JP4618765B2 - Image sensor and digital camera equipped with the image sensor - Google Patents

Description

  The present invention relates to an image sensor and a digital camera including the image sensor.

  In recent years, image pickup devices (hereinafter also referred to as “image sensors”) used in digital still cameras and the like have been improved in image quality by increasing the number of pixels, but at a lower price by reducing the chip size. It is planned.

  FIG. 13 is a schematic cross-sectional view of a conventional CMOS image sensor 1030 used in a digital still camera.

  In the CMOS image sensor 1030 configured as shown in FIG. 13, light reaching the image sensor 1030 from a photographing lens (not shown) is converted into a photoelectric conversion unit formed on the Si substrate 1031 by a microlens 1038 formed of resin. Focused on 1032. A green color filter 1036 and a red color filter 1037 are alternately formed in each pixel of the image sensor 1030, and the photoelectric conversion unit 1032 of the pixel in which the green and red color filters 1036 and 1037 are formed. An image is generated by the output and the output of the photoelectric conversion unit of the pixel on which a blue color filter (not shown) is formed.

In the figure, reference numerals 1033 and 1034 denote Al (aluminum) wiring layers, which are formed via an interlayer film 1035 made of SiO ₂ or the like. The Al wiring layers 1033 and 1034 control a transfer switch for transferring photoelectric charges generated in the photoelectric conversion unit 1032 to a floating diffusion unit (FD unit) (not shown), and output the potential of the FD unit. Is for.

In Patent Document 1, an image pickup device is manufactured by forming a color filter layer and a microlens on a glass substrate, and bonding the substrate on which the color filter layer and the microlens are formed and a substrate having a photoelectric conversion unit. A method is disclosed.
JP-A-3-107101

  However, since the conventional image sensor uses a dye or pigment type color filter for color separation of light, a part of the light transmitted through the color filter layer is absorbed by the color filter, and the image sensor There was a drawback in that the sensitivity of the was reduced.

  Further, as in the imaging device disclosed in Patent Document 1, when the bonding surface of the optical substrate having the microlens and the color filter layer and the sensor substrate having the photoelectric conversion unit is flat, two substrates are provided. It is difficult to position each other, and there is a possibility that the relative position between the microlens and the photoelectric conversion unit is shifted due to the positional shift that occurs at the time of bonding. If the relative positions of the microlens and the photoelectric conversion unit are deviated, the light is not guided well to the photoelectric conversion unit, so that the sensitivity of the image sensor is reduced.

  The present invention has been made in view of the problems of the above-described conventional technology, and an object thereof is to provide an imaging device having higher sensitivity.

In order to achieve the above object, an imaging device of the present invention includes a plurality of photoelectric conversion units provided on a semiconductor substrate, a color filter serving as a waveguide disposed on each photoelectric conversion unit, and each color filter. and air layers arranged a so as to surround is provided between the adjacent pre Kisora air layer, and a plurality of interlayer film covering the plurality of wiring layers, respectively, before SL corresponding to each color filter, the It has a color filter, the air layer, and a plurality of microlenses arranged directly on the interlayer film.

According to the present invention, it is possible to provide an imaging device having a higher sensitivity.

  Next, embodiments of the present invention will be described with reference to the drawings.

( Reference form )
1 to 5 are views showing a reference embodiment of the present invention, FIG. 1 is a schematic cross-sectional view of the imaging device reference embodiment of the present invention, FIGS. 2A and 2B of the sensor substrate of the imaging device shown in FIG. 1 FIG. 3A and FIG. 3B are diagrams showing a manufacturing process of the optical substrate of the image sensor shown in FIG. 1, FIG. 4 is a spectral characteristic diagram of the dichroic filter of the image sensor shown in FIG. 1, and FIG. It is a ray tracing diagram in the image sensor shown in FIG.

As shown in FIG. 1, the image pickup device of this reference embodiment includes a sensor substrate 10 and an optical substrate 12.

The sensor substrate 10 has a Si substrate 100 provided with a plurality of photoelectric conversion units 104 on the upper surface. On the Si substrate 100, two Al wiring layers 107 and 113 are formed via interlayer films 110 and 114 formed of SiO ₂ or the like. The Al wiring layers 107 and 113 control a transfer switch for transferring photocharge generated in the photoelectric conversion unit 104 to a floating diffusion unit (FD unit) (not shown), and output the potential of the FD unit. This is a wiring layer.

In addition, above each photoelectric conversion unit 104 on the Si substrate 100 and in a portion surrounded by the Al wiring layers 107 and 113, a waveguide 117 formed of TiO ₂ which is a material having a relatively high refractive index is provided. It is configured. The opening on the light incident side (the upper side in the drawing) of the waveguide 117 is large so that more light can enter the waveguide 117.

  As described above, the sensor substrate 10 includes the photoelectric conversion unit 104 provided on the Si substrate 100, the Al wiring layers 107 and 113 formed thereon, and the waveguide 117.

The optical substrate 12 has a glass substrate 120 which is a transparent substrate, and a microlens 124 is provided on the lower surface of the glass substrate 120 via a low refractive index layer 121 made of SiO ₂ having a relatively low refractive index. Is provided. The microlens 124 is made of TiO ₂ having a relatively high refractive index, and its lens shape is determined so that a light beam incident from a photographing lens (not shown) is condensed on the photoelectric conversion unit 104.

On the lower surface of the microlens 124 provided on the glass substrate 120, a first refractive index layer 125 made of SiO ₂ or the like having a relatively low refractive index, and a _second refractive index layer made of TiO ₂ or the like having a relatively high refractive index. A refractive index layer 129 is further provided. The refractive index interface between the first refractive index layer 125 and the second refractive index layer 129 is formed in a prism shape.

Further, on the lower surface of the second refractive index layer 129, Bayer-arrayed dichroic filter layers 132 and 135 that transmit light of a predetermined wavelength and reflect light of other wavelengths are provided. ing. The dichroic filter layers 132 and 135 are composed of alternating multilayer films of SiO ₂ having a relatively low refractive index and TiO ₂ having a relatively high refractive index.

As described above, the optical substrate 12 includes the glass substrate 120, the low refractive index layer 121, the microlens 124, the first refractive index layer 125, the second refractive index layer 129, and the dichroic filter layer formed thereon. The optical member is composed of two kinds of transparent materials of SiO ₂ and TiO ₂ having different refractive indexes.

The imaging device of this reference embodiment has a structure in which the upper surface of the sensor substrate 10 and the lower surface of the optical substrate 12 described above are bonded together.

  Next, a method for manufacturing the sensor substrate 10 shown in FIG. 1 will be described with reference to FIGS. 2A and 2B.

First, as shown in FIG. 2A (a), the upper surface of the Si substrate 100 is oxidized to form a silicon oxide film 101 made of SiO _{2 on} the upper surface of the Si substrate 100. Further, in order to form a photoelectric conversion region on the upper surface of the Si substrate 100, a photoresist 102 is applied on the silicon oxide film 101, and this is covered with a photomask 103 and exposed (FIG. 2A (b)). The photomask 103 is configured such that the region corresponding to the photoelectric conversion region transmits light and the other regions block light. Further, since the photoresist 102 is a positive type photoresist, a region irradiated with light, that is, a region corresponding to the photoelectric conversion region is dissolved by the development process, and a part of the silicon oxide film 101 is exposed. Further, by performing a dry etching process using plasma, the silicon oxide film 101 in a region not covered with the photoresist 102 is removed (FIG. 2A (c)).

  Further, by implanting ions into the upper surface of the Si substrate 100, the photoelectric conversion unit 104 is formed in a region not covered with the silicon oxide film 101 on the upper surface of the Si substrate 100 (FIG. 2A (d)). At this time, since ions are absorbed in the region covered with the silicon oxide film 101, the photoelectric conversion portion 104 is not formed in the region.

  After the photoelectric conversion unit 104 is formed on the upper surface of the Si substrate 100, an electrode for transferring charges stored in the photoelectric conversion unit 104 is formed on the upper surface of the Si substrate 100.

  First, a photoresist 105 is applied to the upper surface of the Si substrate 100 on which the photoelectric conversion portion 104 and the silicon oxide film 101 are formed, and this is covered with a photomask 106 and exposed (FIG. 2A (e)). The photomask 106 is configured such that a region corresponding to the first wiring layer 107 transmits light, and the other regions block light. In addition, since the photoresist 105 is a positive type photoresist, a region irradiated with light by development processing, that is, a region corresponding to the first wiring layer is dissolved, and a part of the silicon oxide film 101 is exposed. To do. Further, by performing a dry etching process, the silicon oxide film 101 in a region not covered with the photoresist 105 is removed (FIG. 2A (f)).

  Further, for example, Al (aluminum) is deposited on the Si substrate 100 by a CVD apparatus or the like, thereby forming the first wiring layer 107 on the Si substrate 100 (FIG. 2A (g)).

  After forming the first wiring layer 107, an etching stopper film 109 is formed on the photoelectric conversion unit 104. First, a photoresist 108 is applied to the upper surface of the Si substrate 100, and this is covered with a photomask 103 and exposed (FIG. 2A (h)). The photomask 103 is configured such that a region corresponding to the photoelectric conversion unit 104 transmits light and the other regions block light. Further, since the photoresist 108 is a positive type photoresist, the region irradiated with light by the development process, that is, the region corresponding to the photoelectric conversion unit 104 is dissolved. Further, SiN is vapor-deposited on the photoelectric conversion unit 104 by a CVD apparatus or the like, thereby forming an etching stopper film 109 on the photoelectric conversion unit 104 (FIG. 2A (i)). Further, an etching process is performed to remove the photoresist 108 (FIG. 2A (j)).

Next, in order to form the second wiring layer 113 on the sensor substrate 10, as shown in FIG. 2B (k), first, the interlayer film 110 made of SiO ₂ is formed on the silicon oxide film 101 on the Si substrate 100, It is formed on the first wiring layer 107 and the etching stopper film 109 by a CVD apparatus. Then, after the interlayer film 110 is subjected to surface treatment and planarized, a photoresist 111 is applied on the interlayer film 110, and is covered with a photomask 112 and exposed. The photomask 112 is configured such that a region corresponding to the second wiring layer 113 transmits light and the other regions block light. In addition, since the photoresist 111 is a positive type photoresist, a region irradiated with light, that is, a region corresponding to the second wiring layer 113 is dissolved by the development process.

  Further, the second wiring layer 113 is formed on the interlayer film 110 by depositing Al on the interlayer film 110 by a CVD apparatus or the like (FIG. 2B (l)). Further, an etching process is performed to remove the photoresist 111 (FIG. 2B (m)).

Further, an interlayer film 114 made of SiO ₂ is formed on the interlayer film 110 and the second wiring layer 113 by a CVD apparatus, and the interlayer film 114 is subjected to surface treatment for planarization (FIG. 2B (n)).

  Next, a well structure for forming the waveguide 117 is formed. First, a photoresist 115 is applied on the interlayer film 114 that has been subjected to planarization, and this is covered with a photomask 116 and exposed (FIG. 2B (o)). The photomask 116 is configured such that a region corresponding to the waveguide transmits light and the other regions block light. Further, since the photoresist 115 is a positive type photoresist, the region irradiated with light, that is, the region corresponding to the waveguide, is dissolved by the development process (FIG. 2B (p)).

  Further, by performing an etching process on the interlayer film 114, a well structure for forming the waveguide 117 in the interlayer film 114 is formed (FIG. 2B (q)). Since the etching stopper film 109 is formed between the interlayer film 114 and the photoelectric conversion unit 104, the photoelectric conversion unit 104 is not etched.

Finally, TiO ₂ is deposited on the photoelectric conversion unit 104 by the CVD apparatus to form the waveguide 117, thereby completing the sensor substrate 10 (FIG. 2B (r)).

  Next, a method for manufacturing the optical substrate 12 shown in FIG. 1 will be described with reference to FIGS. 3A and 3B.

  First, the microlens 124 is formed on the surface (upper surface shown in FIG. 3A) of the glass substrate 120 that is a transparent substrate. The microlens 124 is formed by a known registry flow method.

For this purpose, first, a low refractive index layer 121 made of SiO ₂ which is a material having a relatively low refractive index is deposited on a glass substrate 120 by a CVD apparatus (FIG. 3A (b)), and a photoresist 122 is further formed thereon. It is applied (FIG. 3A (c)), covered with a photomask 123 and exposed (FIG. 3A (d)). In order to form the shape of the microlens 124, the transmittance distribution of the photomask 123 is set so that the transmittance at the center of the pixel is low and the transmittance at the periphery of the pixel is high. Further, since the photoresist 122 is a negative type photoresist, the region not irradiated with light, that is, the region corresponding to the microlens 124 is dissolved by the development process (FIG. 3A (e)).

Further, by performing an etching process on the low refractive index layer 121, a recess for forming the microlens 124 is formed in the low refractive index layer 121 (FIG. 3A (f)). At this time, if the selection ratio in the etching process between the photoresist 122 and the low refractive index layer 121 is 1: 1, the shape of the photoresist 122 is transferred to the low refractive index layer 121 as it is. Further, TiO ₂ , which is a material having a relatively high refractive index, is deposited on the low refractive index layer 121 by a CVD apparatus, thereby forming the microlens 124 on the low refractive index layer 121 (FIG. 3A (g)). ).

  After forming the microlens 124, a prism-shaped layer composed of the first and second refractive index layers 125 and 129 is formed. This prism shape layer is formed by a known registry flow method.

First, SiO ₂ , which is a material having a relatively low refractive index, is vapor-deposited on the microlens 124 by a CVD apparatus to form the first refractive index layer 125 (FIG. 3A (h)). Further, a photoresist 126 is applied on the first refractive index layer 125, and this is covered with a photomask 127 and exposed (FIG. 3A (i)). The transmittance distribution of the photomask 127 is set so that the transmittance increases linearly from the pixel central portion to the pixel peripheral portion in order to form a prism shape in the first refractive index layer 125. Further, since the photoresist 126 is a positive type photoresist, the region irradiated with light, that is, the region corresponding to the bottom of the prism is dissolved by the development process (FIG. 3A (j)).

By further etching the first refractive index layer 125, a prism shape is formed in the first refractive index layer 125 (FIG. 3B (k)). Further, TiO ₂ , which is a material having a relatively high refractive index, is deposited on the first refractive index layer 125 by a CVD apparatus to form the second refractive index layer 129, and planarization is performed to perform the second refractive index layer 129. The surface of the refractive index layer 129 is smoothed (FIG. 3B (l)).

Finally, dichroic filter layers 132 and 135 are formed. The dichroic filter layers 132 and 135 are composed of alternating multilayer films of SiO ₂ having a relatively low refractive index and TiO ₂ having a relatively high refractive index, and the spectral transmittance is adjusted by adjusting each film thickness. be able to. The spectral transmission characteristics of the dichroic filter layers 132 and 135 will be described later.

  First, the process of forming the dichroic filter layer 132 that transmits red light will be described.

  First, a photoresist 130 is applied on the second refractive index layer 129, covered with a photomask 131, masked, and exposed (FIG. 3B (m)). The photomask 131 is configured so that the transmittance of the region where the dichroic filter layer 132 for red light is formed becomes high. In addition, since the photoresist 130 is a positive type photoresist, a region irradiated with light by development processing, that is, a region where the dichroic filter layer 132 for red light is formed is dissolved, and pixels having other hues are dissolved. The area does not dissolve. Therefore, the pixel areas of other hues are still protected by the photoresist 130.

Next, alternating multilayer films of SiO ₂ and TiO ₂ are formed on the second refractive index layer 129 by a sputtering apparatus. At this time, SiO ₂ and TiO ₂ are formed to have predetermined film thicknesses, respectively. The dichroic filter layer 132 is usually composed of about 10 alternating multilayer films of SiO ₂ and TiO ₂ (FIG. 3B (n)). Further, an etching process is performed to remove the photoresist 130 (FIG. 3B (o)).

  Next, a process of forming a dichroic filter layer 135 that transmits green light will be described.

  First, a photoresist 133 is applied on the second refractive index layer 129 and the dichroic filter layer 132, and this is masked with a photomask 134 and exposed (FIG. 3B (p)). The photomask 133 is configured so that the transmittance of the region where the dichroic filter layer for green light is formed becomes high. In addition, since the photoresist 133 is a positive type photoresist, a region irradiated with light by development processing, that is, a region where the dichroic filter layer 135 for green light is formed is dissolved, and pixels having other hues are dissolved. The area does not dissolve. Therefore, the pixel regions of other hues are protected by the photoresist 133.

Finally, an alternating multilayer film of SiO ₂ and TiO ₂ is formed on the second refractive index layer 129 by a sputtering apparatus. At this time, SiO ₂ and TiO ₂ are formed to have predetermined film thicknesses, respectively. The dichroic filter layer 135 is usually composed of about 10 alternating multilayer films of SiO ₂ and TiO ₂ (FIG. 3B (q)). Further, when the photoresist 133 is removed by performing an etching process, the optical substrate 12 is completed (FIG. 3B (r)).

Then, the upper surface of the sensor substrate 10 and the lower surface of the optical substrate 12 are bonded to each other based on a positioning index (not shown), thereby completing the imaging device of this reference embodiment.

Thus, in this reference embodiment, by manufacturing in a different process sensor substrate 10 of the optical substrate 12 having a complex configuration, such as a dichroic filter layer 132 and 135, thereby improving the yield of the image sensor. Further, in order to form each optical member constituting the optical substrate 12 with as few kinds of materials as possible, the optical member formed on the glass substrate 120 which is the transparent substrate of the optical substrate 12 is divided into two types having different refractive indexes. By using a transparent material, the manufacturing apparatus for manufacturing the image sensor is reduced in size, and the yield is improved due to the small number of materials used.

Next , the state of light incident on the image sensor will be described with reference to FIGS.

5 (a) is, the light flux of the field angle of F1.4 to predetermined pixels of the imaging device of this preferred embodiment is a ray tracing diagram in the case of incident. As shown in FIG. 5A, the light that has passed through the glass substrate 120, passed through the low-refractive index layer 121, and passed through the microlens 124 is provided between the microlens 124 and the dichroic filter layer 135. After being refracted at the interface between the first refractive index layer 124 and the second refractive index layer 129, the light enters the dichroic filter layer 135.

Here, with reference to FIG. 4, the spectral characteristics of each dichroic filter layer will be described. The dichroic filter layer is composed of alternating multilayer films of SiO ₂ and TiO ₂ which are transparent materials, and hardly absorbs light. The dichroic filter layer 132 exhibits a spectral transmission characteristic that transmits red light, and a characteristic that reflects blue and green light. Similarly, the dichroic filter layer 135 exhibits a spectral transmission characteristic that transmits green light, and a characteristic that reflects blue and red light. In addition, the dichroic filter layer 138 (not shown in FIGS. 1 and 5) exhibits a spectral transmission characteristic that transmits blue light, and exhibits a characteristic that reflects green and red light.

Referring to FIG. 5A again, the green component of the light incident on the dichroic filter layer 135 passes through the dichroic filter layer 135 and enters the waveguide 117. Light incident on the interface between the waveguide 117 and the interlayer film 110 undergoes total reflection and is guided to the photoelectric conversion unit 104. The waveguide 117 is made of a transparent material TiO ₂ having a relatively high refractive index, and the light beam guided to the waveguide 117 is entirely at the interface with the interlayer film 110 made of SiO ₂ having a relatively low refractive index. The light is guided to the photoelectric conversion unit 104 while being reflected.

  In addition, a metal reflection layer (not shown) is provided at a boundary portion between the dichroic filter layer 135 and an adjacent pixel so that light that does not enter the waveguide 117 is guided to the adjacent pixel. Such light contributes to an improvement in sensitivity in adjacent pixels.

Thus, the imaging device of this preferred embodiment, since even when the wide light beam angle of view is incident can be derived to effectively photoelectric conversion unit 104 to light, sensitivity is improved.

  On the other hand, as shown in FIG. 5B, among the light incident on the dichroic filter layer 135, blue and red lights other than green light are reflected by the dichroic filter layer 135. The blue and red light reflected by the dichroic filter layer 135 is totally reflected at the refractive index interface between the first refractive index layer 125 and the second refractive index layer 129. This is because the refractive index of the second refractive index layer 129 is higher than the refractive index of the first refractive index layer 125. In addition, since the refractive index interface between the first refractive index layer 125 and the second refractive index layer 129 is formed in a prism shape, the light totally reflected at the refractive index interface is the first refracted light of the adjacent pixel. The light is again totally reflected at the refractive index interface between the refractive index layer 125 and the second refractive index layer 129 and enters the dichroic filter layer 132 of the adjacent pixel.

  The spectral transmission characteristic of the dichroic filter layer 132 has a characteristic of transmitting red light as shown in FIG. Therefore, of the blue and red light reflected by the dichroic filter layer 135, the red light passes through the dichroic filter layer 132 and is guided to the photoelectric conversion unit 104 through the waveguide 117.

In conventional pigment-type color filters, light of a color that does not pass through the filter is absorbed by the filter, which is a factor that decreases the sensitivity of the image sensor. However, according to this preferred embodiment, the light which has been absorbed in the color filter of the conventional pigment type can also be incorporated into the photoelectric conversion unit 104, thereby it becomes possible to improve the sensitivity of the imaging element.

Furthermore, the imaging device of the present reference embodiment, to guide the red light incident on the pixels having a dichroic filter layer 135 the green light is transmitted, adjacent thereto, the pixel having a dichroic filter layer 132 which transmits red Thus, it is possible to prevent so-called false color from occurring. That is, the imaging device having a color filter layer of a conventional pigment type, although green red image be incident red light to a pixel having a color filter layer which transmits light has not been reproduced, the reference In the image pickup device of the embodiment, red light incident on a pixel having a dichroic filter layer 135 that transmits green light reproduces a red image at a pixel having a dichroic filter layer 132 that transmits red adjacent thereto. Is possible.

  Note that light incident on a pixel having a dichroic filter layer of another hue also acts in the same manner, and thus description of the other hue is omitted.

In this reference embodiment, an example in which two types of transparent materials of TiO ₂ as a transparent material having a relatively high refractive index and SiO ₂ as a transparent material having a relatively low refractive index is used for the optical member constituting the optical substrate 12 is shown. However, the loss due to reflection at the refractive index interface between the microlens 124 made of a transparent material having a relatively high refractive index and the first refractive index layer 125 made of a transparent material having a relatively low refractive index is reduced. to, as in the modified example of the imaging device of this reference embodiment shown in FIG. 6, between the microlens 124 and the first refractive index layer 125, for example, an intermediate refractive index made of a transparent material such as SiN It is also effective to provide the antireflection layer 136 having the optical member and to form the optical member with three kinds of transparent materials. Furthermore, it is also effective to form an optical member with four types of transparent materials by coating the light incident surface of the optical substrate 12 with MgF ₂ , which is a transparent material having a relatively low refractive index, as an antireflection film.

(First Embodiment)
7-11 are views showing a first embodiment of the present invention, FIG. 7 is a schematic sectional view of the imaging device of the first embodiment of the present invention, FIGS. 8A and 8B shown in FIG. 7 FIGS. 9A and 9B are diagrams showing a manufacturing process of the sensor substrate of the image sensor, and FIGS. 9A and 9B are diagrams showing a manufacturing process of the optical substrate of the image sensor shown in FIG.

  As shown in FIG. 7, the image pickup device of the present embodiment also includes a sensor substrate 20 and an optical substrate 22.

The sensor substrate 20 has a Si substrate 200 provided with a plurality of photoelectric conversion units 204 on the upper surface. On the Si substrate 200, two Al wiring layers 207 and 213 are formed via interlayer films 210 and 216 formed of SiO ₂ or the like. The Al wiring layers 207 and 213 control a transfer switch for transferring photoelectric charges generated in the photoelectric conversion unit 204 to a floating diffusion unit (FD unit) (not shown), and output the potential of the FD unit. This is a wiring layer.

  As described above, the sensor substrate 20 includes the Si substrate 200, the photoelectric conversion unit 204, the Al wiring layers 207 and 213, and the interlayer films 210 and 216. Further, on the upper surface of the sensor substrate 20, an uneven portion having a well structure composed of Al wiring layers 207 and 213 and interlayer films 210 and 216 is formed.

The optical substrate 22 has a glass substrate 220 which is a transparent substrate, and a microlens 224 is provided on the lower surface of the glass substrate 220 via a low refractive index layer 221 made of SiO ₂ having a relatively low refractive index. Is provided. The microlens 224 is made of TiO ₂ having a relatively high refractive index, and its lens shape is determined so that a light beam incident from a photographing lens (not shown) is condensed on the photoelectric conversion unit 204.

  On the lower surface of the microlens 224, for example, pigment type color filters 227 and 230 having a function as a waveguide for guiding light transmitted through the microlens 224 to the photoelectric conversion unit 204 are provided. On the light incident side of the color filters 227 and 230 that are also waveguides, the opening is large so that more light can enter.

  As described above, the optical substrate 22 includes the glass substrate 220, the low refractive index layer 221, the microlens 224, and the color filters 227 and 230. In addition, an uneven portion made of color filters 227 and 230 is formed on the lower surface of the optical substrate 22.

  The imaging device of the present embodiment has a structure in which the sensor substrate 20 and the optical substrate 22 are bonded to each other so as to engage each other with the concave and convex portions. The sensor substrate 20 and the optical substrate 22 include the sealing material 234. It is bonded in a sealed state. After the sensor substrate 20 and the optical substrate 22 are bonded together, the color filters 227 and 230 that also serve as waveguides are formed between the concave and convex portions of the sensor substrate 20 and the optical substrate 22 when bonded together. Surrounded by the air layer 233 in the gap. Therefore, even if the refractive indexes of the color filters 227 and 230 are somewhat small, the total reflection condition is satisfied by the difference in refractive index with the air layer, and the color filters 227 and 230 function as waveguides. As a result, also in this embodiment, the photographing light flux is substantially the same as the ray tracing diagram shown in FIG. 5A, and the light flux with a wide photographing angle of view also passes through the color filters (waveguides) 227 and 230 and the photoelectric conversion unit 204. Therefore, the sensitivity of the image sensor can be improved.

In this embodiment, since the color filters 227 and 230 provided on the microlens 224 of the optical substrate 22 also have a role as a waveguide, compared with the configuration of the reference embodiment shown in FIG. The optical path length from the microlens 224 to the photoelectric conversion unit 204 is structurally short. Therefore, the loss of light that occurs while exiting from the microlens 224 and reaching the photoelectric conversion unit 204 is reduced, so that the sensitivity of the image sensor can also be improved with this configuration.

  Next, a method for manufacturing the sensor substrate 20 shown in FIG. 7 will be described with reference to FIGS. 8A and 8B.

First, as shown in FIG. 8A (a), the upper surface of the Si substrate 200 is oxidized to form a silicon oxide film 201 made of SiO _{2 on} the upper surface of the Si substrate 200. Further, in order to form a photoelectric conversion region on the upper surface of the Si substrate 200, a photoresist 202 is applied on the silicon oxide film 201, which is covered with a photomask 203 and exposed (FIG. 8A (b)). The photomask 203 is configured such that a region corresponding to the photoelectric conversion region transmits light, and the other regions block light. Further, since the photoresist 202 is a positive type photoresist, the region irradiated with light by the development process, that is, the region corresponding to the photoelectric conversion region is dissolved, and a part of the silicon oxide film 201 is exposed. Further, by performing a dry etching process using plasma, the silicon oxide film 201 in a region not covered with the photoresist 202 is removed (FIG. 8A (c)).

  Further, by implanting ions into the upper surface of the Si substrate 200, the photoelectric conversion unit 204 is formed in a region not covered with the silicon oxide film 201 on the upper surface of the Si substrate 200 (FIG. 8A (d)). At this time, ions are absorbed in the region covered with the silicon oxide film 201, and thus the photoelectric conversion portion 204 is not formed in the region.

  After the photoelectric conversion unit 204 is formed on the upper surface of the Si substrate 200, an electrode for transferring charges stored in the photoelectric conversion unit 204 is formed on the upper surface of the Si substrate 200.

  First, a photoresist 205 is applied to the upper surface of the Si substrate 200 on which the photoelectric conversion portion 204 and the silicon oxide film 201 are formed, and this is covered with a photomask 206 and exposed (FIG. 8A (e)). The photomask 206 is configured such that a region corresponding to the first wiring layer 207 transmits light and the other regions block light. Further, since the photoresist 205 is a positive type photoresist, a region irradiated with light by the development process, that is, a region corresponding to the first wiring layer is dissolved, and a part of the silicon oxide film 201 is exposed. To do. Furthermore, by performing a dry etching process, the silicon oxide film 201 in a region not covered with the photoresist 205 is removed (FIG. 2A (f)).

  Further, for example, Al (aluminum) is deposited on the Si substrate 200 by a CVD apparatus or the like, thereby forming the first wiring layer 207 on the Si substrate 200 (FIG. 8A (g)).

  After the first wiring layer 207 is formed in this way, an etching process is performed to remove the photoresist 205 (FIG. 8A (h)).

  Next, an interlayer film 210 is formed in order to form the second wiring layer 213. First, a photoresist 208 is applied to the upper surface of the Si substrate 200, and this is covered with a photomask 209 and exposed (FIG. 8A (i)). The photomask 208 is configured such that a region corresponding to the photoelectric conversion unit 204 blocks light and other regions transmit light. Further, since the photoresist 208 is a positive type photoresist, a region irradiated with light by the development process, that is, a region not corresponding to the photoelectric conversion unit 204 is dissolved.

Then, an interlayer film 210 made of SiO ₂ is formed by a CVD apparatus (FIG. 8B (j)). After the interlayer film 210 is formed, an etching process is performed to remove the photoresist 208 (FIG. 8B (k)).

  Next, a photoresist 211 is applied, covered with a photomask 212 and exposed (FIG. 8B (l)). The photomask 212 is configured such that a region corresponding to the second wiring layer 213 transmits light, and the other regions block light. Further, since the photoresist 211 is a positive type photoresist, the region irradiated with light by the development process, that is, the region corresponding to the second wiring layer 213 is dissolved. Then, the second wiring layer 213 is formed by depositing Al by a CVD apparatus or the like (FIG. 8B (m)). Thereafter, an etching process is performed to remove the photoresist 211 (FIG. 8B (n)).

Further, an interlayer film 216 is formed on the second wiring layer 213. First, a photoresist 214 is applied on the Si substrate 200 on which the second wiring layer 213 is formed, and this is covered with a photomask 215 and exposed (FIG. 8B (o)). The photomask 215 is configured such that a region corresponding to the well structure that houses the color filters 227 and 230 that also function as waveguides blocks light, and the other regions transmit light. Further, since the photoresist 215 is a positive type photoresist, the region irradiated with light by the development process, that is, the region not corresponding to the well structure is dissolved. Further, an interlayer film 216 made of SiO ₂ is formed by a CVD apparatus (FIG. 8B (p)).

  Further, when the photoresist 214 is removed by performing an etching process in order to form the well structure, the sensor substrate 20 is completed (FIG. 8B (q)).

  Next, a method for manufacturing the optical substrate 22 shown in FIG. 7 will be described with reference to FIGS. 9A and 9B.

  First, the microlens 224 is formed on the surface (upper surface shown in FIG. 9A) of the glass substrate 220 that is a transparent substrate. The microlens 224 is formed by a known registry flow method.

For this purpose, first, a low refractive index layer 221 made of SiO ₂ which is a material having a relatively low refractive index is deposited on a glass substrate 220 by a CVD apparatus (FIG. 9A (b)), and a photoresist 222 is further formed thereon. It is applied (FIG. 9A (c)), covered with a photomask 223 and exposed (FIG. 9A (d)). In order to form the shape of the microlens 224, the transmittance distribution of the photomask 223 is set so that the transmittance is low in the central portion of the pixel and high in the peripheral portion of the pixel. Further, since the photoresist 222 is a negative type photoresist, the region not irradiated with light, that is, the region corresponding to the microlens 224 is dissolved by the development process (FIG. 9A (e)).

Further, by performing an etching process on the low refractive index layer 221, a recess for forming the microlens 224 is formed in the low refractive index layer 221 (FIG. 9A (f)). At this time, if the selection ratio in the etching process between the photoresist 222 and the low refractive index layer 221 is 1: 1, the shape of the photoresist 222 is transferred to the low refractive index layer 221 as it is. Furthermore, TiO ₂ , which is a material having a relatively high refractive index, is deposited on the low refractive index layer 221 by a CVD apparatus, thereby forming the microlens 224 on the low refractive index layer 221 (FIG. 9A (g)). ).

  After the microlens 224 is formed, color filters 227 and 230 that also serve as waveguides are created.

  First, a color filter 227 that transmits green light is formed. First, a photoresist 225 is applied on the microlens 224, and this is masked with a photomask 226 and exposed (FIG. 9A (h)). The photomask 226 is configured so that the transmittance of the region where the green color filter 227 is formed becomes high. Further, since the photoresist 226 is a positive type photoresist, the region irradiated with light by the development process, that is, the region where the green color filter 227 is formed is dissolved, and the pixel region of the other hue is dissolved. do not do. Accordingly, the pixel regions of other hues are protected by the photoresist 225.

  Next, a pigment type green color filter 227 is formed (FIG. 9A (i)), and an etching process is performed to remove the photoresist 225.

  Next, a color filter 230 that transmits red light is formed. First, a photoresist 228 is applied, masked with a photomask 229, and exposed (FIG. 9B (j)). The photomask 233 is configured so that the transmittance of the region where the red color filter 230 is formed is high. Further, since the photoresist 228 is a positive type photoresist, the region irradiated with light by the development process, that is, the region where the red color filter 230 is formed is dissolved, and the other pixel regions of the hue are dissolved. do not do. Accordingly, the pixel regions of other hues are protected by the photoresist 228.

  Next, a pigment-type red color filter 230 is formed (FIG. 9B (k)), and an etching process is performed to remove the photoresist 228 (FIG. 9B (l)).

  Finally, these are formed in a tapered shape so that the color filters 227 and 230 function as waveguides. The color filters 227 and 230 are formed in a waveguide shape by a known registry flow method.

  First, a photoresist 231 is applied on the color filters 227 and 230 formed on the glass substrate 220, and the photoresist 231 is exposed through the photomask 232 (FIG. 9B (m)). In order to form the color filters 227 and 230 in the waveguide shape, the photomask 232 has a transmittance distribution so that the transmittance at the center of the pixel is low and the transmittance at the periphery of the pixel is high. In addition, since the photoresist 231 is a negative type photoresist, a region that is not irradiated with light, that is, a region that does not correspond to the waveguide is dissolved by the development process (FIG. 9B (n)).

  Here, if the selection ratio in the etching process between the photoresist 231 and the color filters 227 and 230 is 1: 1, the shape of the photoresist 231 is transferred to the color filters 227 and 230 as they are. Then, by performing an etching process, the color filters 227 and 230 are formed in a waveguide shape, and the optical substrate 22 is completed (FIG. 9B (o)).

  Then, the sensor substrate 20 and the optical substrate 22 are bonded to each other so that the uneven portion formed of the well structure portion of the sensor substrate 20 and the uneven portion formed of the waveguide portions 227 and 230 of the optical substrate 22 are engaged with each other. The image sensor of the form is completed. According to the configuration of the present embodiment, the sensor substrate 20 and the optical substrate 22 are positioned relative to each other when the concave and convex portions of the sensor substrate 20 and the concave and convex portions of the optical substrate 22 are engaged. The positional accuracy of the substrate 22 is improved, and it is possible to prevent a decrease in sensitivity of the image sensor due to a positional shift that occurs when the two are bonded together.

  FIG. 10 is a schematic cross-sectional view showing a modification of the sensor substrate of the image sensor shown in FIG.

  The sensor substrate 20 of the present embodiment shown in FIG. 7 and the like has a configuration in which the first wiring layer 207 and the second wiring layer 213 are covered with the interlayer films 210 and 216, respectively. In order to form the first wiring layer 207 and the interlayer film 210 in the same pattern and the second wiring layer 213 and the interlayer film 216 in the same pattern as in the modified example of the sensor substrate It is possible to reduce the types of photomasks.

  FIG. 11 is a schematic cross-sectional view showing a modification of the image sensor shown in FIG.

  In the present embodiment, as shown in FIG. 7 and the like, the optical substrate 22 is provided with a waveguide made of color filters 227 and 230, and the sensor substrate 20 having a well structure wider than the waveguide portions 227 and 230 of the optical substrate 22 is provided. An image sensor having a structure in which the optical substrate 22 is bonded is shown.

Instead of this structure, as shown in FIG. 11, the sensor substrate 20 has the same configuration as that of FIG. 7, and the optical substrate 22 is formed with ordinary pigment type color filters 227 and 230 under the microlens 224. The waveguide 235 is formed on the lower surface of the color filters 227 and 230 with a transparent material having a relatively high refractive index (for example, TiO ₂ ), and the image pickup device is configured by bonding the sensor substrate 20 and the optical substrate 22 together. Also good.

(Other embodiments)
Next, with reference to FIG. 12, an embodiment when the image sensor of the present invention is applied to a digital camera will be described in detail. FIG. 12 is a block diagram showing a digital camera to which the image sensor of the present invention is applied.

  In FIG. 12, reference numeral 301 denotes a barrier that serves as a protection and a main switch for the lens 302, reference numeral 302 denotes a lens that forms an optical image of a subject on the solid-state imaging device 304, and reference numeral 303 denotes a light amount that passes through the lens 302. Aperture, reference numeral 304 is a solid-state imaging device for capturing an object imaged by the lens 302 as an image signal, reference numeral 305 is an imaging signal processing circuit, and reference numeral 306 is an analog-digital conversion of an image signal output from the solid-state imaging element 304 A reference numeral 307 denotes a signal processing unit that performs various corrections on the image data output from the A / D converter 306 and compresses the data. A reference numeral 308 denotes a solid-state imaging device 304, and an imaging signal. Timing for outputting various timing signals to the processing circuit 305, the A / D converter 306, and the signal processing unit 307 309 is a general control / arithmetic unit for controlling various operations and the entire digital still camera, 310 is a memory unit for temporarily storing image data, and 311 is for recording or reading on a recording medium. An interface unit, 312 is a detachable recording medium such as a semiconductor memory for recording or reading image data, and 313 is an external interface unit for communicating with an external computer or the like.

  Next, the operation at the time of shooting of the digital camera of this embodiment will be described.

  When the barrier 301 is opened, the main power supply is turned on, then the control system power supply is turned on, and the power supply of the imaging system circuit such as the A / D converter 306 is turned on.

  Then, in order to control the exposure amount, the overall control / arithmetic unit 309 opens the aperture 303, and after the signal output from the solid-state image sensor 304 is converted by the A / D converter 306, the signal processing unit 307 receives the signal. Entered. The overall control / calculation unit 309 calculates exposure based on the data. The overall control / calculation unit 309 determines the brightness based on the result of the photometry, and controls the diaphragm 303 according to the result.

  Next, the overall control / arithmetic unit 309 extracts a high-frequency component by the imaging signal processing circuit 305 based on the signal output from the solid-state imaging device 304 and calculates the distance to the subject. Thereafter, the overall control / arithmetic unit 309 determines whether or not the lens 302 is in focus and determines whether it is in focus, and when it determines that the lens is not in focus, it drives the lens 302 again to perform distance measurement. Then, the overall control / calculation unit 309 starts the main exposure after confirming the in-focus state.

  When the exposure is completed, the image signal output from the solid-state imaging device 304 is A / D converted by the A / D converter 306 through the imaging signal processing circuit 305, passes through the signal processing unit 307, and is stored in the memory by the overall control / calculation unit 309. Written in the unit 310.

  Thereafter, the data stored in the memory unit 310 is recorded on a removable recording medium 312 such as a semiconductor memory via the recording medium control I / F unit 311 under the control of the overall control / arithmetic unit 309. If this data is directly input to a computer or the like via the external I / F unit 313, the image can be processed by the computer or the like.

  As described above, the digital camera according to the present embodiment is configured to obtain an image signal by photoelectrically converting the subject image formed by the lens 302 by the image sensor 304. As the imaging device 304, the imaging device described with reference to FIGS. 1 and 7 can be used.

It is a schematic sectional drawing of the image pick-up element of the reference form of this invention. It is a figure which shows the manufacturing process of the sensor board | substrate of the image pick-up element shown in FIG. It is a figure which shows the manufacturing process of the sensor board | substrate of the image pick-up element shown in FIG. It is a figure which shows the manufacturing process of the optical board | substrate of the image pick-up element shown in FIG. It is a figure which shows the manufacturing process of the optical board | substrate of the image pick-up element shown in FIG. It is a spectral characteristic figure of the dichroic filter of the image sensor shown in FIG. It is a ray tracing diagram in the image sensor shown in FIG. It is a schematic sectional drawing which shows the modification of the image pick-up element shown in FIG. It is a schematic sectional drawing of the image sensor of the 1st Embodiment of this invention. It is a figure which shows the manufacturing process of the sensor board | substrate of the image pick-up element shown in FIG. It is a figure which shows the manufacturing process of the sensor board | substrate of the image pick-up element shown in FIG. It is a figure which shows the manufacturing process of the optical board | substrate of the image pick-up element shown in FIG. It is a figure which shows the manufacturing process of the optical board | substrate of the image pick-up element shown in FIG. It is a schematic sectional drawing which shows the modification of the sensor board | substrate of the image pick-up element shown in FIG. 8A and 8B are schematic cross-sectional views showing a modification of the image pickup device shown in FIG. 7 and the like, in which FIG. 7A is the optical substrate, FIG. 7B is the sensor substrate, and FIG. Fig. 4 shows an assembly with a substrate. It is a block diagram which shows the digital camera to which the image pick-up element of this invention is applied. It is a schematic sectional drawing which shows the conventional CMOS image sensor.

Explanation of symbols

10, 20 Sensor substrate 12, 22 Optical substrate 100, 200 Si substrate 101, 201 Silicon oxide film 102, 105, 108, 111, 115, 122, 126, 130, 133, 202, 205, 208, 211, 214, 222 , 225, 228, 231 Photoresist 103, 106, 112, 116, 123, 127, 131, 134, 230, 206, 209, 212, 215, 223, 226, 229, 232 Photomask 104, 204 Photoelectric converter 107 , 207 First wiring layer (Al wiring layer)
109 Etching stopper film 110, 114, 210, 216 Interlayer film 113, 213 Second wiring layer (Al wiring layer)
117 Waveguide 120, 220 Glass substrate 121, 221 Low refractive index layer 124, 224 Micro lens 125 First refractive index layer 129 Second refractive index layer 132, 135, 138 Dichroic filter layer 136 Antireflection layer 227, 230 Color Filter 235 Waveguide 301 Barrier 302 Lens 303 Diaphragm 304 Solid-state imaging device 305 Imaging signal processing circuit 306 A / D converter 307 Signal processing unit 308 Timing generation unit 309 Overall control / calculation unit 310 Memory unit 311 Recording medium control interface unit 312 Recording Medium 313 External interface section

Claims (5)

A plurality of photoelectric conversion units provided on a semiconductor substrate;
A color filter serving as a waveguide disposed on each of the photoelectric conversion units;
And the air layer in which the disposed so as to surround each of the color filter,
Disposed between adjacent pre Kisora air layer, and a plurality of interlayer film covering the plurality of wiring layers, respectively,
Before SL corresponding to each color filter, and the color filter, the air layer, and a plurality of microlenses arranged directly on the interlayer film,
An image pickup device comprising:   The imaging device according to claim 1, wherein an opening of the color filter serving as the waveguide increases from the photoelectric conversion unit toward the microlens. A glass substrate disposed on the microlens, and a low-refractive index layer having a lower refractive index than the microlens and containing silicon oxide, between the glass substrate and the microlens. The imaging device according to claim 1 or 2.   The imaging device according to claim 1, wherein an end portion in a direction orthogonal to the thickness direction is sealed with a sealing material. A digital camera that obtains an image signal by photoelectrically converting a subject image formed by an imaging lens with an imaging device,
A digital camera comprising the image pickup device according to any one of claims 1 to 4 as the image pickup device.

Images