JP2000280366A - Manufacture of microlens, microlens manufactured by the manufacturing method, optical device using the microlens and slider of the optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacture of a microlens capable of manufacturing easily the high NA microlens. SOLUTION: The method for manufacture of a microlens contains a process [fig.1 (C)] for manufacturing the first and second substrates wherein a microlens 105 is respectively formed at a position deeper than that of the substrate surface at least on one side, and a procee [fig.1 (E) ] for pasting together both faces wherein each microlens 105 of the first or second substrate 102 is formed by opposing them to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method of manufacturing a microlens, a microlens manufactured by the method,
More specifically, the present invention relates to an optical device using the microlens and a slider of the optical device, and more particularly, to a method of manufacturing a microlens used for an optical device such as an optical disk pickup, an optical communication device, a CCD, and the like. The present invention relates to a manufactured microlens, an optical device using the microlens, and a slider of the optical device.

[0002]

2. Description of the Related Art Recently, as the use range of a microlens has been expanded, it has been desired to increase the NA of the microlens and make it aspherical. In particular, in information recording devices such as optical disks and magneto-optical disks, in order to reduce the size and increase the recording density, like a hard disk, a slider that floats on the recording medium using the air current generated by the rotation of the recording medium is used. It has been considered to mount an objective lens. In such an application, a microlens having a high NA and a small aberration is required.

As a method for manufacturing a microlens, for example, there is a method in which a lens shape is formed from a photoresist and the shape is transferred to a transparent substrate by anisotropic etching. According to such a method, it is possible to create an aspherical microlens by devising a method of exposing the photoresist. Hereinafter, a conventionally proposed method of manufacturing a microlens will be described.

For example, in Japanese Patent Laid-Open Publication No. Hei 8-504515, a lens to be formed is divided into a plurality of minute areas, and the distribution of transmittance on a photomask is determined according to the thickness of the lens in each area. In the case of (1), the aperture ratio of each minute area is changed), and the remaining film thickness of the exposed resist is made to have a desired shape.

In Japanese Patent Application Laid-Open No. Hei 8-21908,
There is disclosed a technique for changing the distribution of the remaining film thickness of a photoresist by exposing a plurality of masks having different shapes of open regions to the same place a plurality of times.

Japanese Patent Application Laid-Open No. Hei 7-181303 proposes a method of fabricating a microlens having a wider range of functions. Two substrates having microlenses formed on one side are opposed to microlenses. There is disclosed a technique of bonding the two flat surfaces to each other.

[0007]

However, in a conventional method of forming a microlens using a photoresist pattern as in the prior art, it is necessary to increase the thickness of the microlens in order to increase the NA of the microlens. For this reason, a considerably deep etching is required, and there are problems that the resist is deteriorated during the etching and that the time required for the etching is long.

In addition, since it is difficult to form a resist pattern that is too deep, it is necessary to increase the selectivity of the substrate / resist at the time of etching to deepen the shallow resist pattern by etching. Since the error of the resist pattern is enlarged according to the selection ratio, there is a problem that the shape accuracy is reduced.

Further, when a slider or the like using these microlenses is created, the slider or 1 /
Since it is necessary to combine with a four-wavelength plate, a prism, and the like, it is necessary to make the substrate on which the microlens is formed into a shape that can be easily combined with them.

The present invention has been made in view of the above, and a method of manufacturing a microlens capable of easily manufacturing a high NA microlens, a microlens manufactured by the manufacturing method, and a microlens manufactured by the manufacturing method It is an object to provide an optical device used and a slider of the optical device.

[0011]

According to a first aspect of the present invention, there is provided a microlens manufacturing method for manufacturing a microlens by bonding two substrates together. A first step of manufacturing a first substrate having microlenses formed at a position deeper than the surface of the substrate, a second step of manufacturing a second substrate having microlenses formed on at least one surface, A third step of bonding the surfaces of the first and second substrates on which the microlenses are formed to face each other,
Is included.

According to a second aspect of the present invention, in the method of manufacturing a microlens according to the first aspect, in the third step, between the microlenses of the first and second substrates is performed. The substrate is to be filled with an adhesive having at least one of a refractive index, a transmittance, and a wavelength dependency different from each other.

According to a third aspect of the present invention, in the method of manufacturing a microlens according to the first or second aspect, in the first and second steps, the first and second substrates are provided. In the third step, the grooves are filled with an adhesive, and the first and second substrates are bonded together in the third step.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a microlens according to the first aspect, further comprising the step of: bonding the first substrate and the second substrate to each other. The method includes a step of forming a groove for connecting a cavity formed between the lenses to the outside of the substrate.

The microlens according to claim 5 is
It is manufactured by the method for manufacturing a microlens according to any one of claims 1 to 4.

Further, the optical device according to claim 6 is:
A microlens according to claim 5 is used.

The optical device according to claim 7 is:
7. The optical device device according to claim 6, wherein the microlens according to claim 5 is used for an optical pickup head, and a hemispherical or hyperhemispherical solid immersion lens is provided on a surface of the optical pickup head facing the recording medium. Is formed.

Further, the optical device according to claim 8 is:
A microlens according to claim 5 is used.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the accompanying drawings, a method of manufacturing a microlens according to the present invention, a microlens manufactured by the method, an optical device using the microlens, and a slider of the optical device will be described. Preferred embodiments of the [method of manufacturing a micro lens],
The details will be described in the order of [optical device device].

[Method of Manufacturing Micro Lens] The method of manufacturing a micro lens will be described in the order of (Production Example 1), (Production Example 2), and (Production Example 3).

(Production Example 1) A production example 1 of a method for producing a microlens will be described in detail with reference to FIG. FIG. 1 is an explanatory diagram for explaining a microlens manufacturing process (manufacturing example 1). 6A to 6C and 6E are cross-sectional views showing the manufacturing process, and FIG. 6D is a top view of FIG. In the figure, 101 is a photoresist, 102 is a glass substrate, 103 is a microlens pattern, 104
Denotes an alignment mark pattern, 105 denotes a micro lens, 106 denotes an alignment mark, and 107 denotes an adhesive.

First, as shown in FIG. 1A, a photoresist 10 is formed on one surface (laminated surface) of a glass substrate 102.
1 is applied. Subsequently, the resist 101 is exposed through a photomask on which a microlens pattern and an alignment mark are formed. After exposure, development is performed to form a photoresist pattern as shown in FIG.

In this case, as shown in FIG. 1B, the micro lens
3 is formed lower than the surface of the surrounding photoresist 101. Also, as shown in the figure, an alignment mark pattern 104 (four places, as shown in FIG. 4D) is used as a mark when the glass substrate 102 is bonded to another glass substrate.
Reference). This alignment mark pattern 1
The formation of 04 facilitates optical axis alignment when bonding glass substrates.

As a method of exposing the photoresist 101, various methods can be used. For example, a method of exposing light passing through a diffusion plate through a mask having a circular hole (or a light shielding portion), A method of exposing using a mask with a change in transmittance of a light-shielding portion, a method of exposing a mask pattern having a circular opening or a light-shielding portion using a projection exposure apparatus in an out-of-focus state, and a method of exposing a rectangular section. A method in which a circular pattern is formed and then deformed by heating to form a lens shape can be used.

Further, since the photomask is usually formed by an apparatus having a position accuracy of sub-μm order such as an EB lithography apparatus or a laser writer, the position of the lens is determined by using an alignment mark formed simultaneously with the microlens. Even if the alignment is performed, the deviation of the optical axis hardly causes a problem.

Next, anisotropic etching is performed on the glass substrate 102 on which the photoresist pattern shown in FIG. 1B has been formed, and as shown in FIG. Transfer to As shown in the figure, the tip of the microlens 105 is formed lower than the surface of the surrounding glass substrate 102. In the example shown in FIG. 1C, the anisotropic etching is performed until the photoresist 101 is completely removed, but the etching is performed halfway (until the microlens pattern is transferred), and then the photoresist is removed. It may be removed.

FIG. 1D shows a top view of FIG. 1C. As shown in the figure, alignment marks 106 are formed at four positions around a micro lens 105 located at substantially the center. The number and shape of the alignment marks 104 may be any. However, when the alignment marks 104 are superimposed on another glass substrate, the alignment marks 104 are alternately arranged so that they can be easily observed.
In the case where the superposition apparatus automatically performs the positioning, the shape may be set to the designated shape or the like.

Next, the same steps as described above (FIG. 1A)
To (D)), a glass substrate 102 on which another microlens pattern is formed is formed. And
A small amount of an ultraviolet curable adhesive 107 is applied to the glass substrate 102
Is applied to the surface portion (flat portion) of the surface on which the microlens 105 is formed (laminated surface), and then, as shown in FIG. The two glass substrates 102 are aligned while observing the mark 106. After the positions are determined, the two glass substrates are joined by irradiating ultraviolet rays to cure the adhesive. The thinner the adhesive layer, the higher the accuracy of the microlens spacing can be improved, so the thinner the adhesive layer, the better. Note that if the tip of the microlens of one glass substrate 102 to be bonded is formed lower than the surface of the surrounding glass substrate 102, the glass substrate 102 can be bonded without contacting the microlens. The tip of the microlens on the other glass substrate 102 does not necessarily need to be formed lower than the surface of the surrounding glass substrate 102. In short, it is only necessary that the glass substrate 102 can be bonded without contacting the microlenses.

Here, as an example of the method of joining the glass substrates, an example is shown in which the joining is performed using an ultraviolet-curable adhesive, but the present invention is not limited to this, and the alignment state is maintained. Any bonding means may be used as long as it can be fixed as it is.

When the microlens is used in an environment where the temperature rises (for example, when the microlens is used inside a housing where the temperature rises), a cavity 105A between the microlenses 105 (FIG. 1E) ) May expand and affect the characteristics of the microlens 105. Therefore, if use in such an environment is expected, a groove for taking in outside air is formed in the cavity 105A in the above-described manufacturing process, and the gap (the cavity 10) of the microlens 105 is formed.
It is sufficient that no pressure is applied to 5A).

As described above, according to Production Example 1,
First and second glass substrates 102 on which microlenses are formed are formed at positions deeper than the substrate surface, and the surfaces (bonded surfaces) of the first and second glass substrates 102 on which the microlenses 105 are formed face each other. Let the adhesive 10
7, the micro-lens is manufactured by bonding the substrates together. Therefore, even when the etching amount of the micro-lens on each glass substrate is reduced, when the substrates are bonded together, it is possible to increase the NA. A lens can be easily and accurately created. In addition, since the surface on which the microlens is formed is on the inside, the surface can be flattened, and lithography is performed on the surface to add a pattern having a function such as a grating to a portion other than the lens. Processing becomes easy, and combination with other parts becomes easy.

(Production Example 2) A production example 2 of a method for producing a microlens will be described in detail with reference to FIG. FIG. 2 is an explanatory diagram for explaining a microlens manufacturing process (manufacturing example 2). FIG. 1A is a top view of a glass substrate, and FIG. 1B is a cross-sectional view of the case where a glass substrate is attached. 2, the same parts as those in FIG. 1 are denoted by the same reference numerals.

In Production Example 1, as shown in FIG.
Since a layer of the adhesive 107 is formed between the two glass substrates 102, it is necessary to consider the thickness of the adhesive layer when designing the interval between the two microlenses 105. Therefore, in Production Example 2, in addition to the steps of Production Example 1, the adhesive 1
07 for filling the micro lens 10
The accuracy of the interval of 5 is increased.

In Production Example 2, the same steps as in Production Example 1 (FIGS. 1A to 1C) are performed by using a photomask on which a groove pattern is formed in addition to the photomask used in Production Example 1.
2C, a glass substrate 102 having a groove 201 for filling with an adhesive is formed as shown in FIG.

Then, as shown in FIG. 2B, the groove 107 of the two glass substrates 102 is filled with the adhesive 107,
The two glass substrates are joined by bringing the surfaces of the respective glass substrates 102 into contact with each other. Thus, the distance between the microlenses 105 can be designed based on the surface of the glass substrate 102 in contact with the microlens 105, and errors in the distance between the microlenses 105 can be reduced. The shape of the groove 201 is shown in FIG.
The shape is not limited to the shape shown in the figure, and any shape may be used as long as the adhesive flows when the glass substrates are overlapped and does not affect the distance between the glass substrates. For example, any shape such as a radial shape or a concentric shape may be used. It is good. Also, the groove
The two substrates may have different shapes.

As described above, according to Production Example 2,
An adhesive 107 is attached to the surface of each glass substrate 102 to be bonded.
Is formed, and the grooves 201 are filled with the adhesive 107, and the surfaces of the respective glass substrates 102 are brought into contact with each other and bonded to each other. Becomes possible.

(Production Example 3) A production example 3 of a method for producing a microlens will be described in detail with reference to FIG. FIG. 3 is an explanatory diagram for explaining a microlens manufacturing process (manufacturing example 3) and shows a cross-sectional view. In FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals.

In Production Example 3, the adhesive between the glass substrate 102 and the glass substrate 102 is different from the glass substrate 102 in at least one of the refractive index, the transmittance, and the wavelength dependency at the wavelength of the light to be used. Fill.

In Production Example 3, first, a glass substrate 102 as shown in FIG. 3 is formed on the same principle as in Production Example 1. Then, the adhesive 301 is applied to the entire surface of the bonding surfaces of the respective glass substrates. At this time, the adhesive 301 is also filled in the microlenses 105 and the two glass substrates 102 are bonded.

As described above, according to Production Example 3,
The glass substrate 102 is a wavelength of light to be used, and the refractive index, the transmittance, and the adhesive 301 different in at least one of the wavelength dependency are used, and the microlens 105 is filled with the adhesive 301. The part of the adhesive 301 can also be used as a part of the microlens. Further, in addition to facilitating the application of the adhesive, microlenses having various functions can be produced by selecting the refractive index of the adhesive. For example, when an adhesive having a different light dispersion characteristic from that of a glass substrate is used, it is possible to correct chromatic aberration.

[Optical Device] An optical device incorporating the microlenses produced by the production methods of Production Examples 1 to 3 will be described with reference to FIGS. Hereinafter, an optical disk device will be described as an example of the optical device device. FIG. 4 is a diagram showing a schematic configuration of an optical disk device to which a microlens manufactured by the method for manufacturing a microlens of the present invention is applied.

The optical disk device shown in FIG. 4 includes an optical pickup head 408 including a micro lens,
9 and an optical unit 410 in which a laser light source, a photodiode, and the like are integrally formed. In the same figure, reference numeral 407 denotes an optical disk.

In the optical disk apparatus having the above structure, the laser light emitted from the optical unit 410 enters the pickup head 408 including the microlens, and writes / reads signals to / from the optical disk 407 via the optical pickup head 408. I do. Next, the slider of the optical pickup head 408 will be described in the order of (Configuration Example 1) and (Configuration Example 2).

(Structural Example 1) FIGS. 5 and 6 are views for explaining a structural example 1 of the slider of the optical pickup head 408. FIG. FIG. 5 shows the optical pickup head 4 of FIG.
08 shows an enlarged sectional view. FIG. 6 shows a view of the slider of the optical pickup head 408 of FIG. 5 viewed from below. 5 and 6, reference numeral 412 denotes a slider. The microlens of the optical pickup head shown in FIGS. 5 and 6 is manufactured by the manufacturing method of Manufacturing Example 2 described above.

As shown in FIG. 5, the substrate 405 and the substrate 40
After bonding 6, the prism 404 is bonded to the flat upper surface of the substrate 405. As described above, since the surface of the microlens of the present invention can be flat, it can be easily combined with other elements.

As shown in FIG. 6, the slider 412 has a groove 403 for controlling the flying height on the lower surface (the surface opposite to the bonding surface) of the substrate 406 on which the microlenses 105 are formed. , Leading edge 402 and trailing edge 401 are formed. These grooves are formed on the lower substrate 406 by using the same photolithography method as used for manufacturing a microlens before being bonded to the upper substrate 405.

In the example shown in FIG. 5, one set of microlenses is formed on one slider. However, by using a plurality of microlenses, a plurality of tracks can be read and written at the same time. By changing the NA of each lens, it is possible to support various recording media.

When the microlens is used as an optical pickup head, the microlens is irradiated with laser light for a long time, so that the temperature is expected to rise.
If there is such a temperature rise, air between the microlenses expands, which may affect the characteristics of the lenses. In such a case, a groove for taking in outside air may be formed on the surface to be bonded, so that pressure is not applied to the gap between the microlenses.

As described above, when the microlens manufactured by the manufacturing method of the present invention is used for the objective lens of the optical pickup head, it is possible to realize a small size, light weight, and high NA. Since the curved surface is formed inside the substrate, it is easy to combine or process other components on the substrate surface.

(Structural Example 2) FIG. 7 is a view for explaining a structural example 2 of the slider 412 of the optical pickup head 408. FIG. 7 shows a configuration in which a solid immersion lens (SIL) is formed on the slider 412. 7, the same parts as those in FIG. 5 are denoted by the same reference numerals.

In FIG. 7, reference numeral 411 denotes a solid immersion lens. In order to further reduce the laser spot formed on the recording medium 407, a hemispherical or super hemispherical surface is provided on the surface of the slider 412 facing the recording medium 407 (the lower surface of the lower substrate 406) as shown in FIG. A solid immersion lens (SIL) 411 is formed.

The solid immersion lens 411
In the step of manufacturing a microlens, a hemispherical microconcave lens is formed at a position where light is condensed by the microlens, and the formed microconcave lens is formed by embedding a resin or an inorganic material having a higher refractive index than the substrate 406. When the solid immersion lens 411 is formed, when the refractive index of the substrates 405 and 406 is n1 and the refractive index of the embedded material is n2, the NA can be increased by (n2 / n1). For example, when SiN (n2 = 2) is embedded in a quartz glass substrate (n1 = 1.45), the NA is 1.38 times as large as that without a solid immersion lens (SIL).

As described above, according to the configuration example 2,
Since the immersion lens is formed on the slider, a smaller light spot can be formed, and the recording density on the optical disc can be improved.

In the above-described embodiment, the optical disk device in which the microlens created by the method of the above-described manufacturing example 2 is implemented has been described as an example.
Alternatively, a microlens created by the method of Manufacturing Example 2 may be implemented.

Further, in the above-described embodiment, the optical disk device has been described as an example of the optical device device. However, the present invention is not limited to this, and may be applied to any optical device device implementing a microlens. The present invention is applicable to, for example, a magneto-optical disk device and an optical communication device.

The present invention is not limited to the above-described embodiment, and can be appropriately modified without changing the gist of the invention.

[0057]

As described above, according to the method of manufacturing a microlens according to the first aspect, at least one side has:
Manufacturing a first substrate having a microlens formed at a position deeper than the substrate surface and a second substrate having a microlens formed on at least one surface, and forming the microlenses of the first and second substrates; Since the surfaces facing each other are bonded together, it is possible to easily form a high-NA microlens by combining microlenses that are thin and have a small NA.

According to the method of manufacturing a microlens according to the second aspect, in the method of manufacturing a microlens according to the first aspect, the distance between the microlenses of the first and second substrates is defined as: Since at least one of the refractive index, the transmittance, and the wavelength dependency is filled with a different adhesive, in addition to the effects of the invention according to claim 1,
It becomes easy to apply the adhesive, and it is possible to produce microlenses having various functions such as correction of chromatic aberration.

According to the method of manufacturing a microlens according to the third aspect, grooves are respectively formed on the surfaces of the first and second substrates to be bonded, and the formed grooves are filled with an adhesive. Since the surfaces of the first and second substrates are brought into contact with each other and bonded to each other, it is possible to increase the precision of the interval between the microlenses in addition to the effect of the first aspect.

According to a method of manufacturing a microlens according to a fourth aspect, in the method of manufacturing a microlens according to the first aspect, further, when the first substrate and the second substrate are bonded to each other, Since a groove for connecting the cavity formed between the lenses to the outside of the substrate is formed, in addition to the effect of the invention described in claim 1, the microlens is used in an environment where the temperature rises. In this case, the expansion of the air between the micro lenses can be prevented, and the characteristics of the lenses can be prevented from being adversely affected.

Further, according to the microlens according to the fifth aspect, since the microlens is manufactured by the method for manufacturing a microlens according to any one of the first to fourth aspects, an optical pickup requiring a high NA is required. It becomes possible to use the microlens for such purposes.

According to the optical device of the sixth aspect, since the microlens described in the fifth aspect is used, the size and weight of the pickup head can be reduced.

According to the optical device of the seventh aspect, in the optical device of the sixth aspect, a hemispherical or hyperhemispherical solid immersion lens is formed on a surface of the optical pickup head facing the recording medium. Because a smaller light spot can be formed,
It is possible to improve the recording density on the recording medium.

According to the slider of the optical device according to the eighth aspect, since the microlens according to the fifth aspect is used, the slider can be made smaller and smaller.
It is possible to reduce the weight.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram for explaining a manufacturing process (manufacturing example 1) of a microlens.

FIG. 2 is an explanatory diagram for explaining a microlens manufacturing process (manufacturing example 2).

FIG. 3 is an explanatory diagram for explaining a microlens manufacturing process (manufacturing example 3).

FIG. 4 is a diagram showing a schematic configuration of an optical disk device using the microlens of the present invention.

5 is an enlarged sectional view of the optical pickup head of FIG. 4 (Configuration Example 1).

6 is a diagram of a slider of the optical pickup head shown in FIG. 5 as viewed from below (configuration example 1).

FIG. 7 is a diagram showing a configuration in which an SIL is formed on the slider of FIG. 5 (configuration example 2).

[Explanation of symbols]

 Reference Signs List 101 photoresist 102 glass substrate 103 microlens pattern 104 alignment mark pattern 105 microlens 105A cavity 106 alignment mark 107 adhesive 201 groove 301 adhesive 401 trailing edge of slider 402 leading edge of slider 403 controlling airflow below slider Grooves 404 Prism 405 Substrate (upper) 406 Substrate (lower) 407 Optical disk 408 Optical pickup head 409 Arm 410 Optical unit 411 Solid immersion lens 412 Slider

Claims (8)

[Claims] 1. A microlens manufacturing method for manufacturing a microlens by bonding two substrates to each other, comprising: a first method for manufacturing a first substrate having a microlens formed at least on one surface at a position deeper than the substrate surface. A second step of manufacturing a second substrate on which a microlens is formed on at least one side; and a step of bonding the first and second substrates with the surfaces on which the microlenses are formed facing each other. 3. A method of manufacturing a microlens, comprising: 2. The method of manufacturing a microlens according to claim 1, wherein, in the third step, a refractive index, a transmittance, and a distance between the microlenses of the first and second substrates are determined. A method for producing a microlens, wherein at least one of wavelength dependency is filled with a different adhesive. 3. The method of manufacturing a microlens according to claim 1, wherein in the first and second steps, the surface of the first and second substrates to be bonded is Grooves are respectively formed, and in the third step, an adhesive is filled in each of the grooves, and the surfaces of the first and second substrates are brought into contact with each other and bonded to each other. Production method. 4. The method of manufacturing a microlens according to claim 1, further comprising: forming a cavity formed between the microlenses of each substrate when the first substrate and the second substrate are bonded to each other. Forming a groove for connection to the outside of the substrate. 5. A microlens manufactured by the method for manufacturing a microlens according to claim 1. Description: 6. An optical device using the microlens according to claim 5. Description: 7. The optical device according to claim 6, wherein the microlens according to claim 5 is used for an optical pickup head, and a surface of the optical pickup head facing the recording medium is hemispherical or super hemispherical. An optical device device, wherein a solid immersion lens is formed. 8. A slider for an optical device using the microlens according to claim 5.