JP2007115872A - Solid-state imaging apparatus and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid-state imaging apparatus for realizing reduction in noise without occurrence of increase in smear, and also to provide a manufacturing method of the same solid-state imaging apparatus. <P>SOLUTION: A photodiode including a first conductivity-type impurity diffusing layer 13 is formed within a substrate. Next, a second conductivity-type impurity diffusing layer 14 formed sequentially of low concentration region, high concentration region, and intermediate concentration region is formed on the first conductivity-type impurity diffusing layer of the substrate toward the light receiving side from the photodiode side. Here, the high concentration region and the intermediate concentration region are formed to enclose the high concentration region except for the circumference in the light receiving side in the intermediate concentration region. Moreover, the intermediate concentration region is formed by introducing the first conductivity-type impurity to the upper layer of the high concentration region, so that the impurity concentration becomes lower than the high concentration region. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a solid-state imaging device and a manufacturing method thereof, and more particularly, to a solid-state imaging device and a manufacturing method thereof for reducing noise in a light receiving unit.

  Hereinafter, a conventional solid-state imaging device will be described.

  FIG. 8 shows a cross-sectional structure of a conventional CCD solid-state imaging device. In FIG. 8, 11 is an n-type semiconductor substrate, 12 is a first p-type well region formed on the surface of the n-type semiconductor substrate 11, 13 is an n-type diffusion layer, 14 is a p-type diffusion layer for noise reduction, 15 is a second p-type well region, 16 is an n-type well region, 17 is a p-type diffusion layer for separation, 18 is a gate oxide film, 19 is a gate electrode, 20 is a light-shielding film, 21 is an aluminum light-shielding portion, and 22 is It is a protective film.

  Here, the first p-type well region 12 and the n-type diffusion layer 13 constitute a photodiode section that performs photoelectric conversion and generates signal charges. The second p-type well region 15 and the n-type well region 16 A charge transfer unit for transferring signal charges is configured.

  The operation of the CCD solid-state imaging device configured as described above will be described below. When light enters from above the noise-reducing p-type diffusion layer 14, photoelectric conversion is performed in the noise-reducing p-type diffusion layer 14, the n-type diffusion layer 13, and the first p-type well region 12, and electron-hole pairs Will occur. The generated electrons gather in the n-type diffusion layer 13 of the photodiode portion and are accumulated as signal charges. Next, when a pulse signal is applied to the gate electrode 19, the signal charge is read to the n-type well region 16 of the charge transfer unit, then transferred to the external extraction stage, and extracted outside. Thereby, the intensity | strength of the light which injected into each CCD solid-state image sensor can be determined.

  Here, the noise reducing p-type diffusion layer 14 is for reducing noise due to defects formed near the substrate surface when the CCD solid-state imaging device is manufactured. The p-type diffusion layer 14 is formed on the n-type diffusion layer 13. By forming the diffusion layer, the upper portion of the n-type diffusion layer 13 is prevented from being depleted. The noise reducing p-type diffusion layer 14 is formed by ion implantation using the gate electrode 19 as a mask.

  There are two points to be noted in the formation of the noise reducing p-type diffusion layer 14. One is that the impurity concentration should not be too high. When the impurity concentration of the noise reducing p-type diffusion layer 14 is high, the hole concentration is also increased. For this reason, the probability of recombination of the holes and the electrons generated by photoelectric conversion increases, so that the signal charge is likely to disappear. Become. This reduces the photosensitivity of the CCD solid-state imaging device. Particularly in the short wavelength region, since the absorption coefficient is large, almost all photons are photoelectrically converted in the noise reducing p-type diffusion layer 14 without reaching the n-type diffusion layer 13. Therefore, if the impurity concentration of the noise reducing p-type diffusion layer 14 is high, most of the signal charges are lost, and the photosensitivity in the short wavelength region is significantly lowered. The other is that the noise reducing p-type diffusion layer 14 must be formed sufficiently deeper than the distribution position of defects formed on the substrate surface. If the p-type diffusion layer 14 for noise reduction is not formed deep enough, the region where the defect exists is depleted and noise cannot be reduced.

  Further, in order to reduce the occurrence of smear, the noise reducing p-type diffusion layer 14 includes a light receiving surface side region 14b having a relatively high impurity concentration and a photodiode portion side region 14c having a relatively low impurity concentration. In this configuration, the impurity concentration distribution in the noise reduction p-type diffusion layer 14 does not have a positive peak, and the potential distribution during light reception does not have a negative gradient in the vicinity of the light receiving surface. It has become.

  As described above, the low-density and deep structure of the noise reducing p-type diffusion layer 14 is a condition for realizing a CCD solid-state imaging device with high sensitivity and low noise. In addition, it is a condition for reducing the occurrence of smear that the potential distribution during light reception does not have a negative gradient in the vicinity of the light receiving surface.

In the ion implantation method, the impurity concentration and depth of the impurity diffusion layer to be formed can be adjusted by the dose amount and implantation energy. Therefore, in order to form an impurity diffusion layer having a low concentration and a deep structure so that the potential distribution during light reception does not have a negative gradient in the vicinity of the light receiving surface, ion implantation with a low dose and high implantation energy is performed. Can be done. In the conventional technique, boron is implanted under conditions of a dose amount of about 1E13 / cm ² and an implantation energy of about 100 keV, and further boron is implanted under conditions of a dose amount of about 6E13 / cm ² and an implantation energy of about 40 keV, A method of forming a p-type diffusion layer 14 for noise reduction having a low concentration and a deep structure is employed.
JP-A-8-97392

  FIG. 9 shows an impurity concentration distribution along the line ABC in FIG. In FIG. 9, 31 is the high concentration region 14a of the noise reduction p-type diffusion layer 14, 32 is the low concentration region 14b of the noise reduction p-type diffusion layer 14, 33 is the n-type diffusion layer 13, and 34 is the first. Respectively corresponding to the p-type well regions 12.

  FIG. 10 shows the impurity concentration, hole concentration, and potential distribution during light reception in the line AB in FIG. 9 and 10, a represents a boundary, that is, a light receiving surface, between the gate oxide film 19 and the noise reduction p-type diffusion layer 14, and b represents a boundary between the noise reduction p-type diffusion layer 14 and the n-type diffusion layer 13. Is shown.

  Looking at the potential distribution in FIG. 10, the interface has a peak, and electrons generated by photoelectric conversion or interface order near the light receiving surface try to move in the substrate depth direction and move toward the n-type diffusion layer 13. To do. This is because, in order to reduce the occurrence of smear, the noise reducing p-type diffusion layer 14 is configured so that the potential distribution during light reception does not have a negative gradient in the vicinity of the light receiving surface. Most electrons disappear due to recombination in the noise-reducing p-type diffusion layer, but some electrons reach the n-type diffusion layer 13. These electrons cause a so-called noise signal, and all electrons that cannot be recombined in the noise reducing p-type diffusion layer become noise.

  As described above, in the conventional technique, if an attempt is made to further improve the photosensitivity, even an electronic signal that becomes noise increases, and further improvement in photosensitivity cannot be realized.

  Accordingly, an object of the present invention is to solve the above-described problems, and to provide a solid-state imaging device capable of realizing noise reduction without causing an increase in smear and a method for manufacturing the same.

  In order to solve the above-described problem, a solid-state imaging device according to claim 1 of the present invention includes a photodiode unit that has a first conductivity type impurity diffusion layer and generates a signal charge by photoelectric conversion, and the first conductivity. A solid-state imaging device including a second conductivity type impurity diffusion layer formed on the type impurity diffusion layer, wherein the second conductivity type diffusion layer is sequentially from the photodiode portion side toward the light receiving surface side. It consists of a low concentration region, a high concentration region, and a medium concentration region, and the medium concentration region is surrounded by the high concentration region except for the light receiving surface side.

  The solid-state imaging device according to claim 2, wherein in the solid-state imaging device according to claim 1, the photodiode unit includes a second conductive type well region connected to the first conductive type impurity diffusion layer, and the signal A charge transfer part for transferring charges is formed connected to the second conductivity type well region.

  The solid-state imaging device according to claim 3 is the solid-state imaging device according to claim 1 or 2, wherein the second conductivity type impurity diffusion layer has a function of reducing noise in the photodiode portion.

  The solid-state imaging device according to claim 4 is the solid-state imaging device according to claim 1, 2, or 3, wherein the first conductivity type impurity diffusion layer is n-type and the second conductivity type impurity diffusion layer is p-type. is there.

  6. The method of manufacturing a solid-state imaging device according to claim 5, wherein a first step of forming a photodiode portion having a first conductivity type impurity diffusion layer in the substrate, and on the first conductivity type impurity diffusion layer in the substrate. A second step of forming a second conductivity type impurity diffusion layer composed of a low concentration region, a high concentration region, and a medium concentration region in order from the photodiode part side toward the light receiving surface side. In the second step, The medium concentration region is formed so as to surround the periphery of the medium concentration region except the light receiving surface side with the high concentration region.

  The solid-state imaging device manufacturing method according to claim 6 is the solid-state imaging device manufacturing method according to claim 5, wherein the photodiode portion includes a second conductivity type well region connected to the first conductivity type impurity diffusion layer. And a step of forming a charge transfer portion for transferring a signal charge of the photodiode portion connected to the second conductivity type well region.

  The solid-state imaging device manufacturing method according to claim 7 is the solid-state imaging device manufacturing method according to claim 5 or 6, wherein in the second step, a first conductivity type impurity is introduced into an upper layer portion of the high concentration region. Then, the intermediate concentration region having an impurity concentration lower than that of the high concentration region is formed.

  The solid-state imaging device manufacturing method according to claim 8 is the solid-state imaging device manufacturing method according to claim 5, 6 or 7, wherein the second conductivity type impurity diffusion layer has a function of reducing noise in the photodiode portion. Have.

  The method for manufacturing a solid-state imaging device according to claim 9 is the method for manufacturing a solid-state imaging device according to claim 5, 6 or 7, wherein the first conductivity type impurity diffusion layer is n-type and the second conductivity type impurity. The diffusion layer is p-type.

The solid-state imaging device manufacturing method according to claim 10 is the solid-state imaging device manufacturing method according to claim 9, wherein the low concentration region, the high concentration region, and the medium concentration region have a dose amount of 1E12 / cm in the substrate. First ion implantation using boron ions of ^{2 to} 2E13 / cm ² and implantation energy of 80 keV to 140 keV, Boron ions having a dose of 3E13 / cm ^{2 to} 1E14 / cm ² and implantation energy of 30 keV to 50 keV were used. It is formed by performing second ion implantation and third ion implantation using arsenic ions having a dose amount of 1E11 / cm ^{2 to} 2E13 / cm ² and an implantation energy of 10 keV to 40 keV.

  According to the solid-state imaging device of the first aspect of the present invention, the second conductivity type impurity diffusion layer is composed of a low concentration region, a high concentration region, and a medium concentration region in order from the photodiode portion side to the light receiving surface side. Therefore, a potential barrier is formed by forcibly giving a negative gradient in the vicinity of the surface of the potential distribution in the second conductivity type impurity diffusion layer, and electrons that cause noise generated in the interface order are generated in the photodiode portion. Noise can be reduced. In addition, since the medium concentration region is surrounded by the high concentration region except for the light receiving surface side, a potential barrier is formed in the lateral direction, preventing electron diffusion and preventing smearing. It becomes possible to do.

  According to a second aspect of the present invention, the photodiode unit has a second conductivity type well region connected to the first conductivity type impurity diffusion layer, and the charge transfer unit for transferring signal charges is connected to the second conductivity type well region. Thus, the signal charge accumulated in the first conductivity type impurity diffusion layer can be read out by the charge transfer unit when light enters from above the second conductivity type impurity diffusion layer.

  According to the third aspect of the present invention, since the second conductivity type impurity diffusion layer has a function of reducing noise in the photodiode portion, it is possible to reduce noise due to defects formed in the vicinity of the substrate surface when the solid-state imaging device is manufactured.

  Preferably, the first conductivity type impurity diffusion layer is n-type and the second conductivity type impurity diffusion layer is p-type.

  According to the method for manufacturing a solid-state imaging device according to claim 5 of the present invention, the low concentration region and the high concentration are sequentially formed on the first conductivity type impurity diffusion layer in the substrate from the photodiode portion side toward the light receiving surface side. A step of forming a second conductivity type impurity diffusion layer composed of a region and a medium concentration region, so that the potential distribution in the second conductivity type impurity diffusion layer is forced to have a negative gradient in the vicinity of the surface. A barrier is formed, and electrons that cause noise generated in the interface order do not reach the photodiode portion, and noise can be reduced. In the second step, since the periphery of the medium concentration region except the light receiving surface side is formed so as to be surrounded by the high concentration region, a potential barrier is also formed in the lateral direction, and diffusion of electrons can be prevented. Further, it is possible to prevent the occurrence of smear.

  According to another aspect of the present invention, the photodiode portion has a second conductivity type well region connected to the first conductivity type impurity diffusion layer, and the charge transfer portion for transferring the signal charge of the photodiode portion is used as the second conductivity type well region. Since the step of connecting and forming is included, when the light enters from above the second conductivity type impurity diffusion layer, the signal charge accumulated in the first conductivity type impurity diffusion layer can be read out by the charge transfer unit.

  According to the seventh aspect of the present invention, in the second step, the first conductivity type impurity is introduced into the upper layer portion of the high concentration region to form an intermediate concentration region having an impurity concentration lower than that of the high concentration region. Thus, the impurity concentration in the medium concentration region can be relatively reduced.

  According to the eighth aspect of the present invention, since the second conductivity type impurity diffusion layer has a function of reducing noise in the photodiode portion, it is possible to reduce noise due to defects formed in the vicinity of the substrate surface when the solid-state imaging device is manufactured.

  Preferably, the first conductivity type impurity diffusion layer is n-type, and the second conductivity type impurity diffusion layer is p-type.

The low-concentration region, the high-concentration region, and the medium-concentration region may include first ions using boron ions having a dose amount of 1E12 / cm ^{2 to} 2E13 / cm ² and an implantation energy of 80 keV to 140 keV in the substrate. infusion, a second ion implantation dose is injected energy 3E13 ^/ cm ² ~1E14 ^/ cm 2 using boron ions 30KeV～50keV, and dose amount is injected energy 1E11 ^/ cm ² ~2E13 ^/ cm 2 Since the p-type diffusion layer for noise reduction of the solid-state imaging device is formed by performing third ion implantation using arsenic ions of 10 keV to 40 keV, the light receiving surface portion in which the hole concentration is relatively reduced with n-type impurities Regions on the light-receiving surface side where the impurity concentration is relatively high, and regions on the photodiode side where the impurity concentration is relatively low It can be constructed from a.

  Hereinafter, a solid-state imaging device according to an embodiment of the present invention will be described with reference to FIGS.

  FIG. 1 shows a cross-sectional structure of a CCD solid-state imaging device according to this embodiment. In FIG. 1, 11 is an n-type semiconductor substrate, 12 is a first p-type well region formed on the surface of the n-type semiconductor substrate 11, 13 is an n-type diffusion layer (first conductivity type impurity diffusion layer), 14 Is a p-type diffusion layer for noise reduction (second conductivity type impurity diffusion layer), 15 is a second p-type well region, 16 is an n-type well region, 17 is a p-type diffusion layer for isolation, 18 is a gate oxide film, Reference numeral 19 denotes a gate electrode, 20 denotes an interlayer insulating film, 21 denotes a light shielding film, 22 denotes a protective film, 23 denotes a microlens, and 24 denotes an insulating film on the sidewall. The first p-type well region 12 and the n-type diffusion layer 13 constitute a photodiode portion that performs photoelectric conversion and generates a signal charge. The second p-type well region 15 and the n-type well region 16 form a signal charge. Is formed.

  The p-type diffusion layer 14 for noise reduction is formed on the n-type diffusion layer 13 and is for reducing noise due to defects formed near the substrate surface when the solid-state imaging device is manufactured. As a feature of the present embodiment, a region (medium concentration region) 14a of the light receiving surface portion in which the hole concentration is relatively reduced by n-type impurities, a high concentration region 14b having a relatively high impurity concentration, and the n-type diffusion layer 13 are used. And a low concentration region 14c having a relatively low impurity concentration located on the side. In addition, the light receiving surface region 14a in which the hole concentration is relatively reduced with n-type impurities has a structure surrounded by a high concentration region 14b having a relatively high impurity concentration.

  FIG. 2 shows the impurity concentration distribution along the line ABC in FIG. In FIG. 2, 30 is an n-type impurity in the region 14a of the light-receiving surface portion where the hole concentration is relatively reduced with an n-type impurity, 31 is a high-concentration region 14b of the p-type diffusion layer 14 for noise reduction, and 32 is noise. The reduction p-type diffusion layer 14 corresponds to the low concentration region 14 c, 33 corresponds to the n-type diffusion layer 13, and 34 corresponds to the first p-type well region 12.

  FIG. 3 shows the impurity concentration, hole concentration, and potential distribution during light reception in the line AB in FIG. 2 and 3, a indicates the boundary, that is, the light receiving surface, between the gate oxide film 19 and the noise reduction p-type diffusion layer 14, and b indicates the boundary between the noise reduction p-type diffusion layer 14 and the n-type diffusion layer 13. Is shown.

  In the present embodiment, the impurity concentration in the substrate depth direction in the noise reducing p-type diffusion layer 14 is such that, as shown in FIGS. 2 and 3, the p-type impurities are canceled by n-type impurities in the vicinity of the light receiving surface (near the light receiving surface). The p-type impurity concentration is reduced).

  For this reason, the hole concentration once has a positive gradient from the light receiving surface to the inside, and then gradually decreases toward the inside. As a result, the potential once has a negative gradient from the light receiving surface portion toward the inside, and then gradually increases toward the inside.

  Therefore, in order for electrons that cause noise generated in the vicinity of the light receiving surface due to the interface order to move to the photodiode portion, the electrons must overcome the potential barrier having a negative gradient and reach the n-type diffusion layer 13. It becomes difficult to reduce noise.

  On the other hand, the electrons remaining in the region 14a of the light-receiving surface portion where the hole concentration is relatively reduced with n-type impurities are recombined with holes that are majority carriers in the noise reducing p-type diffusion layer 14 and disappear.

  In addition, the light receiving surface region 14a, in which the hole concentration is relatively reduced with n-type impurities, has a structure surrounded by a high concentration region 14b having a relatively high impurity concentration, so that the potential in the lateral direction is also increased. A barrier is formed, so that the diffusion of electrons into the n-type well region 16 can be prevented, and the occurrence of smear can also be prevented. Therefore, according to the present embodiment, noise can be reduced without causing an increase in smear.

  Hereinafter, the process for forming the p-type diffusion layer 14 for noise reduction will be described with respect to a method for manufacturing a solid-state imaging device having the above structure.

  FIG. 4 shows a cross-sectional structure of the solid-state imaging device immediately before boron implantation for forming the noise reducing p-type diffusion layer 14. As shown in FIG. 4, a first p-type well region 12, an n-type diffusion layer 13, a second p-type well region 15, an n-type well region 16, a separation p-type are formed on an n-type semiconductor substrate 11. Diffusion layer 17, gate oxide film 18 and gate electrode 19 have already been formed.

  Next, as shown in FIG. 5, the p-type diffusion layer 14 for noise reduction is obtained by performing heat treatment at 850 ° C. to 1100 ° C. after performing ion implantation using boron twice with the gate electrode 19 as a mask. Form. As a result, a high concentration region 14b is formed on the light receiving surface side, and a low concentration region 14c is formed on the photodiode portion side.

Here, the two ion implantations are the first ion implantation under the conditions of dose amount: 1E12 / cm ^{2 to} 2E13 / cm ² and implantation energy: 80 keV to 140 keV, and dose amount: 3E13 / cm ^{2 to} 1E14 / cm. ² and implantation energy: second ion implantation under a condition of 30 keV to 50 keV.

  This ion implantation condition range is such that when the gate oxide film 18 has a thickness of 30 nm to 100 nm, the high concentration region 14b of the p-type diffusion layer 14 for noise reduction is 0.1 μm from the substrate surface to the inside. The low concentration region 14c of the p-type diffusion layer 14 for noise reduction reaches a depth of about 0.4 μm to 0.7 μm from the substrate surface to the inner side.

  Next, as shown in FIG. 6, after the high concentration region 14b and the low concentration region 14c of the noise reduction p-type diffusion layer 14 are formed, an insulating film is formed and the entire surface is etched to form the sidewall 24. An ion implantation using arsenic to reduce the surface hole concentration is performed once and a heat treatment at 850 ° C. to 1100 ° C. is performed. Region 14a is formed.

Here, the third ion implantation has a dose amount of 1E11 / cm ^{2 to} 2E13 / cm ² and an implantation energy of 10 keV to 40 keV, and is implanted into the surface portion of the high concentration region 14b to relatively reduce the hole concentration. A region 14a of the light-receiving surface portion thus formed is formed.

  The heat treatment when the high concentration region 14b and the low concentration region 14c are formed on the light receiving surface side can be combined with the heat treatment when forming the region 14a of the light receiving surface portion in which the hole concentration is relatively reduced. It can be omitted.

  Next, as shown in FIG. 7, an interlayer insulating film 20, a light shielding film 21, a protective film 22, and a microlens 23 are formed above the semiconductor substrate, thereby completing a solid-state imaging device.

  As described above, according to the solid-state imaging device and the manufacturing method thereof according to the present embodiment, the p-type diffusion layer for noise reduction of the solid-state imaging device has the light receiving surface portion in which the hole concentration is relatively reduced with the n-type impurity. The potential distribution in the p-type diffusion layer for noise reduction is made near the surface by comprising a region, a region on the light receiving surface side with a relatively high impurity concentration, and a region on the photodiode portion side with a relatively low impurity concentration. By forcing a negative gradient into the potential barrier, a potential barrier is formed, and electrons that cause noise generated at the interface order do not reach the photodiode, thereby reducing noise.

  In the present embodiment, the case where the photodiode portion is configured by the p-type well region and the n-type diffusion layer and the noise reduction diffusion layer is configured by the p-type diffusion layer has been described as an example. The same applies to the case where the photodiode portion is constituted by the p-type diffusion layer and the noise reduction diffusion layer is constituted by the n-type diffusion layer.

  The solid-state imaging device of the present invention provides a solid-state imaging device capable of reducing noise without causing an increase in smear, and a method for manufacturing the solid-state imaging device. It is useful for an apparatus and a manufacturing method thereof.

It is sectional drawing of the solid-state imaging device which concerns on embodiment of this invention. It is a figure which shows the impurity concentration distribution of the semiconductor substrate depth direction of the p-type diffusion layer for noise reduction, an n-type diffusion layer, and the 1st p-type well area | region in the solid-state imaging device which concerns on embodiment of this invention. It is a figure which shows the distribution of the electric potential at the time of the impurity concentration of a substrate depth direction of a p-type diffused layer for noise reduction, a hole concentration, and the light reception in the solid-state imaging device which concerns on embodiment of this invention. It is sectional drawing which shows the process of the manufacturing method of the solid-state imaging device which concerns on embodiment of this invention. FIG. 5 is a cross-sectional view showing a step subsequent to FIG. 4. FIG. 6 is a cross-sectional view showing a step subsequent to FIG. 5. FIG. 7 is a cross-sectional view showing a step subsequent to FIG. 6. It is sectional drawing of the conventional solid-state imaging device. It is a figure which shows the impurity concentration distribution of the semiconductor substrate depth direction of the p-type diffused layer for noise reduction, an n-type diffused layer, and the 1st p-type well area | region in the conventional solid-state imaging device. It is a figure which shows distribution of the electric potential at the time of the impurity concentration of a substrate depth direction of a p-type diffusion layer for noise reduction in the said conventional solid-state imaging device, hole concentration, and light reception.

Explanation of symbols

11 n-type semiconductor substrate 12 first p-type well region 13 n-type diffusion layer 14 noise-reducing p-type diffusion layer 14a light-receiving surface region 14b in which the hole concentration is relatively reduced by n-type impurities 14b high-concentration region 14c low Concentration region 15 Second p-type well region 16 n-type well region 17 Isolation p-type diffusion layer 18 Gate oxide film 19 Gate electrode 20 Light-shielding film 21 Aluminum light-shielding part 22 Protective film 23 Microlens 24 Side wall 30 With n-type impurities The n-type impurity concentration distribution 31 in the substrate depth direction of the region 14a of the light receiving surface portion where the hole concentration is relatively reduced. The impurity concentration distribution 32 in the substrate depth direction of the high concentration region 14a of the p-type diffusion layer 14 for noise reduction. Impurity concentration distribution 33 in the substrate depth direction of the low-concentration region 14b of the p-type diffusion layer 14 for reduction 33 Impurity concentration distribution 34 in the substrate depth direction of the n-type diffusion layer 13 Impurity concentration distribution in the substrate depth direction of the p-type well region 12

Claims (10)

A photodiode portion having a first conductivity type impurity diffusion layer and generating a signal charge by photoelectric conversion;
A solid-state imaging device comprising a second conductivity type impurity diffusion layer formed on the first conductivity type impurity diffusion layer,
The second conductivity type diffusion layer is composed of a low concentration region, a high concentration region, and a medium concentration region in order from the photodiode portion side to the light receiving surface side,
The solid-state imaging device, wherein the medium concentration region is surrounded by the high concentration region except for the light receiving surface side.   The photodiode portion has a second conductivity type well region connected to the first conductivity type impurity diffusion layer, and a charge transfer portion for transferring the signal charge is connected to the second conductivity type well region. The solid-state imaging device according to claim 1.   The solid-state imaging device according to claim 1, wherein the second conductivity type impurity diffusion layer has a function of reducing noise in the photodiode portion.   4. The solid-state imaging device according to claim 1, wherein the first conductivity type impurity diffusion layer is n-type and the second conductivity type impurity diffusion layer is p-type. A first step of forming a photodiode portion having a first conductivity type impurity diffusion layer in a substrate;
On the first conductivity type impurity diffusion layer in the substrate, a second conductivity type impurity diffusion layer comprising a low concentration region, a high concentration region, and a medium concentration region in order from the photodiode portion side to the light receiving surface side. A second step of forming,
In the second step, a solid-state imaging device manufacturing method is characterized in that the medium concentration region is formed so as to surround the periphery of the light-receiving surface side with the high concentration region.   The photodiode unit has a second conductivity type well region connected to the first conductivity type impurity diffusion layer, and a charge transfer unit for transferring a signal charge of the photodiode unit is connected to the second conductivity type well region. The method for manufacturing a solid-state imaging device according to claim 5, further comprising a step of forming the same.   The solid according to claim 5 or 6, wherein in the second step, a first conductivity type impurity is introduced into an upper layer portion of the high concentration region to form the intermediate concentration region having an impurity concentration lower than that of the high concentration region. Manufacturing method of imaging apparatus.   The method of manufacturing a solid-state imaging device according to claim 5, wherein the second conductivity type impurity diffusion layer has a function of reducing noise in the photodiode portion.   8. The method of manufacturing a solid-state imaging device according to claim 5, wherein the first conductivity type impurity diffusion layer is n-type and the second conductivity type impurity diffusion layer is p-type. The low concentration region, the high concentration region, and the medium concentration region are formed by first ion implantation using boron ions having a dose amount of 1E12 / cm ^{2 to} 2E13 / cm ² and an implantation energy of 80 keV to 140 keV in the substrate. second ion implantation amount is injected energy 3E13 ^/ cm ² ~1E14 ^/ cm 2 using boron ions 30KeV～50keV, and dose amount is injected energy ^{1E11 / cm 2 ~2E13 / cm 2} 10keV~40keV The method for manufacturing a solid-state imaging device according to claim 9, wherein the solid-state imaging device is formed by performing third ion implantation using arsenic ions.

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