TWI452161B - Method for producing oxygen-containing copper alloy film - Google Patents

Description

Method for producing oxygen-containing copper alloy film

The present invention relates to a method for producing an oxygen-containing copper alloy film which is used as a wiring of a flat panel display (hereinafter referred to as FPD) manufactured by forming a thin film on a substrate. membrane.

As an FPD manufactured by laminating a thin film on a glass substrate or a bismuth (Si) wafer, for example, a liquid crystal display (hereinafter referred to as LCD) and a plasma display panel (hereinafter referred to as a plasma display panel) are being actively researched and developed. Various novel products such as PDP), Field Emission Display (hereinafter referred to as FED), Electro Luminescence Display (hereinafter referred to as ELD), and electronic paper.

As the display is enlarged, high-speed driving is required to display a moving image. Therefore, a wiring film such as a thin film transistor (TFT) used in these FPDs is made of aluminum (Al) and an aluminum alloy of a low-resistance wiring film. Aluminum film. In recent years, as the size of the display has been further increased and the resolution has been increased, copper wiring of wiring having lower resistance has been attracting attention.

Since copper has a lower resistance than aluminum, it is expected to become a next-generation wiring material in the field of FPD. However, copper has a problem of poor adhesion to a glass substrate or a ruthenium-based underlayer, and a problem that it is easily diffused to the ruthenium layer.

Therefore, in order to improve the adhesion between the copper wiring and the glass substrate and to suppress the diffusion of copper into the ruthenium layer, the following method has been proposed (for example, refer to Patent Document 1 and Non-Patent Document 1): use of a relatively small amount of copper added A target formed of a copper alloy of zirconium (Zr) or molybdenum (Mo) which is easily oxidized is subjected to reactive sputtering by argon (Ar) and oxygen to form a copper-based wiring.

[Previous Technical Literature]

[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2008-112989.

[Non-patent literature]

[Non-Patent Document 1] "Copper wiring process technology for TFT liquid crystals for mass production lines", NIKKEI MICRODEVICES, March 2008, Nikkei BP, March 1, 2008, page 100 - 101 pages.

A film formed by using a copper-zirconium (Cu-Zr) alloy or a copper-molybdenum (Cu-Mo) alloy and sputtering by argon gas and oxygen as proposed in Patent Document 1 or Non-Patent Document 1 is a glass. A useful copper-based wiring film which is excellent in adhesion of a substrate and can suppress diffusion into a ruthenium layer. However, according to the study by the inventors of the present invention, when the proposed copper-based wiring film is formed on a glass substrate, the resistance value of the copper-based wiring film cannot be sufficiently lowered even if the heat treatment in the manufacturing process is performed.

In a liquid crystal display (LCD) using an amorphous germanium TFT as the most common FPD, that is, a driving element, a device is formed on a transparent glass substrate, and the heating temperature in the manufacturing step is about 250 to 350 °C. Therefore, it has been desired to develop a copper-based wiring film which is most suitable for FPD, and it is possible to reduce the electric resistance by heat treatment in a temperature range of a manufacturing process of about 250 ° C to 350 ° C.

In view of the above problems, it is an object of the present invention to provide an oxygen-containing copper alloy which is excellent in adhesion to a glass substrate, a tantalum layer, and a SiN _X protective film layer in a process temperature region of a wiring film such as FPD. A method of producing a film.

The inventors of the present invention conducted active research to solve the above problems, and as a result, found that argon gas was introduced by using an appropriate amount of B in copper and an appropriate amount of a copper alloy target capable of producing a compound with B. The present invention has been achieved by sputtering in an oxygen atmosphere to obtain an oxygen-containing copper alloy film having improved adhesion and low electrical resistance.

That is, the present invention is a method for producing an oxygen-containing copper alloy film which is obtained by sputtering a copper alloy target in an environment in which argon gas and oxygen are introduced to obtain an oxygen-containing copper alloy film, wherein the copper alloy target includes 0.1at% (atomic percent) to 1.0at% of B, even containing 0.1at% to 2.0at% of at least one or more elements capable of producing a compound with B as an additive element, and the balance containing copper and inevitable impurities .

Further, the above copper alloy target is preferably selected from the group consisting of magnesium (Mg), aluminum (Al), bismuth (Si), titanium (Ti), manganese (Mn), nickel (Ni), zirconium (Zr), and molybdenum ( At least one or more elements of Mo), silver (Ag), and strontium (Sm) are used as elements capable of producing a compound with B.

Further, a copper target having a purity of 99.9% or higher may be used on the oxygen-containing copper alloy film, and sputtering may be performed in an argon atmosphere to laminate a copper film.

[Effects of the Invention]

According to the present invention, it is possible to realize an oxygen-containing copper alloy film which is excellent in adhesion to a glass substrate, a tantalum layer, or a SiN _X protective film layer by reducing the electric resistance during the low-temperature heat treatment in the process of manufacturing the FPD. Therefore, in the future, it can be used extremely effectively as a wiring film for FPDs such as large-sized liquid crystal televisions (TVs) or electronic papers that require low resistance.

The above described features and advantages of the present invention will be more apparent from the following description.

An oxygen-containing copper alloy film which is excellent in adhesion to a glass substrate, a tantalum layer, or a SiN _X protective film layer in order to obtain a wiring film for FPD, is an important feature of the present invention in that argon gas is introduced. The most suitable alloy composition for the copper alloy target used for sputtering in the environment of oxygen is added to copper by using B and an element capable of producing a compound with B.

First, the effect of adding B to copper is that after the copper alloy film is formed by sputtering, even if heat treatment is performed at a temperature of, for example, about 350 ° C, the resistance value can be remarkably lowered as compared with the case of film formation. Although the reason for obtaining this effect is not clear, those skilled in the art believe that the reason is that since there is almost no solid solution region of B and Cu, and B is a light element, even at a lower heating temperature. B is also ejected from the copper matrix to the grain boundary or film surface.

Further, when B is added in an amount of 0.1 at% or more, the above effect becomes clear. When B is added in excess of 1.0 at%, the resistance value after heating cannot be sufficiently lowered. Therefore, the amount of addition of B is set to 0.1 at% to 1.0. At%.

Further, by adding 0.1 at% to 2.0 at% of copper to the element capable of producing a compound with B, the electric resistance value after heating can be lowered while maintaining the effect of the prior copper alloy. Although the reason is not clear, those skilled in the art believe that the reason is that B can be ejected from the copper matrix by heat treatment, B, and an element capable of producing a compound with B. In addition, the above effect is exhibited from 0.1 at%. However, when the amount added exceeds 2.0 at%, the resistance value increases and it is difficult to obtain a low resistance value after heating, so the addition amount is set to 0.1 at% to 2.0 at. %.

Further, in order to obtain a low-resistance oxygen-containing copper alloy film, it is preferred that B is from 0.1 at% to 0.5 at%, and an element capable of producing a compound with B is from 0.1 at% to 1.0 at%.

Further, the elements forming a compound with B include: magnesium (Mg) and calcium (Ca) of Group 2, strontium (Sc), yttrium (Y), lanthanum (La), cerium (Ce), lanthanum (Group 3). Pr), 钕 (Nd), 钐 (Sm), 铕 (Eu), 釓 (Gd), 鋱 (Tb), 镝 (Dy), Group 4 titanium (Ti), zirconium (Zr), 铪 (Hf ), Group 5 vanadium (V), niobium (Nb), tantalum (Ta), Group 6 chromium (Cr), molybdenum (Mo), tungsten (W), Group 7 manganese (Mn), Group 8 iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), silver (Ag) of Group 9, aluminum (Al) of Group 11, lanthanum (Si) of Group 12, etc. Various elements. Among these elements, in terms of easy availability, Mg, Al, Si, Ti, Mn, Ni, Zr, Mo, Ag, and Sm are particularly preferable.

In the present invention, an oxygen-containing copper alloy film can be obtained by sputtering a copper alloy target having the above composition in an environment in which argon gas and oxygen gas are introduced. At the time of sputtering, oxygen in the environment is combined with copper or an additive element on the surface of the target, so that part of the oxygen is again sputtered onto the substrate in the form of an oxide. Therefore, the formed copper alloy film contains an oxide formed of oxygen and copper or an additive element in the copper matrix. Since this oxide adheres to the interface of a glass substrate or the like, it has an anchoring effect, and therefore has an effect of improving the adhesion of the copper alloy film.

In addition, controlling the concentration of oxygen in the environment when introducing argon gas and oxygen gas can effectively improve the adhesion of the obtained oxygen-containing copper alloy film and achieve the purpose of low resistance. The environment in which argon gas and oxygen are introduced is preferably such that the overall gas pressure in the environment is 0.1 Pa to 1.0 Pa, and the oxygen concentration (oxygen pressure / (argon pressure + oxygen pressure) × 100) is 20% or less. The reason for this is that although the appropriate oxygen concentration differs depending on the desired value as the wiring film, if the oxygen concentration is too high, it is difficult to obtain low resistance characteristics. A more desirable oxygen concentration is 15% or less. Further, in order to obtain sufficient adhesion, the oxygen concentration is more preferably 5% or more.

In addition, the power supply during sputtering affects the film formation rate, the oxygen content in the oxygen-containing copper alloy film, and the formation of oxide on the target surface. When the supply power at the time of sputtering is low, productivity is lowered and an oxide is formed on the surface of the target, and foreign matter such as particles is likely to be generated. Further, if the supply of electric power is excessively increased, abnormal discharge or the like is likely to occur. Therefore, in order to suppress generation of fine particles or abnormal discharge during sputtering, an oxygen-containing copper alloy film whose oxygen content is controlled to an appropriate amount is formed, and the power supply is preferably converted in terms of the unit area of the sputtering surface of the target to control the power density. It is about 2 W/cm ² to 10 W/cm ² .

Further, in order to make the copper alloy film and the oxygen-containing glass substrate, a silicon layer, adhesion of the protective film excellent SiN _X, X-ray diffraction peak intensity of (111) crystal plane of the main surface of the Cu ₂ O Cu ₂ O ( 111), the intensity of the X-ray diffraction peak intensity Cu(111) with respect to the main crystal plane (111) plane of copper is preferably greater than or equal to 0.01 for Cu ₂ O(111)/Cu(111), in order to be heated A low resistance is obtained, and the above-described strength ratio Cu ₂ O(111)/Cu(111) is preferably 1.0 or less.

Further, the oxygen-containing copper alloy film obtained by the production method of the present invention is excellent in adhesion to a glass substrate. Therefore, a copper target having a purity of 99.9% or more can be used, and sputtering can be performed in an argon atmosphere to deposit a pure copper film as a main wiring film on the obtained oxygen-containing copper alloy film.

Further, the method for producing a copper alloy target used in the present invention has various methods, and generally, it is sufficient to achieve high purity, uniform structure, high density, and the like required for the target. For example, it can be produced by casting a molten liquid of a predetermined composition into a metal mold by a vacuum melting method, and then processing it into a plate shape by plastic working such as forging or rolling, and precision by machining. Processed into a target of a defined shape. Further, in order to obtain a more uniform structure, an ingot obtained by rapid solidification such as a powder sintering method or a spray molding method (droplet deposition method) may be used.

[Example 1]

Hereinafter, specific examples of the invention will be described.

First, a copper alloy target was produced by the method described below.

The raw material was prepared in substantially the same manner as the target composition of the copper alloy film obtained by adding various additive elements to copper, and was melted by a vacuum melting furnace and then cast to prepare a copper alloy ingot. Then, the copper alloy ingot was formed into a sputtering target having a diameter of 100 mm and a thickness of 5 mm by mechanical processing.

Next, using the targets of the various compositions prepared above, sputtering was carried out in an environment in which argon gas and oxygen gas were introduced, and an oxygen-containing copper alloy having a film thickness of 200 nm was formed on a smooth glass substrate having a size of 100 mm × 100 mm. membrane. Further, the sputtering conditions were set as follows: gas pressure in a sputtering environment: 0.5 Pa, oxygen concentration: 10%, and power density: 9.5 W/cm ² .

The resistivity of each sample was measured by a four probe method, and the results are shown in Table 1.

Further, the oxygen-containing copper alloy film formed as described above was cut into a size of 25 mm × 50 mm, and the heating temperature was set to a vacuum atmosphere of 1 × 10 ^-1 Pa or 1 × 10 ^-1 Pa or more. After heat treatment at 150 ° C, 250 ° C, and 350 ° C for 1 hour, the specific resistance was measured. The results are collectively shown in Table 1.

Further, the following test was conducted as a adhesion test: the oxygen-containing copper alloy film obtained by sputtering the film of each sample was subjected to heat treatment at 250 ° C, and then a checker-shaped slit was cut at intervals of 2 mm, and then The surface of the film was bonded to the tape, and the area ratio of the lattice remaining on the substrate at the time of peeling was calculated and evaluated. The above results are shown in Table 1.

It is understood that the oxygen-containing copper alloy films of Samples 1 and 2 which do not contain B have a good adhesion of 90% to 100%, but the resistance value does not significantly decrease at a heating temperature of 250 °C. On the other hand, it is understood that the oxygen-containing copper alloy film containing B and the element capable of producing a compound with B shown in Samples 3 to 12 of the present invention has a good adhesion of 100%, and is at 250 ° C. At the process temperature, the resistance value is greatly lowered. Therefore, when these oxygen-containing copper alloy films are used as the wiring film, it is easy to obtain low resistance. Further, it was found that the sample 13 containing an oxygen-containing copper alloy film containing more than 2.0 at% of an element capable of producing a compound with B had a good adhesion of 100%, but even after heating at a process temperature of 250 ° C, the resistance was obtained. The value also exceeds 11 μΩcm, and a low resistance value cannot be obtained.

[Example 2]

Cu-0.3Ni-0.2B (at%) copper alloy target was sputtered in an environment in which argon gas and oxygen gas were introduced, and a film thickness of 200 nm was formed on a smooth glass substrate having a size of 100 mm × 100 mm. Oxygen-containing copper alloy film. Further, the sputtering conditions were set as follows: gas pressure in a sputtering environment: 0.5 Pa, oxygen concentration: 20%, and power density: 9.5 W/cm ² .

In the same manner as in Example 1, the adhesion test of the oxygen-containing copper alloy film formed as described above was carried out, and as a result, the adhesion was 100%.

Further, the X-ray diffraction intensity of the oxygen-containing copper alloy film was measured using an X-ray diffraction device RINT2500 manufactured by Rigaku Co., Ltd. The X-ray diffraction results are shown in Fig. 1. According to Figure 1, in addition to copper about rays, also appeared around ray Cu ₂ O, the reaction can be confirmed that portion of the copper oxide formed Cu ₂ O is present in the film. The intensity ratio at this time was 0.06 for Cu ₂ O(111)/Cu(111).

[Example 3]

Cu-0.3Ni-0.2B (at%) copper alloy target was introduced with argon gas and oxygen at a power density of 9.5 W/cm ² , a gas pressure of 0.5 Pa in a sputtering environment, and a change in oxygen concentration. In the environment, sputtering was performed to form an oxygen-containing copper alloy film having a film thickness of 200 nm on a smooth glass substrate having a size of 100 mm × 100 mm.

The resistivity of each sample of the oxygen-containing copper alloy film formed in the above was measured by a four-probe method. Further, in the same manner as in Example 1, the resistivity measurement and the adhesion test after heat treatment of each sample were carried out. The above results are shown in Table 2.

According to Table 2, when the oxygen concentration is 20% or less, a sufficiently low resistance value can be obtained by heating at 250 ° C to 350 ° C in the process temperature region. Further, it is also known that if the oxygen concentration is 10% or more, 100% adhesion can be obtained.

[Example 4]

A Cu-0.3Ni-0.2B (at%) copper alloy target was used to cause a change in the power density applied to the target during sputtering and to be sputtered in an environment in which argon gas and oxygen gas were introduced, in a size of 100 mm. An oxygen-containing copper alloy film having a film thickness of 200 nm was formed on a smooth glass substrate of ×100 mm. In addition, the sputtering conditions were set as follows: gas pressure in a sputtering environment: 0.5 Pa, oxygen concentration: 10%.

The film formation speed and the number of abnormal discharges when the oxygen-containing copper alloy film was formed as described above were measured. The measurement results are shown in Table 3. Further, the presence or absence of fine particles on the surface of each film formed on the glass substrate was observed 400 times using an optical microscope.

As can be seen from Table 3, as the power density increases, the film formation speed increases. However, the sample 34 having a power density of more than 10 W/cm ² was subjected to a few abnormal discharges. In addition, as a result of confirming the fine particles of each of the films formed on the glass substrate, no particles of 10 μm or more which were visible at 400 times using an optical microscope were observed in the sample 31, the sample 32, and the sample 33. On the other hand, in the sample 34, three particles of 10 μm or more were confirmed in a field of view of 600 μm × 500 μm. As described above, by controlling the power density to a range of ² W/cm ² to 10 W/cm ² , abnormal discharge does not occur, and an oxygen-containing copper alloy film capable of suppressing generation of fine particles can be stably produced on the substrate. .

[Example 5]

Each of the copper alloy targets disclosed in Table 4 was sputtered under various oxygen concentrations and power densities to form an oxygen-containing copper alloy having a film thickness of 30 nm on a smooth glass substrate having a size of 100 mm × 100 mm. The film acts as a base film. Thereafter, a copper film of each film thickness disclosed in Table 4 was formed on the oxygen-containing copper alloy film using a copper target having a purity of 99.99%. Further, in the case of forming an oxygen-containing copper alloy film, a mixed gas of argon gas and oxygen gas having a gas pressure of 0.5 Pa was used, and when a copper film was formed, argon gas having a gas pressure of 0.5 Pa was used.

Further, as a reference example, a copper target having a purity of 99.99% was used, and sputtering was performed in an argon atmosphere to form a single-layer pure copper film (sample 41) having a film thickness of 200 nm on a glass substrate.

The resistivity obtained from the total film thickness of the single layer film and the laminated film was measured for each sample by a four-probe method. Further, the adhesion was measured by the same method as in Example 1. The above results are shown in Table 4.

According to Table 4, in the sample 42 to the sample 46 in which a pure copper film was formed on the oxygen-containing copper alloy base film formed by using a mixed gas of argon gas and oxygen gas, a single layer film of pure copper with the sample 41 was obtained. A low resistance film is obtained, and high adhesion can be achieved. Further, in Comparative Samples 44 to 46, it was found that the film thickness of the pure copper film formed on the oxygen-containing copper alloy film was thick, and the resistance value was further lowered.

[Example 6]

A substrate having a 200 nm tantalum film and a 300 nm tantalum nitride film was formed on a smooth glass substrate having a size of 100 mm × 100 mm. Next, each target of Cu-0.3Ag-0.5B (at%) and Cu-0.3Ni-0.2B (at%) was used for sputtering in an environment in which argon gas and oxygen gas were introduced, and prepared as described above. An oxygen-containing copper alloy film having a film thickness of 300 nm was formed on each of the substrates. Further, the sputtering conditions were set as follows: gas pressure in a sputtering environment: 0.5 Pa, oxygen concentration: 10%, and power density: 9.5 W/cm ² .

Further, as a reference example, a pure copper film (sample 51 and sample 61) formed by sputtering was prepared by using a copper target having a purity of 99.99% in an argon atmosphere.

The resistivity and adhesion at the time of film formation of each sample were measured in the same manner as in Example 1. Further, the resistivity after heat treatment of each sample for 1 hour at a heating temperature of 250 ° C in a vacuum atmosphere of reduced pressure to 1 × 10 ^-1 Pa or 1 × 10 ^-1 Pa or more was also measured. The measurement results of the sample formed on the ruthenium film are shown in Table 5, and the measurement results of the sample formed on the tantalum nitride film are shown in Table 6.

According to Tables 5 and 6, the oxygen-containing copper alloy film of the sample 52, the sample 53, the sample 62, and the sample 63 obtained by the method for producing an oxygen-containing copper alloy film of the present invention is obtained from the ruthenium film. The upper and the tantalum nitride film also have a high adhesion of 100%, and when heated at a process temperature of 250 ° C, the resistance value can be greatly reduced. In addition, it is understood that the copper film of the sample 51 formed on the ruthenium film has an increased resistance value after heat treatment, and copper and ruthenium mutually diffuse, but the resistance values of the sample 52 and the sample 53 of the present invention after heat treatment are lowered, and It does not diffuse into oxygen-containing copper alloys.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims.

1 is an X-ray diffraction pattern of the oxygen-containing copper alloy film of Example 2.

Claims (3)

A method for producing an oxygen-containing copper alloy film, characterized in that a copper alloy target is used for sputtering in an environment in which argon gas and oxygen are introduced to obtain an oxygen-containing copper alloy film, the copper alloy target comprising 0.1 At% to 1.0 at% of B and 0.1 at% to 2.0 at% of at least one or more elements capable of producing a compound with B as an additive element, and the remainder including copper and unavoidable impurities. The method for producing an oxygen-containing copper alloy film according to claim 1, wherein the copper alloy target uses at least Mg, Al, Si, Ti, Mn, Ni, Zr, Mo, Ag, Sm. One or more elements serve as an element capable of producing a compound with B. A method for producing an oxygen-containing copper alloy film, which is characterized in that it is obtained on an oxygen-containing copper alloy obtained by the method for producing an oxygen-containing copper alloy film according to claim 1 or 2 A copper target having a purity of 99.9% or higher was used, and sputtering was performed in an argon atmosphere to laminate a copper film.