JP2007027604A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve miniaturization and thickness reduction while preventing deterioration in image quality of an imaging apparatus in a range where the device is affected by wave motion due to microfabrication of pixels, in a camera module employing a semiconductor imaging device. <P>SOLUTION: The imaging apparatus is provided with a semiconductor imaging device having a plurality of photodiodes 56 and a color filter 51; and an image pickup optical system for guiding a light from a subject to the semiconductor imaging device. The semiconductor imaging device has a reflection layer 57 for reflecting a light having transmitted through a photodiode 56, on an opposite side of an incident surface of at least a certain photodiode 56 among the plurality of photodiodes 56. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image pickup apparatus using a semiconductor image pickup device, and more particularly to a device used for a small terminal such as a mobile terminal or a mobile phone.

  2. Description of the Related Art Conventionally, an imaging apparatus using a semiconductor imaging element has a configuration including an imaging optical system such as a lens and a semiconductor imaging element such as a CCD, as described in Patent Document 1. And the imaging device converted the light from the subject incident through the imaging optical system into an electrical signal by the semiconductor imaging device, and took out the video. With the downsizing of portable devices, there has been a further demand for downsizing and weight reduction of imaging devices. For this reason, thinning of the imaging device has been realized by making each component of the imaging device as thin as possible.

  Regarding the image pickup device, there has been a trend toward a shift to a higher number of pixels and a reduction in size. The imaging optical system is usually designed to have a minimum circle of confusion with the same pixel size. As the size and the number of pixels increase, it is predicted that light will enter a region where the wave nature of light must be considered in addition to ray tracing based on Snell's law.

  Patent Document 2 points out that when the opening of the photodiode is 1 μm or less, it is necessary to consider the wave optical effect at, for example, the wavelength of red light (0.650 μm). Yes. A proposal has been made to provide a red sensitivity region on an electrode that vertically transmits a signal from a pixel.

Patent Document 3 discloses an element in which photodiodes are arranged for different colors in the thickness direction of a semiconductor substrate, and light having a longer wavelength is shorter than light having a shorter wavelength than a semiconductor substrate. It is disclosed to reach the back of the material.
JP 2004-327914 A JP 2004-200291 A JP-T-2002-513145

  As described above, in conventional imaging devices, components have been miniaturized in order to reduce the size and thickness of the device, and the imaging optical system has also been improved in performance by using an aspheric glass lens.

  However, if the size of the semiconductor imaging device is further reduced to increase the number of pixels and the pixels are further miniaturized, the conventional development technology cannot be applied, and a new breakthrough is required. For example, it has become necessary to consider the wave optical effect disclosed in Patent Document 2.

  On the other hand, in a conventional imaging device, pixels corresponding to each color filter are usually arranged two-dimensionally, and a Bayer arrangement is well known. There are many reading methods and color correction methods corresponding to this arrangement. There is a demand for an imaging device that is small and thin and that can effectively utilize these resources and that has a high pixel count.

  In view of the above background, an object of the present invention is to provide an imaging apparatus that can cope with downsizing, thinning, and high pixels.

  An imaging apparatus of the present invention includes a semiconductor imaging device having a plurality of photodiodes and color filters, and an imaging optical system that guides light from a subject to the semiconductor imaging device, and the semiconductor imaging device includes the plurality of photodiodes. A reflection layer that reflects light transmitted through the photodiode is provided on the opposite side of the incident surface of at least some of the photodiodes.

  With this configuration, light that has passed through the photodiode is reflected by the reflection layer and is incident on the photodiode again, so that the output of the photodiode can be increased. Further, among the plurality of photodiodes, if the configuration is such that the reflective layer is disposed on the photodiode corresponding to the red pixel on the long wavelength side that is easily affected by wave optics when the imaging device is downsized, It is possible to increase the sensitivity of the photodiode having sensitivity on the long wavelength side, compensate for the output decrease due to the wave optical effect, and realize downsizing of the imaging device. In general, long-wavelength light reaches the back of the semiconductor chip. Therefore, when the color filter transmits long-wavelength light, it is efficient to place a reflective layer on the opposite side of the incident surface of the photodiode. Thus, the output can be increased, and the sensitivity to light having a long wavelength that is easily affected by wave optics can be increased.

  In the imaging apparatus, the size or reflectance of the reflective layer is determined according to the wavelength of light transmitted through the color filter provided on the incident surface side of the photodiode.

  With this configuration, it is possible to determine the degree of increasing the sensitivity by changing the size or reflectance of the reflective layer in accordance with the wavelength of light transmitted through the color filter. For example, a photodiode provided with a color filter that transmits light having a long wavelength has a great wave-optical effect. Therefore, the size or reflectance of the reflective layer is increased to increase the degree of sensitivity. A photodiode provided with a color filter that transmits light having a short wavelength has a small wave-optical effect. Therefore, the size or reflectance of the reflective layer is reduced to reduce the degree of sensitivity. As a result, it is possible to compensate for the wave optical effect that varies depending on the wavelength for each wavelength, and to balance the sensitivity of the entire imaging apparatus.

  The imaging apparatus includes a three-dimensional substrate that does not transmit visible light and near-infrared light that accommodates the semiconductor imaging element.

  With this configuration, since the imaging element is housed inside a three-dimensional substrate that does not transmit visible light and near infrared light, a light shielding member that blocks light to the imaging device is provided when mounted on a portable device such as a mobile phone. There is no need to reduce the size. Further, since the semiconductor image pickup device and the image pickup optical system can be assembled to the three-dimensional substrate, workability is improved.

  In the imaging apparatus, the reflective layer is made of silver white metal.

  With this configuration, the reflective layer can be added by a simple process. Further, since silver-white metal is used, the reflectance from the reflective layer can be made almost constant in the visible light range, and the color reproducibility is good. Further, unnecessary incident light such as near infrared light from the back side of the semiconductor image sensor can be shielded, and image quality deterioration due to unnecessary light can be reduced.

  In the imaging apparatus, the reflective layer is formed of a semiconductor.

  With this configuration, since the reflective layer can be formed by changing the refractive index depending on the material to be doped, the reflective layer can be formed in a normal diffusion process without changing the process. A multilayer reflective layer can also be easily formed.

  The imaging apparatus includes an optical filter disposed between the semiconductor imaging element and the imaging optical system, and the size or reflectance of the reflective layer is incident on a region on the optical filter corresponding to the photodiode. It is determined according to the incident angle of the light to be transmitted.

  With this configuration, it is possible to reduce image quality degradation caused by an increase in incident angle. As a characteristic of the optical filter, when the incident angle increases, the half-value wavelength of the optical filter shifts to the short wavelength side. Along with this, the attenuation of red on the long wavelength side increases, so the degradation of image quality progresses, but the size of the photodiode corresponding to the red pixel on the long wavelength side is changed to the size of the reflective layer corresponding to light of other wavelengths By making it larger or increasing the reflectance, image quality degradation can be prevented.

  In the imaging apparatus, the semiconductor imaging element has a pixel pitch of 2 microns or less.

  In the semiconductor imaging device, the diameter of the opening of the photodiode is about half of the pixel pitch. Therefore, when the pixel pitch is 2 microns or less, the diameter of the opening is reduced accordingly, and the output is reduced due to the influence of wave optics. According to the configuration of the present invention, it is possible to increase the sensitivity of a photodiode to which light having a long wavelength that causes a problem of output reduction is incident, and to prevent output reduction even at a long wavelength side.

  A cellular phone device of the present invention has a configuration including the above-described imaging device.

  With this configuration, similarly to the imaging device of the present invention, the light transmitted through the photodiode is reflected by the reflective layer and is incident on the photodiode again, so that the output of the photodiode can be increased.

  A semiconductor imaging device according to the present invention includes a plurality of photodiodes that convert incident light into an electric signal, a color filter provided on an incident surface side of the photodiode, and at least a part of the photodiodes of the plurality of photodiodes. And a reflective layer having a size or a reflectance corresponding to the wavelength of transmitted light from the color filter incident on the photodiode, which is disposed on the opposite side of the incident surface.

  With this configuration, similarly to the imaging device of the present invention, the light transmitted through the photodiode is reflected by the reflective layer and is incident on the photodiode again, so that the output of the semiconductor imaging device can be increased. In addition, it is possible to compensate for the wave optical influence that varies depending on the wavelength for each wavelength, and to balance the sensitivity of the entire semiconductor imaging device.

  According to the present invention, since the light transmitted through the photodiode is reflected by the reflection layer and is incident on the photodiode again, the output of the imaging apparatus can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First embodiment)
FIG. 1 is a diagram for explaining a semiconductor imaging device used in the imaging apparatus of the present embodiment. In the description of the present embodiment, first, the overall configuration of an imaging apparatus including a semiconductor imaging device will be described with reference to FIG. 2 and thereafter, and then the configuration of the semiconductor imaging device will be described.

  2 is a perspective view showing the imaging apparatus 1 according to the first embodiment of the present invention, FIG. 3 is a cross-sectional view of the imaging apparatus 1 of FIG. 2 as viewed from the III-III direction, and FIG. It is an enlarged view.

  As shown in FIG. 3, the imaging apparatus 1 includes an aspheric lens 6 a and 6 b, an optical filter 5, a semiconductor imaging device 4 arranged along the optical axis L, a three-dimensional substrate 2 that holds these, and a three-dimensional substrate. 2 is provided with a printed circuit board (FPC) 15 connected to 2. A metal foil 14 is stretched on the lower surface of the FPC 15 to prevent visible light and infrared light from entering the semiconductor imaging device 4 from the lower surface. In the present embodiment, the three-dimensional substrate 2 has a role of fixing the semiconductor imaging device 4 and also serves as a holding member that holds the optical filter 5. The three-dimensional substrate 2 includes a cylindrical lens barrel portion 17 and a bottom portion 7 continuous with one end surface of the lens barrel portion 17. In the following description, the lens barrel portion 17 side is referred to as an upward direction, and the bottom portion 7 side is referred to as a downward direction.

  First, the three-dimensional substrate 2 will be described. The lens barrel portion 17 is located on the upper surface of the bottom portion 7 and extends in the vertical direction. The bottom portion 7 is formed with a recess at the center of the lower surface thereof. A rectangular through hole 10 is formed in the bottom 7. The through hole 10 corresponds to the imaging area of the semiconductor imaging device 4.

  The material of the three-dimensional substrate 2 is glass reinforced PPA (polyphthalamide resin) or the like, and is black in order to prevent transmission of visible light from the outside. As the three-dimensional substrate 2, a material obtained by kneading carbon black or the like into pellets is used, and the light transmittance is 0.5% or less. As for the light transmittance, it is desirable that light having a wavelength longer than that of visible light can be shielded. However, considering the sensitivity in the infrared region, the light transmittance is appropriately selected according to the characteristics of the semiconductor imaging device 4 to be specifically used. It is possible.

  Two aspherical lenses (hereinafter abbreviated as lenses) 6a and 6b, each having different optical characteristics, are fitted into the lens holder 20 in the barrel of the lens barrel portion 17 so that a fixed positional relationship can be maintained. A lens 6 is configured. The lens holder 20 is fixed to the outer side of the lens barrel portion 17 by an adhesive or the like via an adjustment ring 21 arranged on the outer side. The lens holder 20 and the adjustment ring 21 are fixed by screwing a screw portion 20 a provided in the lens holder 20 and a screw portion 21 a provided in the adjustment ring 21.

  The lens holder 20 is formed with a stop 3 for introducing light into the lens barrel portion 17. The aperture of the diaphragm 3 is narrowed toward the inside of the lens barrel portion 17. With this configuration, the light incident on the inside of the lens barrel portion 17 strikes the wall surface of the diaphragm 3 and is scattered to reduce the phenomenon of entering the lens. Thereby, incidence of unnecessary light to the lens can be reduced, and generation of ghost can be reduced.

  The lens 6 is made of a resin that satisfies necessary optical characteristics such as transmittance and refractive index. For example, the trade name ZEONEX (registered trademark) manufactured by Nippon Zeon can be used. As the configuration of the lens 6, a so-called pan focus configuration is adopted in which a two-lens configuration forms an image farther than a certain distance. In the present embodiment, adjustment is made so that a subject farther than about 30 cm is in focus. These configurations and characteristics can be appropriately selected.

The optical filter 5 is mounted on the upper surface of the bottom 7 where the through hole 10 is formed so as to cover the through hole 10. The optical filter 5 cuts unnecessary infrared light and transmits light having a wavelength in the visible region. As the optical filter 5, a quartz filter or a glass having a coating called an IR coat is used. In the present embodiment, shelf silicate glass is used for the base material of the optical filter 5, and ultraviolet light is cut. An IR (Infra Red) cut coat is applied to one side of the substrate, and an AR (Anti Reflection) coat for antireflection is applied to the other side. The IR coat is formed, for example, by vapor-depositing silicon dioxide (SiO ₂ ) / titanium oxide (TiO ₂ ) on glass. The AR coat is formed, for example, by vapor-depositing magnesium fluoride (MgF ₂ ), titanium oxide (TiO ₂ ), zirconium oxide (ZrO ₂ ) or the like on glass. The film configuration and the number of laminated layers of the IR cut coat and AR coat can be appropriately selected depending on the visible light region and the property of suppressing transmission / reflection outside the region.

  FIG. 5 is a diagram showing the spectral characteristics of the optical filter 5 in the present embodiment. The transmittance in the visible light region having a wavelength of about 400 nm to 750 nm is approximately 93% or more, and the transmittance is sufficiently low in other bands. This spectral characteristic can be changed as appropriate. By providing the optical filter 5, it is possible to reduce the generation of noise due to the incident light other than visible light entering the semiconductor imaging device 4.

  A groove 11 is formed on the surface on which the optical filter 5 is mounted (see FIG. 4). Thereby, the air which expand | swells with the heat | fever applied from the outside by hardening of an adhesive agent etc. at the time of manufacture of the imaging device 1 can be escaped from the groove | channel 11.

  On the lower surface of the bottom 7 where the through hole 10 is formed, the semiconductor imaging device 4 and a chip component (not shown) are mounted (see FIG. 4). A connection land 7 c for bare mounting of the semiconductor image pickup device 4 and a bump 8 of the semiconductor image pickup device 4 are bonded by a conductive adhesive 8 a and sealed with a sealant 9. On the bottom surface of the bottom portion 7, a wiring pattern 7b of copper base, nickel, and gold is formed by electroless plating. The connection land 7c and the terminal portion 7a provided outside the bottom portion 7 of the three-dimensional board 2 are electrically connected by the wiring pattern 7b. The terminal portion 7 a is connected to a connection land 15 a with the FPC 15 by solder 16. Video signals obtained from the semiconductor imaging device 4 and chip parts (not shown), and electrical signals such as external control signals and power supply are transmitted and received via the wiring pattern 7b.

  Next, the semiconductor image sensor 4 will be described. The semiconductor imaging device 4 is a ¼-inch SXGA CCD sensor having about 1.3 million pixels, and converts incident light into a required electrical signal. The semiconductor image sensor 4 outputs an image signal having a screen aspect ratio of 4: 3 and 15 frames per second.

  The semiconductor image pickup device 4 is electrically connected to a connection land 7c provided on the three-dimensional board 2 by an SBB (Stud Bump Bond). An output from the semiconductor image pickup device 4 is led to a terminal portion 7a connected to an external FPC 15 provided on the bottom portion 7 via a wiring pattern 7b.

  FIG. 1 is an enlarged view showing one pixel of the semiconductor image sensor 4. As shown in FIG. 1, the semiconductor imaging device 4 includes a photodiode 56 that converts incident light into an electrical signal.

  On the light incident side of the photodiode 56, a microlens 50, a color filter 51, an inner lens, a protective film 52, an Al wiring / mask 53, an insulating layer 54, polysilicon 55 and the like are provided. The semiconductor imaging device 4 has a reflection layer 57 that reflects light transmitted through the photodiode 56 in the direction of the photodiode 56 on the opposite side of the incident surface of the photodiode 56.

  The reflective layer 57 uses aluminum as a silver-white metal. Aluminum is easy to use because it is frequently used in semiconductors as electrodes and internal wiring. Moreover, since it is low in density, it can be realized in light weight, and the unit price is lower than other silver-white metals. In this embodiment, aluminum is used, but nickel, titanium, or the like can be used as another example of a silver-white metal. When nickel is used, electromagnetic shielding can be performed on the photodiode 56, which is advantageous in terms of EMI. Note that the material of the reflective layer and the thickness and size of the reflective film can be appropriately selected so as to obtain the required reflectance.

  The size and reflectance of the reflective layer 57 are determined according to the wavelength of light transmitted through the color filter 51 provided on the incident surface side of the photodiode 56. When the color filter 51 that transmits light of a long wavelength is provided, the reflective layer 57 having a large size and reflectivity is used, and when the color filter 51 that transmits light of a short wavelength is provided, the size and reflectivity are small. A reflective layer 57 is used. Further, when the color filter 51 that transmits light having a short wavelength is provided, the reflective layer 57 may not be provided. In the present embodiment, the size and reflectance of the reflective layer 57 are determined according to the wavelength of light transmitted through the color filter 51, but only the size of the reflective layer 57 or only the reflectance may be changed. .

  FIG. 6 is a diagram in which the pixel size of the semiconductor image sensor and the sensitivity characteristics for each wavelength are obtained by simulation. In FIG. 6, the horizontal axis indicates the pixel size, and the vertical axis indicates the relative value of the output of the photodiode. Pixel size means the length of one side of a square pixel. For example, 2 μm indicates a square pixel having a side of 2 μm. As the photodiode, an opening having a shape about half the pixel size was used.

  From the characteristics of FIG. 6, when the pixel size is 1.5 μm, the sensitivity is reduced by about 15% at 650 nm in the vicinity of the R sensitivity center and about 5% at 550 nm in the vicinity of the G sensitivity center. In the present embodiment, the size and the reflectance of the reflective layer 57 are set so as to compensate for the sensitivity reduction accompanying the reduction in pixel size. For example, a photodiode 56 provided with a color filter 51 that transmits R (650 nm) having a large sensitivity drop is provided with a reflective layer 57 having a large size and reflectance, and a color that transmits G (550 nm) having a small sensitivity drop. The photodiode 56 provided with the filter 51 is provided with a reflective layer 57 having a small size and reflectance. As the size and reflectance of the reflective layer 57 increase, the sensitivity of the photodiode 56 increases.

  In general, since light having a longer wavelength reaches the depth of the semiconductor image sensor, the amount of light reflected by the reflection layer 57 increases as the wavelength of the light that is easily affected by the wave increases. Although light with a short wavelength has a small amount of light reaching the reflective layer 57, it is difficult to be affected by waves, so that a large output can be obtained by light incident from the incident surface side of the photodiode 56. Based on this correlation, a change in output obtained by the reflected light from the reflective layer 57 may be obtained to determine the optimal size and reflectance of the reflective layer 57.

  The microlens 50 collects the light transmitted through the optical filter 5 and causes the light to enter the photodiode 56. The position of the center of the microlens 50 is shifted in the direction of the center of the semiconductor imaging device 4 as it goes from the center of the semiconductor imaging device 4 to the periphery. This is a method called scaling. By the scaling, deterioration of the characteristics of the photodiode 56 in the peripheral portion of the semiconductor image sensor 4 is prevented.

  The pitch (A dimension in the figure) of the microlenses 50 is called a pixel pitch. The opening part (B dimension in the figure) of the Al wiring / mask is the opening dimension with respect to the photodiode 56. Usually, the B dimension is set to about half of the A dimension.

  The color filter 51 is a primary color including a filter that transmits light with a red (R) wavelength, a filter that transmits light with a blue (B) wavelength, and a filter that transmits light with a green (G) wavelength. It is a system filter. In FIG. 1, since one pixel is described, the color filter 51 transmits one of RGB wavelengths. By providing the color filter 51, the photodiode 56 can extract RGB color signals as an output.

  The photodiode 56 photoelectrically converts light incident from the incident surface side where the color filter 51 is provided and light reflected by the reflective layer 57, and outputs an electrical signal. The output of the photodiode 56 is led to a readout circuit (not shown). In the reading method, charges are transmitted horizontally and vertically as in the conventional method. With this configuration, the output of the photodiode 56 can be taken out.

  FIG. 7 is a diagram showing sensitivity characteristics with respect to the wavelength of the photodiode 56. The horizontal axis indicates the wavelength, and the vertical axis indicates the sensitivity. This photodiode is made of silicon and has sensitivity up to the near infrared region. A sensitivity (spectral sensitivity) 60 for a blue pixel when the pixel size is 2.5 μm, similarly a sensitivity 61 for green and a sensitivity 62 for red are shown. Further, the output 63 of the photodiode 56 for red when the pixel size is 1.5 μm and the output 64 of the photodiode by the light re-entered by the reflection layer 57 are shown. The spectral characteristics slightly change between the output 63 of the photodiode 56 and the output 64 by the light re-entered by the reflection layer 57. This is probably because the short wavelength component is attenuated more and reaches the reflection layer 57.

  As shown in FIG. 7, the photodiode 56 has sensitivity up to the near-infrared region. Since light with a long wavelength is difficult to attenuate, it is necessary to consider incident light from the back surface of the element. In the present embodiment, the metal foil 14 provided on the back surface of the FPC 15 prevents visible light / infrared light from entering. The sensitivity for each color is compared by integrating the sensitivity characteristic values. The sensitivity varies depending on the characteristics of the color filter and the characteristics of the pigment-based dye used. The configuration of the imaging device 1 according to the present embodiment has been described above.

  Next, prior to describing the effects of the imaging device 1 of the present invention, the relationship between the pixel size and sensitivity of the semiconductor imaging device will be described.

  As can be seen from FIG. 6, when the pixel size is reduced, the relative sensitivity of the longer wavelength is significantly reduced. If the pixel size is reduced and the opening of the photodiode becomes as large as the wavelength, it is considered that the characteristic as the wave of light cannot be ignored. When the pixel size is 2.5 μm or more, the characteristics as light waves can be ignored. However, when the pixel size is 2 μm or less, the sensitivity of the pixel corresponding to the long wavelength is lowered, and it is considered that the image quality is deteriorated. The limits of downsizing / thinning the imaging device are governed by the pixel size. For the same pixel size, the output decreases as the wavelength increases.

  FIG. 8 is a diagram showing the relationship between the pixel size of the semiconductor image sensor and the number of pixels for each size of the imaging device. The horizontal axis indicates the pixel size, and the vertical axis indicates the number of pixels. From FIG. 8, it can be seen that as the size of the image sensor decreases, the pixel size tends to decrease and the number of pixels tends to increase. An arrow TR in the figure indicates a trend of the apparatus. Conventionally, an image pickup element of 1 million pixel class was about 1/2 to 1/3 type (corresponding to inch), but is currently realized with 1/4 type. In the future, when the size is further reduced and 1 million pixels are realized with the 1/6 type, the pixel size becomes about 2 μm. Therefore, it is predicted that the problem of image quality degradation due to the above-described characteristics as the wave of light will surface.

Hereinafter, effects of the imaging device 1 of the present embodiment will be described.
In the imaging device 1 of the present embodiment, a reflective layer 57 is disposed on the opposite side of the incident surface of the photodiode 56. As a result, the light transmitted through the photodiode 56 is reflected by the reflective layer 57 and is incident on the photodiode 56 again. Therefore, the sensitivity of the photodiode 56 can be increased.

  In the imaging device 1 of the present embodiment, the size and reflectance of the reflective layer 57 are determined according to the wavelength of light transmitted through the color filter 51 provided on the incident surface side of each photodiode 56. That is, when the color filter 51 that transmits light having a long wavelength is provided, the amount of reflected light is increased and the sensitivity of the photodiode 56 is increased by using the reflective layer 57 having a large size and reflectivity. As a result, in the photodiode having sensitivity to light having a long wavelength, it is possible to realize a characteristic as if there is no reduction in sensitivity by compensating the wave optical effect.

  As can be seen from FIG. 7, by adding the output 63 of the photodiode 56 and the output 64 of the reflective layer 57, the red pixel size can be taken out as equivalent to 2.5 μm, that is, with almost no reduction in output. Similarly, for the green pixel, the reduction in output can be reduced by the light re-entered by the reflective layer 57.

  Further, in the present embodiment, since an array of Bayer-arranged semiconductor image pickup devices is used, conventional reading methods and techniques such as color correction / interpolation can be applied. Accordingly, development efficiency can be improved, and various know-how can be inherited and applied.

(Second Embodiment)
Next, a second embodiment of the present invention will be described. The image pickup apparatus of the second embodiment has the same basic configuration as the image pickup apparatus 1 of the first embodiment, but has a configuration in which the three-dimensional substrate 2 does not transmit visible light and near infrared light. Is different. Here, the configuration that does not transmit visible light and near-infrared light means a configuration that does not substantially deteriorate the image quality. The specific transmittance is about 0.5% or less, preferably 0.2% or less. In this embodiment, it is about 0.15%.

  The semiconductor image sensor 4 is made of silicon. Therefore, the upper limit on the long wavelength side of the sensitivity region is determined by the wavelength exceeding the band gap energy (Eg) of silicon. Since the band gap energy of silicon is about 1.12 eV, the limit wavelength is obtained by λ≈1240 / Eg where the wavelength is λ [nm] and the band gap energy is E g [eV]. The limit of sensitivity is up to far infrared rays of about 1100 nm (1.1 μm).

The three-dimensional substrate 2 in the present embodiment is configured by adding carbon black having good dispersibility effective for visible light and short wavelength side and shelf silicate glass that absorbs ultraviolet light to a resin material (PAA). Moreover, you may mix about 2 wt% of aluminum as a metal filler with good thermal conductivity. Thereby, the transmittance of visible light and near-infrared light is sufficiently low with respect to the sensitivity range of the semiconductor imaging device 4. The thickness of the resin of the three-dimensional substrate is also optimized by evaluating image deterioration. Since near-infrared light having a long wavelength is more easily transmitted deeper, it is important to fully consider this point. When near-infrared light having a wavelength of 1.1 μm or less enters the semiconductor imaging device 4, it appears as noise and the image quality deteriorates. In order to prevent this, it is effective to increase the amount of the metal filler mixed in the resin material. When aluminum is used as the metal filler, it is preferable to use aluminum oxide (alumina Al ₂ O ₃ ) in order not to lower the electrical insulation resistance.

  In the present embodiment, since the three-dimensional substrate 2 is configured not to transmit visible light and near-infrared light, a device such as a mobile phone is provided without providing a light shielding member for blocking extra light to the imaging device 1. Can be implemented. As a result, the degree of freedom in designing the portable device is increased, the device can be downsized, and the convenience can be improved.

  Although the imaging apparatus of the present invention has been described in detail with reference to the embodiment, the present invention is not limited to the above-described embodiment.

  In this embodiment mode, an example in which silver-white metal is used for the reflective layer 57 has been described. However, the reflective layer 57 may be formed of a semiconductor. A reflective layer made of a semiconductor can be obtained by stacking multiple layers having different optical refractive indexes depending on the material to be doped. Alternatively, the polysilicon layer can be used as a reflective film instead of a conductive film. The refractive index, the number of layers of the film, the reflectance, and the like can be selected as appropriate.

  When the pixel size is reduced to about 1 μm, it is preferable to provide the reflective layer 57 for all pixels corresponding to RGB. In addition, it is desirable to select the sensitivity so that the sensitivity ratios of RGB are balanced. As a result, the image pickup apparatus can be reduced in size and thickness.

  Considering that the half-value wavelength value on the long wavelength side shifts to the short wavelength side depending on the incident angle with respect to the optical filter 5, the peripheral pixel of the semiconductor imaging device 4 in which the incident angle with respect to the optical filter 5 is increased. The sensitivity may be increased from the vicinity of the center. This point will be described in detail.

  Since the optical filter 5 is a reflection type as described above, a multilayer film is attached to one side. When the incident angle increases, the optical path length becomes relatively long with respect to the multilayer film. Therefore, the increase in the incident angle is considered to be equivalent to an increase in the thickness of the multilayer film, and the half-value position on the long wavelength side shifts to the short wavelength side.

  FIG. 5 shows the relationship between the incident angle with respect to the optical filter 5 and the transmittance. The solid line, the broken line, and the two-dot chain line in the figure indicate the transmittance characteristics when the incident angles to the optical filter 5 are 0 °, 10 °, and 20 °, respectively. As shown in FIG. 5, when the incident angle is changed to 10 ° and 20 °, the half-value position on the long wavelength side is shifted to the short wavelength side by about 5 nm and 10 nm, respectively, compared to the incident angle of 0 °. 745 nm and 740 nm. When the image quality was evaluated, it was visually noticed that the image quality deteriorated when the image visually changed by 10 nm.

  In order to reduce the thickness, the incident angle must be increased in the peripheral pixels. Therefore, by setting the sensitivity of the peripheral pixel of the semiconductor image sensor that increases the incident angle with respect to the optical filter 5 from the vicinity of the center, image quality deterioration of the peripheral pixel due to the increase of the incident angle is reduced. it can.

  As a method of obtaining the sensitivity in this case, for example, the sensitivity to be reduced due to the influence of the incident angle is obtained with respect to the peripheral pixels of the semiconductor imaging device 4, and the sensitivity after correcting the sensitivity deterioration is obtained, and then the optimization as a whole is performed. I do. Conversely, the peripheral pixels may be corrected after obtaining the sensitivity as a whole. The method for obtaining the sensitivity can be changed as appropriate in accordance with the characteristics of the imaging apparatus.

  According to the present invention, even a photodiode having sensitivity on the long wavelength side has an excellent effect of being able to compensate for a decrease in output due to wave optical influence, and includes an imaging device using a semiconductor imaging element. It is useful as a portable terminal or a mobile phone.

Sectional view enlarging one pixel of a semiconductor image sensor The perspective view which shows the imaging device of embodiment Sectional view of the imaging device cut along III-III Enlarged view of IV part of imaging device The figure which shows the relationship between the incident angle of the optical filter in embodiment, and a half value wavelength The figure which shows the sensitivity characteristic with respect to the pixel size and wavelength of the semiconductor image pick-up element in embodiment The figure which shows the sensitivity characteristic with respect to the wavelength of the photodiode in embodiment. The figure which shows the relationship between the pixel size of a semiconductor image sensor, and the number of pixels

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Imaging device 2 Three-dimensional substrate 3 Aperture 4 Semiconductor imaging device 5 Optical filter 6 Lens 6a, 6b Aspherical lens 7 Bottom part 7a Terminal part 7b Wiring pattern 7c Connection land 10 Through hole 14 Metal foil 15 FPC
15a Land 16 Solder 17 Lens barrel portion 20 Lens holder 21 Adjustment ring 50 Micro lens 51 Color filter 52 Protective film 53 Al wiring / mask 54 Insulating layer 55 Polysilicon 56 Photo diode 57 Reflective layer

Claims (9)

A semiconductor imaging device having a plurality of photodiodes and color filters;
An imaging optical system for guiding light from a subject to the semiconductor imaging device;
With
The image pickup apparatus according to claim 1, wherein the semiconductor image pickup device includes a reflection layer that reflects light transmitted through the photodiode on a side opposite to an incident surface of at least some of the plurality of photodiodes.   The imaging device according to claim 1, wherein the size or reflectance of the reflective layer is determined according to a wavelength of light transmitted through a color filter provided on an incident surface side of the photodiode.   The imaging apparatus according to claim 1, further comprising a three-dimensional substrate that does not transmit visible light and near infrared light that accommodates the semiconductor imaging element.   The imaging device according to claim 1, wherein the reflective layer is made of silver white metal.   The imaging device according to claim 1, wherein the reflective layer is formed of a semiconductor. Comprising an optical filter disposed between the semiconductor imaging device and the imaging optical system;
The size or reflectance of the reflective layer is determined according to an incident angle of light incident on a region on the optical filter corresponding to the photodiode. The imaging device described.   The imaging apparatus according to claim 1, wherein the semiconductor imaging element has a pixel pitch of 2 microns or less.   A mobile phone device comprising the imaging device according to claim 1. A plurality of photodiodes for converting incident light into electrical signals;
A color filter provided on the incident surface side of the photodiode;
A size or a reflectance corresponding to the wavelength of the transmitted light from the color filter that is disposed on the opposite side of the incident surface of at least some of the photodiodes and is incident on the photodiodes. A reflective layer;
A semiconductor imaging device comprising:

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