A charge coupled device and a method of fabricating a charge coupled device

Abstract

The application provides a charge coupled device and a preparation method of the charge coupled device. The charge coupled device comprises a functional layer, a silicon semiconductor layer located on a surface of the functional layer, and a colloidal quantum dot semiconductor layer located on a side of the silicon semiconductor layer away from the functional layer. The colloidal quantum dot semiconductor layer has a short-wave infrared absorption characteristic, is used for absorbing photons, and converts the photons into electric charges. The charge coupled device of the application can realize a higher spectral detection range than a traditional silicon-based charge coupled device by using the colloidal quantum dot semiconductor layer to absorb infrared light of a specific wave band.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of sensors, in particular to a charge coupled device and a preparation method of the charge coupled device. BACKGROUND

[0002] A CCD (Charge Coupled Device) is an image sensor for digital imaging, which is usually made of silicon material and is a device with a MOS pixel structure. The working of the CCD device includes four steps: absorption, storage, transfer and readout. Based on the absorption characteristics of silicon to light, the conventional CCD can realize the absorption of photons with a wavelength of 300-1100 nm, and convert the photon signals in the pixel into electronic signals and store them in the gate capacitor of the corresponding pixel MOS structure; by controlling the gate voltage of the MOS tube, the charges stored in the gate capacitors of different pixels can be transferred to the shift register in turn, and the signal readout can be realized through the last readout circuit.

[0003] At present, the CCD mainly includes a surface channel type CCD and a buried channel type CCD. The surface channel type CCD is composed of a gate electrode / dielectric layer / P-type Si, and the storage capacitor of the CCD is mainly derived from the capacitor of the gate dielectric layer. The highest point of the electric potential is at the interface between the dielectric layer and the P-type silicon, and the electrons are collected to the interface to form an inversion layer; however, due to many defect sites on the surface of silicon, the charges stored at the interface are easily captured by the interface defects, so the buried channel type CCD introduces a layer of highly doped N-type silicon between the dielectric layer and the P-type silicon to realize the transfer of the highest point of the electric potential to the inside and away from the interface of silicon.

[0004] Since the silicon material can only absorb photons below 1100 nm, the CCD can only image visible light and near-infrared light below 1100 nm, and cannot detect short-wave infrared light above 1100 nm. In recent years, short-wave infrared imaging has been increasingly widely used in the fields of food detection, article sorting, semiconductor detection, etc., so the CCD needs to realize a higher spectral detection range while maintaining its charge transfer characteristics. SUMMARY

[0005] The present application provides a charge coupled device and a preparation method of the charge coupled device, which can realize a higher spectral detection range.

[0006] To solve the above technical problems, the first technical solution provided by the application is to provide a charge coupled device, comprising: a functional layer; a silicon semiconductor layer located on the surface of the functional layer; a colloidal quantum dot semiconductor layer located on the side of the silicon semiconductor layer away from the functional layer; the colloidal quantum dot semiconductor layer has short-wave infrared absorption characteristics, is used to absorb photons, and converts them into electric charges.

[0007] The functional layer comprises: a carrier sheet, a gate layer and an insulating layer; the gate layer is located on the surface of the carrier sheet; the insulating layer is located on the side of the gate layer away from the carrier sheet, and the silicon semiconductor layer is located on the side of the insulating layer away from the carrier sheet; or the functional layer comprises a gate layer and an insulating layer; the insulating layer is located on a surface of the gate layer, and the silicon semiconductor layer is located on the side of the insulating layer away from the gate layer.

[0008] The colloidal quantum dot semiconductor layer comprises a metal oxide film; the material of the metal oxide film is a material with an absorption coefficient less than a threshold value for visible light and near-infrared light.

[0009] The colloidal quantum dot semiconductor layer comprises a metal oxide film, a colloidal quantum dot film and a transparent conductive film; the metal oxide film is arranged on the side of the colloidal quantum dot film close to the silicon semiconductor layer or on the side of the colloidal quantum dot film away from the silicon semiconductor layer; the transparent conductive film is arranged above the colloidal quantum dot film; the colloidal quantum dot film comprises at least one of a lead sulfide quantum dot film, a lead selenide quantum dot film and a mercury telluride quantum dot film; the material of the metal oxide film is a material with an absorption coefficient less than a threshold value for visible light and near-infrared light.

[0010] The material of the metal oxide film is an N-type semiconductor material; the material of the metal oxide film comprises at least one of zinc oxide, tin dioxide and titanium dioxide.

[0011] The transparent conductive film is at least one of indium tin oxide and fluorine-doped SnO2 film.

[0012] The silicon semiconductor layer comprises an N-type silicon semiconductor layer, a P-type silicon semiconductor layer and a P++ type silicon substrate; the N-type silicon semiconductor layer is arranged on one side surface of the insulating layer, the P++ type silicon substrate is arranged close to the colloidal quantum dot semiconductor layer, and the P-type silicon semiconductor layer is arranged between the N-type silicon semiconductor layer and the P++ type silicon substrate; the N-type silicon semiconductor layer is realized by ion implantation.

[0013] The dielectric constant of the insulating layer is greater than a preset value.

[0014] The gate layer is provided with a plurality of patterned arrays.

[0015] To solve the above technical problems, the second technical solution of the present application provides a preparation method of a charge coupled device, comprising: preparing a silicon semiconductor layer; disposing a functional layer on a surface of the silicon semiconductor layer; disposing a colloidal quantum dot semiconductor layer on a side of the silicon semiconductor layer away from the functional layer, the colloidal quantum dot semiconductor layer having a short-wave infrared absorption characteristic, for absorbing photons and converting them into electric charges.

[0016] The charge coupled device of the present application comprises: a functional layer; a silicon semiconductor layer located on a surface of the functional layer; and a colloidal quantum dot semiconductor layer located on a side of the silicon semiconductor layer away from the functional layer; the colloidal quantum dot semiconductor layer has a short-wave infrared absorption characteristic for receiving light. The colloidal quantum dot can adjust its band gap by adjusting the size of its nanoparticles. By adjusting the size of the CQD, light absorption in the 250-2500 nm wavelength range can be achieved. Due to the quantum confinement effect, it has a high absorption coefficient and can fully absorb short-wave infrared light. Its solution processability ensures its strong substrate compatibility, and high-quality CQD thin films can be prepared on different substrates by solution methods such as spin coating, spraying, and printing. That is, the colloidal quantum dot semiconductor layer 15 has a short-wave infrared absorption characteristic and simultaneously has a photoelectric effect and a field effect. The present application sets a colloidal quantum dot semiconductor layer on the surface of the silicon semiconductor layer, which can utilize the short-wave infrared absorption characteristic of the colloidal quantum dot to make the device have similar absorption characteristics to quantum dots. Unlike traditional charge coupled devices that can only detect visible light and near-infrared light below 1100 nm, this device can achieve a spectral detection range of up to 2500 nm. Therefore, the charge coupled device can achieve a higher spectral detection range. BRIEF DESCRIPTION OF DRAWINGS

[0017] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0018] Figure 1 The structure diagram of the first embodiment of the charge coupled device of the present application;

[0019] Figure 2 The flowchart of the first embodiment of the preparation method of the charge coupled device of the present application;

[0020] Figure 3 Flow chart of a second embodiment of a method for manufacturing a charge-coupled device. Detailed implementation method

[0021] The terms "first", "second", "third" in the present application are only for descriptive purpose, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second", "third" can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise explicitly and specifically limited. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present application are only used to explain the relative position relationship, movement condition, etc. between components in a certain posture (as shown in the drawings), and if the certain posture changes, the directional indications also change accordingly. In addition, the terms "include" and "have" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device including a series of steps or units is not limited to the listed steps or units, but can optionally include steps or units not listed, or can optionally include other steps or units inherent to the process, method, product or device.

[0022] In this document, reference to "an embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor are they necessarily mutually exclusive of one another. As will be apparent to those of ordinary skill in the art, embodiments described herein can be combined with other embodiments.

[0023] The embodiments described in the present application are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of the present application.

[0024] Please refer to Figure 1 , the structure diagram of a first embodiment of a charge-coupled device, specifically, the charge-coupled device includes a functional layer 10, a silicon semiconductor layer 14 and a colloidal quantum dot semiconductor layer 15. Among them, the silicon semiconductor layer 14 is located on the surface of the functional layer 10; the colloidal quantum dot semiconductor layer 15 is located on the side of the silicon semiconductor layer 14 away from the functional layer 10; the colloidal quantum dot semiconductor layer 15 has short-wave infrared absorption characteristics and is used for receiving light.

[0025] Specifically, the colloidal quantum dot (CQD) is a kind of nanomaterial, and the band gap thereof can be adjusted by adjusting the size of the nanoparticles thereof. By adjusting the size of the PbS CQD, the light absorption in the wavelength range of 250-2500 nm can be realized. Due to the quantum confinement effect, the CQD has a high absorption coefficient and can fully absorb short-wave infrared light. Moreover, the solution processability of the CQD can ensure the strong substrate compatibility of the CQD. By using a solution method such as spin coating, spraying, printing and the like, a high-quality CQD film can be prepared on different substrates. That is, the colloidal quantum dot semiconductor layer 15 has a short-wave infrared absorption characteristic, and the colloidal quantum dot semiconductor layer 15 has photoelectric effect and field effect at the same time. The colloidal quantum dot semiconductor layer 15 is arranged on the surface of the silicon semiconductor layer 14, so that the device has similar absorption characteristics to the quantum dot. Unlike the traditional charge-coupled device that can only detect visible light and near-infrared light below 1100 nm, the device can realize spectral detection in the range of up to 2500 nm.

[0026] In an embodiment, the functional layer 10 comprises a carrier sheet 11 and a metal layer, a gate dielectric layer, and it can be understood that the metal layer is the gate layer 12 and the gate dielectric layer is the insulating layer 13. The gate layer 12 is located on the surface of the carrier sheet 11, and the insulating layer 13 is located on the side of the gate layer 12 away from the carrier sheet 11, and the silicon semiconductor layer 14 is located on the side of the insulating layer 13 away from the carrier sheet 11.

[0027] In another embodiment, the functional layer 10 comprises a metal and a gate dielectric layer, and it can be understood that the metal layer is the gate layer 12 and the gate dielectric layer is the insulating layer 13. The insulating layer 13 is located on the surface of the gate layer 12, and the silicon semiconductor layer 14 is located on the side of the insulating layer 13 away from the gate layer 12.

[0028] The gate layer 12 is provided with a plurality of patterned arrays. The patterned array is a pixel point.

[0029] In an embodiment, the colloidal quantum dot semiconductor layer 15 comprises a metal oxide film. It should be noted that the material of the metal oxide film is a material with an absorption coefficient less than a threshold value for visible light and near-infrared light. For example, the material of the metal oxide film comprises at least one of zinc oxide, tin dioxide and titanium dioxide.

[0030] In an embodiment, the colloidal quantum dot semiconductor layer 15 comprises a metal oxide film, a colloidal quantum dot film and a transparent conductive film. The metal oxide film is arranged on the side of the colloidal quantum dot film close to the silicon semiconductor layer, or the metal oxide film is arranged on the side of the colloidal quantum dot film away from the silicon semiconductor layer; the transparent conductive film is arranged above the colloidal quantum dot film; the material of the metal oxide film is a material with an absorption coefficient less than a threshold value for visible light and near-infrared light.

[0031] Specifically, in an embodiment, the colloidal quantum dot semiconductor layer 15 comprises, from bottom to top (from the direction of the carrier sheet to the direction of the silicon semiconductor layer 14), a metal oxide film, a colloidal quantum dot film and a transparent conductive film. Alternatively, in another embodiment, the colloidal quantum dot semiconductor layer 15 comprises, from bottom to top (from the direction of the carrier sheet to the direction of the silicon semiconductor layer 14), a colloidal quantum dot film, a metal oxide film and a transparent conductive film.

[0032] The transparent conductive film is at least one of an indium tin oxide film and a fluorine-doped SnO2 film. The colloidal quantum dot film comprises at least one of a lead sulfide quantum dot film, a lead selenide quantum dot film and a mercury telluride quantum dot film.

[0033] In the embodiment, the silicon semiconductor layer 14 comprises an N-type silicon semiconductor layer, a P-type silicon semiconductor layer and a P++ silicon substrate; the N-type silicon semiconductor layer is arranged on one side surface of the insulating layer, the P++ silicon substrate is arranged close to the colloidal quantum dot semiconductor layer, and the P-type silicon semiconductor layer is arranged between the N-type silicon semiconductor layer and the P++ silicon substrate; the N-type silicon semiconductor layer is realized by particle injection. In an embodiment, the doping concentration of the N-type silicon semiconductor at room temperature is between 1e15cm -3 and 5e17cm -3 , the doping concentration of the P-type silicon semiconductor at room temperature is between 1e12cm -3 and 5e15cm -3 , and the doping concentration of the P++ silicon semiconductor at room temperature is between 1e15cm -3 and 5e21cm -3 .

[0034] Specifically, the P-type silicon semiconductor layer is a lightly doped P-type doped layer. The N-type silicon semiconductor layer is an N-type heavily doped layer, which is realized by ion injection, i.e., the N-type silicon semiconductor layer is realized by particle injection. The dielectric constant of the insulating layer 13 is greater than a preset value.

[0035] In the embodiment, the silicon semiconductor layer 14 is a wide bandgap semiconductor.

[0036] The working principle of the colloidal quantum dot semiconductor layer in the present application is that a built-in electric field is formed in the colloidal quantum dot semiconductor layer, and the direction of the electric field is conducive to the movement of electrons to the gate; when the charge-coupled device is irradiated from above by short-wave infrared light, corresponding photons are absorbed by the colloidal quantum dots to be converted into electrons and holes, the electrons move to the gate under the action of the built-in electric field, and are collected in the silicon semiconductor structure through the action of drift and diffusion; the holes are collected by the transparent conductive film under the action of the built-in electric field. In general, a negative bias is applied to the side of the transparent conductive film, and a positive bias is applied to the side of the gate, so that the width of the depletion region in the colloidal quantum dot film increases, and the strength of the built-in electric field increases. The number of collected electrons can reflect the intensity of the light at the same time.

[0037] The charge-coupled device array is usually prepared by standard semiconductor process, the charge-coupled device in the present application is compatible with the current standard semiconductor process, the colloidal quantum dot semiconductor layer of the charge-coupled device can be prepared by a solution method, which greatly reduces the manufacturing cost of the device.

[0038] The charge-coupled device of the present application is based on the existing CCD structure, and the colloidal quantum dot CQD, which is an infrared sensitive material, can be integrated into the CCD through a simple integration method without major structural changes. The colloidal quantum dot semiconductor layer is prepared on the back-illuminated charge-coupled device as a light-absorbing material, so that the device has similar absorption characteristics as quantum dots. Unlike traditional charge-coupled devices that can only detect visible light and near-infrared light below 1100 nm, this device can achieve a spectral detection range of up to 2500 nm, and has part of the spectral response of quantum dots. Since CQD can efficiently absorb light in the wide spectral range of 250-2500 nm, the CCD device integrated with CQD can also detect light in this wide spectral range. The solution method can also be used to prepare the colloidal quantum dot semiconductor layer as the light-absorbing layer of the CCD, which helps to optimize the process steps, and compared with surface treatment techniques such as black silicon, this process has lower cost and fewer process steps.

[0039] Please refer to Figure 2 , which is a flowchart of an embodiment of the preparation method of the charge-coupled device of the present application, specifically comprising:

[0040] Step S21: preparing a silicon semiconductor layer.

[0041] Specifically, the silicon semiconductor layer includes an N-type silicon semiconductor layer, a P-type silicon semiconductor layer, and a P++ silicon substrate.

[0042] In an embodiment, a P++ silicon substrate is first provided, and a P-type silicon semiconductor layer is epitaxially grown on a surface of the P++ silicon substrate, please refer toFigure 3 In step 1, an N-type silicon semiconductor layer is prepared on the P-type silicon semiconductor layer by ion implantation. For details, please refer to step 3 in the method shown in FIG. 2. Figure 3 In step 2, the N-type silicon semiconductor layer is annealed.

[0043] In an embodiment, the doping concentration of the N-type silicon semiconductor at room temperature is between 1e15cm -3 and 5e17cm -3 , the doping concentration of the P-type silicon semiconductor at room temperature is between 1e12cm -3 and 5e15cm -3 , and the doping concentration of the P++-type silicon semiconductor at room temperature is between 1e15cm -3 and 5e21cm -3 .

[0044] Step S22: A functional layer is arranged on the surface of the silicon semiconductor layer.

[0045] Specifically, the functional layer is prepared by:

[0046] An insulating layer is prepared on the N-type silicon semiconductor layer, and a gate layer is prepared on the insulating layer. Then, the carrier sheet is bonded to the gate layer by ACF glue. For details, please refer to step 3 in the method shown in FIG. 2. Figure 3 Finally, the surface of the carrier sheet away from the gate layer is polished. In an embodiment, the carrier sheet can be completely polished away; in another embodiment, the carrier sheet can be polished to a preset thickness. For details, please refer to step 4 in the method shown in FIG. 2. That is, if the carrier sheet is completely polished away, the functional layer only includes the insulating layer and the gate layer; if the carrier sheet is polished to a preset thickness, the functional layer includes the carrier sheet, the insulating layer, and the gate layer. Figure 3

[0047] Step S23: A colloidal quantum dot semiconductor layer is arranged on the side of the silicon semiconductor layer away from the functional layer.

[0048] Specifically, a metal oxide layer, a colloidal quantum dot layer, and a transparent conductive layer are sequentially prepared on the surface of the P++-type silicon substrate away from the functional layer. The positions of the metal oxide layer and the colloidal quantum dot layer can be interchanged, that is, the colloidal quantum dot layer, the metal oxide layer, and the transparent conductive layer can be sequentially prepared on the surface of the P++-type silicon substrate away from the functional layer.

[0049] It should be noted that the carrier sheet of the device is a silicon sheet, and all processes are prepared based on this epitaxial sheet.

[0050] It should be noted that the carrier sheet, the gate layer, the insulating layer, the silicon semiconductor layer, and the colloidal quantum dot semiconductor in the present embodiment are the same as those shown in the method shown in FIG. 2, and will not be described here. Figure 1

[0051] ​​The charge coupled device of the present application is based on the existing CCD structure, and the colloidal quantum dot CQD infrared sensitive material can be integrated into the CCD through a simple integration method without large structural changes. The colloidal quantum dot semiconductor layer is prepared on the back-illuminated charge coupled device as the light absorbing material, so that the device has similar absorption characteristics as the quantum dots. Unlike the conventional charge coupled device which can only detect visible light and near-infrared light below 1100 nm, the device can realize spectral detection up to 2500 nm, and has partial spectral response of the quantum dots. Since the CQD can realize high-efficiency absorption of light in the wide spectral range of 250-2500 nm, the CCD device integrated with the CQD can also realize detection of light in the wide spectral range. The colloidal quantum dot semiconductor layer can also be prepared as the light absorbing layer of the CCD through the solution method, which helps to optimize the process steps, and compared with the surface treatment technology such as black silicon, the process has lower cost and fewer process steps.

[0052] The above is only the implementation method of the present application, and does not limit the patent scope of the present application. Any equivalent structure or equivalent flow transformation using the content of the specification and drawings, or direct or indirect application in other related technical fields, is also included in the patent protection scope of the present application.

Claims

1. A charge-coupled device, characterized by The application relates to a functional layer, a silicon semiconductor layer, a colloidal quantum dot semiconductor layer and a preparation method of the colloidal quantum dot semiconductor layer. The application relates to a functional layer, a silicon semiconductor layer, a colloidal quantum dot semiconductor layer and a preparation method of the colloidal quantum dot semiconductor layer. The colloidal quantum dot semiconductor layer is located on the side of the silicon semiconductor layer away from the functional layer; the colloidal quantum dot semiconductor layer has short-wave infrared absorption characteristics and is used for absorbing photons and converting the photons into electric charges. The colloidal quantum dot semiconductor layer is composed of a metal oxide film, a colloidal quantum dot film and a transparent conductive film. The metal oxide film is arranged on the side of the colloidal quantum dot film close to the silicon semiconductor layer or on the side of the colloidal quantum dot film away from the silicon semiconductor layer; the transparent conductive film is arranged above the colloidal quantum dot film; the colloidal quantum dot film comprises at least one of a lead selenide quantum dot film and a mercury telluride quantum dot film. The material of the metal oxide film is a material with an absorption coefficient less than a threshold value for visible light and near-infrared light. The functional layer comprises a carrier sheet, a gate layer and an insulating layer.

2. The charge-coupled device of claim 1, wherein, The gate layer is located on the surface of the carrier sheet. The insulating layer is located on the side of the gate layer away from the carrier sheet, and the silicon semiconductor layer is located on the side of the insulating layer away from the carrier sheet. The functional layer comprises a gate layer and an insulating layer. The insulating layer is located on the surface of the gate layer, and the silicon semiconductor layer is located on the side of the insulating layer away from the gate layer. The material of the metal oxide film is an N-type semiconductor material.

3. The charge-coupled device of claim 1, wherein, The material of the metal oxide film comprises at least one of zinc oxide, tin dioxide and titanium dioxide. The transparent conductive film is at least one of indium tin oxide and fluorine-doped SnO2 film.

4. The charge-coupled device of claim 1, wherein, The silicon semiconductor layer comprises an N-type silicon semiconductor layer, a P-type silicon semiconductor layer and a P++ type silicon substrate.

5. The charge-coupled device of claim 2, wherein, The N-type silicon semiconductor layer is arranged on the side surface of the insulating layer, the P++ type silicon substrate is arranged close to the colloidal quantum dot semiconductor layer, and the P-type silicon semiconductor layer is arranged between the N-type silicon semiconductor layer and the P++ type silicon substrate. The N-type silicon semiconductor layer is realized by particle injection. The dielectric constant of the insulating layer is greater than a preset value.

6. The charge-coupled device of claim 2, wherein, The gate layer is provided with a plurality of patterned arrays.

7. The charge-coupled device of claim 2, wherein, The application relates to a functional layer, a silicon semiconductor layer, a colloidal quantum dot semiconductor layer and a preparation method of the colloidal quantum dot semiconductor layer.

8. A method of fabricating a charge-coupled device, comprising: The silicon semiconductor layer is prepared. The functional layer is arranged on the surface of the silicon semiconductor layer. The colloidal quantum dot semiconductor layer is arranged on the side of the silicon semiconductor layer away from the functional layer, and the colloidal quantum dot semiconductor layer has short-wave infrared absorption characteristics and is used for absorbing photons and converting the photons into electric charges. The colloidal quantum dot semiconductor layer is composed of a metal oxide film, a colloidal quantum dot film and a transparent conductive film. The metal oxide film is arranged on the side of the colloidal quantum dot film close to the silicon semiconductor layer or on the side of the colloidal quantum dot film away from the silicon semiconductor layer; the transparent conductive film is arranged above the colloidal quantum dot film; the colloidal quantum dot film comprises at least one of a lead selenide quantum dot film and a mercury telluride quantum dot film. ​ The material of the metal oxide thin film is a material having an absorption coefficient less than a threshold value for visible light and near-infrared light. The metal oxide thin film is formed on the surface of the substrate.

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