JP2015221937A - Material for sputtering target - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material for sputtering targets which enables adjustment of the sputter rate.SOLUTION: A material for sputtering targets has an aspect ratio of the crystal structure of the surface to be sputtered of 3 or greater. The material for sputtering targets contains molybdenum or is composed of molybdenum, and the Vickers hardness of the to-be-sputtered surface is Hv 200 or higher.

Description

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

  Conventionally, sputtering target materials include, for example, JP 2000-45066 A (Patent Document 1), JP 2007-113033 A (Patent Document 2), JP 2013-32597 A (Patent Document 3), and Patent 4945037. (Patent Document 4), JP-A 2000-234167 (Patent Document 5), JP-A 2013-154403 (Patent Document 6), JP 2010-535943 (Patent Document 7), and JP-A 2014. No.-12893 (Patent Document 8).

JP 2000-45066 A JP 2007-113033 A JP 2013-32597 A Japanese Patent No. 4945037 JP 2000-234167 A JP 2013-154403 A Special table 2010-535943 gazette JP 2014-12893 A

  Patent Document 1 discloses a molybdenum target that generates less abnormal discharge and particles. In addition, an invention relating to a molybdenum-based target that generates less particles even when crystal grains are miniaturized is disclosed.

  Patent Document 2 discloses performing plastic working after molybdenum pressure sintering. It is disclosed that the relative strength of the (110) surface is defined to improve the pressure sintering of Mo powder, the relative density, and the mechanical properties.

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

Patent Document 4 discloses a tungsten target.
Patent Document 5 discloses a molybdenum target. It is disclosed that the recrystallized structure suppresses the occurrence of arcing.

  Patent Document 6 discloses manufacturing a sputtering target by tilt rolling. Diagonal rolling is required, and the ratio of particles per unit volume of bcc metal oriented within 15 ° of <110> // ND of bcc metal is more than 20.4%.

  Patent Documents 7 and 8 disclose sputtering targets in which the uniformity of 100 structure and 111 structure in the plate thickness direction in bcc metal is improved.

  Patent Documents 6-8 disclose bcc metal, and a high-melting point metal is processed by a tilt rolling method, which is a special processing method, in order to obtain a uniform structure. This inclined rolling method can be applied to a metal with good workability. Even in this patent document, there is a description of Ta and Nb having relatively good workability as bcc metals, but there is no mention of W and Mo having particularly poor workability even with high melting point metals. When the tilt rolling method is actually applied to W and Mo, laminar cracks are generated due to the small allowable strain, and processing is impossible.

  None of the conventional techniques disclose or suggest any adjustment of the sputtering rate.

  An object of this invention is to provide the material for sputtering targets which can adjust a sputtering rate.

  In the sputtering target material according to one embodiment of the present invention, the aspect ratio of the crystal structure of the surface to be sputtered is 3 or more.

  A material for a sputtering target capable of adjusting the sputtering rate can be provided.

It is a figure which expands and shows the TD surface manufactured according to the Example (condition A). It is a figure which expands and shows the TD surface manufactured according to the comparative example (condition B). It is a graph which shows the result of XRD with molybdenum powder (Fsss Fisher method: particle size 5 micrometers).

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.

  In the sputtering target material according to one embodiment of the present invention, the aspect ratio of the crystal structure of the surface to be sputtered is 3 or more.

  With the molybdenum plate target having a body-centered cubic lattice structure that has existed up to now, it has been impossible to control the sputtering rate. By controlling the crystal structure, a molybdenum target with low target consumption can be obtained. Since the consumption by sputtering is small, the target life can be extended. Also, film thickness controllability is improved in response to the recent demand for thinning. That is, it is suitable for uses other than when a high sputtering rate is required.

  As a conventional method, there is a technique aimed at increasing the sputtering rate in a random orientation without performing orientation control, such as a sintered body target and a heat treatment target. Further, although there is a material in which the sputtering rate is slightly slowed by controlling the structure to some extent, the present invention is to provide a material having a low sputtering rate by controlling the residual processing strain.

  This is because a thin barrier layer has come to exhibit a sufficient effect as a barrier metal for preventing diffusion of Al wiring, which is a recent main application. The film thickness controllability and uniformity can be improved by lowering the sputtering rate in response to the demand for thinning.

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

Preferably, the sputtering target material includes molybdenum.
Preferably, it consists of a sputtering target material molybdenum.

  Preferably, when the aspect ratio of the TD surface (plate cross section parallel to the rolling direction), which is the surface to be sputtered, is 3 or more, the sputtering rate is 400 nm / h or less. At this time, the average particle size in the thickness direction was 50 μm or less.

  Preferably, the Vickers hardness of the surface to be sputtered is Hv200 or more. If the hardness is Hv 200 or more, the sputtering rate is 400 nm / h or less.

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

[Details of the embodiment of the present invention]
Specific examples according to embodiments of the present invention will be described below with reference to the drawings. In addition, this invention is not limited to these illustrations, is shown by the claim, and intends that all the changes within the meaning and range equivalent to a claim are included.

(Example)
(1) Manufacturing method Molybdenum powder having a particle diameter of 1 to 20 μm was measured by the Fsss Fischer method, and the powder was hydrostatically pressed using a rubber bag under a pressure of 150 to 300 MPa. Thereafter, the press-molded body is 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 of the sintered body was performed in the following manner using a two-high rolling mill. Primary hot rolling with a processing rate of 76% was performed so that the plate thickness after rolling was 24 mm. In order to prevent recrystallization coarsening of molybdenum crystal grains due to high temperature heating during hot rolling, the furnace heating temperature of initial hot rolling was controlled to 1400 ° C. or lower.

  Next, the rolled sheet after the initial hot rolling is bisected using a cutting machine, one of which is a rolled sheet (condition A) for carrying out the rolling pass schedule of the example, and one of which is for carrying out the normal rolling pass schedule. As a rolled sheet (Condition B) of the comparative example, hot rolling was performed.

  For condition A, after the rolled plate was made uniform in a hydrogen atmosphere heating furnace at a temperature of 900 to 1150 ° C., a rolled plate of an example having a total rolling ratio of 37.5% and a plate thickness of 15 mm was obtained in 4 passes. .

  For condition B, the rolled sheet was made uniform in a hydrogen atmosphere heating furnace at a temperature of 1150 to 1300 ° C. After 5 passes, the total rolling ratio was 37.5%, and a rolled sheet of a comparative example having a sheet thickness of 15 mm was obtained. . In both conditions A and B, the processing rate of the latter half of hot rolling was 37.5%, the total rolling rate from the sintered body was 85%, and the relative density was 99.9%.

  Condition A has a large amount of residual strain, and it is considered that there is a high possibility of cracking in the cutting process for sampling. Strain removal for 15 minutes in a hydrogen heating furnace at a temperature of 600 to 1000 ° C. does not cause recrystallization Annealing was performed. Condition B was heat-treated at 1000-1300 ° C. for 60-120 minutes.

(2) Observation of structure FIG. 1 is an enlarged view of a TD surface manufactured according to an example (condition A). The metal structure of the TD surface under Condition A of the example is shown in FIG. Holds a so-called rolled structure in which the dimension in the direction parallel to the rolling direction (X direction; longitudinal 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. Was.

  FIG. 2 is an enlarged view showing a TD surface manufactured according to the comparative example (condition B). The condition B of the comparative example heat-treated as usual is that the dimension in the direction parallel to the rolling direction (X direction; longitudinal direction) is about 100 μm to 150 μm, and the dimension in the vertical direction (Y direction; thickness direction) is about 50 μm to 100 μm. The tissue was relatively equiaxed (Fig. 2).

(3) Relationship between aspect ratio and sputtering rate The relationship between the aspect ratio and the sputtering rate in the sample manufactured under the condition A of the example and the sample manufactured under the condition B of the comparative example was examined.

(3-1) Definition The size of the fibrous structure and equiaxed structure was calculated by the intercept method. Specifically, the tissue is observed at a magnification of 100 to 200 times using an optical microscope with the long side of the tissue as the horizontal direction. The number of points where the horizontal and vertical lines cross and cross the grain boundaries of the structure is counted. The value obtained by dividing the length of the horizontal line by the number of crossing points is taken as the major axis of the crystal grains. The value obtained by dividing the length of the vertical line by the number of vertical cut points is taken as the minor axis. The aspect ratio is a value obtained by dividing the major axis of a crystal grain by the minor axis.

(3-2) Production of Sputtering Target Specimen A diameter φ75 mm × thickness T2 mm sputtering target specimen used for the sputtering rate evaluation was prepared in the following manner. Both samples manufactured under the condition A of the example and the condition B of the comparative example were used as material plates. Both surfaces of the material plate (thickness T = 15 mm) were ground by 6 mm each with a surface grinder to a thickness of 3 mm, and then processed into a disk having a diameter of 75 mm and a thickness of T3 mm by a discharge wire processing machine. The circular plate having a diameter of 75 mm was polished with a SiC grindstone on both surfaces using a rotary polishing machine to finish a 2 mm thick sputtering target specimen. At this time, in order to unify the sputtering conditions, the surface accuracy of the sputtering target specimen was unified to Ra 3 μm or less.

(3-3) Sputtering conditions The sputtering rate of the sputtering target specimen manufactured under the condition A of the example and the condition B of the comparative example was measured using a small sputtering apparatus (model SH-250-T4) manufactured by ULVAC, Inc. Compared. After the inside of the apparatus was evacuated to 5 × 10 ⁻⁵ Pa or less, the argon gas flow was 0.06 MPa, 6.0 sccm (0 ° C., 1013 hPa at a flow rate of 6.0 dm ^{3 /} min), the output was 100 W, 400 V Then, sputtering was performed for 60 minutes. In order to remove the edge effect, a region of about 60 mm in the center was sputtered, a glass preparation was set on the opposite cathode side, and the film thickness sputtered on the preparation was determined to confirm the sputtering rate.

(3-4) Measurement of Sputtered Film Thickness Sputtered film thickness was measured using a surface shape measuring device (PGI1200 manufactured by Taylor Hobson Co., Ltd.), full scale 12.5 mm, data length 4.8 mm, and run-up distance 0.3 mm. The measurement was performed under the conditions of a measurement speed of 1 mm / s (measurement analysis conditions were performed by specifying the LS line and the primary).

(3-5) Evaluation The results of sputtering were evaluated in an area of ± 20% from the center of the plate thickness so that average information of sputtering was obtained.

  Samples 1 to 3 in Table 1 are values of the sputtering rate of the rolled plate (sputtering target specimen) manufactured under condition A and sample 4 under 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. In addition, the sputtering rate decreases as the aspect ratio increases. That is, it suggests that the sputtering rate decreases as the fiber structure becomes stronger.

  This also indicates that when the sputtering rate exceeds 400 nm / h, the consumption amount is 4 mm or more at a usage time of 10000 h and 8 mm or more at 20000 h, and the sputtering target replacement frequency is increased.

(4) Vickers hardness and sputter rate Samples were produced according to conditions A and B. These samples were subjected to strain relief annealing as a final heat treatment. Specifically, a sample was prepared in which the hardness was changed while keeping the orientation substantially constant by keeping the temperature of the sample constant at 800 ° C. and adjusting the length of the annealing time. The Vickers hardness of each sample was measured at a load of 10 kg. The sputter rate of each sample was examined by the method described in “(3) Relationship between aspect ratio and sputter rate”. The results are shown in Table 2.

  Sample No. 11 and 12 were manufactured from Condition A, and Sample 13 was manufactured from Condition B. It was found that the residual amount of strain correlates with the sputtering rate, and that the higher the hardness, the lower the sputtering rate.

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

  Rolled sheets were produced under two types of conditions A and B. A sample having a thickness of about 15 mm × □ 10 mm was taken from each rolled plate for the purpose of investigating crystal orientation.

  The crystal orientation investigation (XRD) was performed using a ceramic X-ray tube LFF Cu by a Spectraly Co., Ltd. PANalytical X-ray diffractometer and Empirean system. Crystal orientation was measured with a semiconductor detector under conditions of 40 kv and 45 mA with an X-ray lens (0.3 °) and a flat plate collimator (0.27 °). The slit conditions were a divergence slit of 1/2 ° and a scattering of 1 °. Unless otherwise specified, the XRD measurement angle was 35 ° to 135 °, and the scan speed (Time per step) was 10.2 seconds. The evaluation of the measurement results was compared with standard data using the ICDD database PDF2.

  The sputter rate of each sample was examined by the method described in “(3) Relationship between aspect ratio and sputter rate”.

  The results of XRD and sputtering were evaluated in an area of ± 20% from the center of the plate thickness so that average information of sputtering was obtained. The results are shown in Table 3.

  Sample No. 21 to 24 are manufactured under the condition A and sample No. 25 and 26 were produced under Condition B. The ratio of the reflection intensity at each diffraction surface was taken as the crystal orientation index. When the relationship between the (222) / (200) intensity ratio and the sputtering rate was investigated, the sputtering rate tended to decrease as the intensity ratio increased (Table 3). In addition, this tendency is different between the condition A of the example and the condition B of the comparative example, and the fibrous tissue board (sample No. 21-24) has a lower sputter rate.

  The sputtering rate of Comparative Example Condition B exceeded 400 nm / h. For example, a sputtering rate of 420 nm / h corresponds to the equivalent lifetime of a G5 (fifth generation) sputtering target with respect to input power under actual use conditions. On the other hand, if the sputtering rate is about 370 nm / h indicated by the condition A of the embodiment, the effect of extending the life in inverse proportion to the sputtering rate can be obtained. If the sputtering rate is 400 nm / h or less, the sputtering target has a long lifetime, and a long-life sputtering target that has not been obtained so far can be obtained.

  Regarding the crystal orientation, the (222) / (200) strength ratio did not exceed 50% (0.5).

  In general, the powder exhibits a random orientation. FIG. 3 is a graph showing the results of XRD with molybdenum powder. The crystal orientation did not exceed 35% in the processed structure of the example of Table 3, compared to 37% of the powder (FIG. 3; 2351 cps of (222) / 6278 cps of (200) = 37.4%). . The molybdenum sintered body also shows 37%.

(6) Full width at half maximum and sputter rate For the sample manufactured under condition A and the sample manufactured under condition B, (222) Full width at half maximum (FWHM) of the diffraction surface using profile fitting with the High Score Plus software of the XRD apparatus ) The sputter rate of each sample was examined by the method described in “(3) Relationship between aspect ratio and sputter rate”. The results are shown in Table 4.

  As a result of these samples, as shown in Table 4, it was found that the sputtering rate has a strong correlation with the (222) reflection full width at half maximum (Full Width Half Maximum).

  Sample No. 31 and 32 were manufactured from Condition A, and Sample 33 was manufactured from Condition B. If the FWHM is small, the strain is released and the sputter rate is considered to be high. In the rolling conditions of the examples, the FWHM did not exceed 0.5 even when the rolling rate was increased.

  In Table 5, the example of XRD in the sample manufactured on condition A of the Example is shown. “Diffraction intensity in powder” means diffraction intensity in Mo powder, “Example of working range” means relative intensity when X-ray diffraction intensity ((200) intensity is 100) in a rolled plate manufactured under condition A Value).

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

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

Preferably, the sputtering target material contains molybdenum.
Preferably, the sputtering target material is made of molybdenum.

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

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

  A sputtering target material comprising molybdenum having a crystal orientation ratio (222) / (200) of crystal planes (222) and (200) of 0.08 or more and less than 0.35 determined by X-ray diffraction of the surface to be sputtered The manufacturing method uses a powder having an average particle size of 5 μm or more in molybdenum powder, and a step of manufacturing a sintered body by sintering at a temperature of 1500 ° C. to 2000 ° C., and a step of hot rolling the sintered body And a step of performing a final heat treatment after hot rolling, the total rolling ratio from the sintered body is 85%, the heating temperature is 1000-1150 ° C., and the final heat treatment temperature is 800-1000 ° C.

  The present invention can be used in the field of sputtering targets.

Claims (4)

  A material for a sputtering target, wherein the aspect ratio of the crystal structure of the surface to be sputtered is 3 or more.   The material for sputtering targets according to claim 1, comprising molybdenum.   The sputtering target material according to claim 2, which is made of molybdenum. The material for sputtering targets according to any one of claims 1 to 3, wherein a Vickers hardness of a surface to be sputtered is Hv200 or more.