JP2006126243A - Exposure mask, microlens array and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an exposure mask for patterning a light-shielding film, the exposure mask which can be easily aligned to a microlens of a microlens array or to an exposure mask for lens patterning to form the microlens. <P>SOLUTION: The exposure mask 15 for patterning a light-shielding film is used to irradiate a photoresist for forming a light-shielding film which is layered on the substrate surface for a microlens array, having microlenses 10b of a prescribed size fabricated in a plurality of arrays on a transparent substrate 10, with a light in each portion where the microlens 10b is present through an opening 15c basically being smaller than the lens 10b. At least two openings 15d of the openings are formed, in such a form that when the exposure mask 15 is superposed on the transparent substrate 10 with each center of the opening 15d and the microlens 10b coinciding with each other, at least a part of the edge 10d of the microlens is visible through the opening 15d. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exposure mask for forming a light-shielding film on a microlens array in which a plurality of microlenses are formed in an array, and an exposure method using the exposure mask.

  The present invention also relates to a microlens array formed by the exposure method as described above.

  2. Description of the Related Art Conventionally, as shown in Patent Document 1, for example, a microlens array in which a plurality of convex microlenses having a diameter of about several hundred μm or less are formed in an array on a transparent substrate is known. In recent years, this type of microlens array has been used in a wide range of fields as an optical component constituting a liquid crystal display device, a solid-state imaging device, an optical communication system, an optical disk pickup, and the like. This microlens array is generally manufactured by applying a semiconductor microfabrication technique because the size of the microlens is very small.

  Specifically, as shown in Patent Document 1, for example, a resist pattern is formed on a transparent substrate by photolithography, and then heated to a temperature higher than the temperature at which the resist softens, thereby causing convexity due to surface tension. A method is known in which a curved surface shape is formed and a convex curved surface shape is transferred to a substrate by dry etching to form a microlens.

  In this microlens array, there is a flat substrate surface and a lens curved surface forming part, so transmitted light that passes through the flat surface, stray light that enters from other lenses when the lenses are arranged in an array, etc. There are factors that degrade optical performance.

Conventionally, in order to cut such stray light, it has been considered to provide a light-shielding film in a region other than the microlens forming portion of the transparent substrate, or in a region in which the peripheral portion of the microlens is added to the region. Various methods for producing such a microlens array having a light shielding film have also been proposed. For example, Patent Document 2 discloses a method of forming a microlens by heating and melting a resin after forming a light-shielding film by photolithography, and Patent Document 3 patterns the light-shielding film by photolithography on the surface of the microlens. Further, Patent Document 4 discloses a method of forming a light shielding film by plating other than the lens forming portion.
JP-A-6-194502 JP-A-7-174902 JP-A-8-313706 Japanese Patent Laid-Open No. 10-160905

  By the way, when producing a light shielding film by applying photolithography as described above, in more detail, a metal film and a positive photoresist are laminated in this order on a microlens formed on a transparent substrate. A metal exposure mask having an opening is arranged on the top, the photoresist is exposed through the exposure mask, the photoresist is then developed to remove the portion of the photoresist that has been viewed through the opening, and then the photo Many processes are used in which etching is performed through a resist to remove a portion corresponding to the opening of the metal film and to use the metal film as a light-shielding film.

  In that case, when the opening of the exposure mask disposed on the microlens is smaller than that of the microlens, that is, when the light shielding film has a shape covering the peripheral area of the microlens, alignment of the exposure mask is performed. Since the target microlens is behind the exposure mask, it is difficult to accurately align the exposure mask so that the center of the opening coincides with the center of the microlens. FIG. 6 shows the above-described state. In the figure, reference numeral 100 denotes a microlens, 101 denotes a peripheral edge thereof, 102 denotes an exposure mask, and 103 denotes an opening thereof.

  Contrary to the above, when the light shielding film and the microlens are formed in this order on the transparent substrate, a light shielding film having openings arranged in an array is formed on the transparent substrate. A positive type photoresist is applied to the lens, and a lens patterning exposure mask having a light-shielding portion larger than the opening of the exposure mask corresponding to the microlens shape is disposed thereon, and the lens patterning exposure mask is interposed therebetween. After irradiating the photoresist with exposure light, the photoresist is developed to leave the photoresist only in the portion covered by the light-shielding portion of the lens patterning exposure mask, and the remaining photoresist is softened. A resin pattern having a shape corresponding to the shape of the microlens is formed, and then the transparent substrate is dry-etched from the resin pattern side. By ring, to form a micro lens arranged in an array shape is transferred to the transparent substrate of the resin patterns, processes are often applied as.

  Also in this case, when the opening of the exposure mask for patterning the light-shielding film is smaller than the microlens to be formed, the opening of the light-shielding film formed to be approximately the same size as this opening is the light shielding portion of the exposure mask for lens patterning (that The lens pattern exposure mask is precisely aligned so that the center of the light-shielding part coincides with the center of the opening of the light-shielding film. The problem is difficult to do. FIG. 7 shows the above-described state. In the figure, 200 indicates a light-shielding film, 201 indicates an opening thereof, 202 indicates a transparent member constituting the exposure mask for lens patterning (the light-shielding film 200 can be seen through this transparent member), and 203 is held in an array. It is the light-shielding part.

  For this reason, a method is generally employed in which alignment marks are separately formed on two members that require alignment, and alignment is performed based on the alignment marks. However, in normal photomask fabrication, alignment marks are microlenses, light-shielding films, and the like. Since the optical element is formed as data different from the data for producing the optical element, there is a problem that a pattern arrangement error due to the stage accuracy of the drawing apparatus occurs when drawing the optical element and the alignment mark. In addition, the alignment mark is formed at a position apart from the microlens array area that is actually used, but due to the shrinkage and warpage of the substrate due to the thermal process and the formation of the light-shielding film, there is a deviation from the actual lens pattern. Sometimes it ends up.

  Furthermore, as shown in Patent Document 4, a method for forming a light-shielding film by self-alignment has also been proposed. However, in such a method, the process is complicated, and the aperture shape depends on the lens shape. Therefore, problems such as a reduction in the degree of freedom of beam shaping are recognized.

  In view of the above circumstances, the present invention provides a light-shielding film patterning exposure that can be easily aligned with a microlens of a microlens array or a light-shielding portion of a lens patterning exposure mask for forming the microlens array. The object is to provide a mask.

  Another object of the present invention is to provide a method capable of producing a microlens array in which the microlens and the opening of the light shielding mask are accurately aligned using such an exposure mask.

The first exposure mask according to the present invention is applied when a light shielding film is formed on a microlens formed on a substrate,
The part where the microlens has the light for exposing the light-shielding film forming photoresist formed in a layer on the surface of the microlens array in which a plurality of microlenses of a predetermined size are formed in an array on a transparent substrate In an exposure mask for patterning a light-shielding film that is irradiated through an opening basically smaller than the lens every time,
At least two of the openings have a shape in which at least a part of the periphery of the microlens can be seen through the opening in a state where the exposure mask is superimposed on the transparent substrate so that the centers of the openings and the microlenses coincide with each other. It is characterized by being said.

  The above-mentioned opening is “essentially smaller” than the microlens. At least two openings formed so that at least a part of the periphery of the microlens can be seen may be larger than the microlens as described later. This means that almost all of the apertures are smaller than the microlenses.

  In the first exposure mask, as described above, the opening in which at least a part of the periphery of the microlens can be seen is more specifically formed larger than the microlens. Is desirable. In addition, it is desirable that the openings are provided at positions that match the microlenses formed in the area where the microlens array is not actually used.

Further, the second exposure mask according to the present invention is applied when a microlens is formed on a light shielding film formed on a substrate,
Using a lens patterning exposure mask having a light-shielding part corresponding to the lens shape, a light-shielding film forming photo formed in layers on the substrate surface against a transparent substrate on which a plurality of microlenses of a predetermined size are formed in an array In a light-shielding film patterning exposure mask that irradiates light for exposing a resist through an opening basically smaller than the light-shielding portion for each portion where a microlens is formed,
When at least two of the openings are overlaid with the lens patterning exposure mask on the light-shielding film patterning exposure mask so that the centers of the openings and the light-shielding portions coincide with each other, at least one of the openings. The portion is shaped to appear to protrude from the light shielding portion.

  Note that “the opening is“ essentially smaller ”than the light shielding part of the exposure mask for lens patterning” means that at least two openings that appear to protrude from the light shielding part are larger than the light shielding part as described later. However, it means that almost all other openings are smaller than the light shielding portion.

  In addition, in the step of producing a microlens array using the second exposure mask for patterning a light shielding film according to the present invention, the exposure mask for lens patterning is usually superimposed directly on the exposure mask as described above. There is no. The above-mentioned “at least a part of the opening appears to protrude from the light shielding portion” means that if both masks are overlapped, it becomes so.

  In the second exposure mask, it is desirable that the opening having a part that appears to protrude from the light shielding portion is more specifically formed larger than the light shielding portion. In addition, it is desirable that the openings are provided at positions that match the microlenses formed in the area where the microlens array is not actually used.

On the other hand, in the first method for producing a microlens array according to the present invention, a microlens and a light shielding film are formed in this order on a substrate.
A plurality of microlenses of a predetermined size are formed in an array on a transparent substrate,
A metal film and a positive photoresist are laminated in this order on the surface of the transparent substrate on which the microlenses are formed,
The first exposure mask according to the present invention described above is arranged on the photoresist so that the opening and each center of a microlens larger than the opening are aligned with each other.
Irradiating the photoresist with exposure light through this exposure mask,
The photoresist is developed to remove the portion of the photoresist irradiated with exposure light through the opening of the exposure mask,
The metal film is etched using the remaining photoresist as an etching mask to form a light-shielding film made of a metal film from which a portion corresponding to the opening is removed.

Also, the second microlens array manufacturing method according to the present invention is similar to the above, in which a microlens and a light shielding film are formed in this order on a substrate,
A plurality of microlenses of a predetermined size are formed in an array on a transparent substrate,
Laminating a negative photoresist on the surface of the transparent substrate on which the microlenses are formed,
The first exposure mask according to the present invention described above is arranged on the photoresist so that the opening and each center of a microlens larger than the opening are aligned with each other.
Irradiating the photoresist with exposure light through this exposure mask,
This photoresist is developed to remove the photoresist other than the portion irradiated with the exposure light through the opening of the exposure mask,
Laminating a metal film on the remaining photoresist and the transparent substrate,
Next, the photoresist is lifted off to form a light-shielding film made of a metal film from which a portion corresponding to the opening is removed.

The third method for producing a microlens array according to the present invention is to form a light shielding film and a microlens in this order on a substrate,
A metal film and a positive first photoresist are laminated in this order on a transparent substrate,
Disposing the second exposure mask according to the present invention as described above on the first photoresist;
Irradiating exposure light to the first photoresist through the exposure mask,
The first photoresist is developed to remove a portion of the photoresist irradiated with the exposure light through the opening of the exposure mask,
Etching the metal film using the remaining first photoresist as an etching mask to form a light-shielding film made of a metal film from which a portion corresponding to the opening has been removed,
Apply a positive type second photoresist on the light shielding film,
In addition, the lens patterning exposure mask corresponding to the lens shape and having a light shielding part larger than the opening of the exposure mask is positioned so that the centers of the light shielding part and the opening formed in the light shielding film coincide with each other. Put together,
Irradiating the second photoresist with exposure light through the lens patterning exposure mask,
The second photoresist is developed to leave the second photoresist only in the portion covered by the light-shielding portion of the lens patterning exposure mask,
The remaining second photoresist is softened to form a resin pattern having a shape corresponding to the shape of the microlens,
Next, the transparent substrate is dry-etched from the resin pattern side to transfer the shape of the resin pattern to the transparent substrate to form microlenses arranged in an array.

The present invention also provides a microlens array with a light-shielding film produced by the above methods, and the first microlens array according to the present invention is produced by the first method,
A plurality of microlenses of a predetermined size formed in an array are formed on a transparent substrate, and a light-shielding film having openings that are basically smaller than the microlenses and aligned with the microlenses is formed thereon. And
At least two of the openings are shaped so that at least a part of the periphery of the microlens can be seen through the openings.

The second microlens array according to the present invention is manufactured by the second method,
A plurality of microlenses having a predetermined size formed in an array are formed on a transparent substrate, and an opening between the microlens and the substrate that is basically smaller than the microlens and aligns with the microlens. A light-shielding film having
At least two of the openings have a shape in which at least a part thereof protrudes from the periphery of the microlens.

  In the first exposure mask according to the present invention, at least two of the openings are microscopic through the openings under the condition that the exposure mask is overlapped with the transparent substrate in a state where the centers of the openings and the microlenses coincide with each other. Since the lens is shaped so that at least a part of the periphery of the lens can be seen, when the exposure mask is placed on a transparent substrate and both of them are in the above state or a state close thereto, the position of the microlens is confirmed through the opening. It becomes possible. Therefore, it is possible to accurately align the exposure mask with respect to the transparent substrate so that the apertures and the centers of the microlenses coincide.

  Since the first and second microlens array fabrication methods according to the present invention use the first exposure mask according to the present invention as described above, the microlenses in which the centers of the microlens and the light-shielding film are precisely coincident with each other. A lens array can be produced.

  In addition, the second exposure mask according to the present invention is arranged such that when the lens patterning exposure mask is superimposed on the opening and the lens patterning exposure mask so that the centers of the light shielding portions of the lens patterning exposure mask coincide with each other. At least two of them have a shape in which at least a part of the opening appears to protrude from the light shielding portion of the exposure mask for lens patterning. 2 is substantially coincident with the opening of the exposure mask 2), and when the lens patterning exposure mask is disposed thereon, at least a part of the opening of the light shielding film is exposed to the lens patterning. It appears to protrude from the shading part of the mask. Therefore, the lens patterning exposure mask can be accurately aligned with respect to the light shielding film so that the centers of the light shielding portion and the opening of the light shielding film coincide with each other.

  Since the third microlens array manufacturing method according to the present invention uses the second exposure mask according to the present invention as described above, the centers of the microlens and the light-shielding film also coincide with each other in this case. A microlens array can be produced.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 schematically shows a process of producing a microlens array by the method of the first embodiment of the present invention. First, as shown in FIG. 1 (1), a positive photoresist 11 is applied on one surface 10a of a transparent substrate 10 made of, for example, SiO ₂ glass and the like, dried, and then exposed to an exposure mask 12 for lens patterning. Place. This lens patterning exposure mask 12 is formed by forming, on an transparent substrate 12a, light-shielding portions 12b having the same planar shape (for example, circular shape) as the microlenses to be manufactured in an array.

  Next, the photoresist 11 is exposed through the exposure mask 12 and developed to leave the photoresist 11 having a shape corresponding to the lens shape at the position where the light shielding portion 12b is present, as shown in FIG. .

  Next, the substrate 10 is heated to a temperature (130 to 150 ° C.) at which the photoresist 11 is softened, thereby forming a convex resin pattern 11 ′ made of photoresist as shown in FIG. The resin pattern 11 ′ has a shape corresponding to the three-dimensional shape of the microlens to be manufactured.

Next, the transparent substrate 10 is etched from the resin pattern 11 ′ side by dry etching using a fluorine-based gas such as CF ₄ , CHF ₃ , C ₂ F ₆ , SF _6, etc., and the shape of the resin pattern 11 ′ is changed. Transfer to the transparent substrate 10. As a result, a large number of microlenses 10b are formed in an array on the transparent substrate 10, as shown in FIG.

  As the dry etching method, it is desirable to adopt a method in which the bias can be independently controlled with high-density plasma such as ICP or ECR. In these methods, by appropriately setting the etching conditions, the etching rate of the resin pattern 11 ′ and the transparent substrate 10 can be controlled, and a desired lens shape can be formed on the transparent substrate 10. It is also possible to change the etching rate difference between the resin pattern 11 ′ and the transparent substrate 10 over time by changing the conditions during etching, and to manufacture an aspheric lens.

  Next, as shown in FIG. 5 (5), a light-shielding metal such as Cr is formed on the microlens 10b by sputtering to form a metal film 13 having a thickness of about 50 to 200 nm. The positive photoresist 14 is applied to the substrate and dried.

  Next, as shown in FIG. 6 (6), an exposure mask 15 for patterning a light-shielding film according to the present invention is disposed on the positive photoresist 14. The exposure mask 15 has a light shielding portion 15b formed on a transparent substrate 15a. The light shielding portion 15b has a circular opening 15c having a slightly smaller diameter corresponding to each microlens 10b. It is patterned to have a shape. At this time, the exposure mask 15 is aligned so that the center of each opening 15c of the light shielding portion 15b coincides with the center of the microlens 10b, which will be described in detail later.

  Next, when the positive photoresist 14 is exposed through the exposure mask 15 and developed, only the exposed portion is removed through the opening 15c as shown in FIG. A circular opening 14a is formed.

  Next, when the metal film 13 is wet-etched or dry-etched through the positive photoresist 14, the metal film 13 is removed only at a portion corresponding to the opening 14a of the positive photoresist 14, and then the positive photoresist 14 is removed. As shown in FIG. 8 (8), a light shielding film 13 'made of a metal film having an opening 13a is formed. The opening 13a of the light shielding film 13 'is slightly smaller in diameter than the microlens 10b, so that the peripheral portion of the microlens 10b and the portion near the periphery of the microlens 10b are covered with the light shielding film 13'. .

  Next, if necessary, antireflection coating or the like is applied to both surfaces of the transparent substrate 10 to complete the microlens array 20 with a light shielding film. In the microlens array 20, the light shielding film 13 'formed as described above functions to block light that has passed through the transparent substrate 10 outside the microlens 10b and the vicinity of the periphery of the microlens 10b. This is an explanation of the case where the light to be condensed passes through the microlens array 20 from the lower side to the upper side in FIG. 1 (8). The same light shielding action can be obtained by the light shielding film 13 'even when passing through.

  Next, description will be made on the alignment of the light-shielding film patterning exposure mask 15 shown in FIG. 1 (6) so that the center of each opening 15c coincides with the center of the microlens 10b. FIG. 2 is a plan view showing the relative positional relationship between the exposure mask 15 and the transparent substrate 10 when this alignment is performed. Since each opening 15c of the exposure mask 15 is basically smaller than the microlens 10b, the peripheral edge 10d of the microlens 10b is located when the exposure mask 15 is arranged in the state shown in FIG. It is hidden behind the exposure mask 15 and cannot be confirmed.

  However, here, as an example, a square opening 15d is formed in the light-shielding portion 15b of the exposure mask 15 at a position where the opening 15c should originally be provided. In this case, since the metal film 13 is formed on the microlens 10b so as to follow the shape, the fact that the peripheral edge 10d of the microlens is “visible” means that the peripheral edge 10d is directly visible. In other words, it means that the peripheral edge of the raised portion of the metal film 13 (which corresponds to the microlens peripheral edge 10d) can be seen.

  A large number of microlenses 10b are provided in a two-dimensional array on the transparent substrate 10, but in general, not all of them are actually used, and an area close to the edge of the transparent substrate 10 is a surplus array portion. The microlens 10b formed in the region is not actually used. The square opening 15d is provided in alignment with one microlens 10b formed in the surplus array portion. Although only one opening 15d is shown in the figure, it is formed in a surplus array portion (not shown) on the opposite side across an actual use region where a large number of actually used microlenses 10b are formed. A similar square opening 15d (not shown) is also formed at a position aligned with one microlens 10b.

  As described above, when the exposure mask 15 is provided with two openings 15d large enough to see the entire periphery 10d of the microlens, the operator aligns the exposure mask 15 and the transparent substrate 10 as described above. In trying, a total of two microlens perimeters 10d can be seen through each of these openings 15d. Therefore, the operator can easily align the exposure mask 15 and the transparent substrate 10 with reference to the position of the visible microlens periphery 10d so that the center of the exposure mask opening 15c coincides with the center of the microlens 10b. Become.

  Note that only two large openings 15d are basically provided, but three or more may be provided.

  Further, such an opening 15d may be provided at a position aligned with the microlens 10b formed in the actual use region of the transparent substrate 10. In such a case, since the opening of the light shielding film 13 '(see (8) in FIG. 1) formed based on these openings 15d is larger than the microlens 10b, the surrounding portion of the microlens 10b is shielded from light. The original effect is not obtained. However, when the microlens array 20 is used, for example, when image exposure is performed with light passing through the microlens array 20, the light that has passed through the microlens 10b is used by correcting the image data. Can be prevented. Further, the microlens array 20 may be used as it is without any particular treatment.

  Further, the large opening provided in the exposure mask 15 is not limited to the opening 15d where the entire periphery 10d of the microlens can be seen as described above, but may have other shapes where at least a part of the periphery 10d can be seen. FIG. 8 shows another example of such an opening shape. The opening 15e provided in the exposure mask 15 shown in FIG. 1A is a square shape like the opening 15d, but is sized so that the peripheral edge 10d of the microlens can be seen as four pieces. Even with such an opening 15e, it can be confirmed whether or not the center of the microlens is aligned with each other.

  Also, the opening 15f provided in the exposure mask 15 shown in FIG. 2B is a cross shape having a certain width. Even with such an opening 15f, it is possible to confirm whether or not the center of the microlens is aligned with each other.

  The opening 15g provided in the exposure mask 15 shown in FIG. 3 (3) has a square outer shape and a central portion filled with a circular light shielding film slightly smaller than the peripheral edge 10d of the microlens. Even with such an opening 15g, it can be confirmed whether the center of the microlens and the center of the microlens are aligned with each other.

  In this embodiment, as a method for forming the lens-shaped resin pattern 11 ′, a method of softening the photoresist 11 and forming a curved surface by surface tension is employed, but other known methods such as, for example, A photolithography method using a gray scale mask, a lens shape transfer method using a resin mold, or the like can also be used.

  On the other hand, as the substrate 10, any other substrate can be used as long as it is a transparent substrate, and a substrate made of optical glass, transparent resin, or the like can be appropriately used. The metal film 13 constituting the light-shielding film 13 'can also be formed from Al other than Cr, metals such as Ni, Ti, Mo, Ta, and W, alloys thereof, or a laminated film thereof. Furthermore, in order to obtain optimum dry etching conditions, etching conditions such as an etching gas type may be appropriately changed according to the type of the substrate and the type of the light shielding film.

  Next, a second embodiment of the present invention will be described. FIG. 3 schematically shows a process of manufacturing the microlens array 20 by the method of the second embodiment of the present invention. In the present embodiment, instead of etching the metal film 13 using the positive photoresist 14 as a mask in the first embodiment, the metal film 13 is lifted off by using a negative photoresist. In this case, too, as shown in FIG. 1A, first, a large number of microlenses 10b are formed on the transparent substrate 10 in an array. These microlenses 10b are formed by the same process as shown in FIGS. 1 (1) to (4), for example.

  Next, as shown in FIG. 3B, a negative photoresist 44 is applied to the surface of the transparent substrate 10 on the side where the microlenses 10b are formed, and dried. Next, as shown in FIG. 3C, a light-shielding film patterning exposure mask 15 similar to that used in the first embodiment is disposed on the negative photoresist 44. At this time, the exposure mask 15 is aligned so that the center of each circular opening 15c of the light shielding portion 15b coincides with the center of the microlens 10b.

  Next, when the negative photoresist 44 is exposed and developed through the exposure mask 15, only the circular portion 44a exposed through the opening 15c remains and the other portions are removed as shown in FIG. The After patterning the negative photoresist 44 in this way, a light-shielding metal such as Cr is sputtered from above to form a metal film 13 having a thickness of about 50 to 200 nm, as shown in FIG. Form.

  Thereafter, when the negative photoresist 44 remaining in a circular shape is dissolved and the metal film 13 is lifted off, a light shielding film 13 'made of a metal film having an opening 13a is formed, as shown in FIG. The opening 13a of the light shielding film 13 'is slightly smaller in diameter than the microlens 10b, so that the peripheral portion of the microlens 10b and the portion near the periphery of the microlens 10b are covered with the light shielding film 13'. .

  Next, if necessary, antireflection coating or the like is applied to both surfaces of the transparent substrate 10 to complete the microlens array 20 with a light shielding film. As a result, the microlens array 20 is the same as that produced by the method of the first embodiment.

  Also in this embodiment, it is necessary to align the light shielding film patterning exposure mask 15 shown in FIG. 3C so that the center of each opening 15c coincides with the center of the microlens 10b. Similar to the one used in the embodiment, two openings 15d having a size that allows the entire periphery of the microlens 10d to be seen are provided (see FIG. 2). While observing the peripheral edge 10d of the microlens through the opening 15d, the alignment can be performed accurately.

Next, a third embodiment of the present invention will be described. FIG. 4 schematically shows a process of manufacturing a microlens array by the method of the third embodiment of the present invention. First, as shown in FIG. 1A, a metal film 30 is formed by sputtering a light-shielding metal on one surface 10a of a transparent substrate 10 made of, for example, SiO ₂ glass. A mold first photoresist 31 is applied and dried. The metal film 30 is made of, for example, Cr and has a thickness of about 50 to 200 nm.

  Next, as shown in FIG. 2B, a light-shielding film patterning exposure mask 32 is disposed. The light-shielding film patterning exposure mask 32 has a light-shielding portion 32b formed on a transparent substrate 32a, and openings 32c are formed in an array in the light-shielding portion 32b. Each of the openings 32c has the same size as the opening of the light shielding film to be manufactured and is basically slightly smaller than the microlens to be manufactured, and a plurality of micros to be arranged in an array. It is formed at a position corresponding to the position of the lens.

  Next, by exposing and developing the first photoresist 31 through the exposure mask 32, a shape corresponding to the lens shape is formed at the position where the opening 32c of the exposure mask 32 exists, as shown in FIG. The opening 31a is formed.

  Next, when the metal film 30 is wet-etched or dry-etched using the first photoresist 31 as an etching mask, only the portion corresponding to the opening 31a of the first photoresist 31 is removed, and then the first film 31 is removed. When the photoresist 31 is removed, a light shielding film 30 ′ made of a metal film having an opening 30a is formed as shown in FIG.

  Next, as shown in FIG. 5 (5), a positive type second photoresist 33 is applied to the transparent substrate 10 from above the light shielding film 30 'and dried. Next, an exposure mask 34 for lens patterning is arranged thereon as shown in FIG. The exposure mask 34 for lens patterning is formed by forming, on an transparent substrate 34a, light-shielding portions 34b having a planar shape (for example, circular shape) of microlenses to be manufactured in an array. The lens patterning exposure mask 34 is aligned so that the center of each light shielding portion 34b coincides with the center of each opening 30a formed in the light shielding film 30 ', which will be described in detail later. .

  Next, the second photoresist 33 is exposed through the lens patterning exposure mask 34 and developed, so that the lens shape is formed at the position where the opening 30a of the light shielding film 30 'exists as shown in FIG. Leave the corresponding shape of photoresist 33. Note that the remaining photoresist pattern is larger than the opening 30a of the light shielding film 30 '.

  Next, by heating the substrate 10 to a temperature (130 to 150 ° C.) at which the second photoresist 33 is softened, a convex resin pattern 33 ′ made of photoresist is formed as shown in FIG. Form. The resin pattern 33 'has a shape corresponding to the shape of the microlens to be manufactured.

Next, the transparent substrate 10 is etched from the resin pattern 33 'side by dry etching using a fluorine-based gas such as CF ₄ , CHF ₃ , C ₂ F ₆ , SF _6, etc., and the shape of the resin pattern 33 ′ is changed. Transfer to the transparent substrate 10. Thereby, as shown in FIG. 9 (9), a large number of microlenses 10b are formed in an array on the transparent substrate 10.

  At this time, oxygen gas is not added so as not to etch the light shielding film 30 'made of Cr. Therefore, the lens shape is transferred only to the portion directly under the light shielding film opening 30a. As a dry etching method, it is desirable to adopt a method in which the bias can be independently controlled by high-density plasma such as ICP or ECR.

  In this method, by appropriately setting the etching conditions, the etching rate of the resin pattern 33 'and the transparent substrate 10 can be controlled, and a desired lens shape can be formed on the transparent substrate 10. It is also possible to change the etching rate difference between the resin pattern 33 ′ and the transparent substrate 10 over time by changing the conditions during etching, and to manufacture an aspherical lens.

  Next, if necessary, an antireflection coating or the like is applied to both surfaces of the transparent substrate 10 to complete the microlens array 40 with a light shielding film. In the microlens array 40, a light shielding film 30 'is formed around each microlens 10b, and the light shielding film 30' blocks light that has passed through the transparent substrate 10 in portions other than the microlens 10b. This is an explanation of the case where the light to be condensed passes through the microlens array 40 from the lower side to the upper side in FIG. 3. On the contrary, the light passes through the microlens array 40 downward. Even in this case, the same light shielding effect can be obtained by the light shielding film 30 '.

  Here, the microlens 10b must be formed so that the center of the microlens 10b is aligned with the opening 30a of the light shielding film 30 '. To that end, the lens patterning exposure mask 34 shown in FIG. It is necessary to align the centers of the respective light shielding portions 34b so as to exactly coincide with the centers of the respective openings 30a formed in the light shielding film 30 '. Hereinafter, this alignment will be described in detail.

  FIG. 5 is a plan view showing the relative positional relationship between the lens patterning exposure mask 34 and the transparent substrate 10 when this alignment is performed. Since the opening 30a of the light shielding film 30 'on the transparent substrate 10 is basically smaller than the light shielding portion 34b of the lens patterning exposure mask 34, the lens patterning exposure mask 34 is in the state shown in FIG. When placed in a close state, the opening 30a is hidden behind the light shielding portion 34b and cannot be confirmed.

  However, here, as an example, a square opening 30d is formed in the light shielding film 30 ′ on the transparent substrate 10 at a position where the opening 30a should originally exist, and has a size that protrudes entirely from the light shielding portion 34b. Such an opening 30d is provided in the light shielding portion 32b of the light shielding film patterning exposure mask 32 shown in FIG. 4B at the position where the originally circular opening 32c is to be formed. It is formed by keeping.

  A large number of microlenses 10b are provided in a two-dimensional array on the transparent substrate 10, but in general, not all of them are actually used, and an area close to the edge of the transparent substrate 10 is a surplus array portion. The microlens 10b formed in the region is not actually used. The square opening 30d is provided at a position aligned with one microlens 10b formed in the surplus array portion. Although only one opening 30d is shown in the figure, the surplus arrangement portion (not shown) that exists on the opposite side across the actual use region in which a large number of actually used microlenses 10b are formed. A similar square opening 30d (not shown) is also formed at a position where it is aligned with one microlens 10b.

  As described above, when the opening 30d is formed in the light-shielding film 30 'on the transparent substrate 10 so as to protrude from the light-shielding portion 34b, the operator can use the lens patterning exposure mask 34, the transparent substrate 10, and the like. These two apertures 30d can be viewed through the transparent substrate 34a of the mask 34 when attempting to align them as described above. Therefore, the operator refers to the positions of the two visible openings 30d, the lens patterning exposure mask 34 and the transparent substrate 10, and the center of each light shielding portion 34b of the mask 34 is each opening 30a of the light shielding film 30 '. It is possible to easily align the positions so as to be exactly coincident with the center.

  Note that only two large openings 30d are basically provided, but three or more may be provided.

  Further, such an opening 30d may be provided at a position that is aligned with the microlens 10b formed in the actual use region of the transparent substrate 10. In this case, the opening 30d is larger than the microlens 10b formed on the basis of the light shielding portion 34b, so that the original action of the light shielding film 30 'around the opening 30d to shield the periphery of the microlens 10b is obtained. I can't. However, when the microlens array 40 is used, for example, when image exposure is performed with light passing through the microlens array 40, the light that has passed through the microlens 10b is used by correcting the image data. Can be prevented. Further, the microlens array 40 may be used as it is without any particular treatment.

  The large opening provided in the light shielding film 30 'on the transparent substrate 10 (that is, the large opening provided in the light shielding portion 32b of the light shielding film patterning exposure mask 32 shown in FIG. 4B) is lens patterning as described above. The exposure mask 34 is not limited to the opening 30d that completely protrudes from the light shielding portion 34b, but may have other shapes that at least partially appear to protrude from the light shielding portion 34b. Specifically, shapes similar to the openings 15e, 15f, and 15g shown in (1), (2), and (3) of FIG. 8 can also be adopted here.

  Further, in the present embodiment, as a method of forming the resin pattern 33 ′ having a lens shape, a method of softening the photoresist 33 and forming a curved surface by surface tension is employed, but other known methods, for example, A photolithography method using a gray scale mask, a lens shape transfer method using a resin mold, or the like can also be used.

  On the other hand, as the substrate 10, any other substrate can be used as long as it is a transparent substrate, and a substrate made of optical glass, transparent resin, or the like can be appropriately used. The light-shielding film 30 'can also be formed from Al other than Cr, metals and alloys such as Ni, Ti, Mo, Ta, and W, or a laminated film thereof. Furthermore, in order to obtain optimum dry etching conditions, etching conditions such as an etching gas type may be appropriately changed according to the type of the substrate and the type of the light shielding film.

Schematic which shows the process of producing a microlens array by the method of the 1st Embodiment of this invention. The top view which shows the relative positional relationship of the exposure mask and transparent substrate applied to the method shown in FIG. Schematic which shows the process of producing a microlens array by the method of the 2nd Embodiment of this invention. Schematic which shows the process of producing a microlens array by the method of the 3rd Embodiment of this invention. The top view which shows the relative positional relationship of the exposure mask for lens patterning applied to the method shown in FIG. 4, and a transparent substrate Schematic explaining the problems when using a conventional exposure mask Schematic explaining another problem when using a conventional exposure mask The top view which shows the example of the shape of the opening applied to the exposure mask of this invention

Explanation of symbols

10 Transparent substrate
10a One surface of transparent substrate
10b Micro lens
11 Positive photoresist
11 ′ resin pattern
12 Exposure mask for lens patterning
13 'light shielding film
13a Opening of light shielding film
14 Positive photoresist
15 Exposure mask for light shielding film patterning
15b Shading part
15c, 15d, 15e, 15f, 15g Exposure mask opening
20, 40 micro lens array
30 'light shielding film
30a Opening of light shielding film
31 Positive type first photoresist
31a Opening of photoresist
32 Exposure mask for light shielding film patterning
32c Exposure mask opening
33 Positive second photoresist
33 ′ resin pattern
34 Exposure mask for lens patterning
34b Shading part of exposure mask
44 Negative photoresist

Claims (11)

The part where the microlens has the light for exposing the light-shielding film forming photoresist formed in a layer on the surface of the microlens array in which a plurality of microlenses of a predetermined size are formed in an array on a transparent substrate In an exposure mask for patterning a light-shielding film that is irradiated through an opening basically smaller than the lens every time,
At least two of the openings have a shape in which at least a part of the periphery of the microlens can be seen through the opening in a state where the exposure mask is superimposed on the transparent substrate so that the centers of the openings and the microlenses coincide with each other. An exposure mask characterized by that.   2. The exposure mask according to claim 1, wherein an opening having a shape in which at least a part of a peripheral edge of the microlens can be seen is formed to be larger than the microlens as a whole.   2. An opening having a shape in which at least a part of a peripheral edge of the microlens can be seen is provided at a position matching a microlens formed in a region where the microlens array is not actually used. 2. The exposure mask according to 2. Using a lens patterning exposure mask having a light-shielding part corresponding to the lens shape, a light-shielding film forming photo formed in layers on the substrate surface against a transparent substrate on which a plurality of microlenses of a predetermined size are formed in an array In a light-shielding film patterning exposure mask that irradiates light for exposing a resist through an opening basically smaller than the light-shielding portion for each portion where a microlens is formed,
When at least two of the openings are overlaid with the lens patterning exposure mask on the light-shielding film patterning exposure mask so that the centers of the openings and the light-shielding portions coincide with each other, at least one of the openings. An exposure mask characterized in that the portion is shaped to protrude from the light shielding portion.   The exposure mask according to claim 4, wherein the opening in which the part is seen to protrude from the light shielding part is formed larger than the light shielding part as a whole.   The opening having a shape in which the part is seen to protrude from the light-shielding portion is provided at a position matching a microlens formed in a region where the microlens array is not actually used. 5. The exposure mask according to 5. A plurality of microlenses of a predetermined size are formed in an array on a transparent substrate,
A metal film and a positive photoresist are laminated in this order on the surface of the transparent substrate on which the microlenses are formed,
The exposure mask according to any one of claims 1 to 3, wherein the exposure mask is positioned on the photoresist so that the openings and the centers of the microlenses larger than the openings are aligned,
Irradiating the photoresist with exposure light through this exposure mask,
The photoresist is developed to remove the portion of the photoresist irradiated with exposure light through the opening of the exposure mask,
Etching the metal film using the remaining photoresist as an etching mask to form a light-shielding film made of a metal film from which a portion corresponding to the opening has been removed. Fabrication of a microlens array with a light-shielding film Method. A plurality of microlenses of a predetermined size are formed in an array on a transparent substrate,
Laminating a negative photoresist on the surface of the transparent substrate on which the microlenses are formed,
The exposure mask according to any one of claims 1 to 3, wherein the exposure mask is positioned on the photoresist so that the openings and the centers of the microlenses larger than the openings are aligned,
Irradiating the photoresist with exposure light through this exposure mask,
This photoresist is developed to remove the photoresist other than the portion irradiated with the exposure light through the opening of the exposure mask,
Laminating a metal film on the remaining photoresist and the transparent substrate,
Next, a method of manufacturing a microlens array with a light-shielding film is formed by lifting off the photoresist to form a light-shielding film made of a metal film from which a portion corresponding to the opening is removed. A metal film and a positive first photoresist are laminated in this order on a transparent substrate,
An exposure mask according to any one of claims 4 to 6 is disposed on the first photoresist,
Irradiating exposure light to the first photoresist through the exposure mask,
The first photoresist is developed to remove a portion of the photoresist irradiated with the exposure light through the opening of the exposure mask,
Etching the metal film using the remaining first photoresist as an etching mask to form a light-shielding film made of a metal film from which a portion corresponding to the opening has been removed,
Apply a positive type second photoresist on the light shielding film,
In addition, the lens patterning exposure mask corresponding to the lens shape and having a light shielding part larger than the opening of the exposure mask is positioned so that the centers of the light shielding part and the opening formed in the light shielding film coincide with each other. Put together,
Irradiating the second photoresist with exposure light through the lens patterning exposure mask,
The second photoresist is developed to leave the second photoresist only in the portion covered by the light-shielding portion of the lens patterning exposure mask,
The remaining second photoresist is softened to form a resin pattern having a shape corresponding to the shape of the microlens,
Next, by dry etching the transparent substrate from the resin pattern side, the shape of the resin pattern is transferred to the transparent substrate to form microlenses arranged in an array. Manufacturing method. A microlens array produced by the method according to claim 7 or 8,
A plurality of microlenses of a predetermined size formed in an array are formed on a transparent substrate, and a light-shielding film having openings that are basically smaller than the microlenses and aligned with the microlenses is formed thereon. And
At least two of the openings have a shape in which at least a part of the periphery of the microlens can be seen through the openings. A microlens array produced by the method of claim 9,
A plurality of microlenses having a predetermined size formed in an array are formed on a transparent substrate, and an opening between the microlens and the substrate that is basically smaller than the microlens and aligns with the microlens. A light-shielding film having
At least two of the openings have a shape in which at least a part thereof protrudes from the periphery of the microlens.

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