阅读说明：本技术 一种背沟道蚀刻型的薄膜电晶体及其制作方法 (Back channel etching type thin film transistor and manufacturing method thereof ) 是由 葛世民 于 2021-09-03 设计创作，主要内容包括：一种背沟道蚀刻型的薄膜电晶体(thin-film transistor,TFT)及其制作方法,在蚀刻TFT之源极及漏级的过程中,通过使用含有氟元素的双氧水系铜酸作为蚀刻液,能够在蚀刻源极及漏极的同时去除背沟道处受损伤的氧化物半导体层,解决了传统TFT器件中氧化物半导体层损伤而导致器件电性稳定性差的问题,在完成蚀刻后,再通过具有氧元素的气体或是氟元素的气体对所述背沟道进行修复,填补了背沟道处因蚀刻而产生的过量的氧空位,进一步地增加了TFT器件的电性稳定性。(A back-channel etching type Thin Film Transistor (TFT) and a manufacturing method thereof are provided, in the process of etching a source electrode and a drain electrode of the TFT, a hydrogen peroxide system copper acid containing fluorine is used as an etching solution, an oxide semiconductor layer damaged at a back channel can be removed while the source electrode and the drain electrode are etched, the problem that the electrical stability of a device is poor due to damage of the oxide semiconductor layer in a traditional TFT device is solved, after etching is completed, the back channel is repaired by gas containing oxygen or fluorine, excessive oxygen vacancies generated by etching at the back channel are filled, and the electrical stability of the TFT device is further improved.)

1. A method for fabricating a back channel etched thin film transistor, comprising:

s1: forming a gate layer;

s2: forming a gate insulating layer on the gate layer;

s3: forming an oxide semiconductor layer on the gate insulating layer; and

s4: forming a source electrode and a drain electrode on the oxide semiconductor layer, wherein the oxide semiconductor layer between the source electrode and the drain electrode is a back channel;

in step S4, the source electrode, the drain electrode, and the back channel are formed by the same etching process, and an etching solution used includes hydrogen peroxide based copper acid containing fluorine.

2. The method of claim 1, wherein the fluorine-containing aqueous hydrogen peroxide copper acid has a fluorine content of 0.02 to 0.04 wt%.

3. The method of claim 1, wherein the oxide semiconductor layer comprises izo.

4. The method as claimed in claim 3, wherein the ratio of indium is smaller than the ratio of zinc and smaller than the ratio of gallium at the surface of the back channel.

5. The method as claimed in claim 1, further comprising the following steps after the step S4:

s5: and repairing the back channel by using gas containing oxygen or gas containing fluorine.

6. The method as claimed in claim 5, wherein the oxygen-containing gas is N₂O, the gas containing the fluorine element is NF₃。

7. The method of claim 1, wherein the oxide semiconductor layer at the back channel is etched to a depth of 20nm to 30nm after the step S4 is completed.

8. The method of claim 1, further comprising:

a gate layer;

a gate insulating layer disposed over the gate layer;

an oxide semiconductor layer disposed over the gate insulating layer; and

a source electrode and a drain electrode arranged on the oxide semiconductor layer, wherein the oxide semiconductor layer between the source electrode and the drain electrode is a back channel;

wherein the back channel contains fluorine.

9. The back-channel etched thin film transistor according to claim 8, wherein the oxide semiconductor layer includes izo, and a proportion of indium in the oxide semiconductor layer is smaller than a proportion of zinc and smaller than a proportion of gallium at a surface of the back channel.

10. The back-channel-etched thin film transistor according to claim 8, wherein a thickness of the oxide semiconductor layer at the back channel is 20nm to 30nm thinner than a thickness of the oxide semiconductor layer at a portion other than the back channel.

[ technical field ] A method for producing a semiconductor device

The present invention relates to the field of thin film transistors, and more particularly, to a back channel etching type thin film transistor and a method for fabricating the same.

[ background of the invention ]

In an active matrix driven display panel, a thin-film transistor (TFT) is generally used to control an electric field in each pixel. The semiconductor materials commonly used in TFTs include amorphous silicon, oxide, and polysilicon, etc., wherein oxide semiconductors have unique advantages in high-order display technologies such as large size, high resolution, and high refresh rate due to higher mobility and simpler process track.

The Back Channel Etched (BCE) TFT (hereinafter referred to as BCE-TFT) does not need an etch-stop layer (ESL), and the back channel can be significantly reduced compared to the TFT structure having the ESL, thereby having relatively lower production cost and technical advantages. Because of the high mobility of oxide devices, they are often used in high-end and high-specification products, and therefore, copper processes are often used to synchronously reduce the RC delay of the wiring and the charging time required by the devices.

Referring to fig. 1, a conventional BCE-TFT includes a gate layer 900, a gate insulating layer 901, an oxide semiconductor layer 902, a source 904, and a drain 905, and in an etching process of a conventional source/drain, the oxide semiconductor layer 902 is easily damaged to generate a damaged oxide semiconductor layer 903, which causes a defect in a back channel between the source 904 and the drain 905, and a device characteristic is difficult to control, so that an electrical stability is poor.

[ summary of the invention ]

In order to solve the above problems, the present application provides a method for fabricating a back channel etching type thin film transistor, comprising the steps of: s1: forming a gate layer; s2: forming a gate insulating layer on the gate layer; s3: forming an oxide semiconductor layer on the gate insulating layer; and S4: forming a source electrode and a drain electrode on the oxide semiconductor layer, wherein the oxide semiconductor layer between the source electrode and the drain electrode is a back channel; in step S4, the source electrode, the drain electrode, and the back channel are formed by the same etching process, and an etching solution used includes hydrogen peroxide based copper acid containing fluorine.

Furthermore, in the hydrogen peroxide system cuprate containing the fluorine element, the weight percentage concentration of the fluorine element is between 0.02 and 0.04 percent.

Further, the oxide semiconductor layer includes izo and is formed by applying ito to the semiconductor layer.

Furthermore, at the surface of the back channel, the proportion of the indium element is smaller than that of the zinc element and smaller than that of the gallium element.

Still further, the step S4 is followed by the steps of: s5: and repairing the back channel by using gas containing oxygen or gas containing fluorine.

Further, the gas containing oxygen is N₂O, the gas containing the fluorine element is NF₃。

Further, after the step S4 is completed, the oxide semiconductor layer at the back channel is etched by 20nm to 30 nm.

In order to solve the above problem, the present application further provides a thin film transistor, including:

a gate layer; a gate insulating layer disposed over the gate layer; an oxide semiconductor layer disposed over the gate insulating layer; and a source electrode and a drain electrode arranged on the oxide semiconductor layer, wherein the oxide semiconductor layer between the source electrode and the drain electrode is a back channel; wherein the back channel contains fluorine.

Further, the oxide semiconductor layer contains indium, gallium, zinc and indium, and the proportion of indium element in the oxide semiconductor layer is smaller than the proportion of zinc element and smaller than the proportion of gallium element at the surface of the back channel.

Further, the thickness of the oxide semiconductor layer at the back channel is 20nm to 30nm thinner than that of the oxide semiconductor layer at a position other than the back channel. .

The method has the advantages that in the process of etching the source electrode and the drain electrode of the TFT, the oxide semiconductor layer damaged at the back channel can be removed while the source electrode and the drain electrode are etched by using the hydrogen peroxide system copper acid containing fluorine as the etching solution, the problem of poor electrical stability of a device caused by damage of the oxide semiconductor layer of the traditional TFT is solved, after etching is completed, the back channel is repaired by gas containing oxygen or gas containing fluorine, oxygen vacancies generated by etching at the back channel are filled, and the electrical stability of the TFT device is further improved.

In order to make the aforementioned and other objects of the present application more comprehensible, preferred embodiments accompanied with figures are described in detail below.

[ description of the drawings ]

FIG. 1 is a schematic diagram of a conventional back channel etching type TFT.

FIG. 2 is a flowchart illustrating a method of fabricating a back channel etched thin film transistor according to a first embodiment of the present invention.

FIG. 3 is a schematic structural diagram of a back channel etching type thin film transistor according to a second embodiment of the present application.

[ detailed description ] embodiments

In order to make the aforementioned and other objects, features and advantages of the present disclosure comprehensible, preferred embodiments accompanied with figures are described in detail below. Furthermore, directional phrases used in this disclosure, such as, for example, upper, lower, top, bottom, front, rear, left, right, inner, outer, lateral, peripheral, central, horizontal, lateral, vertical, longitudinal, axial, radial, uppermost or lowermost, etc., refer only to the orientation of the attached drawings. Accordingly, the directional terms used are used for the purpose of illustration and understanding of the present disclosure, and are not used to limit the present disclosure.

The back channel of the conventional back channel etching type thin film transistor (BCE-TFT) is easily damaged in the etching process of a source electrode and a drain electrode, so that the defects of the back channel are more, the characteristics of a device are difficult to control, and the stability of the device is poor.

First embodiment

Referring to fig. 2 and fig. 3, the present application provides a novel method for fabricating a BCE-TFT 10, comprising the following steps: s1: forming a gate layer 100; s2: forming a gate insulating layer 101 on the gate layer 100; s3: forming an oxide semiconductor layer 102 over the gate insulating layer 101; and S4: forming a source electrode 103 and a drain electrode 104 on the oxide semiconductor layer 102, wherein the oxide semiconductor layer 102 between the source electrode 103 and the drain electrode 104 is a back channel 50; in step S4, the source electrode 103, the drain electrode 104, and the back channel 50 are formed by the same etching process, and the etching solution used includes hydrogen peroxide based copper acid containing fluorine.

The fluorine element in the aqueous hydrogen peroxide cuprate containing the fluorine element can effectively remove the oxide semiconductor layer 102 damaged at the back channel 50, wherein the oxide semiconductor layer 102 is damaged by: in the process of etching the source electrode 103 and the drain electrode 104, weak bonds or broken bonds are generated between the metal of the oxide semiconductor layer 102 and oxygen atoms, ions are generated, and these ions generate impurities, so that the stability of the device is affected.

Preferably, the weight percentage concentration of the fluorine element in the aqueous hydrogen peroxide copper acid containing the fluorine element is between 0.02% and 0.04%, if the fluorine content in the aqueous hydrogen copper acid is too high, the oxide semiconductor layer 102 and the source electrode 104 and the drain electrode 105 have insufficient selectivity (i.e. the ratio of the etching rate of the oxide semiconductor layer 102 to the etching rate of the source electrode 104 and the drain electrode 105), which may cause the oxide semiconductor layer 102 to be completely etched away, thereby causing device failure; on the contrary, if the fluorine content in the hydrogen peroxide-based copper acid is too small, the damaged oxide semiconductor layer 102 at the back channel 50 cannot be etched sufficiently, and in the conventional BCE-TFT, the thickness of the damaged oxide semiconductor layer is about 20 to 30nm, and the preferred fluorine element ratio provided in this embodiment can remove the damaged oxide semiconductor layer at the back channel while satisfying the selection ratio, thereby increasing the stability of the device.

In this embodiment, the oxide semiconductor layer 102 contains Indium Gallium Zinc Oxide (IGZO) and is formed by oxidizing indium gallium zinc oxide (ito), and the present embodiment adjusts the composition of the dioxygen water-based copper acid containing the fluorine element, so that the ratio of the indium element on the surface of the back channel 50 is smaller than the ratio of the zinc element and smaller than the ratio of the gallium element, thereby further increasing the stability of the device.

The etched back channel 50 mayA new weak bond or broken bond between the metal and the oxygen atom can be generated, and therefore, in this embodiment, the step S4 further includes the following steps: s5: the back channel 50 is repaired using a gas containing an oxygen element or a gas containing a fluorine element. Specifically, this step fills oxygen vacancies generated by the broken bond between metal and oxygen atoms in the oxide semiconductor layer 102 at the back channel 50 with oxygen or fluorine to avoid generating ions, wherein the gas containing oxygen may be N₂O, the gas containing fluorine element can be NF₃Of course, N₂O gas and NF₃Gases may be used simultaneously in this step to achieve better healing.

In the embodiment, the hydrogen peroxide system cuprate containing the fluorine element is used as the etching solution for etching the source and drain electrodes, so that the oxide semiconductor layer damaged at the back channel can be removed while the source and drain electrodes are etched, the electrical stability of the device is improved, and in addition, compared with the traditional etching solution for etching the source and drain electrodes, the hydrogen peroxide system cuprate containing the fluorine element has a better wire breaking effect on the data wire in the TFT device, so that the device manufactured by the method provided by the embodiment has higher yield and lower cost.

Second embodiment

In order to solve the above problem, please refer to fig. 3, the present application further provides a BCE-TFT 10 fabricated by the method provided in the first embodiment, including: a gate layer 100; a gate insulating layer 101 disposed over the gate layer 100; an oxide semiconductor layer 102 provided over the gate insulating layer 101; and a source electrode 103 and a drain electrode 104 disposed on the oxide semiconductor layer 102, wherein the metal oxide layer 102 between the source electrode 103 and the drain electrode 104 is a back channel 50; wherein the metal oxide layer 102 at the back channel 50 contains fluorine.

In the embodiment, the metal oxide layer 102 at the back channel 50 is etched by hydrogen peroxide copper acid containing fluorine, and is etched by NF₃The oxygen vacancies of the metal oxide layer 102 at the back channel 50 are gas repaired becauseThis contains fluorine elements.

In the present embodiment, the oxide semiconductor layer 102 contains izo, and the ratio of indium is smaller than the ratio of zinc and smaller than the ratio of gallium at the surface of the back channel 50, such element ratios can improve the stability of the semiconductor carriers in the oxide semiconductor layer 102.

In the present embodiment, the thickness of the oxide semiconductor layer 102 at the back channel 50 is 20nm to 30nm thinner than that of the oxide semiconductor layer 102 not at the back channel 50, because the thickness of the damaged oxide semiconductor layer is about 20nm to 30nm in the prior art, the damaged oxide semiconductor layer 102 at the back channel 50 is removed in the present embodiment, and the oxide semiconductor layer 102 not at the back channel 50 (i.e., under the source electrode 103 and the drain electrode 104) still includes the damaged oxide semiconductor layer 105 which is not removed.

The foregoing is merely a preferred embodiment of the present disclosure, and it should be noted that modifications and refinements may be made by those skilled in the art without departing from the principle of the present disclosure, and these modifications and refinements should also be construed as the protection scope of the present disclosure.