JP4316117B2 - Thin film transistor manufacturing method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention Manufacturing method of thin film transistor (hereinafter also referred to as TFT) In particular, it is suitable as a switching element for large-sized and high-definition liquid crystal display devices. Thin film transistor manufacturing method About.
[0002]
[Prior art]
A liquid crystal display device is advantageous in that it is thin and lightweight, can be driven at a low voltage and consumes less power, and is widely used in various electronic devices.
In particular, an active matrix type liquid crystal display device in which a TFT is provided for each pixel is superior in terms of display quality to comparable to a CRT (Cathode-Ray Tube). For this reason, active matrix liquid crystal display devices are also used in displays such as portable televisions and personal computers.
[0003]
A general TN (Twisted Nematic) type liquid crystal display device has a structure in which liquid crystal is sealed between two transparent glass substrates. A black matrix, a color filter, a counter electrode, and the like are formed on one of the two surfaces (facing surfaces) facing each other of the glass substrate, and a TFT, a pixel electrode, and the like are formed on the other surface. Is formed. Furthermore, a polarizing plate is attached to the surface opposite to the facing surface of each glass substrate. These two polarizing plates are, for example, arranged so that the polarizing axes of the polarizing plates are orthogonal to each other, and according to this, a mode that transmits light when no electric field is applied and shields light when an electric field is applied, That is, the normally white mode is set. Further, when the polarization axes of the two polarizing plates are parallel, the light is blocked when no electric field is applied, and the mode is a normally black mode in which light is transmitted when an electric field is applied. Hereinafter, the substrate on which the TFT and the pixel electrode are formed is called a TFT substrate, and the substrate on which the color filter and the counter electrode are formed is called a CF substrate.
[0004]
FIG. 1 is a plan view showing a TFT substrate of a liquid crystal display device. FIG. 2 is a cross-sectional view taken along line AA in FIG. 1 and shows the structure of a conventional inverted stagger type TFT.
As shown in FIG. 1, a plurality of gate bus lines 12a and a plurality of data bus lines 18a are formed on the TFT substrate. The gate bus line 12a and the data bus line 18a intersect at right angles, and each rectangular area defined by the gate bus line 12a and the data bus line 18a is a pixel. A TFT 25 and a pixel electrode 20 are formed in each pixel. The gate electrode 12b of the TFT 25 is connected to the gate bus line 12a, and the drain electrode 18b is connected to the data bus line 18a. Further, the source electrode 18c of the TFT 25 is connected to the pixel electrode 20 through the contact hole 19h.
[0005]
The configuration of the TFT substrate will be described in more detail with reference to the cross-sectional view of FIG. On the glass substrate 11, a gate bus line 12a and a gate electrode 12b are formed. The gate bus line 12 a and the gate electrode 12 b are covered with an insulating film (gate insulating film) 14 formed on the substrate 11.
An amorphous silicon film 15 serving as an active layer of the TFT 25 is formed in a predetermined region on the gate insulating film 14. A channel protective film 16 made of an insulating material such as SiN is formed on the amorphous silicon film 15.
[0006]
On both sides of the channel protective film 16, n connected to the amorphous silicon film 15, respectively. ⁺ Type amorphous silicon film (ohmic contact layer) 17 is formed. ⁺ A data bus line 18 a, a drain electrode 18 b and a source electrode 18 c of the TFT 25 are formed on the type amorphous silicon film 17.
[0007]
The data bus line 18a, the drain electrode 18b, and the source electrode 18c are covered with a protective insulating film 19. A pixel electrode 20 made of ITO is formed on the protective insulating film 19. The pixel electrode 20 is electrically connected to the source electrode 18 c of the TFT 25 through a contact hole 19 h formed in the protective insulating film 19. The pixel electrode 20 is covered with an alignment film (not shown) made of polyimide or the like.
[0008]
By the way, the gate bus line 12a and the gate electrode 12b are heated to a high temperature of 300 ° C. or higher when the gate insulating film 14 is formed, so that heat resistance against hillock generation is required. Further, since the gate bus line 12a is connected to the ITO film at the terminal portion of the gate bus line 12a, the contact resistance to the ITO film is required to be low. For this reason, Cr (chromium) or the like is conventionally used as the material for the gate bus line 12a and the gate electrode 12b, not Al (aluminum or aluminum alloy: hereinafter the same), which is generally used as a wiring material for semiconductor devices. Refractory metals are used.
[0009]
[Problems to be solved by the invention]
In recent years, with the increase in size and definition of liquid crystal display devices, the width of the gate bus line 12a tends to be narrow and the wiring length tends to be long. However, when the gate bus line and the gate electrode of the large-sized and high-definition liquid crystal display device are formed of a refractory metal such as Cr, the resistance value becomes high and switching failure occurs.
[0010]
In order to avoid such a problem, the gate bus line and the gate electrode may have a laminated structure of an Al film and a refractory metal film such as Ti or Mo. However, in the case of an inverted stagger type TFT, the temperature is 300 ° C. or higher when the gate insulating film is formed. Therefore, in the laminated structure of the Al film and the refractory metal, mutual diffusion occurs at the interface between the Al film and the refractory metal film. As a result, a high resistance layer is formed. Because of this high resistance layer, the resistance value of the gate bus line cannot be made sufficiently small even though Al is used.
[0011]
In order to prevent interdiffusion between Al and the refractory metal, there is a method of forming a titanium nitride (TiN) film between the Al film and the refractory metal film. However, although nitride is stable in physical properties and does not generate a high resistance layer due to diffusion, there is a drawback that the insulating property of the gate insulating film is hindered due to film roughness. An object of the present invention is to prevent the generation of a high resistance layer due to mutual diffusion at the interface between Al and a refractory metal, and to avoid film roughness. Thin film transistor manufacturing method Is to provide.
[0012]
[Means for Solving the Problems]
In the method of manufacturing a thin film transistor including a gate electrode, a semiconductor layer, and a source / drain electrode on a substrate, at least one of the gate electrode and the source / drain electrode is formed by sputtering aluminum or an aluminum alloy. A step of forming a first layer made of aluminum or an aluminum alloy, and an intermediate layer containing oxygen by sputtering aluminum on the first layer in an atmosphere containing oxygen gas at a ratio of 20% or more Produced by a step and a step of forming a second layer made of a refractory metal by sputtering a refractory metal on the intermediate layer And then The substrate including the intermediate layer; Above 300 ℃ The problem is solved by a method for manufacturing a thin film transistor, which includes a heating step.
[0013]
In addition, the above-described problems include a step of forming a first layer made of aluminum or an aluminum alloy on an insulating substrate, and aluminum on the first layer in an atmosphere containing oxygen gas at a ratio of 20% or more. A step of forming an intermediate layer containing oxygen by sputtering, a step of forming a second layer made of a refractory metal on the intermediate layer, the first layer, the intermediate layer, and the second layer. Patterning the laminated film to form a gate electrode and a gate bus line; and Over 300 ℃ Forming a gate insulating film on the gate electrode and the gate bus line while heating, forming an active layer of a thin film transistor, a source electrode, a drain electrode, and a data bus line on the gate insulating film; Forming a protective insulating film on the entire upper surface of the insulating substrate; forming a transparent conductive film on the protective insulating film; and patterning the transparent conductive film to form a pixel electrode. The problem is solved by the manufacturing method of the liquid crystal display device.
[0014]
As a result of various experimental studies to avoid mutual diffusion between the Al film and the refractory metal film, the inventors of the present application have formed a film containing oxygen between the Al film and the refractory metal film. The knowledge that it was good was obtained. It has also been found that the sheet resistance of an Al film containing oxygen formed by sputtering Al in an atmosphere having an oxygen gas ratio of 20% or more decreases when annealed at a high temperature.
[0015]
In FIG. 3, the horizontal axis represents the oxygen gas ratio of the atmosphere during film formation of the Al film and the Ti film (where the balance is Ar gas), the vertical axis represents the sheet resistance, and the Al / Ti laminated film immediately after film formation. It is a figure which shows the result of having measured the sheet resistance of this, and the sheet resistance value of the Ai / Ti laminated film after annealing on temperature conditions (350 degreeC for 1 hour) equivalent to the time of gate insulating film formation by a 4 terminal method. .
[0016]
As apparent from FIG. 3, when the oxygen gas ratio is less than 20%, the sheet resistance value of the laminated film after annealing increases as compared with that before the annealing, but when the oxygen gas ratio exceeds 20%, annealing is performed. The sheet resistance value of the later laminated film is reduced as compared with that before annealing. Moreover, the laminated film after annealing has no surface roughness, and even if an insulating film is formed on the laminated film, the insulating property is not hindered.
[0017]
Therefore, in the present invention, at least one of the gate electrode and the source / drain electrode has a first layer made of Al (aluminum or aluminum alloy), a second layer made of a refractory metal, and the first of these. A stacked structure including an intermediate layer containing oxygen sandwiched between the layer and the second layer is employed.
Thereby, it can be avoided that a high resistance layer is formed between the Al film (first layer) and the refractory metal film (second layer) due to heat.
[0018]
Note that the oxygen-containing layer is not limited to an oxidized state as long as oxygen is contained in the metal. However, it is necessary that the conductivity between the Al film and the refractory metal film is not impaired by the layer containing oxygen. The thickness of the layer containing oxygen is preferably 2 nm or more.
As the refractory metal, for example, any one metal selected from the group consisting of Ti (titanium), Mo (molybdenum), Cr (chromium), Ta (tantalum), and W (tungsten) or an alloy thereof is used. be able to.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
(First embodiment)
4 is a cross-sectional view of a TN type liquid crystal display device to which the thin film transistor of the first embodiment of the present invention is applied, FIG. 5 is a plan view of the TFT substrate of the liquid crystal display device, and FIG. It is an expanded sectional view of the TFT part by a line.
[0020]
As shown in FIG. 4, the liquid crystal display device includes a TFT substrate 30, a CF substrate 50, and a liquid crystal 49 sealed between the TFT substrate 30 and the CF substrate 50.
As shown in FIG. 5, a plurality of gate bus lines 32 a and a plurality of data bus lines 38 a are formed on the TFT substrate 30. The gate bus line 32a and the data bus line 38a intersect at right angles, and each rectangular area defined by the gate bus line 32a and the data bus line 38a is a pixel. In each pixel, a transparent pixel electrode 40 and a TFT 45 are formed. The gate electrode 32b of the TFT 45 is connected to the gate bus line 32a, and the drain electrode 38b is connected to the data bus line 38a. Further, the source electrode 38c of the TFT 45 is connected to the pixel electrode 40 through the contact hole 39h.
[0021]
The configuration of the TFT substrate 30 will be described in more detail with reference to the cross-sectional view of the TFT portion of FIG. On a substrate (hereinafter referred to as a glass substrate) 31 made of a transparent insulator such as glass, a gate bus line 32a and a gate electrode 32b are formed as a first wiring layer. The gate bus line 32a and the gate electrode 32b have a three-layer structure including an Al film (first layer) 33a, an Al film (intermediate layer) 33b containing oxygen, and a Ti film (second layer) 33c from the bottom. The Al film 33b containing oxygen functions as a diffusion preventing layer.
[0022]
The gate bus line 32 a and the gate electrode 32 b are covered with an insulating film (gate insulating film) 34 formed on the substrate 31.
In a predetermined region on the gate insulating film 34 (above the gate electrode 32b), an amorphous silicon film 35 that becomes an active layer of the TFT 45 is formed. A channel protective film 36 made of an insulating material such as SiN is formed on the amorphous silicon film 35.
[0023]
On both sides of the channel protective film 36, n connected to the amorphous silicon film 35, respectively. ⁺ Type amorphous silicon film (ohmic contact layer) 37 is formed. ⁺ On the type amorphous silicon film 37, a data bus line 38a, a drain electrode 38b of the TFT 45, and a source electrode 38c are formed as a second wiring layer.
[0024]
The data bus line 38a, the drain electrode 38b, and the source electrode 38c are covered with a protective insulating film 39. A pixel electrode 40 made of ITO is formed on the protective insulating film 39. The pixel electrode 40 is electrically connected to the source electrode 38 c of the TFT 45 through a contact hole 39 h formed in the protective insulating film 39. The pixel electrode 40 is covered with an alignment film 41 as shown in FIG.
[0025]
The alignment film 41 is formed of, for example, polyimide, and an alignment process is performed on the surface in order to determine the alignment direction of the liquid crystal molecules when a voltage is applied. As a typical method for the alignment treatment, a rubbing method is known in which the surface of the alignment film 41 is rubbed in one direction with a cloth roller.
On the other hand, as shown in FIG. 4, the CF substrate 50 includes a glass substrate 51 and a black matrix 52, a color filter 53, a counter electrode 54, and an alignment film 55 formed on the lower surface side of the glass substrate 51.
[0026]
The black matrix 52 is formed of, for example, a metal material such as Cr so as to shield the formation region of the gate bus line 32a, the data bus line 38a, and the TFT 45 of the TFT substrate 30. There are three types of color filters 53, red (R), green (G), and blue (B), and one color filter 53 faces one pixel electrode 40.
[0027]
Under the color filter 53, a transparent counter electrode 54 made of ITO is formed. Under the counter electrode 54, an alignment film 55 made of polyimide, for example, is formed. An alignment process is also applied to the surface of the alignment film 55.
7 to 11 are cross-sectional views showing the method of manufacturing the thin film transistor of this embodiment in the order of steps.
[0028]
First, as shown in FIG. 7A, a glass substrate 31 is placed in a chamber of a sputtering apparatus, and Al is sputtered while Ar gas is introduced into the chamber at a flow rate of 140 sccm to form an Al film on the glass substrate 31. (First layer) 33a is formed to a thickness of about 100 nm. Thereafter, Al is sputtered by a reactive sputtering method while introducing Ar gas at a flow rate of 127 sccm and oxygen at a flow rate of 54 sccm to form an oxygen-containing Al film (intermediate layer) 33b with a thickness of about 5 nm. .
[0029]
Next, the glass substrate 31 is transferred to another chamber without breaking the vacuum. Then, Ti is sputtered while introducing Ar gas into the chamber at a flow rate of 140 sccm to form a Ti film (second layer) 33c having a thickness of 50 nm.
Next, a photoresist film is applied on the Ti film 33c, exposed and developed, and the photoresist film 51 is patterned into a predetermined shape as shown in FIG. 7B. Thereafter, as shown in FIG. 7C, reactive ion etching using a chlorine-based gas is performed using the photoresist film 51 as a mask, and the Ti film 33c, the Al film 33b containing oxygen, and the Al film 33a are collectively processed. The gate electrode 32b is formed by etching.
[0030]
Next, as shown in FIG. 8A, the resist film 51 is removed. Then, as shown in FIG. 8B, a silicon nitride (SiN) film is formed as the gate insulating film 34 by the CVD method. At this time, the temperature of the glass substrate 31 is 300 ° C. or higher. In this embodiment, since the Al film 33b containing oxygen is formed between the Al film 33a and the Ti film 33c, this film is diffused. It functions as a prevention layer, prevents mutual diffusion of Al and Ti, and avoids the generation of a high resistance layer.
[0031]
Thereafter, an amorphous silicon film 35 serving as an active layer of the TFT 45 is formed on the gate insulating film 34 by CVD, and a silicon nitride film 36x serving as a channel protective film 36 is further formed thereon. Then, a photoresist film is applied on the silicon nitride film 36x, exposed and developed, and the photoresist film 52 is patterned into a desired channel protective film shape as shown in FIG. 8C.
[0032]
Next, the silicon nitride film 36x is etched using the resist film 52 as a mask to form a channel protective film 36 as shown in FIG. Thereafter, the resist film 52 is removed.
Next, as shown in FIG. 9B, n to be an ohmic contact layer is formed by CVD. ⁺ After the type amorphous silicon film 37 is formed on the entire upper surface of the glass substrate 31, Ti, Al, and Ti are successively formed in this order by a sputtering method to form the conductive film 38x.
[0033]
Next, by photolithography, as shown in FIG. 9C, the conductive films 38x, n ⁺ The pattern amorphous silicon film 37 and the amorphous silicon film 35 are patterned to form a data bus line 38a, a drain electrode 38b, and a source electrode 38c.
Thereafter, as shown in FIG. 10A, a protective insulating film 39 is formed by depositing silicon nitride on the entire upper surface of the glass substrate 31 by a CVD method. Then, as shown in FIG. 10B, a contact hole 39 h reaching the source electrode 38 c is formed in the protective insulating film 39. At the same time, openings (not shown) from which the terminal portions at the ends of the gate bus line 32a and the data bus line 38a are exposed are also formed.
[0034]
Next, as shown in FIG. 11A, ITO is sputtered on the entire upper surface of the glass substrate 31 to form an ITO film 40x. Then, as shown in FIG. 11B, the ITO film 40x is patterned to cover the pixel electrode 40 and the cover film (not shown) that covers the terminal portions of the end portions of the gate bus line 32a and the data bus line 38a. Form. Thereafter, an alignment film 41 that covers the pixel electrode 40 is formed of polyimide or the like. Thereby, the TFT substrate is completed.
[0035]
In this embodiment, the gate bus line 32a and the gate electrode 32b have a three-layer structure of an Al film 33a, an Al film 33b containing oxygen that functions as a diffusion prevention layer, and a Ti film 33c made of a refractory metal. Therefore, even when the gate insulating film 34 is heated to a temperature of 300 ° C. or higher, the formation of the high resistance layer between the Al film 33a and the Ti film 33c is avoided. Thereby, in the liquid crystal display device of the present embodiment, the resistance value of the gate bus line is reduced.
[0036]
A 15-inch XGA (1024 × 768 dots) type liquid crystal display device is actually manufactured by the above method, the resistance value of the gate bus line is measured, and the resistance value of the gate bus line of the liquid crystal display device of the conventional structure is compared. did. As a result, in the liquid crystal display device having the conventional structure, the resistance value of the gate bus line was 18 kΩ, but in the structure of this embodiment, it could be lowered to 14.7 kΩ. However, the width of the gate bus line is 8 μm and the length is 304 mm.
[0037]
In the above embodiment, the present invention is applied to the gate bus line 32a and the gate electrode 32b that are affected by heat during the formation of the gate insulating film, and the data bus line 38a, the drain electrode 38b, and the source electrode 38c It has an Al / Ti laminated structure. Since the protective insulating film 39 on the data bus line 38a, the drain electrode 38b and the source electrode 38c is formed at a relatively low temperature, the data bus line 38a, the drain electrode 38b and the source electrode 38c are made of Ti / Al / Ti. Even in a laminated structure, a high resistance layer is hardly generated due to mutual diffusion of Al and Ti. However, the data bus line 38a, the drain electrode 38b, and the source electrode 38c may have a structure in which a film containing oxygen is sandwiched between the Al film and the refractory metal film, similarly to the gate bus line 32a and the gate electrode 32b. .
[0038]
In the above embodiment, the second layer is formed of Ti, but any one selected from the group consisting of Ti (titanium), Mo (molybdenum), Cr (chromium), Ta (tantalum), and W (tungsten). Alternatively, it may be formed of one kind of metal or an alloy thereof.
(Second Embodiment)
FIG. 12 is a cross-sectional view showing a method of forming a thin film transistor according to the second embodiment of the present invention.
[0039]
First, as shown in FIG. 12 (a), a glass substrate 31 is placed in a chamber of a sputtering apparatus, and Al is sputtered while introducing Ar gas at a flow rate of 140 sccm into the chamber. A film (first layer) 33a is formed.
Thereafter, the glass substrate 31 is transferred to another chamber without breaking the vacuum, Ti is sputtered by a reactive sputtering method while introducing Ar gas into the chamber at a flow rate of 127 sccm and oxygen at a flow rate of 54 sccm, and a Ti layer containing oxygen (Intermediate layer) 33d is formed to a thickness of about 5 nm.
[0040]
Next, in the same chamber, Ti is sputtered in an atmosphere in which Ar gas is introduced at a flow rate of 140 sccm to form a Ti film (second layer) 33c with a thickness of about 50 nm.
Next, a photoresist film is applied on the Ti film 33c, exposed and developed, and the photoresist film 51 is patterned into a predetermined pattern as shown in FIG. Thereafter, as shown in FIG. 12C, reactive ion etching using a chlorine-based gas is performed using the photoresist film 51 as a mask, and the Ti film 33c, the Ti film 33d containing oxygen, and the Al film 33a are collectively processed. The gate electrode 32b is formed by etching.
[0041]
Since the subsequent steps are the same as those in the first embodiment, description thereof is omitted here. In the present embodiment, the Ti film 33d containing oxygen functions as a diffusion preventing layer, and mutual diffusion between the Al film 33a and the Ti film 33c is prevented when the gate insulating film is formed. Thereby, also in this invention, the effect similar to 1st Embodiment can be acquired.
[0042]
In the above embodiment, the intermediate layer and the second layer are formed by sputtering of Ti, but the group consisting of Ti (titanium), Mo (molybdenum), Cr (chromium), Ta (tantalum), and W (tungsten). It may be formed by sputtering any one kind of metal selected from the above or an alloy thereof.
(Third embodiment)
The third embodiment will be described below. This embodiment is different from the first embodiment in that the method of forming the gate bus line and the gate electrode is different, and other configurations are basically the same as those in the first embodiment. The description of the overlapping part is omitted.
[0043]
FIG. 13 is a block diagram showing a thin film transistor manufacturing apparatus. This apparatus includes a carry-in chamber 61, a substrate standby chamber 62, an Al film forming chamber (first chamber) 63, a vent processing chamber (second chamber) 64, a Ti film forming chamber (third chamber) 65, a substrate take-out chamber 66, A transfer chamber 67 is used. Each of the chambers 61 to 67 is partitioned by a door. Each of the chambers 61 to 67 is connected to an exhaust device so that each chamber can be individually exhausted.
[0044]
Hereinafter, a method for manufacturing a thin film transistor using the above-described apparatus will be described. First, the air in each of the substrate standby chamber 62, the Al film forming chamber 63, the vent processing chamber 64, the Ti film forming chamber 65, the take-out chamber 66, and the transfer chamber 67 is sufficiently exhausted.
Next, after putting a glass substrate in the carrying-in chamber 61, the inside of the carrying-in chamber 61 is exhausted sufficiently. Then, the substrate is transferred from the carry-in chamber 61 to the substrate standby chamber 62 through the transfer chamber 67. Then, the glass substrate is transferred from the substrate standby chamber 62 to the Al film forming chamber 63 via the transfer chamber 67.
[0045]
Next, in the Al film forming chamber 63, Al is sputtered while introducing Ar gas at a flow rate of 140 sccm to form an Al film (first layer) with a thickness of about 100 nm on the substrate.
Thereafter, the glass substrate is transferred from the Al film forming chamber 63 to the vent processing chamber 64 through the transfer chamber 67. In the vent processing chamber 64, when the glass substrate is transferred into the room, air is introduced into the room. Thereby, a natural oxide film (intermediate layer) is formed on the surface of the Al film.
[0046]
After the natural oxide film is formed on the surface of the Al film in this way, the inside of the vent processing chamber 64 is evacuated again. Then, the glass substrate is transferred from the vent processing chamber 64 to the Ti film forming chamber 65 through the transfer chamber 67.
In the Ti film forming chamber 64, Ti is sputtered while introducing Ar gas at a flow rate of 140 sccm to form a Ti film (second layer) with a thickness of 50 nm. Thereby, a laminated film having a structure in which a natural oxide film is sandwiched between the Al film and the Ti film is formed.
[0047]
Next, the glass substrate is transferred from the Ti film forming chamber 65 to the take-out chamber via the transfer chamber 67. Then, after closing the door between the transfer chamber 67 and the take-out chamber 66, the take-out chamber 66 is brought to atmospheric pressure, and the glass substrate is taken out.
Next, a laminated film having a three-layer structure of an Al film, a natural oxide film, and a Ti film is patterned by photolithography to form a gate bus line and a gate electrode. Since the subsequent steps are the same as those in the first embodiment, description thereof is omitted here.
[0048]
According to the present embodiment, since the gate bus line and the gate electrode have a three-layer structure of an Al film, a natural oxide film, and a Ti film, mutual diffusion due to heat between the Al film and the Ti film is caused by the natural oxide film. Is prevented. Thereby, a low-resistance electrode wiring can be obtained.
In the above first to third embodiments, the case where the present invention is applied to a TN liquid crystal display device has been described. However, the scope of application of the present invention is limited to the TN liquid crystal display device. Instead, the present invention is applied to liquid crystal display devices such as IPS (In-Plane Switching) type liquid crystal display devices and MVA (Multi-domain Vertical Alignment) type liquid crystal display devices, and other electronic devices using thin film transistors. Can do.
[0049]
(Supplementary Note 1) In a thin film transistor including a gate electrode, a semiconductor layer, and a source / drain electrode on a substrate, at least one of the gate electrode and the source / drain electrode includes a first layer made of aluminum or an aluminum alloy; A thin film transistor having a stacked structure of a second layer made of a refractory metal and an intermediate layer containing oxygen sandwiched between the first layer and the second layer.
[0050]
(Supplementary note 2) The thin film transistor according to supplementary note 1, wherein the intermediate layer is made of any one of aluminum containing oxygen, an aluminum alloy containing oxygen, and a refractory metal containing oxygen.
(Appendix 3) The refractory metal is any one metal selected from the group consisting of Ti (titanium), Mo (molybdenum), Cr (chromium), Ta (tantalum), and W (tungsten), or its The thin film transistor according to appendix 1, which is an alloy.
[0051]
(Appendix 4) In the method of manufacturing a thin film transistor including a gate electrode, a semiconductor layer, and a source / drain electrode on a substrate, aluminum or an aluminum alloy is sputtered on at least one of the gate electrode and the source / drain electrode, A step of forming a first layer made of aluminum or an aluminum alloy, and an atmosphere containing oxygen gas in a ratio of 20% or more, and the first layer is selected from the group consisting of aluminum, an aluminum alloy and a refractory metal Sputtering any one of the above metals to form an intermediate layer containing oxygen, and sputtering a refractory metal on the intermediate layer to form a second layer made of the refractory metal A manufacturing method of a thin film transistor, characterized by being manufactured by a process.
[0052]
(Supplementary Note 5) In the method of manufacturing a thin film transistor including a gate electrode, a semiconductor layer, and a source / drain electrode on a substrate, aluminum or an aluminum alloy is sputtered on at least one of the gate electrode and the source / drain electrode. Alternatively, a step of forming a first layer made of an aluminum alloy, a step of oxidizing the surface of the first layer in an oxygen-containing atmosphere to form an intermediate layer made of an oxide film, A method of manufacturing a thin film transistor, comprising: forming a second layer made of a refractory metal by sputtering a refractory metal thereon.
[0053]
(Appendix 6) A plurality of gate bus lines formed on an insulating substrate, a plurality of data bus lines formed on the insulating substrate in a direction intersecting the gate bus lines, the gate bus lines, In a liquid crystal display device having a thin film transistor and a pixel electrode formed in each pixel region partitioned by a data bus line, at least one of the gate bus line and the data bus line is a first made of aluminum or an aluminum alloy. And a second layer made of a refractory metal, and an intermediate layer containing oxygen sandwiched between the first layer and the second layer. Display device.
[0054]
(Appendix 7) A step of forming a first layer made of aluminum or an aluminum alloy on an insulating substrate, a step of forming an intermediate layer containing oxygen on the first layer, and a step of forming a high layer on the intermediate layer Forming a second layer made of a melting point metal, patterning a laminated film of the first layer, the intermediate layer, and the second layer to form a gate electrode and a gate bus line, Forming a gate insulating film on the gate electrode and the gate bus line; forming an active layer of a thin film transistor on the gate insulating film; a source electrode; a drain electrode; and a data bus line; and an upper side of the insulating substrate. Forming a protective insulating film on the entire surface; removing the insulating film above the source electrode and above the terminals of the gate gas line and the drain bus line; Method of manufacturing a liquid crystal display device in which the transparent conductive film on the protective insulating film is formed, characterized in that a step of forming a pixel electrode by patterning the transparent conductive film.
[0055]
(Supplementary Note 8) The oxygen-containing intermediate layer is formed by sputtering any one metal selected from the group consisting of aluminum, an aluminum alloy, and a refractory metal in an atmosphere containing 20% or more of oxygen gas. The method for manufacturing a liquid crystal display device according to appendix 7, wherein:
(Additional remark 9) The said intermediate | middle layer containing oxygen forms the surface of the said aluminum or aluminum alloy film | membrane naturally, and forms it, The manufacturing method of the liquid crystal display device of Additional remark 7 characterized by the above-mentioned.
[0056]
【The invention's effect】
As described above, according to the thin film transistor of the present invention, at least one of the gate electrode and the source / drain electrode has the first layer made of aluminum or aluminum alloy, the second layer made of refractory metal, Since it has a laminated structure with an intermediate layer containing oxygen sandwiched between the first and second layers, a high resistance layer is not formed between the aluminum film and the refractory metal film, There is no film roughness. Therefore, when the thin film transistor of the present invention is used as a switching element of a liquid crystal display device, a large-sized and high-definition liquid crystal display device is realized.
[0057]
In addition, according to the method of manufacturing a thin film transistor of the present invention, since an intermediate layer functioning as a diffusion prevention layer is formed by sputtering Al or a refractory metal in an atmosphere containing oxygen gas at a ratio of 20% or more, an Al film And mutual diffusion between the refractory metal film can be prevented. The same applies when a natural oxide film is used as the diffusion preventing layer.
[Brief description of the drawings]
FIG. 1 is a plan view showing a TFT substrate of a liquid crystal display device.
FIG. 2 is a cross-sectional view taken along line AA in FIG. 1, and shows a structure of a conventional inverted stagger type TFT.
FIG. 3 is a graph showing the relationship between the oxygen gas ratio in the atmosphere during film formation, the sheet resistance of the Al / Ti laminated film immediately after film formation, and the sheet resistance value of the Ai / Ti laminated film after annealing. It is.
FIG. 4 is a cross-sectional view of a liquid crystal display device to which the thin film transistor according to the first embodiment of the present invention is applied.
FIG. 5 is a plan view of the liquid crystal display device.
6 is an enlarged cross-sectional view of a TFT portion taken along the line BB in FIG. 5;
FIG. 7 is a cross-sectional view (part 1) illustrating the method for manufacturing the thin film transistor according to the first embodiment;
FIG. 8 is a cross-sectional view (No. 2) illustrating the method for manufacturing the thin film transistor according to the first embodiment;
FIG. 9 is a cross-sectional view (part 3) illustrating the method for manufacturing the thin film transistor according to the first embodiment;
FIG. 10 is a cross-sectional view (part 4) illustrating the method for manufacturing the thin film transistor according to the first embodiment;
11 is a sectional view (No. 5) showing the method for manufacturing the thin film transistor according to the first embodiment. FIG.
FIG. 12 is a cross-sectional view showing a method of forming a thin film transistor according to the second embodiment of the present invention.
FIG. 13 is a block diagram showing an apparatus for manufacturing a thin film transistor according to a third embodiment of the present invention.
[Explanation of symbols]
11, 31, 51 ... glass substrate,
12a, 32a ... gate bus line,
12b, 32b ... gate electrodes,
14, 34 ... gate insulating film,
15, 35 ... amorphous silicon film (active layer),
16, 36 ... Channel protective film,
17, 37 ... n ⁺ Type amorphous silicon film (ohmic contact layer),
18a, 38a ... data bus line,
18b, 38b ... drain electrodes,
18c, 38c ... source electrode,
19, 39 ... Protective insulating film,
20, 40 ... pixel electrodes,
25 ... TFT,
30 ... TFT substrate,
33a ... Al film,
33b ... Al film containing oxygen,
33c ... Ti film,
49 ... Liquid crystal,
50: CF substrate.

Claims (2)

In a method of manufacturing a thin film transistor including a gate electrode, a semiconductor layer, and a source / drain electrode on a substrate,
At least one of the gate electrode and the source / drain electrode,
Sputtering aluminum or aluminum alloy to form a first layer of aluminum or aluminum alloy;
Forming an intermediate layer containing oxygen by sputtering aluminum on the first layer in an atmosphere containing oxygen gas at a ratio of 20% or more;
Forming a second layer made of a refractory metal by sputtering a refractory metal on the intermediate layer ,
Then, the manufacturing method of the thin-film transistor characterized by having the process of heating the said board | substrate containing the said intermediate | middle layer at 300 degreeC or more . Forming a first layer made of aluminum or an aluminum alloy on an insulating substrate;
Forming an intermediate layer containing oxygen by sputtering aluminum on the first layer in an atmosphere containing oxygen gas at a ratio of 20% or more;
Forming a second layer made of a refractory metal on the intermediate layer;
Patterning a laminated film of the first layer, the intermediate layer, and the second layer to form a gate electrode and a gate bus line;
Forming a gate insulating film on the gate electrode and the gate bus line while heating the insulating substrate at 300 ° C. or higher ;
Forming an active layer, a source electrode, a drain electrode and a data bus line of the thin film transistor on the gate insulating film;
Forming a protective insulating film on the entire upper surface of the insulating substrate;
Forming a transparent conductor film on the protective insulating film, and patterning the transparent conductor film to form a pixel electrode.

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