JP6859840B2 - Sputtering target - Google Patents

Description

The present invention relates to a sputtering target, and more particularly to a sputtering target composed of a sintered body of _{Si 3} N ₄ and SiO _{2 and Mg O.}

The _{sputtered film formed using a sputtering target consisting of a sintered body of Si 3} N ₄ (silicon nitrogen), SiO ₂ (silicon dioxide) and MgO (magnesium oxide) is chemically stable to heat. Moreover, it has high hardness and excellent wear resistance. Therefore, it is used as a protective film for thermal print heads.

_{Patent Document 1 describes Si 3} N ₄ , SiO ₂ as a sputtering target for forming a protective layer of a thermal print head, an average particle size of 0.5 μm or more and 1.0 μm or less, and a content of 0.1% by weight. A powder produced by sintering a powder containing MgO of 5.0% by weight or less is disclosed. In Patent Document 1, the powder is sintered by calcining the powder compact obtained by cold pressing the powder in a nitrogen atmosphere of 1 atm at about 1700 ° C. for several hours. The highest density sputtering target obtained in the examples described in Patent Document 1 is 2.6 g / cm ³ (theoretical density ratio of about 90%) (Example 1).

Japanese Patent No. 3965508

By the way, in order to improve the production efficiency of the thermal print head, it is desired to increase the film forming speed of the protective film. As a method of increasing the film forming speed by sputtering, a method of increasing the sputtering power of the sputtering apparatus is effective.
However, according to the study of the present inventor, in the conventional sputtering target described in Patent Document 1, when the sputtering power is increased, cracks and cracks are likely to occur, and it is difficult to form a uniform sputtering film. In some cases.

As a method of suppressing the occurrence of cracks and cracks, it is conceivable to make the sputtering target denser, that is, to increase the density. However, although the sputtering target produced by the present inventor by the method of firing a compact of powder in an air atmosphere has a high density, the effect of suppressing cracks and cracks at high sputtering power is insufficient. there were.

The present invention has been made in view of the above-mentioned circumstances, and is a _{sputtering target composed of a sintered body of Si 3} N ₄ and SiO ₂ and Mg O, and cracks or cracks even if a film is formed even with a high sputtering power. It is an object of the present invention to provide a sputtering target in which

In order to solve the above problems, the sputtering target of the present invention comprises a _{sintered body of Si 3} N ₄ and SiO ₂ and Mg O, and the density ^{exceeds 2.70 g / cm 3} , and the Si ₃ N ₄ is β. It is characterized in that the fraction is 7% or less. Si ₃ N ₄ has two phases, an α phase (low temperature phase) and a β phase (high temperature phase), and the coefficient of thermal expansion is larger in the α phase. The α phase is trigonal and the β phase is hexagonal. The phase transition from the α phase to the β phase is said to occur at a temperature of 1400 to 1600 ° C.

The sputtering target of the present invention having such a configuration has a density ^{of more than 2.70 g / cm 3} and is dense and has few pores existing inside the target. Therefore, even if a film is formed with high sputtering power. Cracks and cracks starting from holes are less likely to occur. Further, Si ₃ N ₄ has a β fraction of 7% or less and contains a relatively large amount of α phase having a higher coefficient of thermal expansion than β phase, so that even if a film is formed with high sputtering power, sputtering is performed. Cracks and cracks due to thermal expansion of the target are less likely to occur. As described above, the sputtering target of the present invention is less likely to cause cracks or cracks even if a film is formed with a high sputtering power, so that a sputtering film can be stably formed with a high sputtering power.

According to the present invention, _{it is possible to provide a sputtering target composed of a sintered body of Si 3} N ₄ and SiO ₂ and Mg O, which is less likely to crack or crack even if a film is formed even with a high sputtering power. It will be possible.

It is an element distribution diagram of the sputtering surface of the sputtering target produced in Example 1 of this invention. It is an element distribution diagram of the sputtering surface of the sputtering target produced in Comparative Example 11.

The sputtering target according to the embodiment of the present invention will be described below.
The sputtering target according to the present embodiment is used, for example, when a protective layer of a thermal print head is formed by sputtering.

The sputtering target according to this embodiment is composed of a sintered body of _{Si 3} N ₄ and SiO _{2 and Mg O. It is preferable that Si 3} N ₄ and Mg O of the sputtering target structure are uniformly dispersed or solid-solved, respectively. Further, _{it is preferable that SiO 2 is} also uniformly dispersed or solid-solved. That is, it is preferable that no clear crystal particles _{of Si 3} N ₄ , SiO ₂ , and Mg O are found in the sputtering target structure. Crystal particles of Si ₃ N ₄ , SiO ₂ , and MgO can be confirmed by element mapping analysis by EPMA (electron probe microanalyzer). If the sputtering target structure is non-uniform, cracks and cracks are likely to occur due to thermal stress caused by the difference in thermal expansion between _{Si 3} N ₄ and SiO ₂ and Mg O when the temperature of the surface of the sputtering target rises due to sputtering. There is a risk of becoming.

Further, the sputtering target according to the present embodiment has a density of more than ^{2.7 g / cm 3.} Here, the density is an actually measured density obtained by measuring the mass and dimensions of the sputtering target and dividing the measured mass by the volume of the sputtering target obtained from the measured dimensions.
Density is an index of the compactness of the sintered body. That is, high density means that it is dense and has few pores. When the density of the sputtering target is 2.7 g / cm ³ or less, cracks or cracks starting from pores may easily occur when the film is formed with high sputtering power. Therefore, in the present embodiment, the density of the sputtering target is set to a value exceeding ^{2.7 g / cm 3.} The upper limit of the density is not particularly limited, but the density is usually 3.0 g / cm ³ or less.

The density of the sputtering target according to the present embodiment is preferably 90% or more as a density ratio [= (measured density / theoretical density) × 100] with respect to the theoretical density.
In this case, since the sputtering target is denser and has fewer pores, cracks and cracks starting from the pores are less likely to occur when the film is formed with high sputtering power.

Further, the sputtering target according to the present embodiment has _{a β fraction of Si 3} N ₄ of 7% or less. Si ₃ N ₄ in the crystalline form has alpha phase and β-phase, alpha-phase is known to be relatively thermal expansion coefficient is high. When _{the β fraction of Si 3} N ₄ exceeds 7%, when the temperature of the surface of the sputtering target rises due to sputtering, cracks occur due to thermal stress caused by the thermal expansion difference between _{Si 3} N ₄ and SiO _{2 and MgO.} Cracks may easily occur. Therefore, in the present embodiment, _{the β fraction of Si 3} N ₄ is set to 7% or less. The lower limit of the β fraction is not particularly limited, but the β fraction is usually 3% or more.

The β fraction of Si ₃ N ₄ can be measured, for example, as follows.
Three main peaks of α phase and β phase are selected from the X-ray diffraction pattern of the sputtering target, and calculated from their intensity ratios. Specifically, _{the peak intensity α1 on the (101) plane of the α phase of Si 3} N ₄ , the peak intensity α2 on the (201) plane, the peak intensity α3 on the (301) plane, and the peak on the (200) plane of the β phase. The intensity β1, the peak intensity β2 on the (101) plane, and the peak intensity β3 on the (120) plane are measured, respectively. Then, the β fraction (%) is calculated using the following formula (1).
β fraction = {(β1 + β2 + β3) / (α1 + α2 + α3 + β1 + β2 + β3)} × 100 ... (1)

The sputtering target according to the present embodiment is obtained, for example, a raw material powder mixture preparation step of mixing raw material powders to prepare a raw material powder mixture, and a sintering step of firing and sintering the obtained raw material powder mixture. It can be manufactured by a method having a machining process of machining the sintered body.

(Raw material powder mixture preparation process)
As raw material powders, preparing a _Si 3 _{N 4} powder and SiO ₂ powder and MgO powder. Each of these raw material powders preferably has a purity of 99.9% by mass or more. The average particle size is preferably in the range of 0.1 μm or more and 10 μm or less, respectively. The Si ₃ N ₄ powder preferably has an α fraction of 95% or more.

_{The mixing ratio of Si 3} N ₄ and SiO ₂ and Mg O of this sintered body is in the range of 60% by mass or more and 80% by mass or less of _{Si 3} N _{4 and} 0 of MgO, assuming that the whole is 100%. It is preferable that the ratio is in the range of 1% by mass or more and 2% by mass or less, and the balance is SiO _2.

Si ₃ N ₄ has higher strength against sputtering than SiO _{2 and MgO.} Therefore, when _{the mixing ratio of Si 3} N ₄ is 60% by mass or more, it becomes easy to manufacture a sputtering target in which cracks and cracks are unlikely to occur even if a film is formed with a high sputtering power. On the other hand, when _{the content ratio of Si 3} N ₄ is 80% by mass or less, the sinterability of the raw material powder mixture is improved, so that it becomes easy to manufacture a high-density sputtering target.

MgO is a material that acts as a sintering aid and has the effect of increasing the density of the sputtering target. When the mixing ratio of MgO is 0.1% by mass or more, it becomes easy to manufacture a high-density sputtering target. On the other hand, if the mixing ratio of MgO becomes too high _{, the phase transition of Si 3} N _{4 from} the α phase to the β phase may be promoted. From the viewpoint of suppressing the phase transition of Si ₃ N _{4 from} the α phase to the β phase, the mixing ratio of MgO is preferably 2% by mass or less.

The raw material powder may be mixed by a dry method or a wet method. As the mixing device, a normal mixing device used for mixing powders such as a ball mill can be used.

(Sintering process)
In the sintering step, the raw material powder mixture obtained in the raw material powder mixture preparation step is heated and sintered. A hot press is used as the sintering method of the raw material powder mixture. The hot press method is a method of sintering a raw material powder mixture by filling a mold with the raw material powder mixture and heating while pressurizing in the uniaxial direction. As described above, the phase transition of Si ₃ N _{4 from} the α phase to the β phase is said to occur at a temperature of 1400 to 1600 ° C. Therefore, _{in order to suppress the phase transition of Si 3} N _{4 from} the α phase to the β phase, it is preferable that the heating temperature of the raw material powder mixture is low. By using a hot press, the raw material powder mixture can be sintered at a lower temperature than normal pressure sintering without pressurization, so that _{the phase transition of Si 3} N _{4 from} the α phase to the β phase is suppressed. It becomes possible to do. In the case of atmospheric pressure sintering, for example, in Patent Document 1, it is sintered at a high temperature of about 1700 ° C.

The hot press is preferably performed in a vacuum atmosphere. The pressurizing pressure (press pressure) is preferably 9.8 MPa or more. The upper limit of the press pressure is not particularly limited, but the press pressure is usually 100 MPa or less. The heating temperature is preferably 1500 ° C. or higher. The upper limit of the heating temperature is not particularly limited, but the heating temperature is preferably 1600 ° C. or lower from the viewpoint of suppressing the phase transition of _{Si 3} N _{4 from the α phase to the β phase.} The sintering time varies depending on the above-mentioned conditions such as the press pressure, the heating temperature, and the composition of the raw material powder mixture, and therefore cannot be uniformly determined, but is generally in the range of 1 hour or more and 5 hours or less.

(Machining process)
In the machining step, the sintered body obtained in the sintering step is cut or ground to be processed into a sputtering target having a predetermined shape.

The sputtering target according to the present embodiment is manufactured by the above steps. This sputtering target is used by joining it to a backing plate using a solder material.

According to the sputtering target of the present embodiment having the above configuration, the density ^{exceeds 2.70 g / cm 3} , and the density is dense and there are few pores existing inside the target, so that the sputtering power is high. Even if the film is used, cracks and cracks starting from the pores are less likely to occur. Further, Si ₃ N ₄ has a β fraction of 7% or less and contains a relatively large amount of α phase having a higher coefficient of thermal expansion than β phase, so that even if a film is formed with high sputtering power, sputtering is performed. Cracks and cracks due to thermal expansion of the target are less likely to occur. As described above, since the sputtering target of the present embodiment is less likely to cause cracks and cracks, it is possible to stably form a sputtering film even at a high sputtering power.

The size of the sputtering target of the present embodiment is not particularly limited, but the sputtering target of the present embodiment can be made large because of its high strength. For example, in the case of a disk-shaped sputtering target, the diameter of the sputtered surface to be sputtered can be 150 mm or more.

The results of the evaluation test for evaluating the action and effect of the sputtering target according to the present invention will be described below.

[Example 1 of the present invention]
As raw material powder, Si ₃ N ₄ powder (Ube Kosan Co., Ltd .: SN-E10, average particle size: 0.5 μm, average particle size: 0.5 μm, α fraction: 96.6%) and SiO ₂ powder ( Admatex Co., Ltd .: SO-E5 / 24C, average particle size: 1.8 μm) and MgO powder (High Purity Chemical Laboratory Co., Ltd .: MgO Powerer, average particle size: 7 μm) were prepared.
The prepared Si ₃ N ₄ powder, SiO ₂ powder, and MgO powder are mixed in mass% at a mixing ratio of 74.6: 24.9: 0.5 (Si ₃ N ₄ : SiO ₂ : MgO). Mixing was performed using a ball mill. The obtained raw material powder mixture was filled in a mold, and a hot press was performed in a vacuum atmosphere to sinter the powder mixture. The sintering conditions were a heating temperature of 1500 ° C., a press pressure of 34.3 Mpa, and a heating time of 2 hours.

The obtained sintered body was machined into a disk having a diameter of 150 mm and a thickness of 6 mm to produce a sputtering target.

[Examples 2 to 9 of the present invention, Comparative Examples 1 to 16]
A sputtering target was produced in the same manner as in Example 1 of the present invention, except that the mixing ratio of the raw material powder was set to the ratio shown in Table 1 below and the sintering conditions by hot pressing were set to the conditions shown in Table 1 below. did.

[Comparative Examples 17 to 19]
The mixing ratio of the raw material powder was set to the ratio shown in Table 1 below. The obtained raw material powder mixture was filled in a mold and pressed to obtain a molded product. The obtained molded product was sintered by atmospheric pressure sintering. The sintering conditions were an air atmosphere, a firing temperature of 1650 ° C., and a firing time of 2 hours. Then, the obtained sintered body was machined into a disk having a diameter of 150 mm and a thickness of 6 mm to produce a sputtering target.

[Evaluation]
The sputtering targets prepared in Examples 1 to 9 of the present invention and Comparative Examples 1 to 19 were evaluated as follows. The results are shown in Table 1.

(Theoretical density)
The theoretical density (g / cm ³ ) of the sputtering target was calculated from the density and mixing ratio of the raw material powder using the following formula.
Theoretical density = 100 / {(Wa / Da) + (Wb / Db) + (Wc / Dc)}
Wa is _{the mixing ratio of Si 3} N ₄ powder (mass%), Da is _{the theoretical density of Si 3} N ₄ powder (3.44 g / cm ³ ), Wb is _{the mixing ratio of SiO 2} powder (mass%), and Db is SiO. ₂ The theoretical density of the powder (2.2 g / cm ³ ), Wc is the mixing ratio (mass%) of the MgO powder, and Dc is the theoretical density of the MgO powder (3.65 g / cm ³ ).

(Actual measurement density)
The mass of the sputtering target was measured. The measured density was calculated by dividing the measured mass by the volume obtained from the diameter and thickness of the sputtering target.

(Density ratio)
The density ratio (%) of the sputtering target was calculated from the following formula.
Density ratio = (measured density / theoretical density) x 100

(Β fraction)
The X-ray diffraction pattern of the sputtering target was measured by the θ / 2θ method using an X-ray diffractometer based on the Bragg-Brentano centralized optical system using Cu-Kα rays as the X-ray source.
From the obtained X-ray diffraction pattern, the peak intensities of the α phase (101) plane, (201) plane, and (301) plane of _{Si 3} N _{4 and the (200) plane, (101) plane, and (120) plane of the β phase.} ) The peak intensities of the surfaces were measured respectively. Then, _{the β fraction of Si 3} N ₄ was calculated using the above formula (1).

(Tissue uniformity)
The texture uniformity of the sputtered surface of the sputtering target was evaluated by observation with an SEM (scanning electron microscope) and element mapping analysis with an EPMA (electron probe microanalyzer). Those in which it can be clearly confirmed that MgO is unevenly distributed from the element distribution on the sputtered surface are marked with "x", and those in which it cannot be clearly confirmed that MgO is unevenly distributed are marked with "○".

FIG. 1 shows an element distribution diagram of the sputtered surface of the sputtering target produced in Example 1 of the present invention, and FIG. 2 shows an element distribution diagram of the sputtered surface of the sputtering target produced in Comparative Example 11.
Comparing the element distribution map of FIG. 1 with the element distribution map of FIG. 2, the element distribution map of FIG. 1 is obtained for any of the elements N (nitrogen), O (oxygen), Mg (magnesium), and Si (silicon). Has a smaller difference in shades of black and white. Therefore, the sputtering target produced in Example 1 of the present invention, compared with the sputtering target produced in Comparative Example _{11, Si 3 N 4, MgO} , SiO 2 is uniformly dispersed, it is highly tissue uniformity I understand.

(Sputter test)
The sputtering target was joined to the backing plate using a solder material, and set in the chamber of a sputtering apparatus (manufactured by Nippon Vacuum (ULVAC), SIH-450). After exhausting the inside of the chamber to 1 × 10 ^-4 Pa, Ar gas was used as the sputtering gas to set the flow rate to 50 sccm and the pressure to 0.67 Pa. The sputtering test was carried out under two conditions of ^{cm 2} ) and 1500 W (8.5 W / cm ^2). In the sputtering test, after sputtering for 5 hours under the above conditions, a good or bad judgment was made by visually observing the state of the target. “○” indicates no cracks or cracks, “△” indicates that even one small crack is visually observed along the plasma shape, and “×” indicates that the entire target is broken apart. And said.

From the results in Table 1, the sputtering targets of Examples 1 to 9 of the present invention having a density of more than ^{2.70 g / cm 3} _{and a β fraction of Si 3} N ₄ of 7% or less have a sputtering power of either 750 W or 1500 W. It was confirmed that cracks and cracks did not occur even in the case of, and a sputter film could be stably formed. On the other hand, the sputtering targets of Comparative Examples 1 to 19 having a density of 2.70 g / cm ³ or less or _{a β fraction of Si 3} N ₄ exceeding 7% had cracks or cracks when the sputtering power was 750 W. Although it did not occur, cracks or cracks occurred when the sputtering power became 1500 W, and the sputtering film could not be stably formed.

Claims (1)

It consists of a sintered body of Si ₃ N ₄ and SiO _{2 and MgO.}
Sputtering target density exceeds 2.70 g / cm ^3, the _Si 3 _{N 4} is characterized in that β fraction is less than 7%.

Images