CN108899335A - Back side illumination image sensor and preparation method thereof - Google Patents

Abstract

The technical solution of the present invention discloses a back-illuminated image sensor and a manufacturing method thereof. The back-illuminated image sensor includes a semiconductor substrate, a photodiode and a photodiode isolation structure located in the semiconductor substrate; An epitaxial layer, a floating diffusion region in the epitaxial layer, and a transfer gate penetrating through the epitaxial layer. The image sensor increases the area of the photodiode, effectively improving the quantum efficiency of the back-illuminated image sensor.

Description

Back-illuminated image sensor and manufacturing method thereof

technical field

The invention relates to a manufacturing technology of a semiconductor device, in particular to a back-illuminated image sensor and a manufacturing method thereof.

Background technique

An image sensor is a device that converts an optical image into an electrical signal. With the development of the computer and communication industries, the demand for high-performance image sensors is increasing. These high-performance image sensors are widely used in digital cameras, video recorders, personal communication systems (PCS), game consoles, security cameras, and medical miniature cameras. various fields.

Image sensors are generally of two types, Charge Coupled Device (CCD) sensors and CMOS Image Sensors (CMOS Image Sensors, CIS). Compared with CCD image sensors, CMOS image sensors have the advantages of high integration, low power consumption, and low production cost.

In the traditional CMOS photosensitive element, the photosensitive diode is located behind the circuit transistor, and the amount of incoming light will be affected by shading. The so-called back-illuminated CMOS is to turn it around so that the light first enters the photosensitive diode, thereby increasing the light sensitivity and significantly improving the shooting effect under low light conditions.

However, in a back-illuminated image sensor (BSI-CMOS Image Sensor) using a global shutter capture technology, its floating diffusion region (Floating Diffusion region, FD) is usually adjacent to the photodiode. This reduces the fill factor (eg size) of the photodiode, thus reducing the quantum efficiency (Quantum Efficiency) of the photodiode. In addition, the floating diffusion region is generally similar to a photodiode structure, so the floating diffusion region accumulates charge in response to incident radiation. This accumulation will contaminate the charge stored in the floating diffusion region and may cause imaging artifacts. To prevent radiation from contaminating the floating diffusion region, a metal shield is usually covered on the surface of the floating diffusion region. However, even if there is a metal shield, usually a lot of radiation reaches the floating diffusion region, making the global shutter efficiency (Global Shutter Efficiency, GSE) worse.

Contents of the invention

The technical problem to be solved by the technical solution of the present invention is: aiming at the defects that the quantum efficiency of the photodiode is reduced and the global shutter efficiency is deteriorated due to the adjacent arrangement of the floating diffusion region and the photodiode of the existing back-illuminated image sensor, to provide a A new structure of a back-illuminated image sensor and a fabrication method thereof improve the quantum efficiency of the back-illuminated image sensor and improve the global shutter efficiency.

In order to solve the above technical problems, the present invention provides a method for manufacturing a back-illuminated image sensor, comprising: providing a semiconductor substrate, forming a photodiode and a photodiode isolation structure in the semiconductor substrate; forming an epitaxial layer on the semiconductor substrate ; forming a floating diffusion region in the epitaxial layer; forming a transfer gate penetrating through the epitaxial layer in the epitaxial layer.

Optionally, the position of the floating diffusion area corresponds to the position of the photodiode and is not connected to the photodiode.

Optionally, the transmission gate includes a polysilicon layer and an insulating material layer between the polysilicon layer and the epitaxial layer for isolating the epitaxial layer and the polysilicon layer.

Optionally, the cross-sectional structure of the transmission grid is a rectangle, a circle, a rhombus or a cross.

Optionally, the doping type of the semiconductor substrate and the epitaxial layer is the same.

Optionally, when the photodiode is N-type doped, the photodiode isolation structure is P-type doped. The floating diffusion region is N-type doped, and the transmission gate is N-type doped.

The present invention also provides a back-illuminated image sensor, including:

A semiconductor substrate, a photodiode in the semiconductor substrate and a photodiode isolation structure; an epitaxial layer on the semiconductor substrate, a floating diffusion region in the epitaxial layer, and a transmission gate through the epitaxial layer.

Optionally, the position of the floating diffusion area corresponds to the position of the photodiode and is not connected to the photodiode.

Optionally, the transmission gate includes a polysilicon layer and an insulating material layer between the polysilicon layer and the epitaxial layer for isolating the epitaxial layer and the polysilicon layer.

Optionally, the cross-sectional structure of the transmission grid is a rectangle, a circle, a rhombus or a cross.

Optionally, the doping type of the semiconductor substrate and the epitaxial layer is the same.

Optionally, when the photodiode is N-type doped, the photodiode isolation structure is P-type doped. The floating diffusion region is N-type doped, and the transfer gate is N-type doped.

The technical solution has the following beneficial effects:

In the back-illuminated image sensor structure of the present invention, the photodiode and the photodiode isolation structure are arranged in the semiconductor substrate, an epitaxial layer is formed on the semiconductor substrate, and the transmission gate TG and the floating diffusion region are arranged in the epitaxial layer In this way, the area of the photodiode is increased, the quantum efficiency of the back-illuminated image sensor is effectively improved, and the incident radiation is prevented from accumulating charges in the floating diffusion area to pollute the floating diffusion area, and the global shutter efficiency of the image sensor is improved.

The manufacturing method of the back-illuminated image sensor according to the present invention first forms a photodiode and a photodiode isolation structure in the semiconductor substrate, then grows an epitaxial layer on the surface of the semiconductor substrate, and then forms a penetrating epitaxial layer in the epitaxial layer. Layer transfer gate TG and floating diffusion area, this transfer gate can control 4 photodiodes and floating diffusion area at the same time. Because the process of the present invention only forms the photodiode and the photodiode isolation structure in the semiconductor substrate, the transfer gate and the floating diffusion region are formed in the epitaxial layer, which increases the area of the photodiode and effectively improves the The quantum efficiency of the illuminated image sensor is improved, and the global shutter efficiency of the image sensor is improved by preventing the incident radiation from accumulating charges in the floating diffusion area to contaminate the floating diffusion area.

Description of drawings

1 to 9 are structural schematic diagrams corresponding to each step of the manufacturing method of the back-illuminated image sensor in the embodiment of the present invention;

FIG. 10 is a top structural view of the back-illuminated image sensor formed in the present invention;

FIG. 11 is another top structural view of the back-illuminated image sensor formed in the present invention;

Fig. 12 is another top structural view of the back-illuminated image sensor formed in the present invention;

FIG. 13 is another top structural view of the back-illuminated image sensor formed in the present invention.

Detailed ways

The inventive concept will be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the inventive concept are shown. Advantages and features of the inventive concept and methods of achieving them will be presented through the following exemplary embodiments described in more detail with reference to the accompanying drawings. It should be noted, however, that the inventive concept is not limited to the following exemplary embodiments but may be implemented in various forms. Therefore, the exemplary embodiments are provided only for the purpose of disclosing the present inventive concept and enabling those skilled in the art to understand the scope of the present inventive concept. In the drawings, embodiments of the inventive concept are not limited to the specific examples provided herein and are exaggerated for clarity.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular terms "a," "an," and "the" are intended to include the plural unless the context clearly dictates otherwise. As used herein, the term "and/or" includes any and all combinations of one or more of the associated listed items. It will be understood that when an element is referred to as being "connected" or "coupled" to another element, it can be directly connected or coupled to the other element or intervening elements may also be present.

Similarly, it will be understood that when an element such as a layer, region or substrate is referred to as being "on" another element, it can be directly on the other element or intervening elements may also be present. In contrast, the term "directly" means that there are no intervening elements. It should also be understood that the terms "comprising", "comprising", "comprising" and/or "comprising", when used herein, indicate the presence of stated features, integers, steps, operations, elements and/or components, but It does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and/or groups thereof.

In addition, the embodiments in the detailed description will be described using cross-sectional views that are idealized exemplary views of the inventive concept. Accordingly, the shapes of the exemplary illustrations may vary according to manufacturing techniques and/or allowable errors. Accordingly, embodiments of the inventive concepts are not limited to specific shapes shown in the exemplary diagrams, but may include other shapes that may be produced according to manufacturing processes. Regions illustrated in the figures have general attributes and are used to illustrate specific shapes of elements. Therefore, this should not be construed as limiting the scope of the inventive concept.

It will also be understood that although the terms first, second, third etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. Thus, a first element in some embodiments could be termed a second element in other embodiments without departing from the teachings of the present invention. The same reference numerals or the same reference designators denote the same elements throughout the specification.

Furthermore, exemplary embodiments are described by reference to cross-sectional illustrations and/or plan illustrations that are idealized exemplary illustrations. Accordingly, variations from the illustrated shapes as a result, for example, of manufacturing techniques and/or tolerances are to be expected. Thus, example embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an etched region illustrated as a rectangle will, typically, have rounded or curved features. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of example embodiments.

The technical solution of the present invention will be described in detail below in conjunction with the embodiments and the accompanying drawings.

1 to 9 are structural schematic diagrams corresponding to each step of the manufacturing method of the back-illuminated image sensor in the embodiment of the present invention. The manufacturing method of the back-illuminated image sensor includes: providing a semiconductor substrate 10, forming a photodiode 11 and a photodiode isolation structure 12 in the semiconductor substrate 10; forming an epitaxial layer 20 on the semiconductor substrate 10; A floating diffusion region 13 is formed in the epitaxial layer 20 ; a transmission gate 14 penetrating through the epitaxial layer 20 is formed in the epitaxial layer 20 .

Referring to Fig. 1, a semiconductor substrate 10 is provided, the semiconductor substrate 10 can be a silicon substrate, or the material of the semiconductor substrate 10 can also be germanium, silicon germanium, silicon carbide, gallium arsenide or gallium indium The semiconductor substrate 10 may also be a silicon-on-insulator substrate or a germanium-on-insulator substrate, or a substrate grown with an epitaxial layer.

In this embodiment, the semiconductor substrate 10 includes P-type silicon, and the P-type silicon is realized by performing P-type doping in the silicon substrate, for example, ion implantation or diffusion process is used to achieve full doping. When performing the doping process, the energy and doping concentration of the doping ions can be selected according to the prior art. The dopant ions are, for example, B, BF ₂ , etc., and the concentration range of the dopant ions is 1E14˜1E16/cm ³ .

As shown in FIG. 1, a first photomask pattern 31 is formed on the semiconductor substrate 10 by deposition and etching processes, and the first photomask pattern 31 is used to define the photoelectric pattern located in the semiconductor substrate. The position of the diode 11 (PD), the photodiode 11 is used to convert the received optical signal into an electrical signal. The photodiodes 11 described above can be arranged in a Bayer array in the semiconductor substrate 10 , and can also be arranged in any other array as required. In order to meet the requirement of thinning the total thickness of the semiconductor substrate 10 , generally, the positions of the photodiodes 11 in the semiconductor substrate 10 are substantially at the same depth.

Afterwards, referring to FIG. 1 and FIG. 2 , the first ion implantation process is performed more than once to form the photodiode 11 at a set position in the semiconductor substrate 10 , and then the first photomask pattern 31 is removed.

The first ion implantation process is, for example, N-type ion doping, the doping ion concentration range is 1E11-5E12/cm ³ , the doping ions include phosphorus, _AS plasma, and its doping in the semiconductor substrate The impurity depth is 2-2.5 microns.

The photodiode 11 is formed by performing more than one first ion implantation process, and the photodiode 11 is formed by adjusting the concentration and implantation depth of dopant ions implanted each time. The dopant ion implantation concentration and ion implantation depth used for each first ion implantation can be adjusted according to process requirements, which are not further limited here. After each execution of the first ion implantation process, an annealing process may be performed, on the one hand, for repairing the damage to the crystal lattice caused by the first ion implantation process, and on the other hand, to make the implanted ions in the first ion implantation process diffuse further and evenly.

In this embodiment, the first photomask pattern 31 is a hard mask layer (Hard mask), which is used to prevent the surface roughness of the semiconductor substrate during the subsequent ion implantation, and the first photomask pattern 31 is removed. The process of the pattern 31 is, for example, a wet etching process.

As shown in FIG. 3 and FIG. 4, a second photomask pattern 32 is formed on the semiconductor substrate 10 by deposition and etching processes, and the second photomask pattern 32 is used to define the The position of the photodiode isolation structure 12 (Photodiode Isolation, PDI) in 10 .

The photodiode isolation structure 12 is used to isolate each photodiode, and the arrangement of each photodiode isolation structure 12 in the semiconductor substrate 10 varies according to the change of the arrangement structure of the photodiodes 11. In selected embodiments, it is arranged as a well-shaped array. The positions of each of the photodiode isolation structures 12 in the semiconductor substrate 10 are substantially set at the same depth.

After that, referring to FIG. 3 and FIG. 4 , a second ion implantation process is performed to form the photodiode isolation structure 12 at a set position in the semiconductor substrate 10 , and then the second photomask pattern 32 is removed.

In the case that the semiconductor substrate is P-type doped and the photodiode is N-type doped, the second ion implantation process is, for example, a P-type ion doping process, and the doping ion concentration range is 1E12-1E13/cm ^3. The dopant ions include B ions, BF ₂ and so on. Its doping depth in the semiconductor substrate is 2-2.5 microns.

The dopant ion implantation type and ion implantation concentration used in the second ion implantation can be adjusted by those skilled in the art according to the process requirements, and the ion implantation depth can be adjusted according to the ion implantation depth of the photodiode, and no further details will be given here. limit. After performing the second ion implantation process, an annealing treatment process may be performed, on the one hand, to repair the damage to the crystal lattice caused by the second ion implantation process, and on the other hand, to make the implanted ions in the second ion implantation process diffuse further and evenly.

The process of removing the second photomask pattern 32 is, for example, a wet etching process.

Subsequently, the semiconductor substrate 10 is cleaned to remove the damage caused to the surface of the semiconductor substrate 10 during the above process of forming the photodiode 11 and the photodiode isolation structure 12 . The cleaning process includes: using the RCA cleaning method to clean the surface of the semiconductor substrate, performing a deionized water cleaning process on the surface of the semiconductor substrate after cleaning and drying, and performing low-temperature annealing on the surface of the semiconductor substrate to repair Surface defects.

The RCA cleaning method mainly uses SPM (H ₂ SO ₄ /H ₂ O ₂ ), DHF (H ₂ O ₂ /H ₂ O), APM (NH ₄ OH/H ₂ O ₂ /H ₂ O), HPM (HCL/H ₂ O ₂ /H ₂ O) and other chemical reagents to clean the semiconductor substrate.

Referring to FIG. 5 , an epitaxial layer 20 is formed on the semiconductor substrate 10 , the doping type of the epitaxial layer 20 is the same as that of the semiconductor substrate, and the doping ion concentration is also the same as that of the semiconductor substrate. In this embodiment, the formed epitaxial layer 20 has P-type doping.

The process for forming the epitaxial layer can be any epitaxial growth process known to those skilled in the art, and then the epitaxial layer is subjected to a P-type doping process, and the doping ions are, for example, B, BF ₂ , etc., The dopant ion concentration range is 1E14-1E16/cm ³ .

Referring to FIG. 6 and FIG. 7, a third photomask pattern 33 is formed on the epitaxial layer 20 by deposition and etching processes, and the third photomask pattern 33 is used to define the floating The position of the diffusion region 13 (Floating Diffusion region, FD), the floating diffusion region 13 is embedded in the epitaxial layer 20, its position corresponds to the position of the photodiode in the semiconductor substrate, it is located above the photodiode 11, and is not connected with The photodiode is connected.

Afterwards, referring to FIG. 6 and FIG. 7 , a third ion implantation process is performed to form the floating diffusion region 13 at a set position in the epitaxial layer 20 , and then the third photomask pattern 33 is removed.

The floating diffusion region 13 can receive the charges stored in the photodiode to accumulate the charges in the floating diffusion region. In this embodiment, the floating diffusion region 13 has N-type doping, and the doping ion concentration range is 1E13˜2E15/cm ³ .

The third ion implantation process includes at least one doping process of N-type ions, the doping ion concentration range is 1E13-2E15/cm ³ , and the doping ions include P ions and the like. The process of removing the third photomask pattern 33 is, for example, a wet etching process.

Referring to FIG. 8 , a fourth photomask pattern 34 is formed on the epitaxial layer 20 by deposition and etching processes, and the fourth photomask pattern 34 is used to define the transmission gate 14 located in the epitaxial layer 20 s position. Using the fourth photomask pattern 34 as a mask, the epitaxial layer 20 is etched to expose the semiconductor substrate to form a trench penetrating through the epitaxial layer 20 . The etching process is, for example, plasma etching.

Referring to Fig. 9, a transfer gate 14 is formed in the trench. The process of forming the transfer gate 14 includes: first filling the insulating material layer 14a on the epitaxial layer and the sidewall of the trench, then filling the insulating material layer 14a and the trench with N-type doped polysilicon 14b, and then using chemical The grinding process CMP removes the polysilicon 14b and the insulating material layer 14a on the epitaxial layer to form the transfer gate 14 filling the trench.

The transfer gate 14 is used to improve the transfer efficiency of the charge in the photodiode to the floating diffusion region 14, thereby improving the charge transfer efficiency of the image sensor.

Wherein, the insulating material layer may include silicon oxide or silicon nitride. The process for forming the insulating material layer is preferably a chemical vapor deposition process, such as plasma chemical vapor deposition.

After the manufacturing process of the back-illuminated image sensor described in the accompanying drawings 1 to 9 above, the top view of the formed back-illuminated image sensor is shown in FIG. 10 , wherein FIG. 9 is a cross-sectional structure along the AA direction in FIG. 10 schematic diagram.

It can be seen from FIG. 10 that the cross-sectional structure of the transmission grid 14 is a rectangular structure. According to the needs of process design, the cross-sectional structure of the transmission grid 14 can also be deformed in various ways, such as square. Except for the first time, refer to As shown in Figures 11 to 13, the cross-sectional structure of the transmission grid can also be a regular or irregular structure such as a circle, a rhombus, and a cross. The different cross-sectional structures can obtain channels with different lengths, which can adapt to different process requirements.

Using the manufacturing method of the back-illuminated image sensor described in the embodiment of the present invention, the photodiode (N-type) and the photodiode isolation structure PDI (P-type) are formed by ion implantation in the P-type semiconductor substrate first, and then in the semiconductor substrate A P-type epitaxial layer is grown on the surface of the substrate, and then a vertical transmission gate TG and a floating diffusion region 13 (N-type) are formed in the epitaxial layer. The transmission gate can simultaneously control four photodiodes and the floating diffusion region 13 . Because the process of the present invention only forms the photodiode and the photodiode isolation structure in the semiconductor substrate, the transfer gate and the floating diffusion region are formed in the epitaxial layer, which increases the area of the photodiode and effectively improves the The quantum efficiency of the illuminated image sensor is improved, and the global shutter efficiency of the image sensor is improved by preventing the incident radiation from accumulating charges in the floating diffusion area to contaminate the floating diffusion area.

Example 2

An embodiment of the present invention provides a back-illuminated image sensor structure, as shown in FIG. 9 , the back-illuminated image sensor structure includes:

Semiconductor substrate 10 and photodiode 11 and photodiode isolation structure array 12 located in semiconductor substrate 10; epitaxial layer 20 located on semiconductor substrate 10 and floating diffusion region 13 located in epitaxial layer 20 and penetrating the epitaxial layer 20 of the transmission grid 14 .

The semiconductor substrate 10 may be a silicon substrate, or the material of the semiconductor substrate 10 may also be germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, and the semiconductor substrate 10 may also be A silicon-on-insulator substrate or a germanium-on-insulator substrate, or a substrate grown with an epitaxial layer.

In this embodiment, the semiconductor substrate 10 includes P-type silicon, and the P-type silicon is realized by performing P-type doping in the silicon substrate, for example, ion implantation or diffusion process is used to achieve full doping. When performing the doping process, the energy and doping concentration of the doping ions can be selected according to the prior art. The dopant ions are, for example, B, BF ₂ , etc., and the concentration range of the dopant ions is 1E14˜1E16/cm ³ .

The photodiode 11 is used to convert the received optical signal into an electrical signal. The photodiodes 11 described above can be arranged in a Bayer array in the semiconductor substrate 10 , and can also be arranged in any other array as required. In order to meet the requirement of thinning the total thickness of the semiconductor substrate 10 , generally, the positions of the photodiodes 11 in the semiconductor substrate 10 are substantially at the same depth.

The photodiode 11 is doped with N-type ions, the doping ion concentration range is 1E11-5E12/cm ³ , the doping ions include phosphorus, _AS plasma, and its doping depth in the semiconductor substrate is 2-2.5 Microns.

The photodiode 11 is formed by performing more than one first ion implantation process, and the photodiode 11 is formed by adjusting the concentration and implantation depth of dopant ions implanted each time.

The photodiode isolation structure 12 is used to isolate each photodiode 11, and the arrangement of each photodiode isolation structure 12 in the semiconductor substrate 10 changes according to the arrangement structure of the photodiode 11. In one In an optional embodiment, they are arranged in a well-shaped array. The positions of each of the photodiode isolation structures 12 in the semiconductor substrate 10 are substantially set at the same depth.

When the semiconductor substrate is P-type doped and the photodiode is N-type doped, the photodiode isolation structure 12 is P-type doped, and the doping ion concentration range is 1E12-1E13/cm ³ . Ions include B _ions , BF2, etc. Its doping depth in the semiconductor substrate is 2-2.5 microns.

The doping type of the epitaxial layer 20 is the same as that of the semiconductor substrate, and the concentration of doping ions is also the same as that of the semiconductor substrate. In this embodiment, the formed epitaxial layer 20 has P-type doping. The dopant ions are, for example, B, BF ₂ , etc., and the concentration range of the dopant ions is 1E14˜1E16/cm ³ .

The floating diffusion region 13 is embedded in the epitaxial layer 20 , its position corresponds to that of the photodiode in the semiconductor substrate, it is located above the photodiode 11 , and is not connected to the photodiode. The floating diffusion region 13 can receive the charges stored in the photodiode to accumulate the charges in the floating diffusion region. In this embodiment, the floating diffusion region 13 has N-type doping, and the doping ion concentration range is 1E13˜2E15/cm ³ .

The transfer gate 14 runs through the epitaxial layer 20 and is used to improve the transfer efficiency of the charge in the photodiode to the floating diffusion region 14 , thereby improving the charge transfer efficiency of the image sensor.

The transfer gate 14 includes a polysilicon layer 14b and an insulating material layer 14a between the polysilicon layer and the epitaxial layer for isolating the epitaxial layer and the polysilicon layer. Wherein, the insulating material layer may include silicon oxide or silicon nitride.

The top view of the back-illuminated image sensor is shown in FIG. 10 , wherein FIG. 9 is a schematic cross-sectional structure diagram along the A'A' direction in FIG. 10 .

It can be seen from FIG. 10 that the cross-sectional structure of the transmission grid 14 is a rectangular structure. According to the needs of process design, the cross-sectional structure of the transmission grid 14 can also be deformed in various ways, such as a square. In addition, Referring to accompanying drawings 11 to 13, the cross-sectional structure of the transmission grid can also be a circle, a rhombus, a cross, etc., which are regular or irregular structures. The different cross-sectional structures can obtain channels with different lengths, which can adapt to different process requirements.

In the back-illuminated image sensor structure described in this embodiment, the photodiode and the photodiode isolation structure are arranged in the semiconductor substrate, an epitaxial layer is formed on the semiconductor substrate, and the transmission gate TG and the floating diffusion region are arranged in the epitaxial layer. In this way, the area of the photodiode is increased, the quantum efficiency of the back-illuminated image sensor is effectively improved, and the incident radiation is prevented from accumulating charges in the floating diffusion area to pollute the floating diffusion area, which improves the global shutter efficiency of the image sensor.

Although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art can use the methods and technical contents disclosed above to analyze the present invention without departing from the spirit and scope of the present invention. Therefore, any simple modification, equivalent change and modification made to the above implementation methods according to the technical essence of the present invention, which do not depart from the content of the technical solution of the present invention, all belong to the technical solution of the present invention. protected range.

Claims (14)

1. a kind of back side illumination image sensor, which is characterized in that including：

Semiconductor substrate and photodiode and photodiode isolation structure in semiconductor substrate；

Epitaxial layer in semiconductor substrate and the floating diffusion region in epitaxial layer and through the epitaxial layer Transmit grid.

2. back side illumination image sensor as described in claim 1, which is characterized in that the floating diffusion region position and photoelectricity two The position of pole pipe is corresponding and is not connected with photodiode.

3. back side illumination image sensor as described in claim 1, which is characterized in that the transmission grid include polysilicon layer and position For the insulation material layer of the epitaxial layer and polysilicon layer to be isolated between polysilicon layer and epitaxial layer.

4. back side illumination image sensor as described in claim 1, which is characterized in that the cross section structure of the transmission grid is rectangular Shape, round, diamond shape or cross.

5. back side illumination image sensor as described in claim 1, which is characterized in that the doping of the semiconductor substrate and epitaxial layer Type is identical.

6. back side illumination image sensor as described in claim 1, which is characterized in that when the photodiode is n-type doping, The photodiode isolation structure is p-type doping.

7. back side illumination image sensor as claimed in claim 6, which is characterized in that the floating diffusion region is n-type doping, institute Stating transmission grid is n-type doping.

8. a kind of production method of back side illumination image sensor, which is characterized in that including：

Semiconductor substrate is provided, photodiode and photodiode isolation structure are respectively formed in semiconductor substrate；

Epitaxial layer is formed on a semiconductor substrate；

Floating diffusion region is formed in the epitaxial layer；

The transmission grid for running through the epitaxial layer are formed in the epitaxial layer.

9. the production method of back side illumination image sensor as claimed in claim 8, which is characterized in that the floating diffusion region Position is corresponding with the position of photodiode and is not connected with photodiode.

10. the production method of back side illumination image sensor as claimed in claim 8, which is characterized in that the transmission grid include Polysilicon layer and the insulation material layer for being used to be isolated the epitaxial layer and polysilicon layer between polysilicon layer and epitaxial layer.

11. the production method of back side illumination image sensor as claimed in claim 8, which is characterized in that the transmission grid Cross section structure is rectangle, round, diamond shape or cross.

12. the production method of back side illumination image sensor as claimed in claim 8, which is characterized in that the semiconductor substrate It is identical as the doping type of epitaxial layer.

13. the production method of back side illumination image sensor as claimed in claim 8, which is characterized in that two pole of photoelectricity When pipe is n-type doping, the photodiode isolation structure is p-type doping.

14. the production method of back side illumination image sensor as claimed in claim 13, which is characterized in that the floating diffusion region Domain is n-type doping, and the transmission grid are n-type doping.