CN104934491B - Photodiode, its preparation method and image sensing device - Google Patents

Abstract

The application discloses a photodiode, its manufacturing method and an image sensing device. The photodiode includes: an N-type doped region formed inside the substrate; a first P-type doped region formed inside the N-type doped region; a second P-type doped region formed in the substrate, It is located above the N-type doped region, and the lower surface is connected to the N-type doped region. The manufacturing method includes: doping the upper surface of the substrate to form an N-type doping preparation area; doping the inside of the N-type doping preparation area to form a first P-type doping area; Perform secondary doping to form a second P-type doped region above the first P-type doped region, and form an N-type doped region connected to the lower surface of the second P-type doped region. In the photodiode, the first P-type doped region will form a PN junction depletion layer in the N-type doped region, thereby improving the photoelectric conversion efficiency of the photodiode.

Description

Photodiode, its manufacturing method and image sensing device

technical field

The present application relates to the technical field of manufacturing semiconductor integrated circuits, in particular, to a photodiode, its manufacturing method and an image sensing device.

Background technique

As a photoelectric conversion device, a photodiode can be applied to a CMOS image sensor. The basic unit of a CMOS image sensor is called a pixel, which consists of a photodiode and 3 or 4 MOS transistors, referred to as 3T type or 4T type for short. Among them, the photodiode is used to convert the light signal into a corresponding current signal, and the MOS transistor is used to read the current signal converted by the photodiode.

FIG. 1 is a schematic structural diagram of a 4T type CMOS image sensor in the prior art. As shown in FIG. 1, this CMOS image sensor includes: a substrate 10', a photodiode 20', a transfer transistor 30' and a potential well 40' sequentially formed on the substrate 10', wherein the photodiode 20' includes a direction toward An N-type doped region 21' and a P-type doped region 23' are sequentially formed away from the substrate 10'; an active follower transistor 50', a reset transistor 60', and a selection transistor 70' are formed on the potential well 40' and shallow trench isolation structure 80'. The transfer transistor 30' is located between the photodiode 20' and the potential well 40', and the source region of the transfer transistor 30' is connected to the photodiode 20', and the drain region of the transfer transistor 30' is connected to the source follower transistor 50'.

The performance of the image sensor (such as sensitivity, spectral response, etc.) is related to the photoelectric conversion efficiency of the photodiode. However, the photoelectric conversion efficiency of existing photodiodes is low, resulting in a small photocurrent in the photodiodes, which in turn affects the performance of image sensors. Technologists try to increase the effective photosensitive area of the photodiode by increasing the roughness of the photosensitive surface, but this method cannot solve the problem of low photoelectric conversion efficiency of the photodiode.

Contents of the invention

The purpose of the present application is to provide a photodiode, its manufacturing method and image sensing device, so as to solve the problem of low photoelectric conversion efficiency of the photodiode in the prior art.

In order to achieve the above object, according to one aspect of the present application, a photodiode is provided, the photodiode includes: an N-type doped region formed inside the substrate; a first P-type doped region formed in the N-type doped Inside the impurity region; the second P-type doping region is formed in the substrate, located above the N-type doping region, and the lower surface is connected to the N-type doping region.

Further, in the photodiode mentioned above in this application, the photodiode includes one or more first P-type doped regions, and the ratio of the total volume of the first P-type doped regions to the volume of the N-type doped regions< 0.2.

Further, in the photodiode mentioned above in the present application, the ratio of the doping amount of P-type ions in the first P-type doping region to the doping amount of N-type ions in the N-type doping region is 1.05˜1.2.

Further, in the photodiode mentioned above in this application, when the photodiode includes a first P-type doped region, the first P-type doped region is located on the centerline of the N-type doped region perpendicular to the substrate surface; including When there are multiple first P-type doped regions, the multiple first P-type doped regions are symmetrically arranged on both sides of the center line of the N-type doped region perpendicular to the surface of the substrate.

Further, in the photodiode mentioned above in the present application, the thickness of the second P-type doped region is 1/10-1/20 of the thickness of the N-type doped region.

According to another aspect of the present application, a method for manufacturing a photodiode is provided. The method includes: doping the upper surface of the substrate to form an N-type doping preparation area; Doping to form a first P-type doped region; doping the upper surface of the substrate twice to form a second P-type doped region above the first P-type doped region, and to form a second P-type doped region The N-type doped region connected to the lower surface of the N-type doped region.

Further, in the above-mentioned photodiode manufacturing method of the present application, in the step of forming the N-type doping preparatory region, the concentration of dopant ions is 1.0E+17～1.0E+21atoms/cm ³ , and the implantation of dopant ions The energy is 100-400Kev.

Further, in the above-mentioned photodiode manufacturing method of the present application, in the step of forming the first P-type doped region, the inside of the N-type doped preparatory region is doped to form a The first P-type doped region with ratio<0.2.

Further, in the above-mentioned photodiode manufacturing method of the present application, in the step of forming the first P-type doped region, the concentration of doped ions is 1.05E+17～1.2E+21atoms/cm ³ , and the concentration of doped ions The injection energy is 300-600Kev.

Further, in the above-mentioned photodiode manufacturing method of the present application, in the step of forming the second P-type doped region and N-type doped region, the upper surface of the substrate is doped twice to form a thickness of N-type The thickness of the doped region is 1/10-1/20 of the second P-type doped region.

The present application also provides an image sensing device, including a photodiode disposed on a substrate, wherein the photodiode is the photodiode provided in the present application.

Applying the technical solution of the present application to a photodiode, its manufacturing method and image sensing device, a first P-type doped region is formed in the N-type doped region of the photodiode. The first P-type doping region will form a PN junction depletion layer in the N-type doping region, thereby improving the photoelectric conversion efficiency of the photodiode.

Description of drawings

The accompanying drawings constituting a part of the present application are used to provide further understanding of the present application, and the schematic embodiments and descriptions of the present application are used to explain the present application, and do not constitute improper limitations to the present application. In the attached picture:

FIG. 1 shows a schematic cross-sectional structure diagram of an existing image sensor device;

Fig. 2 shows a schematic cross-sectional structure diagram of a photodiode provided according to the present application;

Fig. 3 shows a schematic flow chart of the fabrication method of the photodiode provided according to the present application;

FIG. 4 shows a schematic cross-sectional structure diagram of the substrate after doping the upper surface of the substrate to form an N-type doping preparation region in the method for manufacturing a photodiode provided by an embodiment of the present application;

FIG. 5 shows a schematic diagram of the cross-sectional structure of the substrate after doping the inside of the N-type doped preparation region shown in FIG. 4 to form the first P-type doped region;

FIG. 6 shows that the upper surface of the substrate shown in FIG. 5 is doped twice to form a second P-type doped region above the first P-type doped region, and to form a second P-type doped region. Schematic diagram of the cross-sectional structure of the substrate behind the N-type doped region connected to the lower surface of the region; and

FIG. 7 shows a schematic cross-sectional structure diagram of an image sensing device provided according to an embodiment of the present application.

detailed description

It should be noted that, in the case of no conflict, the embodiments in the present application and the features in the embodiments can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and embodiments.

It should be noted that the terminology used here is only for describing specific implementations, and is not intended to limit the exemplary implementations according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should also be understood that when the terms "comprising" and/or "comprising" are used in this specification, it indicates There are features, steps, operations, means, components and/or combinations thereof.

For the convenience of description, spatially relative terms may be used here, such as "on ...", "over ...", "on the surface of ...", "above", etc., to describe the The spatial positional relationship between one device or feature shown and other devices or features. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, devices described as "above" or "above" other devices or configurations would then be oriented "beneath" or "above" the other devices or configurations. under other devices or configurations”. Thus, the exemplary term "above" can encompass both an orientation of "above" and "beneath". The device may be oriented differently (rotated 90 degrees or at other orientations) and the spatially relative descriptions used herein interpreted accordingly.

As introduced in the background art, there is a problem of low photoelectric conversion efficiency of photodiodes in the prior art. The applicant of the present application conducted research on the above problems and proposed a photodiode. As shown in FIG. 2, the photodiode 20 includes: an N-type doped region 21 formed inside the substrate 10; a first P-type doped region 22 formed inside the N-type doped region 21; a second P-type doped region 21 formed inside the substrate 10; The N-type doped region 23 is formed in the substrate 10 , located above the N-type doped region 21 , and the lower surface (part) is connected to the upper surface of the N-type doped region 21 .

In the above photodiode, the first P-type doped region 22 is formed inside the N-type doped region 21 of the photodiode. The first P-type doped region 22 will form a PN junction depletion layer in the N-type doped region 21, that is, form a photoelectric recombination center in the N-type doped region 21, thereby increasing the light generation in the N-type doped region 21. The number of carriers increases, thereby improving the light absorption ability of the photodiode, and finally improving the photoelectric conversion efficiency of the photodiode.

In the above photodiode, the smaller the volume of the first P-type doped region 22 is, the stronger the light absorption capability of the photodiode is, and thus the higher the photoelectric conversion efficiency of the photodiode is. In a preferred embodiment of the present application, the ratio of the volume of the first P-type doped region 22 to the volume of the N-type doped region 21 is <0.2. Setting the volume of the first P-type doped region 22 within the above range can improve the performance of the photodiode without affecting the potential well capacity of the photodiode.

In the above-mentioned photodiode, the doping amount of P-type ions in the first P-type doped region 22 needs to be greater than the doping amount of dopant ions in the N-type doped region 21, so as to form in the N-type doped region 21 P-type doped region. In a preferred embodiment of the present application, the ratio of the doping amount of P-type ions in the first P-type doping region 22 to the doping amount of N-type ions in the N-type doping region is 1.05˜1.2. Setting the ratio of the doping amounts of the two within the above-mentioned range can improve the light intensity of the first P-type doped region 22 located in the N-type doped region 21 without affecting the effect of the N-type doped region 21. absorption capacity, thereby improving the photoelectric conversion efficiency of the photodiode.

In the above-mentioned photodiode, the number and position of the first P-type doped region 22 can be set according to the size and position of the N-type doped region 21, so as to improve the effect of the N-type doped region 21 without affecting the effect. The photoelectric conversion efficiency of the photodiode 20. In a preferred embodiment, when only one first P-type doped region 22 is included in the photodiode 20, the first P-type doped region 22 is located on the centerline of the N-type doped region 21 perpendicular to the surface of the substrate 10 When the photodiode 20 includes a plurality of first P-type doped regions 22, the plurality of first P-type doped regions 22 are symmetrically arranged on the center line of the N-type doped region 21 perpendicular to the surface of the substrate 10 sides. The first P-type doped region 22 in the above-mentioned position can make the photoelectric recombination center evenly distributed in the N-type doped region 21, thereby improving the uniformity of photogenerated carriers in the N-type doped region 21, and further improving the photoelectricity. Photoelectric conversion efficiency of the diode.

In the above photodiode, the second P-type doped region 23 is the light absorption surface of the photodiode, and those skilled in the art can reasonably set the thickness of the second P-type doped region 23 according to the size of the CMOS image sensor. In a preferred embodiment of the present application, the thickness of the second P-type doped region 23 is 1/10˜1/20 of the thickness of the N-type doped region. If the thickness of the second P-type doped region 23 is too small, the photoelectric conversion efficiency increase of the photodiode may not be obvious; if the thickness of the second P-type doped region 23 is too large, the capacity of the potential well of the photodiode will be reduced , which may affect the photoelectric conversion efficiency. In this application, it is preferred that the thickness of the second P-type doped region 23 is 1/10-1/20 of the thickness of the N-type doped region, which is beneficial to improve the photoelectric conversion efficiency of the photodiode.

The application also provides a method for manufacturing the photodiode. As shown in FIG. 3, the manufacturing method includes: doping the upper surface of the substrate to form an N-type doped preparatory region; performing doping inside the N-type doped preparatory region to form a first P-type doped region; The upper surface of the substrate is doped twice to form a second P-type doped region above the first P-type doped region, and an N-type doped region connected to the lower surface of the second P-type doped region is formed. Miscellaneous area.

Exemplary embodiments according to the present application will be described in more detail below. These example embodiments may, however, be embodied in many different forms and should not be construed as limited to only the embodiments set forth herein. It should be understood that these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of these exemplary embodiments to those of ordinary skill in the art. and the thickness of the region, and the same reference numerals are used to designate the same devices, and thus their descriptions will be omitted.

FIG. 4 to FIG. 6 show schematic cross-sectional structure diagrams of the substrate obtained after various steps in the method for manufacturing the photodiode provided in the present application. The fabrication method of the photodiode provided by the present application will be further described below with reference to FIG. 4 to FIG. 6 .

Firstly, the upper surface of the substrate 10 is doped to form an N-type doped preparation region 21 ′, and then the base structure as shown in FIG. 4 is formed. In the above doping step, the energy and doping concentration of the doping ions can be selected according to the prior art. Preferably, the concentration of dopant ions is 1.0E+17˜1.0E+21 atoms/cm ³ , and the energy of dopant ion implantation is 100˜400 KeV. The above-mentioned doped ions may be phosphorous ions, and the doping process may include but not limited to ion implantation. It should be noted that the above substrate 10 may be single crystal silicon, silicon on insulator (SOI) or silicon germanium (SiGe), etc., and the substrate 10 is a P-type substrate, or a P well is formed in the substrate 10 .

In the step of forming the N-type doping preparation region 21 ′, defects will be introduced into the substrate 10 when doping the upper surface of the substrate 10 . Therefore, after the above-mentioned doping step, the substrate 10 may also be annealed to remove defects in the substrate 10 . In an optional implementation manner of the present application, the above annealing process conditions are as follows: the annealing temperature is 900-1200° C., and the annealing time is 30-60 seconds. Annealing under the above process conditions can remove defects in the substrate 10 and will not introduce new defects (such as lattice distortion caused by stress, etc.) into the substrate 10 .

After completing the step of doping the upper surface of the substrate 10 to form an N-type doped preparatory region 21', doping the inside of the N-type doped preparatory region 21' to form a first P-type doped region 22, and then Form the base structure as shown in Figure 5. In the above doping step, the N-type doping preparation region 21' is doped with doping ions having higher energy (much higher than the energy of the doping ions in the step of forming the N-type doping preparation region 21'), so as to The first P-type doped region 22 is formed by doping inside the N-type doped preparation region 21'; preferably, the doping ion concentration of the first P-type doped region 22 is higher than that of the N-type doped preparation region 21' The concentration of doping ions in the step is to form a P-type doping region. Preferably, the concentration of dopant ions in this step is 1.05E+17˜1.2E+21 atoms/cm ³ , and the implantation energy of dopant ions is 300˜600 KeV. The above-mentioned doped ions may be boron ions, and the doping process may include but not limited to ion implantation.

In the above step of forming the first P-type doped region 22 , when doping the above-mentioned N-type doped preparatory region 21 ′, defects will be introduced into the N-type doped preparatory region 21 ′. Therefore, after the above-mentioned doping of the N-type doping preparation region 21 ′, the substrate 10 may also be annealed to remove defects in the substrate 10 . In an optional implementation manner of the present application, the above annealing process conditions are as follows: the annealing temperature is 900-1200° C., and the annealing time is 30-60 seconds. Annealing under the above process conditions can remove defects in the N-type doped preparatory region 21 ′, and will not introduce new defects (such as lattice distortion caused by stress, etc.) into the N-type doped preparatory region 21 ′.

In the above step of forming the first P-type doped region 22 , the smaller the volume of the formed first P-type doped region 22 , the stronger the light absorption capability of the photodiode, and thus the higher the photoelectric conversion efficiency of the photodiode. In a preferred embodiment of the present application, the ratio of the volume of the first P-type doped region 22 formed by doping the inside of the N-type doped preparation region 21 ′ to the volume of the N-type doped region is <0.2. If the volume of the first P-type doped region 22 is larger than the above-mentioned volume, the potential well capacity of the photodiode will be affected, thereby reducing the performance of the photodiode.

After completing the step of doping the inside of the N-type doping preparatory region 21' to form the first P-type doping region 22, the upper surface of the substrate 10 is doped twice to form the first P-type doping region 22. A second P-type doped region 23 is formed above the region 22, and an N-type doped region 21 connected to the lower surface of the second P-type doped region 23 is formed, thereby forming a base structure as shown in FIG. 6 . In the second doping step, the dopant elements partly enter the N-type doping preparatory region 21 ′, and partly enter the substrate around the N-type doping preparatory region 21 ′. After the second doping step, part of the N-type doped preparatory region 21 ′ becomes the second P-type doped region 23 , and the remaining part forms the N-type doped region 21 . Preferably, the concentration of the dopant ions in this step is 1.05E+17˜1.2E+21 atoms/cm ³ , and the energy of the dopant ions is 300˜600 KeV. The above-mentioned doped ions may be boron ions, and the doping process may include but not limited to ion implantation.

In the above step of forming the second P-type doped region 23 and the N-type doped region, defects may be introduced into the substrate 10 when the upper surface of the substrate 10 is doped twice. Therefore, after the above-mentioned doping of the upper surface of the substrate 10 to form the second P-type doped region 23 and the N-type doped region, the substrate 10 may also be annealed to remove defects in the substrate 10 . In an optional implementation manner of the present application, the above annealing process conditions are as follows: the annealing temperature is 900-1200° C., and the annealing time is 30-60 seconds. Annealing under the above process conditions can remove defects in the substrate 10 and will not introduce new defects (such as lattice distortion caused by stress, etc.) into the substrate 10 .

In the step of forming the second P-type doped region 23 and the N-type doped region, the thickness of the second P-type doped region 23 formed by doping will affect the photoelectric conversion efficiency of the photodiode. In a preferred embodiment of the present application, the upper surface of the substrate 10 is doped so that the ratio of the thickness of the second P-type doped region 23 to the thickness of the N-type doped region is 1/10˜1/10. 20. If the thickness of the second P-type doped region 23 is less than the minimum value of the above range, the photoelectric conversion efficiency of the photodiode may not increase significantly; if the thickness of the second P-type doped region 23 is greater than the maximum value of the above range, the photodiode The potential well capacity will be significantly affected, which may affect the photoelectric conversion efficiency.

The present application also provides an image sensing device. The image sensor includes: a photodiode disposed on a substrate 10, wherein the photodiode is a photodiode provided in this application. Among them, the basic unit of an image sensor is a pixel, which is composed of a photodiode and 3 or 4 MOS transistors, referred to as 3T type or 4T type for short. Those skilled in the art can choose to use the 3T type or the 4T type according to the actual application field of the image sensor.

In a preferred implementation manner of the present application, the basic unit of the image sensor is composed of one photodiode and four MOS transistors, as shown in FIG. 7 . The CMOS image sensor includes: a substrate 10 and a photodiode 20, a transfer transistor 30, and a potential well 40 sequentially formed on the substrate 10, wherein the photodiode 20 includes an N-type doped region formed inside the substrate 10, forming The first P-type doped region inside the N-type doped region, and the second P-type doped region formed in the substrate 10 above the N-type doped region, the upper part of the second P-type doped region The surface can be exposed on the outside of the substrate 10, or it can be inside the N-type doped region, and the lower surface is connected to the upper surface of the N-type doped region; an active follower transistor 50 and a reset transistor 60 are formed on the potential well 40 , select the transistor 70 and the shallow trench isolation structure 80 . The transfer transistor 30 is located between the photodiode 20 and the potential well 40 , and the source region of the transfer transistor 30 is connected to the photodiode 20 , and the drain region of the transfer transistor 30 is connected to the source follower transistor 50 . In the above image sensor, the composition of the MOS transistor is a prior art, and will not be repeated here. The photoelectric conversion efficiency of the image sensor with the above structure is improved, thereby improving the photoelectric performance of the image sensor.

The fabrication method of the photodiode provided by the present application will be further described below with reference to the embodiments.

Example 1

This embodiment provides a method for fabricating a photodiode, comprising the following steps:

Phosphorus ion doping is performed on the upper surface of the Si substrate to form an N-type doped preparatory region. The doping concentration of phosphorus ions is 1.0E+17atoms/cm ³ , and the implantation energy of phosphorus ions is 100Kev. The thickness of the preparation area is 220nm;

Boron ions are doped inside the above-mentioned N-type doping preparation region to form the first P-type doping region, wherein the doping concentration of boron ions is 1.05E+17atoms/cm ³ , and the implantation energy of doping ions is 300Kev. The volume of the first P-type doped region is 2.4E+3nm ³ ;

Doping the upper surface of the Si substrate with boron ions to form a second P-type doped region above the first P-type doped region, and form an N-type doped region connected to the lower surface of the second P-type doped region. The doped region, wherein the doping concentration of boron ions is 1.05E+17atoms/cm ³ , the energy of the doped ions is 100Kev, the thickness of the second P-type doped region formed is 20nm, and the thickness of the N-type doped region is 200 nm, the volume of the N-type doped region is 8.6E+6nm ³ , and the ratio of the volume of the first P-type doped region to the volume of the N-type doped region is 2.8×10 ^-4 .

Example 2

This embodiment provides a method for fabricating a photodiode, comprising the following steps:

Phosphorus ion doping is performed on the upper surface of the Si substrate to form an N-type doped preparatory region. The doping concentration of phosphorus ions is 1.0E+ ²¹ atoms/cm ³ , and the implantation energy of phosphorus ions is 400Kev. The thickness of the preparation area is 420nm;

Boron ion doping is carried out to the inside of the above-mentioned N-type doping preparation area, and four first P-type doping regions 22 are formed on both sides of the centerline of the N-type doping region 21 perpendicular to the surface of the substrate 10, wherein boron The doping concentration of ions is 1.2E+21atoms/cm ³ , the implantation energy of doping ions is 600Kev, and the total volume of the formed first P-type doped region is 7.2E+4nm ³ ;

Doping the upper surface of the Si substrate with boron ions to form a second P-type doped region above the first P-type doped region, and form a N type doped region, wherein the doping concentration of boron ions is 1.2E+21atoms/cm ³ , the energy of the doped ions is 400Kev, the thickness of the second P-type doped region formed is 20nm, and the thickness of the N-type doped region The thickness is 400nm, the volume of the N-type doped region is 9.2E+6nm ³ , and the ratio of the volume of the first P-type doped region to the volume of the N-type doped region is 7.8×10 ^-3 .

Example 3

This embodiment provides a method for fabricating a photodiode, comprising the following steps:

Phosphorus ion doping is performed on the upper surface of the Si substrate to form an N-type doped preparatory region. The doping concentration of phosphorus ions is 1.1E+ ²¹ atoms/cm ³ , and the implantation energy of phosphorus ions is 500Kev. The thickness of the impurity preparation area is 500nm;

Boron ions are doped inside the above-mentioned N-type doping preparation region to form the first P-type doping region, wherein the doping concentration of boron ions is 1.6E+21atoms/cm ³ , and the implantation energy of doping ions is 700Kev. The volume of the first P-type doped region is 3.1E+5nm ³ ;

Doping the upper surface of the Si substrate with boron ions to form a second P-type doped region above the first P-type doped region, and form an N-type doped region connected to the lower surface of the second P-type doped region. The doping region, wherein the doping concentration of boron ions is 1.4E+21atoms/cm ³ , the energy of the doping ions is 600Kev, the thickness of the second P-type doping region formed is 20nm, and the thickness of the N-type doping region is The volume of the N-type doped region is 1.1E+6nm ³ , and the ratio of the volume of the first P-type doped region to the volume of the N-type doped region is 0.28.

Comparative example 1

This embodiment provides a method for fabricating a photodiode, comprising the following steps:

Phosphorus ion doping is performed on the upper surface of the Si substrate to form an N-type doped preparatory region. The doping concentration of phosphorus ions is 1.0E+17atoms/cm ³ , and the implantation energy of phosphorus ions is 100Kev. The thickness of the impurity preparation region was 220 nm.

The upper surface of the Si substrate is doped with boron ions to form a P-type doped region in part of the N-type doped preparation region and part of the Si substrate connected to it, and the remaining N-type doped preparation region is used as N type doped region, wherein the doping concentration of boron ions is 1.05E+17atoms/cm ³ , the energy of the doped ions is 100Kev, the thickness of the formed P-type doped region is 20nm, and the thickness of the N-type doped region is 200nm .

The photodiodes obtained in Examples 1 to 3 and Comparative Example 1 were tested by using the volt-ampere characteristic test method, and their photoelectric conversion efficiencies were calculated. Please refer to Table 1 for the test results.

Table 1

Photoelectric conversion efficiency Example 1 88% Example 2 89% Example 3 82% Comparative example 1 72%

As can be seen from the data in Table 1, the photoelectric conversion efficiency of the photodiodes obtained in Examples 1 to 3 is 82% to 89%, while the photoelectric conversion efficiency of the photodiodes obtained in Comparative Example 1 is only 72%, which is significantly lower than The photoelectric conversion efficiency of the photodiode that embodiment 1 to 3 obtains.

From the above description, it can be seen that the above-mentioned embodiments of the present application achieve the following technical effect: the first P-type doped region is formed in the N-type doped region of the photodiode. The first P-type doping region will form a PN junction depletion layer in the N-type doping region, thereby improving the photoelectric conversion efficiency of the photodiode.

The above descriptions are only preferred embodiments of the present application, and are not intended to limit the present application. For those skilled in the art, there may be various modifications and changes in the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of this application shall be included within the protection scope of this application.

Claims (10)

1. a kind of photodiode, it is characterised in that the photodiode includes：

N-type doping area, is formed in the inside of substrate；

First p-type doped region, is formed in the inside in the n-type doping area；

Second p-type doped region, is formed in the substrate, is mixed with the N-type positioned at n-type doping area top, and lower surface Miscellaneous area is connected；

In the photodiode,

During including the first p-type doped region, the first p-type doped region is located normal to the described of the substrate surface On the center line in n-type doping area；

During including multiple first p-type doped regions, multiple first p-type doped regions are symmetrically disposed in perpendicular to the lining The both sides of the center line in the n-type doping area of basal surface.

2. photodiode according to claim 1, it is characterised in that the photodiode includes one or more The first p-type doped region, and the ratio between the cumulative volume of the first p-type doped region and the volume in the n-type doping area ＜ 0.2.

3. photodiode according to claim 1, it is characterised in that p-type ion mixes in the first p-type doped region The ratio between miscellaneous amount and doping of N-type ion in the n-type doping area are 1.05~1.2.

4. photodiode according to any one of claim 1 to 3, it is characterised in that the second p-type doped region Thickness is the 1/10~1/20 of n-type doping area thickness.

5. a kind of preparation method of photodiode, it is characterised in that the preparation method includes：

Upper surface to substrate is doped to form n-type doping dark zone；

Inside to the n-type doping dark zone is doped, and forms the first p-type doped region；

Upper surface to the substrate carries out secondary doping, is adulterated with forming the second p-type in the top of the first p-type doped region Area, and form the n-type doping area being connected with the second p-type doped region lower surface；

In the photodiode,

During including the first p-type doped region, the first p-type doped region is located normal to the described of the substrate surface On the center line in n-type doping area；

During including multiple first p-type doped regions, multiple first p-type doped regions are symmetrically disposed in perpendicular to the lining The both sides of the center line in the n-type doping area of basal surface.

6. preparation method according to claim 5, it is characterised in that in the step of forming the n-type doping dark zone, mix The concentration of heteroion is 1.0E+17~1.0E+21atoms/cm³, the Implantation Energy of Doped ions is 100~400Kev.

7. preparation method according to claim 5, it is characterised in that right in the step of forming the first p-type doped region The inside of the n-type doping dark zone is doped, and forms the P with the ratio between the volume in n-type doping area ＜ 0.2 Type doped region.

8. preparation method according to claim 5, it is characterised in that in the step of forming the first p-type doped region, mix The concentration of heteroion is 1.05E+17~1.2E+21atoms/cm³, the Implantation Energy of Doped ions is 300~600Kev.

9. preparation method according to claim 5, it is characterised in that form the second p-type doped region and n-type doping area The step of in, the upper surface to the substrate carries out secondary doping, forms the thickness 1/10~1/ that thickness is the n-type doping area 20 the second p-type doped region.

10. a kind of image sensing device, including it is arranged at the photodiode on substrate, it is characterised in that the pole of the photoelectricity two Manage the photodiode any one of Claims 1-4.