Image sensor and forming method thereof

Abstract

An image sensor and a forming method thereof, the image sensor comprising: a floating diffusion region located in a substrate at a side portion of a photoelectric conversion region, the floating diffusion region comprising a first floating diffusion region and a second floating diffusion region located at a top portion of the first floating diffusion region, and the first floating diffusion region and the second floating diffusion region being spaced by the substrate; the vertical transmission grid electrode is located on the substrate of the floating diffusion region and located in the substrate of the side wall of the floating diffusion region, the vertical transmission grid electrode deviates from the side wall of the photoelectric conversion region, and the side walls of the first floating diffusion region and the second floating diffusion region are in contact with the vertical transmission grid electrode; the first gate structure is located on the substrate of the photoelectric conversion region and on the substrate between the photoelectric conversion region and the floating diffusion region. By arranging the first floating diffusion region and the second floating diffusion region located at the top of the first floating diffusion region, the junction capacitance of the image sensor can be adjusted, and the saturation and sensitivity of the image sensor are both improved.

Description

Technical Field

[0001] The embodiments of the present invention relate to the field of semiconductor manufacturing, and in particular to an image sensor and a method for forming the same. Background Art

[0002] An image sensor is a device that converts light signals into electrical signals. Its working principle is based on the photoelectric effect, which refers to the phenomenon that when light shines on certain substances, the electrons of the substances absorb the energy of photons and produce corresponding electrical effects.

[0003] For example, CCD (Charge Coupled Device) image sensors and CMOS (CMOS Image Senser, CIS) image sensors use the photoelectric conversion function to convert optical images into electrical signals and then output digital images. They are currently widely used in digital cameras and other electronic optical devices. CMOS image sensors are gradually replacing CCDs due to their advantages such as simple process, easy integration with other devices, small size, light weight, low power consumption, and low cost. Currently, CMOS image sensors are widely used in digital cameras, camera phones, digital video cameras, medical imaging devices (such as gastroscopes), automotive imaging devices, and other fields.

[0004] Currently, the performance of image sensors still needs to be improved. Summary of the invention

[0005] The problem solved by the embodiments of the present invention is to provide an image sensor and a method for forming the same, so as to improve the photosensitivity of the image sensor.

[0006] To solve the above problems, an embodiment of the present invention provides an image sensor, comprising: a substrate, the substrate having a first type of doped ions; a photoelectric conversion region, located in the substrate, and the substrate exposes the top surface of the photoelectric conversion region; a floating diffusion region, located in the substrate at the side of the photoelectric conversion region, the floating diffusion region comprising a first floating diffusion region and a second floating diffusion region located at the top of the first floating diffusion region, the substrate exposes the top surface of the second floating diffusion region, and the first floating diffusion region and the second floating diffusion region are separated by the substrate, the floating diffusion region has a second type of doped ions, and the second type of doped ions are different from the first type of doped ions; a vertical transfer gate, located on the substrate of the floating diffusion region, and in the substrate at the side wall of the floating diffusion region, the vertical transfer gate is separated from the side wall of the photoelectric conversion region, and the side walls of the first floating diffusion region and the second floating diffusion region are in contact with the vertical transfer gate; a first gate structure, located on the substrate of the photoelectric conversion region, and on the substrate between the photoelectric conversion region and the floating diffusion region.

[0007] Optionally, the concentration of doped ions in the first floating diffusion region is 1E14 atom / cm 3 To 9E20atom / cm 3 ; The concentration of doped ions in the second floating diffusion region is 1E14atom / cm3 to 9E20atom / cm3.

[0008] Optionally, a distance between the first floating diffusion region and the second floating diffusion region is 20 nanometers to 100 nanometers.

[0009] Optionally, along a normal direction to the surface of the substrate, a thickness of the first floating diffusion region is 20 nanometers to 100 nanometers; and along a normal direction to the surface of the substrate, a thickness of the second floating diffusion region is 20 nanometers to 100 nanometers.

[0010] Optionally, the image sensor also includes: a first interconnection through hole located on the top of the vertical transfer gate, and the first interconnection through hole is electrically connected to the vertical transfer gate; a second interconnection through hole located on the top of the first gate structure, and the second interconnection through hole is electrically connected to the first gate structure.

[0011] Optionally, the material of the vertical transfer gate includes polysilicon; and the material of the first gate structure includes polysilicon.

[0012] Correspondingly, an embodiment of the present invention also provides a method for forming an image sensor, comprising: providing a substrate, the substrate having a first type of doped ions, a photoelectric conversion region being formed in the substrate, and the substrate exposing a top surface of the photoelectric conversion region; forming a floating diffusion region in the substrate at a side of the photoelectric conversion region, the floating diffusion region comprising a first floating diffusion region and a second floating diffusion region located at the top of the first floating diffusion region, the substrate exposing a top surface of the second floating diffusion region, and the first floating diffusion region and the second floating diffusion region being separated by the substrate, the floating diffusion region having a second type of doped ions, the second type of doped ions being of a different type from the first type of doped ions; forming a vertical transfer gate on the substrate of the floating diffusion region and in the substrate located at a side wall of the floating diffusion region, the vertical transfer gate being opposite to the side wall of the photoelectric conversion region, and the side walls of the first floating diffusion region and the second floating diffusion region being in contact with the vertical transfer gate; forming a first gate structure on the substrate of the photoelectric conversion region and on the substrate between the photoelectric conversion region and the floating diffusion region.

[0013] Optionally, after forming the vertical transfer gate, the first gate structure is formed; or, after forming the first gate structure, the vertical transfer gate is formed.

[0014] Optionally, the step of forming the floating diffusion area includes: performing a first doping treatment on the substrate on the side of the photoelectric conversion area to form the first floating diffusion area; after forming the first floating diffusion area, performing a second doping treatment on the substrate of the top part of the thickness of the first floating diffusion area to form a second floating diffusion area on the top of the first floating diffusion area, and the first floating diffusion area and the second floating diffusion area are separated by the substrate.

[0015] Optionally, the process of forming the floating diffusion region includes an ion implantation process.

[0016] Optionally, in the process of forming the first floating diffusion region, the parameters of the ion implantation process include: a doping dose range of 1E14atom / cm 3 To 9E20atom / cm 3 ; The injection energy range is 250kev to 500kev; In the process of forming the second floating diffusion region, the parameters of the ion implantation process include: the doping dose range is 1E14atom / cm 3 To 9E20atom / cm 3 ; The implantation energy range is 20kev to 100kev.

[0017] Optionally, along a normal direction to the surface of the substrate, a thickness of the first floating diffusion region is 20 nanometers to 100 nanometers; and along a normal direction to the surface of the substrate, a thickness of the second floating diffusion region is 20 nanometers to 100 nanometers.

[0018] Optionally, a distance between the first floating diffusion region and the second floating diffusion region is 20 nanometers to 100 nanometers.

[0019] Optionally, the step of forming the vertical transfer gate includes: forming an opening in the substrate of the side wall of the floating diffusion region, the opening being opposite to the side wall of the photoelectric conversion region; and forming a vertical transfer gate on the substrate of the floating diffusion region and in the opening.

[0020] Optionally, the process of forming the opening includes a dry etching process.

[0021] Optionally, after forming the vertical transfer gate and the first gate structure, the method for forming the semiconductor structure further includes: forming a first interconnection through hole on the top of the vertical transfer gate, the first interconnection through hole being electrically connected to the vertical transfer gate; and forming a second interconnection through hole on the top of the first gate structure, the second interconnection through hole being electrically connected to the first gate structure.

[0022] Compared with the prior art, the technical solution of the embodiment of the present invention has the following advantages:

[0023] In the method for forming an image sensor provided by an embodiment of the present invention, a floating diffusion region is formed in a substrate at a side of the photoelectric conversion region, the floating diffusion region includes a first floating diffusion region and a second floating diffusion region located on the top of the first floating diffusion region, the substrate exposes the top surface of the second floating diffusion region, and the first floating diffusion region and the second floating diffusion region are separated by the substrate, the floating diffusion region has a second type of doped ions, the second type of doped ions are different from the first type of doped ions, the floating diffusion region is equivalent to a junction capacitor, and is used to store electrons generated by photoelectric conversion. By providing the first floating diffusion region and the second floating diffusion region located on the top of the first floating diffusion region, the junction capacitance of the image sensor can be adjusted. When the image sensor is in a high brightness environment, a high voltage is applied through a vertical transfer gate. The first floating diffusion area is connected to the second floating diffusion area, so that the capacitance of the image sensor is increased, that is, the signal strength detectable by the image sensor is enhanced, and the saturation of the image sensor is improved. When the image sensor is in a low-brightness environment, a low voltage is applied through the vertical transfer gate to prevent the first floating diffusion area from being connected to the second floating diffusion area, so that the capacitance of the image sensor is only the capacitance of the second floating diffusion area, and the capacitance of the image sensor becomes smaller. Correspondingly, a small amount of light signal in a low-brightness environment can also cause a large voltage to increase, thereby enhancing the sensitivity of the image sensor. In summary, by setting the first floating diffusion area and the second floating diffusion area located on top of the first floating diffusion area, the junction capacitance of the image sensor can be adjusted, thereby improving the saturation and sensitivity of the image sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 1 is a schematic diagram of the corresponding structure of an embodiment of the image sensor of the present invention.

[0025] Figures 2 to 7 It is a schematic structural diagram corresponding to each step in an embodiment of a method for forming an image sensor of the present invention. DETAILED DESCRIPTION

[0026] As can be seen from the background technology, the saturation of the image sensor represents the maximum detectable signal strength, and the sensitivity of the image sensor represents the ability to obtain a clear image when the light is dim or the exposure time is short. The image sensor has a high demand for both high saturation and high sensitivity, but the current technology uses a single photoelectric conversion area and floating diffusion area (FD) and it is difficult to achieve this demand. For example: outdoor surveillance cameras are difficult to use indoors because their sensitivity is not enough; indoor cameras are difficult to be compatible with outdoor high-brightness environments because their saturation values ​​are not enough. The fundamental reason is that the capacitance value of the floating diffusion area is fixed. The outdoor high-brightness environment requires the floating diffusion area capacitance value of the image sensor to be higher, and the indoor dark light environment sensor requires the floating diffusion area capacitance value of the image sensor to be lower. Therefore, it is difficult for the image sensor to be compatible with both high saturation and high sensitivity.

[0027] In order to solve the technical problem, an embodiment of the present invention provides a method for forming an image sensor, comprising: providing a substrate, the substrate having a first type of doping ions, a photoelectric conversion region being formed in the substrate, and the substrate exposing the top surface of the photoelectric conversion region; forming a floating diffusion region in the substrate at the side of the photoelectric conversion region, the floating diffusion region comprising a first floating diffusion region and a second floating diffusion region located at the top of the first floating diffusion region, the substrate exposing the top surface of the second floating diffusion region, and the first floating diffusion region and the second floating diffusion region are separated by the substrate, the floating diffusion region having a second type of doping ions, and the second type of doping ions are of a different type from the first type of doping ions; forming a vertical transfer gate on the substrate of the floating diffusion region and in the substrate located at the side wall of the floating diffusion region, the vertical transfer gate being away from the side wall of the photoelectric conversion region, and the side walls of the first floating diffusion region and the second floating diffusion region being in contact with the vertical transfer gate; forming a first gate structure on the substrate of the photoelectric conversion region and on the substrate between the photoelectric conversion region and the floating diffusion region.

[0028] In the method for forming an image sensor provided by an embodiment of the present invention, the floating diffusion region is equivalent to a junction capacitor, which is used to store electrons generated by photoelectric conversion. By setting a first floating diffusion region and a second floating diffusion region located on the top of the first floating diffusion region, the junction capacitance of the image sensor can be adjusted. When the image sensor is in a high-brightness environment, a high voltage is applied through a vertical transmission gate to make the first floating diffusion region and the second floating diffusion region conduct, thereby increasing the capacitance of the image sensor, that is, the signal intensity detectable by the image sensor is enhanced, and the saturation of the image sensor is improved. When the image sensor is in a low-brightness environment, a low voltage is applied through a vertical transmission gate to make the first floating diffusion region and the second floating diffusion region unable to conduct, so that the capacitance of the image sensor is only the capacitance of the second floating diffusion region, and the capacitance of the image sensor becomes smaller. Correspondingly, a small amount of light signal in a low-brightness environment can also cause a large voltage to increase, thereby enhancing the sensitivity of the image sensor. In summary, by setting a first floating diffusion region and a second floating diffusion region located on the top of the first floating diffusion region, the junction capacitance of the image sensor can be adjusted, thereby improving the saturation and sensitivity of the image sensor.

[0029] In order to make the above-mentioned purposes, features and advantages of the embodiments of the present invention more obvious and understandable, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0030] Figure 1 1 is a schematic diagram of the corresponding structure of an embodiment of the image sensor of the present invention.

[0031] The image sensor includes: a substrate 200, the substrate 200 having a first type of doped ions; a photoelectric conversion region 208, located in the substrate 200, and the substrate 200 exposes the top surface of the photoelectric conversion region 208; a floating diffusion region 204, located in the substrate 200 at the side of the photoelectric conversion region 208, the floating diffusion region 204 includes a first floating diffusion region 202 and a second floating diffusion region 203 located on the top of the first floating diffusion region 202, the substrate 200 exposes the top surface of the second floating diffusion region 203, and the first floating diffusion region 202 and the second floating diffusion region 203 are separated by the substrate 200, and the floating diffusion region 204 is located in the substrate 200 at the side of the photoelectric conversion region 208. The floating diffusion region 204 has second-type doping ions, which are different from the first-type doping ions; a vertical transfer gate 210 is located on the substrate of the floating diffusion region 204 and in the substrate of the sidewall of the floating diffusion region 204, and the vertical transfer gate 210 is opposite to the sidewall of the photoelectric conversion region 208, and the sidewalls of the first floating diffusion region 202 and the second floating diffusion region 203 are in contact with the vertical transfer gate 210; a first gate structure 216 is located on the substrate 200 of the photoelectric conversion region 208 and on the substrate 200 between the photoelectric conversion region 208 and the floating diffusion region 204.

[0032] It should be noted that the floating diffusion area 204 in the image sensor is equivalent to a junction capacitor, which is used to store electrons generated by photoelectric conversion. By setting the first floating diffusion area 202 and the second floating diffusion area 203 located on the top of the first floating diffusion area 202, the junction capacitance of the image sensor can be adjusted. When the image sensor is in a high-brightness environment, a high voltage is applied through the vertical transmission gate 210 to make the first floating diffusion area 202 and the second floating diffusion area 203 conductive, so that the capacitance of the image sensor becomes larger, that is, the signal strength that can be detected by the image sensor is enhanced, and the saturation of the image sensor is improved. When the image sensor is in a low-brightness environment, the first floating diffusion area 202 and the second floating diffusion area 203 are connected. In a low-brightness environment, a low voltage is applied through the vertical transfer gate 210, so that the first floating diffusion area 202 and the second floating diffusion area 203 cannot be turned on, so that the capacitance of the image sensor is only the capacitance of the second floating diffusion area 203, and the capacitance of the image sensor becomes smaller. Correspondingly, a small amount of light signal in a low-brightness environment can also cause a large voltage to increase, thereby enhancing the sensitivity of the image sensor. In summary, by setting the first floating diffusion area 202 and the second floating diffusion area 203 located on the top of the first floating diffusion area 202, the junction capacitance of the image sensor can be adjusted, thereby improving the saturation and sensitivity of the image sensor.

[0033] The substrate 200 provides a process platform for forming an image sensor.

[0034] As an example, the image sensor is a CMOS image sensor.

[0035] In other embodiments, the image sensor may also be a CCD (Charge Coupled Device) image sensor, a DTOF (Direct Time of Flight) sensor, or an iTOF (indirect Time of Flight) sensor, etc.

[0036] In this embodiment, the substrate 200 is a substrate 200 of a pixel wafer, and the substrate 200 of the pixel wafer is a silicon substrate.

[0037] In other embodiments, the material of the substrate of the pixel wafer may also be other materials such as germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, and the substrate of the pixel wafer may also be other types of materials such as a silicon substrate on an insulator or a germanium substrate on an insulator.

[0038] As an example, the substrate 200 is a P-type substrate. The mobility of free electrons in a P-type substrate is three times that of holes. By selecting a P-type substrate, the photoelectric conversion efficiency of the image sensor is improved, and the performance of the image sensor is improved. To this end, the type of doped ions in the substrate 200 is P-type ions, such as boron, indium or gallium.

[0039] It should be noted that the photoelectric conversion region 208 is used as a region for receiving optical signals and converting optical signals into electrical signals.

[0040] It should also be noted that the substrate 200 exposes the top surface of the photoelectric conversion region 208, which facilitates the incident light to directly enter the photoelectric conversion region 208, reduces the probability of the incident light being blocked, and can maximize the photoelectric conversion efficiency of the image sensor.

[0041] There are a plurality of photoelectric conversion regions 208 in the substrate 200, and the plurality of photoelectric conversion regions 208 are arranged in a matrix. As an example, there is one photoelectric conversion region 208.

[0042] In this embodiment, the semiconductor structure further includes: a shallow trench isolation structure 201 located in the substrate 200 , and a photoelectric conversion region 208 and a subsequently formed floating conversion region are disposed between adjacent shallow trench isolation structures 201 .

[0043] The shallow trench isolation structure 201 is used to reduce the probability of optical crosstalk between adjacent photoelectric conversion regions 208 and improve the performance of the image sensor.

[0044] The material of the shallow trench isolation structure 201 is an insulating material. As an example, the material of the shallow trench isolation structure 201 is silicon oxide. In other embodiments, the material of the shallow trench isolation structure may also be one or more of silicon nitride, silicon carbide and silicon oxynitride.

[0045] It should be noted that in the process of forming the first floating diffusion area 202 and the second floating diffusion area 203, by first forming the first floating diffusion area 202 and then forming the second floating diffusion area 203 on top of the first floating diffusion area 202, the probability of mutual influence between the first floating diffusion area 202 and the second floating diffusion area 203 is reduced.

[0046] It should also be noted that the concentration of the doped ions in the first floating diffusion area 202 should not be too large or too small. If the concentration of the doped ions in the first floating diffusion area 202 is too large, it is easy to cause the capacitance of the image sensor to increase, affecting the sensitivity of the image sensor; if the concentration of the doped ions in the first floating diffusion area 202 is too small, it is easy to cause the capacitance value of the first floating diffusion area 202 to be too small, thereby making the junction capacitance value of the image sensor too small, and then when the image sensor is in a high-brightness environment, the detectable signal intensity of the image sensor is not enhanced, affecting the saturation of the image sensor. For this reason, in this embodiment, the concentration of the doped ions in the first floating diffusion area 202 is 1E14atom / cm 3 To 9E20atom / cm 3 .

[0047] Specifically, along the normal direction of the surface of the substrate 200, the thickness of the first floating diffusion area 202 should not be too large or too small. If the thickness of the first floating diffusion area 202 is too large, it is easy to cause the capacitance of the image sensor to increase, affecting the sensitivity of the image sensor; if the thickness of the first floating diffusion area 202 is too small, it is easy to cause the capacitance value of the first floating diffusion area 202 to decrease, thereby reducing the junction capacitance value of the image sensor. When the image sensor is in a high-brightness environment, the signal intensity that can be detected by the image sensor is not enhanced, affecting the saturation of the image sensor. For this reason, in this embodiment, along the normal direction of the surface of the substrate 200, the thickness of the first floating diffusion area 202 is 20 nanometers to 100 nanometers.

[0048] It should be noted that the concentration of doped ions in the second floating diffusion area 203 should not be too large or too small. If the concentration of doped ions in the second floating diffusion area 203 is too large, it is easy to cause the capacitance value of the second floating diffusion area 203 to be too large. Accordingly, when the image sensor is in a low-brightness environment, the electrical signal generated by a small amount of light signal is too small, so that the voltage change generated by the capacitance value of the second floating diffusion area 203 is not obvious, thereby weakening the sensitivity of the image sensor and affecting the performance of the image sensor; if the concentration of doped ions in the second floating diffusion area 203 is too small, the capacitance value of the second floating diffusion area 203 is too small, so that the junction capacitance value of the image sensor is also too small, and then when the image sensor is in a high-brightness environment, the signal intensity that the image sensor can detect is not enhanced, affecting the saturation of the image sensor. For this reason, in this embodiment, the concentration of doped ions in the second floating diffusion area 203 is 1E14atom / cm3 to 9E20atom / cm3.

[0049] Specifically, along the normal direction of the surface of the substrate 200, the thickness of the second floating diffusion area 203 should not be too large or too small. If the thickness of the second floating diffusion area 203 is too large, the capacitance value of the second floating diffusion area 203 is too large. When the image sensor is in a low-brightness environment, a low voltage is applied through the rear vertical transfer gate 210, so that the first floating diffusion area 202 and the second floating diffusion area 203 cannot be turned on, so that the capacitance of the image sensor is only the capacitance of the second floating diffusion area 203. Since the thickness of the second floating diffusion area 203 is too large, the capacitance value of the second floating diffusion area 203 is too large. Accordingly, when the image sensor is in a low-brightness environment, the electrical signal generated by a small amount of light signal is too small, so that the voltage change generated by the capacitance value of the second floating diffusion area 203 is not obvious, so that If the thickness of the second floating diffusion area 203 is too small, the capacitance value of the second floating diffusion area 203 is too small, so that the junction capacitance value of the image sensor is also too small, and then when the image sensor is in a high brightness environment, the signal intensity that the image sensor can detect is not enhanced, affecting the saturation of the image sensor. At the same time, if the depth of the second floating diffusion area 203 is too small, the distance between the first floating diffusion area 202 and the second floating diffusion area 203 is increased, and the difficulty of mutual conduction between the first floating diffusion area 202 and the second floating diffusion area 203 is increased, thereby affecting the performance of the image sensor. To this end, in this embodiment, along the normal direction of the surface of the substrate 200, the thickness of the second floating diffusion area 203 is 20 nanometers to 100 nanometers.

[0050] It should be noted that the distance between the first floating diffusion area 202 and the second floating diffusion area 203 should not be too large or too small. If the distance between the first floating diffusion area 202 and the second floating diffusion area 203 is too large, when a voltage is applied through the vertical transfer gate 210, the difficulty of mutual conduction between the first floating diffusion area 202 and the second floating diffusion area 203 is increased, so that the junction capacitance value of the image sensor is only the capacitance value of the second floating diffusion area 203. When the image sensor is in a high-brightness environment, the signal intensity detectable by the image sensor is not enhanced, which affects the saturation of the image sensor; if the distance between the first floating diffusion area 202 and the second floating diffusion area 203 is too small, the probability of mutual conduction between the first floating diffusion area 202 and the second floating diffusion area 203 when no voltage is applied is increased, so that the effect of the adjustable capacitance value of the floating diffusion area 204 is affected, and then the saturation and sensitivity of the image sensor cannot be compatible, which affects the performance of the image sensor. Therefore, in this embodiment, the distance between the first floating diffusion region 202 and the second floating diffusion region 203 is 20 nanometers to 100 nanometers.

[0051] In this embodiment, the floating diffusion region 204 has second-type doping ions, and the second-type doping ions are different from the first-type doping ions.

[0052] Specifically, the ions doped in the floating diffusion region 204 are N-type ions.

[0053] In the present embodiment, the first floating diffusion area 202 and the second floating diffusion area 203 are separated by the substrate 200. Since the doped ions in the substrate 200 are P-type ions, when no voltage is subsequently applied to the vertical transfer gate 210, the substrate 200 located between the first floating diffusion area 202 and the second floating diffusion area 203 plays a role in electrically isolating the first floating diffusion area 202 from the second floating diffusion area 203, thereby reducing the probability of mutual conduction between the first floating diffusion area 202 and the second floating diffusion area 203, so that the image sensor can achieve the effect of adjustable junction capacitance value formed by the floating diffusion area 204, thereby improving the saturation and sensitivity of the image sensor.

[0054] A high voltage is applied through the vertical transfer gate 210 to conduct the first floating diffusion area 202 and the second floating diffusion area 203, thereby increasing the capacitance of the image sensor. As an example, the high voltage value is at least greater than or equal to 0.5V.

[0055] A low voltage is applied through the vertical transfer gate 210 to prevent the first floating diffusion area 202 and the second floating diffusion area 203 from being turned on, thereby reducing the capacitance of the image sensor. As an example, the low voltage is at least less than or equal to 0V.

[0056] Specifically, the vertical transfer gate 210 is used as a conduction switch between the first floating diffusion area 202 and the second floating diffusion area 203. By applying a voltage to the vertical transfer gate 210, the first floating diffusion area 202 and the second floating diffusion area 203 are controlled to be turned on and off, thereby achieving an adjustable effect on the junction capacitance formed by the floating diffusion area 204.

[0057] In this embodiment, the vertical transfer gate 210 is separated from the side wall of the photoelectric conversion region 208, that is, the vertical transfer gate 210 is not located on the substrate 200 between the photoelectric conversion region 208 and the floating diffusion region 204, so that the electrical signal in the photoelectric conversion region 208 can enter the floating diffusion region 204 through the substrate 200 between the photoelectric conversion region 208 and the floating diffusion region 204.

[0058] In this embodiment, the material of the vertical transmission gate 210 includes polysilicon.

[0059] Polysilicon is a commonly used material for forming gates. It has the characteristics of low process cost. At the same time, polysilicon has a high melting point, which can increase the upper limit of the ambient temperature of the image sensor.

[0060] It should be noted that the first gate structure 216 is used as a transmission switch between the photoelectric conversion region 208 and the floating diffusion region 204 .

[0061] In this embodiment, the material of the first gate structure 216 includes polysilicon.

[0062] Specifically, polysilicon is a commonly used material for forming a gate, and has the characteristics of low process cost. At the same time, polysilicon has a high melting point, which can increase the upper limit of the ambient temperature of the image sensor.

[0063] In this embodiment, the image sensor further includes: a first interconnection through hole 230 located on the top of the vertical transmission gate 210 , and the first interconnection through hole 230 is electrically connected to the vertical transmission gate 210 .

[0064] The first interconnection through hole 230 is electrically connected to the vertical transfer gate 210 , so that the vertical transfer gate 210 can be electrically connected to an external circuit structure through the first interconnection through hole 230 , thereby enabling the external circuit structure to apply a voltage to the vertical transfer gate 210 through the first interconnection through hole 230 .

[0065] In this embodiment, the material of the first interconnection via 230 is copper.

[0066] Specifically, copper has good conductivity and low resistivity, and can reduce the voltage value of the first interconnection via 230 itself during the process of applying voltage to the vertical transmission gate 210 , that is, reduce the electrical influence of the first interconnection via 230 on the vertical transmission gate 210 .

[0067] In this embodiment, the image sensor further includes: a second interconnection through hole 240 located on the top of the first gate structure 216 , and the second interconnection through hole 240 is electrically connected to the first gate structure 216 .

[0068] The second interconnection through hole 240 is electrically connected to the first gate structure 216 , so that the first gate structure 216 can be electrically connected to an external circuit structure through the second interconnection through hole 240 , thereby enabling the external circuit structure to apply voltage to the first gate structure 216 through the second interconnection through hole 240 .

[0069] In this embodiment, the material of the second interconnection via 240 is copper.

[0070] Specifically, copper has good conductivity and low resistivity, and can reduce the voltage value of the second interconnection via 240 itself during the process of applying voltage to the vertical transmission gate 210 , that is, reduce the electrical impact of the second interconnection via 240 on the first gate structure 216 .

[0071] It should be noted that in the process of forming the first interconnection through-hole 230 and the second interconnection through-hole 240 , the first interconnection through-hole 230 and the second interconnection through-hole 240 are formed in the same step, thereby reducing the process steps and the process cost.

[0072] In other embodiments, the first interconnection via and the second interconnection via may also be formed in different steps.

[0073] Accordingly, the present invention also provides a method for forming an image sensor. Figures 2 to 7 It is a schematic structural diagram corresponding to each step in an embodiment of a method for forming an image sensor of the present invention.

[0074] refer to Figure 2 , providing a substrate 100 , wherein the substrate 100 has first type doping ions, a photoelectric conversion region 108 is formed in the substrate 100 , and the substrate 100 exposes a top surface of the photoelectric conversion region 108 .

[0075] The substrate 100 provides a process platform for subsequently forming an image sensor.

[0076] As an example, the image sensor is a CMOS image sensor.

[0077] In other embodiments, the image sensor may also be a CCD (Charge Coupled Device) image sensor, a DTOF (Direct Time of Flight) sensor, or an iTOF (indirect Time of Flight) sensor, etc.

[0078] In this embodiment, the substrate 100 is a substrate 100 of a pixel wafer, and the substrate 100 of the pixel wafer is a silicon substrate.

[0079] In other embodiments, the material of the substrate of the pixel wafer may also be other materials such as germanium, silicon germanium, silicon carbide, gallium arsenide or indium gallium, and the substrate of the pixel wafer may also be other types of materials such as a silicon substrate on an insulator or a germanium substrate on an insulator.

[0080] As an example, the substrate 100 is a P-type substrate. The mobility of free electrons in a P-type substrate is three times that of holes. By selecting a P-type substrate, the photoelectric conversion efficiency of the image sensor is improved, and the performance of the image sensor is improved. To this end, the type of doped ions in the substrate 100 is P-type ions, such as boron, indium or gallium.

[0081] It should be noted that the photoelectric conversion region 108 is used as a region for receiving optical signals and converting optical signals into electrical signals.

[0082] It should also be noted that the substrate 100 exposes the top surface of the photoelectric conversion region 108 , which facilitates the incident light to directly enter the photoelectric conversion region 108 , reduces the probability of the incident light being blocked, and can maximize the photoelectric conversion efficiency of the image sensor.

[0083] There are a plurality of photoelectric conversion regions 108 in the substrate 100, and the plurality of photoelectric conversion regions 108 are arranged in a matrix. As an example, there is one photoelectric conversion region 108.

[0084] In this embodiment, a shallow trench isolation structure 101 is further formed in the substrate 100 , and a photoelectric conversion region 108 and a floating conversion region formed subsequently are formed between adjacent shallow trench isolation structures 101 .

[0085] The shallow trench isolation structure 101 is used to reduce the probability of optical crosstalk between adjacent photoelectric conversion regions 108 and improve the performance of the image sensor.

[0086] The material of the shallow trench isolation structure 101 is an insulating material. As an example, the material of the shallow trench isolation structure 101 is silicon oxide. In other embodiments, the material of the shallow trench isolation structure may also be one or more of silicon nitride, silicon carbide and silicon oxynitride.

[0087] refer to Figure 3 A floating diffusion region 104 is formed in the substrate 100 at the side of the photoelectric conversion region 108, and the floating diffusion region 104 includes a first floating diffusion region 102 and a second floating diffusion region 103 located on the top of the first floating diffusion region 102, the substrate 100 exposes the top surface of the second floating diffusion region 103, and the first floating diffusion region 102 and the second floating diffusion region 103 are separated by the substrate 100, and the floating diffusion region 104 has second-type doping ions, and the second-type doping ions are different from the first-type doping ions.

[0088] Specifically, in the image sensor, the floating diffusion area 104 is equivalent to a junction capacitor, which is used to store electrons generated by photoelectric conversion. By setting a first floating diffusion area 102 and a second floating diffusion area 103 located on top of the first floating diffusion area 102, the junction capacitance of the image sensor can be adjusted. When the image sensor is in a high-brightness environment, a high voltage is applied through the vertical transmission gate to make the first floating diffusion area 102 and the second floating diffusion area 103 conductive, thereby increasing the capacitance of the image sensor, that is, the signal strength detectable by the image sensor is enhanced, and the saturation of the image sensor is improved. When the image sensor is in a low-brightness environment, the first floating diffusion area 102 and the second floating diffusion area 103 are connected. When the first floating diffusion area 102 and the second floating diffusion area 103 are connected, a low voltage is applied through the vertical transfer gate, so that the first floating diffusion area 102 and the second floating diffusion area 103 cannot be turned on, so that the capacitance of the image sensor is only the capacitance of the second floating diffusion area 103, and the capacitance of the image sensor becomes smaller. Correspondingly, a small amount of light signal in a low-brightness environment can also cause a large voltage to increase, thereby enhancing the sensitivity of the image sensor. In summary, by setting the first floating diffusion area 102 and the second floating diffusion area 103 located on the top of the first floating diffusion area 102, the junction capacitance of the image sensor can be adjusted, thereby improving the saturation and sensitivity of the image sensor.

[0089] In this embodiment, the step of forming the floating diffusion area 104 includes: performing a first doping treatment on the substrate 100 on the side of the photoelectric conversion area 108 to form the first floating diffusion area 102; after the first floating diffusion area 102 is formed, performing a second doping treatment on the substrate 100 with a thickness of the top part of the first floating diffusion area 102 to form a second floating diffusion area 103 on the top of the first floating diffusion area 102, and the first floating diffusion area 102 and the second floating diffusion area 103 are separated by the substrate 100.

[0090] It should be noted that by first forming the first floating diffusion region 102 and then forming the second floating diffusion region 103 on top of the first floating diffusion region 102 , the probability of mutual influence between the first floating diffusion region 102 and the second floating diffusion region 103 is reduced.

[0091] In this embodiment, the process of forming the floating diffusion region 104 includes an ion implantation process.

[0092] It should be noted that the ion implantation process has the characteristics of high implantation depth accuracy and excellent process controllability. By selecting the ion implantation process to form the floating diffusion area 104, the implantation depth of the floating diffusion area 104 in the substrate 100 can meet the process requirements, so that the first floating diffusion area 102 and the second floating diffusion area 103 are separated and do not affect each other, which is conducive to achieving the adjustable junction capacitance of the image sensor.

[0093] It should also be noted that, during the process of forming the first floating diffusion region 102 , the doping dosage should not be too large or too small. If the doping dose is too large, it is easy to cause the depth of the first floating diffusion area 102 to be too large. When the thickness of the second floating diffusion area 103 formed subsequently is constant, it is easy to cause the distance between the first floating diffusion area 102 and the second floating diffusion area 103 to be too large, which increases the difficulty of the first floating diffusion area 102 and the second floating diffusion area 103 to be connected to each other, so that the junction capacitance value of the image sensor is only the capacitance value of the second floating diffusion area 103. When the image sensor is in a high-brightness environment, the signal intensity detectable by the image sensor is not enhanced, which affects the saturation of the image sensor; if the doping dose is too small, it is easy to cause the depth of the first floating diffusion area 102 to be too small, which is easy to cause the space area reserved for the second floating diffusion area 103 to be too small, so that the capacitance value of the second floating diffusion area 103 is too small, and thus the junction capacitance value of the image sensor is also too small, and then when the image sensor is in a high-brightness environment, the signal intensity detectable by the image sensor is not enhanced, which affects the saturation of the image sensor. To this end, in this embodiment, during the process of forming the first floating diffusion region 102 , the doping dosage ranges from 1E14 atom / cm 3 to 9E20 atom / cm 3 .

[0094] Specifically, during the process of forming the first floating diffusion region 102 , the injection energy should not be too large or too small. If the injected energy is too large, it is easy to cause the depth of the first floating diffusion area 102 to be too large. When the thickness of the formed second floating diffusion area 103 is constant, it is easy to cause the distance between the first floating diffusion area 102 and the second floating diffusion area 103 to be too large, which increases the difficulty of the first floating diffusion area 102 and the second floating diffusion area 103 to be connected to each other, so that the junction capacitance value of the image sensor is only the capacitance value of the second floating diffusion area 103. When the image sensor is in a high-brightness environment, the signal intensity detectable by the image sensor is not enhanced, which affects the saturation of the image sensor. If the injected energy is too small, it is easy to cause the depth of the first floating diffusion area 102 to be too small, which is easy to cause the space area reserved for the second floating diffusion area 103 to be too small, so that the capacitance value of the second floating diffusion area 103 is too small, and thus the junction capacitance value of the image sensor is also too small, and then when the image sensor is in a high-brightness environment, the signal intensity detectable by the image sensor is not enhanced, which affects the saturation of the image sensor. Therefore, in this embodiment, during the process of forming the first floating diffusion region 102 , the implantation energy ranges from 250kev to 500kev.

[0095] It should be noted that the thickness of the first floating diffusion area 102 along the normal direction of the surface of the substrate 100 should not be too large or too small. If the thickness of the first floating diffusion area 102 is too large, it is easy to cause the capacitance of the image sensor to increase, affecting the sensitivity of the image sensor; if the thickness of the first floating diffusion area 102 is too small, it is easy to cause the capacitance value of the first floating diffusion area 102 to decrease, thereby reducing the junction capacitance value of the image sensor. When the image sensor is in a high-brightness environment, the signal intensity that can be detected by the image sensor is not enhanced, affecting the saturation of the image sensor. For this reason, in this embodiment, along the normal direction of the surface of the substrate 100, the thickness of the first floating diffusion area 102 is 20 nanometers to 100 nanometers.

[0096] Specifically, in the process of forming the second floating diffusion area 103, the doping dose should not be too large or too small. If the doping dose is too large, it is easy to cause the depth of the second floating diffusion area 103 to be too large. When the thickness of the first floating diffusion area 102 is constant, it is easy to cause the distance between the first floating diffusion area 102 and the second floating diffusion area 103 to be too small, which increases the probability of the first floating diffusion area 102 and the second floating diffusion area 103 being connected to each other when no voltage is applied, thereby affecting the effect of the floating diffusion area 104 on the adjustable capacitance value, and further making the saturation and sensitivity of the image sensor incompatible, affecting the performance of the image sensor; if the doping dose is too small, It is easy to cause the depth of the second floating diffusion area 103 to be too small, so that the capacitance value of the second floating diffusion area 103 is too small, and the junction capacitance value of the image sensor is also too small, and then when the image sensor is in a high brightness environment, the signal strength that the image sensor can detect is not enhanced, affecting the saturation of the image sensor. At the same time, the depth of the second floating diffusion area 103 is too small, which also increases the distance between the first floating diffusion area 102 and the second floating diffusion area 103, and increases the difficulty of mutual conduction between the first floating diffusion area 102 and the second floating diffusion area 103, thereby affecting the performance of the image sensor. For this reason, in the present embodiment, in the process of forming the second floating diffusion area 103, the doping dosage is 1E14atom / cm3 to 9E20atom / cm3.

[0097] It should be noted that, in the process of forming the second floating diffusion area 103, the injection energy should not be too large or too small. If the injection energy is too large, it is easy to cause the depth of the second floating diffusion area 103 to be too large. When the thickness of the first floating diffusion area 102 is constant, it is easy to cause the distance between the first floating diffusion area 102 and the second floating diffusion area 103 to be too small, which increases the probability of the first floating diffusion area 102 and the second floating diffusion area 103 being connected to each other without applying voltage, thereby affecting the effect of the floating diffusion area 104 on the adjustable capacitance value, and further making the saturation and sensitivity of the image sensor incompatible, affecting the performance of the image sensor; if the injection energy is too small, It is easy to cause the depth of the second floating diffusion area 103 to be too small, so that the capacitance value of the second floating diffusion area 103 is too small, and the junction capacitance value of the image sensor is also too small, and then when the image sensor is in a high brightness environment, the signal strength that the image sensor can detect is not enhanced, affecting the saturation of the image sensor. At the same time, the depth of the second floating diffusion area 103 is too small, which also increases the distance between the first floating diffusion area 102 and the second floating diffusion area 103, and increases the difficulty of mutual conduction between the first floating diffusion area 102 and the second floating diffusion area 103, thereby affecting the performance of the image sensor. For this reason, in the present embodiment, in the process of forming the second floating diffusion area 103, the injection energy is 20kev to 100kev.

[0098] Specifically, along the normal direction of the surface of the substrate 100, the thickness of the second floating diffusion area 103 should not be too large or too small. If the thickness of the second floating diffusion area 103 is too large, the capacitance value of the second floating diffusion area 103 is too large. When the image sensor is in a low-brightness environment, a low voltage is applied through the vertical transfer gate formed later, so that the first floating diffusion area 102 and the second floating diffusion area 103 cannot be turned on, so that the capacitance of the image sensor is only the capacitance of the second floating diffusion area 103. Since the thickness of the second floating diffusion area 103 is too large, the capacitance value of the second floating diffusion area 103 is too large. Accordingly, when the image sensor is in a low-brightness environment, the electrical signal generated by a small amount of light signal is too small, so that the voltage change generated by the capacitance value of the second floating diffusion area 103 is not obvious, so that If the thickness of the second floating diffusion area 103 is too small, the capacitance value of the second floating diffusion area 103 is too small, so that the junction capacitance value of the image sensor is also too small, and then when the image sensor is in a high brightness environment, the signal intensity that the image sensor can detect is not enhanced, affecting the saturation of the image sensor. At the same time, if the depth of the second floating diffusion area 103 is too small, the distance between the first floating diffusion area 102 and the second floating diffusion area 103 is increased, and the difficulty of mutual conduction between the first floating diffusion area 102 and the second floating diffusion area 103 is increased, thereby affecting the performance of the image sensor. To this end, in this embodiment, along the normal direction of the surface of the substrate 100, the thickness of the second floating diffusion area 103 is 20 nanometers to 100 nanometers.

[0099] It should be noted that the distance between the first floating diffusion area 102 and the second floating diffusion area 103 should not be too large or too small. If the distance between the first floating diffusion area 102 and the second floating diffusion area 103 is too large, when a voltage is applied through the vertical transfer gate formed later, the difficulty of mutual conduction between the first floating diffusion area 102 and the second floating diffusion area 103 is increased, so that the junction capacitance value of the image sensor is only the capacitance value of the second floating diffusion area 103. When the image sensor is in a high-brightness environment, the signal intensity detectable by the image sensor is not enhanced, which affects the saturation of the image sensor; if the distance between the first floating diffusion area 102 and the second floating diffusion area 103 is too small, the probability of mutual conduction between the first floating diffusion area 102 and the second floating diffusion area 103 when no voltage is applied is increased, so that the effect of the adjustable capacitance value of the floating diffusion area 104 is affected, and then the saturation and sensitivity of the image sensor cannot be compatible, which affects the performance of the image sensor. Therefore, in this embodiment, the distance between the first floating diffusion region 102 and the second floating diffusion region 103 is 20 nanometers to 100 nanometers.

[0100] In this embodiment, the floating diffusion region 104 has second-type doping ions, and the second-type doping ions are different from the first-type doping ions.

[0101] Specifically, the ions doped in the floating diffusion region 104 are N-type ions.

[0102] In the present embodiment, the first floating diffusion area 102 and the second floating diffusion area 103 are separated by the substrate 100. Since the doped ions in the substrate 100 are P-type ions, when no voltage is subsequently applied to the vertical transfer gate, the substrate 100 located between the first floating diffusion area 102 and the second floating diffusion area 103 plays a role in electrically isolating the first floating diffusion area 102 from the second floating diffusion area 103, thereby reducing the probability of mutual conduction between the first floating diffusion area 102 and the second floating diffusion area 103, so that the image sensor can achieve the effect of adjustable junction capacitance value formed by the floating diffusion area 104, thereby improving the saturation and sensitivity of the image sensor.

[0103] A high voltage is applied through the vertical transfer gate to conduct the first floating diffusion area 102 and the second floating diffusion area 103, thereby increasing the capacitance of the image sensor. As an example, the high voltage value is at least greater than or equal to 0.5V.

[0104] A low voltage is applied through the vertical transfer gate to prevent the first floating diffusion area 102 and the second floating diffusion area 103 from being turned on, thereby reducing the capacitance of the image sensor. As an example, the low voltage is at least less than or equal to 0V.

[0105] refer to Figures 4 to 5 A vertical transfer gate 110 is formed on the substrate 100 of the floating diffusion area 104 and in the substrate 100 located at the side wall of the floating diffusion area 104, the vertical transfer gate 110 is opposite to the side wall of the photoelectric conversion area 108, and the side walls of the first floating diffusion area 102 and the second floating diffusion area 103 are in contact with the vertical transfer gate 110.

[0106] Specifically, the vertical transfer gate 110 is used as a conduction switch between the first floating diffusion area 102 and the second floating diffusion area 103. By applying a voltage to the vertical transfer gate 110, the first floating diffusion area 102 and the second floating diffusion area 103 are controlled to be turned on and off, thereby achieving an adjustable effect on the junction capacitance formed by the floating diffusion area 104.

[0107] In this embodiment, the step of forming the vertical transfer gate 110 includes: forming an opening 190 in the substrate 100 of the side wall of the floating diffusion area 104, and the opening 190 is opposite to the side wall of the photoelectric conversion area 108; forming the vertical transfer gate 110 on the substrate 100 of the floating diffusion area 104 and in the opening 190.

[0108] The opening 190 provides a space for forming the vertical transfer gate 110 .

[0109] In this embodiment, the process of forming the opening 190 includes a dry etching process.

[0110] It should be noted that the dry etching process includes an anisotropic dry etching process. The anisotropic dry etching process has the characteristics of anisotropic etching, and its longitudinal etching rate is greater than the lateral etching rate, and the process controllability is high. In the process of forming the opening 190 in the substrate 100 on the side wall of the floating diffusion area 104, it is easy to ensure the morphology quality of the side wall of the opening 190, and at the same time, the probability of causing damage to the side wall of the floating diffusion area 104 is also reduced.

[0111] In this embodiment, the vertical transfer gate 110 is separated from the side wall of the photoelectric conversion region 108, that is, the vertical transfer gate 110 is not located on the substrate 100 between the photoelectric conversion region 108 and the floating diffusion region 104, so that the electrical signal in the photoelectric conversion region 108 can enter the floating diffusion region 104 through the substrate 100 between the photoelectric conversion region 108 and the floating diffusion region 104.

[0112] In this embodiment, the process of forming the vertical transfer gate 110 on the substrate 100 in the floating diffusion region 104 and in the opening 190 includes a chemical vapor deposition process or an atomic layer deposition process.

[0113] In this embodiment, the material of the vertical transmission gate 110 includes polysilicon.

[0114] Polysilicon is a commonly used material for forming gates and has the characteristics of low process cost. At the same time, polysilicon has a high melting point and can increase the upper limit of the ambient temperature of the image sensor.

[0115] refer to Figure 6 A first gate structure 116 is formed on the substrate 100 in the photoelectric conversion region 108 and on the substrate 100 between the photoelectric conversion region 108 and the floating diffusion region 104 .

[0116] It should be noted that the first gate structure 116 is used as a transmission switch between the photoelectric conversion region 108 and the floating diffusion region 104 .

[0117] It should also be noted that, as an example, the first gate structure 116 is formed after the vertical transmission gate 110 is formed. During the process of forming the vertical transmission gate 110, the first gate structure 116 does not undergo the etching process for forming the opening 190, thereby reducing the probability of the surface of the first gate structure 116 being damaged, thereby improving the electrical performance of the first gate structure 116.

[0118] In other embodiments, the vertical transfer gate may be formed after the first gate structure is formed.

[0119] In this embodiment, the material of the first gate structure 116 includes polysilicon.

[0120] Specifically, polysilicon is a commonly used material for forming a gate, and has the characteristics of low process cost. At the same time, polysilicon has a high melting point, which can increase the upper limit of the ambient temperature of the image sensor.

[0121] In this embodiment, the steps of forming the first gate structure 116 include: forming a blocking layer covering the vertical transfer gate 110; forming a gate material layer on the top of the substrate 100 exposed by the blocking layer; and patterning the gate material layer, and the remaining gate material layer located on the substrate 100 in the photoelectric conversion area 108 and between the photoelectric conversion area 108 and the floating diffusion area 104 serves as the first gate structure 116.

[0122] The shielding layer protects the vertical transmission gate 110 and reduces the probability of the vertical transmission gate 110 being damaged.

[0123] In this embodiment, the material of the shielding layer includes photoresist.

[0124] It should be noted that after forming the first gate structure 116 , the method for forming the semiconductor structure further includes: removing the blocking layer.

[0125] Specifically, the blocking layer is removed to provide a process window for subsequently forming a first interconnection through hole electrically connected to the vertical transfer gate 110 .

[0126] In this embodiment, the process of removing the shielding layer includes an ashing process.

[0127] refer to Figure 7After forming the vertical transfer gate 110 and the first gate structure 116, the method for forming the semiconductor structure further includes: forming a first interconnection through hole 130 on the top of the vertical transfer gate 110, and the first interconnection through hole 130 is electrically connected to the vertical transfer gate 110; forming a second interconnection through hole 140 on the top of the first gate structure 116, and the second interconnection through hole 140 is electrically connected to the first gate structure 116.

[0128] The first interconnection via 130 is electrically connected to the vertical transfer gate 110 , so that the vertical transfer gate 110 can be electrically connected to an external circuit structure through the first interconnection via 130 , thereby enabling the external circuit structure to apply a voltage to the vertical transfer gate 110 through the first interconnection via 130 .

[0129] In this embodiment, the material of the first interconnection via 130 is copper.

[0130] Specifically, copper has good electrical conductivity and low resistivity, and can reduce the voltage value of the first interconnection via 130 itself during the process of applying voltage to the vertical transmission gate 110 , that is, reduce the electrical influence of the first interconnection via 130 on the vertical transmission gate 110 .

[0131] The second interconnection through hole 140 is electrically connected to the first gate structure 116 , so that the first gate structure 116 can be electrically connected to an external circuit structure through the second interconnection through hole 140 , thereby enabling the external circuit structure to apply voltage to the first gate structure 116 through the second interconnection through hole 140 .

[0132] In this embodiment, the material of the second interconnection via 140 is copper.

[0133] Specifically, copper has good conductivity and low resistivity, and can reduce the voltage value of the second interconnection via 140 itself during the process of applying voltage to the vertical transmission gate 110 , that is, reduce the electrical impact of the second interconnection via 140 on the first gate structure 116 .

[0134] In this embodiment, the first interconnection through-hole 130 and the second interconnection through-hole 140 are formed in the same step, thereby reducing the process steps and the process cost.

[0135] In other embodiments, the first interconnection via and the second interconnection via may also be formed in different steps.

[0136] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the scope defined by the claims.

Claims

1. An image sensor, characterized in that: include: a substrate having first type dopant ions; A photoelectric conversion region is located in the substrate, and the substrate exposes a top surface of the photoelectric conversion region; a floating diffusion region located in the substrate at the side of the photoelectric conversion region, the floating diffusion region comprising a first floating diffusion region and a second floating diffusion region located on the top of the first floating diffusion region, the substrate exposing the top surface of the second floating diffusion region, the first floating diffusion region and the second floating diffusion region are separated by the substrate, the floating diffusion region has second-type doping ions, and the second-type doping ions are different from the first-type doping ions; A vertical transfer gate is located on the substrate of the floating diffusion area and in the substrate of the side wall of the floating diffusion area, and the vertical transfer gate is separated from the side wall of the photoelectric conversion area, and the side walls of the first floating diffusion area and the second floating diffusion area are in contact with the vertical transfer gate; The first gate structure is located on the substrate of the photoelectric conversion region and on the substrate between the photoelectric conversion region and the floating diffusion region.

2. The image sensor according to claim 1, wherein: The concentration of doped ions in the first floating diffusion region is 1E12atom / cm 3 To 9E20atom / cm 3 ; The concentration of doped ions in the second floating diffusion region is 1E12 atom / cm3 to 9E20 atom / cm3.

3. The image sensor according to claim 1, wherein: The first floating diffusion region is spaced apart from the second floating diffusion region by a distance of 20 nanometers to 100 nanometers.

4. The image sensor according to claim 1, wherein: Along the normal direction of the substrate surface, the thickness of the first floating diffusion region is 20 nanometers to 100 nanometers; Along the normal direction of the substrate surface, the thickness of the second floating diffusion region is 20 nanometers to 100 nanometers.

5. The image sensor according to claim 1, wherein: The image sensor further includes: a first interconnection through hole located on top of the vertical transfer gate, and the first interconnection through hole is electrically connected to the vertical transfer gate; The second interconnection through hole is located on the top of the first gate structure, and the second interconnection through hole is electrically connected to the first gate structure.

6. The image sensor according to claim 1, wherein: The material of the vertical transmission gate includes polysilicon; The material of the first gate structure includes polysilicon.

7. A method for forming an image sensor, characterized in that: include: Providing a substrate, wherein the substrate has first-type doping ions, a photoelectric conversion region is formed in the substrate, and the substrate exposes a top surface of the photoelectric conversion region; A floating diffusion region is formed in the substrate at the side of the photoelectric conversion region, the floating diffusion region includes a first floating diffusion region and a second floating diffusion region located on the top of the first floating diffusion region, the substrate exposes the top surface of the second floating diffusion region, and the first floating diffusion region and the second floating diffusion region are separated by the substrate, and the floating diffusion region has second-type doping ions, and the second-type doping ions are different from the first-type doping ions; A vertical transfer gate is formed on the substrate of the floating diffusion region and in the substrate located at the side wall of the floating diffusion region, wherein the vertical transfer gate is separated from the side wall of the photoelectric conversion region, and the side walls of the first floating diffusion region and the second floating diffusion region are in contact with the vertical transfer gate; A first gate structure is formed on the substrate of the photoelectric conversion region and on the substrate between the photoelectric conversion region and the floating diffusion region.

8. The method for forming an image sensor according to claim 7, wherein: After forming the vertical transfer gate, the first gate structure is formed; or, after forming the first gate structure, the vertical transfer gate is formed.

9. The method for forming an image sensor according to claim 7, wherein: The steps of forming the floating diffusion area include: performing a first doping treatment on the substrate on the side of the photoelectric conversion area to form the first floating diffusion area; after forming the first floating diffusion area, performing a second doping treatment on the substrate of the top part of the thickness of the first floating diffusion area to form a second floating diffusion area on the top of the first floating diffusion area, and the first floating diffusion area and the second floating diffusion area are separated by the substrate.

10. The method for forming an image sensor according to claim 7, wherein: The process of forming the floating diffusion region includes an ion implantation process.

11. The method for forming an image sensor according to claim 10, wherein: In the process of forming the first floating diffusion region, the parameters of the ion implantation process include: the doping dose range is 1E14atom / cm 3 To 9E20atom / cm 3 ; The implantation energy range is 250kev to 500kev; In the process of forming the second floating diffusion region, the parameters of the ion implantation process include: the doping dose range is 1E14atom / cm 3 To 9E20atom / cm 3 ; The implantation energy range is 20kev to 100kev.

12. The method for forming an image sensor according to claim 7, wherein: Along the normal direction of the substrate surface, the thickness of the first floating diffusion region is 20 nanometers to 100 nanometers; Along the normal direction of the substrate surface, the thickness of the second floating diffusion region is 20 nanometers to 100 nanometers.

13. The method for forming an image sensor according to claim 7, wherein: The first floating diffusion region is spaced apart from the second floating diffusion region by a distance of 20 nanometers to 100 nanometers.

14. The method for forming an image sensor according to claim 7, wherein: The step of forming the vertical transfer gate includes: forming an opening in the substrate of the floating diffusion area sidewall, the opening being away from the sidewall of the photoelectric conversion area; and forming the vertical transfer gate on the substrate of the floating diffusion area and in the opening.

15. The method for forming an image sensor according to claim 14, wherein: The process of forming the opening includes a dry etching process.

16. The method for forming an image sensor according to claim 7, wherein: After forming the vertical transfer gate and the first gate structure, the method for forming the image sensor further includes: forming a first interconnection through hole on top of the vertical transfer gate, the first interconnection through hole being electrically connected to the vertical transfer gate; A second interconnection via is formed on top of the first gate structure, the second interconnection via being electrically connected to the first gate structure.

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