CN109207941B

CN109207941B - MoNb target material

Info

Publication number: CN109207941B
Application number: CN201810723639.0A
Authority: CN
Inventors: 福冈淳; 青木大辅; 齐藤和也; 上野英
Original assignee: Hitachi Metals Ltd
Current assignee: Proterial Ltd
Priority date: 2017-07-05
Filing date: 2018-07-04
Publication date: 2020-09-29
Anticipated expiration: 2038-07-04
Also published as: KR102161580B1; JP7110749B2; JP2019065383A; TW201907023A; TWI674325B; KR20190005120A; CN109207941A

Abstract

A MoNb target material. Provided is a MoNb film target material which can solve the problems of high resistance appearing on a wiring film, an undercoat film of an electrode film, and a cover film, and nodules caused by surface roughness of the target material during sputtering, and which can form a MoNb film suitable for a flat-panel display device having low resistance and stable TFT characteristics. [ solving means ] A MoNb target having a composition containing 5 to 30 atomic% of Nb, the balance being Mo and unavoidable impurities, per 200000 [ mu ] m²The number of Nb phases having a maximum length exceeding 70 μm in the sputtering surface of (2) is less than 1.0, and the average circle-equivalent diameter of the Nb phases is preferably 15 to 65 μm.

Description

MoNb target material

Technical Field

The present invention relates to a MoNb target used for forming a MoNb film as, for example, a wiring film, a base film of an electrode film, and a coating film of a flat-panel image display device.

Background

As a wiring thin film or an electrode thin film of a 1-type thin film transistor (hereinafter, referred to as "TFT") liquid crystal display or the like of the flat panel display device, a thin film made of a pure metal such as Al, Cu, Ag, Au or the like having a low resistance value (hereinafter, referred to as "low resistance") or a thin film made of an alloy thereof is used. These wiring thin films and electrode thin films may be accompanied by a heating step depending on the production process, and may have a problem of deterioration of any of heat resistance, corrosion resistance and adhesion required for the wiring and the electrode, and a problem of loss of necessary electrical characteristics due to formation of a diffusion layer between the elements constituting the alloy.

In order to solve these problems, pure Mo or Mo alloy of a high melting point metal has been used as a base film or a cover film for the wiring film or the electrode film. In particular, Mo alloy thin films such as MoNb are used for Al-based wiring thin films, base films of electrode thin films, and coating films, and proposals have been made for targets for forming the Mo alloy thin films, such as those in patent document 1.

Patent document 1 proposes a proposal for a Mo alloy target material having a high possibility of generating cracks or defects during machining to reduce variations in hardness, and is a useful technique in that wear and damage of the blade of the cutting tool can be suppressed, and damage of the Mo alloy target material itself can be suppressed.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2016 + 188394

Disclosure of Invention

Problems to be solved by the invention

The present inventors have confirmed that when MoNb is used as a certain Mo alloy described in patent document 1 and a MoNb target (hereinafter, also simply referred to as "target") is used to form a MoNb thin film, a new problem may arise in that the resistivity of the MoNb thin film becomes high (hereinafter, referred to as "high resistance"). The problem of high resistance may hinder the original function of low resistance of the wiring thin film and the electrode thin film, and may adversely affect the reliability of the flat-panel display device, for example, destabilize the TFT characteristics.

Further, the present inventors have also confirmed that, when sputtering is performed at a high power using the above-described target for the purpose of increasing the film formation rate, the surface roughness of the target may increase with an increase in the integrated power, and nodules may be formed on the sputtering surface of the target. The nodule problem may cause particles to adhere to the obtained MoNb thin film, which may adversely affect the reliability of the flat panel display device, for example, destabilizing the TFT characteristics.

In view of the above-described problems, an object of the present invention is to provide a MoNb thin film target material that can solve the problems of high resistance occurring in a wiring thin film, an underlying film of an electrode thin film, and a cover film, and nodules due to surface roughness of the target material during sputtering, and that can form a low resistance MoNb thin film suitable for a flat panel display device that can obtain stable TFT characteristics.

Means for solving the problems

The MoNb target material of the invention has a composition containing 5-30 atomic% of Nb, and the balance of Mo and inevitable impurities, and each of the composition is 200000 mu m²The number of Nb phases having a maximum length exceeding 70 μm in the sputtering surface of (2) is less than 1.0.

In addition, the MoNb target of the invention is preferably at least 200000 μm²The average equivalent circle diameter of the Nb phase in the sputtering surface of (2) is 15 to 65 μm.

ADVANTAGEOUS EFFECTS OF INVENTION

The target material of the invention can inhibit the resistivity of the formed MoNb film from increasing. In addition, the target material of the present invention can suppress the generation of nodules because the sputtering surface is smooth even after sputtering at high power.

The present invention can thus suppress the adhesion of particles, can form a wiring film, a base film of an electrode film, and a MoNb film of a cover film having low resistance and suitable for a flat-panel image display device, and is a technique useful for manufacturing, for example, a TFT liquid crystal display or the like.

Drawings

Fig. 1 is a photograph of a sputtering surface of a target material before sputtering, which is example 1 of the present invention, observed by using a scanning electron microscope.

Fig. 2 is a photograph of a sputtering surface of a target material before sputtering, which is example 2 of the present invention, observed by using a scanning electron microscope.

Fig. 3 is a photograph of a sputtering surface of a target as a comparative example before sputtering, which was observed using a scanning electron microscope.

Fig. 4 is a photograph of a sputtering surface of the target material of inventive example 1 after sputtering, which was observed by using an optical microscope.

Fig. 5 is a photograph of a sputtering surface of the target material of inventive example 2 after sputtering, which was observed using an optical microscope.

Fig. 6 is a photograph of a sputtering surface of a target material as a comparative example after sputtering, which was observed using an optical microscope.

Detailed Description

The target material of the present invention has a thickness of 200000 μm²The number of Nb phases having a maximum length exceeding 70 μm in the sputtering surface of (2) is less than 1.0. That is, in the target of the present invention, Nb having a sputtering rate lower than Mo is present in the structure of the target in an uncrystallized state in which the maximum length is 70 μm or less. Thus, the target material of the present invention has an effect of suppressing an increase in resistivity of the obtained MoNb thin film. In addition, in the target material of the present invention, for the purpose of increasing the film deposition rate, Mo and Nb are uniformly sputtered during sputtering at high power, and therefore, the target material also has the effect of suppressing the increase in surface roughness of the sputtering surface and suppressing the generation of nodules.

For the same reason as described above, the target material of the present invention is preferably 200000 μm per target²In the sputtering surface of (2), less than 1.0 Nb phases having a maximum length exceeding 50 μm, and more preferably less than 1.0 Nb phases having a maximum length exceeding 40 μm.

Here, the maximum length and the average circle-equivalent diameter of the Nb phase according to the invention may be arbitrarily set to 200000 μm per sputtering surface of the target²In the field of view of (1), Mo and Nb phases are captured with high contrast by a scanning electron microscope, and the images are measured by using image analysis software (for example, "Scandium" manufactured by OLYMPUS SOFT IMAGING SOLUTION GMBH). In the present invention, the maximum length of the Nb phases when a plurality of Nb phases are connected is the maximum length formed by the outermost peripheries of the connected Nb phases.

In addition, the target material of the present invention is preferably 200000 μm per each Nb, from the viewpoint of finely dispersing Nb having a sputtering rate lower than Mo in the structure of the target material²OfThe average equivalent circle diameter of the Nb phase in the shot surface is 15 to 65 μm. Accordingly, the target of the present invention is preferable because Mo and Nb can be uniformly sputtered even in the case of sputtering at high power for the purpose of increasing the film deposition rate, and a MoNb thin film having a composition similar to that of the target can be obtained. For the same reason as described above, the average equivalent circle diameter of the Nb phase is more preferably 50 μm or less, and still more preferably 45 μm or less.

From the viewpoint of productivity such as adjustment of the raw material powder, the average equivalent circular diameter of the Nb phase is more preferably 20 μm or more, and still more preferably 25 μm or more.

The target material of the present invention has a composition containing 5 atomic% to 30 atomic% of Nb, and the balance of Mo and unavoidable impurities. The Nb content is limited to a range in which a MoNb film can be used as a wiring film, a base film of an electrode film, or a cover film, and a flat-panel image display device can be manufactured while maintaining characteristics such as low resistance and etching resistance to an etchant. For the same reason as described above, the content of Nb is preferably 7 at% or more, and more preferably 9 at% or more. For the same reason as described above, the content of Nb is preferably 20 at% or less, and more preferably 15 at% or less.

An example of the method for manufacturing a target according to the present invention will be described. The target material of the present invention can be obtained as follows: for example, Mo powder and Nb powder are prepared as raw material powders, the raw material powders are mixed and filled into a pressure vessel, the pressure vessel is pressure-sintered to prepare a sintered body, and the sintered body is machined and polished. Here, the Mo powder used for the raw material powder is preferably a Mo powder having an average particle diameter (cumulative particle size distribution D50, hereinafter referred to as "D50") of 2 μm to 10 μm or a mixed Mo powder obtained by mixing the Mo powder and a Mo powder having a D50 of 25 μm to 55 μm, because segregation of the Mo phase in the target material can be suppressed.

The use of Nb powder of 70 μm or less obtained by sieving Nb powder having a D50 value of 25 to 65 μm is preferable for the Nb powder used as the raw material powder because a target material having a uniform and fine structure in which no coarse Nb phase having a maximum length of more than 70 μm and no Nb phase having an average equivalent circular diameter of 15 to 65 μm is present can be obtained.

Further, assuming that sputtering is performed at a higher power for the purpose of increasing the film formation rate, it is more preferable to use a Nb powder of 45 μm or less obtained by sieving a Nb powder having a D50 of 25 μm to 65 μm in order to suppress the generation of nodules.

In order to obtain the target material of the present invention, it is preferable that the pressurizing container is heated to 400 to 500 ℃ before the raw material powder is pressure-sintered, vacuum-degassed, and sealed, since the growth of Nb grains can be suppressed at the time of pressure sintering in the next step.

The pressure sintering can be carried out, for example, by hot isostatic pressing or hot pressing, preferably at 1000 to 1500 ℃ under 80 to 160MPa for 1 to 15 hours. The selection of these conditions depends on the composition, size, pressure sintering apparatus, etc. of the target material to be obtained. For example, hot isostatic pressing is easily applicable under low-temperature and high-pressure conditions, and hot pressing is easily applicable under high-temperature and low-pressure conditions. In the present invention, hot isostatic pressing is preferably used, which enables obtaining a large target material having a long side of 2m or more.

Here, it is preferable that the sintering temperature be set to 1000 ℃ or higher because sintering is promoted and a dense target material can be obtained. Further, it is preferable to set the sintering temperature to 1500 ℃ or lower because the grain growth of Nb can be suppressed and a uniform and fine structure can be obtained.

It is preferable that the applied pressure is 80MPa or more because sintering is promoted and a dense target material can be obtained. Further, it is preferable that the applied pressure is 160MPa or less because a general-purpose pressure sintering apparatus can be used.

It is preferable to set the sintering time to 1 hour or more because sintering is promoted and a dense target material can be obtained. Further, by setting the sintering time to 15 hours or less, a dense target material in which the grain growth of Nb is suppressed can be obtained without impairing the production efficiency, and therefore, it is preferable.

Examples

Mo powder having a D50 value of 4 μm was mixed with Nb powder having a D50 value of 55 μm and a particle size of 70 μm or less in a cross-rotating mixer to prepare a mixed powder having a composition containing 10 atomic% of Nb, the balance being Mo and unavoidable impurities.

Then, the mixed powder prepared above was filled into a pressure vessel made of mild steel, and an upper lid having a degassing port was welded. Then, the pressurized container was vacuum degassed at 450 ℃ and sealed, and then subjected to hot isostatic pressing at 1250 ℃, 145MPa for 10 hours to obtain a sintered body as a raw material of the target material of invention example 1.

Mo powder having a D50 value of 4 μm was mixed with Nb powder having a D50 value of 35 μm and a particle size of 45 μm or less in a cross-rotating mixer to prepare a mixed powder having a composition containing 10 atomic% of Nb, the balance being Mo and unavoidable impurities.

Then, the mixed powder prepared above was filled into a pressure vessel made of mild steel, and an upper lid having a degassing port was welded. Then, the pressurized container was vacuum degassed at 450 ℃ and sealed, and then subjected to hot isostatic pressing at 1250 ℃, 145MPa for 10 hours to obtain a sintered body as a raw material of the target material of invention example 2.

Mo powder having a D50 value of 4 μm was mixed with Nb powder having a D50 value of 115 μm in a cross-rotating mixer to prepare a mixed powder having a composition containing 10 atomic% of Nb, and the balance of Mo and inevitable impurities.

Then, the mixed powder prepared above was filled into a pressure vessel made of mild steel, and an upper lid having a degassing port was welded. Then, the pressurized container was vacuum degassed at 450 ℃ and sealed, and then subjected to hot isostatic pressing at 1250 ℃, 145MPa for 10 hours to obtain a sintered body as a raw material of the target of the comparative example.

Each of the sintered bodies obtained above was subjected to machining and polishing to prepare targets having a diameter of 180 mm. times.5 mm in thickness.

The reflection electron image of the sputtering surface of each target obtained as described above by a scanning electron microscope was analyzed to find a cross direction of 591 μm × and a longitudinal direction of 435 μm (area: 257085 μm)²) In the field of view of (2), 3 of the above-mentioned samples were observed to have a size of 200000 μm²Visual field observation of visual field, the maximum length of each Nb phase present in each visual field was measured, and the number of Nb phases having a maximum length exceeding 70 μm was measured. Further, the circle equivalent diameter of the Nb phase present in each field was measured, and the average circle equivalent diameter of 3 fields was calculated.

Here, the measurement was performed by taking a high-contrast image of the Mo phase and the Nb phase with a scanning electron microscope, and using image analysis software (Scandium) manufactured by OLYMPUS SOFT IMAGING methods GMBH for the image. The results are shown in table 1.

Fig. 1 to 3 show the results of observation of the sputtering surface of each target before sputtering by a scanning electron microscope.

For each target, a MoNb film having a thickness of 300nm was formed on a glass substrate under Ar atmosphere at a pressure of 0.5Pa and a power of 500W using a DC magnetron sputtering apparatus (model: C3010) manufactured by Canon ANELVA, to obtain 3 samples for measuring resistivity. The resistivity was measured using a 4-terminal thin film resistivity measuring instrument (MCP-T400) manufactured by Dia Instruments, Inc. The results are shown in table 1.

Each target was sputtered under Ar atmosphere, pressure 0.5Pa, power 1000W, and sputtering time 30 minutes using a DC magnetron sputtering apparatus (model C3010) manufactured by Canon ANELVA.

Further, the surface roughness of the sputtering surface before and after sputtering was measured for each target. Surface roughness was measured using a compact surface roughness measuring instrument (SU-210) manufactured by Mitutoyo corporation, JIS B0601: 2001, the arithmetic average roughness (Ra) as defined in. The results are shown in table 1.

Fig. 4 to 6 show the results of observation of the sputtering surface of each target after sputtering by an optical microscope.

[ Table 1]

As shown in fig. 1 and 2, it is understood that the Mo phase 1 as a base of the target material of the present invention has the fine Nb phase 2 dispersed therein. In addition, the average equivalent circle diameter of the Nb phase in the target material of the invention is 30 to 49 μm in all the visual fields. Also, 1 Nb phase having a maximum length of more than 70 μm was not observed, and the average number of 3 fields was less than 1.0.

In addition, it was confirmed that the maximum length of the Nb phase in the confirmed 3 fields was only 68 μm even at the maximum value.

As shown in fig. 4 and 5, it was confirmed that the target of the present invention has an arithmetic mean roughness Ra of less than 2.00 μm after sputtering, and is useful for the generation of nodules due to the continuous sputtering with high power, that is, the problem of particle adhesion on the wiring film, the base film of the electrode film, and the coating film.

Further, it was confirmed that the MoNb thin film formed using the target material of the present invention has a resistivity of 15.2 μ Ω · cm or less, and is a thin film having low resistance and useful as a wiring thin film, a base film of an electrode thin film, and a coating film.

As shown in fig. 3, it is found that coarse Nb phases 2 are dispersed in the Mo phase 1 as the base of the target material of the comparative example. In the target of the comparative example, the average circle-equivalent diameter of the Nb phase exceeded 65 μm in all the visual fields. Further, it was confirmed that the maximum length of Nb phases exceeding 70 μm was 2 or more, and the average number of 3 visual fields was 4.3. In addition, for the target material of the comparative example, the maximum length of the Nb phase reached 117 μm in the confirmed 3 fields.

As shown in fig. 6, it was confirmed that the arithmetic mean roughness Ra of the target material of the comparative example after sputtering exceeded 2.20 μm, and nodules were likely to be generated by the high-power continuous sputtering.

Further, it was confirmed that the resistivity of the MoNb thin film formed using the target material of the comparative example exceeds 15.5 μ Ω · cm, and the MoNb thin film has high resistance as a base film or a coating film of a wiring thin film or an electrode thin film, and is not suitable.

Description of the reference numerals

1 Mo phase

2 Nb phase

Claims

1. A MoNb target material having a composition containing 5 to 30 atomic% of Nb, the balance being Mo and unavoidable impurities, and having a particle size of 200000 [ mu ] m²The sputtering surface of (2) has less than 1.0 Nb phases having a maximum length exceeding 70 μm, and the average circle-equivalent diameter of the Nb phases is 25 to 65 μm.