KR100781434B1 - Bonding structure of thin film circuit - Google Patents

Abstract

SUMMARY OF THE INVENTION An object of the present invention is to provide a bonding structure in which a thin film circuit having a transparent electrode layer and an Al alloy electrode layer can be directly bonded to a transparent electrode layer and an Al alloy electrode layer without having a so-called cap layer. The present invention provides a junction structure of a liquid crystal display device having a transparent electrode layer and an Al alloy electrode layer directly bonded to the transparent electrode layer, wherein the precipitate having a redox potential in the range of -1.2 V to -0.6 V in the Al alloy electrode layer. It is characterized by being dispersed.

Transparent electrode layer, Al alloy electrode layer, thin film circuit

Description

Bonding structure of thin film circuit {BONDING STRUCTURE OF THIN FILM CIRCUIT}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film circuit constituting a display device, and more particularly, to a junction structure of a thin film circuit having an Al alloy electrode and a transparent electrode such as a liquid crystal display.

As display devices for information equipment, AV equipment, home appliances, and the like, for example, displays employing thin film transistors (hereinafter, abbreviated as TFTs) have been widely used. In such a display, various device structures have been proposed, such as liquid crystal display (LCD) based on an active matrix system such as TFT, self-luminous organic EL (OELD), or organic EL based on a passive matrix system. Is constituted by a thin film circuit formed of a thin film, and its display control is performed.

In the device structure of these various display devices, many are provided with the transparent electrode which represents an ITO electrode, and the conductive electrode for wiring. The structure of such a thin film circuit directly affects factors such as the quality of the display device, power consumption, and product cost, and its structure is required every day.

As for the structure of the thin film circuit, a liquid crystal display (LCD) is taken as an example, specifically, the following matters are desired as improvements.

In liquid crystal displays (LCDs), which tend to occupy the center of the display device, high definition and low cost are conspicuous, and the TFT element structure is widely adopted as the thin film circuit.

As the wiring material of the thin film circuit, an aluminum (Al) alloy is used. In thin film circuits such as TFTs, an aluminum alloy thin film is often used to form an electrode layer constituting a wiring or an electrode, which is a high melting point material such as tantalum, chromium, titanium, or alloys thereof. The reason that the specific resistance is too high is that aluminum is a low specific resistance and easy to wire wiring as a substitute material.

However, when forming an electrode layer (A1 alloy electrode layer) by this aluminum alloy thin film, it is known that the following phenomenon arises in the contact part with transparent electrodes, such as an ITO electrode layer in LCD. That is, when the A1 alloy electrode layer and the ITO electrode layer are directly bonded together, electrochemical reactions occur at the bonding interface due to the difference in the electrochemical properties of both layers, resulting in breakage of the bonding interface and increase in resistance value. Therefore, when using an Al alloy electrode layer for a liquid crystal display element, it is formed from Mo, Cr, etc., and a concept which includes a contact barrier layer in what is called a cap layer (or a contact barrier layer. Hereinafter, a "cap layer"). Is used) (for example, see Non Patent Literature 1).

[Non-Patent Document 1: Edited by Tatsuo Uchida, "Next-Generation Liquid Crystal Display Technology," First Edition, Industrial Society of Japan, November 1, 1994, p.36-38]

Thus, in the TFT provided with an Al alloy electrode layer, a cap layer made mainly of Cr, Mo, or the like is provided. In the case where the aluminum alloy thin film is used as the TFT constituent material, the cap layer must be formed inevitably, so that the laminated structure becomes complicated, leading to an increase in production cost. In recent years, among the materials constituting the cap layer, there is a market trend that excludes the use of Cr, and there is a situation that a great restriction has arisen in the technology for forming the cap layer.

By the way, in recent TFT manufacturing techniques, several manufacturing techniques which can omit the cap layer mentioned above are proposed. For example, Patent Document 1 discloses an A1 wiring film that is supposed to be directly bonded to an ITO electrode layer and a sputter target therefor. In this Patent Document 1, an element forming an intermetallic compound with A1 or an element having a higher standard electrode potential than A1 and an Al wiring film containing C, 0, N, and H in a predetermined amount in Al can be omitted. It is described as making it.

[Patent Document 1: International Publication No. WO97 / 13885]

In addition, Patent Document 2 discloses a display device and a manufacturing technique using an aluminum alloy film which enables direct contact between an aluminum alloy film and a transparent electrode and enables the omission of a barrier metal. In this patent document 2, if some or all of the alloy components constituting the aluminum alloy film are present as precipitates or concentrated layers at the interface where the aluminum alloy film and the pixel electrode are in direct contact, the barrier metal ( It is described that the cap layer) can be omitted.

[Patent Document 2: Japanese Patent Laid-Open No. 2004-214606]

These prior art basically focuses on alloying elements or precipitates (for example, intermetallic compounds) in aluminum alloys, and illustrates many aluminum alloys with the possibility of direct joining.

[Problem to Solve Invention]

However, the various compositions of aluminum alloys and the presence of precipitates (intermetallic compounds) in aluminum alloys have been known in the past, and various alloying elements and intermetallic compounds are also known in Patent Documents 1 and 2. It is only confirmed that the existence of is contributing to the direct conjugation. That is, in these prior arts, there is no particular explanation on whether the element or the precipitate in the aluminum alloy suppresses the interfacial reaction when directly bonded due to some factor.

Therefore, in the development of the liquid crystal display element that can be omitted in the cap layer, since there is no specific index indicating that the interfacial reaction of direct bonding can be suppressed, aluminum alloys of various compositions have to be verified. Also, in the aluminum alloy composition capable of suppressing the interfacial reaction, the liquid crystal display device satisfies the total characteristics of the liquid crystal display device, the current-voltage characteristic corresponding to the so-called ohmic junction, the bonding resistance, the wiring resistance, the heat resistance, and the like. It is a fact that it is still difficult to find a structure.

In addition, the bonding structure which enables direct bonding like this liquid crystal display element is similarly required also in thin film circuits, such as other organic EL (OELD) or organic EL by a passive matrix system.

The present invention is based on the above circumstances, and in a thin film circuit having a transparent electrode layer and an A1 alloy electrode layer, even if the cap layer is omitted, ohmic bonding can be performed without causing an interfacial reaction and excellent bonding. It is to provide a junction structure of a thin film circuit having characteristics. In the case where a liquid crystal display element is employed as the thin film circuit, even when directly bonded to a transparent electrode layer representative of the ITO electrode layer, the interfacial reaction can be reliably suppressed and the ohmic bonding characteristics, low junction resistance, wiring film resistance, heat resistance, and the like can be ensured. It is possible to satisfy the total liquid crystal display device characteristics, and to provide a practical and extremely desirable bonding structure of a thin film circuit.

[Means for solving the problem]

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the present inventors bonded various aluminum alloys directly with a transparent electrode, and since earnestly studied the phenomenon of the interfacial reaction, the precipitate which has a predetermined | prescribed redox potential exists in the directly bonded junction interface. In this case, the phenomenon that the interfacial reaction of the direct bonding can be suppressed and the ohmic bonding can also be found has led to the present invention.

The present invention provides a junction structure of a thin film circuit having a transparent electrode layer and an A1 alloy electrode layer directly bonded to the transparent electrode layer, wherein the A1 alloy electrode layer has a redox potential in the range of -1.2 V to -0.6 V. The precipitate is characterized by being dispersed.

According to the researches of the present inventors, if a precipitate having a potential close to the redox potential value of the transparent electrode layer and a so-called redox potential is present in the A1 alloy electrode layer, the electrochemical reaction between the transparent electrode layer and the A1 alloy electrode layer is performed. It is discovered that it is suppressed and the outstanding bonding characteristic can be implement | achieved without causing the breakage phenomenon in a joining interface, or the increase of resistance. On the other hand, this "redox potential" refers to the potential when the oxidation rate and the reduction rate become equal in the redox reaction of a reaction product, and so-called equilibrium potential.

If the redox potential of the precipitate is a potential value lower than -1.2 V, breakage phenomenon at the junction interface tends to occur, and if the potential value is higher than -0.6 V, the resistance value of the Al alloy electrode layer itself increases. In the precipitate having a redox potential in the range of -1.2 V to -0.6 V, an intermetallic compound containing Al is typically mentioned as being able to reliably suppress the interfacial reaction. For example, there are intermetallic compounds of elements such as Ni, Co, Fe, Nd, Y, Pd, and Al. Specifically, Al ₃ Ni, Al ₉ Co ₂ , Al ₃ Fe, Al ₇ NdNi ₂ , Al ₄ Co ₁ Ni ₁ , Al ₄ Pd, Al ₃ Y ₁ are preferred.

Moreover, in the junction structure of the thin film circuit of this invention, it is preferable that the hybrid potential of A1 alloy electrode layer is -1.4V--0.6V. This hybrid potential is the potential of the whole A1 alloy electrode layer, and is the potential of the A1 alloy electrode layer in the state containing a precipitate, and the said redox potential and the measuring method are the same. If the mixed potential is lower than -1.4 V, when an alkaline developing solution or the like is used in the development process in a so-called pattern forming step for forming a thin film circuit, a cell chemical reaction occurs and the transparent electrode layer is formed. It is easy to cause defects such as discoloration. Further, when the potential value is higher than -0.6 V, the amount of precipitates in the Al alloy electrode layer increases, and the portion of the high potential and the portion of the low potential are generated in the Al alloy electrode layer, so that the etching process in the so-called pattern forming process is performed. If it does, Al itself will melt | dissolve and it will become difficult to form a circuit.

In the bonding structure of the thin film circuit of the present invention, it is preferable that the transparent electrode layer is made of a film containing indium oxide, and the bonding resistance value between the transparent electrode and the Al alloy electrode layer is 1 to 200? It is because the practicality as a liquid crystal display element will disappear if it is the junction resistance value exceeding 200 (ohm) * 10micrometer. As the film containing this indium oxide, there are a so-called indium oxide transparent electrode (ITO film (lndium Tin Oxide), IZO film (lndium Zinc Oxide)). In addition, this junction resistance value is measured by constructing a so-called Kelvin element, and the junction resistance value prescribed | regulated by this invention is the value measured on the contact surface of a 10 micrometer angle.

Furthermore, in the junction structure of the thin film circuit according to the present invention, the A1 alloy electrode layer preferably has a specific resistance value of 3.5 to 35 μΩcm after heat treatment at 300 ° C. for 1 hour, and the A1 alloy electrode layer has a heat treatment at 300 ° C. for 1 hour. It is preferable that the dimple generation rate formed on the surface of the later A1 alloy electrode layer is 3.0% or less. When the specific resistance exceeds 35 mu OMEGA cm, practical thin film circuits cannot be formed, more preferably 10 mu OMEGA cm or less, and still more preferably 5.0 mu OMEGA cm or less. In addition, dimples are defects on the pits formed on the surface of the A1 alloy electrode layer after heat treatment, and are meant to occur due to volume shrinkage, as opposed to protrusions such as hillocks. The dimple incidence rate is observed by scanning electron microscope (SEM: 10,000 times) on the surface of the Al alloy electrode layer after heat treatment, measuring the area of the pit abnormality observed on the surface, and the area of the upper pit with respect to the observed total viewing area. It is calculated by this ratio. If this dimple generation rate exceeds 3.0%, favorable bonding state will not be realized when the transparent electrode layer is directly bonded.

In the bonded structure of the liquid crystal display element of this invention mentioned above, it is preferable that Al alloy electrode layer contains 0.5 to 25 at% of nickel, and 0.1 to 7.Oat% of cobalt and / or iron is preferable. In addition, it is also possible to further contain 0.1 to 3.Oat% of neodium. In these elements, the above-mentioned precipitate, which is an intermetallic compound containing A1, is present in the Al alloy electrode layer, the interfacial reaction is suppressed, and direct bonding with the transparent electrode layer is surely realized.

In the nickel alloy-containing Al alloy electrode layer, if nickel is less than 0.5 at%, the amount of precipitates decreases, and the suppression of the interfacial reaction is insufficient. When it exceeds 25 at%, wiring resistance value will become large too much and it will become a practical joining structure. Also, with respect to cobalt or iron, if the amount is less than 0.1 at% as in nickel, the amount of precipitates is excessively reduced, and the suppression of the interfacial reaction is insufficient, and if it exceeds 7.Oat%, the wiring resistance value becomes too large and is not practical. Further, in the case of further containing neodium, if less than 0.1 at%, dimples are generated. If more than 3.Oat%, the bonding durability decreases when directly bonded to the transparent electrode layer.

Moreover, in the bonding structure of the liquid crystal display element of this invention, it is preferable to contain 0.1-3.Oat% of carbon in an A1 alloy electrode layer. This carbon has the effect | action which improves the heat resistance characteristic which prevents generation | occurrence | production of hillock and dimples. In addition, studies by the inventors of the present invention estimate that the inclusion of carbon has the effect of improving the inhibitory effect of the interfacial reaction caused by the precipitate in the A1 alloy electrode. When the carbon content is less than 0.1 at%, the dimples tend to be easily generated. When the carbon content exceeds 3.Oat%, the specific resistance value of the A1 alloy electrode layer is increased.

In the junction structure of the thin film circuit according to the present invention, the thin film circuit is a liquid crystal display element, the transparent electrode layer is an ITO electrode layer, and the precipitate has an Al reduction potential having a redox potential in the range of ± 0.2 V of the transparent electrode layer. It is especially preferable that it is a system intermetallic compound. Even if the cap layer employed in the conventional liquid crystal display element is omitted, a liquid crystal display element capable of realizing ohmic bonding can be configured without causing an interfacial reaction.

Further, when employing the present invention a liquid crystal display device, the precipitate of Al intermetallic compound is particularly preferably Al ₃ Ni. The Al-based intermetallic compound preferably has an average particle diameter of 10 to 150 nm, and the junction diffusion layer formed at the interface between the ITO electrode layer, which is a transparent electrode layer, and the A1 intermetallic compound, which is a precipitate of the A1 alloy electrode layer, is 3-20 nm. It is preferable that it is thickness. It is because a low junction resistance characteristic and high junction durability characteristic can be implement | achieved as a liquid crystal display element as it is such a junction structure.

When employ | adopting this invention for the joining structure of a liquid crystal display element, the composition whose Al alloy electrode layer is 0.5-7.Oat% nickel, 0.1-3.Oat% carbon, and remainder is especially preferable. With such a composition, even as a bonded structure directly bonded to the transparent electrode, the interfacial reaction can be reliably suppressed, realizing ohmic bonding, providing excellent bonding resistance and bonding durability, and forming a wiring free of hillocks and dimples. In practical use, all of the total characteristics required for the liquid crystal display device can be satisfied.

Fig. 1 is a photograph showing the cross section of the junction between the A1 alloy electrode layer and the Si layer of the example by TEM.

Fig. 2 is a photograph showing the cross section of the junction between the A1 alloy electrode layer and the ITO electrode layer in the example by TEM.

3 is an enlarged photograph of a cross section of the junction of FIG.

4 is a schematic perspective view of a test sample laminated by crossing the ITO electrode layer and the Al alloy electrode layer.

5 is a graph measuring current-voltage characteristics in the case of the embodiment.

6 is a graph measuring current-voltage characteristics in the case of the comparative example.

7 is an Arennius plot graph measuring junction durability characteristics.

8 is a graph showing the relationship between the stress applied to the electrode layer and the heat treatment temperature.

9 is a graph showing the relationship between junction resistance and ITO potential difference.

10 is a SEM observation photograph of the surface of the Al alloy electrode layer after heat treatment.

Fig. 11 is a graph of the junction resistance value showing the results of the life endurance test with the IZO electrode layer.

Best Mode for Carrying Out the Invention

EMBODIMENT OF THE INVENTION Hereinafter, the best embodiment in this invention is described.

1st Embodiment In this 1st Embodiment, the case where the aluminum alloy thin film containing nickel (Ni) and carbon (c) is used as an A1 alloy electrode layer is demonstrated. In addition, as a comparative example, the case where the aluminum alloy thin film containing neodium (Nd) is used for an Al alloy electrode layer is illustrated. Table 1 shows the compositions of the A1 alloy electrode layers of Example 1 and Comparative Example 1 herein.

Table 1

Electrode layer Al Ni C Nd Example 1 96.8 3.0 0.2 - Comparative Example 1 98.0 - - 2.0

                                     (at%)

In addition, the thin film formation at the time of forming each electrode layer was performed by the magnetron sputtering apparatus on the conditions of input electric power 3.OWatt / cm <^2> , argon gas flow volume 100ccm, and argon pressure 0.5Pa.

First, the bonding structure of the liquid crystal display element which concerns on this invention is demonstrated. 1-3, the result of having observed the junction part about the junction structure of an ITO electrode layer and Al alloy electrode layer of Example 1 is demonstrated. Fig. 1 shows the junction between the Al alloy electrode layer and the Si layer of the first embodiment, and Fig. 2 and 3 shows the junction between the Al alloy electrode layer and the ITO electrode layer of the first embodiment with a transmission electron microscope (TEM). It shows a picture.

Fig. 1 shows a p-type a-Si layer (a white portion of about 80 nm thick in the center) on an n-type Si substrate (black portion in the lower half of the photo), and the p-type a- A sample in which the Al alloy electrode layer (part in the photograph, about 200 nm thick in the upper half) of Example 1 was formed on the surface of the Si layer was prepared, heat-treated at a temperature of 250 ° C. for 1 hour, and the sample cross section was observed by FIB. It processed and it was a photograph observed by TEM (magnification of 100,000 times). In addition, the crystal structure was specifically determined by electron diffraction in several places of the cross section, and the structure of the part was identified. According to the cross-sectional observation of FIG. 1, when the A1 alloy electrode layer of Example 1 is bonded to the Si layer and subjected to heat treatment, the intermetallic of AI ₃ Ni (part of reference numeral 4 in the photo) is placed at the interface between the A1 alloy electrode layer and the Si layer. It was found that the compound precipitates.

Fig. 2 shows the A1 alloy electrode layer of Example 1 (approximately 200 nm thick in the top of the center) on the surface of the ITO (In ₂ O ₃ -10 wt% SnO ₂ ) electrode layer (the dark bottom of the bottom of the center in the picture). Is a photograph prepared by preparing a sample formed with a white light-colored portion), performing a heat treatment at a temperature of 300 ° C. for 1 hour, and processing the sample cross section by FIB, and observing with a TEM (magnification of 100,000 times). . FIG. 3 is a photograph in which the junction interface of FIG. 2 is enlarged (magnification 1 million times). In the enlarged photograph of Fig. 3, a precipitate on the nose was observed between the ITO electrode layer side (lower black portion in the photo) and the A1 alloy electrode layer side (white portion in the upper image). This precipitate was found to be an intermetallic compound of Al ₃ Ni identified in FIG. 1.

From the observation results of FIGS. 1 to 3, when the Al alloy electrode layer of Example 1 is directly bonded to the ITO electrode layer, an intermetallic compound of Al ₃ Ni having a particle diameter of about 10 to 150 nm at the interface by subsequent heat treatment (FIG. 1). It turned out that code | symbol 4) is precipitated in it. In addition, according to the enlarged observation of FIG. 3, in the vicinity of the intermetallic compound of Al ₃ Ni deposited at the bonding interface between the Al alloy electrode layer and the ITO electrode layer of this Example 1, the portion in the state of diffusion bonding is about 3-20 nm. The layered diffusion part of thickness was seen.

Next, the result of having investigated the current-voltage characteristic when joining with an ITO electrode layer with respect to the Al alloy electrode layer of this Example 1 and the comparative example 1 is demonstrated. This bonding endurance test is performed by creating a test sample shown in FIG. The test sample has a structure called a Kelvin element, and is formed to cross the A1 alloy electrode layer (0.2 μm thickness) on the ITO (ln ₂ O ₃ −10 wt% SnO ₂ ) electrode layer (0.2 μm thickness) as shown in FIG. 4. Then, it is possible to conduct electricity from the terminal portions 10 and 40 at the arrow portions. This current-voltage characteristic was performed by measuring the current flowing between terminals when a voltage was applied between the terminals. In addition, the area of a junction part is 100 micrometer <^2> (10 micrometers x 10 micrometers).

5 and 6 show the results of measuring the current-voltage characteristics in the A1 alloy electrode layer and the ITO electrode of Example 1 and Comparative Example 1. FIG. 5 shows measurement results of Example 1 and FIG. 6 of Comparative Example 1. FIG. Moreover, in each measurement result graph, when the solid line is as-depo, the case where a dashed line heat-processes 250 degreeC and 1 hour is shown.

As can be seen from Fig. 5, in the case of the Al alloy electrode layer of Example 1, it was confirmed that the current-voltage characteristic was in a linear relationship with or without heat treatment. From this, it was found that ohmic bonding is realized between the Al alloy electrode layer and ITO of the first embodiment.

On the other hand, as can be seen from Fig. 6, in the Al alloy electrode layer of Comparative Example 1, a nonlinear current-voltage relationship was generated when the heat treatment was performed. This indicates that the junction of Al alloy electrode layer and ITO of Comparative Example 1 has a structure having a rectifying action, and is the same as the metal-insulator-metal structure (MIM structure) described by the so-called full-frenchel mechanism. It was expected. That is, in the case of the A1 alloy electrode layer of Comparative Example 1, it was estimated that an aluminum oxide film was formed on the bonding interface with ITO by heat treatment. On the other hand, as shown in Fig. 4, since the current and voltage are measured between the two terminals (10 and 40 in Fig. 4), the wiring portions other than the junction portions formed at right angles (Al) are measured. It is the result obtained in the state containing the wiring resistance in alloy electrode layer and ITO).

Subsequently, the results of the bonding endurance test with the ITO electrode will be described. This bonding endurance test is performed by creating a test sample shown in FIG. 4 described above. The test sample is formed on the ITO (ln ₂ O ₃ -10 wt% SnO ₂ ) electrode layer (0.2 μm thick) so as to be orthogonal to the Al alloy electrode layer (0.2 μm thick) as described above, and conducts electricity at the terminal portion of the arrow portion. I would have to. The energization durability was measured by measuring the resistance between the terminals and measuring the energization time until the resistance between the terminals changed. As the electrode layer, three types of structures in which a Cr film (0.05 mu m thickness), which is one of the constituent materials of the cap layer, were formed between the pure A1 electrode layer and the transparent electrode, as in Example 1, Comparative Example 1, and a conventional example, It was done. In the measurement method, the measurement environment was set in an air atmosphere, the current value was set to two types of 10 µA and 3 mA, and the life point was the time when the resistance value of the junction portion became 100 times the initial value. And the temperature at the time of energization was performed as 85 degreeC, 100 degreeC, 150 degreeC, 200 degreeC, and 250 degreeC.

In Fig. 7, the time at which the resistance rise (at the time of becoming 100 times the initial value) of the junction portion at each temperature was measured, and the Arrhenius plot of the life time with respect to the inverse of the holding temperature at the time of energization. The graph is shown. In Fig. 7, the vertical axis represents life time, and the horizontal axis represents 1000 / absolute temperature. The activation energy at which the resistance rises at the junction is calculated from the inclination of the first straight line extrapolated from the Areneus plotted graph, which is found to be 1.35 eV in Example 1 and 0.42 eV in Comparative Example 1. lost. From this result, it was confirmed that the Al alloy electrode layer of Example 1 had activation energy about 3.3 times higher than that of Comparative Example 1. In the case of Example 1, it was estimated that the resin had a durability of about 70,000 hours at 85 ° C., and the result was close to that of the electrode layer interposed between the Cr film which was used as a conventional example.

Next, the result of having investigated the hillock characteristic regarding the Al alloy electrode layer of Example 1 is demonstrated. After the aluminum alloy film is formed on the wafer substrate by sputtering and wired, this hillock is formed of an aluminum alloy film if heat of 300 to 400 ° C. is applied to the wired aluminum alloy film when the insulating film is formed by the CVD method. It refers to the process of nose injury on the surface. From this, it is considered that hillock occurs due to the stress applied to the aluminum alloy film by heat treatment. There, the pure Al electrode layer and the Al alloy electrode layer of Example 1 were each formed on a Si wafer substrate, and it was investigated what kind of change occurred in the stress generated in the electrode layer when heat was applied. Specifically, the sample which laminated | stacked the electrode layer of thickness 0.2micrometer by sputtering on the Si wafer substrate of (phi) 100mm was created. Then, the stress generated in the electrode layer in the laser was measured by the laser stress measuring device FLX-2320 (manufactured by KLA TENCOR: nitrogen gas flow (5 L / min), solid laser 670 nm). The measurement results are shown in FIG.

Fig. 8 shows the result of measuring the stress state of the electrode layer at each temperature when the temperature is raised from room temperature to 500 ° C, and the temperature is subsequently lowered from 500 ° C to 100 ° C (temperature-fall rate 5 ° C / min). The negative stress value is a state in which compressive stress is applied to the electrode layer, and the positive stress value indicates that the tensile stress is applied to the electrode layer. It is the case of Example 1 that is shown with the thick line, and the case of pure A1 is shown with the thin line. As can be seen from the stress state of the pure A1, the stress value of -100 MPa is continuous from around 180 deg. C at the temperature to about 400 deg. C, but when the compressive stress is applied to the electrode layer of the pure A1, It has shown that the phenomenon which generate | occur | produced and the compressive stress is relieved is generate | occur | produced. On the other hand, in the case of Example 1, but the state in which the large parts of the stress is relaxed in the vicinity of 200 ℃ during the temperature increase, this is due to an intermetallic compound of Ni ₃ AI alloy precipitated on the A1 electrode of the first embodiment. In other words it was confirmed that to relieve compression stress applied to the Al alloy electrode layer without generating an, embodiment, if, by the intermetallic compound of Ni ₃ AI precipitation, hillock.

Furthermore, in Example 1, Comparative Example 1, the constituent material of the cap layer Cr, Mo, ITo film, a description will be given of the results of the measurement of the redox potential of the Al ₃ Ni. The measurement of this redox potential was made into the dislocation measurement sample by forming the thin film of the predetermined thickness (0.2 micrometer) by each composition on the glass substrate with the sputtering apparatus, and cutting out the glass substrate. Then, the surface of the dislocation measurement sample was masked so as to expose an area corresponding to 1 cm ² , thereby forming a measurement electrode. The redox potential was measured using 3.5% sodium chloride aqueous solution (liquid temperature 27 degreeC), and the reference electrode measured using silver / silver chloride. Furthermore, it was used in the composition of the ITO _{film, In 2 O 3 -10wt% Sn0} 2. The results are shown in Table 2.

[Table 2]

Sample Redox potential Example 1 -1.02 Comparative Example 1 -1.58 Al ₃ Ni -0.73 Cr -0.78 Mo -0.51 ITO membrane -0.82

As shown in Table 2, it was confirmed that the redox potential of Example 1 was very close to that of the ITO film. In addition, it was found that Al ₃ Ni, which is an intermetallic compound, is a value very close to the redox potential value of the ITO film like Cr.

Subsequently, the evaluation of the junction resistance with the ITO electrode layer will be described. Fig. 9 is a graph showing the difference between the redox potential value of each electrode layer and the redox potential value of ITO by plotting the result of measuring the resistance value by bonding each electrode layer to the ITO electrode layer. In the measurement method, the test sample shown in Fig. 7 was prepared, and the resistance measured in the sample without as heat treatment (as-depo) and with heat treatment (after 1 hour annealing at each temperature of 200 ° C, 250 ° C, and 300 ° C) was measured. Value.

The measurement of the junction resistance value was performed by the test sample shown in FIG. 4, and was formed on the electrode layer 10 (0.2 μm thickness) on the ITO (In ₂ O ₃ −10 wt% SnO ₂ ) electrode layer 40 (0.2 μm thickness). Were formed so as to cross each other, the resistance was measured by energizing the terminal portion of the arrow portion, and the junction resistance of the portion where the film overlapped (10 µm x 10 µm) was calculated. As the electrode layer, Example 1 and Comparative Example 1 shown in Table 1, three kinds of electrode layers having a structure in which the pure A1 film and the Cr film were laminated were performed. The electrode layer of this laminated structure is formed by forming 0.2 m of pure A1 film on 0.03 m of Cr film. In addition, the potential difference between ITO and each electrode layer was calculated from the redox potential values shown in Table 2, and the junction resistance values measured were plotted with the horizontal axis as shown in Fig. 9 (Fig. 9).

As can be seen from Fig. 9, it was confirmed that the junction resistance was very low in the case of the electrode via the Cr film having a potential almost equal to the redox potential of ITO. In the case of the A1 alloy electrode layer of Example 1 and Comparative Example 1, the bonding resistance of Example 1, in which the potential difference between ITO was not large, was low, and the bonding resistance of the A1 alloy electrode layer of Comparative Example 1 was significantly increased when the heat treatment was performed. It was confirmed. On the other hand, the measurement of the bonding resistance exemplifies the case where the Al alloy electrode layer is formed on the ITO electrode layer, but the same bonding resistance characteristics are obtained even when the opposite structure is formed in which the ITO electrode layer is formed on the Al alloy electrode layer. I am checking.

From the above results, the Al alloy electrode layer of Example 1 has a value close to that of ITO because its redox potential itself is low, so that the bonding resistance when directly bonded to the ITO electrode layer is low, and the heat treatment is further performed to bond the interface. The intermetallic compound of Al ₃ Ni precipitates at, and therefore, it is considered that excellent bonding characteristics have been realized. The reason is that since the redox potential of Al ₃ Ni becomes a value very close to that of ITO, the electrochemical reaction with ITO is unlikely to occur, resulting in no breakage of the junction or the like.

From this, when forming the A1 alloy electrode layer which is directly bonded to the transparent electrode of the ITO film, the A1-based intermetallic compound (AI3Ni) having a redox potential in the range of +/- 200 mV at the ITO electrode, It has been found that excellent bonding characteristics can be realized as long as the bonding structure is deposited at the interface between the ITO electrode layer and the A1 alloy electrode layer. Further, in the average particle diameter of 10-150nm A1 intermetallic compound (Ni ₃ AI), the junction formed by the diffusion layer which A1 intermetallic compound precipitated at the interface was assumed that it is preferred that the thickness of 3-20nm.

Second Embodiment Next, in this second embodiment, an Al alloy electrode layer having various compositions is formed using nickel, cobalt, iron, neodium, and carbon, and the results of investigating the characteristics of the liquid crystal display device will be described. do. Table 3 shows the composition of the Al alloy electrode layer examined in this second embodiment. Each alloy film shown in this Table 3 is formed in the same manner as the film forming conditions shown in the first embodiment.

Table 3

Furtherance Precipitate Precipitate potential Hybrid potential at% V V Example 2 Al-0.3C-3.0Ni Al ₃ Ni -0.73 -1.02 Example 3 Al-0.5C-3.0Ni Al ₃ Ni -0.73 -1.05 Example 4 Al-0.3C-5.0Ni Al ₃ Ni -0.73 -1.01 Example 5 Al-1.0Nd-2.0Ni Al ₇ NdNi ₂ -0.92 -1.05 Example 6 Al-0.2C-2.0Ni-3.0Co Al ₈ Co ₁ Ni ₁ -0.70 -0.93 Example 7 Al-3.0Ni Al ₃ Ni -0.73 -1.04 Example 8 Al-10Ni Al ₃ Ni -0.73 -0.86 Example 9 Al-25Ni Al ₃ Ni -0.73 -0.73 Example 10 Al-2.0Fe Al ₃ Fe -1.08 -1.37 Example 11 Al-2.0Co Al ₉ Co ₂ -1.09 -1.25 Example 12 Al-Pd Al ₄ Pd -0.94 -1.10 Example 13 Al-4Y Al ₃ Y ₁ -0.70 -0.86 Comparative Example 2 Al-2.0Nd Al ₁₁ Nd ₃ -1.53 -1.58 Comparative Example 3 Net-Al - - -1.68 Big Art 4 Net-Cr - - -0.78

Table 3 shows the results of measuring the alloy films of the respective compositions of Example 2-13 and Comparative Example 2-3, the precipitates in the alloy film, the redox potential of the precipitates, and the hybrid potential of the alloy film. . The potential measurement method is the same as that described in Table 2.

Next, Table 4 shows the results of examining the specific resistance, the heat resistance and the dimple characteristics of the alloy films of Examples 2 to 9 and Comparative Examples 2 to 3 in Table 3.

Table 4

A specific resistance value is the result of measuring the single film (about 0.3 micrometer in thickness) of each alloy film on a glass substrate, and measuring it by the 4-terminal resistance measuring apparatus about the film | membrane after 300 degreeC and heat processing for 1 hour. In addition, Hillock heat resistance forms a single film (about 0.3 micrometer in thickness) of each alloy film on a glass substrate, and scans electrons after heat processing for 1 hour at each temperature of 100 degreeC, 200 degreeC, 300 degreeC, and 400 degreeC. The film surface was observed by the microscope (SEM), and Table 4 shows the temperature at which the presence of the protrusion of submicrometer or more was confirmed. In addition, the dimple incidence rate was observed by SEM (10,000 times) after the heat treatment at 300 ° C. for 1 hour using a sample such as a resistivity measurement, and the abnormal hole portion (0.3 μm to 0.5 μm in diameter) observed on the surface. , The total area of the above pit abnormality in the observation field was measured, and the ratio of the total area of the above pit above the total viewing area was calculated. In addition, Table 4 shows the average of the sample generation rate values calculated from five different places on each film surface.

From Table 4, in the alloy thin film of Example 2-6, there was no hillock generation and no dimples occurred below 400 ° C. However, in the alloy film of Examples 7-9, the tendency which dimple generate | occur | produced was recognized. This is because carbon is contained in the composition of Examples 2-4, 6, and neodium is contained in the composition of Example 6, and this carbon and neodium prevent generation of hillock and dimples. It turned out to be possible.

Furthermore, the voltage-current characteristics and the bonding characteristics (contact resistance, bonding durability) of the alloy films of the compositions of Examples 2 to 9 and Comparative Examples 2-3 of Table 3 when directly bonded to the ITO electrode layer were examined. Is shown in Table 5. On the other hand, the test sample which investigated the joining characteristic in this 2nd Embodiment is a predetermined heat processing (inert gas (nitrogen, argon) atmosphere after joining a transparent electrode layer and each alloy film layer directly, in order to make a favorable joining state. , 300 ° C. for 60 minutes) was used.

Table 5

The current-voltage characteristics shown in Table 5 were measured in the same manner as described in Figs. 5 and 6 of the first embodiment, each graph of current-voltage characteristics was generated, and whether the rectifying action was generated by the graph. The result of having judged whether or not is shown.

In the investigation of the bonding properties, the case where each alloy film is formed and the ITO film is formed on the film is called the bonding property 1, and the case where each alloy film is formed on the ITO electrode layer is called the bonding property 2. The junction resistance value of the junction characteristic forms a Kelvin element similar to the measurement of the current-voltage characteristic in the first embodiment, flows a current of 3 mA after a heat treatment at 250 ° C. for 1 hour, and a sudden change in voltage. The junction resistance value at the time of performing the is shown. On the other hand, in the fabrication of the Kelvin element that measured the bonding characteristics 1, first, an alloy film was formed on the substrate by sputtering, and the alloy film was etched to form a linear circuit. Then, an amorphous ITO film is formed on the surface, and only the ITO film is etched with a weak acid oxalic acid etchant that does not dissolve the linear circuit of the alloy film in the base, thereby linear circuit of the alloy film in the base. It is produced by forming a linear circuit of the ITO film so as to be orthogonal to.

The bonding endurance produced the graph of the Areneus plot shown in FIG. 7 of 1st Embodiment, respectively, and estimated the activation energy from the inclination of the Arenius plot in applied current of 3 mA and 10 microamperes, and it turned out at 85 degreeC. (The measurement of the joining durability is performed by referring to the failure rate test method of the JIS-C-5003 electronic component and the JIS-C-0021 heating test method.)

As a result of Table 5, in the case of Example 2, the bonding resistance value was slightly higher than that of the Cr film, but it was found to have the same bonding characteristics as Cr used as the cap layer. In addition, in the case of Examples 3 and 4 and Example 6-9, it was found to have practically satisfactory characteristics with respect to both the junction resistance value and the bonding durability. In the case of Example 5, the result was that the joining durability of the joining characteristic 2 was not good, but this is considered to be influenced by the difference in the process of forming the structure of the direct joining.

Third Embodiment Next, in this third embodiment, the relationship between the bonding resistance characteristics and the heat treatment of the A1 alloy electrode layer of Example 4 (A1-0.3at% C-5.Oat% Ni) was examined. It demonstrates.

The bonding resistance was measured in the same manner as in the bonding characteristic 1 (bonding the A1 alloy electrode layer on the ITO film) described in Table 5 of the second embodiment. However, the test sample which measured the junction resistance value in 3rd Embodiment is 250 degreeC, 300 degreeC, 350 degreeC in an inert gas (nitrogen) atmosphere after directly bonding a transparent electrode layer (ITO film) and an A1 alloy electrode layer. The thing which heat-processed (60 minutes) was used at three temperature of the was used. The results are shown in Table 6.

Table 6

10, a test sample was formed on a glass substrate by sputtering (input power 3.OWatt / cm ² , argon gas flow rate 100ccm, argon pressure 0.5 Pa) to form an A1 alloy electrode layer having a thickness of 0.2 µm. The test sample was subjected to heat treatment (200 ° C. to 400 ° C.) for 1 hour in a nitrogen gas atmosphere, and the test sample surface after the heat treatment was observed with a scanning electron microscope (SEM: 10000 times).

As can be seen from Table 6, it was confirmed that as the heat treatment temperature after joining increased, the joining resistance value decreased. In addition, visible also, as shown in 10, 300 ℃ ~ In the heat treatment of 400 ℃ (D, E, F), Al intermetallic compound in the Al alloy electrode layer formed precipitate of (Al ₃ Ni) (whitening during each observation picture It was confirmed that the part of the spot) existed, and it was also confirmed that the precipitate became large as the temperature became high. Further, although the precipitates are not clearly shown in B (200 ° C.) and C (250 ° C.) in FIG. 10, in consideration of the result of FIG. 1 shown in the first embodiment, the Al intermetallic compound (Al ₃ ) in the Al alloy electrode layer is shown. Ni) is depositing

From the results of Table 6 and FIG. 10, it was considered effective to perform a heat treatment of 280 DEG C or higher in order to realize the bonding state so that the junction resistance value would be 200? /? 10 mu m or less. This is thought to be due to the fact that the heat treatment is performed to a certain extent so that an appropriate A1 intermetallic compound is dispersed and present in the A1 alloy electrode layer, and the precipitated A1 intermetallic compound is aggregated to some extent to obtain an appropriate particle size, thereby achieving a good bonding state. Because it becomes. In addition, when the upper limit temperature of this heat processing considers the heat resistance of an A1 alloy electrode layer, the manufacturing conditions of various elements, etc., it is thought that it is practical to set it as 400-500 degreeC.

Fourth Embodiment: Finally, in this fourth embodiment, the A1 alloy electrode layers of the compositions of Examples 2, 4, 5 and Comparative Example 2 described above are bonded to an IZO electrode layer as a transparent electrode. The result of having investigated the joining characteristic in is demonstrated.

In this 4th Embodiment, the joining characteristic 1 in the said 2nd Embodiment was investigated. That is, each alloy film is formed, and an IZO film is formed on each alloy film by the IZO target (ln ₂ O ₃ -10.7 wt% ZnO). In this case, the manufacturing conditions of the test sample and the measuring method of the bonding characteristic 1 are the same as that of the said 2nd Embodiment. However, the test sample which investigated the joining characteristic 1 of this 4th embodiment performed the joining area at the time of constructing a Kelvin element as 2500 micrometer <^2> (50 micrometer x 50 micrometers). Table 7 shows the measurement results of the junction resistance values, and FIG. 11 shows the life endurance test results. The bonding resistance values shown in Table 7 and FIG. 11 are the results of measurement of heat treatment (60 powders) at 250 ° C. in an inert gas (nitrogen) atmosphere after test sample preparation.

Table 7

In the case of Example 2, Example 4, Example 5, and the comparative example 2 rather than the result shown in Table 7, it turned out that the junction with an IZO electrode layer shows favorable junction resistance value. However, as can be seen from the life endurance test results in Fig. 11, in the case of Example 2, Example 4 and Example 5, even if the endurance time exceeded 200 hours, no significant change was found in the junction resistance value. On the other hand, in the case of the comparative example 2, it showed that the junction resistance value suddenly increased from the vicinity which passed about 20 hours, and it was confirmed that breakage of a junction part occurs.

As described above, according to the present invention, in the thin film circuit including the transparent electrode layer and the A1 alloy electrode layer, even if the cap layer is omitted, ohmic bonding is possible without causing an interfacial reaction, and the thin film having excellent bonding characteristics. The circuit can be configured. In the case where a liquid crystal display element is employed as the thin film circuit, even when directly bonded with a transparent electrode layer representative of the ITO electrode layer, the interfacial reaction can be reliably suppressed and the ohmic bonding characteristics, low junction resistance, wiring film resistance, heat resistance, and the like can be ensured. The total liquid crystal display device characteristics can be satisfied, and thus, a practical and extremely desirable thin film circuit can be said.

Claims (12)

In a junction structure of a thin film circuit having a transparent electrode layer and an Al alloy electrode layer directly bonded to the transparent electrode layer, The Al alloy electrode layer is a bonded structure of a thin film circuit, characterized in that a precipitate which is an intermetallic compound containing Al having a redox potential in the range of -1.2 V to -0.6 V is dispersed. delete The method of claim 1, A junction structure of a thin film circuit, wherein a mixed potential of an Al alloy electrode layer is -1.4 V to -0.6 V. The method according to claim 1 or 3, The transparent electrode layer is made of a film containing indium oxide, the junction structure of the thin film circuit, characterized in that the junction resistance value of the transparent electrode and the Al alloy electrode layer is 1 ~ 200Ω / □ 10㎛. The method according to claim 1 or 3, The Al alloy electrode layer has a resistivity value of 3.5-35 μΩcm after heat treatment at 300 ° C. for 1 hour, wherein the thin film circuit is a bonded structure. The method according to claim 1 or 3, The Al alloy electrode layer has a dimple occurrence rate of 3.0% or less formed on the surface of the Al alloy electrode layer after heat treatment at 300 ° C. for 1 hour, wherein the bonding structure of the thin film circuit. The method according to claim 1 or 3, The Al alloy electrode layer contains 0.5 to 25 at% of nickel, wherein the thin film circuit is a bonded structure. The method according to claim 1 or 3, The Al alloy electrode layer contains 0.1-7.Oat% of cobalt and / or iron. The method of claim 7, wherein The Al alloy electrode layer further comprises 0.1 to 3.Oat% of neodium, and the bonding structure of the thin film circuit. The method of claim 7, wherein The Al alloy electrode layer contains 0.1 to 3.Oat% of carbon. The method of claim 8, The Al alloy electrode layer further comprises 0.1 to 3.Oat% of neodium, and the bonding structure of the thin film circuit. The method of claim 8, The Al alloy electrode layer further contains 0.1 to 3.Oat% of carbon, wherein the thin film circuit is a bonded structure.

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