TWI674325B - MoNb target - Google Patents

Abstract

The invention provides a target material which can solve the problem of high resistance generated in the base film or cover film of a wiring film or an electrode film, and the problem of nodules caused by the surface roughness of the target material during sputtering, and A low-resistance MoNb thin film suitable for a flat image display device having stable TFT characteristics. Preferably, the target is a MoNb target having a composition containing 5 atomic% to 30 atomic% of Nb and the remaining portion including Mo and unavoidable impurities, and has more than 70 μm per 200,000 μm ² of the sputtered surface. The maximum length of the Nb phase is less than 1.0, and the average circle equivalent diameter of the Nb phase is 15 μm to 65 μm.

Description

MoNb target

The present invention relates to a MoNb target, which is used to form a MoNb film that is a base film or a cover film that becomes a wiring film or an electrode film of a flat image display device, for example.

As a thin film transistor (hereinafter referred to as a "TFT") type liquid crystal display of a type of a flat image display device, a wiring film or an electrode film having a low resistance value (hereinafter referred to as "low resistance") is used. Thin films of pure metals such as Al, Cu, Ag, and Au, or thin films containing these alloys. These wiring films or electrode films may be accompanied by a heating step depending on the manufacturing process, and there may be a case in which any of the heat resistance, corrosion resistance, and adhesion required for wiring or electrodes is inferior, or There is a problem that a diffusion layer is formed between the elements constituting the alloy and necessary electrical characteristics are lost.

In order to solve these problems, as a base film or a cover film for the wiring film or the electrode film, pure Mo or a Mo alloy as a high melting point metal is being used. In particular, an Mo-based alloy film such as MoNb is used for an Al-based wiring film or an electrode film as a base film or a cover film. As a target for forming the Mo-alloy film, for example, a patent document 1 has been proposed. This patent document 1 proposes to reduce the variation in hardness in Mo alloy targets with high possibility of cracks or defects during machining, and to suppress wear and tear of wafers of cutting tools while suppressing the body of Mo alloy targets. The broken aspect is a useful technique. [Prior Art Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2016-188394

[Problems to be Solved by the Invention] The present inventors confirmed that if MoNb is used as the Mo alloy described in Patent Document 1, and a MoNb target is formed using a MoNb target (hereinafter also referred to simply as a "target"), there is a problem. The case where the specific resistance of the MoNb film becomes higher (hereinafter referred to as "high resistance") will be described. In addition, the high resistance problem has a problem that the original function of the low resistance provided in the wiring film or the electrode film is hindered, and the reliability of a flat image display device such as destabilization of TFT characteristics is adversely affected. Case.

In addition, the inventors also confirmed that, for the purpose of improving the film forming speed, if the target is sputtered at a high power, the surface roughness of the target increases with the increase of the cumulative power, and When nodule is generated on the sputtering surface of the target. Furthermore, the problem of the nodules may cause particles to adhere to the obtained MoNb thin film and adversely affect the reliability of a flat image display device such as destabilization of TFT characteristics.

In view of the above-mentioned problems, an object of the present invention is to provide a target which can solve the problem of high resistance generated in a base film or a cover film of a wiring film or an electrode film, and caused by the surface roughness of the target during sputtering. The MoNb thin film is suitable for obtaining a flat image display device with stable TFT characteristics with low resistance. [Means for solving problems]

The MoNb target of the present invention has a composition containing 5 atomic% to 30 atomic% of Nb and the remainder contains Mo and unavoidable impurities. It has a maximum length exceeding 70 μm per 200,000 μm ² of the sputtered surface The Nb phase is less than 1.0.

In addition, the MoNb target of the present invention preferably has an average circular equivalent diameter of the Nb phase of 15 to 65 μm per 200,000 μm ² of the sputtered surface. [Effect of the invention]

The target of the present invention can suppress the specific resistance of the formed MoNb thin film from increasing. In addition, the target of the present invention has a smooth sputtering surface even after sputtering at a high power, and thus can suppress the generation of nodules. With this, the present invention can suppress the adhesion of particles, and form a MoNb film suitable for a base film or a cover film of a wiring film or an electrode film of a flat image display device with a low resistance, for example, for the manufacture of a TFT liquid crystal display or the like. Speak useful techniques.

The target of the present invention has less than 1.0 Nb phases per 200,000 μm ² of the sputtered surface having a maximum length exceeding 70 μm. That is, in the target of the present invention, Nb having a lower sputtering rate than Mo exists in the structure of the target in a non-roughened state with a maximum length of 70 μm or less. Thereby, the target of this invention exhibits the effect which can suppress the specific resistance of the obtained MoNb thin film from becoming high. In addition, the target of the present invention also exhibits the following effects: Mo and Nb are evenly sputtered when sputtering is performed at high power for the purpose of improving the film forming speed, so that the surface roughness of the sputtered surface can be suppressed. The degree of increase and inhibit the formation of tumor mass. In addition, for the same reason as described above, the target of the present invention preferably has less than 1.0 Nb phases having a maximum length exceeding 50 μm per 200,000 μm ² of the sputtered surface, more preferably Nb phases having a maximum length exceeding 40 μm are less than 1.0.

Here, the maximum length and average circle equivalent diameter of the Nb phase mentioned in the present invention can be compared with a scanning electron microscope with a high contrast in an arbitrary field of view per 200,000 μm ² of the sputtering surface of the target. The Mo phase and the Nb phase were taken, and the image was analyzed using image analysis software (for example, "Scandium" manufactured by OLYMPUS SOFT IMAGING SOLUTIONS GMBH) Determination. In the present invention, the maximum length of the Nb phase in the case where a plurality of Nb phases are connected is the maximum length of the outermost periphery including the connected Nb phases.

In addition, from the viewpoint of finely dispersing Nb, which has a lower sputtering rate than Mo, in the structure of the target, the target of the present invention is preferably an average Nb phase per 200,000 μm ² of the sputtering surface. The circle equivalent diameter is set to 15 μm to 65 μm. With this, the target of the present invention has the purpose of improving the film forming speed. When sputtering is performed at high power, Mo and Nb can be evenly sputtered, and a composition similar to that of the target can be obtained. MoNb films are preferred in this respect. In addition, for the same reason as described above, the average circular equivalent diameter of the Nb phase is more preferably 50 μm or less, and even more preferably 45 μm or less. From the viewpoint of productivity, such as adjustment of raw material powder, the average circular equivalent diameter of the Nb phase is more preferably 20 μm or more, and even more preferably 25 μm or more.

The target of the present invention has a composition containing 5 atomic% to 30 atomic% of Nb, and the remainder includes Mo and unavoidable impurities. The content of Nb is specified in a range capable of manufacturing a flat image display device that can maintain low resistance or resist etching when a MoNb film is used as a base film or a cover film of a wiring film or an electrode film. Etchant and other characteristics. For the same reason as described above, the content of Nb is preferably 7 atomic% or more, and more preferably 9 atomic% or more. In addition, for the same reason as described above, the content of Nb is preferably 20 atomic% or less, and more preferably 15 atomic% or less.

An example of a method for producing a target of the present invention will be described. The target material of the present invention can be obtained, for example, by preparing Mo powder and Nb powder as raw material powders, mixing and filling the raw material powders into a pressure vessel, and sintering the pressure vessel to produce a sintered body, The sintered body is machined and ground. Here, as the Mo powder used for the raw material powder, a Mo powder having an average particle diameter (D50 of cumulative particle size distribution, hereinafter referred to as “D50”) of 2 μm to 10 μm, or a Mo powder and D50 of 25 is used. A mixed Mo powder in which a Mo powder of μm to 55 μm is mixed can suppress the segregation of the Mo phase in the target, which is preferable in this respect.

Regarding the Nb powder used in the raw material powder, a Nb powder having a D50 of 25 μm to 65 μm was sieved, and the obtained Nb powder having a size of 70 μm or less was used, thereby obtaining a coarse Nb phase having a maximum length of 70 μm or less. A target having a uniform and fine structure with an average circular equivalent diameter of the Nb phase in the range of 15 μm to 65 μm is preferred in this respect. In addition, for the purpose of improving the film formation speed, it is envisaged that sputtering at a higher power is used. In order to suppress the formation of nodules, it is more preferable that the Nb powder having a D50 of 25 μm to 65 μm be sieved and the obtained 45 μm The following Nb powder. In addition, in order to obtain the target material of the present invention, the pressure container is heated to 400 ° C to 500 ° C and vacuum degassed and then sealed before the raw material powder is subjected to pressure sintering, thereby suppressing the pressure below. It is preferable in this respect that Nb undergoes particle growth in one-step pressure sintering.

The pressure sintering is preferably performed under conditions of 1000 ° C. to 1500 ° C., 80 MPa to 160 MPa, and 1 to 15 hours, for example, by applying hot isostatic pressing or hot pressing. The selection of these conditions depends on the composition, size, pressure sintering device, etc. of the target to be obtained. For example, hot isostatic pressing is easy to apply the conditions of low temperature and high pressure, and hot pressing is easy to apply the conditions of high temperature and low pressure. In the present invention, it is preferred to use hot isostatic pressing to obtain a large target with a long side of 2 m or more.

Here, by setting the sintering temperature to 1000 ° C. or higher, it is possible to promote sintering and obtain a dense target, which is preferable in this respect. In addition, by setting the sintering temperature to 1500 ° C. or lower, it is possible to suppress the growth of Nb particles and obtain a uniform and fine structure, which is preferable in this respect. By setting the applied pressure to 80 MPa or more, sintering can be promoted and a dense target can be obtained, which is preferable in this respect. In addition, by setting the applied pressure to 160 MPa or less, a general-purpose pressure sintering device can be used, which is preferable in this respect. By setting the sintering time to 1 hour or more, sintering can be promoted and a dense target can be obtained, which is preferable in this respect. In addition, by setting the sintering time to 15 hours or less, a dense target material that suppresses the growth of Nb particles can be obtained without hindering production efficiency, which is preferable in this respect. [Example]

Using a cross rotary mixer, a Mo powder having a D50 of 4 μm and an Nb powder having a D50 of 55 μm were obtained using a sieve of 70 μm or less Nb powder to obtain 10 atomic% Nb and the remainder Mo and unavoidable impurities are mixed to prepare a mixed powder. Then, the prepared mixed powder was filled in a pressurized container made of mild steel, and an upper lid having a degassing port was welded. Then, the pressure vessel was vacuum degassed and sealed at 450 ° C, and then subjected to hot isostatic pressing treatment at 1250 ° C, 145 MPa, and 10 hours, thereby obtaining the target of Example 1 of the present invention. Sintered body of material.

The Mo powder with D50 of 4 μm and the Nb powder with D50 of 35 μm were obtained by using a sieve with a cross-rotating mixer. The mixed powder is prepared in a manner to avoid the composition of impurities. Then, the prepared mixed powder was filled in a pressurized container made of mild steel, and an upper lid having a degassing port was welded. Then, the pressure vessel was vacuum degassed and sealed at 450 ° C, and then subjected to hot isostatic pressing treatment at 1250 ° C, 145 MPa, and 10 hours, thereby obtaining the target of Example 2 of the present invention. Sintered body of material.

Mo powder with a D50 of 4 μm and Nb powder with a D50 of 115 μm were mixed by a cross-rotating mixer so as to have a composition containing 10 atomic% of Nb and the remainder containing Mo and unavoidable impurities to prepare for mixing. powder. Then, the prepared mixed powder was filled in a pressurized container made of mild steel, and an upper lid having a degassing port was welded. Then, the pressurized container was vacuum degassed and sealed at 450 ° C, and then subjected to hot isostatic pressing treatment at 1250 ° C, 145 MPa, and 10 hours to obtain a target material of a comparative example. Sintered body of material.

Each of the obtained sintered bodies was subjected to machining and grinding, and targets each having a diameter of 180 mm × a thickness of 5 mm were produced. Regarding the obtained sputtered surfaces of the targets, a reflected electron image of a scanning electron microscope was used to align them in an arbitrary field of view: 591 μm × length: 435 μm (area: 257085 μm ² ). Three fields of view were observed at a field of 200,000 μm ² , the maximum length of each Nb phase existing in each field of view was measured, and the number of Nb phases with a maximum length exceeding 70 μm was measured. In addition, the circle equivalent diameter of the Nb phase present in each field of view was measured, and the average circle equivalent diameter of the three fields of view was calculated. Here, the Mo phase and the Nb phase were photographed with high contrast by a scanning electron microscope, and image analysis software (Scantime (SCANTIM) manufactured by GMBH, OLYMPUS SOFT IMAGING SOLUTIONS Scandium)) measuring the image. The results are shown in Table 1. In addition, the results obtained by observing the sputtered surface of each target before sputtering with a scanning electron microscope are shown in FIGS. 1 to 3.

For each target, a direct current (DC) magnetron sputtering device (model: C3010) manufactured by Canon Anelva Co., Ltd. was used under the conditions of Ar environment, pressure 0.5 Pa, and power 500 W. Next, a 300-nm-thick MoNb thin film was formed on a glass substrate, and three samples each for specific resistance measurement were obtained. The specific resistance was measured using a four-terminal thin-film resistivity tester (MCP-T400) manufactured by Dia Instrument Co., Ltd. The results are shown in Table 1.

For each target, a DC magnetron sputtering device (model: C3010) manufactured by Canon Anelva Co., Ltd. was used under the conditions of Ar environment, pressure 0.5 Pa, power 1000 W, and sputtering time 30 minutes. Next, sputtering is performed. For each target, the surface roughness of the sputtered surface before and after sputtering was measured. As for the surface roughness, a small surface roughness measuring machine (SU-210) manufactured by Mitutoyo Co., Ltd. was used to measure the Japanese Industrial Standards (JIS) in a right-angle direction with respect to the polishing direction. B 0601: Arithmetic average roughness (Ra) specified in 2001. The results are shown in Table 1. In addition, the results obtained by observing the sputtered surface of each target after sputtering with an optical microscope are shown in FIGS. 4 to 6.

[Table 1]

As shown in FIGS. 1 and 2, the target of the present invention shows that the fine Nb phase 2 is dispersed in the Mo phase 1 serving as a base. Moreover, the average circular equivalent diameter of the Nb phase of the target of the present invention in any field of view is 30 μm to 49 μm. In addition, one Nb phase with a maximum length exceeding 70 μm was not confirmed, and the average number of the three fields of view was less than 1.0. In addition, the target of the present invention confirmed that the maximum value of the maximum length of the Nb phase was 68 μm in the three fields of view.

In addition, as shown in FIG. 4 and FIG. 5, regarding the target material of the present invention, it was confirmed that the arithmetic average roughness Ra after sputtering was less than 2.00 μm, and it was a nodule caused by continuous sputtering with high power. It is a useful target for the problem of generation of particles, that is, the problem that particles adhere to the base film or cover film of a wiring film or an electrode film. In addition, the MoNb thin film formed using the target of the present invention was confirmed to have a specific resistance of 15.2 μΩ · cm or less, and was a low-resistance and useful thin film as a base film or a cover film of a wiring film or an electrode film.

On the other hand, regarding the target of the comparative example, as shown in FIG. 3, it can be seen that the coarse Nb phase 2 is dispersed in the Mo phase 1 serving as the base. In the target of the comparative example, the average circular equivalent diameter of the Nb phase exceeded 65 μm in any field of view. In addition, two or more Nb phases with a maximum length exceeding 70 μm were confirmed, and the average number of the three fields of view was 4.3. In the target of the comparative example, the maximum value of the maximum length of the Nb phase in the three fields of view was 117 μm.

In addition, as shown in FIG. 6, regarding the target material of the comparative example, the arithmetic average roughness Ra after sputtering was found to exceed 2.20 μm, and there was a possibility that nodules were generated due to high-power continuous sputtering. In addition, the MoNb thin film formed using the target material of the comparative example was found to have a specific resistance exceeding 15.5 μΩ · cm, which was unsuitable as a base film or a cover film of a wiring film or an electrode film, which was not suitable.

1‧‧‧Mo phase

2‧‧‧Nb phase

FIG. 1 is a photograph obtained by observing a sputtering surface to be a target material of Example 1 of the present invention before sputtering by a scanning electron microscope. FIG. 2 is a photograph obtained by observing a sputtering surface of a target material of Example 2 of the present invention before sputtering by a scanning electron microscope. FIG. 3 is a photograph obtained by observing a sputtering surface of a target material as a comparative example before sputtering by a scanning electron microscope. FIG. 4 is a photograph obtained by observing the sputtered surface of the target material of Example 1 of the present invention after sputtering by an optical microscope. FIG. 5 is a photograph obtained by observing the sputtered surface of the target material of Example 2 of the present invention after sputtering by an optical microscope. FIG. 6 is a photograph obtained by observing a sputtering surface of a target material as a comparative example after sputtering by an optical microscope.

Claims (1)

A MoNb target having a composition containing 5 atomic% to 30 atomic% of Nb and the remainder containing Mo and unavoidable impurities. It has an Nb phase with a maximum length of more than 70 μm per 200,000 μm ² of the sputtering surface Less than 1.0, in which the average circle equivalent diameter of the Nb phase is 25 μm to 65 μm.