WO2017168594A1 - Thin film transistor, display panel, and method for manufacturing thin film transistor - Google Patents

Abstract

Provided are: a thin film transistor enabling to improve optical stability; a display panel that is provided with the thin film transistor; and a method for manufacturing the thin film transistor. A thin film transistor of the present invention is provided with: a gate electrode film formed on the front surface of a substrate; an amorphous oxide semiconductor film formed on the upper side of the gate electrode film; first and second low-resistance oxide semiconductor films formed by having the amorphous oxide semiconductor film therebetween; a source electrode film formed on the first low-resistance oxide semiconductor film; and a drain electrode film formed on the second low-resistance oxide semiconductor film. The amorphous oxide semiconductor film is disposed in a region corresponding to the gate electrode film in a projection state wherein the gate electrode film and the amorphous oxide semiconductor film are projected on the front surface of the substrate.

Description

Thin film transistor, display panel, and method of manufacturing thin film transistor

The present invention relates to a thin film transistor, a display panel including the thin film transistor, and a method for manufacturing the thin film transistor.

A TFT (thin film transistor) type liquid crystal display (display panel) has a required gap between a TFT substrate and a color filter substrate having colors of R (red), G (green), and B (blue). The image can be displayed by bonding, injecting liquid crystal between the TFT substrate and the color filter substrate, and controlling the light transmittance of the liquid crystal molecules for each pixel.

On the TFT substrate, data lines and scanning lines are arranged in a grid pattern in the vertical and horizontal directions, and pixels in which TFTs are arranged at respective locations where the data lines and the scanning lines intersect are formed. In addition, a driving circuit for driving the data lines and the scanning lines is formed around a display area including a plurality of pixels.

As the TFT, amorphous silicon (amorphous, a-Si) TFT using a silicon semiconductor, low-temperature polysilicon TFT using a semiconductor layer of polysilicon (polycrystalline, p-Si), and the like are being developed. On the other hand, in recent years, research on TFTs using oxide semiconductors has been actively conducted. A TFT using an oxide semiconductor has advantages of higher electron mobility than an amorphous silicon TFT and less leakage current than a silicon semiconductor.

Conventionally, a TFT using an oxide semiconductor (also referred to as an oxide semiconductor TFT) is configured so that the region of the gate electrode film and the region of the source / drain electrode film do not overlap in the thickness direction of the TFT. The self-alignment type (self-alignment) that has improved characteristics such as reduction has been attracting attention. For example, in a bottom gate type oxide semiconductor TFT in which a gate electrode film is disposed in the lowermost layer, a region of the oxide semiconductor layer (source / drain region) that does not overlap with the gate electrode film when irradiated with predetermined light from the back side of the substrate An oxide semiconductor TFT is disclosed in which the resistance is reduced to improve the characteristics (see Patent Document 1).

JP 2014-140005 A

However, in the conventional self-aligned oxide semiconductor TFT, the region that does not overlap the gate electrode film region is a low-resistance oxide semiconductor layer, but the region that overlaps the gate electrode film region is amorphous (non- (Crystalline). Therefore, when backlight light is incident from the back side of the substrate, the backlight light is easily incident on the amorphous oxide semiconductor layer corresponding to the channel region above the gate electrode film. become. For this reason, at the time of light irradiation, for example, there is a problem that characteristic fluctuation such as a relatively large shift of the threshold voltage of the gate voltage occurs and the light stability is lacking.

The present invention has been made in view of such circumstances, and an object thereof is to provide a thin film transistor capable of improving light stability, a display panel including the thin film transistor, and a method for manufacturing the thin film transistor.

A thin film transistor according to an embodiment of the present invention includes a gate electrode film formed on a surface of the substrate and an amorphous oxide formed on the gate electrode film in the thin film transistor having an oxide semiconductor film on the substrate. A material semiconductor film, first and second low-resistance oxide semiconductor films formed with the amorphous oxide semiconductor film in between, and a source electrode formed on the first low-resistance oxide semiconductor film An amorphous oxide semiconductor film between the first and second low resistance oxide semiconductor films, and a drain electrode film formed on the second low resistance oxide semiconductor film. The gate electrode film and the amorphous oxide semiconductor film are arranged in a region corresponding to the gate electrode film in a projected state in which the gate electrode film and the amorphous oxide semiconductor film are projected onto the surface of the substrate.

A display panel according to an embodiment of the present invention includes the thin film transistor according to the above-described embodiment.

A method for manufacturing a thin film transistor according to an embodiment of the present invention includes a method for manufacturing a thin film transistor having an oxide semiconductor film on a substrate, wherein a gate electrode film is formed on a surface of the substrate, and an amorphous material is formed on the gate electrode film. When forming the oxide semiconductor film, the gate electrode film and the amorphous oxide semiconductor film are projected onto the surface of the substrate, and the amorphous oxide semiconductor film is used as the gate electrode film. A first and second low resistance oxide semiconductor films are formed by irradiating an energy beam to a required portion of the amorphous oxide semiconductor film which is formed in a corresponding region, and the first low resistance oxidation semiconductor film is formed. A source electrode film is formed on the physical semiconductor film, and a drain electrode film is formed on the second low-resistance oxide semiconductor film.

According to the present invention, light stability can be improved.

It is a principal part plane schematic diagram which shows an example of the structure of the thin-film transistor of 1st Embodiment. FIG. 2 is a schematic cross-sectional view of a main part viewed from the line II-II in FIG. It is a manufacturing process figure which shows an example of the manufacturing method of the thin-film transistor of 1st Embodiment. It is a schematic diagram which shows an example of a structure of a partial irradiation type laser. It is a schematic diagram which shows an example of the mode at the time of light irradiation of the thin-film transistor of 1st Embodiment. It is a schematic diagram which shows an example of the characteristic fluctuation | variation of the thin-film transistor of 1st Embodiment. It is a schematic diagram which shows an example of the characteristic fluctuation | variation of the conventional thin-film transistor. It is a principal part plane schematic diagram which shows an example of the structure of the thin-film transistor of 2nd Embodiment. It is a schematic diagram which shows an example of the drain current-gate voltage characteristic of the thin-film transistor of 2nd Embodiment. It is a principal part plane schematic diagram which shows an example of the structure of the thin-film transistor of 3rd Embodiment. It is a schematic diagram showing an example of drain current-gate voltage characteristics of a thin film transistor used in the GOA circuit section.

(First embodiment)
Hereinafter, the present invention will be described with reference to the drawings illustrating embodiments thereof. FIG. 1 is a schematic plan view of an essential part showing an example of the structure of the thin film transistor of the first embodiment, and FIG. As shown in FIGS. 1 and 2, a thin film transistor (TFT: Thin Film Transistor, also referred to as a TFT substrate) has a gate electrode film 2 formed on the surface of a glass substrate 1 (also referred to as a substrate). A gate insulating film 3 (for example, a SiO ₂ film) is formed so as to cover the surface.

On the surface of the gate insulating film 3 and above the gate electrode film 2, an amorphous oxide semiconductor film 4 and a first low-resistance oxide semiconductor film 5 with the amorphous oxide semiconductor film 4 interposed therebetween. The second low-resistance oxide semiconductor film 6 is formed. The amorphous oxide semiconductor film 4 is an amorphous (amorphous) oxide semiconductor film. The low resistance oxide semiconductor films 5 and 6 are oxide semiconductor films having a lower resistance than the amorphous oxide semiconductor film 4 due to oxygen deficiency caused by energy beam irradiation and increase of free electrons. For example, an oxide semiconductor film including crystals or an oxide semiconductor film having crystallinity may be used. The crystal state may be a state in which the directions of crystal axes are disordered or a state having a certain orientation.

The oxide semiconductor film (4, 5, 6) is, for example, an oxide of three elements of indium (In), gallium (Ga), and zinc (Zn), but is not limited to this. In addition, an oxide containing at least one element from elements such as gallium, zinc, tin, aluminum, silicon, germanium, titanium, molybdenum, boron, and manganese can also be used.

A source electrode film 7 is formed on the first low-resistance oxide semiconductor film 5. A drain electrode film 8 is formed on the second low resistance oxide semiconductor film 6. Note that the first low-resistance oxide semiconductor film 5 and the second low-resistance oxide semiconductor film 6 are also referred to as low-resistance oxide semiconductor films 5 and 6, respectively. Further, an etch stopper film as a protective film is formed after or before the formation of the first low-resistance oxide semiconductor film 5, the second low-resistance oxide semiconductor film 6, and the amorphous oxide semiconductor film 4. May be.

A passivation film 9 is formed on the entire TFT substrate so as to cover the source electrode film 7 and the drain electrode film 8, and an organic film 10 is formed on the surface of the passivation film 9 to flatten the surface. . Through holes are formed at required positions of the passivation film 9 and the organic film 10 so that the transparent conductive film (for example, ITO) 11 and the drain electrode film 8 are electrically connected through the through holes. A pixel electrode (not shown) is connected to the transparent conductive film 11.

FIG. 1 shows a gate electrode film 2, an amorphous oxide semiconductor film 4, a first low resistance oxide semiconductor film 5, a second low resistance oxide semiconductor film 6, a source electrode film 7 and a drain electrode film 8. The projection state projected on the surface of the substrate 1 is schematically shown. 1 shows a region on the substrate 1 corresponding to the gate electrode film 2, a region on the substrate 1 corresponding to the amorphous oxide semiconductor film 4, and the substrate 1 corresponding to the low-resistance oxide semiconductor films 5 and 6. An upper region, a region on the substrate 1 corresponding to the source electrode film 7 and a region on the substrate 1 corresponding to the drain electrode film 8 are schematically shown. In FIG. 1, reference numeral 21 denotes a wiring portion to the gate electrode film. In addition, the shape of each area | region shown in FIG. 1 is shown typically for convenience, and an actual shape may differ.

As shown in FIG. 1, in the thin film transistor of this embodiment, in the projection state in which the gate electrode film 2 and the amorphous oxide semiconductor film 4 are projected onto the surface of the substrate 1, the amorphous oxide semiconductor film 4 is It is arranged in a region corresponding to the gate electrode film 2. The amorphous oxide semiconductor film 4 between the first low-resistance oxide semiconductor film 5 and the second low-resistance oxide semiconductor film 6 is also disposed in a region corresponding to the gate electrode film 2. .

FIG. 3 is a manufacturing process diagram showing an example of a manufacturing method of the thin film transistor of the first embodiment. Hereinafter, a manufacturing process of the thin film transistor of this embodiment will be described. As shown in FIG. 3, an aluminum (Al) film is formed on a substrate (glass substrate) 1 using a sputtering method, and the aluminum (Al) film is patterned using a photolithography method and an etching method. A gate electrode film 2 having a width of is formed (S11). The material used for the gate electrode film 2 is not limited to aluminum, and for example, elemental elements such as copper, titanium, tungsten, gold, platinum, molybdenum, or nickel, or alloys thereof may be used.

Next, the gate insulating film 3 is formed on the substrate 1 using the plasma CVD method so as to cover the gate electrode film 2 (S12).

Next, an oxide semiconductor film is formed on the gate insulating film 3 by using a sputtering method (S13). This oxide semiconductor film is the amorphous oxide semiconductor film 4 and is formed, for example, in an environment below a temperature at which the oxide semiconductor has a low resistance. Note that as a method for forming the above-described oxide semiconductor film or the like, other film formation methods such as a pulsed laser deposition method, an electron beam deposition method, or a coating deposition method may be used instead of the sputtering method.

Next, partial laser annealing is performed by irradiating a required portion of the amorphous oxide semiconductor film 4 with an energy beam such as an excimer laser (S14). In the partial laser annealing, a required portion (for example, a portion indicated by reference numerals 5 and 6 in FIGS. 1 and 2) of the amorphous oxide semiconductor film 4 is changed to the low resistance oxide semiconductor films 5 and 6. The required portion is a region corresponding to the source region and the drain region in the amorphous oxide semiconductor film 4 formed on the gate insulating film 3.

Next, exposure processing and development processing are performed (S15), and a required pattern is formed on the amorphous oxide semiconductor film 4 and the low-resistance oxide semiconductor films 5 and 6. The required pattern can be appropriately determined according to the arrangement or structure of the source electrode film 7, the drain electrode film 8, and the semiconductor layer.

Next, required portions such as the amorphous oxide semiconductor film 4 and the low resistance oxide semiconductor films 5 and 6 are etched (S16), and the source electrode film is formed on the low resistance oxide semiconductor films 5 and 6 after the etching. 7 and the drain electrode film 8 are formed (S17). The source electrode film 7 and the drain electrode film 8 are often formed at the same time.

FIG. 4 is a schematic diagram showing an example of the configuration of a partial irradiation type laser. As shown in FIG. 4, the substrate 1 on which the amorphous oxide semiconductor film 4 is formed is placed on a mounting table (not shown) so as to translate in the direction of the arrow in FIG. 4 at a required speed. It is. Above the substrate 1, a multi-lens array is arranged in which individual lenses are arranged at an appropriate distance along a direction intersecting the moving direction of the substrate 1. By making a laser beam from a laser light source (not shown) enter the multi-lens array, the laser beam is partially irradiated to a plurality of required locations separated via different optical paths for each lens. That is, partial laser annealing can be performed. Thereby, only a required region of the amorphous oxide semiconductor film 4 can be selectively changed to the low resistance oxide semiconductor films 5 and 6. Although not shown in FIG. 4, a laser mask (light-shielding member) is disposed between the laser light source and the multi-lens array or between the multi-lens array and the substrate 1. The beam shape of the laser beam can be shaped into, for example, a rectangular shape or a required size by the mask.

That is, in the thin film transistor of this embodiment, the first low-resistance oxide semiconductor film 5 and the second low-resistance oxide semiconductor film 6 are amorphous oxides formed on the upper side of the gate electrode film 2. It is formed by irradiating an energy beam (for example, an energy beam of an excimer laser or the like) to a required separated portion of the physical semiconductor film 4. The required portion is a region corresponding to the source region and the drain region in the amorphous oxide semiconductor film 4, and the amorphous oxide semiconductor film 4 is reduced to a low-resistance oxide semiconductor film 5 by irradiation with an energy beam. , 6 can be changed.

In the case of a conventional self-aligned thin film transistor, for example, the entire surface of the substrate is irradiated with laser light, so that the laser light is blocked by the gate electrode film. The region of the amorphous oxide semiconductor film above the gate electrode film and corresponding to the region of the gate electrode film is not irradiated with laser light, so that the resistance is not lowered and remains amorphous.

In contrast, in the case of the thin film transistor of the present embodiment, an energy beam (for example, a laser) is locally (or partially) applied to a required portion of the amorphous oxide semiconductor film 4 formed on the upper side of the gate electrode film 2. The low-resistance oxide semiconductor films 5 and 6 can be formed so that the amorphous oxide semiconductor film 4 is disposed in a region corresponding to the gate electrode film 2. .

In the case of a conventional self-aligned thin film transistor, the entire surface is irradiated with laser light from the back side of the substrate, so the laser light is irradiated to all locations, such as the gate electrode film, the tapered portion of the gate electrode film, and the opening. It is difficult to obtain uniform crystallinity due to non-uniformity of the intensity distribution of laser light or variations in intensity for each irradiation.

On the other hand, in the case of the thin film transistor of this embodiment, the resistance can be reduced by focusing only on a required portion of the amorphous oxide semiconductor film 4 on the upper side of the gate electrode film 2, so that the variation in resistance reduction is small. A display panel with high reliability can be manufactured.

FIG. 5 is a schematic view showing an example of the state of the thin film transistor according to the first embodiment during light irradiation. FIG. 5 shows how the light from the backlight is incident from the back side of the substrate 1. For convenience, a part of the configuration shown in FIG. 2 is omitted. As described above, the thin film transistor of this embodiment includes the first low-resistance oxide corresponding to the channel region in a projected state in which the gate electrode film 2 and the amorphous oxide semiconductor film 4 are projected onto the surface of the substrate 1. The amorphous oxide semiconductor film 4 between the semiconductor film 5 and the second low resistance oxide semiconductor film 6 is disposed in a region corresponding to the gate electrode film 2.

As shown in FIG. 5, when backlight light (indicated by an arrow in FIG. 5) is incident from the back side of the substrate 1, the backlight light is oblique with respect to the surface of the substrate 1 and the gate electrode Even if it is incident on the upper side of the film 2, the amorphous oxide semiconductor film 4 corresponding to the channel region is disposed in the region corresponding to the gate electrode film 2, so that the amorphous oxide semiconductor film The light incident on 4 can be reduced.

FIG. 6 is a schematic diagram illustrating an example of characteristic variation of the thin film transistor of the first embodiment, and FIG. 7 is a schematic diagram illustrating an example of characteristic variation of the conventional thin film transistor. 6 and 7, the horizontal axis represents the gate voltage, and the vertical axis represents the drain current. In addition, the arrows in the figure indicate the passage of time from the start of applying a positive or negative voltage under a light irradiation environment (also referred to as an optical bias stress state).

As shown in FIG. 6, the initial drain current-gate voltage characteristics of the thin film transistor according to the present embodiment are as shown by the graph indicated by symbol A. As time elapses in the optical bias stress state, symbols B and C indicate the time. It changes as follows. That is, as shown in FIG. 5, light incident on the amorphous oxide semiconductor film 4 corresponding to the channel region can be reduced. Therefore, as shown in FIG. The shift of the threshold voltage of the gate voltage can be reduced, and light stability can be improved.

On the other hand, in the case of a conventional self-aligned thin film transistor, the oxide semiconductor film immediately above the gate electrode film is an amorphous oxide semiconductor film without being reduced in resistance. Therefore, when backlight light is incident from the back side of the substrate, the backlight light is easily incident on the amorphous oxide semiconductor film on the upper side of the gate electrode film. As shown in FIG. 7, the initial drain current-gate voltage characteristic of the conventional thin film transistor is as shown by a graph indicated by symbol a, and changes with time elapse in an optical bias stress state as indicated by symbols b and c. . That is, in the optical bias stress state, for example, characteristic variation such as a relatively large shift of the threshold voltage of the gate voltage occurs, resulting in lack of light stability. Note that the threshold voltage shift is considered to be caused by oxygen vacancies generated at the channel-gate insulating film interface.

(Second Embodiment)
FIG. 8 is a schematic plan view of an essential part showing an example of the structure of the thin film transistor of the second embodiment. In the thin film transistor of the second embodiment, the first low-resistance oxide semiconductor film 51, the amorphous oxide semiconductor film 4 formed on the upper side of the gate electrode film 2, and the source electrode film 7 are projected onto the surface of the substrate 1. In the projected state, the area of the region where the source electrode film 7 and the first low-resistance oxide semiconductor film 51 overlap (the region marked with a pattern in FIG. 8) is the same as that of the source electrode film 7 and the amorphous oxide semiconductor film. 4 is larger than the area of a region where 4 overlaps (region indicated by reference numeral 41 in FIG. 8).

Most of the low-resistance oxide semiconductor film 51 immediately below the source electrode film 7 (a region overlapping with the source electrode film 7) does not form a channel region but has a parasitic resistance. Therefore, by making the area of the low-resistance oxide semiconductor film 51 immediately below the source electrode film 7 larger than the area of the amorphous oxide semiconductor film 41 immediately below the source electrode film 7, in the region directly below the source electrode film 7. The ratio of the region occupied by the low-resistance oxide semiconductor film 51 can be increased, the parasitic resistance can be lowered, and the current driving capability can be increased. In FIG. 8, the entire region of the amorphous oxide semiconductor film 41 immediately below the source electrode film 7 may be the low resistance oxide semiconductor film 51. In this case, the ratio of the region occupied by the low-resistance oxide semiconductor film 51 in the region immediately below the source electrode film 7 is 100%.

Further, in the projection state in which the second low-resistance oxide semiconductor film 61, the amorphous oxide semiconductor film 4 formed on the gate electrode film 2 and the drain electrode film 8 are projected onto the surface of the substrate 1, the drain electrode The area of the region where the film 8 and the second low-resistance oxide semiconductor film 61 overlap (the region with a pattern in FIG. 8) overlaps the region where the drain electrode film 8 and the amorphous oxide semiconductor film 4 overlap ( In FIG. 8, the area is larger than the area indicated by reference numeral 42.

Most of the low-resistance oxide semiconductor film 61 immediately below the drain electrode film 8 (region overlapping with the drain electrode film 8) does not form a channel region and has a parasitic resistance. Therefore, by making the area of the low-resistance oxide semiconductor film 61 immediately below the drain electrode film 8 larger than the area of the amorphous oxide semiconductor film 42 immediately below the drain electrode film 8, in the area directly below the drain electrode film 8. By increasing the ratio of the region occupied by the low-resistance oxide semiconductor film 61, the parasitic resistance can be lowered and the current driving capability can be increased. In FIG. 8, the entire region of the amorphous oxide semiconductor film 42 immediately below the drain electrode film 8 may be the low resistance oxide semiconductor film 61. In this case, the ratio of the region occupied by the low-resistance oxide semiconductor film 61 in the region immediately below the drain electrode film 8 is 100%.

FIG. 9 is a schematic diagram showing an example of drain current-gate voltage characteristics of the thin film transistor of the second embodiment. In FIG. 9, the horizontal axis represents the gate voltage, and the vertical axis represents the drain current. As shown in FIG. 9, by increasing the region of the low-resistance oxide semiconductor films 51 and 61 on at least one side of the source electrode film 7 side or the drain electrode film 8 side, the resistance can be lowered and the drain current can be reduced. Can be increased. In addition, the value of the parasitic resistance can be controlled by controlling the width (for example, area) of the regions of the low-resistance oxide semiconductor films 51 and 61. The description of the same parts as those in the first embodiment is omitted.

(Third embodiment)
FIG. 10 is a schematic plan view of an essential part showing an example of the structure of the thin film transistor of the third embodiment. The thin film transistor shown in FIG. 10 is used, for example, in a GOA (Gate Driver On Array) circuit section. As shown in FIG. 10, the gate electrode film 2 having a rectangular shape in plan view is provided on the substrate, and the elongated amorphous oxide semiconductor film 4 and the elongated shape are formed in a region corresponding to the gate electrode film 2. The low resistance oxide semiconductor films 5 and 6 are arranged in order. A source electrode film 7 is formed on the first low resistance oxide semiconductor film 5, and a drain electrode film 8 is formed on the second low resistance oxide semiconductor film 6.

That is, the thin film transistor according to the third embodiment is in a projected state in which the gate electrode film 2, the first low-resistance oxide semiconductor film 5, and the second low-resistance oxide semiconductor film 6 are projected onto the surface of the substrate 1. The low resistance oxide semiconductor film 5 and the second low resistance oxide semiconductor film 6 are disposed in a region corresponding to the gate electrode film 2.

In the case of a conventional self-aligned thin film transistor, for example, the entire surface of the substrate is irradiated with laser light, so that the laser light is blocked by the gate electrode film. Therefore, the region of the amorphous oxide semiconductor film above the gate electrode film and corresponding to the region of the gate electrode film is not irradiated with laser light, so that the resistance cannot be reduced.

On the other hand, in the case of the thin film transistor of the third embodiment, as in the first embodiment and the second embodiment, a local (or a local) (or a local area) is formed on a required portion of the amorphous oxide semiconductor film 4 formed above the gate electrode film 2. Since an energy beam (for example, a laser beam) can be irradiated partially, the low-resistance oxide semiconductor films 5 and 6 can be formed at required positions in the region corresponding to the gate electrode film 2.

FIG. 11 is a schematic diagram showing an example of drain current-gate voltage characteristics of a thin film transistor used in the GOA circuit section. In FIG. 11, the horizontal axis represents the gate voltage, and the vertical axis represents the drain current. A graph indicated by a symbol D indicates characteristics when the thin film transistor of the present embodiment is used in the GOA circuit portion, and a graph indicated by the symbol d indicates characteristics when a self-aligned thin film transistor is used in the GOA circuit portion. Indicates. As shown in FIG. 11, in this embodiment, the resistance of the oxide semiconductor can be reduced in the GOA (Gate Driver On Array) circuit portion in which the oxide semiconductor film is formed inside the gate electrode film. Compared with a GOA circuit portion using a conventional self-aligned thin film transistor using an amorphous oxide semiconductor film, the current driving capability can be increased.

The thin film transistor of each of the above embodiments can be used for a display panel. That is, the thin film transistor (TFT substrate) of each embodiment and a color filter substrate having colors of R (red), G (green), and B (blue) are bonded to each other with a necessary gap, and the TFT substrate and the color filter are bonded. By injecting liquid crystal between the substrate and the substrate, a TFT liquid crystal display panel (liquid crystal display) can be manufactured. Thus, a display panel including a thin film transistor that can improve light stability can be realized.

(1) The thin film transistor of this embodiment is a thin film transistor having an oxide semiconductor film on a substrate, a gate electrode film formed on the surface of the substrate, and an amorphous oxide formed on the gate electrode film. A material semiconductor film, first and second low-resistance oxide semiconductor films formed with the amorphous oxide semiconductor film in between, and a source electrode formed on the first low-resistance oxide semiconductor film An amorphous oxide semiconductor film between the first and second low resistance oxide semiconductor films, and a drain electrode film formed on the second low resistance oxide semiconductor film. The gate electrode film and the amorphous oxide semiconductor film are arranged in a region corresponding to the gate electrode film in a projected state in which the gate electrode film and the amorphous oxide semiconductor film are projected onto the surface of the substrate.

(7) The method for manufacturing a thin film transistor of this embodiment is a method for manufacturing a thin film transistor having an oxide semiconductor film on a substrate, in which a gate electrode film is formed on the surface of the substrate, and an amorphous film is formed above the gate electrode film. When forming the oxide semiconductor film, the gate electrode film and the amorphous oxide semiconductor film are projected onto the surface of the substrate, and the amorphous oxide semiconductor film is used as the gate electrode film. A first and second low resistance oxide semiconductor films are formed by irradiating an energy beam to a required portion of the amorphous oxide semiconductor film which is formed in a corresponding region, and the first low resistance oxidation semiconductor film is formed. A source electrode film is formed on the physical semiconductor film, and a drain electrode film is formed on the second low-resistance oxide semiconductor film.

In the thin film transistor and the thin film transistor manufacturing method of the present embodiment, the gate electrode film formed on the surface of the substrate, the amorphous oxide semiconductor film formed on the gate electrode film, the amorphous oxide First and second low-resistance oxide semiconductor films formed with a physical semiconductor film interposed therebetween, and a source electrode film and a second low-resistance oxide semiconductor formed on the first low-resistance oxide semiconductor film A drain electrode film formed on the film. The amorphous oxide semiconductor film is an amorphous (amorphous) oxide semiconductor film. The low-resistance oxide semiconductor film is an oxide semiconductor film having a lower resistance than an amorphous oxide semiconductor film because oxygen vacancies are generated by energy beam irradiation and free electrons increase.

In the projected state in which the gate electrode film and the amorphous oxide semiconductor film are projected onto the surface of the substrate, the amorphous oxide semiconductor film (for example, in the channel region) between the first and second low-resistance oxide semiconductor films. The corresponding amorphous oxide semiconductor film) is disposed in a region corresponding to the gate electrode film. When backlight light is incident from the back side of the substrate, even if the backlight light is incident obliquely with respect to the surface of the substrate and toward the upper side of the gate electrode film, the amorphous oxide semiconductor film Is disposed in a region corresponding to the gate electrode film, so that light incident on the amorphous oxide semiconductor film can be reduced. Thereby, at the time of light irradiation, for example, the shift of the threshold voltage of the gate voltage can be reduced, and the light stability can be improved.

(2) In the thin film transistor of this embodiment, the first and second low resistance oxide semiconductor films are energized at a required separated position of the amorphous oxide semiconductor film formed on the upper side of the gate electrode film. It is formed by irradiating a beam.

In the thin film transistor of this embodiment, the first and second low-resistance oxide semiconductor films are provided with energy beams (in the required positions separated from the amorphous oxide semiconductor film formed above the gate electrode film). For example, it is formed by irradiation with an energy beam such as an excimer laser. The required part is a region corresponding to the source region and the drain region in the amorphous oxide semiconductor film, and the amorphous oxide semiconductor film is changed to a low-resistance oxide semiconductor film by irradiation with an energy beam. Can do.

In the case of a conventional self-aligned thin film transistor, for example, the entire surface of the substrate is irradiated with laser light, so that the laser light is blocked by the gate electrode film. The region of the amorphous oxide semiconductor film above the gate electrode film and corresponding to the region of the gate electrode film is not irradiated with laser light, so that the resistance is not lowered and remains amorphous.

On the other hand, in the case of the thin film transistor of this embodiment, an energy beam (for example, laser light) is irradiated locally (or partially) to a required portion of the amorphous oxide semiconductor film formed over the gate electrode film. Therefore, the low-resistance oxide semiconductor film can be formed so that the amorphous oxide semiconductor film is disposed in a region corresponding to the gate electrode film. In the case of using a partial irradiation laser, the resistance of the amorphous oxide semiconductor film is reduced by using a laser mask, so that the area of the low resistance oxide semiconductor film can be controlled by the shape of the laser mask.

(3) In the thin film transistor of this embodiment, the first low-resistance oxide semiconductor film, the amorphous oxide semiconductor film formed on the gate electrode film, and the source electrode film are formed on the surface of the substrate. In the projected state, the area of the region where the source electrode film and the first low-resistance oxide semiconductor film overlap is larger than the area of the region where the source electrode film and the amorphous oxide semiconductor film overlap. It is characterized by that.

In the thin film transistor of this embodiment, the first low-resistance oxide semiconductor film, the amorphous oxide semiconductor film formed over the gate electrode film, and the source electrode film are projected onto the surface of the substrate. The area of the region where the source electrode film and the first low-resistance oxide semiconductor film overlap is larger than the area of the region where the source electrode film and the amorphous oxide semiconductor film overlap.

Most of the low-resistance oxide semiconductor film directly under the source electrode film (a region overlapping with the source electrode film) does not form a channel region and has a parasitic resistance. Therefore, by making the area of the low resistance oxide semiconductor film immediately below the source electrode film larger than the area of the amorphous oxide semiconductor film immediately below the source electrode film, the low resistance oxide semiconductor is formed in the region immediately below the source electrode film. By increasing the ratio of the area occupied by the film, the parasitic resistance can be lowered and the current driving capability can be increased.

(4) In the thin film transistor of this embodiment, the second low-resistance oxide semiconductor film, the amorphous oxide semiconductor film formed on the upper side of the gate electrode film, and the drain electrode film are formed on the surface of the substrate. In the projected state, the area of the region where the drain electrode film and the second low-resistance oxide semiconductor film overlap is larger than the area of the region where the drain electrode film and the amorphous oxide semiconductor film overlap. It is characterized by that.

In the thin film transistor of this embodiment, the second low-resistance oxide semiconductor film, the amorphous oxide semiconductor film formed above the gate electrode film, and the drain electrode film are projected onto the surface of the substrate. The area of the region where the drain electrode film and the second low-resistance oxide semiconductor film overlap is larger than the area of the region where the drain electrode film and the amorphous oxide semiconductor film overlap.

Most of the low-resistance oxide semiconductor film immediately below the drain electrode film (a region overlapping with the drain electrode film) does not form a channel region and has a parasitic resistance. Therefore, by making the area of the low resistance oxide semiconductor film immediately below the drain electrode film larger than the area of the amorphous oxide semiconductor film immediately below the drain electrode film, the low resistance oxide semiconductor is formed in the area immediately below the drain electrode film. By increasing the ratio of the area occupied by the film, the parasitic resistance can be lowered and the current driving capability can be increased.

(5) In the thin film transistor of this embodiment, the first and second low-resistance oxide semiconductor films are the gate electrode film and the first and second low-resistance oxide semiconductor films on the surface of the substrate. In the projected state, it is arranged in a region corresponding to the gate electrode film.

In the thin film transistor of this embodiment, the first and second low-resistance oxide semiconductor films are in a projected state in which the gate electrode film and the first and second low-resistance oxide semiconductor films are projected onto the surface of the substrate. Are disposed in a region corresponding to the gate electrode film.

In the case of a conventional self-aligned thin film transistor, for example, the entire surface of the substrate is irradiated with laser light, so that the laser light is blocked by the gate electrode film. Therefore, the region of the amorphous oxide semiconductor film above the gate electrode film and corresponding to the region of the gate electrode film is not irradiated with laser light, so that the resistance cannot be reduced.

On the other hand, in the case of the thin film transistor of this embodiment, an energy beam (for example, laser light) is irradiated locally (or partially) to a required portion of the amorphous oxide semiconductor film formed over the gate electrode film. Therefore, a low-resistance oxide semiconductor film can be formed at a required position in a region corresponding to the gate electrode film. Thereby, for example, in the GOA (Gate Driver On Array) circuit portion in which the oxide semiconductor film is formed inside the gate electrode, the resistance of the oxide semiconductor can be reduced. Compared with the used GOA circuit unit, the current drive capability can be increased.

The display panel of this embodiment includes the thin film transistor according to the above-described embodiment.

The display panel of this embodiment includes a thin film transistor. Thus, a display panel including a thin film transistor that can improve light stability can be realized.

1 Glass substrate (substrate)
2 Gate electrode film 3 Gate insulating film 4 Amorphous oxide semiconductor film 5, 51 Low resistance oxide semiconductor film (first low resistance oxide semiconductor film)
6, 61 Low resistance oxide semiconductor film (second low resistance oxide semiconductor film)
7 Source electrode film 8 Drain electrode film

Claims (7)

In a thin film transistor having an oxide semiconductor film over a substrate,
A gate electrode film formed on the surface of the substrate;
An amorphous oxide semiconductor film formed above the gate electrode film;
First and second low-resistance oxide semiconductor films formed with the amorphous oxide semiconductor film interposed therebetween;
A source electrode film formed on the first low-resistance oxide semiconductor film;
A drain electrode film formed on the second low-resistance oxide semiconductor film,
The amorphous oxide semiconductor film between the first and second low-resistance oxide semiconductor films is
A thin film transistor, wherein the gate electrode film and the amorphous oxide semiconductor film are disposed in a region corresponding to the gate electrode film in a projected state in which the surface of the substrate is projected. The first and second low-resistance oxide semiconductor films are
2. The thin film transistor according to claim 1, wherein the thin film transistor is formed by irradiating an energy beam to a required separated portion of an amorphous oxide semiconductor film formed on the gate electrode film. The first low resistance oxide semiconductor film, the amorphous oxide semiconductor film formed above the gate electrode film, and the source electrode film are projected onto the surface of the substrate, and the source electrode film and The area of the region where the first low-resistance oxide semiconductor film overlaps is larger than the area of the region where the source electrode film and the amorphous oxide semiconductor film overlap. 2. The thin film transistor according to 2. In the projected state in which the second low-resistance oxide semiconductor film, the amorphous oxide semiconductor film formed on the gate electrode film and the drain electrode film are projected onto the surface of the substrate, the drain electrode film and The area of the region where the second low-resistance oxide semiconductor film overlaps is larger than the area of the region where the drain electrode film and the amorphous oxide semiconductor film overlap. 4. The thin film transistor according to any one of up to 3. The first and second low-resistance oxide semiconductor films are
The gate electrode film and the first and second low-resistance oxide semiconductor films are arranged in a region corresponding to the gate electrode film in a projected state projected onto the surface of the substrate. The thin film transistor according to any one of claims 1 to 4. A display panel comprising the thin film transistor according to any one of claims 1 to 5. In a method for manufacturing a thin film transistor having an oxide semiconductor film over a substrate,
Forming a gate electrode film on the surface of the substrate;
When an amorphous oxide semiconductor film is formed on the gate electrode film, the amorphous oxide semiconductor film is projected in a state in which the gate electrode film and the amorphous oxide semiconductor film are projected onto the surface of the substrate. Forming a physical semiconductor film in a region corresponding to the gate electrode film;
Irradiating an energy beam to a required separated portion of the amorphous oxide semiconductor film to form first and second low resistance oxide semiconductor films;
Forming a source electrode film on the first low-resistance oxide semiconductor film;
A method of manufacturing a thin film transistor, comprising forming a drain electrode film on the second low-resistance oxide semiconductor film.

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