BACKGROUND
1. Technical Field
The disclosure generally relates to display panel technologies; and more particularly, to a thin film transistor, a thin film transistor substrate and a method of manufacturing the thin film transistor substrate.
2. Description of Related Art
Generally, a channel layer of a thin film transistor is made of an amorphous oxide semiconductor. However, a density of oxygen ions in the channel layer is easily decreased during an etching process of a source electrode or a drain electrode of the thin film transistor. Therefore, electron mobility in the channel layer is adversely affected.
Thus it is desirable to provide a means which can overcome the above-mentioned problems.
BRIEF DESCRIPTION OF THE DRAWINGS
Many aspects of the disclosure can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the disclosure. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
FIG. 1 is a cross-sectional view of a thin film transistor substrate in accordance with an exemplary embodiment of the present disclosure, the thin film transistor substrate including a channel layer.
FIG. 2 is an enlarged view of a portion I of FIG. 1, showing a high oxygen ion concentration region in a lower part of the channel layer, according to a first example of the exemplary embodiment.
FIG. 3 is similar to FIG. 2, but showing a high oxygen ion concentration region in an upper part of the channel layer, according to a second example of the exemplary embodiment.
FIG. 4 is similar to FIGS. 2 and 3, but showing two high oxygen ion concentration regions in both a lower part and an upper part of the channel layer, according to a third example of the exemplary embodiment.
FIG. 5 is a flowchart of an exemplary embodiment of a method of manufacturing the thin film transistor substrate of FIG. 1.
FIGS. 6-24 are cross-sectional views of successive steps of the manufacturing method of FIG. 5, wherein FIGS. 17-19 respectively relate to the first, second and third examples of the exemplary embodiment.
DETAILED DESCRIPTION
The disclosure is illustrated by way of example and not by way of limitation in the figures of the accompanying drawings in which like references indicate similar elements. It should be noted that references to “an” or “one” embodiment in this disclosure are not necessarily to the same embodiment, and such references can mean “at least one.”
FIG. 1 shows an exemplary embodiment of a thin film transistor substrate 2. The thin film transistor substrate 2 includes a substratum 200, a gate electrode 211, a gate insulating layer 220, a channel layer 231, a source electrode 241, a drain electrode 242, a passivation layer 260, a connection hole (or via) 261, and an electrode pattern 271.
The gate electrode 211 is formed on the substratum 200. In the illustrated embodiment, the substratum 200 is transparent. The gate insulating layer 220 is formed on the substratum 200 to cover the gate electrode 211. The channel layer 231 is formed on the gate insulating layer 220 corresponding to the gate electrode 211. The source electrode 241 and the drain electrode 242 are correspondingly formed at two opposite sides of the channel layer 231, and are symmetrical about the gate electrode 211. The passivation layer 260 is formed on the gate insulating layer 220 to cover the source electrode 241, the channel layer 231 and the drain electrode 242. The connection hole 261 is defined in the passivation layer 260 corresponding to the drain electrode 242. The electrode pattern 271 is formed on the passivation layer 260, and is connected to the drain electrode 242 via the connection hole 261.
The channel layer 231 is made of an amorphous oxide semiconductor (AOS), such as Indium Gallium Zinc Oxide (IGZO).
FIG. 2 shows details of a first example of the thin film transistor substrate 2. The channel layer 231 includes a high oxygen ion concentration region A. An oxygen ion density of the high oxygen ion concentration region A is in a range of from about 1×1018 to about 1×1021 per cubic centimeter. The high oxygen ion concentration region A is defined at a portion of the channel layer 231 which is adjacent to the gate insulating layer 220, and corresponds to the gate electrode 211. A thickness of the high oxygen ion concentration region A is substantially equal to or less than half of a thickness of the channel layer 231.
FIG. 3 shows details of a second example of the thin film transistor substrate 2. The channel layer 231 includes a high oxygen ion concentration region B. An oxygen ion density of the high oxygen ion concentration region B is in a range of from about 1×1018 to about 1×1021 per cubic centimeter. The high oxygen ion concentration region B is defined in a top part of the channel layer 231 far away from the gate insulating layer 220.
FIG. 4 shows details of a third example of the thin film transistor substrate 2. The channel layer 231 includes a high oxygen ion concentration region A and a high oxygen ion concentration region B. An oxygen ion density of each of the high oxygen ion concentration regions A and B is in a range of from about 1×1018 to about 1×1021 per cubic centimeter. The high oxygen ion concentration region A is defined at a portion of the channel layer 231 which is adjacent to the gate insulating layer 220, and corresponds to the gate electrode 211. A thickness of the high oxygen ion concentration region A is substantially equal to or less than half of a thickness of the channel layer 231. The high oxygen ion concentration region B is defined in a top part of the channel layer 231 far away from the gate insulating layer 220. A sum of the thicknesses of the high oxygen ion concentration regions A and B is less than the thickness of the channel layer 231.
Because the channel layer 231 is made of amorphous oxide semiconductor, the electron mobility of the channel layer 231 is dependent upon the oxygen ion density of the channel layer 231. In general, an amorphous oxide semiconductor has maximum electron mobility when the oxygen ion density of the amorphous oxide semiconductor is in a range of from about 1×1018 to about 1×1021 per cubic centimeter.
Thus, because the oxygen ion density in the high oxygen ion concentration regions A and B of the channel layer 231 in the above-described examples is in a range of from about 1×1018 to about 1×1021 per cubic centimeter, the channel layer 231 has maximum electron mobility.
The thin film transistor substrate 2 further includes conventionally known scan lines and data lines.
FIG. 5 is a flowchart of an exemplary embodiment of a method of manufacturing the thin film transistor substrate. Depending on the embodiment, additional steps may be added, others deleted, and the ordering of the steps may be changed.
In step S101, a substratum 200 is provided, and a gate electrode 211 is formed on the substratum 200. In detail, FIG. 6 shows the substratum 200, and a first metal layer 210 formed on the substratum 200. The substratum 200 is made of transparent material, such as glass, quartz, organic material or polymer. The first metal layer 210 is made of elemental metal, alloy, metallic oxide or metallic nitride. Referring to FIG. 7, after the first metal layer 210 has been formed on the substratum 200, the gate electrode 211 is defined by patterning the first metal layer 210 using a photoresist etching process. Moreover, the scan lines are also defined by patterning the first metal layer 210 using the photoresist etching process.
In step S102, a gate insulating layer 220 is formed on the substratum 200 to cover the gate electrode 211. In detail, FIG. 8 shows that the gate insulating layer 220 is deposited on the substratum 200 and the gate electrode 211. The gate insulating layer 220 is made of inorganic material or organic material. The gate insulating layer 220 is deposited by a plasma chemical vapor deposition process.
In step S103, a channel layer 231 is formed on the gate insulating layer 220 corresponding to the gate electrode 211. In detail, FIG. 9 shows that an amorphous oxide semiconductor (AOS) layer 230 is deposited on the gate insulating layer 220. The AOS layer 230 is made of, for example, Indium Gallium Zinc Oxide (IGZO). Referring to FIG. 10, after the AOS layer 230 has been deposited on the gate insulating layer 220, the position of the channel layer 231 is defined by patterning the AOS layer 230 using a photoresist etching process.
In step S104, a second metal layer 240 is formed on the gate insulating layer 220 covering the channel layer 231, and a photoresist layer 250 is formed on the second metal layer 240. In detail, FIG. 11 shows that the second metal layer 240 is formed on the gate insulating layer 220 covering the channel layer 231. The second metal layer 240 is made of elemental metal, alloy, metallic oxide or metallic nitride. Referring to FIG. 12, after the second metal layer 240 has been formed, the photoresist layer 250 is formed on the second metal layer 240. In the illustrated embodiment, the photoresist layer 250 is positive photoresist. In other embodiments, the photoresist layer 250 can be a selected negative photoresist.
In step S105, a source electrode 241 and a drain electrode 242 are formed by patterning the photoresist layer 250 and etching the second metal layer 240. The source electrode 241 and the drain electrode 242 are correspondingly formed at two opposite sides of the channel layer 231, and are symmetrical about the gate electrode 211. In detail, FIG. 13 shows exposing the photoresist layer 250 to light from a light source, while shielding particular positions of the photoresist layer 250 from the light by using a mask 300. Then after the exposing process, referring to FIG. 14, the photoresist layer 250 is developed. In detail, the portion of the photoresist layer 250 exposed to the light is removed. Referring to FIG. 15, after the developing process, a portion of the second metal layer 240 not covered by the remaining photoresist layer 250 is etched. Thus the source electrode 241 and the drain electrode 242 are formed under the remaining photoresist layer 250. Moreover, the data lines are defined by the same etching process along with the forming of the source electrode 241 and the drain electrode 242.
In step S106, referring to FIG. 16, oxygen ions are implanted into a portion of the channel layer 231. Because the channel layer 231 is made of amorphous oxide semiconductor, the electron mobility of the channel layer 231 is dependent upon the oxygen ion density thereof. In general, an amorphous oxide semiconductor has maximum electron mobility when the oxygen ion density of the amorphous oxide semiconductor is in a range of from about 1×1018 to about 1×1021 per cubic centimeter. However, a density of oxygen ions in the channel layer 231 is easily decreased during an etching process. Therefore the electron mobility in the channel layer 231 is adversely affected, and the cut off current and the threshold voltage of the finally-formed thin film transistor substrate 2 are liable to be unstable.
Thus, oxygen ions are implanted into a portion of the channel layer 231 to improve the oxygen ion concentration of the channel layer 231. The depth of the implanted oxygen ions can be controlled by modulating an implantation energy of the implanting process.
The depth of the implanted ions can be selected for any position of the channel layer 231 according to need. FIG. 17 shows that oxygen ions can be implanted into a portion of the channel layer 231 adjacent to the gate insulating layer 220 and corresponding to the gate electrode 211, in order to form a high oxygen ion concentration region A whose oxygen ion concentration is not easily adversely affected. A thickness of the high oxygen ion concentration region A is substantially equal to or less than half of a thickness of the channel layer 231. An oxygen ion density of the high oxygen ion concentration region A is in a range of from about 1×1018 to about 1×1021 per cubic centimeter.
FIG. 18 shows that oxygen ions can be implanted in a top part of the channel layer 231 away from the gate insulating layer 220, in order to form a high oxygen ion concentration region B. The high oxygen ion concentration region B protects the channel layer 231 from damage while forming a passivation layer 260 after the implanting process (see below). An oxygen ion density of the high oxygen ion concentration region B is in a range of from about 1×1018 to about 1×1021 per cubic centimeter.
FIG. 19 shows that oxygen ions can be implanted in both a high oxygen ion concentration region A and a high oxygen ion concentration region B. The high oxygen ion concentration region A is defined at a portion of the channel layer 231 which is adjacent to the gate insulating layer 220, and corresponds to the gate electrode 211. The high oxygen ion concentration region B is defined in a top part of the channel layer 231 away from the gate insulating layer 220. A thickness of the high oxygen ion concentration region A is substantially equal to or less than half of a thickness of the channel layer 231. An oxygen ion density of each of the high oxygen ion concentration regions A and B is in a range of from about 1×1018 to about 1×1021 per cubic centimeter.
In all the above-described examples shown in FIGS. 17-19, the implanted ions are focused on the portion of the channel layer 231 which is not covered by the photoresist layer 250 or the source or drain electrodes 241, 242.
In step S107, referring to FIG. 20 and FIG. 21, the photoresist layer 250 is removed, and then the passivation layer 260 is formed on the gate insulating layer 220 and covers the source electrode 241, the channel layer 231 and the drain electrode 242. The passivation layer 260 is made of inorganic material or organic material, and serves as an insulating layer.
In step S108, referring to FIG. 22 through FIG. 24, a connection hole 261 is defined in the passivation layer 260 corresponding to the drain electrode 242, and an electrode pattern 271 is formed on the passivation layer 260 including in the connection hole 261. The electrode pattern 271 is connected to the drain electrode 242 via the connection hole 261. The position of the connection hole 261 is defined by patterning the passivation layer 260 using a photoresist etching process. In detail, an electrode layer 270 is deposited on the passivation layer 260 including in the connection hole 261. The electrode layer 270 is made of a transparent conducting material, such as Indium Tin Oxide (ITO) or Indium Zinc Oxide (IZO). After the electrode layer 270 has been deposited, the electrode pattern 271 is defined by patterning the electrode layer 270 using a photoresist etching process. The present thin film transistor substrate 2 is thus obtained.
It is believed that the present embodiments and their advantages will be understood from the foregoing description, and it will be apparent that various changes may be made thereto without departing from the spirit and scope of the disclosure or sacrificing all of its material advantages, the examples hereinbefore described merely being preferred or exemplary embodiments of the disclosure.
Patent Grant
9117922
