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

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[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 in camera focusing, headsets 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 Patent Application Laid-Open No. 2012-098548 (Patent Document 1) describes a diffractive optical element using materials having different refractive indexes.

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, a method for manufacturing an optical tool having an inclined protrusion is provided, wherein an etching source is applied to a mask having an inclined surface rising diagonally from the surface of the substrate at the inclination angle of the inclined surface, thereby etching the substrate and forming an inclined protrusion along the inclination angle from the inside of the substrate toward the surface.

[0006] In the method for manufacturing optical tools having inclined protrusions, etching is performed by applying an etching source to a mask having an inclined surface that rises diagonally from the substrate surface at the inclination angle of the inclined surface. As a result, the dimensional conversion difference caused by the mask casting a shadow and resulting in a difference between the actual groove dimension and the desired groove dimension can be reduced. Therefore, the accuracy of dimensional control is improved, and a decrease in yield can be prevented. Furthermore, since an optical tool can be obtained that forms inclined protrusions along the inclination angle from the inside of the substrate toward the surface, the obtained optical tool can be used for VR applications and other uses where the presence of inclined surfaces and irregularities on the substrate surface is required.

[0007] Furthermore, according to one aspect of this disclosure, the mask can be a method for manufacturing an optical instrument having a substantially frustoconical shape with the substrate side as its base. Since the mask is shaped like a frustoconical pyramid with the substrate side as its base, the irradiation angle of the etching source can be matched to the inclination angle of the mask, allowing for the etching of desired grooves.

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

[0009] In one aspect of this disclosure, the inclination angle can be adjusted by the amount of film deposited on the coating material and the height of the core material in a method for manufacturing optical instruments. Since the inclination angle is adjusted by the amount of film deposited on the coating material and the height of the core material, the inclination angle can be controlled, and an optical tool having an inclined groove or inclined protrusion with a desired inclination angle can be obtained.

[0010] Furthermore, according to one aspect of this disclosure, the substrate can be a glass substrate in the method for manufacturing optical instruments. Since the aforementioned substrate is a glass substrate, it is suitable as a method for manufacturing optical tools that takes advantage of the transparency of glass. [Effects of the Invention]

[0011] According to the present invention, the dimensional conversion error when machining oblique grooves on optical tools can be reduced, making it possible to manufacture optical tools with high dimensional accuracy. [Brief explanation of the drawing]

[0012] [Figure 1] This is a schematic cross-sectional view showing the state after the resist has been formed, as part of the manufacturing process for the optical tool of the present invention. [Figure 2] This is a schematic cross-sectional view showing the state after the optical instrument manufacturing method of the present invention has been coated with a coating material. [Figure 3] This is a schematic cross-sectional view showing the state in which a mask of a desired shape has been formed during the manufacturing process of the optical instrument manufacturing method of the present invention. [Figure 4] This diagram illustrates the relationship between the width and height of a mask, using an example where the base angle is 60 degrees. Figure 4(A) is a schematic cross-sectional view, and Figure 4(B) is a schematic plan view. [Figure 5] This is an explanatory diagram illustrating the relationship between the width and height of a mask, using an example where the base angle is 30 degrees. It is a schematic cross-sectional view corresponding to Figure 4(A) in Figure 4. [Figure 6] This is an explanatory diagram illustrating the spacing between masks. [Figure 7] This is another diagram illustrating the spacing between masks. [Figure 8]This is a schematic cross-sectional view showing a state in which an etching source is irradiated along the inclination of a mask during the manufacturing process of the method for manufacturing an optical device of the present invention. [Figure 9] This is a schematic cross-sectional view for explaining the shape of the obtained optical device during the manufacturing process of the method for manufacturing an optical device of the present invention. [Figure 10] This is a schematic plan view of the optical device of the present invention. [Figure 11] This is another optical device of the present invention. Sub-diagram 11(A) is its schematic plan view, and sub-diagram 11(B) is its schematic cross-sectional view. [Figure 12] This is a view corresponding to FIG. 4 of a mask used in another manufacturing method of the optical device of the present invention. [Figure 13] This is an explanatory diagram for explaining that there is a large dimensional conversion difference in the method using a conventional mask.

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 reduction 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 instrument of this embodiment and its manufacturing method will now be described. Figures 1 to 3, 8, and 9 are schematic cross-sectional views illustrating the manufacturing process of this optical instrument 10. First, a resist 12 is patterned on a substrate 11 such as a glass substrate using a method such as photolithography or RIE, as shown in Figure 1 (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. As shown in Figure 2, the resist 12 is used as the core material 13, and a Ni film or the like is used to cover the top and sides of the core material 13 by electroless plating or vapor deposition to form a coating material 14 (Step 2). If this coating material 14 is a Ni film, it is preferable because it has a high selectivity ratio with the glass substrate 11 and with the resist 12. However, even if it is not Ni, a material with a high selectivity ratio in relation to the glass substrate 11 and the resist 12 can be used.

[0017] Then, the mask surface material 15 is molded into the desired shape as shown in Figure 3 (Step 3). The mask surface material 15 is formed by anisotropic etching perpendicular to the surface of the substrate 11 using RIE or the like on the coating material 14. Through this anisotropic etching, the mask surface material 15, which is formed by removing the coating material 14 so that it has an inclined surface, and the core material 13 can be used to obtain a mask 16 of the desired shape.

[0018] Figure 4 shows the case where the inclination angle (bottom angle) of the mask 16, which has a roughly trapezoidal cross-section, is designed to be 60 degrees, and Figure 5 shows the case where the inclination angle (bottom 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, if the length L of the width from the core material 13 at the bottom surface of the mask 16 is "1", the ideal height of the mask 16 is "√3". Therefore, in step 1 above, the height of the resist 12 which will become the core material 13 is formed to be "√3". Also, in step 2 above, a Ni film is deposited on the mask 16 so that the width of the mask surface material 15 is "1". Then, in step 3, by etching the coating material 14 until the substrate 11 is exposed, the coating material 14 attached to the top surface of the core material 13 is peeled off, and the coating material 14 attached to the sides of the core material 13 also becomes rounded. In this case, the top surface of the core material 13 and the top surface of the mask skin material 15 are over-etched, so their height is slightly recessed from "√3". In this way, the mask skin material 15 covers the sides of the core material 13, and a mask 16 with a roughly frustoconical shape, having a trapezoidal cross-section and an inclination angle of 60 degrees, is obtained.

[0019] Similarly, a mask 16 with a tilt angle of 30 degrees, as shown in Figure 5, can also be formed. In this case, if the length L of the width from the core material 13 at the bottom surface of the mask 16 is "1", the ideal height of the mask 16 will be "1 / √3". Therefore, in step 1 above, the height of the resist 12 which will become the core material 13 is formed to "1 / √3". In step 2 above, a coating material 14 made of Ni film is formed so that the width of the mask surface material 15 is "1". Then, in step 3, the coating material 14 is etched until the substrate 11 is exposed, thereby obtaining a mask 16 with a tilt angle of 30 degrees and a roughly frustoconical shape with a trapezoidal cross-section, as shown in Figure 5.

[0020] Based on the above, the multiple masks 16 and their spacing 18 that constitute the mask pattern 17 are designed as follows. That is, as shown in Figure 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 amount of film deposited on the covering material 14 which becomes the mask surface material 15. The length of “D”, which is the spacing 18 between the masks 16, is adjusted by the pitch of the core material 13. By making these adjustments and performing steps 1 to 3 above, the desired mask pattern 17 can be obtained. Therefore, for example, if you want to form a mask pattern 17 in which the width of one mask 16 is “1” and the spacing 18 is “1”, as shown in Figure 7, you just need to adjust the dimensions of each part so that A + B + C = D in Figure 6.

[0021] Next, the substrate 11 is etched using the mask pattern 17 obtained in this way. That is, by irradiating the surface of the substrate 11 at an oblique angle with the inclination angle of the inclined surface of the mask 16 (step 4), inclined grooves 19 formed at a desired angle and opening width can be obtained, as shown in Figure 8. Here, the size of the grooves, such as the depth and width of the grooves, can be adjusted by appropriately selecting the processing time in etching and the type of etching source, but in a preferred embodiment, the groove width 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), an optical tool 10 having obliquely inclined recesses is obtained, as shown in Figure 9. Figure 10 is a schematic plan view of the optical tool 10 in Figure 9, and as shown in this figure, the optical tool 10 is obtained with multiple obliquely cylindrical inclined protrusions 20 (see especially the partially enlarged schematic diagram R in Figure 10) protruding from the surface 11a of the etched substrate 11. In other words, the optical tool 10 has obliquely inclined grooves 19 recessed from the outermost surface 11b of the substrate 11.

[0023] The arrangement of the inclined protrusions 20 shown in Figure 10 is just one example. By adjusting the resist 12 to form the core material 13, optical tools 10 can be formed with the inclined protrusions 20 arranged randomly or in other arrangements. Alternatively, although an example has been shown in which the mask 16 is formed in a roughly frustoconical shape, the mask can also be formed in a rectangular shape such that the same cross-section as in Figure 3 is produced in the depth direction of Figure 3. By forming such a mask, an optical tool 10a as shown in Figure 11 can be obtained. In this optical tool 10a, the inclined protrusions 20 are formed in a columnar shape extending parallel to the planar direction of the base material, and the recesses sandwiched between the inclined protrusions 20 are also formed in a columnar shape.

[0024] <Second Embodiment>: In the optical tool and its manufacturing method of this embodiment, the mask 16 is formed by thermal melting rather than etching. In the above embodiment, the coating material 14 was formed by a metal film (Ni film) by electroless plating or vapor deposition, but instead, a thermoplastic resin film is formed by coating or spraying. By blowing hot air with a temperature higher than the glass transition temperature (Tg) of the resin from the top side of the mask 16, the top of the mask is melted to produce a mask with the desired inclined surface. By this method as well, an optical instrument 10 having an inclined protrusion 20 can be obtained.

[0025] <Third Embodiment>: In the optical tool and its manufacturing method according to this embodiment, the shape and forming method of the mask 16 to be created differ from those of previous examples. In the above embodiment, the top shape of the mask 16 was tapered with chamfers on all four sides. However, in this embodiment, after coating with the covering material 14, the mask is etched by sputter etching of Ar or the like in one direction, such as diagonally upwards, of the core material 12. This results in a shape in which the upper part of the mask 16 appears to be cut with a diagonal plane. It is preferable to use an organic material for the covering material 14 as it is easier to etch.

[0026] In the method of this embodiment, unlike previous embodiments in which anisotropic etching perpendicular to the surface of the substrate 11 was performed to form the mask 16, anisotropic etching is performed from an oblique direction to the surface of the substrate 11, resulting in a mask 16a with the shape shown in Figure 12.

[0027] The above embodiments are illustrative examples of the present invention, and modifications to the embodiments or additions or combinations of known technologies may be made without departing from the spirit of the present invention, and such technologies are also included within the scope of the present invention. [Explanation of symbols]

[0028] 10,10a optical equipment 11. Substrate (glass substrate, etc.) 11a Etched surface of the substrate 11b Outermost surface of the substrate 12 Resist 13 Core material 14 Covering material 15 Mask surface material 16,16a Mask 17 Mask Patterns 18 intervals 19 Slant groove 20 Inclined protrusion R Partial Enlarged Schematic Diagram

Claims

1. A method for manufacturing a mask for producing an optical instrument having an inclined protrusion along a predetermined inclination angle from the inside toward the surface, A step of providing on a substrate a core material that has been patterned with its height adjusted, and a covering material that covers the core material with an adjusted film deposition amount and rises diagonally from the surface to form an inclined surface along the inclination angle, The process includes an anisotropic etching step, A method for manufacturing a mask, characterized by forming a mask that is substantially frustoconical in shape, with the inclined surface being part of the side surface of the substantially frustoconical shape.

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

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