JP2011129693A - Al ALLOY FILM FOR DISPLAY DEVICE, DISPLAY DEVICE, AND Al ALLOY SPUTTERING TARGET - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an Al alloy film for a display device that can further secure low contact resistance when connected directly to a transparent pixel electrode by eliminating a barrier metal layer. <P>SOLUTION: The Al alloy film is connected directly to a transparent conductive film on a substrate of the display device, and characterized by containing 0.2 to 1.0 atom% Ni, 0.2 to 0.8 atom% Cu, and 0.05 to 0.5 atom% Ti. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an Al alloy film for a display device, a display device, and an Al alloy sputtering target.

  A liquid crystal display device used in various fields ranging from a small mobile phone to a large television exceeding 30 inches uses a thin film transistor (hereinafter sometimes referred to as “TFT”) as a switching element and is transparent. A TFT substrate having a pixel electrode, a wiring portion such as a gate wiring and a source-drain wiring, a semiconductor layer such as amorphous silicon (a-Si) or polycrystalline silicon (p-Si), and a predetermined with respect to the TFT substrate And a counter substrate provided with a common electrode, and a liquid crystal layer filled between the TFT substrate and the counter substrate.

  In the TFT substrate, wiring materials such as gate wiring and source-drain wiring are made of Al alloy such as pure Al or Al-Nd (hereinafter referred to as these) because of its low electrical resistivity and easy microfabrication. In general, Al alloys are sometimes used. In a conventional TFT substrate, a barrier metal layer made of a refractory metal such as Mo, Cr, Ti, or W is usually provided between the Al-based alloy wiring and the transparent pixel electrode. As described above, the reason why the Al-based alloy wiring is connected via the barrier metal layer is to ensure heat resistance and electrical conductivity when the Al-based alloy wiring is directly connected to the transparent pixel electrode.

  However, in order to form a barrier metal layer, an apparatus having a film forming chamber necessary for forming the wiring must be additionally equipped with a film forming chamber for forming a barrier metal layer. As cost reduction associated with mass productivity of liquid crystal display devices progresses, an increase in manufacturing cost and a decrease in productivity due to the formation of the barrier metal layer cannot be neglected.

  Therefore, a direct contact technique that can eliminate the formation of the barrier metal layer has been proposed. For example, in Patent Documents 1 and 2, even when the formation of the barrier metal layer is omitted and the Al alloy wiring is directly connected to the transparent pixel electrode, the contact resistance is low (hereinafter, such characteristics are referred to as “low contact resistance”). There is a proposal for a direct contact technique in which the electrical resistivity of the Al alloy wiring itself is small and the heat resistance is also excellent. Specifically, it is described that by adding a predetermined amount of elements such as Ni, Ag, Zn, Co, etc., the contact resistance with the transparent pixel electrode can be lowered and the electrical resistivity of the wiring itself can be kept low. . It also describes that the heat resistance can be improved by adding rare earth elements such as La, Nd, Gd, and Dy. Further, in Patent Document 3, if a wiring material of a display device having a structure directly connected to a transparent pixel electrode or a semiconductor layer is used, an Al—Ni alloy containing a predetermined amount of B is used for direct connection. It is described that contact resistance does not increase and connection failure does not occur.

JP 2004-214606 A JP 2006-261636 A JP 2007-186777 A

  As shown in Patent Documents 1 to 3 above, by adding an alloying element to pure Al, electrical conductivity characteristics (ITO direct contact property) between the transparent conductive film / Al alloy film can be ensured, etc. Various functions that were not present are added. However, realization of an Al alloy film that can secure a further low contact resistance is desired.

  The present invention has been made paying attention to such a situation, and the object thereof is to further ensure a low contact resistance when the barrier metal layer is omitted and the transparent pixel electrode is directly connected. An object is to provide an Al alloy film for a display device.

  The Al alloy film of the present invention capable of achieving the above object is an Al alloy film directly connected to a transparent conductive film (transparent pixel electrode) on a substrate of a display device, and the Al alloy film is Ni: It is characterized in that it contains 0.2 to 1.0 atomic%, Cu: 0.2 to 0.8 atomic%, and Ti: 0.05 to 0.5 atomic%, respectively. The Al alloy film may further contain a rare earth element at 1.0 atomic% or less (not including 0%).

  The present invention also includes a display device in which the Al alloy film is used in a thin film transistor.

  The present invention also provides a sputtering target used for forming an Al alloy film directly connected to a transparent conductive film (transparent pixel electrode) on a substrate of a display device, wherein Ni: 0.2 to 1.0 atom %, Cu: 0.2-0.8 atomic% and Ti: 0.05-0.5 atomic%, respectively, and an Al alloy sputtering target characterized in that the balance is Al and inevitable impurities. . This Al alloy sputtering target may further contain a rare earth element of 1.0 atomic% or less (not including 0%).

  ADVANTAGE OF THE INVENTION According to this invention, even when it connects directly with a transparent pixel electrode (a transparent conductive film, an oxide conductive film) without interposing a barrier metal layer, the Al alloy film for display apparatuses which can fully reduce contact resistance can be provided. . If the Al alloy film of the present invention is applied to a display device, the barrier metal layer can be omitted. Therefore, if the Al alloy film of the present invention is used, a display device with excellent productivity, low cost and high performance can be obtained.

It is a SEM observation photograph of an Al-0.6% Ni-0.5% Cu alloy film. It is a SEM observation photograph of an Al-0.6% Ni-0.5% Cu-0.12% Ti alloy film. It is a SEM observation photograph of an Al-0.6% Ni-0.5% Cu-0.24% Ti alloy film.

  In order to realize a novel Al alloy film that can reduce the contact resistance when the barrier metal layer is omitted and directly connected to the transparent pixel electrode (transparent conductive film) even after the filing of the above-mentioned patent document. We have continued to study further. As a result, when a predetermined amount of Ti, which is a refractory metal, is contained in an Al alloy film containing Ni and Cu, the Al-based compound precipitated at the interface between the transparent pixel electrode and the Al alloy film becomes coarse, and the conduction path at the interface As a result, it was found that an excellent low contact resistance can be realized by enlarging the thickness of the film.

  The Al alloy film of the present invention contains Ni: 0.2 to 1.0 atomic% and Cu: 0.2 to 0.8 atomic% as basic components. By containing these elements, the contact resistance can be kept low.

  In order to sufficiently exhibit the above effects, Ni is contained in an amount of 0.2 atomic% or more (preferably 0.5 atomic% or more) and Cu is contained in an amount of 0.2 atomic% or more (preferably 0.4 atomic% or more). . However, when the content of these elements is excessive, the wiring resistance is remarkably increased. Therefore, Ni is suppressed to 1.0 atomic% or less (preferably 0.8 atomic% or less), and Cu is suppressed to 0.8 atomic% or less (preferably 0.6 atomic% or less).

  In the Al alloy film of the present invention, the contact resistance can be further reduced by containing a predetermined amount of Ti which is a refractory metal. This is presumably because the conductivity is high, for example, a coarse Al compound having a maximum diameter of 200 nm or more is deposited on the interface. Specifically, in the present invention, the Al alloy film after film formation is preferably subjected to a heat treatment at 330 ° C. for 30 minutes or more. Although it does not precipitate, it is the temperature at which Ni and Cu are precipitated and the Al—Ni—Cu compound is precipitated, and this is thought to enlarge the precipitate.

  The “coarse Al-based precipitate” means a compound containing at least Ni and having a maximum diameter of approximately 80 to 200 nm. Such a coarse precipitate can be obtained by holding the Al alloy film in a temperature range of 270 to 300 ° C. for as long as possible. The precipitation temperature of the Al alloy is governed by the composition. In the case of the Al-Ni-Cu-La system, Al-Cu-based precipitates are formed near 200 ° C, and Al-Ni-Cu precipitates at grain boundaries up to 270 ° C. Therefore, Al—Ni—Cu is also present at the grain boundary after the heat treatment at 330 ° C. However, since grain growth is suppressed when Ti is added, it is considered that the precipitates are coarsened by further diffusing Ni and Cu into the once precipitated Al-Ni-Cu.

  In order to effectively exhibit the effect of Ti, its content needs to be 0.05 atomic% or more. However, if the Ti content is excessive, the wiring resistance is remarkably increased, so it is necessary to set it to 0.5 atomic% or less. In addition, the minimum with preferable Ti content is 0.1 atomic%, and a preferable upper limit is 0.3 atomic%.

  The Al alloy of the present invention contains the above components, and the balance is Al: inevitable impurities.

  In addition to the above basic components, it is also useful that the Al alloy film of the present invention further contains a rare earth element if necessary. By including a rare earth element in the Al alloy film, it is possible to sufficiently increase the resistance to the resist stripping solution used in the manufacturing process. In addition, a silicon nitride film (protective film) is subsequently formed on the substrate on which the Al alloy film is formed by a CVD method or the like. At this time, the high temperature heat applied to the Al alloy film causes a gap between the substrate and the substrate. It is said that a difference in thermal expansion occurs and hillocks (cove-like projections) are formed. However, the inclusion of the rare earth element can suppress the formation of hillocks and improve the heat resistance.

  The above effect increases as the content of the rare earth element increases (that is, more than 0%), but it is more preferable to contain 0.2 atomic% or more. However, if the rare earth element is contained excessively, the electrical resistivity of the Al alloy film itself tends to increase. Therefore, the rare earth element content is preferably 1.0 atomic% or less (more preferably 0.5 atomic% or less).

  The rare earth element referred to here is Sc (scandium) and Y (yttrium) added to a lanthanoid element (a total of 15 elements from La with atomic number 57 to Lu with atomic number 71 in the periodic table). Means an element group. Among the above elements, for example, use of La, Nd, Y, Gd, Ce, Dy, Ti, and Ta is more preferable, La, Nd, and Gd are more preferable, and La and Nd are particularly preferable. Of these, one or more can be used in any combination.

  The Al alloy film is desirably formed by a sputtering method using a sputtering target (hereinafter also referred to as “target”). This is because a thin film having excellent in-plane uniformity of components and film thickness can be easily formed as compared with a thin film formed by ion plating, electron beam vapor deposition or vacuum vapor deposition.

  Moreover, in order to form the Al alloy film by the sputtering method, 0.2 to 1.0 atomic% of Ni, 0.2 to 0.8 atomic% of Cu, and 0.05 of Ti are used as the target. -0.5 atomic%, and if necessary, further containing rare earth elements in an amount of 1.0 atomic% or less (not including 0%), the balance being made of Al and inevitable impurities, and a desired Al alloy film, If Al alloy sputtering targets having the same composition are used, an Al alloy film having a desired component / composition can be formed without causing a composition shift.

  The shape of the target includes those processed into an arbitrary shape (such as a square plate shape, a circular plate shape, or a donut plate shape) according to the shape or structure of the sputtering apparatus. As a method for producing the above target, a method of producing an ingot made of an Al-based alloy by a melt casting method, a powder sintering method, or a spray forming method, or a preform made of an Al-based alloy (the final dense body is prepared) Examples thereof include a method obtained by producing an intermediate before being obtained) and then densifying the preform by a densification means.

  The present invention also includes a display device characterized in that the Al alloy film is used in a thin film transistor. As an aspect of the display device, the Al alloy film includes a source electrode and / or a drain electrode of a thin film transistor and a signal. It is used for the wire, and the drain electrode is directly connected to the transparent conductive film.

  The transparent conductive film used in the present invention is preferably an indium tin oxide (ITO) film or an indium zinc oxide (IZO) film.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited by the following examples, and appropriate modifications are made within a range that can meet the above and the following purposes. Of course, it is possible to implement them, and they are all included in the technical scope of the present invention.

  Al alloy films having various alloy compositions shown in Table 1 below were formed, and contact resistance was measured by the following method. The content of each alloy element in each Al alloy film is determined by an ICP emission analysis (inductively coupled plasma emission analysis) method.

First, an Al alloy having a thickness of 300 nm was formed on a glass substrate by sputtering. Then, the Al alloy film was patterned to form a gate electrode. Next, a silicon nitride film (SiN _x ) having a thickness of 300 nm was formed by plasma CVD. The film formation temperature (heating temperature after the Al alloy film formation) at this time was 330 ° C., and the film formation time was 30 minutes.

  Subsequently, this silicon nitride film was patterned and ashed with oxygen plasma. Thereafter, the photoresist is stripped with a stripping solution immediately before the ITO film is formed, and the oxide film on the Al alloy film is removed, and tetramethylammonium hydroxide (TMAH) is used to deposit precipitates on the outermost surface of the film. It was immersed in an alkaline solution diluted to 0.4% for 50 seconds. Thereafter, an ITO film having a thickness of 200 nm was formed by sputtering. Further, a pixel electrode was formed by patterning.

(Measurement of contact resistance)
In the above process, a contact chain pattern having a contact hole size of 10 μm square was prepared, and two-terminal measurement was conducted to pass current through the ITO-Al alloy, and contact resistance converted per contact hole was determined. The contact chain was composed of 50 contact holes, and the contact resistivity R (contact resistance) was determined as R = V / (I × 50) from the current I and the voltage V between the pads. The obtained contact resistivity R was 100 Ω or less. The results are shown in Table 1 below.

  From the results shown in Table 1, it can be considered as follows. First, an experiment No. 1 containing no rare earth element (La in this example) was used. Considering 1 to 3, in the composition not containing Ti (Al-0.6Ni-0.5Cu: Experiment No. 1), the contact resistance exceeds 100Ω, but Ti is contained. In (Experiment No. 2, 3), the contact resistance was reduced to 100Ω or less in all cases. Such an effect of promoting the reduction of contact resistance by addition of Ti was also observed in the case of further containing a rare earth element (refer to Experiment Nos. 4, 5 and 6, 7).

  Next, the precipitate size was analyzed by the following procedure. First, an Al alloy with a thickness of 300 nm was formed on a glass substrate by a sputtering method. Subsequently, in order to reproduce the formation process of the silicon nitride film, heating was performed using a plasma CVD apparatus. After the temperature in the apparatus reached 330 ° C., the temperature was maintained for 30 minutes.

  The various Al alloy films thus obtained were observed with a reflection SEM, and the precipitation size was analyzed. The results are shown in Table 1 and examples thereof are shown in FIGS. FIG. 1 is a SEM observation photograph of an Al-0.6% Ni-0.5% Cu alloy film (Experiment No. 1), and FIG. 2 is Al-0.6% Ni-0.5% Cu-0.12. SEM observation photograph of% Ti alloy film (Experiment No. 2), FIG. 3 shows Al-0.6% Ni-0.5% Cu-0.24% Ti alloy film (Experiment No. 3: Numerical unit is atom %, Balance Al and inevitable impurities) SEM observation photographs are shown respectively.

  1-3, the part which looks white is a precipitate. As apparent from comparison between FIG. 1 and FIGS. 2 and 3, Ti is contained in comparison with the precipitate (FIG. 1) of the Al-0.6% Ni-0.5% Cu alloy film not containing Ti. The deposits of the Al-0.6% Ni-0.5% Cu-0.12% Ti alloy film and the Al-0.6% Ni-0.5% Cu-0.24% Ti alloy film become larger. (Figs. 2 and 3). In addition, as shown in the precipitates surrounded by white circles in FIGS. 2 and 3, a large one having a maximum diameter of 138 nm or more is recognized.

Claims (5)

An Al alloy film directly connected to the transparent conductive film on the substrate of the display device,
The Al alloy film contains Ni: 0.2 to 1.0 atomic%, Cu: 0.2 to 0.8 atomic%, and Ti: 0.05 to 0.5 atomic%, respectively. A characteristic Al alloy film for a display device.   Furthermore, Al alloy film for display apparatuses of Claim 1 which contains rare earth elements 1.0 atomic% or less (it does not contain 0%).   3. A display device, wherein the Al alloy film for a display device according to claim 1 is used for a thin film transistor.   Ni: 0.2-1.0 atomic%, Cu: 0.2-0.8 atomic% and Ti: 0.05-0.5 atomic%, respectively, with the balance being Al and inevitable impurities Sputtering target characterized.   Furthermore, the sputtering target of Claim 4 which contains a rare earth element 1.0 atomic% or less (excluding 0%).