JP2015167219A - Image sensor, manufacturing equipment, electronic equipment - Google Patents

Abstract

Optical color mixing and flare are reduced even when the pixel size is large. A unit pixel includes a plurality of unit pixels formed in a light receiving region, a light shielding film formed at a boundary portion between the unit pixels, and a microlens formed for each unit pixel, and the unit pixel is 1.98 μm. The above-described substantially square lattice, and the microlenses are formed as squares each having a natural number of 2 or more, each having a square shape with a side of less than 1.98 μm. The light shielding film is further formed at the boundary portion between the microlenses. The present technology can be applied to an imaging device having a large pixel size. [Selection] Figure 15

Description

  The present technology relates to an image sensor, a manufacturing apparatus, and an electronic device. Specifically, the present invention relates to an imaging device, a manufacturing apparatus, and an electronic device that can suppress flare and ghost and improve image quality.

  In recent years, digital video cameras and digital still cameras have been required to reduce the size of devices that emphasize high resolution and portability to project details of the subject. In the imaging apparatus, development has been performed for reducing the pixel size while maintaining the imaging characteristics.

  In recent years, in addition to continuous demands for high resolution and miniaturization, there has been an increasing demand for improvements in minimum subject illuminance, high-speed imaging, etc. There is an increasing expectation for improved image quality. Japanese Patent Application Laid-Open No. H10-260260 proposes to improve image quality by reducing optical color mixing and flare by forming a light shielding film formed through an insulating layer at the pixel boundary of the light receiving surface.

JP 2010-186818 A

  In Patent Document 1, in order to improve the image quality of a back-illuminated imaging device having a unit pixel size of 1.75 μm, a light-shielding film is formed at the unit pixel boundary, so that optical color mixing caused by diffracted reflected light from the surface of the microlens Reducing flare is disclosed.

  However, in an imaging device having a unit pixel size exceeding approximately 2.0 μm, when a microlens is formed corresponding to a unit pixel, in other words, when the formation size of the microlens is increased, the diffraction order of diffracted reflected light ( m) and the diffraction angle (θ) at the same diffraction order (m) becomes small. When the diffraction order increases and the angle decreases, the optical color mixture and flare in the image sensor deteriorate due to re-reflection from the seal glass formed on the light incident side front surface of the image sensor and the infrared cut filter (IRCF). May deteriorate.

  For this reason, there is a need for a mechanism that improves image quality without deteriorating optical color mixing and flare even when the unit pixel size is large.

  This technique is made in view of such a situation, and makes it possible to improve image quality.

  An imaging device according to one aspect of the present technology includes a plurality of unit pixels formed in a light receiving region, a light shielding film formed at a boundary portion between the unit pixels, and a microlens formed for each unit pixel. The unit pixel is a substantially square lattice of 1.98 μm or more, and the microlens is a square having a side of less than 1.98 μm and squares of 2 or more natural numbers for each unit pixel. Yes.

  The light shielding film may be further formed at a boundary portion between the microlenses.

  An inner lens is further provided between the micro lens and the photodiode, and the inner lens is a main of at least one of the plurality of condensing spots collected by the plurality of micro lenses. The light beam may be formed so as to be condensed toward the unit pixel center direction.

  By detecting the phase difference, the pixel for detecting the focus can be obtained.

  A light-shielding film formed from the boundary portion to the substantially central portion of the microlens can be further provided.

  The unit pixel may include a light receiving unit that acquires light information from different directions.

  A light shielding wall provided in a direction perpendicular to the light shielding film may be further provided.

  A manufacturing apparatus according to one aspect of the present technology includes a plurality of unit pixels formed in a light receiving region, a light shielding film formed at a boundary portion between the unit pixels, and a microlens formed for each unit pixel. The unit pixel is a substantially square lattice of 1.98 μm or more, and the microlens is a square having a side of less than 1.98 μm and squares of 2 or more natural numbers for each unit pixel. Manufacturing an image sensor.

  The microlens can be formed by a hot melt flow method.

  The microlens can be formed by a dry etching method.

  An electronic apparatus according to an aspect of the present technology includes a plurality of unit pixels formed in a light receiving region, a light shielding film formed at a boundary portion between the unit pixels, and a microlens formed for each unit pixel. The unit pixel is a substantially square lattice of 1.98 μm or more, and the microlens is a square having a side of less than 1.98 μm and squares of 2 or more natural numbers for each unit pixel. And a signal processing unit that performs signal processing on a signal output from the image sensor.

  An imaging device according to one aspect of the present technology includes a plurality of unit pixels formed in a light receiving region, a light shielding film formed at a boundary portion between the unit pixels, and a microlens formed for each unit pixel. . The unit pixel is a substantially square lattice of 1.98 μm or more, and the microlens is a square having a side of less than 1.98 μm for each unit pixel, and squares of 2 or more natural numbers are formed.

  In the manufacturing apparatus according to one aspect of the present technology, the imaging element is manufactured.

  In the electronic apparatus according to one aspect of the present invention, a signal from the imaging element is processed.

  According to one aspect of the present technology, it is possible to improve image quality.

  Note that the effects described here are not necessarily limited, and may be any of the effects described in the present disclosure.

It is a figure which shows the structure of a surface irradiation type imaging device. It is a figure which shows the structure of a back irradiation type imaging device. It is a figure for demonstrating diffraction reflection light. It is a figure for demonstrating diffraction reflection light. It is a figure for demonstrating diffraction reflection light. It is a figure for demonstrating diffraction reflection light. It is a figure for demonstrating diffraction reflection light. It is a figure for demonstrating the structure of a micro lens. It is a figure for demonstrating manufacture of an image pick-up element. It is a figure for demonstrating manufacture of an image pick-up element. It is a figure for demonstrating the shape of a light shielding film. It is a figure for demonstrating the shape of a light shielding film. It is a figure for demonstrating the other structure of a micro lens. It is a figure for demonstrating an image pick-up element provided with an inner lens. It is a figure for demonstrating an image pick-up element provided with an inner lens. It is a figure for demonstrating kicking. It is a figure for demonstrating kicking. It is a figure for demonstrating the autofocus by a phase difference system. It is a figure for demonstrating the autofocus by a phase difference system. It is a figure for demonstrating a curvature. It is a figure for demonstrating curvature flatness. It is a figure for demonstrating curvature flatness. It is a figure for demonstrating the light shielding film of the pixel for phase difference detection. It is a figure for demonstrating the light shielding film of the pixel for phase difference detection. It is a figure for demonstrating the light shielding film of the pixel for phase difference detection. It is a figure for demonstrating the light shielding film of the pixel for phase difference detection. It is a figure for demonstrating the light shielding film of the pixel for phase difference detection. It is a figure for demonstrating a light-shielding wall. It is a figure for demonstrating a light-shielding wall. It is a figure for demonstrating a light-shielding wall. It is a figure for demonstrating arrangement | positioning of a pixel. It is a figure for demonstrating arrangement | positioning of a pixel. It is a figure which shows the structure of an example of an electronic device.

Hereinafter, modes for carrying out the present technology (hereinafter referred to as embodiments) will be described. The description will be given in the following order.
1. 1. Configuration of surface-illuminated image sensor 2. Configuration of back-illuminated image sensor 3. Effects of diffracted light, etc. 4. Configuration of micro lens 5. About manufacturing 1 of image sensor 6. About manufacturing of image sensor 2 Other configurations of microlenses 8. 8. Configuration including an inner lens About effect 10. 10. About autofocus pixels Electronics

  The present technology described below can be applied to an image sensor that can suppress optical color mixing and flare and improve image quality. For comparison, first, a front-illuminated image sensor and a back-illuminated image sensor will be described, optical color mixing and flare will be described, and then an image sensor to which the present technology is applied will be described.

<Configuration of surface-illuminated image sensor>
As a CMOS (Complementary MOS) image pickup device, a front side illumination type shown in FIG. 1 and a back side illumination type shown in FIG. 2 are known.

  FIG. 1 is a configuration diagram of a front-illuminated image sensor 110. As shown in FIG. 1, a semiconductor substrate 112 is configured to include a pixel region 113 in which a plurality of unit pixels 116 each including a photodiode (PD) 111 serving as a photoelectric conversion unit and a plurality of pixel transistors are formed.

  Although the pixel transistor is not shown, the gate electrode 114 is shown in FIG. 1 to schematically show the presence of the pixel transistor. Each photodiode 111 is isolated by an element isolation region 115 by an impurity diffusion layer. A multilayer wiring layer 119 in which a plurality of wirings 118 are arranged via an interlayer insulating film 117 is formed on the surface side of the semiconductor substrate 112 where the pixel transistors are formed.

  The wiring 118 is formed except for a portion corresponding to the position of the photodiode 111. An on-chip color filter 121 and an on-chip microlens 122 are sequentially formed on the multilayer wiring layer 119 via a planarizing film 120. The on-chip color filter 121 is configured by arranging, for example, red (R), green (G), and blue (B) color filters.

  In the front-illuminated imaging device 110, the substrate surface on which the multilayer wiring layer 119 is formed is the light receiving surface 123, and light L is incident from the substrate surface side. Here, each of the microlens 122 and the color filter 121 is formed in a single unit corresponding to the unit pixel 116.

<Configuration of Back-illuminated Image Sensor>
FIG. 2 is a configuration diagram of the backside illumination type image sensor 130. The same parts as those of the front-illuminated image sensor 110 shown in FIG.

  As shown in FIG. 2, the semiconductor substrate 112 includes a pixel region 113 in which a plurality of unit pixels 116 each including a photodiode 111 serving as a photoelectric conversion unit and a plurality of pixel transistors are formed. Although not shown, the pixel transistor is formed on the surface side of the substrate, and in FIG. 2, the gate electrode 114 is shown to schematically indicate the presence of the pixel transistor.

  Each photodiode 111 is isolated by an element isolation region 115 by an impurity diffusion layer. A multilayer wiring layer 119 in which a plurality of wirings 118 are formed through an interlayer insulating film 117 is formed on the surface side of the semiconductor substrate 112 where the pixel transistors are formed.

  In the back irradiation type, the wiring 118 can be formed regardless of the position of the photodiode 111. On the other hand, an insulating layer 128, an on-chip color filter 121, and an on-chip microlens 122 are sequentially formed on the back surface of the semiconductor substrate 112 facing the photodiode 111.

  In the backside illuminating type image pickup device 130, the back surface of the substrate opposite to the surface of the substrate on which the multilayer wiring layer and the pixel transistor are formed is the light receiving surface 132, and light L is incident from the back surface side of the substrate.

Since the light L is incident on the photodiode 111 without being restricted by the multilayer wiring layer 119, the opening of the photodiode 111 can be widened, and high sensitivity can be achieved. 2 also includes a microlens 122 and a color filter 121.
Are unitarily formed corresponding to the unit pixel 116.

<Influence of diffracted light>
The back-illuminated image sensor 130 is generally used for a relatively small camera called a compact digital camera or a mobile camera. For this reason, the back-illuminated image sensor 130 is often composed of unit pixels 116 of less than about 2.0 μm, and so-called fine pixel sensitivity and shading characteristics are improved.

  The back-illuminated image sensor 130 can also be applied to an image sensor for a digital still camera (DSC) such as an APS size or a 35 mm size. However, the pixel size of these image sensors is a fine pixel as described above. Generally, it is approximately 2.0 μm or more as compared with the image pickup device provided.

  In order to achieve higher sensitivity and high-definition image quality even with an APS or 35 mm-size image sensor, in other words, a relatively large image sensor, it may be possible to use a back-illuminated type. . As shown in FIG. 2, the back-illuminated image sensor 130 has a multilayer wiring layer on the front surface side, so that the opening area of the photodiode 111 can be formed wide, so that more incident light can be taken in, and imaging is performed. The sensitivity and shading characteristics of the element are improved.

  The size of the microlens 122 formed corresponding to the unit pixel 116 of the image sensor is normally formed approximately equal to the size of the unit pixel 116. Here, in FIG. 3, light is incident on the unit pixel group A of the back-illuminated image sensor 130 (incident light), and the formation pitch of the microlenses 122 formed on the surface of the back-illuminated image sensor 130 (P lens). A state in which diffracted and reflected light is generated in correspondence with FIG.

  FIG. 3 shows an example in which the pitch of the unit pixels 116 (P pixels) and the formation pitch of the micro lenses 122 (P lenses) are equal.

The diffraction order (m) and diffraction angle (θ) of the diffracted reflected light can be expressed by the following formula (1).
(P lens) × sin θ = m × λ (1)

  In equation (1), λ is the wavelength of the incident light. From equation (1), it can be seen that when λ is constant, the diffraction order m decreases as the P lens, which is the formation pitch of the microlenses 122, decreases, and as the P lens increases, the diffraction order m increases.

  It can also be seen that the diffraction angle θ at the same diffraction order m increases as the microlens formation pitch P lens decreases. Furthermore, it can be read that the diffraction order m increases as the wavelength λ is relatively small.

  For the purpose of reducing optical color mixing and flare of the back-illuminated image sensor 130, light is shielded through the insulating layer 128 at the boundary of the unit pixel 116 in the light receiving region where the unit pixels 116 including the photoelectric conversion unit (photodiode 111) are arranged. A film 141 is formed.

  For example, in the case of the back-illuminated image sensor 130 with the unit pixel 116 having a size of 1.75 μm, by forming a light shielding film 141 at the boundary of the unit pixel 116, optical color mixing caused by diffracted reflected light from the surface of the microlens 122, Flare can be reduced.

  However, in the imaging device in which the size of the unit pixel 116 exceeds 1.75 μm, when the formation size of the microlens 122 is increased in accordance with the size, as described with reference to the above formula (1). The diffraction order (m) of the diffracted reflected light and the diffraction angle (θ) at the same diffraction order (m) are reduced.

  When the diffraction order (m) increases and the angle decreases, optical color mixing and flare in the image sensor due to re-reflection from a seal glass or an infrared cut filter (IRCF) formed on the front surface of the light incident side of the image sensor described later. Gets worse. Therefore, when the size of the unit pixel 116 is increased, it is necessary to provide a mechanism that does not deteriorate optical color mixing and flare.

  Here, the structure of an image sensor that can improve optical color mixing and flare characteristics even if the image sensor is larger than about 2.0 μm in size of the unit pixel 116 will be described.

  In order to improve optical color mixing and flare characteristics, it is necessary to consider a wavelength of about 400 nm to 700 nm in the visible light region. For example, although the light beam of the diffracted and reflected light shown in FIG. 3 is shown as a single straight line, it is actually reflected in a state having a width such as θ1 to θ2 as shown in FIG.

  At this time, light having a short wavelength of about 400 nm is reflected at an angle of θ1 having a small diffraction reflection angle, and light having a short wavelength of about 700 nm has a diffraction reflection angle of about 700 nm, as can be seen from the calculation of equation (1). Reflects at a large angle of θ2. Therefore, for example, the diffraction reflection angle of the diffraction order (m) is diffracted and reflected light having a width of (θ2−θ1) in the figure.

  FIG. 5A shows a plan view of the back-side illuminated image sensor 130 (a view when the back-side illuminated image sensor 130 is viewed from above), and FIG. 5B shows a light receiving area composed of a plurality of unit pixels 116.

  FIG. 5B shows a cross-sectional view taken along line ab shown in FIG. 5A. The incident light shown in FIG. 5B enters the image sensor through the IRCF 151 and the seal glass 152 formed above the image sensor.

  The light incident on the imaging device generates diffracted reflected light having a certain diffraction order (m) and a diffraction reflection angle (θ) according to the formation pitch (P lens) of the surface of the microlens 122 ((− (minus ) Diffracted reflected light is not shown))).

  The diffracted reflected light is reflected by the seal glass 152 formed above the image sensor and becomes reflected light having a visible light component. Further, the light component that has passed through the seal glass 152 is reflected by the IRCF 151 formed further above, and becomes reflected light having a large red component in the visible light region (indicated by a broken line in FIG. 6).

  The light reflected by the seal glass 152 and the IRCF 151 travels again toward the image sensor, and a part of the components is photoelectrically converted by the photodiode 111 of the image sensor. This becomes optical color mixing or flare, which may deteriorate the image quality of the image sensor.

  As described with reference to FIG. 4, the diffracted and reflected light from the microlens 122 shown in FIG. 5 has a width and proceeds to the seal glass 152 and the IRCF 151. Therefore, since the light reflected by the seal glass 152 and re-entering the image sensor is also incident with a width, it becomes a substantially streak-like optical color mixture or flare as shown in FIG. ).

  On the other hand, the light reflected by the IRCF 151 becomes reflected light having a large red component due to the light transmittance characteristics of the IRCF 151 (the reflected light obtained by extracting the reflected light component of the red component light from the reflected light component having a width). Therefore, it becomes a substantially spot-like optical color mixture or flare (shown in the shape of a spot in the figure).

  Here, FIG. 6 shows a table in which the orders at which diffracted and reflected light is generated when the size of the unit pixel 116 is made larger than 1.75 μm.

  The numerical value of the order of the diffracted and reflected light shown in FIG. 6 is calculated at 400 nm on the short wavelength side in the visible light region where the diffraction order is likely to be generated, as can be seen from the equation (1). The unit pixel side direction in the table shown in FIG. 6 is the length in the side direction of the square lattice pixel shown in FIG. 7 (unit pixel size), and the unit pixel diagonal direction is the diagonal direction of the square lattice pixel. Length (unit pixel size × √2).

  As shown in FIG. 6, in the unit pixel side direction, the order of the diffracted and reflected light generated is 1. ± .4 until 1.750 to 1.999 .mu.m, and ". ± .5" at 2.000 .mu.m. The generation order is increased by “2”.

  On the other hand, in the diagonal direction of the unit pixel, the length becomes √2 times longer than the length of the unit pixel in the side direction, so that from ± 1750 to 1.979 μm from equation (1), “± 6” 1. It becomes “± 7” at 980 μm, and the generation order increases by “2”.

  Further, when the unit pixel size is further increased and the formation pitch (P lens) of the microlenses 122 formed corresponding to the unit pixel size is increased, the diffraction angle of the diffracted reflected light of the same order shown in FIG. θ) is also reduced.

  When the diffraction reflection light increases and the diffraction reflection angle at the same order becomes small, as shown in FIGS. 5A and 5B, streaky and spot-like optical color mixture and flare shift to the incident light side (in the figure, (Indicated by a thick arrow), it is separated from the end of the light receiving area shown in FIG. 5A and is easily taken into the light receiving area. As a result, when the formation pitch (P lens) of the microlenses 122 is increased, the image quality of the image sensor is significantly deteriorated due to optical color mixing or flare.

  From FIG. 6, when the unit pixel 116 exceeds 1.980 μm, the diffraction reflection order in the unit pixel diagonal direction increases by “2”, and the diffraction reflection angle (θ) also decreases, so that the optical color mixture and flare taken into the light receiving region are reduced. It turns out that the light of a component increases. When the optical color mixture or flare light increases, the image quality of the image sensor deteriorates. Therefore, even when the size of the unit pixel 116 exceeds 1.980 μm, it is necessary to suppress the image quality deterioration.

  Therefore, a configuration that can suppress image quality degradation even when the size of the unit pixel 116 exceeds 1.980 μm will be described below.

<Configuration of micro lens>
Specifically, the size of the unit pixel 116 formed in the light receiving region is configured to be at least 1.980 μm or more, and the pixel boundary portion of the unit pixel 116 has at least the pixel in plan view. A light shielding film is formed so as to surround the periphery.

  A plurality of microlenses 122 are formed corresponding to the unit pixel 116. The length of one side of the microlens 122 is less than 1.980 μm, and a plurality of unit pixels 116 are formed so as to divide the unit pixels 116 into substantially equal areas with n squares of approximately squares. Note that n is a natural number of 2 or more.

  8A to 8D show a configuration of an embodiment of the microlens 122 to which the present technology is applied. FIG. 8A is a unit pixel 116 formed in the light receiving region of the image sensor, and a broken line in the figure indicates a boundary line between adjacent pixels.

  FIG. 8B shows a state in which one side of the unit pixel 116 is divided into two in the vertical and horizontal directions, and four microlenses are formed in the unit pixel 116. When the length of one side of the unit pixel 116 is 1.980 μm, the length of one side of the microlens 122 is ½ of 1.980 μm.

  FIG. 8C shows a state in which nine microlenses are formed in the unit pixel 116 by dividing one side of the unit pixel 116 in the vertical and horizontal directions. When the length of one side of the unit pixel 116 is 1.980 μm, the length of one side of the microlens 122 is one third of 1.980 μm.

  Further, FIG. 8D shows a state in which one side of the unit pixel 116 is divided into four in the vertical and horizontal directions to form 16 microlenses in the unit pixel 116. When the length of one side of the unit pixel 116 is 1.980 μm, the length of one side of the microlens 122 is a quarter of 1.980 μm.

  8B to 8D show examples in which one side of the unit pixel 116 is divided into 2 to 4 and the number of microlenses is 4, 9, and 16, respectively, but the present technology is limited to these. It is not described. That is, the plurality of microlenses formed corresponding to the unit pixel 116 have a side length of less than 1.980 μm, and n (n is a natural number equal to or greater than 2) square square unit pixels. Any image sensor may be used as long as it is formed in a plurality so as to divide 116 into substantially equal areas.

<Regarding Manufacturing 1 of Image Sensor>
Next, a description will be given of the manufacture of an image sensor when a plurality of microlenses are provided in the unit pixel 116 as shown in FIG.

  As a first manufacturing method, a case where the microlens 122 is manufactured by a thermal melt flow method will be described with reference to FIG. The manufacturing method described with reference to FIG. 9 can be applied to the manufacture of the back-illuminated image sensor 130 in which the size of the unit pixel 116 formed in the light receiving region is 1.98 μm or more.

  In the process shown in FIG. 9A, a light shielding film 141 is formed between adjacent pixels through an insulating film 128 formed on the semiconductor substrate 112 that constitutes the backside illumination type imaging device 130.

  In the process shown in FIG. 9B, a planarizing film 201 made of, for example, an acrylic resin is formed.

  In the process shown in FIG. 9C, a color filter 121 made of, for example, primary colors such as red, blue, and green is formed to output a color image of the image sensor.

  As the color filter 121, complementary colors such as yellow, cyan, and magenta may be used. Further, the color filter 121 may not be used depending on the use of the image sensor. The color filter 121 is made of, for example, a photosensitive negative resist and is formed by a photolithography method.

  In the process shown in FIG. 9D, a planarizing film 202 made of, for example, an acrylic resin is formed.

  In the process shown in FIG. 9E, the microlens material 203 made of, for example, a novolak-based, styrene-based, acrylic-based, or copolymerized positive photosensitive resin thereof is formed into a substantially rectangular shape by photolithography.

  When the microlens material 203 includes, for example, a diazonaphthoquinone photosensitive material, the sensitivity characteristics of the image sensor deteriorate due to light absorption on the visible light short wavelength side. In this case, the microlens material 203 that has been developed by the photolithography method is irradiated with ultraviolet rays such as i-rays and bleaching exposure is performed so that light absorption is reduced. Also good.

  A plurality of microlens materials 203 are formed in substantially the same shape corresponding to the unit pixel 116. Although FIG. 9E shows a state in which two are formed in the cross-sectional direction, as described with reference to FIG. 8, the number of microlens materials corresponding to the number of microlenses 122 to be formed, such as three or four. 203 is formed.

  In the process shown in FIG. 9F, the microlens material 203 having been subjected to the development processing is subjected to a heat treatment at or above the thermal softening point, and a microlens 122 having a microlens shape is formed by performing a thermal melt flow treatment. The Thus, a plurality of microlenses 122 are formed in substantially the same shape corresponding to the unit pixel 116. FIG. 9F shows a state in which two are formed in the cross-sectional direction.

  In this way, a plurality of microlenses 122 are formed on the unit pixel 116.

<Regarding Manufacturing 2 of Image Sensor>
Next, the second manufacturing method of the image sensor will be described with reference to FIG. In the second manufacturing method, the case where the microlens 122 is manufactured by, for example, a dry etching method will be described as an example. Also in the second manufacturing method, the size of the unit pixel 116 formed in the light receiving region can be applied when manufacturing the back-illuminated image sensor 130 having a size of 1.98 μm or more.

  In the process shown in FIG. 10A, the microlens material 221 made of a styrene resin or the like is formed on the imaging element in a state where the color filter 121 is formed through the processes described with reference to FIGS. 9A to 9C. Is done.

  In the process shown in FIG. 10B, a positive photosensitive resin 222 made of, for example, a novolak type is formed in a substantially rectangular shape by development processing in a photolithography method. A plurality of positive photosensitive resins 222 are formed in substantially the same shape corresponding to the unit pixel 116. FIG. 10 illustrates the case where two are formed in the cross-sectional direction.

  In the process shown in FIG. 10C, a microlens shape is obtained by performing a heat treatment at or above the thermal softening point of the positive photosensitive resin 222 that has been subjected to the development treatment, and performing a thermal melt flow treatment.

  In the step shown in FIG. 10D, the positive type photosensitive resin 222 having a microlens shape is subjected to a dry etching process using a fluorocarbon-based gas or the like on the microlens material 221 formed on the base. The microlens 122 is transferred by etching so that the effective area of the microlens 122 is enlarged.

  In this manner, a plurality of microlenses 122 are formed in substantially the same shape corresponding to the unit pixel 116. FIG. 10D shows a state in which two are formed in the cross-sectional direction.

  In this way, a plurality of microlenses are formed on the unit pixel 116.

  With reference to FIGS. 11 and 12, supplementary explanation regarding the manufacturing described with reference to FIGS. 9 and 10 will be given. FIG. 11A shows a light shielding film 141 formed with one opening corresponding to the unit pixel 116. This corresponds to the cross section of FIG. 9A.

  In FIG. 11, the broken line represents the boundary of the unit pixel 116, and the thick line around it represents the light shielding film 141. When the state of the image sensor shown in FIG. 7A is viewed from above, as shown in FIG. 11A, a light-shielding film 141 is provided on the periphery of one unit pixel 116, respectively. In this case, the opening of the light shielding film 141 has substantially the same size and shape as the opening of the unit pixel 116.

  FIG. 11B shows red, blue, and green color filters 121 formed corresponding to the unit pixels 116. This corresponds to FIG. 9C, and when the state of the image sensor shown in FIG. 9C is viewed from above, a filter of a color assigned to each unit pixel 116 is provided for each unit pixel 116. The diagonal lines in FIG. 11B are different diagonal lines for each color, and indicate that the red, blue, and green color filters 121 are arranged.

  FIG. 11C shows a plurality of microlenses 122 formed in substantially the same shape corresponding to the unit pixel 116. FIG. 11C shows an example in which four microlenses 122 are formed corresponding to one unit pixel 116. FIG. 11C corresponds to FIG. 9F and FIG. 10D, and a plurality of microlenses 122 are provided for each unit pixel 116 when the state of the imaging device shown in FIG. 9F and FIG. 10D is viewed from above.

  FIG. 11D shows a cross section of the image sensor when the light shielding film 141 is provided around the one unit pixel 116 as shown in FIG. 11A. Moreover, the arrow shown with the broken line in FIG. 11D represents the stray light component that becomes an optical color mixture or flare component.

  As shown in FIG. 11D, when the light shielding film 141 is provided around the one unit pixel 116, the stray light component may enter the photodiode 111.

  FIG. 12 is a diagram for explaining a case where the light shielding film 141 is provided not only in the vicinity of one unit pixel 116 but also in the unit pixel 116 in accordance with the shape of the microlens 122.

  FIG. 12A is a diagram illustrating the shape of the light-shielding film 141 formed on the image sensor as in FIG. 11A. The light shielding film 141 shown in FIG. 12A is provided with a light shielding film 141 in the periphery of one unit pixel 116, and also in the unit pixel 116 is a light shielding film 141 in a cross shape.

  In this case, the light shielding film 141 is provided on the outer peripheral portion of one microlens 122. In this case, since one unit pixel 116 is provided with four microlenses 122, the opening of the light shielding film 141 is about ¼ the size of the opening of the unit pixel 116, It becomes a shape. In other words, the opening portions of the four light shielding films 141 correspond to one unit pixel 116.

  12B is the same as the color filter 121 shown in FIG. 11B, and FIG. 12C is the same as the microlens 122 shown in FIG. 11C.

  FIG. 12D shows a cross section of the image sensor when the light shielding film 141 is provided around and inside the one unit pixel 116 as shown in FIG. 12A. In addition, an arrow indicated by a broken line in FIG. 12D represents a stray light component that becomes an optical color mixture or a flare component.

  As shown in FIG. 12D, when the light shielding film 141 is provided around and inside the unit pixel 116, the light shielding film 141 in the unit pixel 116 causes the stray light component to enter the photodiode 111. It is possible to prevent the intrusion from being stopped and entering the photodiode 111.

  In this manner, a plurality of microlenses 122 formed in pairs corresponding to the openings of the light shielding films 141 of the light shielding films 141 formed with the plurality of openings corresponding to the unit pixels 116 are formed. In this case, the opening area of the light shielding film 141 is reduced, and the sensitivity characteristics of the image sensor are slightly deteriorated. However, with respect to optical color mixing and flare, the light shielding function by the light shielding film 141 works and is advantageous.

<Other configurations of microlenses>
FIG. 13 is a cross-sectional view of the image sensor for explaining another shape of the microlens. FIG. 13A is a plan view of the image sensor as viewed from above. A broken line indicates the boundary of the unit pixel 116, and a hatched portion in the broken line indicates a microlens. FIG. 13A illustrates an example in which four microlenses are formed in one unit pixel 116.

  13B and 13C are cross-sectional views taken along line ab shown in FIG. 13A, respectively. The image sensor shown in FIG. 13B is different from the image sensor shown in FIG. 13C only in the portion where the light shielding film 141 is provided, and the other portions are the same.

  The light shielding film 141 of the image pickup device illustrated in FIG. 13B is provided on the outer peripheral portion of the one unit pixel 116, similarly to the light shielding film 141 illustrated in FIG. The light shielding film 141 of the imaging element illustrated in FIG. 13C is provided in the outer peripheral portion and inside of the one unit pixel 116, similarly to the light shielding film 141 illustrated in FIG.

  The microlens 311 shown in FIG. 13B is formed in a substantially rectangular shape and a substantially rectangular shape in plan view. The microlens 311 shown in FIG. 13B includes a microlens region 312 formed of a material having a refractive index n and a non-microlens region 313 having a refractive index n ′, and uses the refractive index difference (n> n). '), And is configured to collect light by utilizing the phase difference of the light incident on the image sensor.

  FIG. 13C shows a plurality of microlenses 311 formed in pairs corresponding to the openings of the light shielding films 141 of the light shielding films 141 formed to have a plurality of openings corresponding to the unit pixels 116. FIG. 13C shows an example in which four light shielding film openings are formed for one unit pixel 116, and microlenses 311 are formed corresponding to the four light shielding film openings, respectively. .

  As described above, the present technology can be applied even to the case of the microlens 311 including the microlens region 312 formed of the material having the refractive index n and the non-microlens region 313 having the refractive index n ′.

  Further, as shown in FIG. 13B, the light shielding film 141 may be formed in a portion corresponding to the outer peripheral portion of the unit pixel 116 as a portion of the non-microlens region 313, or as shown in FIG. 13C. As described above, the non-microlens region 313 may be formed.

<Configuration with inner lens>
Next, an image sensor provided with an inner lens will be described. FIG. 14B and FIG. 15 show cross-sectional views of an image pickup device having an inner lens, and for comparison, FIG. 14A shows a cross-sectional view of an image pickup device without an inner lens. In the figure, broken arrows indicate the traveling direction of light.

  14A, 14B, and 15 is a back-illuminated image sensor 130 in which a plurality of microlenses 122 are provided in one unit pixel 116. Here, an example in which four microlenses 122 are provided in the unit pixel 116 is shown.

  14A is configured such that an inner lens is not formed, and the back-illuminated image sensor 130 illustrated in FIG. 14B is configured such that an inner lens 411 is formed. .

  In the image sensor shown in FIG. 14A, the margin between the focused end portion and the edge of the light shielding film 141 is small. In FIG. 14A, a circle is shown in the margin portion of the focused end portion and the edge portion of the light shielding film 141 that are collected. The distance between the focusing end and the edge of the light shielding film 141 in this circle is short.

  In the imaging device shown in FIG. 14B, the margin between the focused end portion that has been condensed and the edge of the light shielding film 141 is large. Also in FIG. 14B, a circle is described in the margin part of the focused end portion and the edge portion of the light shielding film 141 that are collected. The distance between the focusing end and the edge of the light shielding film 141 in this circle is wide.

  From this, it can be seen that by providing the inner lens 411, the light from the microlens 122 can be collected more efficiently.

  Although the inner lens 411 may not be formed, the inner lens 411 is provided particularly when, for example, an improvement in sensitivity deterioration (luminance shading) at the outer periphery of the light receiving area where the oblique incident light component increases. It is good to have a configuration.

  The inner lens 411 is made of, for example, plasma silicon nitride (P-SiN; refractive index: about 1.9 to 2.0), and the planarizing film 201 is made of, for example, acrylic resin (having a refractive index of about 1.5). be able to.

  The shape of the inner lens 411 may be a hemispherical shape as in the case of the microlens 122 shown in FIG. 14B, but may be other shapes. For example, a rectangular inner lens 421 as shown in FIG. 15 may be provided in the planarization film 422.

  The inner lens 421 shown in FIG. 15 has a substantially rectangular shape in a cross-sectional view and is formed in a substantially rectangular shape as shown in FIG. 13A in a plan view, like the micro lens 311 shown in FIGS. 13B and 13C. . Such a rectangular inner lens 421 may be used.

  The inner lens 421 is the same as the inner lens 411, for example, plasma silicon nitride (P-SiN; refractive index: about 1.9 to 2.0), and the planarizing film 201 is made of, for example, acrylic resin (refractive index: about 1.5). Etc.).

  The inner lens 411 and the inner lens 421 direct the principal ray of at least one of the plurality of condensing spots collected by the plurality of micro lenses 122 toward the center of the unit pixel 116. What is necessary is just to be formed so that it may condense.

<About effect>
Here, again, schematic views of the front side illumination type imaging device 110 and the back side illumination type imaging device 130 are shown in FIGS. 16A and 16B, respectively.

  In the front-illuminated imaging device 110, a transistor electrode (a gate electrode 114 in FIG. 16A) is formed above the photodiode 111, and a multilayer wiring layer 119 (in the drawing, the first layer, the first layer from the photodiode 111 side) is formed above the transistor electrode. 2 layers and 3rd layers) are formed, and contact holes for driving transistors are also formed.

  As described above, in the front-illuminated image sensor 110, since the multilayer wiring layer 119 and the like are provided, the distance d1 from the surface of the photodiode 111 to the microlens 122 becomes long. Since the distance d1 is long, the microlens 122 is formed so that the thickness t1 is reduced and the curvature is increased.

  On the other hand, in the back-illuminated image sensor 130, the transistor and the multilayer wiring layer 119 are formed on the surface opposite to the surface on which the microlens 122 is formed. It is not shown in FIG. 16B.

  Due to such a structure, in the back-illuminated image sensor 130, a light shielding film 141 is formed as a single layer corresponding to the unit pixel 116 above the photodiode 111 on the surface side where the microlens 122 is formed. Therefore, the distance d2 from the surface of the photodiode 111 to the microlens 122 is shortened.

  Since the distance d2 is short, the microlens 122 is formed so that the thickness t2 is increased and the curvature is decreased.

  However, as shown in FIG. 16B, it is difficult to form the microlens 122 whose cross-section has a circular arc with high accuracy with an increase in the size of the unit pixel 116 of the image sensor. As a result, as shown in FIG. There is a possibility that part of the emitted light is kicked by the light shielding film. If a part of the light is kicked by the light shielding film, the sensitivity of the image sensor and the luminance shading characteristics deteriorate.

  Here, it will be described that it is more difficult to form the microlens 122 thick with high accuracy, in particular, as the size of the unit pixel 116 of the image sensor is larger.

  In the manufacturing of the imaging device described with reference to FIG. 9, when forming a microlens having a large film thickness and a small curvature by the thermal melt flow method, it is necessary to form the photosensitive microlens material 203 thick.

  When the microlens material 203 of adjacent pixels comes into contact with each other when the microlens material 203 formed by thickening the microlens material 203 is obtained by thermal reflow after the development processing by the photolithography method, the microlens 122 is fused. The shape will collapse.

  This is more difficult to control because the microlens 122 is thicker and the larger the unit pixel 116 of the image sensor, the greater the deposition of the microlens material 203 after the development process.

  In the manufacture of the imaging device described with reference to FIG. 10, when the microlens 122 is formed by dry etching, the microlens material 221 is formed thick, the positive photosensitive resin 222 is formed thick, and the microlens 122 is formed by heat reflow. After obtaining the lens shape (in this case, it is also difficult to control during thermal reflow), it is necessary to carry out dry etching for a long time.

  In addition to the difficulty in thermal reflow, dry etching is required for a long time, which may increase the manufacturing cost. Further, when dry etching is performed for a long time, the dark current characteristics of the image sensor may be deteriorated due to damage (PID: Plasma Induced Damage) caused by plasma processing during dry etching.

  However, by applying the above-described present technology and providing a plurality of microlenses in the unit pixel 116, the above-described problem can be improved.

  FIG. 17 is a diagram illustrating a state in which the present technology is applied to the backside illumination type image sensor 130 illustrated in FIG. 16B and a plurality of microlenses 122 are formed in one unit pixel 116.

  As described with reference to the back-illuminated image sensor 130 of FIG. 16B, even when a part of the light collected by the microlens 122 is kicked by the light shielding film 141, the back surface shown in FIG. According to the irradiation type imaging device 130, for example, even if the film thickness t2 of the microlens 122 is the same, the size of the bottom of the microlens 122 is half (1/2) in the illustrated microlens 122. Since the curvature of the minute microlens is reduced, the light can be collected efficiently.

  If the light collection efficiency is improved, the sensitivity characteristic of the image sensor can be improved. In addition, since the size of the bottom of the microlens 122 is half (1/2) in the illustrated microlens 122, the size of the microlens 122 itself is small even when the size of the unit pixel 116 is large. It is not necessary to form the microlens 122 thick with high accuracy.

  Therefore, it is possible to solve the problem that it is difficult to form the microlens 122 with a large thickness with high accuracy, in particular, the larger the size of the unit pixel 116 of the image pickup device. This technique can also be reduced according to the present technology.

<About autofocus pixels>
In the above-described embodiment, the image sensor that captures (captures) an image has been described. Hereinafter, such an image sensor is appropriately referred to as an imaging pixel. Some pixels are used for autofocusing, and such pixels are appropriately described as phase difference detection pixels.

  Here, a description will be given of autofocus. The autofocus method for digital cameras mainly includes a contrast method and a phase difference method. The contrast method is a method in which the lens is moved so that the point with the highest contrast is in focus. In the case of a digital camera, auto-focusing can be performed by reading a part of the image of the image sensor, and no other auto-focus optical system is required.

  The phase difference method is a method to which so-called triangulation technology is applied, and is a method for obtaining a distance by an angle difference when the same subject is viewed from two different points. In the case of the phase difference method, images of light passing through different parts of the lens, for example, light beams on the right and left sides of the lens are used. In the phase difference method, by measuring the distance, it is required how much the lens needs to be moved to the in-focus position.

  Autofocus by the phase difference method (hereinafter referred to as phase difference autofocus as appropriate) performs autofocus by the phase difference method using some of the imaging pixels. As described above, the imaging element is provided with a condensing microlens, for example, a microlens 122 (FIG. 17), and a diaphragm member for limiting light incident on the microlens, for example, a light shielding film 141. By making the size different from that of other light-shielding films, an imaging element for phase difference autofocus can be obtained.

  In the case of the contrast method, since it is necessary to move the lens back and forth in order to find a place with the highest contrast, it may take time to focus. In contrast to the contrast method, the phase difference method does not require time for moving the lens back and forth in order to find the focal position, so that high-speed autofocus can be realized.

  Here, the description will be continued with an example in which the present technology is applied to an image sensor that performs phase difference autofocus. In addition, the back side illumination type imaging device will be described as an example, but the present technology described below can be applied to a front side illumination type imaging device.

  First, general phase difference autofocus will be described. FIG. 18 is a diagram for explaining phase difference autofocus. A predetermined number of pixels in a pixel array unit (not shown) in which pixels are two-dimensionally arranged in a matrix are assigned to phase difference detection pixels. A plurality of phase difference detection pixels are provided at predetermined positions in the pixel array section.

  The configuration of the phase difference detection pixel shown in FIG. 18 is, for example, a part of the back-illuminated image sensor 130 shown in FIG. 17 and a portion including the phase difference detection pixel. FIG. 2 is a diagram illustrating a part necessary for the imaging, in which an imaging element provided with one microlens per photodiode is illustrated.

  The phase difference detection pixel is a pixel used when detecting a focal point by the phase difference method, and the imaging pixel is a pixel different from the phase difference detection pixel and is a pixel used for imaging. Suppose there is.

  The imaging element shown in FIG. 18 includes microlenses 511-1 to 510-4, light shielding films 512-1 to 512-3, and photodiodes 513-1 to 513-4. The image sensor is configured such that light enters through the lens group 501.

  Of the solid-state imaging device shown in FIG. 18, the photodiode 513-2 and the photodiode 513-3 function as phase difference detection pixels, and are pixels for acquiring an image signal for autofocus (focus detection). It is said that. The photodiode 513-1 and the photodiode 513-4, which are arranged at a position between the photodiode 513-2 and the photodiode 513-3, are used as imaging pixels, and acquire an image signal by light from a subject. It is a pixel for this purpose.

  The photodiode 513-1 receives light from the subject collected by the microlens 511-1. The photodiode 513-2 receives light from the subject collected by the microlens 511-2. The photodiode 513-3 receives light from the subject condensed by the microlens 511-3, and the photodiode 513-4 receives light from the subject condensed by the microlens 511-4. It is configured.

  The light shielding film 512-1 is provided so that the light from the microlens 511-1 does not enter the photodiode 513-2 and the light from the microlens 511-2 does not enter the photodiode 513-1. It has been. Similarly, the light shielding film 512-3 prevents light from the microlens 511-4 from entering the photodiode 513-3, and prevents light from the microlens 511-3 from entering the photodiode 513-4. It is provided as follows.

  The light shielding film 512-1 and the light shielding film 512-3 are thus provided mainly to prevent light leaking to adjacent pixels (photodiodes), and thus are provided between the adjacent photodiodes 214. ing. In contrast to the light shielding film 512, the light shielding film 512-2 has a function of selecting a light incident angle and receiving light in addition to a function of preventing light leaking to an adjacent pixel (photodiode) (hereinafter referred to as a light receiving film). It also has a function for realizing (described as separation ability).

  That is, as shown in FIG. 18, light that has passed through the A side (left side in the figure) of the lens group 501 is incident on the photodiode 513-3 and passes through the B side (right side in the figure) of the lens group 501. The light-shielding film 512-2 is provided from approximately the center of the photodiode 513-2 to approximately the center of the photodiode 513-3 so that the light enters the photodiode 513-2.

  With the light shielding film 512-2, light coming from the left part of the lens group 501 and light coming from the right part can be separated and received. The focus position is detected as shown in FIG. 19 by receiving the light coming from the left part and the light coming from the right part of the lens group 501 by the photodiode 513-2 and the photodiode 513-3, respectively. Can do.

  In other words, the output from the photodiode 513-2 and the output from the photodiode 513-3 do not match (the outputs of the paired phase difference detection pixels do not match) at the rear pin or the front pin. Sometimes, the output from the photodiode 513-2 and the output from the photodiode 214-3 coincide (the outputs of the paired phase difference detection pixels coincide). When it is determined that the pin is a rear pin or a front pin, the focus detection is realized by moving the lens group 501 to a focus position.

  When the focus position is detected by such a phase difference method, the focus position can be detected at a relatively high speed, and high-speed autofocus can be realized. However, the imaging pixel and the phase difference detection pixel are mixedly formed. In order to improve the respective pixel characteristics, for example, it is necessary to optimize the focal length of the microlens corresponding to each pixel.

  As described above, the same applies to a configuration in which a single photodiode is provided with a plurality of microlenses. When imaging pixels and phase difference detection pixels are formed in a mixed manner, the respective pixel characteristics are improved. In order to achieve this, it is necessary to perform optimization corresponding to each pixel.

  With reference to FIG. 20, an appropriate curvature in the imaging pixel and the phase difference detection pixel will be described. 20A and 20B represent imaging pixels having different curvatures, and FIGS. 20C and 20D represent phase difference detection pixels having different curvatures. The imaging pixels shown in FIGS. 20A and 20B are provided above the photodiode 513, provided with light shielding films 512 at both ends of the photodiode 513, and receive light incident on the microlens 511.

  The phase difference detection pixels shown in FIG. 20C and FIG. 20D are above the photodiode 513, and are provided with light shielding films 512 at both ends of the photodiode 513, respectively, and one of the light shielding films extends to the central portion of the photodiode 513. It is comprised so that it may cover, and the light which injected into the micro lens 511 is light-received through the part opened.

  In FIG. 20, a line indicated by an arrow represents light, and light that enters the photodiode 513 through the microlens 511. The curvature of the imaging pixel shown in FIG. 20A is the same as that of the phase difference detection pixel shown in FIG. 20C. The curvature of the imaging pixel shown in FIG. 20B and the phase difference shown in FIG. 20D are the same. The curvature of the detection pixel is the same.

  Please refer to FIG. 20A and FIG. 20B. The imaging pixel shown in FIG. 20A shows a case where the curvature radius of the microlens 511 is large, and the imaging pixel shown in FIG. 20B shows a case where the curvature radius of the microlens 511 is small. As shown in FIG. 20A, in the case of an imaging pixel, if the radius of curvature of the microlens 511 is large, light is easily collected on the photodiode 513, and the light receiving sensitivity is increased.

  As shown in FIG. 20B, in the case of an imaging pixel, if the radius of curvature of the microlens 511 is small, the light that has passed through the microlens 511 diverges, making it difficult for light to be collected on the photodiode 513, and the light receiving sensitivity is It will decline. Thus, in the case of the imaging pixel, it can be seen that the larger the radius of curvature of the microlens 511, the better the light collecting performance.

  As shown in FIG. 20C, in the case of the phase difference detection pixel, when the radius of curvature of the microlens 511 is large, the light is condensed on the photodiode 513, but the light incident from the left side and the light incident from the right side are collected. Adds an opening and is condensed. That is, in this case, there is a possibility that the decomposing ability is lowered.

  As shown in FIG. 20D, in the case of the phase difference detection pixel, if the radius of curvature of the microlens 511 is small, it is difficult for light to be collected on the photodiode 513, and the light receiving sensitivity is lowered. For this reason, in the case of the phase difference detection pixel, although not shown, the radius of curvature of the microlens 511 is good.

  As described above, the optimum radius of curvature of the microlens 511 of the imaging pixel is different from the optimum radius of curvature of the microlens 511 of the phase difference detection pixel. When the imaging pixels and the phase difference detection pixels are mixed, the radius of curvature of the microlens 511 is configured so that both the imaging pixels and the phase difference detection pixels have an appropriate focal length as much as possible. .

  In the imaging pixel, when importance is placed on sensitivity and luminance shading characteristics, the layer thickness from the microlens 511 to the photodiode 513 is thin, and the focal position is preferably on the side of the photodiode 513 including the light shielding film 512. On the other hand, the focal length of the phase difference detection pixel is preferably on the light shielding film 512 side.

  In addition, as the radius of curvature radius of the microlens 511 formed in the phase difference detection pixel is closer to 1.0, the phase difference from the two directions of the subject is separated. Since the noise component at the time is reduced, the separation characteristics are improved.

  The ratio of the radius of curvature in the horizontal direction and the oblique direction will be described with reference to FIG. FIG. 21A shows a case where one phase difference detection pixel is viewed from above. In the drawing, a square at the center represents one pixel, and a microlens 511 is formed in the one pixel. At this time, an area ratio of one pixel in a plan view and an area ratio of the microlens 511 (area of the microlens 511 / area of one pixel) is 80% or more.

  As shown in FIG. 21A, FIG. 21B shows a cross section when the phase difference detection pixel is cut in the horizontal direction a-a ′, and FIG. 21C shows a cross section when it is cut in the oblique direction b-b ′. Referring to FIGS. 21B and 21C, the radius of curvature of the microlens 511 decreases in the horizontal direction of the phase difference detection pixel, but the radius of curvature of the microlens 511 increases in the oblique direction. This is because the length of the bottom surface of the microlens is different (horizontal direction a-a '<oblique direction b-b').

In the figure, r1 represents the radius of curvature of the microlens 511 in the horizontal direction, and r2 represents the radius of curvature of the microlens 511 in the oblique direction. In the case of the phase difference detection pixel shown in FIG. 21, the curvature radius r1 is smaller than the curvature radius r2. The ratio of the curvature radius r1 and the curvature radius r2 is defined as the curvature flatness.
Curvature flatness = r2 / r1

  The closer the curvature flatness is to 1.0, the smaller the noise component at the time of separating the phase difference from the two directions of the subject, thereby improving the separation characteristics of the phase difference detection pixels. This curvature flatness depends on the pixel size. An example of the relationship between the curvature flatness and the pixel size is shown in FIG.

  In FIG. 22, the vertical axis represents the ratio of curvature radii (curvature flatness), and the horizontal axis represents the unit pixel size (the length of one side of the unit pixel). FIG. 22 shows that the curvature flatness is 1.2 or less when the pixel size is 3 μm or less. As described above, the closer the curvature flatness is to 1.0, the better the separation characteristics, but until about 1.2, it is known that the separation characteristics will not be significantly reduced. The micro lens 511 may be configured as follows.

  When forming the micro lens 511 of the phase difference detection pixel so that the curvature flatness is 1.2 or less, it is preferable that the size of the unit pixel is 3 μm or less.

  By the way, in recent years, a configuration in which an imaging pixel and a phase difference detection pixel are provided in the same light receiving region is applied particularly to an APS-C size or 35 mm full size imaging device, and various studies are made to improve its performance. Has been made. The pixel size in such an imaging device is generally about 3 to 6 μm.

  For example, in an imaging device having a pixel size of 6 μm, the curvature flatness of the phase difference detection pixel is, for example, 1.6 or more with reference to FIG. Therefore, there is a possibility that it is not suitable for an image pickup apparatus having a large pixel size if the autofocus by the phase difference method is used.

  Here, FIG. 8 will be referred to again. As described with reference to FIG. 8, the imaging pixel to which the present technology is applied includes a plurality of microlenses for one pixel. Therefore, by applying this technology, even if the pixel size of one pixel is formed to be 6 μm, the size of one microlens is 6 μm or less. For example, as shown in FIG. 8B, when four microlenses are formed for one pixel and the pixel size is 6 μm, the size of one microlens is 1.5 (= 6/4).

  In this case, since the size of the microlens is 1.5 μm and smaller than 3 μm, the curvature flatness is 1.2 or less. When the microlens size is 1.5 μm, referring to FIG. 22, it can be seen that the curvature flatness is a value close to 1.0.

  As described above, by applying the present technology, it is possible to provide a plurality of microlenses on a unit pixel, and it is possible to reduce the size of one microlens by providing a plurality of microlenses. Become. By reducing the size of the microlens, the curvature flatness becomes a value close to 1.0 as described above, and the performance as a phase difference detection pixel can be improved.

  Next, the light shielding film of the phase difference detection pixel when a plurality of microlenses are provided on the unit pixel will be described. In the following description, as shown in FIG. 8B, a case where four microlenses are provided in a unit pixel will be described as an example. The present technology relating to the light shielding film described below can be applied to other numbers of microlenses such as nine or sixteen.

  FIG. 23 is a diagram showing an example of the shape of the light shielding film when four microlenses are provided on a unit pixel. The light shielding film shown in FIG. 23 is a case where light information from one direction is received, and FIG. 23 shows the shape of the light shielding film when light information from the right side is received.

  In FIG. 23, one pixel is represented by a dotted square, and the description will be continued assuming that the pixel 513 is represented here. The four microlenses are referred to as microlenses 511-1 to 511-4, respectively.

  FIG. 24 shows a cross-sectional view of the phase difference detection pixel having the light shielding film 512 shown in FIG. The phase difference detection pixels shown in FIG. 24 are cross-sectional views of the microlens 511-2 and the microlens 511-3 shown in FIG.

  The light shielding film 512 is continuously provided between adjacent pixels. That is, a quadrangular portion representing a unit pixel indicated by a dotted line in the drawing is a boundary portion between adjacent pixels, and a light shielding film 512 is provided in such a portion. In addition, the light shielding film 512-1 and the light shielding film 512-2 located on the right side of each microlens 511 in the drawing so that the unit pixel illustrated in FIGS. 23 and 24 functions as a phase difference detection pixel are as follows. The width is wide.

  A light shielding film 512 is provided so as to cover up to the central portion of the two microlenses 511 arranged in the vertical direction among the four microlenses 511. A light shielding film 512-1 is provided from the right side to the center of the microlens 511-1 and microlens 511-2 arranged in the vertical direction. Similarly, a light shielding film 512-2 is provided from the right side to the center of the microlens 511-3 and the microlens 511-4 arranged in the vertical direction.

  As described above, in the case of the photodiode 513 that receives light information from the right side, the light shielding film positioned on the right side of the photodiode 513 is configured to have a wide width and configured to have an opening on the left side. The In addition, when there are a plurality of microlenses 511, a light shielding film is provided for each microlens 511.

  Further, as shown in FIG. 23B, a light shielding film 512 may be provided at a boundary portion between the four microlenses 511-1 to 511-4 provided in the unit pixel. In the example shown in FIG. 23B, the light shielding film 512 is also provided between the microlens 511-1 and the microlens 511-2 and between the microlens 511-3 and the microlens 511-4.

  In this manner, the light shielding film 512 is provided so as to surround one microlens 511, and one of the sides is configured to be larger than the other side, whereby the opening with respect to the photodiode 513 is reduced, and the direction from a predetermined direction is reduced. A structure that can selectively receive light may be used.

  As shown in FIG. 24, a plurality of microlenses 511 and a plurality of light shielding films 512 may be provided on one photodiode 513, or a plurality of microlenses may be provided as shown in FIG. A plurality of photodiodes 513 may be configured in accordance with 511.

  In the following description, a case where a plurality of photodiodes are provided in the unit pixel will be described as an example. The unit pixel here is an area having the same size as the imaging pixel. It is assumed that it is a pixel inside.

  FIG. 25 is a cross-sectional view and a plan view of a phase difference detection pixel when a photodiode 513 is formed in accordance with the microlens 511. In the cross section of the phase difference detection pixel shown in FIG. 25A, similarly to the phase difference detection pixel shown in FIG. 24, the microlens 511-2 and the microlens 511-3 are arranged side by side, and the phase difference detection pixel. A light shielding film 512-1 and a light shielding film 512-2 for functioning as

  In the phase difference detection pixel shown in FIG. 25, a photodiode 513-1 that receives light from the microlens 511-2 and a photodiode 513-2 that receives light from the microlens 511-3 are provided. ing. The photodiode 513-1 and the photodiode 513-2 correspond to the photodiode configured as one photodiode 513 in the phase difference detection pixel shown in FIG.

  That is, in this case, two photodiodes 513 are arranged in one unit pixel. As shown in FIG. 25B, the photodiode 513-1 is disposed below the microlens 511-1 and the microlens 511-2, and from the right direction via the microlens 511-1 and the microlens 511-2. It is configured to receive incident light.

  Similarly, as shown in FIG. 25B, the photodiode 513-2 is disposed below the microlens 511-3 and the microlens 511-4, and is interposed via the microlens 511-3 and the microlens 511-4. It is configured to receive light incident from the right direction.

  In this manner, two photodiodes 513-1 and 513-2 are provided in a region where one unit pixel is provided, and a light shielding film 512 for functioning as a phase difference detection pixel on each photodiode 513. -1 and the light-shielding film 512-2 may be provided.

  In FIG. 25, a phase difference detection pixel that receives light incident from the right direction and extracts light information from the right direction is shown. However, as shown in FIG. It is also possible to configure a phase difference detection pixel including a photodiode 513 that receives incident light and a photodiode 513 that receives light incident from the left direction.

  FIG. 26 shows a phase difference detection pixel in which two photodiodes 513-1 and 513-2 that receive light from the left direction and the right direction are provided in one unit pixel. It is a figure which shows a structure.

  In the cross section of the phase difference detection pixel shown in FIG. 26A, the microlens 511-2 and the microlens 511-3 are arranged side by side as in the phase difference detection pixel shown in FIG. 25A. In the phase difference detection pixel shown in FIG. 26A, a light shielding film 512-2 for functioning as a phase difference detection pixel is arranged between the photodiode 513-1 and the photodiode 513-2.

  As shown in FIG. 26B, the light-shielding film 512-2 is provided in the central portion of the unit pixel, covers the left side to the central portion of the photodiode 513-2, and extends from the right side to the central portion of the photodiode 513-2. It is comprised continuously so that it may cover.

  In other words, the photodiode 513-2 is configured with the right half opened, and the photodiode 513-3 is configured with the left half opened.

  As shown in FIG. 26B, the photodiode 513-1 is disposed below the microlens 511-1 and the microlens 511-2, and is incident from the left through the microlens 511-1 and the microlens 511-2. It is configured to receive the received light.

  On the other hand, as shown in FIG. 26B, the photodiode 513-2 is arranged below the microlens 511-3 and the microlens 511-4, and passes through the microlens 511-3 and the microlens 511-4. It is configured to receive light incident from the direction.

  In this manner, two photodiodes 513-1 and 513-2 are provided in a region where one unit pixel is provided, and a light shielding film 512 for functioning as a phase difference detection pixel on each photodiode 513. It is good also as a structure which provides. In addition, when configured in this way, light information from different directions can be acquired by one unit pixel, and therefore, a configuration in which a phase difference is detected only by this unit pixel can be employed.

  In FIG. 26, the case where the photodiodes 513 are provided in the left-right direction (horizontal direction) when the phase difference detection pixel is viewed in plan from above is described as an example. However, as shown in FIG. The photodiodes 513 may be provided in the vertical direction (vertical direction).

  FIG. 27 shows a phase difference detection pixel in which two photodiodes 513-1 and 513-2 that receive light from the left direction and the right direction are provided in one unit pixel. It is a figure which shows a structure.

  In the cross section of the phase difference detection pixel shown in FIG. 27A, the microlens 511-1 and the microlens 511-4 are arranged side by side. In the phase difference detection pixel shown in FIG. 27A, a light shielding film 512-1 and a light shielding film 512-2 for functioning as a phase difference detection pixel are arranged.

  The light shielding film 512-1 is configured to cover from the right side to the center part of the microlens 511-1, and the light shielding film 512-2 is configured to cover from the right side to the center part of the microlens 511-2.

  In other words, the left half of the microlens 511-1 is open and the left half of the microlens 511-4 is open.

  In the cross section of the phase difference detection pixel shown in FIG. 27B, microlenses 511-2 and microlenses 511-3 are arranged side by side. In the phase difference detection pixel shown in FIG. 27B, a light shielding film 512-5 and a light shielding film 512-6 for functioning as a phase difference detection pixel are arranged.

  The light shielding film 512-5 is configured to cover from the left side of the microlens 511-2 to the central portion, and the light shielding film 512-6 is configured to cover from the left side of the microlens 511-3 to the central portion.

  In other words, the micro lens 511-2 is configured with the right half opened, and the micro lens 511-3 is configured with the right half opened.

  As shown in FIG. 27C, the photodiode 513-1 is arranged below the microlens 511-1 and the microlens 511-4 that are arranged side by side, and the microlens 511-1 and the microlens 511-4 are arranged. It is comprised so that the light which injected from the right direction through may be received.

  On the other hand, as shown in FIG. 27C, the photodiode 513-2 is disposed below the microlens 511-2 and the microlens 511-3, and left via the microlens 511-2 and the microlens 511-3. It is configured to receive light incident from the direction.

  In this manner, two photodiodes 513-1 and 513-2 are provided in a region where one unit pixel is provided, and a light shielding film 512 for functioning as a phase difference detection pixel on each photodiode 513. It is good also as a structure which provides. Further, when configured in this way, light information from different directions can be acquired by one unit pixel, and therefore, it is possible to adopt a configuration in which a phase difference is detected by this unit pixel.

  Although the above-described light shielding film is provided in the horizontal direction, it may also be provided in the vertical direction. FIG. 28 is a diagram showing a cross section of a phase difference detection pixel when a light shielding film is provided in the vertical direction. In the following description, the light shielding film in the vertical direction is described as a light shielding wall.

  In the following description, a phase difference detection pixel will be described as an example, but an example in which one microlens is provided in one photodiode will be described, but a plurality of microlenses are provided. In such a case, the imaging pixel can be provided with a light shielding wall described below.

  The light shielding wall is provided on the light shielding film 512 as shown in FIG. In the phase difference detection pixel shown in FIG. 28, the light shielding film 512-1 is provided up to the center of the photodiode 513 and is provided as a film for functioning as the phase difference detection pixel. A light shielding wall 551-1 is provided on the light shielding film 512-1.

  Similarly, a light shielding wall 551-2 is provided on the light shielding film 512-2. The light shielding wall 551-1 is provided in a direction perpendicular to the light shielding film 512-1, and the light shielding wall 551-2 is provided in a direction perpendicular to the light shielding film 512-2.

  In the example shown in FIG. 28, the example in which the light shielding wall 551 is provided on the light shielding film 512 (on the microlens 511 side) is shown, but the light shielding wall 551 may be provided below the light shielding film 512 (on the photodiode 513 side). In the example shown in FIG. 28, the light shielding film 512 and the light shielding wall 551 are illustrated as lines, but the light shielding film 512 and the light shielding wall 551 are formed as a film (wall) having a predetermined thickness and size.

  By providing the light shielding wall 551, it is possible to more reliably shield light leaking from adjacent pixels.

  FIG. 29 is a diagram of a phase difference detection pixel having a light shielding wall as viewed from the microlens 511 side. In the drawing, the shaded film 512 indicates the light shielding film 512, and the light shielding wall 551 is outlined on the light shielding film 512.

  The light shielding wall 551-2 provided on the light shielding film 512-2 is formed in a quadrangular shape. The light shielding wall 551-2 is provided so that stray light components from adjacent pixels do not enter.

  The light shielding wall 551-1 provided on the light shielding film 512-1 has a curved shape. The light shielding wall 551-1 has a curved shape, for example, an arc, and has a shape such that the inside of the arc faces the opening side. The light-shielding wall 551-1 is provided so that stray light components from adjacent pixels do not enter, and is provided so as to easily collect light at the opening by reflecting incident light. .

  Since the light-shielding film 512 is provided in the phase difference detection pixel, the opening is configured to be small, so that the sensitivity is lower than that of the imaging pixel. In order to improve the sensitivity of the phase difference detection pixel, it is conceivable to increase the amount of light incident on the photodiode 513 through the opening.

  Therefore, in order to increase the amount of light incident on the photodiode 513 (light reception amount), the light shielding wall 551-1 is curved, and the light reflected by the light shielding wall 551-1 is collected on the opening side. The configuration is as follows.

  By providing such a light shielding wall 551, it becomes possible to shield stray light components from adjacent pixels, reflect incident light, improve light collection efficiency, and improve sensitivity. It becomes possible.

  Such a light shielding wall may be continuously formed so as to surround the opening as shown in FIG. 30, for example. The light shielding wall 551 shown in FIG. 30 is formed so as to surround the photodiode 513 similarly to the light shielding film 512.

  In the light shielding wall 551 shown in FIG. 30, the portion provided on the light shielding film 512-1 provided for functioning as a phase difference detection pixel is formed in a curved shape, but the other portion. Is formed in a straight line shape like the light shielding film 512.

  The light shielding wall 551 provided in a linear shape may also be formed in a shape capable of condensing light to the opening.

  Thus, by forming the light shielding wall 551, stray light components from adjacent pixels arranged in the vertical direction can be shielded.

  Here, the phase difference detection pixel has been described as an example, but a configuration in which a light shielding wall is provided also for the imaging pixel can be employed. Even when a light-shielding wall is provided on the imaging pixel, the stray light component from the adjacent pixel can be shielded as in the case of the phase difference detection pixel described above, and the light collecting performance is improved by reflecting the incident light. It can also be improved.

  Here, a case where the above-described phase difference detection pixels and imaging pixels are arranged on the same imaging surface will be described.

  FIG. 31 is a diagram illustrating a pixel when both the phase difference detection pixel and the imaging pixel are configured by microlenses having the same size. In the example shown in FIG. 31, four microlenses are formed on one unit pixel in both the phase difference detection pixel and the imaging pixel.

  In FIG. 31, the pixel located at the center is the phase difference detection pixel 602, and the surrounding pixels are the imaging pixels 601-1 to 601-8. Thus, by making the size of the microlens the same in all the pixels, the gap generated at the corner portion between the microlenses can be reduced.

  FIG. 32 shows an example in which a phase difference detection pixel 612 is arranged at the center and an imaging pixel 611 is arranged around the phase difference detection pixel 612, as in the example shown in FIG. 31. However, in the example shown in FIG. 32, the imaging pixel 611 has one microlens formed in the unit pixel, and the phase difference detection pixel 612 has four microlenses formed in the unit pixel. .

  As shown in FIG. 32, the number of microlenses provided in the imaging pixel 611 and the phase difference detection pixel 612 is different, in other words, the size of the microlens provided in the imaging pixel 611 and the phase difference detection pixel 612, respectively. It is also possible to configure the lengths to be different.

  In the case of the configuration shown in FIG. 32, the gap generated at the corner portion between the imaging pixel 611 and the phase difference detection pixel 612 becomes large, but the effect of the gap is reduced by providing a step of filling the gap. Is possible.

  Here, as illustrated in FIG. 32, the imaging pixel 611 includes one microlens and the phase difference detection pixel 612 includes an example including four microlenses. The pixel 611 may include a plurality of microlenses, and the phase difference detection pixel 612 may include one microlens.

  Thus, the present technology can also be applied to pixels for realizing phase difference autofocus.

<Electronic equipment>
The present technology is not limited to application to an image sensor, but an image sensor such as a digital still camera or a video camera, a portable terminal device having an image capture function such as a cellular phone, or a copy using an image sensor for an image reading unit. The present invention can be applied to all electronic devices that use an image sensor in an image capturing unit (photoelectric conversion unit) such as a computer. In some cases, a module-like form mounted on an electronic device, that is, a camera module is used as an imaging device.

  FIG. 33 is a block diagram illustrating a configuration example of an image sensor that is an example of the electronic apparatus of the present disclosure. As illustrated in FIG. 33, an imaging apparatus 1000 according to the present disclosure includes an optical system including a lens group 1001 and the like, an imaging element 1002, a DSP circuit 1003 that is a camera signal processing unit, a frame memory 1004, a display device 1005, a recording device 1006, An operation system 1007, a power supply system 1008, and the like are included.

  A DSP circuit 1003, a frame memory 1004, a display device 1005, a recording device 1006, an operation system 1007, and a power supply system 1008 are connected to each other via a bus line 1009. The CPU 1010 controls each unit in the imaging apparatus 1000.

  The lens group 1001 takes in incident light (image light) from a subject and forms an image on the imaging surface of the imaging element 1002. The imaging element 1002 converts the amount of incident light imaged on the imaging surface by the lens group 1001 into an electrical signal in units of pixels and outputs it as a pixel signal. As the image sensor 1002, the image sensor according to the above-described embodiment can be used.

  The display device 1005 includes a panel type display device such as a liquid crystal display device or an organic EL (electroluminescence) display device, and displays a moving image or a still image captured by the image sensor 1002. The recording device 1006 records a moving image or a still image captured by the image sensor 1002 on a recording medium such as a video tape or a DVD (Digital Versatile Disk).

  The operation system 1007 issues operation commands for various functions of the imaging device under operation by the user. The power source system 1008 appropriately supplies various power sources serving as operation power sources for the DSP circuit 1003, the frame memory 1004, the display device 1005, the recording device 1006, and the operation system 1007 to these supply targets.

  Such an imaging apparatus 1000 is applied to a camera module for a mobile device such as a video camera, a digital still camera, and a mobile phone. In the imaging apparatus 1000, the imaging element according to the above-described embodiment can be used as the imaging element 1002.

  Further, in this specification, the system represents the entire apparatus constituted by a plurality of apparatuses.

  In addition, the effect described in this specification is an illustration to the last, and is not limited, Moreover, there may exist another effect.

  The embodiments of the present technology are not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present technology.

  In addition, this technique can also take the following structures.

(1)
A plurality of unit pixels formed in the light receiving region;
A light shielding film formed at a boundary portion between the unit pixels;
A microlens formed for each unit pixel,
The unit pixel is a substantially square lattice of 1.98 μm or more,
The microlens is formed of a square of approximately 2 squares with a side of less than 1.98 μm for each unit pixel.
(2)
The imaging device according to (1), wherein the light shielding film is further formed at a boundary portion between the microlenses.
(3)
An inner lens is further provided between the microlens and the photodiode,
The inner lens collects the principal ray of at least one of the plurality of condensing spots collected by the plurality of microlenses toward the unit pixel center direction. The imaging device according to (1) or (2), wherein the imaging device is formed.
(4)
The imaging device according to (1), wherein the imaging element is a pixel for detecting a focal point by detecting a phase difference.
(5)
The imaging device according to (4), further including a light shielding film formed from a boundary portion to a substantially central portion of the microlens.
(6)
The image sensor according to (4), wherein the unit pixel includes a light receiving unit that acquires light information from different directions.
(7)
The imaging device according to any one of (1) to (6), further including a light shielding wall provided in a direction perpendicular to the light shielding film.
(8)
A plurality of unit pixels formed in the light receiving region;
A light shielding film formed at a boundary portion between the unit pixels;
A microlens formed for each unit pixel,
The unit pixel is a substantially square lattice of 1.98 μm or more,
The microlens is a manufacturing apparatus that manufactures an image pickup device in which each unit pixel has a substantially square shape with a side of less than 1.98 μm and is a square of two or more natural numbers.
(9)
The manufacturing apparatus according to (8), wherein the microlens is formed by a thermal melt flow method.
(10)
The manufacturing apparatus according to (8), wherein the microlens is formed by a dry etching method.
(11)
A plurality of unit pixels formed in the light receiving region;
A light shielding film formed at a boundary portion between the unit pixels;
A microlens formed for each unit pixel,
The unit pixel is a substantially square lattice of 1.98 μm or more,
The microlens is formed of an approximately square with a side of less than 1.98 μm and squares of two or more natural numbers for each unit pixel.
An electronic device comprising: a signal processing unit that performs signal processing on a signal output from the imaging element.

  130 Back-illuminated imaging device, 111 photodiode, 122 microlens, 141 light shielding film

Claims (11)

A plurality of unit pixels formed in the light receiving region;
A light shielding film formed at a boundary portion between the unit pixels;
A microlens formed for each unit pixel,
The unit pixel is a substantially square lattice of 1.98 μm or more,
The microlens is formed of a square of approximately 2 squares with a side of less than 1.98 μm for each unit pixel. The imaging device according to claim 1, wherein the light shielding film is further formed at a boundary portion between the microlenses. An inner lens is further provided between the microlens and the photodiode,
The inner lens collects the principal ray of at least one of the plurality of condensing spots collected by the plurality of microlenses toward the unit pixel center direction. The imaging device according to claim 1, wherein the imaging device is formed. The imaging device according to claim 1, wherein the imaging element is a pixel for detecting a focal point by detecting a phase difference. The imaging device according to claim 4, further comprising a light shielding film formed from a boundary portion to a substantially central portion of the microlens. The imaging device according to claim 4, wherein the unit pixel includes a light receiving unit that acquires light information from different directions. The imaging device according to claim 1, further comprising a light shielding wall provided in a direction perpendicular to the light shielding film. A plurality of unit pixels formed in the light receiving region;
A light shielding film formed at a boundary portion between the unit pixels;
A microlens formed for each unit pixel,
The unit pixel is a substantially square lattice of 1.98 μm or more,
The microlens is a manufacturing apparatus that manufactures an image pickup device in which each unit pixel has a substantially square shape with a side of less than 1.98 μm and is a square of two or more natural numbers. The manufacturing apparatus according to claim 8, wherein the microlens is formed by a thermal melt flow method. The manufacturing apparatus according to claim 8, wherein the microlens is formed by a dry etching method. A plurality of unit pixels formed in the light receiving region;
A light shielding film formed at a boundary portion between the unit pixels;
A microlens formed for each unit pixel,
The unit pixel is a substantially square lattice of 1.98 μm or more,
The microlens is formed of an approximately square with a side of less than 1.98 μm and squares of two or more natural numbers for each unit pixel.
An electronic device comprising: a signal processing unit that performs signal processing on a signal output from the imaging element.

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