region including the fifth square but not including the fourth square, is referred to as a second peripheral region, a region enclosed by the sixth square and the fifth square, the region including the sixth square but not including the fifth square, is referred to as a second edge region, a region inside the fifth square, the region including the fifth square, is referred to as a second non-edge region, and a region inside the sixth square, the region including the sixth square, is referred to as a second effective region; a profile of the second surface is judged as a convex profile or a concave profile in the same manner as in the case of the first surface; a peak-to-valley (PV) value in the second effective region is 70 nm or less; in a case where the profile of the second surface is the convex profile, when the same manipulations as performed in the case of the first surface are performed, a mode which a first straight line obtained by straight-line-approximating measurement points of the profile in the first section or third section of the second edge region is located under the first reference curve R 1 and a second straight line obtained by straight-line-approximating measurement points of the profile in the second section or fourth section of the second edge region is located under the second reference curve R 2 holds in 75% or more of the cross sections taken along all of the particular vertical lines and the particular horizontal lines; in a case where the profile of the second surface is the convex profile, when the same manipulations as performed in the case of the first surface are performed, a mode which a first straight line obtained by straight-line-approximating measurement points of the profile in the first section or third section of the second edge region is located over the first reference curve R 1 and a second straight line obtained by straight-line-approximating measurement points of the profile in the second section or fourth section of the second edge region is located over the second reference curve R 2 holds in 75% or more of the cross sections taken along all of the particular vertical lines and the particular horizontal lines; in a case where the profile of the first surface is the convex profile, when the central region of the first surface and the second central region of the second surface are integrally observed from a direction perpendicular to a thickness direction of the glass substrate, the central region of the first surface relatively projects to the side opposite to the second central region and the second central region relatively projects to the side of the central region of the first surface; and in a case where the profile of the first surface is the concave profile, when the central region of the first surface and the second central region of the second surface are integrally observed from a direction perpendicular to a thickness direction of the glass substrate, the central region of the first surface relatively projects to the side of the second central region and the second central region relatively projects to the side opposite to the central region of the first surface.",
    "10. The mask blank according to claim 9, wherein the film comprises an absorption film that absorbs light in a particular wavelength range and a reflection film that reflects the light.",
    "11. A photomask comprising: a glass substrate; and a patterned film formed on a surface of the glass substrate, wherein: the glass substrate comprises a first surface and a second surface, which face each other and each of which is approximately square having a vertical length (P) and a horizontal length (P) being equal to the vertical length (P); in the first surface, a first square having a center coinciding with a center of the first surface and sides which are parallel with respective sides of the first surface and have a length P 1 of 104 mm, a second square having a center coinciding with the center of the first surface and sides which are parallel with the respective sides of the first surface and have a length P 2 of 132 mm, and a third square having a center coinciding with the center of the first surface and sides which are parallel with the respective sides of the first surface and have a length P 3 of 142 mm, are assumed; a region inside the first square, the region including the first square, is referred to as a central region, a region enclosed by the second square and the first square, the region including the second square but not including the first square, is referred to as a peripheral region, a region enclosed by the third square and the second square, the region including the third square but not including the second square, is referred to as an edge region, a region inside the second square, the region including the second square, is referred to as a non-edge region, and a region inside the third square, the region including the third square, is referred to as an effective region; in the effective region of the first surface, 100 or more vertical lines are drawn in the vertical direction at same interval d and 100 or more horizontal lines are drawn in the horizontal direction at same interval d, and a profile is recognized by measuring relative heights at respective measurement positions in a cross section taken along each of the vertical lines and the horizontal lines; the profile of the first surface is judged as a convex profile if an average value of heights at measurement positions on all of the vertical lines and the horizontal lines in the central region is higher than an average value of heights at measurement positions on all of the vertical lines and the horizontal lines in the peripheral region, whereas the profile of the first surface is judged as a concave profile if the average value of heights at the measurement positions on all of the vertical lines and the horizontal lines in the central region is lower than the average value of heights at the measurement positions on all of the vertical lines and the horizontal lines in the peripheral region; among the vertical lines, a vertical line that crosses, in the following order, the edge region which is referred to as a first section of the edge region, the peripheral region which is referred to as a first section of the peripheral region, the central region, the peripheral region which is referred to as a second section of the peripheral region, and the edge region which is referred to as a second section of the edge region, is referred to as a particular vertical line; among the horizontal lines, a horizontal line that crosses, in the following order, the edge region which is referred to as a third section of the edge region, the peripheral region which is referred to as a third section of the peripheral region, the central region, the peripheral region which is referred to as a fourth section of the peripheral region, and the edge region which is referred to as a fourth section of the edge region, is referred to as a particular horizontal line; a peak-to-valley (PV) value in the effective region is 70 nm or less; (i) in a case where the profile of the first surface is the convex profile, when a profile curve is drawn by a curve fitting based on each measurement point in the non-edge region in a profile in a cross section taken along each of the particular vertical line and the particular horizontal line, an extrapolation curve having a first portion ϕ 1 in the first section or third section of the edge region and a second portion ϕ 2 in the second section or fourth section of the edge region is drawn by extrapolating the profile curve to the ends of the effective region, and a first reference curve R 1 and a second reference curve R 2 are drawn by adding 3 nm to heights of the first portion ϕ 1 and the second portion ϕ 2, respectively, a mode which a first straight line obtained by straight-line-approximating measurement points of the profile in the first section or third section of the edge region is located under the first reference curve R 1 and a second straight line obtained by straight-line-approximating measurement points of the profile in the second section or fourth section of the edge region is located under the second reference curve R 2 holds in 75% or more of the cross sections taken along all of the particular vertical lines and the particular horizontal lines; and (ii) in a case where the profile of the first surface is the concave profile, when a profile curve is drawn by a curve fitting based on each measurement point in the non-edge region in a profile in a cross section taken along each of the particular vertical lines and the particular horizontal lines, an extrapolation curve having a first portion ϕ 1 in the first section or third section of the edge region and a second portion ϕ 2 in the second section or fourth section of the edge region is drawn by extrapolating the profile curve to the ends of the effective region, and a first reference curve R 1 and a second reference curve R 2 are drawn by subtracting 3 nm from heights of the first portion ϕ 1 and the second portion ϕ 2, respectively, a mode which a first straight line obtained by straight-line-approximating measurement points of the profile in the first section or third section of the edge region is located over the first reference curve R 1 and a second straight line obtained by straight-line-approximating measurement points of the profile in the second section or fourth section of the edge region is located over the second reference curve R 2 holds in 75% or more of the cross sections taken along all of the particular vertical lines and the particular horizontal lines.",
    "12. The photomask according to claim 11, wherein the film is a light shield film that interrupts light in a particular wavelength range and is formed on the side of the first surface.",
    "13. The photomask according to claim 11, wherein: in the second surface, a fourth square having a center coinciding with a center of the second surface and sides which are parallel with respective sides of the second surface and have a length P 1 of 104 mm, a fifth square having a center coinciding with the center of the second surface and sides which are parallel with the respective sides of the second surface and have a length P 2 of 132 mm, and a sixth square having a center coinciding with the center of the second surface and sides which are parallel with the respective sides of the second surface and have a length P 3 of 142 mm, are assumed; a region inside the fourth square, the region including the fourth square, is referred to as a second central region, a region enclosed by the fifth square and the fourth square, the region including the fifth square but not including the fourth square, is referred to as a second peripheral region, a region enclosed by the sixth square and the fifth square, the region including the sixth square but not including the fifth square, is referred to as a second edge region, a region inside the fifth square, the region including the fifth square, is referred to as a second non-edge region, and a region inside the sixth square, the region including the sixth square, is referred to as a second effective region; a profile of the second surface is judged as a convex profile or a concave profile in the same manner as in the case of the first surface; a peak-to-valley (PV) value in the second effective region is 70 nm or less; in a case where the profile of the second surface is the convex profile, when the same manipulations as performed in the case of the first surface are performed, a mode which a first straight line obtained by straight-line-approximating measurement points of the profile in the first section or third section of the second edge region is located under the first reference curve R 1 and a second straight line obtained by straight-line-approximating measurement points of the profile in the second section or fourth section of the second edge region is located under the second reference curve R 2 holds in 75% or more of the cross sections taken along all of the particular vertical lines and the particular horizontal lines; in a case where the profile of the second surface is the convex profile, when the same manipulations as performed in the case of the first surface are performed, a mode which a first straight line obtained by straight-line-approximating measurement points of the profile in the first section or third section of the second edge region is located over the first reference curve R 1 and a second straight line obtained by straight-line-approximating measurement points of the profile in the second section or fourth section of the second edge region is located over the second reference curve R 2 holds in 75% or more of the cross sections taken along all of the particular vertical lines and the particular horizontal lines; in a case where the profile of the first surface is the convex profile, when the central region of the first surface and the second central region of the second surface are integrally observed from a direction perpendicular to a thickness direction of the glass substrate, the central region of the first surface relatively projects to the side opposite to the second central region and the second central region relatively projects to the side of the central region of the first surface; and in a case where the profile of the first surface is the concave profile, when the central region of the first surface and the second central region of the second surface are integrally observed from a direction perpendicular to a thickness direction of the glass substrate, the central region of the first surface relatively projects to the side of the second central region and the second central region relatively projects to the side opposite to the central region of the first surface.",
    "14. The photomask according to claim 13, wherein the film comprises an absorption film that absorbs light in a particular wavelength range and a reflection film that reflects the light."
  ],
  "description_excerpt": "The present invention relates to a glass substrate for a mask blank, a mask blank, and a photomask.\n\nSemiconductor manufacturing processes employ photolithography technologies using a photomask. In these technologies, the pattern of a photomask is transferred to a target substrate to be processed, by irradiating the photomask with exposing light using an exposing machine.\n\nIn recent years, to enable transfer of a very fine pattern, it has come to be studied to use short-wavelength exposing light such as ArF excimer laser light and even EUV (extreme ultraviolet) light.\n\nThe term “EUV light” means light that includes soft X rays and vacuum ultraviolet light and, more specifically, is approximately in a wavelength range of 0.2 nm to 100 nm. At present, use of EUV light having a wavelength of about 13.5 nm as exposing light is mainly being studied.\n\nIn photolithography technologies, the quality and accuracy of a transferred pattern are influenced by the flatness of the surface of a photomask. In particular, it is expected that the influence of the flatness of the surface of a photomask will become more remarkable as the degree of miniaturization of transfer patterns increases.\n\nIn the above circumstances, photomasks have come to be required be increased in flatness.\n\nVarious surface polishing methods have been proposed so far to increase the flatness of a glass substrate for a mask blank (i.e. to control the flatness of the glass substrate to be low) from which a photomask is to be formed.",
  "cpc": [
    "G03F 1/60",
    "B32B 17/06",
    "B32B 2307/71",
    "G03F 1/22",
    "G03F 1/24",
    "G03F 1/52",
    "G03F 1/54"
  ],
  "ipc": [
    "B32B 17/06",
    "G03F 1/22",
    "G03F 1/24",
    "G03F 1/52",
    "G03F 1/54",
    "G03F 1/60"
  ],
  "assignees": [
    "Asahi Glass Co Ltd"
  ],
  "inventors": [
    "Yuzo OKAMURA"
  ],
  "filing_date": "2018-01-29",
  "publication_date": "2020-03-24",
  "grant_date": "2020-03-24",
  "priority_date": "2017-01-30",
  "application_number": "US-201815881968-A",
  "family_id": "62979782",
  "cited_by_count": 3,
  "citations": [
    "WO2010110139A1",
    "US20110262846A1",
    "US20120208112A1"
  ]
}