CN108470741A - Imaging sensor and forming method thereof - Google Patents

Abstract

A kind of imaging sensor and forming method thereof, wherein forming method includes：Substrate is provided, the substrate includes opposite the first face and the second face, and the substrate includes several pixel regions being separated from each other, and includes Resistance between adjacent pixel area, has well region in the substrate, has the first Doped ions in the well region；The first isolation opening is formed in the Resistance substrate, and the first face exposes the first isolation opening；The second isolation opening is formed in the substrate of Resistance, and second face exposes the second isolation opening；It is formed after the first isolation opening, or it is formed after the second isolation opening, the first barrier structure is formed in the substrate of Resistance, has the second Doped ions, the conduction type of second Doped ions identical as the conduction type of the first Doped ions in first barrier structure.The better performances for the imaging sensor that the method is formed.

Description

Image sensor and method of forming the same

technical field

The invention relates to the technical field of semiconductor manufacturing, in particular to an image sensor and a forming method thereof.

Background technique

Image sensors are semiconductor devices that convert optical image signals into electrical signals. CMOS (Complementary Metal Oxide Semiconductor) image sensor is a fast-growing solid-state image sensor. Since the image sensor part and the control circuit part of the CMOS image sensor are integrated in the same chip, the CMOS image sensor is small in size and low in power consumption. , low price, compared with the traditional CCD (charge-coupled) image sensor, it has more advantages and is easier to popularize.

Existing CMOS image sensors include photosensors for converting optical signals into electrical signals, and the photosensors are photodiodes formed in a silicon substrate. In addition, a dielectric layer is formed on the surface of the silicon substrate on which the photodiodes are formed, and a metal interconnection layer is formed in the dielectric layer, and the metal interconnection layer is used to electrically connect the photodiodes to peripheral circuits. For the above-mentioned CMOS image sensor, the side of the silicon substrate having a dielectric layer and a metal interconnection layer is the front side of the CMOS image sensor, and the side opposite to the front side is the back side of the CMOS image sensor. According to the difference in the direction of light irradiation, the CMOS image sensors can be classified into front-side illumination (FSI) CMOS image sensors and back-side illumination (Back-side Illumination) CMOS image sensors.

For the front-illuminated CMOS image sensor, the light shines on the front of the CMOS image sensor. However, since the light needs to pass through the dielectric layer and the metal interconnection layer before it can irradiate the photodiode, due to the dielectric layer and the metal interconnection layer in the light path More layers limit the amount of light absorbed by the photodiode, resulting in lower quantum efficiency. For the back-illuminated CMOS image sensor, light is incident on the photodiode from the back of the CMOS image sensor, thereby eliminating the loss of light and improving the conversion efficiency of photons to electrons.

However, existing back-illuminated CMOS image sensors have poor performance.

Contents of the invention

The technical problem solved by the present invention is to provide an image sensor and its forming method to improve the performance of the image sensor.

In order to solve the above-mentioned technical problems, an embodiment of the present invention provides a method for forming an image sensor, including: providing a substrate, the substrate includes opposite first surfaces and second surfaces, the substrate includes several mutually separated pixel regions, and There is a barrier area between the adjacent pixel areas, the base has a well area, and the well area has first dopant ions; a first isolation opening is formed in the base of the barrier area, and the first surface is exposed A first isolation opening; a second isolation opening is formed in the barrier region substrate, and the second surface exposes the second isolation opening; after the first isolation opening is formed or after the second isolation opening is formed, the barrier A first barrier structure is formed in the base of the region, the first barrier structure has second dopant ions inside, and the conductivity type of the second dopant ions is the same as that of the first dopant ions.

Optionally, the thickness of the substrate is: 2 microns to 3 microns.

Optionally, the depth of the first isolation structure is: 0.3 micron to 0.4 micron; the depth of the second isolation structure is: 0.3 micron to 0.4 micron.

Optionally, it also includes: forming a first isolation structure in the first isolation opening; the depth of the first isolation opening is 0.3 micron to 0.4 micron; the material of the first isolation structure includes silicon oxide or oxynitride silicon.

Optionally, after forming the first isolation opening and before forming the first isolation structure, the first barrier structure is formed; the method for forming the first barrier structure includes: forming a first photoresist on the first surface of the pixel region; The first barrier region is formed in the substrate at the bottom of the first isolation opening by using the first photoresist as a mask.

Optionally, the first barrier structure includes a multilayer stacked first barrier portion; the method for forming the first barrier portion includes: using the first photoresist as a mask, using a first ion implantation process in A first barrier portion is formed in the substrate at the bottom of the first isolation opening; the method for forming the first barrier structure includes performing a first ion implantation process several times, and the energy of each first implantation is sequentially increased.

Optionally, the first ion implantation process includes a first implantation energy; when the thickness of the first photoresist is: 1.8 microns to 4 microns, the maximum value of the first implantation energy is: 600 keV to 1200 keV; the size of the first barrier structure along the direction perpendicular to the surface of the substrate is: 0.4 microns to 2 microns.

Optionally, it also includes: forming a second isolation structure in the second isolation opening; the depth of the second isolation opening is 0.3 micron to 0.4 micron; the material of the second isolation structure includes silicon oxide or oxynitride silicon.

Optionally, after forming the second isolation opening, and before forming the first isolation structure in the second isolation opening, a second barrier structure is formed, the second barrier structure has third dopant ions in it, and the The conductivity type of the third doping ions is the same as that of the first doping ions; the method for forming the second barrier structure includes: forming a second photoresist on the second surface of the pixel region; using the second photoresist as a mask film, forming a second barrier region in the base at the bottom of the second isolation opening.

Optionally, the second barrier structure includes a multi-layer stacked second barrier portion; the method for forming the second barrier portion includes: using the second photoresist as a mask, using a second ion implantation process in A second blocking portion is formed in the base at the bottom of the second isolation opening; the method for forming the second blocking structure includes performing a second ion implantation process several times.

Optionally, the second ion implantation process includes a second implantation energy; when the thickness of the second photoresist is: 1.8 microns to 4 microns, the maximum value of the second implantation energy is 600 keV to 1200 KeV; the size of the second barrier structure along the direction perpendicular to the surface of the substrate is: 0.4 microns to 2 microns.

Optionally, there is a photoelectric doping region in the well region of the pixel region, and there is a fourth doping ion in the photoelectric doping region, and the conductivity type of the fourth doping ion is the same as that of the first doping ion. on the contrary.

Optionally, the forming method includes: forming a color filter on the second surface of the pixel area, one color filter is formed in one pixel area; forming a lens structure on the surface of the color filter; the color filter is a red color filter, a green color filter or a blue color filter.

Optionally, the first isolation opening is formed before forming the second isolation opening; or, the first isolation opening is formed after the second isolation opening is formed.

Correspondingly, the present invention also provides an image sensor, including: a substrate, the substrate includes opposite first surfaces and second surfaces, the substrate includes several pixel regions separated from each other, and barrier regions are provided between adjacent pixel regions , there are first dopant ions in the well region; a first isolation opening in the substrate of the barrier region, and the first surface exposes the first isolation opening; a second isolation in the substrate of the barrier region opening, and the second surface exposes a second isolation opening; a first barrier structure located at the bottom of the first isolation opening or in the bottom substrate of the second isolation opening, the first barrier structure has second dopant ions , the conductivity type of the second dopant ions is the same as the conductivity type of the first dopant ions.

Compared with the prior art, the technical solutions of the embodiments of the present invention have the following beneficial effects:

In the method for forming a pattern sensor provided by the technical solution of the present invention, after forming the first isolation opening or the second isolation opening, a first barrier structure is formed in the barrier region substrate, so that the difficulty of forming the first barrier structure is relatively low. The first isolation opening is used for subsequently accommodating the first isolation structure, and the second isolation opening is used for subsequently accommodating the second isolation structure. The barrier region not only has the first isolation structure and the second isolation structure, but also has the first barrier structure, therefore, the first isolation structure, the second isolation structure and the first barrier structure prevent electrons from diffusing or overflowing to adjacent The ability in the pixel area is strong, that is, the ability to reduce electrical crosstalk and dispersion is strong.

Further, after forming the second isolation opening, before forming the second isolation structure in the second isolation opening, a second barrier structure is formed at the bottom of the second isolation opening, so that the difficulty of forming the second barrier structure is low. Moreover, the first barrier structure and the second barrier structure are formed at the same time, so that the doping of ions in the barrier region between the bottom of the first isolation opening and the bottom of the second isolation opening is more sufficient, so that the first barrier structure and the second barrier structure are Electrons are more resistant to blocking.

Description of drawings

FIG. 1 is a schematic structural view of a back-illuminated CMOS image sensor;

2 to 10 are structural schematic diagrams of each step of an embodiment of the method for forming an image sensor of the present invention.

Detailed ways

As mentioned in the background, image sensors have poor performance.

FIG. 1 is a schematic structural diagram of a back-illuminated CMOS image sensor.

Please refer to FIG. 1, a substrate (not shown in the figure), the substrate has a well region 100 inside, and the well region 100 has first dopant ions inside, and the substrate 100 includes several pixel regions I separated from each other. There is a barrier region II between adjacent pixel regions I, and there are second dopant ions in the pixel region I, the conductivity type of the second dopant ions is opposite to that of the first dopant ions, and the substrate has a relatively The first surface 1 and the second surface 2, the barrier region II substrate has a first barrier structure 101 and a second barrier structure 104, the first surface 1 exposes the first barrier structure 101, the second surface 2 exposing the second barrier structure 104; the color filter 102 located on the second surface 2 of the substrate 100 of the pixel region I and the second barrier structure 104; and the lens structure 103 located on the surface of the color filter 101.

In the above image sensor, the conductivity type of the first dopant ions is opposite to that of the second dopant ions, therefore, a photodiode is formed in the pixel region I, and the photodiode is used to absorb photons to generate electrons. The first blocking structure 101 and the second blocking structure 104 are used to prevent electrons from drifting or diffusing into adjacent pixel regions I.

A method for forming the first barrier structure 101 and the second barrier structure 104 includes: forming a first opening in the substrate of the barrier region II, and the first surface exposes the first opening; Forming the first barrier structure 101 in; the forming method of the second barrier structure 104 includes: forming a second opening in the substrate of the barrier region II, the second surface exposes the second opening; A second barrier structure 104 is formed therein. The forming process of the first opening and the second opening includes a dry etching process. However, with the continuous improvement of the integration level of semiconductor devices, the widths of the first opening and the second opening are continuously reduced, making it difficult for etching gas to enter the first opening and the second opening, so that the formed first opening and the second opening The depth of the opening is difficult to make deep. Specifically, the depth of the first barrier structure 101 is 0.3 micron to 0.4 micron, and the depth of the second barrier structure 104 is 0.3 micron to 0.4 micron. The thickness of the base is 2 microns to 3 microns, therefore, the bottom of the first isolation structure 101 is not in contact with the bottom of the second barrier structure 104, so that electrons can easily flow between the first barrier structure 101 and the second barrier structure. 104 drift or diffuse into the adjacent pixel area I, which is likely to generate electrical crosstalk. Moreover, when the light is strong, too many electrons are generated, and the excess electrons are easy to diffuse into the adjacent pixel area I. Therefore, the performance of the image sensor is poor.

A method for reducing optical crosstalk and dispersion phenomenon includes: increasing the depths of the first blocking structure 101 and the second blocking structure 104 . Specifically, the method for forming the first barrier structure 101 includes: using a first ion implantation process to form the first barrier structure 101 in the substrate of the barrier region II; the method for forming the second barrier structure 104 includes: using In the second ion implantation process, a second blocking structure 104 is formed in the substrate of the blocking region II. However, due to the deep depth of the first barrier structure 101 , it is very difficult to form the first barrier structure 101 by using the first ion implantation process. Likewise, due to the deep depth of the second barrier structure 104 , it is more difficult to form the second barrier structure 104 by the second ion implantation process.

In order to solve the above technical problem, the present invention provides a method for forming an image sensor, comprising: forming a first isolation opening in the substrate of the barrier region, and the first surface exposes the first isolation opening; A second isolation opening is formed in the barrier region substrate, and the second surface exposes the second isolation structure; after the first isolation opening or the second isolation opening is formed, the first barrier structure is formed in the barrier region substrate. The method can reduce the difficulty of forming the first barrier structure, and at the same time, the first barrier structure and the subsequently formed first isolation structure and second isolation structure have a strong ability to diffuse or disperse electrons into adjacent pixel regions.

In order to make the above objects, features and beneficial effects of the present invention more comprehensible, specific embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings.

2 to 10 are structural schematic diagrams of each step of an embodiment of the method for forming an image sensor of the present invention.

Please refer to FIG. 2, a substrate (not shown in the figure) is provided, the substrate includes opposite first surfaces 11 and second surfaces 12, the substrate includes several pixel regions A separated from each other, and between adjacent pixel regions A There is a blocking area B, a well area 200 is provided in the substrate, and first dopant ions are provided in the well area 200; a photoelectric doping area 201 is formed in the base of the pixel area A, and the photoelectric doping area 201 There are fourth dopant ions inside, and the conductivity type of the fourth dopant ions is opposite to that of the first dopant ions.

In this embodiment, the material of the base is silicon. In other embodiments, the material of the substrate includes: germanium or silicon germanium.

The pixel region A is used to form a photoelectric doped region 201 , and the blocking region B is used to form a blocking structure subsequently.

There are first dopant ions in the well region 200, and the conductivity type of the first dopant ions is opposite to that of the fourth dopant ions. Therefore, the photoelectric doped region 201 and the well region 200 form a photodiode , the photodiode is used to absorb photons to generate electrons.

In this embodiment, the first dopant ions are P-type ions, such as boron ions, and the fourth dopant ions are N-type ions, such as phosphorus ions or arsenic ions. In other embodiments, the first dopant ions are N-type ions, such as phosphorus ions or arsenic ions, and the fourth dopant ions are P-type ions, such as boron ions.

The method for forming the photoelectric doped region 201 includes: forming a first mask layer on the base surface of the barrier region B; The photoelectric doped region 201 is formed therein.

The material of the first mask layer includes silicon nitride or titanium nitride. The first mask layer is used to form a mask for the photoelectric doped region 201 .

The base comprises a first 11 and a second 12 opposing faces.

In this embodiment, the image sensor is a Back-side Illumination CMOS image sensor, therefore, the first surface 11 is used for subsequent layout of metal lines, and the second surface 12 is used for subsequent formation of color filters.

In other embodiments, the image sensor is a front-side illumination (FSI) CMOS image sensor, therefore, the first surface is used for subsequent formation of color filters, and the second surface is used for subsequent layout of metal lines.

Subsequently, a first isolation opening and a second isolation opening are formed in the barrier region B substrate. In this embodiment, after the first isolation opening is formed, the second isolation opening is formed, please refer to FIG. 3 to FIG. 7 for details.

Referring to FIG. 3 , a first isolation opening 203 is formed in the base of the barrier region B, and the first surface 11 exposes the first isolation opening 203 .

The method for forming the first isolation opening 203 includes: forming a first photoresist 202 on the first surface 11 of the pixel region A; using the first photoresist 202 as a mask, etching the substrate, and A first isolation opening 203 is formed in the substrate.

The first photoresist 202 is used as a mask for forming the first isolation opening 203 and the subsequent first barrier structure.

The subsequent forming process of the first barrier structure includes a first ion implantation process, the first ion implantation process includes second dopant ions and first implantation energy, and in the process of forming the first barrier structure, the first photolithography The glue 202 is used to prevent the pixel area A from being implanted with the second dopant ions. Therefore, the thickness of the first photoresist 202 is closely related to the maximum value of the first implant energy.

In this embodiment, the thickness of the first photoresist 202 is: 1.8 μm˜4 μm.

Using the first photoresist 202 as a mask, the process of etching the substrate includes: one or a combination of a dry etching process and a wet etching process.

The depth of the first isolation opening 203 is: 0.3 μm˜0.4 μm.

The first isolation opening 203 is used for subsequently accommodating the first isolation structure. After forming the first isolation opening 201 and before forming the second isolation structure, a first barrier structure is formed in the substrate at the bottom of the first isolation opening 203 , please refer to FIG. 4 for details.

Please refer to FIG. 4 , a first barrier structure 204 is formed in the substrate at the bottom of the first isolation opening 203 , the first barrier structure 204 has second dopant ions inside, and the second dopant ions are mixed with the first dopant The heteroions are of the same conductivity type.

The method for forming the first barrier structure 204 includes: using the first photoresist 202 as a mask to form the first barrier structure 204 in the well region 200 at the bottom of the first isolation opening 203 .

The first barrier structure 204 includes a multi-layer stacked first barrier portion; the method for forming the first barrier portion includes: using the first photoresist 202 as a mask, forming a layer at the bottom of the first isolation opening 203 The well region 200 forms a first barrier.

Using the first photoresist 202 as a mask, the process of forming the first barrier portion at the bottom of the first isolation opening 201 includes a first ion implantation process, and the first ion implantation process includes a first implantation energy.

The method for forming the first barrier structure 204 includes performing the first ion implantation process several times, and the maximum value of the first implantation energy is determined by the thickness of the first photoresist 202 .

In this embodiment, the thickness of the first photoresist 202 is 1.8 micrometers to 4 micrometers, and the maximum value of the first injection energy is 600 keV to 1200 keV.

In this embodiment, since the first dopant ions are P-type ions, the second dopant ions are P-type ions, such as boron ions. In other embodiments, since the first dopant ions are N-type ions, the second dopant ions are N-type ions, such as phosphorus ions or arsenic ions.

The meaning of forming the first barrier structure 204 in the substrate at the bottom of the first isolation opening 203 is: after the first isolation opening 203 is formed, the first barrier structure 204 is formed, so that the difficulty of forming the first barrier structure 204 is relatively low. . Moreover, since the first implantation energy is relatively small, the damage to the base of the barrier region B during the first ion implantation process is low, which is beneficial to reducing defects, thereby reducing dark current and improving the performance of the image sensor.

Moreover, since the first barrier structure 204 is located in the barrier region B, and the barrier region B is located between adjacent pixel regions A, the first barrier structure 204 is separated from the subsequent first isolation structure and second isolation structure. The structure has a strong ability to prevent electrons from drifting or diffusing into adjacent pixel regions A, which is beneficial to further reducing electrical crosstalk. Moreover, when the intensity of the incident light is too large, that is, when the photodiode generates too many electrons, the first blocking structure 204 and the subsequent first isolation structure and second isolation structure block excessive electron diffusion. The ability to enter the adjacent pixel area A is relatively strong, so it is beneficial to further reduce the diffusion phenomenon, and the performance of the image sensor formed by the method is relatively good.

After forming the first barrier structure 204, the forming method further includes a first annealing treatment. The process of the first annealing treatment includes: a rapid annealing process, and the first annealing treatment is used to activate the second dopant ions.

The depth of the first barrier structure 204 is: 0.4 μm˜2 μm. The significance of selecting the depth of the first barrier structure 204: if the depth of the first barrier structure 204 is less than 0.4 microns, the first barrier structure 204 and the subsequent first and second isolation structures prevent electrons from drifting or diffusing to The power in the adjacent pixel area A is relatively weak, and electrical crosstalk and dispersion phenomenon are still prone to occur; when the depth of the first barrier structure 204 is greater than 2 μm, it is difficult to form the first barrier structure 204 .

Referring to FIG. 5 , after the first barrier structure 204 is formed, a first isolation structure 205 is formed in the first isolation opening 203 (see FIG. 4 ).

After forming the first barrier structure 204 and before forming the first isolation structure 205, the forming method further includes: removing the first photoresist 202; before removing the first photoresist 202, A first liner oxide layer (not shown) is formed on the sidewall and bottom of the isolation opening 203 .

The process of removing the first photoresist 202 includes: an ashing process.

The material of the first pad oxide layer includes silicon oxide.

Before forming the first isolation structure 205, the significance of forming the first pad oxide layer on the sidewall and bottom of the first isolation opening 203 is that the sidewall and bottom of the first isolation opening 203 formed by etching process There are defects, and the first pad oxide layer is formed on the sidewall and bottom of the first isolation opening 203, which is conducive to filling the defects, so that the subsequently formed first isolation structure 205 and the substrate have better compactness, which is beneficial to Reduce dark current and improve image sensor performance.

The method for forming the first isolation structure 205 includes: forming a first isolation material film in the first isolation opening 203 and the first surface 11 of the substrate; removing part of the first isolation material film until the first surface of the substrate is exposed 11. Form a first isolation structure 205 in the first isolation opening 203 .

The material of the first isolation material film includes silicon oxide or silicon oxynitride, and correspondingly, the material of the first isolation structure 205 includes silicon oxide or silicon oxynitride.

The forming process of the first isolation material film includes: a chemical vapor deposition process or a physical vapor deposition process.

The process of removing part of the first isolation material film includes: a chemical mechanical polishing process.

The first isolation structure 205, the first barrier structure 204, and the subsequent second isolation structure are used to prevent optical crosstalk and dispersion phenomenon.

Referring to FIG. 6 , a dielectric layer 206 and a passivation layer 207 located on the surface of the dielectric layer 206 are formed on the first surface 11 of the well region 200 and the surface of the first isolation structure 205 .

The material of the dielectric layer 206 includes silicon oxide or silicon oxynitride. The formation process of the dielectric layer 206 includes a chemical vapor deposition process or a physical vapor deposition process.

Metal wires (not shown in the figure) are provided in the dielectric layer 206 .

The material of the passivation layer 207 includes silicon nitride, and the formation process of the passivation layer 207 includes a chemical vapor deposition process or a physical vapor deposition process.

The passivation layer 207 is used to protect the top surface of the dielectric layer 206 .

Please refer to FIG. 7 , after the passivation layer 207 is formed, a second photoresist 208 is formed on the second surface 12 of the pixel area A; using the second photoresist 208 as a mask, the barrier area is etched. The base of B, in which the second isolation opening 209 is formed.

After forming the passivation layer 207 and before forming the second photoresist 208 , the forming method further includes: performing thinning treatment on the second surface 11 of the substrate.

After the thinning treatment, the thickness of the substrate is 2-3 microns. Both the subsequently formed first isolation structure and the second barrier structure are located in the substrate, therefore, the thickness of the substrate determines the depth of the subsequent first isolation structure and the second barrier structure.

The second photoresist 208 is used as a mask for forming the second isolation opening 209 and the subsequent second blocking structure.

The subsequent forming process of the second barrier structure includes a second ion implantation process, the second ion implantation process includes third doping ions and a second implantation energy, and during the process of forming the second barrier structure, the second photolithography The glue 208 is used to prevent the pixel area A from being implanted with the third dopant ions. Therefore, the thickness of the second photoresist 208 is closely related to the maximum value of the second implantation energy. In this embodiment, the thickness of the second photoresist 208 is: 1.8 μm˜4 μm.

Using the second photoresist 208 as a mask, the process of etching the base of the barrier region B includes: one or a combination of a dry etching process and a wet etching process.

The depth of the second isolation opening 209 is: the depth is: 0.3 μm˜0.4 μm.

In other embodiments, the second isolation opening is formed before the first isolation opening is formed.

Please refer to FIG. 8, using the second photoresist 208 as a mask, a second barrier structure 210 is formed in the base at the bottom of the second isolation opening 209, and the second barrier structure 210 has a third doped ions, the conductivity type of the third dopant ions is the same as that of the first dopant ions.

The method for forming the second barrier structure 210 includes: using the second photoresist 208 as a mask to form the second barrier structure 210 in the well region 200 at the bottom of the first isolation opening 209 .

The second barrier structure 210 includes a multi-layer stacked second barrier portion; the method for forming the second barrier portion includes: using the second photoresist 208 as a mask, forming a layer at the bottom of the second isolation opening 209 The well region 200 forms the second barrier. Using the second photoresist 208 as a mask, the process of forming the second barrier portion at the bottom of the second isolation opening 209 includes a second ion implantation process, and the second ion implantation process includes a second implantation energy.

The method for forming the second barrier structure 210 includes performing a second ion implantation process several times, and the maximum value of the second implantation energy is determined by the thickness of the second photoresist 208 .

In this embodiment, the thickness of the second photoresist 208 is 1.8 micrometers to 4 micrometers, and the maximum value of the second injection energy is 600 keV to 1200 keV.

The significance of forming the second barrier structure 210 at the bottom of the second isolation opening 209 is that the second barrier structure 210 is formed after the second isolation opening 209 is formed, so that the difficulty of forming the second barrier structure 210 is relatively low. Moreover, since the second implantation energy is relatively small, the damage to the substrate of the barrier region B during the second ion implantation process is low, which is beneficial to reducing defects, thereby reducing dark current and improving the performance of the image sensor.

In this embodiment, the first blocking structure 204 and the second blocking structure 210 are formed at the same time, which means that the second doped The hetero ions and the third dopant ions are more sufficient, so that the first barrier structure 204 and the second barrier structure 210 have a stronger ability to prevent electron diffusion or overflow into the adjacent pixel area A, which is conducive to further reducing electrical crosstalk and dispersion phenomena .

In other embodiments, no second barrier structure is formed.

The depth of the second barrier structure 210 is: 0.4 μm˜2 μm.

In this embodiment, the significance of selecting the depth of the second barrier structure 210 is: if the depth of the second barrier structure 210 is less than 0.4 microns, the second barrier structure 210, the first barrier structure 204, the first isolation The ability of the structure 205 and the subsequent second isolation structure to prevent electron drift or diffusion into the adjacent pixel area A is relatively weak, and electrical crosstalk and diffusion phenomena are still prone to occur; if the depth of the second isolation structure 210 is greater than 2 microns, the formation The second blocking structure 210 is more difficult.

In this embodiment, the first dopant ions are P-type ions, therefore, the third dopant ions are P-type ions, such as boron ions.

In other embodiments, the first dopant ions are N-type ions, therefore, the third dopant ions are N-type ions, such as phosphorus ions or arsenic ions.

The second barrier structure 210 is located between adjacent pixel regions A, therefore, the second barrier structure 210, the first barrier structure 204, the first isolation structure 205 and the subsequent second isolation structure prevent electrons from drifting or diffusing to phase The ability in the adjacent pixel area A is stronger, which is beneficial to further reduce the electrical crosstalk. Moreover, the ability of the second barrier structure 210, the first barrier structure 204, the first isolation structure 205 and the subsequent second isolation structure to prevent excess electrons from diffusing into the adjacent pixel area A is also relatively strong, which is beneficial to further Bleeding is reduced and, therefore, the performance of the image sensor formed by the method is better.

After forming the second barrier structure 210, the forming method further includes a second annealing treatment. The process of the second annealing treatment includes: a laser annealing process, and the second annealing treatment is used to activate the third dopant ions. Although the temperature of the laser annealing is relatively high, the time of the laser annealing process is short so that the metal wires in the dielectric layer 206 will not be melted, which is beneficial to ensure the properties of the metal wires.

Referring to FIG. 9 , after forming the second barrier region 210 , a second isolation structure 211 is formed in the second isolation opening 209 (see FIG. 8 ).

After forming the second barrier structure 210 and before forming the second isolation structure 211, the forming method further includes: removing the second photoresist 208; after removing the second photoresist 208, A second liner oxide layer (not shown) is formed on the sidewalls and bottom of the two isolation openings 209 .

The process of removing the second photoresist 208 includes: an ashing process.

The material of the second pad oxide layer includes silicon oxide.

Before forming the second isolation structure 211, the significance of forming the second pad oxide layer on the sidewall and bottom of the second isolation opening 209 is that the sidewall and bottom of the second isolation opening 209 formed by etching process There are defects, and the second pad oxide layer is formed on the sidewall and bottom of the second isolation opening 209, which is conducive to filling the defects, so that the subsequent formation of the second isolation structure 211 and the substrate are more compact, which is conducive to Reduce dark current and improve image sensor performance.

The method for forming the second isolation structure 211 includes: forming a first isolation material film on the second surface 12 of the substrate and the second isolation opening 209; planarizing the second isolation material film until the second surface of the substrate is exposed. surface 12 , forming a second isolation structure 211 in the second isolation opening 209 .

The material of the second isolation material includes silicon oxide or silicon oxynitride. The forming process of the second isolation material film includes: a chemical vapor deposition process or a physical vapor deposition process.

The second isolation material film is used to form the second isolation structure 211 , therefore, the material of the second isolation structure 211 includes silicon oxide or silicon oxynitride.

The process of planarizing the second isolation material film includes a chemical mechanical polishing process.

The second isolation structure 211 , the second barrier structure 210 , the first barrier structure 204 and the first isolation structure 205 have a strong ability to prevent electrons from drifting or diffusing into adjacent pixel regions A, which is beneficial to further reduce electrical crosstalk. Moreover, the ability of the second isolation structure 211, the second barrier structure 210, the first barrier structure 204 and the first isolation structure 205 to prevent excessive electrons from diffusing into the adjacent pixel area A is also relatively strong, which is beneficial to further Bleeding is reduced and, therefore, the performance of the image sensor formed by the method is better.

Referring to FIG. 10 , a color filter 212 is formed on the second surface 12 of the base of the pixel area A, and one color filter 212 is formed in one pixel area A; a lens structure 213 is formed on the surface of the color filter 212 .

The color filter 212 includes a red color filter 212a, a green color filter 212b or a blue color filter 212c, and a color filter 212 of one color is formed in one pixel area A, the light entering the color filter 212 can be filtered by the color filter 212 of one color, Then the incident light irradiated on the photodiode is monochromatic light.

The lens structures 213 are used to focus light, so that the incident light passing through one lens structure 213 can be irradiated on the photodiode corresponding to the lens structure 213 .

The barrier area B not only has the first isolation structure 205 and the second isolation structure 211, but also has the first barrier structure 204 and the second barrier structure 210, so that the ability to prevent electrons from drifting into the adjacent pixel area A is relatively strong. . Moreover, when the incident light intensity is strong, the photodiode generates too many electrons, and the first isolation structure 205, the second isolation structure 211, the first blocking structure 204, and the second blocking structure 210 prevent excessive electrons from diffusing to The capability in the adjacent pixel area A is stronger, which is beneficial to further reduce the dispersion phenomenon, and the performance of the image sensor formed by the method is better.

Correspondingly, the present invention also provides an image sensor, please refer to FIG. 10, including:

A substrate, the substrate includes opposite first surfaces 11 and second surfaces 12, the substrate includes a number of pixel regions A separated from each other, a barrier region B is provided between adjacent pixel regions A, and a well region 200 is provided in the substrate , there are first dopant ions in the well region 200;

A first isolation opening 203 (see FIG. 3 ) located in the base of the barrier region B, and the first surface 11 exposes the first isolation opening 203;

A second isolation opening 209 (see FIG. 7 ) located in the base of the barrier region B, and the second surface 12 exposes the second isolation opening 209;

The first barrier structure 204 located at the bottom of the first isolation opening 203 or the bottom of the second isolation opening 209 in the barrier region B substrate, the first barrier structure 204 contains second dopant ions, and the second dopant ions The conductivity type of is the same as that of the first dopant ion.

Although the present invention is disclosed 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, so the protection scope of the present invention should be based on the scope defined in the claims.

Claims (15)

1. A method for forming an image sensor, comprising: A substrate is provided, the substrate includes opposite first surfaces and second surfaces, the substrate includes several pixel regions separated from each other, barrier regions are provided between adjacent pixel regions, a well region is provided in the substrate, and the well region There are first dopant ions in it; forming a first isolation opening in the barrier region substrate, and the first surface exposes the first isolation opening; A second isolation opening is formed in the barrier region substrate, and the second surface exposes a second isolation opening; After the first isolation opening is formed, or after the second isolation opening is formed, a first barrier structure is formed in the barrier region substrate, the first barrier structure contains second dopant ions, and the second dopant ion contains The conductivity type is the same as that of the first dopant ions. 2 . The method for forming an image sensor according to claim 1 , wherein the substrate has a thickness of 2 micrometers to 3 micrometers. 3. The method for forming an image sensor according to claim 2, wherein the depth of the first isolation structure is: 0.3 microns to 0.4 microns; the depth of the second isolation structure is: 0.3 microns to 0.4 microns . 4. The method for forming an image sensor according to claim 1, further comprising: forming a first isolation structure in the first isolation opening; the depth of the first isolation opening is 0.3 μm to 0.4 μm ; The material of the first isolation structure includes silicon oxide or silicon oxynitride. 5. The method for forming an image sensor according to claim 4, wherein after forming the first isolation opening and before forming the first isolation structure, the first barrier structure is formed; the method for forming the first barrier structure The method includes: forming a first photoresist on the first surface of the pixel area; using the first photoresist as a mask to form the first barrier region in the base at the bottom of the first isolation opening. 6 . The method for forming an image sensor according to claim 5 , wherein the first barrier structure comprises a first barrier portion stacked in multiple layers; the method for forming the first barrier portion comprises: using the first barrier structure A photoresist is used as a mask, and a first barrier portion is formed in the base at the bottom of the first isolation opening by using a first ion implantation process; the method for forming the first barrier structure includes performing the first ion implantation process several times. 7. The method for forming an image sensor according to claim 6, wherein the first ion implantation process includes a first implantation energy; when the thickness of the first photoresist is: 1.8 microns to 4 microns, the The maximum value of the first injection energy is: 600 keV-1200 keV; the size of the first blocking structure along the direction perpendicular to the substrate surface is: 0.4 microns-2 microns. 8. The method for forming an image sensor according to claim 1, further comprising: forming a second isolation structure in the second isolation opening; the depth of the second isolation opening is 0.3 μm˜0.4 μm ; The material of the second isolation structure includes silicon oxide or silicon oxynitride. 9. The method for forming an image sensor according to claim 8, wherein after forming the second isolation opening and before forming a second isolation structure in the second isolation opening, the forming method further comprises: A second barrier structure is formed at the bottom of the second isolation opening, and there are third dopant ions inside the second barrier structure, and the conductivity type of the third dopant ions is the same as that of the first dopant ions; The forming method of the barrier structure includes: forming a second photoresist on the second surface of the pixel region; using the second photoresist as a mask to form a second barrier structure in the base at the bottom of the second isolation opening. 10. The method for forming an image sensor according to claim 9, wherein the second barrier structure comprises a multi-layered second barrier portion; the method for forming the second barrier portion comprises: using the first The second photoresist is used as a mask, and a second barrier part is formed in the base at the bottom of the second isolation opening by a second ion implantation process; the method for forming the second barrier structure includes performing several second ion implantation processes. 11. The method for forming an image sensor according to claim 10, wherein the second ion implantation process includes a second implantation energy; when the thickness of the second photoresist is: 1.8 microns to 4 microns, the The maximum value of the second injection energy is 600 keV-1200 keV; the size of the second barrier structure along the direction perpendicular to the substrate surface is: 0.4 microns-2 microns. 12. The method for forming an image sensor according to claim 1, characterized in that, there is a photoelectric doped region in the well region of the pixel region, and there is a fourth doping ion in the photoelectric doped region, and the fourth The conductivity type of the dopant ions is opposite to the conductivity type of the first dopant ions. 13. The method for forming an image sensor according to claim 1, characterized in that the forming method comprises: forming a color filter on the second surface of the pixel area, forming one color filter in one pixel area; forming a lens structure on the surface of the color filter ; The color filter is a red color filter, a green color filter or a blue color filter. 14. The method for forming an image sensor according to claim 1, wherein the first isolation opening is formed before forming the second isolation opening; or, the first isolation opening is formed after forming the second isolation opening. 15. An image sensor formed by the method according to any one of claims 1 to 14, characterized in that it comprises: A base, the base includes opposite first surfaces and second surfaces, the base includes a plurality of mutually separated pixel regions, barrier regions are provided between adjacent pixel regions, a well region is provided in the substrate, and a well region is provided in the well region having a first dopant ion; a first isolation opening located in the base of the barrier region, and the first surface exposes the first isolation opening; a second isolation opening located in the base of the barrier region, and the second surface exposes the second isolation opening; A first barrier structure located in the bottom of the first isolation opening or in the bottom substrate of the second isolation opening, the first barrier structure has second dopant ions, the conductivity type of the second dopant ions is the same as that of the first dopant The heteroions are of the same conductivity type.