JP2017022313A - Camera module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a camera module capable of reducing aberration.SOLUTION: A camera module includes: an imaging element having a first surface to which light is incident and a second surface of an opposite side to the first surface, being provided with an imaging region onto the first surface and curved into a concave shape at an incidence side of the light as going from a center portion of the imaging region toward a periphery portion of the imaging region; a transparent adhesive layer being provided on micro lenses provided on the first surface and including a material having a refractive index less than that of a material constituting the micro lenses; and a lens member provided on the transparent adhesive layer.SELECTED DRAWING: Figure 1

Description

  The present embodiment relates to a camera module.

The camera module has an image sensor and an imaging lens. The imaging element has an imaging region in which pixels including photoelectric conversion elements are arranged in a matrix on a substrate. The imaging lens is provided on the upper side of the imaging element in order to form an image of the subject on the imaging area.

Light incident on the imaging lens in parallel to the optical axis and light having an angle with respect to the optical axis are incident. For this reason, even when focusing on the center of the imaging region of the imaging device having a planar shape, aberration such as defocusing occurs at the outer peripheral portion in the imaging region.

In a camera module, it is known that aberration generated in an image sensor is corrected by connecting a plurality of imaging lenses. However, connecting a plurality of imaging lenses is difficult and difficult to focus.

JP 2005-64060 A

  This embodiment provides a camera module that can reduce aberration.

The camera module according to the embodiment includes a first surface on which light is incident and a second surface opposite to the first surface.
An imaging device having an imaging area provided on the first surface, curved in a concave shape on the light incident side from the center of the imaging area toward the outer periphery of the imaging area, and on the first surface A transparent adhesive layer including a material having a refractive index lower than that of the material constituting the microlens, and a lens member provided on the transparent adhesive layer.

The cross-sectional schematic diagram which shows the camera module which concerns on 1st Embodiment. The cross-sectional schematic diagram which expanded a part of imaging device which comprises the camera module which concerns on 1st Embodiment. FIG. 3 is a schematic cross-sectional view showing an image sensor that constitutes the camera module according to the first embodiment. The cross-sectional schematic diagram which shows the camera module which concerns on 2nd Embodiment.

(First embodiment)
Hereinafter, embodiments will be described with reference to the drawings. In addition, in each drawing, the same code | symbol is attached | subjected about the same component, and detailed description is abbreviate | omitted suitably.

The camera module according to the first embodiment will be described with reference to FIGS. FIG. 1 is a schematic cross-sectional view showing the camera module according to the first embodiment. FIG. 2 is a schematic cross-sectional view enlarging a part of the image sensor constituting the camera module according to the first embodiment. FIG. 3 shows the first
It is a cross-sectional schematic diagram which shows the image pick-up element which comprises the camera module which concerns on embodiment.

In the first embodiment, the image sensor 1 will be described as a back-illuminated image sensor. The back-illuminated image sensor has a structure in which a wiring layer is provided on the side opposite to the surface of the substrate on which light is incident. The wiring layer will be described later.

As shown in FIG. 1, the camera module 100 includes an imaging lens 21, a lens member 20, and an imaging device 1 that converts incident light incident through the imaging lens 21 into an electrical signal.

The lens member 20 includes a transparent substrate 22. The lens member 20 has a lens holder 23 for fixing the imaging lens 21. The number of imaging lenses 21 may be one, three, or more depending on the performance of the camera lens. Although not shown in the drawing, an IR (Infrared Ray) cut filter is provided on the image pickup device 1 side of the lens holder 23. The transparent substrate 22 has a role of providing the lens member 20 on the image sensor 1.
The material of the transparent substrate 22 is, for example, a glass substrate. In the first embodiment, the lens member 20
However, the present invention can be implemented even if the transparent substrate 22 is not included.

  The transparent adhesive layer 9 is provided on the first surface 2a and the microlens 7 described later.

The transparent substrate 22 is provided on the light receiving side of the image sensor 1 through the transparent adhesive layer 9. Transparent substrate 2
When 2 adheres to the transparent adhesive layer 9, the imaging region 3 of the imaging element 1 is sealed. For this reason, a cavity is not formed between the transparent adhesive layer 9 and the transparent substrate 22. The lens member 20 is provided on the transparent substrate 22. The transparent adhesive layer 9 has a low refractive index, for example, the refractive index is 1.4 or less. Examples of the material having transparency include SiO2 fluoropolymer, silicon resin, polysiloxane resin, and epoxy resin containing hollow silica.

Also, polytetrafluoroethylene (PTFEP) having a refractive index of 1.34, perfluoroalkoxy (PFA) having a refractive index of 1.35, polyvinyl fluoride having a refractive index of 1.33 to 1.38 (
Polyvinyl fluoride resin containing PVF), or perfluoroethylene propene copolymer (PFEP), chlorotrifluoroethylene (CTFE), ethylene chlorotrifluoroethylene (ECTFE), or the like.

Next, the image sensor 1 will be described. As shown in FIG. 2, the imaging device 1 has a first surface 2a.
And a first substrate 2 as a first member having a second surface 2b opposite to the first surface 2a;
A laminated structure in which a wiring layer 5 provided on the surface 2b of the first substrate and a second substrate 10 as a second member provided on the second surface 2b via the wiring layer 5 are joined.

  The first substrate 2 has an imaging region 3 and a circuit region 3a.

The imaging region 3 is a region where pixels including the photoelectric conversion elements 4 are arranged in a matrix. First
In the embodiment, the point where the optical axis and the imaging region 3 intersect is the center. Here, the optical axis is considered as an imaginary line passing through the center and focal point of the imaging lens 21.

The circuit region 3a is a region where circuit elements for operating pixels are provided. A detailed description of the circuit area 3a will be omitted.

The material of the first substrate 2 is, for example, silicon (Si), gallium arsenide (GaAs), gallium phosphide (GaP), gallium nitride (GaN), or silicon germanium (SiGe). As an example of the first embodiment, the first substrate 2 will be described as being composed of silicon (Si).

  The wiring layer 5 is composed of, for example, a wiring 5a, a transistor 5b, and an insulating film.

The transistor 5b has a role of reading out charges accumulated in the photoelectric conversion element 4 when a signal output from the circuit element in the circuit region 3a is input via the wiring 5a.

The second substrate 10 is provided on the second surface 2b with the wiring layer 5 interposed therebetween. The second substrate 10 has a role of bending the first substrate 2 in a concave shape toward the imaging lens 21 side. Thereby, the image sensor 1
The outer peripheral part of the imaging region 3 is curved in a concave shape toward the imaging lens 21 as it goes from the central part of the imaging region 3 to the outer peripheral part of the imaging region 3. The second substrate 10 has a larger thermal expansion coefficient than the first substrate 2, and the thermal expansion coefficient of the second substrate 10 is not less than 3 times and not more than 9 times the expansion coefficient of the first substrate 2. The second substrate 10 is, for example, copper (Cu), gold (Au), or aluminum (Al). As an example of the first embodiment, the second substrate 10 will be described as being made of copper (Cu). The thermal expansion coefficient of silicon is 2.0 to 4.0 (μm / ° C.). The thermal expansion coefficient of copper is 16.0 to 17.0 (μm / ° C.). Here, the thermal expansion coefficient is not limited to the rate at which the length of the object expands per 1 K (Kelvin) due to temperature rise, but also includes the rate at which the volume expands.

The support substrate 8 is provided via the wiring layer 5 on the second surface 2b. In the back-illuminated image sensor, the support substrate 8 has a role of maintaining the strength of the image sensor 1 in order to polish the first substrate 2 thinly.

  The color filter 6 is provided corresponding to the photoelectric conversion element 4 on the first surface 2a.

The micro lens 7 is provided on the color filter 6. The microlenses 7 are provided corresponding to the photoelectric conversion elements 4 via the color filters 6. As shown in FIG. 3, the top of the microlens 7 provided at the center of the imaging region 3 is defined as a first top 7 a, and the top of the microlens 7 provided at the outer periphery of the imaging region 3 is defined as a second top. 7b, the second top
7b is located on the light incident side from the first apex portion 7a. Thereby, when focusing on the center of the imaging region 3, it is possible to suppress curvature of field that occurs at the outer periphery of the imaging region 3. The field curvature will be described later. . The refractive index of the microlens 7 is 1.5 or more, for example, 1.5 to 1
. 6 transparent materials. The material constituting the microlens 7 is, for example, an acrylic resin.

  Next, functions and effects of the camera module according to the first embodiment will be described.

In the camera module 100, the light is collected by passing through the imaging lens 21 and imaged on the upper surface of the image sensor 1. The distance from the center of the imaging lens 21 to the outer periphery of the imaging region 3 is longer than the distance from the center of the imaging lens 21 to the center of the imaging region 3. Therefore, incident light close to the optical axis is focused on the plane of the image sensor 1 perpendicular to the optical axis, but incident light having an angle with respect to the optical axis is not necessarily focused on the plane of the image sensor 1. Without it, an image is formed on the curved surface. This phenomenon is called field curvature. Therefore, when an image is formed by focusing on the center of the imaging region 3 using a lens whose field curvature is not corrected, an image that is out of focus is formed as the distance from the center of the imaging region 3 increases. For this reason, as it goes from the center of the imaging region 3 to the outer peripheral portion of the imaging region 3, the imaging element 1 is curved in a concave shape toward the imaging lens 21, and is incident at an angle with respect to the optical axis. The position where the collected light gathers can be brought close to the image sensor 1. By bending the imaging element 1 into a concave shape, it is not necessary to increase the number of lenses in order to correct the curvature of field, and the occurrence of curvature of field that occurs at the outer periphery of the imaging region 3 can be reduced. In addition, in order to obtain a camera module 100 with high sensitivity by collecting light,
It is desirable that the light refracted on the surface of the microlens 7 is focused on the image sensor. The refraction of light is the refractive index of the material of the microlens 7, the transparent adhesive layer 9 provided on the upper surface of the microlens 7,
It depends on the shape of the microlens 7. When the refractive index of the microlens 7 on the light receiving surface of the image sensor 1 is 1.5 or more, the refractive index of the transparent adhesive layer 9 provided on the microlens 7 is 1.5.
By being below, the condensing property of the micro lens 7 can be improved. Thereby, the camera module 100 with high sensitivity can be provided while reducing the overall height.

(Second Embodiment)
A camera module according to the second embodiment will be described with reference to FIG. FIG. 4 is a schematic cross-sectional view showing a camera module according to the second embodiment.

The camera module according to the second embodiment is different from the first embodiment in that a member 11 is provided between the imaging region 3 and the circuit region 3a. Since the camera module according to the second embodiment is the same as the structure of the camera module according to the first embodiment except for the above points, the same parts are denoted by the same reference numerals and detailed description thereof is omitted.

The imaging device 1 according to the camera module of the second embodiment includes a first substrate 2 as a first member,
This is a laminated structure in which a second substrate 10 as a second member provided on the second surface 2b is joined.

  The first substrate 2 is divided into an imaging area 3 and a circuit area 3a.

The member 11 is provided between the imaging region 3 and the circuit region 3a so as to surround the imaging region 3. The member 11 is made of a black resist such as carbon. Further, aluminum (Al), copper (Cu), silver (Ag), gold (Au), tungsten (W), etc., which are coated with a black resist can also be implemented.

In the second embodiment, the member 11 is provided between the imaging region 3 and the circuit region 3a. By providing the member 11, it is possible to reduce the incidence of light incident on the imaging device 1 by a strong light source and reflected on the lens or the like and entering the imaging region 3. For this reason, flare in which part or the whole of the image becomes whitish can be reduced by reflecting light from the lens surface or the like with a strong light source.

Although the embodiment of the present invention has been described, this embodiment is presented as an example and is not intended to limit the scope of the invention. The novel embodiment can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. This embodiment and its modifications are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Imaging device 2 ... 1st board | substrate 2a ... 1st surface 2b ... 2nd surface 3 ... Imaging region 3a ... Circuit region 4 ... Photoelectric conversion element 5 ..Wiring layer 5a ... wiring 5b ... transistor 6 ... color filter 7 ... micro lens 7a ... first top 7b ... second top 8 ... support substrate 9 ... Transparent adhesive layer 10 ... second substrate 11 ... member 20 ... lens member 21 ... imaging lens 22 ... transparent substrate 23 ... lens folder 100 ... camera module

Claims (7)

A first surface on which light is incident and a second surface opposite to the first surface, an imaging region is provided on the first surface, and the imaging region from the center of the imaging region An image sensor that is curved in a concave shape on the light incident side toward the outer periphery of
A transparent adhesive layer that is provided on a microlens provided on the first surface and includes a material having a refractive index lower than that of the material constituting the microlens;
A lens member provided on the transparent adhesive layer;
Having a camera module. The camera module according to claim 1, further comprising a member provided between the imaging region and a circuit region adjacent to the imaging region so as to surround the imaging region on the imaging element. The second top of the microlens provided on the outer periphery of the imaging region is positioned closer to the light incident side than the first top of the microlens provided on the center of the imaging region. The camera module according to claim 1 or 2, characterized in that 4. The camera module according to claim 1, wherein the transparent adhesive layer has a refractive index of 1.3 or more and 1.4 or less. The imaging element has a laminated structure of a first member and a second member having the first surface provided with the imaging region, and the second member has a larger thermal expansion coefficient than the first member. The camera module according to any one of claims 1 to 4, characterized in that: The camera module according to claim 5, wherein the second member has a coefficient of thermal expansion that is not less than 3 times and not more than 9 times the thermal expansion coefficient of the first member. The camera module according to claim 5, wherein the imaging element includes a wiring layer between the first member and the second member.

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