JP2013077839A - Solid-state imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state imaging apparatus having a uniform characteristic without particular requirement for flattening layer made by a complicated process for severely controlling flatness of a part except a micro-lens in the solid-state imaging apparatus utilizing the micro-lenses arranged in a shape of an array.SOLUTION: In a solid-state imaging apparatus for focusing light with micro-lenses arranged corresponding to photoelectric converting elements for each pixel in a light receiving part, the micro-lenses are arranged within an internal surface in a side of the photoelectric converting elements of a cap glass for a sealing package. This arrangement is particularly suitable for a linear sensor.

Description

  The present invention relates to a solid-state imaging device having a solid-state imaging element in which a photoelectric conversion element composed of a CCD or a CMOS is formed.

  In recent years, imaging devices have been widely used with the expansion of the contents of image recording, communication, and broadcasting. Although various types of imaging devices have been proposed, imaging devices using solid-state imaging devices that have been stably manufactured with small size, light weight, and high performance have become widespread. .

The solid-state imaging device has a plurality of photoelectric conversion elements that receive an optical image from a subject and convert incident light into an electrical signal. The types of photoelectric conversion elements are roughly classified into CCD (charge coupled device) type and CMOS (complementary metal oxide semiconductor) type. In addition, there are two types of photoelectric conversion elements: linear sensors (line sensors) in which photoelectric conversion elements are arranged in a row, and area sensors (surface sensors) in which photoelectric conversion elements are two-dimensionally arranged vertically and horizontally. It is divided roughly into.
In any sensor, the larger the number of photoelectric conversion elements (number of pixels), the more accurate the captured image. In addition, a color sensor that can obtain color information of an object by providing various color filters that transmit light of a specific wavelength in the path of light incident on the photoelectric conversion element is also widespread. As the color of the color filter, three primary colors consisting of three colors of red (R), blue (B), and green (G), or cyan (C), magenta (M), and yellow (Y) are used. A complementary color system is generally used.

  One of the important issues in performance required for a solid-state imaging device is to improve the sensitivity to incident light. In order to increase the amount of information of a photographed image, it is necessary to miniaturize and highly integrate a photoelectric conversion element serving as a light receiving unit. However, when the photoelectric conversion element is miniaturized, the area of each photoelectric conversion element is reduced, and the area for capturing light is reduced. Therefore, the amount of light that can be captured by the photoelectric conversion element is reduced. Further, in a solid-state imaging device provided with a color filter, wavelength separation and absorption of light by the color filter occur when light passes through the color filter, so that the amount of light incident on the photoelectric conversion element decreases. Therefore, the sensitivity to light decreases as a solid-state imaging device.

As a means for preventing such a decrease in the sensitivity of the solid-state imaging device, in order to efficiently capture light into the photoelectric conversion element (light receiving unit), the light incident from the object is condensed and the photoelectric conversion element A technique for forming a microlens leading to a (light receiving unit) has been proposed (see Patent Document 1).
By condensing light with a microlens and guiding it to a photoelectric conversion element (light-receiving part), it becomes possible to increase the apparent aperture ratio (area) of the light-receiving part and improve the sensitivity of the solid-state image sensor. Is possible.

  The photoelectric conversion element converts the incident light into an electrical signal, but when the light does not enter the predetermined photoelectric conversion element and enters a different photoelectric conversion element (for example, an adjacent photoelectric conversion element), Noise is generated. In particular, in the case of a color sensor provided with a color filter, if light that has passed through the color filter enters a different photoelectric conversion element, a problem of color mixing occurs in the obtained image. Such erroneous incidence is likely to occur in light incident on the photoelectric conversion element from an oblique direction. For this reason, in order to prevent obliquely incident light from entering a photoelectric conversion element different from the desired photoelectric conversion element, a technique is proposed in which a light shielding wall is provided between the side edge of the solid-state image sensor and between individual color filters. (See Patent Document 2).

  When a foreign substance such as dust adheres to the solid-state imaging element on which the photoelectric conversion element is formed, the foreign substance blocks light and noise such as a black spot is generated in the photographed image. For this reason, a sealed (packaged) solid-state imaging device that prevents foreign matter from adhering to the solid-state imaging device is used. FIG. 2 schematically shows a cross-sectional view of an example of a sealed (packaged) solid-state imaging device.

  In the solid-state imaging device 12 of FIG. 2, a solid-state imaging device 4 in which a plurality of photoelectric conversion elements 1 are formed on a silicon (Si) substrate is placed on a wiring substrate 10 having an electrical wiring portion 5. The solid-state imaging device 4 and the electrical wiring unit 5 are electrically connected (not shown), and an electrical signal from the solid-state imaging device 4 is transmitted to the electrical wiring unit 5.

  A sealing portion 6 made of a resin or the like is formed on the wiring substrate 10 around the solid-state imaging device 4, and the sealing portion 6 and the wiring substrate 10 form a space portion. The space is an open space above the solid-state image sensor 4 so that light incident on the solid-state image sensor 12 reaches the photoelectric conversion element 1. A transparent cap glass 3 that transmits light is provided above the solid-state imaging device 4, and a sealing space is formed by the cap glass 3, the sealing portion 6, and the wiring substrate 10, and solid-state imaging is performed in the sealing space. Element 4 is placed. This prevents foreign matter from adhering to the solid-state imaging device 4.

  The solid-state image sensor 4 is provided with a plurality of color filters 7 of a predetermined color for transmitting light of a specific wavelength corresponding to each photoelectric conversion element 1. Further, as described above, the light shielding wall 8 is provided between the side end portion of the solid-state imaging device 4 and the individual color filters 7 in order to shield obliquely incident light. For the formation of the color filter, a photolithographic method is widely used in which a colored photosensitive resin is applied, pattern exposure is performed on the coating film, development is performed, and the remaining coating film is used as a color filter. There has also been proposed a technique in which resins having different colors are laminated to form the light shielding wall 8 when forming a color filter.

  In the solid-state imaging device 4, microlenses 2 for condensing incident light and guiding them to the photoelectric conversion device 1 are formed corresponding to the individual photoelectric conversion devices 1. When forming the microlens, if the base surface on which the microlens is formed has irregularities, it becomes difficult to form the microlens into a desired shape. Therefore, the planarizing layer 9 is provided on the color filter 7 and the microlens 2 is formed on the flat surface. In the example of FIG. 2, the flattening layer 9 flattens unevenness not only on the color filter 7 but also on the light shielding wall 8.

JP 2004-207461 A JP 2005-353799 A

  The height (thickness) of each color filter is not necessarily uniform, and the height (thickness) varies for each color to obtain the desired spectral characteristics, or the height (thickness) varies when forming the color filter. In some cases, a light shielding wall may be provided on the color filter, and the flatness of the surface of the color filter is greatly impaired. As described above, the flattening layer 9 formed on the color filter 7 is provided for flattening the base surface on which the microlens is formed. However, when the flatness of the color filter surface is greatly impaired, In order to give flatness to the surface of the planarizing layer 9, it is necessary to increase the thickness of the planarizing layer 9.

In forming the planarizing layer 9, a technique of applying a transparent resin is often used. When the flattening layer 9 is formed by application of a transparent resin, the flattening layer 9 may be formed by a single application, but when the viscosity of the transparent resin is low, the transparent resin is applied in several steps. Then, the planarizing layer 9 in which a transparent resin is laminated is performed.

  The shape and height of the microlens 2 are set in advance depending on the distance from the bottom surface of the microlens to the photoelectric conversion element (light receiving unit). Therefore, when a plurality of solid-state imaging devices are manufactured after the shape and height of the microlens 2 are set, the thickness of the planarization layer 9 varies for each solid-state imaging device. Variations occur, resulting in variations in the performance of individual solid-state imaging devices.

  Therefore, the flattening layer forming process must be strictly controlled, and the burden on the manufacturing process of the solid-state imaging device is large. In addition, when a planarization layer is formed by laminating a transparent resin, the number of processes increases by that amount, so that the manufacturing process becomes complicated and the burden of the manufacturing process becomes larger. In order to strictly control the formation process of the planarization layer, various control devices and drive devices are required, which requires equipment costs. In addition, the number of steps increases, resulting in an increase in the manufacturing cost of the solid-state imaging device. It might be.

  In addition, the shorter the distance between the microlens 2 and the photoelectric conversion element 1 (light receiving unit), the more light is collected by the microlens and incident on the photoelectric conversion element (light receiving unit) (so-called light transmission). The capture angle will increase). However, if the thickness of the flattening layer 9 is increased in order to give flatness to the surface of the flattening layer 9, the distance between the microlens 2 and the photoelectric conversion element 1 (light receiving portion) is increased by that amount. The amount of light that is collected and incident on the photoelectric conversion element (light receiving unit) is reduced.

  The present invention has been made in view of the above problems, and the problem is that a complicated manufacturing process of forming a flattening layer is unnecessary, and there is no variation in the light collecting property of the microlens. An object of the present invention is to obtain a solid-state imaging device having characteristics and improved light collecting performance.

In order to solve the above problem, the invention according to claim 1
A solid-state imaging device on which a plurality of photoelectric conversion elements are formed is placed, and a space part opened above the solid-state imaging element so that incident light enters the photoelectric conversion element, and provided above the space part. A solid-state imaging device having a cap glass that transmits incident light, wherein the micro-lens corresponding to the photoelectric conversion element is arranged on the surface of the cap glass on the photoelectric conversion element side. is there.
According to a second aspect of the present invention, there is provided a solid-state imaging device characterized in that the solid-state imaging element according to the first aspect is a linear sensor.

  According to the solid-state imaging device of the present invention, the microlens for condensing incident light on the photoelectric conversion element (image receiving portion) and improving the apparent aperture ratio is disposed on the cap glass with a flat surface. The formation layer is unnecessary. Therefore, when manufacturing individual solid-state imaging devices, a complicated process for obtaining a planarized layer having a flat surface and a uniform thickness is not necessary, and the manufacturing process can be shortened. In addition, the flat surface that supports the microlens is a cap glass with good flatness, and the flatness of the flattening layer is one of the factors that make the distance between the microlens and the photoelectric conversion element (image receiving portion) non-uniform. Therefore, it is easy to form a uniform distance between the microlens and the photoelectric conversion element (image receiving unit) in each solid-state imaging device. Therefore, it is possible to easily obtain a solid-state imaging device with low manufacturing cost and uniform performance.

In addition, since the distance between the microlens and the photoelectric conversion element (image receiving portion) can be shortened by the amount of not forming the planarizing layer, the light capturing angle is increased, and the light condensing property to the photoelectric conversion element (image receiving portion) is increased. Can be improved, and a solid-state imaging device with high sensitivity can be obtained.

  Furthermore, the microlens of the same shape was formed by unifying (standardizing) the distance between the cap glass and the photoelectric conversion element (image receiving portion) or by changing the height of the sealing portion 6 of the cap glass as needed. Cap glass can be applied to other types of individual imaging devices, and a solid-state imaging device with low manufacturing cost can be obtained. In that case, the thickness control in the manufacturing process may be performed preferentially in the thickness control of the color filter.

  In linear sensors (line sensors) in which photoelectric conversion elements are arranged in a row, a light shielding wall is often formed on the color filter to prevent noise such as color mixing due to obliquely incident light. The unevenness becomes larger. Therefore, it can be said that it is particularly effective to apply the present invention to a solid-state imaging device in which the solid-state imaging element is a linear sensor.

Cross-sectional explanatory drawing which shows typically an example of the solid-state imaging device of this invention. Cross-sectional explanatory drawing which shows an example of the conventional solid-state imaging device typically.

  An example of an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a cross-sectional view schematically showing an example of the solid-state imaging device of the present invention.
The solid-state imaging device 4 shown in FIG. 1 is a linear sensor in which a photoelectric conversion device 1 (light receiving unit) having a CCD or CMOS structure is arranged in a row on a substrate made of Si (silicon). The solid-state imaging device 4 is placed on a wiring board 10 having an electrical wiring portion 5. The solid-state imaging device 4 and the electrical wiring unit 5 are electrically connected (not shown), and an electrical signal obtained by the photoelectric conversion element 1 is transmitted to the electrical wiring unit 5. The electrical wiring unit 5 is connected to a terminal unit for electrical connection with an external device.

  Next, in order to perform color separation of incident light above each photoelectric conversion element 1, a three-primary color filter 7 composed of three colors of red (R), blue (B), and green (G) is provided in a predetermined manner. It is formed by color arrangement. Each color filter 7 is a photolithographic method in which red (R), blue (B), and green (G) colored photosensitive resins are used, and pattern exposure and development are performed and the remaining colored photosensitive resin film is a color filter. Formed. In addition, a light shielding wall 8 is provided between the side end of the solid-state imaging device 4 and each color filter 7 in order to shield obliquely incident light. The light shielding walls 8 between the color filters 7 were formed by laminating the resins having different colors while forming the color filters. The light shielding wall 8 at the side end of the solid-state imaging device 4 is formed by remaining and laminating colored resins of respective colors when forming the color filters.

  A sealing portion 6 made of resin or the like is formed on the wiring substrate 10 around the solid-state imaging device 4. A space portion is formed by the sealing portion 6 and the wiring substrate 10. The space portion is a space opened above the solid-state imaging device 4 so that light incident on the solid-state imaging device 12 reaches the photoelectric conversion element 1. Next, a transparent cap glass 3 that transmits light is provided above the solid-state imaging device 4 through the sealing portion 6. When a sealing agent is used for bonding the sealing portion 6 and the cap glass 3, the sealing agent may be provided on the sealing portion 6 side, the cap glass 3 side, or the sealing portion 6 side. You may provide in both the cap glass 3 side. The cap glass 3, the sealing part 6, and the wiring substrate 10 form a sealing space, and the solid-state imaging device 4 is placed in the sealing space.

  In the present invention, the microlens is not provided on the color filter via the planarizing layer, and the microlens is provided on the surface of the cap glass 3 on the solid-state image sensor 4 side as shown in FIG. 2 is formed. The microlens can be formed by using a thermal reflow method in which a resin pattern formed on glass by photolithography is heated to form a lens shape by the surface tension of the melted resin. Alternatively, the glass surface may be formed in a lens shape by a dry etching method in which dry etching is performed on the glass using a lens matrix made of a resin formed on the glass by a thermal reflow method as a mask. can do.

  The surface of the cap glass is flat, and even if it is not flat, it is easy to polish the glass surface before forming the microlens or press the curved glass to make it flat. It becomes easy to form a good microlens.

  In the present invention, it is necessary to bond the cap glass 3 on which the microlenses are formed so that each microlens and each photoelectric conversion element correspond to each other, and the positional accuracy of the bonding is required. However, in the case of a linear sensor, since the pixel arrangement pitch (photoelectric conversion element arrangement pitch) is about 25 μm to 75 μm, it can be said that bonding is easy.

  Although the embodiment of the present invention has been described above, the present invention is not limited to this, and various modifications may be made based on the spirit of the present invention. For example, in this embodiment, a space for mounting the solid-state imaging device 4 is formed by the wiring board 10 and the sealing portion 6. However, the solid-state imaging device 4 may be mounted in a package having a recess made of ceramic, plastic, or the like to form a solid-state imaging device. In this case, the concave portion of the package corresponds to the space portion referred to in the present application. That is, the solid-state imaging device 4 is placed on the bottom of a concave portion of a package made of ceramic or the like, and the opening of the concave portion is sealed with a cap glass 3 having a microlens formed so that the microlens faces the solid-state imaging device 4 side. You can stop it.

Further, the height of the sealing portion 6 or the depth of the concave portion of the package is also set as appropriate so that incident light is condensed on the photoelectric conversion element 1 in order to double the gap between the photoelectric conversion element 1 and the microlens 2. It doesn't matter. Furthermore, as the material of the sealing portion, a material that can be easily formed at a predetermined height and has little fluctuation in height after formation may be selected as appropriate. Further, the color filter may be a complementary color system composed of cyan (C), magenta (M), and yellow (Y), and the solid-state imaging device has photoelectric conversion elements arranged two-dimensionally vertically and horizontally. It is also possible to use an area sensor (surface sensor).

DESCRIPTION OF SYMBOLS 1 ... photoelectric conversion element 2 ... micro lens 3 ... cap glass 4 ... solid-state image sensor 5 ... electric wiring part 6 ... sealing part 7 ... · Color filter 8 ··· Shading wall 9 ··· Flattening layer 10 · · · Wiring substrate 12 · · · Solid-state imaging device

The present invention has been made in view of the above-mentioned problems.
Cap glass with microlenses of the same shape by unifying (standardizing) the distance between the cap glass and the photoelectric conversion element (image receiving part) or by changing the height of the sealing part of the cap glass as needed. It is also possible to obtain a solid-state imaging device that can be applied to other types of individual imaging devices, has uniform characteristics with no variation in light condensing performance by the microlens, and has improved light collecting performance. .

In order to solve the above-described problem, a solid-state imaging device according to the present invention provides:
A space in which a solid-state image sensor composed of an area sensor in which a plurality of photoelectric conversion elements are two-dimensionally arranged vertically and horizontally is placed, and is open above the solid-state image sensor so that incident light enters the photoelectric conversion element In a solid-state imaging device having a portion and a cap glass provided above the space portion and transmitting incident light,
A sealing part made of resin is formed around the solid-state imaging element, and a transparent cap glass that transmits light is sealed above the solid-state imaging element through the sealing part, and is opened above the solid-state imaging element. It is characterized by forming an open space.
For the resin-made sealing portion, it is preferable to select a material that can easily set the height for adjusting the gap of the space portion as appropriate and has a small variation in height after formation.

According to the solid-state imaging device of the present invention, it is effective in unifying (standardizing) the distance between the cap glass and the photoelectric conversion element (image receiving portion), and the height of the cap glass sealing portion 6 is changed as needed. Thus, it becomes possible to apply the cap glass on which microlenses having the same shape are formed to other types of individual imaging devices, and to obtain a solid-state imaging device with low manufacturing cost.
In that case, the thickness control in the manufacturing process may be performed preferentially in the thickness control of the color filter.

Claims (2)

  A solid-state imaging device on which a plurality of photoelectric conversion elements are formed is placed, and a space part opened above the solid-state imaging element so that incident light enters the photoelectric conversion element, and provided above the space part. A solid-state imaging device having a cap glass that transmits incident light, wherein a microlens corresponding to the photoelectric conversion element is disposed on a surface of the cap glass on a photoelectric conversion element side.   The solid-state imaging device according to claim 1, wherein the solid-state imaging device is a linear sensor.

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