JP2014232761A - Solid-state imaging device - Google Patents

Abstract

To suppress the generation of noise. A first region in which photoelectric conversion units are arranged and a second region in which photoelectric conversion units are arranged overlap in a direction perpendicular to the direction in which the photoelectric conversion units are arranged in the second region. , A photoelectric conversion device in which an insulating region is disposed between the first region and the second region, each of the photoelectric conversion unit of the first region and the photoelectric conversion unit of the second region in the insulating region A light guide path corresponding to at least one of the photoelectric conversion units is arranged. [Selection] Figure 1

Description

  The present invention relates to an imaging device having a plurality of photoelectric conversion layers.

  As a photoelectric conversion device using the spectral characteristics of the photoelectric conversion layer, Patent Literature 1 describes a solid-state imaging device that performs color separation for each semiconductor chip stacked in a plurality of stages.

JP 2010-135700 A

  In the technique described in Patent Document 1, there is not enough study on photoelectric conversion by an appropriate photoelectric conversion unit. That is, in a certain photoelectric conversion unit, light that should not be photoelectrically converted is photoelectrically converted, and noise may be generated by a signal generated as a result.

  Means for solving the above problem is that the first region in which the photoelectric conversion units are arranged and the second region in which the photoelectric conversion units are arranged are in the direction in which the photoelectric conversion units in the second region are arranged. A photoelectric conversion device that overlaps in a vertical direction and has an insulating region disposed between the first region and the second region, wherein each of the photoelectric conversion units in the first region and the photoelectric conversion unit in the insulating region A light guide path corresponding to at least one of the photoelectric conversion units in the second region is arranged.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion apparatus with which generation | occurrence | production of noise was suppressed can be provided.

FIG. 6 is a schematic cross-sectional view of an example of a photoelectric conversion device. The cross-sectional schematic diagram of an example of the manufacturing method of a photoelectric conversion apparatus. FIG. 6 is a schematic cross-sectional view of an example of a photoelectric conversion device. FIG. 6 is a schematic cross-sectional view of an example of a photoelectric conversion device. The plane schematic diagram of an example of the pattern of a filter layer. FIG. 6 is a schematic cross-sectional view of an example of a photoelectric conversion device.

  Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In the following description and drawings, a plurality of drawings can be referred to each other. The same or similar components are denoted by common reference numerals, and the description of the elements denoted by the common reference numerals is omitted as appropriate.

  FIGS. 1A and 1B are schematic cross-sectional views of examples of the first embodiment of the photoelectric conversion device. 1A and 1B are different in the structure of a light guide path to be described later. First, matters common to the photoelectric conversion devices in FIGS. 1A and 1B will be described.

  The photoelectric conversion device 100 has a configuration in which three photoelectric conversion layers of a first photoelectric conversion layer 101, a second photoelectric conversion layer 102, and a third photoelectric conversion layer 103 are stacked in order from the light incident side. Here, the photoelectric conversion layer has three layers. However, as long as there are a plurality of layers, the photoelectric conversion layer may have two layers, or may have four or more layers.

  The material of the photoelectric conversion layer may be an inorganic material or an organic material. The inorganic material is, for example, a single crystal or polycrystalline semiconductor material, and an elemental semiconductor such as Si or Ge or a compound semiconductor such as GaAs or ZnO is used. The constituent material may be different for each photoelectric conversion layer.

  A plurality of photoelectric conversion units are arranged in each photoelectric conversion layer. Each photoelectric conversion unit can be configured by a semiconductor element such as a photodiode or a photogate. 1A and 1B show first photoelectric conversion units 1011 and 1012 as photoelectric conversion units of the first photoelectric conversion layer 101. FIG. Similarly, the second photoelectric conversion units 1021 and 1022 are shown as the photoelectric conversion units of the second photoelectric conversion layer 102, and the third photoelectric conversion units 1031 and 1032 are shown as the photoelectric conversion units of the third photoelectric conversion layer 103. Although the number of photoelectric conversion units arranged in each photoelectric conversion layer is two here, 10,000 or more or 10 million or more photoelectric conversion units can be arranged in a matrix, for example. A direction in which the photoelectric conversion units are arranged in a certain photoelectric conversion layer is referred to as an arrangement direction. This arrangement direction is a direction along the main surface of the photoelectric conversion layer, that is, an in-plane direction of the photoelectric conversion layer.

  In the photoelectric conversion layer, a region where the photoelectric conversion units are arranged is a photoelectric conversion region. For example, the first photoelectric conversion layer 101 has a first photoelectric conversion region in which first photoelectric conversion units 1011 and 1012 are arranged. For example, the second photoelectric conversion layer 102 has a second photoelectric conversion region in which the second photoelectric conversion units 1021 and 1022 are arranged. The photoelectric conversion region may be the whole or a part of the photoelectric conversion layer, and the photoelectric conversion layer may have a signal processing region for processing signals generated in the photoelectric conversion region in addition to the photoelectric conversion region. it can. In FIG. 1, a photoelectric conversion region as a part of the photoelectric conversion layer is partially illustrated. The plurality of photoelectric conversion layers 101, 102, and 103 are stacked so that the photoelectric conversion regions of the respective photoelectric conversion layers overlap. The direction in which the photoelectric conversion regions overlap substantially coincides with the stacking direction of the photoelectric conversion layers. In the direction in which the first photoelectric conversion region of the first photoelectric conversion layer 101 and the second photoelectric conversion region of the second photoelectric conversion layer 102 overlap, the second photoelectric conversion units 1021 and 1022 of the second photoelectric conversion layer 102 are arranged. Perpendicular to the direction. In the direction in which the second photoelectric conversion region of the second photoelectric conversion layer 102 and the third photoelectric conversion region of the third photoelectric conversion layer 103 overlap, the third photoelectric conversion units 1031 and 1032 of the third photoelectric conversion layer 103 are arranged. Perpendicular to the direction. The arrangement direction of the photoelectric conversion units in the first photoelectric conversion layer 101 is typically parallel to the arrangement direction of the photoelectric conversion units in the second photoelectric conversion layer 102, but may be non-parallel.

  Here, a group of photoelectric conversion units configured by photoelectric conversion units that overlap each other in the stacking direction of the plurality of photoelectric conversion layers is referred to as a photoelectric conversion unit. In this example, the first photoelectric conversion unit 1011, the second photoelectric conversion unit 1021, and the third photoelectric conversion unit 1031 constitute a first photoelectric conversion unit as one photoelectric conversion unit. In addition, the first photoelectric conversion unit 1012, the second photoelectric conversion unit 1022, and the third photoelectric conversion unit 1032 constitute a second photoelectric conversion unit as one photoelectric conversion unit. The number of photoelectric conversion units may or may not match the number of photoelectric conversion units arranged in each photoelectric conversion layer. For example, one photoelectric conversion unit may include two photoelectric conversion units of the first photoelectric conversion layer 101 and four photoelectric conversion units of the second photoelectric conversion unit 102.

  The first photoelectric conversion layer 101, the second photoelectric conversion layer 102, and the third photoelectric conversion layer 103 are stacked through insulating regions (first insulating region 104 and second insulating region 105), respectively. That is, the insulating region is located between the plurality of photoelectric conversion regions. Due to this insulating region, mixing of charges generated in the photoelectric conversion regions between the photoelectric conversion regions is reduced. Note that the mixing of charges between the photoelectric conversion portions in the photoelectric conversion region can be reduced by a known element isolation structure. The photoelectric conversion region is composed of a single layer or multiple layers of insulating layers, and this insulating layer is referred to as an interlayer insulating layer. The insulator constituting the interlayer insulating layer of this example is a solid, but may be a liquid or a gas. The solid interlayer insulating layer constitutes an interlayer insulating film. The interlayer insulating film may be a single layer film including only one interlayer insulating layer or a multilayer film including a plurality of interlayer insulating layers. In this example, a first interlayer insulating film 111 constituting the first insulating region 104 is provided between the first photoelectric conversion layer 101 and the second photoelectric conversion layer 102. Between the second photoelectric conversion layer 102 and the third photoelectric conversion layer 103, the second interlayer insulating film 112 on the second photoelectric conversion layer 102 side constituting the second insulating region 104, and the third photoelectric conversion layer 103 side The third interlayer insulating film 113 is provided. In this example, the first interlayer insulating film 111, the second interlayer insulating film 112, and the third interlayer insulating film 113 are each a multilayer film including a plurality of interlayer insulating layers.

  A light guide (for example, the first light guide 1311 and the second light guide 1312) is arranged in the insulating region between the photoelectric conversion regions. The photoelectric conversion unit corresponding to the light guide path only needs to be positioned on at least one of the light incident side and the light output side with respect to the light guide path. By this light guide path, light can be photoelectrically converted by a photoelectric conversion unit associated between the photoelectric conversion layers. Therefore, generation of noise can be suppressed. The photoelectric conversion units associated between the photoelectric conversion layers are, for example, photoelectric conversion units that constitute one photoelectric conversion unit. The specific structure of the light guide will be described later.

Light to be subjected to photoelectric conversion enters the photoelectric conversion device 100 from the opposite side of the first photoelectric conversion layer 101 to the second photoelectric conversion layer 102. The light to be photoelectrically converted is, for example, first type light, second type light, and third type light having different wavelengths. The wavelength of the first type light is λ ₁ , the wavelength of the second type light is λ ₂ , and the wavelength of the third type light is λ ₃ . The first type light is photoelectrically converted by the first photoelectric conversion layer 101, the second type light is photoelectrically converted by the second photoelectric conversion layer 102, and the third type light is photoelectrically converted by the third photoelectric conversion layer 103. However, the first photoelectric conversion layer 101 can also photoelectrically convert second type light and third type light other than the first type light. The same applies to the second photoelectric conversion layer 102 and the third photoelectric conversion layer 103. The first type light, the second type light, and the third type light have different extinction coefficients in the first photoelectric conversion layer 101, the second photoelectric conversion layer 102, and the third photoelectric conversion layer 103. Most of the first type light is absorbed by the first photoelectric conversion layer 101, and most of the second type light and third type light are transmitted through the first photoelectric conversion layer 101. Most of the second type light is absorbed by the second photoelectric conversion layer 102, and most of the third type light passes through the second photoelectric conversion layer 102. When the photoelectric conversion layer is a silicon layer, in the visible light region, the shorter the wavelength, the higher the extinction coefficient. Therefore, the wavelength becomes longer in the order of first type light, second type light, and third type light (λ ₁ <λ ₂ <λ ₃ ). In this example, the first type light is blue light, the second type light is green light, and the third type light is red light. The light photoelectrically converted by the photoelectric conversion device 100 is not limited to visible light, and may be ultraviolet light or infrared light.

The thickness of each photoelectric conversion layer is set according to the wavelength of light mainly photoelectrically converted in each photoelectric conversion layer. In this example, the first photoelectric conversion layer 101, the second photoelectric conversion layer 102, and the third photoelectric conversion layer 103 are silicon layers. The thickness of the silicon layer as the first photoelectric conversion layer 101 is 0.4 μm or more and 0.8 μm or less so that green light and red light can be transmitted and blue light can be efficiently absorbed. The thickness of the silicon layer as the second photoelectric conversion layer 102 is 1.2 μm or more and 2.0 μm or less so that the red light can be transmitted and the green light can be efficiently absorbed. The thickness of the silicon layer as the third photoelectric conversion layer 103 is 3.0 μm or more so that red light can be efficiently absorbed. In this example, since the third photoelectric conversion layer 103 is also used as a support of the photoelectric conversion device 100, the thickness of the third photoelectric conversion layer 103 is 100 μm or more, for example, 700 μm or more and 800 μm or less. By adopting the silicon layer having the above thickness as the photoelectric conversion layer, light (blue light) in a wavelength band of 400 nm or more and less than 500 nm is mainly photoelectrically converted in the first photoelectric conversion layer 101. In the second photoelectric conversion layer 102, light (green light) having a wavelength band of 500 nm or more and less than 600 nm is mainly photoelectrically converted. In the third photoelectric conversion layer 103, light (red light) having a wavelength band of 600 nm or more and less than 700 nm is mainly photoelectrically converted. In this example, for convenience, the wavelength λ ₁ of the first type light is set to 450 nm, the wavelength λ ₂ of the second type light is set to 550 nm, and the wavelength λ ₃ of the third type light is set to 650 nm.

  As described above, the photoelectric conversion device 100 can perform color separation based on the spectral transmission characteristics of the photoelectric conversion layer itself. Since color separation can be performed in a direction perpendicular to the light receiving surface, the resolution can be improved. Further, since color separation can be performed without providing a color filter, light utilization efficiency is improved. However, a primary color (RGB) or complementary color (CMY) filter (wavelength selection layer) may be used on the photoelectric conversion layer or on the light receiving surface for the purpose of increasing color purity or selecting a specific wavelength. . For example, a filter that absorbs the first type light and transmits the second type light and the third type light can be provided between the first photoelectric conversion layer 101 and the second photoelectric conversion layer 102. For example, a filter that absorbs the first type light and the second type light and transmits the third type light can be provided between the second photoelectric conversion layer 102 and the third photoelectric conversion layer 103.

  The photoelectric conversion device 100 is provided with a lens array 120 composed of a plurality of microlenses on the first photoelectric conversion layer 101 opposite to the second photoelectric conversion layer 102 side, that is, on the light incident side. ing. In the photoelectric conversion apparatus 100, one microlens corresponds to a plurality of photoelectric conversion units arranged over a plurality of photoelectric conversion layers. In this example, the first microlens 1201 corresponds to the three photoelectric conversion units 1011, 1021, and 1031 of the first photoelectric conversion unit. Similarly, the three photoelectric conversion units 1012, 1022, and 1032 of the second photoelectric conversion unit correspond to the second microlens 1202.

  A translucent film 121 is provided between the lens array 120 and the first photoelectric conversion layer 101. The translucent film 121 has a light transmission characteristic that transmits at least one of the first type light, the second type light, and the third type light. The translucent film 121 of this example is a single layer film composed of one translucent layer, but may be a multilayer film. The translucent film 121 may have a filter layer. The translucent film 121 of this example has a light transmission characteristic that transmits the first type light, the second type light, and the third type light.

  A first wiring 141 is provided inside the first interlayer insulating film 111. The first wiring 141 is a multilayer wiring composed of a plurality of wiring layers (three layers in this example) interconnected by vias (not shown). In this example, each interlayer insulating layer of the first interlayer insulating film 111 performs insulation between wiring layers in addition to insulation between photoelectric conversion layers. The first wiring 141 is connected to a semiconductor element such as a transistor in which a semiconductor region such as a source / drain region or a channel region is provided in the first photoelectric conversion layer 101 which is a semiconductor layer. The semiconductor element may be a charge coupled device (CCD). 1A and 1B show a transistor 151. FIG. The electrode (gate electrode) of the transistor 151 is located between the first photoelectric conversion layer 101 and the first interlayer insulating film 111.

  A second wiring 142 is provided inside the second interlayer insulating film 112. The second wiring 142 is also a multilayer wiring. The second wiring 142 is connected to a semiconductor element having a semiconductor region in the second photoelectric conversion layer 102. 1A and 1B show a transistor 152 as a semiconductor element. The electrode (gate electrode) of the transistor 152 is located between the second photoelectric conversion layer 102 and the second interlayer insulating film 112. That is, the transistor 152 is located on the third photoelectric conversion layer 103 side (the opposite side to the first photoelectric conversion layer 101 side) of the second photoelectric conversion layer 102.

  A third wiring 143 is provided inside the third interlayer insulating film 113. The third wiring 143 is also a multilayer wiring. The third wiring 143 is connected to a semiconductor element having a semiconductor region in the third photoelectric conversion layer 103. 1A and 1B show a gate electrode 153 of a transistor as a semiconductor element. The gate electrode 153 is located between the third photoelectric conversion layer 103 and the third interlayer insulating film 113. That is, the gate electrode 153 is located on the second photoelectric conversion layer 102 side of the third photoelectric conversion layer 103. As described above, the transistor 151 and the transistor 152 are arranged on the opposite side of the light incident side of the corresponding photoelectric conversion layer. Thereby, for example, the second type light transmitted through the first photoelectric conversion layer 101 is scattered by the gate electrode 152 of the second photoelectric conversion layer 102 and is incident on the photoelectric conversion unit of the first photoelectric conversion layer 101 to be photoelectrically It is possible to reduce the conversion. In this example, the transistor 152 and the transistor 153 are located between the second photoelectric conversion layer 102 and the third photoelectric conversion layer 103. However, like the transistors 151 and 152, the transistor 153 can be disposed on the opposite side of the third photoelectric conversion layer 103 from the second photoelectric conversion layer 102 side.

  The transistor may be a transfer transistor that transfers a signal charge of a corresponding photoelectric conversion unit or an amplification transistor that generates an electric signal from the signal charge. In addition, it may be a reset transistor that resets the signal charge or a selection transistor that controls the output of the amplification transistor. Peripheral circuits including, for example, a shift register, a decoder, an AD converter, and the like are included around the area where the photoelectric conversion units are arranged. A peripheral circuit can be provided for each photoelectric conversion layer.

  As the main component of the material of the wiring layer, aluminum, copper, gold, tungsten, titanium, tantalum, titanium nitride, tantalum nitride, or the like can be used. If necessary, polysilicon or metal can be used as the electrode material. A transparent electrode can also be used.

  The photoelectric conversion device of this embodiment is used for various applications. Most typically, it is an imaging device (image sensor). In the imaging apparatus, a plurality of photoelectric conversion units provided in different photoelectric conversion layers corresponding to one microlens, that is, one photoelectric conversion unit can constitute one pixel. A color image can be obtained by processing a signal for each color obtained in the photoelectric conversion portion of each photoelectric conversion layer. For each photoelectric conversion layer, a signal generation circuit for generating an electric signal that is a voltage or current corresponding to the amount of signal charge generated by photoelectric conversion in the photoelectric conversion unit can be provided. In addition, a signal processing circuit that processes the electrical signal may be provided for each photoelectric conversion layer. The light photoelectrically converted by the first photoelectric conversion layer 101 is treated as a signal corresponding to the first type light. Therefore, if the second type light or the third type light photoelectrically converted by the first photoelectric conversion layer 101 exists, it appears as a mixed color in the signal of the first type light. By providing an antireflection film on at least one of the upper surface and the lower surface of the photoelectric conversion layer, the reflected light of the second type light that is originally to be photoelectrically converted by the second photoelectric conversion layer 102 is photoelectrically converted by the first photoelectric conversion layer 101. Can be suppressed. Therefore, color mixing is reduced.

  Other than the imaging device, it can also be used as a photometric device (AE sensor) or a focus detection device (AF sensor). A form in which a photoelectric conversion layer having a plurality of photoelectric conversion layers has an imaging function and another photoelectric conversion layer has a focus detection function and a photometric function can also be employed. The photoelectric conversion device can also be used as a power generation device such as a solar battery. In a solar cell, improvement in power generation efficiency is expected by photoelectrically converting light of a certain wavelength with a photoelectric conversion layer having higher quantum efficiency.

  A first example of the light guide will be described with reference to FIG. A first light guide path 1311 and a second light guide path 1312 are disposed in an insulating region between the first photoelectric conversion layer 101 and the second photoelectric conversion layer 102. The first light guide path 1311 is located between the first photoelectric conversion unit 1011 of the first photoelectric conversion layer 101 and the second photoelectric conversion unit 1021 of the second photoelectric conversion layer 102 constituting the first photoelectric conversion unit. The second light guide 1312 is located between the first photoelectric conversion unit 1012 of the first photoelectric conversion layer 101 and the second photoelectric conversion unit 1022 of the second photoelectric conversion layer 102 that constitute the second photoelectric conversion unit.

  Each of the arrayed light guide paths can be provided, for example, between the photoelectric conversion unit of one photoelectric conversion layer of the plurality of photoelectric conversion layers and the photoelectric conversion unit of the other photoelectric conversion layer. Each light guide is preferably disposed between the corresponding upper and lower photoelectric conversion units in the stacking direction of the plurality of photoelectric conversion layers. Further, in order to deal with obliquely incident light, the light guide path may be arranged so as to correspond to a set of photoelectric conversion units constituting one photoelectric conversion unit in a direction inclined with respect to the stacking direction. Thereby, the light guide path can suppress noise generated in the photoelectric conversion unit when light is incident on the photoelectric conversion unit that is not in a correspondence relationship. There is no photoelectric conversion unit for detecting a signal on the light incident side on the light guide path, and the light incident on the light guide path may simply pass through the photoelectric conversion layer. Alternatively, there is no photoelectric conversion unit for detecting a signal on the light emission side with respect to the light guide, and the light incident on the light guide is simply transmitted or absorbed by the photoelectric conversion layer. There may be.

  Similarly, the first light guide path upper part 1321 and the second light guide path upper part 1322 are arranged in the insulating region between the second photoelectric conversion layer 102 and the third photoelectric conversion layer 103. In addition, a first light guide path lower part 1331 and a second light guide path lower part 1332 are arranged in an insulating region between the second photoelectric conversion layer 102 and the third photoelectric conversion layer 103. The first light guide path upper part 1321 and the first light guide path lower part 1331 are the second photoelectric conversion part 1021 of the second photoelectric conversion layer 102 and the third photoelectric conversion part 1031 of the third photoelectric conversion layer 103 that constitute the first photoelectric conversion unit. Located between. The second light guide path upper portion 1322 and the second light guide path lower portion 1332 include the second photoelectric conversion unit 1022 of the second photoelectric conversion layer 102 and the third photoelectric conversion unit 1032 of the third photoelectric conversion layer 103 that constitute the second photoelectric conversion unit. Located between. In other words, the upper part of the second light guide path can be restated as the first part of the light guide path, and the lower part of the second light guide path can be restated as the second part of the light guide path.

  The light guide path guides light that has passed through the photoelectric conversion unit of a certain photoelectric conversion unit positioned above the light guide path to a photoelectric conversion unit that belongs to the same photoelectric conversion unit and is positioned below the light guide path. And a light guide path suppresses that the light which permeate | transmitted the photoelectric conversion part located in the upper and lower sides injects into the photoelectric conversion part of photoelectric conversion units other than the photoelectric conversion unit to which the said photoelectric conversion part belongs. For example, in the first light guide path 1311 located between the first photoelectric conversion unit 1011 and the second photoelectric conversion unit 1021 of the first photoelectric conversion unit, the light transmitted through the first photoelectric conversion unit 1011 is converted into the second photoelectric conversion unit. The incident on the second photoelectric conversion unit 1022 of the unit is suppressed.

  As described above, even when there is no corresponding photoelectric conversion unit on one of the light incident side and the light emitting side of the light guide, it is useful for suppressing noise. For example, light that has passed through a certain first photoelectric conversion unit can be prevented from being photoelectrically converted by a second photoelectric conversion unit that does not correspond to the first photoelectric conversion unit. In addition, for example, only light that is not used as a signal in the first photoelectric conversion layer can be photoelectrically converted using the second photoelectric conversion unit of the second photoelectric conversion layer as a signal. At this time, it can be suppressed that the light transmitted through the first photoelectric conversion unit becomes noise due to photoelectric conversion by the second photoelectric conversion unit.

  In order to obtain the above effect, the light guide path has a structure with a barrier against light to be emitted from the light guide path. This barrier may be a barrier using light reflection, but may be a barrier using light absorption. Examples of the barrier using light reflection include reflection caused by a difference in refractive index and reflection caused by metal reflection. As the reflection caused by the difference in refractive index, it is desirable to use a so-called core-cladding that causes total reflection in the light guide path using a material having a higher refractive index than the surrounding material. However, since reflection occurs if the refractive index is different, the refractive index of the light guide may be lower than the surrounding material (insulator). In addition, the barrier using light absorption can be configured by using a transparent substance in the light guide path and arranging a light shielding body such as a black material having a low reflectance around the light guide.

  The light guide path can also suppress light from being reflected by the wiring layer and becoming stray light. Of course, such stray light also causes noise. Therefore, it is preferable that the thickness of the light guide path (the length of the light guide path in the stacking direction) is larger than the thickness of the wiring pattern (wiring layer thickness) constituting a certain wiring layer. Moreover, it is preferable that the wiring layer is disposed away from the light guide. For this purpose, the width of the light guide path (the length of the light guide path in the arrangement direction) may be made smaller than the interval between the wiring patterns constituting a certain wiring layer around the light guide path.

  In the example of FIG. 1A, each of the first light guide 1311 and the second light guide 1312 is surrounded by the first interlayer insulating film 111 in the direction along the arrangement direction. The light guides 1311 and 1312 in this example have a refractive index different from that of at least one insulating layer of the first interlayer insulating film 111 surrounding the light guiding paths 1311 and 1312. Light reflected from the interface between the light guide path and the insulating layer due to the refractive index difference between the insulating layer around the light guide path and the light guide path causes light emitted from one corresponding photoelectric conversion section to enter the other corresponding photoelectric conversion section. Can be guided to do. For example, light emitted from the first photoelectric conversion unit 1011 of the first photoelectric conversion layer 101 is guided to the second photoelectric conversion unit 1021 of the second photoelectric conversion layer 102 through the first light guide path 1311.

  The light guide path preferably has a higher refractive index than the surrounding insulating layer. If it does so, the light which satisfy | fills the conditions which produce a total reflection in the interface of a light-guide path and an insulating layer can be entered into the photoelectric conversion part of the 2nd photoelectric converting layer 102 with a low loss. For example, nitrogen silicon or silicon oxynitride having a refractive index of 1.6 to 2.1 is used for the light guide, and silicon oxide having a refractive index of about 1.5 is used for the insulating layer of the interlayer insulating film. realizable.

  A second example of the light guide will be described with reference to FIG. Also in this example, a first light guide path 1311 and a second light guide path 1312 are arranged between the first photoelectric conversion layer 101 and the second photoelectric conversion layer 102. A first light guide path upper part 1321 and a second light guide path upper part 1322 are arranged between the second photoelectric conversion layer 102 and the third photoelectric conversion layer 103. A first light guide path lower portion 1331 and a second light guide path lower portion 1332 are disposed between the second photoelectric conversion layer 102 and the third photoelectric conversion layer 103.

  The first light guide path 1311 and the second light guide path 1312 are each a separation unit 161 positioned between the first interlayer insulating film 111 and the first light guide path 1311 or the second light guide path 1312 in the direction along the arrangement direction. Surrounded by Similarly, the first light guide upper part 1321 and the second light guide upper 1322 are each in the direction along the arrangement direction, the second interlayer insulating film 112, the first light guide upper 1321, or the second light guide upper 1322. It is surrounded by the upper separation part 162 located between the two. The first light guide path lower portion 1331 and the second light guide path lower portion 1332 are each between the third interlayer insulating film 113 and the first light guide path lower portion 1331 or the second light guide path lower portion 1332 in the direction along the arrangement direction. Is surrounded by a lower separation portion 163 located at

  Each separation part of the separation part 161, the upper separation part 162, and the lower separation part 162 may be a region having a refractive index different from that of the light guide path that they surround. The separation portion is preferably a region having a lower refractive index than the light guide path surrounded by the separation portion. Thereby, total reflection can be generated at the interface between the separation unit and the light guide path, and light can be guided to the associated photoelectric conversion unit. The substance constituting the separation part may be any of gas, liquid, and solid, and the separation part may be a vacuum space.

  When such a separation part is used, the refractive index of the light guide may be the same as the refractive index of the interlayer insulating film located outside the separation part, and the light guide and the interlayer insulating film may be the same material. Good. For example, the light guide path may be a portion surrounded by a groove formed in the interlayer insulating film in the interlayer insulating film. The separation part corresponds to the region of this groove.

  In this way, instead of the separation part having a refractive index different from that of the light guide path, the separation part may be formed using a substance (light-shielding body) having a light transmittance lower than that of the light guide path. Examples of the material having low light transmittance include metals and black members. If a metal is used, the light shielding property of the separation part and the improvement of sensitivity by reflection can be realized at a high level.

  In the second example, a separation part is also arranged in the photoelectric conversion layer. The separation part in the photoelectric conversion layer has a light barrier function with respect to the photoelectric conversion part. Such a separation portion can be realized by disposing a material (for example, silicon oxide or silicon nitride) having a lower refractive index than the material of the photoelectric conversion layer (for example, silicon) or a gap around the photoelectric conversion portion. . In this example, the first photoelectric conversion layer 101 is provided with a first separation unit 171 around the first photoelectric conversion units 1011 and 1012. In the second photoelectric conversion layer 102, a second separation unit 172 is disposed around the second photoelectric conversion units 1021 and 1022. For example, the third photoelectric conversion layer 103 is provided with a third separation unit 173 around the third photoelectric conversion units 1031 and 1032. In the first example, a separation part can also be provided in the photoelectric conversion layer. In the second example, the separation part may not be provided in the photoelectric conversion layer.

  The structure in which the photoelectric conversion regions overlap through the insulating regions as in this embodiment has the following characteristics. That is, it is separated from one photoelectric conversion region (for example, the first photoelectric conversion layer 101) from the other photoelectric conversion layer (for example, the third photoelectric conversion layer 103). Therefore, when oblique light is incident, the amount of light shift in the arrangement direction of the photoelectric conversion units between different photoelectric conversion layers increases. In other words, there is a high possibility of erroneous incidence on the photoelectric conversion units of different photoelectric conversion units. In a simple model that ignores refraction and the like, the distance between the plurality of photoelectric conversion layers is g, the incident angle is θ, and the deviation amount is expressed by g × tan θ. On the other hand, by providing the light guide path, it is possible to suppress the oblique incident light from being subjected to photoelectric conversion by an inappropriate photoelectric conversion unit.

  Next, a method for manufacturing the photoelectric conversion device according to this example will be described in detail with reference to FIGS. 2 (a-1), (a-2), (a-3), (b), and (c). 2 (a-1), (a-2), and (a-3) show members before the photoelectric conversion layer is laminated. FIG. 2A-1 shows the first member 10 including the first substrate 1010 that is a base material of the first photoelectric conversion layer 101. FIG. 2A-2 shows the second member 20 including the second substrate 1020 that is a base material of the second photoelectric conversion layer 102. FIG. 2A-3 shows the third member 30 including the third substrate 1030 that is a base material of the third photoelectric conversion layer 103. Photoelectric conversion portions 1011, 1012, 1021, 1022, 1031, and 1032 are formed on a substrate that is a base material of each member. As each substrate, a bulk silicon wafer, an SOI wafer, or the like can be used.

  As described above, each photoelectric conversion unit has a different wavelength region for photoelectric conversion for each photoelectric conversion layer. Therefore, it is formed with a desired depth by individually setting the implantation energy of impurity implantation when forming each photoelectric conversion portion. Although not described in detail, each member is provided with a transfer transistor, an amplification transistor, a reset transistor, a selection transistor, and the like, and a circuit for reading out an electrical signal obtained by photoelectric conversion is formed. Further, on each substrate, wirings (141, 142, 143), interlayer insulating films (111, 112, 113) and light guides (1311, 1312, 1321, 1322, 1331, 1332) constituting each circuit are formed. Is formed.

  A method for forming a light guide formed in each member will be described by taking the first member 10 as an example. A first interlayer insulating film 111 including a first wiring 141 and a silicon oxide layer having a refractive index of 1.4 to 1.6 serving as a cladding of the light guide as an interlayer insulating layer is formed on the first substrate 1010. Then, an opening is formed in the first interlayer insulating film 111 by dry etching. Further, a high refractive index material such as silicon nitride, silicon oxynitride, titanium oxide, or resin having a refractive index of 1.6 to 2.5 is embedded in the opening formed by the dry etching to form the core of the light guide. . Further, the surface of the high refractive index material is flattened by using a flattening method such as CMP or etchback to form a light guide. In this embodiment, the light guide path is formed by embedding the above-described high refractive index material, but the light guide path can be formed using other configurations such as using a groove provided in the first interlayer insulating film 111 as a separation portion. Can be formed.

  Next, a process of stacking the three members shown in FIGS. 2A-1 to 2A-3 will be described with reference to FIGS. 2B and 2C. First, the second member 20 and the third member 30 are bonded onto the third member 30 with the bonding surface 115 as a boundary so that the third interlayer insulating film 113 and the second interlayer insulating film 112 are in contact with each other. In this example, a light guide path is formed in both the second member 20 and the third member 30, and a light guide path having an upper portion and a lower portion is formed by integrating them. However, it is not essential that the two light guides are in contact with each other. The first light guide upper part 1321 and the second light guide upper part 1322 are in the second interlayer insulating film 112, and the first light guide lower part 1331 and the second light guide lower part 1332 are in contact. A form embedded in the third interlayer insulating film 113 may also be used. Moreover, the structure by which the light guide path is formed only in either the 2nd member 20 or the 3rd member 30 may be sufficient. In this way, the laminated structure shown in FIG. 2B is obtained.

  Next, the second substrate 1020 of the second member 20 bonded to the third member 30 is subjected to processing such as grinding, polishing, and etching, so that the thickness is reduced to a desired thickness. In this example, a silicon layer having a thickness of 1.2 μm to 2.0 μm is formed so that the second photoelectric conversion layer 102 transmits red light and can efficiently capture green light. In this example, a bulk silicon wafer is used as the second substrate 1020. However, even if a method of thinning the wafer by using an SOI wafer and using the BOX layer as a polishing stop and an etch stop layer is applied. good.

  Thereafter, the dielectric film 122 is formed on the surface of the second photoelectric conversion layer 102 which is thinned and obtained from the second substrate 1020. The dielectric film 122 is configured to obtain an antireflection effect by laminating layers having different refractive indexes, such as a laminated film of a silicon oxide layer and a silicon nitride layer, or a laminated film of a hafnium oxide layer and a tantalum oxide layer. Good.

  Next, the first member 10 is bonded to the formed second photoelectric conversion layer 102 with the bonding surface 116 as a boundary so that the dielectric film 122 and the first interlayer insulating film 111 are in contact with each other. Next, the first photoelectric conversion layer 101 is formed by thinning the first substrate 1010 using a method similar to the thinning of the second photoelectric conversion layer 102 described above. In this embodiment, the silicon film thickness is in the range of 0.4 to 0.8 μm so that the first photoelectric conversion layer 101 transmits green and red light and can efficiently capture blue light. Thereafter, the translucent film 121 and the lens array 120 are formed. Although not shown here, an electrical signal obtained in each photoelectric conversion layer by forming a through electrode or the like in the peripheral circuit portion with respect to the laminated structure in which the members 10, 20, and 30 are stacked. Can be read out. The through electrode may be formed after all three photoelectric conversion layers are stacked.

  Regarding the second embodiment of the photoelectric conversion device, the first example in FIG. 3A, the second example in FIG. 3B, the third example in FIG. 4A, and the second example in FIG. The cross-sectional schematic diagram of 4 examples is shown.

  In the second embodiment, in the insulating region 104 between the first photoelectric conversion layer 101 and the second photoelectric conversion layer 102, the first light guide path upper part 1341 and the first light guide path lower part each corresponding to the first photoelectric conversion unit. 1351 is provided. The insulating region 104 between the first photoelectric conversion layer 101 and the second photoelectric conversion layer 102 is provided with a second light guide path upper part 1342 and a second light guide path lower part 1352, each corresponding to the second photoelectric conversion unit. ing. The first light guide path lower portion 1351 is located between the first light guide path upper portion 1341 and the second photoelectric conversion portion 1021 of the second photoelectric conversion layer 102, and the second light guide path lower portion 1352 is connected to the second light guide path upper portion 1342 and the second photoelectric conversion portion 1021. It is located between the photoelectric conversion layer 102 and the second photoelectric conversion unit 1022.

  A first interlayer insulating film 111 and a first wiring 141, a second interlayer insulating film 112 and a second wiring 142 are provided between the first photoelectric conversion layer 101 and the second photoelectric conversion layer 102. . The first light guide path upper part 1341 and the second light guide path upper part 1342 are each surrounded by the first interlayer insulating film 111. The first light guide path lower portion 1351 and the second light guide path lower portion 1352 are each surrounded by the second interlayer insulating film 112. More specifically, each light guide is surrounded by one or more interlayer insulating layers provided around the light guide. An interlayer insulating layer representing the first interlayer insulating film 111 is referred to as a first interlayer insulating layer, and an interlayer insulating layer representing the second interlayer insulating film 112 is referred to as a second interlayer insulating layer.

  The positional relationship of the constituent members of the photoelectric conversion device in the present embodiment is the same as the relationship between the second photoelectric conversion layer 102 and the third photoelectric conversion layer 103 in the first embodiment.

  In the first example shown in FIG. 3A, the first light guide path upper part 1341 and the first light guide path lower part 1351 are in contact with each other through the joint surface 117.

  In the second example shown in FIG. 3B, the width R1 of the first light guide path upper portion 1341 is different from the width R2 of the first light guide path lower portion 1351. The area of the orthogonal projection of the first light guide path upper portion 1341 onto the first photoelectric conversion layer 101 (or the second photoelectric conversion layer 102) is equal to the second photoelectric conversion layer 102 (or the first photoelectric conversion layer) in the first light guide path lower portion 1351. This is different from the area of the orthogonal projection onto the conversion layer 101). Here, R1 <R2 is satisfied, but R1> R2 may be satisfied. Similarly, the second light guide upper portion 1342 and the second light guide lower portion 1352 have different widths and orthogonal projection areas.

  By doing in this way, even when the misalignment occurs between the first light guide path upper part 1341 and the first light guide path lower part 1351 at the joint surface 117, the influence can be reduced. Further, by setting R1 <R2, light that has passed through the first light guide path upper part 1341 can be efficiently guided to the first light guide path lower part 1351. Therefore, it is possible to more stably suppress light leaking to adjacent photoelectric conversion units.

  In the third example shown in FIG. 4A, the refractive index of the first light guide upper portion 1341 and the refraction of the first light guide lower portion 1351 are provided between the first light guide upper portion 1341 and the first light guide lower portion 1351. A dielectric having a refractive index lower than the refractive index is located. Specifically, a first low-refractive index dielectric layer 1110 and a second low-refractive index dielectric layer 1120. The first low-refractive index dielectric layer 1110 and the second low-refractive index dielectric layer 1120 extend between the second light guide path upper part 1342 and the second light guide path lower part 1352. A bonding surface 117 is located between the low refractive index dielectric layer 1110 and the low refractive index dielectric layer 1120.

  In the fourth example shown in FIG. 4B, a first high refractive index dielectric layer 1310 and a second high refractive index dielectric layer are provided between the first light guide path upper part 1341 and the first light guide path lower part 1351. 1320 is located. The high refractive index dielectric layers 1310 and 1320 have a refractive index higher than at least one of the refractive index of the first interlayer insulating film 111 and the refractive index of the second interlayer insulating film 112. The refractive indexes of the high refractive index dielectric layers 1310 and 1320 may be higher or lower than the refractive index of at least one of the light guide upper portion 1341 and the light guide lower portion 1351, or may be the same as these. . In this example, the high refractive index dielectric layer 1310 and the high refractive index dielectric layer 1320 are made of the same material and have substantially the same refractive index as those of the upper portion of the light guide path.

  The high refractive index dielectric layers 1310 and 1320 extend between the second light guide path upper part 1342 and the second light guide path lower part 1352. A bonding surface 117 is located between the high refractive index dielectric layer 1310 and the high refractive index dielectric layer 1320.

  In the 3rd example and the 4th example, since both sides of joint surface 117 are constituted by a homogeneous dielectric layer over a plurality of photoelectric conversion units, it is possible to suppress joint failures such as voids during joining. . Also in the third example and the fourth example, the diameters of the upper part of the light guide path and the lower part of the light guide path can be made different as in the second example shown in FIG.

  In the first example of the second embodiment, the translucent film 121 includes a filter layer (wavelength selection layer) 1212. Similarly, in other examples of the first embodiment and the second embodiment, the light-transmitting film 121 having the filter layer can be similarly used.

  5A to 5F are examples of a planar layout of the filter layer 1212. FIG. FIGS. 5A to 5G show the types of transmitted light of the filters corresponding to 4 × 4 16 photoelectric conversion units, respectively. Ir is infrared light, R is red light, Y is yellow light (or red light and green light), G is green light, B is blue light, W is white light (or red light, green light and blue light) is there. If these have wavelength selectivity with respect to visible light, the wavelength selection filter can be called a color filter.

  FIG. 5 (a) shows a form in which R, G, and B filters are arranged in a 2 × 2 section in a conventionally known Bayer system, and FIG. 5 (b) is a diagram of G in FIG. 5 (a). Is replaced with Ir. In the example of FIG. 5B, for example, in a photoelectric conversion unit having an R (G or B) filter, red light (green light or blue light) is photoelectrically converted by the first photoelectric conversion layer 101. On the other hand, in the photoelectric conversion unit having an Ir filter, infrared light can be photoelectrically converted by the second photoelectric conversion layer 102. In addition, by setting the R, G, and B filters to transmit infrared light, the second photoelectric conversion layer 102 also photoelectrically converts infrared light in the R, G, and B photoelectric conversion units. Can do.

  FIG. 5C shows a case where a W filter is provided in addition to the R, G, and B filters. In this example, the intensity of white light can be detected by arranging a W filter. Light having an intensity not exceeding the saturation charge amount of the first photoelectric conversion layer 101 can be detected by the first photoelectric conversion layer 101. And about the light of strong intensity | strength exceeding the saturated charge amount of the 1st photoelectric converting layer 101, not only the 1st photoelectric converting layer 101 but the light which permeate | transmitted the 1st photoelectric converting layer 101 is sent to the 2nd photoelectric converting layer 102. Can be detected. By adding the signal obtained from the first photoelectric conversion layer 101 and the signal obtained from the second photoelectric conversion layer 102, the actual light intensity can be detected. Thus, in the present embodiment, the light intensity detection range (dynamic range) can be widened.

  Further, the output of the photoelectric conversion unit corresponding to the W filter is arithmetically processed based on the output of the photoelectric conversion unit having R, G, and B filters in the vicinity thereof, thereby expanding the dynamic range of the obtained image. It becomes possible.

  The layout of W and RGB in FIG. 5C is an example, and the ratio of the W filter may be reduced or increased as compared with FIG.

  FIG. 5D uses a Y filter. The Y filter transmits green light and red light. Among the transmitted incident light, green light is photoelectrically converted by the first photoelectric conversion layer 101, and red light is transmitted through the first photoelectric conversion layer 101 and is photoelectrically converted by the second photoelectric conversion layer 102. By doing in this way, the light utilization efficiency in the photoelectric conversion unit which has a Y filter can be improved. Although a filter that transmits yellow light is used here, a filter that transmits cyan light (blue light and green light) and magenta light (red light and blue light) may be used.

  FIG. 6 shows an example of the photoelectric conversion apparatus according to the third embodiment. In this example, the second photoelectric conversion layer 102 provided on the first main surface side (the side opposite to the incident light) of the first photoelectric conversion layer 101 is an example of constituting a focus detection (AF: autofocus) function. As the focus detection method, phase difference detection type focus detection or contrast detection type focus detection can be used, but the phase difference detection type is more preferable.

  A configuration of the second photoelectric conversion layer 102 in the phase difference detection method will be described. A image photoelectric conversion regions 1021A and 1022A for capturing the light beam that has passed through the viewpoint A and B image photoelectric conversion regions 1021B and 1022B for capturing the light beam that has passed through the viewpoint B are provided. One microlens 1201 corresponds to the A-image photoelectric conversion region 1021A and the B-image photoelectric conversion region 1021B of the second photoelectric conversion unit 1021. Another one microlens 1202 corresponds to the A-image photoelectric conversion region 1022A and the B-image photoelectric conversion region 1022B of the second photoelectric conversion unit 1022. From the photoelectric conversion area for A image, A image data that captures the luminous flux of viewpoint A is obtained, and from the photoelectric conversion area for B image, B image data that captures the luminous flux of viewpoint B is obtained. By performing these correlation calculations, it is possible to detect the defocus amount, change the optical system to a desired state, and perform focus detection.

  In this embodiment, it is possible to reduce a deviation in a correspondence relationship between an image photoelectrically converted by the first photoelectric conversion layer 101 and used for imaging and an image photoelectrically converted by the second photoelectric conversion layer 102 and used for focus detection. That is, high-precision focus detection can be realized as compared with an imaging system using a reflex structure such as a single-lens reflex camera. Further, if the phase difference detection method is used, focus detection can be performed at a higher speed than the contrast detection method. In the present embodiment, the first light guide path 1361 and the second light guide path 1362 are arranged between the first photoelectric conversion layer 101 and the second photoelectric conversion layer 102. Therefore, the loss of light between the first photoelectric conversion layer 101 and the second photoelectric conversion layer 102 is reduced, and focus detection can be performed by the second photoelectric conversion layer 102 with a sufficient amount of light. In addition, focus detection accuracy is improved because focus detection based on an erroneous signal from the photoelectric conversion unit hardly occurs.

  Here, an example in which focus detection is performed with the second photoelectric conversion layer in the photoelectric conversion device using two photoelectric conversion layers is shown, but the first layer may be used, or three or more photoelectric conversion layers may be used. It is also possible to perform focus detection on the third and subsequent photoelectric conversion layers.

  In the photoelectric conversion device described above, the first photoelectric conversion layer and the second photoelectric conversion layer are stacked via an interlayer insulating layer disposed between the first photoelectric conversion layer and the second photoelectric conversion layer. . A photoelectric conversion unit is arranged in the first photoelectric conversion layer, and a photoelectric conversion unit is also arranged in the second photoelectric conversion layer. And the light guide is arranged between the 1st photoelectric conversion layer and the 2nd photoelectric conversion layer. Thereby, it is possible to provide a high-performance photoelectric conversion device in which generation of noise is suppressed. The present invention can be modified as appropriate without departing from the technical idea thereof.

101 1st photoelectric conversion layer 1011, 1012 1st photoelectric conversion part 111 Interlayer insulation film 1131 1st light guide path 1132 2nd light guide path 102 2nd photoelectric conversion layer 1021, 1022 2nd photoelectric conversion part

Claims (10)

The first region in which the photoelectric conversion units are arranged and the second region in which the photoelectric conversion units are arranged overlap in a direction perpendicular to the direction in which the photoelectric conversion units are arranged in the second region, and the first region A photoelectric conversion device in which an insulating region is disposed between the region and the second region,
A photoelectric conversion device, wherein a light guide path corresponding to at least one of the photoelectric conversion unit in the first region and the photoelectric conversion unit in the second region is arranged in the insulating region.   The light guide path is surrounded by a material having a refractive index lower than that of the light guide path or a light shielding body in the direction in which the photoelectric conversion units in the second region are arranged. Photoelectric conversion device.   The photoelectric conversion device according to claim 1, wherein the light guide path is surrounded by a region having a lower refractive index than an insulator provided in the light guide channel and the insulating region.   The photoelectric conversion device according to claim 1, wherein a wiring layer is provided in the insulating region, and the light guide path is provided apart from the wiring layer.   In the first region, a portion having a refractive index different from that of the photoelectric conversion unit is provided between the photoelectric conversion units of the first region in a direction in which the photoelectric conversion units of the first region are arranged. The photoelectric conversion device according to claim 1, wherein the photoelectric conversion device is provided. The light guide path includes a first portion, and a second portion located between the first portion and the second region,
6. The area according to claim 1, wherein an area of the orthogonal projection of the first portion onto the first region is different from an area of the orthogonal projection of the second portion onto the second region. The photoelectric conversion device described. The light guide path includes a first portion, and a second portion located between the first portion and the second region,
The dielectric material having a lower refractive index than at least one of the first part and the second part is provided between the first part and the second part. 6. The photoelectric conversion device according to any one of items 6. The insulating region is provided with a first interlayer insulating layer, and a second interlayer insulating layer located between the first interlayer insulating layer and the second photoelectric conversion layer,
The light guide path includes a first portion surrounded by the first interlayer insulating layer and a second portion surrounded by the second interlayer insulating layer, and between the first portion and the second portion. A dielectric layer having a higher refractive index than the first interlayer insulating layer and the second interlayer insulating layer extends between the first interlayer insulating layer and the second interlayer insulating layer. The photoelectric conversion device according to claim 1, wherein the photoelectric conversion device is characterized in that:   The photoelectric conversion according to claim 1, wherein a lens array and a wavelength selection filter are provided on a side opposite to the second region with respect to the first region. apparatus.   10. The photoelectric conversion apparatus according to claim 1, wherein focus detection is performed based on a signal obtained by one of the photoelectric conversion units in the second region and the first region.

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