JP2003248156A - Method for overlapping substrate and optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for overlapping substrates which can make aligning accuracy for an overlap location high without using a high accuracy stage and an optical system for observing marks, etc. <P>SOLUTION: In the method for overlapping two substrates 41, 43 having micro lenses 42, 44, a first protruding alignment mark 48 is formed on the first substrate 41, and a recessed second alignment mark 51 is formed on the second substrate 43 so as to have a dimension for permitting intrusion of at least a part in the vicinity of a top of the first alignment mark 48. The part in the vicinity of the top of the first protruding alignment mark 48 intrudes into the second recessed alignment mark 51, and the first and the second substrates 41, 43 are overlapped. The positioning accuracy for the overlap location can be high without using the high accuracy stage and the optical system for observing the marks, etc. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method of superposing substrates and an optical element.

[0002]

2. Description of the Related Art In recent years, with the spread of electronic equipment with a liquid crystal display device represented by a liquid crystal projector or the like, the demand for higher performance of the liquid crystal display device has increased, and the liquid crystal display device has higher definition and higher brightness. Improvements are underway. This liquid crystal display device generally includes a substrate (hereinafter referred to as a drive substrate) on which a thin film transistor (hereinafter, simply referred to as “TFT”) for controlling each pixel and a storage capacitor are formed, and a color filter (color A liquid crystal panel) or a substrate on which a black matrix is formed (hereinafter,
(Referred to as a counter substrate).

The drive substrate of the liquid crystal display device is the above-mentioned TF.
It is composed of a T portion and an opening for displaying an image, and as a result of the area being occupied by the TFT portion, sufficient transmittance may not be secured in some cases. For this reason, a structure in which a micro-condensing lens for pixels (hereinafter simply referred to as “microlens”) is provided in the opening of each pixel in the related art, and the light originally irradiated to the TFT section is condensed in the opening Has been adopted. As a method of forming a microlens, there is known a method of independently forming a microlens array and bonding the microlens array to a counter substrate.

By the way, in such a liquid crystal display device, the two substrates (driving substrate and counter substrate) are laminated (positioned) with the alignment mark as a reference and then bonded to each other. .

As a method for superposing such two substrates, there is a method described in Japanese Patent Laid-Open No. 9-189901. According to the method of superposing two substrates described in Japanese Patent Laid-Open No. 9-189901, alignment marks are formed on the liquid crystal panel and the microlens array by transparent materials, respectively, and two alignment marks are formed using these alignment marks. The substrates are stacked.

Further, as another method of superposing two substrates, there is a method described in Japanese Patent Laid-Open No. 2000-131508. According to the method of superposing two substrates described in Japanese Patent Application Laid-Open No. 2000-131508, cross-shaped markers are formed at the four corners of the first substrate used for forming the first lens, and the second lens is formed. Cross-shaped markers are also formed at the four corners of the second substrate used to form the two substrates, and the two substrates are superposed using these cross-shaped markers.

[0007]

However, JP-A-9-189901 and JP-A-2000-131508 are known.
According to the method of superposing two substrates described in the publication, alignment marks and markers are formed on the two substrates respectively, and the two substrates are superposed using these alignment marks and markers. However, in order to perform such an overlaying work, a highly accurate stage and an optical system for observing the alignment mark are required, which is very costly.

An object of the present invention is to provide a substrate superposition method capable of achieving high precision in the superposition position alignment without using a high-precision stage or an optical system for observing marks. Is.

It is an object of the present invention to provide a substrate superposing method capable of easily adjusting the distance between the first substrate and the second substrate.

An object of the present invention is to provide at least one pair of microlenses capable of achieving high accuracy in alignment of superposition positions without using a highly accurate stage or an optical system for observing marks. An optical element having the above is provided.

[0011]

The invention according to claim 1 is
A method for stacking two substrates having a microlens on at least one side, wherein a first hemispherical convex alignment mark serving as a reference for alignment of the microlenses is provided on the first substrate. A first alignment mark forming step to form and a concave shape formed on the second substrate, which is a size that allows entry at least near the apex of the first alignment mark, which serves as a reference for alignment of the microlenses. A second alignment mark forming step of forming a second alignment mark, the first alignment mark of the first substrate and the second alignment mark of the second substrate are opposed to each other, and at least the first alignment mark is formed. The vicinity of the apex of the alignment mark of the first substrate and the second substrate to penetrate into the second alignment mark. Superimposed substrate superposing preparative comprises a step.

Therefore, a convex first alignment mark is formed on one of the two substrates to be aligned, and at least the first alignment mark is formed on the other second substrate. The second alignment mark having a concave shape is formed in a size that allows entry near the apex of the. Then, the first substrate and the second substrate are superposed by causing the vicinity of the apex of the convex first alignment mark to enter the inside of the concave second alignment mark. As a result, it becomes possible to make the alignment accuracy of the overlay position highly accurate without using a highly accurate stage or an optical system for observing marks.

According to a second aspect of the present invention, in the substrate superposing method according to the first aspect, the first alignment mark forming step uses a photolithography process and an etching process for the first substrate. A recess forming step of forming a ring-shaped recess; a thermoplastic material attaching step of attaching a thermoplastic material to the inside of the recess formed in the first substrate; and a thermoplastic material attaching step of attaching the thermoplastic material to the inside of the recess. A hemispherical shape forming step of heating and melting the thermoplastic material to form the thermoplastic material into a substantially hemispherical shape by surface tension.

Therefore, since the shape of the first alignment mark on the first substrate can be accurately made into a substantially hemispherical shape by a simple method, the positioning accuracy of the superposition position can be further improved. Will be possible.

According to a third aspect of the present invention, in the substrate superposing method according to the first aspect, the first alignment mark forming step includes a photoresist applying step of applying a photoresist to the surface of the first substrate. Exposing the photoresist so that the photoresist except the position corresponding to the first alignment mark is removed,
It includes an exposure / development step of developing and a hemispherical shape forming step of heating the photoresist to form a substantially hemispherical shape.

Therefore, the shape of the first alignment mark on the first substrate can be accurately made into a substantially hemispherical shape by a simple method, so that the alignment accuracy of the overlay position can be further improved. Will be possible.

The invention according to claim 4 is the invention according to claims 1 to 3.
In the method of superimposing the substrates according to any one of 1, the first alignment mark formed on the first substrate is deformed after completion of the substrate superimposing step, and the first substrate and the second substrate The method further includes an interval adjusting step of adjusting an interval with the substrate.

Therefore, it becomes easy to adjust the distance between the first substrate and the second substrate.

According to a fifth aspect of the present invention, in the substrate superposing method according to the fourth aspect, the gap adjusting step makes the first substrate and the second substrate perpendicular to an overlapping surface thereof. Pressure is applied to deform the first alignment mark.

Therefore, it is possible to surely adjust the gap between the first substrate and the second substrate.

According to a sixth aspect of the present invention, in the substrate superimposing method according to the fourth aspect, the gap adjusting step makes the first substrate and the second substrate perpendicular to an overlapping surface thereof. Pressure is applied and the first alignment mark is heated and melted to deform the first alignment mark.

Therefore, it is possible to surely adjust the gap between the first substrate and the second substrate.

According to a seventh aspect of the invention, in an optical element having at least one pair of microlenses,
A first substrate having one of the microlenses forming a pair and a substantially first hemispherical convex convex alignment mark serving as a reference for alignment of the microlenses,
A pair of the other microlenses, and a second alignment mark having a concave shape formed into a size that allows entry of at least the vicinity of the apex of the first alignment mark, which serves as a reference for alignment of the microlenses. And a second substrate having.

Therefore, the first alignment mark having a convex shape is formed together with the microlens on one of the first substrates, and at least the vicinity of the apex of the first alignment mark is penetrated into the other second substrate. A concave second alignment mark formed to an allowable size is formed together with the microlens. Then, by intruding the vicinity of the apex of the convex first alignment mark into the inside of the concave second alignment mark,
The first substrate and the second substrate are overlaid. As a result, it becomes possible to make the alignment accuracy of the overlay position highly accurate without using a highly accurate stage or an optical system for observing marks.

[0025]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a first embodiment of the present invention.
Or, it demonstrates based on FIG. The two substrates of this embodiment are applied to two microlens array substrates for manufacturing an optical element used in a liquid crystal display device such as a liquid crystal projector.

Here, FIG. 1 shows a first microlens array substrate, (a) is a plan view thereof, and (b) is a sectional view taken along line XX ′ of (a). As shown in FIG. 1, a first microlens array substrate A (hereinafter, referred to as a first lens substrate A) is a microlens array 2 which is an assembly of microlenses 1 formed in a hemispherical shape.
And the alignment area 4 other than the area in which the microlens array 2 is formed. Such a first lens substrate A is
It is formed of BK7 which is optical glass. In FIG. 1, the microlens array 2 is formed of 7 × 8 microlenses 1 for the sake of explanation, but the actual microlens array 2 is composed of a larger number of microlenses 1.

Alignment marks 5 are formed at the four alignment corners of the first lens substrate A in the alignment area 4 of the first lens substrate A. The alignment mark 5 has a groove 5a that is a ring-shaped recess formed in the first lens substrate A, and a hemispherical protrusion 6 formed of resin on a portion 5b surrounded by the groove 5a. is doing. The diameter of the projection 6 of the alignment mark 5 on the first lens substrate A of the present embodiment is 100 μm.

Now, the procedure for forming the alignment mark 5 will be described with reference to FIG. As shown in FIG. 2A, first, a resist pattern having the shape of the groove 5a is formed on the substrate by photolithography, and the resist pattern is transferred to the substrate by etching. In addition, using the reflow method and gradation mask, the microlens 1
Since a photolithography process and an etching process are used when forming the above, the resist pattern pattern of the shape of the groove 5a may be formed at the same time. Thereby, the alignment mark 5 can be formed without shifting the relative position with respect to the microlens 1.

Next, as shown in FIG. 2B, a thermoplastic resin P, which is a thermoplastic material, is attached onto the portion 5b surrounded by the groove 5a. In this embodiment, a hot melt adhesive is used as the thermoplastic resin P. At this time,
The thermoplastic resin P may be attached to a position where it does not protrude from the portion 5b surrounded by the circular groove 5a, and it is not necessary to accurately attach it to the center of the portion 5b surrounded by the circular groove 5a. Absent.

Finally, as shown in FIG. 2 (c), the substrate having the thermoplastic resin P attached thereto is heated to cause the thermoplastic resin P to flow. Here, since the groove 5a is formed in a circular shape, when the thermoplastic resin P is made to flow, the contact angle of the thermoplastic resin P sharply decreases at the corner of the groove 5a.
The range in which the thermoplastic resin P flows is limited to the inside of the groove 5a, and the surface tension acts. That is, since the surface of the thermoplastic resin P can be formed into a hemispherical shape having the portion 5b surrounded by the circular groove 5a as the base, the center of the groove 5a and the apex of the hemispherical projection 6 can be exactly aligned. be able to. After that, the substrate is cooled and the thermoplastic resin P is cured to complete the alignment mark 5.

Therefore, the shape of the first alignment mark 5 on the first substrate A can be accurately made into a substantially hemispherical shape by a simple method, so that the alignment accuracy of the overlay position can be further improved. It becomes possible to do.

Although the side wall of the groove 5a is vertical in FIG. 2, it does not have to be vertical as long as it has an angle with respect to the thermoplastic resin P that can suppress the spread due to surface tension.

Next, the second microlens array substrate will be described. Here, FIG. 3 shows a second microlens array substrate, (a) is a plan view thereof, and (b) is a sectional view taken along line YY ′ of (a). As shown in FIG. 3, the second microlens array substrate B (hereinafter referred to as the second lens substrate B) has a microlens array 8 which is an assembly of hemispherical microlenses 7. It has a lens area 9 formed therein and an alignment area 10 other than the area in which the microlens array 8 is formed. Such a second lens substrate B is formed of BK7 which is optical glass. Note that, in FIG. 3, the microlens array 8 is formed by 7 × 8 microlenses 7 for the sake of explanation, but the actual microlens array 8 is composed of a larger number of microlenses 7.

Alignment marks 11 are formed at the four alignment corners of the second lens substrate B in the alignment area 10 of the second lens substrate B. The alignment mark 11 has a circular hole 11a formed in the second lens substrate B. The diameter of the hole 11a of the alignment mark 11 of the second lens substrate B of the present embodiment is 90 μm. The circular hole 11a is formed by forming a resist pattern in the shape of the hole 11a on the substrate using photolithography and transferring the resist pattern to the substrate by etching. In addition,
Since the photolithography process and the etching process are used when the microlens 7 is formed by using the reflow method or the gradation mask, the pattern of the resist pattern in the shape of the hole 11a may be formed at the same time.
Thereby, the alignment mark 11 can be formed without shifting the relative position with respect to the microlens 7.

Although the side wall of the hole 11a is vertical in FIG. 3, the side wall does not necessarily have to be vertical. Protrusion 6 of alignment mark 5 on first lens substrate A
The side wall may have an inclination or a curved shape as long as it has a shape that makes stable contact with the side wall.

Next, the procedure for bonding the first lens substrate A and the second lens substrate B together will be described with reference to FIGS. First, as shown in FIG. 4, the first lens substrate A
And the second lens substrate B are superposed so that the positions of the alignment mark 5 and the alignment mark 11 are substantially aligned with each other. More specifically, at least the first lens substrate A
It is only necessary that the apex of the protrusion 6 of the alignment mark 5 is inside the hole 11a of the alignment mark 11 of the second lens substrate B. Although the first lens substrate A is placed downward in FIG. 4, either substrate may be placed underneath.

By the way, in the present embodiment, the diameter of the protrusion 6 of the alignment mark 5 on the first lens substrate A is
100 μm, alignment mark 11 on second lens substrate B
Since the diameter of the hole 11a is 90 μm, the accuracy of superposition at this point should be within ± 45 μm. For example, when manufacturing the first lens substrate A and the second lens substrate B, dicing is performed so that the distances from the end surfaces of the first lens substrate A and the second lens substrate B to the alignment marks 5 and 11 are the same. Easy to cut by using a saw and overlap by using the jig to align the end faces.
It is possible to obtain an accuracy of about 10 μm.

Next, as shown in FIG. 5, the alignment mark 5 on the first lens substrate A and the alignment mark 11 on the second lens substrate B are aligned with each other. More specifically, when the surface of the alignment mark 5 of the first lens substrate A and the surface of the alignment mark 11 of the second lens substrate B are smooth and have little friction, as shown in FIG. When the second lens substrate B and the second lens substrate B are superposed on each other, the alignment marks 5 on the first lens substrate A are aligned with the alignment marks 11 on the second lens substrate B by the weights of the substrates A and B.
Therefore, the alignment mark 5 on the first lens substrate A and the alignment mark 11 on the second lens substrate B coincide with each other. On the other hand, when there is a lot of friction on the surface of the alignment mark 5 of the first lens substrate A and the surface of the alignment mark 11 of the second lens substrate B, the alignment marks 5 of the first lens substrate A due to the weight of each substrate A and B. Is the alignment mark 11 on the second lens substrate B.
It does not slip on the substrate, and the substrates A and B are moved by giving vibrations to the substrates A and B, so that the alignment mark 5 of the first lens substrate A and the alignment mark 11 of the second lens substrate B To match.

In order to accurately align the alignment mark 5 on the first lens substrate A with the alignment mark 11 on the second lens substrate B, as shown in FIG. 5, the first lens substrate A and the second lens substrate A are aligned. It is desirable that there is a slight gap between the substrate B and the substrate.

Finally, as shown in FIG. 6, after the alignment mark 5 on the first lens substrate A and the alignment mark 11 on the second lens substrate B are aligned, the adhesive 20 is applied to the end faces of the substrates A and B. Is applied to bond the first lens substrate A and the second lens substrate B together.

FIG. 7 shows an example of a bonding apparatus for bonding the first lens substrate A and the second lens substrate B as described above. Laminating apparatus 30 shown in FIG.
Is a substrate holding means 31 for holding a lower substrate (for example, the first lens substrate A), an end face of the substrate (for example, the first lens substrate A) held by the substrate holding means 31, and this substrate ( For example, the abutting means 32 for abutting the end surface of the substrate (for example, the second lens substrate B) superposed on the first lens substrate A) to perform a rough alignment.
And a vibration generating means 3 for applying vibration to each of the substrates A and B.
3, a substrate fixing means 34 for pressing the two substrates A and B so as not to move after alignment, and a moving means 35 for vertically moving the substrate fixing means 34. Here, the substrate holding means 31 is a lower substrate (for example, the first lens substrate A) by means such as vacuum suction.
Is to fix. Further, as the vibration generating means 33, since it is necessary to set the displacement amount to about several μm, a piezo stage or the like can be used. By using such a bonding apparatus 30, it is possible to realize the procedure of bonding the first lens substrate A and the second lens substrate B as described above.

Although not specifically shown, the laminating apparatus 30 may include an adhesive applying means for applying an adhesive, an adhesive curing means for curing the adhesive, and the like.

With this method, the alignment marks 5 and 11 of the two substrates A and B can be accurately measured even when using a low-precision alignment device such as simply aligning the end faces of the substrates with a jig. Can be matched. When the photolithography of the alignment mark portion is performed at the same time when the microlens is manufactured, the alignment marks 5 and 11 are created with the same positional accuracy as the photomask. Therefore, even when an alignment device with an error of about 10 μm is used, it is possible to easily perform high-precision alignment with an error of several μm or less.

A convex first alignment mark 5 is formed on the first substrate A, which is one of the two microlens substrates A and B for alignment, and the other second substrate B is formed. At this point, a concave second alignment mark 11 having a size that allows entry of at least the vicinity of the apex of the first alignment mark 5 is formed. Then, the first substrate A and the second substrate B are caused to enter the inside of the concave second alignment mark 11 near the apex of the convex first alignment mark 5.
And are overlaid. As a result, it becomes possible to make the alignment accuracy of the overlay position highly accurate without using a highly accurate stage or an optical system for observing marks.

In this embodiment, a thermoplastic resin for forming the projections 6 of the alignment mark 5 by forming the groove 5a at the alignment mark position of the microlens substrate A by the photolithography process and the etching process. Although the alignment mark 5 can be formed at an accurate position even if the position where P is attached is slightly deviated, if the position accuracy when attaching the thermoplastic resin P is sufficient for the required alignment accuracy, Groove 5a
It does not matter if the formation is not made.

Next, a second embodiment of the present invention will be described with reference to FIGS. The same or corresponding portions as those in the above-described embodiment are indicated by the same reference numerals,
The description is also omitted (the same applies to each of the following embodiments). The two substrates of this embodiment are used to fabricate an objective lens that is an optical element used in an optical pickup that optically records, reproduces, or erases information by irradiating a light spot on the recording surface of the information recording medium. It is applied to two microlens substrates for

Nowadays, with the increase in capacity of optical discs (increased optical recording density), it is necessary to make the size of the spot condensed by the objective lens as small as possible. Therefore, by constructing the objective lens of the present embodiment with a plurality of lenses,
The numerical aperture NA of the objective lens is increased to make the size of the spot condensed by the objective lens as small as possible.

Schematically, as shown in FIG. 8, the objective lens 40 includes a first lens 42 formed on a first microlens substrate 41 (hereinafter referred to as a first lens substrate 41). , The second lens 44 formed on the second microlens substrate 43 (hereinafter, referred to as the second lens substrate 43) and the first lens substrate 41 are arranged so as to face each other on the same optical axis. It has a structure in which the second lens substrate 43 and the second lens substrate 43 are attached by an adhesive 45.

First, the first lens substrate 41 will be described. Here, FIG. 9 is a plan view showing the first lens substrate 41. As shown in FIG. 9, the first lens substrate 41 has a lens area 46 in which a hemispherical microlens 42 is formed and an alignment area 47 other than the area in which the microlens 42 is formed. is doing. Such a first lens substrate 41 is made of BK7 which is optical glass.

Alignment marks 48 are formed on the alignment areas 47 of the first lens substrate 41 and at the four corners of the first lens substrate 41. The alignment mark 48 has a groove 48a which is a ring-shaped recess formed in the first lens substrate 41, and a circular groove 48b in which a portion surrounded by the groove 48a is formed.
Further, the groove 48b is filled with a hot melt adhesive which is a thermoplastic resin, and a projection 48c formed in a hemispherical shape by surface tension is formed. This protrusion 48
Since the range in which the thermoplastic resin flows is limited to the inside of the groove 48a by the surface tension and the portion c can be formed into a hemispherical shape having the portion surrounded by the groove 48a as the bottom side, the shape of the center of the groove 48a and the shape of the hemispherical shape is The vertices of the protrusion 48c can be accurately matched.

Although the procedure for forming the alignment mark 48 is not particularly shown, a resist pattern in the shape of the grooves 48a and 48b is formed on the substrate by using photolithography, and after transferring the resist pattern to the substrate by etching, After filling the hot melt adhesive which is a thermoplastic resin and heating the substrate, the substrate is cooled and the thermoplastic resin is cured, whereby the alignment mark 48 is obtained.
Is completed. Since the photolithography process and the etching process are used when the microlens 42 is formed using the reflow method or the gradation mask,
At the same time, a resist pattern having the shape of the grooves 48a and 48b may be formed. Accordingly, the alignment mark 48 can be formed without shifting the relative position with respect to the microlens 42.

Next, the second lens substrate 43 will be described. Here, FIG. 10 is a plan view showing the second lens substrate 43. As shown in FIG. 10, the second lens substrate 43 is
It has a lens area 49 in which a hemispherical microlens 44 is formed and an alignment area 50 other than the area in which the microlens 44 is formed. Such a second lens substrate 43 is formed of BK7 which is optical glass.

Alignment marks 51 are formed at the four corners of the second lens substrate 43 in the alignment area 50 of the second lens substrate 43. The alignment mark 51 has a circular hole 51 a formed in the second lens substrate 43. This circular hole 51a
Is formed by forming a resist pattern in the shape of the hole 51a on the substrate using photolithography and transferring the resist pattern to the substrate by etching.
When the microlens 44 is formed by using the reflow method or the gradation mask, the photolithography process and the etching process are used.
It is only necessary to form a resist pattern having a shape of a. Thereby, the alignment mark 51 can be formed without shifting the relative position with respect to the microlens 44.

Next, a procedure for bonding the first lens substrate 41 and the second lens substrate 43 will be described with reference to FIG. First, as shown in FIG. 11A, the first lens substrate 41 and the second lens substrate 43 are superposed so that the positions of the alignment mark 48 and the alignment mark 51 are substantially aligned with each other. More specifically, at least the protrusion 48 of the alignment mark 48 on the first lens substrate 41.
The apex of c is the alignment mark 5 on the second lens substrate 43.
It suffices if it is inside the first hole 51a. Note that FIG.
In the above, the first lens substrate 41 is placed downward, but either substrate may be placed below.

When the surface of the alignment mark 48 of the first lens substrate 41 and the surface of the alignment mark 51 of the second lens substrate 43 are smooth and have little friction,
At the stage where the first lens substrate 41A and the second lens substrate 43 are superposed, the alignment mark 48 of the first lens substrate 41 naturally slides into the alignment mark 51 of the second lens substrate 43 due to the weight of each substrate 41, 43. As a result, the alignment mark 48 on the first lens substrate 41
And the alignment mark 51 on the second lens substrate 43 match. On the other hand, when there is much friction on the surface of the alignment mark 48 of the first lens substrate 41 and the surface of the alignment mark 51 of the second lens substrate 43, each of the substrates 41, 4
The alignment mark 48 of the first lens substrate 41 is aligned with the alignment mark 5 of the second lens substrate 43 due to its own weight.
It does not slip into 1, and by moving each substrate 41, 43 by giving vibration to each substrate 41, 43,
The alignment mark 48 on the first lens substrate 41 and the alignment mark 51 on the second lens substrate 43 are aligned.

In order to accurately align the alignment mark 48 on the first lens substrate 41 with the alignment mark 51 on the second lens substrate 43, as shown in FIG. It is desirable that there is a slight gap with the second lens substrate 43.

Next, as shown in FIG. 11B, after the alignment mark 48 of the first lens substrate 41 and the alignment mark 51 of the second lens substrate 43 are aligned, the alignment mark of the first lens substrate 41 is aligned. 48 protrusions 48
Transform c. The protrusion 48c of the alignment mark 48 on the first lens substrate 41 is deformed by heating.
May be softened and deformed, or the protrusion 48c may be deformed by pressurization. Here, since the protrusion 48c is formed by the hot melt adhesive which is a thermoplastic resin, the protrusion 48c is formed by heating.
To soften and deform.

The protrusion 48 of the alignment mark 48
The amount of deformation of c can be controlled by the pressure applied to the substrates 41 and 43, the heating temperature, the time for which they are applied, and the like, but in order to perform it more accurately, the first lens substrate 41 and the second lens substrate It is desirable to deform while measuring the distance to 43.

When the projections 48c of all the alignment marks 48 are deformed at once, the substrates 41 and 43 are
May shift laterally. In such a case, the misalignment can be reduced by not deforming the protrusions 48c of all the alignment marks 48 collectively but deforming them into several groups and deforming each group.

Finally, as shown in FIG. 11C, the protrusion 48c of the alignment mark 48 is completely crushed and the surfaces of the upper and lower substrates 41 and 43 are butted against each other to form the protrusion 48c.
The first lens substrate 41 and the second lens substrate 43 are attached to each other by a hot melt adhesive which is a thermoplastic resin forming the.

However, the hot melt adhesive, which is the material for forming the protrusion 48c of the alignment mark 48, should not be left as much as possible between the butted substrates 41 and 43.
Alignment mark 4 formed on the first lens substrate 41
It is necessary to allow excess hot melt adhesive to enter the groove 48a of No. 8 and the hole 51a of the alignment mark 51 formed on the second lens substrate 43.

As shown in FIG. 12, the hole 51a of the alignment mark 51 formed on the second lens substrate 43 is formed.
Since the volume of the hole 51a can be increased by making the shape of the rectangular mark or the like, the alignment mark 4
The hot melt adhesive, which is the material for forming the protrusion 48c of No. 8, can be made to enter much into the hole 51a of the alignment mark 51. In this case, it is not necessary to finely control the height of the protrusion 48c of the alignment mark 48 and the pressure and temperature when pressing the substrate.

FIG. 13 shows an example of a bonding apparatus for bonding the first lens substrate 41 and the second lens substrate 43 as described above. The bonding apparatus 60 shown in FIG. 13 has a lower substrate (for example, the first lens substrate 41).
Substrate holding means 31 for holding the substrate and substrate holding means 3
The end surface of the substrate (for example, the first lens substrate 41) held by 1 and the end surface of the substrate (for example, the second lens substrate 43) superposed on this substrate (for example, the first lens substrate 41) are butted against each other, An abutting unit 32 for performing rough alignment, a vibration generating unit 33 for applying vibration to the substrates 41 and 43, and two substrates 4 after alignment.
Substrate fixing means 34 for pressing 1 and 43 so as not to move and moving means 35 for vertically moving the substrate fixing means 34 are provided. Here, the substrate holding means 31 fixes the lower substrate (for example, the first lens substrate 41) by means such as vacuum suction. Further, as the vibration generating means 33, since it is necessary to set the displacement amount to about several μm, a piezo stage or the like can be used.

In addition, the bonding device 60 includes a heating means 61 such as a heater for heating the protrusion 48c of the alignment mark 48 formed on the first lens substrate 41.
And pressurizing means 62 for vertically applying pressure to the substrates 41 and 42. Here, the pressurizing means 62 needs to prevent the substrates 41 and 43 from moving horizontally when pressure is applied. A vacuum chuck or the like may be used as the substrate fixing means 34 so that the substrates 41 and 43 can be fixed. It should be noted that a measuring unit for measuring the change in the position of the substrate fixing unit 34 may be provided so that the change in the substrate interval due to the pressurization can be measured. Also, the heating means 61
Needs to be able to be overheated to such an extent that the material is softened according to the material used for forming the protrusion 48c of the alignment mark 48 formed on the first lens substrate 41. In the case where a material such as indium that is easily deformed by pressure is used as the material for forming the protrusion 48c of the alignment mark 48 formed on the first lens substrate 41, and the necessary surface spacing can be adjusted only by pressurization, It is not necessary to provide the heating means 61.

If such a bonding device 60 is used, the first lens substrate 41 and the second lens substrate 4 as described above are used.
It is possible to realize a procedure of bonding with No. 3.

Although not particularly shown, the laminating apparatus 60 may include an adhesive applying means for applying an adhesive, an adhesive curing means for curing the adhesive, and the like.

In an optical pickup application in which a light spot is irradiated on the recording surface of an information recording medium to optically record, reproduce or erase information, it is necessary to suppress wavefront aberration in order to obtain a focused spot close to the resolution limit. Therefore, high accuracy is required for the distance between the lens surfaces. Therefore, in the present embodiment, after the substrates 41 and 43 are aligned, the alignment marks 48 are deformed by applying pressure or heating to adjust the surface spacing.

Next, a third embodiment of the present invention will be described with reference to FIG.
It will be described based on. This embodiment shows a method using a photoresist as another method for producing a microlens substrate having a convex alignment mark as described above.

As shown in FIG. 14A, first, a concave surface 82 is formed on a glass substrate 81, a resin 83 having a high refractive index is embedded therein to form a microlens, and then a cover glass 8 is formed.
Attach 4.

Next, for example, a photoresist 85 is applied to the surface on the side where the CCD is bonded (see FIG. 14B), and exposed and developed so that the photoresist 85 at the alignment mark position remains (see FIG. 14B). 14 (c)), and finally, baking is performed at a high temperature to flow the photoresist 85 to complete the microlens substrate 80 having the hemispherical alignment mark 86 (FIG. 14 (d)).

Since elements such as CCDs and liquid crystal panels manufactured by using a semiconductor process are manufactured by repeating a film forming process, a photolithography process and an etching process several times, it is easy to form a concave alignment mark. Can be created. For example, the pattern of the alignment mark may be formed at the same time when the opening pattern for taking out the electrode portion is formed in the passivation film for protecting the surface of the element. Thereby, the alignment mark 86 can be formed without shifting the relative position with respect to the microlens.

Therefore, if a convex alignment mark 86 is formed in advance on the side of the microlens substrate 80 to be used by bonding with an element manufactured by using a semiconductor process such as CCD or liquid crystal panel, bonding can be performed. It will be easier.

Here, since the shape of the first alignment mark 86 of the first substrate 80 can be accurately made into a substantially hemispherical shape by a simple method, the alignment accuracy of the overlay position can be further improved. It becomes possible to

[0074]

According to the first aspect of the present invention, there is provided a method of stacking two substrates having a microlens on at least one side, which serves as a reference for positioning the microlens on the first substrate. A first alignment mark forming step of forming a convex first alignment mark having a substantially hemispherical shape, and at least a vertex of the first alignment mark serving as a reference for alignment of the microlenses on the second substrate. A second alignment mark forming step of forming a concave second alignment mark formed in a size that allows the invasion of the vicinity, the first alignment mark of the first substrate and the second substrate The second alignment mark is opposed to the second alignment mark, and at least the vicinity of the apex of the first alignment mark is included in the second alignment mark. The first substrate, which is one of the two substrates to be aligned, including a first substrate having a convex shape, and a substrate superposing step of superposing the first substrate and the second substrate on each other. Is formed on the other second substrate, and a concave second alignment mark is formed on the other second substrate so as to have a size that allows entry at least near the apex of the first alignment mark. Then, a high-accuracy stage is obtained by causing the vicinity of the apex of the convex first alignment mark to enter the inside of the concave second alignment mark and superposing the first substrate and the second substrate. The alignment accuracy of the overlay position can be made high without using an optical system or the like for observing the marks.

According to a second aspect of the invention, in the substrate superimposing method according to the first aspect, the first alignment mark forming step includes a photolithography process and an etching process for the first substrate. A step of forming a ring-shaped recess using the step of forming a ring-shaped recess, a step of applying a thermoplastic material to the inside of the recess formed in the first substrate, and a step of applying a thermoplastic material to the inside of the recess. Hemispherical shape forming step of heating the thermoplastic material and melting it to form the thermoplastic material into a substantially hemispherical shape by surface tension, thereby forming the shape of the first alignment mark of the first substrate. Since the substantially hemispherical shape can be accurately obtained by a simple method, the alignment accuracy of the overlay position can be further increased.

According to a third aspect of the present invention, in the substrate superimposing method according to the first aspect, the first alignment mark forming step applies a photoresist to the surface of the first substrate. A step, an exposure / development step of exposing and developing the photoresist so that the photoresist except the position corresponding to the first alignment mark is removed, and a substantially hemispherical shape by heating the photoresist. And the step of forming a hemispherical shape, the shape of the first alignment mark on the first substrate can be accurately formed into a substantially hemispherical shape by a simple method. Can be made even more precise.

According to the invention described in claim 4, in the method of stacking the substrates according to any one of claims 1 to 3, the substrate formed on the first substrate after the substrate stacking step is completed. The distance between the first substrate and the second substrate can be easily adjusted by further including a distance adjusting step of deforming the first alignment mark and adjusting the distance between the first substrate and the second substrate. Can be done.

According to a fifth aspect of the present invention, in the method of superposing the substrates according to the fourth aspect, in the gap adjusting step, the first substrate and the second substrate are placed with respect to an overlapping surface thereof. By vertically pressing and deforming the first alignment mark, the gap between the first substrate and the second substrate can be reliably adjusted.

According to a sixth aspect of the present invention, in the method of superimposing the substrates according to the fourth aspect, in the gap adjusting step, the first substrate and the second substrate are placed with respect to an overlapping surface thereof. By vertically pressing, heating and melting the first alignment mark, and deforming the first alignment mark, the gap between the first substrate and the second substrate is surely adjusted. You can

According to the seventh aspect of the present invention, in an optical element having at least one pair of microlenses, one pair of the microlenses and a substantially hemisphere serving as a reference for aligning the microlenses. A first substrate having a convex first alignment mark, a pair of the other microlenses, and at least the apex of the first alignment marks serving as a reference for alignment of the microlenses. A second substrate having a concave second alignment mark formed in a size that allows the invasion of the vicinity, and a microlens having a convex first alignment mark on one of the first substrates. And a concave shape formed on the other second substrate at least large enough to allow entry near the apex of the first alignment mark. The second alignment mark is formed together with the microlens. Then, a high-accuracy stage is obtained by causing the vicinity of the apex of the convex first alignment mark to enter the inside of the concave second alignment mark and superposing the first substrate and the second substrate. The alignment accuracy of the overlay position can be made high without using an optical system or the like for observing the marks.

[Brief description of drawings]

1A and 1B show a first microlens array substrate of a first embodiment of the present invention, FIG. 1A is a plan view thereof, and FIG. 1B is a sectional view taken along line XX ′ of FIG.

FIG. 2 is an explanatory diagram showing a process of creating an alignment mark.

FIG. 3 shows a second microlens array substrate,
(A) is the top view, (b) is sectional drawing in YY 'of (a).

FIG. 4 is a first explanatory diagram showing a bonding procedure of the first lens substrate and the second lens substrate.

FIG. 5 is a second explanatory diagram showing a bonding procedure of the first lens substrate and the second lens substrate.

FIG. 6 is a third explanatory diagram showing a bonding procedure of the first lens substrate and the second lens substrate.

FIG. 7 is a front view showing an example of a bonding apparatus for bonding the first lens substrate and the second lens substrate.

FIG. 8 is a vertical cross-sectional side view showing an objective lens composed of two microlens substrates according to a second embodiment of the present invention.

FIG. 9 is a plan view showing a first lens substrate.

FIG. 10 is a plan view showing a second lens substrate.

FIG. 11 is an explanatory diagram showing a bonding procedure of the first lens substrate and the second lens substrate.

FIG. 12 is a plan view showing a modified example of the second lens substrate.

FIG. 13 is a front view showing an example of a bonding apparatus for bonding the first lens substrate and the second lens substrate.

FIG. 14 is an explanatory diagram showing another method for producing a microlens substrate with a convex alignment mark according to the third embodiment of the present invention.

[Explanation of symbols]

1,7,42,44 Micro lens 5,48,86 First alignment mark 5a, 48a Ring-shaped recess 11,51 Second alignment mark 40 Optical element 41,80, A First substrate 43, B Second substrate 85 photoresist P thermoplastic material

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G02F 1/1335 G02F 1/1335 (72) Inventor Yoshiyuki Kiyozawa 1-3-3 Nakamagome, Ota-ku, Tokyo No. in Ricoh Co., Ltd. (72) Inventor Hironori Mifune 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2H043 AE02 AE18 AE23 2H044 AA02 AA04 AA09 AA11 AA18 AA20 2H088 EA12 FA01 FA16 FA30 HA01 HA25 MA20 2H090 JA04 JA16 JA19 JC12 JD01 LA12 2H091 FA29Z FB07 FC10 FC26 FD06 FD12 FD17 GA01 LA12 MA07

Claims (7)

[Claims] 1. A method for stacking two substrates having a microlens on at least one side, wherein a substantially hemispherical and convex first substrate is used as a reference for alignment of the microlenses. A first alignment mark forming step of forming one alignment mark; and forming a size on the second substrate that allows entry of at least the vicinity of the apex of the first alignment mark, which serves as a reference for alignment of the microlenses. A second alignment mark forming step of forming a concave second alignment mark, and the first alignment mark of the first substrate and the second alignment mark of the second substrate are opposed to each other. , At least the vicinity of the apex of the first alignment mark is intruded into the second alignment mark,
A substrate superposing step of superposing the first substrate and the second substrate on each other. 2. The first alignment mark forming step includes: a concave portion forming step of forming a ring-shaped concave portion on the first substrate by using a photolithography process and an etching process; Inside of the formed recess, a thermoplastic material attaching step of attaching a thermoplastic material, and heating and melting the thermoplastic material attached to the inside of the recess, the thermoplastic material by surface tension And a hemispherical shape forming step of forming the substrate into a substantially hemispherical shape. 3. The first alignment mark forming step comprises a photoresist applying step of applying a photoresist to the surface of the first substrate, and removing the photoresist except a position corresponding to the first alignment mark. 2. The method according to claim 1, further comprising: an exposure / development step of exposing and developing the photoresist as described above; and a hemispherical shape forming step of heating the photoresist to form a substantially hemispherical shape. Substrate stacking method. 4. After the completion of the substrate superposing step, the first alignment mark formed on the first substrate is deformed to adjust the distance between the first substrate and the second substrate. 4. The method of stacking substrates according to claim 1, further comprising a space adjusting step. 5. The gap adjusting step deforms the first alignment mark by pressing the first substrate and the second substrate perpendicularly to an overlapping surface thereof. Item 5. A method of stacking substrates according to item 3 or 4. 6. The gap adjusting step pressurizes the first substrate and the second substrate perpendicularly to an overlapping surface thereof, and heats and melts the first alignment mark, The substrate superposition method according to claim 3, wherein the first alignment mark is deformed. 7. An optical element having at least one set of a pair of microlenses, wherein a pair of said one microlens and a substantially hemispherical convex shape serving as a reference for alignment of these microlenses are provided. A first substrate having one alignment mark; a size that allows entry of at least the vicinity of the apex of the first alignment mark, which serves as a reference for alignment of the other microlens forming a pair with the other microlens And a second substrate having a concave second alignment mark formed on the optical element.