JP2007080926A - Photoelectric conversion element, manufacturing method thereof, fixed imaging device, imaging apparatus, and image reading apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element or the like having excellent wavelength (color) separation accuracy and desirably capable of restraining a dark current from being generated. <P>SOLUTION: The photoelectric conversion element comprises a semiconductor substrate 1, a photodiode part 2, a concave lens 3, and a convex lens 4. The photodiode part 2 is formed in the semiconductor substrate 1. Moreover, the photodiode part 2 comprises a plurality of photodiodes which are constituted by alternately and successively laminating p-type semiconductor regions 2a, 2c and 2e, and n-type semiconductor regions 2b, 2d. The convex lens 4 focuses incident light to the photodiode part 2. Further, the concave lens 3 is disposed on an optical path extending between the photodiode part 2 and the convex lens 4. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion element, a fixed image pickup device, an image pickup apparatus, an image reading apparatus, and a method for manufacturing a photoelectric conversion element, and in particular, in a semiconductor substrate, a bonding surface of a plurality of photodiodes in a vertical direction is provided. It can be applied to a formed photoelectric conversion element or the like.

  A photoelectric conversion element having the following structure already exists (Patent Documents 1 and 2).

  In the photoelectric conversion element according to Patent Document 1, a photodiode portion is formed in the surface of a semiconductor substrate. Here, the photodiode portion is composed of a plurality of photodiodes. In addition, the photodiode unit is configured by alternately stacking first semiconductor regions of the first conductivity type and second semiconductor regions of the second conductivity type in the semiconductor substrate. .

  With the configuration of the photoelectric conversion element, bonding surfaces are sequentially formed in the semiconductor substrate as it proceeds in the depth direction. When light having different wavelengths is incident on each joint surface, photoelectric conversion occurs at each joint surface.

  By the way, the position where photoelectric conversion can be efficiently performed for each light of each wavelength varies depending on the transmission distance of the light within the semiconductor substrate.

  For example, consider the case of photoelectrically converting light having the first wavelength. Here, it is assumed that the position where the light having a predetermined wavelength can be efficiently photoelectrically converted is the position where the light in the semiconductor substrate has advanced by X μm. Therefore, the bonding surface for photoelectrically converting the light having the predetermined wavelength is usually formed at a position where the vertical depth is X μm from the horizontal surface of the semiconductor substrate. Here, the joint surface existing at the position of the vertical depth X μm is substantially parallel to the surface of the semiconductor substrate.

  In order to efficiently photoelectrically convert light having a short wavelength, it is necessary to form a bonding surface for photoelectrically converting light having a short wavelength at a relatively shallow position. On the other hand, in order to efficiently photoelectrically convert light having a long wavelength, it is necessary to form a bonding surface for photoelectrically converting light having a long wavelength at a relatively deep position.

US Pat. No. 5,965,875 JP 2003-298102 A

  Since each joint surface is formed at the position described above, the power generation conversion element according to the related art has the following problems.

  That is, the light incident on the surface of the semiconductor substrate has all angles with respect to the surface. That is, not only light that is incident perpendicular to the surface of the semiconductor substrate (referred to as vertical light) but also light that is incident obliquely (referred to as oblique light) is included. A difference occurs between the vertical light and the oblique light in the reach distance from the surface of the semiconductor substrate to the predetermined bonding surface.

  Here, as described above, the position where the photoelectric conversion can be efficiently performed for each wavelength of light varies depending on the traveling distance of the light within the semiconductor substrate. Therefore, the formation position of the above-described bonding surface (that is, the surface of the semiconductor substrate and each bonding surface existing at a predetermined depth are substantially parallel, and each bonding surface is set according to the vertical depth from the surface. When the vertical light is taken into consideration, light having a desired wavelength can be efficiently photoelectrically converted at each joint surface. However, for oblique light, light having a desired wavelength cannot be efficiently photoelectrically converted at each joint surface.

  In other words, for oblique light, light having a wavelength slightly different from the desired wavelength is efficiently photoelectrically converted at each joint surface. Then, due to the matter, there is a problem that the wavelength (color) separation accuracy for white light is lowered.

  When a solid-state imaging device configured by arranging a plurality of photoelectric conversion elements having the above configuration is configured, there is a problem that the color intensity of the captured image is lowered and the color reproducibility is deteriorated.

  Furthermore, in the photoelectric conversion element according to the conventional technique, each bonding surface appears on the surface of the semiconductor substrate. Therefore, for example, in the process of manufacturing the photoelectric conversion element, the joint surface near the surface is easily contaminated.

  As described above, when the joint surface is contaminated, a dark current is generated. The dark current is noise. Therefore, when a solid-state imaging device is configured using photoelectric conversion elements that generate a large amount of dark current, the performance of the solid-state imaging device is degraded.

  Thus, a photoelectric conversion element that can suppress the generation of dark current as much as possible is desired.

  SUMMARY OF THE INVENTION An object of the present invention is to provide a photoelectric conversion element that has good wavelength (color) separation accuracy and that can desirably suppress generation of dark current. Furthermore, it aims at providing the manufacturing method of the said photoelectric conversion element, the solid-state imaging device which has the said photoelectric conversion element, and an imaging device provided with the said solid-state imaging device.

  In order to achieve the above object, a photoelectric conversion element according to claim 1 according to the present invention includes a semiconductor substrate, a first semiconductor region of the first conductivity type, and a second conductivity in the semiconductor substrate. A photodiode portion composed of a plurality of photodiodes, and a convex lens for condensing incident light on the photodiode portion, and the photodiodes. A concave lens disposed on the optical path between the portion and the convex lens.

  A solid-state imaging device according to a twenty-second aspect is configured by arranging a plurality of photoelectric conversion elements according to the first to twenty-first aspects in a plan view.

  An image pickup apparatus according to a twenty-third aspect includes the solid-state image pickup device according to the twenty-second aspect.

  An image reading apparatus according to a twenty-fourth aspect includes the solid-state imaging device according to the twenty-second aspect.

  The method for manufacturing a photoelectric conversion element according to claim 25, wherein (A) a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type are provided in the semiconductor substrate. (1) forming a photodiode portion composed of a plurality of photodiodes in the surface of the semiconductor substrate by sequentially laminating; (B) applying a resin on the photodiode portion; C) forming a depression in the resin, and (D) forming a concave lens by subjecting the resin having the depression to a heat-melting treatment.

  In the method for manufacturing a photoelectric conversion element according to claim 27, (A) a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type in the semiconductor substrate. A step of forming a photodiode portion composed of a plurality of photodiodes in the surface of the semiconductor substrate by sequentially laminating, and (B) having an opening for a predetermined region of the photodiode portion; A step of forming a light shielding film, (C) a step of forming a glass layer on at least a side surface of the opening, and (D) applying a predetermined amount of resin to the opening, and the resin and the glass layer. A step of making the resin into a concave shape by utilizing surface tension generated therebetween.

  The photoelectric conversion element according to claim 1 of the present invention includes a semiconductor substrate, and a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type in the semiconductor substrate, A photodiode unit composed of a plurality of photodiodes that are alternately stacked, a convex lens that collects incident light on the photodiode unit, and an optical path between the photodiode unit and the convex lens. In addition, since the concave lens is provided, the light emitted from the convex lens enters the photodiode portion via the concave lens. Therefore, substantially parallel light can be incident on the photodiode portion. Therefore, when each bonding surface is disposed substantially in parallel with the surface of the semiconductor substrate, the reaching distance of the light from the surface to the bonding surface can be made substantially the same. Therefore, a photoelectric conversion element with improved color separation accuracy can be provided.

  In addition, since the solid-state imaging device, the imaging apparatus, and the image reading apparatus according to claims 22 to 24 are configured by the photoelectric conversion element according to claim 1, it is possible to provide an apparatus with high color separation accuracy. .

  The method for manufacturing a photoelectric conversion element according to claim 25, wherein (A) a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type are provided in the semiconductor substrate. (1) forming a photodiode portion composed of a plurality of photodiodes in the surface of the semiconductor substrate by sequentially laminating; (B) applying a resin on the photodiode portion; C) forming a depression in the resin, and (D) forming a concave lens by subjecting the resin having the depression to a heat melting treatment. The described photoelectric conversion element can be easily produced.

  In the method for manufacturing a photoelectric conversion element according to claim 27, (A) a first semiconductor region of a first conductivity type and a second semiconductor region of a second conductivity type in the semiconductor substrate. A step of forming a photodiode portion composed of a plurality of photodiodes in the surface of the semiconductor substrate by sequentially laminating, and (B) having an opening for a predetermined region of the photodiode portion; A step of forming a light shielding film, (C) a step of forming a glass layer on at least a side surface of the opening, and (D) applying a predetermined amount of resin to the opening, and the resin and the glass layer. The step of making the resin into a concave shape by utilizing the surface tension generated between them, for example, also for a photoelectric conversion element having a metallic light-shielding film, according to claim 1. Easier photoelectric conversion element It can be formed.

  Hereinafter, the present invention will be specifically described with reference to the drawings showing embodiments thereof. In each embodiment, the same member is denoted by the same reference numeral.

<Embodiment 1>
FIG. 1 is a cross-sectional view showing the configuration of the photoelectric conversion element according to the first embodiment.

  As shown in FIG. 1, the photoelectric conversion element according to this embodiment includes a semiconductor substrate 1, a photodiode portion 2, a concave lens 3, a convex lens 4, and the like. As shown in FIG. 1, a photodiode portion 2 is formed in a semiconductor substrate 1, and a passivation film 5, a light shielding film 6, a concave lens 3, a planarizing film 7, and a convex lens are formed on the semiconductor substrate 1. Each member is formed by laminating in the order of 4.

  In the semiconductor substrate 1, a plurality of photodiodes are formed by alternately laminating first semiconductor regions of the first conductivity type and second semiconductor regions of the second conductivity type alternately, A photodiode portion 2 is formed by the plurality of photodiodes.

  In FIG. 1, in the semiconductor substrate 1, the first semiconductor region and the second semiconductor region are formed in a nested manner. Therefore, the bonding surface between the first semiconductor region and the second semiconductor region exists on the upper surface of the semiconductor substrate 1.

  As shown in FIG. 1, the semiconductor substrate 1 is n-type. A p-type semiconductor region 2 a is formed in the upper layer portion of the n-type semiconductor substrate 1. In addition, an n-type semiconductor region 2b is formed in an upper layer portion of the p-type semiconductor region 2a. A p-type semiconductor region 2c is formed in the upper layer portion of the n-type semiconductor region 2b. In addition, an n-type semiconductor region 2d is formed in the upper layer portion of the p-type semiconductor region 2c. A p-type semiconductor region 2e is formed in the upper layer portion of the n-type semiconductor region 2d.

  A plurality of photodiodes are formed in the semiconductor substrate 1 by the semiconductor regions 2a to 2e, and the photodiode unit 2 is configured by the plurality of photodiodes. In addition, each contact surface of each photodiode existing at a predetermined depth from the surface of the semiconductor substrate 1 is substantially parallel to the surface.

  In the present embodiment, as an example, the photodiode portion 2 is composed of five layers of semiconductor regions 2a to 2e of pnpnp.

  By the way, for each light of each wavelength, the position where the photoelectric conversion can be efficiently performed differs depending on the transmission distance of the light in the semiconductor substrate 1. Here, the longer the wavelength, the deeper the semiconductor substrate 1 is reached.

  For example, blue component light having a short wavelength in visible light is efficiently photoelectrically converted in a region close to the surface of the semiconductor substrate 1. In addition, red component light having a long wavelength in visible light is efficiently photoelectrically converted in a deep region of the semiconductor substrate 1. Further, the green component light in the middle of these wavelengths is efficiently photoelectrically converted in the intermediate region of the semiconductor substrate 1.

  Therefore, when it is desired to photoelectrically convert light having a desired wavelength, the positions of the connection surfaces of the semiconductor regions 2a to 2e are determined in consideration of the wavelength of the light and the transmission distance of the light having the wavelength. There is a need to. Each joint surface is usually set with reference to the vertical depth from the horizontal surface of the semiconductor substrate.

  For example, consider a case where light having the first wavelength is efficiently photoelectrically converted. Here, it is assumed that the position where the light of a predetermined wavelength can be efficiently photoelectrically converted is the position where the light in the semiconductor substrate 1 has advanced by X μm.

  Therefore, when it is desired to efficiently photoelectrically convert light having the first wavelength, the junction surface of the photodiode that photoelectrically converts the light at a position of vertical depth X μm from the horizontal surface of the semiconductor substrate 1 is usually used. Set.

  The depth of each of the semiconductor regions 2a to 2e needs to be set between 0.3 μm and 8.0 μm from the relationship between the wavelength of visible light and the transmission distance of light having the wavelength in the semiconductor substrate 1. is there.

  As shown in FIG. 1, a SiO 2 film, a SiON film, a SiN film, etc. (hereinafter referred to as a passivation film 5) are formed on the semiconductor substrate 1 so as to cover the photodiode portion 2. Here, the passivation film 5 may function as an antireflection film. Further, the passivation film 5 is light transmissive. As a method for forming the passivation film 5, for example, a molecular deposition method can be employed.

  Further, as shown in FIG. 1, a light shielding film 6 is formed on the passivation film 5.

  Here, the light shielding film 6 is formed with an opening for a predetermined region of the photodiode portion 2. The light shielding film 6 is formed as follows, for example. First, a resin is applied on the passivation film 5. The resin is made of a pigment containing black pigment. Next, the photoengraving method is applied to the resin. Thereby, the light shielding film 6 having an opening can be formed.

  Next, as shown in FIG. 1, the concave lens 3 is formed in the opening of the light shielding film 6. As can be seen from FIG. 1, the concave lens is disposed on the optical path between the photodiode portion 2 and a convex lens 4 described later. The concave lens 3 is formed as follows, for example.

  First, a resin is applied on the passivation film 5 and the light shielding film 6 so as to fill the opening of the light shielding film 6. The resin has light permeability and photosensitivity. Next, the photoengraving method is applied to the resin. Thereby, a depression is formed in the resin in the opening. Thereafter, the resin having the depression is subjected to a heat melting treatment. Thereby, the rounded concave lens 3 can be formed in the opening.

  It can be seen that the concave lens 3 formed by this method is formed of a resin having photosensitivity. In the present embodiment, the concave lens 3 is single.

  Next, as shown in FIG. 1, a planarization layer 7 is formed so as to cover the concave lens 3. Here, as can be seen from FIG. 1, the planarization layer 7 is formed between the concave lens 3 and a convex lens 4 described later.

  Further, the refractive index of the planarizing layer 7 is different from the refractive index of the concave lens 3. More preferably, the refractive index of the planarizing layer 7 is different from the refractive indexes of the concave lens 3 and the convex lens 4 described later. In the present embodiment, the refractive index of the concave lens 3 and the refractive index of the convex lens 4 are substantially the same, and the refractive index of the planarizing layer 7 is smaller than the refractive indexes of both lenses 3 and 4. To proceed.

  The planarizing layer 7 is formed as follows, for example.

  First, a light transmissive resin is applied on the concave lens 3. Thereafter, the resin is subjected to thermosetting (curing) treatment and flattening treatment. Thereby, the planarization layer 7 can be formed.

  As shown in FIG. 1, a convex lens 4 is formed on the planarizing layer 7. Here, the convex lens 4 is a lens that condenses incident light on the photodiode unit 2. The convex lens 4 is formed as follows, for example.

  First, a resin is applied on the planarizing layer 7. The resin has light permeability and photosensitivity. Next, the photoengraving method is applied to the resin. As a result, the resin is formed into a substantially cylindrical projection or the like. Thereafter, the resin that is the protrusion is subjected to a heat melting treatment. Thereby, the rounded convex lens 4 can be formed.

  It can be seen that the concave lens 4 formed by this method is formed of a resin having photosensitivity.

  As described above, in the photoelectric conversion element according to the present embodiment, the concave lens 3 is disposed between the photodiode portion 2 and the convex lens 4.

  Therefore, each light incident on the semiconductor substrate 1 can be made substantially perpendicular to the horizontal surface of the semiconductor substrate 1. That is, it is possible to minimize the light that enters obliquely with respect to the horizontal surface of the semiconductor substrate 1.

  Therefore, in each light incident on the photodiode portion 2, a predetermined bonding surface (each bonding surface existing at a predetermined vertical depth from the surface of the semiconductor substrate 1 is substantially parallel to the surface from the surface of the semiconductor substrate 1. It is possible to suppress the occurrence of a difference in the reach distance until reaching

  Therefore, only the light of the wavelength initially planned can be efficiently photoelectrically converted at the predetermined bonding surface. That is, in the photoelectric conversion element according to this embodiment, the wavelength (color) separation accuracy with respect to white light can be improved (that is, color mixing of photoelectric conversion signals can be suppressed).

  The concave lens 3 and the convex lens 4 are made of a resin having photosensitivity. Therefore, a lens having a desired shape (specifically, a lens shape before heating and melting) can be easily produced by the photolithography method.

  Further, in the photoelectric conversion element according to the present embodiment, a planarizing layer 7 is formed between the concave lens 3 and the convex lens 4. The refractive index of the flattening layer 7 is different from the refractive index of the concave lens 3.

  Therefore, the function of the concave lens 3 that makes the light substantially parallel to the optical axis can be more effectively applied to the light that has passed through the convex lens 4.

  The refractive index of the concave lens 3 and the refractive index of the convex lens 4 are substantially the same, and the refractive index of the planarizing layer 7 is smaller than the refractive index of the concave lens 3 and the refractive index of the convex lens 4. Therefore, with a simple configuration, the function of the concave lens 3 can be more effectively applied to the light that has passed through the convex lens 4.

  In addition, the photoelectric conversion element according to the present embodiment includes a passivation film 5 such as a SiO 2 film, a SiON film, and a SiN film that covers the photodiode portion 2.

  Therefore, the photodiode film 2 can be protected by the passivation film 5. Furthermore, when the concave lens 3 is formed on the passivation film 5, the adhesion between the semiconductor substrate 1 and the passivation film 5 and the adhesion between the passivation film 5 and the concave lens 3 are improved. Therefore, as a result, the concave lens 3 can be fixed to the semiconductor substrate 1 with good adhesion.

  In the photoelectric conversion element according to this embodiment, the light shielding film 6 having the opening is formed. Accordingly, it is possible to prevent light from entering the photodiode portion 2 more than necessary. That is, electrons generated by photoelectric conversion of the unnecessary light can be reduced. Therefore, even if a solid-state imaging device is manufactured using the photoelectric conversion element, malfunction of the solid-state imaging device can be prevented.

  Moreover, in the manufacturing method of the photoelectric conversion element concerning this Embodiment, after forming a hollow in resin, the concave lens 3 is produced by heat-melting with respect to the said resin. In other words, the concave lens 3 is manufactured using a resin having good transparency and high refractive index. Therefore, the concave lens 3 with good optical characteristics can be provided.

  Further, the resin has photosensitivity, and a depression is made in the resin by a photoengraving method. Therefore, the optical shape of the concave lens 3 can be easily controlled.

<Embodiment 2>
FIG. 2 is a cross-sectional view showing the configuration of the photoelectric conversion element according to the second embodiment. In FIG. 2, the configuration, formation method, and the like of the semiconductor substrate 1, the photodiode portion 2, the passivation film 5, the planarization layer 7, and the convex lens 4 are the same as those in the first embodiment. Therefore, detailed description thereof will be omitted here.

  Now, also in the photoelectric conversion element according to the present embodiment, as shown in FIG. 2, the light shielding film 11 is formed on the passivation film 5. Here, in the present embodiment, the light shielding film 11 is made of a metal or a metal silicide film.

  For example, tungsten silicide (WSi), molybdenum silicide (MoSi), titanium silicide (TiSi), tungsten (W), molybdenum (Mo), titanium (Ti), aluminum (Al), or the like may be employed as the light shielding film 11. it can.

  The light shielding film 11 can be formed using, for example, a sputtering method or a CVD method. Further, in the present embodiment, the light shielding film 11 functions as a wiring in addition to functioning as a light shielding film. Also in the present embodiment, the light shielding film 11 has an opening as in the first embodiment.

  Next, in the present embodiment, as shown in FIG. 2, the glass layer 12 is formed on the light shielding film 11 and on the side surface and the bottom surface of the opening of the light shielding film 11 (glass layer 12 Is formed at least on the side surface of the opening).

  Here, as can be seen from FIG. 2, the glass layer 12 is a member interposed between the light shielding film 11 and the concave lens 13. Here, it is desirable to employ boron phosphorus silicide glass (BPSG) as the glass layer 12. Moreover, the said glass layer 12 can be formed, for example using CVD method.

  Next, in the present embodiment, as shown in FIG. 2, a concave lens 13 is formed on the glass layer 12. More specifically, the concave lens 13 is formed in the opening of the light shielding film 11. Of course, the concave lens 13 has transparency. Here, the concave lens 13 can be formed as follows.

  A predetermined amount of resin is applied to the glass layer 12 in the opening of the light shielding film 11. Here, the resin has optical transparency. Here, due to the presence of the glass layer 12, surface tension acts between the glass layer 12 and the resin.

  Therefore, by adjusting the coating amount of the resin, a concave resin can be formed in the opening using the surface tension. The resin is formed to reach the corner of the opening due to the surface tension.

  Thereafter, the resin is subjected to thermosetting (curing) treatment. Thus, the concave lens 13 can be formed in the opening.

  As described above, in FIG. 2, the configuration and forming method of the planarizing layer 7 and the convex lens 4 are the same as those in the first embodiment.

  In the present embodiment, the light shielding film 11 is composed of a metal silicide film or a metal film. Therefore, it is possible to block light more reliably.

  Moreover, since the light shielding film 11 has conductivity, it can be effectively used as a wiring. Further, by using the light shielding film 11 as a wiring in this way, the volume of the entire photoelectric conversion element can be further reduced.

  It is assumed that a resin for forming the concave lens 13 is directly applied to the metallic light shielding film 11. In this case, the resin does not reach the corner of the opening of the light shielding film 11. However, in this embodiment, after the glass layer 12 is formed, the resin is applied to the glass layer 12.

  Therefore, as described above, the resin can be spread to the corners of the openings of the light shielding film 11 using the surface tension between the glass layer 12 and the resin. Further, as described above, when the concave lens 13 is formed, the amount of resin applied is adjusted. Therefore, the concave resin can be easily formed in the opening of the light shielding film 11 by utilizing the surface tension between the glass layer 12 and the resin.

  In particular, by using BPSG having a dense composition as the glass layer 12, irregular reflection of light in the glass layer 12 can be suppressed.

  Moreover, since the thermosetting (curing) process is performed with respect to the concave shaped resin thereafter, the hardened concave lens 13 can be formed from the resin by a simple process.

<Embodiment 3>
FIG. 3 is a cross-sectional view showing the configuration of the photoelectric conversion element according to the third embodiment.

  In the photoelectric conversion element according to the present embodiment, as shown in FIG. 3, a plurality (two in the present embodiment) of concave lenses 13a and 13b are arranged in series between the photodiode portion 2 and the convex lens 4. It is installed. In addition, the metal wiring 22 is arrange | positioned in the layer in which the 1st step | paragraph concave lens 13a is arrange | positioned.

  In FIG. 3, the configuration, formation method, and the like of the semiconductor substrate 1, the photodiode portion 2, and the passivation film 5 are the same as those in the first embodiment. Therefore, detailed description thereof will be omitted here.

  Now, in the photoelectric conversion element according to the present embodiment, as shown in FIG. 3, a metal wiring 22 is disposed on the passivation film 5. Here, the metal wiring 22 is extended in the front-back direction of FIG. The metal wiring 22 can be formed by a combination of a molecular deposition method and a photoengraving method, for example.

  Further, as shown in FIG. 3, a glass layer 21 is formed on the passivation film 5 so as to cover the metal wiring 22. Here, it is desirable to employ boron phosphorus silicide glass (BPSG) as the glass layer 21. Moreover, the said glass layer 21 can be formed, for example using CVD method.

  Next, as shown in FIG. 3, a concave lens 13 a is formed on the glass layer 21. More specifically, the concave lens 13 a is formed above the photodiode portion 2. The concave lens 13a is formed between the two metal wirings 22 arranged in parallel. Of course, the concave lens 13a has transparency.

  Since the method of forming the concave lens 13a is the same as that of the second embodiment, the description thereof is omitted here. Here, by adjusting the coating amount of the resin, a concave resin can be formed between the metal wirings by utilizing the surface tension between the glass layer 21 and the resin. The resin is formed to reach the corner of the step formed by the metal wiring 22 due to the surface tension.

  Further, as shown in FIG. 3, a planarization layer 23 is formed so as to cover the concave lens 13a and the like. The configuration, formation method, and the like of the planarization layer 23 are the same as those of the planarization layer 7 described in the first embodiment. Therefore, detailed description here is omitted.

  As shown in FIG. 3, the light shielding film 11, the glass layer 12, the concave lens 13 b, the planarizing layer 7, the convex lens 4, and the like are formed on the planarizing layer 23. These structures, formation methods, and the like are the same as those described in the first and second embodiments. Therefore, detailed description here is omitted.

  As described above, in the present embodiment, the concave lenses 13a and 13b are arranged in series. Therefore, the photoelectric conversion element according to the present embodiment is more effective, for example, when the power of the concave lens is small.

  That is, by arranging the concave lenses 13a and 13b in series, it is possible to make the light from the convex lens 4 parallel to the optical axis more than in the case where there is a single concave lens with low power.

<Embodiment 4>
FIG. 4 is a cross-sectional view showing the configuration of the photoelectric conversion element according to the fourth embodiment.

  In the photoelectric conversion element according to the present embodiment, as shown in FIG. 4, a plurality of convex lenses 4 a and 4 b (two in the present embodiment) are arranged in series above the photodiode portion 2.

  The configuration from the semiconductor substrate 1 to the planarization layer 23, the manufacturing method, and the like are the same as in the third embodiment. Therefore, detailed description here is omitted. The metal wiring 22 also functions as a light shielding film.

  In the photoelectric conversion element according to the present embodiment, as shown in FIG. 4, a convex lens 4 a is disposed on the planarizing layer 23. Further, the convex lens 4b is disposed above the convex lens 4a via the planarization layer 31. That is, as described above, the convex lenses 4 a and 4 b are arranged in series via the planarization layer 31. Here, the convex lenses 4 a and 4 b are disposed above the photodiode portion 2.

  The configuration and the formation method of the flattening layer 31 and the convex lenses 4a and 4b are the same as those of the flattening layer 7 and the convex lens 4 described in the first embodiment. Therefore, detailed description is omitted.

  As described above, in the present embodiment, the convex lenses 4a and 4b are arranged in series. Therefore, the photoelectric conversion element according to the present embodiment is more effective, for example, when the power of the convex lens is small.

  That is, by arranging the convex lenses 4a and 4b in series, incident light can be collected more than in the case where there is only one convex lens with low power.

<Embodiment 5>
FIG. 5 is a cross-sectional view showing the configuration of the photoelectric conversion element according to the fifth embodiment.

  In the photoelectric conversion element according to the present embodiment, an infrared cut filter 35 is formed above the photodiode portion 2 as shown in FIG.

  As shown in FIG. 5, an infrared cut filter 35 is formed on the photoelectric conversion element according to the second embodiment (specifically, on the planarization layer 7 and above the photodiode portion 2). The infrared cut filter 35 is a member for suppressing (preventing) infrared light from entering the photodiode unit 2. The infrared cut filter 35 can be formed as follows.

  In FIG. 5, a light transmissive resin is applied on the planarizing layer 7. Here, a pigment is mixed in the resin. Thereafter, the resin is shaped by photolithography. Thereafter, the shaped resin is subjected to thermosetting (curing) treatment. Thus, the infrared cut filter 35 is formed.

  Further, a planarizing layer 36 is formed on the infrared cut filter 35, and the convex lens 4 is disposed on the planarizing layer 36. Here, the configuration and forming method of the planarizing layer 36 and the convex lens 4 are the same as those of the planarizing layer 7 and the convex lens 4 described in the first embodiment. Therefore, detailed description here is omitted.

  As described above, the infrared cut filter 35 is disposed above the photodiode portion 2. Therefore, it is possible to suppress (prevent) infrared light from entering the semiconductor substrate 1. Therefore, malfunction of the photodiode portion 2 and other circuit portions and deterioration of the semiconductor substrate 1 due to the infrared light can be prevented. Furthermore, the red color separation characteristics can be improved.

<Embodiment 6>
FIG. 6 is a cross-sectional view showing the configuration of the photoelectric conversion element according to the sixth embodiment.

  In the photoelectric conversion element according to the present embodiment, as shown in FIG. 6, a high concentration impurity diffusion layer 41 having a high impurity concentration is formed on the junction surface where the semiconductor regions 2a to 2d are joined in the photodiode portion 2. ing.

  Here, the high-concentration impurity diffusion layer 41 is formed particularly on each bonding surface existing on the upper surface of the semiconductor substrate 1 (that is, so as to cover each bonding surface exposed from the upper surface of the semiconductor substrate 1). ing). The conductivity type of the high-concentration impurity diffusion layer 41 may be p-type or n-type (in this embodiment, it is p-type). The impurity concentration of the high concentration impurity diffusion layer 41 is higher than the impurity concentration of the semiconductor regions 2a to 2d forming the junction surface.

  As shown in FIG. 6, the high-concentration impurity diffusion layer 41 includes a junction surface between the n-type semiconductor substrate 1 and the p-type semiconductor region 2a, and a junction surface between the p-type semiconductor region 2a and the n-type semiconductor region 2b. , N-type semiconductor region 2b and p-type semiconductor region 2c, and p-type semiconductor region 2c and n-type semiconductor region 2d, respectively.

  Here, it is desirable that each high-concentration impurity diffusion layer 41 covers the entire surface of the semiconductor substrate 1 where the photodiode portion 2 is formed as much as possible or almost entirely.

  Note that it is desirable to form the high concentration impurity diffusion layer 41 on each bonding surface so that the bonding surface is not exposed from the surface of the semiconductor substrate 1 as much as possible. However, if the high-concentration impurity diffusion layer 41 is formed on at least one joint surface, the joint surface can exhibit the effects described later.

  Further, as shown in FIG. 6, a passivation film 5 is formed on the upper surface of the semiconductor substrate 1 where the high concentration impurity diffusion layer 41 is formed.

  The configuration of the photodiode portion 2 formed in the semiconductor substrate 1 is the same as that of the photodiode portion 2 described in the first embodiment. Therefore, detailed description here is omitted. Here, in FIG. 6, the configuration above the passivation film 5 is omitted. Above the passivation film 5, for example, the lens configuration shown in FIGS. 1 to 5 is formed.

  As described above, in this embodiment, each bonding surface exposed from the surface of the semiconductor substrate 1 is covered with the high-concentration impurity diffusion layer 41. That is, the bonding surfaces of the semiconductor regions 2 a to 2 d having relatively low concentrations are prevented from being exposed from the surface of the semiconductor substrate 1.

  Here, the electrical characteristics of the bonding surfaces of the semiconductor regions 2a to 2d having a low impurity concentration easily change with respect to contaminants such as N ions generated during the manufacturing process. That is, dark current is likely to occur due to the contaminant.

  In contrast, the high concentration impurity diffusion layer 41 having a relatively high impurity concentration and the junction between the high concentration impurity diffusion layer and another semiconductor region have electrical characteristics even if they are slightly contaminated by contaminants. There is no change. That is, it can be understood that generation of dark current due to the contaminant can be suppressed (electrons (or holes) that cause dark current can be trapped in the high-concentration impurity diffusion layer 41. it can).

  Therefore, by employing the photoelectric conversion element according to this embodiment, a photoelectric conversion element with less dark current can be provided.

  Note that the higher the impurity concentration of the high-concentration impurity diffusion layer 41 is, the more remarkable the effect of suppressing the occurrence of dark current is.

<Embodiment 7>
FIG. 7 is a cross-sectional view showing the configuration of the photoelectric conversion element according to the seventh embodiment. Here, the cross-sectional view shown in FIG.

  In FIG. 7, the configuration of the photodiode portion 2 and the high-concentration impurity diffusion layer 41 formed in the semiconductor substrate 1 and the configuration of the passivation film 5 formed on the semiconductor substrate 1 are described in the embodiment. This is the same as the configuration of the photodiode portion 2 and the like described in 1 and 6. Although not shown in FIG. 7 because of different cross sections, for example, the lens configuration shown in FIGS. 1 to 5 is formed above the passivation film 5.

  In the photoelectric conversion element according to the present embodiment, as shown in FIG. 7, the semiconductor regions 2a to 2e forming the photodiode portion 2 and the wiring metal 45 connected thereto are formed ( The wiring metal 45 is connected to the first semiconductor region and / or the second semiconductor region). The wiring metal 45 is formed by opening predetermined portions of the passivation film 5, exposing the semiconductor regions 2a to 2e, and filling the openings with a conductor such as metal.

  Here, the selective opening process of the passivation film 5 can be performed by, for example, a photoengraving method. Further, the filling of the conductor in the opening can be performed by, for example, a combination of a molecular deposition method and a photoengraving method.

  In addition, on the passivation film 5, each wiring metal 45 is formed separately as shown in FIG.

  Here, ohmic contact regions 46 are formed at the connection portions between the wiring metal 45 and the semiconductor regions 2a to 2d. Here, in the present embodiment, the high concentration impurity diffusion layer 41 also serves as an ohmic contact region.

  Specifically, a high-concentration impurity diffusion layer 41 having an ohmic contact function is formed between the p-type semiconductor region 2a and the wiring metal 45. The conductivity type of the high-concentration impurity diffusion layer 41 is the same conductivity type as that of the semiconductor region 2a. The impurity concentration of the high concentration impurity diffusion layer 41 is higher than the impurity concentration of the semiconductor region 2a.

  An ohmic contact region 46 is formed between the n-type semiconductor region 2 b and the wiring metal 45. The ohmic contact region 46 has the same conductivity type as that of the semiconductor region 2b. Further, the impurity concentration of the ohmic contact region 46 is higher than the impurity concentration of the semiconductor region 2b.

  A high concentration impurity diffusion layer 41 having an ohmic contact function is formed between the p-type semiconductor region 2 c and the wiring metal 45. The conductivity type of the high-concentration impurity diffusion layer 41 is the same conductivity type as that of the semiconductor region 2c. The impurity concentration of the high concentration impurity diffusion layer 41 is higher than the impurity concentration of the semiconductor region 2c.

  An ohmic contact region 46 is formed between the n-type semiconductor region 2d and the wiring metal 45. The conductivity type of the ohmic contact region 46 is the same as that of the semiconductor region 2d. The impurity concentration of the ohmic contact region 46 is higher than the impurity concentration of the semiconductor region 2d.

  The p + -type semiconductor region 2 e is directly connected to the wiring metal 45.

  As described above, each of the semiconductor regions 2 a to 2 e is connected to the wiring metal 45. Therefore, for example, electrons generated as a result of photoelectric conversion in the photodiode portion 2 can be taken out via the wiring metal 45.

  Also, between each of the semiconductor regions 2a to 2d and each of the wiring metals 45, an ohmic contact region 46 (or a high concentration impurity diffusion layer 41 having a higher impurity concentration than the connected semiconductor regions 2a to 2d) is also provided. Can be grasped as an ohmic contact region). Therefore, a good ohmic contact can be realized between each of the semiconductor regions 2a to 2d and each wiring metal 45.

  Further, the predetermined wiring metal 45 may be connected to a ground potential or a fixed potential. By adopting this configuration, electrons generated by photoelectric conversion can be extinguished in the semiconductor regions 2a to 2e that are electrically connected to the ground potential or the fixed potential. That is, it can be considered that photoelectric conversion of light having a predetermined wavelength has not occurred. As can be seen from the above, this configuration can provide a function equivalent to the optical filter characteristic.

  Further, the predetermined wiring metal 45 may be connected to an amplifier that amplifies an electric signal. By adopting this configuration, the electrons generated by the photoelectric conversion in the predetermined semiconductor regions 2a to 2e of the photodiode unit 2 have a potential that can be electrically processed as a video signal in a predetermined circuit. Can be amplified.

  In addition, a predetermined wiring metal 45 may be connected to a switch that enables the change of the conduction destination. By adopting this configuration, the conduction destination of electrons generated by photoelectric conversion in a predetermined semiconductor region can be arbitrarily changed. For example, the switch is included when performing a change process such as emphasizing a predetermined color, mixing the predetermined colors, or erasing the predetermined color during the operation of the imaging apparatus. The configuration of the photoelectric conversion element is beneficial.

  In the structure shown in FIG. 7, the wiring metal 45 is used as an active element (not shown) such as a MOS transistor formed on the semiconductor substrate 1 or a passive element (not shown) such as a capacitor or a resistor. You may connect. In this case, the entire semiconductor substrate 1 can function as a semiconductor integrated circuit including a photoelectric conversion element.

  In the above embodiments, the semiconductor regions 2a to 2e may be configured as follows. That is, the semiconductor regions 2a to 2e may be configured so as to be in a (complete) depleted state by applying a predetermined voltage (which can be grasped as a fully depleted voltage) to the semiconductor regions 2a to 2e. . As a method of configuring the semiconductor regions 2a to 2e, for example, there is adjustment of impurity concentration.

  By adopting this configuration, a predetermined charge is stored in the semiconductor regions 2a to 2e based on the application of the predetermined voltage, and from the charge stored when the photoelectric conversion occurs, it is caused by the photoelectric conversion. It is possible to provide a photoelectric conversion element that eliminates the amount of charge.

  The photoelectric conversion element of this type has a larger amount of charge stored in the semiconductor regions 2a to 2e after photoelectric conversion than the photoelectric conversion element of the type that stores the charge generated by photoelectric conversion. Therefore, a solid-state imaging device with high imaging accuracy can be provided, for example, by configuring a solid-state imaging device using the former type of photoelectric conversion element.

  Moreover, you may employ | adopt the following shapes as a shape of the junction surface between semiconductor regions. That is, a part of the joint surface may have a substantially concentric shape. Specifically, when attention is paid to the lower side of the end portion of the light shielding film 6 shown in FIG. 8, each of the bonding surfaces a to d has a substantially concentric shape centering on the end portion of the light shielding film 6. have.

  By adopting the above as the shape of the joint surface, even if light refraction and diffraction occur at the end of the light shielding film 6 and the traveling direction of the light is changed, the following effects are obtained. That is, the semiconductor substrate of the light whose traveling direction is changed by diffraction or the like, the distance from the surface of the semiconductor substrate 1 to the bonding surface (that is, the photoelectric conversion place), and the light traveling in the direction perpendicular to the semiconductor substrate 1 The distance from the surface of 1 to the bonding surface (that is, the photoelectric conversion place) can be made substantially the same (see FIG. 9).

  As described above, by adopting the bonding surface having the above shape, it is possible to prevent the color separation characteristics of the photoelectric conversion element from deteriorating even if light diffraction or the like occurs at the end of the light shielding film 6.

  In each of the above embodiments, the semiconductor regions 2a to 2e are five layers, and the photodiode portion 2 is configured. However, the photodiode portion 2 may be configured from a semiconductor region of multiple layers other than the five layers (for example, two to four layers, or six layers or more).

  Moreover, in each said embodiment, the semiconductor substrate 1 showed the example using n type. However, the semiconductor substrate 1 may be p-type. In this case, the conductivity types of the semiconductor regions 2a to 2e are opposite to those shown above.

  Moreover, a solid-state imaging device can be comprised by arrange | positioning the photoelectric conversion element concerning each said embodiment on the semiconductor substrate 1 in planar view. The solid-state imaging device includes a plurality of photoelectric conversion elements that function as sensor units, and an electronic circuit connected to the photoelectric conversion elements by wiring.

  Note that the solid-state imaging device can be used to configure an imaging apparatus such as a digital camera or an image reading apparatus such as a scanner. Here, when an imaging apparatus is configured using a solid-state imaging device, the photoelectric conversion elements are usually arranged two-dimensionally. When an image reading apparatus is configured using a solid-state imaging device, the photoelectric conversion elements are usually arranged one-dimensionally.

1 is a cross-sectional view illustrating a schematic configuration of a photoelectric conversion element according to Embodiment 1. FIG. 6 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element according to Embodiment 2. FIG. 6 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element according to Embodiment 3. FIG. 6 is a cross-sectional view illustrating a schematic configuration of a photoelectric conversion element according to Embodiment 4. FIG. 6 is a cross-sectional view showing a schematic configuration of a photoelectric conversion element according to Embodiment 5. FIG. 10 is a cross-sectional view illustrating a schematic configuration of a photoelectric conversion element according to Embodiment 6. FIG. 10 is a cross-sectional view illustrating a schematic configuration of a photoelectric conversion element according to Embodiment 7. FIG. It is sectional drawing which shows that a part of joining surface is substantially concentric. It is sectional drawing which shows a mode that the light diffracted by the light shielding film reaches | attains the joint surface which has a substantially concentric shape in part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate, 2 Photodiode part, 2a-2e Semiconductor area | region, 3,13,13a, 13b Concave lens, 4,4a, 4b Convex lens, 5 Passivation film | membrane, 6,11 Light shielding film, 7 Planarization layer, 12 Glass layer, 35 Infrared cut filter, 41 high-concentration impurity diffusion layer, 45 wiring metal, 46 ohmic contact region.

Claims (28)

A semiconductor substrate;
In the semiconductor substrate, the first semiconductor region of the first conductivity type and the second semiconductor region of the second conductivity type are composed of a plurality of photodiodes configured by alternately laminating one after another. A photodiode section;
A convex lens for condensing incident light on the photodiode part;
A concave lens disposed on the optical path between the photodiode portion and the convex lens,
The photoelectric conversion element characterized by the above-mentioned. The concave lens is at least 2 or more;
Between the photodiode part and the convex lens, it is arranged in series.
The photoelectric conversion element according to claim 1. The concave lens is
Formed of a resin having photosensitivity,
The photoelectric conversion element according to claim 1. The convex lens is
Formed of a resin having photosensitivity,
The photoelectric conversion element according to claim 1. A flattening layer formed between the concave lens and the convex lens;
The refractive index of the planarizing layer is
Different from the refractive index of the concave lens,
The photoelectric conversion element according to claim 1. The refractive index of the concave lens is
The refractive index of the convex lens is substantially the same,
The refractive index of the planarizing layer is
Smaller than the refractive index of the concave lens and the refractive index of the convex lens,
The photoelectric conversion element according to claim 5. A SiO2 film, a SiON film, or a SiN film formed to cover the photodiode portion;
The photoelectric conversion element according to claim 1. A light-shielding film having an opening for a predetermined region of the photodiode portion;
The photoelectric conversion element according to claim 1. The light shielding film is
Composed of metal or metal silicide,
The photoelectric conversion element according to claim 8. The light shielding film is
Functioning as wiring,
The photoelectric conversion element according to claim 9. A glass layer is further formed between the light shielding film and the concave lens,
The photoelectric conversion element according to claim 9. The glass layer is
BPSG,
The photoelectric conversion element according to claim 11. An infrared cut filter disposed on the photodiode portion is further provided,
The photoelectric conversion element according to claim 1. The first semiconductor region and the second semiconductor region are formed in a nested manner,
The first semiconductor region or the second semiconductor, which is formed so as to cover at least a part of a joint surface between the first semiconductor region and the second semiconductor region existing on the upper surface of the semiconductor substrate. A high-concentration impurity diffusion layer having a higher impurity concentration than the impurity concentration of the region,
The photoelectric conversion element according to claim 1. Further comprising a wiring metal connected to the first semiconductor region or the second semiconductor region,
The photoelectric conversion element according to claim 1. Between the first semiconductor region or the second semiconductor region and the wiring metal, an ohmic contact region having an impurity concentration higher than that of the connected semiconductor region is formed,
The photoelectric conversion element according to claim 15. The wiring metal is plural,
At least one of the wiring metals is
Connected to ground potential or fixed potential,
The photoelectric conversion element according to claim 15. The wiring metal is plural,
At least one of the wiring metals is
Connected to an amplifier that amplifies the electrical signal,
The photoelectric conversion element according to claim 15. The wiring metal is plural,
At least one of the wiring metals is
Connected to a switch that allows the change of the conduction destination,
The photoelectric conversion element according to claim 15. The first semiconductor region and the second semiconductor region are:
By applying a predetermined voltage to each of the semiconductor regions, it becomes a depletion state.
The photoelectric conversion element according to claim 1. The first semiconductor region and the second semiconductor region are formed in a nested manner,
The bonding surface between the first semiconductor region and the second semiconductor region is
Below the light shielding film, it has a substantially concentric shape centered on the end of the light shielding film,
The photoelectric conversion element according to claim 8. The photoelectric conversion element according to any one of claims 1 to 21 is configured by arranging a plurality of the photoelectric conversion elements in a plan view.
A solid-state imaging device. The solid-state imaging device according to claim 22 is provided.
An imaging apparatus characterized by that. The solid-state imaging device according to claim 22 is provided.
An image reading apparatus. (A) In the semiconductor substrate, a first semiconductor region of the first conductivity type and a second semiconductor region of the second conductivity type are stacked alternately and sequentially in the surface of the semiconductor substrate. Forming a photodiode portion composed of a plurality of photodiodes;
(B) applying a resin on the photodiode portion;
(C) forming a recess in the resin;
(D) A step of forming a concave lens by subjecting the resin having the depression to a heat melting treatment,
A method for producing a photoelectric conversion element. The resin has photosensitivity,
The step (C)
It is a step of forming the depression in the resin by applying a photoengraving method to the resin.
The method for producing a photoelectric conversion element according to claim 25. (A) In the semiconductor substrate, a first semiconductor region of the first conductivity type and a second semiconductor region of the second conductivity type are stacked alternately and sequentially in the surface of the semiconductor substrate. Forming a photodiode portion composed of a plurality of photodiodes;
(B) forming a light-shielding film having an opening in which a predetermined region of the photodiode portion is desired;
(C) forming a glass layer on at least the side surface of the opening;
(D) applying a predetermined amount of resin to the opening, and using the surface tension generated between the resin and the glass layer to make the resin concave.
A method for producing a photoelectric conversion element. (H) The method further includes a step of forming a concave lens by performing a thermosetting process on the resin after the step (C).
The method for producing a photoelectric conversion element according to claim 27.

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