CN222582875U - Image sensors, electronic devices - Google Patents

Abstract

The utility model provides an image sensor and electronic equipment, wherein the image sensor comprises a semiconductor substrate, a device functional layer, a semiconductor device and a light absorption driving layer, wherein the semiconductor substrate comprises an ion doped layer with a first doping type, the device functional layer is arranged on the semiconductor substrate, the semiconductor device is arranged in the device functional layer and comprises a photoelectric conversion element with a second doping type, and the light absorption driving layer is formed between the interface of the semiconductor substrate and the device functional layer. The image sensor structure comprises the light absorption driving layer, so that the quantum efficiency of the image sensor can be improved based on the existence of the light absorption driving layer, particularly the quantum efficiency of near infrared light is improved, and the application flexibility of the device is improved.

Description

Image sensor and electronic device

Technical Field

The utility model belongs to the technical field of image acquisition, and particularly relates to an image sensor and electronic equipment.

Background

The image sensor is an important component constituting the digital camera. The two main types of devices are CCD (Charge Coupled Device ) and CMOS (Complementary Metal-Oxide Semiconductor, metal oxide semiconductor device). With the continuous development of CMOS integrated circuit manufacturing processes, particularly CMOS image sensor design and manufacturing processes, CMOS image sensors have gradually replaced CCD image sensors as the mainstream. Compared with the CMOS image sensor, the CMOS image sensor has the advantages of low voltage, low power consumption, low cost, high integration level and the like, and has important application value in the fields of machine vision, consumer electronics, high-definition monitoring, medical imaging and the like.

In addition, near Infrared (NIR) imaging is a very valuable technique that can be used in a variety of applications including agriculture, food detection, medical diagnostics, and environmental monitoring. The near infrared camera adopts CMOS technology, can capture images in the infrared wavelength range under visible light, and reveals information hidden under the common spectrum for us. Near infrared imaging is an infrared band between visible and thermal infrared imaging, which includes light that is not perceived by the human eye and can be used to measure chemical composition, moisture content and temperature of objects, and thus has wide application in agriculture, medicine and food industry. However, the main problem faced by near infrared band response is that the QE (Quantum Efficiency ) value is small, 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, since the QE value is low, in order to image in the near infrared band, the power of the light supplementing light source needs to be increased, which can lead to a sharp rise of heat loss of the system, thus increasing energy cost and reducing the reliability of the system.

Therefore, how to provide an image sensor, a manufacturing method thereof and an electronic device are needed to solve the problems of high quantum efficiency, high heat loss and high power consumption of the system in the prior art.

It should be noted that the foregoing description of the technical background is only for the purpose of providing a clear and complete description of the technical solution of the present application and for the convenience of understanding by those skilled in the art. The above-described solutions cannot be considered to be known to the person skilled in the art simply because they are set forth in the background section.

Disclosure of utility model

In view of the above drawbacks of the prior art, an object of the present utility model is to provide an image sensor and an electronic device, which are used for solving the problems of low quantum efficiency, high heat loss and high power consumption of the system of the image sensor in the prior art.

To achieve the above and other related objects, the present utility model provides a method for manufacturing an image sensor, the method comprising:

Providing a semiconductor substrate, wherein the semiconductor substrate comprises an ion doped region of a first doping type;

forming a device functional layer on the semiconductor substrate;

Performing heat treatment on the semiconductor substrate to diffuse the doped ions of the ion doped region into the material layer above the semiconductor substrate to form a light absorption driving layer, and

And preparing a semiconductor device in the device functional layer, wherein the semiconductor device comprises a photoelectric conversion element with a second doping type different from the first doping type so as to obtain the image sensor.

Optionally, the photoelectric conversion element has an extension portion extending into the light absorption driving layer, wherein a depth of the extension portion is not more than 20% of a depth of the photoelectric conversion element.

Optionally, before forming the device functional layer, the preparation method further includes:

and forming an absorption auxiliary layer on the semiconductor substrate, wherein doping ions of the ion doping region are diffused into at least the absorption auxiliary layer in the heat treatment process.

Optionally, a pre-ion doped layer of the first doping type is formed in the absorption assisting layer.

Optionally, the prefabricated ion doped layer includes N sub ion doped layers, and the concentration of the N sub ion doped layers decreases from the semiconductor substrate toward the device functional layer.

Optionally, the prefabricated ion doped layer is a single-layer material layer with concentration decreasing from the semiconductor substrate towards the device functional layer.

Optionally, during the heat treatment, the dopant ions of the pre-ion doped layer diffuse into a material layer located above the semiconductor substrate to form a light absorption driving assistance layer.

Optionally, when the prefabricated ion doped layer includes N ion doped layers, a thickness of the top ion doped layer is 3 μm or more.

Optionally, the treatment temperature of the heat treatment process is greater than or equal to 950 ℃ and less than or equal to 1150 ℃.

Alternatively, when an absorption auxiliary layer is formed on the semiconductor substrate, the absorption auxiliary layer has a thickness of between 1 and 6 μm.

Optionally, the doping concentration of the ion doped layer of the first doping type of the semiconductor substrate is greater than the doping concentration of the ion doping of the first doping type in the prefabricated ion doped layer.

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, the concentration is less than 2E15 atom/CM3, and when the image sensor includes a prefabricated ion doped layer having the first doping type, the doping concentration is between 5E15-1E17atom/CM 3.

Optionally, the first doping type is P-type, and the second doping type is N-type.

The utility model also provides an image sensor, which can be prepared by adopting the preparation method, and of course, the image sensor can also be prepared by adopting other methods, and the image sensor comprises:

A semiconductor substrate comprising an ion doped layer of a first doping type;

A device functional layer located on the semiconductor substrate;

A semiconductor device in the device functional layer, the semiconductor device including a photoelectric conversion element having a second doping type different from the first doping type;

Wherein, the interface interval of the semiconductor substrate and the device function layer is provided with a light absorption driving layer.

Optionally, the light absorbing driving layer extends from the bottom of the device functional layer to the inside and has ion doping of the first doping type.

Optionally, the image sensor further includes an absorption auxiliary layer, the absorption auxiliary layer is located between the semiconductor substrate and the device function layer, and the light absorption driving layer is disposed to extend inward from a bottom of the absorption auxiliary layer.

Optionally, the absorption assisting layer includes a pre-ion doped layer having ion doping of the first doping type, and the light absorption driving layer is formed at least in the pre-ion doped layer.

Optionally, the prefabricated ion doping layer comprises N sub ion doping layers, the concentration of the N sub ion doping layers decreases gradually from the semiconductor substrate towards the device functional layer, or the prefabricated ion doping layer is a single-layer material layer, the concentration of the single-layer material layer decreases gradually from the semiconductor substrate towards the device functional layer.

Optionally, the image sensor further includes a light absorbing driving assistance layer extending inward from the device functional layer bottom and having ion doping of the first doping type.

Optionally, the image sensor further includes a plurality of pixel units arranged in an array, an isolation structure is disposed between two adjacent pixel units, each pixel unit shares the light absorption driving layer, and when the absorption auxiliary layer exists, each pixel unit shares the light absorption driving layer.

Optionally, the image sensor is a front-lit image sensor.

The utility model also provides electronic equipment comprising the image sensor according to any one of the schemes.

The image sensor and the electronic device have the advantages that the light absorption driving layer is included in the image sensor structure, in addition, in the preparation of the image sensor, the light absorption driving layer is formed based on the mode of carrying out heat treatment on the semiconductor substrate, the quantum efficiency of the image sensor on light signals, particularly the quantum efficiency of near infrared light, can be improved based on the existence of the light absorption driving layer, and the application flexibility of the device is improved.

Drawings

Fig. 1 is a block diagram showing the basic structure of an image sensor system.

Fig. 2 shows a schematic diagram of a pixel circuit of an image sensor.

FIG. 3 is a flow chart showing the preparation of an image sensor in an embodiment of the application.

Fig. 4 is a schematic view showing a semiconductor substrate provided in the preparation of an image sensor according to an embodiment of the present application.

Fig. 5 is a schematic diagram of a device functional layer formed in the preparation of an image sensor according to an embodiment of the present application.

Fig. 6 is a schematic diagram showing formation of a light absorption driving layer in the manufacture of an image sensor according to an embodiment of the present application.

Fig. 7 is a schematic view showing a semiconductor device formed in the fabrication of an image sensor according to an embodiment of the present application.

Fig. 8 is a schematic diagram showing formation of an absorption assisting layer in the manufacture of an image sensor according to an embodiment of the present application.

Fig. 9 is a schematic view showing the formation of a light absorption driving layer in the example of the structure shown in fig. 8.

Fig. 10 shows a schematic view of a semiconductor device formed in an example of the structure shown in fig. 8.

Fig. 11 is a schematic view showing the formation of the light absorption driving assistance layer in the example of the structure shown in fig. 8.

Fig. 12 shows the effect of different heat treatment times on the diffusion of B ion doping in this example.

Fig. 13 shows the effect of heat treatment on near infrared light sensitivity, both with and without heat treatment, in this example.

Fig. 14 shows the effect of whether or not the absorption auxiliary layer preparation and the heat treatment were performed on the dark current performance of the image sensor in the present embodiment, compared with the reference example.

Description of element reference numerals

101. Semiconductor substrate

201. Device functional layer

300. Light absorbing driving layer

401. First isolation structure

402. Second isolation structure

501. Pixel circuit

502. Photoelectric conversion element

503. Transistor with a high-voltage power supply

600. Absorption auxiliary layer

700. Light absorbing driving auxiliary layer

Detailed Description

Other advantages and effects of the present utility model will become apparent to those skilled in the art from the following disclosure, which describes the embodiments of the present utility model with reference to specific examples. The utility model may be practiced or carried out in other embodiments that depart from the specific details, and the details of the present description may be modified or varied from the spirit and scope of the present utility model.

It should be emphasized that the term "comprises/comprising" when used herein is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps or components.

Features that are described and/or illustrated with respect to one embodiment may be used in the same way or in a similar way in one or more other embodiments in combination with or instead of the features of the other embodiments.

As described in detail in the embodiments of the present utility model, the cross-sectional view of the device structure is not partially enlarged to a general scale for convenience of explanation, and the schematic drawings are only examples, which should not limit the scope of the present utility model. In addition, the three-dimensional dimensions of length, width and depth should be included in actual fabrication.

For ease of description, spatially relative terms such as "under", "below", "beneath", "above", "upper" and the like may be used herein to describe one element or feature's relationship to another element or feature as illustrated in the figures. 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 figures. Furthermore, 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.

In the context of the present application, a structure described as a first feature being "on" a second feature may include embodiments where the first and second features are formed in direct contact, as well as embodiments where additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

It should be noted that, the illustrations provided in the present embodiment merely illustrate the basic concept of the present utility model by way of illustration, and only the components related to the present utility model are shown in the drawings rather than the number, shape and size of the components in actual implementation, and the form, number and proportion of each component in actual implementation may be arbitrarily changed, and the layout of the components may be more complex.

The present utility model will be described in detail with reference to the accompanying drawings.

Fig. 1 is a block diagram showing the basic structure of an image sensor system. The image sensor includes a readout circuit and a control circuit connected to the pixel array, and in addition, the functional logic unit is connected to the readout circuit, and the readout circuit and the control circuit are connected to the status register to realize 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), and pixel signals output from the pixel array are output to the readout circuit via the column lines. In some applications, after the pixels acquire image data, they are read out using a readout mode specified by a status register and then transferred to a functional logic unit. In particular implementations, the readout circuitry may include analog-to-digital conversion (ADC) circuitry, among other circuitry.

In some applications, the status register may include a programmable selection system for determining whether the readout system is to be read by rolling exposure mode (rolling shutter) or global exposure mode (global shutter). The functional logic may store the original image data or the image data after image processing. In some implementations, the readout circuitry may read out one row of image data at a time along the readout column lines, although other ways of reading out image data may be used. The operation of the control circuit may be determined by the current setting of the status register, for example, the control circuit generates a shutter signal for controlling image acquisition, which may be a global exposure signal in some applications such that all pixels of the pixel array acquire their image data simultaneously through a single acquisition window, or a rolling exposure signal in other applications such that pixels of each pixel row of the pixel array perform exposure read operations consecutively through the acquisition window.

Fig. 2 is a schematic diagram of a pixel unit in an image sensor. As shown in fig. 2, each pixel unit includes a photoelectric conversion element (e.g., a photodiode) and a pixel circuit (shown as a transistor within a broken line frame in the figure). The photodiode may be a buried photodiode (PPD) applied in the current image sensor. In an application example, the pixel circuit includes a reset transistor (RST), a source follower transistor (SF), and a pixel selection transistor (RS), connected to a transfer Transistor (TX) and a photodiode as shown in fig. 2. In one example of a stacked architecture application, the pixel circuit includes a reset transistor, a source follower transistor, and a pixel select transistor disposed on a first circuit chip, and a transfer transistor disposed on a second circuit chip, the photodiode in the second circuit chip being connected to other transistors in the first circuit chip based on the transfer transistor. In a further application example, the pixel circuit may further include a gain control transistor (DCG) connected between the floating diffusion region (FD) and the reset transistor. In operation, the photoelectric conversion element generates photo-charges in response to incident light during exposure, the transfer transistor is connected to a transfer signal that controls the transfer transistor to transfer charges accumulated in the photoelectric conversion element to a floating diffusion region, a reset transistor is connected between a power supply voltage and the floating diffusion region, the floating diffusion region is connected to a gate of a source follower transistor in response to the reset signal to reset a sensor pixel circuit (e.g., discharge or charge the floating diffusion region and photodiode to a current voltage), the source follower transistor is connected between the power supply voltage and a pixel select transistor, the pixel select transistor is connected to the source follower transistor and a bit line in response to a potential of the floating diffusion region and outputs it, and pixel select readout is achieved in response to a pixel select control signal and output it to a readout column.

However, in the existing image sensor, the main problem faced by the near infrared band response is that the QE value is small, the silicon substrate is weak in absorption in the near infrared band of 750-1100 nm, and in addition, because the QE value is low, in order to image in the near infrared band, the power of the light supplementing light source needs to be increased, which leads to the rapid rise of the heat loss of the system, thus not only increasing the energy cost, but also reducing the reliability of the system. The utility model can effectively improve the problems through the arrangement of the light absorption driving layer and the design of the process. The following will explain the embodiments in detail.

Embodiment one:

Referring to fig. 3, the present embodiment provides a method for manufacturing an image sensor, and fig. 3 shows a flowchart of the manufacturing method, wherein the manufacturing method includes the following steps:

S1, providing a semiconductor substrate, wherein the semiconductor substrate comprises an ion doped region with a first doping type;

s2, forming a device function layer on the semiconductor substrate;

S3, performing heat treatment on the semiconductor substrate to diffuse the doped ions of the ion doped region into the material layer above the semiconductor substrate to form a light absorption driving layer, and

And S4, preparing a semiconductor device in the device functional layer, wherein the semiconductor device comprises a photoelectric conversion element with a second doping type different from the first doping type, so as to obtain the image sensor.

In this embodiment, the light absorption driving layer is formed in the image sensor based on the semiconductor substrate, so that photoelectric conversion and signal transmission can be further compensated based on the light absorption driving layer, which is favorable for improving quantum efficiency of various optical signals, in particular, the infrared light quantum efficiency, so that application flexibility of the image sensor can be improved, application fields of the image sensor can be widened, and image quality can be improved. The preparation sequence of the steps can be changed according to the actual process, and the realization of the light absorption driving layer is not affected.

The preparation of the image sensor of the present application will be described in detail with reference to specific examples.

First, as shown in fig. 4, a step S1 is performed in which a semiconductor substrate 101 is provided, the semiconductor substrate 101 including an ion doped region of a first doping type, which is described as a P-type in this embodiment.

In an example, the ion doping of the first doping type may be performed on the entire semiconductor substrate 101, so that the entire semiconductor substrate is considered to be the ion doped region, and in other examples, the ion doping of the first doping type may be performed on a desired region to obtain the ion doped region.

Specifically, in this example, the semiconductor substrate 101 has a first surface 101a (upper surface) and a second surface 101b (lower surface) that are opposite to each other. The semiconductor substrate 101 may be a structure formed of a single layer of material, including but not limited to a silicon substrate, and the material may be single crystal silicon, single crystal germanium, polycrystalline silicon, amorphous silicon, a silicon germanium compound, or the like, and of course, the semiconductor substrate 101 may be a silicon on insulator SOI, or the like. In addition, the semiconductor substrate 101 may further have an N-type doped or P-type doped region to meet practical requirements. The semiconductor substrate 101 may be used as a base of an image sensor, and an epitaxial layer is prepared thereon to realize the preparation of a device of the image sensor, in addition, in other embodiments, the semiconductor substrate 101 may be any structure used for preparing a functional area of the image sensor in the field of the image sensor, and a photosensitive element, each transistor, interconnection wiring, and the like of a CMOS image sensor may be prepared based on the semiconductor substrate 101.

Next, as shown in fig. 5, step S2 is performed in which a device functional layer 201 is formed on the semiconductor substrate 101.

Specifically, the device functional layer 201 is formed on the semiconductor substrate 101, and each functional region in the image sensor can be prepared therein. Of course, the structures required for the image sensor may also be prepared in the semiconductor substrate 101 or in other material layers, in other cases where desired. In this example, the device functional layer 201 has opposing first and second surfaces 201a (upper and lower surfaces) 201 b. Wherein the second surface 201b of the device functional layer 201 is prepared on the first surface 101a of the semiconductor substrate 101.

In a specific example, the device functional layer 201 may be an epitaxial layer (EPI) formed on the semiconductor substrate 101 (e.g., a silicon substrate), and the device functional layer 201 may be directly formed using an epitaxial process. For example, the epitaxial layer may be a P-type silicon epitaxial layer in which photoelectric conversion elements, transistor elements (including charge transport elements, for example), and the like are fabricated. Of course, other ways of forming the device functional layer 201 using existing processes may be used. Further, a front-illuminated image sensor may be prepared based on the semiconductor substrate and the device functional layer.

Next, as shown in fig. 6, a step S3 is performed in which the semiconductor substrate 101 is subjected to a heat treatment to diffuse the doping ions of the ion doping region into the material layer located above the semiconductor substrate 101 to form the light absorption driving layer 300, and in this embodiment, the doping ions of 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 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 is beneficial to photoelectric conversion of an interval at the bottom of the device functional layer 201 and transfer of generated electrons to a collecting area, so that improvement of quantum efficiency of an optical signal, in particular to near infrared light with longer wavelength, can be facilitated.

As an example, the treatment temperature of the heat treatment process is greater than or equal to 950 ℃ and less than or equal to 1150 ℃. For example, 980 ℃, 1000 ℃, 1080 ℃, etc. can be selected, and the formation efficiency and performance of the light absorption driving layer 300 can be improved while satisfying the performance of the device of the present application. In addition, the heat treatment process is performed before the device functional layer 201 and the semiconductor device are formed in this example, and the influence of high temperature on other devices can be prevented.

Referring to fig. 12 and 13, the results of SIMS testing under different pre-annealing process conditions show that the degree of upward diffusion of the P-type dopant of the substrate becomes larger and larger with increasing thermal budget, wherein fig. 12 shows a B-element SIMS diagram under different heat treatment conditions (time h is an example). In addition, as shown in fig. 13, by comparing the near infrared light sensitivity of different heat treatment conditions (illustrated as a comparison of being performed and not being performed), it was found that the heat treatment can effectively improve the sensitivity of near infrared light, and it was found that the heat treatment increases the width of the concentration gradient from the substrate to the epitaxial layer, and can improve the near infrared performance.

Finally, as shown in FIG. 7, a step S4 is performed of preparing a semiconductor device including a photoelectric conversion element 502 of a second doping type different from the first doping type in the device functional layer 201 to obtain an image sensor. Further, other transistors in the image sensor may be prepared, and the transfer transistor 503 is shown in the figure, and of course, other transistors may be formed corresponding to the photoelectric conversion element to form the pixel unit 501.

With continued reference to fig. 7, in one example, the photoelectric conversion element 502 has an extension that extends into the light absorbing driving layer 300, wherein the depth of the extension is no more than 20% of the depth of the photoelectric conversion element.

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, so that dark current problems generated in the device operation process can be improved at the same time, and electrons are prevented from being transferred into adjacent pixel units, thereby affecting image quality. Further, in a further example, the depth into which the extension is set is less than 20% of the depth of the photoelectric conversion element itself, as shown in fig. 7, the distance D2 is less than 20% of the distance D1, for example, 2%, 8%, 10%, 12%, 15%, or the like may be selected, and the full well is optimized while improving the dark current.

Referring to fig. 8-10, in an example, before forming the device functional layer 201, the method of manufacturing the image sensor further includes forming an absorption assisting layer 600 on the semiconductor substrate 101. The formation of the absorption assisting layer 600 on the semiconductor substrate 101 may be made using an epitaxial process.

In the process of performing the heat treatment, the doped ions of the ion doped region in the semiconductor substrate 101 are diffused at least into the absorption auxiliary layer 600, so that the width of the light absorption driving layer 300 can be further enlarged, and the quantum efficiency of the image sensor can be improved. In addition, in this example, forming the absorption auxiliary layer 600 before the heat treatment process, defects generated during the preparation of the absorption auxiliary layer 600 may be improved while forming the light absorption driving layer 300 based on the heat treatment annealing process. The material of the absorption assisting layer 600 may be the same as the material of the semiconductor substrate 101, including but not limited to silicon. Further, a configuration of doping ions may also be performed in the absorption auxiliary layer 600 to further assist the optical signal absorption driving based on the heat treatment.

In addition, the design of the absorption auxiliary layer 600 can improve the problem that the annealing has a limit on the increase of ion diffusion due to the heat treatment, and the structure can greatly increase the width of the concentration gradient between the epitaxial layer and the substrate, thereby obtaining higher near infrared sensitivity. In addition, due to the limitation of the epitaxial layer process, as the thickness of the epitaxial layer (the absorption auxiliary layer 600) increases, lattice defects of the epitaxial layer and the like may increase, so that the high-temperature performance of the chip itself is deteriorated, and based on the design of the process method of the present application, these adverse effects can be alleviated, the process conditions of front-end annealing thermal budget improvement are combined on the basis of the structure of the absorption auxiliary layer 600, and the lattice defects of the epitaxial layer can be reduced through reasonable annealing thermal budget. Reference is made to fig. 14, which shows an example in which the auxiliary absorption layer is prepared without heat treatment, and a comparative example in which only the auxiliary absorption layer is prepared and heat treatment is simultaneously performed, with the other conditions being the same. It can be seen that the thermal annealing can raise the high temperature performance (dark current performance) to the level of the original structure, so that the near infrared sensitivity is raised, and meanwhile, the side effect of the high temperature performance is not worried, and the comprehensive performance is improved.

Further, the doping ions of the ion-doped region in the semiconductor substrate 101 are further diffused from the absorption assisting layer 600 up into the device functional layer 201. The absorption assisting layer 600 has a second surface 600b (lower surface) formed on the surface of the first surface 101a of the semiconductor substrate 101 and a first surface 600a (upper surface) of the absorption assisting layer 600 opposite thereto. As shown in fig. 9, the dopant ions of the ion doped region in the semiconductor substrate 101 diffuse upward from the first surface 101a of the semiconductor substrate 201, diffuse into the device functional layer 201 via the absorption auxiliary layer 600, and form the light absorption driving layer 300.

In a further example, the absorption assisting layer 600 has a pre-ion doped layer of the first doping type formed therein. The pre-ion doped layer may be formed on the entire absorption assisting layer 600, that is, the entire absorption assisting layer 600 may be regarded as a pre-ion doped layer, and of course, in other examples, a portion of the absorption assisting layer 600 may be doped to form a pre-ion doped layer. The pre-ion doped layer with the first doping type doping may be directly formed in the epitaxial process, or of course, the ion implantation may be performed after the absorption auxiliary layer base material layer is formed, for example, P-type ion implantation is performed in the silicon material.

Referring to fig. 10, a schematic structure of a semiconductor device manufactured after forming the light absorption driving layer 300 by heat treatment is shown when the absorption auxiliary layer 600 is formed, and the depth relationship between the photoelectric conversion element 502 and the extension of the light absorption driving layer 300 can be described by 20% above.

Referring to fig. 11, in the process of performing the heat treatment, the dopant ions of the pre-ion doped layer are diffused into the material layer located above the semiconductor substrate 101 to form the light absorption driving assistance layer 700.

Specifically, in this example, the doped ions of the pre-ion doped layer diffuse into the material layer above it and diffuse into the device functional layer 201, thereby forming the light absorption driving auxiliary layer 700, and in addition, the doped ions in the ion doped layer in the semiconductor substrate 101 diffuse into the material layer above to form the light absorption driving layer 300, where the light absorption driving layer 300 contacts with the light absorption driving auxiliary layer 700 or extends further from the contact surface to form an overlap, which can further improve the signal conversion driving efficiency based on the combination of the two, and facilitate the formation of an electron transport gradient from the surface of the semiconductor substrate upwards. It should be noted that diffusion during the heat treatment process also includes diffusion itself, and is not strictly limited to diffusion into the upper material layer described in the present utility model, as those skilled in the art will appreciate, and the above description is for ease of understanding the description of the utility model.

With continued reference to fig. 8, in one example, the doping concentration of the ion doped layer of the first doping type of the semiconductor substrate is greater than the doping concentration of the ion doping of the first doping type in the device functional layer in the pre-ion doped layer of the absorption assisting layer. Thereby being beneficial to forming a concentration gradient from bottom to top in the heat treatment process, and further forming an electric field from bottom to top so as to drive charge transmission. When the prefabricated ion doping layer comprises N sub-ion doping layers or the prefabricated ion doping layer has a variable doping concentration, the doping concentration of the ion doping layer of the first doping type of the semiconductor substrate is larger 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 larger than the doping concentration of the ion doping of the first doping type in the device functional layer.

As an example, the doping concentration of the ion doped region in the semiconductor substrate 101 is greater than 2E18 atom/CM3, the device functional layer 201 has a doping of the first doping type, the concentration is less than 2E15 atom/CM3, and the doping concentration is between 5E15-1E17atom/CM3 when the image sensor includes a pre-ion doped layer having the first doping type. In a specific example, the ion doping concentration in the semiconductor substrate 101 may be 3E18atom/CM3, or the like, the ion concentration of the device functional layer 201 may be 2E14 atom/CM3, 1E15 atom/CM3, or the like, and the ion doping concentration of the pre-ion doped layer may be 6E15atom/CM3, or doping with a gradient. In other examples, the doping layer concentrations may be actually designed.

In an alternative example, the pre-ion doped layer is a single-layer material layer with a concentration decreasing from the semiconductor substrate 101 toward the device functional layer 201, or the pre-ion doped layer includes N sub-ion doped layers (a stacked structure is not specifically shown in the figure), and the concentration of the N sub-ion doped layers decreases from the semiconductor substrate 101 toward the device functional layer 201. Here, the decreasing trend means that the concentration value gradually decreases, and of course, there are cases where at least two adjacent concentration values are equal.

In this example, by setting a decreasing concentration gradient, a gradient factor can be further introduced in the light absorption driving layer 300 of the present application, thereby further facilitating the formation of an electric field for electron transfer, that is, an electric field for upward transfer of the lower bottom side of the photoelectric conversion element, improving the transmission power of the photoelectric conversion signal.

As an example, the thickness of the absorption assisting layer 600 may be set to be between 1 and 6 μm, for example, 2 μm, 3 μm, 4 μm, 5 μm, so that the quantum efficiency of the optical signal, particularly the quantum efficiency of the infrared light, may be improved in combination with the heat treatment process of the present application, while the thickness of the absorption assisting layer 600 is advantageously increased on the basis of the heat treatment process, so that the light absorption driving efficiency is formed based on the material layer, and furthermore, the design of the above range is advantageous in alleviating the problems of lattice defects and the like caused by the excessively thick absorption assisting layer 600.

In an alternative example, the pre-ion doped layer includes N sub-ion doped layers, and the thickness of the multi-layered sub-ion doped layers may be set according to the actual requirement and the total thickness of the absorption assisting layer 600 required for practice. Optionally, the thickness of each of the sub-ion doped layers is the same. In a further example, for a top ion doped layer having a thickness greater than or equal to 3 μm, for example, 3.5 μm, 4 μm may be selected, and the design of the thickness ranges described above may be advantageous in reducing defects to enhance the performance of the device functional layer 201 located thereabove.

With continued reference to fig. 7 and 11, the image sensor further includes a plurality of pixel units arranged in an array, and an isolation structure is disposed between the adjacent pixel units, for example, the pixel units are formed by a first isolation structure 401 and a second isolation structure 402 in the figure, each pixel unit shares the light absorption driving layer 300, and when the absorption auxiliary layer 600 exists, each pixel unit shares the light absorption driving layer 600, and may further form a shared light absorption driving auxiliary layer 700. In one example, the first isolation structure 401 is a P-type doped isolation and the second isolation structure 402 is a shallow trench isolation structure STI. In addition, in the present embodiment, the first doping type is P-type, and the second doping type is N-type, which can be exchanged when forming other types of image sensors. In addition, the image sensor of the present embodiment can be a front-illuminated image sensor, so that the problem of long wavelength, particularly infrared quantum efficiency, of the photoelectric conversion element of the front-illuminated image sensor due to limited depth can be further solved.

Embodiment two:

Referring to fig. 7, 10 and 11, the present application further provides an image sensor, where the image sensor in this embodiment is manufactured by using the manufacturing method of the image sensor in the embodiment, and the related structure and the corresponding features may be referred to the description of the manufacturing method and are not repeated herein. Of course, in other embodiments, other fabrication methods are also contemplated wherein the image sensor includes a semiconductor substrate, a device functional layer, and a semiconductor device and light absorbing driving layer. Specific:

The semiconductor substrate 101 includes an ion doped layer of a first doping type;

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

A semiconductor device is located in the device functional layer, the semiconductor device comprising a photoelectric conversion element 502 having a second doping type different from the first doping type;

The light absorption driving layer 300 is formed between the interface of the semiconductor substrate 101 and the device functional layer 201. The interface region may be understood as the opposing surface regions closest to or in contact with each other, including a layer of material extending upwardly from the corresponding surface of the semiconductor substrate or further into the functional layers of the device. The light absorbing driving layer 300 may be formed by diffusion from a semiconductor substrate as described in the preparation method, however, in other embodiments, the light absorbing driving layer may be formed by other methods, so as to be formed in an image sensor, thereby facilitating photoelectric conversion and driving transmission of an electrical signal, and improving quantum efficiency.

In an example, the light absorbing driving layer 300 is disposed extending inward from the bottom of the device functional layer 201 and has ion doping of the first doping type, which may be formed based on diffusion in the description of the method.

In an example, the image sensor further includes an absorption assisting layer 600 between the semiconductor substrate 101 and the device functional layer 201, and the light absorption driving layer 300 is disposed to extend inward from the bottom of the absorption assisting layer 600, may be located only in the absorption assisting layer 600, or may further extend into the device functional layer 201, in this example, the light absorption driving layer extends from the absorption assisting layer into the device functional layer.

In an example, the absorption assisting layer 600 includes a pre-ion doped layer having ion doping of a first doping type, and the light absorbing driving layer 300 is formed at least in the pre-ion doped layer, and in this example, the light absorbing driving layer 300 extends from the pre-ion doped layer into the device functional layer 201.

As an example, the image sensor further includes a light absorbing driving assistance layer 700, and the light absorbing driving assistance layer 700 is provided to extend inward from the bottom of the device functional layer 201 and has ion doping of the first doping type. May be formed by diffusion of a pre-ion doped layer of the auxiliary absorption layer 600 based on the method description.

In one example, the pre-ion doped layer includes N sub-ion doped layers, the concentration of the N sub-ion doped layers decreases from the semiconductor substrate towards the device functional layer, or the pre-ion doped layer is a single-layer material layer with the concentration decreasing from the semiconductor substrate towards the device functional layer.

Embodiment III:

The utility model also provides electronic equipment comprising the image sensor according to any one of the schemes. The electronic equipment can be security monitoring equipment, vehicle-mounted electronic equipment, a mobile phone camera, machine vision equipment and the like, and the image sensor can acquire high-quality image information, and is particularly used for infrared utilization equipment.

In summary, the image sensor structure of the present utility model includes the light absorption driving layer, and in addition, in the preparation of the image sensor of the present utility model, the light absorption driving layer is formed based on the manner of performing the heat treatment on the semiconductor substrate, and the quantum efficiency of the image sensor to the light signal, especially the quantum efficiency of the near infrared light, can be improved based on the design of the light absorption driving layer, thereby improving the application flexibility of the device. Therefore, the utility model effectively overcomes various defects in the prior art and has high industrial utilization value.

The above embodiments are merely illustrative of the principles of the present utility model and its effectiveness, and are not intended to limit the utility model. Modifications and variations may be made to the above-described embodiments by those skilled in the art without departing from the spirit and scope of the utility model. All equivalent modifications and variations which can be accomplished by those skilled in the art without departing from the spirit and technical spirit of the present utility model are intended to be covered by the claims of the present utility model.

Claims (9)

1. An image sensor, characterized in that, the image sensor includes:

A semiconductor substrate comprising an ion doped layer of a first doping type;

A device functional layer located on the semiconductor substrate;

A semiconductor device in the device functional layer, the semiconductor device including a photoelectric conversion element having a second doping type different from the first doping type;

Wherein, the interface interval of the semiconductor substrate and the device function layer is provided with a light absorption driving layer.

2. The image sensor of claim 1, further comprising an absorption assisting layer between the semiconductor substrate and the device functional layer, the light absorption driving layer extending inward from a bottom of the absorption assisting layer.

3. The image sensor of claim 2, wherein the absorption assisting layer comprises a pre-ion doped layer having ion doping of the first doping type, the light absorption driving layer being formed at least in the pre-ion doped layer.

4. The image sensor of claim 3, wherein when the pre-ion doped layer comprises N sub-ion doped layers, a thickness of a top sub-ion doped layer is 3 μm or more.

5. The image sensor of claim 2, wherein the thickness of the absorption assisting layer is between 1-6 μm.

6. The image sensor of claim 1, further comprising a plurality of pixel units arranged in an array, wherein an isolation structure is provided between adjacent pixel units, wherein each pixel unit shares the light absorbing driving layer, and wherein each pixel unit shares the absorbing auxiliary layer when the absorbing auxiliary layer is present.

7. The image sensor of claim 1, wherein the photoelectric conversion element has an extension portion extending into the light-absorbing driving layer, the depth of the extension portion is not more than 20% of the depth of the photoelectric conversion element, and/or the light-absorbing driving layer is provided extending 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 of any of claims 1-7, further comprising a light absorbing drive assist layer extending inwardly from a bottom of the device functional layer and having ion doping of the first doping type.

9. An electronic device comprising an image sensor as claimed in any one of claims 1-8.