JP5662767B2 - Mask for imprint lithography - Google Patents

Description

  The present invention relates to a mask for imprint lithography.

  In recent years, the miniaturization of semiconductor patterns has advanced remarkably. A semiconductor is generally manufactured in such a manner that a pattern drawn on a mask is reduced and projected onto a wafer. Therefore, there is a limit to the fine processing of semiconductors due to the influence of diffraction in the reduction projection optical system.

  The minimum pattern size that can be accommodated by the reduction projection optical system is proportional to the wavelength of light used. For this reason, the shortening of the wavelength of the light source of the semiconductor exposure apparatus has progressed to 193 nm. However, there is almost no glass material that can cope with shorter wavelength. Therefore, it is considered that the next-generation exposure apparatus progresses at a stretch to those using extreme ultraviolet rays (EUV light) composed of a reflection optical system in a vacuum.

  However, the apparatus using extreme ultraviolet rays has many problems to be solved and is very expensive. For this reason, imprint lithography has been studied as one alternative.

  The principle of imprint lithography is to press a glass mask engraved with a transfer pattern of the same size as the semiconductor pattern against the imprint resist, irradiate ultraviolet rays through the glass mask, cure the resist with ultraviolet rays, and peel off the mask. It is the principle of the stamp. Therefore, as disclosed in Patent Document 1, a mask for imprint lithography has a convex shape in which a pattern region protrudes from a peripheral non-pattern region.

  Patent Document 2 discloses a method for detecting the position of a semiconductor substrate in which an alignment mark is formed by a concavo-convex portion having a planar shape having a size smaller than the resolution of an observation lens.

JP 2009-23113 A Japanese Patent Laid-Open No. 9-22864

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an imprint lithography mask having an easily manufactured alignment mark.

The imprint lithography mask of one embodiment of the present invention is formed by a transfer pattern formed by unevenness in which the surface of a substrate made of a transparent material is dug, and an unevenness in which the surface of a portion different from the transfer pattern is dug. that the alignment mark, have a concavo-convex for forming the alignment mark has a periodicity, wherein the maximum period is less than the resolution of the optical system for alignment when the defect of the mask inspection.

  In the imprint lithography mask of the above aspect, it is desirable that the uneven depth of the transferred pattern and the recessed depth of the alignment mark are equal.

  In the imprint lithography mask of the above aspect, it is desirable that the unevenness forming the alignment mark has periodicity and the maximum period is less than 189 nm.

  In the mask for imprint lithography of the above aspect, it is desirable that the recess depth of the unevenness forming the alignment mark is 46 nm or more and 66 nm or less.

  ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the mask for imprint lithography provided with the alignment mark which can be manufactured easily.

It is a schematic diagram of the mask for imprint lithography of 1st Embodiment. It is a schematic diagram of the alignment mark of 1st Embodiment. It is a schematic diagram of the alignment mark of 2nd Embodiment.

  Embodiments of the present invention will be described below with reference to the drawings.

  In the present specification, values such as “period” and “depth” mean average values when measured at a plurality of corresponding locations.

  In the present specification, the “transfer pattern” means a pattern used for manufacturing an element structure, such as a circuit pattern, among patterns transferred to a resist or the like. For example, even if the alignment mark pattern is transferred to a resist or the like, this pattern is not referred to as a transfer pattern.

(First embodiment)
The imprint lithography mask according to the present embodiment has a transfer pattern formed by unevenness dug in the surface of a substrate made of a transparent material, and an alignment formed by unevenness dug in the surface of a portion different from the transfer pattern. And a mark.

  FIG. 1 is a schematic diagram of an imprint lithography mask according to the present embodiment. 1A is a top view, FIG. 1B is an AA sectional view of FIG. 1A, and FIG. 1C is an enlarged view of a broken-line circle in FIG. 1B.

  A substrate 12 made of a transparent material is used for the imprint lithography mask 10. The substrate 12 is, for example, quartz glass.

  A pattern region 14 and a non-pattern region 16 exist on the upper surface of the imprint lithography mask 10. As shown in FIG. 1B, the pattern region 14 is formed to protrude from the tens of microns to several hundreds of microns from the non-pattern region 16. For this reason, at the time of stamping on a wafer or the like, only the pattern region 14 contacts the resist applied on the wafer, and the non-pattern region 16 does not contact.

  In the pattern region 14, the pattern portion 18 on which a transfer pattern such as a circuit pattern to be transferred to a semiconductor wafer or the like is formed, and the mask 10 is aligned with a defect inspection apparatus during the defect inspection of the mask 10 ( An alignment mark 20 used for positioning) is provided. The alignment is performed in order to correct a positional deviation or an inclination of the mask with respect to the defect inspection apparatus prior to the mask defect inspection.

  The alignment marks 20 are provided at the four corners of the pattern region 14. The transfer pattern and the alignment mark 20 exist on the same plane.

As shown in FIG. 1C, the transfer pattern of the pattern portion 18 is formed by irregularities formed by digging a transparent material on the surface of the substrate 12. This transfer pattern has, for example, a period p ₁ and a recess depth d ₁ .

  The alignment mark 20 is formed by irregularities formed by digging a transparent material on the surface of a portion different from the transfer pattern of the pattern portion 18. FIG. 2 is a schematic diagram of the alignment mark of the present embodiment. FIG. 2A is a top view, and FIG. 2B is an enlarged cross-sectional view of a broken-line circle portion in FIG.

The alignment mark 20 includes a first mark 20a in which four rectangular interdigital patterns having periodicity are arranged, and a second mark having a non-periodic cross pattern arranged in the center of the first mark 20a. 20b. The first mark 20a is, for example, a period _{p 2} and a recess depth _{d 2.} The second mark 20b having a cross pattern is formed by, for example, two intersecting linear recesses.

  In the imprint lithography mask 10 of the present embodiment, the alignment mark 20 is also formed with irregularities formed by digging a transparent material on the surface of the substrate 12, similarly to the pattern portion 18. Therefore, it is not necessary to employ an additional structure / manufacturing process for the alignment mark 20 such as, for example, providing another type of film on the transparent material. Therefore, it is possible to easily manufacture a mask for imprint lithography at low cost.

Further, it is desirable that the concave / convex concave portion depth d ₁ of the transfer pattern of the pattern portion 18 is equal to the concave / convex concave portion depth d ₂ of the alignment mark 20. This is because when the mask 10 is manufactured, simultaneous formation of the transfer pattern of the pattern portion 18 and the alignment mark 20 is facilitated.

  Next, an example of a mask alignment method in the mask defect inspection apparatus using the imprint lithography mask 10 of the present embodiment will be briefly described.

  In the mask defect inspection apparatus, first, rough first alignment is performed by a low-magnification first alignment optical system using visible light. At this time, alignment is performed using the first mark 20a. By this alignment, the approximate center position of the first mark 20a is determined. That is, the position of the alignment mark 20a is specified with an accuracy that the second mark 20b fits in the field of view in the next second alignment.

  Next, the second alignment with higher accuracy is performed by the second alignment optical system using ultraviolet light. At this time, alignment is performed using the second mark 20b in the center of the first mark 20a. That is, alignment is performed using the intersections of the cross pattern.

  In the second alignment optical system, it is possible to observe at a higher magnification than in the first alignment optical system. The second alignment optical system is common to, for example, a defect inspection optical system used for defect inspection.

  Thus, 2 suitable for each of the first alignment optical system for performing alignment at low magnification using visible light and the second alignment optical system for performing alignment at high magnification using ultraviolet light. By having the kind of alignment mark, it becomes possible to realize higher-precision mask alignment.

  Here, it is desirable that the maximum period of the alignment mark is less than the resolution of the alignment optical system at the time of mask defect inspection. Here, the maximum cycle means the one having the longest cycle when the alignment mark pattern has a plurality of cycles. As in the case of the first mark 20a in FIG. 2, in the case of a single period, the maximum period means that single period.

Also, the resolution is determined when the wavelength of the alignment light of the alignment optical system is λ and the numerical aperture of the objective lens is NA.
Resolution = λ / (2NA) (Formula 1)
It shall be represented by

  When the maximum period of the first mark 20a is less than the resolution of the first alignment optical system at the time of mask defect inspection, the first mark 20a to be imaged is not resolved, and four rectangular dark solids Recognized as a region. In other words, since the maximum period is less than the resolution, the first mark 20a is not resolved, but is observed as a dark region that is uniformly darker than the surroundings. Therefore, image processing is facilitated, and the mark position detection accuracy is improved. Therefore, it is possible to stably guide the second mark 20b to the field of view of the second alignment optical system.

  For example, when the alignment light of the first alignment optical system is visible light having a wavelength of 400 nm and the numerical aperture of the objective lens is 0.70, the resolution is 286 nm from (Equation 1). As the alignment light of the first alignment optical system, it is preferable to use a short wavelength of 400 nm or more and less than 420 nm of visible light in view of the apparatus configuration.

Moreover, it is desirable that the concave / convex depth d ₂ forming the alignment mark is 20% or more and 30% or less of the wavelength of the alignment light at the time of mask defect inspection. If the wavelength of the alignment light is λ, the depth of the concave portion is 25% of the wavelength λ, that is, λ / 4, so that the light reflected from the surface of the convex portion and the light reflected from the bottom surface of the concave portion This is because the phase difference is λ / 2 and high contrast is obtained. The reason for setting it to 20% or more and 30% or less is to take into account processing variations and the like. Moreover, if it is in the range of ± 5%, high contrast can be realized.

  For example, if the alignment light of the first alignment optical system is visible light having a wavelength of 400 nm and the alignment light of the second alignment optical system is ultraviolet light having a wavelength of 193 nm, the depth of the recess of the first mark is 80 nm or more and 120 nm or less is desirable. Further, it is desirable that the recess depth of the second mark is 39 nm or more and 58 nm or less.

  In particular, increasing the contrast when performing alignment at a high magnification is important for improving alignment accuracy. From this viewpoint, it is desirable to improve the contrast of the alignment mark in the alignment performed using the defect inspection optical system.

  The wavelength of light assumed to be used in the defect inspection optical system is ultraviolet light of 185 nm to 265 nm. Below this range, there are almost no suitable light sources or compatible glass materials. Moreover, if it exceeds this range, the inspection accuracy decreases. Therefore, it is desirable that the concave / convex recess depth forming the alignment mark is a depth corresponding to λ / 4 having a wavelength of 185 nm to 265 nm, that is, 46 nm to 66 nm.

(Second Embodiment)
The imprint lithography mask of this embodiment is the same as that of the first embodiment except that the alignment mark does not have a cross-shaped pattern mark. Therefore, the description of the content overlapping with that of the first embodiment is omitted.

  FIG. 3 is a schematic diagram of the alignment mark of the present embodiment. FIG. 3A is a top view, and FIG. 3B is an enlarged cross-sectional view of a broken-line circle portion in FIG.

The alignment mark 30 is a mark in which four rectangular interdigital patterns having periodicity are arranged. The alignment mark 30 has, for example, a period p ₃ and a recess depth d ₃ . The maximum period of the unevenness forming the alignment mark 30, here the period p _3, is set to be less than the resolution of the defect inspection optical system used in the second alignment.

  The imprint lithography mask of the present embodiment is configured so that both alignment by visible light and alignment by ultraviolet light for defect inspection can be achieved with one type of alignment mark.

  Next, an example of a mask alignment method in the mask defect inspection apparatus using the imprint lithography mask 30 of the present embodiment will be briefly described.

  In the mask defect inspection apparatus, first rough alignment is performed by the first alignment optical system using visible light. At this time, the approximate center position of the alignment mark 30 is determined. At this time, since the maximum period of the unevenness is set to be less than the resolution of the optical system for defect inspection using ultraviolet light, the alignment mark 30 is not resolved even by visible light having a longer wavelength, and the darkness of the four rectangles. Recognized as a solid region.

  Next, the second alignment with higher accuracy is performed by the second alignment optical system using ultraviolet light, that is, the defect inspection optical system. At this time, alignment is performed using the corners of the alignment mark 30. Also in this case, the maximum period of the unevenness is set to be less than the resolution of the defect inspection optical system using ultraviolet light, so that the alignment mark is not resolved and is recognized as four rectangular dark solid regions.

  As described above, the wavelength of light assumed to be used in the defect inspection optical system is 185 nm or more and 265 nm or less. The NA of the objective lens used in the defect inspection optical system is assumed to be 0.7 or more.

Therefore, using (Equation 1), it is desirable that the period p ₃ is less than resolution = 265 nm / (2 × 0.7), that is, less than 189 nm. The NA that can be realized by the defect inspection apparatus is 0.9 or less. Therefore, it is more desirable that the period p ₃ is resolution = 185 nm / (2 × 0.9), that is, less than 103 nm. If the maximum period is within the above range, the alignment mark is not resolved in both the first alignment by visible light and the second alignment by ultraviolet light, and is recognized as four rectangular dark solid regions. Therefore, highly accurate mask alignment can be realized.

  With the imprint lithography mask of the present embodiment, high-precision mask alignment can be realized by using a mark simplified from that of the first embodiment.

  The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples.

  For example, although the interdigital pattern and the cross pattern have been described as examples of the alignment mark shape, other shapes such as a lattice pattern and a random pattern with no periodicity may be employed.

  In the embodiment, the case where the alignment marks are arranged at the four corners of the pattern area has been described as an example. However, the alignment marks are not necessarily arranged at the four corners. For example, the alignment marks may be arranged at the two corners on the diagonal line. You may arrange | position to the center part of 4 sides of a part.

  In addition, the case where the transfer pattern of the pattern portion and the recess depth of the alignment mark are the same has been mainly described as an example. However, the depth of the pattern portion is optimized for pattern transfer, and the alignment mark is used to obtain contrast during alignment. The depth can be optimized and the depth can be different.

  In the present embodiment, the case where the first and second alignment optical systems are used as an alignment method has been described as an example. However, the imprint lithography mask of the embodiment is effective even when alignment is performed with only one alignment optical system, for example, a defect inspection optical system.

  Moreover, although description was omitted about the part etc. which are not directly required for description of this invention, the structure etc. which are required can be selected suitably and can be used. In addition, all masks for imprint lithography that include the elements of the present invention and can be appropriately modified by those skilled in the art are included in the scope of the present invention.

DESCRIPTION OF SYMBOLS 10 Mask for imprint lithography 12 Board | substrate 14 Pattern area | region 16 Non-pattern area | region 18 Pattern part 20 Alignment mark 20a 1st mark 20b 2nd mark 30 Alignment mark

Claims (4)

A transfer pattern formed by irregularities dug into the surface of a substrate made of a transparent material;
Have a, an alignment mark formed by the digging the surface of the different locations and the transfer pattern irregularities,
The mask for imprint lithography is characterized in that the unevenness forming the alignment mark has periodicity, and the maximum period is less than the resolution of the alignment optical system at the time of defect inspection of the mask.   2. The imprint lithography mask according to claim 1, wherein the concave and convex depth of the transfer pattern is equal to the concave and convex depth of the alignment mark.   3. The imprint lithography mask according to claim 1, wherein the unevenness forming the alignment mark has periodicity, and the maximum period is less than 189 nm. The mask for imprint lithography according to any one of claims 1 to 3, wherein a recess depth of the unevenness forming the alignment mark is 46 nm or more and 66 nm or less.

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