Thin film phototransistor and preparation method thereof

Abstract

The invention provides a thin film phototransistor and a preparation method thereof, and the preparation method comprises the steps: providing an insulating substrate, forming a gate electrode on the insulating substrate, forming a passivation layer on the insulating substrate, enabling the passivation layer to cover the gate electrode, forming an active layer on the passivation layer, enabling the active layer to comprise an indium tin oxide layer and an indium gallium zinc oxide layer, the indium gallium zinc oxide layer is located on the indium tin oxide layer, the active layer is etched to expose the passivation layer, a source electrode and a drain electrode are formed on the passivation layer, the source electrode and the drain electrode are located at the two ends of the active layer respectively and partially cover the active layer, the passivation layer is etched to expose the gate electrode, and the thin film phototransistor is obtained. According to the thin film photoelectric transistor, the light response wave band range of a metal oxide thin film transistor can be widened, and the light response capability is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of semiconductor integrated circuit manufacturing, and relates to a thin film photoelectric transistor and a preparation method thereof. Background Art

[0002] With the vigorous development of optoelectronic technology, phototransistors, as a core photoelectric conversion device, have shown irreplaceable roles in many fields such as communication, imaging and detection. However, the shortcomings of the light response range and photoelectric film quality of traditional phototransistors have become key factors restricting their application breadth and performance improvement. Therefore, tackling the problems of few oxygen vacancy defects in photoelectric metal oxide films, poor film quality and narrow light response range of phototransistors has far-reaching significance for the overall development of optoelectronic technology.

[0003] At present, the manufacturing process of phototransistors is relatively cumbersome, involving the use of special materials and complex processes, which not only increases manufacturing costs but also reduces production efficiency, making it difficult to adapt to the urgent needs of large-scale production and application. It is worth mentioning that photoelectric oxide thin-film transistors have the potential to be integrated with storage and computing units, and it is expected to build a photosynaptic transistor to apply a sensing, storage and computing integrated system that simulates human vision, thereby greatly enhancing computing power and reducing energy consumption. However, due to the wide band gap of existing oxide channel materials (over 3.0 eV), their response range is mainly limited to the ultraviolet band, while practical applications involve more visible light bands (420-700nm) and longer wavelengths.

[0004] Therefore, how to provide a thin film phototransistor and a preparation method thereof to expand the visible light response band of wide oxide thin film transistors and improve the response capability has become an important problem to be solved urgently by those skilled in the 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 the present 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 of the present application. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a thin film photoelectric transistor and a preparation method thereof, which are used to solve the problem that the wide bandgap oxide thin film transistor in the prior art has a small light response band range to visible light and a weak light response ability.

[0007] To achieve the above object and other related objects, the present invention provides a method for preparing a thin film phototransistor, comprising the following steps:

[0008] Providing an insulating substrate, and forming a gate electrode on the insulating substrate;

[0009] forming a passivation layer on the insulating substrate, wherein the passivation layer covers the gate electrode;

[0010] forming an active layer on the passivation layer, wherein the active layer comprises an indium tin oxide layer and an indium gallium zinc oxide layer, wherein the indium gallium zinc oxide layer is located on the indium tin oxide layer;

[0011] etching the active layer to expose the passivation layer;

[0012] forming a source electrode and a drain electrode on the passivation layer, wherein the source electrode and the drain electrode are respectively located at two ends of the active layer and partially cover the active layer;

[0013] The passivation layer is etched to expose the gate electrode, thereby obtaining a thin film phototransistor.

[0014] Optionally, the thickness of the indium tin oxide layer is smaller than the thickness of the indium gallium zinc oxide layer.

[0015] Optionally, forming the gate electrode comprises the following steps:

[0016] forming a first photoresist layer on the insulating substrate, and patterning the first photoresist layer to obtain a gate trench;

[0017] Metal is filled in the gate trench to form the gate electrode, and the first photoresist layer is removed.

[0018] Optionally, forming the active layer comprises the following steps:

[0019] applying a voltage to the insulating substrate;

[0020] The indium tin oxide layer is deposited on the passivation layer by magnetron sputtering, the working gas includes argon and oxygen, and the content ratio of argon to oxygen is in the range of 8 to 10;

[0021] The indium gallium zinc oxide layer is deposited on the indium tin oxide layer by magnetron sputtering, and the working gas includes argon.

[0022] Optionally, etching the active layer comprises the following steps:

[0023] forming a second photoresist layer on the active layer, and patterning the second photoresist layer to expose an etched region of the active layer;

[0024] Wet etching is used to remove the active layer in the etching area and the second photoresist layer.

[0025] Optionally, forming the source electrode and the drain electrode comprises the following steps:

[0026] Forming a third photoresist layer on the passivation layer, the third photoresist layer covers the active layer, and patterning the third photoresist layer to obtain a source trench and a drain trench, wherein the source trench and the drain trench partially expose two ends of the active layer respectively;

[0027] Metal is filled in the source trench and the drain trench to form the source electrode and the drain electrode, and the third photoresist layer is removed.

[0028] Optionally, etching the passivation layer comprises the following steps:

[0029] forming a fourth photoresist layer on the passivation layer, wherein the fourth photoresist layer covers the active layer, the source electrode and the drain electrode;

[0030] Patterning the fourth photoresist layer to expose an etched region of the passivation layer;

[0031] Etching is performed to remove the passivation layer in the etched area to expose the gate electrode, and the fourth photoresist layer is removed.

[0032] Optionally, the method further includes placing the thin film phototransistor in an inert gas for annealing.

[0033] Optionally, the active layer has defects, the defects include oxygen vacancies, and the percentage of the oxygen vacancies is greater than 40%.

[0034] Optionally, the roughness of the active layer is less than 0.5 nm.

[0035] Optionally, the light response range of the thin film phototransistor is 365nm to 700nm.

[0036] Optionally, the thin film phototransistor has a light response of greater than 2000 A / W to a wavelength of 620 nm.

[0037] The present invention also provides a thin film phototransistor, comprising:

[0038] Insulating substrate;

[0039] A gate electrode, located on the insulating substrate;

[0040] a passivation layer, located on the insulating substrate and partially covering the gate electrode;

[0041] An active layer, located on the passivation layer, the active layer comprising an indium tin oxide layer and an indium gallium zinc oxide layer, the indium gallium zinc oxide layer being located on the indium tin oxide layer;

[0042] A source electrode and a drain electrode, wherein the source electrode is located at one end of the active layer and partially covers the active layer, and the drain electrode is located at the other end of the active layer and partially covers the active layer.

[0043] Optionally, the thickness of the indium tin oxide layer is smaller than the thickness of the indium gallium zinc oxide layer.

[0044] Optionally, the active layer has defects, the defects include oxygen vacancies, and the percentage of the oxygen vacancies is greater than 40%.

[0045] Optionally, the roughness of the active layer is less than 0.5 nm.

[0046] Optionally, the light response range of the thin film phototransistor is 365nm to 700nm.

[0047] Optionally, the thin film phototransistor has a light response of greater than 2000 A / W to a wavelength of 620 nm.

[0048] As described above, the preparation method of the thin film phototransistor of the present invention includes: providing an insulating substrate, forming a gate electrode on the insulating substrate, forming a passivation layer on the insulating substrate, the passivation layer covers the gate electrode, forming an active layer on the passivation layer, the active layer includes an indium tin oxide layer and an indium gallium zinc oxide layer, the indium gallium zinc oxide layer is located on the indium tin oxide layer, etching the active layer to expose the passivation layer, forming a source electrode and a drain electrode on the passivation layer, the source electrode and the drain electrode are respectively located at both ends of the active layer and partially cover the active layer, etching the passivation layer to expose the gate electrode, and obtaining a thin film phototransistor. The thin film phototransistor of the present invention can broaden the light response band range of the metal oxide thin film transistor and improve the light response capability. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 Shown is a process flow chart of a method for preparing a thin film phototransistor of the present invention.

[0050] Figure 2 It is a schematic diagram showing the structure obtained after providing an insulating substrate and forming a gate electrode in the method for preparing a thin film phototransistor of the present invention.

[0051] Figure 3 It is a schematic diagram showing the structure obtained after forming a patterned first photoresist layer in the method for preparing a thin film phototransistor of the present invention.

[0052] Figure 4 It is a schematic diagram showing the structure obtained after forming a passivation layer in the method for preparing a thin film phototransistor of the present invention.

[0053] Figure 5 It is a schematic diagram showing the structure obtained after forming an active layer in the method for preparing a thin film phototransistor of the present invention.

[0054] Figure 6 It is a schematic diagram showing the structure obtained after etching the active layer in the method for preparing the thin film phototransistor of the present invention.

[0055] Figure 7 It is a schematic diagram showing the structure obtained after forming a patterned second photoresist layer in the method for preparing a thin film phototransistor of the present invention.

[0056] Figure 8 It is a schematic diagram showing the structure obtained after forming the source electrode and the drain electrode in the method for preparing the thin film phototransistor of the present invention.

[0057] Fig. 9 It is a schematic diagram showing the structure obtained after forming a patterned third photoresist layer in the method for preparing a thin film phototransistor of the present invention.

[0058] Fig.10 Display as Figure 8 Top view of the structure shown.

[0059] Fig.11 It shows a top view of the structure obtained after etching the passivation layer in the method for preparing the thin film phototransistor of the present invention.

[0060] Fig.12 It is a schematic diagram showing the structure obtained after forming the fourth photoresist layer in the method for preparing the thin film phototransistor of the present invention.

[0061] Fig.13 It is a top view of the structure obtained after forming a patterned fourth photoresist layer in the method for preparing a thin film phototransistor of the present invention.

[0062] Fig.14 A schematic diagram showing a structure of a thin film phototransistor of the present invention is shown.

[0063] Fig.15 (αhv) showing a single InGaZnO layer 2 -hv relationship diagram.

[0064] Fig.16 (αhv) showing a single ITO layer 2 -hv relationship diagram.

[0065] Fig.17 The (αhv) of the active layer of the present invention is shown 2 -hv relationship diagram.

[0066] Fig.18 FIG. 1 is a schematic diagram showing another structure of a thin film phototransistor of the present invention.

[0067] Fig.19Shown is a diagram of the oxygen vacancy content of a single-InGaZnO thin-film phototransistor.

[0068] Fig. 20 Shown is a graph of oxygen vacancy content of the thin film phototransistor of the present invention.

[0069] Fig.21 Shown is a graph of the photoresponse of a single-InGaZnO thin-film phototransistor.

[0070] Fig. 22 Shown is a photoresponse diagram of the thin film phototransistor of the present invention.

[0071] Fig.23 Shown is a graph of the photoresponsivity of a single-layer InGaZnO thin-film phototransistor.

[0072] Fig.24 Shown is a diagram of the photoresponsivity of the thin film phototransistor of the present invention.

[0073] Fig.25 Shown is a light pulse test diagram of the thin film phototransistor of the present invention.

[0074] Description of Reference Numerals

[0075] 1 Insulating substrate

[0076] 11 Silicon substrate

[0077] 12 Silicon dioxide layer

[0078] 2 First photoresist layer

[0079] 21 Gate trench

[0080] 3. Gate electrode

[0081] 4 Passivation layer

[0082] 5 Active layer

[0083] 51 Indium Tin Oxide Layer

[0084] 52 InGaZnO layer

[0085] 6 Second photoresist layer

[0086] 7 Source electrode

[0087] 8 Drain electrode

[0088] 9 Third photoresist layer

[0089] 91 Source Trench

[0090] 92 Leakage groove

[0091] 10 Fourth photoresist layer

[0092] Steps S1 to S6 DETAILED DESCRIPTION

[0093] The following describes the embodiments 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 embodiments, 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.

[0094] 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.

[0095] 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.

[0096] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the schematic 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.

[0097] 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.

[0098] 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 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.

[0099] 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 arbitrarily, and the component layout may also be more complicated.

[0100] See also Figure 1 , which is a process flow chart of a method for preparing a thin film phototransistor of the present invention, comprising the following steps:

[0101] S1: providing an insulating substrate, and forming a gate electrode on the insulating substrate;

[0102] S2: forming a passivation layer on the insulating substrate, wherein the passivation layer covers the gate electrode;

[0103] S3: forming an active layer on the passivation layer, wherein the active layer comprises an indium tin oxide layer and an indium gallium zinc oxide layer, and the indium gallium zinc oxide layer is located on the indium tin oxide layer;

[0104] S4: etching the active layer to expose the passivation layer;

[0105] S5: forming a source electrode and a drain electrode on the passivation layer, wherein the source electrode and the drain electrode are respectively located at two ends of the active layer and partially cover the active layer;

[0106] S6: etching the passivation layer to expose the gate electrode to obtain a thin film phototransistor.

[0107] The following will be combined Figures 2 to 14 , detailing each step of the method for preparing the thin film phototransistor of the present invention.

[0108] First see Figure 2 , perform the step S1: provide an insulating substrate 1, and form a gate electrode 3 on the insulating substrate 1.

[0109] As an example, before forming the gate electrode 3 on the insulating substrate 1, a step of cleaning the insulating substrate 1 is also included. In this embodiment, the insulating substrate 1 is placed in acetone and isopropanol solutions for ultrasonic cleaning, so that the surface of the insulating substrate 1 is clean.

[0110] As an example, forming the gate electrode 3 includes the following steps:

[0111] (1) Please refer to Figure 3 , forming a first photoresist layer 2 on the insulating substrate 1, and patterning the first photoresist layer 2 to obtain a gate trench 21;

[0112] (2) Filling metal in the gate trench 21 to form the gate electrode 3, removing the first photoresist layer 2, and obtaining Figure 2 The structure shown.

[0113] As an example, the method of filling the source electrode 7 and the drain electrode 8 includes any one of chemical vapor deposition, atomic layer deposition, electroplating and evaporation. In this embodiment, sputtering in chemical vapor deposition is preferably used to deposit the gate electrode 3.

[0114] As an example, the gate electrode 3 may be made of any one of gold, molybdenum and tungsten.

[0115] Please see again Figure 4 , performing the step S2: forming a passivation layer 4 on the insulating substrate 1 , wherein the passivation layer 4 covers the gate electrode 3 .

[0116] As an example, the method for forming the passivation layer 4 includes any one of chemical vapor deposition, atomic layer deposition, electroplating and evaporation. In the present embodiment, the chemical vapor deposition method is preferably used to deposit the passivation layer 4.

[0117] As an example, the material of the passivation layer may be any one of HfO2, Al2O3, SiO2 or TiO2.

[0118] Please see again Figure 5 , perform the step S3: forming an active layer 5 on the passivation layer 4, the active layer 5 comprising an indium tin oxide layer 51 (ITO) and an indium gallium zinc oxide layer 52 (IGZO), the indium gallium zinc oxide layer 52 being located on the indium tin oxide layer 51, so that the number of defects in the active layer 5 increases, the band gap becomes smaller, and the light response band range of the thin film phototransistor is increased.

[0119] As an example, forming the active layer 5 includes the following steps:

[0120] (1) applying a voltage to the insulating substrate 1;

[0121] (2) depositing the indium tin oxide layer 51 on the passivation layer 4 by magnetron sputtering, wherein the working gas includes argon and oxygen, and the content ratio of argon to oxygen is in the range of 8 to 10;

[0122] (3) The indium gallium zinc oxide layer 52 is deposited on the indium tin oxide layer 51 by magnetron sputtering, and the working gas includes argon.

[0123] Specifically, adding a bias power supply to the sample stage of the magnetron sputtering equipment can enhance the quality of the film during the sputtering process and solve the problem of poor quality reliability of the optoelectronic film. In this embodiment, the roughness of the active layer 5 is less than 0.5 nm.

[0124] As an example, the thickness of the indium tin oxide layer 51 is smaller than the thickness of the indium gallium zinc oxide layer 52. In this embodiment, the thickness of the indium tin oxide layer 51 is in the range of 3 nm to 5 nm, and the thickness of the indium gallium zinc oxide layer 52 is 35 nm.

[0125] As an example, the active layer 5 has defects, and the defects include oxygen vacancies, and the percentage of the oxygen vacancies is greater than 40%, thereby reducing the band gap of the active layer 5.

[0126] Please see again Figure 6 , performing the step S4: etching the active layer 5 to expose the passivation layer 4.

[0127] As an example, etching the active layer 5 comprises the following steps:

[0128] (1) Please refer to Figure 7 , forming a second photoresist layer 6 on the active layer 5, and patterning the second photoresist layer 6 to expose the etched area of ​​the active layer 5;

[0129] (2) using a wet etching process to etch the film layer in the etching area, and removing the second photoresist layer 6 after the etching is completed, to obtain Figure 6 The structure shown.

[0130] Specifically, in the present embodiment, in order to accurately etch the active layer 5 without damaging other layers, after adopting the photolithography patterning process, wet etching is selected to selectively etch the surface of the active layer 5 film, and a 10% dilute hydrochloric acid solution is used as the wet etchant. After the etching is completed, the device is immersed in a debonding agent such as an N-methylpyrrolidone solution for 20 minutes to remove the photoresist layer, and then washed with pure water and dried with a nitrogen air gun to ensure that the surface of the passivation layer 4 and the active layer 5 are clean.

[0131] Please see again Figure 8 , performing the step S5: forming a source electrode 7 and a drain electrode 8 on the passivation layer 4 , wherein the source electrode 7 and the drain electrode 8 are respectively located at two ends of the active layer 5 and partially cover the active layer 5 .

[0132] As an example, forming the source electrode 7 and the drain electrode 8 includes the following steps:

[0133] (1) Please refer to Fig. 9 , forming a third photoresist layer 9 on the passivation layer 4, the third photoresist layer 9 covers the active layer 5, and patterning the third photoresist layer 9 to obtain a source trench 91 and a drain trench 92, the source trench 91 and the drain trench 92 partially expose two ends of the active layer 5 respectively;

[0134] (2) Filling metal in the source trench 91 and the drain trench 92 to form the source electrode 7 and the drain electrode 8, and then removing the third photoresist layer 9 to obtain Figure 8 The structure shown.

[0135] As an example, see Fig.10 , displayed as Figure 8 In the top view of the structure shown, since the gate electrode 3 is covered by the passivation layer 4, the passivation layer 4 needs to be further etched later.

[0136] As an example, the method of filling the source electrode 7 and the drain electrode 8 includes any one of chemical vapor deposition, atomic layer deposition, electroplating and evaporation. In this embodiment, sputtering in chemical vapor deposition is preferably used to deposit the source electrode 7 and the drain electrode 8.

[0137] As an example, the material of the source electrode 7 and the drain electrode 8 can be any one of gold, molybdenum, tungsten and high-conductivity silicon. Among them, high-conductivity silicon has the advantages of high conductivity, structural stability and chemical stability, and is suitable for use as an electrode material like metal materials.

[0138] Please see again Fig.11 , performing the step S6: etching the passivation layer 4 to expose the gate electrode 3 to obtain a thin film phototransistor.

[0139] As an example, etching the passivation layer 4 comprises the following steps:

[0140] (1) Please refer to Fig.12 , forming a fourth photoresist layer 10 on the passivation layer 4, wherein the fourth photoresist layer 10 covers the active layer 5, the source electrode 7 and the drain electrode 8;

[0141] (2) Please refer to Fig.13 , patterning the fourth photoresist layer 10 to expose the etched area of ​​the passivation layer 4;

[0142] (3) Please refer to Fig.14 , etching the film layer in the etching area to expose the gate electrode 3, and then removing the fourth photoresist layer 10.

[0143] As an example, the method further includes placing the thin film phototransistor in an inert gas for annealing. The annealing time can be adjusted as needed. In the present embodiment, the annealing time can be, for example, 30 minutes.

[0144] Specifically, the annealing step (i.e., atmosphere deoxidation method) can further increase the oxygen vacancy defect content in the active layer 5 and reduce the band gap of the active layer 5. That is to say, after the thin film phototransistor is annealed, the performance of the device will be further optimized, its light response band range will be wider, and its light response ability will be stronger.

[0145] Specifically, for semiconductor materials, the relationship between the optical band gap and the absorption coefficient is:

[0146]

[0147] Where α is the molar absorption coefficient, h is Planck's constant, ν is the incident photon frequency, B is the proportional constant, Eg is the optical band gap of the semiconductor material, and the value of n is related to the semiconductor material and the transition type. When the semiconductor material is a direct band gap, When the semiconductor material has an indirect band gap, n=2.

[0148] According to the Lambert-Beer law, absorbance is proportional to the absorption coefficient, that is,

[0149] A=Kα (2)

[0150] Where A is the sample absorbance, and K can be regarded as a constant that is independent of the absorption coefficient. From equations (1) and (2), we can deduce:

[0151]

[0152] In In the plot with the value of as the ordinate and the value of hν as the abscissa, equation (3) can be regarded as a linear equation, and the intercept of the straight line on the X-axis represents the band gap of the semiconductor material.

[0153] In order to more clearly show the band gap of the single indium gallium zinc oxide layer, the single indium tin oxide layer and the active layer 5, please refer to Figures 15 to 17 The absorption spectra of the single indium gallium zinc oxide layer, the single indium tin oxide layer and the active layer 5 were tested respectively, and the (αhv) of the single indium gallium zinc oxide layer, the single indium tin oxide layer and the active layer 5 were plotted. 2 -hv relationship diagram (here ), it can be seen from the figure that the band gaps of the single indium gallium zinc oxide layer, the single indium tin oxide layer and the active layer 5 are 3.51ev, 3.61ev and 3.45ev respectively, and the band gap of the active layer 5 is the smallest.

[0154] As an example, the light response range of the thin film phototransistor is 365nm to 700nm.

[0155] As an example, see Fig.18, which is a schematic diagram showing another structure of a thin film phototransistor of the present invention, wherein the insulating substrate 1 adopts a silicon substrate 11 partially covered with an oxide layer, for example, a silicon substrate 11 covered with a 100 nm thick silicon dioxide layer 12, and there is no need to form the gate electrode 3 and the passivation layer 4, wherein the oxide layer (i.e., the silicon dioxide layer 12) can be used as the passivation layer 4, and the silicon substrate 11 can be used as the gate electrode 3, thereby omitting the deposition step of the passivation layer 4 and simplifying the preparation.

[0156] See also Figures 19 to 20 ,in, Fig.19 Shown is a diagram of the oxygen vacancy content of a single InGaZnO thin film phototransistor. Fig. 20 The graph shows the oxygen vacancy content of the thin film phototransistor of the present invention. It can be seen from the graph that the oxygen vacancy content of the thin film phototransistor of the present invention is higher. The specific reason is that in the present invention, after depositing the indium tin oxide layer 51, the working gas is switched to pure argon gas, and the indium gallium zinc oxide layer 52 is continuously deposited on the indium tin oxide layer 51, thereby increasing the oxygen vacancy content (i.e., defect content) in the active layer 5.

[0157] It should be noted that the InGaZnO layer 52 should be located on the InGaZnO layer 51 (ie, the InGaZnO layer 52 is deposited after the InGaO 51 is deposited). If the order of the two is reversed, the oxygen vacancy content in the active layer 5 cannot be increased.

[0158] See also Figure 21 to Figure 22 ,in, Fig.21 Shown is a photoresponse diagram of a single-layer InGaZnO thin-film phototransistor. Fig. 22 It shows the light response diagram of the thin film phototransistor of the present invention. Since the single indium gallium zinc oxide layer in the control example has a small content of oxygen vacancies, the single indium gallium zinc oxide layer thin film phototransistor only responds to light of 420nm and 520nm wavelengths, and has no light response to light of 620nm wavelength. However, the active layer 5 of the present invention has a large content of oxygen vacancies, and the thin film phototransistor responds to light of 420nm, 520nm and 620nm wavelengths. It can be seen that the thin film phototransistor of the present invention broadens the corresponding visible light band.

[0159] See also Figure 23 to Figure 24 ,in, Fig.23 Shown is a photoresponsivity diagram of a single-layer InGaZnO thin-film phototransistor. Fig.24Shown is a diagram of the light response of the thin-film phototransistor of the present invention. By comparing the two diagrams, it can be seen that the light response band range of the thin-film phototransistor of the present invention is wider and the light response is higher, indicating that the thin-film phototransistor of the present invention improves the light response band range and response capability of the thin-film transistor, wherein the light response of the thin-film phototransistor to a wavelength of 620nm is greater than 2000A / W.

[0160] In order to better demonstrate the light response band of the thin film phototransistor of the present invention, a light pulse test diagram is also performed on the thin film phototransistor of the present invention. Fig.25 , which is a light pulse test diagram of the thin-film phototransistor of the present invention. It can be seen from the figure that the visible light response band of the thin-film phototransistor of the present invention is widened to 700nm.

[0161] The present invention also provides a thin film phototransistor. Fig.14 The thin film phototransistor comprises an insulating substrate 1, a gate electrode 3, a passivation layer 4, an active layer 5, a source electrode 7 and a drain electrode 8, wherein the gate electrode 3 is located on the insulating substrate 1, the passivation layer 4 is located on the insulating substrate 1 and partially covers the gate electrode 3, the active layer 5 is located on the passivation layer 4, the active layer 5 comprises an indium tin oxide layer 51 and an indium gallium zinc oxide layer 52, the indium gallium zinc oxide layer 52 is located on the indium tin oxide layer 51, the source electrode 7 is located at one end of the active layer 5 and partially covers the active layer 5, and the drain electrode 8 is located at the other end of the active layer 5 and partially covers the active layer 5.

[0162] As an example, the thickness of the indium tin oxide layer 51 is smaller than the thickness of the indium gallium zinc oxide layer 52. In this embodiment, the thickness of the indium tin oxide layer 51 is in the range of 3 nm to 5 nm, and the thickness of the indium gallium zinc oxide layer 52 is 35 nm.

[0163] As an example, the roughness of the active layer 5 is less than 0.5 nm.

[0164] As an example, the active layer 5 has defects, and the defects include oxygen vacancies, and the percentage content of the oxygen vacancies is greater than 40%.

[0165] As an example, the light response range of the thin film phototransistor is 365nm to 700nm.

[0166] As an example, the thin film phototransistor has a light responsivity of greater than 2000 A / W to a wavelength of 620 nm.

[0167] In summary, the preparation method of the thin film phototransistor of the present invention includes: providing an insulating substrate, forming a gate electrode on the insulating substrate, forming a passivation layer on the insulating substrate, the passivation layer covers the gate electrode, forming an active layer on the passivation layer, the active layer includes an indium tin oxide layer and an indium gallium zinc oxide layer, the indium gallium zinc oxide layer is located on the indium tin oxide layer, etching the active layer to expose the passivation layer, forming a source electrode and a drain electrode on the passivation layer, the source electrode and the drain electrode are respectively located at both ends of the active layer and partially cover the active layer, etching the passivation layer to expose the gate electrode, and obtaining a thin film phototransistor. The thin film phototransistor of the present invention can broaden the light response band range of the metal oxide thin film transistor and improve the light response capability. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has a high industrial utilization value.

[0168] 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 art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A method for preparing a thin film phototransistor, characterized in that: The following steps are involved: Providing an insulating substrate, and forming a gate electrode on the insulating substrate; forming a passivation layer on the insulating substrate, wherein the passivation layer covers the gate electrode; forming an active layer on the passivation layer, wherein the active layer comprises an indium tin oxide layer and an indium gallium zinc oxide layer, wherein the indium gallium zinc oxide layer is located on the indium tin oxide layer; etching the active layer to expose the passivation layer; forming a source electrode and a drain electrode on the passivation layer, wherein the source electrode and the drain electrode are respectively located at two ends of the active layer and partially cover the active layer; The passivation layer is etched to expose the gate electrode, thereby obtaining a thin film phototransistor.

2. The method for preparing a thin film phototransistor according to claim 1, characterized in that: The thickness of the indium tin oxide layer is smaller than the thickness of the indium gallium zinc oxide layer.

3. The method for preparing a thin film phototransistor according to claim 1, characterized in that: Forming the gate electrode comprises the following steps: forming a first photoresist layer on the insulating substrate, and patterning the first photoresist layer to obtain a gate trench; Metal is filled in the gate trench to form the gate electrode, and the first photoresist layer is removed.

4. The method for preparing a thin film phototransistor according to claim 1, characterized in that: Forming the active layer comprises the following steps: applying a voltage to the insulating substrate; The indium tin oxide layer is deposited on the passivation layer by magnetron sputtering, the working gas includes argon and oxygen, and the content ratio of argon to oxygen is in the range of 8 to 10; The indium gallium zinc oxide layer is deposited on the indium tin oxide layer by magnetron sputtering, and the working gas includes argon.

5. The method for preparing a thin film phototransistor according to claim 1, characterized in that: Etching the active layer comprises the following steps: forming a second photoresist layer on the active layer, and patterning the second photoresist layer to expose an etched region of the active layer; Wet etching is used to remove the active layer in the etching area and the second photoresist layer.

6. The method for preparing a thin film phototransistor according to claim 1, characterized in that: Forming the source electrode and the drain electrode comprises the following steps: Forming a third photoresist layer on the passivation layer, the third photoresist layer covers the active layer, and patterning the third photoresist layer to obtain a source trench and a drain trench, wherein the source trench and the drain trench partially expose two ends of the active layer respectively; Metal is filled in the source trench and the drain trench to form the source electrode and the drain electrode, and the third photoresist layer is removed.

7. The method for preparing a thin film phototransistor according to claim 1, characterized in that: Etching the passivation layer comprises the following steps: forming a fourth photoresist layer on the passivation layer, wherein the fourth photoresist layer covers the active layer, the source electrode and the drain electrode; Patterning the fourth photoresist layer to expose an etched region of the passivation layer; Etching is performed to remove the passivation layer in the etched area to expose the gate electrode, and the fourth photoresist layer is removed.

8. The method for preparing a thin film phototransistor according to claim 1, characterized in that: The method also includes placing the thin film phototransistor in an inert gas for annealing.

9. The method for preparing a thin film phototransistor according to claim 1, characterized in that: The active layer has defects, the defects include oxygen vacancies, and the percentage of the oxygen vacancies is greater than 40%.

10. The method for preparing a thin film phototransistor according to claim 1, characterized in that: The roughness of the active layer is less than 0.5 nm.

11. The method for preparing a thin film phototransistor according to claim 1, characterized in that: The light response range of the thin film phototransistor is 365nm-700nm.

12. The method for preparing a thin film phototransistor according to claim 11, characterized in that: The thin film photoelectric transistor has a light response of greater than 2000 A / W to a wavelength of 620 nm.

13. A thin film phototransistor, characterized in that: include: Insulating substrate; A gate electrode, located on the insulating substrate; a passivation layer, located on the insulating substrate and partially covering the gate electrode; An active layer, located on the passivation layer, the active layer comprising an indium tin oxide layer and an indium gallium zinc oxide layer, the indium gallium zinc oxide layer being located on the indium tin oxide layer; A source electrode and a drain electrode, wherein the source electrode is located at one end of the active layer and partially covers the active layer, and the drain electrode is located at the other end of the active layer and partially covers the active layer.

14. The thin film phototransistor according to claim 13, characterized in that: The thickness of the indium tin oxide layer is smaller than the thickness of the indium gallium zinc oxide layer.

15. The thin film phototransistor according to claim 13, characterized in that: The active layer has defects, the defects include oxygen vacancies, and the percentage of the oxygen vacancies is greater than 40%.

16. The thin film phototransistor according to claim 13, characterized in that: The roughness of the active layer is less than 0.5 nm.

17. The thin film phototransistor according to claim 13, characterized in that: The light response range of the thin film phototransistor is 365nm-700nm.

18. The thin film phototransistor according to claim 17, characterized in that: The thin film photoelectric transistor has a light response of greater than 2000 A / W to a wavelength of 620 nm.

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