JP5988140B2 - Manufacturing method of MoTi target material and MoTi target material - Google Patents

Description

  The present invention relates to a method for producing a MoTi target material used in a physical vapor deposition technique such as sputtering and a MoTi target material.

  In recent years, pure metal films such as low resistance Al, Cu, Ag, Au, etc. or alloy films mainly composed of them are used for thin film electrodes and thin film wirings of thin film transistor type liquid crystal displays which are a kind of flat display devices. It is like that. However, in general, these thin films have problems such as inferior heat resistance, corrosion resistance, and adhesion required for electrodes and wiring, and problems such as formation of diffusion layers with other elements and loss of necessary electrical characteristics. is there.

  Therefore, in order to solve these problems, Mo or Mo alloy, which is a refractory metal, has been used as a base film or cover film for a substrate. In particular, MoTi has been proposed as a base film or a cover film for wiring and electrode films such as Al and Cu-based materials. For a target material for forming a MoTi film, for example, a mixed powder of Mo and Ti described in Patent Document 1 is used. It has been proposed to use a MoTi target material that is solidified and then pressure sintered.

Special table 2009-513823

In the manufacturing method of the MoTi target material disclosed in the example of Patent Document 1, since Mo powder having a large particle size of under 100 mesh is used, the dispersibility of Mo in the MoTi target material may deteriorate. .
Moreover, even if it uses the fine Mo powder with the average particle diameter of 20 micrometers or less which reduced the oxidation Mo generally marketed as it is, the dispersibility of Mo in a MoTi target material may worsen by sintering.
When sputtering is performed using a MoTi target material having poor Mo dispersibility as described above, the homogeneity of the formed MoTi film is lost due to generation of particles or the like, and the resistance value required for electrodes and wiring is low. Unsatisfactory problems and problems of poor adhesion may occur.

  In view of the above problems, an object of the present invention is to provide a MoTi target material having a uniform and fine structure with good Mo dispersibility and a method for producing the same.

The present inventor has found that, in the method for producing a MoTi target material, the Mo powder to be used is optimized, thereby improving the dispersibility of Mo and obtaining a MoTi target material having a uniform and fine structure. The invention has been reached. That is, the present invention
(1) a step of pulverizing the Mo aggregate in which Mo primary particles are aggregated to an average particle size of 10 μm or less to produce Mo powder;
(2) A step of mixing the Mo powder and a Ti powder having an average particle size of 50 μm or less to produce a mixed powder;
(3) A step of pressure-sintering the mixed powder to produce a MoTi sintered body.
Moreover, in this invention, it is preferable that the hydrogen content of the said Ti powder shall be 50 mass ppm or less.
Moreover, in this invention, it is preferable that the hydrogen content of the said Ti powder shall be 50 mass ppm or less by the hydrodehydrogenation method.
Moreover, the manufacturing method of the MoTi target material of this invention is suitable for manufacture of the MoTi target material which contained 20-80 atomic% of Ti.
The pressure sintering in the present invention is preferably performed at a sintering temperature of 800 to 1500 ° C. and a pressure of 10 to 200 MPa for 1 to 10 hours.

The MoTi target material of the present invention has a composition comprising 20 to 80 atomic% of Ti and the balance of Mo and unavoidable impurities, hydrogen as an unavoidable impurity is limited to 150 mass ppm or less, and MoTi in a cross-sectional microstructure The alloy phase preferably has an inscribed circle diameter of 50 μm or less, and is obtained by dividing the bulk density measured by the Archimedes method by the theoretical density obtained as a weighted average calculated by the mass ratio obtained from the composition ratio of Mo and Ti. The value of the relative density obtained by multiplying 100 by 100 is 99.5% or more.
Moreover, it is preferable that hydrogen, which is an inevitable impurity, is limited to 50 mass ppm or less.

  According to the present invention, since a MoTi target material manufacturing method and a MoTi target material having a uniform fine structure with good Mo dispersibility can be provided, the industrial value thereof is extremely high.

It is the optical microscope photograph which observed the cross section of the target material of the sample 1 used as the example of this invention. It is the optical microscope photograph which observed the cross section of the target material of the sample 2 used as the example of the present invention. It is the optical microscope photograph which observed the cross section of the target material of the sample 3 used as a comparative example. It is the scanning electron micrograph which observed the cross section of the target material of the sample 4 used as the example of this invention.

  The greatest feature of the present invention is that, in order to obtain a MoTi target material having a uniform and fine structure with good Mo dispersibility, Mo powder obtained by pulverizing Mo agglomerates of Mo primary particles is employed. is there. The features of the present invention will be described in detail below.

As described above, the present inventor used a commercially available fine Mo powder having an average particle diameter of 20 μm or less as it is, but agglomerated as if Mo primary particles were connected in a network by sintering. Since it became a form, it confirmed that the dispersibility of Mo in a MoTi target material was not favorable. When sputtering is performed using a MoTi target material having such poor Mo dispersibility, the homogeneity of the formed MoTi film is lost due to generation of particles and the like, and the resistance value required as an electrode or wiring is reduced. Unsatisfactory problems and problems of poor adhesion may occur.
Therefore, the present inventor has found a production method having the following steps in order to obtain a uniform and fine structure with good Mo dispersibility in producing the MoTi target material.

(1) Step of producing Mo powder by pulverizing Mo aggregates composed of Mo primary particles to an average particle size of 10 μm or less In the present invention, a porous structure in which Mo primary particles having a particle size of about 5 μm are connected in a network shape. The Mo agglomerates are crushed to a mean particle size of 10 μm or less by a jet mill, impact mill or the like. Thereby, this invention can improve the dispersibility of Mo, when it mixes with Ti powder. Here, when the average particle diameter of the Mo powder after pulverization is larger than 10 μm, the coarse Mo aggregate is included in the target, so that the sintering may not be sufficiently performed and the relative density may be reduced. The dispersibility of Mo is inhibited. For this reason, this invention needs to crush Mo aggregate until an average particle diameter becomes 10 micrometers or less. At this time, as the Mo powder used in the present invention, a powder having an average particle size of 0.1 μm or more can be used as a minimum particle size that can be actually obtained.

(2) Step of mixing the Mo powder and Ti powder having an average particle size of 50 μm or less to produce a mixed powder Next, the crushed Mo powder and Ti powder having an average particle size of 50 μm or less are mixed into a V-type mixer. By mixing with a cross rotary mixer, a ball mill or the like, a uniform mixed powder can be obtained. Here, the reason why the average particle size of the Ti powder is set to 50 μm or less is that when the average particle size of the Ti powder is larger than 50 μm, a uniform fine structure cannot be obtained in the MoTi sintered body. At this time, as the Ti powder used in the present invention, a powder having an average particle size of 0.1 μm or more can be used as the minimum particle size that can be actually obtained. Moreover, in this invention, if it is the size of the range mentioned above, commercially available Ti powder can be used.
Further, the Ti content is desirably 20 to 80 atomic%. This is because if the amount is less than 20 atomic%, the effect of improving the corrosion resistance of the formed film is low, and if it exceeds 80 atomic%, the etching property of the film is lowered.

(3) Step of pressure-sintering the mixed powder to produce a MoTi sintered body In the present invention, MoTi is sintered by pressure sintering. The pressure sintering can be performed by hot isostatic pressing or hot pressing, and is preferably performed at a sintering temperature of 800 to 1500 ° C. and a pressure of 10 to 200 MPa for 1 to 10 hours.
The selection of these conditions depends on the pressure sintering equipment. For example, hot isostatic pressing is easy to apply low temperature and high pressure conditions, and hot pressing is easy to apply high temperature and low pressure conditions. In the present invention, it is preferable to use a low temperature and high pressure hot isostatic press in order to suppress the reaction between the pressurized container and the Ti powder at a high temperature in the pressure sintering.
Note that if the sintering temperature is less than 800 ° C., it is difficult to proceed with sintering, and if it exceeds 1500 ° C., the apparatus that can withstand is limited, the crystal growth of the sintered body becomes remarkable, and a uniform fine structure is formed. This is because it becomes difficult to obtain.
Further, if the pressure is 10 MPa or less, sintering is difficult to proceed and it is not practical, and if it exceeds 200 MPa, there is a problem that an apparatus that can endure is limited.
Further, if the sintering time is 1 hour or less, it is difficult to sufficiently advance the sintering, and if it exceeds 10 hours, it is better to avoid the production efficiency.

  In addition, when performing pressure sintering by hot isostatic pressing or hot pressing, it is desirable to deaerate under reduced pressure while heating after filling the mixed powder into a pressure vessel or a pressure die. The vacuum degassing is desirably performed under a reduced pressure lower than the atmospheric pressure (101.3 kPa) in the heating temperature range of 100 to 600 ° C. This is because oxygen in the obtained sintered body can be further reduced.

Hydrogen, which is an inevitable impurity contained in the MoTi target material of the present invention, needs to be limited to 150 ppm by mass or less. This is because when the hydrogen content is higher than 150 mass ppm, the hydrogen released from the MoTi target material during sputtering may cause an increase in stress and an increase in specific resistance of the formed MoTi film. . Here, there is a concern that the increase in the film stress may lead to problems such as film peeling in the next process such as etching and cleaning. Further, when it is used as a base film or a cover film of an electrode, it is preferable that the resistance is low as in the case of the electrode. Therefore, hydrogen contained in the MoTi target material of the present invention is limited to 150 ppm by mass or less. Moreover, in this invention, it is preferable to restrict | limit hydrogen contained in a MoTi target material to 50 mass ppm or less.
In order to limit the hydrogen in the MoTi target material of the present invention to 150 ppm by mass or less, for example, it is possible to use Ti powder having a low hydrogen content. As a method for obtaining Ti powder having a low hydrogen content in the present invention, for example, the hydrogen content is suppressed to 150 mass ppm or less by producing by an atomizing method or by dehydrogenating the Ti powder under high temperature and high vacuum. be able to. In the present invention, in order to further reduce the hydrogen content of the Ti powder, it is preferable to treat by a hydrodehydrogenation method. Thereby, the amount of hydrogen in the MoTi target material can be suppressed to 150 mass ppm or less.

In the MoTi target material of the present invention, the inscribed circle diameter of the MoTi alloy phase in the cross-sectional microstructure is 50 μm or less. This is because when the inscribed circle diameter is larger than 50 μm, there is a variation in hardness inside the target material, which may cause cracks and chipping during surface grinding in the MoTi target material manufacturing process. It is. In addition, the uniformity of the formed MoTi film is lost due to the generation of particles during sputtering, which may cause problems that the resistance value required for electrodes and wiring cannot be satisfied, and that the adhesion decreases. It is because there is sex. The preferred lower limit of the inscribed circle diameter is 0.1 μm.
The inscribed circle diameter referred to in the present invention is the longest diameter inscribed in the maximum MoTi alloy phase not including a pure Mo phase in an arbitrary field of view. In addition, the MoTi alloy phase of the MoTi target material of the present invention may include a pure Ti phase.

The relative density of the MoTi target material of the present invention is preferably 99.5% or more. When the relative density of the target material is lowered, voids present in the target material increase, and nodules that cause abnormal discharge are likely to occur during the sputtering process with the void as a base point. In particular, if the relative density is less than 99.5%, there is a case where the probability that nodules are generated may increase. Therefore, the relative density is more preferably 100% or more.
The relative density in the present invention is calculated by multiplying the value obtained by dividing the bulk density measured by the Archimedes method by the theoretical density by 100. The theoretical density of the MoTi alloy is calculated on the assumption that it consists only of Mo and Ti that do not include an alloy phase. Specifically, as the densities of Mo and Ti, the weights calculated by the mass ratio obtained from the composition ratio using values of 10.22 × 10 ³ kg / m ³ and 4.50 × 10 ³ kg / m ³ respectively. The value obtained as the average was used as the theoretical density value. In the present invention, since the density of the MoTi alloy is higher than that in which the Mo phase and the Ti phase are independent, it is more preferable that the relative density exceeds 100%.

Examples of the present invention will be described below.
First, as Inventive Example 1 (Sample No. 1) and Inventive Example 2 (Sample No. 2), Mo aggregates in which Mo primary particles having a particle size of 5 μm are aggregated are crushed by a jet mill and average particle size is obtained. 8 μm of pulverized Mo powder was obtained. Subsequently, the obtained pulverized Mo powder and the hydrodehydrogenated Ti raw material powder having an average particle diameter of 25 μm were mixed with a cross rotary mixer so that the atomic percentage was 50% Mo-50% Ti. Then, after filling the pressurized vessel made of mild steel, an upper lid having a deaeration port was welded to the pressurized vessel. Subsequently, vacuum deaeration was performed at a temperature of 450 ° C., and a MoTi sintered body was obtained by hot isostatic pressing that was held for 5 hours under conditions of a temperature of 1000 ° C. and a pressure of 118 MPa.
Further, as a comparative example (sample No. 3), the Mo aggregate in which Mo primary particles having a particle size of 5 μm were aggregated was crushed to a mean particle size of 500 μm after being consolidated by cold isostatic pressing. Thus, Mo powder was obtained. This Mo powder and hydrodehydrogenated Ti raw material powder with an average particle size of 25 μm are mixed with a cross rotary mixer so as to be 50% Mo-50% Ti in atomic% and filled into a pressure vessel made of mild steel. After that, an upper lid having a deaeration port was welded to the pressurized container. Subsequently, vacuum deaeration was performed at a temperature of 450 ° C., and a MoTi sintered body was obtained by hot isostatic pressing that was held for 5 hours under conditions of a temperature of 1000 ° C. and a pressure of 118 MPa.

The test piece was extract | collected by machining from each MoTi sintered compact obtained above, and the result of having observed the microstructure of a cross section with the optical microscope is shown in FIGS. The maximum inscribed circle diameter of the MoTi alloy phase shown in the white part of FIGS. 1 and 2 as an example of the present invention is 50 μm or less, and the MoTi target has a fine structure in which Mo shown in the gray part is uniformly dispersed. It was confirmed that the material was obtained.
On the other hand, it was confirmed that the maximum inscribed circle diameter of the MoTi alloy phase shown by the white part in FIG. 3 as a comparative example is a coarse alloy phase exceeding 50 μm.

From each MoTi sintered body obtained above, a sputtering target material having a diameter of 164 mm and a thickness of 5 mm was cut out by machining and brazed to a copper backing plate. Thereafter, each sputtering target material obtained above was attached to a sputtering apparatus (manufactured by Canon Anelva Co., Ltd., model number: C-3010), and a MoTi film having a thickness of 300 nm was formed on the glass substrate. The sputtering discharge conditions at this time were an argon gas atmosphere with a pressure of 0.5 Pa and an input power of 1000 W.
The stress and specific resistance of the MoTi thin film obtained above were measured using a four-terminal thin film resistivity meter (manufactured by Dia Instruments Co., Ltd., model number: MCP-T400). The film stress was measured by forming a 300 nm MoTi thin film on a Si wafer and measuring the warpage using a laser displacement meter (manufactured by Hamamatsu Photonics, model number: PM-3). The results are shown in Table 1.
From this result, it can be seen that the lower the hydrogen content of the MoTi sintered body, the smaller the stress and the specific resistance of the MoTi film formed by sputtering, and the higher performance MoTi film was obtained.

Sample No. prepared above 1 to Sample No. 3 is placed in the chamber of a DC magnetron sputtering apparatus (manufactured by Canon Anelva Co., Ltd., model number: C3010), and the pressure inside the chamber is reduced to 2 × 10 ⁻⁵ Pa or less, and then the Ar gas pressure is 0. The discharge test was conducted for 120 seconds under the conditions of .6 Pa and input power of 800 W. At this time, changes in applied voltage every 0.1 seconds are recorded, and the absolute value of the applied voltage difference is used as a statistical management standard for monitoring abnormal values. The median (average value) is three times the standard deviation. The number of times that became equal to or greater than the value obtained by adding was measured as the number of times abnormal discharge occurred.
Since there is a strong positive correlation between the amount of particles generated from the target material and the number of abnormal discharges, it is possible to evaluate the number of particles generated during sputtering by measuring the number of abnormal discharges. is there. The number of abnormal discharges was measured by the above method. Table 1 shows the results of the abnormal discharge occurrence ratio obtained with reference to Comparative Example 1 (100%).

  As shown in Table 1, when sputtering was performed using the MoTi target material of the present invention, Sample No. as a comparative example. It was confirmed that the abnormal discharge generation ratio of 3 could be reduced. Moreover, by manufacturing within the range of the conditions of the present invention, the inscribed circle diameter of the MoTi alloy phase can be reduced, the dispersibility of Mo can be improved, and as a result, the generation of particles during sputtering can be reduced. The effectiveness of the present invention was confirmed.

  Next, as Invention Example 3 (sample No. 4), the hydrogen content of the Ti powder was changed by a hydrodehydrogenation method to prepare a MoTi sintered body. These production conditions were the same as those of Example 1 of the present invention except that the hydrogen content of the Ti powder to be mixed was different.

  A test piece was collected from the MoTi sintered body obtained above by machining, and the result of observation of the cross-sectional microstructure with a scanning electron microscope is shown in FIG. The maximum inscribed circle diameter of the MoTi alloy phase shown by the gray part in FIG. 4 is 50 μm or less, and it was confirmed that a MoTi target material having a fine structure in which Mo shown by the white part was uniformly dispersed was obtained. did it.

  Next, as Invention Example 4 (Sample No. 5) and Invention Example 5 (Sample No. 6), MoTi sintered bodies were produced when the hydrogen content of the Ti powder was changed by the hydrodehydrogenation method. . These production conditions were different from those of Invention Example 1 except that the hydrogen content of the Ti powder to be mixed was different, and the others were produced under the same conditions.

The hydrogen content of each MoTi sintered body obtained above, the relative density, the maximum inscribed circle diameter of the MoTi alloy phase, and the stress and specific resistance of the formed MoTi film were measured by the same method as in Example 1. The results are shown in Table 2.
From this result, it can be seen that the lower the hydrogen content of the MoTi sintered body, the smaller the stress and specific resistance of the MoTi film formed by sputtering, and the higher performance MoTi film was obtained.

From the above, according to the production method of the present invention, it was confirmed that a MoTi target material having a uniform and fine structure can be obtained by using Mo powder obtained by pulverizing Mo aggregates.
Moreover, in the MoTi target material of this invention, it has confirmed that the stress and specific resistance of a film | membrane could be made lower by making hydrogen content 50 mass ppm or less.

Claims (2)

(1) a step of pulverizing the Mo aggregate in which Mo primary particles are aggregated to an average particle size of 10 μm or less to produce Mo powder;
(2) Mixing the Mo powder and Ti powder having a hydrogen content of 50 mass ppm or less by a hydrodehydrogenation method having an average particle size of 50 μm or less so that the Ti content is 20 to 80 atomic%. Producing a mixed powder;
(3) pressure-sintering the mixed powder to produce a MoTi sintered body;
The manufacturing method of the MoTi target material characterized by having. It has a composition comprising 20 to 80 atomic% of Ti and the balance Mo and unavoidable impurities, hydrogen as an unavoidable impurity is limited to 50 mass ppm or less, and the inscribed circle diameter of the MoTi alloy phase in the cross-sectional microstructure is Relative density value obtained by multiplying by 100 the value obtained by dividing the bulk density measured by the Archimedes method by a weighted average calculated by the mass ratio obtained from the composition ratio of Mo and Ti. Is 99.5% or more, MoTi target material characterized by the above-mentioned.