CN118263263A

CN118263263A - Photoelectric sensor and forming method thereof

Info

Publication number: CN118263263A
Application number: CN202211682866.6A
Authority: CN
Inventors: 高长城; 张伟; 石强
Original assignee: Semiconductor Manufacturing International Shanghai Corp; Semiconductor Manufacturing International Beijing Corp
Current assignee: Semiconductor Manufacturing International Shanghai Corp; Semiconductor Manufacturing International Beijing Corp
Filing date: 2022-12-27
Publication date: 2024-06-28

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 forming method thereof

Technical Field

The embodiment of the invention relates to the field of semiconductor manufacturing, in particular to a photoelectric sensor and a forming method thereof.

Background

A photosensor is a device that converts an optical signal into an electrical signal. The working principle is based on the photoelectric effect, which means that when light irradiates on certain substances, electrons of the substances absorb photon energy and corresponding electric effect phenomenon occurs.

For example, a CCD (Charge Coupled Device ) image sensor and a CMOS (CMOS IMAGE SENSER, CIS) image sensor, which convert an optical image into an electrical signal by using a photoelectric conversion function and output the digital image, are widely used in digital cameras and other electronic optical devices. CMOS image sensors are increasingly replacing CCDs due to their simple process, easy integration with other devices, small size, light weight, low power consumption, low cost, etc. Currently, CMOS image sensors are widely used in the fields of digital cameras, camera phones, digital video cameras, medical imaging devices (for example, gastroscopes), and vehicle imaging devices.

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

Disclosure of Invention

The embodiment of the invention solves the problem of providing a photoelectric sensor and a forming method thereof, and improves imaging quality.

To solve the above problems, an embodiment of the present invention provides a photoelectric sensor, including: 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 embodiment of the invention also provides a method for forming the photoelectric sensor, which comprises the following steps: providing a substrate, wherein the substrate comprises a photosensitive pixel region, the photosensitive pixel region comprises a plurality of pixel unit regions distributed in a matrix, a grid structure is formed on the substrate of the pixel unit region, and a first doped region is formed in the substrate at one side of the grid structure in the pixel unit region; and carrying out ion implantation on the substrate to form a second type doped region in the substrate positioned at the top of the photosensitive pixel region, wherein the second type doped region 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.

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

In the photoelectric sensor provided by the embodiment of the invention, the covering part of the second type doped region extends to cover the photosensitive pixel region, the doping types of the second type doped region and the first type doped region are different, so that the covering part can reduce the leakage of electrons at the top of the first type doped region when photoelectric conversion is carried out, thereby reducing the probability of generating electric leakage at the top of the first type doped region, the raised part of the second type doped region is positioned in the first type doped region and protrudes out of the covering part, the raised part positioned in the first type doped region is different from the doping type of the first type doped region, the PN junction can be formed by the raised part positioned in the first type doped region and the first type doped region, and the contact area of the first type doped region and the second type doped region is increased by adding the second type doped region in the first type doped region, so that the PN junction area is favorably increased, the rate of electrons generated by the PN junction is favorably increased, the full-well capacity of the photoelectric sensor is favorably improved, and the imaging quality is favorably improved.

In the method for forming the photoelectric sensor provided by the embodiment of the invention, the covering part of the second type doped region extends to cover the photosensitive pixel region, the doping types of the second type doped region and the first type doped region are different, so that the covering part can reduce the leakage of electrons at the top of the first type doped region when photoelectric conversion is carried out, thereby reducing the probability of generating electric leakage at the top of the first type doped region, the raised part of the second type doped region is positioned in the first type doped region and protrudes out of the covering part, the doping types of the second type doped region and the first type doped region are different, the raised part positioned in the first type doped region can form a PN junction with the first type doped region, and the contact area of the first type doped region and the second type doped region is increased by adding the second type doped region in the first type doped region in the photoelectric sensor, so that the PN junction area is favorably increased, the rate of electrons generated by the PN junction is favorably increased, the full-well capacity of the photoelectric sensor is favorably improved, and the imaging quality is favorably improved.

Drawings

Fig. 1 to 3 are schematic structural views of a photoelectric sensor according to an embodiment of the present invention;

fig. 4 to 9 are schematic structural views corresponding to each step in an embodiment of a method for forming a photoelectric sensor according to the present invention.

Detailed Description

As known from the background art, the imaging quality of the currently formed photoelectric sensor needs to be improved.

The Full Well Capacity (FWC) is the maximum charge amount that can be accumulated by the capacitance of the photodiode, and is an important index of the CIS image sensor, and when the full well capacity is saturated, the energy of the new electrons collected by the photodiode is reduced, and the imaging quality, especially in a high dynamic range, is greatly affected.

The mode of improving the capacity of the full well can increase the size of the pixel unit area, but the mode tends to influence the integration level of the photoelectric sensor, which is not beneficial to the development trend of higher integration level in the field of semiconductor manufacturing; the full well capacity can be improved by increasing the doping concentration of the N-type doped region, but the isolation effect of the mode on the P-type doped region between the adjacent N-type doped regions is higher, and the problem of electric leakage between the adjacent pixel unit regions is easily caused by the overlarge concentration of the N-type doped region; the full well capacity can also be increased by increasing the depth of the pixel cell region, but this approach has a greater challenge for the ion implantation process to form the N-doped region.

Therefore, it is currently difficult to better increase the full well capacity, thereby making it difficult to improve the imaging quality of the photosensor.

In order to solve the technical problem, an embodiment of the present invention provides a photoelectric sensor, including: 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.

In the photoelectric sensor provided by the embodiment of the invention, the covering part of the second type doped region extends to cover the photosensitive pixel region, the doping types of the second type doped region and the first type doped region are different, so that the covering part can reduce the leakage of electrons at the top of the first type doped region when photoelectric conversion is carried out, thereby reducing the probability of generating electric leakage at the top of the first type doped region, the raised part of the second type doped region is positioned in the first type doped region and protrudes out of the covering part, the raised part positioned in the second type doped region is different from the doping type of the first type doped region, and the PN junction can be formed by the raised part positioned in the first type doped region and the first type doped region.

In order that the above objects, features and advantages of embodiments of the invention may be readily understood, a more particular description of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.

Referring to fig. 1 to 3, schematic structural diagrams of a photoelectric sensor according to an embodiment of the present invention are shown.

Referring to fig. 1 to 3 in combination, fig. 1 (a) is a top view of a substrate, fig. 1 (b) is a partial enlarged view of any one of the photosensitive pixel regions 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, where the photoelectric sensor includes: the substrate 101, the substrate 101 includes a photosensitive pixel region P, the photosensitive pixel region P includes a plurality of pixel unit regions 101a distributed in a matrix, and a gate structure 201 is formed on the substrate 101 of the pixel unit regions 101 a; a first type doped region 111 located in the substrate 101 at one side of the gate structure 201 in the pixel unit region 101 a; the second type doped region 141 is located in the substrate 101 on top of the photosensitive pixel region P, the second type doped region 141 includes a covering portion 131 extending to cover the photosensitive pixel region P, and a raised portion 121 located in the first type doped region 111 and protruding from the covering portion 131, and the doping types of the second type doped region 141 and the first type doped region 111 are different.

As an example, the present embodiment is described taking a photosensor as a CMOS image sensor as an example.

In other embodiments, the photosensor may also be a CCD (Charge Coupled Device, charge-coupled device) image sensor, a DTOF (DIRECT TIME of Flight ) sensor, or a iTOF (INDIRECT TIME of Flight, indirect time of Flight) sensor, or the like.

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 substrate of the pixel wafer may be made of other materials such as germanium, silicon carbide, gallium arsenide, or indium gallium arsenide, and the substrate of the pixel wafer may be made of other types of materials such as a silicon substrate on an insulator or a germanium substrate on an insulator.

The photosensitive pixel region P is used for receiving an optical signal so as to convert the optical signal into an electrical signal.

In the pixel wafer, the number of the photosensitive pixel areas P is a plurality of, and the photosensitive pixel areas P are arranged in a matrix. The pixel cell area 101a is used to form a pixel.

The gate structure 201 is used to perform normal device functions in the pixel wafer for controlling the opening and closing of channels in the semiconductor structure.

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

Dielectric layer 211 is used to isolate the devices from each other.

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 oxycarbonitride.

In this embodiment, the photosensor is a front-lit (Frontside Illumination, FSI) photosensor.

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 the present embodiment, only a part of the photosensitive pixel region P and the pixel unit region 101a is shown in the figure, and the pixel unit region 101a may further include a device structure such as a photoelectric element (e.g., a photodiode). Wherein the photodiode may be a back-illuminated Single Photon Avalanche Diode (SPAD). For the sake of simplicity, the detailed structure of the above components is not shown in the embodiments of the present invention.

In other embodiments, the photosensors may also be back-illuminated (Backside Illumination, BSI) photosensors.

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

The logic wafer is used for analyzing and processing the electric signals provided by the pixel wafer.

The photosensitive pixel area and the logic area are respectively arranged on the two wafers, and the pixel wafer and the logic wafer are bonded together, so that a larger pixel area can be obtained, the path of light reaching the photoelectric element is shortened, the scattering of the light is reduced, the light is more focused, the photosensitive capacity of the photoelectric sensor in a weak light environment is improved, and the system noise and crosstalk are reduced.

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

Accordingly, in other embodiments, logic transistors are also formed in the logic wafer, and the logic transistors are used for performing logic processing on the electrical signals provided by the pixel wafer. Specifically, the logic transistor may include a logic gate structure on a logic wafer, and a logic drain region and a logic source region respectively located in the logic wafer at both sides of the logic gate structure.

Bonding between the pixel wafer and the logic wafer is achieved by Hybrid bonding.

Specifically, a first interconnection structure is formed on the pixel wafer, a second interconnection structure is formed on the logic wafer, the pixel wafer and the logic wafer can be bonded together by using a dielectric bonding mode, and then electrical connection between the first interconnection structure and the second interconnection structure is performed.

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

It should be noted that the above manner of bonding between the pixel wafer and the logic wafer is merely an example, and the bonding manner between the pixel wafer and the logic wafer is not limited thereto. For example: in other embodiments, the bonding of the pixel wafer and the logic wafer may also be direct bonding (e.g., fusion bonding and anodic bonding) or indirect bonding techniques (e.g., metal eutectic, thermocompression bonding and adhesive bonding), etc.

During operation of the photosensor, electrons generated move to the first-type doped region 111, and the first-type doped region 111 is used for accumulating electrons during photoelectric conversion.

Specifically, in the present embodiment, the doping type of the first type doped region 111 is N type, the doping ions of the N type doped region are N type ions, and the N type ions include P ions, as ions or Sb ions.

The N-type doped region receives high potential in the working process of the photoelectric sensor, carriers in the N-type doped region are electrons, and the free electron concentration is far greater than the hole concentration, so that the N-type doped region is a region for accumulating electrons.

The N-type doped region is used as a main photo-generated carrier generation and storage region and is located below the light trapping groove (not shown), so that the photo-generated carrier generation efficiency can be effectively increased, and the performance of the photoelectric sensor can be improved.

In this embodiment, the second type doped 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 doped region 111 and protruding from the covering portion 131, where the doping types of the second type doped region 141 and the first type doped region 111 are different.

Wherein the doping type of the second type doped region 141 is different from that of the first type doped region 111 means that the conductivity type of the doping ions in the second type doped region 141 is different from that of the first type doped region 111.

By sealing the top of the first type doped region 111 with the cover 131 having different doping ion conductivity types, electron leakage from the top of the first type doped region 111 when photoelectric conversion is performed is reduced.

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

In this embodiment, the covering portion 131 of the second type doped region 141 extends to cover the photosensitive pixel region P, the doping types of the second type doped region 141 and the first type doped region 111 are different, so that the covering portion 131 can reduce the leakage of electrons at the top of the first type doped region 111 during photoelectric conversion, thereby reducing the probability of generating electric leakage at the top of the first type doped region 111, the raised portion of the second type doped region 141 is located in the first type doped region 111 and protrudes from the covering portion 131, the doping types of the second type doped region 141 and the first type doped region 111 are different, the raised portion 121 located in the first type doped region 111 can form a PN junction with the first type doped region 111, and the contact area of the first type doped region 111 and the second type doped region 141 is increased by adding the second type doped region 141 in the first type doped region 111, so as to facilitate increasing the rate of generating electrons at the PN junction, thereby facilitating the improvement of the full-well capacity of the photoelectric sensor, the improvement of the signal-to-noise ratio and the dynamic range of the image sensor.

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

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

In this embodiment, the doping concentration of the second type doped region 141 is not too large or too small. If the doping concentration of the second type doped region 141 is too high, the second type doped region 141 is easy to diffuse too much into the first type doped region 111, so that the second type doped region 141 occupies too much area of the first type doped region 111, and accordingly the occupied area of the first type doped region 111 is reduced, which affects the accumulation capacity of the first type doped region 111 on electrons, so as to affect the full well capacity of the photoelectric sensor; if the doping concentration of the second type doped region 141 is too small, the effect of forming the PN junction between the second doped region 141 and the first doped region 111 is easily affected, thereby affecting the effect of increasing the PN junction area, and thus it is difficult to increase the full well capacity of the photosensor. For this reason, in the present embodiment, the doping concentration of the second type doping region 121 is 1E12 atom/cm ³ to 1E14atom/cm ³.

In the present embodiment, in the pixel unit region 100a, each of the first type doped regions 111 has a plurality of raised portions 121 protruding from the covering portion 131.

Each first type doped region 111 is provided with a plurality of raised parts 121 protruding from the covering part 131, so that the number of the side walls of the raised parts 121 in the first type doped region 111 is correspondingly increased, the area of the side walls of the second type doped region 121, which are in contact with the first type doped region 111, is favorably increased, the PN junction area is favorably further increased, the electron generation rate of the PN junction is favorably increased, the full-well capacity of the photoelectric sensor is favorably improved, the signal-to-noise ratio and the dynamic range of the image sensor are improved, and the imaging quality is improved.

In practical application, the shape of the raised portion 121 can be adjusted according to practical requirements, so that different contact areas of the second type doped region 121 and the first type doped region 111 are obtained, and different PN junction areas are correspondingly obtained, so that the full-well capacity of the photoelectric sensor can be flexibly adjusted.

Specifically, referring to fig. 3, fig. 3 shows a distribution of the raised portions 121 in the first type doping region 111, and in the pixel cell region 100a, a top view shape of the distribution of the raised portions 121 of the second doping region 141 in the first type doping region 111 includes a stripe shape, a ring shape, an array shape, or a lattice shape.

In this embodiment, the covering portion 131 and the raised portion 121 are integrally formed, so that the covering portion 131 and the raised portion 121 of the second doped region 141 are formed in the same step during the formation of the photoelectric sensor, and thus no additional step is required to be added to form the raised portion 121, which is beneficial to simplifying the process flow and improving the process efficiency.

In this embodiment, the doping depth of the raised portion 121 in the second type doped region 141 is not too large or too small. If the doping depth of the raised portion 121 in the second type doped region 141 is too large, the raised portion 121 is likely to occupy too much area of the first type doped region 111, and accordingly the occupied area of the first type doped region 111 is reduced, which affects the accumulation capacity of the first type doped region 111 for electrons, thereby affecting the full well capacity of the photoelectric sensor; if the doping depth of the raised portion 121 in the second type doped region 141 is too small, the contact area between the raised portion 121 and the sidewall of the first type doped region 111 is too small, so that the effect of increasing the PN junction area is difficult to achieve, the rate of generating electrons at the PN junction is difficult to increase, and the full well capacity of the photoelectric sensor is difficult to increase. For this reason, in the present embodiment, the doping depth of the protrusion 121 in the second type doping region 141 is 10nm to 500nm.

In the present embodiment, the doping depth of the covering portion 131 in the second type doped region 141 is not too large or too small. If the doping depth of the covering portion 131 in the second type doped region 141 is too large, the covering portion 131 is easy to occupy too much area of the first type doped region 111, and accordingly the occupied area of the first type doped region 111 is reduced, which affects the accumulation capacity of the first type doped region 111 on electrons, thereby affecting the full well capacity of the photoelectric sensor; if the doping depth of the cover portion 131 in the second type doped region 141 is too small, the cover portion 131 is difficult to perform a good sealing effect on the top of the first type doped region 111, so that it is difficult to reduce the leakage of electrons at the top of the first type doped region 111 during photoelectric conversion, and further it is difficult to reduce the probability of generating electric leakage at the top of the first type doped region 111, which affects the performance of the photoelectric sensor. For this reason, in the present embodiment, the doping depth of the cover portion 131 in the second type doping region 141 is 10nm to 100nm.

In this embodiment, the photoelectric sensor further includes: a third type doped region (not shown) in the substrate 101 of the photosensitive pixel region P and surrounding the sidewall and bottom surface of the first type doped region 111, the doping type of the third type doped region being different from that of the first type doped region 111.

The doping type of the third type doped region is the same as the doping type of the first type doped region 111, and correspondingly, the doping type of the third type doped region is P type, the doping ions of the P type doped region are P type ions, and the P type ions comprise B ions, ga ions or In ions.

The third type doped region is used for isolating the adjacent first type doped region 111, and the third type doped region coats the side wall and the bottom surface of the first type doped region 111, so that electron leakage of the side wall and the bottom surface of the first type doped region 111 during photoelectric conversion is reduced, the third type doped region is in contact with the first type doped region 111, and a PN junction can be formed with the first type doped region 111, so that the normal function of the photoelectric sensor is realized.

Referring to fig. 4 to 5 in combination, fig. 4 (a) is a top view of a substrate, fig. 4 (b) is a partial enlarged view of any one of the photosensitive pixel regions in fig. 4 (a), and fig. 5 is a cross-sectional view corresponding to fig. 4 (a), a substrate 100 is provided, the substrate 100 includes a photosensitive pixel region P, the photosensitive pixel region P includes a plurality of pixel unit regions 100a distributed in a matrix, a gate structure 200 is formed on the substrate 100 of the pixel unit region 100a, and a first type doped region 110 is formed in the substrate 100 on one side of the gate structure 200 in the pixel unit region 100 a.

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 substrate of the pixel wafer may be made of other materials such as germanium, silicon carbide, gallium arsenide, or indium gallium arsenide, and the substrate of the pixel wafer may be made of other types of materials such as a silicon substrate on an insulator or a germanium substrate on an insulator.

In the pixel wafer, the number of the photosensitive pixel areas P is a plurality of, and the photosensitive pixel areas P are arranged in a matrix. The pixel cell area 100a is used to form a pixel.

The gate structure 200 is used to perform normal device functions in a pixel wafer for controlling the turning on and off of channels in a semiconductor structure.

During operation of the photosensor, electrons generated move to the first type doping region 110, and the first type doping region 110 is used for accumulating electrons during photoelectric conversion.

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

In the step of providing the substrate 100, a third type doped region (not shown) is further formed in the substrate 100 of the photosensitive pixel region P to cover the sidewall and the bottom of the first type doped region 110, and the doping type of the third type doped region is different from that of the first type doped region 110.

The doping type of the third type doped region is different from the doping type of the first type doped region 110, and correspondingly, the doping type of the third type doped region is P type, the doping ions of the P type doped region are P type ions, and the P type ions comprise B ions, ga ions or In ions.

The third type doped region is used for isolating the adjacent first type doped region 110, and the third type doped region coats the side wall and the bottom surface of the first type doped region 110, so that electron leakage of the side wall and the bottom surface of the first type doped region 110 during photoelectric conversion is reduced, the third type doped region is in contact with the first type doped region 110, and a PN junction can be formed with the first type doped region 110, so that the normal function of the photoelectric sensor is realized.

Referring to fig. 6 to 9 in combination, fig. 9 is a top view, and the substrate 100 is ion-implanted to form a second type doped region 140 in the substrate 100 on top of the photosensitive pixel region P, wherein the second type doped region 140 includes a cover portion 130 extending to cover the photosensitive pixel region P, and a raised portion 120 in the first type doped region 110 and protruding from the cover portion 130, and the doping types of the second type doped region 140 and the first type doped region 110 are different.

In this embodiment, the second type doped 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 doped region 110 and protruding from the covering portion 130, where the doping types of the second type doped region 140 and the first type doped region 110 are different.

Wherein the doping type of the second type doped region 140 is different from that of the first type doped region 110 means that the conductivity type of the doping ions in the second type doped region 140 is different from that of the first type doped region 110.

By sealing the top of the first type doped region 110 with the cover 130 having different doping ion conductivity types, electron leakage from the top of the first type doped region 110 when photoelectric conversion is performed is reduced.

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

In this embodiment, the cover portion 130 of the second type doped region 140 extends to cover the photosensitive pixel region P, the doping types of the second type doped region 140 and the first type doped region 110 are different, so that the cover portion 130 can reduce the leakage of electrons at the top of the first type doped region 110 during photoelectric conversion, thereby reducing the probability of generating electric leakage at the top of the first type doped region 110, the raised portion of the second type doped region 140 is located in the first type doped region 110 and protrudes out of the cover portion 130, the doping types of the second type doped region 140 and the first type doped region 110 are different, the raised portion 120 located in the first type doped region 110 can form a PN junction with the first type doped region 110, and the contact area of the first type doped region 110 and the second type doped region 140 is increased by adding the second type doped region 140 in the first type doped region 110, so as to facilitate increasing the rate of generating electrons at the PN junction, thereby facilitating the improvement of the full-well capacity of the photoelectric sensor, the improvement of the signal-to-noise ratio and the dynamic range of the image sensor.

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

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

In this embodiment, the doping concentration of the second type doped region 140 is not too large or too small. If the doping concentration of the second type doped region 140 is too high, the second type doped region 140 is easy to diffuse too much into the first type doped region 110, so that the second type doped region 140 occupies too much area of the first type doped region 110, and accordingly the occupied area of the first type doped region 110 is reduced, which affects the accumulation capacity of the first type doped region 110 on electrons, so as to affect the full well capacity of the photoelectric sensor; if the doping concentration of the second type doped region 140 is too small, the effect of forming the PN junction between the second doped region 140 and the first doped region 110 is easily affected, thereby affecting the effect of increasing the PN junction area, and thus it is difficult to increase the full well capacity of the photosensor. For this reason, in the present embodiment, the doping concentration of the second type doping region 120 is 1E12 atom/cm ³ to 1E14atom/cm ³.

In the present embodiment, in the pixel unit area 100a, each of the first type doped regions 110 has a plurality of raised portions 120 protruding from the covering portion 130.

Each first type doped region 110 is provided with a plurality of raised parts 120 protruding from the covering part 130, so that the number of the side walls of the raised parts 120 in the first type doped region 110 is correspondingly increased, the area of the side walls of the second type doped region 120, which are in contact with the first type doped region 110, is favorably increased, the PN junction area is favorably further increased, the electron generation rate of the PN junction is favorably increased, the full-well capacity of the photoelectric sensor is favorably improved, the signal-to-noise ratio and the dynamic range of the image sensor are improved, and the imaging quality is improved.

In practical application, the shape of the raised portion 120 can be adjusted according to practical requirements, so as to obtain different contact areas of the second type doped region 120 and the first type doped region 110, and correspondingly obtain different PN junction areas, thereby flexibly adjusting the full well capacity of the photoelectric sensor.

Specifically, referring to fig. 9, fig. 9 shows a distribution of the raised portions 120 in the first type doping region 110, and in the pixel unit region 100a, a top view shape of the distribution of the raised portions 120 of the second doping region 140 in the first type doping region 110 includes a stripe shape, a ring shape, an array shape, or a lattice shape.

In this embodiment, the cover portion 130 and the raised portion 120 are integrally formed, so that the cover portion 130 and the raised portion 120 of the second doped region 140 are formed in the same step during the formation of the photoelectric sensor, and thus no additional steps are required to be added to form the raised portion 120, which is beneficial to simplifying the process flow and improving the process efficiency.

It should be noted that, in the present embodiment, the doping depth of the raised portion 120 in the second type doped region 140 is not too large or too small. If the doping depth of the raised portion 120 in the second type doped region 140 is too large, the excessive occupation of the raised portion 120 on the area of the first type doped region 110 is easily caused, and accordingly, the occupation area of the first type doped region 110 is reduced, which affects the accumulation capacity of the first type doped region 110 on electrons, thereby affecting the full well capacity of the photoelectric sensor; if the doping depth of the raised portion 120 in the second type doped region 140 is too small, the contact area between the raised portion 120 and the sidewall of the first type doped region 110 is too small, so that the effect of increasing the PN junction area is difficult to achieve, the rate of generating electrons at the PN junction is difficult to increase, and the full well capacity of the photoelectric sensor is difficult to increase. For this reason, in the present embodiment, the doping depth of the raised portion 120 in the second type doped region 140 is 10nm to 500nm.

It should be noted that, in the present embodiment, the doping depth of the covering portion 130 in the second type doped region 140 is not too large or too small. If the doping depth of the cover portion 130 in the second type doped region 140 is too large, the excessive area of the cover portion 130 occupying the first type doped region 110 is easily caused, and accordingly, the occupied area of the first type doped region 110 is reduced, which affects the accumulation capacity of the first type doped region 110 for electrons, thereby affecting the full well capacity of the photoelectric sensor; if the doping depth of the cover portion 130 in the second type doped region 140 is too small, the cover portion 130 has a difficulty in performing a good sealing function on the top of the first type doped region 110, so that it is difficult to reduce the leakage of electrons from the top of the first type doped region 110 during photoelectric conversion, and further it is difficult to reduce the probability of generating electric leakage at the top of the first type doped region 110, which affects the performance of the photoelectric sensor. For this reason, in the present embodiment, the doping depth of the cover portion 130 in the second type doped region 140 is 10nm to 100nm.

Accordingly, in the present embodiment, the doping type of the third type doped region is the same as the doping type of the second type doped region 140.

Specifically, referring to fig. 6, the step of ion implanting the substrate 100 includes: a mask layer 300 is formed to cover 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 doped region 110.

Mask opening 310 is used to define the location where raised portion 120 is formed, and substrate 100 is ion implanted through mask layer 300 and mask opening 310.

Referring to fig. 7, the substrate 100 of the photosensitive pixel region P is ion-implanted through the mask layer 300 and the mask opening 310.

The substrate 100 is ion-implanted through the mask opening 310 to form the raised portion 120, and the substrate 100 is ion-implanted through the mask layer 300 to form the covering portion 130.

In the embodiment, in the step of implanting ions into the substrate 100 of the photosensitive pixel region P through the mask layer 300 and the mask opening 310, the implantation concentration of the ions is not too high or too low. If the implantation concentration of the ion implantation is too large, the second type doped region 140 is easy to diffuse too much into the first type doped region 110, so that the second type doped region 140 occupies too much area of the first type doped region 110, and accordingly the occupied area of the first type doped region 110 is reduced, which affects the accumulation capacity of the first type doped region 110 on electrons, and thus affects the full well capacity of the photoelectric sensor; if the implantation concentration of the ion implantation is too small, the effect of forming the PN junction between the second type doped region 140 and the first doped region 110 is easily affected, thereby affecting the effect of increasing the PN junction area, and thus it is difficult to increase the full well capacity of the photosensor. For this reason, in the step of ion implantation of the first type doped region 110 in this embodiment, the implantation concentration of ion implantation is 1E12atom/cm ³ to 1E14atom/cm ³.

In the embodiment, in the step of performing the ion implantation on the substrate 100 of the photosensitive pixel region P through the mask layer 300 and the mask opening 310, 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, the doping depth of the second type doped region 140 is easily too large, so that the second type doped region 140 is easily too much to occupy the area of the first type doped region 110, and accordingly the occupied area of the first type doped region 110 is reduced, which affects the accumulation capacity of the first type doped region 110 on electrons, thereby affecting the full well capacity of the photoelectric sensor; if the implantation energy of the ion implantation is too small, the doping depth of the second type doped region 140 is easily too small, the contact area between the raised portion 120 and the first type doped region 110 is easily too small, the effect of increasing the PN junction area is difficult to achieve, the rate of electrons generated by the PN junction is difficult to increase, and further the full well capacity of the photoelectric sensor is difficult to increase, particularly, for the cover portion 130, it is necessary to form the cover portion 130 on top of the substrate 100 through the ion implantation penetrating the mask layer 300, and if the implantation energy of the ion implantation is too small, the formation of the cover portion 130 is easily affected, so that it is difficult to reduce the leakage of electrons from the top of the first type doped region 110 during photoelectric conversion, and further the probability of electric leakage from the top of the first type doped region 110 is difficult to reduce, and the performance of the photoelectric sensor is affected. For this reason, in the step of ion implantation of the substrate 100 of the photosensitive pixel region P through the mask layer 300 and the mask opening 310 in this embodiment, the implantation energy of the ion implantation is 5KeV to 200KeV.

Accordingly, the substrate 100 of the photosensitive pixel region P is ion-implanted along the mask layer 300 and the mask opening 310, so that the formed covering portion 130 and the protruding portion 120 are in 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: mask layer 300 is removed in preparation for the subsequent formation of a dielectric layer.

Referring to fig. 8, after forming the second type doped region 140 in the substrate 100 on top of the photosensitive pixel region P, the forming method further includes: a dielectric layer 210 is formed on the substrate 100 overlying the gate structure 200.

Dielectric layer 210 is used to isolate the devices from each other.

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 oxycarbonitride.

Correspondingly, in the present 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 the present embodiment, only a part of the photosensitive pixel region P and the pixel unit region 100a is shown in the drawing, and the pixel unit region 100a may further include a device structure such as a photoelectric element (e.g., a photodiode). Wherein the photodiode may be a back-illuminated Single Photon Avalanche Diode (SPAD). For the sake of simplicity, the detailed structure of the above components is not shown in the embodiments of the present invention.

Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.

Claims

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 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.