阅读说明：本技术 图像传感器及其制造方法 (Image sensor and method for manufacturing the same ) 是由 薛广杰 于 2020-12-08 设计创作，主要内容包括：本发明提供了一种图像传感器及其制造方法,所述图像传感器的制造方法包括：提供一衬底,所述衬底包含多个像素单元区以及位于所述像素单元区之间的隔离区；对所述隔离区执行第二次离子注入；以及,对所述衬底执行高温退火处理,以在所述隔离区形成隔离层。本发明的技术方案使得在降低图像传感器中的暗电流的同时,还提高隔离效率。(The invention provides an image sensor and a manufacturing method thereof, wherein the manufacturing method of the image sensor comprises the following steps: providing a substrate, wherein the substrate comprises a plurality of pixel unit areas and isolation areas positioned between the pixel unit areas; performing a second ion implantation on the isolation region; and carrying out high-temperature annealing treatment on the substrate to form an isolation layer in the isolation region. According to the technical scheme, the dark current in the image sensor is reduced, and meanwhile, the isolation efficiency is improved.)

1. A method of manufacturing an image sensor, comprising:

providing a substrate, wherein the substrate comprises a plurality of pixel unit areas and isolation areas positioned between the pixel unit areas;

performing a second ion implantation on the isolation region; and the number of the first and second groups,

and carrying out high-temperature annealing treatment on the substrate to form an isolation layer in the isolation region.

2. The method of manufacturing an image sensor according to claim 1, wherein a first ion implantation is further performed on a bottom of the pixel cell region before the high temperature annealing process is performed on the substrate, so that the isolation layer is further formed on the bottom of the pixel cell region, the isolation layer of the isolation region being connected to the isolation layer at the bottom of the pixel cell region.

3. The method of claim 2, wherein the first ion implantation is performed to a depth of 1.1 to 1.2 times a depth of a doped region in the pixel cell region at a bottom of the pixel cell region.

4. The method of claim 2, wherein the performing the first ion implantation into the bottom of the pixel cell region and the second ion implantation into the isolation region comprises:

forming a protective layer on the substrate;

performing first ion implantation on the bottom of the pixel unit area;

forming a patterned photoresist layer on the protective layer, wherein the patterned photoresist layer exposes the protective layer on the isolation region;

sequentially performing second ion implantation from the bottom of the isolation region to the top of the isolation region by taking the patterned photoresist layer as a mask so as to implant ions with different gradients in the isolation region; and the number of the first and second groups,

removing the patterned photoresist layer;

or, the steps of performing the first ion implantation on the bottom of the pixel unit region and performing the second ion implantation on the isolation region include:

forming a protective layer on the substrate;

forming a patterned photoresist layer on the protective layer, wherein the patterned photoresist layer exposes the protective layer on the isolation region;

sequentially performing second ion implantation from the bottom of the isolation region to the top of the isolation region by taking the patterned photoresist layer as a mask so as to implant ions with different gradients in the isolation region;

removing the patterned photoresist layer; and the number of the first and second groups,

and performing first ion implantation on the bottom of the pixel unit area.

5. The method of claim 4, wherein the distance between the ions of different gradients is 0.1 μm to 0.3 μm.

6. The method of claim 2, wherein the ion species of the first ion implantation and the second ion implantation comprise nitrogen and/or oxygen.

7. The method of manufacturing an image sensor according to claim 1, wherein after the high temperature annealing process is performed on the substrate, a low temperature annealing process is also performed on the substrate.

8. The method of manufacturing an image sensor according to claim 7, wherein the high temperature annealing is performed at a temperature of 1000 ℃ to 1100 ℃ for 3s to 5 s; the temperature of the low-temperature annealing treatment is 550-650 ℃, and the time is 25-40 min.

9. The method of manufacturing an image sensor according to any one of claims 1 to 8, further comprising:

forming a doped region in the pixel unit region;

forming a device layer to cover the substrate; and the number of the first and second groups,

and providing a bearing wafer, and bonding the device layer and the bearing wafer through a bonding layer.

10. An image sensor, comprising:

a substrate including a plurality of pixel cell regions and isolation regions between the pixel cell regions; and the number of the first and second groups,

and the isolation layer is formed in the isolation region and is formed by performing ion implantation on the isolation region and performing high-temperature annealing treatment on the substrate after the ion implantation.

11. The image sensor of claim 10, wherein the isolation layer is further formed at a bottom of the pixel cell region, and the isolation layer of the isolation region is connected to the isolation layer at the bottom of the pixel cell region.

12. The image sensor of claim 11, wherein a material of the isolation layer comprises silicon oxide, silicon nitride, or silicon oxynitride.

13. The image sensor of any of claims 10-12, wherein the image sensor further comprises:

a doped region formed in the pixel unit region;

a device layer overlying the substrate; and the number of the first and second groups,

and the bearing wafer is bonded with the device layer through a bonding layer.

Technical Field

The present invention relates to the field of semiconductor integrated circuit manufacturing, and more particularly, to an image sensor and a method for manufacturing the same.

Background

An image sensor refers to a device that converts an optical signal into an electrical signal. According to the principle, the image sensor can be classified into a CCD (Charge Coupled Device) image sensor and a CMOS (Complementary Metal-Oxide Semiconductor) image sensor. Because the CMOS image sensor is manufactured by adopting the traditional CMOS circuit process, the CMOS image sensor and peripheral circuits required by the CMOS image sensor can be integrated, so that the CMOS image sensor has wider application prospect.

The CMOS image sensor may be classified into a front-illuminated image sensor and a back-illuminated image sensor according to a position where light is received. Wherein the front-illuminated image sensor receives light from the front side; the back-illuminated image sensor turns the incident light path of the element of the photosensitive layer, so that light can penetrate into the back directly, the influence of the structure and the thickness between the lens and the photodiode on the light in the front-illuminated image sensor is avoided, and the light receiving efficiency is improved.

The light conversion efficiency of the image sensor is the most important performance parameter, and a Shallow Trench Isolation (STI) structure or an inversion ion Implantation (IMP) region is often used as isolation between different pixels to reduce crosstalk between the pixels, where the inversion ion implantation is, for example, P-type or N-type. However, STI as an isolation causes much damage and charge accumulation to the substrate due to the etching process, thereby causing a dark current source; the inversion IMP is usually implanted with deeper ions to increase the voltage resistance of the device in order to prevent dark current in the substrate direction, and the formed doped region is not efficient as an isolation region, which may cause a leakage problem.

Therefore, how to improve the isolation structure between different pixels in the conventional image sensor to reduce the dark current in the image sensor and improve the isolation efficiency is a problem that needs to be solved at present.

Disclosure of Invention

An object of the present invention is to provide an image sensor and a method of manufacturing the same, which can improve isolation efficiency while reducing dark current in the image sensor.

To achieve the above object, the present invention provides a method of manufacturing an image sensor, comprising:

providing a substrate, wherein the substrate comprises a plurality of pixel unit areas and isolation areas positioned between the pixel unit areas;

performing a second ion implantation on the isolation region; and the number of the first and second groups,

and carrying out high-temperature annealing treatment on the substrate to form an isolation layer in the isolation region.

Optionally, before performing the high temperature annealing process on the substrate, a first ion implantation is further performed on the bottom of the pixel unit region, so that the isolation layer is further formed on the bottom of the pixel unit region, and the isolation layer of the isolation region is connected to the isolation layer on the bottom of the pixel unit region.

Optionally, the depth of the first ion implantation performed on the bottom of the pixel unit region is 1.1 to 1.2 times the depth of the doped region in the pixel unit region.

Optionally, the step of performing the first ion implantation on the bottom of the pixel unit region and the second ion implantation on the isolation region includes:

forming a protective layer on the substrate;

performing first ion implantation on the bottom of the pixel unit area;

forming a patterned photoresist layer on the protective layer, wherein the patterned photoresist layer exposes the protective layer on the isolation region;

sequentially performing second ion implantation from the bottom of the isolation region to the top of the isolation region by taking the patterned photoresist layer as a mask so as to implant ions with different gradients in the isolation region; and the number of the first and second groups,

removing the patterned photoresist layer;

or, the steps of performing the first ion implantation on the bottom of the pixel unit region and performing the second ion implantation on the isolation region include:

forming a protective layer on the substrate;

forming a patterned photoresist layer on the protective layer, wherein the patterned photoresist layer exposes the protective layer on the isolation region;

sequentially performing second ion implantation from the bottom of the isolation region to the top of the isolation region by taking the patterned photoresist layer as a mask so as to implant ions with different gradients in the isolation region;

removing the patterned photoresist layer; and the number of the first and second groups,

and performing first ion implantation on the bottom of the pixel unit area.

Optionally, the distance between ions of different gradients is 0.1 μm to 0.3 μm.

Optionally, the ion species of the first ion implantation and the second ion implantation include nitrogen and/or oxygen.

Optionally, after performing the high temperature annealing process on the substrate, a low temperature annealing process is further performed on the substrate.

Optionally, the temperature of the high-temperature annealing treatment is 1000-1100 ℃, and the time is 3-5 s; the temperature of the low-temperature annealing treatment is 550-650 ℃, and the time is 25-40 min.

Optionally, the method for manufacturing the image sensor further includes:

forming a doped region in the pixel unit region;

forming a device layer to cover the substrate; and the number of the first and second groups,

and providing a bearing wafer, and bonding the device layer and the bearing wafer through a bonding layer.

The present invention also provides an image sensor comprising:

a substrate including a plurality of pixel cell regions and isolation regions between the pixel cell regions; and the number of the first and second groups,

and the isolation layer is formed in the isolation region and is formed by performing ion implantation on the isolation region and performing high-temperature annealing treatment on the substrate after the ion implantation.

Optionally, the isolation layer is further formed at the bottom of the pixel unit region, and the isolation layer of the isolation region is connected to the isolation layer at the bottom of the pixel unit region.

Optionally, the isolation layer is made of silicon oxide, silicon nitride, or silicon oxynitride.

Optionally, the image sensor further includes:

a doped region formed in the pixel unit region;

a device layer overlying the substrate; and the number of the first and second groups,

and the bearing wafer is bonded with the device layer through a bonding layer.

Compared with the prior art, the technical scheme of the invention has the following beneficial effects:

1. the manufacturing method of the image sensor of the invention, through carrying out the second ion implantation to the isolation region located between pixel unit regions; and performing a high temperature annealing process on the substrate to form an isolation layer in the isolation region, so that the dark current in the image sensor is reduced while the isolation efficiency is also improved.

2. According to the image sensor, the isolation layer is formed in the isolation region between the pixel unit regions and is formed by performing ion implantation on the isolation region and performing high-temperature annealing treatment on the substrate after the ion implantation, so that the dark current in the image sensor is reduced, and the isolation efficiency is improved.

Drawings

Fig. 1a to 1b are schematic cross-sectional views of a conventional image sensor;

FIG. 2 is a flow chart of a method of fabricating an image sensor according to an embodiment of the invention;

fig. 3a to 3i are schematic views of devices in the method of manufacturing the image sensor shown in fig. 2.

Wherein the reference numerals of figures 1a to 3i are as follows:

11-a carrier wafer; 12-a bonding layer; 13-a device wafer; 131-a substrate; 132-pixel cell area; 1331-shallow trench isolation structure; 1332-isolating the doped region; 134-a dielectric layer; 135-transistor structure; 136-metal interconnect structures; 137-deep trench isolation structures; 20-a device wafer; 21-a substrate; 211-pixel unit area; 212-an isolation region; 22-a protective layer; 23-a patterned photoresist layer; 24-an isolation layer; 25-a transistor structure; 26-a first dielectric layer; 27-a second dielectric layer; 28-metal interconnect structures; 30-carrying the wafer; 40-a bonding layer.

Detailed Description

Taking the structure of the conventional image sensor shown in fig. 1a to 1b as an example, and fig. 1a to 1b show the structure of a back-illuminated image sensor, wherein each pixel in the image sensor shown in fig. 1a is isolated by a shallow trench isolation structure, and each pixel in the image sensor shown in fig. 1b is isolated by a doped region formed by inverse ion implantation. As shown in fig. 1a and 1b, the front sides of the carrier wafer 11 and the device wafer 13 are bonded by the bonding layer 12, the device wafer 13 includes a substrate 131, a plurality of pixel unit regions 132 (i.e., pixels) located on the front side of the substrate 131, a dielectric layer 134 formed on the pixel unit regions 132, and a transistor structure 135 and a metal interconnection structure 136 formed in the dielectric layer 134, a deep trench isolation structure 137 is further formed in the substrate 131 on the back side of the device wafer 13, wherein, the pixel unit regions 132 in FIG. 1a are isolated by shallow trench isolation structures 1331, the pixel unit regions 132 in fig. 1b are isolated by the isolation doped regions 1332 formed by reverse ion implantation, the positions of the shallow trench isolation structures 1331 and the isolation doped regions 1332 are both aligned with the positions of the deep trench isolation structures 137, and the deep trench isolation structures 137 can reduce the optical crosstalk between the adjacent pixel unit regions 132.

However, the pixel unit regions 132 in fig. 1a are isolated by the shallow trench isolation structure 1331, which may cause much damage and charge accumulation to the substrate 131 due to the process of forming the trench by etching, thereby causing a dark current source; however, the isolation doped region 1332 formed by the inversion ion implantation between the pixel unit regions 132 in fig. 1b is not efficient, and may cause a leakage problem.

Therefore, the present invention provides an image sensor and a method for manufacturing the same, which improves an isolation structure between different pixel unit regions in an existing image sensor to reduce dark current in the image sensor and improve isolation efficiency.

To make the objects, advantages and features of the present invention more apparent, the image sensor and the method for manufacturing the same according to the present invention will be described in further detail with reference to the accompanying drawings. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.

An embodiment of the present invention provides a method for manufacturing an image sensor, and referring to fig. 2, fig. 2 is a flowchart of a method for manufacturing an image sensor according to an embodiment of the present invention, where the method for manufacturing an image sensor includes:

step S1, providing a substrate, wherein the substrate comprises a plurality of pixel unit areas and isolation areas located between the pixel unit areas;

step S2, performing second ion implantation on the isolation region;

and step S3, performing high-temperature annealing treatment on the substrate to form an isolation layer in the isolation region.

The method for manufacturing the image sensor according to the present embodiment is described in detail with reference to fig. 3a to 3i, in which fig. 3a is a schematic top view of the pixel unit region and the isolation region, and fig. 3b to 3i are schematic longitudinal cross-sectional views.

According to step S1, a substrate 21 is provided, and referring to fig. 3a and 3b, the substrate 21 includes a plurality of pixel unit regions 211 and isolation regions 212 located between the pixel unit regions 211. The substrate 21 is made of a material known to those skilled in the art, such as silicon, silicon germanium, silicon-on-insulator (SOI), and the like.

The substrate 21 includes opposite front and back surfaces, and the plurality of pixel unit regions 211 are located on the front surface of the substrate 21. The pixel unit regions 211 are arranged in an array, and an isolation structure is fabricated in the isolation region 212 between two adjacent pixel unit regions 211 to isolate the adjacent pixel unit regions 211, so as to avoid electrical crosstalk between different pixel unit regions 211.

A second ion implantation is performed on the isolation region 212 to form an isolation layer on the isolation region 212, as per step S2.

Before the second ion implantation is performed on the isolation region 212, or after the second ion implantation is performed on the isolation region 212 and before the subsequent high-temperature annealing treatment is performed on the substrate 21, the first ion implantation may be further performed on the bottom of the pixel unit region 211, so that an isolation layer may be further formed on the bottom of the pixel unit region 211, and the isolation layer of the isolation region is connected to the isolation layer on the bottom of the pixel unit region.

The steps of performing the first ion implantation on the bottom of the pixel unit region 211 and performing the second ion implantation on the isolation region 212 include: first, referring to fig. 3c, a protection layer 22 is formed on the substrate 21, the protection layer 22 covers the pixel unit region 211 and the isolation region 212, the protection layer 22 is used to protect the substrate 21 during the subsequent first and second ion implantations to avoid excessive damage to the surface of the substrate 21, and the protection layer 22 is, for example, silicon oxide; then, a first ion implantation is performed on the bottom of the pixel unit region 211, as shown in fig. 3d, and ions I1 are implanted, and the depth of the first ion implantation can be controlled by adjusting the energy of the ion implantation; then, referring to fig. 3e, a patterned photoresist layer 23 is formed on the protection layer 22, and the patterned photoresist layer 23 exposes the protection layer 22 on the isolation region 212; then, referring to fig. 3e, using the patterned photoresist layer 23 as a mask, a second ion implantation is sequentially performed from the bottom of the isolation region 212 to the top of the isolation region 212 to implant ions I2 with different gradients (i.e. different depths of ions) into the isolation region 212; next, the patterned photoresist layer 23 is removed.

Alternatively, the steps (not shown) of performing the first ion implantation on the bottom of the pixel unit region 211 and performing the second ion implantation on the isolation region 212 include: firstly, forming a protective layer on the substrate, wherein the protective layer covers the pixel unit area and the isolation area; then, forming a patterned photoresist layer on the protective layer, wherein the patterned photoresist layer exposes the protective layer on the isolation region; then, taking the patterned photoresist layer as a mask, and sequentially performing second ion implantation from the bottom of the isolation region to the top of the isolation region to implant ions with different gradients (i.e. different depths of the ions) in the isolation region; then, removing the patterned photoresist layer; then, the first ion implantation is performed on the bottom of the pixel unit area.

The first ion implantation and the second ion implantation described in this embodiment represent two implantation processes, and do not represent the order of implantation.

Since the doped region is formed in the pixel unit region 211 in the subsequent step, the depth of the first ion implantation performed on the bottom of the pixel unit region 211 may be 1.1 times to 1.2 times the depth of the doped region in the pixel unit region 211, so that the isolation layer formed at the bottom of the pixel unit region 211 in the subsequent step can be located below the doped region. Alternatively, the first ion implantation may be deeper, for example, may be implanted into the substrate 21 below the pixel unit region 211, so that a subsequently formed isolation layer can be located below the pixel unit region 211.

Moreover, the patterned photoresist layer 23 formed by photolithography uses the same photomask as the isolation region 212, so that the protective layer 22 on the pixel unit region 211 is covered and the protective layer 22 on the isolation region 212 is exposed.

In the second ion implantation process, multiple times of ion implantation are performed from the bottom of the isolation region 212 to the top of the isolation region 212, that is, after ion implantation is performed at the same depth in the isolation region 212, the energy of ion implantation is adjusted and reduced to perform ion implantation at a shallower position in the isolation region 212, and the steps of adjusting and reducing the energy of ion implantation and ion implantation are repeated and circularly performed, so that ions with different gradients are implanted from the bottom of the isolation region 212 to the top of the isolation region 212. Wherein, the distance between the ions with different gradients can be 0.1-0.3 μm, so that an uninterrupted isolation layer is formed in the subsequent annealing process after the ions with different gradients are diffused uniformly. Moreover, the deepest depth of the second ion implantation may be the same as or greater than the depth of the first ion implantation, that is, the deepest depth of the second ion implantation may be 1.1 to 1.2 times the depth of the doped region in the pixel unit region 211 or may be implanted into the substrate 21 below the pixel unit region 211, so that a subsequently formed isolation layer can completely isolate the adjacent pixel unit regions 211 and surround the pixel unit regions 211 from the sides and the bottom, thereby avoiding crosstalk between the adjacent pixel unit regions 211.

Wherein, the ion species of the first ion implantation and the second ion implantation may include nitrogen or oxygen, or implanted nitrogen and oxygen. The ion species of the first ion implantation and the second ion implantation may be the same or different. The type of ion implantation is not limited to the above range, and may be another material that can react with the material of the substrate 21 to form an insulating spacer, for example, carbon.

According to step S3, referring to fig. 3f, a high temperature annealing process is performed on the substrate 21 after the first ion implantation and the second ion implantation are completed to form an isolation layer 24 in the isolation region 212. And after the high temperature annealing process is performed on the substrate 21, a low temperature annealing process may also be performed on the substrate 21.

As shown in fig. 3g, the protective layer 22 may be removed after performing a low temperature annealing process.

By performing the high-temperature annealing process, the ions implanted into the isolation region 212 and the bottom of the pixel unit region 211 can rapidly react with the material of the substrate 21 to form the isolation layer 24. For example, if the material of the substrate 21 is silicon and the implanted ions are oxygen, the isolation layer 24 is formed of silicon oxide; the implanted ions are nitrogen, and the formed isolation layer 24 is silicon nitride; the implanted ions are nitrogen and oxygen and the resulting isolation layer 24 is silicon oxynitride. Moreover, by performing the low-temperature annealing treatment, the structure of the isolation layer 24 is more compact, so that the isolation effect of the isolation layer 24 is better.

The temperature of the high-temperature annealing treatment can be 1000-1100 ℃, and the time of the high-temperature annealing treatment can be 3-5 s; the temperature of the low-temperature annealing treatment can be 550-650 ℃, and the time of the low-temperature annealing treatment can be 25-40 min. The temperature and time of the high-temperature annealing treatment and the low-temperature annealing treatment are not limited to the above ranges, and other suitable temperatures and times may be selected according to the type of implanted ions, the structure of the isolation layer 24 to be formed, and the like.

As can be seen from the above, by performing the second ion implantation on the isolation region 212 and performing the high temperature annealing treatment on the substrate 21 after the second ion implantation, so as to form the isolation layer 24 on the isolation region 212 to isolate the pixel unit regions 211, compared with the image sensor shown in fig. 1a in which the isolation layer 132 is isolated by the shallow trench isolation structure 1331, the embodiment of the present invention avoids the substrate from being damaged and accumulated by the process of forming the trench by etching, reduces the dark current, and omits the step of forming the shallow trench isolation structure 1331, thereby reducing the production cost; in addition, compared with the isolation doped region 1332 formed by the inversion ion implantation in fig. 1b for isolating the pixel unit region 132, in the embodiment of the present invention, the implanted ions react with the material of the substrate 21 to form the isolation layer 24, so that the isolation effect is improved, and the leakage is avoided. Accordingly, embodiments of the present invention improve isolation efficiency while reducing dark current in an image sensor.

In addition, the method of manufacturing the image sensor further includes: first, a doped region is formed in the pixel unit region 211, for example, the doped region may be a photoelectric doped region (not shown) having a conductivity type opposite to that of doped ions in the substrate 21 of the pixel unit region 211 to constitute a photodiode for converting photons in incident light into electrons; then, as shown in fig. 3h, a device layer is formed to cover the substrate 21, and the device layer may include a first dielectric layer 26 and a second dielectric layer 27 covering the front surface of the substrate 21, a transistor structure 25 located in the first dielectric layer 26, and a metal interconnection structure 28 located in the first dielectric layer 26 and the second dielectric layer 27, wherein the transistor structure 25 is located on the pixel unit region 211, and the metal interconnection structure 28 includes a metal interconnection line (not shown) and a conductive plug (not shown).

The substrate 21 and the device layer may form a device wafer 20 (as shown in fig. 3 h), that is, the image sensor may include a single device wafer 20; the image sensor may be a front-illuminated image sensor in which light enters from the front surface of the device wafer 20, or may be a back-illuminated image sensor in which light enters from the back surface of the device wafer 20. If the image sensor is a front-illuminated image sensor, the depth of the isolation layer 24 of the isolation region 212 may be increased to enhance the isolation effect between the adjacent pixel unit regions 211, for example, the isolation layer 24 between the adjacent pixel unit regions 211 may be extended into the substrate 21 below the isolation region 212, and at this time, the isolation layer 24 may not be formed at the bottom of the pixel unit region 211, and only the isolation layer 24 formed on the isolation region 212 may achieve the isolation effect; alternatively, the isolation effect between the adjacent pixel cell regions 211 may be enhanced by forming the isolation layer 24 at the bottom of the isolation region 212 and the pixel cell region 211 at the same time. If the image sensor is a back-illuminated image sensor, the isolation layer 24 is formed at the bottom of the isolation region 212 and the pixel unit region 211 at the same time, so as to avoid that the back surface of the substrate 21 is thinned and then too thick due to the fact that the depth of the isolation layer 24 of the isolation region 212 is increased to enhance the isolation effect when the isolation layer 24 is formed only in the isolation region 212, thereby avoiding much loss of light when light propagates in the substrate 21.

In addition, referring to fig. 3i, the method of manufacturing the image sensor further includes: a carrier wafer 30 is provided, and the device wafer 20 and the carrier wafer 30 are bonded, that is, the image sensor may include a bonded structure formed by bonding the device wafer 20 and the carrier wafer 30. The device layer and the carrier wafer 30 are bonded through a bonding layer 40, and the bonding layer 40 may be formed on the front surfaces of the device wafer 20 and the carrier wafer 30. After bonding, the back side of the substrate 21 of the device wafer 20 may also be thinned. The carrier wafer may be a wafer only for carrying or a wafer having other device structures.

At this time, the image sensor may be a back-illuminated image sensor in which light is incident from the back surface of the bonding structure (i.e., the back surface of the substrate 21), and the isolation layer 24 is formed at the bottom of the isolation region 212 and the pixel unit region 211 at the same time. Then, since the isolation layer 24 is further formed in the isolation region 212 through the annealing process after the second ion implantation, compared with the isolation doping region 1332 formed through the inverse ion implantation in fig. 1b for isolating the pixel unit regions 132, the isolation efficiency of the isolation layer 24 for isolating the pixel unit regions 211 is improved, so that the back surface of the substrate 21 of the device wafer 20 can be thinned normally; furthermore, the isolation doped region 1332 formed by the inversion ion implantation in fig. 1b isolates the pixel unit region 132, in order to control the dark current to the substrate 131, the isolation doped region 1332 formed by the inversion ion implantation needs to be deep, and the deep doping causes the substrate 131 to be still thick after the thinning process of the substrate 131, which causes much loss of light when propagating in the substrate 131, therefore, compared with the method shown in fig. 1b, the embodiment of the present invention can avoid the loss of light when propagating in the substrate. Moreover, since the first ion implantation is also performed on the bottom of the pixel cell region 211 to form the isolation layer 24 at the bottom of the pixel cell region 211, so that the pixel cell region 211 can be surrounded from the side and the bottom of the pixel cell region 211, an effect of avoiding crosstalk between adjacent pixel cell regions has been achieved, and thus, compared with the method shown in fig. 1a and 1b, the embodiment of the present invention can omit the step of forming the deep trench isolation structure 137, further reducing the production cost.

In summary, the method for manufacturing an image sensor provided by the present invention includes: providing a substrate, wherein the substrate comprises a plurality of pixel unit areas and isolation areas positioned between the pixel unit areas; performing a second ion implantation on the isolation region; and carrying out high-temperature annealing treatment on the substrate to form an isolation layer in the isolation region. The manufacturing method of the image sensor of the invention can reduce dark current in the image sensor and improve isolation efficiency.

Referring to fig. 3h, an embodiment of the present invention provides an image sensor, which includes a substrate 21 and an isolation layer 24, where the substrate 21 includes a plurality of pixel unit regions 211 and isolation regions located between the pixel unit regions 211; the isolation layer 24 is formed on the isolation region, and the isolation layer 24 is formed by performing ion implantation on the isolation region and performing high-temperature annealing treatment on the substrate 21 after the ion implantation.

The image sensor provided by the present embodiment is described in detail below with reference to fig. 3h to 3 i.

The substrate 21 includes a plurality of pixel cell regions 211 and isolation regions (i.e., isolation regions 212 shown in fig. 3a and 3 b) between the pixel cell regions 211. The substrate 21 is made of a material known to those skilled in the art, such as silicon, silicon germanium, silicon-on-insulator (SOI), and the like.

The substrate 21 includes opposite front and back surfaces, and the plurality of pixel unit regions 211 are located on the front surface of the substrate 21. The pixel unit regions 211 are arranged in an array, and an isolation structure is fabricated in the isolation region 212 between two adjacent pixel unit regions 211 to isolate the adjacent pixel unit regions 211, so as to avoid electrical crosstalk between different pixel unit regions 211.

The isolation layer 24 is formed on the isolation region 212, and the isolation layer 24 is formed by performing ion implantation on the isolation region 212 and performing high-temperature annealing treatment on the substrate 21 after the ion implantation; after the high-temperature annealing treatment is performed on the substrate 21, a low-temperature annealing treatment may also be performed on the substrate 21, so that the structure of the isolation layer 24 is more dense, and the isolation effect of the isolation layer 24 is better.

Ion implantation may also be performed on the bottom of the pixel cell region 211, so that the isolation layer 24 is also formed on the bottom of the pixel cell region 211, and the isolation layer 24 on the bottom of the pixel cell region 211 is located below a doped region (e.g., a photoelectric doped region) in the pixel cell region 211; alternatively, the isolation layer 24 is located below the pixel unit region 211, and the isolation layer 24 of the isolation region 212 is connected to the isolation layer 24 at the bottom of the pixel unit region 211. Therefore, the isolation layer 24 can completely isolate the adjacent pixel unit regions 211 and surround the doped regions in the pixel unit regions 211 from the side and the bottom, thereby preventing crosstalk between the adjacent pixel unit regions 211.

The material of the isolation layer 24 may include silicon oxide, silicon nitride or silicon oxynitride. The material of the isolation layer 24 is not limited to the above-mentioned kind, and may be another insulating isolation material, such as silicon carbide.

As can be seen from the above, since the isolation region 212 between the pixel unit regions 211 is formed with the isolation layer 24, and the isolation layer 24 is formed by performing ion implantation on the isolation region 212 and performing high temperature annealing treatment on the substrate 21 after ion implantation, compared with the image sensor shown in fig. 1a in which the isolation is performed between the pixel unit regions 132 through the shallow trench isolation structure 1331, the embodiment of the present invention avoids much damage and charge accumulation on the substrate 21 due to the process of forming the trench by etching, reduces dark current, and omits the step of forming the shallow trench isolation structure 1331, thereby reducing production cost; in addition, compared with the isolation doped region 1332 formed by the inversion ion implantation in fig. 1b for isolating the pixel unit region 132, in the embodiment of the present invention, the implanted ions react with the material of the substrate 21 to form the isolation layer 24, so that the isolation effect is improved, and the leakage is avoided. Accordingly, embodiments of the present invention improve isolation efficiency while reducing dark current in an image sensor.

In addition, the image sensor further includes: doped regions formed in the pixel cell region 211 and device layers overlying the substrate 21. For example, the doped region may be a photoelectric doped region (not shown) having a conductivity type opposite to that of doped ions in the substrate 21 of the pixel unit region 211 to constitute a photodiode for converting photons in incident light into electrons; as shown in fig. 3h, the device layer may include a first dielectric layer 26 and a second dielectric layer 27 covering the front surface of the substrate 21, a transistor structure 25 located in the first dielectric layer 26, and a metal interconnection structure 28 located in the first dielectric layer 26 and the second dielectric layer 27, wherein the transistor structure 25 is located on the pixel unit region 211, and the metal interconnection structure 28 includes a metal interconnection line (not shown) and a conductive plug (not shown).

The substrate 21 and the device layer may form a device wafer 20 (as shown in fig. 3 h), that is, the image sensor may include a single device wafer 20; the image sensor may be a front-illuminated image sensor in which light enters from the front surface of the device wafer 20, or may be a back-illuminated image sensor in which light enters from the back surface of the device wafer 20. If the image sensor is a front-illuminated image sensor, the depth of the isolation layer 24 of the isolation region 212 may be increased to enhance the isolation effect between the adjacent pixel unit regions 211, for example, the isolation layer 24 between the adjacent pixel unit regions 211 may be extended into the substrate 21 below the isolation region 212, and at this time, the isolation layer 24 may not be formed at the bottom of the pixel unit region 211; alternatively, the isolation effect between the adjacent pixel cell regions 211 may be enhanced by forming the isolation layer 24 at the bottom of the isolation region 212 and the pixel cell region 211 at the same time. If the image sensor is a back-illuminated image sensor, the isolation layer 24 is formed at the bottom of the isolation region 212 and the pixel unit region 211 at the same time, so as to avoid that the back surface of the substrate 21 is thinned and then too thick due to the fact that the depth of the isolation layer 24 of the isolation region 212 is increased to enhance the isolation effect when the isolation layer 24 is formed only in the isolation region 212, thereby avoiding much loss of light when light propagates in the substrate 21.

In addition, referring to fig. 3i, the image sensor may include a bonding structure formed by bonding the device wafer 20 and the carrier wafer 30. The bonding layer 40 may be formed on the front surfaces of the device wafer 20 and the carrier wafer 30, and the device wafer 20 and the carrier wafer 30 are bonded through the bonding layer 40. After bonding, the back side of the substrate 21 of the device wafer 20 may also be thinned.

At this time, the image sensor may be a back-illuminated image sensor in which light is incident from the back surface of the bonding structure (i.e., the back surface of the substrate 21), and the isolation layer 24 is formed at the bottom of the isolation region 212 and the pixel unit region 211 at the same time. Then, since the isolation layer 24 between the pixel unit regions 211 is formed by performing ion implantation on the isolation region 212 and performing high temperature annealing treatment on the substrate 21 after ion implantation, compared with the isolation doping region 1332 formed by inverse ion implantation in fig. 1b for isolating the pixel unit regions 132, the isolation efficiency of the isolation layer 24 between the pixel unit regions 211 is improved, so that the back surface of the substrate 21 of the device wafer 20 can be thinned normally; furthermore, the isolation doped region 1332 formed by the inversion ion implantation in fig. 1b isolates the pixel unit region 132, in order to control the dark current to the substrate 131, the isolation doped region 1332 formed by the inversion ion implantation needs to be deep, and the deep doping causes the substrate 131 to be still thick after the thinning process of the substrate 131, which causes much loss when light propagates in the substrate 131, therefore, compared with the structure shown in fig. 1b, the embodiment of the present invention can avoid the loss when light propagates in the substrate. Moreover, since the isolation layer 24 is further formed at the bottom of the pixel unit region 211, so that the pixel unit region 211 can be surrounded from the side and the bottom of the pixel unit region 211, the effect of avoiding crosstalk between the adjacent pixel unit regions 211 is already achieved, and therefore, compared with the structure shown in fig. 1a and 1b, the embodiment of the present invention can omit the step of forming the deep trench isolation structure 137, thereby further reducing the production cost.

In summary, the image sensor provided by the present invention includes: a substrate including a plurality of pixel cell regions and isolation regions between the pixel cell regions; and the isolation layer is formed in the isolation region and is formed by performing ion implantation on the isolation region and performing high-temperature annealing treatment on the substrate after the ion implantation. The image sensor of the invention can reduce dark current in the image sensor and improve isolation efficiency.

The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.