JP2010102008A - Photomask and method for making sawtooth pattern - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photomask for inexpensively and easily making a sawtooth pattern, and to provide a method for making a sawtooth pattern by using the photomask. <P>SOLUTION: The photomask 27 includes small regions 41a to 41h adjacent to each other so as to sequentially incline a grating direction 33 to a given direction. The small regions 41a to 41h are made of a photonic crystal 31 that transmits linearly polarized light having an electric field oscillating in a direction parallel to the grating direction 33 and reflects linearly polarized light having an electric field oscillating in a direction perpendicular to the grating direction 33. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a relief having a concavo-convex shape provided in a diffraction grating, and a photomask used at that time, and more particularly to a method and a photomask for manufacturing a serrated relief.

  A diffraction grating that diffracts incident light is widely used in various applications, such as being used as a device that splits laser light with an optical pickup. As a diffraction grating, a diffraction grating provided with a rectangular relief in a straight line, a diffraction grating whose refractive index is periodically modulated, and the like are known. In addition, the relief of the diffraction grating and its prototype are manufactured by electron beam lithography, photolithography, mechanical deletion processing, and the like.

  When light is incident on the diffraction grating as described above, ± 1st-order diffracted light is generated in symmetrical directions around the 0th-order diffracted light. However, depending on the use of the diffraction grating, only the + 1st order diffracted light may be used without using the -1st order diffracted light. In such a case, it is required to reduce the diffraction efficiency of the −1st order diffracted light as much as possible and to increase the diffraction efficiency of the + 1st order diffracted light as much as possible.

  A saw-tooth type diffraction grating is known as a diffraction grating satisfying such a demand. A sawtooth diffraction grating is a diffraction grating in which reliefs having a right triangle shape (so-called blazed shape) are arranged like a sawtooth. Compared with other diffracted light including zeroth order diffracted light, + 1st order diffracted light It is known to greatly improve the diffraction efficiency.

  As a method for manufacturing such a blazed sawtooth diffraction grating, a method of mechanically removing a substrate or a mold, or a method of performing oblique etching with an ion beam using a patterned resist as a mask ( Patent Document 1) and the like are known.

  In addition, the relief of the sawtooth diffraction grating has a diffracted light rate of + 1st order diffracted light of 100% when the cross section has a strict blaze shape. However, a relief that includes an inclined surface can be obtained by electron beam lithography or photolithography. It is difficult to manufacture. For this reason, when the sawtooth diffraction grating or the prototype of the sawtooth diffraction grating is manufactured by photolithography or the like, the actual shape of the relief is manufactured in a shape that increases in height in a stepped manner (so-called multistage binary shape). . In addition, since the number of steps in a multi-stage binary relief is closer to the blazed shape, the diffraction efficiency of the + 1st order diffracted light due to the multi-stage binary relief is closer to the diffraction efficiency due to the blazed relief. Yes.

  As described above, as a method of manufacturing a sawtooth diffraction grating having a multi-stage binary relief, a method of patterning for each stage using a plurality of photomasks (Non-patent Document 1), an electron while changing the dose, and so on. A method of performing line lithography (Patent Document 2), a method of using a photomask whose transmittance is modulated depending on a location (hereinafter referred to as a transmittance modulation type photomask) (Patent Documents 3 and 4), and the like are known.

Incidentally, as a photomask, there is known a photomask in which the polarization state of light is actively used. For example, a phase shift type photomask in which the contrast of an exposure pattern is improved by shifting the phase by 90 degrees between adjacent exposure regions is known. In such a photomask using polarized light, exposure is performed using light in a specific polarization state, so that the light use efficiency is lowered. For this reason, in order to improve the light utilization efficiency with a photomask that uses polarized light, a so-called photonic crystal in which a plurality of types of dielectrics are combined in a two-dimensional (three-dimensional) lattice shape is used in the adjacent region. It has been proposed that the directions are different by 90 degrees (Patent Document 5).
JP-A-63-271265 Japanese Patent Laying-Open No. 2005-2491943 JP-A-5-224398 JP 2003-228160 A JP 2006-30568 A Optonics "Optical Device Precision Machining Handbook" p391

  As described above, a blazed relief sawtooth diffraction grating can be manufactured by mechanically removing a substrate or a mold, but is expensive because it requires precise precision of the removal. . Further, in the oblique etching using the resist pattern as a mask, the inclination direction of the blaze-shaped relief is limited to one direction, and only a sawtooth diffraction grating having a linear grating can be manufactured.

  On the other hand, when manufacturing a relief of a sawtooth diffraction grating into a multi-stage binary shape, if patterning is performed for each stage using a plurality of photomasks, the patterning process increases as the diffraction efficiency of + 1st order diffracted light increases. The manufacturing process becomes complicated. At the same time, the photomask must be aligned with high precision in each patterning step, which is very laborious.

  Further, according to electron beam lithography, a relief having a multi-stage binary shape can be manufactured by one lithography. However, since the electron beam lithography itself is an expensive technique, the sawtooth diffraction grating manufactured thereby is also expensive. It becomes a thing.

  Similarly, according to the transmittance modulation type photomask, a relief having a multi-stage binary shape can be manufactured by one lithography, but with a transmittance modulation type photomask, a relief having a pitch finer than about 100 μm is manufactured. Difficult to do. For this reason, the sawtooth diffraction grating manufactured by the transmittance modulation type photomask has a small separation angle of the diffracted light, and it is difficult to use this for an optical system of a small apparatus that requires a large separation angle.

  The present invention has been made in view of the above-described problems. A relief pattern for a sawtooth diffraction grating, a photomask that can be manufactured inexpensively and easily, and a relief pattern for a sawtooth diffraction grating using the photomask. An object is to provide a manufacturing method. In addition, a relief pattern of a sawtooth diffraction grating having a large separation angle of diffracted light and suitable for an optical system of a small device, a photomask that can be manufactured inexpensively and easily, and a sawtooth relief pattern using the photomask It aims at providing the manufacturing method of.

  The photomask of the present invention is a small area comprising selective polarized light transmitting means that transmits linearly polarized light whose electric field vibrates in a direction parallel to the grating direction and reflects linearly polarized light whose electric field vibrates in a direction perpendicular to the grating direction. Are provided adjacent to each other so that the lattice direction is sequentially inclined in a fixed direction.

  In addition, a plurality of large areas each having a predetermined number of small areas as a set are provided adjacent to each other.

  The small regions are arranged so that the lattice direction changes by 90 degrees within the large region.

  Further, the selective polarized light transmitting means has a structure in which a plurality of dielectrics having different refractive indexes are alternately laminated, and has an uneven structure with a pitch shorter than the wavelength of the linearly polarized light to be transmitted. It is characterized by that.

  The method according to any one of claims 1 to 4, wherein the method for manufacturing a sawtooth pattern according to the present invention comprises: a resist coating step for uniformly applying a resist to a substrate for patterning a sawtooth pattern; A resist patterning step of patterning the resist in a sawtooth shape by arranging a mask, exposing the resist through the photomask with linearly polarized light and developing the resist, and forming the base material on the patterned resist. And etching to pattern the surface of the substrate into a sawtooth shape corresponding to the resist pattern.

  The direction in which the linearly polarized electric field used for exposing the resist in the resist patterning step oscillates is parallel to the lattice direction of any one of the small regions provided adjacent to each other. It is characterized by being.

  The mold of the present invention is characterized in that a sawtooth pattern is formed on the molding surface by the above-described sawtooth pattern manufacturing method.

  The sawtooth diffraction grating of the present invention is characterized in that it has a sawtooth relief formed by the above-described mold and having the unevenness of the sawtooth pattern on the molding surface inverted.

  In addition, a sawtooth-type relief is formed by the above-described sawtooth-type pattern manufacturing method.

  According to the present invention, a sawtooth pattern can be manufactured inexpensively and easily.

  In addition, according to the present invention, a relief pattern of a sawtooth diffraction grating having a large separation angle and suitable for an optical system of a small apparatus can be manufactured inexpensively and easily.

  As shown in FIG. 1A, the sawtooth diffraction grating 10 is a transmission diffraction grating that diffracts when transmitting incident light 11 having a wavelength of 405 nm, and is made of a transparent material having a refractive index n of 1.5. Become. The sawtooth diffraction grating 10 is provided with a relief 12 on the surface on the side where incident light 11 having a wavelength of 405 nm is incident. The relief 12 is a concavo-convex structure that diffracts the incident light 11, and has a structure in which a plurality of concavo-convex portions of the same shape are repeated in the horizontal direction (direction along the cross section in FIG. 1), and the vertical direction (perpendicular to the cross section). In a straight direction). Moreover, the cross section of the relief 12 is a so-called sawtooth type, the cross section of each concavo-convex structure is a substantially right triangle, and these slopes are provided so as to face a certain direction.

  The incident light 11 is diffracted by the sawtooth diffraction grating 10 into a 0th-order diffracted light 16, a + 1st-order diffracted light 17, a −1st-order diffracted light 18, and a higher-order diffracted light (not shown). At this time, since the relief 12 has a sawtooth shape as described above, the diffraction efficiency of the + 1st order diffracted light 17 is larger than the diffraction efficiency of other diffracted lights.

  In addition, as shown in FIG. 1B, the relief 12 does not have a complete right-angled triangle blazed shape, but a so-called binary shape that is approximately blazed with an eight-step staircase structure. Yes. The height H of the relief 12 is 0.71 μm, and the pitch P is 8 μm. In addition, the width w of each step of the relief 12 is uniform, and all have a width of 1 μm.

Note that the multistage binary relief has a height H at which the diffracted light rate of the + 1st order diffracted light is maximized when the widths of the steps are provided at equal intervals, the wavelength λ of the incident light 11, the number of steps m, Using the refractive index n of the sawtooth diffraction grating 10, H = {(m−1) λ} / {m (n−1)}. When the relief height H satisfies this relational expression, the maximum diffraction efficiency of the + 1st order diffracted light is expressed as sinc ² (π / m). For these reasons, the dimensions of the relief 12 are determined so that the diffraction efficiency of the + 1st order diffracted light 17 is maximum (95%) with respect to the incident light 11 having a wavelength of 405 nm.

  The sawtooth diffraction grating 10 is manufactured by molding with a mold 21 as shown in FIG. The mold 21 is made of a hard metal material and includes an upper mold 22a and a lower mold 22b. The molding surface 23a of the upper mold 22a is configured to be flat, and a relief pattern 26 (sawtooth pattern) for fitting with the relief 12 is provided on the molding surface 23b of the lower mold 22b. Further, as shown in FIG. 2B, the relief pattern 26 has a serrated uneven structure that fits into the relief 12. For this reason, the relief pattern 26 has a multi-stage binary-shaped sawtooth-type uneven structure, and its depth H is 0.71 μm, the pitch P is 8 μm, and the width w of each step is 1 μm.

  The relief pattern 26 is provided by photolithography using linearly polarized light having a wavelength of 365 nm. A photomask 27 used at this time is provided with a mask pattern 28 corresponding to the relief pattern 26 as shown in FIG. The mask pattern 28 is composed of a plurality of stripe-shaped large areas 29, and the widths of the large areas 29 are all equal to the pitch P of the relief pattern 26 (and the relief 12).

  The mask pattern 28 includes a so-called photonic crystal 31 (selective polarized light transmitting means) in which a plurality of dielectrics having different refractive indexes are stacked. As shown in FIG. 4, the photonic crystal 31 constituting the mask pattern 28 is formed by alternately laminating a plurality of high refractive index dielectric layers 32a and low refractive index dielectric layers 32b on a transparent glass substrate. It has a structure.

The dielectric layer 32a is made of tantalum pentoxide (Ta ₂ O ₅ ) formed by ion plating, and the dielectric layer 32b is made of silicon oxide (SiO ₂ ). The thickness of each dielectric layer 32a is 70 nm, and the thickness of each dielectric layer 32b is 97 nm. In the photonic crystal 31, 20 dielectric layers 32a and 32b are laminated in total, ie, 20 layers in total, and the total thickness of the dielectric deposited layer structure of the photonic crystal 31 is 1670 nm.

  Furthermore, the photonic crystal 31 has a structure in which triangular irregularities are repeated at a constant pitch Lx in a constant direction (x direction). The pitch Lx is 180 nm, which is shorter than the wavelength of light (365 nm) used in photolithography in which the relief pattern 26 is provided on the mold 21, and is approximately half the pitch. On the other hand, this concavo-convex structure continues in a straight line in a direction (y direction) perpendicular to the x direction. For this reason, the photonic crystal 31 is a lattice in which triangular irregularities are repeated in the x direction parallel to the y direction. Hereinafter, the direction of the ridge line (y direction) along the concavo-convex structure is referred to as a lattice direction 33.

  Since the photonic crystal 31 is configured as described above, it reflects substantially 100% of linearly polarized light 36 (so-called TE polarized light) whose electric field vibrates in the lattice direction 33. On the other hand, almost 100% of linearly polarized light 37 (so-called TE polarized light) whose electric field vibrates in a direction perpendicular to the grating direction 33 (x direction) is transmitted. In addition, when the polarized light incident on the photonic crystal 31 is not linearly polarized light, or when the vibration direction of the electric field (hereinafter referred to as the polarization direction) is not perpendicular or parallel to the lattice direction 33, the photonic crystal 31 is in the lattice direction. The TE polarization component parallel to 33 is reflected and the TM polarization component perpendicular to the grating direction 33 is transmitted.

  The photonic crystal 31 is preferably produced by a so-called self-cloning method. For this reason, in the photonic crystal 31, the above-described triangular concavo-convex structure is substantially automatically formed by laminating the dielectric layers 32a and 32b on the substrate in which the rectangular concavo-convex structure is repeated at the pitch P. Formed.

  As described above, the mask pattern 28 is composed of the photonic crystal 31, but the entire mask pattern 28 is not composed of the photonic crystal 31 in the uniform lattice direction 33. Photonic crystals 31 are arranged so that the lattice direction 33 sequentially changes in the region 29. Therefore, as shown in FIG. 5, each large region 29 of the mask pattern 28 is composed of eight small regions 41a to 41h. The widths w of these small regions 41 a to 41 h are all set to the same width, and are equal to the width w of each step of the relief pattern 26.

  The small region 41 a is located at one end (left end) in the large region 29, and is composed of the photonic crystal 31 in which the lattice direction 33 is substantially perpendicular to the longitudinal direction of the large region 29. The small area 41 a corresponds to the highest step 43 a of the serrated uneven structure of the relief pattern 26. On the other hand, the small region 41 h is located at the other end (right end) in the large region 29 and is composed of the photonic crystal 31 in which the lattice direction 33 is substantially parallel to the longitudinal direction of the large region 29. This small area 41 h corresponds to the lowest step 43 h of the serrated uneven structure of the relief pattern 26.

  The small regions 41b to 41g are located between the small region 41a and the small region 41h, and the lattice direction 33 of these small regions 41b to 41g is inclined in order from the small region 41b from the small region 41a to the small region 41h. Yes. For example, the small region 41b is an area adjacent to the small region 41a, and the photonic crystal 31 constituting the small region 41b is such that the lattice direction 33 is lower than the lattice direction 33 of the small region 41a. It is inclined. Similarly, in the photonic crystal 31 constituting the small regions 41c to 41g, the lattice direction 33 is sequentially inclined from the small region 41a side to the small region 41h side. The small regions 41b to 41g correspond to the respective steps 43b to 43g of the relief pattern 26, respectively. In the mask pattern 28, the other large areas 29 are similarly composed of small areas 41a to 41h.

  The large region 29 is composed of small regions 41 a to 41 h in which the lattice direction 33 is changed in order as described above, and the polarization direction transmitting (reflecting) the photonic crystal 31 depends on the lattice direction 33 as described above. To do. For this reason, when light is incident on the photomask 27, the transmittances of the small regions 41a to 41h are different.

  As shown in FIG. 6, the polarization direction 42 (hereinafter referred to as the transmission direction) of light transmitted through each of the small regions 41a to 41h is a direction perpendicular to the lattice direction 33 of each of the small regions 41a to 41h. In each of the small areas 41a to 41h, the lattice direction 33 is linear and has a constant direction. Therefore, the transmission direction 42 of each of the small areas 41a to 41h is also linear in each of the small areas 41a to 41h. It is a certain direction. In the small region 41 a, the transmission direction 42 is a direction substantially parallel to the longitudinal direction of the large region 29, and in the small region 41 h, the transmission direction 42 is a direction perpendicular to the longitudinal direction of the large region 29. Similarly, in the small regions 41 b to 41 g, the transmission direction 42 is a direction perpendicular to the lattice direction 33. For this reason, in the large region 29, the transmission direction 42 is inclined in order from the small region 41a to the small region 41h, and the change of the transmission direction 42 in the large region 29 is approximately 90 degrees.

  As described above, since the transmission direction 42 is different for each of the small regions 41a to 41h, when the polarized light is incident on the photomask 27, the transmittance of each of the small regions 41a to 41h is different. For example, when linearly polarized light whose polarization direction is perpendicular to the longitudinal direction of the large region 29 is incident on the photomask 27, the transmissivities of the small regions 41a to 41h differ as shown in FIG. In the small region 41a, since the grating direction 33 is parallel to the polarization direction of the incident light, the transmission direction 42 is perpendicular to the polarization direction. For this reason, the transmittance of the small region 41a is approximately 0%. In the small region 41h, since the grating direction 33 is perpendicular to the polarization direction, the transmission direction 42 is parallel to the polarization direction. For this reason, the transmittance of the small region 41h is approximately 100%. Further, in the small regions 41b to 41g, since the grating direction 33 is inclined with respect to the polarization direction, the transmission direction 42 is also inclined with respect to the polarization direction. For this reason, the transmittance of the small regions 41b to 41g is a transmittance according to the inclination angle in the lattice direction 33, and the transmittance increases as the inclination angle in the lattice direction 33 increases.

  Hereinafter, a procedure for providing the relief pattern 26 on the mold 21 using the photomask 27 configured as described above will be described. First, as shown in FIG. 8A, a resist 53 is applied to the flat surface 52 of the lower mold base material 51 (resist application step). At this time, the resist 53 is uniformly applied so as to have a predetermined thickness T1. The predetermined film thickness T1 is determined in consideration of the exposure amount, the ratio of the etching rate between the lower mold base material 51 and the resist 53, the depth H of the relief pattern 26 (the height H of the relief 12), and the like.

  Next, as shown in FIGS. 8A and 8B, a photomask 27 is placed in close contact with the resist 53, exposed through the photomask 27, and developed (resist patterning step). Light 56 used for exposure at this time (hereinafter referred to as lithography light) is linearly polarized light having a wavelength of 365 nm and passes through a polarization filter (not shown) so that the polarization direction is perpendicular to the longitudinal direction of the large region 29. Adjusted to be.

  Thus, when the lithography light 56 is passed through the photomask 27 and the resist 53 is exposed, the light amount of the lithography light 56 that passes through the photomask 27 differs for each of the small regions 41a to 41h. For this reason, the actual exposure amount of the resist 53 differs for each of the portions 57a to 57h corresponding to the small regions 41a to 41h. For this reason, when the exposed resist 53 is developed, as shown in FIG. 8B, the resist 53 remains with a film thickness corresponding to the actual exposure amount for each of the portions 57a to 57h. A sawtooth-shaped uneven resist pattern 58 similar to that of No. 12 is formed.

  Since the transmission direction 42 of the small area 41a and the polarization direction of the lithography light 56 are substantially parallel, the lithography light 56 hardly transmits the small area 41a. For this reason, the portion 57a located immediately below the small region 41a is hardly exposed, and the resist 53 having a height T2 substantially equal to the film thickness T1 of the applied resist 53 remains. On the other hand, since the transmission direction 42 of the small region 41h and the polarization direction of the lithography light 56 are substantially perpendicular to each other, the lithography light 56 transmits substantially all of the small region 41h. For this reason, almost all of the portion 57h located immediately below the small region 41h is dissolved in the developer, and the surface 52 of the lower mold base 51 is exposed after development.

  Further, since the lattice direction 33 and the transmission direction 42 of the small regions 41b to 41g are inclined with respect to the polarization direction of the lithography light 56, the lithography light 56 partially transmits the small regions 41b to 41g. At this time, the light amount of the lithography light 56 that passes through the small regions 41 b to 41 g is a light amount corresponding to the angle at which the lattice direction 33 of each of the small regions 41 b to 41 g is inclined with respect to the polarization direction of the lithography light 56. . For this reason, in the portions 57b to 57g corresponding to the small regions 41b to 41g, a part of the resist 53 on the photomask 27 side is dissolved to a depth corresponding to the light amount of the lithography light 56 actually transmitted through the small regions 41b to 41g. Then, a part on the lower mold 22 b side remains on the surface 52 of the lower mold base material 51.

  As described above, the developed resist 53 has different remaining film thicknesses depending on the transmittance of the lithography light 56 in each of the small regions 41a to 41h. Therefore, the resist 53 after development forms a multistage binary pattern in which the remaining film thickness gradually decreases over the portions 57a to 57h. In addition, since the mask pattern 28 includes a plurality of large regions 29 including small regions 41a to 41h, the resist 53 after development is similarly a saw-tooth resist in which a plurality of the above-described multistage binary patterns are arrayed. Pattern 58 is obtained.

  The resist pattern 58 patterned here is a saw-tooth pattern like the relief pattern 26 and the relief 12, but the height T2 is the film thickness of the resist 53 applied to the lower mold base material 51. It is substantially equal to T1. As described above, the film thickness T1 of the resist 53 applied by the lower mold base material 51 is determined according to the etching rate of the lower mold base material 51 and the resist 53, and the etching rate of the resist 53 is set. When the etching rate of the lower mold base material 51 is higher, the resist pattern 58 has a height T2 that is higher than the height H of the relief pattern 26 in accordance with the ratio of the etching rate. A film thickness T1 of 53 is determined. Therefore, although the resist pattern 58 is a sawtooth pattern, it does not match the shape of the relief pattern 26 or the relief 12. In the following, the etching rate of the resist pattern 58 and the lower mold base material 51 is the time required for the resist pattern 58 to be etched by the height T2, and the lower mold base material 51 is etched by the depth H. It is assumed that the time required for

  When the resist pattern 58 is thus patterned on the lower mold base material 51, the lower mold base material 51 is etched from above the resist pattern 58, and a sawtooth pattern corresponding to the shape of the resist pattern 58 is formed on the lower mold base material 51. Patterned on the surface 52 (etching step).

  The etching performed here is so-called ion milling, and the resist pattern 58 and the lower mold base 51 are both deleted by irradiating the resist pattern 58 with argon ions. At this time, in the portion covered with the resist pattern 58, a deviation occurs when the lower mold base material 51 is started to be deleted according to the thickness of the resist pattern 58. The time when the base material 51 starts to be deleted is delayed. When the etching is performed for a time when the lowest portion 57h of the resist pattern 58 (the portion where the surface 52 of the lower mold base material 51 is exposed) is etched by the depth H, as shown in FIG. The portion 59a of the lower mold base 51 just under the portion 57a of the resist pattern 58 is not etched. Further, in the portions 59 b to 59 g of the lower mold base material 51 corresponding to the portions 57 b to 57 g of the resist pattern 58, the thickness of the resist pattern 58 according to the thicknesses of the portions 57 b to 57 g of the resist pattern 58. As the thickness increases, the depth of etching decreases. As a result, a multistage binary-shaped saw-tooth pattern (relief pattern 26) is formed on the lower mold base material 51 on the surface 52 of the lower mold base material 51 in accordance with the shape of the resist pattern 58.

  As described above (see FIG. 2), the lower mold 22b on which the relief pattern 26 is formed is used to manufacture the sawtooth diffraction grating 10 by molding the material of the sawtooth diffraction grating 10 together with the upper mold 22a.

  As described above, the photomask 27 includes the large region 29 in which the transmission direction of polarized light is changed in order. Therefore, by making the linearly polarized lithography light 56 incident on the photomask 27, a sawtooth relief can be obtained easily and inexpensively. A pattern can be formed.

  Further, since the photomask 27 realizes the transmission direction 42 of polarized light in the large region 29 by sequentially changing the lattice direction 33 of the photonic crystal 31, the pitch P is shorter than the order of 100 μm. A sawtooth pattern can be easily patterned.

In the above-described embodiment, the height of the resist pattern 58 is set to a height T2 that is not etched well when the lower mold base material 51 is etched by the depth H. The film thickness, exposure and development conditions can be determined in advance from the ratio of the etching rate between the resist 53 and the lower mold base 51, the exposure amount, the type of the resist 53, the development time, and the like. For example, when HPR-204 manufactured by FUJIFILM Electronics Materials Co., Ltd. is used as the resist 53, the thickness of the resist 53 applied to the lower mold base material 51 (initial film thickness) is 2.4 μm, and lithography light with a wavelength of 365 nm. FIG. 9 shows the relationship between the development time, the remaining thickness of the unexposed portion, and the remaining thickness of the exposed portion when exposure is performed at 56 and an exposure amount of 21 mj / cm ² .

On the other hand, from the above relational expression, when the refractive index n of the material of the sawtooth diffraction grating 10 is 1.5, an 8-stage multistage binary sawtooth pattern with respect to 405 nm light has a substantially maximum diffraction efficiency. In order to realize the above, it can be seen that the height H of the relief 12 may be about 710 nm. As a result, when the lower mold base material 51 is made of a material having an etching rate ratio of 2: 1 between the resist 53 and the lower mold base material 51, the height T2 of the resist pattern 58 after the development is calculated as follows: It can be seen that the difference from the unexposed portion needs to be 1.4 μm. For this reason, when the film thickness T1 of the resist 53 applied to the lower mold base material 51 is set to 2.4 μm and exposure is performed with the lithography light 56 having a wavelength of 365 nm at an exposure amount of 21 mj / cm ² , the road light is obtained from the graph of FIG. It can be seen that the development time may be 45 seconds so that the difference between the portion and the unexposed portion is 1.4 μm.

  In the above-described embodiment, the relief 12 of the sawtooth diffraction grating 10 is provided on the surface on the side on which the incident light 11 is incident. However, the present invention is not limited thereto, and the relief 12 is provided on the surface on the exit side. May be.

  In the above-described embodiment, the example in which the relief 12 and the relief pattern 26 are multi-stage binary sawtooth patterns of eight stages has been described. However, the present invention is not limited to this, and the relief 12 and the relief pattern 26 may be a desired pattern. Any number of stages may be used depending on the diffraction efficiency.

  In the above-described embodiment, the example in which the relief pattern 26 is provided on the mold 21 (lower mold 22b) as the sawtooth pattern and the sawtooth diffraction grating 10 is manufactured using the mold 21 has been described. The material of the mold diffraction grating 10 may be formed in a plate shape, and the relief 12 may be directly patterned using the photomask 27.

  In the above-described embodiment, when the lower mold base material 51 is etched, the etching is performed by ion milling. However, the present invention is not limited to this, and reactive ion etching or wet etching may be used.

  In the above-described embodiment, the large area 29 of the photomask 27 is configured by the small areas 41a to 41h, and the small areas 41a to 41h are all set to the same width w. However, the resist pattern 58 is a multistage binary. The width w may be changed for each of the small regions 41a to 41h.

  In the above-described embodiment, the sawtooth diffraction grating 10 in which the sawtooth concavo-convex structure is arranged in one direction has been described as an example. However, the present invention is not limited to this, and other shapes of diffraction gratings, hologram gratings, and diffraction lenses are used. The present invention can be preferably applied to the above. Further, in the above-described embodiment, the sawtooth diffraction grating 10 provided with the relief 12 on the plane has been described as an example. However, the present invention is not limited thereto, and the present invention is preferably applied to the case where the relief 12 is provided on the lens surface or the like. Can be used.

  For example, when the reliefs are provided concentrically, a photomask 71 shown in FIG. 10A is used. The photomask 71 includes a mask pattern 72 provided with a plurality of annular large regions 73, and each large region 73 is composed of small regions 74 that are concentric and have the same width in eight stages. These small regions 74 are made of the photonic crystals 31 having different lattice directions, as in the above-described embodiment, and the lattice direction of each small region 74 is a constant direction in each small region 74. Furthermore, the lattice direction of each small region 74 is arranged so that the lattice direction inclines in order from the center of the circle to the outside in the large region 73.

  When a sawtooth pattern is patterned on the lower mold base 51 using the photomask 71 configured as described above, a serrated relief pattern 77 is formed concentrically on the lower mold 76 as shown in FIG. Is formed. At this time, the sawtooth shape of the relief pattern 77 is a shape in which the slope is lowered from the center toward the outside. Therefore, when the sawtooth diffraction grating 78 is formed using the lower mold 76, the sawtooth relief 79 is provided concentrically on the sawtooth diffraction grating 78 as shown in FIG. The slope of this is shaped to rise from the center to the outside.

  In this way, by changing the arrangement of the photonic crystals 31, the grating shape of the sawtooth diffraction grating 10 can be provided in a desired shape. Further, by changing the arrangement of the photonic crystals 31 in this way, the sawtooth pattern can be provided at an arbitrary position and at an arbitrary pitch at an arbitrary position.

  In the above-described embodiment, the sawtooth diffraction grating 10 that functions with respect to light having a wavelength of 405 nm has been described as an example. However, the present invention is not limited thereto, and the present invention also applies to a sawtooth diffraction grating that functions with respect to other wavelengths. Can be suitably applied. At this time, in order to form the relief pattern 26 with higher accuracy, it is preferable that light having a wavelength shorter than the wavelength used for the formed sawtooth diffraction grating is used as the lithography light 56 as in the above-described embodiment. .

  In the above-described embodiment, when the relief pattern 26 is formed by photolithography, the linearly polarized lithography light 56 whose polarization direction coincides with the lattice direction of the small region 41a is used. Linearly polarized light that matches the lattice direction of the region may be used as the lithography light 56. Further, it is sufficient that a difference in transmittance occurs due to a difference in the lattice direction for each of the small regions 41 a to 41 h, and elliptically polarized light or the like may be used as the lithography light 56.

  In the above-described embodiment, the photonic crystal 31 used for the photomask 27 has been described by taking an example in which tantalum pentoxide and silicon oxide are alternately stacked. Not limited to combinations. As long as dielectric materials having different refractive indexes are alternately stacked to form the above-described photonic crystal 31 and the polarization direction of transmission is selective according to the lattice direction, the material of each dielectric layer is arbitrarily selected. be able to.

  In the above-described embodiment, an example in which the sawtooth relief pattern 26 is patterned on the lower die 22b and the sawtooth diffraction grating 10 (relief 12) is manufactured using the pattern is described. In the same manner as in the embodiment, by changing the arrangement and arrangement of the small regions 41 and the large regions 29, a desired sawtooth relief pattern and a sawtooth relief can be suitably patterned. For example, a more complicated sawtooth diffraction grating or the like having different relief directions and pitches depending on the position in the photomask can be easily manufactured in the same manner as in the above-described embodiment.

  In the above-described embodiment, the lattice direction 33 is configured to be linear in each of the small regions 41a to 41h. However, the present invention is not limited thereto, and the lattice direction 33 is curved in the small regions 41a to 41h. It may be provided. For example, the lattice direction 33 may sequentially change in the small regions 41a to 41h with a curvature corresponding to the change rate of the lattice direction 33 in the large region 29. In addition, the lattice direction 33 is changed in a curved line at a change rate similar to that in the above-described embodiment without dividing the large region 29 into the small regions 41a to 41h as in the above-described embodiment. It may be composed of two photonic crystals. Such a photonic crystal in which the lattice direction 33 is curved is easily manufactured by the self-cloning method as in the above-described embodiment. In the self-cloning method, the photonic crystal 31 is formed by laminating a dielectric on a substrate having a concavo-convex structure that is the source of the lattice direction 33. For example, a concavo-convex structure that changes in a curved manner within a small region is formed. By laminating a dielectric on the substrate, a photonic crystal whose lattice direction changes in a curved manner in the small regions 41a to 41h can be formed.

It is sectional drawing which shows the sawtooth type diffraction grating whose relief is multistage binary shape. It is sectional drawing which shows the metal mold | die which shape | molds a sawtooth type | mold diffraction grating. It is a figure which shows the photomask used when patterning the relief pattern of a sawtooth type diffraction grating. It is a schematic diagram which shows the structure of the photonic crystal which comprises a mask pattern. It is explanatory drawing which shows the detailed structure of a mask pattern. It is explanatory drawing which shows the grating | lattice direction of a mask pattern, and the transmission direction of polarized light. It is a graph which shows the lattice direction and the transmittance | permeability of each small area | region. It is explanatory drawing which shows the manufacturing method of a relief pattern. It is a graph which shows an example of the property of a resist. It is explanatory drawing which shows the example of the photomask used when providing a concentric relief pattern.

Explanation of symbols

10,78 Sawtooth type diffraction grating 11 Incident light 12,79 Relief 16 0th order diffracted light 17 + 1st order diffracted light 18 -1st order diffracted light 21 Mold 22a Upper mold 22b, 76 Lower mold 26,77 Relief pattern (sawtooth pattern)
27, 71 Photomask 28, 72 Mask pattern 29, 73 Large area 31 Photonic crystal 32a, 32b Dielectric layer 33 Lattice direction 36, 37 Linearly polarized light 41a-41h, 74 Small area 42 Transmission direction 51 Lower mold base material 53 Resist 56 Lithography light 58 Resist pattern

Claims (9)

  The grating direction is constant in a small area consisting of selective polarization transmitting means that transmits linearly polarized light whose electric field oscillates in a direction parallel to the grating direction and reflects linearly polarized light whose electric field oscillates in a direction perpendicular to the grating direction. A photomask comprising a plurality of adjacent photomasks so as to incline in order.   The photomask according to claim 1, further comprising a plurality of adjacent large areas each having a predetermined number of small areas as a set.   3. The photomask according to claim 2, wherein the small regions are arranged so that the lattice direction changes by 90 degrees in the large region.   The selective polarized light transmitting means has a structure in which a plurality of dielectrics having different refractive indexes are alternately laminated, and has an uneven structure with a pitch shorter than the wavelength of the linearly polarized light to be transmitted. The photomask according to claim 1, wherein the photomask is a photomask. A resist coating step for uniformly coating a resist on a substrate for patterning a sawtooth pattern;
The photomask according to any one of claims 1 to 4 is disposed in close contact with the resist, and the resist is exposed to light through the photomask by linearly polarized light and developed, whereby the resist is patterned into a sawtooth shape. A resist patterning step;
Etching the substrate from above the patterned resist, and patterning the surface of the substrate into a sawtooth shape according to the resist pattern;
A sawtooth pattern manufacturing method comprising:   The direction in which the electric field of linearly polarized light used for exposing the resist in the resist patterning step oscillates is parallel to the lattice direction of any one of the small regions provided adjacent to each other. The sawtooth pattern manufacturing method according to claim 5.   A die having a sawtooth pattern formed on the molding surface by the method of manufacturing a sawtooth pattern according to claim 5 or 6.   A sawtooth-type diffraction grating, which is formed by the mold according to claim 7 and has a sawtooth-type relief in which the unevenness of the sawtooth pattern on the molding surface is reversed.   A sawtooth-type relief is formed by the sawtooth pattern manufacturing method according to claim 5 or 6.

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