JP5096522B2 - Display device - Google Patents

Description

  The present invention relates to a thin film display device and a method for producing the same, and in particular, a transparent conductive film and an aluminum alloy film used for active and passive matrix flat panel displays such as liquid crystal displays, reflection films, optical components, and the like as constituent elements. The present invention relates to a novel display device including the same and a manufacturing method thereof.

For example, an active matrix liquid crystal display device uses a thin film transistor (TFT) as a switching element, a TFT array substrate having a transparent conductive film and wiring portions such as a scanning line and a signal line, and a predetermined distance from the TFT array substrate. And a liquid crystal layer filled between the TFT array substrate and the counter substrate. Further, in the passive matrix liquid crystal display device, a wiring portion such as a scanning line and a signal line, a counter electrode provided with a common electrode opposed to the wiring substrate at a predetermined interval, a wiring substrate and a counter substrate, It is comprised by the liquid-crystal layer filled between. As the transparent conductive film, an indium tin oxide (ITO) film in which indium oxide (In ₂ O ₃ ) contains about 10% by mass of tin oxide (SnO) is used.

  In addition, as the signal line of the wiring portion electrically connected to the transparent conductive film, pure aluminum or an aluminum alloy such as Al-Nd is used, but in order to prevent direct contact between these and the transparent conductive film, A laminated film made of a refractory metal such as Mo, Cr, Ti, or W is interposed as a barrier metal. Recently, however, attempts have been made to omit these refractory metals and connect a transparent conductive film directly to the signal line.

  For example, according to Patent Document 1, if a transparent conductive film made of an IZO film containing about 10% by mass of zinc oxide in indium oxide is used, direct contact with a signal line is possible.

  Patent Document 2 discloses a method of performing surface treatment on the drain electrode by plasma treatment or ion implantation. Patent Document 3 discloses N, O, Si, and the like as the first layer gate, source, and drain electrodes. A method of forming a laminated film in which a second phase containing impurities such as C is laminated is disclosed. If these methods are employed, contact resistance with a transparent conductive film can be obtained even when the refractory metal is omitted. It has been shown that can be maintained at a low level.

Japanese Patent Laid-Open No. 11-337976 JP-A-11-283934 JP-A-11-284195

  The reason why the barrier metal is interposed in the prior art described above is that when the aluminum or aluminum alloy wiring constituting the signal line is directly brought into contact with the transparent conductive film, the contact resistance increases and the display quality of the screen decreases. This is because aluminum is very easily oxidized, and the surface is easily oxidized in the atmosphere. Also, since the transparent conductive film is a metal oxide, aluminum is formed by oxygen generated during film formation and oxygen added during film formation. This is because it is oxidized and a high resistance aluminum oxide layer is formed on the surface. When the insulating layer is formed at the contact interface between the signal line and the transparent conductive film in this manner, the contact resistance between the signal line and the transparent conductive film increases, and the display quality of the screen decreases.

  On the other hand, the barrier metal originally has the effect of preventing the surface oxidation of the aluminum alloy and improving the contact between the aluminum alloy film and the transparent conductive film, but in order to obtain a conventional structure in which the barrier metal is interposed at the contact interface. Since a barrier metal formation process is indispensable, an additional film formation chamber for barrier metal formation must be provided in addition to the sputtering apparatus for film formation required for forming the gate electrode, source electrode, and drain electrode. I must. However, as the cost of liquid crystal panels and the like by mass production advances, the increase in manufacturing cost and the decrease in productivity due to the formation of barrier metal cannot be neglected.

  For these reasons, recently, electrode materials and manufacturing processes that can eliminate the barrier metal have been demanded. In response to such a request, in the above-mentioned Patent Document 2, a step for surface treatment is weighted by one step. On the other hand, in Patent Document 3, a gate electrode, a source electrode, or a drain electrode can be continuously formed in the same film formation chamber, but an increase in the number of steps is unavoidable. In addition, due to the difference in thermal expansion coefficient between the film containing impurities and the film not containing impurities, the film frequently peels off from the wall of the chamber during continuous use. There must be. Furthermore, in Patent Document 1, since the most popular indium tin oxide (ITO) film must be changed to an indium zinc oxide (IZO) film, the material cost is high.

  Under the circumstances as described above, the present inventors can omit the barrier metal as described above, simplify it without increasing the number of steps, and make the aluminum alloy film directly and reliably on the transparent conductive film. Establish a technology that can be contacted, and achieve both excellent electrical characteristics and heat resistance that can realize low electrical resistance and low contact resistance. In addition, reflective electrodes and TABs (tabs) in display devices We have conducted extensive research with the aim of establishing a technology that can make the connection electrode and material common. As a result, a technology that allows the transparent conductive film to be in direct contact with the wiring portion without the refractory metal as described above has been developed, and a patent application has already been filed (Japanese Patent Application No. 2002-368786).

  The inventors of the present invention have continued research for further improvement, but the object of the present invention is not inferior to that of the prior application invention due to improvements from a viewpoint different from the prior application invention. An object of the present invention is to provide an aluminum alloy wiring technology capable of realizing stable and long-term reliable contact.

  The configuration of the display device according to the present invention that has solved the above problems includes a thin film transistor and a transparent conductive film disposed on a substrate, and an aluminum alloy film that electrically connects the thin film transistor and the transparent conductive film. An oxide film of the aluminum alloy is formed at the interface between the aluminum alloy film and the transparent conductive film, the oxide film has a thickness of 1 to 10 nm, and the oxygen content in the oxide film is 44 atomic%. There is a summary where:

  The aluminum alloy film preferably contains 0.1 to 6 atomic% of at least one selected from the group consisting of Au, Ag, Zn, Cu, Ni, Sr, Sm, Ge, and Bi as an alloy component. Those containing at least Ni are optimal.

  In the aluminum alloy film, at least one selected from the group consisting of Nd, Y, Fe, Co, Ti, Ta, Cr, Zr, and Hf as a further alloy component is in the range of 0.1 to 6 atomic%. May be included.

  The aluminum alloy film containing Ni as an alloy component has a Ni concentrated layer of 0.5 to 10 nm from the surface of the film, and the average Ni concentration in the Ni concentrated layer is the average in the aluminum alloy film. It is desirable that it is twice or more the Ni concentration.

  These aluminum alloy films effectively function as reflective films or tab connection electrodes in display devices. A preferable material for the transparent conductive film is indium tin oxide (ITO) or indium zinc oxide (IZO).

  Moreover, this invention has as another embodiment the transparent conductive film arrange | positioned on a board | substrate, and the aluminum alloy film which electrically connects this transparent conductive film, The aluminum alloy film and the said transparent conductive film Provided is a passive matrix driving display device in which an oxide film of the aluminum alloy is formed at the interface, the oxide film has a thickness of 1 to 10 nm, and the oxygen content in the oxide film is 44 atomic% or less. To do.

  Furthermore, in the display device according to the present invention, when the transparent conductive film is formed on the aluminum alloy film formed on the substrate, the electrode film is formed in a non-oxidizing gas atmosphere at an initial stage while the substrate temperature is increased. After the formation, the latter half can be easily manufactured by forming an electrode film in an oxygen-containing atmosphere.

  According to the present invention, a direct contact between an aluminum alloy film and a transparent conductive film can be realized under stable controllability, a barrier metal can be omitted, and a long-term reliable, inexpensive and high-performance display device. Can provide.

FIG. 1 is a schematic cross-sectional enlarged explanatory view illustrating the configuration of a liquid crystal panel substrate and a liquid crystal display device to which a display device array substrate according to the present invention is applied. FIG. 2 is a schematic cross-sectional explanatory view illustrating the structure of a thin film transistor applied to the display device array substrate according to the first embodiment of the invention. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is explanatory drawing which shows an example of the manufacturing process of the array substrate for display devices shown in the said FIG. 2 later on in order. It is a graph which shows the relationship between the oxygen content in the oxide film formed in the interface with ITO which comprises the transparent conductive film of an aluminum alloy film, contact resistance, and an electrical resistivity. It is a graph which shows the relationship between the storage time in air | atmosphere, and an oxide film thickness about pure aluminum and Al-2 primitive% Ni alloy. It is a TEM photograph which shows the example of the oxidation layer and Ni concentration layer which were formed in the direct contact interface of the ITO film | membrane and Al-2 atomic% Ni alloy which comprise a transparent conductive film. It is a graph which shows the influence which Ni content contained in Ni concentration layer has on contact resistance and an oxide film thickness. FIG. 5 is a schematic cross-sectional explanatory view illustrating the structure of a thin film transistor applied to a display device array substrate according to another embodiment of the invention. FIG. 17 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 16 in order. FIG. 17 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 16 in order. FIG. 17 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 16 in order. FIG. 17 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 16 in order. FIG. 17 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 16 in order. FIG. 17 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 16 in order. FIG. 17 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 16 in order. FIG. 17 is an explanatory diagram showing an example of a manufacturing process of the display device array substrate shown in FIG. 16 in order. It is a figure which shows the Kelvin pattern used for the contact resistance measurement of an aluminum alloy film and a transparent conductive film.

  According to the present invention, when the transparent conductive film and the aluminum alloy film are brought into contact with each other, the electrical resistivity of the aluminum oxide layer formed at the interface is reduced and the conductivity of the aluminum alloy oxide layer is increased. It enables direct contact between the transparent conductive film and the aluminum alloy. At this time, in order to reduce the electrical resistivity of the aluminum alloy oxide layer, it is effective to control the film thickness and oxygen content of the aluminum alloy oxide layer at the interface. As a result, the contact resistance is reduced and stabilized. Can be controlled.

Incidentally, in the conventional method, since the transparent conductive film is brought into direct contact with pure aluminum, Al—Nd alloy or the like, the contact resistance is high and non-ohmic contact is obtained. The reason is that the aluminum oxide layer formed at the contact interface becomes a high-resistance film containing almost the same amount of oxygen as the stoichiometric aluminum oxide (Al ₂ O ₃ ), and the thickness of the aluminum oxide layer Seems to be thicker.

  On the other hand, in the present invention, at least one element selected from the group consisting of Au, Ag, Zn, Cu, Ni, Sr, Sm, Ge, and Bi, particularly preferably Ni, is used as an alloy component in the aluminum layer. An appropriate amount is contained, thereby imparting conductivity to the aluminum alloy oxide layer by suppressing oxidation of aluminum when forming the transparent conductive film, and preferably by further concentrating the alloy component at the contact interface. It is possible to achieve stable and highly reliable contact characteristics, that is, low contact resistance, even with different alloy materials. As a result, the number of processes and manufacturing costs can be greatly reduced while maintaining the display quality of the liquid crystal display at a high level.

  Hereinafter, embodiments of a display device according to the present invention will be described in detail with reference to the drawings. However, the present invention is not limited to the illustrated examples, and a range that can be adapted to the purpose described above and below. The present invention can be carried out with appropriate modifications, all of which are included in the technical scope of the present invention.

  In the present invention, a passive matrix driving display device that does not include a thin film transistor, a reflective electrode of a reflective liquid crystal display device, and a TAB (tab) connection electrode used for signal input / output to the outside are also used for aluminum. Although an alloy film can be similarly applied, these embodiments are omitted.

  FIG. 1 is a schematic enlarged cross-sectional view of a liquid crystal panel structure mounted on a liquid crystal display device to which the present invention is applied.

  The liquid crystal panel of FIG. 1 is disposed between a TFT array substrate 1, a counter substrate 2 disposed to face the TFT array substrate 1, and between the TFT array substrate 1 and the counter substrate 2, and serves as a light modulation layer. A functioning liquid crystal layer 3 is provided. The TFT array substrate 1 includes a thin film transistor (TFT) 4 disposed on an insulating glass substrate 1a, a transparent conductive film 5, and a wiring portion 6 including scanning lines and signal lines.

  The counter substrate 2 includes a common electrode 7 formed on the entire surface of the TFT array substrate 1, a color filter 8 disposed at a position facing the transparent conductive film 5, a thin film transistor (TFT) 4 on the TFT array substrate 1, and wiring The light shielding film 9 is disposed at a position facing the portion 6.

  Further, polarizing plates 10 and 10 are disposed on the outer surface side of the insulating substrate constituting the TFT array substrate 1 and the counter substrate 2, and the liquid crystal molecules contained in the liquid crystal layer 3 are placed on the counter substrate 2 in a predetermined manner. An alignment film 11 for aligning in the direction is provided.

  In the liquid crystal panel having such a structure, the alignment direction of the liquid crystal molecules in the liquid crystal layer 3 is controlled by the electric field formed between the counter electrode 2 and the transparent conductive film 5, so that the TFT array substrate 1 and the counter substrate 2 The light passing through the liquid crystal layer 3 is modulated, whereby the amount of transmitted light passing through the counter substrate 2 is controlled to display an image.

  The TFT array is driven by a driver circuit 13 and a control circuit 14 by a TAB tape 12 drawn out of the TFT array.

  In the figure, 15 is a spacer, 16 is a sealing material, 17 is a protective film, 18 is a diffusion plate, 19 is a prism sheet, 20 is a light guide plate, 21 is a reflector, 22 is a backlight, 23 is a holding frame, and 24 is a print. Each of the substrates is shown and will be described later.

  FIG. 2 is a schematic cross-sectional explanatory view illustrating the structure of the thin film transistor portion according to the first embodiment applied to the array substrate employed in the present invention. As shown in FIG. 2, a scanning line 25 is formed of an aluminum alloy film on the glass substrate 1a, and a part of the scanning line 25 functions as a gate electrode 26 for controlling on / off of the thin film transistor. A signal line is formed of an aluminum alloy film so as to cross the scanning line 25 with the gate insulating film 27 interposed therebetween, and a part of the signal line functions as a source electrode 28 of the thin film transistor. This type is generally called a bottom gate type.

In the pixel region on the gate insulating film 27, for example, a transparent conductive film 5 formed of an ITO film containing SnO in In ₂ O ₃ is disposed. The drain electrode 29 of the thin film transistor formed of the aluminum alloy film is in direct contact with and electrically connected to the transparent conductive film 5.

  When a gate voltage is supplied to the TFT array substrate 1 via the scanning line 25 to the gate electrode 26, the thin film transistor is turned on, and the driving voltage previously supplied to the signal line is transparent from the source electrode 28 via the drain electrode 29. It is supplied to the conductive film 5. Then, when a predetermined level of driving voltage is supplied to the transparent conductive film 5, a potential difference is generated between the transparent electrode 5 and the counter electrode 2, as described in FIG. Done.

  Next, a method for manufacturing the TFT array substrate 2 shown in FIG. 2 will be briefly described. Here, an example of the thin film transistor formed as the switching element is an amorphous silicon TFT using hydrogenated amorphous silicon as a semiconductor layer.

  An outline of the manufacturing process of the TFT array substrate 1 according to the first embodiment will be described with reference to FIGS.

  First, an aluminum alloy thin film having a film thickness of, for example, about 200 nm is formed on the glass substrate 1a by a method such as sputtering, and the gate electrode 26 and the scanning line 25 are formed by patterning the aluminum alloy thin film (FIG. 3). At this time, it is preferable to etch the periphery of the aluminum alloy thin film in a taper shape of about 30 to 40 degrees so that the coverage of the gate insulating film 27 described later is improved. Next, as shown in FIG. 4, a gate insulating film 27 is formed of a silicon oxide film (SiOx) having a film thickness of, for example, about 300 nm by a method such as plasma CVD, and further, a hydrogenated amorphous film having a film thickness of, for example, about 50 nm. A silicon film (a-Si: H) and a silicon nitride film (SiNx) having a thickness of about 300 nm are formed.

Subsequently, as shown in FIG. 5, the silicon nitride film (SiNx) is patterned by backside exposure using the gate electrode 26 as a mask to form a channel protective film. Further, after an n + type hydrogenated amorphous silicon film (n ⁺ a-Si: H) having a thickness of, for example, about 50 nm doped with phosphorus is formed thereon, a hydrogenated amorphous silicon film (a -Si: H) and an n + type hydrogenated amorphous silicon film (n ⁺ a-Si: H) are patterned.

Then, an aluminum alloy film having a film thickness of, for example, about 300 nm is formed thereon, and patterned as shown in FIG. 7, so that the source electrode 28 integrated with the signal line and the drain electrode in contact with the transparent conductive film 5 are formed. 29 is formed. Further, the n ⁺ type hydrogenated amorphous silicon film (n ⁺ a-Si: H) on the channel protective film (SiNx) is removed using the source electrode 28 and the drain electrode 29 as a mask.

  Then, as shown in FIG. 8, a protective film is formed by forming a silicon nitride film 30 with a film thickness of, for example, about 300 nm using, for example, a plasma CVD apparatus. The film formation at this time is performed at about 260 ° C., for example. Then, after a photoresist layer 31 is formed on the silicon nitride film 30, the silicon nitride film 30 is patterned, and contact holes 32 are formed in the silicon nitride film 30 by, for example, dry etching. Although not shown, a contact hole is formed at a portion corresponding to connection with TAB on the gate electrode at the end of the panel.

  Further, as shown in FIG. 9, after passing through an ashing process using, for example, oxygen plasma, the photoresist layer 31 is stripped using, for example, an amine-based stripping solution, and finally, for example, within a storage time of about 8 hours, FIG. For example, an ITO film having a thickness of about 40 nm is formed, and the transparent conductive film 5 is formed by patterning. At the same time, when an ITO film is patterned for bonding to the TAB at the connection portion of the gate electrode at the edge of the panel, the TFT array substrate is completed.

  In the present invention, when the ITO film constituting the transparent conductive film 5 is formed on the aluminum alloy film constituting the drain electrode 29 or the like by sputtering, the aluminum alloy film is electrically conductive at the interface with the transparent conductive film 5. In order to form this oxide film, a multi-stage film forming method having two or more stages is preferably employed. As an example of a preferable film forming method, the substrate temperature is preferably set in a range of 100 to 200 ° C., and first, for example, a film thickness of 5 to 20 nm (preferably about 10 nm) is used without adding oxygen using a non-oxidizing gas such as argon. Film formation is performed. During this period, that is, in the initial stage of forming the ITO film constituting the transparent conductive film 5, the film is formed in an atmosphere without oxygen addition so that the surface of the aluminum alloy film is not oxidized as much as possible. When film formation is performed without adding oxygen, the oxygen content in the ITO film formed by sputtering decreases, and the conductivity of the film itself decreases. However, if appropriate substrate heating is performed at this time, the crystallinity of ITO increases, and the decrease in conductivity as the transparent conductive film 5 can be compensated.

Next, while maintaining the substrate temperature, the atmospheric gas is changed to an oxygen-containing gas in which oxygen is mixed in a non-oxidizing gas, and a film having a thickness of about 20 to 200 nm (preferably around 40 nm) is formed, for example. At this time, the amount of oxygen added to the atmospheric gas is not particularly limited, but as a typical condition, for example, oxygen is controlled to about 10 to 50 μTorr (preferably about 20 μTorr) with respect to about 1 to 5 mTorr (preferably about 3 mTorr). It is preferable. Incidentally, it has been confirmed that when such a condition is adopted, the electric resistance of the formed ITO film becomes the lowest and becomes about 1 × 10 ⁻⁴ Ω · cm or less. In addition to the addition of oxygen, the same effect can be obtained by addition of water vapor. In this way, the formation of the ITO film by sputtering is performed in two stages (or multiple stages) by changing the oxygen content of the atmospheric gas, while suppressing the oxidation of the aluminum alloy film at the initial stage of ITO film formation, while the ITO film As such, it is possible to ensure a sufficiently high conductivity.

  Incidentally, while the ITO film is amorphous at low temperatures, it becomes polycrystalline when the temperature at the time of film formation is increased, and the conductivity is greatly increased by the improvement of the crystallinity, and in the oxygen-containing atmosphere gas at the later stage of film formation. The conductivity of the ITO film is increased by the film formation.

  By the way, according to the present inventors, for example, when an Al-Ni alloy and pure Al are compared, there is almost a difference in the oxygen content of the oxide film and the thickness of the oxide film when these are naturally oxidized. Despite the absence (see FIG. 12 below), a difference occurs after the ITO film is formed thereon. From this, it is considered that the final oxidation form of the oxide film on the surface of the aluminum alloy film is determined when the ITO film forming the transparent conductive film is formed. Moreover, the change in the form of the oxide film is considered to be influenced by the alloying elements (Ni, etc.) added to Al, and the oxygen in the oxide layer is selected by selecting the alloying elements and setting appropriate conditions during the ITO film formation. By appropriately controlling the content and the film thickness, a low and stable contact resistance can be realized.

  Incidentally, when the ITO film is formed under the conditions as described above, the contact resistance between the ITO film and the Al-2 atomic% Ni alloy film is 2 to 17Ω, whereas the two-stage film formation is not performed. It has been confirmed that when the ITO film is formed under the condition that oxygen is mixed in the atmospheric gas from the beginning without heating the substrate, the contact resistance is 750Ω or more. It can be seen that this is extremely effective in reducing the above.

  In addition to the above Ni, the effect of the additive alloy element can be obtained with Au, Ag, Zn, Cu, Sr, Sm, Ge, and Bi. One or two of these alloy elements can be obtained. It has been confirmed that the contact resistance is significantly reduced by using the above-described two-stage film method using an aluminum alloy containing an appropriate amount of the above.

In Japanese Patent Application No. 2002-368786 presented as a prior invention, since the oxygen content of the oxide film as described above is not actively controlled, the oxygen content in the aluminum alloy oxide film present at the contact interface is large. The oxygen content is almost stoichiometric with respect to Al ₂ O ₃ and the contact resistance is high. Therefore, in order to reduce the contact resistance at the contact interface, the oxide film is removed by overetching or a stripping solution, or a metal compound or the like is deposited on the contact interface with the ITO film. However, in the present invention, such treatment is completely unnecessary by reducing the contact resistance by suppressing the oxygen content in the oxide film present at the contact interface as described above.

By the way, when oxygen is contained in the atmosphere gas at the initial stage of ITO film formation and the substrate is heated, the contact resistance is reduced to some extent to 250Ω compared to 750Ω when the substrate is not heated. When the film is formed while heating the substrate without adding oxygen, the contact resistance is reduced to about 3 to 33Ω, but the electrical resistivity of the ITO film itself is as high as about 8 × 10 ⁻⁴ Ω · cm.

  However, when the two-stage film formation method preferably employed in the present invention is employed, the contact resistance at the contact interface between the aluminum alloy film and the ITO film formed thereon is lowered, and the electrical property of the ITO film itself is reduced. The resistivity is also kept low. In addition, it is conceivable to increase the conductivity of the ITO film by mixing water vapor or hydrogen in the atmosphere gas instead of oxygen, and among these, water vapor particularly acts as an oxidizing gas under heating conditions. On the other hand, it is effective because it exhibits an oxidizing action like oxygen.

  As described above, in the present invention, the type of the alloy element in the aluminum alloy film is specified, and the characteristics of the oxide film formed on the contact interface and the ITO are controlled by controlling the film forming conditions of the ITO film formed thereon. By improving the characteristics of the film, even if an oxide film is present at the contact interface, direct contact can be made without removing it.

  In particular, as described in detail later, the oxygen content in the aluminum alloy oxide film at the contact interface is suppressed to 44 atomic% or less, more preferably 42 atomic% or less, and the thickness of the oxide film is preferably 1 to 10 nm. The contact resistance can be reduced as much as possible by adjusting the range, more preferably 2 to 8 nm, and particularly preferably around 5 nm. For this reason, in the present invention, proper selection of alloy elements constituting the aluminum alloy film and control of ITO film forming conditions are extremely important.

  In the TFT array substrate manufactured by the above method, for example, the drain electrode 29 formed of an aluminum alloy and the transparent conductive film 5 are in direct contact, and the gate electrode 26 and the ITO film for TAB connection are also directly connected. Contacted.

  At this time, for example, as the aluminum alloy film material constituting the drain electrode 29, at least selected from the group consisting of Au, Ag, Zn, Cu, Sr, Sm, Ge, Bi other than the Al—Ni alloy as described above. When an aluminum alloy containing 0.1 to 6 atomic% as one alloy component is used, the aluminum alloy film and the transparent conductive film constituting the drain electrode 29 are controlled by appropriately controlling the formation conditions of the drain electrode 29. The contact resistance with 5 can be significantly reduced.

  Incidentally, when the amount of the alloy element contained in the aluminum alloy film is less than 0.1 atomic%, the oxygen content of the oxide layer formed at the contact interface with the transparent conductive film 5 is not sufficiently lowered, and is intended in the present invention. Therefore, it is difficult to obtain a contact resistance reduction effect at a certain level. On the contrary, if the amount of the alloy element exceeds 6 atomic% and becomes excessively large, the electrical resistance of the aluminum alloy film itself is increased, the response speed of the pixel is decreased, the power consumption is increased, and the display quality is lowered. Making it difficult to put to practical use. Therefore, in consideration of these interests, the content of the alloy element is 0.1 atomic% or more, more preferably 0.2 atomic% or more, and 6 atomic% or less, more preferably 5 atomic% or less. Is desired.

  In the present invention, it is also effective to further contain at least one element selected from the group consisting of Nd, Y, Fe, Co, Ti, Ta, Cr, Zr, and Hf as an alloy element other than the above. That is, these elements are preferably contained in an aluminum alloy in an amount of 0.1 to 6 atomic%, more preferably 0.2 to 2 atomic%, thereby preventing hillocks and voids and increasing the heat resistance to 300 ° C. or higher. This is because it exhibits an effect of increasing mechanical strength, corrosion resistance, and the like. Among these, at least one selected from the group consisting of Nd, Y, Fe, and Co is particularly preferable. From the viewpoint of electrical resistivity, these four elements can sufficiently reduce the electrical resistivity of the aluminum alloy wiring even by heat treatment at 300 ° C.

  Furthermore, in the present invention, as a more preferable embodiment capable of further reducing the contact resistance between the aluminum alloy film and the transparent conductive film 5, in the aluminum alloy film containing the alloy element as described above, for example, Ni, the interface side with the transparent conductive film 5 is used. It is effective to form a Ni concentrated layer on the surface of the aluminum alloy film. The preferred thickness of the Ni concentrated layer is 0.5 nm or more, more preferably 1.0 nm or more and 10 nm or less, more preferably 5 nm or less. The average Ni concentration in the Ni concentrated layer is an aluminum alloy. It is desirable that the average Ni concentration in the total amount of the film is 2 times or more, more preferably 2.5 times or more. In the case of an aluminum alloy containing an alloy component such as Au, Ag, Zn, Cu, Sr, Sm, Ge, Bi as well as Ni as described above, similarly, the surface of the aluminum alloy film has the same thickness and concentration. It is effective to form a concentrated layer.

  In the case of an aluminum alloy film containing an alloy element such as Ni, Ni exceeding the solid solubility limit (0.1%) of Ni in the aluminum alloy film is precipitated at the grain boundary of the aluminum alloy by heat treatment or the like, and a part of the aluminum alloy film A Ni concentrated layer is formed by diffusing and concentrating on the surface of the alloy film. In the present invention, for example, when etching a contact hole, a halogen compound of Ni is less likely to volatilize because it has a vapor pressure lower than that of aluminum, and remains on the surface of the aluminum alloy film. Becomes a higher concentration state than the Ni concentration of the aluminum alloy bulk material. Therefore, the Ni concentration of the surface layer and the thickness of the concentrated layer can also be controlled by appropriately controlling the etching conditions.

  If a display device including a TFT array substrate formed in this way is used as, for example, a liquid crystal display device, the contact resistance between the transparent conductive film and the connection wiring portion can be minimized. The adverse effect on the display quality of the screen can be suppressed as much as possible.

By the way, in the conventional manufacturing method, when pure aluminum or an Al—Nd alloy is used as a wiring material and brought into direct contact with the transparent conductive film, a high-resistance aluminum oxide layer is formed at the contact interface, resulting in non-ohmic contact. According to the results of cross-sectional TEM observation and EDX composition analysis, the oxygen content in the aluminum oxide layer formed at the contact interface at this time is almost the same as that of aluminum oxide (Al ₂ O ₃ ) of the stoichiometric composition, and oxygen The content was 60 atomic% (composition ratio: Al: O = 1: 1.5), and the thickness in the oxide layer was about 6.5 to 7 nm. When the contact resistance at this time was measured with a contact hole of 80 μm, it was about 150 kΩ. Al ₂ O ₃ having a stoichiometric composition is an insulator, and is generally said to have an electric resistivity of about 10 ¹⁴ Ω · cm. As a high-resistance insulating film even with a film thickness of only 6.5 to 7 nm, It is thought that it worked.

  In contrast to such a conventional technique, the oxygen content of the aluminum alloy oxide layer is, for example, 40.2 atomic% (composition ratio: Al: O = 1: 0.67) and the film thickness is 4-4. It was confirmed that the contact resistance was 12Ω when controlled to 5 nm. As described above, in the case of an oxide layer having a low oxygen content and rich in metallic aluminum, the oxide layer exhibits n-type semiconducting characteristics and exhibits electrical conductivity like metallic aluminum. In addition, although the influence on the contact resistance value is small when the film thickness is about several nm, the contact resistance becomes smaller as the film thickness is thinner. Therefore, the thickness of the oxide layer is preferably suppressed to about 10 nm or less.

  FIG. 11 is a graph showing the results of examining the relationship between the oxygen content contained in the aluminum alloy oxide layer, the electrical resistivity, and the contact resistance value. As is clear from this figure, when the oxygen content of the aluminum alloy oxide layer exceeds 40 atomic% (composition ratio: O / Al = 0.67), both the contact resistance and the electrical resistivity rapidly increase. When it exceeds 44 atomic% (O / Al = 0.79), it exceeds 200Ω, and when it exceeds 49 atomic% (O / Al = 0.96), it exceeds 150 kΩ. When it further reaches 56 atomic% (O / Al = 1.27), it changes from ohmic contact to non-ohmic contact. If the contact resistance exceeds 200 Ω, the display quality and the yield may be deteriorated, which is considered undesirable. Therefore, it is desirable to suppress the oxygen content to 44 atomic% or less.

  By the way, it is considered that the surface of the aluminum alloy film undergoes natural oxidation even when stored in the atmosphere, and further oxidation proceeds during the ITO film formation, thereby forming a thicker oxide film at the contact interface. For example, the growth rate of the natural oxide film of aluminum analyzed from the measurement result of XPS (X-ray photoelectron spectroscopy) is, for example, as shown in FIG. Almost the same in the case of alloys. For example, when stored in the atmosphere for 16 hours, an oxide film having a film thickness of 3 nm is formed, and the oxygen content of the oxide film has a stoichiometric composition of about 60 atomic% (Al: O = 1: 1.5). Become.

  On the other hand, when the ITO film was formed on the surface of the Al-2 atomic% Ni alloy film by the above-described method (two-stage film forming method according to the present invention), and the cross section of the contact portion was observed by TEM, the oxide film film The thickness is thicker than the natural oxide film and increases to 4 to 4.5 nm (4/3 times to 4.5 / 3 times, ie 1.3 to 1.5 times), but the oxygen content of the oxide film is 40. .2 atomic%. As described above, the volume of the oxide film before ITO film formation is 1.3 to 1.5 times higher. However, since no new oxygen is taken in during the volume increase process, about 60 atomic% of the oxygen content contained before ITO film formation is reduced to about 40 atomic% (ie, about 60 atomic% / 1.5). Presumed to have been reduced.

  For this reason, in order to reduce the oxygen content of the aluminum alloy oxide film layer, it is important to suppress the oxidation of aluminum that occurs during ITO film formation, and for that reason, at least at the initial stage of film formation, a non-oxidizing gas that does not contain oxygen It is necessary to carry out under atmospheric conditions. The electrical resistivity of the oxide layer at this time is estimated to be about 200 μΩ · cm from the tendency of FIG. 11, and the contact resistance is considered to be about 12Ω. It is also clear that controlling the amount of oxygen taken in the ITO film formation process is effective in reducing contact resistance.

  Next, it will be described that impurities contained in the aluminum alloy oxide film can effectively work to improve conductivity.

For example, it is well known that when an alkali metal such as sodium or potassium is added as an impurity to β-Al ₂ O ₃ , an ion conductive material having an electrical resistivity of about 10 ² Ω · cm is obtained. This is because the size of the alkali metal ions is sufficiently small relative to the crystal lattice of Al ₂ O ₃ and can move freely between the lattices. However, when alkali metal ions are mixed in a semiconductor material such as TFT, they may become mobile ions and become an obstacle.

Therefore, it is also conceivable to increase the electrical conductivity in the same manner by adding Ni or the like, which has less influence on the semiconductor element than the alkali metal, into the aluminum oxide layer. When Al-2 atomic% Ni and ITO are directly connected, according to EDX analysis using a cross-sectional TEM sample, the amount of Ni contained in the Ni concentrated layer is 4-8 atomic%. It was confirmed that Ni was contained at least 2 atomic%.

  In the case of an Al—Ni alloy, for example, as shown in FIG. 13 (TEM observation photograph of an aluminum oxide layer and a Ni concentrated layer formed at the direct contact interface between ITO and an Al—Ni alloy film), aluminum oxide (AlOx ) And a bulk Al—Ni alloy thin film, a Ni concentrated layer having a thickness of about 1 nm is formed. This is because aluminum diffuses in the direction of the oxide film as the oxidation of aluminum progresses, Ni diffuses in the bulk direction, and Ni tends to remain as a residue when dry etching the contact hole. Conceivable. When the Ni concentrated layer is formed by these influences, the diffusion of aluminum ions from the aluminum alloy bulk is suppressed, and the effect of suppressing oxidation of aluminum is expected.

  Further, FIG. 14 is a graph showing the relationship between the amount of Ni contained in the Ni concentrated layer, the oxide film thickness (nm), and the contact resistance (Ω). As the amount of Ni increases, the thickness of the aluminum oxide film observed after the ITO film formation decreases. At the same time, the oxygen content decreases, for example, as shown in FIG. 15, and the contact resistance also decreases. Therefore, it can be said that the Ni concentrated layer plays an important role.

  In order to effectively exhibit the action of the Ni concentrated layer, as described above, the thickness of the concentrated layer is adjusted to a range of 1 to 10 nm, and the Ni content in the concentrated layer is Al—Ni. It has been confirmed that the Ni content of the entire alloy layer should be twice or more.

  By the way, even when pure aluminum or an Al—Nd alloy is used, in contrast to the case of FIG. 2, when the ITO is used as the lower layer and the aluminum alloy material is formed on the upper layer side, the oxidation at the interface is suppressed. Ohmic contact may be possible. This is because when the film formation order is changed and an aluminum alloy film is formed after ITO film formation, a high-resistance aluminum oxide film is not formed at the interface.

  In addition, when an aluminum alloy containing Ni or the like is oxidized, aluminum diffuses in the aluminum oxide and is combined with oxygen on the surface to oxidize. On the other hand, Ni with a small solid solution amount in the aluminum oxide is bulky. It diffuses in the direction and is left behind to form a Ni enriched layer. In addition, the Ni content can be controlled by etching the aluminum surface by dry etching that leaves Ni on the surface, or by forming a concentrated layer by heating. In the case of heating, according to the depth profile measurement by Auger spectroscopy, for example, when heating at 150 to 300 ° C. for 1 hour, the Ni content increases from 3.1 atomic% to 5.1 atomic%, and when dry etching is performed. Concentration to 10.2 atomic% has been confirmed.

  Therefore, in order to form the Ni concentrated layer having the preferable thickness and Ni content as described above, the concentrated layer is utilized by utilizing the phenomenon as described above, for example, by using the substrate heating employed when forming the insulating film. Examples of preferable methods include a method of forming aluminum, a method of surface-treating aluminum wiring with an etching agent such as plasma or acid / alkali, and a method of continuously etching a small amount of the aluminum surface.

By the way, when the pure aluminum wiring is directly contacted with the ITO film, the contact resistance is 1.5 × 10 ⁵ Ω, and when Al—Nd, which is a typical aluminum alloy wiring, is directly contacted with the ITO film. The contact resistance is 8.4 × 10 ⁸ Ω. Further, as a conventional structure, the contact resistance is 1.0 × 10 ¹ Ω when Mo is interposed as a barrier metal between the ITO film and the Al—Nd wiring. In contrast, the contact resistance of the Al—Ni alloy wiring is 1.2 × 10 ¹ Ω, the contact resistance of the Al—Ni—Nd alloy wiring is 1.5 × 10 ¹ Ω, and the contact resistance of the Al—Ni—Y alloy wiring. Was 1.3 × 10 ¹ Ω, and both were substantially equivalent to the conventional structure using Mo as the barrier metal.

  Next, the results of the constant temperature and humidity test will be described. The constant temperature and humidity test is one type of environmental load test, and is a test for examining the influence on a device when held at a constant temperature and humidity (usually high temperature and high humidity atmosphere) for a long time. In this example, the contact resistance before and after the test was compared. In the test, a test material for evaluation in which an aluminum alloy and ITO were directly connected to each other in a constant temperature bath at 80 ° C. and 80 RH% was stored, taken out after 120 hours and 240 hours, and contact resistance was measured. For comparison, a SiN film is formed on an aluminum alloy by a CVD method, a contact hole is formed by dry etching and then an ITO film is formed, and an ITO film is directly formed on the aluminum alloy. In addition, a heat treatment at 150 ° C. or higher and dry etching were not applied. As a result, it was confirmed that the contact characteristics did not change before and after the treatment when the aluminum alloy wiring was subjected to heat of 150 ° C. or higher or dry etching. For example, in the case of Al-2 atomic% Ni-0.6 atomic% Nd, the contact resistance ratio before and after the treatment was almost 1, and no change was observed.

Next, the results of the energization test will be described. This test is also a kind of reliability test, and a change in contact resistance was observed by continuously applying a high-density pulse current to the connection portion for a long time. A pulse current that repeatedly turns on and off a current of 5 mA with a constant pulse width from the aluminum alloy to the ITO side is continuously applied to the 80 μm square contact hole evaluation specimen in which the aluminum alloy and ITO are directly connected. The value of 5 mA is a value of 78 A / cm ² in terms of the current density at the contact surface, which is a relatively large current. Similarly, in the case of Al-2 atomic% Ni-0.6 atomic% Nd subjected to heating and dry etching, the initial contact resistance was 15Ω, and no change was observed after 14 hours of energization.

In this way, the contact resistance when the aluminum alloy according to the present invention is used is compared with the case where the pure aluminum wiring is directly contacted to the ITO film (the contact resistance is 1.5 × 10 ⁵ Ω as described above). It turns out that it reduces to about 1/10 < ⁴ >.

  When the liquid crystal display device is prototyped in the embodiment of the present invention as described above, the manufacturing yield and display quality are exactly the same level as the case of combining the ITO film and the barrier metal (Mo or the like). Therefore, in this liquid crystal display device, it is possible to obtain the same performance as a conventional liquid crystal display device without disposing a barrier metal. For this reason, omission of a barrier metal can simplify a manufacturing process and can contribute to reduction of manufacturing cost. That is, instead of the conventional pure aluminum, aluminum alloy, and Mo-W film, if the above-mentioned aluminum alloy film is used as an electrode, direct contact with the transparent conductive film is possible, simplifying the manufacturing process and reducing the manufacturing cost. it can.

  Next, a passive matrix display element will be described as another example applied to the array substrate of the present invention.

  In the passive matrix type, vertical and horizontal electrode lines are configured like a mesh, and pixels are driven for each line. In this example, even when the interlayer insulating film of the electrode does not exist, that is, even when heat sufficient to form an intermetallic compound as described in the above-mentioned prior application is not applied to the electrode wire, it is used for the electrode wire. The aluminum alloy film and the ITO film can be directly connected with low contact resistance. In this case, heat is not applied to the aluminum alloy, contact etching or the like is not performed, and it is not necessary to etch the aluminum alloy surface. In the previous embodiment, heat is applied when, for example, SiNx is formed by the CVD method or the like, and the surface of the aluminum alloy film is also etched by a small amount when SiNx is contact-etched.

  However, in the present invention, direct contact is possible even when heat or etching is not applied to the aluminum alloy film. Incidentally, the contact resistance when the ITO film constituting the transparent conductive film was brought into contact with the Al-2 atomic% Ni alloy was 9Ω. Alloy elements such as Ni at the contact interface are concentrated not only by heating and surface etching but also by natural oxidation. For example, the solid solubility limit of Ni in aluminum is smaller than 0.1 atomic%, and an ITO film is formed. In this case, it is considered that Ni exceeding the solid solubility limit appears at the grain boundary in at least the surface layer portion of the aluminum alloy film by substrate heating or plasma heating. At that time, the amount of oxygen in the aluminum alloy oxide layer does not change, the film thickness increases, the oxygen content (concentration) decreases, and a small amount of Ni is taken into the oxide film to increase conductivity. I believe.

  FIG. 16 is an enlarged cross-sectional explanatory view schematically showing the structure of a thin film transistor according to another embodiment applied to the array substrate of the present invention. In this example, a thin film transistor having a top gate structure is applied.

  As shown in FIG. 17, a scanning line is formed of an aluminum alloy thin film on the glass substrate 1a, and a part of the scanning line functions as a gate electrode 26 for controlling on / off of the thin film transistor. Further, a signal line is formed of an aluminum alloy so as to cross the scanning line through an interlayer insulating film (SiOx), and a part of the signal line functions as a source electrode 28 of the thin film transistor.

The pixel region on the interlayer insulating film (SiOx), for example, In ₂ O ₃ transparent conductive film 5 made of ITO film containing SnO in is arranged, also, the drain electrode of the thin film transistor formed by an aluminum alloy Reference numeral 29 functions as a connection electrode portion that is electrically connected to the transparent conductive film 5. That is, the drain electrode 29 of the thin film transistor formed of an aluminum alloy is in direct contact with and electrically connected to the transparent conductive film 5.

  Accordingly, when the gate voltage is supplied to the TFT array substrate via the scanning line to the gate electrode 26 as in the example of FIG. 2, the thin film transistor is turned on, and the driving voltage supplied in advance to the signal line is applied to the source electrode. When a predetermined level of driving voltage is supplied to the transparent conductive film 5 from the drain 28 through the drain electrode 29, a potential difference is generated between the counter electrode 10 and the liquid crystal as described with reference to FIG. The liquid crystal molecules contained in the layer 3 are aligned to perform light modulation.

  Next, a manufacturing method of the TFT array substrate shown in FIG. 16 will be described. The thin film transistor provided in the array substrate according to this embodiment has a top gate structure using a polysilicon film (poly-Si) as a semiconductor layer, and FIGS. 17 to 23 illustrate the TFT array substrate according to the second embodiment. It is the figure which showed the manufacturing process schematically.

First, a silicon nitride film (SiNx) having a film thickness of about 50 nm, a silicon oxide film (SiOx) having a film thickness of about 100 nm, and a film are formed on the glass substrate 1a by, for example, a plasma CVD method at a substrate temperature of about 300 ° C. A hydrogenated amorphous silicon film (a-Si: H) having a thickness of, for example, about 50 nm is formed, and heat treatment and laser annealing are performed to convert the hydrogenated amorphous silicon film (a-Si: H) into polysilicon. The heat treatment is performed by, for example, an atmosphere heat treatment at about 470 ° C. for about one hour, and after dehydrogenation treatment, the laser is irradiated with hydrogen, for example, using an excimer laser annealing apparatus with an energy of about 230 mJ / cm ^2. The film (a-Si: H) is irradiated to obtain a polysilicon film (poly-Si) having a thickness of about 0.3 μm, for example (FIG. 17).

  Thereafter, as shown in FIG. 18, the polysilicon film (poly-Si) is patterned by plasma etching or the like. Next, as shown in FIG. 19, a silicon oxide film (SiOx) is formed to a thickness of, for example, about 100 nm to form a gate insulating film 27. On the obtained gate insulating film 27, by sputtering or the like, an aluminum alloy film that becomes the gate electrode 26 integrated with the scanning line is formed with a film thickness of, for example, about 200 nm, and then patterned by a method such as plasma etching, A gate electrode 26 integral with the scanning line is formed.

Subsequently, as shown in FIG. 20, a mask is formed with a photoresist 31, and, for example, phosphorus is doped with about 1 × 10 ¹⁵ atoms / cm ^{2 at} about 50 KeV by an ion implantation apparatus or the like, and a polysilicon film (poly-Si) is formed. An n ⁺ type polysilicon film (n ⁺ poly-Si) is formed on a part of the photoresist 31, and then the photoresist 31 is peeled off and diffused by heat treatment at about 500 ° C., for example.

Subsequently, as shown in FIG. 21, a silicon oxide film (SiOx) is formed with a film thickness of, for example, about 500 nm and a substrate temperature of about 300 ° C. by using, for example, a plasma CVD apparatus or the like. After patterning the photoresist, the interlayer insulating film (SiOx) and the silicon oxide film of the gate insulating film 27 are dry-etched, contact holes are formed, and an aluminum alloy film is formed to a thickness of, for example, about 450 nm by sputtering. By patterning, the source electrode 28 and the drain electrode 29 integrated with the signal line are formed. As a result, the source electrode 28 and the drain electrode 29 are contacted with the n ⁺ type polysilicon film (n ⁺ poly-Si) through the contact holes, respectively.

  Thereafter, as shown in FIG. 22, a silicon nitride film (SiNx) is formed at a film thickness of, eg, about 500 nm and a substrate temperature of about 300 ° C. by using a plasma CVD apparatus or the like to form an interlayer insulating film. Then, after forming a photoresist layer 31 thereon, the silicon nitride film (SiNx) is patterned, and contact holes 32 are formed in the silicon nitride film (SiNx) by, for example, dry etching.

  Thereafter, as shown in FIG. 23, after performing an ashing process using, for example, oxygen plasma, and stripping the photoresist using an amine-based stripping solution as described above, it is non-oxidizing in the initial stage under heating as described above. An ITO film having a film thickness of about 100 nm is formed by a two-step process in an atmosphere gas and then in an oxygen-containing atmosphere gas, and patterned by wet etching to form the transparent conductive film 5. In this process, the drain electrode 29 is in direct contact with the transparent conductive film 5, but at the interface between the aluminum alloy film constituting the drain electrode 29 and the transparent conductive film 5, the film thickness is 1 to 10 nm and the oxygen content is 44. An oxide film of atomic percent or less is formed, and contact is made with a low contact resistance.

  Thereafter, in order to stabilize the characteristics of the transistor, for example, annealing is performed at about 350 ° C. for about 1 hour, thereby completing a polysilicon TFT array substrate.

  According to the TFT array substrate according to the second embodiment described above and the liquid crystal display device including the TFT array substrate, the same effects as those of the first embodiment described above can be obtained. Similarly to the first embodiment, in the second embodiment, the aluminum alloy of the present invention can also be used as a reflective electrode of a reflective liquid crystal.

  The material of the transparent conductive film 5 is preferably indium tin oxide or indium zinc oxide, and the aluminum alloy film has a concentrated layer of a part or all of the alloy components that are solid-solved in a non-equilibrium state. It is preferable that the electrical resistivity is adjusted to 8 μΩ · cm or less, more preferably 5 μΩ · cm or less. If an oxide film having a thickness of 1 to 10 nm and an oxygen content of 44 atomic% or less is present at the contact interface between the aluminum alloy film and the transparent conductive film, the contact resistance can be significantly reduced.

  Examples of the method for forming the aluminum alloy film include a vapor deposition method and a sputtering method. Among these, a sputtering method is particularly preferable.

  The TFT array substrate thus obtained is used to complete a liquid crystal display device as a flat display device as shown in FIG.

  That is, for example, polyimide is applied to the surface of the TFT array substrate 1 completed as described above, and after drying, a rubbing process is performed to form an alignment film.

  On the other hand, the counter substrate 2 first forms a light shielding film 9 on a glass substrate by patterning, for example, chromium in a matrix pattern. Then, resin red, green, and blue color filters 8 are formed in the gaps between the light shielding films 9. A counter electrode is formed by disposing a transparent conductive film such as ITO as the common electrode 7 on the light shielding film 9 and the color filter 8. Then, for example, polyimide is applied to the uppermost layer of the counter electrode, and after drying, a rubbing process is performed to form the alignment film 11.

  Then, the surfaces of the array substrate 1 and the counter substrate 2 on which the alignment film 11 is formed are arranged so as to face each other, and the two substrates are bonded together with a sealing material 16 made of resin, excluding the liquid crystal sealing port. At this time, the gap between the two substrates is kept substantially constant by interposing a spacer 15 between the two substrates.

  By placing the empty cell thus obtained in a vacuum and gradually returning it to atmospheric pressure with the sealing port immersed in liquid crystal, a liquid crystal material containing liquid crystal molecules is injected into the empty cell to form a liquid crystal layer, Seal the sealing port. Finally, polarizing plates 10 are attached to both sides of the cell to complete the liquid crystal panel.

  Further, as shown in FIG. 1, a driver circuit for driving the liquid crystal display device is electrically connected to the liquid crystal panel and disposed on the side portion or the back surface portion of the liquid crystal panel. Then, the liquid crystal panel is held by a frame including an opening that defines a display surface of the liquid crystal panel, a backlight 22, a light guide plate 20, and a holding frame 23 that form a surface light source, thereby completing the liquid crystal display device.

  Next, Table 1 shows the results of measuring the contact resistance between the transparent conductive film 5 and the aluminum alloy film when directly contacting the transparent conductive film 5 on the array substrate.

  The measurement experiment was as follows.

  1) Configuration of transparent conductive film: Indium tin oxide (ITO) in which 10% by mass of tin oxide is added to indium oxide, or indium zinc oxide (IZO) in which 10% by mass of zinc oxide is added to indium oxide, Both are 200 nm.

  2) Structure of aluminum alloy film: Al-2 atomic% Ni alloy or Al-2 atomic% Ni-0.6 atomic% Nd alloy.

3) Transparent conductive film formation conditions:
Initial stage of film formation (Condition A): atmosphere gas = argon, pressure = 3 mTorr, sputtering power density = 1.9 W / cm ² , film thickness = 20 nm,
Late film formation (Condition B): atmosphere gas = argon / oxygen mixed gas, pressure = 3 mTorr (argon partial pressure; 2.98 Torr, oxygen partial pressure: 0.02 mTorr), sputtering power density = 1.9 W / cm ² , film Thickness = 180 nm.

  4) Heating conditions: substrate temperature during ITO film formation is room temperature or 150 ° C.

  Experiment No. No. 10 was patterned after forming the Al alloy film, and an experiment was performed by forming an ITO film and patterning it without forming the SiN film and the etching process using fluorine plasma so as to be in an 80 μm square contact state.

5) Contact resistance measurement method:
A Kelvin pattern as shown in FIG. 24 is prepared and measured at four terminals [a method of passing a current through an ITO (or IZO) -Al alloy and measuring a voltage drop between the ITO (or IZO) -Al alloy at another terminal] I do. That is, by passing the current I between I _{1 and} I ₂ in FIG. 24 and monitoring the voltage V between V _{1 and} V ₂ , the contact resistance R of the contact portion C is set to [R = (V ₂ −V ₁ ). / I ₂ ]. The method for producing the pattern was as follows.

  Further, the amount of Ni in the aluminum alloy is ICP emission analysis (inductively coupled plasma emission analysis) method, the thickness of the Ni concentrated layer, the thickness of the oxide film is the cross-sectional TEM observation, the Ni content in the Ni concentrated layer, the oxidation The measurement of the oxygen content of the film was performed by analyzing the composition of the cross-sectional TEM observation sample by EDM.

Instead of a glass substrate, a silicon wafer with a 400 nm thick oxide film (SiO ₂ thermal oxide film) formed on the surface is used to insulate the substrate from the surface, and an Al alloy 300 nm is formed by sputtering and patterned. After that, an insulating film (SiNx) having a thickness of 300 nm is formed by a CVD method. Thereafter, the heat treatment is carried out for 1 hour in a vacuum film forming chamber as it is, and then taken out. Thereafter, 80 μm square contact holes are patterned by photolithography, and contact holes are formed by etching with fluorine-based plasma. Thereafter, a 200 nm ITO (or IZO) film is formed on the surface of the aluminum alloy with a holding time of 8 hours or less by the above two-stage sputtering film forming method, and patterning is performed.

For measuring the contact resistance between the aluminum alloy film and ITO (or IZO), a 4-terminal manual prober and a semiconductor parameter analyzer “HP4156A” (manufactured by Hewlett-Packard) were used. In this measurement, the pure resistance value of the ITO (or IZO) / Al alloy joint portion represented by R (contact resistance) = [I ₂ / (V ₂ −V ₁ )] and excluding the influence of the wiring resistance. Can be measured.

By the way, when a pure aluminum wiring is directly contacted with the ITO film, the contact resistance is 1.5 × 10 ⁵ Ω, and an Al—Nd alloy, which is a typical aluminum alloy wiring, is directly contacted with the ITO film. In this case, the contact resistance is 8.4 × 10 ⁴ Ω. Further, as a conventional structure, when Mo is arranged as a barrier metal between the ITO film and the Al—Nd wiring, the contact resistance is 1.0 × 10 ¹ Ω.

On the other hand, in the above embodiment of the present invention, the contact resistance of the Al—Ni wiring in which the oxide film having a low oxygen content is formed on the contact interface is 1.2 × 10 ¹ Ω in the 80 μm square contact hole, and Al—Ni—Nd. The contact resistance of the wiring is 1.5 × 10 ¹ Ω, and the contact resistance of the Al—Ni—Y wiring is 1.3 × 10 ¹ Ω, both of which are almost equivalent to the case where Mo having a conventional structure is used as a barrier metal. Met.

  As described above, when a liquid crystal display device was prototyped in the embodiment of the present invention, both the manufacturing yield and the display quality were at the same level as when the ITO film and the barrier metal were combined. Therefore, in this liquid crystal display device, it is possible to obtain the same performance as a conventional liquid crystal display device without disposing a barrier metal.

  Therefore, the barrier metal can be omitted and the manufacturing process can be simplified, so that the manufacturing cost can be greatly reduced.

  In other words, instead of the conventional pure aluminum, aluminum alloy, or Mo-W film, an aluminum alloy containing a specific element as described above is used as an electrode material, and an oxide film with a reduced oxygen content is present at the contact interface. By doing so, direct contact with the transparent conductive film becomes possible, the manufacturing process is simplified, and the manufacturing cost can be greatly reduced.

1 TFT array substrate 2 Counter electrode 3 Liquid crystal layer 4 Thin film transistor (TFT)
DESCRIPTION OF SYMBOLS 5 Transparent conductive film 6 Wiring part 7 Common electrode 8 Color filter 9 Light-shielding film 10 Polarizing plate 11 Orientation film 12 TAB tape 13 Driver circuit 14 Control circuit 15 Spacer 16 Sealing material 17 Protective film 18 Diffusion plate 19 Prism sheet 20 Light guide plate 21 Reflection Plate 22 Backlight 23 Holding frame 24 Printed circuit board 25 Scan line 26 Gate electrode 27 Gate insulating film 28 Source electrode 29 Drain electrode 30 Protective film (silicon nitride film)
31 Photoresist 32 Contact hole

Claims (5)

A thin film transistor and a transparent conductive film disposed on the substrate, and an aluminum alloy film that electrically connects the thin film transistor and the transparent conductive film,
The aluminum alloy film comprises 0.1 to 6 atomic% in total of Ni and at least one selected from the group consisting of Au, Ag, Zn, Cu, Sr, Sm, Ge, Bi as alloy components. Including
An oxide film of the aluminum alloy is formed at the interface between the aluminum alloy film and the transparent conductive film. The film thickness of the oxide film is 1 to 10 nm, and the oxygen content in the oxide film is 44 atomic% or less. der is,
At the interface between the aluminum alloy film and the oxide film, there is a Ni concentrated layer having a thickness of 0.5 to 10 nm, and the average Ni concentration in the Ni concentrated layer is the average Ni concentration in the aluminum alloy film. display device according to claim der Rukoto more than twice. The aluminum alloy film further contains 0.1 to 6 atomic% of at least one selected from the group consisting of Nd, Y, Fe, Co, Ti, Ta, Cr, Zr, and Hf as another element. The display device according to claim 1. The transparent conductive film, a display device according to claim 1 or 2, indium tin oxide (ITO) or indium zinc oxide (IZO). Display device according to any one of claims 1 to 3, wherein the aluminum alloy film functions as a reflective film. Display device according to any one of claims 1-4 for use as a tab connection electrodes by stacking a transparent conductive film on the aluminum alloy film.