JP4188299B2 - Ag-based alloy wiring electrode film for flat panel display, Ag-based alloy sputtering target, and flat panel display - Google Patents

Description

  The present invention relates to a wiring film or an electrode film of a flat panel display (FPD), a sputtering target for forming the wiring film or an electrode film by a sputtering method, and an FPD including the wiring film or the electrode film.

  Liquid crystal display (LCD: Liquid Crystal Display, specific examples are amorphous Si TFT LCD and poly-Si TFT LCD), field emission display (FED), electroluminescence display (ELD: Electro Luminescence Display, specific example is organic) Flat display devices such as ELD and inorganic ELD) and plasma display panels (PDPs) are called flat panel displays (FPDs). There are two known driving types of display pixels of the FPD, an active type (thin film transistor driving type) and a passive type.

The active FPD has a large number of display pixels provided with a reflective electrode film or transparent electrode film 1 as shown in FIG. As shown in FIG. 2, each display pixel includes a thin film transistor (TFT) 2 for driving the display pixel. The TFT 2 has electrode films called a gate, a source, and a drain. On the other hand, two types of wiring films 3 and 5 for supplying a current to the TFT 2 are arranged vertically and horizontally around each display pixel, and one wiring film (herein referred to as an address wiring film) 3 is a gate. The other wiring film (referred to as a data wiring film in this case) 5 is connected to the TFT 2 through the source electrode 6 through the electrode film 4, and the reflective electrode from the TFT 2 through the drain electrode film 7. Connected to the film or transparent electrode film 1. The wiring films (address wiring film and data wiring film) 3, 5 and the electrode films (gate electrode film, source electrode film, drain electrode film) 4, 6, 7 are different from the reflective electrode film or the transparent electrode film 1. The required characteristics are different, and in the present invention, these are collectively referred to as a wiring electrode film.
On the other hand, the TFT of the passive type FPD does not exist in the active type FPD, and as shown in FIG. Further, a scanning electrode 23 and a data electrode 24 made of a large number of transparent electrodes are formed, and a structure in which liquid crystal is filled therebetween is provided. A pixel is displayed by applying a voltage to these electrodes. The electrodes of the scanning electrode and the data electrode are also referred to as an electrode film or a wiring film. Like the electrode film or the wiring film of the active FPD, these are collectively referred to as a wiring electrode film in the present invention. Hereinafter, when the active type or passive type FPD is not particularly distinguished, both types of FPDs are simply referred to as “FPD”.

  Conventionally, the wiring electrode film has been formed of an Al-based alloy that is excellent in electrical conductivity and heat resistance and excellent in fine workability by wet etching. However, in recent years, as the FPD has a larger screen, higher definition, and diversification, the wiring electrode film is required to have further lower electrical resistivity, higher heat resistance, and higher fine workability. Hereinafter, these required characteristics will be described.

  First, the low electrical resistivity will be described. With the increase in the screen size of FPDs such as large televisions, the line length of the wiring electrode film tends to increase. In addition, the line width of the wiring electrode film tends to become narrower as the FPD with higher definition such as a high-quality television is taken as an example. When the line length becomes long or the line width becomes narrow, the electric resistance of the wiring electrode portion increases, which causes a problem of electric signal delay. In order to suppress the electrical signal delay, it is preferable to use a wiring electrode film material having a low electrical resistivity. If the required specification of low electrical resistivity is set to a lower value than the conventional one, for example, 3.0μΩcm or less (value obtained after heat treatment at 300 ° C), Al-based materials that have been used in the past cannot be handled. Therefore, attention has been focused on Ag-based materials that can handle 3.0 μΩcm or less.

  Next, high heat resistance will be described. In addition to conventional amorphous Si TFT LCDs, new FPDs such as low-temperature poly Si TFT LCDs and FEDs have recently appeared and the diversification of FPDs is progressing. In these new FPDs, the wiring electrode film is heated at a high temperature in a specific manufacturing process. For example, low-temperature poly-Si TFT LCD receives 450-500 ° C. heating once under vacuum at the time of poly-Si activation, and FED heats 450-500 ° C. three times under air at the time of glass sealing. receive. Such high heat resistance against high temperature heating is not required in the conventional amorphous Si TFT LCD, and is a new problem caused by the appearance of a new FPD. Conventionally used Al-based materials are difficult to meet the high heat resistance required specifications for heating at 450 to 500 ° C., and applicable Ag-based materials are attracting attention.

  Further, high fine workability will be described. The line width of the wiring electrode film tends to become narrower as the FPD becomes higher in definition. The wiring electrode film of FPD is usually finely processed into a predetermined shape by wet etching, but it becomes difficult to control the shape when the line width is narrowed. Therefore, a wiring electrode film material excellent in fine workability is used. It is preferable to do. Ag-based materials attracting attention from the viewpoints of low electrical resistivity and high heat resistance generally have a high wet etching rate and a large etching amount (side etching amount) on both side surfaces of the wiring electrode film, making it difficult to control the shape. In order to apply to an FPD in which the line width of the wiring electrode film is 10 μm or less, it is necessary to improve the fine workability. Note that the difficulty of microfabrication due to the narrowing of the line width is not a problem with a reflective electrode film or a reflective film having a large processing size, but is a problem only with a wiring electrode film having a small processing size.

  Various Ag-based materials for wiring electrode films have been proposed in response to the demands for low electrical resistivity and high heat resistance. For example, in Japanese Patent Laid-Open No. 2001-102325 (Patent Document 1), an Ag- (0-25) wt% Ru- (0-25) wt% Cu alloy is disclosed in Japanese Patent Laid-Open No. 2001-192752 (Patent Document 2). For example, an alloy of Ag- (0.1-3) wt% Pd- (0.1-3) wt% (Al, Au, Pt, Cu, Ta, Cr, Ti, Ni, Co, Si) is disclosed in JP, 2002-140929 (Patent Document 3) discloses Ag- (0.1-10) wt% Au- (0.1-5) wt% (Cu, Al, Ti, Pd, Ni, V, Ta, W). , Mo, Cr, Ru, Mg) are disclosed in Japanese Patent Application Laid-Open No. 2003-113433 (Patent Document 4) as Ag- (0.1-2) at% (Sc, Y, Sm, Eu, Tb, Dy, An Er, Yb)-(0.1-3) at% (Cu, Au) alloy is described. Incidentally, as a reflective electrode film or a reflective film having a larger processing size than the wiring electrode film, Japanese Patent Laid-Open No. 2002-323611 (Patent Document 5) discloses Ag- (0.1-3.0) at% rare earth. A metal (Nd, Y)-(0.1-2.0) at% Cu- (0.1-1.5) at% Au alloy is described.

JP 2001-102325 A JP 2001-192752 A JP 2002-140929 A JP 2003-113433 A JP 2002-323611 A

  The FPD Ag-based alloy wiring electrode films according to Patent Documents 1 to 4 are roughly classified into an Ag-based alloy wiring electrode film to which a noble metal element (Ru, Pd, Au) is added, and a rare earth metal element (Sc, Y, Sm). , Eu, Tb, Dy, Er, Yb) to which two types of Ag-based alloy wiring electrode films are added. These wiring electrode films have a low electrical resistivity and a noble metal element by using Ag as a main component. And heat resistance is improved by adding rare earth metal elements. It should be noted that the suppression of migration during heat treatment and the stability to heat treatment have the same technical significance, and the improvement in heat resistance is that an increase in surface roughness due to aggregation of Ag caused by heating is suppressed. .

  However, the conventional Ag- (Ru, Pd, Au) alloy and the Ag- (Sc, Y, Sm, Eu, Tb, Dy, Er, Yb) alloy satisfy a certain degree of low electrical resistivity and high heat resistance. In particular, the high fine workability is not satisfactory. Patent Document 5 mentions an Ag—Nd alloy intended to suppress Ag crystal grain growth and aggregation due to heating by addition of Nd. The reflective film is different from the wiring electrode film in size and required characteristics such as line width, and is different in use and object from the present invention.

  The present invention has been made in view of such problems, and in order to form an Ag-based alloy wiring electrode film for FPD having low electrical resistivity, high heat resistance, and high fine workability, and this Ag-based alloy wiring electrode film. An Ag-based alloy sputtering target for FPD to be used and an FPD provided with this Ag-based alloy wiring electrode film are provided.

  The present inventor has investigated the addition of various alloy elements to Ag for Ag alloys having low electrical resistivity, high heat resistance and high fine workability required for the wiring electrode film of FPD. It was found that the addition of Nd was very effective, and the present invention was completed based on this.

That is, the Ag-based alloy wiring electrode film for FPD of the present invention is formed of an Ag-based alloy containing 0.1 to 1.5 at% Nd and 0.01 to 1.5 at% Bi, and the balance Ag and impurities. It has been done .

  Moreover, the sputtering target for forming the Ag-based alloy wiring electrode film for FPD of the present invention is formed of the Ag-based alloy. In the FPD of the present invention, the wiring electrode film is formed of the Ag-based alloy. It is equipped with things.

  Since the Ag-based alloy wiring electrode film for FPD of the present invention has low electrical resistivity, high heat resistance, and high fine workability, the performance and reliability of FPD can be achieved for both active type and passive type FPDs. It can be significantly improved. The Ag-based alloy sputtering target of the present invention is preferably used for forming the Ag-based alloy wiring electrode film, and the Ag-based alloy wiring electrode film formed using the Ag-based alloy wiring electrode film has an alloy composition, alloy element distribution, and film thickness. Therefore, it is possible to produce a high-performance and highly-reliable FPD that exhibits excellent in-plane uniformity and exhibits excellent characteristics as a wiring electrode film. And since the FPD of this invention is equipped with the said Ag base alloy wiring electrode film, it is equipped with the outstanding performance and reliability.

An Ag-based alloy wiring electrode film according to an embodiment of the present invention is formed of an Ag-based alloy containing 0.1 to 1.5 at% Nd, 0.01 to 1.5 at% Bi, and the balance Ag and impurities. It has been done . Hereinafter, the effect | action of these components and the reason for limitation are demonstrated.

  By adding Nd to Ag, the wet etching rate is reduced and the amount of side etching is reduced, so that the fine workability is improved. And even if it receives high-temperature heating under a vacuum and air | atmosphere, the increase in the surface roughness by aggregation of Ag is suppressed and it has the effect of improving heat resistance. Furthermore, the low electrical resistivity is exhibited while the effect of improving the fine workability and the effect of improving the heat resistance are obtained at the same time. Due to these Nd addition effects, the Ag—Nd alloy can satisfy all of the low electrical resistivity, high heat resistance, and high fine workability required for the wiring electrode film for FPD. Therefore, the performance and reliability of the FPD can be remarkably improved by forming the wiring electrode film from this Ag-based alloy.

  However, when the Nd content is less than 0.1 at%, the effect of improving the fine workability (decreasing the wet etching rate, reducing the side etching amount) and improving the heat resistance (suppressing the increase in surface roughness due to Ag aggregation) are obtained. It is too small. Further, if it exceeds 1.5 at%, the limit electrical resistivity of the Al-based alloy is 3.0 μΩcm (value obtained after heat treatment at 300 ° C. Hereinafter, unless otherwise specified, the electrical resistivity is determined by the above heat treatment. It is a later value.) Lower electrical resistivity cannot be obtained. Therefore, the lower limit of the Nd content is 0.1 at%, preferably 0.2 at%, and the upper limit is 1.5 at%, preferably 1.0 at%. A more preferable range of Nd content is 0.3 to 0.7 at%.

The Bi has the effect of further improving the corrosion resistance (chemical stability) of the Ag—Nd alloy. In addition, it has an effect of further suppressing Ag halogenation reaction and Ag aggregation starting from the reaction in an environment containing halogen ions such as chlorine ions.

However, if the amount of Bi is less than 0.01 at%, these improvement effects are too small. On the other hand, if it exceeds 1.5 at%, a low electrical resistivity of 3.0 μΩcm or less cannot be obtained. Therefore, the Bi amount is set to 0.01 to 1.5 at%, preferably 0.05 to 1.2 at%, more preferably 0.1 to 1.0 at%.

  Here, the relationship between the content of additive elements such as Nd and the electrical resistivity will be described. In the same manner as in the examples described later, a pure Ag film having a target film thickness of 300 nm, an Ag-2.2 at% Nd alloy film, an Ag-2.5 at% Y alloy film, and an Ag— film on a glass substrate by DC magnetron sputtering. A 3.1 at% Ru alloy film, an Ag-3.0 at% Pd alloy film, and an Ag-2.9 at% Au alloy film were formed.

The obtained thin film for evaluation was heated at 300 ° C. to 0.5 h under vacuum (degree of vacuum: 0.27 × 10 ⁻³ Pa or less) using a heat treatment apparatus in a rotating magnetic field manufactured by Naruse Scientific Instruments Co., Ltd. The electrical resistivity after heat processing was calculated | required with the following method. The sheet resistance Rs was measured by a direct current four-probe method using a 3226 mΩ Hi TESTER manufactured by Hioki Electric Co., Ltd., and the film thickness t was measured using an alpha-step 250 manufactured by TENCOR INSTRUMENTS. It was determined from resistance Rs × film thickness t).

FIG. 1 is a graph showing the relationship between the electrical resistivity (after heat treatment under vacuum of 300 ° C.-0.5 h) and the amount of alloy elements in various Ag alloys prepared based on the measurement results of the electrical resistivity. Since electrical resistivity shows a linear relationship with the amount of alloying elements, the upper limit of the amount of alloying elements with electrical resistivity of 3.0 μΩcm or less is as follows for various Ag alloys. It was confirmed that the -Nd alloy achieves a low electrical resistivity of 3.0 μΩcm or less with a relatively small alloy addition amount (1.5 at% or less).
Ag—Nd alloy: 1.5 at%, Ag—Y alloy: 1.0 at%, Ag—Ru alloy: 1.8 at%, Ag—Pd alloy: 2.0 at%, Ag—Au alloy: 3.0 at%

  The Ag-based alloy wiring electrode film for FPD can be formed on a substrate by a vacuum deposition method, an ion plating method, a sputtering method, etc., but among these thin film formation methods, those formed by a sputtering method are recommended. Is done. The Ag-based alloy wiring electrode film formed by sputtering is superior in in-plane uniformity of the alloy composition, alloy element distribution, and film thickness compared to thin films formed by other thin film forming methods. This is because excellent characteristics (low electrical resistivity, high heat resistance, and high fine workability) can be satisfactorily extracted as an electrode film, and high-performance and highly reliable FPD can be produced.

  In addition, the Ag-based alloy sputtering target used to form the Ag-based alloy wiring electrode film for FPD can be manufactured by any method such as a melting / casting method, a powder sintering method, or a spray forming method. Among these production methods, the production by the vacuum melting / casting method is particularly recommended. The sputtering target manufactured by this method has a lower content of impurity components such as nitrogen and oxygen than those manufactured by other methods, and is excellent in wiring electrode films formed using this sputtering target. This is because the characteristics (low electrical resistivity, high heat resistance, high fine workability) are effectively extracted, and high-performance and highly reliable FPD can be produced.

  An FPD including the above Ag-based alloy wiring electrode film for FPD can achieve remarkably superior performance and reliability by the Ag-based alloy wiring electrode film. The FPD of the present invention only needs to include the FPD Ag-based alloy wiring electrode film of the present invention, and other configurations are not particularly limited, and configurations known in the FPD field can be employed.

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not interpreted limitedly by this Example.

An evaluation thin film was prepared according to the following procedure. Pure Ag sputtering target (size φ101.6 mm × t5 mm), or a composite sputtering target in which a predetermined number of alloy element chips (size 5 mm × 5 mm × t1 mm) are arranged on the pure Ag sputtering target, and a sputtering apparatus (Shimadzu Corporation) HSR-552), DC magnetron sputtering method (back pressure: 0.27 × 10 ⁻³ Pa or less, Ar gas pressure: 0.27 Pa, Ar gas flow rate: 30 sccm, sputtering power: DC 200 W, distance between electrodes: 52 mm, substrate temperature: room temperature) on a glass substrate (Corning # 1737, diameter: 50.8 mm, thickness: 0.7 mm) on a pure Ag or Ag base having a target film thickness of 300 nm shown in Table 1 or Table 2 An alloy thin film was formed. Among these thin films for evaluation, the composition was a value determined by ICP (Inductively Coupled Plasma) emission analysis or ICP mass spectrometry except for a pure Ag film (sample No. 1). The heat resistance and fine workability were evaluated in the following manner using the thin film for evaluation.

  The heat resistance was evaluated by the amount of increase in surface roughness (average roughness Ra) by heat treatment. The surface roughness was measured in an AFM (Atomic Force Microscope) observation mode using a scanning probe microscope (Nanoscope IIIa manufactured by Digital Instruments). For the evaluation thin film, the surface roughness (average roughness Ra) before and after heat treatment was measured, and the amount of increase in surface roughness by heat treatment (= (surface roughness after heat treatment) − ( The surface roughness before heat treatment)) was calculated. In the heat treatment, the heating atmosphere is 2 conditions (in a vacuum and in the air), the heating temperature is 3 conditions (350, 450, 500 ° C.) under a heating time of 0.5 h, and the number of repetitions is 3 conditions (1, 2). 18 heating conditions were set (3 times). As for heat resistance, those having an increase in surface roughness of 1.0 nm or less were judged as excellent (◯), those exceeding 1.0 nm were judged as inferior (x), and the evaluation results are shown in Table 1 (for heat treatment under vacuum) Heat resistance evaluation results) and Table 2 (heat resistance evaluation results for heat treatment in air).

From Tables 1 and 2, Sample Nos. 3, 4, 5 and 6 having the Nd amount of the Ag-based alloy according to the present invention were superior to the heat treatment under all conditions from the heat resistance improvement effect by adding Nd. It shows heat resistance. However, sample No. 6 has a problem that the Nd content is 3.0 at% and thus does not exhibit low electrical resistivity. Sample No. 2 having an Nd content of 0.04 at% has an insufficient heat resistance improvement effect because of the small amount of Nd. Sample No. 11 of the invention example having the Nd content and Bi content of the Ag-based alloy according to the present invention exhibits high heat resistance against heat treatment under all conditions.
On the other hand, Comparative Sample Nos. 7, 8, 9, and 10 which are other Ag alloys satisfying the required specification of low electrical resistivity have a small effect of improving heat resistance by adding any alloy element. It does not show excellent high heat resistance for heat treatment under all conditions.

  Moreover, the fine workability was evaluated by the following method. Using AZP4110 manufactured by Clariant Japan Co., Ltd. as a photoresist and AZ developer manufactured by Clariant Japan Co., Ltd. as a photoresist developer, photolithography (process: photoresist coating → pre-baking → exposure → photoresist development → water washing → By drying), a stripe-shaped resist pattern having a line width / line interval = 10 μm / 10 μm was formed on the evaluation thin film. Thereafter, wet etching using a wet etchant composed of a mixed acid of phosphoric acid: nitric acid: water = 800: 3: 20 (step: wet etching → washing → drying → photoresist peeling → drying) was performed.

  During the wet etching, the time until the wet etching of the thin film was completed was measured, and the wet etching rate (= thickness of the thin film / time until the wet etching of the thin film was completed) was calculated. Also, an SEM photograph of the thin film after wet etching was taken, the line width was measured from the photograph, and the side etching amount (= (line width 10 μm−line width after wet etching) / line width 10 μm × 100%) was calculated. did. The fine workability is evaluated based on these wet etching rates and side etching amounts, and the wet etching rate is 3 nm / s or less (twice or less than the pure Al wet etching rate of 1.5 nm / s), and the side etching amount. Of 10% or less (line width of 10μm can be processed into a shape with a line width of 9 to 10μm with respect to the target) is excellent in fine workability (○), and inferior in that it does not satisfy both conditions (X) was determined. Table 3 shows the measurement results and the determination results.

From Table 3 , Sample Nos. 3, 4, 5 and 6 show superior fine workability than the effect of improving fine workability by adding Nd. However, sample No. 6 has an excessive amount of Nd, and the electrical resistivity is high. Sample No. 2 has a small Nd content of 0.04 at%, so that the effect of improving the fine workability is small. Sample No. 11 of the inventive example shows high fine workability.
On the other hand, comparative sample Nos. 7, 8, 9, and 10 that satisfy the required specification of low electrical resistivity are comparatively good in micromachining improvement effect (sample No. 7). It does not show excellent fine workability.

It is a graph which shows the relationship between the electrical resistivity in various Ag alloys, and the amount of alloy elements. It is a plane explanatory view showing the structure of a display pixel of an active type FPD. It is a perspective explanatory view showing the structure of a display pixel of a passive FPD.

Claims (3)

A wiring electrode film for a flat panel display,
The wiring electrode film contains 0.1 to 1.5 at% of Nd and 0.01 to 1.5 at% of Bi, and is formed of an Ag-based alloy composed of the remaining Ag and impurities. Electrode film. A sputtering target for forming an Ag-based alloy wiring electrode film for a flat panel display,
  An Ag-based alloy sputtering target comprising the Ag-based alloy according to claim 1. A flat panel display comprising a wiring electrode film, wherein the wiring electrode film comprises the Ag-based alloy wiring electrode film according to claim 1.

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