JPH09228035A - Aluminum alloy film for thin film wiring and aluminium alloy sputtering target material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce an Al alloy film in which low resistance and heat resistance so as to prevent' the generation of hillocks are compatible and to produce a target material forming the same. SOLUTION: This Al alloy film for thin film wiring is the one in which, by atom, <=2% Zr as a primary element to be added and <=2% of one or more kinds among W, Nb and Mo as secondary elements to be added are compositely added, the total content of the primary element to be added and the secondary elements to be added is regulated to 0.2 to 2%, and the balance substantially Al, and the specific resistance is regulated to <=15μΩcm. This thin film can be formed concretely by sputtering. Furthermore, the sputtering target material providing the above thin film has the above compsn.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an aluminum alloy film for thin film wiring (hereinafter referred to as an Al alloy film) used as an electrode portion or a wiring portion of a liquid crystal display or the like and this Al.
The present invention relates to a sputtering target for forming an alloy film.

[0002]

2. Description of the Related Art Recently, a liquid crystal display has attracted attention as a display device of a computer. Among the liquid crystal displays, thin film transistors (Thin Film)
Transistor (hereinafter abbreviated as TFT) Active matrix type liquid crystal display (Liqu)
The development of an id Cristal Display (hereinafter abbreviated as LCD) has been urgently promoted because it has a wide field of view and can display near a cathode ray tube system. Conventionally, in an LCD in which a thin film device is formed on a glass substrate, a pure Cr film, which is a refractory metal, or a pure Ta film is used for an electric wiring film, an electrode, etc.
A film, a pure metal film such as a pure Ti film, or an alloy film thereof has been used.

Recently, with the demand for large-sized and high-definition LCDs, there has been an increasing demand for lower resistance, lower stress and stabilization in the wiring film electrode film in order to prevent signal delay. For example, for electrodes used in a large-sized color LCD of 12 inches or more, it is desired to be 15 μΩcm or less. However, a conventional Cr or Ta-based high melting point alloy film is excellent in stability but high in resistance value. For example, Cr is about 30, Ta is about 180, and Ti is about 60 μΩcm.
Therefore, attention has been paid to the application of an Al film that can obtain a low resistance in place of the above-mentioned refractory metal.

Further, as a sputtering apparatus used for stably producing a metal film of high quality as the LCD becomes finer, a conventional substrate transfer type in-line type apparatus can be used as a sputtering apparatus. A device called a single-wafer system for forming a film by allowing the film to stand still has come into wide use.
Then, as the LCD becomes larger, the thin film forming substrate becomes larger, and accordingly, the target for forming the thin film is also required to become larger. In particular, in the above-described single-wafer type sputtering apparatus, a target larger than the substrate size is required in order to form a film while standing still on the substrate. Conventionally, as a method of coping with an increase in the target size, the targets manufactured in the size of two-division or three-division have also been bonded and used. However, in the divided target, foreign matter is generated from the joint and becomes defective, so that an integrated target is required to obtain a high quality thin film.

The substrate size for the LCD, which is currently the mainstream, is 3
70 × 470 mm, and a target for a single-wafer sputtering apparatus for forming a metal film on this substrate is 550 ×
It is required to integrally manufacture an extremely large target of about 650 mm. If an attempt is made to manufacture such a large target as a single unit, the pure C
High melting point metals such as r, pure Ta, and pure Ti are very expensive, such as large melting furnaces and electron beam melting furnaces at high temperatures, special forging machines that can be used at high temperatures for plastic working, and rolling machines. There is a problem that a device is needed. In the future, it is expected that the size of the substrate will increase as the size of the LCD further increases, and it is extremely difficult to manufacture a larger target with a refractory metal as one body.

With respect to the above refractory metal target,
Al, which has an advantage of obtaining low resistance, also has an advantage of being excellent in plastic workability when obtaining the target. Therefore, the Al film has attracted attention because it has an advantage that a large target material for obtaining a thin film can be easily manufactured. However, the above-mentioned low resistance is excellent,
The Al film to which a large target can be applied has a very serious problem that the heat resistance is inferior to that of the refractory metal.

More specifically, the heating step (250 to 400) after the electrode film formation is inevitable in the TFT manufacturing process.
There is a problem that minute projections called hillocks are formed on the surface of the formed thin film at about (° C.). This hillock is considered to be generated by stress migration, thermal migration, etc. When this hillock occurs, an insulating film, a protective film, etc. are formed on the Al wiring film,
Further, there is a problem that an electric short circuit occurs when an interconnection film, an electrode film, or the like is formed, and an etching solution or the like enters through the hillocks to corrode the Al interconnection film.

In order to prevent such deterioration of heat resistance, a method of adding various metals to Al instead of pure Al has been proposed. For example, JP-A-4-323872
Japanese Patent Laid-Open Publication No. 2005-242242 discloses that Mn, Zr, and Cr are added at 0.05 to 1.0
% Addition is said to be effective. Moreover, in Japanese Patent Publication No. 4-48854, B is 0.002.
~ 0.5 wt%, Hf, Nb, Ta, Mo, W 0.0
02-0.7 wt% addition, and further adding Si to 0.
A method of adding 5 to 1.5 wt% is disclosed. Also,
Japanese Unexamined Patent Publication (Kokai) No. 5-65631 describes that adding Ti, Zr, and Ta in an amount of 0.2 to 10 at% is effective in suppressing the generation of hillocks. Furthermore, JP-A-7
-Fe, Co, N as described in U.S. Pat.
i, Ru, Rh, Ir of 0.1 to 10 at% and a rare earth element of 0.05 to 15 at%, or Cu and T added to an Al-Si alloy as disclosed in JP-A-5-335271.
0.01 to 3 wt% of i, Pd, Zr, Hf, Y and Sc
A method of adding is known.

[0009]

As described above, as described above, Al
The method of adding various alloying elements to Al to form an Al alloy is effective for improving heat resistance because hillock generation can be suppressed. However, Rh, which is proposed in JP-A-7-45555 and JP-A-5-335271,
Addition of Ir, Y, Sc or rare earth elements is expensive and should be avoided as much as possible. In addition, the addition of easily oxidizable elements such as the above-mentioned rare earth elements is likely to be subject to a slight difference in the film forming atmosphere in the process of manufacturing a thin film, and the resistance value and hillock generation in the formed substrate or between substrate lots may occur. There is a problem that the variability of the situation increases. There is also a problem that the oxygen amount of the target is increased and the resistance value is increased.

On the other hand, JP-A-5-65631 discloses
JP-A-7-45555 or JP-A-5-33527
The addition of a metal having a high melting point as in JP-A-1 is effective in improving heat resistance. However, these elements have a higher resistance value than Al as described above, and it is desirable to add as little amount as possible, but it is necessary to increase the amount of added elements in order to improve heat resistance. In terms of compatibility of sex, it was not yet fully satisfactory. In view of the above-mentioned problems, an object of the present invention is to make Al having both low resistance and heat resistance capable of preventing the generation of hillocks.
It is an object to provide an alloy film and an Al alloy target material suitable for forming the above Al alloy film.

[0011]

Means for Solving the Problems The present inventor has studied in detail the action of alloying elements added to Al, using Zr as the first additive element, and adding one or more of W, Nb and Mo to the second additive. The inventors have found that, when they are added as elements, when they are added in combination, it is possible to achieve both low resistance and heat resistance that can prevent the generation of hillocks, which were not obtained by single addition.

That is, the present invention uses Z as the first additive element.
2 at% or less of r, and W, N as the second additive element
b, 1 or more kinds of Mo are contained at 2 at% or less, and the total amount of the first additive element and the second additive element is 0.2 to 2 at
%, With the balance being essentially Al, with a specific resistance of 15
It is an Al alloy film for thin film wiring having a thickness of μΩcm or less. Specifically, the thin film of the present invention can be specifically formed by sputtering.

The target material of the present invention which provides the above-mentioned thin film contains Zr as a first additive element in an amount of 2 at% or less and at least one of W, Nb and Mo as an additive element in an amount of 2 at% or less. It has a composition in which the total amount of the first additive element and the second additive element is 0.2 to 2 at%, and the balance is substantially Al.

[0014]

As described above, an important feature of the present invention is that when Zr is the first additive element and one or more of W, Nb and Mo is the second additive element, they are combined. The reason for this is that the low resistance and the heat resistance capable of preventing the generation of hillocks have both been achieved by the addition of. The present inventor manufactured Al alloy target materials in which various elements were added to Al, and examined the characteristics of these target materials in order to perform detailed studies on the action of the elements added to Al. Then, various Al alloy films are formed by sputtering using various target materials, and their composition, impurities and electrodes, resistance value as a wiring film, etching property,
Characteristics such as hillock generation during heating were investigated. As a result, it has been found that the combined addition of Zr and one or more of W, Nb and Mo significantly improves the above characteristics. This will be described in detail below.

Zr which is essential in the present invention has an atomic radius of 0.160 nm and an atomic radius of Al of 0.144 nm.
Greater than. Therefore, when Al forms crystal nuclei and grows in the formed thin film, they are extruded and precipitated at the Al crystal grain boundaries. This is an element in which Zr has a low density and is light, and is a metal whose crystal structure transforms from hexagonal (hcp) to body-centered cubic at 862 ° C., and is an element in which atoms easily move at a relatively low temperature. This is because. Zr thus precipitated on the grain boundaries can be expected to prevent the atomic migration of Al when heated and suppress the generation of hillocks due to stress migration and thermal migration.

As with Zr, atomic migration is likely to occur, and Ti is an element that precipitates at Al grain boundaries.
However, Ti has an atomic radius of 0.147 nm and an Al.
When an intermetallic compound is formed near 144 nm, the crystal structure of Al is not disturbed so much that it is incorporated into the crystal of Al and grain boundary precipitation is less likely to occur than Zr, so the hillock suppressing effect is small. Therefore, if an effect similar to that of Zr is to be obtained, the added amount increases, so that the specific resistance increases. Further, a Ti-containing thin film is apt to take in oxygen and the like during formation, and an Al-Ti thin film is not desirable as an additive element because it has a problem that the resistivity changes greatly with respect to the atmosphere. Therefore, in the present invention, Zr is selected as the additive element.

However, although the addition of Zr was considered to be effective from the above-mentioned point, the effect of suppressing hillocks by the addition of Zr alone showed a large difference as compared with the case of adding Ta, Ti, Cr or the like. I couldn't do it. As a result of further study by the present inventor, W, Nb, and the like were added as the second additive elements to remarkably enhance the hillock suppressing effect of Zr precipitated at the grain boundaries.
I found Mo. The present inventor tends to lose energy on the substrate when forming a thin film because these elements have a high melting point and are heavy, and cannot form and move an intermetallic compound or the like with the surrounding Al. Suppress A
Attention was paid to the formation of 1 crystal nucleus. By promoting the formation of Al crystal nuclei in this way, Zr
It has succeeded in promoting the grain boundary precipitation and dramatically increasing the hillock suppressing effect. In the present invention, W, Nb, and Mo are selected as the refractory metal because the resistance value of the bulk material is 100 μΩcm or less, the increase in the resistance value of the thin film can be minimized, and the cost is low. . For example, Ta is expensive and has a resistance value of 180 μΩcm as a bulk material, which is not preferable for the present invention aiming at low resistance.

In the present invention, the total amount of the additive elements of Zr, W, Nb, and Mo described above is 0.2 to 2 at% because the effect of suppressing hillocks is not sufficient at 0.2 at% or less and 2% or more. This is because the specific resistance becomes 15 μΩcm or more. Preferably, it is in the range of 0.4 to 1.5%. More preferably, Zr is 0.2 at
% Or more, and at least one of W, Nb, and Mo is 0.2 at% or more, and the effect of suppressing hillocks is more sufficient. In the present invention, with such a small amount of additional element, there is a sufficient effect of suppressing hillocks, it is possible to prevent an increase in resistance value, and it is caused by the additional element when patterning the Al alloy thin film by the photoetching process. Since the etching residue can be reduced, there is also an advantage that the Al alloy film can be stably manufactured with high yield.

In addition to the characteristics of the thin film described above, as a target for sputtering, when the total amount of additive elements exceeds 2 at%, the amount of intermetallic compound that can be formed in the target is large, and a large target, specifically However, when a target with a sputter surface of more than 0.3 m ² is produced, there is a problem that cracks and fine cracks are likely to occur. Further, if the total amount of additive elements is large, the amount of segregation of the intermetallic compound that precipitates in the target increases, which causes variations in thin film composition and variations in thin film resistance.
Therefore, also in the target of the present invention, the total amount of additional elements is set to 2 at% or less.

[0020]

【Example】

(Example 1) First, Al, Ti, Zr, Ta, Cr, M
φ of a binary Al alloy ingot containing 0.2 to 10 at% of any one of n was plastically worked at a working rate of 65%
A 300 mm target was manufactured. Using this target, sputtering was performed by a DC magnetron system to form a binary Al alloy thin film of a comparative example having a thickness of 250 nm as a reference for evaluation of the present invention on a glass substrate. At this time, the conditions for forming the thin film were Ar pressure of 0.2 Pa, power applied to the target of 8 W / cm ² , and substrate temperature of 200 ° C. After reaching a predetermined film thickness, the glass substrate was cooled to room temperature to form a thin film. I took it out.

The composition of the obtained Al alloy thin film was analyzed by ICP (Inductively Coupled Plasma Atomic Emission Spectroscopy) to determine the ratio of the additive element in the thin film. Further, the specific resistance value of the Al alloy thin film was measured at room temperature by the 4-terminal (probe) method. Also,
In order to evaluate heat resistance, a striped pattern having a strip shape of 10 μm was processed by photolithography and wet etching, and then heat treatment was performed at 400 ° C. for 1 hour in vacuum. The number of projections (hillocks) generated on the stripe pattern by this heat treatment was measured, the density of hillock generations per unit area was determined, and the heat resistance was evaluated.

The specific resistance value with respect to the content of the additive element in the thin film is shown in FIG. 3, and the hillock generation density is shown in FIG. When the amount of alloy added is increased, the specific resistance is increased as shown in FIG. 3 and the generation of hillocks is reduced as shown in FIG. However, among the additional elements evaluated, Mn increases the specific resistance as compared with the other elements and is not preferable, but no significant difference is observed in the other additional elements.

From the results of the binary alloy target described above,
Sputtering was performed by using a target of Ti, Zr, Cr, and Ta in which the increase in specific resistance was small, and disposing W on the surface so that the alloy thin film contained 1 at%. The relationship between the composition of the obtained thin film, the specific resistance and the hillock number is shown in FIGS. 1 and 2. As shown in FIGS. 1 and 2,
Unlike Ti, Cr, and Ta, Zr has a small hillock generation density due to the combined addition of W, although the resistance value hardly increases in a small additive element region. That is, Ti, Cr, and Ta could not be expected to have the effect of reducing the resistance and improving the heat resistance by adding W together, but Zr has a low resistance and heat resistance due to the addition of W together. It can be seen that the contradictory property of high property can be satisfied.

Even when Zr is added, Al
When the content of the additional element with respect to 1 exceeds 2%, that is, when the amount of alloy X exceeds 1% in FIG. 1, the specific resistance becomes 15 μΩcm, and in order to secure low resistance, the total amount of the additional element is 2 μm. It can be seen that the content is preferably not more than%.

Example 2 After casting an ingot having the composition shown in Table 1, plastic working was performed at a working rate of 72% to obtain a TFT.
-Manufactured a large target with 550 x 650 mm sputtering surface for LCD. A sample was taken from around the obtained target and analyzed on the surface of the fluorescent X-ray component composition analyzer to evaluate the variation in the target composition. The results are shown in Table 1. In Table 1, the sample No. As shown in FIG. 4, when the total amount of the additive elements exceeds 2 at%, cracks may occur inside the target at a high processing rate of 72%. Further, as shown in Table 1, it is recognized that when the total amount of the additional elements exceeds 2%, the variation in the target composition due to the gravity segregation of these elements becomes large. Therefore, it is understood that the total amount of the additional elements as the alloy target is preferably 2% or less.

[0026]

[Table 1]

Among the targets shown in Table 1, a target in which no cracks or cracks were generated was used to perform sputtering by a DC magnetron system to form a glass substrate with a thickness of 2
A 50 nm Al alloy thin film was formed. At this time, the conditions for forming the thin film were Ar pressure of 0.2 Pa, power applied to the target of 8 W / cm ² , and substrate temperature of 200 ° C. After reaching a predetermined film thickness, the glass substrate was cooled to room temperature to form a thin film. I took it out. The surface of the obtained Al alloy thin film is rubbed with a scrubber, and ultrasonically cleaned in pure water.
A defect density of 0.3 μm or more in the film was determined using a transmitted light type defect detector. Composition analysis by ICP (inductively coupled plasma emission spectroscopy) confirmed that a thin film having the same composition as the target composition was obtained.

Further, the specific resistance value of the Al alloy thin film was measured at room temperature by the four-terminal (probe) method, and the variation in the specific resistance value within the substrate was obtained. Further, in order to evaluate the heat resistance, a striped pattern having a strip shape of 10 μm was processed by the same heating photolithography and wet etching as in Example 1, and then heat treatment was performed in vacuum at 400 ° C. for 1 hour. The number of projections (hillocks) generated on the stripe pattern by this heat treatment was measured, the density of hillock generations per unit area was determined, and the heat resistance was evaluated. Table 2 shows the results.

[0029]

[Table 2]

As shown in Table 2, Zr and W, Nb, Mo
In the target of the present invention in which the content of the additive element is 2 at% or less, the defect density is 0.05
A high-quality thin film of cm ² or less can be obtained, a specific resistance of 15 μΩcm or less, and the number of hillocks generated is 10 / cm.
^{It was 2} or less, and it can be seen that the generation of hillocks can be greatly reduced in the region of low resistance as compared with the case where Ti, Ta, Zr, and Mn are added alone.

Further, as shown in Table 2, the sample No. of the comparative example in which an additive element amount of 1.5 at% was added with Ta, Ti, Zr, and Mn as simple substances. In 12 to 15, the number of hillocks is 1
The sample N of the present invention, in which the same amount of the additional element was added as a composite of Zr and Nb, while it was 2.9 to 17.5 pieces / cm ^2.
o. 1 or sample No. 1 of the present invention in which Zr, Nb, and Mo were added in combination. In 6, the number of hillocks understood that could be made respectively low and 9.4 months / cm ² and 8.1 months / cm ^2. In addition, the above sample No. 1 and No. No. 6 has a lower specific resistance value than the comparative example, and it is understood that the Al alloy film of the present invention is effective.

[0032]

According to the present invention, the contradictory characteristics of low resistance and heat resistance, which have been problems of the Al alloy type thin film, are exhibited by Zr.
It has become possible to achieve both of them by the combined addition of at least one of W, Nb, and Mo. As a result, the total amount of alloy added to Al can be reduced, and
It is possible to manufacture an LCD that takes advantage of the low resistance characteristic originally possessed by. In addition, reducing the total amount of alloy added to Al is also effective in terms of target production because it can improve the workability when a large target required for an LCD is integrally manufactured as an alloy target. Thus, the present invention is an indispensable technology for manufacturing LCDs.

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the amount of an additive element compounded with W relative to Al and the specific resistance.

FIG. 2 is a diagram showing the relationship between the amount of added elements compounded with W relative to Al and the hillock density.

FIG. 3 is a diagram showing the relationship between the amount of a single element added to Al and the specific resistance.

FIG. 4 is a diagram showing the relationship between the amount of an additional element and the hillock density relative to Al.

Claims (3)

[Claims] 1. A Zr content of 2 at% or less as a first additive element, and one of W, Nb and Mo as a second additive element.
2 at% or less of the seeds, and the first additive element and the second
The total amount of additional elements is 0.2 to 2 at%, the balance is substantially Al.
An Al alloy film for thin film wiring, which has a composition of and a specific resistance of 15 μΩcm or less. 2. The Al alloy film for thin film wiring according to claim 1, which is formed by sputtering. 3. Zr is contained at 2 at% or less as a first additive element, and one of W, Nb and Mo is contained as a second additive element.
2 at% or less of the seeds, and the first additive element and the second
The total amount of additional elements is 0.2 to 2 at%, the balance is substantially Al.
An Al alloy sputtering target material for thin film wiring, which has a composition of