A thin-film transistor of an oxide semiconductor with an improved insulating layer

Abstract

A thin-film transistor of an oxide semiconductor with an improved insulating layer, comprising a gate and an insulating layer disposed on a substrate, as well as an active layer, a source electrode, and a drain electrode; the insulating layer includes a first thin film and a second thin film laminated together; the first thin film is a polycrystalline structure composed of a plurality of first crystal columns, and the second thin film is a polycrystalline structure composed of a plurality of second crystal columns, and each of the second crystal columns is arranged offset from each of the first crystal columns; the insulating layer is manufactured through the following steps: Step (1) grow the first thin film on the substrate through a first PVD process; Step (2) modify the surface of the first thin film to destroy the ends of each of the first crystal columns to form a surface layer; Step (3) grow the second thin film on the surface layer through a second PVD process. The present invention can be completely fabricated using the PVD process, which can not only effectively increase the density of the insulating layer, but also greatly reduce the process complexity and investment in equipment, facilitating the improvement of manufacturing efficiency and safety.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor devices, and particularly to a thin film transistor of an oxide semiconductor with an improved insulating layer. Background Art

[0002] A thin film transistor (referred to as TFT) generally includes an insulating layer and a protective layer, and such an insulating layer is generally required to have high denseness. An oxide thin film transistor (referred to as oxide TFT) is a type of thin film transistor that uses an oxide thin film as an active layer, and it has the advantage of high mobility; in addition, the oxide thin film used as the active layer can be fabricated by PVD process (PVD is physical vapor deposition method), and generally no flammable gas is required as a process gas, so it has advantages such as high safety.

[0003] In the manufacturing process of existing oxide thin film transistors, although their active layers can be fabricated by PVD, their insulating layers still need to be fabricated by CVD process (CVD is chemical vapor deposition method). The CVD process can ensure the denseness of the insulating layer. If the PVD process is used to fabricate the insulating layer, the obtained insulating layer will have a loose columnar crystal structure (gaps are likely to appear between the crystal columns), resulting in defects such as holes in the insulating layer, and its denseness cannot meet the requirements of thin film transistors; therefore, such oxide thin film transistors need to be fabricated by both CVD and PVD processes, and cannot be entirely fabricated by the PVD process, which increases the process complexity, increases the investment of the factory in process equipment, and has problems such as low manufacturing efficiency, high manufacturing cost, and insufficient safety in the manufacturing process. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a thin film transistor of an oxide semiconductor with an improved insulating layer, which can be entirely fabricated by the PVD process. It can not only effectively increase the denseness of its insulating layer, but also greatly reduce the process complexity and the investment of the factory in equipment, which is beneficial to improving manufacturing efficiency and safety. The adopted technical solution is as follows:

[0005] A thin film transistor of an oxide semiconductor with an improved insulating layer, comprising a gate and an insulating layer, as well as an active layer, a source electrode and a drain electrode arranged on a substrate, wherein the gate is covered by the insulating layer, the active layer, the source electrode and the drain electrode are all arranged on the insulating layer, and the source electrode and the drain electrode are arranged oppositely; the characteristic is that: the insulating layer comprises a first thin film and a second thin film formed by stacking, the first thin film is arranged on the substrate, the first thin film has a surface layer formed after modification, and the second thin film is grown on the surface layer of the first thin film; the first thin film and the second thin film are both insulating inorganic thin films, the first thin film is a polycrystalline structure composed of a plurality of first crystal columns, the second thin film is a polycrystalline structure composed of a plurality of second crystal columns, and each second crystal column is arranged staggered with each first crystal column; and the insulating layer is manufactured by the following steps:

[0006] Step (1) growing a first thin film consisting of a plurality of first crystal columns on a substrate through a first PVD process;

[0007] Step (2) modifying the surface of the first film, destroying the ends of each first crystal column, and forming a surface layer;

[0008] Step (3) growing a second thin film consisting of a plurality of second crystal columns on the surface layer of the first thin film through a second PVD process, and the second thin film and the first thin film formed by stacking form the insulating layer.

[0009] In the above manufacturing process of the insulating layer, in step (2), by modifying the surface of the first thin film, the dangling bonds on the surface of the first thin film are neutralized, thereby changing the surface structure, causing the crystal structure inside the first crystal column to be damaged at the end, and thus generating a surface layer different from that inside the first crystal column; in step (3), a second thin film is grown on the modified surface layer through a second PVD process. Since the ends of each first crystal column are damaged, each second crystal column cannot continue to grow at the end of the first crystal column, and its growth will be based on new growth nuclei. The grown second crystal columns are staggered from the first crystal columns, and the holes of the first crystal columns and the holes of the second crystal columns will also be staggered from each other. The first thin film and the second thin film have a mutual shielding effect (that is, each second crystal column can respectively shield the corresponding gaps between each first crystal column, and each first crystal column can respectively shield the corresponding gaps between each second crystal column). In this way, the gaps (or holes) between each first crystal column cannot spread along the first crystal column to the second crystal column, which can not only destroy the single extensibility of the holes, greatly reduce the occurrence probability of through gaps (or holes), reduce the influence of the holes, but also greatly increase the density of the insulating layer. Since both the insulating layer and the active layer can be fabricated by the PVD process, the above thin film transistor can be completely fabricated by the PVD process. Compared with the prior art in which thin film transistors need to be fabricated by two processes, CVD and PVD, it can not only effectively increase the density of its insulating layer, but also greatly reduce the process complexity and the factory's investment in equipment, which is beneficial to improving the manufacturing efficiency and safety.

[0010] In a preferred embodiment, the second thin film and the first thin film are homogeneous thin films. In this way, the second thin film and the first thin film can be better combined. Generally, both the first thin film and the second thin film are made of the same inorganic insulating material (such as Al2O3, SiO2, HfO2), and the thicknesses of the first thin film and the second thin film are both 150 - 600 nm.

[0011] In a preferred embodiment, the thin film transistor further includes a protective layer that covers the active layer, the source electrode, and the drain electrode.

[0012] In a preferred embodiment, in step (2), a reactive plasma is used to modify the surface of the first thin film. By using the reaction of oxygen ions or nitrogen ions in the plasma with the surface of the first thin film, the dangling bonds on the surface of the first crystal column are neutralized and eliminated, causing the crystal structure inside the first crystal column to be damaged at the end and forming a surface layer different from that inside the first crystal column. Therefore, the second crystal column cannot continue to grow at the end of the first crystal column, and its growth will be based on new growth nuclei. The grown second crystal columns are staggered from each other, and the holes of the first crystal columns and the holes of the second crystal columns will also be staggered from each other, thereby greatly increasing the density of the insulating layer.

[0013] In a further preferred embodiment, the first thin film obtained in step (1) is a metal oxide thin film; in step (2), the surface of the first thin film is modified by oxygen plasma.

[0014] In another further preferred embodiment, the first thin film obtained in step (1) is a metal nitride thin film; in step (2), the surface of the first thin film is modified by nitrogen plasma.

[0015] In another preferred embodiment, in step (2), the first thin film is exposed to a high-temperature reaction atmosphere, and the surface of the first thin film is modified by the high-temperature reaction atmosphere. The high-temperature reaction atmosphere reacts with the surface of the first thin film to neutralize and eliminate the dangling bonds on the surface of the first crystal column, so that the crystal structure inside the first crystal column is destroyed at the end to form a surface layer different from that inside the first crystal column. Therefore, the second crystal column cannot continue to grow at the end of the first crystal column, and its growth will be based on new growth nuclei, and the grown second crystal column is discontinuous with the second crystal column. The holes of the first crystal column and the holes of the second crystal column will also be staggered from each other, thereby greatly increasing the density of the insulating layer.

[0016] In a further preferred embodiment, in step (2), the first thin film is exposed to a high-temperature oxygen-containing atmosphere.

[0017] In another further preferred embodiment, in step (2), the first thin film is exposed to a high-temperature nitrogen-containing atmosphere.

[0018] In another preferred embodiment, in step (2), the surface of the first thin film is modified by argon ion bombardment. By bombarding the surface of the first thin film with argon ions, the crystal structure inside the first crystal column is destroyed at the end to form a surface layer different from that inside the first crystal column, thereby generating a surface layer different from that inside the first crystal column.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] This thin film transistor forms an insulating layer by means of multi-layer coating, which can make the first thin film and the second thin film cover each other, and the holes on the first thin film and the holes on the second thin film are staggered. This not only can destroy the single extensibility of the holes, reduce the influence of the holes, make the thin film transistor more dense, but also can be completely fabricated by PVD process. Compared with the thin film transistor in the prior art that needs to be fabricated by both CVD and PVD processes, it can greatly reduce the process complexity and the investment of the factory in equipment, and improve the manufacturing efficiency and safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a schematic structural diagram of a thin film transistor according to Embodiment 1 of the preferred embodiment of the present invention.

[0022] Figure 2 yes Figure 1 Schematic diagram of the structure of the insulating layer in the thin film transistor shown. DETAILED DESCRIPTION Example

[0023] like Figure 1 , Figure 2 As shown, the oxide semiconductor thin film transistor with improved insulating layer includes a gate 1 and an insulating layer 2, as well as an active layer 3, a source 4, a drain 5 and a protective layer 6 arranged on a substrate 0, the gate 1 is covered by the insulating layer 2, the active layer 3, the source 4, and the drain 5 are all arranged on the insulating layer 2, the source 4 and the drain 5 are arranged oppositely, and the protective layer 6 covers the active layer 3, the source 4 and the drain 5; the insulating layer 2 includes a first thin film 21 and a second thin film 22 formed by stacking, the first thin film 21 is arranged on the substrate 0, the first thin film 21 has a surface layer 201 formed after modification, and the second thin film 22 grows on the surface layer 201 of the first thin film 21; the first thin film 21 and the second thin film 22 are both insulating inorganic thin films, the first thin film 21 is a polycrystalline structure composed of a plurality of first crystal columns 211, and the second thin film 22 is a polycrystalline structure composed of a plurality of second crystal columns 221, and each second crystal column 221 is staggered with each first crystal column 211; and the insulating layer 2 is manufactured by the following steps:

[0024] Step (1) growing a first thin film 21 consisting of a plurality of first crystal columns 211 on a substrate 0 through a first PVD process;

[0025] Step (2) using reactive plasma to modify the surface of the first film 21, destroying the ends of each first crystal column 211, and forming a surface layer 201;

[0026] Step (3) A second thin film 22 consisting of a plurality of second crystal columns 221 is grown on the surface layer 201 of the first thin film 21 through a second PVD process, and the second thin film 22 and the first thin film 21 are stacked to form an insulating layer 2.

[0027] During the manufacturing process of the insulating layer 2, in step (2), the surface of the first thin film 21 reacts with oxygen ions or nitrogen ions in the plasma for modification to neutralize and eliminate the dangling bonds on the surface of the first crystal column 211, so that the crystal structure inside the first crystal column 211 is damaged at the end to form a surface layer 201 different from the inside of the first crystal column 211; in step (3), the second thin film 22 is grown on the modified surface layer 201 through the second PVD process. Since the ends of each first crystal column 211 are damaged, each second crystal column 221 cannot continue to grow at the end of the first crystal column 211, and its growth will be based on new growth nuclei. The grown second crystal columns 221 are staggered with the first crystal columns 211, and the holes 202 of the first crystal columns 211 and the holes 202 of the second crystal columns 221 are also staggered with each other. The first thin film 21 and the second thin film 22 have a mutual shielding effect (that is, each second crystal column 221 can respectively shield the corresponding gaps between each first crystal column 211, and each first crystal column 211 can respectively shield the corresponding gaps between each second crystal column 221). In this way, the gaps (or holes 202) between each first crystal column 211 cannot spread along the first crystal column 211 to the second crystal column 221, which can not only destroy the single extensibility of the holes 202, greatly reduce the occurrence probability of through gaps (or holes 202), reduce the influence of the holes 202, but also greatly increase the density of the insulating layer 2. Since both the insulating layer 2 and the active layer 3 can be fabricated by the PVD process, the above thin film transistor can be completely fabricated by the PVD process. Compared with the prior art in which the thin film transistor needs to be fabricated by two processes of CVD and PVD, it can not only effectively increase the density of its insulating layer 2, but also greatly reduce the process complexity and the factory's investment in equipment, which is beneficial to improving the manufacturing efficiency and safety.

[0028] In this embodiment, the second thin film 22 and the first thin film 21 are homogeneous thin films, and the thicknesses of both the first thin film 21 and the second thin film 22 are 150 - 600 nm. In this way, the second thin film 22 and the first thin film 21 can be combined better.

[0029] In one implementation manner, the first thin film 21 prepared in step (1) is a metal oxide thin film; in step (2), oxygen plasma is used to modify the surface of the first thin film 21.

[0030] In another implementation manner, the first thin film 21 prepared in step (1) is a metal nitride thin film; in step (2), nitrogen plasma is used to modify the surface of the first thin film 21. Embodiment

[0031] In the case where other parts are the same as those in the first embodiment, the difference lies in that: in the step (2), the first thin film 21 is exposed to a high-temperature reaction atmosphere, and the surface of the first thin film 21 is modified by using the high-temperature reaction atmosphere. By reacting the high-temperature reaction atmosphere with the surface of the first thin film 21, the dangling bonds on the surface of the first crystal column 211 are neutralized and eliminated, so that the crystal structure inside the first crystal column 211 is damaged at the end to form a surface layer 201 different from the inside of the first crystal column 211. Therefore, the second crystal column 221 cannot continue to grow at the end of the first crystal column 211, and its growth will be based on new growth nuclei, and the grown second crystal column 221 is discontinuous with the second crystal column 221. The holes 202 of the first crystal column 211 and the holes 202 of the second crystal column 221 will also be staggered from each other, thereby greatly increasing the density of the insulating layer 2.

[0032] In one embodiment, in the step (2), the first thin film 21 is exposed to a high-temperature oxygen-containing atmosphere.

[0033] In another embodiment, in the step (2), the first thin film 21 is exposed to a high-temperature nitrogen-containing atmosphere. Embodiment

[0034] In the case where other parts are the same as those in the first embodiment, the difference lies in that: in the step (2), the surface of the first thin film 21 is modified by using an argon ion bombardment method. By bombarding the surface of the first thin film 21 with argon ions, the crystal structure inside the first crystal column 211 is damaged at the end to form a surface layer 201 different from the inside of the first crystal column 211, thereby generating a surface layer 201 different from the inside of the first crystal column 211.

[0035] In addition, it should be noted that for the specific embodiments described in this specification, the names of their respective parts and the like can be different. Any equivalent or simple changes made according to the structure, features, and principles described in the inventive concept of this invention patent are included in the protection scope of this invention patent. Those skilled in the art to which this invention pertains can make various modifications or supplements to the described specific embodiments or use similar methods for substitution, as long as they do not deviate from the structure of this invention or exceed the scope defined by this claim book, they should fall within the protection scope of this invention.

Claims

1. An oxide semiconductor thin film transistor with an improved insulating layer, comprising a gate and an insulating layer, as well as an active layer, a source electrode and a drain electrode arranged on a substrate, wherein the gate is covered by the insulating layer, the active layer, the source electrode and the drain electrode are all arranged on the insulating layer, and the source electrode and the drain electrode are arranged opposite to each other; Features: The insulating layer comprises a first film and a second film which are stacked, the first film is arranged on the substrate, the first film has a surface layer formed after modification, and the second film is grown on the surface layer of the first film; the first film and the second film are both insulating inorganic films, the first film is a polycrystalline structure composed of a plurality of first crystal columns, the second film is a polycrystalline structure composed of a plurality of second crystal columns, and each second crystal column is staggered with each first crystal column; and the insulating layer is manufactured by the following steps: Step (1) growing a first thin film consisting of a plurality of first crystal columns on a substrate through a first PVD process; Step (2) modifying the surface of the first film, destroying the ends of each first crystal column, and forming a surface layer; Step (3) growing a second thin film consisting of a plurality of second crystal columns on the surface layer of the first thin film through a second PVD process, and the second thin film and the first thin film formed by stacking form the insulating layer.

2. The oxide semiconductor thin film transistor with improved insulating layer according to claim 1, Features: The thin film transistor further comprises a protection layer, which covers the active layer, the source electrode and the drain electrode.

3. The oxide semiconductor thin film transistor with improved insulating layer according to claim 1, Features: The second film and the first film are homogeneous films.

4. The oxide semiconductor thin film transistor with improved insulating layer according to any one of claims 1 to 3, Features: In the step (2), reactive plasma is used to modify the surface of the first film.

5. The oxide semiconductor thin film transistor with improved insulating layer according to claim 4, Features: The first film obtained in step (1) is a metal oxide film; and in step (2), oxygen plasma is used to modify the surface of the first film.

6. The oxide semiconductor thin film transistor with improved insulating layer according to claim 4, Features: The first film prepared in step (1) is a metal nitride film; and in step (2), nitrogen plasma is used to modify the surface of the first film.

7. An oxide semiconductor thin film transistor with an improved insulating layer according to any one of claims 1 to 3, Features: In the step (2), the first film is exposed to a high-temperature reaction atmosphere, and the surface of the first film is modified by the high-temperature reaction atmosphere.

8. The oxide semiconductor thin film transistor with improved insulating layer according to claim 7, Features: In the step (2), the first film is exposed to a high temperature oxygen-containing atmosphere.

9. The oxide semiconductor thin film transistor with improved insulating layer according to claim 7, Features: In the step (2), the first thin film is exposed to a high-temperature nitrogen-containing atmosphere.

10. A thin film transistor of an oxide semiconductor with an improved insulating layer according to any one of claims 1-3, wherein: In the step (2), the surface of the first thin film is modified by argon ion bombardment.

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