JP5263665B2 - Cu alloy film for wiring film and sputtering target material for forming wiring film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Cu alloy film which can reduce the resistance of a wiring film of a flat panel display device or the like in a process temperature region, and which has heat resistance to suppress hillocks and voids caused in a Cu based film, and to provide a sputtering target material for forming the Cu alloy film. <P>SOLUTION: The Cu alloy film for wiring film contains, as additional elements, B of 0.1 to 1.0 atomic%, and further contains Mn and/or Ni of 0.1 to 2.0 atomic%, and the balance Cu with inevitable impurities. The sputtering target material is used for forming the Cu alloy film for wiring film. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention relates to a wiring film used in a flat display device (Flat Panel Display, hereinafter referred to as FPD) manufactured by forming a thin film on a substrate, and a sputtering target material used for forming the wiring film. .

  Examples of the FPD manufactured by laminating a thin film on a glass substrate or Si wafer include, for example, a liquid crystal display (hereinafter referred to as LCD), a plasma display panel (hereinafter referred to as PDP), and a field emission display (hereinafter referred to as FED). Various new products such as electroluminescence display (hereinafter referred to as ELD) and electronic paper have been actively researched and developed.

  As a wiring film such as a thin film transistor (TFT) used in these FPDs, high-speed driving for displaying a moving image is required as the display is enlarged, and Al and Al alloys of Al and Al alloys are used as a low resistance wiring film. A membrane is used. In recent years, with further increase in display size and definition, Cu-based wiring has attracted attention as a wiring with lower resistance.

Cu has a lower resistance than Al and is considered to be superior in both resistance to electromigration and stress migration. It has already been used in the LSI field, and is expected as a next-generation wiring material in the FPD field. ing. However, with the high integration of LSI, pure Cu is considered to have insufficient electromigration resistance and stress migration resistance. Therefore, it has been proposed to improve these migration resistances by adding an additive element to Cu (see, for example, Patent Document 1).
JP-A-6-177117

The Cu alloy film proposed in Patent Document 1 is a useful Cu alloy film having higher electromigration property and stress migration property than pure Cu when a device is formed on a Si wafer such as LSI. It is. However, according to the inventor's study, when the proposed Cu alloy film is formed on a glass substrate, it is confirmed that the resistance value does not sufficiently decrease even if the heat treatment during the manufacturing process is performed. did. Further, when heat treatment at about 250 ° C. was performed, protrusions called hillocks and voids called voids were sometimes generated in the Cu alloy film, and it was confirmed that there was a problem in heat resistance.
In addition, in a liquid crystal display (LCD) using amorphous silicon-TFT as a driving element which is the most common FPD, a device is formed on a transparent glass substrate, and the heating temperature during the manufacturing process is about 250 to 350 ° C. Yes, it is expected to further decrease in the future. For this reason, there is a demand for a Cu alloy wiring film that is optimal for an FPD that can realize low resistance by heat treatment in a manufacturing process temperature range of about 200 to 250 ° C. while having heat resistance as the above-described problem.

  In view of the above problems, an object of the present invention is to reduce the resistance of a wiring film such as an FPD in the process temperature range and to have a heat resistance capable of suppressing hillocks and voids generated in a Cu-based film. It is to provide a sputtering target material for forming an alloy film and its Cu alloy film.

As a result of intensive studies to solve the above-mentioned problems, the present inventor has added low amounts of B, Mn and / or Ni to Cu as a Cu alloy film. The inventors have found that it is possible to have heat resistance capable of suppressing the generation of the present invention, and reached the present invention.
That is, the present invention is for a wiring film comprising B as an additive element in an amount of 0.1 to 1.0 atomic%, further containing Mn and / or Ni in an amount of 0.1 to 2.0 atomic%, and the balance being Cu and inevitable impurities. Cu alloy film.
Further, in the present invention, B is 0.1 to 1.0 atomic%, and Mn and / or Ni is 0.1 to 2.0 atomic% as additive elements for obtaining a Cu alloy film for a wiring film having the above composition. It is a sputtering target material for forming a wiring film comprising the remaining Cu and inevitable impurities.

  Since the present invention can realize a Cu alloy film having low resistance, hillock resistance, and void resistance, it is extremely effective as an FPD wiring film for large liquid crystal TVs, electronic papers, and the like that are required to have low resistance in the future. It will be a thing. Moreover, when forming the Cu alloy film for wiring films of the present invention, sputtering using a target material is optimal.

  An important feature of the present invention is that, as an optimum alloy configuration for obtaining a wiring film having sufficient hillock resistance and void resistance while realizing the low resistance required for the wiring film for FPD, A Cu alloy film in which Mn and / or Ni is added in combination is found.

The reason for selecting B and Mn and / or Ni as additive elements and the reason for selecting the addition amount in the Cu alloy film for wiring films of the present invention will be described below.
First, the effect of adding B to Cu is that when a Cu alloy film is formed by sputtering, even when heat treatment is performed at a low temperature range of 150 to 250 ° C., the resistance value can be significantly reduced as compared with the time of film formation. It is in the point which can improve the hillock tolerance at the time and heat-processing. The reason why the effect is obtained is not clear, but is presumed as follows. When a thin film is formed on a substrate by sputtering, the additive element is dissolved in a non-equilibrium state. B has almost no solid solution region with respect to Cu, and since B is a light element, the resistance value is reduced because B is ejected from the Cu matrix to the grain boundaries and the film surface even at low temperature heat treatment. It is considered possible. In addition, it is considered that the hillock resistance is improved because B is discharged from the Cu matrix to the grain boundaries and the film surface during the heat treatment, thereby reducing the compressive stress of the film.
The above effect becomes clear when B is added in an amount of 0.1 atomic% or more, and if B is added in excess of 1.0 atomic%, the film tends to peel off, which is undesirable. ˜1.0 atomic%.

Further, by adding 0.1 to 2.0 atomic% of Mn and / or Ni with respect to Cu, a high effect of suppressing voids generated in the Cu film can be obtained. The reason is presumed as follows. Mn and Ni are elements that are easily dissolved in Cu, and Mn and Ni are dissolved in Cu to suppress the movement of Cu atoms during heating, and as a result, the generation of voids is suppressed. Conceivable.
Furthermore, Cu alloy which has the effect that resistance value falls with 150-250 degreeC heat processing is obtained, suppressing generation | occurrence | production of a hillock and a void by combining and adding B, Mn, and Ni with respect to Cu. be able to. The reason is not clear, but B is an element that expresses Mn, Ni and a compound, so that B and a part of Mn and Ni are combined by heat treatment and discharged as a compound from a Cu matrix. Conceivable. The above effect appears from 0.1 atomic%, but if added over 2.0 atomic%, the resistance value increases and it becomes difficult to obtain a low resistance value even after heating, so Mn and / or Ni The addition amount is 0.1 to 2.0 atomic%.

  In order to obtain a specific resistance of 4 μΩcm or less by heat treatment at 200 to 250 ° C. while maintaining hillock resistance and void resistance, the addition amount of B is 0.1 to 0.5 atomic%, Mn and The addition amount of Ni is preferably 0.1 to 1.0 atomic%.

  Moreover, as a board | substrate used when forming Cu alloy film of this invention, it is suitable to use a glass substrate and Si wafer. These substrates are excellent in process stability in manufacturing a display device, and have a lower resistance than that formed at room temperature by heating the substrate when forming the Cu alloy film of the present invention. An alloy film can be formed.

  Further, the Cu alloy film of the present invention desirably has a film thickness of 100 to 300 nm in order to obtain stable characteristics. When the film thickness is less than 100 nm, since the film is thin, the influence of surface scattering increases, and the resistance value tends to increase. On the other hand, if the film thickness exceeds 300 nm, the crystal grains grow and the unevenness of the film surface form becomes large and smoothness cannot be maintained, and the film becomes easy to peel off due to film stress, or it takes time to form the film. This is because productivity is reduced.

  Moreover, when forming the Cu alloy film for wiring films of the present invention, sputtering using a wiring film forming sputtering target material having the same composition as the Cu alloy film is optimal. This is because sputtering can form a film having almost the same composition as the target material, and the Cu alloy film of the present invention can be formed stably.

  There are various methods for producing the target material, and any method can be used as long as it can achieve the high purity, uniform structure, high density, and the like generally required for the target material. For example, a molten metal adjusted to a predetermined composition by a vacuum melting method is cast into a metal mold, and then processed into a plate shape by plastic processing such as forging and rolling, and finished to a target having a predetermined shape by machining. Can be manufactured. In order to obtain a more uniform structure, an ingot rapidly solidified by a powder sintering method or a spray forming method (droplet deposition method) may be used.

  In the sputtering target material for forming a Cu alloy film and a wiring film of the present invention, component elements other than additive elements are Cu and inevitable impurities. That is, inevitable impurities such as oxygen, nitrogen, and carbon, which are gas components, may be included as long as the effects of the present invention are not impaired. For example, oxygen, nitrogen, and carbon in the gas components are each 50 ppm or less, and the purity excluding the gas components is preferably 99.9% or more.

Next, specific examples of the present invention will be described.
First, a Cu alloy target material was manufactured by the method described below.
A Cu alloy ingot was prepared by casting the raw materials so as to be substantially the same as the target composition of the Cu alloy film obtained by adding various additive elements to Cu, melting in a vacuum melting furnace, and casting. Next, a sputtering target material having a diameter of 100 mm and a thickness of 5 mm was produced by machining a Cu alloy ingot.
Moreover, the pure Cu target of the same dimension was produced by the same method as a comparative example.
A pure Cu film and a Cu alloy film having a film thickness of 200 nm are formed on a smooth glass substrate having a size of 100 × 100 mm by sputtering using the target materials having various compositions prepared as described above. Resistance was measured. The measurement results are shown in Table 1.

Further, the pure Cu film and the Cu alloy film formed as above were cut into a size of 25 × 50 mm and subjected to heat treatment at a temperature of 250 ° C. for 1 hour in a vacuum atmosphere reduced to 0.5 Pa or less, and then the specific resistance. Was measured. Furthermore, the film surface conditions of the pure Cu film and the Cu alloy film were observed with an electrolytic emission scanning electron microscope (hereinafter referred to as FE-SEM). The film surface observation by FE-SEM was performed from a direction oblique to the film surface at an angle of 45 °, and the observation magnification was 50,000 times. The film surface was evaluated as good when no hillocks or voids were generated on the film surface, and was evaluated as x when hillocks or voids were generated on the film surface. It is shown in 1.
In addition, FIGS. 1 to 5 show FE-SEM images obtained by observing the film surface conditions of Samples 1, 2, 7, 8, and 9 after the heat treatment.

  As shown in Table 1 and FIGS. 1 to 5, pure Cu has a low resistance value, but it can be seen that voids are generated along with the growth of crystal grains after the heat treatment. Further, in the Cu—Al alloy or Cu—Si alloy, hillocks are generated after the heat treatment, and at the same time, the specific resistance after the heat treatment exceeds 4 μΩcm, and the resistance cannot be sufficiently lowered. In contrast, Cu-Ni-B and Cu-Mn-B of the present invention do not generate voids or hillocks after heat treatment, and the specific resistance can be reduced to less than 4 μΩcm.

Using the pure Cu, Cu-1.0% Ni-0.5% B (atomic%), Cu-0.5% Mn-0.5% B (atomic%) sputtering target prepared in Example 1. In the same manner as in Example 1, samples were prepared in which pure Cu and Cu alloy films were formed on a glass substrate. Then, the specific resistance was measured after heat-processing for 1 hour in the temperature range of 100-250 degreeC in the vacuum atmosphere which pressure-reduced each sample to 0.5 Pa or less. From the measurement results, the relationship between the heating temperature and the specific resistance is shown in FIG.
From FIG. 6, the specific resistance of the Cu—Ni—B alloy film and the Cu—Mn—B alloy film of the present invention gradually decreases as the heating temperature rises. It turns out that falls.

2 is an electrolytic emission scanning electron micrograph of the film surface observed after heat treatment of a pure Cu film of Sample 1 in Example 1. FIG. It is the electrolysis radiation type scanning electron micrograph which observed the film | membrane surface after heat-processing the Cu alloy film of the sample 2 in Example 1. FIG. FIG. 3 is an electrolytic emission scanning electron micrograph of the film surface observed after heat treatment of the Cu alloy film of Sample 7 in Example 1. FIG. 4 is an electro-radiation scanning electron micrograph of the film surface observed after heat-treating the Cu alloy film of Sample 8 in Example 1. FIG. FIG. 3 is an electrolytic emission scanning electron micrograph of the film surface observed after heat-treating the Cu alloy film of Sample 9 in Example 1. FIG. It is a figure which shows the relationship between the heating temperature and specific resistance in Example 2. FIG.

Claims (2)

  Cu for wiring films, characterized in that it contains 0.1 to 1.0 atomic% of B as an additive element and 0.1 to 2.0 atomic% of Mn and / or Ni, and consists of the balance Cu and inevitable impurities. Alloy film.   For forming a wiring film, comprising 0.1 to 1.0 atomic% of B as an additive element, 0.1 to 2.0 atomic% of Mn and / or Ni, and the balance being Cu and inevitable impurities Sputtering target material.