JP2012058584A - Substrate with antireflection optical structure and method of manufacturing substrate with antireflection optical structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a substrate with an antireflection optical structure having an antireflection surface composed of a fine structure having superior durability, and to provide a method of manufacturing the substrate with the antireflection optical structure.SOLUTION: When projections having a fine conical shape or a fine pyramidal shape are arranged on a substrate surface, the damage caused by the surface contact or the like can be reduced, and the mechanical strength can be improved by connecting apexes of their fine projections in an arc shape. Moreover, a substrate having such continuous projections can be manufactured by growing carbon nano-walls formed on the substrate surface by decomposing hydrocarbon gas such as methane gas in plasma and by transferring their shapes onto the substrate surface through the etching processing or the like.

Description

  The present invention relates to a substrate with an antireflection optical structure in which fine protrusions are arranged on the surface of the substrate and a method for manufacturing the substrate with an antireflection optical structure, and is suitable for use as a substrate with an antireflection optical structure. .

  Conventionally, as an antireflection optical structure, a structure in which conical or pyramidal protrusions are periodically arranged in a two-dimensional manner on a substrate surface is known (see, for example, Non-Patent Document 1). For example, as shown in FIG. 8, the conical protrusions 41 are two-dimensionally arranged with an equal period P. This period P is set smaller than the wavelength of visible light. In the substrate 40 on which such a fine structure of a wavelength or less is formed, this is equivalent to the presence of a thin film layer having an intermediate refractive index between the external medium and the substrate 40, and the reflectance on the substrate surface is reduced. (For example, refer nonpatent literature 2). As shown in FIG. 8B, when the conical cross section is a triangle, the refractive index changes in the depth direction, and the reflectance can be lowered over a wide wavelength region.

  Further, for the production of such a fine structure, an electron beam exposure apparatus often used for forming a fine pattern is used. A periodic dot-shaped resist pattern is formed by an electron beam exposure apparatus. Using this resist pattern as a mask, the substrate can be etched into a conical shape or a pyramid shape to form an antireflection optical structure having a desired structure on the substrate.

E.B.Grann, M.G.Moharam, and D.A.Pommet, “Optimal design for antireflective taperd two-dimensionalsubwavelength grating structures”, Journal of OpticalSociety of America A, 1995, Vol.12, No.2, p333-339 Hisao Kikuta, Koichi Iwata, "Optical control by grating structure finer than wavelength", Optics, 1998, Vol. 27, No. 1, pp. 12-17

  However, as described in Non-Patent Document 1, the tops of the conical and pyramidal protrusions have a thin pattern shape in order to obtain a sufficient antireflection effect. For example, in the antireflection optical structure for the visible light region, the size of the top of the protrusion needs to be about 50 nm. Such fine protrusions are easily damaged by surface contact or the like, and as a result, the antireflection function is lowered. In particular, the risk of damage due to surface contact is significant when anti-reflection optical structures are used in various external environments, such as camera lenses. To increase. Thus, a substrate with an antireflection optical structure in which simple conical or pyramid-shaped protrusions are arranged does not have sufficient mechanical strength compared to a substrate with an antireflection optical structure in which a multilayer film is formed on the substrate surface. There was a big problem in practical use.

  On the other hand, in the manufacturing method using an electron beam exposure apparatus as part of the manufacturing process of a substrate with an antireflection optical structure, the work time for forming a periodic dot-like resist pattern is greatly increased as the area increases. Increasingly, a large-area substrate of 50 mm or more requires a work time in units of one day, which is a heavy burden in terms of manufacturing cost. On the other hand, as a part of the manufacturing process, in a manufacturing method using an ultraviolet light exposure apparatus widely used in semiconductor LSI manufacturing, a periodic dot-shaped resist pattern is formed with an area region of about 20 mm as a unit. As a result, it is not possible to sufficiently suppress the occurrence of the “connecting” portion where the antireflection structure is not formed, so that the pattern quality of the entire substrate deteriorates. Thus, in the production of a substrate with an antireflection optical structure having a large area which is important for practical use, it is difficult to achieve both the manufacturing cost and the pattern quality, which is a big problem.

  The present invention has been made by paying attention to such a problem, and it is possible to reduce the production of a substrate with an antireflection optical structure that can improve mechanical strength and reduce damage due to surface contact, and a substrate with an antireflection optical structure. An object of the present invention is to provide a method of manufacturing a substrate with an antireflection optical structure that can be manufactured with high quality at low cost.

  Therefore, in order to solve the above-described problems, the substrate with an antireflection optical structure according to the present invention is a substrate with an antireflection optical structure in which fine protrusions having a cone shape or a pyramid shape are arranged on the substrate surface. The top of the fine protrusions is formed by arranging continuous protrusions connected in an arc shape.

  The substrate with an antireflection optical structure according to the present invention can improve mechanical strength and can reduce damage due to surface contact or the like.

  In the substrate with an antireflection optical structure according to the present invention, it is preferable that a concavo-convex structure for superimposing the continuous protrusions is arranged below the continuous protrusions in which the tops of the fine protrusions are connected in an arc shape. In this case, it is possible to reduce damage due to surface contact or the like by improving the mechanical strength and reducing the number of contacts of fine continuous protrusions.

  The method of manufacturing a substrate with an antireflection optical structure according to the present invention is a method of decomposing hydrocarbon gas such as methane gas on the substrate surface in plasma before surface processing, instead of resist pattern forming method such as electron beam exposure. Characterized in that it includes a step of growing carbon nanowalls (CNW) formed in this way.

  The method for manufacturing a substrate with an antireflection optical structure according to the present invention is a continuous process in which the tops of fine protrusions are connected in an arc shape by etching the substrate using an arc-shaped carbon pattern that grows as carbon nanowalls as a mask. A substrate with an antireflection optical structure in which protrusions are arranged can be manufactured.

  Since methane gas plasma can control the density and energy in the gas phase by adjusting the gas pressure and high-frequency power, it can be combined with temperature control on the substrate surface to create a large area substrate and a substrate with irregularities. Can be produced.

  According to the present invention, in the substrate with an antireflection optical structure in which projections having a conical shape or a pyramid shape are arranged on the substrate surface, the tops of those fine projections are continuous projections connected in an arc shape, It is possible to improve mechanical strength and reduce damage due to surface contact. Therefore, in the actual use of the substrate with an antireflection optical structure, it is possible to expect an effect of improving the use efficiency and the convenience of attachment / detachment.

  In addition, by providing an uneven structure having a large dimension for superimposing the fine continuous protrusions below the continuous protrusions in which the tops of the fine protrusions are connected in an arc shape, there is an effect of improving the mechanical strength. Even if there is a risk that the arc-shaped protrusion is damaged, it is limited to only the upper convex portion of the large concavo-convex structure, and the damage at the lower concave portion can be prevented. Therefore, in the actual use of the substrate with an antireflection optical structure, it is possible to expect an effect of improving the use efficiency and the convenience of attachment / detachment.

  In addition, as a method of arranging protrusions having a cone shape or a pyramid shape, a step of growing carbon nanowalls formed by decomposing hydrocarbon gas such as methane gas in plasma on the substrate surface as part of the production process By adopting, the continuous protrusions in which the tops of the fine protrusions are approximately connected in an arc shape can be randomly arranged with an average dimension secured. Therefore, since the manufacturing process does not use an electron beam exposure apparatus or an ultraviolet exposure apparatus, an effect of manufacturing a large-area substrate with an antireflection optical structure with high quality at a low manufacturing cost can be expected. Furthermore, since it can also be applied to a substrate with irregularities, it can be widely applied to various optical elements and expected to reduce the reflectance.

BRIEF DESCRIPTION OF THE DRAWINGS (A) Top view which shows the board | substrate with an antireflection optical structure as 1st Example of this invention, (B) X direction sectional drawing which passes along a lattice point, (C) Y direction cross section which passes along a lattice point. It is (A) top view, (B) X direction sectional view, and (C) Y direction cross section which show the board | substrate with an antireflection optical structure as 2nd Example of this invention. It is (A) top view, (B) X direction sectional view, and (C) Y direction cross section which show another board | substrate with an antireflection optical structure as a 2nd Example of this invention. It is explanatory drawing of the manufacturing method of the board | substrate with an antireflection optical structure as 3rd Example of this invention. It is (A) top view, (B) X direction sectional view, (C) Y direction cross section which shows the board | substrate with an antireflection optical structure as 3rd Example of this invention. It is a block diagram which shows the helicon plasma apparatus used for CNW growth with the manufacturing method of the board | substrate with an antireflection optical structure shown in FIG. It is sectional drawing which shows the Example which applies the manufacturing method of the board | substrate with an antireflection optical structure as 3rd Example of this invention to (A) diffraction grating, (B) optical lens, and (C) micro lens. It is (A) top view and (B) X direction sectional drawing which show the board | substrate with the conventional antireflection optical structure which arrange | positions the processus | protrusion which has a fine cone shape and pyramid shape on the substrate surface.

  In order to clarify the above and other objects, features and advantages of the present invention, embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

  A substrate with an antireflection optical structure as a first embodiment of the present invention is shown in FIG. As shown in FIG. 1 (A), the substrate 10 with antireflection optical structure of this example is a square lattice with a continuous projection 12 (the solid line in FIG. 1 (A) is the top and the dotted line is the skirt) with a period of 300 nm. Are arranged on the grid points 11. There are several methods for periodically arranging the continuous protrusions 12 by combining the directions of the protrusions. As can be seen from FIGS. 1B and 1C, the continuous protrusion 12 is a fine structure in which protrusions having a triangular shape or a skirt shape similar to this are continuously connected in an arc shape. Furthermore, if the top flat surface is 50 nm or less, it is suitable as the substrate 10 with an antireflection optical structure in the visible light region (wavelength 400 nm to 900 nm).

  Although the substrate 10 with an antireflection optical structure of the present embodiment is composed of fine continuous protrusions 12, since it is an arc-shaped protrusion, it is possible to disperse an external force due to surface contact or the like generated during actual use. For this reason, compared with the conventional simple conical protrusion etc., intensity | strength increases significantly and it is suitable in use actually.

  FIG. 2 shows a substrate with an antireflection optical structure as a second embodiment of the present invention. As shown in FIG. 2, in the board | substrate 20 with an antireflection optical structure of a present Example, the lower concavo-convex structure 22 is an inverted pyramid shape hole. As shown in FIG. 2A, the inverted pyramid-shaped holes are arranged on a square lattice having a period of 2 μm. Here, four square lattices are shown. The continuous protrusions 21 whose tops are connected in an arc shape (the solid line in FIG. 2A is the top and the dotted line is the skirt) are arranged on a small square lattice with a period of 300 nm. The arc-shaped continuous protrusion 21 has no particular correlation with the pyramid-shaped hole, and is disposed on the slope of the pyramid-shaped hole.

  The substrate 20 with an antireflection optical structure of the present embodiment is composed of fine protrusions, and a concavo-convex structure 22 having a larger size is disposed below a continuous protrusion 21 in which the tops of the fine protrusions are connected in an arc shape. Therefore, even if the strength is further increased and there is a risk that the arc-shaped continuous protrusion 21 may be damaged, the entire structure as the substrate 20 with the antireflection optical structure is limited to the upper portion of the large fine uneven structure 22. Antireflection performance can be secured.

  FIG. 3 shows an example in which continuous protrusions connected in a larger arc shape are arranged as the concavo-convex structure 27 in the lower layer. Four continuous protrusions connected in a larger arc shape are shown. Thus, by arranging two types of large and small continuous protrusions in the upper and lower stages, it is possible to widen the light wavelength region in which the antireflection performance can be obtained along with the strength. For example, when the continuous protrusions 26 connected in an arc shape are arranged with a period of 300 nm, the antireflection performance is an optical wavelength region of a wavelength of 400 nm to 1000 nm, but when a large continuous protrusion connected in an arc shape is arranged in the lower layer with a period of 2 μm, An infrared wavelength region of 3 μm to 7 μm is added to form a substrate 25 with an antireflection optical structure that can be used in a wide wavelength range.

  FIG. 4 shows an embodiment of a manufacturing method of a substrate with an antireflection optical structure as a third embodiment of the present invention. After the substrate 31-f is cleaned in the substrate preparation step 31-a, a CNW growth step 31-b is performed. After the substrate 31-f is set on the heated sample stage of the helicon plasma apparatus and sufficiently evacuated, the sample stage heater is heated to raise the substrate temperature to a predetermined temperature. Thereafter, methane gas is introduced into the apparatus to obtain a predetermined pressure, and then predetermined high-frequency power is applied to the antenna to form high-density helicon plasma (methane gas plasma 31-g). By optimizing the gas pressure and high-frequency power and controlling the plasma density and ion energy, an approximately arc-shaped CNW is grown to a predetermined thickness at a desired average dimension and average interval. This is the CNW growth step 31-b.

Next, the substrate 31-f on which the CNW has been grown is cooled to room temperature, taken out from the helicon plasma apparatus, set in an etching apparatus such as an RIE apparatus, and sufficiently evacuated. A gas mixture with O ₂ single gas or N ₂ gas is introduced into the etching apparatus to obtain a predetermined pressure, and then high frequency power is supplied to the sample stage electrode to form high frequency plasma (oxygen gas plasma 31-h). Then, the CNW shaping process is performed (CNW shaping process 31-c). In this shaping process, by performing vertical etching on the amorphous carbon layer formed near the interface with the substrate 31-f during CNW growth, the width becomes an etching mask for subsequently etching the substrate 31-f. A CNW pattern that is narrow and perpendicular to the substrate 31-f can be formed. This CNW pattern does not have a clear periodicity such as a square lattice and is randomly arranged. However, the length of the CNW pattern and the dimensions such as the mutual interval are approximately determined by the growth condition of the CNW and can be defined as an average dimension. As the dimensions of the CNW pattern, for example, in the wavelength band of visible light (400 nm to 800 nm), a good antireflection function can be realized by setting the average dimension of the length and the mutual interval to about 300 nm and the width to about 50 nm.

Next, the substrate 31-f is cleaned in the substrate surface cleaning step 31-d.
In the final substrate etching process, by performing dry etching suitable for the substrate material with the etching gas plasma 31-j using the shaped CNW pattern of the substrate 31-i after cleaning as an etching mask, a triangular shape or this Are formed, and a continuous projection connected in an arc shape at the top is formed, whereby the substrate with an antireflection optical structure is completed. As this substrate etching, for example, ECR etching using chlorine gas can be used for a Si substrate.

  FIG. 5 shows an embodiment as a substrate with an antireflection optical structure manufactured using the above manufacturing process. As described above, the CNW has a random arrangement with different arc shapes, orientations, and dimensions, and the arrangement of the approximate arc-shaped continuous protrusions 32-b and 32-c does not have a clear periodicity. As for the approximate arc, there are four directions and two types of dimensions, and the arc-shaped continuous protrusions 32-b and 32-c, which are a combination of these, are arranged with a variation from a periodic arrangement. In the substrate 32-a with antireflection optical structure having a random arrangement, the diffraction effect at a specific wavelength can be avoided, so that the substrate does not appear to be colored, and the reflectance is constant over a wide wavelength region. .

  FIG. 6 shows a configuration diagram of a helicon plasma apparatus which is an important apparatus in the above embodiment. As shown in FIG. 6, the methane gas plasma 33-f is formed with high density by the interaction between the externally applied magnetic field 33-h and the high frequency power generated by the high frequency transmitter 33-d at a predetermined gas pressure. The decomposition of methane gas is sufficiently advanced, and CNW can be efficiently grown together with the heating action of the sample stage.

  In the embodiment shown in FIG. 4, gas plasma obtained by decomposing a desired gas in each step with high-frequency power is used in all manufacturing steps from CNW growth, shaping, and substrate etching. Processing techniques such as gas plasma deposition and etching are widely used in the manufacture of semiconductor electronic devices. In particular, in the manufacture of semiconductor Si-LSI, many improvements have been made to large area processing by gas plasma, and a uniform processing technique has been established for a wafer substrate having a diameter of 300 mm. Thus, uniform large area processing is possible with gas plasma, and even in the production of a substrate with an antireflection optical structure using CNW growth shown in the embodiment of FIG. It is possible to uniformly produce a continuous protrusion having a desired average dimension.

  Further, in the process using gas plasma including CNW growth, the CNW growth is flat even when the substrate has unevenness with a depth of up to about 10 μm, or when there is unevenness that changes more slowly than that. 4 can be applied to various optical elements as shown in FIG. 7, and can contribute to performance improvement by suppressing reflection on the element surface.

  Further, in the embodiment shown in FIG. 4, the substrate with the antireflection optical structure in which the two kinds of large and small arc-shaped continuous protrusions shown in FIG. 3 are arranged in two upper and lower stages is manufactured without significantly increasing the production process. I can do it.

DESCRIPTION OF SYMBOLS 10 Substrate with antireflection optical structure 11 Lattice point 12 Continuous protrusion 20 Substrate with antireflection optical structure 21 Continuous protrusion 22 Lower uneven structure 23 X direction cross section position 24 Y direction cross section position 25 Substrate with antireflection optical structure 26 Continuous protrusion 27 Lower unevenness Structure 28 X-direction sectional position 29 Y-direction sectional position 31-a Substrate preparation step 31-b CNW growth step 31-c CNW shaping step 31-d Substrate surface cleaning step 31-e Substrate etching step 31-f Substrate 31-g Methane gas plasma 31-h Oxygen gas plasma 31-i Cleaned substrate 31-j Etching gas plasma 32-a Substrate with antireflection optical structure 32-b (large average dimension) continuous protrusion 32-c (small average dimension) continuous Protrusion 32-d X-direction cross-section position 32-e Y-direction cross-section position 33-a 33-b Methane gas introduction part 33-c Helical antenna 33-d High frequency transmitter 33-e Matching device 33-f Methane (CH4) gas plasma 33-g Heated sample stage 33-h Externally applied magnetic field 33-i Vacuum exhaust 34 -A diffraction grating substrate 34-b diffraction grating pattern 34-c arc-shaped continuous protrusion 34-d lens substrate 34-e arc-shaped continuous protrusion 34-f macro lens substrate 34-g microlens 34-h arc-shaped continuous protrusion 40 substrate 41 Conical protrusion 42 Conical protrusion top 43 Conical protrusion arrangement period (P)

Claims (3)

  A substrate with an antireflection optical structure in which fine projections having a conical shape or a pyramid shape are arranged on the surface of the substrate, wherein the continuous projections in which the tops of the fine projections are connected in an arc shape are arranged, A substrate with an antireflection optical structure.   2. The substrate with an antireflection optical structure according to claim 1, wherein an uneven structure for superimposing the continuous protrusions is arranged below the continuous protrusions in which the tops of the fine protrusions are connected in an arc shape. . A method for producing a substrate with an antireflection optical structure, comprising a step of growing carbon nanowalls formed by decomposing hydrocarbon gas such as methane gas in plasma on a substrate surface before surface processing.