CN118263263A - Photoelectric sensor and forming method thereof - Google Patents

Abstract

A photoelectric sensor and a forming method thereof, the photoelectric sensor includes: the substrate comprises a photosensitive pixel area, the photosensitive pixel area comprises a plurality of pixel unit areas distributed in a matrix, and a grid structure is formed on the substrate of the pixel unit areas; the first type doped region is positioned in the substrate at one side of the grid structure in the pixel unit region; the second type doped region is positioned in the substrate at the top of the photosensitive pixel region, and comprises a covering part which extends to cover the photosensitive pixel region and a protruding part which is positioned in the first type doped region and protrudes from the covering part, and the doping types of the second type doped region and the first type doped region are different. The invention is beneficial to improving the full well capacity of the photoelectric sensor, improving the signal-to-noise ratio and the dynamic range of the image sensor and improving the imaging quality.

Description

Photoelectric sensor and method of forming the same

Technical Field

The embodiments of the present invention relate to the field of semiconductor manufacturing, and in particular to a photoelectric sensor and a method for forming the same.

Background technique

Photoelectric sensors are devices that convert light signals into electrical signals. Their working principle is based on the photoelectric effect, which refers to the phenomenon that when light shines on certain substances, the electrons of the substances absorb the energy of photons and produce corresponding electrical effects.

For example, CCD (Charge Coupled Device) image sensors and CMOS (CMOS Image Senser, CIS) image sensors use the photoelectric conversion function to convert optical images into electrical signals and then output digital images. They are currently widely used in digital cameras and other electronic optical devices. CMOS image sensors are gradually replacing CCDs due to their advantages such as simple process, easy integration with other devices, small size, light weight, low power consumption, and low cost. Currently, CMOS image sensors are widely used in digital cameras, camera phones, digital video cameras, medical imaging devices (such as gastroscopes), automotive imaging devices, and other fields.

Currently, in high-speed CIS image sensors, since the exposure time is very short, a large pixel full well capacity (FWC) is required to increase the sensitivity.

Summary of the invention

The problem solved by the embodiments of the present invention is to provide a photoelectric sensor and a method for forming the same, so as to improve the imaging quality.

To solve the above problems, an embodiment of the present invention provides a photoelectric sensor, including: a substrate, the substrate including a photosensitive pixel area, the photosensitive pixel area including a plurality of pixel unit areas distributed in a matrix, a gate structure formed on the substrate of the pixel unit area; a first-type doping region, located in the substrate on one side of the gate structure in the pixel unit area; a second-type doping region, located in the substrate at the top of the photosensitive pixel area, the second-type doping region including a covering portion extending to cover the photosensitive pixel area, and a protruding portion located in the first-type doping region and protruding from the covering portion, the second-type doping region and the first-type doping region have different doping types.

An embodiment of the present invention also provides a method for forming a photoelectric sensor, including: providing a substrate, the substrate including a photosensitive pixel area, the photosensitive pixel area including a plurality of pixel unit areas distributed in a matrix, a gate structure formed on the substrate of the pixel unit area, and a first-type doped region formed in the substrate on one side of the gate structure in the pixel unit area; performing ion implantation on the substrate to form a second-type doped region in the substrate located at the top of the photosensitive pixel area, the second-type doped region including a covering portion extending to cover the photosensitive pixel area, and a protruding portion located in the first-type doped region and protruding from the covering portion, the second-type doped region and the first-type doped region having different doping types.

Compared with the prior art, the technical solution of the embodiment of the present invention has the following advantages:

In the photoelectric sensor provided by the embodiment of the present invention, the covering portion of the second-type doping region extends to cover the photosensitive pixel region. The second-type doping region has a different doping type from the first-type doping region. The covering portion can reduce the leakage of electrons from the top of the first-type doping region during photoelectric conversion, thereby reducing the probability of leakage at the top of the first-type doping region. The convex portion of the second-type doping region is located in the first-type doping region and protrudes from the covering portion. The second-type doping region has a different doping type from the first-type doping region. The convex portion located in the first-type doping region can form a PN junction with the first-type doping region. In the photoelectric sensor, by adding the second-type doping region to the first-type doping region, the contact area between the first-type doping region and the second-type doping region is increased, which is beneficial to increasing the PN junction area, thereby facilitating an increase in the rate at which the PN junction generates electrons, and further facilitating an increase in the full well capacity of the photoelectric sensor, an improvement in the signal-to-noise ratio and dynamic range of the image sensor, and an improvement in imaging quality.

In the method for forming a photoelectric sensor provided by an embodiment of the present invention, the covering portion of the second-type doping region extends to cover the photosensitive pixel region, and the second-type doping region has a different doping type from the first-type doping region. The covering portion can reduce the leakage of electrons from the top of the first-type doping region during photoelectric conversion, thereby reducing the probability of leakage at the top of the first-type doping region. The convex portion of the second-type doping region is located in the first-type doping region and protrudes from the covering portion. The second-type doping region has a different doping type from the first-type doping region. The convex portion located in the first-type doping region can form a PN junction with the first-type doping region. In the photoelectric sensor, by adding the second-type doping region to the first-type doping region, the contact area between the first-type doping region and the second-type doping region is increased, which is beneficial to increasing the PN junction area, thereby facilitating an increase in the rate at which the PN junction generates electrons, and further facilitating an increase in the full well capacity of the photoelectric sensor, an improvement in the signal-to-noise ratio and dynamic range of the image sensor, and an improvement in imaging quality.

BRIEF DESCRIPTION OF THE DRAWINGS

1 to 3 are schematic structural diagrams corresponding to an embodiment of a photoelectric sensor of the present invention;

4 to 9 are schematic structural diagrams corresponding to the steps in an embodiment of a method for forming a photoelectric sensor of the present invention.

Detailed ways

As can be seen from the background technology, the imaging quality of currently formed photoelectric sensors needs to be improved.

Full well capacity (FWC) refers to the maximum amount of charge that the capacitor of a photodiode can accumulate. It is an important indicator of a CIS image sensor. When the full well capacity is saturated, the energy of the photodiode to collect new electrons decreases, which has a significant impact on the image quality, especially in the high dynamic range.

The way to improve the full well capacity is to increase the size of the pixel unit area, but this method is bound to affect the integration of the photoelectric sensor, which is not conducive to the development trend of higher integration in the semiconductor manufacturing field; the full well capacity can also be improved by increasing the doping concentration of the N-type doping area, but this method has high requirements on the isolation effect of the P-type doping area between adjacent N-type doping areas, and it is easy to cause leakage problems between adjacent pixel unit areas due to excessive concentration of the N-type doping area; the full well capacity can also be improved by increasing the depth of the pixel unit area, but this method has a greater challenge for the ion implantation process for forming the N-type doping area.

Therefore, it is currently difficult to improve the full well capacity and thus difficult to improve the imaging quality of the photoelectric sensor.

In order to solve the technical problem, an embodiment of the present invention provides a photoelectric sensor, including: a substrate, the substrate including a photosensitive pixel area, the photosensitive pixel area including a plurality of pixel unit areas distributed in a matrix, a gate structure formed on the substrate of the pixel unit area; a first-type doping region, located in the substrate on one side of the gate structure in the pixel unit area; a second-type doping region, located in the substrate at the top of the photosensitive pixel area, the second-type doping region including a covering portion extending to cover the photosensitive pixel area, and a convex portion located in the first-type doping region and protruding from the covering portion, the second-type doping region and the first-type doping region have different doping types.

In the photoelectric sensor provided by the embodiment of the present invention, the covering portion of the second-type doping region extends to cover the photosensitive pixel region. The second-type doping region has a different doping type from the first-type doping region. The covering portion can reduce the leakage of electrons from the top of the first-type doping region during photoelectric conversion, thereby reducing the probability of leakage at the top of the first-type doping region. The convex portion of the second-type doping region is located in the first-type doping region and protrudes from the covering portion. The second-type doping region has a different doping type from the first-type doping region. The convex portion located in the first-type doping region can form a PN junction with the first-type doping region. In the photoelectric sensor, by adding the second-type doping region to the first-type doping region, the contact area between the first-type doping region and the second-type doping region is increased, which is beneficial to increasing the PN junction area, thereby facilitating an increase in the rate at which the PN junction generates electrons, and further facilitating an increase in the full well capacity of the photoelectric sensor, an improvement in the signal-to-noise ratio and dynamic range of the image sensor, and an improvement in imaging quality.

In order to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and understandable, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

1 to 3 , which are schematic structural diagrams corresponding to an embodiment of a photoelectric sensor of the present invention.

1( a ) is a top view of the substrate, FIG. 1( b ) is a partial enlarged view of any photosensitive pixel area in FIG. 1( a ), FIG. 2 is a cross-sectional view corresponding to FIG. 1( a ), and FIG. 3 is a top view of FIG. 2 . The photoelectric sensor includes: a substrate 101, the substrate 101 includes a photosensitive pixel area P, the photosensitive pixel area P includes a plurality of pixel unit areas 101 a distributed in a matrix, a gate structure 201 is formed on the substrate 101 of the pixel unit area 101 a; a first-type doping area 111, located in the substrate 101 on one side of the gate structure 201 in the pixel unit area 101 a; a second-type doping area 141, located in the substrate 101 at the top of the photosensitive pixel area P, the second-type doping area 141 includes a covering portion 131 extending to cover the photosensitive pixel area P, and a protruding portion 121 located in the first-type doping area 111 and protruding from the covering portion 131, and the second-type doping area 141 has a different doping type from the first-type doping area 111.

As an example, in this embodiment, the photoelectric sensor is described as a CMOS image sensor.

In other embodiments, the photoelectric sensor may also be a CCD (Charge Coupled Device) image sensor, a DTOF (Direct Time of Flight) sensor, or an iTOF (indirect Time of Flight) sensor, etc.

In this embodiment, the substrate 101 is a substrate of a pixel wafer, and the substrate 101 of the pixel wafer is a silicon substrate. In other embodiments, the material of the substrate of the pixel wafer may also be other materials such as germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, and the substrate of the pixel wafer may also be other types of materials such as a silicon substrate on an insulator or a germanium substrate on an insulator.

The photosensitive pixel area P is used to receive an optical signal so as to convert the optical signal into an electrical signal.

In the pixel wafer, there are a plurality of photosensitive pixel regions P, which are arranged in a matrix. The pixel unit region 101 a is used to form pixels.

The gate structure 201 is used to realize the normal device function in the pixel wafer and to control the opening and closing of the channel in the semiconductor structure.

In this embodiment, a dielectric layer 211 covering the gate structure 201 is further formed on the substrate 101 .

The dielectric layer 211 is used to achieve mutual isolation between devices.

In this embodiment, the material of the dielectric layer 211 is an insulating material, including one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon carbonitride and silicon carbon oxynitride.

In this embodiment, the photoelectric sensor is a frontside illumination (FSI) photoelectric sensor.

Correspondingly, in this embodiment, the pixel wafer is a front-illuminated pixel wafer, and the top surface of the dielectric layer 211 is a photosensitive surface, that is, the surface of the dielectric layer 211 facing away from the substrate 101 is a photosensitive surface.

In this embodiment, only a portion of the photosensitive pixel region P and the pixel unit region 101a are shown in the figure, and the pixel unit region 101a may also include a device structure such as a photoelectric element (e.g., a photodiode). Among them, the photodiode may be a back-illuminated single photon avalanche diode (SPAD). For the purpose of simplicity, the detailed structure of the above components is not shown in the embodiment of the present invention.

In other embodiments, the photosensor may also be a backside illumination (BSI) photosensor.

Correspondingly, in other embodiments, the pixel wafer is a back-illuminated pixel wafer, a logic wafer is bonded to a side of the dielectric layer facing away from the substrate, and a side of the substrate facing away from the logic wafer is a photosensitive surface.

The logic wafer is used to analyze and process the electrical signals provided by the pixel wafer.

By setting the photosensitive pixel area and the logic area on two wafers respectively and bonding the pixel wafer and the logic wafer together, a larger pixel area can be obtained, which helps shorten the path of light reaching the photoelectric element, reduce the scattering of light, and make the light more focused, thereby improving the photosensitivity of the photoelectric sensor in a low-light environment and reducing system noise and crosstalk.

In other embodiments, the substrate of the pixel wafer is used as the first substrate, and the logic wafer has a second substrate. The second substrate of the logic wafer may be a silicon substrate. In other embodiments, the material of the second substrate of the logic wafer may also be other materials such as germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, and the second substrate of the logic wafer may also be other types of materials such as a silicon substrate on an insulator or a germanium substrate on an insulator.

Accordingly, in other embodiments, a logic transistor is also formed in the logic wafer, and the logic transistor is used to perform logic processing on the electrical signal provided by the pixel wafer. Specifically, the logic transistor may include a logic gate structure located on the logic wafer, and a logic drain region and a logic source region located in the logic wafer on both sides of the logic gate structure.

The bonding between the pixel wafer and the logic wafer is achieved through hybrid bonding.

Specifically, a first interconnect structure is formed on the pixel wafer, and a second interconnect structure is formed on the logic wafer. The pixel wafer and the logic wafer can be bonded together by dielectric bonding, and then the first interconnect structure and the second interconnect structure can be electrically connected.

The first interconnect structure may be a first metal line, or the first interconnect structure is a first through silicon via interconnect structure (TSV), or the first interconnect structure includes a first through-hole interconnect structure and a first metal line located on the first through-hole interconnect structure; the second interconnect structure may be a second metal line, or the second interconnect structure is a second through-hole interconnect structure (TSV), or the second interconnect structure includes a second through-hole interconnect structure and a second metal line located on the second through-hole interconnect structure.

It should be noted that the above method of bonding the pixel wafer and the logic wafer is only used as an embodiment, and the bonding method between the pixel wafer and the logic wafer is not limited to this. For example: in other embodiments, the bonding method between the pixel wafer and the logic wafer can also be direct bonding (such as melt bonding and anodic bonding) or indirect bonding technology (such as metal eutectic, hot pressing bonding and adhesive bonding).

During the operation of the photoelectric sensor, the generated electrons move toward the first-type doping region 111 , and the first-type doping region 111 is used to accumulate electrons during the photoelectric conversion process.

Specifically, in this embodiment, the doping type of the first-type doping region 111 is N-type, and the doping ions of the N-type doping region are N-type ions, which include P ions, As ions, or Sb ions.

The N-type doped region is connected to a high potential during the operation of the photoelectric sensor. The majority carriers in the N-type doped region are electrons, and the concentration of free electrons is much greater than the concentration of holes. Therefore, the N-type doped region is an area for accumulating electrons.

The N-type doped region, as the main photogenerated carrier generation and storage region, is located below the light trap (not shown), which can effectively increase the photogenerated carrier generation efficiency and is beneficial to improving the performance of the photoelectric sensor.

In this embodiment, the second-type doping region 141 includes a covering portion 131 extending to cover the photosensitive pixel region P, and a protruding portion 121 located in the first-type doping region 111 and protruding from the covering portion 131. The second-type doping region 141 has a different doping type from the first-type doping region 111.

The different doping types between the second-type doping region 141 and the first-type doping region 111 refer to that the conductivity types of doped ions in the second-type doping region 141 and the first-type doping region 111 are different.

The top of the first-type doping region 111 is sealed with a covering portion 131 having a different conductivity type of doped ions, so as to reduce the leakage of electrons from the top of the first-type doping region 111 during photoelectric conversion.

The raised portion 121 is used to increase the contact area between the first type doping region 111 and the second type doping region 141 , thereby increasing the PN junction area.

In this embodiment, the covering portion 131 of the second-type doping region 141 extends to cover the photosensitive pixel area P. The second-type doping region 141 is different from the first-type doping region 111 in doping type. The covering portion 131 can reduce the leakage of electrons from the top of the first-type doping region 111 during photoelectric conversion, thereby reducing the probability of leakage at the top of the first-type doping region 111. The protruding portion of the second-type doping region 141 is located in the first-type doping region 111 and protrudes from the covering portion 131. The second-type doping region 141 is different from the first-type doping region 111 in doping type. The protruding portion 121 located in the first-type doping region 111 can form a PN junction with the first-type doping region 111. In the photoelectric sensor, by adding the second-type doping region 141 to the first-type doping region 111, the contact area between the first-type doping region 111 and the second-type doping region 141 is increased, which is beneficial to increase the PN junction area, thereby facilitating an increase in the rate at which the PN junction generates electrons, and further facilitating an increase in the full well capacity of the photoelectric sensor, an improvement in the signal-to-noise ratio and dynamic range of the image sensor, and an improvement in imaging quality.

In this embodiment, the doping type of the first-type doping region 111 is N-type, and correspondingly, the doping type of the second-type doping region 141 is P-type. The second-type doping region 141 contacts the first-type doping region 111 to form a PN junction.

Specifically, in the present embodiment, the doping type of the second-type doping region 141 is P-type, and the doping ions of the P-type doping region are P-type ions, and the P-type ions include B ions, Ga ions, or In ions.

It should be noted that, in this embodiment, the doping concentration of the second-type doping region 141 should not be too large or too small. If the doping concentration of the second-type doping region 141 is too large, it is easy to cause the second-type doping region 141 to diffuse too much into the first-type doping region 111, thereby causing the second-type doping region 141 to occupy too much of the area of the first-type doping region 111, which in turn causes the occupied area of the first-type doping region 111 to be reduced, affecting the electron accumulation capacity of the first-type doping region 111, thereby affecting the full well capacity of the photoelectric sensor; if the doping concentration of the second-type doping region 141 is too small, it is easy to affect the effect of forming a PN junction between the second doping region 141 and the first doping region 111, thereby affecting the effect of increasing the PN junction area, and further making it difficult to increase the full well capacity of the photoelectric sensor. For this reason, in this embodiment, the doping concentration of the second-type doping region 121 is 1E12 atom/cm ³ to 1E14atom/cm ³ .

In this embodiment, in the pixel unit region 100 a , each first-type doping region 111 has a plurality of protruding portions 121 protruding from the covering portion 131 .

Each first-type doping region 111 has a plurality of protruding portions 121 protruding from the covering portion 131, which correspondingly increases the number of side walls of the protruding portions 121 in the first-type doping region 111, which is beneficial to increase the side wall area of the second-type doping region 121 in contact with the first-type doping region 111, and is beneficial to further increase the PN junction area, thereby facilitating an increase in the rate at which the PN junction generates electrons, and further facilitating an increase in the full well capacity of the photoelectric sensor, thereby improving the signal-to-noise ratio and dynamic range of the image sensor, and improving the imaging quality.

In practical applications, the morphology of the raised portion 121 can be adjusted according to actual needs to obtain different contact areas between the second-type doping region 121 and the first-type doping region 111, and correspondingly obtain different PN junction areas, thereby flexibly adjusting the full well capacity of the photoelectric sensor.

Specifically, referring to Figure 3, Figure 3 shows the distribution of the protrusions 121 in the first type doping region 111. In the pixel unit area 100a, the top-view shape of the distribution of the protrusions 121 of the second doping region 141 in the first type doping region 111 includes strips, rings, arrays or grids.

In this embodiment, the covering portion 131 and the protruding portion 121 are an integrated structure. In the process of forming the photoelectric sensor, the covering portion 131 and the protruding portion 121 of the second doping region 141 are formed in the same step, so there is no need to add additional steps to form the protruding portion 121, which is conducive to simplifying the process flow and improving process efficiency.

It should be noted that, in this embodiment, the doping depth of the protruding portion 121 in the second-type doping region 141 should not be too large or too small. If the doping depth of the protruding portion 121 in the second-type doping region 141 is too large, it is easy to cause the protruding portion 121 to occupy too much area of the first-type doping region 111, which correspondingly causes the occupied area of the first-type doping region 111 to be reduced, affecting the electron accumulation capacity of the first-type doping region 111, thereby affecting the full well capacity of the photoelectric sensor; if the doping depth of the protruding portion 121 in the second-type doping region 141 is too small, it is easy to cause the contact area between the protruding portion 121 and the side wall of the first-type doping region 111 to be too small, making it difficult to achieve the effect of increasing the PN junction area, thereby increasing the rate at which the PN junction generates electrons, and further increasing the full well capacity of the photoelectric sensor. For this reason, in this embodiment, the doping depth of the protruding portion 121 in the second-type doping region 141 is 10nm to 500nm.

It should also be noted that, in this embodiment, the doping depth of the covering portion 131 in the second-type doping region 141 should not be too large or too small. If the doping depth of the covering portion 131 in the second-type doping region 141 is too large, it is easy to cause the covering portion 131 to occupy too much area of the first-type doping region 111, which correspondingly causes the occupied area of the first-type doping region 111 to be reduced, affecting the first-type doping region 111's ability to accumulate electrons, thereby affecting the full well capacity of the photoelectric sensor; if the doping depth of the covering portion 131 in the second-type doping region 141 is too small, it is difficult for the covering portion 131 to play a good sealing role on the top of the first-type doping region 111, thereby making it difficult to reduce the leakage of electrons at the top of the first-type doping region 111 during photoelectric conversion, and further making it difficult to reduce the probability of leakage at the top of the first-type doping region 111, thereby affecting the performance of the photoelectric sensor. For this reason, in this embodiment, the doping depth of the covering portion 131 in the second-type doping region 141 is 10nm to 100nm.

In this embodiment, the photoelectric sensor also includes: a third-type doping region (not shown), which is located in the substrate 101 of the photosensitive pixel area P and covers the side walls and bottom surface of the first-type doping region 111, and the doping type of the third-type doping region is different from the doping type of the first-type doping region 111.

The doping type of the third-type doping region is the same as the doping type of the first-type doping region 111 . Accordingly, the doping type of the third-type doping region is P-type, and the doping ions of the P-type doping region are P-type ions, which include B ions, Ga ions or In ions.

The third-type doping region is used to isolate the adjacent first-type doping region 111. The third-type doping region covers the sidewalls and bottom surface of the first-type doping region 111, which is beneficial to reduce the electron leakage from the sidewalls and bottom surface of the first-type doping region 111 during photoelectric conversion. The third-type doping region is in contact with the first-type doping region 111 and can also form a PN junction with the first-type doping region 111 to realize the normal function of the photoelectric sensor.

4 to 9 are schematic structural diagrams corresponding to the steps in an embodiment of a method for forming a photoelectric sensor of the present invention.

Referring to Figures 4 to 5, Figure 4(a) is a top view of the substrate, Figure 4(b) is a local enlarged view of any photosensitive pixel area in Figure 4(a), and Figure 5 is a cross-sectional view corresponding to Figure 4(a). A substrate 100 is provided, and the substrate 100 includes a photosensitive pixel area P. The photosensitive pixel area P includes a plurality of pixel unit areas 100a distributed in a matrix. A gate structure 200 is formed on the substrate 100 of the pixel unit area 100a, and a first-type doping area 110 is formed in the substrate 100 on one side of the gate structure 200 in the pixel unit area 100a.

As an example, in this embodiment, the photoelectric sensor is described as a CMOS image sensor.

In other embodiments, the photoelectric sensor may also be a CCD (Charge Coupled Device) image sensor, a DTOF (Direct Time of Flight) sensor, or an iTOF (indirect Time of Flight) sensor, etc.

In this embodiment, the substrate 100 is a substrate of a pixel wafer, and the substrate 100 of the pixel wafer is a silicon substrate. In other embodiments, the material of the substrate of the pixel wafer may also be other materials such as germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, and the substrate of the pixel wafer may also be other types of materials such as a silicon substrate on an insulator or a germanium substrate on an insulator.

The photosensitive pixel area P is used to receive an optical signal so as to convert the optical signal into an electrical signal.

In the pixel wafer, there are multiple photosensitive pixel regions P, and the multiple photosensitive pixel regions P are arranged in a matrix. The pixel unit region 100a is used to form pixels.

The gate structure 200 is used to realize the normal device function in the pixel wafer and to control the opening and closing of the channel in the semiconductor structure.

During the operation of the photoelectric sensor, the generated electrons move toward the first-type doping region 110 , and the first-type doping region 110 is used to accumulate electrons during the photoelectric conversion process.

Specifically, in the present embodiment, the doping type of the first-type doping region 110 is N-type, and the doping ions of the N-type doping region are N-type ions, which include P ions, As ions, or Sb ions.

The N-type doped region is connected to a high potential during the operation of the photoelectric sensor. The majority carriers in the N-type doped region are electrons, and the concentration of free electrons is much greater than the concentration of holes. Therefore, the N-type doped region is an area for accumulating electrons.

The N-type doped region, as the main photogenerated carrier generation and storage region, is located below the light trap (not shown), which can effectively increase the photogenerated carrier generation efficiency and is beneficial to improving the performance of the photoelectric sensor.

In the present embodiment, in the step of providing the substrate 100 , a third type doping region (not shown) is also formed in the substrate 100 of the photosensitive pixel area P, covering the side walls and bottom surface of the first type doping region 110 , and the doping type of the third type doping region is different from the doping type of the first type doping region 110 .

The doping type of the third type doping region is different from the doping type of the first type doping region 110. Accordingly, the doping type of the third type doping region is P type, and the doping ions of the P type doping region are P type ions, which include B ions, Ga ions or In ions.

The third-type doping region is used to isolate the adjacent first-type doping region 110. The third-type doping region covers the sidewalls and bottom surface of the first-type doping region 110, which is beneficial to reduce the electron leakage from the sidewalls and bottom surface of the first-type doping region 110 during photoelectric conversion. The third-type doping region is in contact with the first-type doping region 110 and can also form a PN junction with the first-type doping region 110 to realize the normal function of the photoelectric sensor.

With reference to Figures 6 to 9, Figure 9 is a top view, in which ion implantation is performed on the substrate 100 to form a second-type doping region 140 in the substrate 100 located at the top of the photosensitive pixel region P, the second-type doping region 140 includes a covering portion 130 extending to cover the photosensitive pixel region P, and a protruding portion 120 located in the first-type doping region 110 and protruding from the covering portion 130, and the second-type doping region 140 has a different doping type from the first-type doping region 110.

In this embodiment, the second-type doping region 140 includes a covering portion 130 extending to cover the photosensitive pixel region P, and a protruding portion 120 located in the first-type doping region 110 and protruding from the covering portion 130 . The second-type doping region 140 and the first-type doping region 110 have different doping types.

The different doping types between the second-type doping region 140 and the first-type doping region 110 means that the conductivity types of the doped ions in the second-type doping region 140 and the first-type doping region 110 are different.

The top of the first-type doping region 110 is sealed with a covering portion 130 having a different conductivity type of doped ions, so as to reduce the leakage of electrons from the top of the first-type doping region 110 during photoelectric conversion.

The raised portion 120 is used to increase the contact area between the first type doping region 110 and the second type doping region 140 , thereby increasing the PN junction area.

In this embodiment, the covering portion 130 of the second-type doping region 140 extends to cover the photosensitive pixel area P. The second-type doping region 140 is different from the first-type doping region 110 in doping type. The covering portion 130 can reduce the leakage of electrons from the top of the first-type doping region 110 during photoelectric conversion, thereby reducing the probability of leakage at the top of the first-type doping region 110. The protruding portion of the second-type doping region 140 is located in the first-type doping region 110 and protrudes from the covering portion 130. The second-type doping region 140 is different from the first-type doping region 110 in doping type. The protruding portion 120 located in the first-type doping region 110 can form a PN junction with the first-type doping region 110. In the photoelectric sensor, by adding the second-type doping region 140 to the first-type doping region 110, the contact area between the first-type doping region 110 and the second-type doping region 140 is increased, which is beneficial to increase the PN junction area, thereby facilitating an increase in the rate at which the PN junction generates electrons, and further facilitating an increase in the full well capacity of the photoelectric sensor, an improvement in the signal-to-noise ratio and dynamic range of the image sensor, and an improvement in imaging quality.

In this embodiment, the doping type of the first-type doping region 110 is N-type, and correspondingly, the doping type of the second-type doping region 140 is P-type. The second-type doping region 140 contacts the first-type doping region 110 to form a PN junction.

Specifically, in the present embodiment, the doping type of the second-type doping region 140 is P-type, and the doping ions of the P-type doping region are P-type ions, and the P-type ions include B ions, Ga ions, or In ions.

It should be noted that, in this embodiment, the doping concentration of the second type doping region 140 should not be too large or too small. If the doping concentration of the second type doping region 140 is too large, it is easy to cause the second type doping region 140 to diffuse too much into the first type doping region 110, so that the second type doping region 140 occupies too much area of the first type doping region 110, which correspondingly causes the occupied area of the first type doping region 110 to be reduced, affecting the electron accumulation capacity of the first type doping region 110, thereby affecting the full well capacity of the photoelectric sensor; if the doping concentration of the second type doping region 140 is too small, it is easy to affect the effect of forming a PN junction between the second doping region 140 and the first doping region 110, thereby affecting the effect of increasing the PN junction area, and then it is difficult to improve the full well capacity of the photoelectric sensor. For this reason, in this embodiment, the doping concentration of the second type doping region 120 is 1E12 atom/cm ³ to 1E14atom/cm ³ .

In this embodiment, in the pixel unit region 100 a , each of the first-type doping regions 110 has a plurality of protruding portions 120 protruding from the covering portion 130 .

Each first-type doping region 110 has a plurality of protruding portions 120 protruding from the covering portion 130, which correspondingly increases the number of side walls of the protruding portions 120 in the first-type doping region 110, which is beneficial to increase the side wall area of the second-type doping region 120 in contact with the first-type doping region 110, which is beneficial to further increase the PN junction area, thereby facilitating an increase in the rate at which the PN junction generates electrons, and further facilitating an increase in the full well capacity of the photoelectric sensor, thereby improving the signal-to-noise ratio and dynamic range of the image sensor, and improving the imaging quality.

In practical applications, the morphology of the protrusion 120 can be adjusted according to actual needs to obtain different contact areas between the second-type doping region 120 and the first-type doping region 110, and correspondingly obtain different PN junction areas, thereby flexibly adjusting the full well capacity of the photoelectric sensor.

Specifically, referring to Figure 9, Figure 9 shows the distribution of the protrusions 120 in the first type doping region 110. In the pixel unit area 100a, the top-view shape of the distribution of the protrusions 120 of the second doping region 140 in the first type doping region 110 includes strips, rings, arrays or grids.

In this embodiment, the covering portion 130 and the protruding portion 120 are an integrated structure. In the process of forming the photoelectric sensor, the covering portion 130 and the protruding portion 120 of the second doping region 140 are formed in the same step, so there is no need to add additional steps to form the protruding portion 120, which is conducive to simplifying the process flow and improving process efficiency.

It should be noted that, in this embodiment, the doping depth of the protruding portion 120 in the second-type doping region 140 should not be too large or too small. If the doping depth of the protruding portion 120 in the second-type doping region 140 is too large, it is easy to cause the protruding portion 120 to occupy too much area of the first-type doping region 110, which correspondingly causes the occupied area of the first-type doping region 110 to be reduced, affecting the first-type doping region 110's ability to accumulate electrons, thereby affecting the full well capacity of the photoelectric sensor; if the doping depth of the protruding portion 120 in the second-type doping region 140 is too small, it is easy to cause the protruding portion 120 to have too small a contact area with the sidewall of the first-type doping region 110, making it difficult to achieve the effect of increasing the PN junction area, thereby increasing the rate at which the PN junction generates electrons, and further increasing the full well capacity of the photoelectric sensor. For this reason, in this embodiment, the doping depth of the protruding portion 120 in the second-type doping region 140 is 10nm to 500nm.

It should also be noted that, in this embodiment, the doping depth of the covering portion 130 in the second-type doping region 140 should not be too large or too small. If the doping depth of the covering portion 130 in the second-type doping region 140 is too large, it is easy to cause the covering portion 130 to occupy too much area of the first-type doping region 110, which correspondingly causes the occupied area of the first-type doping region 110 to be reduced, affecting the first-type doping region 110's ability to accumulate electrons, thereby affecting the full well capacity of the photoelectric sensor; if the doping depth of the covering portion 130 in the second-type doping region 140 is too small, it is difficult for the covering portion 130 to play a good sealing role on the top of the first-type doping region 110, thereby making it difficult to reduce the leakage of electrons at the top of the first-type doping region 110 during photoelectric conversion, and further making it difficult to reduce the probability of leakage at the top of the first-type doping region 110, thereby affecting the performance of the photoelectric sensor. For this reason, in this embodiment, the doping depth of the covering portion 130 in the second-type doping region 140 is 10nm to 100nm.

Correspondingly, in this embodiment, the doping type of the third type doping region is the same as the doping type of the second type doping region 140 .

The different doping types between the second-type doping region 140 and the first-type doping region 110 means that the conductivity types of the doped ions in the second-type doping region 140 and the first-type doping region 110 are different.

Specifically, referring to FIG. 6 , the step of performing ion implantation on the substrate 100 includes: forming a mask layer 300 covering the substrate 100 .

The mask layer 300 is used as an implantation mask for ion implantation.

In this embodiment, the mask layer 300 is patterned to form a mask opening 310 exposing the top surface of the first-type doping region 110 .

The mask opening 310 is used to define the position where the protruding portion 120 is formed, and ion implantation is performed on the substrate 100 through the mask layer 300 and the mask opening 310 .

7 , ion implantation is performed on the substrate 100 in the photosensitive pixel region P through the mask layer 300 and the mask opening 310 .

Ions are implanted into the substrate 100 through the mask opening 310 to form the protruding portion 120 , and ions are implanted into the substrate 100 through the mask layer 300 to form the covering portion 130 .

It should be noted that, in the step of performing ion implantation on the substrate 100 of the photosensitive pixel area P through the mask layer 300 and the mask opening 310, the implantation concentration of the ion implantation should not be too large or too small. If the implantation concentration of the ion implantation is too large, it is easy to cause the second-type doping area 140 to diffuse too much into the first-type doping area 110, thereby causing the second-type doping area 140 to occupy too much of the area of the first-type doping area 110, which in turn causes the first-type doping area 110 to occupy an area that is reduced, affecting the first-type doping area 110's ability to accumulate electrons, thereby affecting the full well capacity of the photoelectric sensor; if the implantation concentration of the ion implantation is too small, it is easy to affect the effect of forming a PN junction between the second-type doping area 140 and the first doping area 110, thereby affecting the effect of increasing the PN junction area, and thus it is difficult to increase the full well capacity of the photoelectric sensor. For this reason, in the step of performing ion implantation on the first-type doping area 110, the implantation concentration of the ion implantation is 1E12atom/cm ³ to 1E14atom/cm ³ .

It should also be noted that, in the step of performing ion implantation on the substrate 100 of the photosensitive pixel area P through the mask layer 300 and the mask opening 310 in the present embodiment, the implantation energy of the ion implantation should not be too large or too small. If the implantation energy of the ion implantation is too large, it is easy to cause the doping depth of the second-type doping area 140 to be too large, and it is easy to cause the second-type doping area 140 to occupy too much of the area of the first-type doping area 110, which in turn causes the occupied area of the first-type doping area 110 itself to be reduced, affecting the electron accumulation capacity of the first-type doping area 110, thereby affecting the full well capacity of the photoelectric sensor; if the implantation energy of the ion implantation is too small, it is easy to cause the doping depth of the second-type doping area 140 to be too small, and it is easy to cause the contact surface between the protrusion 120 and the first-type doping area 110 to be too small. If the area of the PN junction is too small, it is difficult to achieve the effect of increasing the PN junction area, thereby increasing the rate at which the PN junction generates electrons, and further increasing the full well capacity of the photoelectric sensor. In particular, for the cover portion 130, it is necessary to form on the top of the substrate 100 by ion implantation through the mask layer 300. If the injection energy of the ion implantation is too small, it is easy to affect the formation of the cover portion 130, thereby making it difficult to reduce the leakage of electrons on the top of the first-type doping region 110 during photoelectric conversion, and further making it difficult to reduce the probability of leakage on the top of the first-type doping region 110, thereby affecting the performance of the photoelectric sensor. For this reason, in the step of performing ion implantation on the substrate 100 of the photosensitive pixel area P through the mask layer 300 and the mask opening 310, the injection energy of the ion implantation is 5KeV to 200KeV.

Accordingly, by performing ion implantation on the substrate 100 of the photosensitive pixel region P along the mask layer 300 and the mask opening 310 , the formed covering portion 130 and the raised portion 120 are formed into an integrated structure, which is beneficial to simplifying the process flow and improving the process efficiency.

In this embodiment, after the ion implantation, the forming method further includes: removing the mask layer 300 to prepare for the subsequent formation of a dielectric layer.

8 , after forming the second-type doping region 140 in the substrate 100 located at the top of the photosensitive pixel region P, the forming method further includes: forming a dielectric layer 210 covering the gate structure 200 on the substrate 100 .

The dielectric layer 210 is used to achieve mutual isolation between devices.

In this embodiment, the material of the dielectric layer 210 is an insulating material, including one or more of silicon oxide, silicon nitride, silicon oxynitride, silicon oxycarbide, silicon carbonitride and silicon carbon oxynitride.

In this embodiment, the photoelectric sensor is a frontside illumination (FSI) photoelectric sensor.

Correspondingly, in this embodiment, the pixel wafer is a front-illuminated pixel wafer, and the top surface of the dielectric layer 210 is a photosensitive surface, that is, the surface of the dielectric layer 210 facing away from the substrate 100 is a photosensitive surface.

In this embodiment, only a portion of the photosensitive pixel region P and the pixel unit region 100a are shown in the figure, and the pixel unit region 100a may also include a device structure such as a photoelectric element (e.g., a photodiode). Among them, the photodiode may be a back-illuminated single photon avalanche diode (SPAD). For the purpose of simplicity, the detailed structure of the above components is not shown in the embodiment of the present invention.

In other embodiments, the photosensor may also be a backside illumination (BSI) photosensor.

Correspondingly, in other embodiments, the pixel wafer is a back-illuminated pixel wafer, a logic wafer is bonded to a side of the dielectric layer facing away from the substrate, and a side of the substrate facing away from the logic wafer is a photosensitive surface.

The logic wafer is used to analyze and process the electrical signals provided by the pixel wafer.

By setting the photosensitive pixel area and the logic area on two wafers respectively and bonding the pixel wafer and the logic wafer together, a larger pixel area can be obtained, which helps shorten the path of light reaching the photoelectric element, reduce the scattering of light, and make the light more focused, thereby improving the photosensitivity of the photoelectric sensor in a low-light environment and reducing system noise and crosstalk.

In other embodiments, the substrate of the pixel wafer is used as the first substrate, and the logic wafer has a second substrate. The second substrate of the logic wafer may be a silicon substrate. In other embodiments, the material of the second substrate of the logic wafer may also be other materials such as germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, and the second substrate of the logic wafer may also be other types of materials such as a silicon substrate on an insulator or a germanium substrate on an insulator.

Accordingly, in other embodiments, a logic transistor is also formed in the logic wafer, and the logic transistor is used to perform logic processing on the electrical signal provided by the pixel wafer. Specifically, the logic transistor may include a logic gate structure located on the logic wafer, and a logic drain region and a logic source region located in the logic wafer on both sides of the logic gate structure.

The bonding between the pixel wafer and the logic wafer is achieved through hybrid bonding.

Specifically, a first interconnect structure is formed on the pixel wafer, and a second interconnect structure is formed on the logic wafer. The pixel wafer and the logic wafer can be bonded together by dielectric bonding, and then the first interconnect structure and the second interconnect structure can be electrically connected.

The first interconnect structure may be a first metal line, or the first interconnect structure is a first through silicon via interconnect structure (TSV), or the first interconnect structure includes a first through-hole interconnect structure and a first metal line located on the first through-hole interconnect structure; the second interconnect structure may be a second metal line, or the second interconnect structure is a second through-hole interconnect structure (TSV), or the second interconnect structure includes a second through-hole interconnect structure and a second metal line located on the second through-hole interconnect structure.

It should be noted that the above method of bonding the pixel wafer and the logic wafer is only used as an embodiment, and the bonding method between the pixel wafer and the logic wafer is not limited to this. For example: in other embodiments, the bonding method between the pixel wafer and the logic wafer can also be direct bonding (such as melt bonding and anodic bonding) or indirect bonding technology (such as metal eutectic, hot pressing bonding and adhesive bonding).

Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims (19)

1. A photoelectric sensor, comprising:

the substrate comprises a photosensitive pixel area, wherein the photosensitive pixel area comprises a plurality of pixel unit areas distributed in a matrix, and a grid structure is formed on the substrate of the pixel unit areas;

the first type doping region is positioned in the substrate at one side of the grid structure in the pixel unit region;

The second type doping region is positioned in the substrate at the top of the photosensitive pixel region, the second type doping region comprises a covering part which extends to cover the photosensitive pixel region and a protruding part which is positioned in the first type doping region and protrudes from the covering part, and the doping types of the second type doping region and the first type doping region are different.

2. The photosensor according to claim 1, wherein in the pixel unit region, each of the first-type doped regions has a plurality of raised portions therein that are raised from the covering portion.

3. The photosensor according to claim 1 or 2, wherein in the pixel unit region, a top view shape of a distribution of the raised portions of the second-type doping region in the first-type doping region includes a stripe shape, a ring shape, an array shape, or a lattice shape.

4. The photoelectric sensor according to claim 1, wherein the cover portion and the raised portion are of a unitary structure.

5. The photosensor of claim 1, wherein the doping concentration of the second type doped region is 1E12 atom/cm ³ to 1E14atom/cm ³.

6. The photosensor of claim 1, wherein the raised portion in the doped region of the second type has a doping depth of 10nm to 500nm.

7. The photosensor according to claim 1, wherein the doping depth of the cover in the second type doped region is 10nm to 100nm.

8. The photosensor of claim 1, wherein the doping type of the first-type doped region is N-type; the doping type of the second type doping region is P type.

9. The photosensor according to claim 1, wherein the photosensor further comprises: and the third type doped region is positioned in the substrate of the photosensitive pixel region and coats the side wall and the bottom surface of the first type doped region, and the doping type of the third type doped region is different from that of the first type doped region.

10. The photosensor of claim 1 wherein the substrate further has a dielectric layer formed thereon that covers the gate structure;

The photoelectric sensor is a front-illuminated photoelectric sensor, and the top surface of the dielectric layer is a photosensitive surface;

Or the photoelectric sensor is a back-illuminated photoelectric sensor, a logic wafer is bonded on one surface of the dielectric layer, which is away from the substrate, and one surface of the substrate, which is away from the logic wafer, is a light sensitive surface.

11. A method of forming a photoelectric sensor, comprising:

providing a substrate, wherein the substrate comprises a photosensitive pixel area, the photosensitive pixel area comprises a plurality of pixel unit areas distributed in a matrix, a grid structure is formed on the substrate of the pixel unit area, and a first type doping area is formed in the substrate at one side of the grid structure in the pixel unit area;

And performing ion implantation on the substrate to form a second type doped region in the substrate at the top of the photosensitive pixel region, wherein the second type doped region comprises a covering part extending to cover the photosensitive pixel region and a raised part which is positioned in the first type doped region and is raised from the covering part, and the doping types of the second type doped region and the first type doped region are different.

12. The method of forming a photosensor of claim 11 where the step of ion implanting the substrate includes: forming a mask layer covering the substrate;

Patterning the mask layer to form a mask opening exposing the top surface of the first type doped region;

ion implantation is carried out on the substrate of the photosensitive pixel area through the mask layer and the mask opening;

After the ion implantation, the forming method further comprises: and removing the mask layer.

13. The method of claim 12, wherein in the step of implanting ions into the substrate of the photosensitive pixel region through the mask layer and the mask opening, the implantation concentration of the ions is 1E12atom/cm ³ to 1E14atom/cm ³, and the implantation energy of the ions is 5Kev to 200Kev.

14. The method of claim 11, wherein in the step of forming a second type doped region in the substrate on top of the photosensitive pixel region, each of the first type doped regions has a plurality of raised portions protruding from the cover portion in the pixel cell region.

15. The method of claim 11 or 13, wherein in the step of forming a second type doped region in the substrate on top of the photosensitive pixel region, a top view shape of a distribution of raised portions of the second type doped region in the first type doped region in the pixel unit region includes a stripe shape, a ring shape, an array shape, or a grid shape.

16. The method of claim 11, wherein in the step of forming a second type doped region in the substrate on top of the photosensitive pixel region, the cover portion and the raised portion are integrally formed.

17. The method of claim 11, wherein in the step of providing the substrate, the doping type of the first type doping region is N-type; in the step of forming the second type doped region, the doping type of the second type doped region is P-type.

18. The method of claim 11, wherein in the step of providing the substrate, a third type doped region is further formed in the substrate of the photosensitive pixel region, the third type doped region having a doping type different from a doping type of the first type doped region, and the sidewall and the bottom surface of the first type doped region are covered with the third type doped region.

19. The method of forming a photosensor of claim 11 where after forming a doped region of a second type in the substrate on top of the photosensitive pixel region, the method further comprises: forming a dielectric layer covering the grid structure on the substrate;

The photoelectric sensor is a front-illuminated photoelectric sensor, and the top surface of the dielectric layer is a photosensitive surface;

the photoelectric sensor is a back-illuminated photoelectric sensor, and after a dielectric layer covering the gate structure is formed on the substrate, the forming method further comprises: and bonding a logic wafer on one surface of the dielectric layer, which is opposite to the substrate, wherein one surface of the substrate, which is opposite to the logic wafer, is a photosensitive surface.