Image sensor and electronic device

Abstract

The utility model provides an image sensor and an electronic device, and the image sensor comprises a semiconductor substrate which comprises an ion doping layer of a first doping type; the device function layer is located on the semiconductor substrate; the semiconductor device is located in the device function layer and comprises a photoelectric conversion element with the second doping type; a light absorption driving layer is formed in an interface interval between the semiconductor substrate and the device function layer. The structure of the image sensor comprises the light absorption driving layer, the quantum efficiency of the image sensor can be improved based on the existence of the light absorption driving layer, especially the quantum efficiency of near-infrared light is improved, and the application flexibility of a device is improved.

Description

Technical Field

[0001] The utility model belongs to the technical field of image acquisition, and in particular relates to an image sensor and electronic equipment. Background Art

[0002] Image sensors are an important component of digital cameras. Depending on the components, they can be divided into two categories: CCD (Charge Coupled Device) and CMOS (Complementary Metal-Oxide Semiconductor). With the continuous development of CMOS integrated circuit manufacturing technology, especially the design and manufacturing technology of CMOS image sensors, CMOS image sensors have gradually replaced CCD image sensors and become the mainstream. Compared with CMOS image sensors, CMOS image sensors have the advantages of low voltage, low power consumption, low cost and high integration, and have important application value in the fields of machine vision, consumer electronics, high-definition monitoring and medical imaging.

[0003] In addition, near-infrared (NIR) imaging is a very valuable technology that can be used in a variety of applications, including agriculture, food testing, medical diagnosis and environmental monitoring. NIR cameras use CMOS technology to capture images in the infrared wavelength range below visible light, revealing information hidden below the ordinary spectrum. NIR imaging is an infrared band between visible light and thermal infrared imaging. This band includes light that cannot be perceived by the human eye. It can be used to measure the chemical composition, moisture content and temperature of objects, so it has a wide range of applications in agriculture, medicine and food industries. However, the main problem facing the response of the NIR band is the small QE (Quantum Efficiency) value. For example, in some CMOS image sensors, the QE at 550nm is nearly 70%, while the QE at 900nm is only about 10%. In addition, due to the low QE value, in order to image in the NIR band, the power of the supplementary light source needs to be increased, which will cause a sharp increase in the heat loss of the system, which not only increases energy costs but also reduces the reliability of the system.

[0004] Therefore, it is necessary to provide an image sensor and a method for manufacturing the same, as well as an electronic device, to solve the problems of quantum efficiency, system heat loss, and high power consumption in the prior art.

[0005] It should be noted that the above introduction to the technical background is only for the convenience of providing a clear and complete description of the technical solutions of this application and for the convenience of understanding by those skilled in the art. It cannot be considered that the above technical solutions are well known to those skilled in the art simply because they are described in the background technology section. Utility Model Content

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide an image sensor and an electronic device to solve the problems of low quantum efficiency of image sensors and high system heat loss and power consumption in the prior art.

[0007] In order to achieve the above-mentioned object and other related objects, the utility model provides a method for preparing an image sensor, the preparation method comprising:

[0008] Providing a semiconductor substrate, the semiconductor substrate comprising an ion-doped region of a first doping type;

[0009] forming a device function layer on the semiconductor substrate;

[0010] Performing a heat treatment on the semiconductor substrate to diffuse the doping ions in the ion-doped region into a material layer located above the semiconductor substrate to form a light absorption driving layer; and

[0011] A semiconductor device is prepared in the device function layer, the semiconductor device including a photoelectric conversion element of a second doping type different from the first doping type, to obtain the image sensor.

[0012] Optionally, the photoelectric conversion element has an extension portion extending into the light absorption driving layer, wherein a depth of the extension portion does not exceed 20% of a depth of the photoelectric conversion element.

[0013] Optionally, before forming the device functional layer, the preparation method further comprises:

[0014] An absorption auxiliary layer is formed on the semiconductor substrate, wherein during the heat treatment, doping ions in the ion doping region at least diffuse into the absorption auxiliary layer.

[0015] Optionally, a prefabricated ion doping layer of the first doping type is formed in the absorption auxiliary layer.

[0016] Optionally, the prefabricated ion-doped layer includes N sub-ion-doped layers, and the concentrations of the N sub-ion-doped layers decrease gradually from the semiconductor substrate toward the device functional layer.

[0017] Optionally, the prefabricated ion-doped layer is a single-layer material layer whose concentration decreases gradually from the semiconductor substrate toward the device functional layer.

[0018] Optionally, during the heat treatment, doping ions of the prefabricated ion-doping layer diffuse into a material layer located above the semiconductor substrate to form a light absorption driving auxiliary layer.

[0019] Optionally, when the prefabricated ion-doped layer includes N sub-ion-doped layers, the thickness of the top sub-ion-doped layer is greater than or equal to 3 μm.

[0020] Optionally, the treatment temperature of the heat treatment process is greater than or equal to 950°C and less than or equal to 1150°C.

[0021] Optionally, when an absorption auxiliary layer is formed on the semiconductor substrate, the thickness of the absorption auxiliary layer is between 1 μm and 6 μm.

[0022] Optionally, the doping concentration of the ion doping layer of the first doping type of the semiconductor substrate is greater than the doping concentration in the prefabricated ion doping layer and greater than the doping concentration of the ion doping of the first doping type in the device functional layer.

[0023] Optionally, the doping concentration of the ion-doped region in the semiconductor substrate is greater than 2E18 atom / CM3, the device functional layer has a doping of the first doping type with a concentration less than 2E15 atom / CM3, and when the image sensor includes a prefabricated ion-doped layer with the first doping type, the doping concentration is between 5E15-1E17atom / CM3.

[0024] Optionally, the first doping type is P type, and the second doping type is N type.

[0025] The utility model also provides an image sensor, which can be prepared by the preparation method described above, or by other methods. The image sensor includes:

[0026] A semiconductor substrate, the semiconductor substrate comprising an ion-doped layer of a first doping type;

[0027] A device functional layer, located on the semiconductor substrate;

[0028] a semiconductor device located in the device functional layer, the semiconductor device comprising a photoelectric conversion element having a second doping type different from the first doping type;

[0029] Wherein, a light absorption driving layer is formed in the interface area between the semiconductor substrate and the device functional layer.

[0030] Optionally, the light absorption driving layer is extended from the bottom of the device functional layer toward the inside and has ion doping of the first doping type.

[0031] Optionally, the image sensor further includes an absorption auxiliary layer, wherein the absorption auxiliary layer is located between the semiconductor substrate and the device functional layer, and the light absorption driving layer is extended inward from the bottom of the absorption auxiliary layer.

[0032] Optionally, the absorption auxiliary layer includes a prefabricated ion-doped layer, the prefabricated ion-doped layer has ion doping of the first doping type, and the light absorption driving layer is at least formed in the prefabricated ion-doped layer.

[0033] Optionally, the prefabricated ion doping layer includes N sub-ion doping layers, and the concentrations of the N sub-ion doping layers decrease from the semiconductor substrate toward the device functional layer; or, the prefabricated ion doping layer is a single-layer material layer whose concentration decreases from the semiconductor substrate toward the device functional layer.

[0034] Optionally, the image sensor further includes a light absorption driving auxiliary layer, wherein the light absorption driving auxiliary layer extends inward from the bottom of the device functional layer and has ion doping of the first doping type.

[0035] Optionally, the image sensor further comprises a plurality of pixel units arranged in an array, an isolation structure is provided between adjacent pixel units, each of the pixel units shares the light absorption driving layer, and when an absorption auxiliary layer is present, each of the pixel units shares the light absorption driving layer.

[0036] Optionally, the image sensor is a front-illuminated image sensor.

[0037] The utility model also provides an electronic device, which comprises the image sensor as described in any one of the above solutions.

[0038] As described above, the image sensor and electronic device of the present invention have the following beneficial effects: the image sensor structure of the present invention includes a light absorption driving layer. In addition, in the preparation of the image sensor of the present invention, the light absorption driving layer is formed based on the heat treatment of the semiconductor substrate. Based on the design of the light absorption driving layer, the quantum efficiency of the image sensor for light signals can be improved based on the existence of the light absorption driving layer, especially the quantum efficiency of near-infrared light, thereby improving the application flexibility of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Shown is a basic structural block diagram of an image sensor system.

[0040] Figure 2 Shown is a schematic diagram of a pixel circuit of an image sensor.

[0041] Figure 3 Shown is a flow chart of image sensor preparation in an embodiment of the present application.

[0042] Figure 4The schematic diagram shows a semiconductor substrate provided in the preparation of an image sensor according to an embodiment of the present application.

[0043] Figure 5 Shown is a schematic diagram of forming a device functional layer during the preparation of an image sensor according to an embodiment of the present application.

[0044] Figure 6 Shown is a schematic diagram of forming a light absorption driving layer during the preparation of an image sensor according to an embodiment of the present application.

[0045] Figure 7 Shown is a schematic diagram of a semiconductor device formed during the preparation of an image sensor according to an embodiment of the present application.

[0046] Figure 8 It is a schematic diagram showing the formation of an absorption auxiliary layer in the preparation of an image sensor according to an embodiment of the present application.

[0047] Fig. 9 Displayed as Figure 8 Schematic diagram of forming a light absorption driving layer in an example of the structure shown.

[0048] Fig.10 Displayed as Figure 8 Schematic diagram of a semiconductor device formed in an example of the structure shown.

[0049] Fig.11 Displayed as Figure 8 Schematic diagram of forming a light absorption driving auxiliary layer in an example of the structure shown.

[0050] Fig.12 It shows the influence of different heat treatment times on the diffusion of B ion doping in this embodiment.

[0051] Fig.13 The effect of heat treatment and non-heat treatment on near-infrared light sensitivity in this example is shown.

[0052] Fig.14 The figure shows the influence of whether the absorption auxiliary layer preparation and heat treatment are performed in this embodiment on the dark current performance of the image sensor compared with the reference example.

[0053] Component number description

[0054] 101 Semiconductor Substrate

[0055] 201 Device functional layer

[0056] 300 Light absorption driving layer

[0057] 401 First Isolation Structure

[0058] 402 Second Isolation Structure

[0059] 501 Pixel Circuit

[0060] 502 Photoelectric conversion element

[0061] 503 Transistor

[0062] 600 Absorption auxiliary layer

[0063] 700 Light absorption driving auxiliary layer DETAILED DESCRIPTION

[0064] The following is an explanation of the implementation of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific implementations, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0065] It should be emphasized that the term “include / comprises” when used herein refers to the presence of features, integers, steps or components, but does not exclude the presence or addition of one or more other features, integers, steps or components.

[0066] Features described and / or illustrated with respect to one embodiment may be used in the same or similar manner in one or more other embodiments, combined with features in other embodiments, or substituted for features in other embodiments.

[0067] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional diagrams showing the device structure will not be partially enlarged according to the general scale, and the schematic diagrams are only examples, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional dimensions of length, width and depth should be included.

[0068] For ease of description, spatially relative terms such as "under", "below", "below", "below", "above", "on", etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatially relative terms are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the drawings. In addition, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.

[0069] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0070] It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and therefore the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed at will, and the component layout may also be more complicated.

[0071] The contents proposed in the present invention are described in detail below in conjunction with the accompanying drawings provided in the present invention.

[0072] Figure 1 The basic structure block diagram of an image sensor system is shown. The image sensor includes a readout circuit and a control circuit connected to a pixel array. In addition, a functional logic unit is connected to the readout circuit, and the readout circuit and the control circuit are connected to a status register to realize the control of the pixel array. The pixel array includes a plurality of pixels (P1, P2, P3) arranged in rows (R1, R2, R3...Ry) and columns (C1, C2, C3...Cx). The pixel signal output by the pixel array is output to the readout circuit via the column line. In some applications, after the pixel acquires the image data, it is read out using the readout mode specified by the status register and then transmitted to the functional logic unit. In a specific implementation, the readout circuit may include an analog-to-digital conversion (ADC) circuit and other circuits.

[0073] In some applications, the status register may include a programmable selection system to determine whether the readout system is exposed and readout through a rolling shutter mode or a global shutter mode. The functional logic unit may store raw image data or image data after image processing. In some implementations, the readout circuit may read out a row of image data at a time along the readout column line. Of course, other methods may also be used to read out the image data. The operation of the control circuit can be determined by the current setting of the status register. For example, the control circuit generates a shutter signal for controlling image acquisition. In some applications, this shutter signal can be a global exposure signal so that all pixels of the pixel array simultaneously acquire their image data through a single acquisition window. In other applications, this shutter signal can also be a rolling exposure signal so that the pixels of each pixel row of the pixel array continuously implement exposure reading operations through the acquisition window.

[0074] Figure 2 A schematic diagram of a pixel unit in an image sensor is shown. Figure 2As shown in the figure, each pixel unit includes a photoelectric conversion element (e.g., a photodiode) and a pixel circuit (as shown in the dotted box in the figure). The photodiode can be a buried photodiode (PPD) used in current image sensors. In one application example, the pixel circuit includes a reset transistor (RST), a source follower transistor (SF), and a pixel selection transistor (RS), which are connected to the transistors shown in the figure. Figure 2 The transfer transistor (TX) and photodiode shown in . In a stacked structure application example, the pixel circuit includes a reset transistor, a source follower transistor, a pixel selection transistor disposed on a first circuit chip, and also includes a transfer transistor disposed on a second circuit chip, and the photodiode in the second circuit chip is connected to other transistors in the first circuit chip based on the transfer transistor. In a further application example, the pixel circuit may also include a gain control transistor (DCG) connected between a floating diffusion region (FD) and a reset transistor. During operation, the photoelectric conversion element generates photocharges in response to incident light during exposure, the transfer transistor is connected to a transfer signal, which controls the transfer transistor to transfer the accumulated charge in the photoelectric conversion element to the floating diffusion region, the reset transistor is connected between the power supply voltage and the floating diffusion region, responds to the reset signal to reset the sensor pixel circuit (for example, discharges or charges the floating diffusion region and the photodiode to the current voltage), the floating diffusion region is connected to the gate of the source follower transistor, the source follower transistor is connected between the power supply voltage and the pixel selection transistor, responds to the potential of the floating diffusion region and outputs it, the pixel selection transistor connects the source follower transistor and the bit line, responds to the pixel selection control signal to implement pixel selection readout and outputs it to the readout column.

[0075] However, the main problem facing the response in the near-infrared band in existing image sensors is the small QE value. The silicon substrate has weak absorption in the near-infrared band of 750nm-1100nm. In addition, due to the low QE value, in order to image in the near-infrared band, it is necessary to increase the power of the supplementary light source, which will cause a sharp increase in the heat loss of the system, increasing energy costs and reducing the reliability of the system. The utility model can effectively improve the above problems through the setting of the light absorption drive layer and the design of the process. The following will be described in detail in conjunction with the embodiments.

[0076] Embodiment 1:

[0077] See also Figure 3 As shown, this embodiment provides a method for preparing an image sensor. Figure 3 The flowchart of the preparation method is shown, wherein the preparation method comprises the following steps:

[0078] S1: providing a semiconductor substrate, wherein the semiconductor substrate comprises an ion doped region of a first doping type;

[0079] S2: forming a device functional layer on the semiconductor substrate;

[0080] S3: performing heat treatment on the semiconductor substrate to diffuse the doping ions in the ion-doped region into a material layer located above the semiconductor substrate to form a light absorption driving layer; and

[0081] S4: preparing a semiconductor device in the device functional layer, wherein the semiconductor device includes a photoelectric conversion element of a second doping type different from the first doping type, to obtain the image sensor.

[0082] In this embodiment, a light absorption driving layer is formed in the image sensor based on a semiconductor substrate, so that the light absorption driving layer can further compensate for photoelectric conversion and signal transmission, which is beneficial to the improvement of the quantum efficiency of various light signals, especially the improvement of infrared light quantum efficiency, thereby improving the application flexibility of the image sensor, broadening its application field, and improving image quality. It should be noted that the preparation order of the above steps can be changed according to the actual process, as long as it does not affect the realization of the light absorption driving layer of this application.

[0083] The preparation of the image sensor of the present application will be described in detail below with reference to specific embodiments.

[0084] First, if Figure 4 As shown, step S1 is performed: a semiconductor substrate 101 is provided, and the semiconductor substrate 101 includes an ion-doped region of a first doping type. In this embodiment, the first doping type is described as P type.

[0085] In one example, the entire semiconductor substrate 101 may be doped with ions of the first doping type, so that the entire semiconductor substrate is considered to be the ion-doped region. Of course, in other examples, ion doping of the first doping type may be performed in a required area to obtain the ion-doped region.

[0086] Specifically, in this example, the semiconductor substrate 101 has a first surface 101a (upper surface) and a second surface 101b (lower surface) relative to each other. The semiconductor substrate 101 can be a structure composed of a single layer of material layers, including but not limited to a silicon substrate, and its material can be single crystal silicon, single crystal germanium, polycrystalline silicon, amorphous silicon, or silicon germanium compounds, etc. Of course, the semiconductor substrate 101 can also be silicon on insulator SOI, etc. In addition, the semiconductor substrate 101 can also have N-type doped or P-type doped regions to meet actual needs. Among them, the semiconductor substrate 101 can be used as a substrate for an image sensor, and an epitaxial layer is prepared thereon to realize the preparation of image sensor devices. In addition, in other embodiments, the semiconductor substrate 101 can be any structure used to prepare an image sensor functional area in the field of image sensors, and the photosensitive elements, various transistors, and interconnection wiring of a CMOS image sensor can be prepared based on the semiconductor substrate 101.

[0087] Then, if Figure 5 As shown, step S2 is performed: forming a device function layer 201 on the semiconductor substrate 101 .

[0088] Specifically, a device function layer 201 is formed on a semiconductor substrate 101, and various functional regions in the image sensor can be prepared therein. Of course, in other cases where necessary, the structure required for the image sensor can also be prepared in the semiconductor substrate 101 or in other material layers. In this example, the device function layer 201 has a first surface 201a (upper surface) and a second surface 201b (lower surface) relative to each other. Among them, the second surface 201b of the device function layer 201 is prepared on the first surface 101a of the semiconductor substrate 101.

[0089] In a specific example, the device function layer 201 may be an epitaxial layer (EPI) formed on a semiconductor substrate 101 (such as a silicon substrate), and the device function layer 201 may be directly formed by an epitaxial process. For example, the epitaxial layer may be a P-type silicon epitaxial layer, and photoelectric conversion elements and transistor components (such as charge transfer elements) are prepared in the epitaxial layer. Of course, the device function layer 201 may also be formed by other methods of existing processes. Further, a front-illuminated image sensor may be prepared based on the semiconductor substrate and the device function layer.

[0090] Then, if Figure 6As shown, step S3 is performed: heat treatment is performed on the semiconductor substrate 101 to diffuse the doped ions in the ion doping region into the material layer located above the semiconductor substrate 101 to form a light absorption driving layer 300; in this embodiment, the doped ions in the ion doping region diffuse into the device function layer 201 located above the semiconductor substrate 101, that is, the light absorption driving layer 300 extends upward from the first surface 101a of the semiconductor substrate 101, and extends inward from the second surface 201b of the device function layer 201. The light absorption driving layer 300 formed based on ion diffusion has ion doping of the first doping type, which can be beneficial to the photoelectric conversion of the interval at the bottom of the device function layer 201 and the transfer of the generated electrons to the collection area, thereby being beneficial to the improvement of the quantum efficiency of the optical signal, especially the near-infrared light with a longer wavelength.

[0091] As an example, the processing temperature of the heat treatment process is greater than or equal to 950°C and less than or equal to 1150°C. For example, it can be selected as 980°C, 1000°C, 1080°C, etc., which can improve the formation efficiency and performance of the light absorption driving layer 300 while meeting the performance of the device in this application. In addition, in this example, the heat treatment process is performed before the device functional layer 201 and the semiconductor device are formed, which can prevent the influence of high temperature on other devices.

[0092] See also Fig.12 and Fig.13 As shown in Figure 2, the SIMS test results of different front-end annealing process conditions show that with the increase of thermal budget, the degree of upward diffusion of substrate P-type doping will become larger and larger, among which, Fig.12 The B element SIMS diagrams are shown for different heat treatment conditions (thermal, taking time h as an example). In addition, see Fig.13 As shown, by comparing the near-infrared light sensitivity under different heat treatment conditions (the figure shows the comparison between those with and without heat treatment), it is found that heat treatment can effectively improve the sensitivity of near-infrared light. It can be seen that heat treatment increases the width of the concentration gradient from the substrate to the epitaxial layer, which can improve the near-infrared performance.

[0093] Finally, if Figure 7 As shown, step S4 is performed: a semiconductor device is prepared in the device functional layer 201, and the semiconductor device includes a photoelectric conversion element 502 of a second doping type different from the first doping type, so as to obtain an image sensor. Further, other transistors in the image sensor can also be prepared, and a transfer transistor 503 is shown in the figure. Of course, there are other transistors, and the corresponding photoelectric conversion element forms a pixel unit 501.

[0094] Continue to see Figure 7As shown, in one example, the photoelectric conversion element 502 has an extension portion extending into the light absorption driving layer 300 , wherein the depth of the extension portion does not exceed 20% of the depth of the photoelectric conversion element.

[0095] In this example, the photoelectric conversion element 502 prepared after the light absorption driving layer 300 is formed extends into the light absorption driving layer 300, which can simultaneously improve the dark current problem generated during the operation of the device and prevent electrons from being transferred to adjacent pixel units, thereby affecting the image quality. In addition, in a further example, the depth of the extended entry is set to be less than 20% of the depth of the photoelectric conversion element itself, such as Figure 7 As shown, the distance D2 is less than 20% of the distance D1. For example, 2%, 8%, 10%, 12%, 15%, etc. can be selected to improve the dark current while optimizing the full well.

[0096] See also Figure 8-10 As shown, in one example, before forming the device function layer 201, the method for manufacturing the image sensor further includes: forming an absorption auxiliary layer 600 on the semiconductor substrate 101. The absorption auxiliary layer 600 formed on the semiconductor substrate 101 may be prepared by an epitaxial process.

[0097] In which, during the heat treatment process, the doped ions in the ion-doped region of the semiconductor substrate 101 diffuse at least into the absorption auxiliary layer 600, so that the width of the light absorption driving layer 300 can be further expanded, and the quantum efficiency of the image sensor can be improved. In addition, in this example, the absorption auxiliary layer 600 is formed before the heat treatment process, and the defects generated during the preparation of the absorption auxiliary layer 600 can be improved while the light absorption driving layer 300 is formed based on the heat treatment annealing process. The material of the absorption auxiliary layer 600 can be the same as that of the semiconductor substrate 101, and its material includes but is not limited to silicon. Furthermore, the configuration of doped ions can also be performed in the absorption auxiliary layer 600 to further assist the light signal absorption drive based on the heat treatment.

[0098] In addition, the design of the absorption auxiliary layer 600 can improve the problem that the increase in ion diffusion caused by heat treatment and annealing is limited. The structure can greatly increase the width of the concentration gradient between the epitaxial layer and the substrate, and can obtain higher near-infrared sensitivity. In addition, due to the limitations of the epitaxial layer process, as the thickness of the epitaxial layer (absorption auxiliary layer 600) increases, the lattice defects of the epitaxial layer may increase, thereby deteriorating the high-temperature performance of the chip itself. Based on the design of the process method of this application, these adverse effects can be alleviated. Based on the structure of the absorption auxiliary layer 600, the process conditions for improving the thermal budget of the front-end annealing are combined. The lattice defects of the epitaxial layer can be reduced through a reasonable annealing thermal budget. See Fig.14As shown, the reference example is an example of preparing an auxiliary absorption layer without heat treatment, and the figure shows a comparative example of only preparing an auxiliary absorption layer and simultaneously preparing an auxiliary absorption layer and heat treatment, and other conditions are the same. It can be seen that thermal annealing can improve the high temperature performance (dark current performance) to the level of the original structure, so that the near-infrared sensitivity can be improved without worrying about the side effects of high temperature performance, thereby improving the overall performance.

[0099] Furthermore, the doping ions in the ion-doped region of the semiconductor substrate 101 further diffuse upward from the absorption auxiliary layer 600 to the device functional layer 201. The absorption auxiliary layer 600 has a second surface 600b (lower surface) formed on the first surface 101a of the semiconductor substrate 101 and a first surface 600a (upper surface) of the absorption auxiliary layer 600 opposite thereto. Fig. 9 As shown, the doping ions in the ion-doped region of the semiconductor substrate 101 diffuse upward from the first surface 101 a of the semiconductor substrate 201 , and diffuse into the device function layer 201 through the absorption auxiliary layer 600 to form the light absorption driving layer 300 .

[0100] In a further example, a prefabricated ion-doped layer of the first doping type is formed in the absorption auxiliary layer 600. The prefabricated ion-doped layer can be formed on the entire layer of the absorption auxiliary layer 600, that is, the entire absorption auxiliary layer 600 can be considered as the prefabricated ion-doped layer. Of course, in other examples, a part of the absorption auxiliary layer 600 can also be doped to form the prefabricated ion-doped layer. The prefabricated ion-doped layer with the first doping type can be directly formed in the epitaxial process. Of course, it can also be formed by ion implantation after the absorption auxiliary layer base material layer is formed, for example, by P-type ion implantation in silicon material.

[0101] See also Fig.10 As shown, it is a structural schematic diagram of the semiconductor device preparation after the absorption auxiliary layer 600 is formed, the light absorption driving layer 300 is formed by heat treatment, and the other structures are similar to the above. The depth relationship between the photoelectric conversion element 502 and the extension of the light absorption driving layer 300 can refer to the above description of 20%.

[0102] See also Fig.11 As shown, during the heat treatment, the doping ions of the prefabricated ion doping layer diffuse into the material layer located above the semiconductor substrate 101 to form the light absorption driving auxiliary layer 700 .

[0103] Specifically, in this example, the doped ions of the prefabricated ion-doped layer diffuse into the material layer located above it, diffuse into the device functional layer 201, thereby forming a light absorption driving auxiliary layer 700. In addition, the doped ions in the ion-doped layer in the semiconductor substrate 101 also diffuse into the material layer above to form a light absorption driving layer 300, wherein the light absorption driving layer 300 is in contact with the light absorption driving auxiliary layer 700 or further extends from the contact surface to form an overlap, both of which can further improve the signal conversion driving efficiency based on the combination of the two, and facilitate the formation of an electron transmission gradient from the surface of the semiconductor substrate upward. It should be noted that the diffusion during the heat treatment process also includes the diffusion itself, and is not strictly limited to the diffusion to the upper material layer described in this application. This is understandable to those skilled in the art, and the above description facilitates the explanation and understanding of the utility model creation.

[0104] Continue to see Figure 8 As shown, in one example, the doping concentration of the ion doping layer of the first doping type of the semiconductor substrate is greater than the doping concentration in the prefabricated ion doping layer of the absorption auxiliary layer, which is greater than the doping concentration of the ion doping of the first doping type in the device functional layer. This is conducive to forming a bottom-up concentration gradient during the heat treatment process, and then forming a bottom-up electric field to drive charge transfer. Among them, when the prefabricated ion doping layer includes N sub-ion doping layers or the prefabricated ion doping layer has a varying doping concentration, the doping concentration of the ion doping layer of the first doping type of the semiconductor substrate is greater than the maximum doping concentration in the prefabricated ion doping layer of the absorption auxiliary layer, and the minimum doping concentration in the prefabricated ion doping layer is greater than the doping concentration of the ion doping of the first doping type in the device functional layer.

[0105] As an example, the doping concentration of the ion doping region in the semiconductor substrate 101 is greater than 2E18 atom / CM3, the device function layer 201 has a first doping type of doping, and the concentration is less than 2E15 atom / CM3. When the image sensor includes a prefabricated ion doping layer having the first doping type, the doping concentration is between 5E15-1E17atom / CM3. In a specific example, the ion doping concentration in the semiconductor substrate 101 can be 3E18atom / CM3, 3E18 atom / CM3, etc., the ion concentration of the device function layer 201 can be 2E14 atom / CM3, 1E15 atom / CM3, etc., and the ion doping concentration of the prefabricated ion doping layer can be 6E15atom / CM3, 6E15atom / CM3, or a gradient doping. In other examples, the concentration of each doping layer can be actually designed.

[0106] In an optional example, the prefabricated ion doping layer is a single material layer whose concentration decreases from the semiconductor substrate 101 toward the device functional layer 201, or the prefabricated ion doping layer includes N sub-ion doping layers (the stacked structure is not specifically shown in the figure), and the concentrations of the N sub-ion doping layers decrease from the semiconductor substrate 101 toward the device functional layer 201. The decreasing trend here means that the concentration value gradually decreases. Of course, there is also a situation where at least two adjacent concentration values ​​are equal.

[0107] In this example, by setting a decreasing concentration gradient, a gradient factor can be further introduced into the light absorption driving layer 300 of the present application, which is further conducive to forming an electric field for electron transmission, that is, an electric field transmitted upward from the bottom side below the photoelectric conversion element, thereby improving the transmission power of the photoelectric conversion signal.

[0108] As an example, the thickness of the absorption auxiliary layer 600 is between 1-6μm, for example, it can be set to 2μm, 3μm, 4μm, 5μm, so that the quantum efficiency of the optical signal can be improved in combination with the heat treatment process of the present application, especially the quantum efficiency of infrared light. At the same time, based on the heat treatment process, it is beneficial to increase the thickness of the absorption auxiliary layer 600, thereby forming a light absorption driving efficiency based on the material layer. In addition, the design within the above range is conducive to alleviating problems such as lattice defects caused by an excessively thick absorption auxiliary layer 600.

[0109] In an optional example, the prefabricated ion doping layer includes N sub-ion doping layers, and the thickness of the multiple sub-ion doping layers can be set according to the actual needs and the thickness of the total absorption auxiliary layer 600 required by the practice. Optionally, the thickness of each sub-ion doping layer is the same. In a further example, the thickness of the top sub-ion doping layer is greater than or equal to 3μm, for example, it can be selected to be 3.5μm, 4μm, and the design of the above thickness range can be beneficial to reduce defects to improve the performance of the device functional layer 201 located thereon.

[0110] Continue reading Figure 7 and Fig.11As shown, the image sensor also includes a number of pixel units arranged in an array, and there is an isolation structure between adjacent pixel units, for example, it is composed of the first isolation structure 401 and the second isolation structure 402 in the figure, each pixel unit shares the light absorption drive layer 300, and when there is an absorption auxiliary layer 600, each pixel unit shares the light absorption drive layer 600, and a shared light absorption drive auxiliary layer 700 can be further formed. In one example, the first isolation structure 401 is a P-type doping isolation, and the second isolation structure 402 is a shallow trench isolation structure STI. In addition, in this embodiment, the first doping type is P-type and the second doping type is N-type. Of course, they can also be interchangeable when forming other types of image sensors. In addition, the image sensor of this embodiment can be a front-illuminated image sensor, so as to further solve the problem of quantum efficiency of long wavelengths, especially infrared light, caused by the limited depth of the photoelectric conversion element of the front-illuminated image sensor.

[0111] Embodiment 2:

[0112] See also Figure 7 , Fig.10 and Fig.11 As shown, the present application also provides an image sensor, wherein the image sensor in this embodiment is prepared by the preparation method of the image sensor in the first embodiment, and the relevant structure and corresponding features can be referred to the description in the preparation method, which will not be repeated here. Of course, in other embodiments, it can also be obtained based on other preparation methods, wherein the image sensor includes: a semiconductor substrate, a device functional layer, and a semiconductor device and a light absorption driving layer. Specifically:

[0113] The semiconductor substrate 101 includes an ion-doped layer of a first doping type;

[0114] The device functional layer 201 is located on the semiconductor substrate;

[0115] The semiconductor device is located in the device functional layer, and the semiconductor device includes a photoelectric conversion element 502 having a second doping type different from the first doping type;

[0116] Among them, a light absorption driving layer 300 is formed in the interface area between the semiconductor substrate 101 and the device functional layer 201. The interface area can be understood as the relative surface area where the two are closest or in contact, including a material layer extending upward from the surface corresponding to the semiconductor substrate or a material layer further extending into the device functional layer. The above-mentioned light absorption driving layer 300 can be formed by diffusion from the semiconductor substrate with reference to the description in the preparation method. Of course, in other embodiments, it can also be formed by other methods to be formed in the image sensor, so as to facilitate photoelectric conversion and drive transmission of electrical signals and improve quantum efficiency.

[0117] In one example, the light absorption driving layer 300 is extended from the bottom of the device function layer 201 to the inside and has ion doping of the first doping type, and can be formed based on the diffusion described in the method.

[0118] In one example, the image sensor also includes an absorption auxiliary layer 600, which is located between the semiconductor substrate 101 and the device functional layer 201. The light absorption driving layer 300 extends inward from the bottom of the absorption auxiliary layer 600. It can be located only in the absorption auxiliary layer 600, or it can further extend to the device functional layer 201. In this example, the light absorption driving layer extends from the absorption auxiliary layer to the device functional layer.

[0119] In one example, the absorption auxiliary layer 600 includes a prefabricated ion doping layer, the prefabricated ion doping layer has ion doping of a first doping type, and the light absorption driving layer 300 is at least formed in the prefabricated ion doping layer. In this example, the light absorption driving layer 300 extends from the prefabricated ion doping layer to the device functional layer 201.

[0120] As an example, the image sensor further includes a light absorption driving auxiliary layer 700, which is extended from the bottom of the device function layer 201 and has ion doping of the first doping type. It can be formed by diffusion through the prefabricated ion doping layer of the auxiliary absorption layer 600 in the method description.

[0121] In one example, the prefabricated ion doping layer includes N sub-ion doping layers, and the concentrations of the N sub-ion doping layers decrease from the semiconductor substrate toward the device functional layer; or, the prefabricated ion doping layer is a single-layer material layer whose concentration decreases from the semiconductor substrate toward the device functional layer.

[0122] Embodiment three:

[0123] The utility model also provides an electronic device, comprising an image sensor as described in any one of the above schemes. The electronic device can be a security monitoring, vehicle-mounted electronics, mobile phone camera, machine vision and other equipment. Based on the image sensor of the utility model, high-quality image information can be obtained, especially for infrared utilization equipment.

[0124] In summary, the image sensor structure of the utility model includes a light absorption driving layer. In addition, in the preparation of the image sensor of the utility model, the light absorption driving layer is formed by heat treating the semiconductor substrate. Based on the design of the light absorption driving layer, the quantum efficiency of the image sensor for light signals can be improved based on the existence of the light absorption driving layer, especially the quantum efficiency of near-infrared light, and the application flexibility of the device can be improved. Therefore, the utility model effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0125] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present invention. All equivalent modifications or changes made by those with ordinary knowledge in the relevant technical field without departing from the spirit and technical ideas disclosed in the present invention shall still be covered by the claims of the present invention.

Claims

1. An image sensor, characterized in that: The image sensor comprises: A semiconductor substrate, the semiconductor substrate comprising an ion-doped layer of a first doping type; A device functional layer, located on the semiconductor substrate; a semiconductor device located in the device functional layer, the semiconductor device comprising a photoelectric conversion element having a second doping type different from the first doping type; Wherein, a light absorption driving layer is formed in the interface area between the semiconductor substrate and the device functional layer.

2. The image sensor according to claim 1, wherein: The image sensor further comprises an absorption auxiliary layer located between the semiconductor substrate and the device functional layer, and the light absorption driving layer is extended inward from the bottom of the absorption auxiliary layer.

3. The image sensor according to claim 2, wherein: The absorption auxiliary layer includes a prefabricated ion doping layer, the prefabricated ion doping layer has ion doping of the first doping type, and the light absorption driving layer is at least formed in the prefabricated ion doping layer.

4. The image sensor according to claim 3, wherein: When the prefabricated ion-doped layer includes N sub-ion-doped layers, the thickness of the top sub-ion-doped layer is greater than or equal to 3 μm.

5. The image sensor according to claim 2, wherein: The thickness of the absorption auxiliary layer is between 1 μm and 6 μm.

6. The image sensor according to claim 1, wherein: The image sensor further comprises a plurality of pixel units arranged in an array, an isolation structure is provided between adjacent pixel units, each of the pixel units shares the light absorption driving layer, and when an absorption auxiliary layer exists, each of the pixel units shares the absorption auxiliary layer.

7. The image sensor according to claim 1, wherein: The photoelectric conversion element has an extension portion extending into the light absorption drive layer, and the depth of the extension portion does not exceed 20% of the depth of the photoelectric conversion element; and / or the light absorption drive layer extends inward from the bottom of the device functional layer and has ion doping of the first doping type; and / or the first doping type is P type and the second doping type is N type; and / or the image sensor is a front-illuminated image sensor.

8. The image sensor according to any one of claims 1 to 7, characterized in that: The image sensor further includes a light absorption driving auxiliary layer, which is extended from the bottom of the device functional layer toward the inside and has ion doping of the first doping type.

9. An electronic device, characterized in that: The electronic device comprises the image sensor as claimed in any one of claims 1-8.

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