JP2002331532A - Microlens forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a microlens forming method capable of simply performing the alignment of the optical axis of an optical device (an optical element, an optical part or the like) with that of a microlens at a low cost. SOLUTION: A photomask (1) having a microlens pattern for forming the microlens and an alignment mark pattern is used, and the alignment mark (5) of the microlens is aligned with the alignment mark (4) of the optical element by setting the alignment mark of the optical device having the optical element (3) to the light emitting or receiving center of the optical element to align the optical axis of the microlens with that of the optical device. A film (9) for a lens marker, to which the microlens pattern having an alignment mark (8) at the center thereof is transferred, is formed on a substrate (12), and a liquid resin for the microlens is injected on the film for the lens marker to form a liquid microlens which is, in turn, irradiated with UV rays to be cured to form the microlens.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for manufacturing a microlens of an optical device.

[0002]

2. Description of the Related Art FIG. 6 shows an example of a conventional microlens manufacturing method described in Japanese Patent Application Laid-Open No. 2000-180605 (Japanese Patent Application No. 10-358956). In this conventional method, a liquid ultraviolet (UV) curable resin is injected onto a substrate 12 by an inkjet head 13 as a liquid resin 14 for a lens, and is spheroidized by surface tension. 15 to form the microlenses 21. Using a piezo drive element or the like, the injection amount of the liquid ultraviolet (UV light) curable resin can be accurately controlled, and a microlens array with high reproducibility and controllability can be manufactured. Further, since a lens can be formed directly on an arbitrary substrate 12, it is easy to integrate a microlens into an optical component such as a semiconductor laser, a light receiving element, and an optical waveguide.
The angle between the dropped liquid resin and the substrate, that is, the contact angle, largely depends on the relationship between the liquid resin and the surface tension of the substrate. The relationship between the liquid resin and the surface tension of the substrate is the viscosity of the resin,
It is determined by the temperature of the resin and the substrate, the surface shape of the substrate, etc.If the conditions are the same, the contact angle is uniquely determined, so it can be applied as a method of manufacturing microlenses. is there. The parameters representing the lens characteristics of the microlens include the focal length, F
Number, lens diameter (opening diameter) and the like. In these lens parameters, the F number can be easily derived from the contact angle of the resin and the refractive index of the resin. That is,
If a combination of a resin (having a known refractive index) and a substrate that forms a predetermined contact angle is prepared, a microlens having a desired F-number can be manufactured. Further, regarding the lens diameter, since the contact angle is constant regardless of the emission amount, it can be controlled only by the emission amount.

In the above prior art, microlenses having various lens characteristics can be easily manufactured. However, this prior art is a method of manufacturing micro lenses one by one, and it is possible to collectively manufacture a micro lens array by forming a multi-nozzle ink jet head. The alignment accuracy greatly depends on the stage driving accuracy of the apparatus, the resolution of the observation system, and the like. That is, in order to increase the accuracy of the formation position of the microlens, it is necessary to increase the precision of the apparatus. Increasing the precision of the device means increasing the price of the device, which increases the manufacturing cost of the microlens. Therefore, in order to manufacture the microlens at low cost, it is necessary to provide a manufacturing method in which the accuracy of the formation position of the microlens is not affected by the accuracy of the device.

FIG. 7 shows an example of a manufacturing method of a microlens proposed as a manufacturing method in which the accuracy of the formation position of the microlens is not affected by the accuracy of the apparatus [for example, Japanese Patent Application Laid-Open No. 62-83337 (Japanese Patent Application No. 60-220375
issue)〕. This is because a photosensitive resin 23 provided on the substrate 12 is exposed to light using a photomask 22, developed, and patterned to form a disc-shaped portion of the photosensitive resin 23 on a portion of the substrate 12 where a microlens is to be formed. (Hereinafter referred to as a convex lens marker film) 24. Since the disc-shaped transparent resin 24 serving as the convex lens marker is manufactured by photolithography using the photomask 22 having a microlens pattern, the shape and the arrangement pitch of the convex lens marker film 24 can be accurately determined. Both sex and reproducibility are high.

When such a convex lens marker film 24 is formed on a target substrate, the ejection position of the droplet of the liquid UV light curable resin 25 is set on the convex lens marker film 24. Since it is enough, the positional accuracy is greatly reduced. The liquid droplets ejected onto the convex lens marker film 24 wet and spread on the convex lens marker film 24, but stop spreading at the peripheral portion, and naturally form a spherical shape.
Since the convex lens marker film 24 is circular, the center of the lens exactly matches the center of the lens marker.
The diameter of the micro lens 26 is the convex lens marker film 24.
Is accurately retained by the diameter of

Here, the alignment of the photomask 22 is usually performed by using an alignment mark formed on the mask. This alignment mark is formed on a portion other than the microlens pattern of the mask, and is aligned as an alignment mark provided on the target surface. The alignment mark pattern provided on the target surface is often a fine pattern formed on the wiring layer, but is aligned on chip components such as optical elements and optical components such as optical waveguides (collectively referred to as optical components). A mark pattern may be produced.

When an alignment mark is formed on a wiring layer on which an optical component is mounted, unless the mounting accuracy of the optical component is improved, the optical axes of the optical component and the microlens will be shifted. Therefore, in order to align the optical axes, a high-precision optical component mounting technique is required, which leads to an increase in mounting cost. When forming an alignment mark on an optical component, the photomask 2
In order to match the alignment marks on the two sides, the size of the optical component must be sufficiently larger than the size of the microlens. Although an alignment mark can be provided in the microlens, it is not preferable to form a mark pattern in a light transmitting portion because the transmitted light has effects such as reflection, scattering, and attenuation.

[0008]

In the above-described conventional method for manufacturing a microlens, the positional accuracy of dropping the ultraviolet curable resin depends on the precision of the apparatus. It is necessary to improve the precision of the device, which results in an increase in the cost of the device and an increase in the manufacturing cost of the microlens. In addition, in order to ease the accuracy of the drop position of the liquid resin, a method of forming a disk-shaped lens marker on a sunset substrate in advance has been proposed. There have been several problems with the formation of alignment marks. For example, an expensive mounting device for accurately mounting an optical component is required, an alignment mark must be formed on the surface of the optical component, or an optical component is required to form an alignment mark. Is required to be larger than the microlens, and when the alignment mark is provided in the microlens, the light transmission characteristics are affected and the lens effect is deteriorated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a micro-lens which can easily and inexpensively align an optical axis of an optical device (optical element, optical component, etc.) with a micro-lens. An object of the present invention is to provide a lens forming method.

[0010]

Means for Solving the Problems In order to achieve the above object, the present invention is configured as described in the claims. That is, a method of forming a microlens on the substrate surface of an optical device (optical element, optical component, etc.) for inputting / outputting an optical signal to / from an optical element through a substrate through which optical signal light passes, A photomask having a microlens pattern that defines a portion to be formed and an alignment mark pattern formed inside the pattern is used, while the alignment mark of the optical device is used as the light emission or light reception center of the optical element. Alternatively, by providing an alignment mark separately formed on the optical element and aligning the alignment mark of the photomask with the alignment mark of the optical device, the photomask and the optical device are aligned with each other, On a substrate on which a lens is formed, a photosensitive material film having a refractive index equal to that of the microlens material is formed. Forming a lens marker film on the photosensitive material film by transferring a microlens pattern having an alignment mark at the center by exposing and developing using the photomask; and A step of injecting a liquid resin for a lens onto the microlens pattern of the marker film to form a liquid microlens, and irradiating UV light to cure the liquid microlens to form a microlens And a method of forming a microlens including at least steps of:

When the microlens is manufactured by the process according to the first aspect, alignment of the optical axis between the optical device (optical element or optical component, etc.) and the microlens becomes much easier as compared with the related art. A highly accurate microlens can be formed at low cost.

According to a second aspect of the present invention, there is provided a method of forming a microlens on a surface of an optical device for inputting / outputting an optical signal to / from an optical element through a substrate through which an optical signal light passes. A photomask having a microlens pattern defining a portion for forming the microlens and an alignment mark pattern formed inside the pattern is used. On the other hand, the alignment mark of the optical device is emitted or received by the optical element. The center or the alignment mark formed separately on the optical element is provided, and the alignment mark of the photomask is aligned with the alignment mark of the optical device, so that the positions of the photomask and the optical device are adjusted. Forming a photosensitive material film on a substrate on which the microlenses are formed; Using the photomask, transferring a microlens pattern defining a portion where the microlens is to be formed and an alignment mark pattern formed inside the pattern to the formed photosensitive material film; Over-developing the material film to erase the alignment mark transferred to the photosensitive material film and forming a lens marker film leaving a portion where the micro lens is formed; and forming the micro lens. A microlens formation including at least a step of injecting a liquid resin for a lens to form a liquid microlens and a step of irradiating UV light to cure the liquid microlens to form a microlens. Method.

[0013] By using the step of performing the over-development, erasing the alignment mark and leaving the portion where the microlens is formed as described above, the refractive index of the resin material of the lens marker and the refractive index of the microlens are matched. This eliminates the necessity to perform the process, and has the effect of widening the range of selection of the resin material for the microlens.

Further, as described in claim 3, claim 2
In the above, the photosensitive material film is over-developed, the alignment mark is erased, and the lens marker film leaving the portion where the microlens is formed is close to the portion where the microlens is formed on the substrate surface. And a method for forming a microlens formed in a region outside a portion where the microlens is formed and made of a material having an absorptivity to the wavelength of the optical signal light.

According to the third aspect of the present invention, the resin material for the lens marker does not need to be transparent to the wavelength to be used, and can be used when the optical elements are arranged in an array. The use of a colored material has the effect of reducing optical crosstalk between adjacent channels.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS <First Embodiment> FIG. 1 shows a first embodiment of the present invention. In FIG. 1, the method of manufacturing a microlens is a method of forming a microlens on the surface of the substrate 12 in an optical device that inputs and outputs optical elements 3 that are die-bonded through a substrate 12 through which optical signal light passes.

Using a photomask 1 (FIG. 1 (a)) having a microlens pattern defining a portion where a microlens is to be formed and an alignment mark pattern (central alignment minute mark) 5 formed inside the pattern.
By aligning the alignment mark (light emission or light receiving center of the optical element) 4 on the optical element 3 with the alignment mark 5 on the photomask 1, the positions of the photomask 1 and the optical device 3 are aligned. The optical axes of the device 3 and the microlens are aligned (FIG. 1B). A photosensitive material film 2 having a refractive index equal to that of the microlens material is formed on a substrate 12 on which a microlens is formed, and the photosensitive material film 2 is exposed using a photomask 1 and then developed. A convex lens marker film 9 having a concave alignment mark 8 at the center (lens marker film to which a microlens pattern is transferred) 9 is formed [FIG.
(C)]. The liquid resin 14 for the lens is injected / discharged onto the microlens pattern of the lens marker film 9 using the ink jet head 13 (FIG. 1D) [FIG.
(E)], a liquid microlens 16 is formed, and UV light irradiation 15 is applied to cure the liquid microlens 16 [FIG. 1 (f)] and a microlens 17 [FIG. 1 (g)].
To form

The microlens pattern (hereinafter referred to as a lens marker film) that defines the portion where the microlenses 17 are formed uses the negative photosensitive material film 2 in which the exposed portions are hardened. A cross-shaped or disk-shaped alignment mark is formed in the portion. Since the alignment mark is a light-shielding portion, a concave alignment mark 8 having a depression (a depression) corresponding to the alignment mark pattern is formed at the center of the convex lens marker film 9. However, the concave portion of the concave alignment mark 8 is closed in the subsequent step of injecting / discharging the droplets of the liquid resin 14 for the lens, and becomes the same solid phase as the film 9 for the convex lens marker. A uniform microlens can be formed. Here, if the refractive indexes of the convex lens marker film and the microlens resin material are matched, the dent between the lens marker film 9 and the concave alignment mark 8 does not become an optical interface, but becomes uniform. Thus, a transparent microlens was obtained.

<Embodiment 2> FIG. 2 shows a second embodiment of the present invention. In FIG. 2, a lens marker is formed by using a positive photosensitive resin from which an exposed portion is removed. By using a positive photosensitive resin,
Contrary to the first embodiment, a lens marker film (concave lens marker film) 10 having a concave (recessed) microlens portion is formed. Using a photomask 1 (FIG. 2A) having a microlens pattern defining a part where a microlens is to be formed and an alignment mark pattern 5 formed inside the pattern, the alignment mark pattern of the optical element 3 is irradiated with light. By aligning the alignment mark pattern 5 of the photomask 1 with the light-emitting or light-receiving center of the element (optical device) 3, the photomask 1 and the optical device 3 are aligned, and a positive photosensitive material film 2 ′ is formed. Is exposed 6 using the photomask 1 having the microlens pattern [FIG.
(B)]. By developing, a concave lens marker film 10 having a convex alignment mark 7 therein is formed [FIG.
(C)]. Hereinafter, the inkjet head 13 [FIG.
(D)] to inject the liquid resin 14 for the lens [FIG.
(E)], a step of forming a liquid microlens 16 and irradiating UV light 15 [FIG. 2 (f)] to form a microlens 17 [FIG. 2 (g)] is substantially the same as that of the first embodiment. The same is true.

In the second embodiment, similarly to the first embodiment, an alignment mark is formed at the center of the microlens in order to align the light emitting / receiving center of the optical element with the position of the microlens. . Since this alignment mark remains without being etched in the developing process, it becomes a minute convex alignment mark 7 as shown in FIG. However, since the minute protrusions are covered by the subsequent liquid resin injection step, by matching the refractive indices of the lens marker resin material and the microlens resin material as in the first embodiment. ,
These minute projections become optically transparent. In the film for the concave lens marker, as a resin material for the lens marker,
It is preferable to use a material having high water repellency.

Third Embodiment In the third embodiment, as shown in FIG. 3, the convex alignment mark 7 formed inside the concave lens marker film 10 in the case of FIG.
A method of forming a microlens that eliminates the need to match the refractive indices of the concave lens marker film and the resin material of the microlens and can increase the selection range of the resin material for the microlens will be described.

As shown in FIG. 3C, a photomask 1 is formed by using a substrate 12 on which a positive photosensitive material film 2 'is formed.
By aligning the alignment mark pattern 5 and the alignment mark pattern (light emitting / receiving center) 4 on the optical element 3, the photomask 1 and the optical element (optical device) are aligned.
After the alignment of 3, the over-development is performed in the step of exposing and developing 6 to remove the convex alignment marks 7 transferred to the positive photosensitive material film 2 ', and the outer peripheral side of the microlens forming portion Of the concave lens marker film 10 'that defines the edge of. Next, the liquid resin 14 for the lens is injected onto the concave lens marker film 10 ', which is the part where the microlens is formed (FIG. 3E), to form the liquid microlens 16 and to irradiate UV light. 15 and curing (FIG. 3F) to form the microlenses 17 (FIG. 3G) are the same as in the first and second embodiments.

By adopting such a method of forming a microlens, it is not necessary to match the refractive indexes of the resin materials of the lens marker and the microlens, and the range of selection of the resin material for the microlens can be widened. In addition, the resin material for the concave lens marker film does not need to be transparent to the wavelength used, and when the optical elements are arranged in an array, for example, by using a colored material, the distance between adjacent channels can be reduced. Can also be expected to reduce optical crosstalk. However, in general, there are few types of positive type (photodecomposition type) photosensitive materials. Therefore, when performance such as resin reliability is prioritized, it is better to use a negative type photosensitive resin. FIG. 5 shows an example of the lens marker manufacturing mask pattern used in the first to third embodiments.
It was shown to. FIG. 5 shows a minute disk-shaped alignment mark, but may have a cross shape or the like.

<Embodiment 4> As shown in FIG. 4, in Embodiment 4, a ring-shaped lens is formed by using a photomask 1 (FIG. 4A) having a ring-shaped lens marker pattern 19. A case where a microlens is manufactured by forming the marker film 11 will be described.
The point of patterning using a positive photosensitive resin is the same as that of the second embodiment, but when the resin material for the microlens is dropped, the ring-shaped lens marker film 11 is formed.
In that the outer shape of the microlens is determined by the outer edge of.

The concave lens marker film 10 (FIG. 2) is formed by using a water-repellent material or increasing the thickness of the lens marker in order to stop the spread of the resin for the micro lens when the resin is dropped. Ingenuity such as was necessary. These are factors that limit and make the manufacturing process difficult, and the resin may spread on the lens marker film due to slight chipping or roughening of the edge.
With the concave lens marker film 10 (FIG. 2) and the convex lens marker film 9 (FIG. 1), the convex lens marker film 9 can form microlenses with higher reproducibility. That is, the ring-shaped lens marker film 11 shown in the fourth embodiment has good reproducibility of microlens production of the convex lens marker film 9 and microlens resin material of the concave lens marker film 10. It has both good points of the breadth of options.

As in the third embodiment, in the ring-shaped lens marker film 11, the alignment mark at the center of the microlens can be removed by overdeveloping. At this time, the ring portion is similarly overdeveloped, so that care must be taken in designing the ring width. In the above embodiment, the method of injecting the liquid resin is as follows.
Although the ink-jet method has been described, this is not limited to the ink-jet method, and any method can be used as long as it can drop a minute amount of liquid droplets with good controllability. For example, a dispenser method is used. It is also possible. In the above embodiment, a single-channel optical device has been described.
This is not limited to a single channel. The microlens forming method of the present invention can be applied to optical element arrays arranged one-dimensionally or two-dimensionally in the same manner.

[0027]

According to the microlens forming method of the present invention utilizing the property that a minute amount of liquid droplets become spherical on a substrate, it is possible to improve the accuracy and reproducibility of the microlens diameter and array arrangement. In the mask pattern of the lens marker to be used, a minute alignment pattern is formed at the center of the microlens, and the alignment of this pattern with the emission / reception center of the optical element (optical device) facilitates the alignment of those optical axes. It becomes possible to match. Used to align the optical axis of the optical element and the micro lens,
There is no need to form a special alignment mark as a lens marker used to improve the formation position accuracy, and it is not necessary to mount an optical element using a high-level mounting method such as a flip chip, It is not necessary to newly provide an alignment mark. Furthermore, even if the alignment mark cannot be formed because the chip outer shape is small and fits within the projection size of the microlens, it is possible to manufacture a microlens with the optical axis aligned with the optical element at low cost. it can. Also,
Although the lens marker used for the alignment of the microlens and the optical element is located in the light transmission region, it can be removed optically or physically, and an unnecessary increase in the boundary surface can be prevented.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a microlens forming method exemplified in Embodiment 1 of the present invention.

FIG. 2 is a diagram illustrating a method of forming a microlens exemplified in Embodiment 2 of the present invention.

FIG. 3 is a diagram illustrating a microlens forming method exemplified in Embodiment 3 of the present invention.

FIG. 4 is a diagram illustrating a microlens forming method exemplified in Embodiment 4 of the present invention.

FIG. 5 is a plan view showing an example of a lens marker manufacturing mask pattern used in Embodiments 1 to 3 of the present invention.

FIG. 6 is an explanatory view showing a conventional method for manufacturing a microlens utilizing the surface tension of a minute amount of droplets.

FIG. 7 is an explanatory view showing a conventional method for manufacturing a micro lens using a lens marker.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Photomask (micro lens pattern) 2 ... Photosensitive material film 2 '... Photosensitive material film 3 ... Optical device (optical element) 4 ... Alignment mark (for example, light emission / light receiving center) on an optical element 5 ... Micro lens Alignment mark (for example, minute mark for center alignment) 6 ... Exposure 7 ... Convex alignment mark 8 ... Concave alignment mark 9 ... Film for convex lens marker 10 ... Film for concave lens marker 10 '... Film for concave lens marker 11 ... Ring Film for lens lens marker 12 ... Substrate 13 ... Inkjet head 14 ... Liquid resin for lens 15 ... UV light irradiation 16 ... Liquid micro lens 17 ... Micro lens 18 ... Mask pattern for producing lens marker 19 ... Ring lens marker pattern 20 ... Stage 21: micro lens 22: photo mask (micro lens Tan) 23 ... photosensitive resin 24 ... disc-like transparent resin (convex lens marker for film) 25 ... liquid UV light curable resin 26 ... microlenses

Claims (3)

[Claims] 1. A method of forming a microlens on a surface of an optical device for inputting / outputting an optical signal to / from an optical element through a substrate through which an optical signal light is transmitted, wherein a portion for forming the microlens is defined. A photomask having a microlens pattern to be formed and an alignment mark pattern formed inside the pattern is used. On the other hand, the alignment mark of the optical device is used as the light emission or light reception center of the optical element or on the optical element. A substrate that forms the microlens by aligning the alignment mark of the photomask with the alignment mark of the optical device, thereby aligning the position of the photomask with the optical device. Forming a photosensitive material film having a refractive index equal to that of the microlens material, Serial on the photosensitive material film, exposed using the photomask,
Forming a lens marker film by transferring a microlens pattern having an alignment mark at the center by developing, and injecting a liquid resin for a lens onto the microlens pattern of the lens marker film, A microlens forming method, comprising: irradiating UV light to cure the liquid microlens to form a microlens. 2. A method for forming a microlens on a surface of an optical device for inputting and outputting an optical signal to and from an optical element through a substrate through which an optical signal light is transmitted, wherein a portion for forming the microlens is defined. A photomask having a microlens pattern to be formed and an alignment mark pattern formed inside the pattern is used. On the other hand, the alignment mark of the optical device is used as the light emission or light reception center of the optical element or on the optical element. A substrate that forms the microlens by aligning the alignment mark of the photomask with the alignment mark of the optical device, thereby aligning the photomask with the optical device. Forming a photosensitive material film on the photosensitive material film formed on the substrate; Using a photomask, transferring a microlens pattern defining a portion where the microlens is to be formed, and an alignment mark pattern formed inside the pattern; and overdeveloping the photosensitive material film, A step of erasing the alignment mark transferred to the photosensitive material film and forming a lens marker film leaving a part where the microlens is formed; and injecting a liquid resin for the lens into the part where the microlens is formed. Forming a microlens in a liquid state; and irradiating UV light to cure the microlens in the liquid state to form a microlens. 3. The lens marker film according to claim 2, wherein the photosensitive material film is overdeveloped to erase the alignment mark and leave a portion where a microlens is to be formed. A microlens forming method, wherein the microlens is formed in a region outside the portion where the microlens is formed, in the vicinity of the portion where the microlens is formed, and which is made of a material that absorbs the wavelength of the optical signal light. .