KR20060002987A - Aluminum alloy wiring material having high resistance to heat and target material - Google Patents

Abstract

[PROBLEMS] To provide an aluminum alloy wiring material which is excellent both in high heat resistance and low electric resistance characteristics and thus is suitable for a low temperature process poly-Si THT being subjected to a heat treatment at a relatively high temperature of 500°C or higher, and a target material for the wiring material. [MEANS FOR SOLVING PROBLEMS] An aluminum alloy wiring material and a target material which contain nickel, cobalt and carbon, characterized in that it has a chemical composition, wherein the formulae: 0.5 at % <= X <= 3.0 at %, 4.0 at % <= X + Y <= 7.0 at %, and 0.1 at % <= Z <= 0.5 at % are satisfied, where X at % represents a nickel content in an atomic percentage, Y at % represents a cobalt content in an atomic percentage, and Z at % represents a carbon content in an atomic percentage, and the balance is aluminum.

Description

High heat resistant aluminum alloy wiring material and target material {ALUMINUM ALLOY WIRING MATERIAL HAVING HIGH RESISTANCE TO HEAT AND TARGET MATERIAL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to aluminum alloy wiring materials constituting thin film wirings, electrodes, liquid crystal display wirings, etc. of liquid crystal displays, and in particular, poly-Si thin film transistors of low temperature processes that perform high temperature heat treatment of 500 ° C or higher. The present invention relates to an aluminum alloy wiring material having high heat resistance and low resistance suitable for polycrystalline-silicon thin film transistors.

Background Art In recent years, liquid crystal displays have been widely used as alternative display devices for so-called CRTs, using electronic devices such as laptops and mobile phones as representative examples. The progress of miniaturization is remarkable. In addition, in the field of liquid crystal displays, the demand for liquid crystal displays in the form of thin film transistors (hereinafter, referred to as TFTs) is rapidly increasing, and the characteristics required for the liquid crystal display are becoming more stringent. In particular, wiring materials having low specific resistance have been demanded with large screens and high resolution of liquid crystal displays. This specific resistance characteristic request is for preventing the occurrence of signal delay that occurs when wiring and thinning of the wiring are performed.

One of the drive structures of this liquid crystal display is an active matrix drive element, which is known as a-Si type TFT (amorphous silicon thin film transistors) and poly-Si type TFT. The a-Si TFT is used for a relatively large liquid crystal display adopting a so-called TAB method (tape automatied bonding), and is inexpensive in view of electron mobility and processing speed due to amorphous Si. There is merit to be able to manufacture easily. In addition, poly-Si TFTs are used in liquid crystal displays of relatively small screens, such as adopting a so-called COF (chip on film) method, and electron mobility is nearly 100 times that of the a-Si type due to polycrystalline Si. It is suitable for high-definition, high aperture ratio, high quality, and high definition, and is used for small screens such as mobile phones and personal digital (data) assistants (PDAs).

On the other hand, the display area of recent liquid crystal displays tends to be enlarged in size, and the trend is also remarkable in electronic devices that become personal information terminals such as mobile phones and PDAs. For this reason, there is a demand for a technology that can cope with large screens in poly-Si type TFTs.

Conventionally, in this poly-Si type TFT, there are two kinds of low temperature processes using a high temperature process using a quartz substrate which performs heat treatment near 1000 占 폚 and a glass substrate subjected to heat treatment of 450 占 폚 to 600 占 폚. The format is known. In addition, low-cost poly-Si TFTs employing low-cost glass substrates are often employed in electronic devices such as mobile phones and PDAs, which are inexpensive. In the low-temperature process poly-Si TFTs, The following subjects are calculated | required about the wiring material used for the.

In the poly-Si type TFT of the low temperature process, since the heat treatment is performed at a high temperature of 450 ° C to 600 ° C, the wiring material should have high heat resistance characteristics. Therefore, high melting point wiring materials such as Mo, Ta, Cr, etc. Mainly used. High-melting-point wiring materials such as Mo can realize stable heat resistance characteristics even with heat treatment at 450 ° C to 600 ° C (see Non-Patent Document 1).

[Non-Patent Document 1] Matsumoto Masakazu, " Liquid Crystal Display Technology ", Industrial Books, Ltd., June 18, 2001, 3rd Printing, pages 115-118

However, high melting point wiring materials such as Mo, Ta, Cr and the like have excellent heat resistance characteristics, but have a property that the resistance value of the wiring material itself is relatively large. However, in a small screen having a small area, since the wiring distance is short due to narrow wiring, even with a high melting point wiring material having a high resistance value, the signal delay is not a problem in practical use. However, when the display screen becomes larger, the wiring becomes longer, and thus, when a wiring material with a high specific resistance is used, there is a possibility that a signal delay may occur. Therefore, it is difficult to cope with the large screen by the poly-Si TFT. It is considered.

The present invention is based on the above circumstances, and provides a wiring material that can adapt to heat treatment at a high temperature such as a poly-Si type TFT and satisfies low resistivity characteristics. An object of the present invention is to provide an aluminum alloy wiring material having a high heat resistance and low resistivity suitable for a poly-Si type TFT of a low temperature process which is subjected to a high temperature heat treatment of not less than ℃, and a target material forming the same.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the present inventors carefully investigated the aluminum alloy wiring material (refer patent document 1) proposed conventionally, and finds the aluminum alloy composition which has the high temperature heat resistance characteristic of 500 degreeC or more, and is low specific resistance. And reached the present invention.

[Patent Document 1] Japanese Patent Laid-Open No. 2003-089864

In general, wiring materials using aluminum alloys have excellent resistivity characteristics of 10 μΩcm or less in heat treatment at 300 ° C., but it has been recognized that the use in high temperature heat treatment at 400 ° C. or higher is very difficult. In particular, in the case of high temperature heat treatment of 500 ° C or higher, it is feared that in the aluminum alloy wiring material, the occurrence of hillock (small lump-like protrusions generated on the wiring surface by heat treatment) cannot be avoided. There is a background that an aluminum alloy was not actively employed in the wiring material for the TFT use. By the way, when the composition of the aluminum alloy (patent document 1) proposed by the present inventors was further studied, when the content of these three elements is adjusted for the aluminum alloy containing nickel, cobalt and carbon, high heat resistance at 500 ° C or higher With the heat treatment at 300 ° C., the specific resistance value could be realized at 10 μΩcm or less.

In the aluminum alloy wiring material containing nickel, cobalt, and carbon, the present invention relates to atomic percentage X at% of nickel content, atomic percentage Y at% of cobalt content, and atomic percentage Z at% of carbon content. It satisfies the relationship of ≤ X ≤ 3.0 at%, 4.0 at% ≤ X + Y ≤ 7.0 at%, 0.1 ≤ Z ≤ 0.5 at%, and the rest is made of aluminum.

The heat-resistant aluminum alloy wiring material according to the present invention is heat produced when hillock is produced by first containing a small amount of carbon in aluminum to thereby finely refine the grain size of the aluminum crystal in the aluminum alloy as a whole. In this process, the compressive stress added to the wiring material is relaxed. In addition, by including nickel and cobalt, the heat resistance characteristics are further improved.

By depositing the Al ₃ Ni phase in the aluminum alloy in the vicinity of 200 ° C., nickel contributes to the relaxation of the compressive stress that causes hillock, and also improves the heat resistance characteristics of the aluminum alloy itself. When the temperature of the precipitated phase due to nickel rises to a higher temperature, for example, around 400 ° C, the Al ₃ Ni phase is excessively precipitated and aggregation of the Al ₃ Ni phase starts to occur. By this, it is confirmed to generate projections such as hillock on the surface of the aluminum alloy wiring material. In order to prevent excessive precipitation of the Al ₃ Ni phase near 400 ° C., the aluminum alloy wiring material according to the present invention contains cobalt. When cobalt is contained together with nickel, excessive precipitation and aggregation of the Al ₃ Ni phase which starts to occur around 400 ° C. can be prevented, and heat resistance at a higher temperature side can be realized. Due to such interaction between nickel and cobalt, in the aluminum alloy wiring material according to the present invention, hillock does not occur even at a high temperature heat treatment of 500 ° C or higher.

In the high heat resistance aluminum alloy wiring material according to the present invention, nickel is 0.5 at% when the atomic percentage of nickel content is X at%, the atomic percentage of cobalt content is Y at%, and the atomic percentage of carbon content is Z at%. ≤ X ≤ 3.0 at%, the sum of nickel and cobalt is 4.0 at% ≤ X + Y ≤ 7.0 at%. If the nickel content is less than 0.5 at%, the heat resistance will be insufficient. If the nickel content is more than 3.0 at%, the balance with the cobalt content will be poor, and the specific resistance will also tend to be large. In addition, if the total content of nickel and cobalt is less than 4.0 at%, it cannot adapt to high temperature heat treatment at 500 ° C for 1 hour, and the tendency to generate hillocks becomes stronger, and if it exceeds 7.0 at%, the resistivity becomes high. It will not satisfy the resistivity characteristic of 10 μΩcm or less. If the carbon content is less than 0.1 at%, the effect of refining the grains by carbon becomes low and tends to be easily generated. If the carbon content is more than 0.5 at%, nickel and cobalt are contained and the resistivity is higher than the refining effect of the grains. The effect of making it grow stronger.

Further, according to the studies of the present inventors, the content of nickel, cobalt and carbon in the composition range is 1.5 at% ≦ X ≦ 2.5 at%, 2.0 at% ≦ Y ≦ 5.0 at%, 0.1 ≦ Z ≦ 0.3 at% In addition, when satisfy | filling the conditions, it was confirmed that it becomes the high heat resistant aluminum alloy wiring material which has the high heat resistance characteristic of 550 degreeC and 1 hour, and the specific resistance after 300 degreeC heat processing becomes about 5 micrometer cm.

In the aluminum alloy wiring material according to the present invention, as described above, it has a heat resistance characteristic of 500 ° C. or higher and has a low specific resistance, and thus is a wiring material constituting a poly-Si type TFT of a low temperature process that has not been conventionally employed. It becomes very suitable. In particular, even when the liquid crystal display of a large screen is manufactured by the poly-Si TFT, the specific resistance of the aluminum alloy wiring material according to the present invention is small, so that the fear of signal delay due to the long distance of wiring can be eliminated.

In order to obtain the aluminum alloy wiring material according to the present invention described above, the atomic percentage X at% of nickel content, the atomic percentage Y at% of cobalt content, and the atomic percentage Z at% of carbon content are 0.5 at% ≦ X ≦ 3.0 at It is preferable to use the target material which satisfy | fills the relationship of%, 4.0 at% <= X + Y <7.0 at%, 0.1 <= Z <0.5 at%, and the remainder consists of aluminum. In addition, when it is a high heat resistant aluminum alloy wiring material which has the high heat resistance characteristic of 550 degreeC and 1 hour, and the specific resistance after 300 degreeC heat processing becomes about 5 microohm-cm, content of nickel, cobalt, and carbon in the said composition range is 1.5 It is preferable to set at% ≦ X ≦ 2.5 at%, 2.0 at% ≦ Y ≦ 5.0 at%, and 0.1 ≦ Z ≦ 0.3 at%. When using the target material of such a composition, although it may depend somewhat on film forming conditions, the aluminum alloy thin film of substantially the same composition as a target material can be easily formed by sputtering.

1 is a graph showing the relationship between the total content of nickel and cobalt and a specific resistance value.

2 is a graph showing the relationship between the content of cobalt and a specific resistance value.

3 is a graph showing the relationship between the heat treatment temperature and the specific resistance value according to Examples 3, 5, and 6;

Figure 4 is a SEM observation picture of the as-depo state of Comparative Example 6.

5 is a SEM observation photograph after heat treatment at 350 ° C for 1 hour in Comparative Example 6. FIG.

6 is a SEM observation photograph after heat treatment at 400 ° C. for 1 hour in Comparative Example 6. FIG.

7 is an SEM observation photograph after heat treatment at 450 ° C for 1 hour in Comparative Example 6. FIG.

8 is an SEM observation photograph after heat treatment at 500 ° C. for 1 hour in Comparative Example 6. FIG.

9 is a SEM photograph of the as-depo state of Example 8.

10 is an SEM observation photograph after heat treatment at 350 ° C. for 1 hour of Example 8. FIG.

11 is an SEM observation photograph after heat treatment at 400 ° C for 1 hour in Example 8.

12 is an SEM observation photograph after heat treatment at 450 ° C for 1 hour in Example 8. FIG.

FIG. 13 is an SEM observation photograph after heat treatment at 500 ° C for 1 hour in Example 8.

14 is a graph showing the effective content ranges of nickel and cobalt.

Best Mode for Carrying Out the Invention The best mode for carrying out the present invention will be described based on Examples and Comparative Examples.

First, the manufacturing method of the aluminum alloy wiring material which concerns on this invention is demonstrated initially. The aluminum alloy wiring material in the present Example is evaluated based on the aluminum alloy thin film formed by the target material obtained through the manufacturing process described below.

First, aluminum of purity 99.99% was added to a carbon crucible (purity 99.9%), and heated to dissolve aluminum in a temperature range of 1600 to 2500 ° C. Dissolution of aluminum by this carbon crucible was performed in argon gas atmosphere (atmospheric pressure). After holding at this melting temperature for about 5 minutes to produce an aluminum-carbon alloy in a carbon crucible, the molten metal was poured into a carbon mold and left to cool naturally to cast.

The ingot of the aluminum-carbon alloy cast in this carbon mold was taken out, a predetermined amount of nickel and cobalt were added, added to a remelting carbon crucible, redissolved by heating to 800 to 900 ° C, and stirred for about 1 minute. . This redissolution was also performed at atmospheric pressure in argon gas atmosphere. After stirring, the molten metal was poured into a copper water-cooled mold to obtain an aluminum alloy ingot of a predetermined shape. And this ingot was rolled, the predetermined shape was processed, and the target material was obtained. The final target material had a size of 8 inches (about 200 mm) x 6 mm in thickness. By the manufacturing method as mentioned above, the target material of each composition was produced, the aluminum alloy thin film which consists of aluminum alloy wiring material of each Example and a comparative example was formed under the following sputtering conditions, and the characteristic was evaluated.

Sputtering conditions for forming a thin film were a sheet type, using a # 1737 glass plate made by Corning Corporation as a substrate with a thickness of 0.8 mm, using an input power of 3 Watt / cm ² , an argon gas flow rate of 100 ccm, and an argon pressure of 0.5 Pa. By the magnetron sputtering apparatus, the film formation time was set to about 60 sec, and the thin film of about 2000 micrometers (about 0.2 micrometer) thickness was formed on the said glass plate. Substrate temperature was 100-200 degreeC.

Specific resistance characteristic : First, the result of having investigated about the specific resistance characteristic of the aluminum alloy wiring material which concerns on this invention is demonstrated. Table 1 lists and shows the results of measuring the film composition and the specific resistance values for Examples 1 to 4 and Comparative Examples 1 to 4.

Each thin film composition shown in Table 1 was subjected to ICP emission spectrometry (inductively coupled plasma emission spectroscopy) for nickel and cobalt, and carbon was quantified by a carbon analyzer. In addition, the specific resistance value was measured by the 4-terminal resistance measuring device (measurement current 100 mA). This specific resistance value is immediately after sputtering (hereinafter abbreviated as 'as-depo'. The same also applies to the tables and drawings), and when the glass plate provided with each thin film is subjected to heat treatment at 300 ° C. for 1 hour in a vacuum. Was measured. The results are as shown in Table 1.

FIG. 1 is a graph showing the total content of cobalt and nickel in Table 1 and the specific resistance after 300 ° C heat treatment. 2 is a graph showing the cobalt content, the as-depo, and the specific resistance after heat treatment at 300 ° C. Each display of FIG. 1 and FIG. 2 has described the result of Example 1 in the graph as "Example 1", for example. In addition, the blackened display in FIG. 2 is the specific resistance value of as-depo, and the whitened display has shown the specific resistance value after 300 degreeC heat processing.

As can be seen from FIG. 1, it was found that the specific resistance after 300 ° C. heat treatment also increased in proportion to the increase in the total content of nickel and cobalt. From this FIG. 1, in order to make the specific resistance value after 300 degreeC heat processing into 10 micrometer cm or less, it turned out that it is necessary to make the total content of nickel and cobalt into 7.0 at% or less.

In addition, in the display result of the specific resistance value of as-depo in FIG. 2, although nickel content of each Example is not constant, it was confirmed that the specific resistance value of as-depo increases with increase of cobalt content. This is presumed to be due to the large resistance value of cobalt itself. On the other hand, it was found that the specific resistance value after heat treatment at 300 ° C. achieved a specific resistance of 10 μΩcm or less regardless of the cobalt content of each example. From this result, in the case where cobalt is dissolved in an aluminum alloy together with nickel and carbon, the specific resistance value tends to increase as the content of cobalt increases, but the alloy of aluminum-nickel-cobalt is caused by heat treatment. When a phase starts to precipitate, it is guessed that a specific resistance falls to 10 microohm-cm or less in order for an alloy matrix to become a rich phase with aluminum.

Next, the result of having investigated about the relationship between a specific resistance value and heat processing temperature (annealing temperature) is demonstrated. In FIG. 3, the result of having measured the specific resistance value at the time of performing heat processing for 1 hour at each temperature (50 degreeC space | interval) from 200 degreeC to 500 degreeC about Examples 2-4 is shown. As a result, it was confirmed that all of Examples 2-4 have a specific resistance value of 10 microohm-cm or less, even if it heat-processes 300 degreeC or more.

Heat resistance characteristic : Then, the result of having evaluated the heat resistance characteristic is demonstrated.

The heat resistance evaluation was performed by observing the film surface after heat treatment for 1 hour at each temperature with a scanning electron microscope (10,000 times of SEM), and examining the state of occurrence of hillock. 4 to 13 show typical SEM pictures of Hillock's observations. 4 to 8 show Al-3.0 at% Ni-0.1 at% C composition (Table 2, Comparative Example 6), and FIGS. 9 to 13 show Al-2.1 at% Ni-2.9 at% Co-0.21. The case of at% C (Table 2, Example 8) is shown.

As can be seen from FIGS. 4 to 8, in the aluminum alloy thin film containing no cobalt, it was confirmed that white projections were generated on the surface when the heat treatment was performed at 450 ° C. and 500 ° C. FIG. In the case of heat treatment at 350 ° C. (FIG. 5) and 400 ° C. (FIG. 6), white spots were found on the surface, but they did not grow to the projections. The white spots shown in FIGS. 5 and 6 are precipitated phases of Al ₃ Ni, and the white projections shown in FIGS. 7 and 8 are formed on the surface as a result of aggregation of the precipitated Al ₃ Ni phases. . On the other hand, looking at the surface of Fig. 8, a concave portion such as a dimple was found in contrast to the white projection, but it is inferred that this was formed due to a volume reduction around the Al ₃ Ni phase when it was aggregated. On the other hand, in Example 8, it was not recognized in any way at the heat processing of 350 degreeC (FIG. 10) and 400 degreeC (FIG. 11). Moreover, in the heat processing at 450 degreeC (FIG. 12) and 500 degreeC (FIG. 13), although the Al ₃ Ni phase of the white spot shape was confirmed, it turned out that a projection was not formed.

In Table 2, the thin film of each composition is heat-treated at each temperature, SEM observation of the surface is performed, and the result of having examined the presence or absence of a hillock is shown. In Table 2, the thing which generate | occur | produced hillock x and that which hillock did not generate | occur | produce at all are described as (circle). In addition, the generation of the hillock is not recognized, and is described in that by aggregation on the Al ₃ Ni known to the recess surface, such as dimples to △. On the other hand, the hillock in this evaluation includes the aggregated Al ₃ Ni phase projections shown in Figs. 7 and 8 in addition to the projections of the aluminum itself.

As can be seen from Table 2, in the aluminum alloy thin film containing no cobalt as in Comparative Examples 5 and 6, the generation of hillock was recognized by heat treatment at 450 ° C or higher. In addition, as in Comparative Examples 7 to 11, out of the composition range of the aluminum alloy wiring material according to the present invention, dimples due to the generation of hillock or agglomeration of Al ₃ Ni phase are recognized on the surface for heat treatment of 500 ° C. or higher. It became. On the other hand, about Examples 5-14, there was no generation of hillock even by the heat processing of 400-500 degreeC. Then, the heat treatment at 550 ° C. for 1 hour and the evaluation of the heat resistance were performed for each of the examples in which hillock was not recognized in the heat treatment at 500 ° C., and in the compositions of Examples 7 to 10, No occurrence was observed. On the other hand, in the evaluation of this heat resistance characteristic, the composition in which the total content of nickel and cobalt is 7.0 at% or more is considered to be a practical wiring material considering that the specific resistance value is 10 μΩcm or more than the result shown in FIG. 1. It did not include in evaluation.

Based on the results of Tables 1 and 2 shown above, the content ranges of nickel and cobalt with specific resistance values of 10 μΩcm or less and high heat resistance to heat treatment of 500 ° C. or higher were examined. It was considered to be determined by the content range of the same diagonal portion. Moreover, also in the heat processing of 550 degreeC, it was considered that the content range which maintains high heat resistance corresponds to the area | region of a mesh pattern part.

Natural potential measurement : Finally, the result of having measured the natural potential of the aluminum alloy wiring material which concerns on a present Example is demonstrated. The thin film (0.2 micrometer) of the composition of Example 8 was formed on the glass substrate, and the glass substrate was cut out, and it was set as the electric potential measurement sample. Moreover, for comparison, the thin film of the composition of the comparative example 6 similarly formed the electric potential measurement sample. Then, the surface of the potential measurement sample was masked to expose an area corresponding to 1 cm ² , to form an electrode for measurement. The natural potential was measured using 3.5% aqueous sodium chloride solution (liquid temperature 27 ° C.) and the reference electrode using silver / silver chloride. Furthermore, it was used in the composition of the ohmic (ohmic) ITO which is the other end of the bonding _{film, In 2 O 3 -10 wt%} SnO 2.

As a result, the natural potential of the ITO membrane was about -820 mV. And in Example 8, about -960 mV, it was confirmed that it is a natural potential close to an ITO membrane. On the other hand, in Comparative Example 6, it was confirmed that it is far from the natural potential of the ITO film as compared with Example 8 at about -1080 mV.

As mentioned above, according to this invention, it becomes the outstanding aluminum alloy wiring material which has the high heat resistance characteristic of 500 degreeC or more which was not realized with the conventional aluminum alloy wiring material, and also realized the low specific resistance characteristic. In particular, it is an aluminum alloy wiring material suitable for forming a relatively large liquid crystal display by poly-Si type TFT of low temperature process which heat-processes 400 to 650 degreeC.

Claims (3)

In an aluminum alloy wiring material containing nickel, cobalt and carbon, As atomic percentage X at% of nickel content, atomic percentage Y at% of cobalt content, atomic percentage Z at% of carbon content, 0.5 at% ≤ X ≤ 3.0 at%, 4.0 at% ≤ X + Y ≤ 7.0 at%, A high heat-resistant aluminum alloy wiring material which satisfies a relationship of 0.1 at% ≤ Z ≤ 0.5 at%, and the rest is made of aluminum. The method of claim 1, High heat-resistant aluminum alloy wiring material used in poly-Si type thin film transistor of low temperature process. In the target material for aluminum alloy wiring material formation containing nickel, cobalt, and carbon, As atomic percentage X at% of nickel content, atomic percentage Y at% of cobalt content, atomic percentage Z at% of carbon content, 0.5 at% ≤ X ≤ 3.0 at%, 4.0 at% ≤ X + Y ≤ 7.0 at%, A target material for forming a high heat resistance aluminum alloy wiring material, which satisfies a relationship of 0.1 at% ≤ Z ≤ 0.5 at%, and the remainder is made of aluminum.

Images