JP2011238781A - Solid-state image pickup device and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance image quality and microfabrication for a pixel characteristic of a solid-state image pickup device.SOLUTION: A solid-state image pickup device has a semiconductor substrate 100 having a pixel region and a peripheral region, and plural diffusion layers 102, 103 formed in the pixel region of the semiconductor substrate 100 and arranged in a matrix form. The solid-state image pickup device further has plural wiring layers 107 formed on the semiconductor substrate 100, plural pixel-side electrodes 108 which are formed on the plural wiring layers so as to be connected to the plural diffusion layers respectively and spaced from one another, a light-shielding film 111 formed in each gap between the plural pixel-side electrodes, an organic photoelectric conversion film 109 formed so as to cover the plural pixel-side electrodes and the light-shielding film, and a transparent electrode 110 which is formed on the organic photoelectric conversion film 109 and transmits visible light therethrough.

Description

  The present invention relates to a solid-state imaging device including a photoelectric conversion film that photoelectrically converts incident light to generate a signal charge, and a manufacturing method thereof.

  Conventionally, a single-plate image sensor represented by a charge coupled device (CCD) image sensor or a complementary metal-oxide-semiconductor (CMOS) image sensor has photoelectric elements arranged in a matrix. By providing three or four types of color filters in a mosaic pattern on the pixel (photodiode) to be converted, a color signal corresponding to each color filter is output. The output color signal is subjected to signal processing to generate a color image.

  However, in the case of an image sensor provided with a mosaic color filter, in the case of a primary color filter, approximately two-thirds of incident light is absorbed by the color filter, so that the light use efficiency is low and the sensitivity is low. . Further, since only one color signal can be obtained for each pixel, the resolution is poor, and false colors are particularly noticeable. In order to avoid this false color, an optical low-pass filter is required, and light loss due to this filter also occurs.

  Therefore, in order to overcome such a problem, an imaging device (hereinafter also referred to as an organic photoconductive imaging device) having a structure in which a photoelectric conversion film made of an organic material is formed on a wiring formed on a substrate. It has been studied and developed (for example, see Patent Document 1 below).

  As shown in FIG. 7, the conventional organic photoconductive imaging device has, for example, a photoelectric that generates a signal charge by each incident light of red (R), green (G), and blue (B) sequentially from the light incident surface. A light receiving portion on which the conversion film 19 is stacked is provided. Further, although not shown, a signal readout circuit is provided that can independently read out signal charges generated in each photoelectric conversion film 19 for each light receiving unit.

  In the case of an organic photoconductive imaging device having such a structure, incident light is almost photoelectrically converted and read out, the utilization efficiency of visible light is close to 80%, and each of the light receiving portions has three colors of R, G, and B. Since a color signal is obtained, it is possible to generate a good image with high sensitivity and high resolution (false colors are not conspicuous).

  As described above, in the conventional organic photoconductive imaging device, the transparent electrode 11 is formed on the photoelectric conversion film 19 formed of an organic film, and the pixel-side electrode 18 is formed below the photoelectric conversion film 19.

  The photoelectric conversion film 19 may be an InGaN-based, InAlN-based, InAlP-based, or InGaAlP-based inorganic semiconductor (compound semiconductor), but since these have a high film-forming temperature, the organic material is ashed during film formation. Therefore, it is limited to the organic material film here.

  In Patent Document 1, the structures of the pixel side electrode 18 and the photoelectric conversion film 19 are optimized. That is, in the organic photoconductive imaging device described in Patent Document 1, with respect to the gap between the pixel side electrodes 18, the gap between the pixel side electrodes 18 is 3 μm so that signal charges can be efficiently read out. It is set as follows. In this way, the pixel-side electrodes 18 are arranged with a gap between each other so as to suppress the afterimage as a solid-state imaging device.

JP 2009-147147 A

  However, when a gap is formed between the pixel side electrodes 18 as in the conventional organic photoconductive solid-state imaging device, the incident light 20 that has not been absorbed by the photoelectric conversion film 19 is diffracted through the gap between the pixel side electrodes 18. Is done. The diffracted light enters the wiring region of the adjacent pixel, propagates through the wiring 17, and enters the readout diffusion region 12 formed in the silicon substrate 10. The incident diffracted light causes photoelectric conversion in the readout diffusion region 12 to deteriorate the color reproducibility. That is, there is a problem that light leaks to adjacent pixels and color mixing occurs in the case of a color image sensor.

  SUMMARY OF THE INVENTION An object of the present invention is to solve the above-described problems and improve the image quality and the miniaturization of the pixel characteristics of a solid-state imaging device.

  In order to achieve the above object, according to the present invention, the solid-state imaging device has a configuration in which a light shielding film is provided in a gap provided between pixel side electrodes (lower electrodes).

  Specifically, a solid-state imaging device according to the present invention includes a semiconductor substrate having a pixel region and a peripheral region, a plurality of diffusion layers formed in a pixel region of the semiconductor substrate and arranged in a matrix, and an upper surface of the semiconductor substrate. A plurality of lower electrodes formed on the plurality of wiring layers, connected to the plurality of diffusion layers and spaced apart from each other, and between the plurality of lower electrodes A photoelectric conversion film formed so as to cover the plurality of lower electrodes and the light shielding film, and an upper electrode formed on the photoelectric conversion film and transmitting visible light.

  According to the solid-state imaging device of the present invention, the photoelectric conversion film is formed so as to cover the plurality of lower electrodes and the light shielding film formed between each of the lower electrodes. Diffracted light of incident light does not enter the semiconductor substrate. This prevents light from leaking into adjacent pixels, so that both high image quality and miniaturization of pixel characteristics in the solid-state imaging device can be achieved.

  In the solid-state imaging device of the present invention, the light shielding film may be made of a black resist material.

  In this case, the film thickness of the black resist material is preferably 500 nm or more and 2000 nm or less.

  In the solid-state imaging device of the present invention, the photoelectric conversion film may be made of an organic material.

  In the solid-state imaging device of the present invention, the lower electrode may be mainly composed of aluminum.

  In the solid-state imaging device of the present invention, the film thickness of the lower electrode may be 500 nm or more and 2000 nm or less.

  The solid-state imaging device of the present invention further includes a light shielding layer and connection pads formed on the peripheral region of the semiconductor substrate and on the plurality of wiring layers, and the light shielding layer and the connection pads are the same as the lower electrode. It may be formed of a material.

  The solid-state imaging device of the present invention may further include a plurality of color filter layers formed on the upper electrode so as to correspond to the plurality of lower electrodes, respectively.

  In this case, the solid-state imaging device of the present invention may further include a plurality of microlenses formed on the color filter layer so as to correspond to the plurality of lower electrodes, respectively.

  A method for manufacturing a solid-state imaging device according to the present invention includes: a step of forming a plurality of diffusion layers in a pixel region of a semiconductor substrate having a pixel region and a peripheral circuit region; and a plurality of wiring layers on the semiconductor substrate. Forming a plurality of lower electrodes connected to the plurality of diffusion layers on the wiring layer, and forming a light shielding film between the plurality of lower electrodes, respectively. A step, a step of forming a photoelectric conversion film so as to cover the lower electrode and the light-shielding film, and a step of forming an upper electrode that transmits visible light on the photoelectric conversion film.

  According to the method for manufacturing a solid-state imaging device of the present invention, the method includes the step of forming a light shielding film between each of the plurality of lower electrodes, so that the diffracted light of the incident light enters the semiconductor substrate from the gap between the lower electrodes. Never get into. This prevents light from leaking into adjacent pixels, so that both high image quality and miniaturization of pixel characteristics in the solid-state imaging device can be achieved.

  The solid-state imaging device manufacturing method of the present invention may further include a step of forming a plurality of color filter layers respectively corresponding to the plurality of lower electrodes on the upper electrode after the step of forming the upper electrode. Good.

  According to the solid-state imaging device according to the present invention, light leakage to adjacent pixels is prevented, so that both high image quality and miniaturization of pixel characteristics in the solid-state imaging device can be achieved.

FIG. 1 is a schematic cross-sectional view showing a pixel portion of a solid-state imaging device according to an embodiment of the present invention. FIG. 2 is a plan view showing a pixel side electrode (lower electrode) and a light shielding film in the solid-state imaging device according to the embodiment of the present invention. FIG. 3A to FIG. 3D are cross-sectional views in order of steps showing a method for manufacturing a solid-state imaging device according to an embodiment of the present invention. FIG. 4A to FIG. 4C are cross-sectional views in order of steps showing a method for manufacturing a solid-state imaging device according to an embodiment of the present invention. FIG. 5 is a schematic cross-sectional view showing a pixel portion of a solid-state imaging device according to a first modification of one embodiment of the present invention. FIG. 6 is a schematic cross-sectional view showing a pixel portion of a solid-state imaging device according to a second modification of one embodiment of the present invention. FIG. 7 is a schematic cross-sectional view showing a pixel portion of a solid-state imaging device according to a conventional example.

(One embodiment)
A solid-state imaging device according to an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, for example, element isolation regions 101 that electrically insulate each pixel portion are formed in a row direction or a column direction on a semiconductor substrate 100 made of p-type silicon (Si). Furthermore, a plurality of n-type high concentration impurity regions (hereinafter referred to as n ⁺ regions) 102 for accumulating signal charges generated in the organic photoelectric conversion film 109 are formed on the semiconductor substrate 100. Note that an organic material is not necessarily used for the photoelectric conversion film, and an inorganic material may be used.

A laminated insulating film 105 is formed on the semiconductor substrate 100, and each n ⁺ region 102 has copper (Cu) and aluminum (Al) formed in a plurality of openings provided in the insulating film 105. Alternatively, the pixel-side electrode 108 which is a lower electrode is electrically connected through a second connection portion 106B made of a metal such as tungsten (W).

  A plurality of stacked wiring layers 107 made of metal such as copper or aluminum are formed below the second connection portion 106B. The plurality of wiring layers 107 are used to transmit a signal charge from the pixel portion to a peripheral circuit (not shown), or to apply a voltage from the peripheral circuit to the gate electrode 104 or the drain portion of the pixel portion. .

In the n ⁺ region 102, electrons generated in the organic photoelectric conversion film 109 formed on the pixel side electrode 108 on the insulating film 105 and moved to the pixel side electrode 108 are transferred to the second connection portion 106B and the wiring layer. 107 and the first connection unit 106A. Electrons accumulated in the n ⁺ region 102 are transferred to the floating diffusion (FD) region 103 by a voltage applied to the gate electrode 104. The charge transferred to the FD region 103 is converted into a signal corresponding to the amount of charge by a CMOS circuit (not shown) formed of an n-channel MOS transistor formed on the semiconductor substrate 100 and output to the outside. The CMOS circuit is connected to a signal readout pad (not shown) by a wiring layer 107. The circuit configuration of the signal reading unit is not limited to the CMOS circuit, and may be configured by a CCD and an amplifier. Specifically, the electrons accumulated in the n ⁺ region 102 are read to the charge transfer channel formed in the semiconductor substrate 100, the read electrons are transferred to the amplifier, and a signal corresponding to the amount of the electrons is amplified. May be output. As described above, the circuit configuration of the signal readout unit may be a CCD or a CMOS circuit, but the CMOS circuit is preferable from the viewpoint of power consumption, high-speed readout, pixel addition, partial readout, and the like. In addition, in the case of a CMOS circuit, there are electrons and holes as signal charges that can be handled, and electrons are superior in terms of high-speed signal readout derived from charge mobility and completeness of process conditions in manufacturing. Therefore, it is preferable to connect the electrode for extracting electrons to the n ⁺ region.

  On each second connection portion 106B, a pixel-side electrode 108 mainly composed of aluminum (Al), an optical black (OB) portion (not shown), and a pad portion (not shown) are formed. . Here, the OB unit is a dark current correction pixel (optical black pixel) provided outside the effective pixel, and removes the direct current component of the dark current by taking a difference from the signal of the effective pixel. Has a function that can. The pixel side electrode 108 is separated in each pixel region of the R region, the G region, and the B region in order to separate electrons generated in the organic photoelectric conversion film 109 for each color. Also, each pixel side electrode 108 and the OB portion, and the OB portion and the pad portion are separated from each other.

A light shielding film 111 made of a black resist material and blocking visible light is formed between the pixel side electrodes 108. The black resist material mainly includes an acrylic resin as a resin, propylene glycol monomethyl ether acetate (PGMEA: C ₆ H ₁₂ O ₃ ) and an additive as a solvent, and is formed by a spin coating method. Here, the light shielding film 111 is defined as a film having a light transmittance of 15% or less in a wavelength region of 400 nm to 600 nm. In addition, if the film thickness of the light shielding film 111 is large, absorption of visible light increases, and it is preferable for color separation of the organic photoelectric conversion film 109 formed thereon. However, when the interval between the pixel-side electrodes 108 is reduced, pattern collapse or the like is caused when the light shielding film 111 is thick. Since the black resist material having the pattern collapse causes particles during the wafer processing process, it is necessary to select an optimum film thickness for the light shielding film 111. Here, the thickness of the light-shielding film 111 is preferably 500 nm or more and 2000 nm or less, and more preferably 700 nm or more and 1000 nm or less.

  Further, the cross-sectional shape of the light shielding film 111 is preferably a square shape or a forward taper (trapezoidal) shape, and a reverse taper (reverse trapezoidal) shape is not suitable.

In the present embodiment, a black resist material, which is an organic material, is used for the light shielding film 111. However, the material is not limited to an organic material, and may be an inorganic material. For example, in the case where an inorganic material is used for the light-shielding film 111, the light-shielding film 111 can be formed by stacking a plurality of materials having different refractive indexes and patterning the materials by lithography and etching. Further, when an insulating material is used for the light shielding film 111, a laminated structure of a silicon oxide film (SiO ₂ ) and a silicon nitride film (SiN) can be used, and when an insulating material and a metal material are used, A stacked structure of a silicon oxide film (SiO ₂ ) and titanium oxide (TiO ₂ ) can be used. Each film thickness of the laminated structure may be a known set value.

  The organic photoelectric conversion film 109 is composed of a photoelectric conversion material that absorbs light of a specific wavelength and generates charges according to the absorbed light. The organic photoelectric conversion film 109 may have a single layer structure or a multilayer structure, and a single layer structure is desirable from the viewpoint of color reproducibility. In the case of a single layer structure, a color filter and a microlens may be unnecessary, and in the case of a multilayer structure, a color filter and a microlens are required. Moreover, the organic photoelectric conversion film is more preferably an organic material having high crystallinity because of high photoelectric conversion performance. Hereinafter, a case where the organic photoelectric conversion film 109 has a single layer structure will be described.

  Examples of the material constituting the organic photoelectric conversion film 109 include a material containing a quinacridone skeleton, a phthalocyanine skeleton, and an anthraquinone skeleton. When quinacridone represented by the following [Chemical Formula 1] is used as the organic photoelectric conversion film 109, the organic photoelectric conversion film 109 may absorb light in the green wavelength region and generate a charge corresponding thereto. It becomes possible. In the case where zinc phthalocyanine represented by the following [Chemical Formula 2] is used as the organic photoelectric conversion film 109, the organic photoelectric conversion film 109 absorbs light in the red wavelength region and generates a charge corresponding thereto. Is possible. In addition, when anthraquinone A represented by the following [Chemical Formula 3] is used as the organic photoelectric conversion film 109, the organic photoelectric conversion film 109 absorbs light in the blue wavelength region and generates a charge corresponding thereto. It becomes possible to do.

The transparent electrode 110 that is the upper electrode needs to make light incident on the organic photoelectric conversion film 109, and thus is made of a conductive material that is transparent to at least a wavelength of 380 nm to 780 nm absorbed by the organic photoelectric conversion film 109. The As a material of the transparent electrode 110, a transparent conductive oxide (TCO) having a high visible light transmittance and a small resistance value can be used. Note that a metal thin film made of gold (Au) or the like can be used for the transparent electrode 110. However, when the metal thin film tries to obtain a transmittance of 90% or more, the resistance value is extremely increased, and therefore TCO is preferable. . In particular, TCO includes ITO (Indium Tin Oxide), IZO (Indium Zinc Oxide), AZO (Al-doped Zinc Oxide), FTO (F-doped-SnO ₂ ), SnO ₂ (tin oxide), TiO ₂ (titanium oxide). ) Or ZnO ₂ (zinc oxide) or the like can be preferably used. Among these, ITO is most preferable from the viewpoints of process simplicity, low resistance, and transparency. In addition, the transparent electrode 110 is configured as a single sheet shared by all the pixel units, but may be configured as a plurality of sheets divided for each pixel unit.

  Here, a microlens 115 is formed on the transparent electrode 110 to have a desirable structure, but the microlens 115 is not necessarily formed.

  FIG. 2 shows a planar configuration of the solid-state imaging device according to the present embodiment. Here, the microlens 115 and the transparent electrode 110 are omitted.

  As shown in FIG. 2, the planar shape of the pixel-side electrode 108 is desirably a square shape or a rectangular shape from the viewpoint of manufacturing, dimensional control, and the like. Here, the pixel side electrode 108 which is a square cell with one side of 1400 nm will be described as an example. The pixel-side electrodes 108 formed at a cell pitch of 1400 nm are formed with an interval of about 200 nm to 300 nm. The smaller this interval is, the better because the transmitted light from the organic photoelectric conversion film 109 can be blocked. However, the characteristics of the adjacent pixel-side electrodes 108 are connected to each other due to the performance of the lithography technique and the etching technique. In order to prevent deterioration, it is desirable to provide the above-mentioned interval.

  Although the light shielding film 111 made of a black resist material depends on the performance of the reduction projection exposure apparatus at the time of film formation, the overlap amount (covered area) with each pixel side electrode 108 is desirably about 50 nm to 100 nm.

  Below, the manufacturing method of the solid-state image sensor which concerns on this embodiment is demonstrated using FIG.3 and FIG.4. In particular, an amplification type solid-state imaging device (CMOS sensor) suitable for high image quality and high speed is given as an example.

First, as shown in FIG. 3A, an element isolation region 101 made of an insulator is selectively formed on a semiconductor substrate 100 made of p-type silicon by a known method. It is divided into pixel (R region, G region and B region) regions. Here, the width of each element isolation region 101 is about 100 nm to 200 nm, and the depth is about 100 nm to 400 nm. Thereafter, a gate insulating film 113 made of silicon oxide having a thickness of about 5 nm to 10 nm is formed on the main surface of the semiconductor substrate 100 by, for example, thermal oxidation. Subsequently, a polysilicon film having a film formation temperature of 600 ° C. to 700 ° C. and a film thickness of 150 nm to 200 nm is formed on the gate insulating film 113 by a chemical vapor deposition (CVD) method. Thereafter, a plurality of gate electrodes 104 are formed in a predetermined shape from the formed polysilicon film by lithography and etching. Subsequently, ion implantation is performed by ion implantation using each gate electrode 104 as a mask to form an n ⁺ region 102 which is a signal storage portion and an FD region 103 in the semiconductor substrate 100.

The ion species at this time may be implantation by a single species using any one of As (arsenic) and P (phosphorus), or both ion species may be used. That is, since the n ⁺ region 102 and the FD region 103 are electrically connected to metal tungsten (W), which is a contact plug forming material, in a later process, ions are implanted so as to have a concentration capable of ohmic connection. Just do it. For that purpose, it is preferable that the impurity concentration of the n ⁺ region 102 and the FD region 103 is a high concentration of 1.0 × 10 ¹⁵ cm ⁻³ or more. For example, in this embodiment, arsenic (As ⁺ ) ions having an acceleration energy of 20 keV and a dose of 3.0 × 10 ¹⁴ cm ⁻² , an acceleration energy of 70 keV and a dose of 1.0 × 10 ¹⁵ cm ⁻ and ² of arsenic (as ⁺⁾ ions, the acceleration energy of the dose is successively injected and 5.0 × the ¹⁰ 13 ^{cm -2} phosphorus ^{(P +)} ions in the upper portion of the semiconductor substrate 100 at 40 keV. At this time, it is preferable that a diffusion region is formed from the surface of the semiconductor substrate 100 to a depth of about 0.1 μm to 0.5 μm.

Next, as shown in FIG. 3B, a BPSG (Boron-Phospho-Silicate-) having a film thickness of 400 nm to 500 nm over the entire surface so as to cover the gate insulating film 113 and each gate electrode 104 on the semiconductor substrate 100. A premetal interlayer insulating film 105A made of glass is formed. Thereafter, the pre-metal interlayer insulating film 105A formed is annealed at a temperature of 900 ° C. for 30 seconds to perform a reflow process. Thereafter, the reflowed premetal interlayer insulating film 105A is polished and planarized by a chemical mechanical polishing (CMP) method. Subsequently, a first connection hole (not shown) is formed on each of the n ⁺ region 102, the FD region 103, the gate electrode 104, and the source / drain regions constituting the transistors of the pixel and the peripheral circuit in the premetal interlayer insulating film 105A. Form. The first connection holes are formed by forming each contact hole in the pre-metal interlayer insulating film 105A by dry etching, and then, for example, filling tungsten (W), which is a metal material, into each contact hole and planarizing it by CMP. Note that the first connection portion 106A shown in FIG. 3B is a part of the first connection hole.

  Next, as shown in FIG. 3C, a first interlayer insulating film 105a made of, for example, silicon oxide is formed on the premetal interlayer insulating film 105A. Thereafter, a plurality of first copper wirings 107a are formed in the first interlayer insulating film 105a by a single damascene method. At this time, a barrier metal film (not shown) made of a laminated film of tantalum (Ta) and tantalum nitride (TaN) is formed between the first interlayer insulating film 105a and the first copper wiring 107a by CVD or sputtering. ). Thereafter, a first diffusion prevention film (not shown) made of silicon nitride having a thickness of 50 nm is formed on the first interlayer insulating film 105a and the first copper wiring 107a. Here, the film thickness of the first interlayer insulating film 105a and the first copper wiring 107a is, for example, 260 nm.

  Subsequently, a second interlayer insulating film 105b made of silicon oxide is formed on the first interlayer insulating film 105a and the first copper wiring 107a, and the upper surface of the formed second interlayer insulating film 105b is formed by CMP. Flatten. Thereafter, a second copper wiring 107b covered with a barrier metal film (not shown) is formed by, for example, a via first method or a dual damascene method. Subsequently, a second diffusion prevention film (not shown) made of silicon nitride having a thickness of 50 nm is formed on the second interlayer insulating film 105b and the second copper wiring 107b. The film thickness of the second interlayer insulating film 105b is 565 nm, and the film thickness of the second copper wiring 107b is 335 nm. At this time, the connecting portion 106 is formed in the same manner as the second copper wiring 107b.

  Similarly, a third interlayer insulating film 105c made of silicon oxide is formed on the second interlayer insulating film 105b and the second copper wiring 107b, and the upper surface of the formed third interlayer insulating film 105c is formed by CMP. Flatten. Thereafter, a third copper wiring 107c covered with a barrier metal film (not shown) is formed by, for example, a via first method or a dual damascene method. Subsequently, a third diffusion prevention film (not shown) made of silicon nitride having a film thickness of 300 nm is formed on the third interlayer insulating film 105c and the third copper wiring 107c. The film thickness of the third interlayer insulating film 105c is 565 nm, and the film thickness of the third copper wiring 107c is 335 nm. At this time, the connecting portion 106 is formed in the same manner as the third copper wiring 107c.

  In the example described above, the wiring layer 107 has a three-layer structure. However, the present invention is not limited to this configuration. In the solid-state imaging device according to the present embodiment, the wiring layer 107 may have a one-layer structure or a two-layer structure. A structure in which four or more layers are stacked may be used.

  Further, although copper (Cu) is used as the material of each wiring layer 107, the present invention is not limited to this, and aluminum (Al) may be used.

  Further, each connection portion 106 may be tungsten. Each connection portion 106 is formed by a stacked via structure, like the wiring layer 107.

Next, as shown in FIG. 3D, the third copper connected to each n ⁺ region 102 is connected to the third diffusion prevention film and the third interlayer insulating film 105c by lithography and dry etching. A plurality of contact holes exposing the wiring 107c are formed. After that, each formed contact hole is filled with tungsten or the like to form the second connection portion 106B. Subsequently, although not shown, by selectively removing a plurality of pixel side electrode formation regions each including the second connection portion 106B in the third diffusion prevention film by a lithography method and a dry etching method, A plurality of pad forming portions are formed. Subsequently, for example, by sputtering, a titanium (Ti) film having a film thickness of 30 nm and a titanium nitride (TiN film having a thickness of 100 nm) constituting the pixel side electrode are formed on the third diffusion prevention film and the third interlayer insulating film 105c. ) An aluminum (Al) film having a film thickness of 800 nm is sequentially formed. At this time, the film thickness of the Al film is sufficient to block visible light, and the step between the OB part and the pad part is formed by forming the organic photoelectric conversion film in the subsequent process by spin coating. Therefore, the total thickness of Ti / TiN / Al is preferably 500 nm to 2000 nm. Subsequently, by the lithography method and the dry etching method, the pixel-side electrodes 108, the pixel-side electrodes 108 and the OB part, and the OB part and the pad part are formed on the Ti / TiN / Al laminated film. A plurality of pixel side electrodes 108 shown in FIG. 2 are obtained by selectively removing the respective regions therebetween. At this time, as described above, when the pixel cell is a square cell having a size of 1400 nm, it is desirable to provide an interval of 200 nm to 300 nm between the pixel side electrodes 108. Here, although not illustrated, a light shielding layer covering the wiring layer and a connection pad connected to the wiring layer are formed on the peripheral region of the semiconductor substrate 100, and the light shielding layer and the connection pad are It is formed of a laminated film of Ti / TiN / Al which is the same material as the pixel side electrode 108.

  Next, as shown in FIG. 4A, a black resist film having a film thickness of 1000 nm is applied on the pixel-side electrode 108 including the third interlayer insulating film 105c by, for example, spin coating. Thereafter, the black resist film is subjected to predetermined exposure and development to form a light shielding film 111 between the pixel side electrodes 108. At this time, as shown in FIG. 2, it is desirable that the peripheral portion of the pixel side electrode 108 is covered with the black resist film. Although depending on the performance of the lithography apparatus, in consideration of the alignment margin, as described above, the overlap amount between the pixel-side electrode 108 and the light shielding film 111 is desirably about 50 nm to 100 nm. When the film thickness is 1000 nm, the light shielding film 111 has a transmittance of 15% or less in the wavelength region of 400 nm to 600 nm. If the total film thickness of the pixel side electrode 108 made of Ti / TiN / Al is reduced in order to reduce the pixel size, the gap between the pixel side electrodes 108 can be reduced. However, in this case, if the thickness of the light shielding film 111 is reduced to about 600 nm, the light transmittance becomes about 20%, so that the light shielding property of the light shielding film 111 is deteriorated.

  When the thickness of the light shielding film 111 is 1200 nm or more, the organic photoelectric conversion film 109 formed in the next step varies in thickness due to the step between the light shielding film 111 and the pixel-side electrode 108, thereby causing organic photoelectric conversion. The photoelectric conversion efficiency of the film 109 varies. In order to prevent this variation, it is desirable that the step due to the light shielding film 111 covering the peripheral edge of the pixel side electrode 108 is suppressed to 50 nm or less. Therefore, it is desirable that the light-shielding film 111 fills the gap between the pixel-side electrodes 108 and has a thin film thickness on the periphery of the pixel-side electrodes 108. That is, the black resist material constituting the light shielding film 111 preferably has a low viscosity, and more preferably a material having a viscosity of 10 cP or less. If the viscosity of the black resist material cannot sufficiently cope with the reduction in the level difference on the pixel side electrode 108, it is possible to obtain a desired shape also by applying the black resist material in a plurality of times. is there.

  Next, as illustrated in FIG. 4B, the organic photoelectric conversion film 109 is formed so as to cover the light shielding film 111 and the plurality of pixel-side electrodes 108 by a dry film forming method or a wet film forming method. Specific examples of the dry film forming method include a physical vapor deposition method such as a vacuum deposition method, a sputtering method, an ion plating method or an MBE (molecular beam epitaxy) method, or a CVD method such as plasma polymerization. Specific examples of the wet film forming method include a casting method, a spin coating method, a dipping method, a Langmuir-Blodgett (LB) method, and the like. Further, a printing method such as ink jet printing or screen printing, or a transfer method such as thermal transfer or laser transfer may be used.

When a high molecular compound is used for the organic photoelectric conversion film 109, it is preferable to form the film by a wet film formation method, a printing method, or a transfer method that is easy to manufacture. Moreover, when using a dry film-forming method such as vapor deposition, it is difficult to use a polymer compound because it may be decomposed. When using a low molecular weight compound, a dry film forming method is preferably used, and a vacuum deposition method is particularly preferably used. The vacuum deposition method is basically based on a compound heating method such as resistance heating deposition or electron beam heating deposition, the shape of a deposition source such as a crucible or a boat, a degree of vacuum, a deposition temperature, a substrate temperature and a deposition rate. It becomes a parameter. In order to enable uniform vapor deposition, it is preferable to perform vapor deposition by rotating the semiconductor substrate 100. The degree of vacuum is preferably higher, and it is 133.32 × 10 ⁻⁴ Pa or less, preferably 133.32 × 10 ⁻⁶ Pa or less, particularly preferably 133.32 × 10 ⁻⁸ Pa or less. The entire deposition process is preferably performed in a vacuum, and basically the compound is not directly in contact with oxygen and moisture in the outside air. In addition, the above-described conditions in the vacuum deposition need to be strictly controlled because they affect the crystallinity, amorphousness, density, and density of the organic film.

  Hereinafter, a specific film formation example of the organic photoelectric conversion film 109 will be described.

  The photoelectric conversion film 109 is mainly sensitive to light in the red wavelength region, and mainly includes a plurality of R photoelectric conversion films (R films) 109r that generate an R signal charge corresponding to the amount of red light in the incident light. A plurality of G photoelectric conversion films (G films) 109g that are sensitive to light in the green wavelength region and generate a G signal charge corresponding to the amount of green light in the incident light, and mainly light in the blue wavelength region A plurality of photoelectric conversion films including a plurality of B photoelectric conversion films (B films) 109b having sensitivity and generating a B signal charge according to the blue light amount of incident light are arranged in a row direction on the same plane. They are arranged in a square lattice pattern in a column direction orthogonal to the above. In the present embodiment, a plurality of R photoelectric conversion films 109r, G photoelectric conversion films 109g, and B photoelectric conversion films 109b arranged in a two-dimensional array are arranged in a Bayer array.

  Here, for example, ZnPc (zinc phthalocyanine) / Alq3 (quinolinol aluminum complex) is used for the R photoelectric conversion film 109r. For example, R6G / PMPS (rhodamine 6G (R6G) -doped polymethylphenylsilane) is used for the G photoelectric conversion film 109g. For the B photoelectric conversion film 109b, for example, C6 / PHPPS (coumarin 6 (C6) -doped poly (m-hexoxyphenyl) phenylsilane) is used.

  The R, G, and B photoelectric conversion films 109r, 109g, and 109b are formed with a film thickness of, for example, 50 nm to 200 nm by the above-described coating method or vacuum deposition method. The organic photoelectric conversion film has a short carrier transportable distance, and when the film thickness is increased, the probability that the carriers cannot reach the electrode and the electrons and holes recombine and disappear, This leads to a decrease in conversion efficiency. Conversely, if the film thickness is reduced, light absorption is insufficient and high conversion efficiency cannot be desired. For this reason, it is necessary to set an optimum film thickness for each of the photoelectric conversion films 109r, 109g, and 109b. The separation of R, G, and B colors is formed in three steps by lithography and etching methods. Or you may form by the shadow mask mask method separated by the metal mask in an apparatus at the time of film-forming. If necessary, a hole transport layer made of an organic material may be provided above or below the organic photoelectric conversion film 109, or an electron injection / transport layer may be provided.

  Note that the R, G, and B photoelectric conversion films 109r, 109g, and 109b are desirably formed separately for each pixel as in a Bayer array.

Next, as illustrated in FIG. 4C, the transparent electrode 110 is formed on the organic photoelectric conversion film 109. Various methods are used for forming the transparent electrode 110 depending on the constituent material of the transparent electrode 110. For example, when ITO (Indiumu Tin Oxide) is used for the transparent electrode 110, an electron beam method, a sputtering method, a resistance heating vapor deposition method, a chemical reaction method (such as a sol-gel method), or a method of applying a dispersion of indium tin oxide is used. It is formed. Here, the film forming conditions of the transparent electrode 110 will be described. The temperature of the semiconductor substrate 100 during film formation of the transparent electrode 110 is preferably 150 ° C. or lower. Further, a gas may be introduced into the furnace during the film formation of the transparent electrode 110. Basically, the gas species is not limited, but argon (Ar), helium (He), oxygen (O ₂ ), nitrogen (N ₂ ), or the like can be used. Further, a mixed gas of these gases may be used. In particular, in the case of an oxide material, oxygen defects are often introduced, so that oxygen is preferably used.

  Further, it is preferable that the transparent electrode 110 is made plasma-free so as not to physically damage the organic photoelectric conversion film 109. By creating the transparent electrode 110 free from plasma, the influence of plasma on the organic photoelectric conversion film 109 and the like can be suppressed, and the photoelectric conversion characteristics can be improved. Here, plasma free means that plasma is not generated during the film formation of the transparent electrode 110, or the distance from the plasma generation source to the semiconductor substrate 100 is 2 cm or more, preferably 10 cm or more, more preferably 20 cm or more, This means a state in which the plasma reaching the substrate (here, the organic photoelectric conversion film 109) is reduced. Since light needs to be incident on the organic photoelectric conversion film 109, the transparent electrode 110 is preferably an electrode transparent to visible light. Here, the term “transparent” means that 80% or more of visible light having a wavelength in the range of about 420 nm to about 660 nm is transmitted.

In addition, when a sputtering method is used for forming the transparent electrode 110, a high-frequency sputtering method using an RF power source, a DC sputtering method, or the like can be used. The power of the sputtering device, preferably a RF ^sputtering, the range of 0.1W / cm ² ~10W / cm 2 is preferred. In this case, the film forming rate is preferably in the range of 0.5 nm / min to 10 nm / min, particularly 1 nm / min to 5 nm / min. The film thickness of the transparent electrode 110 is 10 nm to 200 nm. The reason for forming the transparent electrode 110 is that the organic photoelectric conversion film 109 is protected from moisture and oxygen, and between the organic photoelectric conversion film 109 and the pixel side electrode 108 in order to improve the photoelectric conversion efficiency and the response speed. This is because a voltage is applied.

  Subsequently, as shown in FIG. 1, a known microlens 115 corresponding to each pixel is formed on the transparent electrode 110. In addition, the microlens 115 preferably has a shape such that the focal point is connected to the inside of the organic photoelectric conversion film 109, and is preferably formed so that the focal point is closer to the pixel side electrode 108 than the transparent electrode 110. In this way, since the light condensed by the microlens 115 can be condensed at a position farthest from the pixel-side electrode 108 of the adjacent pixel, color mixing can be prevented. Further, in the case of a solid-state imaging device having a single layer structure, since it is not necessary to provide a color filter, the distance between the microlens 115 and the organic photoelectric conversion film 109 is shortened. Therefore, in this case, it is preferable to increase the radius of curvature of the microlens 115 so that the focal point of each microlens 115 is connected to the inside of the organic photoelectric conversion film 109. A structure without the microlens 115 may be used.

(First Modification of One Embodiment)
Hereinafter, as a first modification of the present embodiment, a case where the organic photoelectric conversion film 109 has a multilayer structure is shown in FIG. The process up to the formation of the light shielding film 111 is the same as that of the single layer structure.

  As shown in FIG. 5, in this modification, the organic photoelectric conversion film 109 is formed in a three-layer stacked structure that spans the R region, the G region, and the B region. Specifically, an R photoelectric conversion film 109r, a G photoelectric conversion film 109g, and a B photoelectric conversion film 109b are sequentially formed on the plurality of pixel side electrodes 108 and the light shielding film 111. Since red light has a longer focal length than other colors of light, the R photoelectric conversion film 109r, which is a red photoelectric conversion film, is located farthest from the color filter 112 and the microlens 115 as in this modification. It is preferable to form. Moreover, the film thickness of each photoelectric conversion film 109r, 109g, and 109b shall be 50 nm-200 nm as above-mentioned.

  Subsequently, the transparent electrode 110 is formed on the organic photoelectric conversion film 109. The manufacturing method of the transparent electrode 110 is the same as that in the case of the single layer structure. When the organic photoelectric conversion film 109 has a multilayer structure, the color filter 112 and the microlens 115 are necessary.

  Therefore, as shown in FIG. 5, a known G, R, B color filter 112 corresponding to each pixel is formed on the formed transparent electrode 110. Thereafter, a transparent planarizing film 114 is formed on each color filter 112, and the upper surface of each color filter 112 is planarized.

  Subsequently, a known microlens 115 corresponding to each pixel is formed on each color filter 112. Note that by providing the color filter 112, the organic photoelectric conversion film 109 can collectively form a material having sensitivity to the visible region in all pixels, so that the manufacturing process can be simplified and the film thickness and film uniformity can be improved. improves.

(Second Modification of One Embodiment)
Hereinafter, as a second modification of the present embodiment, FIG. 6 illustrates a solid-state imaging device in which each pixel has no spectral characteristics even if the organic photoelectric conversion film 109A has a single-layer structure.

  As shown in FIG. 6, the solid-state imaging device according to the second modified example has a configuration in which a single layer organic photoelectric conversion film 109A made of a single material is formed on the pixel-side electrode 108 over all pixels. ing. Since the organic photoelectric conversion film 109 </ b> A does not have spectral characteristics, it is necessary to provide the color filter 112 and the microlens 115.

  Here, for example, poly (N-vinylcarbazole: PVK) can be used as a constituent material of the organic photoelectric conversion film 109A having no spectral characteristics, and the film thickness is preferably 50 nm to 150 nm.

  Note that the solid-state imaging device according to the second modification has the same configuration as that of the first modification except that the single-layer organic photoelectric conversion film 109A is formed, and can be manufactured in the same manner as the first modification.

  As described above, according to the solid-state imaging device according to the present embodiment and the modification thereof, the organic photoelectric conversion film 109 that is a photoelectric conversion device is formed on the plurality of wiring layers 107. Compared with the case where a photoelectric conversion element is formed, the area of the light receiving portion can be enlarged. For this reason, not only the improvement of basic characteristics such as sensitivity and saturation characteristics can be expected, but also light leakage (for example, color mixing) to adjacent pixels does not occur.

  In addition, since the plurality of wiring layers 107 formed on the semiconductor substrate 100 can be manufactured by the same technique as the MOS sensor process similar to the conventional structure, the compatibility with the conventional process is high. Thereby, the pixel characteristics can be improved, and a solid-state imaging device with reduced cost can be obtained without adding a new process.

  The solid-state imaging device according to the present invention prevents light from leaking into adjacent pixels, and can achieve both high image quality and miniaturization of pixel characteristics in the solid-state imaging device. It is useful for a solid-state imaging device having a photoelectric conversion film to be generated, a manufacturing method thereof, and the like.

100 Semiconductor substrate 101 Element isolation region 102 n ⁺ region (n-type high concentration impurity region)
103 Floating diffusion diffusion region (FD region)
104 Gate electrode (transfer gate electrode)
105 Insulating film 105A Pre-metal interlayer insulating film 105a First interlayer insulating film 105b Second interlayer insulating film 105c Third interlayer insulating film 106 Connection part 106A First connection part 106B Second connection part 107 Wiring layer 107a First copper wiring 107b Second copper wiring 107c Third copper wiring 108 Pixel side electrode (lower electrode)
109 Organic photoelectric conversion film 109A Organic photoelectric conversion film 110 Transparent electrode (upper electrode)
111 Light-shielding film 112 Color filter 113 Gate insulating film 114 Transparent planarization film 115 Microlens

Claims (11)

A semiconductor substrate having a pixel region and a peripheral region;
A plurality of diffusion layers formed in a pixel region of the semiconductor substrate and arranged in a matrix;
A plurality of wiring layers formed on the semiconductor substrate;
A plurality of lower electrodes connected to the plurality of diffusion layers and spaced apart from each other on the plurality of wiring layers;
A light shielding film formed between each of the plurality of lower electrodes;
A photoelectric conversion film formed to cover the plurality of lower electrodes and the light shielding film;
A solid-state imaging device comprising an upper electrode formed on the photoelectric conversion film and transmitting visible light.   The solid-state imaging device according to claim 1, wherein the light shielding film is made of a black resist material.   The solid-state imaging device according to claim 2, wherein the black resist material has a film thickness of 500 nm or more and 2000 nm or less.   The solid-state imaging device according to claim 1, wherein the photoelectric conversion film is made of an organic material.   The solid-state imaging device according to claim 1, wherein the lower electrode contains aluminum as a main component.   6. The solid-state imaging device according to claim 1, wherein a film thickness of the lower electrode is not less than 500 nm and not more than 2000 nm. A light shielding layer and connection pads formed on the peripheral region of the semiconductor substrate and on the plurality of wiring layers;
The solid-state imaging device according to claim 1, wherein the light shielding layer and the connection pad are made of the same material as the lower electrode.   8. The solid-state imaging according to claim 1, further comprising a plurality of color filter layers formed on the upper electrode so as to correspond to the plurality of lower electrodes, respectively. 9. element.   The solid-state imaging device according to claim 8, further comprising a plurality of microlenses formed on the color filter layer so as to correspond to the plurality of lower electrodes, respectively. Forming a plurality of diffusion layers in a matrix in the pixel region of the semiconductor substrate having a pixel region and a peripheral circuit region;
Forming a plurality of wiring layers on the semiconductor substrate;
Forming a plurality of lower electrodes respectively connected to the plurality of diffusion layers on the wiring layer, spaced apart from each other;
Forming a light shielding film between each of the plurality of lower electrodes;
Forming a photoelectric conversion film so as to cover the lower electrode and the light shielding film;
And a step of forming an upper electrode that transmits visible light on the photoelectric conversion film. After the step of forming the upper electrode,
The method of manufacturing a solid-state imaging device according to claim 10, further comprising forming a plurality of color filter layers respectively corresponding to the plurality of lower electrodes on the upper electrode.

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