CN112259611A - Oxide semiconductor thin film transistor and manufacturing method thereof - Google Patents
Oxide semiconductor thin film transistor and manufacturing method thereof Download PDFInfo
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- 239000004065 semiconductor Substances 0.000 title claims abstract description 73
- 239000010409 thin film Substances 0.000 title claims abstract description 70
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 12
- 239000000758 substrate Substances 0.000 claims abstract description 22
- 229910052751 metal Inorganic materials 0.000 claims abstract description 10
- 239000002184 metal Substances 0.000 claims abstract description 10
- 229920002120 photoresistant polymer Polymers 0.000 claims description 80
- 229910044991 metal oxide Inorganic materials 0.000 claims description 66
- 150000004706 metal oxides Chemical class 0.000 claims description 65
- 239000001301 oxygen Substances 0.000 claims description 43
- 229910052760 oxygen Inorganic materials 0.000 claims description 43
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 42
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 18
- 239000000463 material Substances 0.000 claims description 16
- 229910052786 argon Inorganic materials 0.000 claims description 9
- 239000007888 film coating Substances 0.000 claims description 7
- 238000009501 film coating Methods 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 7
- 238000005530 etching Methods 0.000 claims description 5
- 238000004544 sputter deposition Methods 0.000 claims description 5
- 239000011248 coating agent Substances 0.000 claims description 4
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- 238000000059 patterning Methods 0.000 claims description 4
- 230000000903 blocking effect Effects 0.000 claims 2
- 239000010410 layer Substances 0.000 description 233
- XLOMVQKBTHCTTD-UHFFFAOYSA-N Zinc monoxide Chemical compound [Zn]=O XLOMVQKBTHCTTD-UHFFFAOYSA-N 0.000 description 17
- 230000037230 mobility Effects 0.000 description 10
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 9
- 229910052733 gallium Inorganic materials 0.000 description 9
- 229910052738 indium Inorganic materials 0.000 description 9
- APFVFJFRJDLVQX-UHFFFAOYSA-N indium atom Chemical compound [In] APFVFJFRJDLVQX-UHFFFAOYSA-N 0.000 description 9
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- 229910021417 amorphous silicon Inorganic materials 0.000 description 6
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- AJNVQOSZGJRYEI-UHFFFAOYSA-N digallium;oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[Ga+3].[Ga+3] AJNVQOSZGJRYEI-UHFFFAOYSA-N 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
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- 229910003437 indium oxide Inorganic materials 0.000 description 1
- PJXISJQVUVHSOJ-UHFFFAOYSA-N indium(iii) oxide Chemical compound [O-2].[O-2].[O-2].[In+3].[In+3] PJXISJQVUVHSOJ-UHFFFAOYSA-N 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/786—Thin film transistors, i.e. transistors with a channel being at least partly a thin film
- H01L29/78606—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device
- H01L29/78639—Thin film transistors, i.e. transistors with a channel being at least partly a thin film with supplementary region or layer in the thin film or in the insulated bulk substrate supporting it for controlling or increasing the safety of the device with a drain or source connected to a bulk conducting substrate
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/66007—Multistep manufacturing processes
- H01L29/66075—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials
- H01L29/66227—Multistep manufacturing processes of devices having semiconductor bodies comprising group 14 or group 13/15 materials the devices being controllable only by the electric current supplied or the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched, e.g. three-terminal devices
- H01L29/66409—Unipolar field-effect transistors
- H01L29/66477—Unipolar field-effect transistors with an insulated gate, i.e. MISFET
- H01L29/66742—Thin film unipolar transistors
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/66—Types of semiconductor device ; Multistep manufacturing processes therefor
- H01L29/68—Types of semiconductor device ; Multistep manufacturing processes therefor controllable by only the electric current supplied, or only the electric potential applied, to an electrode which does not carry the current to be rectified, amplified or switched
- H01L29/76—Unipolar devices, e.g. field effect transistors
- H01L29/772—Field effect transistors
- H01L29/78—Field effect transistors with field effect produced by an insulated gate
- H01L29/786—Thin film transistors, i.e. transistors with a channel being at least partly a thin film
- H01L29/7869—Thin film transistors, i.e. transistors with a channel being at least partly a thin film having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate
Abstract
An oxide semiconductor thin film transistor comprises a substrate, a grid electrode insulating layer, an oxide semiconductor layer and a source drain electrode metal layer, wherein the grid electrode, the grid electrode insulating layer, the oxide semiconductor layer and the source drain electrode metal layer are sequentially arranged on the substrate; and part of the first oxide layer is exposed from two sides of the second oxide layer, and the source electrode and the drain electrode are mutually spaced and are respectively in direct contact connection with the first oxide layer exposed from two sides of the second oxide layer, so that the source electrode, the drain electrode and the oxide semiconductor layer form better ohmic contact, the on-state current of the thin film transistor is effectively improved, and the comprehensive performance of the thin film transistor is optimized. The invention also relates to a manufacturing method of the oxide semiconductor thin film transistor.
Description
Technical Field
The present invention relates to the field of thin film transistors, and more particularly, to an oxide semiconductor thin film transistor and a method for fabricating the same.
Background
The switching elements currently used in displays are still amorphous silicon (a-Si) thin film transistors and polycrystalline silicon (p-Si) thin film transistorsThe amorphous silicon thin film transistor is most widely applied, but the amorphous silicon thin film transistor has low electron mobility (only 0.3-1 cm)2V · s), poor light stability, and the like. Although the polysilicon thin film transistor is much higher than the amorphous silicon thin film transistor in the aspect of electron mobility, the polysilicon thin film transistor has the problems of complex structure, large leakage current, poor film quality uniformity and the like. With the rapid development of display technologies, the video formats are gradually increased from standard definition to high definition to ultra-definition, and the requirements for resolution and shielding of displays are gradually increased, so that higher and higher requirements are put forward on the performance and size of thin film transistors, amorphous silicon thin film transistors and polycrystalline silicon thin film transistors cannot completely meet the requirements, and a high-temperature manufacturing process cannot be used for manufacturing a display panel with a larger size.
In recent years, an Amorphous Oxide Semiconductor Thin Film Transistor (AOS TFT) has attracted much attention in academic and industrial fields because of its excellent electrical and optical characteristics. In particular Amorphous indium gallium zinc oxide Thin Film transistors (a-IGZO TFTs) with high electron mobility (>10cm2V · s), low power consumption, simple process (no need for high temperature fabrication), fast response speed, good large area uniformity, high transmittance in the visible Light range, etc., are considered as core components of Active Matrix Organic Light Emitting Diode (AMOLED) and Active Matrix Liquid Crystal Display (AMLCD) driving circuits, and are also considered as the most competitive backplane driving technologies that are developed along with displays toward large size, flexibility, and portability.
For a thin film transistor with excellent performance, a large threshold voltage, a high on-off current ratio, a small subthreshold swing, and high stability are required. Generally, the larger the field effect mobility of the thin film transistor, the faster the pixel storage capacitor is charged, the smaller the leakage current of the thin film transistor, the faster the pixel storage capacitor is discharged, the smaller the subthreshold swing of the thin film transistor, and the faster the switching state transition of the thin film transistor, the more power saving. However, these have made high demands on the characteristics of the oxide semiconductor layer, such as the structure, surface defect state, carrier concentration, and carrier mobility.
As shown in fig. 1, a conventional oxide semiconductor thin film transistor includes a substrate 1, and a gate electrode 2, a gate insulating layer 3, an oxide semiconductor layer 4, and a source/drain electrode layer 5 sequentially provided on the substrate 1. The oxide semiconductor layer 4 generally has a single-layer structure, and the oxygen content of the oxide semiconductor layer 4 is controlled to adjust the carrier concentration during the process of manufacturing the oxide semiconductor layer 4, so that the oxide semiconductor layer 4 has different electron mobilities. However, the oxide semiconductor layers 4 with different oxygen contents have advantages and disadvantages, for example, although the oxide semiconductor layer 4 with lower oxygen content has high electron mobility and large threshold voltage, the off-state current is also large; the oxide semiconductor layer 4 containing higher oxygen content has lower electron mobility and smaller off-state current, but the threshold voltage is also correspondingly reduced, and the improvement of the comprehensive performance of the thin film transistor is limited by the non-unity characteristic of the oxide semiconductor layer 4 with a single-layer structure.
In order to improve the overall performance of the thin film transistor, another oxide semiconductor thin film transistor using a Double Stacked Channel (DSCL) has been proposed in the prior art, as shown in fig. 2, that is, an oxide semiconductor layer 4 of the oxide semiconductor thin film transistor includes an upper layer and a lower layer, wherein a first oxide layer 41 located in a front Channel of the lower layer is a metal oxide with a lower oxygen content, and a second oxide layer 42 located in a back Channel of the upper layer is a metal oxide with a higher oxygen content. However, in this structure, the back channel in direct contact with the source and drain electrodes in the source-drain electrode layer 5 is made of high-oxygen metal oxide, and because of its high resistivity, it is difficult to form an ideal ohmic contact, and the on-state current of the DSCL oxide semiconductor thin film transistor is still not ideal, which affects the overall performance of the DSCL oxide semiconductor thin film transistor.
Disclosure of Invention
The invention aims to provide an oxide semiconductor thin film transistor, which effectively improves the on-state current of the thin film transistor and optimizes the comprehensive performance of the thin film transistor.
The embodiment of the invention provides an oxide semiconductor thin film transistor, which comprises a substrate, and a grid, a grid insulating layer, an oxide semiconductor layer and a source drain metal layer which are sequentially arranged on the substrate, wherein the source drain metal layer comprises a source electrode and a drain electrode which are arranged at intervals; part of the first oxide layer is exposed from both sides of the second oxide layer, and the source and the drain are spaced apart from each other and are in direct contact with and connected to the first oxide layer exposed from both sides of the second oxide layer, respectively.
Furthermore, the oxygen content of the first oxide layer is 0% -50%, and the oxygen content of the second oxide layer is 4% -60%.
Further, the width M of the first oxide layer exposed from each side of the second oxide layer is 1-8 micrometers.
Further, the source electrode covers the first oxide layer exposed from one side of the second oxide layer and extends towards the second oxide layer to cover a part of the second oxide layer, and the drain electrode covers the first oxide layer exposed from the other side of the second oxide layer and extends towards the second oxide layer to cover a part of the second oxide layer.
Further, the width N of the lamination position of the source electrode and the second oxide layer and the lamination position of the drain electrode and the second oxide layer is greater than or equal to 1 μm.
Furthermore, the thickness D1 of the first oxide layer is 10-90 nm, and the thickness D2 of the second oxide layer is 10-90 nm.
Furthermore, the width X1 of the first oxide layer is 10-20 microns, the width X2 of the second oxide layer is 4-18 microns, the distance between the source electrode and the drain electrode is 2-8 microns, and the width M of the exposed part of the first oxide layer from the two sides of the second oxide layer is 1-8 microns.
Further, the materials of the first oxide layer and the second oxide layer are both metal oxides.
The invention also provides a manufacturing method of the oxide semiconductor thin film transistor, which comprises the following steps: providing a substrate, and patterning the substrate to form a grid electrode. A gate insulating layer is formed on the substrate and covers the gate. And sequentially preparing a first metal oxide layer and a second metal oxide layer on the first metal oxide layer on the gate insulating layer, wherein the oxygen content of the formed first metal oxide layer is less than that of the second metal oxide layer. Coating a layer of photoresist material on the second metal oxide layer and patterning to form a photoresist layer; the photoresist layer comprises a first photoresist area and a second photoresist area, the second photoresist area corresponds to an area where a second oxide layer is formed, and the first photoresist area corresponds to an area where a first oxide layer is removed; the height T1 of the second photoresist region is greater than the height T2 of the first photoresist region. The second metal oxide layer and the first metal oxide layer which are not covered by the photoresist layer are etched to form a first oxide layer. And thinning the photoresist layer to completely remove the photoresist material in the first photoresist region. Under the protection of the second photoresist region, the second metal oxide layer in the first photoresist region is etched away to form a second oxide layer and to expose a portion of the first oxide layer from both sides of the second oxide layer. Removing the photoresist material in the second photoresist region; and forming a source and a drain.
Further, the first metal oxide layer and the second metal oxide layer are sputtered by the same target material, the flow ratio of oxygen to argon entering the film coating chamber in the sputtering process of the first metal oxide layer is x: y, wherein the range of x is 0-3, and the range of y is 5-20; the flow ratio of oxygen to argon entering the film coating chamber in the sputtering process of the second metal oxide layer is a: b, wherein the range of a is 3-10, and the range of b is 5-20; and x: y is less than a: b.
The embodiment of the invention provides an oxide semiconductor thin film transistor and a manufacturing method thereof, wherein the oxide semiconductor thin film transistor comprises a substrate, a grid electrode insulating layer, an oxide semiconductor layer and a source drain electrode metal layer which are sequentially arranged on the substrate, the source drain electrode metal layer comprises a source electrode and a drain electrode which are arranged at intervals, the oxide semiconductor layer comprises a first oxide layer and a second oxide layer which is arranged above the first oxide layer in a stacking mode, and the oxygen content of the first oxide layer is lower than that of the second oxide layer; and part of the first oxide layer is exposed from two sides of the second oxide layer, and the source electrode and the drain electrode are mutually spaced and are respectively in direct contact connection with the first oxide layer exposed from two sides of the second oxide layer, so that the source electrode, the drain electrode and the oxide semiconductor layer form better ohmic contact, the on-state current of the thin film transistor is effectively improved, and the comprehensive performance of the thin film transistor is optimized.
Drawings
Fig. 1 is a schematic structural diagram of a conventional oxide semiconductor thin film transistor.
Fig. 2 is a schematic structural diagram of another conventional oxide semiconductor thin film transistor.
Fig. 3 is a schematic cross-sectional view of an oxide semiconductor thin film transistor according to a preferred embodiment of the invention.
Fig. 4A to 4H are schematic cross-sectional views illustrating a process of fabricating an oxide semiconductor thin film transistor according to a preferred embodiment of the invention.
Fig. 5 is a front view of a partial structure of an oxide semiconductor thin film transistor according to a preferred embodiment of the present invention.
Detailed Description
To further illustrate the technical means and effects of the present invention adopted to achieve the predetermined objects, the following detailed description of the embodiments, structures, features and effects of the present invention will be made with reference to the accompanying drawings and examples.
Fig. 3 is a schematic cross-sectional structure view of an oxide semiconductor thin film transistor according to a preferred embodiment of the present invention, referring to fig. 3, the oxide semiconductor thin film transistor includes a substrate 110, a gate 120, a gate insulating layer 130, an oxide semiconductor layer 140, and a source-drain metal layer 150 sequentially disposed on the substrate 110, the source-drain metal layer 150 includes a source 151 and a drain 152 disposed at an interval, the oxide semiconductor layer 140 includes a first oxide layer 141 and a second oxide layer 142 stacked above the first oxide layer 141, and an oxygen content of the first oxide layer 141 is lower than that of the second oxide layer 142; a portion of the first oxide layer 141 is exposed from both sides of the second oxide layer 142, and the source electrode 151 and the drain electrode 152 are respectively in direct contact with the first oxide layer 141 exposed from both sides of the second oxide layer 142.
The oxide semiconductor layer 140 is a conductive channel (i.e., an active layer) that short-circuits the source and drain electrodes 151 and 152. According to the invention, the second oxide layer 142 with high oxygen content is arranged above the first oxide layer 141 with low oxygen content, and the first oxide layer 141 is exposed from two sides of the second oxide layer 142 and is respectively contacted with the source electrode 151 and the drain electrode 152, so that good ohmic contact is formed between the first oxide layer 141 and the source electrode 151 and the drain electrode 152, the on-state current of the thin film transistor is effectively improved, and the comprehensive performance of the thin film transistor is optimized.
Further, the oxygen content of the first oxide layer 141 is 0% to 50%, and the oxygen content of the second oxide layer 142 is 4% to 60%.
Wherein, the first oxide layer 141 and the second oxide layer 142 are prepared by magnetron sputtering method, and the oxygen content of the first oxide layer 141 and the second oxide layer 142 can be adjusted by adjusting the oxygen (O) entering into the film coating chamber during preparation2) The volume ratio of the flow rate and the argon (Ar) flow rate (oxygen-argon flow rate ratio) was controlled. The first oxide layer 141 has a higher number of oxygen vacancies due to its lower oxygen content, a higher carrier concentration than the second oxide layer 142, and a higher electron mobility.
Further, the width M of the first oxide layer 141 exposed from each side of the second oxide layer 142 is 1 to 8 μ M.
Further, the source electrode 151 and the drain electrode 152 are also in stacked contact connection with a portion of the second oxide layer 142 to completely cover the first oxide layer 141. Specifically, the source electrode 151 covers the first oxide layer 141 exposed from one side of the second oxide layer 142 and extends to a direction of the second oxide layer 142 to cover a portion of the second oxide layer 142, the drain electrode 152 covers the first oxide layer 141 exposed from the other side of the second oxide layer 142 and extends to a direction of the second oxide layer 142 to cover a portion of the second oxide layer 142, and a portion of the second oxide layer 142 is exposed from a middle of the source electrode 151 and the drain electrode 152.
Further, as shown in fig. 4H, the width N of the stacked position of the source electrode 151 and the second oxide layer 142 and the width N of the stacked position of the drain electrode 152 and the second oxide layer 142 are both greater than or equal to 1 μm, and the widths of the stacked positions of the source electrode 151, the drain electrode 152, and the second oxide layer 142 may be equal to each other.
Further, as shown in FIG. 4G, the thickness D1 of the first oxide layer 141 is 10-90 nm, and the thickness D2 of the second oxide layer 142 is 10-90 nm.
Further, as shown in fig. 4G and 4H, the width X1 of the first oxide layer 141 is 10 to 20 micrometers, and the width X2 of the second oxide layer 142 is 4 to 18 micrometers; the distance (i.e., channel length) between the source 151 and the drain 152 is 2-8 μm; the width M of the exposed portion of the first oxide layer 141 from both sides of the second oxide layer 142 is 1 to 8 μ M.
Further, the material of the first oxide layer 141 and the second oxide layer 142 is metal oxide, specifically, Indium Gallium Zinc Oxide (IGZO), for example.
Indium gallium zinc oxide is a mixed oxide based on zinc oxide (ZnO) doped with indium (In) and gallium (Ga), and the main function of indium and gallium as doping elements is to adjust the carrier concentration. The carriers of the indium gallium zinc oxide are mainly generated by Oxygen Vacancies (OV), and under a specific external environment, the metal oxide causes Oxygen in crystal lattices to be desorbed and is lost, so that the Oxygen vacancies are formed. The greater the number of oxygen vacancies, the higher the carrier concentration and vice versa. Therefore, the carrier concentration can be adjusted by controlling the oxygen content, so that the oxide semiconductor layer 140 has different electron mobility.
The oxide semiconductor thin film transistor adopts the oxide semiconductor layer 140 with the double-layer structure of the first oxide layer 141 and the second oxide layer 142, the first oxide layer 141 with lower oxygen content is exposed from the two sides of the second oxide layer 142 with higher oxygen content and is respectively in contact connection with the source 151 and the drain 152, and good ohmic contact is formed between the oxide semiconductor layer 140 and the source 151 and the drain 152, so that the on-state current of the thin film transistor is improved, and the comprehensive performance of the thin film transistor is further improved.
Fig. 4A to 4H are schematic cross-sectional views illustrating a manufacturing process of an oxide semiconductor thin film transistor according to a preferred embodiment of the present invention, please refer to sequentially that the oxide semiconductor thin film transistor adopts a gray-scale Mask (Half-tone Mask) exposure and dry etching technique to realize the above DSCL structure with a special shape, and specifically, the manufacturing method of the oxide semiconductor thin film transistor includes:
as shown in fig. 4A, a substrate 110 is provided, and a gate 120 is patterned on the substrate 110, and the method for forming the gate 120 is a conventional mature technology and is not repeated herein.
As shown in fig. 4B, a gate insulating layer 130 is formed on the substrate 110 and covers the gate 120, and then two metal oxide layers are sequentially formed on the gate insulating layer 130, wherein the two metal oxide layers include a first metal oxide layer 141a directly contacting the gate insulating layer 130 and a second metal oxide layer 142a on the first metal oxide layer 141a, and an oxygen content of the formed first metal oxide layer 141a is less than an oxygen content of the formed second metal oxide layer 142 a. The first metal oxide layer 141a is used to form the first oxide layer 141 of the oxide semiconductor layer 140, and the second metal oxide layer 142a is used to form the second oxide layer 142 of the oxide semiconductor layer 140.
Specifically, the first metal oxide layer 141a and the second metal oxide layer 142a are sequentially prepared by a magnetron sputtering method, in this embodiment, the same target material is used for sputtering, and in the case of indium gallium zinc oxide, the target material is prepared by mixing zinc oxide, indium oxide, and gallium oxide according to a specific ratio.
The method for forming the first metal oxide layer 141a having an oxygen content less than that of the second metal oxide layer 142a includes: when the first metal oxide layer 141a is deposited, the flow ratio of oxygen to argon entering the film coating chamber is x: y, wherein the range of x is 0-3, and the range of y is 5-20; when the second metal oxide layer 142a is deposited, the flow ratio of oxygen to argon entering the film coating chamber is a: b, wherein the range of a is 3-10, and the range of b is 5-20; and x: y is less than a: b, i.e., the flow rate of argon oxygen is higher when depositing the second metal oxide layer 141a than when depositing the first metal oxide layer 141 a.
Taking x: y as 0:10 as an example, the flow rate of oxygen entering the coating chamber during deposition of the first metal oxide layer 141a is 0 standard state milliliter per minute (SCCM), and the flow rate of argon is 10 standard state milliliter per minute (SCCM). Taking a: b as 2:10 as an example, the flow rate of oxygen entering the coating chamber during the deposition of the second metal oxide layer 141a is 2 standard state ml/min (SCCM), and the flow rate of argon is 10 standard state ml/min (SCCM).
The oxide semiconductor layer 140 is prepared by a magnetron sputtering method, the indium gallium zinc oxide is used as the material of the oxide semiconductor layer 140, and the growth and post-treatment temperature of the oxide semiconductor layer 140 is lower than 350 ℃, so that the indium gallium zinc oxide can be grown on the glass substrate in a large scale by the magnetron sputtering method. Therefore, a large-sized display panel can be manufactured using the structure of the oxide semiconductor thin film transistor of the present invention.
As shown in fig. 4C, a photoresist material is coated on the second metal oxide layer 142a, and the photoresist material is patterned by a mask process to form a photoresist layer 200, where the photoresist layer 200 includes a first photoresist region 201 and a second photoresist region 202, where the second photoresist region 202 corresponds to a region where the second oxide layer 142 is formed later, and the first photoresist region 201 corresponds to a region where the second oxide layer 142 is removed from a region where the first oxide layer 141 is formed later, that is, a region where the second oxide layer 142 is exposed from two sides of the first oxide layer 141. Wherein the height T1 of the second photoresist region 202 is greater than the height T2 of the first photoresist region 201. The photoresist material in the other regions is completely removed.
Specifically, the first photoresist region 201 is half-exposed by using a half-tone mask (half-tone mask) or a gray-tone mask (gray-tone mask), wherein the half-tone mask is provided with a semi-transmission film at the position of the first photoresist region 201, and the exposure energy to the photoresist on the first photoresist region 201 is reduced by the semi-transmission film; the gray tone mask has a plurality of slits (slit) closely arranged at intervals at the position of the first photoresist region 201, and the exposure energy to the first photoresist region 201 is reduced by the light diffraction of the slits. Taking the positive photoresist as an example, during the exposure, the photoresist in the second photoresist region 202 is not exposed, the photoresist in the first photoresist region 201 is half exposed, and the photoresist in the other regions is completely exposed, so that after the exposure, the development is performed, so that in the photoresist layer 200 left after the development, the photoresist thickness T2 in the first photoresist region 201 is smaller than the photoresist thickness T1 in the second photoresist region 202.
As shown in fig. 4D, the second metal oxide layer 142a and the first metal oxide layer 141a not covered by the photoresist layer 200 are etched away. That is, the photoresist layer 200 is used as a mask to etch the two metal oxide layers 142a and the first metal oxide layer 141a, and the second metal oxide layer 142a and the first metal oxide layer 141a which are not covered by the photoresist layer 200 are sequentially etched and removed, while the second metal oxide layer 142a and the first metal oxide layer 141a which are covered by the photoresist layer 200 remain after etching, wherein the remaining first metal oxide layer 141a is the first oxide layer 141. This step may use either wet etching or dry etching.
As shown in fig. 4E, the photoresist layer 200 is thinned to completely remove the photoresist material in the first photoresist region 201.
Specifically, the photoresist material remaining in the first photoresist region 201 after the half exposure is completely removed to expose a portion of the second metal oxide layer 142a in the first photoresist region 201. Although the photoresist thickness of the second photoresist region 202 is reduced in this step, a certain thickness of photoresist remains on the first photoresist region 201 because the photoresist thickness T1 of the second photoresist region 202 is much greater than the photoresist thickness T2 of the first photoresist region 201. It should be noted that the method for thinning the photoresist layer 200 includes a wet photoresist Stripping (SPM), a dry photoresist stripping, and an organic solvent cleaning.
As shown in fig. 4F, under the protection of the photoresist material in the second photoresist region 202, the second metal oxide layer 142a in the first photoresist region 201 is etched away to form the second oxide layer 142 and expose a portion of the first oxide layer 141 from both sides of the second oxide layer 142. This step is a half-etching (only the second metal oxide layer 142a of the first photoresist region 201 is removed), and the etching time needs to be precisely controlled, so that dry etching is preferably used. The second metal oxide layer 142a that is not etched away is the second oxide layer 142.
As shown in fig. 4G, the photoresist in the second photoresist region 202 is completely removed, which may be performed in the same manner as the photoresist removal.
As shown in fig. 3, 4H and 5, a source electrode 151 and a drain electrode 152 are formed. Specifically, the source and drain electrodes 151 and 152 are pattern-formed on the oxide semiconductor layer 140, with the source and drain electrodes 151 and 152 spaced apart from each other; the source electrode 151 covers the first oxide layer 141 exposed from one side of the second oxide layer 142 and extends to a direction of the second oxide layer 142 to cover a portion of the second oxide layer 142, the drain electrode 152 covers the first oxide layer 141 exposed from the other side of the second oxide layer 142 and extends to a direction of the second oxide layer 142 to cover a portion of the second oxide layer 142, and a portion of the second oxide layer 142 is exposed from a middle of the source electrode 151 and the drain electrode 152.
According to the oxide semiconductor thin film transistor provided by the invention, the first oxide layer 141 positioned at the lower layer in the oxide semiconductor layer 140 with the double-layer channel is exposed from the two sides of the second oxide layer 142 positioned at the upper layer and is respectively in direct contact connection with the source electrode 151 and the drain electrode 152, and the oxygen content of the first oxide layer 141 is lower than that of the second oxide layer 142, so that the source electrode 151 and the drain electrode 152 form better ohmic contact with the oxide semiconductor layer 140, the on-state current of the thin film transistor is effectively improved, and the comprehensive performance of the thin film transistor is optimized.
Although the present invention has been described with reference to the above embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. An oxide semiconductor thin film transistor comprises a substrate (110), and a gate (120), a gate insulating layer (130), an oxide semiconductor layer (140) and a source drain metal layer (150) which are sequentially arranged on the substrate (110), wherein the source drain metal layer (150) comprises a source electrode (151) and a drain electrode (152) which are arranged at intervals, the oxide semiconductor layer (140) comprises a first oxide layer (141) and a second oxide layer (142) which is arranged above the first oxide layer (141) in a stacking mode, and the oxygen content of the first oxide layer (141) is lower than that of the second oxide layer (142); part of the first oxide layer (141) is exposed from both sides of the second oxide layer (142), and the source electrode (151) and the drain electrode (152) are spaced apart from each other and are in direct contact with the first oxide layer (141) exposed from both sides of the second oxide layer (142), respectively.
2. The oxide semiconductor thin film transistor according to claim 1, wherein an oxygen content of the first oxide layer (141) is 0% to 50%, and an oxygen content of the second oxide layer (142) is 4% to 60%.
3. The oxide semiconductor thin film transistor according to claim 3, wherein a width M of the first oxide layer (141) exposed from each side of the second oxide layer (142) is 1 to 8 μ M.
4. The oxide semiconductor thin film transistor of claim 1, wherein the source electrode (151) covers the first oxide layer (141) exposed from one side of the second oxide layer (142) and extends to cover a portion of the second oxide layer (142) in a direction of the second oxide layer (142), and the drain electrode (152) covers the first oxide layer (141) exposed from the other side of the second oxide layer (142) and extends to cover a portion of the second oxide layer (142) in a direction of the second oxide layer (142).
5. The oxide semiconductor thin film transistor according to claim 4, wherein a width N of a lamination position of the source electrode (151) and the second oxide layer (142) and a lamination position of the drain electrode (152) and the second oxide layer (142) is greater than or equal to 1 μm.
6. The oxide semiconductor thin film transistor of claim 1, wherein the thickness D1 of the first oxide layer (141) is 10-90 nm, and the thickness D2 of the second oxide layer (142) is 10-90 nm.
7. The oxide semiconductor thin film transistor of claim 1, wherein a width X1 of the first oxide layer (141) is 10-20 μ M, a width X2 of the second oxide layer (142) is 4-18 μ M, a distance between the source electrode (151) and the drain electrode (152) is 2-8 μ M, and a width M of a portion of the first oxide layer (141) exposed from both sides of the second oxide layer (142) is 1-8 μ M.
8. The oxide semiconductor thin film transistor according to claim 1, wherein the material of the first oxide layer (141) and the second oxide layer (142) is a metal oxide.
9. A method for fabricating the oxide semiconductor thin film transistor according to any one of claims 1 to 8, comprising:
providing a substrate (110), and patterning to form a grid (120) on the substrate (110);
forming a gate insulating layer (130) on the substrate (110) and covering the gate electrode (120);
sequentially preparing a first metal oxide layer (141a) and a second metal oxide layer (142a) on the first metal oxide layer (141a) on the gate insulating layer (130) and making the oxygen content of the formed first metal oxide layer (141a) less than that of the second metal oxide layer (142 a);
coating a layer of photoresist material on the second metal oxide layer (142a) and patterning to form a photoresist layer (200); the light resistance layer (200) comprises a first light resistance area (201) and a second light resistance area (202), the second light resistance area (202) corresponds to an area where the second oxide layer (142) is formed, and the first light resistance area (201) corresponds to an area where the first oxide layer (141) is formed and the second oxide layer (142) is removed; the height T1 of the second light blocking region (202) is greater than the height T2 of the first light blocking region (201);
etching away the second metal oxide layer (142a) and the first metal oxide layer (141a) not covered by the photoresist layer (200) to form the first oxide layer (141);
thinning the light resistance layer (200) to completely remove the light resistance material of the first light resistance area (201);
under the covering protection of the second photoresist area (202), etching off the second metal oxide layer (142a) positioned in the first photoresist area (201) to form the second oxide layer (142) and expose part of the first oxide layer (141) from two sides of the second oxide layer (142);
removing the photoresist material from the second photoresist region (202); and
a source (151) and a drain (152) are formed.
10. The method for manufacturing the oxide semiconductor thin film transistor according to claim 9, wherein the first metal oxide layer (141a) and the second metal oxide layer (142a) are sputtered by using the same target, and the flow ratio of oxygen to argon entering the film coating chamber during sputtering of the first metal oxide layer (141a) is x: y, wherein x ranges from 0 to 3, and y ranges from 5 to 20; the flow ratio of oxygen to argon entering the film coating chamber in the sputtering process of the second metal oxide layer (142a) is a: b, wherein the range of a is 3-10, and the range of b is 5-20; and x: y is less than a: b.
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