Three-dimensional photomask and method for producing the same, exposure apparatus, and exposure method

Abstract

To provide a three-dimensional photomask enabling formation of a resist pattern having a complex three-dimensional structure.SOLUTION: A three-dimensional photomask 102 of the present invention can be used for exposing an exposure target to a predetermined pattern, wherein the three-dimensional photomask is composed of a light-transmissive material that allows passage of light at a wavelength that sensitizes a photosensitive resin, and the three-dimensional photomask includes a three-dimensional shaped body 11 having a thickness distribution in the direction of light travel.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a three-dimensional photomask, a method for manufacturing the same, an exposure apparatus, and an exposure method.

Background Art

[0002] Photolithography technology is a technology for transferring a pattern drawn on a photomask onto a resist, which is a photosensitive resin, at a scale of 1:1 or reduced.

[0003] Generally used photomasks have patterns of circuits and machine parts drawn on them. As materials, transparent film materials or glass are used. Also, patterns are drawn on the surface with a chromium material for the light-shielding part. The photomask controls the transmission and non-transmission of light using this light-shielding part.

[0004] By applying light from above this photomask, in the case of contact exposure or proximity exposure, the passed light directly hits the resist, which is a photosensitive resin, and the pattern is transferred. Also, in the case of exposure through a projection lens, the transmission and non-transmission of light are transferred to the resist, which is a photosensitive resin, through an equal magnification projection lens or a reduction projection lens. When exposed through a reduction projection lens, the mask pattern of the photomask is reduced and transferred to the resist.

[0005] The resist, which is a photosensitive resin, is a polymer compound whose chemical structure changes in response to light. There are a negative-type resist that hardens when exposed to light and a positive-type resist that becomes easily soluble in a developer when exposed to light. By immersing it in a developer, the part that has reacted to light or the part that has not reacted to light remains as a resist pattern.

[0006] In semiconductor ICs and the like, this resist pattern is formed on a thin film material formed on the surface of a substrate such as a silicon wafer, and then immersed in an etching solution. As a result, the resist pattern serves as a masking material, and the thin film material in the unmasked part is selectively removed, and finally a thin film material pattern with the desired shape is obtained.

[0007] Recently, there are examples of directly using this resist pattern or using it as a mold. For example, the black matrix of the color filter of the liquid crystal panel is directly used after the resist pattern is fabricated. Also, the microchannel is formed by transferring the pattern of the channel onto a thick film resist (from several tens of μm to several hundreds of μm). In addition, there are the fabrication of microconnectors used as molds for plating and metamaterials fabricated by coating an aluminum thin film on the resist pattern surface of microstructures made of photoresist, etc.

[0008] Furthermore, in recent years, there has been an increasing need to create three-dimensional structures by forming this resist pattern from a two-dimensional shape (vertical sidewall shape) into a three-dimensional shape (sidewall shape with steps, inclinations, or smooth curves).

[0009] For example, there are medical micro needles with a sharp tip at the end (a structure with a large number of needle-shaped conical structures arranged), a microlens array which is a micro optical element with curvature (a structure with micro-order lenses arranged in an array), and examples of using it as a mold, an optical waveguide plate using a conical shape, and diffractive optical elements represented by a Fresnel lens using an inclined shape.

[0010] Examples of methods for forming a resist pattern into these three-dimensional shapes include the following. There are fabrication methods such as the laser drawing beam method and the electron beam drawing method, in which a laser or electrons are applied to the resist in a beam shape to create a pattern in one stroke. By controlling the power, scanning speed, and number of scans of the beam at different locations, the amount of light exposure given to the resist can be adjusted, and a three-dimensional resist pattern can be obtained after development processing. Also, there is the rotational exposure method in which a substrate coated with resist is fixed to an inclined stage and exposed obliquely while rotating at a constant speed. By inclining the substrate, the light hits from an oblique direction, so a three-dimensional fine structure with a conical shape, which is impossible with normal exposure, can be fabricated. Furthermore, there is also a method (3D lithography method) of fabricating a planar structure by laminating it in multiple processes using a plurality of photomasks. By changing the photomask for each layer and stacking resist patterns, a structure such as a pyramid can be formed. As an advantage, a 3D structure with a hollow structure can be fabricated.

Prior Art Documents

Patent Documents

[0011]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0012] In the methods listed above, in the fabrication methods of the laser drawing beam method and the electron beam drawing method, since the exposure range for one-time exposure is narrow for continuous exposure, a significant exposure time is required when exposing a complex pattern over a large area. Also, in the case of the rotational exposure method of irradiating light obliquely, a special exposure apparatus is required to tilt and rotate the object to be exposed, and only simple patterns can be fabricated. Furthermore, in the exposure methods that require a plurality of photomasks and fabrication processes, significant costs and fabrication time are required. On the other hand, as a technique that can utilize a conventional exposure apparatus as it is, there is also a method in which the photomask is modified. This is the gray mask (gray scale mask).

[0013] By using a gray mask in which shades are added to the black of the light-shielding portion of a photomask to control the light transmittance, the light passing through the gray mask can have a light intensity distribution with tones corresponding to the gray scale. For this reason, the pattern of the photomask transferred to the resist also has a difference in light intensity in part, and the exposure amount to the resist changes. As a result, the resist pattern after development has a three-dimensional structure.

[0014] As a method for manufacturing this gray mask, a method of adjusting the density of the black light-shielding material drawn on the photomask is generally employed, similar to drawing gray on paper with a printer. For example, a method of adjusting the density and controlling the light transmittance by arranging a large number of fine aperture patterns on the photomask and changing their aperture areas has been disclosed.

[0015] In a method that involves devising the drawing of the photomask, it was necessary to change the width of the fine slit in order to change the black density (transmittance) drawn on the photomask. In the production of fine slits for changing the density of the pattern drawn on the photomask, it was necessary to change the drawing accuracy according to the density. For components with different densities (for example, to produce a curved surface such as a microlens, a photomask with a gradually changing density in the normal direction is required), multiple processes were necessary to produce a single photomask, resulting in high production costs. Also, since the slit width controls the density, it was necessary to draw the slit width in a complex manner for the production of a three-dimensional structure with a complex shape, and there were limitations. Furthermore, it was not possible to produce a resist pattern with a three-dimensional structure finer than the slit of the photomask. That is, to produce a resist pattern with a fine three-dimensional structure, it was necessary to make the slit width sufficiently smaller than desired, and there were limitations.

[0016] The present invention has been made in view of the above circumstances, and an object thereof is to provide a three-dimensional photomask capable of producing a resist pattern with a complex three-dimensional structure, a manufacturing method thereof, an exposure apparatus, and an exposure method.

Means for Solving the Problems

[0017] To solve the above problems, the present invention provides the following means.

[0018] Aspect 1 of the present invention is a photomask that can be used when exposing an object to be exposed to a predetermined pattern, which is a three-dimensional shaped body made of a light-transmissive material that can transmit light having a wavelength that sensitizes a photosensitive resin, and has a thickness distribution with respect to the traveling direction of the light. It is a stereoscopic photomask.

[0019] Aspect 2 of the present invention is the stereoscopic photomask of Aspect 1, wherein the three-dimensional shaped body is formed on a transparent substrate.

[0020] Aspect 3 of the present invention is the stereoscopic photomask of Aspect 1 or Aspect 2, which has a light-shielding portion.

[0021] Aspect 4 of the present invention is the stereoscopic photomask of Aspect 2, wherein the transparent substrate is a substrate made of a material selected from the group consisting of various glasses, quartz, sapphire, and synthetic resins.

[0022] Aspect 5 of the present invention is the stereoscopic photomask of Aspects 1 to 4, wherein the light-transmissive material is a photosensitive resin.

[0023] Aspect 6 of the present invention is the stereoscopic photomask of Aspects 1 to 4, wherein the light-transmissive material is a material selected from the group consisting of various glasses, quartz, sapphire, and synthetic resins.

[0024] Aspect 7 of the present invention is an exposure apparatus including any one of the stereoscopic photomasks of Aspects 1 to 6.

[0025] Aspect 8 of the present invention is an exposure method using any one of the stereoscopic photomasks of Aspects 1 to 6.

[0026] Aspect 9 of the present invention is a method for manufacturing a three-dimensional photomask according to any one of Aspects 1 to 6, which includes a shape determination step of determining the shape of the three-dimensional photomask based on the transmittance of the light-transmitting material constituting the three-dimensional photomask so that the light transmitted through the three-dimensional photomask has a desired light intensity distribution on the resist surface.

[0027] Aspect 10 of the present invention is the method for manufacturing a three-dimensional photomask according to Aspect 9, which includes a shaping step of shaping a three-dimensional photomask having the shape determined in the shape determination step with a 3D printer.

[0028] Aspect 11 of the present invention is the method for manufacturing a three-dimensional photomask according to Aspect 10, which includes an optimization step of repeatedly calculating the three-dimensional shape of the three-dimensional photomask by optical simulation and optimizing the three-dimensional shape so that the intensity distribution of the light passing through the three-dimensional photomask becomes a desired light intensity distribution on the resist surface, with the shape of the three-dimensional photomask as a variable.

Advantages of the Invention

[0029] According to the present invention, it is possible to provide a three-dimensional photomask capable of creating a resist pattern with a complex three-dimensional structure.

Brief Description of the Drawings

[0030]

Figure 1

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Figure 10

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Mode for Carrying Out the Invention

[0031] Hereinafter, the present invention will be described in detail with appropriate reference to the drawings. The drawings used in the following description may show the characteristic parts enlarged for the sake of easy understanding of the characteristics, and the dimensional ratios of the respective components may be different from the actual ones. The dimensions and the like exemplified in the following description are merely examples, and the present invention is not limited thereto, and it is possible to appropriately modify and implement within the range in which the effects of the present invention are achieved. Hereinafter, even when not particularly described, the configuration described in one embodiment may be applied to other embodiments.

[0032] (Stereo photomask) FIG. 1 is a conceptual diagram for explaining an exposure method using a stereo photomask according to an embodiment of the present invention. FIG. 1(a) is a first example, and FIG. 1(b) is a second example.

[0033] The stereo photomask 100 shown in the upper diagram of FIG. 1(a) is a three-dimensional shaped body 10 made of a light-transmissive material capable of transmitting light having a wavelength for exposing a photosensitive resin, and having a thickness distribution with respect to the traveling direction of the exposure light L. The lower diagram of FIG. 1(a) shows a diagram of the light intensity distribution after the exposure light L has passed through the stereo photomask 100.

[0034] When the exposure light L passes through the stereo photomask 100, the thickness of the light-transmissive material changes partially (has a thickness distribution) due to the three-dimensional shape of the stereo photomask 100, and therefore the transmittance of the light transmitted through it changes according to the thickness. For this reason, the light that has passed through the stereo photomask 100 forms a state with an intensity distribution. More precisely, not only the transmittance of light according to the thickness, but also as will be described later, a light intensity distribution corresponding to reflection, refraction, scattering, and diffraction phenomena depending on the material and shape of the stereo photomask 100 is formed.

[0035] Therefore, on the lower surface of the stereo photomask 100, it is possible to obtain an original image with a changed light intensity similar to that of a gray mask.

[0036] The three-dimensional photomask 101 shown in the lower diagram of Fig. 1(b) is composed of a light-transmissive material capable of transmitting light with a wavelength that sensitizes a photosensitive resin, and includes a three-dimensional shaped body 10 having a thickness distribution with respect to the traveling direction of the exposure light L, and a transparent substrate 20 on which the three-dimensional shaped body 10 is formed, which is an example of a configuration. The lower diagram of Fig. 1(b) shows a diagram of the light intensity distribution after the exposure light L has passed through the three-dimensional photomask 101.

[0037] As the light-transmissive material of the three-dimensional shaped body 10 constituting the three-dimensional photomasks 100 and 101, a known material capable of transmitting light with a wavelength that sensitizes a photosensitive resin (resist) can be used, and it can be either an inorganic material or an organic material. Specifically, examples of light-transmissive inorganic materials include various glasses (such as soda-lime glass, borosilicate glass, and quartz glass), quartz, sapphire, etc. The quartz glass can be either fused quartz or synthetic quartz. Also, examples of light-transmissive organic materials include various plastics, acrylics, vinyl chloride, synthetic resins such as epoxy resins, but natural resins can also be used. Additionally, various photoresists can also be used.

[0038] Regarding the shape of the three-dimensional photomasks 100 and 101, after the exposure light L passes through the three-dimensional photomasks 100 and 101, the light intensity distribution for obtaining a resist pattern (three-dimensional shape) of the three-dimensional shape that is ultimately to be made of a photosensitive resin, i.e., a resist, should be able to be formed on the lower surface of the three-dimensional photomask. For example, by combining geometric shapes such as thickness, inclination, curvature, helix, groove, hole, thickness, etc., the shape of the three-dimensional photomasks 100 and 101 can be formed.

[0039] The three-dimensional photomask 102 shown in Fig. 2 is an example in which the shape of the three-dimensional shaped body 11 constituting the three-dimensional photomask 102 is different from the shape of the three-dimensional shaped body 10 constituting the three-dimensional photomasks 100 and 101.

[0040] A light-shielding portion (portion to be transmitted through) may be provided on either one or both of the three-dimensional shaped body 10 and the transparent substrate 20.

[0041] As the transparent substrate 20 constituting the three-dimensional photomask 101, a known substrate capable of transmitting light having a wavelength that sensitizes the photosensitive resin can be used, and it may be a substrate made of an inorganic material or an organic material. Specifically, examples of the light-transmissive inorganic material substrate include substrates made of various glasses (such as soda-lime glass, borosilicate glass, and quartz glass), quartz, sapphire, and the like. The quartz glass may be fused quartz or synthetic quartz. Further, examples of the light-transmissive organic material substrate include substrates made of synthetic resins such as various plastics, acrylics, vinyl chloride, and epoxy resins, but substrates made of natural resins may also be used.

[0042] Figs. 3(a) to (c), (e) show four configuration examples of the three-dimensional photomask.

[0043] Fig. 3(a) is a three-dimensional photomask composed of a plurality of materials, which is constituted by a three-dimensional shaped body and a separate transparent substrate. For example, a three-dimensional photomask in which the three-dimensional shaped body is made of resin and the transparent substrate is a glass substrate can be exemplified.

[0044] Fig. 3(b) is a three-dimensional photomask composed of a single material, which is constituted by a three-dimensional shaped body and an integral transparent substrate. For example, a three-dimensional photomask in which the three-dimensional shaped body and the transparent substrate are made of resin can be exemplified.

[0045] Fig. 3(c) is a three-dimensional photomask having a configuration in which a light-shielding portion 30 made of a material such as chromium is disposed on a part of the lower surface side of the transparent substrate and a separate transparent substrate from the three-dimensional shaped body.

[0046] Fig. 3(d) shows the light intensity distribution formed on the lower surface of the three-dimensional photomask through the three-dimensional photomask shown in Fig. 3(c). By having the light-shielding portion, there is a portion where the transmitted light is completely blocked in the light intensity distribution.

[0047] FIG. 3(e) shows a three-dimensional mask made of a bottle-shaped three-dimensional body and a transparent substrate integrated therewith, having a complex three-dimensional shape and consisting of a single material. For example, a three-dimensional mask made of resin can be exemplified, where the three-dimensional body and the transparent substrate are made of resin.

[0048] FIG. 3(f) shows the light intensity distribution formed on the lower surface of the three-dimensional mask through which the light transmitted through the three-dimensional mask shown in FIG. 3(e) passes. The light intensity distribution has a pattern reflecting the shape of the three-dimensional mask.

[0049] (Exposure Method) FIG. 4 is a diagram for explaining an exposure method using a three-dimensional mask of a three-dimensional shape according to the present embodiment. Shown in FIG. 4 is an example using a three-dimensional mask 100A having a configuration consisting of a three-dimensional body 10A and a transparent substrate 20A on which the three-dimensional body 10A is formed.

[0050] Since the three-dimensional mask according to the present embodiment can be used in the same way as the masks used in conventional exposure apparatuses, it can be easily introduced into the process. Also, since a three-dimensional mask having a shape equivalent to or better than the three-dimensional resist pattern to be created can be used, it can also handle fine patterns. Furthermore, by fabricating a three-dimensional mask with a more complex three-dimensional shape, a complex and highly accurate three-dimensional resist pattern can be obtained. The fabricated three-dimensional resist pattern can be used for micro needles, micro channels, etc. in the same way as before.

[0051] FIG. 4 shows an example of contact or proximity exposure, where the three-dimensional mask according to the present embodiment is installed in a contact or proximity exposure apparatus, and the light intensity distribution pattern formed by the three-dimensional mask 100A is subjected to contact exposure or proximity exposure on a photosensitive material.

[0052] As shown in FIG. 4(a), light guided from a light source having the photosensitive wavelength of the resist is irradiated from above the three-dimensional mask of the three-dimensional shape.

[0053] A three-dimensional solid photomask is formed, for example, by three-dimensionally forming a light-transmissive material on a glass substrate with thickness. When light passes through this light-transmissive material, the transmittance of the passing light changes because the thickness changes partially depending on the shape of the light-transmissive material. Furthermore, due to the addition of light refraction, reflection, scattering, and diffraction phenomena, the light passing through the solid photomask exits with a light intensity distribution. Therefore, on the lower surface of the three-dimensional solid photomask, a state where the light intensity changes stepwise can be obtained in the same manner as a gray mask.

[0054] In this way, by transferring this light intensity distribution onto the surface of the object to be exposed M (for example, a silicon wafer) coated with the negative-type photosensitive resin R under the solid photomask, as shown in Fig. 4(b), a chemical change (latent image) occurs in the resist film, which is a photosensitive resin, and a three-dimensional resist pattern 3D-R having a three-dimensional shape can be obtained by performing a development process.

[0055] Fig. 5 shows an example in which, in projection exposure, an image projected at an equal magnification or reduced magnification by a projection lens 40 is projected onto a surface coated with a resist, which is a photosensitive resin.

[0056] When the resist, which is a photosensitive resin, has a thickness, it is three-dimensionally sensitized within the resist as shown in the figure within the circle in Fig. 5 depending on the light intensity, and a chemical change occurs. As a result, the remaining film thickness amount of the resist remaining after the development process changes. Therefore, a three-dimensional resist pattern 3D-R having a three-dimensional shape can be finally obtained due to the difference in the remaining film thickness amount.

[0057] Fig. 6 shows a flowchart of an exposure method using the solid photomask according to this embodiment.

[0058] First, a photosensitive substance is attached to the object to be exposed (S1). Here, the photosensitive substance to be attached may be either negative-type or positive-type. Next, the object to be exposed with the photosensitive substance attached to the exposure surface is placed on a stage (not shown) for holding the object to be exposed (S2). Next, a stereoscopic photomask (3D shape photomask) is placed at the mask position of the exposure apparatus (S3). Next, the illumination of the light source is turned on (S4). Next, exposure is continued until a predetermined exposure amount is reached (S5). During the process, the exposure amount is checked. If the exposure amount is insufficient, the illumination of the light source is turned on again and exposure is continued. When the predetermined exposure amount is reached, the illumination of the light source is turned off (S6). The exposure is terminated (S7). Next, a desired 3D shape resist pattern is obtained by development processing (S8).

[0059] (Method for manufacturing a stereoscopic photomask) Fig. 7 shows a flowchart of the design process of the shape of the stereoscopic photomask.

[0060] First, a resist pattern of a target 3D shape is set (S1'). This 3D shape resist pattern is designed using computer design software. As the design software, existing software such as Inventer, Pro / ENGINEER (Creo Parametric), or SOLID WORKS of 3D CAD (Computer-Aided Design) can be used.

[0061] Next, considering the relationship between the light intensity or the exposure amount obtained by multiplying the light intensity and the exposure time and the remaining film thickness amount of the resist, the light intensity distribution required on the resist surface to obtain the target shape is calculated (S2'). Although the relationship between this light intensity or exposure amount and the remaining film thickness amount of the resist can also be predicted using simulation, since it depends on the photosensitive characteristics of the resist and the process up to the development process including the exposure apparatus, it is better to obtain it in advance through experiments and create a database.

[0062] Fig. 8 is an image diagram showing the exposure amount and the remaining film thickness amount of the resist obtained by experiments. The image diagram of Fig. 8 is a diagram when the same negative resist as in the examples described later is used. When a positive resist is used, the shape of the curve changes. The relationship shown in the figure is obtained by measuring the light intensity on the imaging surface of the exposure apparatus and measuring the thickness of the resist remaining after development when the resist is exposed for a predetermined time at that light intensity. Since the light intensity can be changed by setting the light source, it is a figure obtained by changing the setting and acquiring a plurality of data. When using the same exposure apparatus under the same conditions, the light intensity on the photomask surface may be substituted. Measure the light intensity on the photomask surface and measure the thickness of the resist remaining after development when the resist is exposed for a predetermined time at that light intensity.

[0063] Assuming the exposure amount is E and the resist remaining film thickness amount (thickness) at each exposure amount is H, Exposure amount E = Light intensity I × Exposure time time E = f 1 (H) Here, f 1 is a polynomial function of H, and a function fitted to the experimental values by the least squares method or the like is used. Thereby, the exposure amount and light intensity required to leave a predetermined resist thickness can be estimated. In the database, the resist material and this polynomial may be stored. The content of the database is the relationship between the light intensity or exposure amount on the imaging surface or photomask surface and the resist remaining film thickness amount after development.

[0064] Next, using the information obtained by examining in advance the transmittance of the material used for the three-dimensional photomask (3D-shaped photomask) and putting it into the database, the shape of the three-dimensional photomask (3D-shaped photomask) is determined so that the transmitted light has a desired light intensity distribution (S5').

[0065] The relationship between this transmittance and the thickness of the material of the three-dimensional photomask can be easily obtained experimentally. FIG. 9 is an image diagram showing the relationship between the transmittance and the thickness of the material of the three-dimensional photomask.

[0066] It is a figure obtained by preparing three-dimensional photomasks with different thicknesses and measuring their respective relative light intensities with an existing transmittance measuring instrument or spectroscopic measuring instrument.

[0067] The incident light intensity is I 0, assuming the transmittance is S (%) and the thickness is t, t = f 2 (S) The light intensity I = the incident light intensity I 0 × the transmittance S Here, f 2 is a polynomial function of S, and a function fitted to the experimental values by the least squares method or the like is used. This polynomial function varies depending on the material. Therefore, the material of the photomask and this polynomial function may be stored in the database.

[0068] Furthermore, if the absorption coefficient specific to the material is known, the transmittance of the material can be simply calculated even by calculation.

[0069] Generally, it is known that the light absorption rate in a light-transmissive material is expressed by the following formula. I out = I in × exp(-α·t) S = I out / I in = exp(-α·t) Here, I in is the incident light intensity, α is the absorption coefficient of the material, and t is the thickness. This formula is called Lambert-Beer's law and shows that light decays exponentially depending on the thickness of the material. Here, α varies depending on the material. When the value is small, the transparency is high, and when the value is large, absorption is large and light decays. Actually, due to optical phenomena such as reflection on the surface of the light-transmissive material and refraction due to the shape, it becomes even more complicated, so it is just a simple calculation.

[0070] The target three-dimensional shape resist pattern to be fabricated is a resist pattern with a three-dimensional shape in which the thickness of the resist pattern is partially different. That is, it is the thickness H at each planar coordinate (x, y). Using this target resist pattern, the mask pattern of the three-dimensional photomask is calculated.

[0071] The exposure amount required for the thickness H of the resist is E. This relational expression is the polynomial f 1It is represented by []. To obtain the exposure amount E, the light intensity I is required. Since the exposure time does not vary depending on the exposure location, the relative thickness of the resist is determined only by the light intensity.

[0072] The light intensity I can be calculated from the transmittance S of the light-transmissive material. Since the incident light intensity I throughout the illumination area of the three-dimensional photomask is constant, the thickness t of the three-dimensional photomask is determined by the transmittance S. 0 That is, by using the transmittance S, the thickness t of the three-dimensional photomask can be calculated. This relational expression is represented by the polynomial f

[0073] That is, by using the transmittance S, the thickness t of the three-dimensional photomask can be calculated. This relational expression is represented by the polynomial f 2 is represented by. Here, assuming the thickness of the resist pattern of the target three-dimensional shape is H and the required thickness of the three-dimensional photomask is t, t = f 3 (H) can be established. Here, f 3 is a polynomial function. f 3 = C × f 2 (f 1 (H)). Here, C is a constant, which is a value determined by the exposure time and the light intensity irradiated on the photomask.

[0074] Therefore, from the resist pattern of the target three-dimensional shape, the shape (x, y, t) of the three-dimensional photomask of the required three-dimensional shape can be calculated.

[0075] Note that the relationship between the relative thickness t of the photomask and the resist remaining film thickness amount H may also be obtained directly through experiments. Fabricate three-dimensional photomasks with different thicknesses step by step, expose them with an exposure apparatus, investigate the remaining film thickness amount of the resist, experimentally obtain the relationship between t and H as shown in Fig. 10, fit the polynomial function by the least squares method, and needless to say, it is also possible to save the polynomial function f 3 in the database.

[0076] For the target shape given in the three-dimensional coordinates (x, y, t), design the three-dimensional solid photomask shape. The design is carried out using design software 3D CAD (Computer-Aided Design) on a computer to design the obtained target shape. Existing software such as Inventer, Pro / ENGINEER (Creo Parametric), and SOLID WORKS can be used. Design using the three-dimensional coordinate data of the obtained target shape.

[0077] Using the obtained data of the three-dimensional solid photomask, fabricate it with an existing three-dimensional processing machine. The existing three-dimensional processing machine is a stereolithography apparatus (e.g., 3D printer) or a processing apparatus using an electron exposure beam.

[0078] In the stereolithography apparatus, a solid photomask is fabricated according to the flow as shown in FIG. 11. Save the three-dimensional solid photomask designed in 3D CAD in a file (intermediate file) in, for example, STL format. In the stereolithography apparatus, load it with dedicated software, set the conditions for lamination, and make preparations (S1”). Then, output the data in a dedicated file format that can be read by the stereolithography apparatus including the conditions, and transfer the data to the stereolithography apparatus using a USB cable or an SD card (S2”).

[0079] In the stereolithography apparatus, processing (fabrication) is performed based on the file including the design data and the conditions for lamination (S3”). In particular, in the stereolithography apparatus, a resin that is a photocurable resin is used, and the shape is fabricated using the image projected on an LCD (Liquid Crystal Display), and the three-dimensional shape is fabricated by stacking them up.

[0080] This can be any device called a 3D printer, for example, one that melts and laminates resins such as PLA and PETG.

[0081] Alternatively, a three-dimensional mold may be fabricated by machining a metal, and a stereolithographic mask may be produced by pressing glass, plastic, or the like against the mold. Although the mold is expensive, it can be reused after being fabricated once, making it effective for mass production of the same product type.

[0082] Furthermore, a stereolithographic mask may be produced using photolithography technology with an exposure apparatus. Methods using an electron exposure beam or a gray mask may be employed. Once the stereolithographic mask is fabricated by the above method, it can be installed at the mask position of the exposure apparatus, enabling reduction projection exposure, proximity exposure, or contact exposure. By performing reduction projection exposure, it becomes possible to obtain a three-dimensional resist pattern that is finer and more accurate than before.

[0083] When calculating the shape of a three-dimensional stereolithographic mask, using a personal computer (PC) and optical simulation software and optimization software enables more accurate design. The design procedure is shown in FIG. 12.

[0084] First, a target three-dimensional resist pattern shape to be fabricated is set (S1”). Here, the target shape is designed using the computer design software. As the design software, existing software such as Inventer, Pro / ENGINEER (Creo Parametric), or SOLID WORKS of three-dimensional CAD (Computer-Aided Design) can be used.

[0085] Considering the relationship between the light intensity and the remaining film thickness of the resist, the required light intensity distribution on the resist surface to obtain the target shape is calculated (S2”). Since the relationship between this light intensity and the remaining film thickness of the resist depends on the photosensitive characteristics of the resist and the process up to the development process including the exposure apparatus, it is advisable to obtain it in advance through experiments and create a database.

[0086] The transmittance and shape of the material used for the three-dimensional solid photomask are utilized to optimize the shape of the three-dimensional solid photomask through optical simulation (S5”).

[0087] As a model for optical simulation, it is necessary to input at least the optical characteristics of the illumination optical system, three-dimensional solid photomask, and projection optical system that make up the device. The optical characteristics include at least wavelength, focal length, projection magnification, R (curvature), D (central thickness), N (refractive index of the material) of the lens, scattering distribution, etc.

[0088] For optimization, taking the shape of the three-dimensional solid photomask as a variable, the three-dimensional shape of the solid photomask is calculated by repeated calculation through optical simulation so that the intensity distribution of the light passing through the three-dimensional shape photomask becomes the required intensity distribution when it reaches the resist surface.

[0089] The software used for this optical simulation can be commercially available. For example, Synopsys LightTools, a lighting design analysis software, can be mentioned. Any software that can calculate the light intensity distribution on the image plane through ray tracing considering optical characteristics (transmittance, scattering distribution, etc.) is acceptable. Also, if the optimization function attached to the optical simulation software is insufficient, for example, using SIMULIA Isight, an optimization simulation software, create the shape of the three-dimensional solid photomask in Excel, import it into the optical simulation software, perform optical simulation, calculate the light intensity when it reaches the resist surface, and it is also possible to automatically perform repeated calculations to achieve the target light intensity.

[0090] When you want to obtain an even finer resist pattern, perform accurate optical simulation using software that can perform ray tracing considering phase, diffraction, and interference, which are wave-optical characteristics. For example, by additionally using electromagnetic field analysis software such as FullWAVE or Diffract MOD, it becomes possible to handle light as a wave, such as phase, diffraction, and interference phenomena due to fine unevenness of a three-dimensional photomask, and calculate the light intensity that cannot be calculated by ordinary geometric ray tracing. By linking with the above LightTools, the light intensity can be obtained more precisely, so that the shape of the three-dimensional photomask you want to obtain can also be calculated accurately down to fine parts.

[0091] The shape distribution of the obtained three-dimensional shape photomask is fabricated using an existing three-dimensional processing machine.

Example

[0092] As an example, an example of a three-dimensional shape photomask fabricated with an "ANYCUBIC's Photon-s Stereolithography 3D Printer", which is a three-dimensional processing machine, is shown. Also shown is a three-dimensional shape resist pattern fabricated according to the principle of the present invention.

[0093] The three-dimensional processing machine used this time is one that fabricates shapes using a stereolithography technique that can be purchased at low cost. As a material for the three-dimensional photomask, a photosensitive transparent resin (Washable Resin (405nm photocurable 3D resin manufactured by NOVA3D)) is used, and an SLA (Stereolithography) method in which an ultraviolet laser is applied to stack the transparent resin in layers, or an image displayed on an FPD (Flat Panel Display) or DLP (Digital Light Processing) is projected, and the transparent resin is stacked in layers to obtain a desired three-dimensional shape. This time, the transmittance of the resin was obtained in advance through experiments, and the relationship between the thickness and the transmittance was obtained. Fig. 13 shows a photograph of the fabricated three-dimensional photomask. As shown in Fig. 13, the three-dimensional shape of the fabricated three-dimensional photomask has a pattern of thickness distribution in which eight rectangles with thicknesses of 0.9 mm, 1.0 mm, 1.1 mm, 1.2 mm, 1.3 mm, and 1.7 mm, which are thicker than the base with the thinnest thickness of 0.7 mm, are arranged in two rows of four each. Fig. 14(a) shows the specific thickness values of each rectangle of the fabricated three-dimensional photomask.

[0094] Next, Fig. 14(b) shows the results of performing projection exposure on a sample in which a negative resist SU-8 100 was spin-coated on a silicon wafer to a thickness of about 50 μm using the fabricated three-dimensional photomask with a three-dimensional shape. An in-house exposure apparatus with a 1:1 magnification was used as the projection exposure apparatus. The results shown in Fig. 14(b) are the resist patterns after exposure and development processing.

[0095] Here, since 1:1 exposure was performed, the vertical and horizontal dimensions are almost the same as those of the three-dimensional photomask. However, due to the change in the light intensity transmitted according to the different thickness patterns of the three-dimensional photomask, no resist pattern was formed where the thickness of the three-dimensional photomask was 1.3 mm or more. Where the thickness of the three-dimensional photomask was 1.2 mm or less and the thickness was thin, the resist pattern was thick, and where the thickness of the three-dimensional photomask was thick, the resist pattern was thin. Thus, resist patterns with three-dimensional shapes having different thicknesses according to the thickness of the three-dimensional photomask were successfully fabricated.

Explanation of Reference Numerals

[0096] 10, 10A, 11 Three-dimensional bodies 20, 20A Transparent substrates 30 Light-shielding portions 100, 100A, 101, 102

Claims

1. A photomask that can be used when exposing an object to be exposed to a predetermined pattern, A three-dimensional shaped body made of a light-transmissive material that can transmit light having a wavelength that sensitizes a photosensitive resin, and having a thickness distribution with respect to the traveling direction of the light.

2. The three-dimensional shaped body is formed on a transparent substrate. The three-dimensional photomask according to Claim 1.

3. The three-dimensional photomask according to Claim 1, having a light-shielding portion.

4. The three-dimensional photomask according to Claim 2, having a light-shielding portion.

5. The transparent substrate is a substrate made of a material selected from the group consisting of glass, crystal, sapphire, and synthetic resin. The three-dimensional photomask according to Claim 2.

6. The light-transmissive material is a photosensitive resin. The three-dimensional photomask according to Claim 1.

7. The light-transmissive material is a material selected from the group consisting of glass, crystal, sapphire, and synthetic resin. The three-dimensional photomask according to Claim 1.

8. An exposure apparatus including the three-dimensional photomask according to any one of Claims 1 to 7.

9. An exposure method using the three-dimensional photomask according to any one of Claims 1 to 7.

10. A method for manufacturing a three-dimensional photomask according to any one of Claims 1 to 7, A method for manufacturing a three-dimensional photomask, having a shape determination step of determining the shape of the three-dimensional photomask based on the transmittance of the light-transmissive material constituting the three-dimensional photomask so that the light transmitted through the three-dimensional photomask has a desired light intensity distribution on the resist surface.

11. The method for manufacturing a three-dimensional photomask according to Claim 10, having a shaping step of shaping the three-dimensional photomask having the shape determined in the shape determination step with a 3D printer.

12. An optimization step of repeatedly calculating the three-dimensional shape of the three-dimensional photomask by optical simulation and optimizing the three-dimensional shape so that the intensity distribution of the light passing through the three-dimensional photomask becomes a desired light intensity distribution on the resist surface, with the shape of the three-dimensional photomask as a variable. The method for manufacturing a three-dimensional photomask according to Claim 10.

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