TWI605131B - Sputter target material - Google Patents

Description

Sputtering target material

The present invention relates to a material for a sputtering target, and more particularly to a material for a sputtering target containing molybdenum.

In the prior art, the material for the sputtering target is disclosed in, for example, JP-A-2000-45066 (Patent Document 1), JP-A-2007-113033 (Patent Document 2), JP-A-2013-32597 (Patent Document 3), and Japanese Patent Publication No. 4,945,037 (Patent Document 4), JP-A-2000-234167 (Patent Document 5), JP-A-2013-154403 (Patent Document 6), and JP-A-2010-535943 (Patent Document 7) Japanese Patent Publication No. 2014-12893 (Patent Document 8).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2000-45066

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2007-113033

[Patent Document 3] Japanese Patent Laid-Open Publication No. 2013-32597

[Patent Document 4] Japanese Patent No. 4945037

[Patent Document 5] Japanese Patent Laid-Open Publication No. 2000-234167

[Patent Document 6] Japanese Laid-Open Patent Publication No. 2013-154403

[Patent Document 7] Japanese Patent Publication No. 2010-535943

[Patent Document 8] Japanese Patent Laid-Open Publication No. 2014-12893

Patent Document 1 discloses a molybdenum-based target which generates less abnormal discharge and fine particles. Further, it is disclosed that a molybdenum-based target which generates fine particles even if the crystal grains are made fine.

Patent Document 2 discloses that plastic working is performed after pressure-sintering of molybdenum. The relative strength of the (110) plane is disclosed to cause pressure sintering of the Mo powder, increase in relative density, and improvement in mechanical properties.

Patent Document 3 discloses a sputtering target using Al, Cu, Ti, Ni, Cr, Co, and Ta in a cold spray method.

In Patent Document 4, a target of tungsten is disclosed.

Patent Document 5 discloses a target of molybdenum. It is revealed that the recrystallized tissue is generated to suppress the occurrence of arcing.

Patent Document 6 discloses that a sputtering target is produced by oblique rolling. The ratio of the average unit volume of the bcc metal in the 15° of the <b>//ND of the bcc metal is greater than 20.4%, and the inclined rolling is necessary.

Patent Documents 7 and 8 disclose a sputtering target which is improved in the uniformity of the thickness of the bcc metal to 100 and 111 structures.

Patent Documents 6 to 8 disclose a bcc metal, and disclose processing for a high melting point metal by a tilting method of a special processing method for obtaining uniformity of a structure. This oblique rolling method can be applied to a metal having good workability. These patent documents also describe Ta and Nb which are excellent in workability as a bcc metal, but there are no W and Mo systems which are particularly poor in workability because of high melting point metals. Said. Actually, when the oblique rolling method is applied to W and Mo, laminar cracks are generated due to a small allowable strain and processing is impossible.

Regarding the adjustment of the sputtering speed, none of the prior art has revealed or inspired at all.

It is an object of the present invention to provide a material for a sputtering target capable of adjusting a sputtering rate.

In the material for a sputtering target according to another aspect of the invention, the aspect ratio of the crystal structure of the surface to be sputtered is 3 or more.

It is possible to provide a material for a sputtering target capable of adjusting a sputtering speed.

Fig. 1 is a view showing an enlarged view of a TD plane which will be produced in accordance with the embodiment (Condition A).

Fig. 2 is a view showing an enlarged TD plane prepared in accordance with the comparative example (Condition B).

Fig. 3 is a graph showing the results of XRD in a molybdenum powder (Fsss Fisher method: particle size 5 μm).

[Description of Embodiments of the Present Invention]

First, an embodiment of the present invention will be described.

A sputtering target material according to an aspect of the present invention, which is sputtered The aspect ratio of the crystal structure is 3 or more.

The molybdenum plate-shaped target of the body-centered cubic lattice structure that has existed so far cannot control the sputtering speed. Because of the ability to control the crystal structure, it is possible to obtain a molybdenum target with less target consumption. The target lifetime can be increased by less consumption due to sputtering. Moreover, in recent years, the demand for thin film formation has also improved the film thickness controllability. That is, it is also suitable for applications other than the case where the sputtering speed must be high.

As far as the previous method is concerned, the azimuth control such as the sintered body target and the heat treatment target is not performed, but a technique in which the random orientation is used to accelerate the sputtering speed is set. Further, the sputtering speed can be reduced by a certain degree of tissue control. However, in the present invention, a material having a low sputtering rate is provided by controlling the residual strain of the processing.

This is because the barrier metal for preventing the diffusion of the Al wiring as a main use has recently been able to exhibit a sufficient effect by using a thin barrier layer. In response to the demand for thin film formation, it is possible to improve film thickness controllability and uniformity by lowering the sputtering rate.

By setting the aspect ratio of the crystal structure of the surface to be sputtered to 3 or more, the sputtering rate can be made 400 nm/h or less, whereby a sputtering target having a long target life can be obtained.

Preferably, the material for the sputtering target contains molybdenum. Preferably, the material for the sputtering target is composed of molybdenum.

When the aspect ratio of the TD surface (the cross section of the sheet parallel to the rolling direction) which is the surface to be sputtered is preferably 3 or more, the sputtering rate is 400 nm/h or less. Moreover, the average particle diameter in the thickness direction at this time is 50 μm or less.

Preferably, the surface to be sputtered has a Vickers hardness of Hv200 or more. hard When the degree is Hv200 or more, the sputtering rate is 400 nm/h or less.

Preferably, the sputtering target material is produced by sintering molybdenum powder, and the purity of the molybdenum powder is 4N (99.99% by mass) or more.

[Details of Embodiments of the Present Invention]

Embodiments of the present invention will be described below with reference to the drawings. The present invention is not intended to be limited by the scope of the invention, and is intended to include all modifications within the scope and scope of the invention.

(Example)

(1) Manufacturing method

The powder was made into a molybdenum powder having a particle diameter of 1 to 20 μm as measured by the Fsss Fisher method, and the powder was subjected to hydrostatic pressure under a pressure of 150 to 300 MPa using a rubber bag. Subsequently, the press-molded body was sintered in a hydrogen gas stream at a temperature of 1500 ° C or higher to obtain a molybdenum sintered body (specific gravity: 9.7 g/cm ³ ).

The hot rolling process of the sintered body was carried out in accordance with the following procedure using a two-stage rolling mill. One-time hot rolling was performed at a reduction ratio of 76% so that the thickness of the sheet after rolling was 24 mm. In order to prevent coarsening of molybdenum crystal grains due to high-temperature heating in hot rolling, the in-furnace heating temperature of the initial hot rolling is controlled to 1400 ° C or lower.

Next, the rolled sheet after the initial hot rolling of the cutting machine is divided into two portions, one portion is used as a rolled sheet for carrying out the rolling schedule of the embodiment (condition A), and the other portion is used for carrying out the usual The rolled sheet (condition B) of the comparative example of the rolling schedule was subjected to hot rolling.

For condition A, after the rolled sheet is made uniform temperature in a hydrogen environment heating furnace at a temperature of 900-1150 ° C, the total reduction ratio of 4 passes is 37.5%. A rolled sheet of the example having a thickness of 15 mm was obtained.

With respect to the condition B, the rolled sheet was brought to a uniform temperature in a hydrogen environment heating furnace at a temperature of 1150 to 1300 ° C, and a rolled sheet of a comparative example having a thickness of 15 mm was obtained at a total rolling reduction ratio of 37.5%. Both conditions A and B were 37.5% of the hot rolling in the second half, and the total rolling reduction from the sintered body was 85%, and the relative density was 99.9%.

It is considered that the condition A has a large amount of residual strain, and there is a high possibility that cracks are generated in the cutting step for taking the sample. Therefore, strain-reduction annealing is performed for 15 minutes in a hydrogen heating furnace at a temperature of 600 to 1000 ° C without causing recrystallization. The condition B is heat treated at 1000-1300 ° C for 60-120 minutes.

(2) Organizational observation

Fig. 1 is a view showing an enlarged view of a TD plane prepared in accordance with an embodiment (Condition A). The metal structure of the TD plane of Condition A of the example is shown in Fig. 1. The dimension in the direction parallel to the rolling direction (X direction; length direction) is about 80 μm to 300 μm, and the dimension in the vertical direction (Y direction; thickness direction) is about 30 μm to 100 μm so-called as-rolled (for example, after rolling) State of the fibrous tissue.

Fig. 2 is a view showing an enlarged view of the TD plane prepared in accordance with the comparative example (Condition B). The condition B of the comparative example after the heat treatment which is usually performed is a dimension in the direction parallel to the rolling direction (X direction; length direction) of about 100 μm to 150 μm, and a direction perpendicular to the direction (Y direction; thickness direction). The size is approximately 50 μm to 100 μm, which is close to the equiaxed structure (Fig. 2).

(3) Relationship between aspect ratio and sputtering speed

Investigation of samples prepared using Condition A of the examples and use of comparative examples The relationship between the aspect ratio of the sample prepared in Condition B and the sputtering rate.

(3-1) Definition

The size of the fibrous structure and the equiaxed structure is calculated by an intercept method. Specifically, the long side of the tissue was set to the lateral direction, and the tissue was observed at a magnification of 100 to 200 times using an optical microscope. Calculate the number of points where the horizontal and vertical lines of the organization cross-cut and slit the crystal grain boundaries. The value obtained by dividing the length of the horizontal line by the number of cross-cut points is set as the long diameter of the crystal grain. The value obtained by dividing the length of the vertical line by the number of slitting points is set as a short diameter. The aspect ratio is a value obtained by dividing the long diameter of the crystal grain by the short diameter.

(3-2) Manufacturing of sputtering target test body

The sputtering target test bodies of diameter ψ 75 mm × thickness T2 mm used for sputtering speed evaluation were prepared in accordance with the following procedures. Two samples prepared using Condition A of the Example and Condition B of the Comparative Example were used as a material plate. The surfaces of the material sheets (thickness T = 15 mm) were each ground to a thickness of 6 mm using a flat grinding disc to have a thickness of 3 mm, and then processed into a circular plate having a diameter of mm75 mm and a thickness of T3 mm using a discharge wire processing machine. The disk having a diameter of 75 mm was rotated by a rotary mill and the both surfaces were ground using SiC abrasive stone to be finished into a sputtering target test body having a thickness of 2 mm. At this time, the sputtering target test surface precision system became Ra3 μm or less to unify the sputtering conditions.

(3-3) Sputtering conditions

The sputtering rate of the sputtering target test body prepared using the condition A of the example and the condition B of the comparative example was compared using a small sputtering apparatus (type SH-250-T4) manufactured by Ulvac Co., Ltd. After the vacuum was applied to the inside of the apparatus to be 5 × 10 ^-5 Pa or less, the argon gas flow was 0.06 MPa, 6.0 sccm (at a flow rate of 0 ° C, 1013 hPa, 6.0 dm ³ per minute), and the output was 100 W and 400 V. Sputter for 60 minutes. In order to remove the edge effect, a central portion of about 60 mm was sputtered, and a glass preparation was attached to the opposite cathode side, and the thickness of the film sputtered on the specimen was determined to confirm the sputtering rate.

(3-4) Determination of sputtered film thickness

The thickness of the sputtered film was measured using a surface shape measuring device (PGII200, manufactured by Taylor Hobson Co., Ltd.) under the conditions of a full size of 12.5 mm, a data length of 4.8 mm, a walking distance of 0.3 mm, and a measurement speed of 1 mm/s. Specify LS LINE, PRIMARY and proceed).

(3-5) Evaluation

The result of the sputtering was evaluated in a region of ±20% from the center of the sheet thickness so as to be the average information of the sputtering.

In the samples 1 to 3 in Table 1, the condition A was used, and the sample 4 was the value of the sputtering rate of the rolled sheet (sputter target test body) prepared using the condition B. As shown in Table 1, when the aspect ratio of the crystal grains of the crystal structure is 3 or more, the sputtering rate is 400 nm/h or less. Further, as the aspect ratio becomes larger, the sputtering speed becomes lower. That is, it is inspired that as the fiber structure becomes stronger, the sputtering speed becomes lower.

Moreover, in this case, when the sputtering speed is greater than 400 nm/h, When the time is 10000 h, the consumption is 4 mm or more, and at 20000 h, the consumption is 8 mm or more, and the sputtering target exchange frequency is increased.

(4) Vickers hardness and sputtering speed

Samples were prepared in accordance with conditions A and B. Strain annealing was performed on the samples as the final heat treatment. Specifically, a sample obtained by keeping the temperature of the sample constant at 800 ° C and changing the hardness by adjusting the length of the annealing time while maintaining the alignment substantially constant was prepared.

The Vickers hardness of each sample was measured using a load of 10 kg. The sputtering rate of each sample was investigated using the method described in "(3) Relationship between aspect ratio and sputtering speed". The results are shown in Table 2.

Sample Nos. 11 and 12 were prepared using Condition A, and Sample 13 was prepared using Condition B. It is known that the residual amount of the strain is also related to the sputtering speed, and the higher the hardness, the lower the sputtering rate can be suppressed.

(5) Surface orientation (222) / (200) and sputtering speed

The relationship between the crystal orientation based on the plane orientation (222)/(200) and the sputtering rate was confirmed.

Rolled sheets were produced using two types of conditions A and B. A sample of about 15 mm × □ 10 mm for the purpose of investigating crystal alignment was taken from each of the rolled sheets.

The crystal alignment test (XRD) was carried out using a PANalytical X-ray diffraction apparatus manufactured by Spectris Co., Ltd., and a ceramic X-ray tube LFF Cu according to the Empyrean system. The crystal alignment was measured by a semiconductor detector using an X-ray lens (0.3°), a flat plate collimator (0.27°), and at 40 kV, 45 mA. The sectioning conditions were set to divergent sections of 1/2° and scattering by 1°. Further, as long as there is no particular case, the XRD measurement angle is 35° to 135°, and the scanning speed (Time per step) is performed at 10.2 seconds. The evaluation of the measurement results was compared with the standard data by ICDD DATABASE PDF2.

The sputtering rate of each sample was investigated using the method described in "(3) Relationship between aspect ratio and sputtering speed".

The results of XRD and sputtering were evaluated in a region of ±20% from the center of the sheet thickness so as to be the average information of sputtering. The results are shown in Table 3.

Sample Nos. 21 to 24 were prepared using Condition A, and Sample Nos. 25 and 26 were prepared using Condition B. The ratio of the reflection intensities at the respective diffraction surfaces was set as the crystal orientation index. When the relationship between the intensity ratio of (222)/(200) and the sputtering rate was investigated, as the intensity ratio became higher, the sputtering rate tends to be smaller (Table 3). Further, this tendency is different between the condition A of the example and the condition B of the comparative example, and is fibrous. The tissue plate (sample No. 21-24) was the result of a low sputtering rate.

The sputtering rate of Condition B of the comparative example was more than 400 nm/h. For example, the sputtering rate of 420 nm/h corresponds to the equivalent G5 (5th generation) sputtering target lifetime with respect to the input power under actual use conditions. On the other hand, in the sputtering rate of about 370 nm/h as shown by the condition A of the example, the life extension effect which is inversely proportional to the sputtering rate can be obtained. The sputtering rate of 400 nm/h or less is a sputtering target having a long time, and a sputtering target having a long life which has not been obtained so far can be obtained.

Further, regarding the crystal orientation, the (222)/(200) strength ratio is not more than 50% (0.5).

Usually the powder system shows a random orientation. Fig. 3 is a graph showing the results of XRD of molybdenum powder. The crystallographic alignment was 37% compared to the powder (Fig. 3; 2,278 cps = 37.4% of 2351 cps/(200) of (222)), and the processed structure of the examples of Table 3 was no more than 35%. Further, the molybdenum sintered body also showed 37% in the same manner.

(6) full width at half maximum and sputtering speed

For the sample prepared using Condition A and the sample prepared using Condition B, the full width at half maximum of the diffractive surface (FWHM) was obtained using the waveform fitting of the High Score Plus software of the XRD apparatus. ). The sputtering rate of each sample was investigated using the method described in "(3) Relationship between aspect ratio and sputtering speed". The results are shown in Table 4.

As a result of the samples, as shown in Table 4, it was found that the sputtering rate was significantly correlated with the (Full-Width Half Maximum) of the (222) reflection.

Samples N0.31 and 32 were prepared using Condition A, and Sample 33 was prepared using Condition B. When the FWHM is small, the strain is released to cause the sputtering speed to become high. Further, under the rolling conditions of the examples, the FWHM was not more than 0.5 even if the rolling reduction ratio was increased.

In Table 5, an example of XRD of the sample prepared using Condition A of the example is shown. The "diffraction intensity of the powder" is the diffraction intensity of the Mo powder, and the "example of the implementation range" indicates the intensity of the X-ray diffraction of the rolled sheet produced under the use condition A (will The intensity of 200) is set as the relative value at 100).

Further, not only a target composed of molybdenum, but also a target of a molybdenum-containing molybdenum alloy target and a body-centered cubic lattice structure can be obtained, and the same tendency as in Tables 1 to 5 can be obtained.

The material for the sputtering target is a crystal orientation ratio (222)/(200) of the crystal faces (222) and (200) obtained by X-ray diffraction of the surface to be sputtered. 0.08 or more and less than 0.35, and has a body-centered cubic lattice structure.

Preferably, the material for the sputtering target contains molybdenum. Preferably, the material for the sputtering target is composed of molybdenum.

Preferably, the half value width of the peak of the crystal plane (222) obtained by the X-ray diffraction of the surface to be sputtered is 0.29 or more and 0.5 or less.

Preferably, the surface to be sputtered has a Vickers hardness of Hv200 or more. Preferably, the crystal structure of the surface to be sputtered has an aspect ratio of 3 or more.

Sputtering composed of molybdenum having a crystal orientation ratio (222)/(200) of crystal faces (222) and (200) determined by X-ray diffraction of the surface to be sputtered to be 0.08 or more and less than 0.35 The method for producing a target material includes the steps of: producing a sintered body by sintering at a temperature of 1500 ° C to 2000 ° C using a powder having an average particle diameter of 5 μm or more of molybdenum powder; and hot rolling the sintered body And the step of performing the final heat treatment after hot rolling; the total rolling reduction rate from the sintered body is set to 85%, the heating temperature is set to 1000-1150 ° C, and the final heat treatment temperature is set to 800-1000 ° C .

[Industrial availability]

The present invention is capable of utilizing the field of sputtering targets.

Claims (5)

A material for a sputtering target is composed of molybdenum, and the crystal structure of the surface to be sputtered has an aspect ratio of 3 or more. The material for a sputtering target according to claim 1, wherein the surface to be sputtered has a Vickers hardness of Hv200 or more. A material for a sputtering target has an aspect ratio of a crystal structure of a surface to be sputtered of 3 or more, and a Vickers hardness of a surface to be sputtered is Hv200 or more. The material for a sputtering target according to claim 3, which contains molybdenum. The material for a sputtering target according to the fourth aspect of the invention is composed of molybdenum.