JP2000336447A - Aluminum alloy thin film, target material and formation of thin film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To increase the heat resistance of the film and to reduce its resistance value as well by allowing it to have a specified compsn. contg. C and Mn, and the balance Al with inevitable impurities. SOLUTION: An Al alloy thin film contains, as alloy components, Al, C and Mn. The contents of C and Mn are amounts satisfying 3XY>=1, X<=2 and Y<=1 in the case the atomic % of C is defined as Y% and that of Mn as X%. This alloy thin film is formed by executing sputtering with a target material having the similar compsn. At the time of its formation, the temp. of a substrate is suitably held to 180 to 400 deg.C. In this way, the compressive stress to be applied on the thin film in a heat process after the film formation is made small as possible, and the generation of hillocks can be suppressed. Moreover, its specific resistance in a state directly after the sputtering is <=10 μΩcm, and, therefore, it is usable as a low resistance wiring material even in the case of being used for a place to be film-formed after the heat process.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aluminum alloy thin film, a sputtering target material for forming an aluminum alloy thin film, and a method for forming an aluminum alloy thin film.
More specifically, heat-resistant and low-resistance aluminum alloy thin film constituting thin film wiring of a liquid crystal display, an electrode, wiring of a semiconductor integrated circuit, etc., a sputtering target material that can be used to form such an aluminum alloy thin film, and the like. A method for forming a thin aluminum alloy thin film.

[0002]

2. Description of the Related Art In recent years, liquid crystal displays used in computer display devices and notebook personal computers have become larger and larger in size. Recently, in the field of liquid crystal displays, thin film transistors (Thin Film Tran
demand for LCD displays for sisters and TFTs)
As a result, the required characteristics for liquid crystal displays have become stricter. In particular, large-screen liquid crystal displays,
As the definition increases, a wiring material having a low specific resistance (10 μΩcm or less) has been required. This requirement comes from preventing signal delays caused by long and thin wires.

Hitherto, high melting point materials such as Ta, Cr, Ti and alloys thereof have been used as wiring materials for liquid crystal displays. However, the high-melting-point material has too high a specific resistance, so that it cannot be used for wiring a liquid crystal display with a large screen and a high definition as described above.

Under these circumstances, the specific resistance is 3 μΩcm
Pure aluminum has been attracting attention as a wiring material because of its extremely low degree and easy wiring processing. However, since pure aluminum has a relatively low melting point of 660 ° C., there is a problem in that heat resistance is low.

After a thin film of aluminum is formed on a substrate by sputtering and wiring processing is performed, heat of 300 to 400 ° C. is applied to aluminum in a CVD process for forming an insulating film. At this time, bump-like projections called hillocks are generated on the surface of the aluminum film. The hillock penetrates the insulating layer to cause a short circuit with an upper layer, or causes a short circuit with an adjacent wiring, thereby causing a defect.

[0006] Therefore, aluminum alloys to which other elements are added have been developed by various companies and are generally used. It is known that hillocks can be considerably suppressed by alloying in this manner.
In an aluminum alloy thin film such as -Ti, hillocks are surely suppressed by the amount of addition.

[0007]

However, at the same time, the specific resistance also exceeds 10 μΩcm. Since the type and amount of the additive element selected in this way greatly affect the properties of the aluminum alloy thin film, an aluminum alloy thin film that has heat resistance while maintaining low resistance and can suppress hillocks is desired. I have.

An object of the present invention is to provide a heat-resistant, low-resistance aluminum alloy thin film which does not generate hillocks even after heat treatment at 300 to 400 ° C. and has a specific resistance of 10 μΩcm or less. Another object of the present invention is to provide a sputtering target material that can be used for forming the above aluminum alloy thin film. Another object of the present invention is to provide a method for forming an aluminum alloy thin film as described above.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, have determined that the alloy composition of the aluminum alloy thin film is Al-C-Mn based and the contents of carbon and manganese are specified. The above-mentioned problem is achieved by being within the range of, and the above-mentioned problem is achieved by using an Al-C-Mn-based material having a specific composition as a target material. It has been found that the above object can be achieved preferably by setting the temperature of the substrate to a specific temperature during the formation, and the present invention has been completed.

That is, the aluminum alloy thin film of the present invention comprises:
Aluminum, carbon and manganese are contained as alloy components, and the contents of carbon and manganese satisfy the formula 3XY ≧ 1 X ≦ 2 Y ≦ 1, where the atomic percentage of carbon is Yat% and the atomic percentage of manganese is Xat%. And the balance is made of aluminum and unavoidable impurities.

In the sputtering target material for forming an aluminum alloy thin film according to the present invention, the components constituting the target material are aluminum, carbon, manganese and unavoidable impurities, and the amount of carbon and manganese is determined by changing the atomic percentage of carbon to Yat. %, And the atomic percentage of manganese is Xat%,
The amount satisfies the formula: 3XY ≧ 1 X ≦ 2 Y ≦ 1, and the balance is made of aluminum and unavoidable impurities.

Further, the method for forming an aluminum alloy thin film of the present invention is carried out while maintaining the temperature of the substrate at 180 to 400 ° C. when forming the aluminum alloy thin film by sputtering using the above sputtering target material. It is characterized by doing.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The heat resistance of an aluminum alloy thin film can be evaluated by whether or not hillocks are generated by heat treatment after film formation. For example, when an aluminum alloy thin film formed on a glass substrate passes through a thermal process at 300 to 400 ° C., the aluminum alloy has a coefficient of thermal expansion that is about one digit larger than that of glass. Receives compressive stress from In the case of an aluminum alloy thin film with a mixture of large and small crystal grains, the small crystal grains become nuclei, aluminum migrates, precipitates and grows grains, relieving the stress, and as a result, near the point where the stress was relieved. It is generally believed that hillocks occur. In other words, the driving force when hillocks are generated is the compressive stress applied to the aluminum alloy thin film during the thermal process, and it can be said that migration occurs when a nucleus crystal is present in the aluminum alloy thin film and hillocks are generated.

By adding a small amount of carbon to aluminum, the crystal grain size in the aluminum alloy thin film becomes smaller as a whole and the crystal structure becomes uniform, so that stress is uniformly dispersed throughout the aluminum alloy thin film. Become like Pure aluminum thin film and Al deposited under the same conditions
When the crystal structure of each of the -C alloy thin films was observed with a transmission electron microscope, the size of the crystal grains in the pure aluminum thin film was about 0.05 to 0.3 [mu] m and varied.
It was found that the size of crystal grains in the l-C alloy thin film was 0.1 μm or less and the variation was small.

However, in the case of the Al-C alloy, hillocks are slightly generated after the thermal process, and the smoothness of the film surface after the thermal process is deteriorated, and the reflectance is also reduced. Al-C
Since carbon hardly forms a solid solution with aluminum in alloys, carbon has less effect of increasing the specific resistance of the film than other elements. However, the hillock cannot be completely suppressed by an Al-C alloy containing a small amount of carbon, and when carbon is added to the extent that the hillock is completely suppressed, the specific resistance may increase. Use is considered difficult.

An Al-Mn alloy containing a small amount of manganese is also known from Japanese Patent Application Laid-Open No. 4-323872.
In the case of l-Mn alloy, when manganese is added in such an amount that hillocks can be completely suppressed, the specific resistance exceeds 10 μΩcm. However, by adding a further small amount of manganese to the Al-C alloy, generation of hillocks after the thermal process can be prevented, surface smoothness can be kept good, and specific resistance can be kept low.

By using an Al—C—Mn alloy, the specific resistance is 10 μΩcm or less, heat resistance is obtained, and generation of hillocks can be suppressed. In addition, since manganese is also an element having an effect of improving corrosion resistance in an aluminum alloy, it can be expected that the corrosion resistance of wiring is also improved.

In the Al—C—Mn alloy, when the carbon content exceeds 1 at%, or when the manganese content is 2a
If it exceeds t%, the specific resistance of the alloy thin film is 10 μΩc
m, which is not preferred. In addition, when the content of carbon and manganese is such that the atomic percentage of carbon is Yat% and the atomic percentage of manganese is Xat%, and satisfies the expression 3XY <1, hillocks tend to occur after heat treatment at 400 ° C. It is not preferable.

Therefore, the aluminum alloy thin film of the present invention contains aluminum, carbon, and manganese as alloy components, and the content of carbon and manganese is expressed by the following formula, where the atomic percentage of carbon is Yat% and the atomic percentage of manganese is Xat%. The amount satisfies 3XY ≧ 1 X ≦ 2 Y ≦ 1, with the balance being aluminum and unavoidable impurities. That is, when the content of carbon is taken on the Y axis and the content of manganese is taken on the X axis, the content of carbon and manganese is represented by the curve 3XY = 1, the straight line X = 2, and the straight line Y = 1 in FIG. It is an amount that falls within the enclosed range.

Preferably, in the aluminum alloy thin film of the present invention, the content of carbon and manganese is represented by the following formula: 3XY ≧ 1 0.5 ≦ X ≦ 1 where the atomic percentage of carbon is Yat% and the atomic percentage of manganese is Xat%. 0.5 0.3 ≦ Y ≦ 0.9.

However, if hillocks are formed after the heat treatment at 400 ° C., but the heat resistance is such that no hillocks are formed after the heat treatment at 300 ° C., the content of carbon and manganese is determined by changing the atomic percentage of carbon to Yat%. , The atomic percentage of manganese may be Xat%, and the amount may satisfy the following expression: 4.5XY ≧ 1 X ≦ 2Y ≦ 1.

The sputtering target material for forming an aluminum alloy thin film of the present invention is capable of forming the above-described aluminum alloy thin film by sputtering, and the components constituting the target material are aluminum, carbon, manganese, and unavoidable components. The amount of carbon and manganese is an amount that satisfies the formula 3XY ≧ 1 X ≦ 2 Y ≦ 1, where the atomic percentage of carbon is Yat% and the atomic percentage of manganese is Xat%, with the balance being aluminum and unavoidable. Of impurities.

There is no particular limitation on the shape and configuration of the above-mentioned target material, and any suitable shapes and configurations may be used depending on the type of sputtering method, type of sputtering apparatus, and the like.
It can be configured. For example, for the configuration, alloys, homogeneous mixtures, embedded chips, and the like can be employed.

When an aluminum alloy is used as the target material, the amounts of carbon and manganese are expressed by the following formula: 3XY ≧ 1 X ≦ 2 Y ≦ 1 where the atomic percentage of carbon is Yat% and the atomic percentage of manganese is Xat%. It is preferable that the amount satisfies 7Y ≦ 3X.

In the method for forming an aluminum alloy thin film of the present invention, the temperature of the substrate is maintained at 180 to 400 ° C. when forming the aluminum alloy thin film by sputtering using the sputtering target material as described above. carry out. If the substrate temperature is lower than 180 ° C., hillocks tend to be generated during a subsequent thermal process, which is not preferable. For the upper limit of the substrate temperature,
Although high temperatures are possible as long as they do not adversely affect the substrate and the thin film, the temperature is preferably about 180 to 350 ° C, more preferably about 180 to 300 ° C in consideration of energy efficiency, operating environment, durability of the apparatus, and the like. .

By performing sputtering at such a substrate temperature, not only the compressive stress applied to the thin film during the thermal process after film formation can be minimized to suppress the generation of hillocks, but also at 300 to 400 ° C. It is also possible to reduce the film specific resistance after the thermal process. In addition, since the specific resistance is 10 μΩcm or less in an as-depo state (immediately after sputtering), it can be used as a low-resistance wiring material even when it is used in a place where a film is formed after a thermal process. In the case of a pure aluminum thin film, the generation of hillocks can be reduced by raising the substrate temperature, but it cannot be completely suppressed.

[0027]

The present invention will be specifically described below based on examples and comparative examples. Examples 1 to 4 and Comparative Examples 1 to 15 A target having the same composition as the film composition described in Table 1 was used as a sputtering target material, and the substrate was maintained at the temperature shown in Table 1 and had a thickness of 1.1 mm. Using a # 1737 glass plate manufactured by the company, a power of 3 Watt / cm ² and a sputtering pressure of 2.5 mTorr, a pure aluminum thin film having a thickness of about 3000 mm or an alloy thin film of various compositions was formed on the glass plate by DC magnetron sputtering. Formed. The film composition and thickness of the obtained thin film, and the specific resistance of the film immediately after sputtering (as-dope) were as shown in Table 1.

With these thin films, the lath plate can be cut in vacuum for 30 minutes.
Heat treatment was performed for 1 hour at each of two levels of 0 ° C. and 400 ° C. The specific resistance of the film after the heat treatment was as shown in Table 1, and the state of generation of hillocks was as shown in Table 1 and FIG. The state of generation of hillocks was observed with a scanning electron microscope at both 500 × and 5000 ×, and hillocks were not generated (hillock free) only when hillocks were not observed at either magnification. The specific resistance of the thin film was measured by a four-terminal resistance measuring device.

As a method for analyzing the carbon concentration, a film for carbon measurement was obtained by forming a film to a thickness of about 10 μm on a substrate under the same conditions as the above method and peeling the thin film from the substrate. The measurement was performed by a gas analyzer for carbon analysis. Regarding the manganese concentration, the manganese concentration in the aluminum alloy thin film was quantified by ICP emission analysis (inductively coupled plasma emission spectroscopy).

[0030]

[Table 1]

Al, which is an aluminum alloy thin film of the present invention obtained by using the target material of the present invention in Examples 1 to 4,
-0.4at% C-1.0at% Mn, Al-0.4a
t% C-1.5at% Mn, Al-0.8at% C-
0.6 at% Mn and Al-0.8 at% C-1.5 a
Regarding the thin film having the t% Mn composition, no hillocks were observed even after the heat treatment at 400 ° C., indicating that the film specific resistance was 10 μΩcm or less.

Comparative Example 1 Pure Aluminum Thin Film, Comparative Example 2
-5, the Al-Mn alloy thin films of Comparative Examples 6-7, and the contents of carbon and manganese are represented by the formula 4.5XY, where the atomic percentage of carbon is Yat% and the atomic percentage of manganese is Xat%. <1-Al-CM of Comparative Examples 10 to 11
Regarding the n-alloy thin film, generation of hillocks was observed in each of the heat treatments at 300 ° C. and 400 ° C.

The Al—Mn alloy thin film of Comparative Example 8 in which the manganese content is 2.6 at%, and the contents of carbon and manganese are expressed by the following formula: 3XY < Comparative Examples 12 to 13 to be 1
No hillocks were observed after the heat treatment at 300 ° C., but hillocks were observed after the heat treatment at 400 ° C. The Al—Mn alloy thin film of Comparative Example 9 in which the manganese content was 6.3 at% was 4
No hillocks were found after the heat treatment at 00 ° C., but the film had a high specific resistance.

When the substrate temperature was set to 100 ° C. as in Comparative Examples 14 and 15, the hillock generation state was worse than in Comparative Examples 12 and 3 having the same composition. Later, the film specific resistance is also increased. That is, the hillock generation state and the film specific resistance are improved by increasing the substrate temperature.

[0035]

The aluminum alloy thin film of the present invention has a thickness of 30
No hillocks are generated even after heat treatment at 0 to 400 ° C.
It is a heat-resistant, low-resistance aluminum alloy thin film having a specific resistance of 10 μΩcm or less, and such an aluminum alloy thin film can be formed by using the sputtering target material of the present invention. By adopting the method of forming an aluminum alloy film, an excellent heat-resistant and low-resistance aluminum alloy thin film as described above can be manufactured.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between the composition of each thin film and the state of hillock generation, with the carbon content taken along the Y axis and the manganese content taken along the X axis.

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Claims (4)

[Claims] An alloy containing aluminum, carbon, and manganese, and the content of carbon and manganese is represented by the following formula: 3XY ≧ 1 X ≦ 2 Y ≦, where the atomic percentage of carbon is Yat% and the atomic percentage of manganese is Xat%. 1. An aluminum alloy thin film which satisfies (1) above, and the balance consists of aluminum and unavoidable impurities. 2. The content of carbon and manganese is represented by the following formula: 3XY ≧ 1 0.5 ≦ X ≦ 1.5 0.3 ≦ Y ≦ 0, where the atomic percentage of carbon is Yat% and the atomic percentage of manganese is Xat%. 9. The aluminum alloy thin film according to claim 1, wherein the amount satisfies the following condition: 0.9. 3. Components of the target material are aluminum, carbon, manganese and unavoidable impurities, and the amounts of carbon and manganese are expressed by the following formula (3XY), where the atomic percentage of carbon is Yat%, and the atomic percentage of manganese is Xat%. A sputtering target material for forming an aluminum alloy thin film, wherein the amount satisfies ≧ 1 X ≦ 2 Y ≦ 1 and the balance consists of aluminum and unavoidable impurities. 4. The method of forming an aluminum alloy thin film according to claim 1 or 2 by sputtering using the sputtering target material according to claim 3, while maintaining the temperature of the substrate at 180 to 400 ° C. A method for forming an aluminum alloy thin film, comprising: