JP6435663B2 - Method for manufacturing solid-state imaging device - Google Patents

Description

  The present invention relates to a method for manufacturing a solid-state imaging device using a solid-state imaging device.

In a solid-state imaging device using a solid-state imaging device such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), light reception of a silicon substrate provided with an image sensor including the solid-state imaging device is provided to improve reliability. It is necessary to seal the surface side.
As a method for sealing the light-receiving surface side of the silicon substrate, a plurality of solid-state imaging elements are provided on a silicon wafer, and a spacer called a dam is provided on the cover glass using a photolithographic technique according to the position of the solid-state imaging element. A method of bonding a silicon wafer and a cover glass so that a dam is interposed is known (for example, Patent Document 1). In such a method for manufacturing a solid-state imaging device, the solid-state imaging device is sealed by bonding the silicon wafer and the dam and between the dam and the cover glass with an adhesive.

JP 2011-176229 A

However, generally, fine wiring is provided on a silicon wafer. For this reason, in the manufacturing method of the solid-state imaging device described in Patent Document 1, when the silicon wafer and the dam are bonded, air bubbles enter between the fine wirings on the silicon wafer, resulting in poor sealing performance. The problem is that the performance is reduced.
Accordingly, the present invention has been made paying attention to the unsolved problems of the above-described conventional example, and an object thereof is to provide a method for manufacturing a solid-state imaging device having excellent sealing performance and high reliability.

In order to achieve the above object, a method for manufacturing a solid-state imaging device according to one aspect of the present invention includes: an image sensor provided on a light receiving surface of a silicon substrate; and a cover glass. Liquid curable ink composed of at least one of ultraviolet curable resin and thermosetting resin at the position where at least one dam of the silicon substrate and the cover glass is bonded together through a dam arranged around the image sensor. the screen printing in a vacuum, in a state disposed in the bonding position of the silicon substrate and the cover glass, to form a dam to cure the screen printed curable ink, a curable ink upon screen printing, silicon Screen-print curable ink on the substrate and cover glass, respectively. Before placing the bonding position and scan, and wherein the Rukoto curing the curable ink which is screen printed on either the silicon substrate or the cover glass.

  According to the method for manufacturing a solid-state imaging device according to the present invention, it is possible to provide a method for manufacturing a solid-state imaging device having excellent sealing performance and high reliability.

1 is a schematic cross-sectional view illustrating a solid-state imaging device according to a first embodiment of the present invention. 1 is a schematic cross-sectional view illustrating an image sensor according to a first embodiment of the present invention. It is a schematic cross section which shows the manufacturing method of the solid-state imaging device of the 1st Embodiment of this invention. It is a schematic cross section which shows the manufacturing method of the solid-state imaging device of the 2nd Embodiment of this invention.

DESCRIPTION OF EMBODIMENTS Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings.
<First Embodiment>
[Configuration of solid-state imaging device]
A solid-state imaging device according to a first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 1, the solid-state imaging device includes a silicon substrate 1, an image sensor 2, a dam 3, a cover glass 4, a conductive layer 5, a solder resist 6, and connection terminals 7.
The silicon substrate 1 is silicon on a wafer. A through-substrate via 10 is formed in the silicon substrate 1 by etching or the like. Further, an insulating layer 11 is formed on the mounting surface side of the silicon substrate 1 and the inner surface of the through-substrate via 10 by chemical vapor deposition (CVD).

  The image sensor 2 is provided on the light receiving surface opposite to the mounting surface of the silicon substrate 1. In the example shown in FIG. 1, three image sensors 2n-1, 2n, 2n + 1 are provided apart from each other by a fixed distance, with through-substrate vias 10a, 10b interposed therebetween. As shown in FIG. 2, the image sensor 2 includes a sensor substrate 21 provided on the light receiving surface of the silicon substrate 1, a color filter 22 provided on the sensor substrate 21, and a microlens 23 provided on the color filter 22. Have.

  The sensor substrate 21 is a solid-state imaging device such as a CCD or a CMOS, and has a plurality of pixels arranged two-dimensionally on a plane parallel to the silicon substrate 1. The color filters 22 are, for example, three types of filters corresponding to RGB, and a plurality of color filters 22 are provided in a Bayer-type arrangement according to the pixels of the sensor substrate 21. The microlens 23 is a lens for collecting light and is provided on each color filter 22. In the example shown in FIG. 2, six color filters 22 a to 22 f and six micro lenses 23 a to 23 f are provided in accordance with the six pixels of the sensor substrate 21 in the illustrated cross section.

The dam 3 is an ink made of a liquid epoxy resin having ultraviolet curable and adhesive properties, and is generally a black curable ink. The dam 3 is formed by screen-printing a curable ink onto the silicon substrate 1 in a vacuum, performing a predetermined process to be described later, and then curing by irradiating with ultraviolet rays. The dam 3 is formed along the outer periphery of each image sensor 2 on the plane of the silicon substrate 1. In the example shown in FIG. 1, dams 3a and 3b are formed on the silicon substrate 1 along the outer periphery of the image sensor _2n in the cross section shown.
The cover glass 4 is translucent glass and is disposed to face the silicon substrate 1 and the image sensor 2. For example, an antireflection film or an infrared shielding film may be formed on the surface of the cover glass as necessary.

The conductive layer 5 is made of a conductor such as metal, and is formed on the surface of the insulating layer 11 opposite to the silicon substrate 1 according to the circuit pattern of the solid-state imaging device. Further, the conductive layer 5 is formed so as to close the opening on the side where the image sensor 2 of the through-substrate via 10 is provided. The end of the conductive layer 5 on the opening side is connected to a wiring (not shown) disposed on the silicon substrate 1. The wiring on the silicon substrate 1 is connected to the sensor substrate 21 corresponding to each pixel.
The solder resist 6 is an insulating film formed by a process such as photolithography.
The connection terminal 7 is a terminal by a BGA (ball grid array) system that connects the conductive layer 5 and an external circuit.

A plurality of solid-state imaging devices are formed on a wafer-like silicon substrate 1, and are further diced into a region D indicated by a broken line in FIG. In the example shown in FIG. 1, the silicon substrate, the dams 3a and 3b, and the cover glass 4 on which the conductive layer 5, the solder resist 6, and the connection terminals 7 are formed are diced as indicated by broken lines. Thereby, the solid-state imaging device divided into the regions D _n−1 , D _n and D _{n + 1} is manufactured.
In the solid-state imaging device, the surface of the silicon substrate 1 on which the image sensor 2 is formed is sealed with the dam 3 and the cover glass 4 to form a closed space 8. In the example illustrated in FIG. 1, closed spaces 8 _n−1 , 8 _n , and 8 _{n + 1} are formed in the solid-state imaging devices in the regions D _n−1 , D _n , and D _{n + 1} , respectively. Here, the enclosed space 8 is formed to have a predetermined height L _1.

[Method for Manufacturing Solid-State Imaging Device]
Next, a method for manufacturing the solid-state imaging device according to the first embodiment of the present invention will be described with reference to FIG. First, as shown in FIG. 3A, the image sensor 2 is provided on the light receiving surface of the silicon substrate 1, and an insulating layer is formed on the mounting surface side of the silicon substrate 1. Thereafter, the through-substrate via 10 is formed in the silicon substrate 1, the conductive layer 5 and the solder resist 6 are formed in the mounting surface side of the silicon substrate 1 and in the through-substrate via 10, and the connection terminal 7 is provided on the mounting surface side.

After FIG. 3A, as shown in FIG. 3B, the curable ink which is the dam 3 is screen-printed in vacuum at a position surrounding the image sensor 2 on the light receiving surface side of the silicon substrate 1. At this time, for example, screen printing is performed using a direct vacuum printing method in a vacuum chamber in which the pressure of the atmosphere can be adjusted. The pressure of the atmosphere when the curable ink is screen-printed may be a vacuum pressure, but is preferably less than 30000 Pa. In the example shown in FIG. 3B, the curable inks that are the dams 3a and 3b are screen-printed between the image sensors 2 _n−1 , 2 _n , and 2 _{n + 1 in} the illustrated cross section.

  Here, as the curable ink which is the dam 3, an ink having properties such as viscosity and thixo ratio selected so as to maintain a predetermined shape after screen printing is used. The predetermined shape is a shape that is separated from the image sensor 2 by a predetermined interval immediately after screen printing and has a desired height described later. For example, a curable ink having a viscosity of 30000 mPa · s to 100000 mPa · s and a thixo ratio of 1.7 to 3.5 is used. When the viscosity and thixo ratio ranges are exceeded, the predetermined shape may not be maintained.

  After FIG. 3 (b), as shown in FIG. 3 (c), the silicon substrate 1 and the cover glass 4 are arranged at the bonding position in a vacuum with a curable ink interposed therebetween, and FIG. ). The pressure of the atmosphere at this time is higher than the pressure of the atmosphere when the curable ink is screen-printed, and preferably 3000 Pa or more and 80000 Pa or less. Moreover, as will be described later, the pressure of the atmosphere when the silicon substrate 1 and the cover glass 4 are disposed at the bonding position is set according to the desired height of the closed space 8.

After FIG. 3D, as shown in FIG. 3E, the pressure of the atmosphere is returned to atmospheric pressure, and the curable ink is irradiated with ultraviolet rays and cured to form the dam 3.
Here, when the pressure of the atmosphere changes from the state shown in FIG. 3D to the state shown in FIG. 3E, the height L of the closed space 9 corresponding to the height of the curable ink is increased by increasing the pressure of the atmosphere. _{1, L 2} are changed to be smaller. That is, the pressure of the atmosphere when the silicon substrate 1 and the cover glass 4 are disposed at the bonding position is P ₁ , the atmospheric pressure is P _2, and the volume of the closed space 8 at the pressures P ₁ and P ₂ is V ₁ and V 2. _In the case of ₂ , the relationship of the following formula (1) is established from Boyle-Charles's law under a constant temperature condition. Further, when the volume of the closed space 8 does not change, the following equation (2) is calculated by modifying the equation (1), and the following equation (3) is calculated by further modifying the equation (2).
P ₁ · V ₁ = P ₂ · V ₂ (1)
P ₂ / P ₁ = V ₁ / V ₂ (2)
P ₂ / P ₁ = L ₁ / L ₂ (3)

In the manufacturing method of the solid-state imaging device according to the first embodiment, the height of the curable ink after screen printing and the silicon substrate 1 and the cover glass 4 are arranged at the bonding position using the relationship of the expression (3). by setting the pressure P ₁ when the height of the closed space 9 can be as high L ₂ which desires.
Through the above steps, the silicon substrate 1 and the cover glass 4 are bonded together, and the solid-state imaging device shown in FIG. 1 can be manufactured.
In the first embodiment, the curable ink that is the dam 3 is screen-printed on the silicon substrate 1. However, the curable ink may be screen-printed on the cover glass 4 without printing on the silicon substrate 1.

In the first embodiment, the curable ink is black, but it may be colorless and transparent or other colors. Furthermore, although the curable ink is an ultraviolet curable resin, it may be a thermosetting resin. When a thermosetting resin is used for the curable ink, the dam 3 is formed by applying heat to the curable ink and curing it when returning the atmospheric pressure to atmospheric pressure.
Furthermore, in the first embodiment, the silicon substrate 1 and the cover glass 4 are disposed at the bonding position in a vacuum, but the present invention is not limited to this example. For example, the silicon substrate 1 and the cover glass 4 may be disposed at the bonding position at atmospheric pressure.

  Furthermore, in said 1st Embodiment, after having provided the insulating layer 11, the conductive layer 5, the soldering resist, and the connection terminal 7 in the silicon substrate 1, it was set as the structure bonded together to the cover glass 4 and the silicon substrate 1, It is not limited to such an example. For example, if the image sensor 2 is provided on the silicon substrate 1, the cover glass 4 may first be bonded to the silicon substrate 1, and then the insulating layer 11, the conductive layer 5, the solder resist, and the connection terminal 7 may be provided. .

[Effect of the first embodiment]
The effects of the first embodiment will be described below.
(1) In the manufacturing method of the solid-state imaging device according to the first embodiment, the image sensor 2 provided on the light receiving surface of the silicon substrate 1 and the cover glass 4 are arranged to face each other, so that the silicon substrate 1 and the cover glass 4 Are bonded to each other through the dam 3 disposed around the image sensor 2, at least one of the ultraviolet curable resin and the thermosetting resin is formed at the position where the dam 3 of the silicon substrate 1 and the cover glass 4 is formed. Liquid curable ink is screen-printed in vacuum, and the dam 3 is formed by curing the screen-printed curable ink in a state where the silicon substrate 1 and the cover glass 4 are arranged at the bonding position.

  According to the said structure, adhesion | attachment between curable ink and the silicon substrate 1 or between curable ink and the cover glass 4 is performed in a vacuum. Thereby, it can prevent that a bubble mixes between curable ink and the silicon substrate 1, or between curable ink and the cover glass 4, and can improve sealing performance. Further, since the curable ink is in a liquid state, even when there are fine irregularities on the surface of the silicon substrate 1 or the cover glass 4, bubbles can be prevented from being mixed and the sealing performance can be improved. Furthermore, even if some bubbles are included, the bubbles are reduced to a level that does not cause a problem in quality when the pressure is returned to the atmospheric pressure. Therefore, as in Patent Document 1, bonding is performed at atmospheric pressure using an adhesive. Compared with the case, sealing performance can be improved. The improvement in the sealing performance of the solid-state imaging device can prevent the corrosion of the wiring due to the outside air mixed in the closed space 8, the oxidation of the surface of the silicon substrate 1, the fogging of the cover glass 4, and the like. Can improve the reliability.

Moreover, according to the said structure, the height of a dam can be made high by using curable ink as the dam 3 compared with the case where a dam is created using a photolithographic technique. For this reason, it can respond also to the request | requirement which raises the height of the closed space 8 on imaging quality.
Furthermore, according to the said structure, the dam 3 can be created only by screen-printing curable ink once. On the other hand, when creating a dam using photolithography technology, it is necessary to create a dam through a plurality of processes such as application of a photosensitive material, exposure, and development. Therefore, since the manufacturing method of the solid-state imaging device according to the first embodiment can simplify the process for creating the dam, the manufacturing cost can be reduced.

(2) When placing the silicon substrate 1 and the cover glass 4 at the bonding position, placing the curable ink in a vacuum higher than the pressure of the atmosphere when screen printing, and curing the curable ink Curing under atmospheric pressure.
According to the above configuration, even when the curable ink is not screen-printed on either the silicon substrate 1 or the cover glass 4, when the silicon substrate 1 and the cover glass 4 are bonded together, the dam 3 is interposed between them. It is possible to prevent bubbles from being generated.

(3) When the silicon substrate 1 and the cover glass 4 are disposed at the bonding position, the curable ink is obtained from the relationship between the ratio of the height of the curable ink and the ratio of the pressure before and after returning the pressure to the atmospheric pressure. Placed at a pressure where the desired height is the desired height.
According to the said structure, the height of the closed space 8 which is the height of curable ink can be adjusted by adjusting the pressure at the time of arrange | positioning in a bonding position.

(4) When screen-printing a curable ink, a curable ink having a viscosity of 30000 mPa · s to 100000 mPa · s and a thixo ratio of 1.7 to 3.5 is screen-printed.
According to the above configuration, since the shape of the curable ink after screen printing can be maintained, the desired height of the closed space 8 can be obtained. In addition, the curable ink can be prevented from coming into contact with the image sensor 2.

<Second Embodiment>
[Method for Manufacturing Solid-State Imaging Device]
Next, a method for manufacturing a solid-state imaging device according to the second embodiment of the present invention will be described with reference to FIG. The solid-state imaging device of the second embodiment is different from the first embodiment in the configuration of the dam as will be described later, but the other configurations are the same as those in the first embodiment described in FIGS. 1 and 2. is there.
In the second embodiment, first, as shown in FIG. 4A, the liquid curable ink which is the first dam 31 is screen-printed on the cover glass 4 in a vacuum. The curable ink and printing method of the second embodiment are the same as those of the first embodiment. In the example illustrated in FIG. 4A, curable ink to be the first dams 31 a and 31 b is screen-printed on the cover glass 4. Note that the width of the curable ink to be the first dams 31a and 31b is set to be smaller than the width of the dam 3 described in FIG.

After FIG. 4A, as shown in FIG. 4B, the curable ink which is the second dam 32 is screen-printed on the silicon substrate 1 in a vacuum. The second dam 32 is the same as the dam 3 described in FIG. 3B, and is provided to be larger than the width of the first dam 31. After the second dam 32 is screen-printed on the silicon substrate 1, the second dam 32 is irradiated with ultraviolet rays and cured. After the second dam 32 is cured, the silicon substrate 1 and the cover glass 4 are arranged at a bonding position in a vacuum with the curable ink as the first dam 31 and the second dam 32 interposed therebetween. The state shown in FIG. At this time, the image sensor 2 is sealed by the silicon substrate 1, the cover glass 4, the first dam 31, and the second dam 32 by directly bonding the first dam 31 and the second dam 32 together. A closed space 8 is formed. In addition, the pressure of the atmosphere at the time of arrange | positioning the silicon substrate 1 and the cover glass 4 in a bonding position is the same as that of 1st Embodiment. In the example shown in FIG. 4B and FIG. 4C, the first dam 31a, 31b and the second dam 32a, 32b are bonded to each other in the illustrated cross section, so that the closed space 8 _n is formed.

After FIG.4 (d), as shown in FIG.4 (e), the atmospheric pressure is returned to atmospheric pressure, and the curable ink which is the 1st dam 31 is irradiated with an ultraviolet-ray, and is hardened. At this time, since the curable ink of the second dam 32 has been cured in the previous step, the height of the closed space is reduced to L by changing the height of the curable ink of the first dam 31 due to the pressure change. ₃ changes so as to decrease to L _4.
By passing through the above process, the silicon substrate 1 and the cover glass 4 are bonded together, and the solid-state imaging device of the second embodiment is manufactured.

In the second embodiment, the width of the first dam 31 is smaller than the width of the second dam 32. However, the present invention is not limited to this example. The width of the first dam 31 may be the same as or larger than the width of the second dam 32.
In the second embodiment, the dam 32 on the silicon substrate 1 side is cured before the silicon substrate 1 and the cover glass 4 are disposed at the bonding position. However, the present invention is not limited to this example. Instead of the dam 32 on the silicon substrate 1 side, the dam 31 on the cover glass 4 side may be cured before bonding.

[Effects of Second Embodiment]
The effects of the second embodiment will be described below.
(1) In the method of manufacturing the solid-state imaging device according to the second embodiment, when the curable ink is screen-printed, the curable ink is screen-printed on the silicon substrate 1 and the cover glass 4, respectively. Before placing the glass 4 at the bonding position, the curable ink screen-printed on either the silicon substrate 1 or the cover glass 4 is cured.
With the above configuration, a two-stage dam, that is, the second dam 32 screen-printed on the silicon substrate 1 and the first dam 31 screen-printed on the cover glass 4 can be formed, compared with the first embodiment. The height of the closed space 8 can be increased.

(2) The width of the first dam 31 is formed smaller than the width of the second dam 32.
With the above configuration, it is possible to form the closed space 8 having such a height that the contact area between the cover glass 4 and the first dam 31 can be reduced and the image sensor 2 can be protected. Thus, for example, when the silicon substrate 1 is diced and the cover glass 4 needs to be removed when the solid-state imaging device is made into chips, the cover glass 4 can be easily removed from the solid-state imaging device due to impact during dicing or the like. it can.

1: Silicon substrate 10, 10a, 10b: Through-substrate via 11: Insulating layer 2: Image sensor 21: Sensor substrate 22, 22a-22f: Color filter 23, 23a-23f: Microlens 3, 3a, 3b: Dam 31, 31a, 31b: 1st dam 32, 32a, 32b: 2nd dam 4: Cover glass 5: Conductive layer 6: Solder resist 7, 7a-7d: Connection terminal 8: Closed space

Claims (4)

When the image sensor provided on the light receiving surface of the silicon substrate and the cover glass are arranged to face each other, when the silicon substrate and the cover glass are bonded together via a dam arranged around the image sensor,
A liquid curable ink composed of at least one of an ultraviolet curable resin or a thermosetting resin is screen-printed in a vacuum at the formation position of the dam on at least one of the silicon substrate and the cover glass,
In the state where the silicon substrate and the cover glass are disposed at the bonding position, the screen-printed curable ink is cured to form the dam ,
When screen-printing the curable ink, screen-print the curable ink on the silicon substrate and the cover glass,
Before placing the said cover glass and the silicon substrate to the bonding position the solid-state imaging device according to claim Rukoto curing the curable ink which is screen printed on one of the silicon substrate or the cover glass Manufacturing method. When placing the silicon substrate and the cover glass at the bonding position, placing in a vacuum higher than the pressure of the atmosphere when screen printing the curable ink,
The method for manufacturing a solid-state imaging device according to claim 1, wherein when the curable ink is cured, the curable ink is cured under atmospheric pressure.   From the relationship between the ratio of the height of the curable ink and the ratio of the atmospheric pressure before and after returning the atmospheric pressure to atmospheric pressure when placing the silicon substrate and the cover glass at the bonding position. The solid-state imaging device manufacturing method according to claim 2, wherein the curable ink is disposed at a pressure of an atmosphere in which a desired height of the curable ink is obtained. The screen-printing of the curable ink having a viscosity of 30000 mPa · s or more and 100000 mPa · s or less and a thixo ratio of 1.7 or more and 3.5 or less when screen-printing the curable ink. The manufacturing method of the solid-state imaging device of any one of 1-3 .

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