Mask manufacturing method

Abstract

To reduce a dimensional conversion difference of oblique groove machining to an optical tool and manufacture an optical tool having high dimensional accuracy.SOLUTION: Provided is a mask manufacturing method for manufacturing an optical tool having oblique protrusions along a prescribed angle of inclination from the inside toward the surface. A height-adjusted and patterned core material and a cladding material for adjusting a deposition amount and covering the core material are disposed on a substrate, and anisotropic etching is applied, thereby forming a mask which comes in shape of substantially a circular truncated cone, and has a slope rising diagonally from the surface along the angle of inclination as part of a side face of the circular truncated cone.SELECTED DRAWING: Figure 8

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an optical tool and a method for manufacturing a mask by a patterning method that minimizes the dimensional conversion difference in oblique groove processing by etching.

Background Art

[0002] Diffractive optical elements and optical filters have the property of irradiating light in a direction different from the incident light or transmitting only the incident light within a predetermined wavelength range, and are used for camera focusing, head-mounted displays for Virtual Reality (VR), color filters, and the like. The surfaces of some diffractive optical elements and optical filters are formed with irregularities, and light is diffracted by the difference in refractive index between the concave and convex portions. For example, Japanese Unexamined Patent Application Publication No. 2012-098548 (Patent Document 1) describes a diffractive optical element using materials having different refractive indices.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Regarding such optical tools as diffractive optical elements and optical filters, optical tools that meet various requirements according to their applications, such as reflecting light in a wide wavelength range or restricting transmitted light, are required, and diffractive optical elements with strictly controlled surface shapes, particularly the size and shape of irregularities, are required. Therefore, the present invention has been developed to meet such requirements.

Means for Solving the Problems

[0005] According to one aspect of the present disclosure, there is provided a method for manufacturing an optical device having an inclined convex portion, the method including etching a substrate by applying an etching source to the substrate at an inclination angle of an inclined surface with respect to a mask having an inclined surface that rises obliquely from the surface of the substrate, to form an inclined convex portion along the inclination angle from the inside of the substrate toward the surface.

[0006] Regarding the method for manufacturing an optical device having an inclined convex portion, since the etching source is applied to the substrate at the inclination angle of the inclined surface with respect to the mask having an inclined surface that rises obliquely from the surface of the substrate for etching, it is possible to reduce a dimensional conversion difference in which a difference occurs between an actually generated groove dimension and a desired groove dimension due to the mask serving as a shadow. Thus, the accuracy of dimension control is improved, and a decrease in yield can be prevented. And since an optical device having an inclined convex portion formed along the inclination angle from the inside of the substrate toward the surface can be obtained, the obtained optical device can be used in VR applications and the like where the presence of unevenness having an inclined surface on the substrate surface is required.

[0007] Also, according to one aspect of the present disclosure, the mask can be formed in a substantially frustum - of - cone shape having the substrate side as the bottom surface in the method for manufacturing an optical device. Since the shape of the mask is a substantially frustum - of - cone shape having the substrate side as the bottom surface, the irradiation angle of the etching source can be adjusted to the inclination angle of the mask, and a desired groove can be etched.

[0008] Also, according to one aspect of the present disclosure, the method for manufacturing an optical device includes a step of forming the mask by subjecting a coating material covering a core material patterned on the substrate to anisotropic etching. Since the method includes a step of forming the mask by subjecting a coating material covering a core material patterned on the substrate to anisotropic etching, a mask having an inclined surface with respect to the substrate can be formed.

[0009] In one aspect of the present disclosure, the inclination angle can be adjusted by the film formation amount of the coating material and the height of the core material in the method for manufacturing an optical device. Since the inclination angle is adjusted based on the film formation amount of the coating material and the height of the core material, it is possible to control the inclination angle and obtain an optical device having an inclined groove or an inclined convex portion with a desired inclination angle.

[0010] According to one aspect of the present disclosure, the method for manufacturing an optical device can be a method for manufacturing an optical device in which the base material is a glass base material. Since the base material is a glass base material, it is suitable as a method for manufacturing an optical device that takes advantage of the transparency of glass.

Advantages of the Invention

[0011] According to the present invention, it is possible to reduce the dimensional conversion difference in oblique groove processing of an optical device and manufacture an optical device with high dimensional accuracy.

Brief Description of the Drawings

[0012]

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Embodiments for Carrying Out the Invention

[0013] The present invention relates to a technique for obtaining, for an optical device such as a diffractive optical element or an optical filter having irregularities on its surface, the shape of a recessed portion recessed from the outermost surface as an inclined groove deeply dug obliquely from the outermost surface. This will be described in detail below.

[0014] Generally, in order to form an inclined groove, a source of etching processing such as plasma, an ion beam, or GCIB is obliquely incident on a substrate to be etched at an angle for processing. However, there is a potential problem of a dimensional conversion difference in which the width dimension of the actually processed groove is different from the desired groove. That is, as shown in the schematic cross-sectional view of FIG. 13, when the etching source 2 is applied obliquely to the mask material 1, the patterning mask material 1 becomes a shadow, and a difference occurs in the width dimension between the desired groove and the actually processed groove. Therefore, the influence of a decrease in yield due to deteriorated dimensional controllability has been an issue. The present invention provides a method for producing an inclined groove with less dimensional conversion difference.

[0015] <First Embodiment>: The optical device of the present embodiment and its manufacturing method will be described. FIGS. 1 to 3, FIG. 8, and FIG. 9 are schematic cross-sectional views for explaining the manufacturing process of this optical device 10. First, as shown in FIG. 1, a resist 12 is patterned on a base material 11 such as a glass substrate by a method such as photolithography or RIE (step 1). It is preferable to use an organic material such as a synthetic resin for the resist 12 because it is easy to pattern and has excellent adhesion to the coating material 14. The height of the resist 12 will be described later.

[0016] Next, a mask material is formed into a film. As shown in FIG. 2, using the resist 12 as a core material 13, a Ni film or the like is deposited on the upper surface and side surface of the core material 13 by a method such as electroless plating or vapor deposition to form a coating material 14 (step 2). When this coating material 14 is a Ni film, the selectivity ratio with the glass substrate 11 and the selectivity ratio with the resist 12 are preferably large. However, even if it is other than Ni, a material having a large selectivity ratio in relation to the glass substrate 11 and the resist 12 can be applied.

[0017] Then, a mask skin material 15 is formed into a desired shape as shown in FIG. 3 (step 3). The mask skin material 15 is formed by performing anisotropic etching in the direction perpendicular to the surface of the base material 11 on the coating material 14 by RIE or the like. By this anisotropic etching, a mask 16 having a desired shape can be obtained with the mask skin material 15 formed by scraping the coating material 14 so as to have an inclined surface and the core material 13.

[0018] FIG. 4 shows the case where the inclination angle (base angle) of the mask 16 with a substantially trapezoidal cross section is designed to be 60 degrees, and FIG. 5 shows the case where the inclination angle (base angle) of the mask 16 is designed to be 30 degrees. In the case of the mask 16 with an inclination angle of 60 degrees, when the lateral width length L from the core material 13 on the bottom surface of the mask 16 is set to "1", the ideal height of the mask 16 is "√3". Therefore, in the above step 1, the resist 12 serving as the core material 13 is formed to have a height of "√3". Further, in the above step 2, a Ni film is formed such that the width of the mask skin material 15 in the mask 16 becomes "1". Then, in step 3, by etching the coating material 14 until the base material 11 appears, the coating material 14 attached to the upper surface of the core material 13 is peeled off, and the coating material 14 attached to the side surface of the core material 13 also has a chamfered shape. In this case, due to over-etching, the upper surface of the core material 13 and the upper surface of the mask skin material 15 are slightly recessed from "√3" in height. Thus, the side surface of the core material 13 is covered with the mask skin material 15, and a substantially frustum-shaped mask 16 with an inclination angle of 60 degrees and a trapezoidal cross section is obtained.

[0019] Similarly, the mask 16 with an inclination angle of 30 degrees shown in FIG. 5 can also be formed. In this case, when the lateral width length L from the core material 13 on the bottom surface of the mask 16 is set to "1", the ideal height of the mask 16 becomes "1 / √3". Therefore, in the above step 1, the resist 12 serving as the core material 13 is formed to have a height of "1 / √3". Further, in the above step 2, a coating material 14 made of a Ni film is formed such that the width of the mask skin material 15 becomes "1". Then, in step 3, by etching the coating material 14 until the base material 11 appears, a substantially frustum-shaped mask 16 with an inclination angle of 30 degrees and a trapezoidal cross section as shown in FIG. 5 is obtained.

[0020] From the above, the plurality of masks 16 constituting the mask pattern 17 and the intervals 18 therebetween are designed as follows. That is, as shown in FIG. 6, the length of "B" in the mask 16 is adjusted by the width of the core material 13, and the lengths of "A" and "C" are adjusted by the film formation amount of the coating material 14 that becomes the mask skin material 15. And the length of "D", which is the interval 18 between the masks 16, is adjusted by the pitch of the core material 13. By performing such adjustments and executing the above steps 1 to 3, a desired mask pattern 17 can be obtained. Therefore, for example, when trying to form a mask pattern 17 in which the width of one mask 16 is "1" and the interval 18 is "1" as shown in FIG. 7, the dimensions of each part may be adjusted so that A + B + C = D in FIG. 6.

[0021] Next, the substrate 11 is etched using the mask pattern 17 thus obtained. That is, when an etching source (etchant) is irradiated obliquely to the surface of the substrate 11 at the inclination angle of the inclined surface of the mask 16 (step 4), as shown in FIG. 8, an inclined groove 19 formed at a desired angle and opening width can be obtained. Here, the size such as the depth and width of the groove can be adjusted by appropriately selecting the processing time in etching, the type of the etching source, etc. As a preferred embodiment, the width of the groove can be 50 to 500 nm, and the groove depth can be 50 to 500 nm.

[0022] Finally, by removing the mask 16 by wet etching or dry etching (step 5), as shown in FIG. 9, an optical device 10 having an obliquely inclined concave portion is obtained. Note that FIG. 10 is a schematic plan view of the optical device 10 in FIG. 9. As shown in this figure, the optical device 10 is obtained in a shape in which a plurality of obliquely columnar inclined convex portions 20 (see the partial enlarged schematic view R in FIG. 10 in particular) protrude with respect to the surface 11a of the etched substrate 11. In other words, it is an optical device 10 having an inclined groove 19 recessed obliquely from the outermost surface 11b of the substrate 11.

[0023] The arrangement of the inclined convex portions 20 shown in FIG. 10 is an example, and by adjusting the resist 12 to form the core material 13, an optical device 10 can be formed in which the inclined convex portions 20 are arranged randomly or in other arrangements. Alternatively, although an example in which the mask 16 is formed in a substantially frustum shape has been shown, for example, the mask can be formed in an angle bar shape such that the same cross section as in FIG. 3 is produced even in the depth direction of FIG. 3. By forming such a mask, an optical device 10a as shown in FIG. 11 can be obtained. In this optical device 10a, the inclined convex portions 20 are formed in a columnar shape extending parallel to the plane direction of the base material, and the recesses sandwiched between the inclined convex portions 20 are also formed in a columnar shape.

[0024] <Second Embodiment>: In the optical device and its manufacturing method of the present embodiment, when forming the mask 16, it is formed by thermal melting instead of etching. In the above embodiment, the coating material 14 was formed by an electroless plating or a metal film (Ni film) by vapor deposition or the like, but instead of this, a thermoplastic resin film is formed by coating or spraying. By blowing hot air higher than the glass transition point (Tg) of the resin from the top side of the mask 16, the top of the mask is melted to manufacture a mask having a desired inclined surface. Also by such a method, an optical device 10 having the inclined convex portions 20 can be obtained.

[0025] <Third Embodiment>: In the optical device and its manufacturing method of the present embodiment, the shape and the forming method of the mask 16 to be created are different from the previous examples. In the above embodiment, the top shape of the mask 16 was a tapered shape chamfered from four sides, but in the mask of the present embodiment, after coating the coating material 14, etching is performed by sputter etching in one direction such as obliquely upward of the core material 12 or by Ar or the like. By doing so, a shape in which the upper part of the mask 16 is cut by an inclined plane can be obtained. Note that it is preferable to use an organic material for the coating material 14 because it is easily scraped.

[0026] In the method of this embodiment, anisotropic etching is performed from an oblique direction with respect to the surface of the substrate 11, whereas anisotropic etching perpendicular to the surface of the substrate 11 was performed to form the mask 16 in the previous embodiments. As a result, a mask 16a having the shape shown in FIG. 12 is obtained.

[0027] The above embodiments are examples of the present invention, and within the scope not departing from the gist of the present invention, changes to the embodiments, addition of known techniques, combinations, etc. can be made, and those techniques are also included in the scope of the present invention.

Explanation of Reference Numerals

[0028] 10, 10a Optical device 11 Substrate (such as a glass substrate) 11a Etched surface of the substrate 11b Outermost surface of the substrate 12 Resist 13 Core material 14 Coating material 15 Mask skin material 16, 16a Mask 17 Mask pattern 18 Spacing 19 Inclined groove 20 Inclined convex portion R Partial enlarged schematic view

Claims

1. A method for manufacturing a mask for manufacturing an optical tool having an inclined convex portion along a predetermined inclination angle from an inside to a surface, comprising the steps of: A method for manufacturing a mask, comprising: providing a core material that has been patterned by adjusting its height, and a coating material that covers the core material by adjusting the amount of film formation, on a substrate; and performing anisotropic etching to form a mask having an approximately truncated cone shape, the mask rising obliquely from the surface and having an inclined surface along the inclination angle as part of a side surface of the approximately truncated cone shape.

2. 2. The method for manufacturing a mask according to claim 1, wherein the substrate is a glass substrate.

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