JP2020080380A - Photoelectric conversion element and manufacturing method thereof - Google Patents

Abstract

To provide a photoelectric conversion element that has a simple structure and in which a layer for suppressing multiple reflection is formed, and a manufacturing method thereof.SOLUTION: A plurality of particles is mixed into a coating agent in order to form a particle layer having a plurality of particles in a light transmitting layer that covers a photodiode portion in which a plurality of photodiodes are arranged in at least one row, the mixed particles and the coating agent is applied to the light transmitting layer, and the particle layer having the particles suppresses multiple reflection.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a photoelectric conversion element used in an image sensor for reading an image and a manufacturing method thereof.

  Conventionally, photoelectric conversion elements have been used as one-dimensional line sensors and two-dimensional area sensors. Some one-dimensional line sensors have a plurality of reading lines (for example, refer to Patent Document 1). In recent years, there has been a demand for high speed and high sensitivity of these sensors, and in order to realize these, miniaturization of the manufacturing process is progressing. Along with the miniaturization of the manufacturing process, a process of polishing each layer is introduced.

  In the conventional photoelectric conversion element, the characteristics of the photoelectric conversion element depended on the in-plane position of the wafer due to manufacturing variations of the semiconductor wafer. The incident light is multiply reflected by the transparent film to cause light interference, and thus interference fringes are generated in the spectral sensitivity characteristic. The surface after polishing the transparent film is extremely flat (for example, refer to Patent Document 2), but the transparent film thickness varies by several hundreds of nm depending on the position inside the chip and the position inside the wafer.

  A slight variation in the transparent film thickness of the photoelectric conversion element causes variations in the wavelength at which interference occurs at the position within the sensor and within the wafer, and the wavelength at which interference fringes of spectral sensitivity characteristics occur within the same sensor and within the same wafer different. As a result, each sensor outputs a significantly different signal with respect to the light of the same wavelength and the same amount of light.

  Regarding the spectral sensitivity characteristics of the photoelectric conversion element, the effect of the thickness of the transparent film on the photodiode is particularly remarkable, but unlike the element used for circuit design, it was difficult to predict the effect in advance. Light interference occurs due to multiple reflections of the incident light on the transparent film, but due to variations in the transparent film thickness, wavelengths causing interference at the sensor position and wafer position vary, and The wavelengths at which the interference fringes of the spectral sensitivity characteristic are generated in the same wafer are different, and signals that are largely different are output for the light of the same wavelength and the same light amount.

  There is a possibility that the uneven surface is effective for multiple reflection. Some photoelectric conversion elements suppress the "space charge effect" by increasing the roughness of the back surface on which light is incident (for example, Patent Document 3). Further, in some photoelectric conversion elements, an uneven portion having a rough surface that scatters light incident on the photoelectric conversion portion is formed on the light receiving surface (for example, Patent Document 4).

JP, 2011-205360, A JP, 2013-4565, A JP, 2005-176904, A JP, 2016-178148, A

  However, the conventional technique described in Patent Document 3 has a problem in that the rough surface is the back surface of the semiconductor substrate and the diameter of the light receiving portion is 50 μm. The conventional technique described in Patent Document 4 has a problem that processing may be difficult in some cases.

  The present invention has been made to solve the above problems, and relates to a photoelectric conversion element having a simple structure and a layer that suppresses multiple reflection, and a method for manufacturing the same.

  The photoelectric conversion element according to the present invention is a photodiode section in which a plurality of photodiodes are arranged in at least one row, a light transmission layer that covers the photodiode section, and is fixed by a coating agent, and is spread on the surface of the light transmission layer. A plurality of particles, comprising a particle layer that scatters or refracts incident light incident on the light transmission layer by the plurality of particles, the photodiode unit, multiple reflection of the incident light, by the particle layer It is characterized in that the incident light is received while being reduced by scattering or refraction.

  The method for producing a photoelectric conversion element according to the present invention is a method for producing a photoelectric conversion element in which a plurality of photodiodes are formed into a particle layer having a plurality of particles in a light transmission layer that covers the photodiode portions arranged in at least two rows. There, a mixing step of mixing the plurality of particles and a coating agent, to a portion of the light transmission layer corresponding to one row of the photodiode section, the plurality of particles and the mixed particles in the mixing step A first applying step of applying a coating agent and a second applying step of applying the plurality of particles mixed in the mixing step and the coating agent to a portion of the light transmitting layer corresponding to the other row of the photodiode section And a coating step.

  The method for manufacturing a photoelectric conversion element according to the present invention is a method for manufacturing a photoelectric conversion element in which a plurality of particles are formed in a light-transmitting layer that covers a photodiode section in which a plurality of photodiodes are arranged in at least one row. And a mixing step of mixing the plurality of colored particles to a coating agent, and an applying step of applying the plurality of particles and the coating agent mixed in the mixing step to the light transmitting layer. It is a feature.

  As described above, according to the present invention, it is possible to obtain a photoelectric conversion element in which multiple reflection is suppressed by a particle layer having particles and a method for manufacturing the photoelectric conversion element.

It is sectional drawing of the photoelectric conversion element which concerns on Embodiment 1 of this invention. It is a top view of the photoelectric conversion element which concerns on Embodiment 1 of this invention. FIG. 6 is a cross-sectional view showing a part of the method for manufacturing the photoelectric conversion element according to the first embodiment of the present invention. It is sectional drawing of the photoelectric conversion element which concerns on Embodiment 1 of this invention. It is sectional drawing of the photoelectric conversion element which concerns on Embodiment 2 of this invention. It is a top view which shows a part of manufacturing method of the photoelectric conversion element which concerns on Embodiment 2 of this invention.

Embodiment 1.
Embodiment 1 of the present invention will be described below with reference to FIGS. 1 to 4. In the drawings, the same reference numerals denote the same or corresponding parts, and detailed description thereof will be omitted. 1 to 4, in the photodiode section 10, a plurality of photodiodes 1 are arranged in at least one row. The arranged direction is referred to as a longitudinal direction or a main scanning direction (scanning direction). The light transmitting layer 11 (protective layer 11) is a layer through which light is transmitted and covers the photodiode section 10. For example, the silicon nitride film 2 is used. The wiring layer 12 is a layer arranged between the light transmission layer 11 and the particles 6 described later, and the metal wiring 3 (conductor wiring 3) is arranged therein. For example, the silicon oxide film 4 is used. The wiring layer 12 is a layer through which light is transmitted, except for the metal wiring 3, as in the light transmission layer 11. The light transmission layer 11 and the wiring layer 12 may be collectively referred to as a light transmission layer.

  In FIG. 1 to FIG. 4, the particles 6 are those through which light is transmitted, and the particles 6 are fixed by the coating agent 5 and have a plurality of particles 6 spread on the surface of the light transmission layer 11. The light incident on the transmission layer 11 is scattered or refracted by the plurality of particles 6. The coating agent 5 also transmits light. Therefore, the photodiode unit 10 can receive the incident light in a state where the multiple reflection of the incident light is reduced by the scattering or refraction of the particles 6. Further, the photodiode section 10 is formed on the silicon substrate 7 (semiconductor substrate 7). A direction orthogonal to the longitudinal direction or the main scanning direction (scanning direction) on the plane where the silicon substrate 7 extends is called the lateral direction or the sub-scanning direction (conveying direction). The incident light direction is orthogonal to the longitudinal direction and the lateral direction. The incident light direction may be referred to as the reading depth direction.

  FIG. 1 is a sectional view of the photoelectric conversion element according to the first embodiment. In the first embodiment, the case where the photoelectric conversion element is an element used as a line sensor in which a plurality of photodiodes 1 are arranged in one or more rows will be described as an example. In the photoelectric conversion element, the photodiode 1 is arranged at the center of the grid of the metal wiring 3 formed in a grid on the silicon substrate 7. The photoelectric conversion element includes the photodiode 1, a light transmission layer (light transmission layer 11 and wiring layer 12) formed on the photodiode 1, and particles 6 arranged on the light receiving surface 101 in the incident light direction. It is configured. The particles 6 (particle layer 13) may be the outermost shell layer of the photoelectric conversion element. In the present application, the case where the particle 6 (particle layer 13) is the outermost shell layer of the photoelectric conversion element is described.

  The photodiode 1 (photodiode unit 10) is a photoelectric conversion unit and converts light energy incident on the light receiving surface 101 into electric energy. The photodiode 1 is connected to a circuit unit including a plurality of transistors, resistors, capacitors, etc., and is switched by the circuit unit. The photodiode 1 is connected to the metal wiring 3 and outputs the converted energy to the metal wiring 3 as an electric signal. As shown in FIG. 1, the metal wiring 3 is arranged at a position that does not prevent the photodiode 1 (photodiode unit 10) from receiving incident light. That is, in the incident light direction, there is at least a portion where the metal wiring 3 is not disposed between the photodiode 1 (photodiode portion 10) and the particle layer 13. The photoelectric conversion element is one in which the photodiode 1 (photodiode unit 10) receives incident light focused by an imaging optical system such as a reduction optical system or an erecting equal-magnification optical system. The optical axis direction of the imaging optical system is often the incident light direction. This is a case where a mirror or the like is inserted between the imaging optical system and the particle layer 13 to reflect incident light and not bend the optical axis.

  The metal wiring 3 is embedded in the silicon oxide film 4 of the light transmitting layer (light transmitting layer 11, wiring layer 12) formed on the silicon substrate 7. The metal wiring 3 is composed of one or more metal layers, and each metal layer is laminated with a silicon oxide film 4 interposed therebetween. In the drawing, three metal layers are illustrated. The metal layer is connected to the photodiode 1 on the silicon substrate 7 via a via. The metal wiring 3 outputs an electric signal to an external circuit. In the drawing, a cross section of a portion where the via does not exist is illustrated.

The light transmitting layer (light transmitting layer 11 and wiring layer 12) is composed of a silicon oxide film 4 formed on the silicon substrate 7 and a silicon nitride film 2 formed on the silicon oxide film 4. The particles 6 arranged on the light transmission layer (light transmission layer 11, wiring layer 12) have a function of providing a plurality of irregularities of particles 6 on the light receiving surface 101 and scattering or refracting incident light. The uneven portion means the particle layer 13. The particle layer 13 has a satin-like unevenness according to the shape of the particles 6.

  FIG. 2 is a view of the surface of the light transmission layer (light transmission layer 11, wiring layer 12) on the photodiode 1 as viewed from above. Other configurations are omitted in order to clarify the positional relationship between the photodiode 1 and the particles 6. Further, the reference numerals of the photodiode 1 and the particles 6 are given to only one in FIG. 2 for simplification, and the others are omitted. The uneven portion is composed of particles 6 arranged on the surface of the light transmitting layer (light transmitting layer 11, wiring layer 12). A large number of particles 6 are arranged in the uneven portion. Since these particles 6 reduce the multiple reflection of incident light, it is possible to reduce the interference fringes of the spectral sensitivity characteristic generated by the reflected light. The uneven portion scatters or refracts light at various angles. Since the light path length of scattered or refracted light differs depending on the direction, light interference is prevented as compared with the case where the surface is flat.

  FIG. 4 is a cross-sectional view showing a part of the method for manufacturing the photoelectric conversion element. In the method for manufacturing a photoelectric conversion element according to the first embodiment, a particle layer 13 having a plurality of particles 6 is formed on a light transmission layer 11 that covers a photodiode section 10 in which a plurality of photodiodes 1 are arranged in at least one row. Is. In the method for manufacturing the photoelectric conversion element before forming the particle layer 13 (uneven portion), the photodiode 1 is formed on the silicon substrate 7 and the light transmission layer (light transmission layer 11) is formed on the silicon substrate 7 as the first stacking step. The silicon oxide film 4 and the silicon nitride film 2 of the wiring layer 12) are laminated. The step of forming the particle layer 13 (uneven portion) is the second laminating step. The second laminating step includes a mixing step and a coating step of applying a coating agent containing particles 6.

  The mixing step is to mix a plurality of particles 6 with the coating agent 5. The particles 6 are provided to provide the uneven portion on the silicon nitride film 2. In the coating step, as shown in the immediately preceding state in FIG. 3, the plurality of particles 6 and the coating agent 5 mixed in the mixing step are coated on the light transmission layer 12 (light transmission layer). A plurality of particles 6 and the coating agent 5 are applied to the light transmitting layer 12 (light transmitting layer), spread on the light transmitting layer 12 (light transmitting layer), and the coating agent 5 is solidified to form the particle layer 13. It Thus, the photoelectric conversion element according to the first embodiment shown in FIG. 1 is formed.

  In the photoelectric conversion element according to the first embodiment, the particles 6 used in the particle layer 13 may have non-uniform sizes as shown in FIG. That is, the plurality of particles 6 may have a mixture of at least two types of shapes. It is to be noted that the shape described here includes a shape having the same outer shape but a different diameter. The plurality of particles 6 may have wavelength selectivity. The wavelength selectivity means that, when the incident light received by the photodiode 1 has a specific wavelength, a plurality of particles transmit the specific wavelength. An example of obtaining wavelength selectivity is coloring a plurality of particles 6 with a color corresponding to a specific wavelength.

  That is, the plurality of particles 6 may be colored. In this case, it can be said that the mixing step is to mix the plurality of colored particles 6 into the coating agent 5. Further, the coating agent 5 may have the same wavelength selectivity as the plurality of particles 6. Therefore, it can be said that the mixing step mixes the colored coating agent 5 with the plurality of particles 6 colored the same color as the coating agent 5. Either one of the coating agent 5 and the particles 6 may be colored, or different colors may be colored.

  In the photoelectric conversion element and the manufacturing method thereof according to the first embodiment, the size of the particles 6 forming the irregularities may be uniform, or the size of the particles 6 may be non-uniform. Further, the particles 6 forming the uneven portion may be arranged regularly, or the particles 6 may be arranged irregularly. It can be said that the mixing step is to mix the particles 6 having at least two types of shapes with the coating agent 5. Furthermore, the particles 6 of the particle layer 13 may be arranged so as to overlap in the incident light direction, or there may be a gap between the particles 6 in the longitudinal direction or the lateral direction. Further, the coating agent 5 may not be spread over the entire particle layer 13 in the longitudinal direction or the lateral direction, may have a gap in part, and the light transmission layer 12 may be exposed.

  Therefore, the photoelectric conversion element and the manufacturing method thereof according to the first embodiment can obtain the photoelectric conversion element in which the multiple reflection of incident light is reduced and the interference fringes of the spectral sensitivity characteristic are reduced. That is, the scattered or refracted light has a different optical path length depending on its direction, so that the interference of light is prevented as compared with the case where the surface is flat. The photoelectric conversion element includes a photoelectric conversion part (photodiode part 10), one or more light transmission parts formed on the light receiving surface 101 of the photoelectric conversion part, and a photoelectric conversion part for the light transmission part on the light receiving surface 101. It is provided with one or more particles 6 forming irregularities for scattering or refracting incident light. Since unevenness is formed by the particles 6 arranged on the light receiving surface 101 of the photoelectric conversion unit and the light incident on the light receiving unit (photodiode 1) is diffused, multiple reflection of light incident on the photoelectric conversion unit is performed. It is possible to provide a photoelectric conversion element in which the interference fringes of the spectral sensitivity characteristic are reduced.

Embodiment 2.
The second embodiment of the present invention will be described below with reference to FIGS. In the drawings, the same reference numerals denote the same or corresponding parts, and detailed description thereof will be omitted. In the photoelectric conversion element and the manufacturing method thereof according to the second embodiment, the photodiode section 10 includes a plurality of photodiodes 1 arranged in two or more rows, and the plurality of particles 6 correspond to the photodiode section in the incident light direction. The target wavelength of the wavelength selectivity is different for each row of 10. As an example, the photodiode unit 10 having three rows is used for description. In the second embodiment, the description will be focused on the parts different from the first embodiment, and in the second embodiment, the description of the parts common to the first and second embodiments may be omitted.

  FIG. 5 is a top view showing the photoelectric conversion element according to the second embodiment. FIG. 5 is a view of the surface of the light transmission layer (light transmission layer 11, wiring layer 12) on the photodiode 1 as viewed from above. As in FIG. 2, in order to clarify the positional relationship between the photodiode 1 and the particles 6, other configurations are omitted. Further, the reference numerals of the photodiode 1 and the particles 6 are attached to only one in FIG. 6 for simplification, and the others are omitted. Specifically, there are three types of photodiodes 1; photodiode 1R, photodiode 1G, and photodiode 1B. 1R means a photodiode 1 for receiving red light. 1G means a photodiode 1 for receiving green light. 1B means a photodiode 1 for receiving blue light. There are three types of particles 6, namely particles 6R, particles 6G, and particles 6B. 6R means particles 6 colored red. 6G means particles 6 colored in green. 6B means particles 6 colored in blue.

  In FIG. 5, the photoelectric conversion element is an element used as a line sensor in which a plurality of photodiodes 1 are arranged in one or more rows, and the case of three rows is shown. The direction in which the three rows are arranged corresponds to the short-side direction or the sub-scanning direction (conveyance direction) described above. More specifically, regarding the plurality of photodiodes 1 and particles 6, a row of photodiodes 1G is arranged between a row of photodiodes 1R and a row of photodiodes 1B. The photoelectric conversion element 1 includes a photodiode 1, a light transmission layer (light transmission layer 11, wiring layer 12) formed on the photodiode 1, and pigments, such as red and blue, which are disposed on the light receiving surface. , Or particles 6 colored in green. Thereby, it is possible to obtain a photoelectric conversion element capable of outputting a signal only for a specific color for each column. Of course, the coating agent 5 may have the same wavelength selectivity as the plurality of particles 6 for each row.

  In the method for manufacturing the photoelectric conversion element according to the second embodiment, the particle layer 13 having the plurality of particles 6 is formed on the light transmission layer 12 that covers the photodiode section 10 in which the plurality of photodiodes 1 are arranged in at least two rows. It is a thing. The first stacking step of the second embodiment is the same as that of the first embodiment except that the photodiodes 1 are arranged in two or more rows on the silicon substrate 7. The second laminating step of the second embodiment includes a mixing step and a coating step (n steps). n is a positive integer of 2 or more. In the mixing step, the plurality of particles 6 and the coating agent 5 are mixed, and more specifically, the coating agent 5 is mixed for each color of the colored particles 6. When n is 2, the particles 6 have two colors.

  The coating step is performed from the first coating step to the nth coating step. When n is 2, the plurality of particles 6 and the coating agent 5 mixed in the mixing step are applied to the portion of the light transmission layer 12 corresponding to one row of the photodiode units 10 as the first application step. In the second application step, the plurality of particles 6 and the coating agent 5 mixed in the mixing step are applied to the portion of the light transmission layer 12 corresponding to the other row of the photodiode units 10. It can be said that the first coating step and the second coating step coat a plurality of particles 6 having different wavelength selectivity. Further, the first coating step and the second coating step may be ones in which the coating agent 5 has the same wavelength selectivity as the plurality of particles 6 for each row.

  FIG. 6 is a top view showing a part of the method for manufacturing the electric conversion element shown in FIG. The upper silicon substrate 8 (manufacturing stage) in FIG. 6 shows a state in which the plurality of particles 6 and the coating agent 5 mixed in the mixing step are applied in the first applying step. At least the particles 6 are colored red. The middle silicon substrate 9 (manufacturing stage) in FIG. 6 shows a state in which the plurality of particles 6 and the coating agent 5 mixed in the mixing step are applied in the second applying step. At least the particles 6 are colored green. The silicon substrate 7 at the bottom of FIG. 6 shows a state in which the plurality of particles 6 and the coating agent 5 mixed in the mixing step are applied in the third applying step. At least the particles 6 are colored green. Any two or more of the first coating step, the second coating step, and the third coating step may be performed simultaneously.

  Therefore, in the photoelectric conversion element and the method for manufacturing the same according to the second embodiment, the particles 6 containing pigments of different colors, specifically, red, green, and blue, are provided in each row of the plurality of photodiodes 1. By arranging, the light incident on the light receiving surface 101 can be prevented from interfering with each other and can also function as a color filter. Therefore, in the photoelectric conversion element and the manufacturing method thereof according to the first and second embodiments, the particle layer having the plurality of particles 6 is added to the light transmission layer 12 that covers the photodiode section 10 in which the plurality of photodiodes 1 are arranged in at least one row. In order to form 13, a plurality of particles 6 are mixed with the coating agent 5, and the mixed particles 6 and the coating agent 5 are applied to the light transmitting layer 12, which has a simple structure and multiple reflection. It is possible to form a layer (particle layer 13) that suppresses

1... Photodiode, 1R... Photodiode, 1B... Photodiode,
1G... Photodiode, 2... Silicon nitride film, 3... Metal wiring (conductor wiring),
4・・Silicon oxide film, 5・・Coating agent, 6・・Particles, 6R・・Particles,
6G・・particles, 6B・・particles, 7・・silicon substrate (semiconductor substrate),
8... Silicon substrate (manufacturing stage), 9... Silicon substrate (manufacturing stage),
10... Photodiode part, 101... Light receiving surface, 11... Light transmission layer (protective layer),
12... Wiring layer, 13... Particle layer.

Claims (13)

  A plurality of photodiodes are arranged in at least one row, a light-transmitting layer that covers the photodiode portions, and a plurality of particles that are fixed by a coating agent and spread on the surface of the light-transmitting layer. A particle layer that scatters or refracts incident light incident on a transmissive layer by the plurality of particles, wherein the photodiode section has a state in which multiple reflection of the incident light is reduced by scattering or refraction by the particle layer. A photoelectric conversion element, which receives the incident light.   The photoelectric conversion element according to claim 1, wherein the particle layer is an outermost shell layer.   The photoelectric conversion element according to claim 1 or 2, wherein the plurality of particles are mixed in at least two kinds of shapes.   The photoelectric conversion device according to any one of claims 1 to 3, wherein the plurality of particles have wavelength selectivity.   The photodiode section, the plurality of photodiodes of two or more rows are arranged, the plurality of particles, for each row of the corresponding photodiode section, the target wavelength of the wavelength selectivity is different. The photoelectric conversion element according to claim 4, which is characterized in that.   The photoelectric conversion element according to claim 4 or 5, wherein the plurality of particles are colored.   The photoelectric conversion element according to any one of claims 4 to 6, wherein the coating agent has the same wavelength selectivity as the plurality of particles.   A method of manufacturing a photoelectric conversion element, wherein a plurality of photodiodes are arranged in at least two rows in a light-transmitting layer that covers the photodiode portions, and a particle layer having a plurality of particles is formed. A mixing step of mixing, a first applying step of applying the plurality of particles and the coating agent mixed in the mixing step to a portion of the light transmitting layer corresponding to one row of the photodiode section, A second coating step of coating the plurality of particles mixed in the mixing step and the coating agent onto a portion of the light transmitting layer corresponding to the other row of the photodiode section. Method for manufacturing conversion element.   9. The method of manufacturing a photoelectric conversion element according to claim 8, wherein in the mixing step, particles having at least two types of particles are mixed with the coating agent.   The said 1st coating step and the said 2nd coating step apply the said some particle|grains which have a respectively different wavelength selectivity, The manufacturing method of the photoelectric conversion element of Claim 8 or Claim 9 characterized by the above-mentioned.   The photoelectric conversion element according to claim 10, wherein in the first coating step and the second coating step, the coating agent is one having the same wavelength selectivity as the plurality of particles. Production method.   The method for manufacturing a photoelectric conversion element according to claim 8, wherein the mixing step mixes the plurality of colored particles with the coating agent.   A method for manufacturing a photoelectric conversion element, wherein a plurality of photodiodes are arranged in at least one row in a light-transmitting layer covering the photodiode portions, and a particle layer having a plurality of particles is formed, wherein the plurality of particles colored into a coating agent. And a coating step of coating the light-transmissive layer with the plurality of particles and the coating agent mixed in the mixing step.

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