JPH1143765A - Aluminum alloy target and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an Al alloy target contg. eutectic structure formable elements remarkably small in defects, i.e., capable of preventing the generation of splashes. SOLUTION: This Al alloy target has a microstructure composed of Al phases and eutectic structural phases composed of Al and eutectic structure formable elements with Al. Preferably, in an Al alloy contg. Al and one or more kinds among eutectic structure formable elements with Al, it has a microstructure composed of eutectic structural phases and Al phases, and the maximum major axis of the eutectic structure is regulated to <=200 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an Al-based alloy target mainly composed of Al, and more particularly to a target suitable for forming a thin film wiring for a liquid crystal display (Liquid Crystal Display) and a method of manufacturing the same.

[0002]

2. Description of the Related Art Thin film devices are formed on a glass substrate.
Conventionally, pure metal films such as pure Cr films, pure Ta films, pure Ti films, or alloy films thereof, which are high melting point metals, have been used for electric wiring films and electrodes used for LCDs, thin film sensors, and the like. .
With the increase in size and definition of LCDs, wiring films and electrode films are required to have low resistance and low stress and to stabilize their characteristics in order to prevent signal delay. For example, for electrodes used in large color LCDs of 12 inches or more, it is required to be 15 μΩ · cm or less. However, conventional Cr and Ta based high melting point alloy films have excellent film stability, but have high resistance, about 30 μΩcm for Cr, about 180 μΩcm for Ta, and about 60 μΩ for Ti.
μΩ · cm. For this reason, an Al alloy-based wiring material having a lower specific resistance than these metals has been used.

[0003] Although the specific resistance of a pure Al film is low, there is a problem in heat resistance, and there is a problem that minute projections called hillocks are formed on the surface in a heating step after forming an electrode film, which is inevitable in a TFT manufacturing process. . This hillock is considered to occur due to stress migration, thermal migration, and the like. When this hillock occurs, an insulating film, a protective film, and the like are formed on the Al wiring film, and further, the wiring film,
When an electrode film or the like is to be formed, there is a problem that an etching solution or the like intrudes through an electric short circuit or a hillock and the Al alloy wiring film is corroded.

Therefore, a high melting point metal is added instead of pure Al for the purpose of solving these problems. For example, Japanese Patent Application Laid-Open No. 4-323872 describes that it is effective to add 0.05 to 1.0 at% of Mn, Zr, and Cr. In addition, special fairness
In No. 4-48854, B is 0.002 to 0.5 wt%, Hf, Nb, Ta, Mo, W
0.002 to 0.7 wt%, and 0.5 to 1.5 wt% of Si
A method of adding is disclosed. Further, Japanese Patent Application Laid-Open No. H5-656631 describes that adding 0.2 to 10 at% of Ti, Zr, and Ta is effective in suppressing hillocks. Furthermore, JP-A-7-
Fe, Co, Ni, Ru, Rh, Ir as stated in 45555
0.1 to 10 at%, and 0.05 to 15 at% of a rare earth element, or Cu, T as described in JP-A-5-335271.
A method of adding 0.01 to 3 wt% of i, Pd, Zr, Hf, Y, and Sc is known.

[0005] All of the above-mentioned alloy-based phases consist of a solid solution phase or an Al phase (hereinafter referred to as an Al matrix) and a precipitate or a compound, and these are dispersed in the grain boundaries or grains of the Al matrix to suppress hillocks. It is considered. Conventionally, when manufacturing an Al alloy target, a small target has been manufactured by performing machining after melting and casting. In addition, large targets have been manufactured by performing plastic working such as rolling to a predetermined size after melting and casting.

[0006]

Generally, when a liquid crystal wiring film is formed, sputtering is performed by a DC magnetron sputtering method. If the Al alloy-based target has a minute defect, a local arc discharge occurs at the defect,
A phenomenon in which a part of the target melts down and adheres to the substrate is observed. This is a phenomenon called splash, which is a serious problem because the production yield of liquid crystal panels is significantly reduced. A target formed by a conventional melting casting method may cause shrinkage cavities due to heat shrinkage, which may be a defect. Also,
In an Al alloy capable of forming an intermetallic compound, when a coarse compound is partially generated by segregation, a compound crack defect may occur during rolling after casting.

A powder sintering method is known as a method of producing no casting defects. However, when the pure Al powder and the additive element powder are mixed and sintered, the additive element powder may be changed to a coarse compound in the sintering process, causing a rolling crack defect. The present inventors have studied a mode in which an element for preventing hillocks is added to Al. Then, it was found that the brittleness caused by the presence form of the additional element in the target structure leads to the generation of vacancies that cause splash.
A target structure in which a compound phase or a precipitation phase generated by an element added for preventing hillocks is present alone in the Al matrix is fragile,
Due to deformation stress applied to processes such as rolling and machining, minute cracks are easily generated and holes are formed.

In view of the above problems, the present inventors have studied various powder forms in the powder sintering method. As a result, a sintered body using a powder obtained by melting an Al alloy having a predetermined composition and quenching and solidifying by a gas atomizing method or the like is easy to obtain a uniform and fine compound phase, and is less likely to cause a compound crack defect due to rolling. understood. However, even when the above-mentioned Al alloy gas atomized powder is used, pores (voids) remain in the sintered body when the amount of added elements increases even when pressure sintering is performed or when rolling is further performed. There are cases.

Here, the cause of the above-mentioned pore remaining will be described. Al alloy powder forming eutectic structure is solid solution A
It is composed of an 1 phase and a precipitated phase or a compound phase. In the structure of each particle, since the precipitated phase or the compound phase is dispersed, the deformation resistance is increased as compared with the pure Al powder. In particular, Al alloy powder having a large amount of added elements and a large number of precipitated phases or compound phases has remarkably high deformation resistance, and it is difficult to complete defect-free complete sintering using ordinary pressure sintering equipment such as HIP and hot press. .

The present invention has been made in view of the above problems. An object of the present invention is to provide an Al alloy target containing an element capable of forming a eutectic structure, which has extremely few defects, that is, a target capable of preventing the occurrence of splash.

[0011]

The present inventors have conducted intensive studies to solve the above-mentioned problems and found that pure Al powder and elements added for preventing hillocks were dispersed as fine compound phases or precipitated phases. It has been found that by mixing an Al alloy powder having a eutectic structure (hereinafter referred to as Al alloy powder) having a predetermined composition and sintering under pressure, the pores (voids) of the sintered body can be significantly reduced. Reached. That is, it has been found that a target with few defects can be obtained by providing a binder effect by interposing an Al phase having a low deformation resistance in an eutectic structure phase formed of an Al alloy having a high deformation resistance. It is. Further, by combining the eutectic structure phase and the Al phase, Al
By reducing the deformation stress applied to the eutectic structure phase by the phase, it is possible to suppress the occurrence of defects due to fine cracks during composition deformation compared to the target of the eutectic structure alone phase, and to suppress the occurrence of splash. I found it.

That is, the present invention provides an Al phase, Al and Al
And a eutectic structure phase composed of an element capable of forming a eutectic structure.
Preferably, in an Al alloy containing at least one element capable of forming a eutectic structure with Al, the Al alloy has a microstructure composed of an eutectic structure phase and an Al phase, and the maximum major axis of the eutectic structure is 200 μm
Adjust to be as follows.

The targets of the present invention are, for example, Al and A
1 and a rapidly solidified powder composed of an element capable of forming a eutectic structure with pure Al powder and pressure-sintered at a temperature of 400 ° C. or more and 600 ° C. or less. At this time, the area ratio between the eutectic structure phase and the Al phase observed in the cross-sectional microstructure of the target is set to satisfy (area of the eutectic structure phase) / (area of the Al phase matrix) <2. Also,
When applied to a large target having a sputter surface area of 0.3 m ² or more, it is necessary to perform hot rolling in a temperature range of 400 ° C. to 600 ° C. after pressure sintering. By forming the above-described target by sputtering, a wiring film for a liquid crystal display with less splash and less hillock can be obtained.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As described above, one of the important features of the present invention is that a eutectic structure phase and an Al phase are present in a target structure. That is, the presence of the eutectic structure phase and the Al phase allows the eutectic structure phase formed of the Al alloy having a large deformation resistance to have the effect of a binder by interposing the Al phase having a small deformation resistance. Generation of defects during sintering can be prevented. Also, the effect of suppressing the occurrence of defects due to fine cracks during composition deformation can be obtained by relaxing the deformation stress applied to the eutectic structure phase by the Al phase having a small deformation resistance.

In the present invention, the effect can be exhibited if the eutectic structure phase and the Al phase are present, but if the volume of the Al phase is small, the effect of preventing the generation of vacancies is small. In the present invention, in particular, (area of eutectic structure phase) / (area of Al phase matrix) in the microstructure of the cross section of the target
When <2 is satisfied, a remarkable effect of preventing the occurrence of splash can be found. Specifically, the eutectic structure phase and A
The 1-phase can be adjusted by the volume ratio between the Al alloy powder having the eutectic structure and the Al powder. In the present invention, more preferably (area of eutectic texture phase) / (A
(area of 1-phase matrix) <1.

Elements capable of forming a eutectic structure with Al include:
Si, Cu, Mg, Fe, Co, Ni, Ru, Rh, Ir, and Sc, Y,
There are rare earth elements such as lanthanoids.
The invention is suitable for producing alloys containing more than one species. The Al alloy powder can be obtained by a rapid solidification method such as a gas atomizing method after dissolving a predetermined composition. Powder obtained by gas atomization or the like has a distribution in particle size, and may include a coarse powder having a diameter of about 5 mm.
If sintering is performed while containing such a coarse powder, distribution in the composition of the target surface will be caused. As a result of the examination,
The size of the precipitate in the alloy powder is correlated with the size of the particle size, and small particles with a fast solidification rate, typically particles with a particle size of 200 μm or less, can easily obtain fine precipitates. It has been found that defects due to deformation stress such as forming and rolling can be further suppressed.

As the composition of the Al alloy powder, it is desirable to select a composition in which the maximum major axis of the compound phase or the precipitated phase in each powder particle does not exceed 40 μm. This is because if the major diameter of the compound phase or the precipitated phase exceeds 40 μm, these phases may cause cracking defects during plastic working. Further, at the time of pressure sintering of the raw material powder, sintering at a temperature of 400 ° C. or more and 600 ° C. or less is desirable. This is 400 ° C
If the temperature is lower than 600 ° C., sintering hardly proceeds, and if the temperature is higher than 600 ° C., there is a risk of melting. Pressure sintering is preferably performed at a pressure of 50 MPa or more in order to obtain a dense sintered body without voids.

In the present invention, rolling is performed after pressure sintering to produce a sputtered area of 0.3 m ² or more. If cold rolling is performed, cracking defects may occur in compounds and precipitates, so the processing temperature should be 400 ° C or higher, and 550 ° C or lower to prevent melting due to local temperature rise due to rolling. .

[0019]

【Example】

(Example 1) An ingot having an additional element content higher than the target composition was melt-cast and subjected to gas atomization to obtain a powder.
Next, this powder was classified by a sieve into a particle size shown in Table 1. Next, after mixing this powder and pure Al powder by a rocking mixer so as to have a predetermined composition, filling the mixture into an iron can having a filling volume of φ133 mm × 10 mm and a thickness of 2 mm, and then exhausting to 10 −3 Pa or less. Degassing was performed at a heating temperature of 400 ° C. for 3 hours while sealing. Thereafter, HIP (hot isostatic pressing) was performed at a heating temperature shown in Table 1 at a pressure of 127 MPa and a holding time of 3 hours. After removing the can, machining was performed to obtain a disk-shaped target of φ100 mm × 4 mm. . As a comparative example, an ingot having a predetermined composition was melt-cast to produce a gas-atomized powder, which was classified so as to have a particle size of 150 μm or less, sintered in the same manner as in the present invention, and machined to form a eutectic structure. A phase target was obtained.

Next, after scraping off the target from which the target was sampled, the number of voids having a major axis of 10 μm or more observed by an optical microscope was counted by a dye penetrant inspection method, and the number was determined as the number of defects per 1 mm ² . Further, the Al matrix phase and the eutectic phase of the microstructure were distinguished, and the area ratio of each was calculated by image processing. Table 1 shows the above results. Also,
As examples showing typical target structures, microstructure photographs taken by subjecting Sample 3 of the present invention shown in Table 1 and Sample 4 of Comparative Example to electropolishing are shown in FIGS. 1 and 2, respectively.

As shown in FIGS. 1 and 2, in the comparative example in which the eutectic structure alone was used, the pores (voids) detected in black were dispersed in the target structure. On the other hand, in the target structure of the present invention having a eutectic structure phase (a mottled phase) and an Al phase (gray phase), almost no pores are observed. Further, as shown in Table 1, when the area of the Al phase is small, the number of voids is small, and the number of defects tends to increase slightly, and when the sintering temperature is lowered, the number of voids tends to increase. .

[0022]

[Table 1]

(Example 2) An ingot having an additional element content higher than the target composition was melt-cast and subjected to gas atomization to obtain a powder. Next, this powder was classified by a sieve into a particle size shown in Table 2. Next, this powder and pure Al powder were mixed by a rocking mixer so as to have a predetermined composition, and then 330 mm × 500 mm
After filling into a 2 ton thick iron can with a filling volume of × 50 mm, the heating temperature was 4
Degassing was performed at 00 ° C. for 3 hours, followed by sealing. After this, the heating temperature is 550
After performing HIP (Hot Isostatic Pressing) at ℃, pressure of 127MPa and holding time of 3h, removing the can, hot rolling at a heating rate shown in Table 1 and a working rate of 75% was performed, followed by machining. 550mm
× 690mm × 6mm target. As a comparative example, an ingot having a predetermined composition was melt-cast to prepare a gas-atomized powder, which was classified to 150 μm or less, sintered as in the above-described present invention, subjected to hot rolling and machining. Thus, a target composed of the eutectic structure phase was obtained.

In the same manner as in Example 1, the number of voids having a major axis of 10 μm or more observed by an optical microscope was counted and determined as the number of defects per 1 mm ² . Table 2 shows the above results. FIGS. 3 and 4 show microstructure photographs taken after electropolishing of Sample 12 of the present invention and Sample 13 of Comparative Example shown in Table 1 as examples showing typical target structures, respectively. As shown in FIGS. 3 and 4, in the comparative example in which the eutectic structure alone was used, the pores detected in black were dispersed in the target structure. On the other hand, in the target structure of the present invention having a eutectic structure phase (a mottled phase) and an Al phase (gray phase), almost no pores are observed even after hot rolling. Further, as shown in Table 1, even when hot rolling was performed, the number of voids was small when the area of the Al phase was small, and the number of defects tended to increase slightly. Tend to increase.

[0025]

[Table 2]

[0026]

According to the present invention, it is possible to obtain a target in which the number of defects of the target, which is a cause of splash, which is a problem when sputtering an Al alloy target, is extremely small. The present invention is expected to increase in size in the future
As an Al alloy target corresponding to TFT-LCD, it is extremely effective in improving the yield of LCD.

[Brief description of the drawings]

FIG. 1 is a micrograph showing a typical metal microstructure of a target of the present invention obtained by sintering.

FIG. 2 is a micrograph showing a typical metal microstructure of a target of a comparative example obtained by sintering.

FIG. 3 is a micrograph showing a typical metal microstructure of a target of the present invention obtained by sintering and hot rolling.

FIG. 4 is a micrograph showing a typical metal microstructure of a target of a comparative example obtained by sintering and hot rolling.

Claims (7)

[Claims] 1. An Al alloy-based target comprising a microstructure comprising an Al phase and a eutectic structure phase composed of an element capable of forming a eutectic structure of Al and Al. 2. An Al alloy system containing at least one element capable of forming a eutectic structure with Al, having a microstructure composed of an eutectic structure phase and an Al phase, wherein the maximum major axis of the eutectic structure is 20 or more.
2. The Al according to claim 1, wherein said Al is not more than 0 μm.
Alloy target. 3. The area ratio between the eutectic structure phase and the Al phase observed in the cross-sectional microstructure is (area of the eutectic structure phase) / (A
3. The Al alloy-based target according to claim 1, wherein an area of an l-phase matrix) <2 is satisfied. 4. The method according to claim 1, wherein the area of the sputtering surface is 0.3 m ² or more.
l-based alloy target. 5. A method comprising mixing a rapidly solidified powder composed of an element capable of forming a eutectic structure of Al and Al with a pure Al powder and subjecting the mixture to pressure sintering at a temperature of 400 ° C. or more and 600 ° C. or less.
1. Manufacturing method of alloy target. 6. The method for producing an Al alloy-based target according to claim 5, wherein the rapidly solidified powder has a particle size of 150 μm or less. 7. The method for producing an Al alloy-based target according to claim 5, wherein after the pressure sintering, hot rolling is performed in a temperature range of 400 ° C. or more and 600 ° C. or less.