JP5476731B2 - Image sensor - Google Patents

Description

  The present invention relates to an image sensor.

  2. Description of the Related Art An imaging device is known in which a focus detection pixel is mixed in a large number of imaging pixels of an imaging element to obtain an imaging signal from the imaging pixel and obtain a focus detection signal from the focus detection pixel (see, for example, Patent Document 1). . In the focus detection pixel arranged in the image pickup device of the image pickup apparatus, the photodiode selectively receives the light beam from the exit pupil region of the photographing lens through the opening provided in the light shielding layer, and performs photoelectric conversion. .

JP 2008-312073 A

  From the viewpoint of manufacturing the imaging device, it is preferable that the imaging pixel and the focus detection pixel have a common structure. However, as described above, in the focus detection pixel, the aperture is imaged for selective light reception. It is necessary to provide a light shielding layer so as to be half the size of the pixel. However, in an image sensor having a complicated wiring configuration such as a MOS type image sensor, stray light entering from the gap between the light shielding layer and the wiring layer cannot be sufficiently shielded, and the accuracy of the focus detection signal is lowered. It was.

Imaging device according to a first aspect of the present invention, a plurality of image pickup having a first microlens, and a first photoelectric conversion unit to output an image signal by receiving the light beam transmitted through the first micro lens a pixel, and a second microlens, the second photoelectric conversion unit that outputs a focus detection signal by receiving the light beam transmitted through said second micro-lens, the second micro-lens and the second a plurality of focus detection pixels having a wiring layer disposed between the photoelectric conversion portion of, is disposed at substantially the same height as the said wiring layer, covering part of the second photoelectric conversion unit A light-shielding mask , the light-shielding mask tip is located at a substantially central portion of the second photoelectric conversion unit, and the light-shielding mask end is located inside the side edge of the second photoelectric conversion unit. , A gap is formed between the end portion of the light shielding mask and the wiring layer. A light-shielding mask made, the gap between the second micro lens arranged between the light-shielding mask, the second light beam transmitted through the microlens of said wiring layer and the light-shielding mask passes, characterized in that it comprises a light shielding member which prevents the incident near the end of the second photoelectric conversion unit.

  According to the present invention, it is possible to prevent a decrease in the accuracy of the focus detection signal due to the light shielding performance.

It is sectional drawing which showed the whole structure of the digital still camera of an interchangeable lens mounting the image pick-up element of one Embodiment. It is the front view which showed typically the imaging | photography screen of this digital still camera. It is the front view which showed a part of imaging device. It is the front view which showed a part of imaging device. It is sectional drawing which showed the principal part of the focus detection optical system of the focus detection pixel shown in FIG. It is sectional drawing which showed the structure of the imaging pixel of FIG. It is sectional drawing which showed the structure of the focus detection pixel of FIG. 3 by 1st Embodiment. It is sectional drawing which showed the structure of the focus detection pixel of FIG. 3 by 2nd Embodiment.

  An image sensor according to an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing the overall configuration of a lens interchangeable digital still camera equipped with an image sensor according to an embodiment. In FIG. 1, the digital still camera 100 has an interchangeable photographing lens 110 and a camera body 120, and the interchangeable lens 110 is detachably attached to the camera body 120 via a mount unit 130.

  The interchangeable lens 110 includes a photographing optical system 111 configured as a zoom lens, a diaphragm device 112 disposed in the photographing optical system 111, a lens drive control device 113, and the like. The photographing optical system 111 includes a zooming lens 111a and a focusing lens 111b. The lens drive control device 113 includes a microcomputer (not shown), a memory, a drive control circuit, and the like, and performs drive control for adjusting the focus of the focusing lens 111b and drive control for adjusting the aperture diameter of the aperture device 112. In addition, detection of the position of the zooming lens 111a, detection of the position of the focusing lens 111b, detection of the aperture diameter of the diaphragm 112, and the like are performed.

  The camera body 120 includes a solid-state image sensor 121, a body drive control device 122, a liquid crystal display element drive circuit 123, a liquid crystal display element 124 driven by the drive circuit 123, and the liquid crystal display according to an embodiment of the present invention. An eyepiece 125 for observing the element 124 and a memory card 126 for recording image data captured by the image sensor 121 are provided.

  As will be described in detail later, the imaging element 121 includes a plurality of imaging pixels that output an imaging signal, that is, an image signal, and a plurality of focus detection pixels that output a focus detection signal. The plurality of focus detection pixels and the plurality of focus detection pixels are two-dimensionally arranged such that the plurality of focus detection pixels are scattered or mixed in the plurality of focus detection pixels. The focus detection pixel is a focus detection pixel for a pupil division phase difference type focus detection device, as will be described in detail later.

  The liquid crystal display element 124 and the eyepiece lens 125 constitute an electronic viewfinder, and the photographer can observe a through image of the subject displayed on the liquid crystal display element 124 via the eyepiece lens 125.

  The body drive control device 122 includes a microcomputer (not shown), a memory, a drive control circuit, and the like. The body drive control device 122 controls the drive of the image sensor 121, reads the image signal and focus detection signal of the image sensor 121, and performs image processing of the image signal. And recording, focus detection calculation based on the focus detection signal, and overall camera operation control such as exposure control.

  The body drive control device 122 and the lens drive control device 113 exchange lens information signals and camera information signals between the camera body 120 and the interchangeable lens 110 via electrical contacts 131 provided on the mount unit 130. I do.

  Next, an outline of the operation of the interchangeable lens digital still camera will be described. The imaging optical system 111 of the interchangeable lens 110 forms a subject image on the imaging device 121. The imaging device 121 outputs an imaging signal from the imaging pixel and outputs a focus detection signal from the focus detection pixel, and these imaging signals. And a focus detection signal are sent to the body drive control device 122. The body drive control device 122 calculates a defocus amount based on the focus detection signal, and sends this defocus amount to the lens drive control device 113 via the electrical contact 131. The lens drive control device 113 calculates the lens drive amount of the focusing lens 111b based on this defocus amount, and drives the focusing lens 111b to the in-focus position according to this lens drive amount.

  The body drive control device 122 further creates a through image based on the imaging signal and displays it on the liquid crystal display element 124 via the liquid crystal display element driving circuit 123, and performs predetermined image processing on the imaging signal in accordance with the shutter release signal. To create image data and record it on the memory card 126.

  FIG. 2 shows a shooting screen of the digital still camera 100. In FIG. 2, a plurality of focus detection areas 201, 202, 203, 204, and 205 are formed on the shooting screen 200 in the illustrated example. In this example, the focus detection areas 201 and 202 extend in the horizontal direction in the figure, and the focus detection areas 203, 204, and 205 extend in the vertical direction. The photographing screen 200 corresponds to the imaging surface of the image sensor 121, and a plurality of focus detection pixels are arranged in the area of the image sensor 121 corresponding to each of the focus detection areas 201 to 205.

  FIG. 3 is a front view showing a part of the image sensor 121. In FIG. 3, a large number of imaging pixels 210 are two-dimensionally arranged on a part 121 a of the imaging element 121. The imaging pixel 210 includes a red (R) pixel, a green (G) pixel, and a blue (B) pixel, and the red pixel, the green pixel, and the blue pixel are regularly arranged according to a Bayer arrangement. Each imaging pixel 210 has a photoelectric conversion unit 210a. The plurality of focus detection pixels 220 are arranged in the vertical direction, and this corresponds to, for example, the focus detection area 204 in the vertical direction of the photographing screen 200 shown in FIG. The plurality of focus detection pixels 220 are arranged such that a part of the image pickup pixels 210 arranged in the Bayer array is replaced with the focus detection pixels 220.

  The plurality of focus detection pixels 220 includes a plurality of focus detection pixels 220a and a plurality of focus detection pixels 220b, and the focus detection pixels 220a and 220b are alternately arranged in the vertical direction. The focus detection pixel 220a has a small photoelectric conversion unit 220a located above the pixel, and the focus detection pixel 220b has a small photoelectric conversion unit 220b located below the pixel. As described above, the size of the photoelectric conversion unit 220a of the focus detection pixel 220a and the size of the photoelectric conversion unit 220b of the focus detection pixel 220b are determined to be approximately half the size of the photoelectric conversion unit 210a of the imaging pixel 210, respectively.

  4 is a front view showing a part of the image sensor 121 as in FIG. 3. The difference from FIG. 3 is that a pair of photoelectric conversion units 230a in which the focus detection pixels 230 are separated from each other in the pixels, 230b. The focus detection pixels 220 and 230 shown in FIGS. 3 and 4 constitute part of the pupil-division phase difference type focus detection device, and the focus detection optical system will be described below.

  FIG. 5 is a cross-sectional view showing the main part of the focus detection optical system of the focus detection pixel 220 shown in FIG. In FIG. 5, the photoelectric conversion unit 220a of the focus detection pixel 220a receives the light beam 241 transmitted through the first portion 240a of the exit pupil 240 of the photographing optical system via the microlens array 250, and the photoelectric conversion of the focus detection pixel 220b. The conversion unit 220 b receives the light beam 242 transmitted through the second portion 240 b of the exit pupil 240 through the microlens array 250. In this way, the defocus amount is calculated by measuring the phase difference between the focus detection signal sequence of the photoelectric conversion unit 220a of the plurality of focus detection pixels 220a and the focus detection signal sequence of the photoelectric conversion unit 220b of the plurality of focus detection pixels 220b. can do.

  In addition, the focus detection pixel 230 shown in FIG. 4 is configured such that one photoelectric conversion unit 230a of the focus detection pixel 230 transmits a light beam 241 transmitted through the first portion 240a of the exit pupil 240 of the photographing optical system in FIG. While receiving light through the lens array 250, the other photoelectric conversion unit 230 b receives the light beam 242 transmitted through the second portion 240 b of the exit pupil 240 through the microlens array 250. Thus, the defocus amount is calculated by measuring the phase difference between the focus detection signal sequence of the photoelectric conversion unit 230a of the plurality of focus detection pixels 230 and the focus detection signal sequence of the photoelectric conversion unit 230b of the plurality of focus detection pixels 230B. can do.

  Next, an embodiment of an image sensor according to the present invention will be described with reference to FIGS. FIG. 6 is a cross-sectional view showing the configuration of the imaging pixel of FIG. The imaging pixel 210 includes a photoelectric conversion unit 210a, a light shielding mask 261, a planarization layer 262, a color filter 263, a planarization layer 264, and a microlens 265.

  More specifically, the photoelectric conversion unit 210a is formed on the semiconductor substrate 260, and a light shielding mask 261 is provided immediately above the photoelectric conversion unit 210a. The light shielding mask 261 shields the outer periphery of the photoelectric conversion unit 210a and defines a light receiving region of the photoelectric conversion unit 210a. Thus, the opening 261a of the light shielding mask 261 defines the light receiving area of the photoelectric conversion unit 210a and corresponds to the size of the photoelectric conversion unit 210a of the imaging pixel 210 in FIG. A planarizing layer 262 is stacked on the light shielding mask 261, and a color filter 263 is formed on the planarizing layer 262. These color filters 263 have spectral characteristics corresponding to the red (R) pixel 210, the green (G) pixel 210, and the blue (B) pixel 210 shown in FIG. A planarizing layer 264 is laminated on the color filter 263, and each microlens 265 of the microlens array 250 shown in FIG. 5 is disposed on the planarizing layer 264.

The color filter 263 is a photonic crystal color filter in which a high refractive inorganic material and a low refractive inorganic material are laminated in multiple layers. TiO ₂ is used as the high refractive inorganic material, and SiO ₂ is used as the low refractive inorganic material. In this photonic crystal color filter, color fractors having spectral characteristics of red, green and blue are adjusted by adjusting the film thicknesses of the high refractive material TiO ₂ and the low refractive material SiO ₂ having a multilayer structure. Can be created. The high refractive inorganic material and the low refractive inorganic material are not limited to TiO ₂ and SiO ₂ , respectively, and other inorganic materials can be used. For example, SiN can be used instead of TiO ₂ .

  FIG. 7 is a cross-sectional view showing the configuration of the focus detection pixels 220a and 220b shown in FIG. 3 according to the first embodiment. In FIG. 7, a photoelectric conversion unit 220a of the focus detection pixel 220a and a photoelectric conversion unit 220b of the focus detection pixel 220b are respectively formed on the semiconductor substrate 260, and a light shielding mask 261 is provided immediately above the photoelectric conversion units 220a and 220b. Is provided. The light shielding mask 261 shields approximately half of the photoelectric conversion unit 220a and approximately half of the photoelectric conversion unit 220b, thereby defining the light receiving regions of the photoelectric conversion units 220a and 220b.

  A first wiring film 280 is disposed on the side of the light shielding mask 261. That is, these first wiring films 280 are arranged in a layer having the same height as the layer in which the light shielding mask 261 is arranged. A planarization layer 262 is stacked on the light shielding mask 261, and the second wiring film 281 and the light shielding film 282 are provided on the planarization layer 262. This light shielding film 282 prevents the generation of stray light.

  Since the light shielding mask 261 has a tip portion located substantially at the center portion of the photoelectric conversion portion 220b and a terminal portion located inside the side end portion of the photoelectric conversion portion 220b, the first wiring film 280, There is a gap between each of the second wiring film 281 and the light shielding film 282 and the light shielding mask 261. Therefore, when the black filter 283 described later is not provided, the light beam 285a that has passed through the microlens 265 enters the photoelectric conversion unit 220b, which may lead to a decrease in the accuracy of the focus detection signal as stray light. If the light shielding mask 261 is extended in the direction approaching the first wiring film 280 so that the gap is reduced, noise due to capacitive coupling is generated, and the accuracy of the focus detection signal is significantly reduced. Therefore, the gap cannot be excluded.

  On the light shielding film 282, a black filter 283 containing a pigment is provided. The black filter 283 is disposed at the same height as the color filter 263 of the imaging pixel 210 in FIG. 6 together with the neutral density filter 266. A planarizing layer 264 is laminated on the black filter 283, and a micro lens 265 is formed on the planarizing layer 264. In the imaging device of this embodiment, the color filter of the imaging pixel 210 and the black filter 283 and the neutral density filter 266 of the focus detection pixel are both made of an organic material.

  The function of the black filter 283 is as follows. That is, the black filter 283 acts as a light shielding member, passes through the microlens 265, and from the gap between each of the first wiring film 280, the second wiring film 281 and the light shielding film 282, and the light shielding mask 261. The light beam 285a incident on the photoelectric conversion unit 220b is shielded. Thereby, a stray light prevention effect is produced.

  In place of the black filter 283, a thin film interference color filter may be used.

  FIG. 8 is a sectional view showing the configuration of the focus detection pixels 220a and 220b shown in FIG. 3 according to the second embodiment. A thin-film light-shielding filter 285 that covers the photoelectric conversion unit 220b so as to shield the light beam 285a incident on the gap is provided in the planarization layer 262 instead of the black filter 283 in FIG. The position of the thin film light-shielding filter 285 in the height direction is immediately above the gap. The other configurations of the focus detection pixels are the same as those in FIG. The thin-film light-shielding filter 285 is desirably disposed as close to the gap as possible in order to reliably shield the light beam 285a.

  The thin-film light-shielding filter 285 acts as a light-shielding member similarly to the black filter 283, passes through the microlens 265, and each of the first wiring film 280, the second wiring film 281, the light-shielding film 282, and the light-shielding mask 261. The light beam 285a incident on the photoelectric conversion unit 220b is shielded from the gap therebetween. Thereby, a stray light prevention effect is produced.

  According to the first or second embodiment described above, it is possible to obtain an operational effect that it is possible to prevent a decrease in accuracy of the focus detection signal due to the light shielding performance.

121 imaging element, 210 imaging pixel, 220 focus detection pixel, 230 focus detection pixel, 210a photoelectric conversion unit, 220a, 220b photoelectric conversion unit, 230a, 230b photoelectric conversion unit, 263 color filter, 265 microlens, 266 dimming filter, 283 Shading member (black filter), 285 Shading member (thin film shading filter)

Claims (5)

A plurality of imaging pixels having a first microlens, and a first photoelectric conversion unit to output an image signal by receiving the light beam transmitted through the first micro lens,
A second microlens; a second photoelectric conversion unit that receives a light beam transmitted through the second microlens and outputs a focus detection signal; the second microlens and the second photoelectric conversion; a plurality of focus detection pixels having a wiring layer disposed between the parts,
Disposed at substantially the same height as the front Sharing, ABS line layer, the second a light shielding mask for covering a part of the photoelectric conversion unit, substantially at the center of the light-shielding mask tip the second photoelectric conversion unit A light-shielding mask that is located at a portion, the light-shielding mask terminal portion is located inside the side edge of the second photoelectric conversion unit, and a gap is formed between the light-shielding mask terminal portion and the wiring layer ,
Wherein disposed between the second micro lens and the light-shielding mask, the second through the gap between the second microlens said shielding mask luminous flux transmitted is a front Sharing, ABS line layer An image pickup device comprising: a light shielding member that prevents light from entering the vicinity of the side end of the photoelectric conversion unit. The imaging device according to claim 1,
In the said first microlens and the first photoelectric conversion unit, wherein the second microlenses second photoelectric conversion unit and the actual qualitatively identical structure of each of the focus detection pixels of the image pickup pixels imaging device, characterized in that there. The imaging device according to claim 2,
The imaging pixel has a color filter under the first microlens,
The focus detection pixel has a neutral density filter at the same height as the color filter of the imaging pixel,
The imaging device , wherein the light shielding member is disposed at the same height as the neutral density filter . The imaging device according to claim 2,
The imaging device, wherein the light shielding member is disposed immediately above the gap so as to cover the gap. The imaging device according to claim 3,
The color filter, the neutral density filter, and the light shielding member are each configured by a thin film of an organic material.

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