TW201619405A - W-Ti sputtering target - Google Patents

Abstract

The W-Ti sputtering target of the present invention has a composition consisting of: 5 to 20 mass% of Ti; 25 to 100 mass ppm of Fe; and a balance of W and inevitable impurities. The W-Ti sputtering target satisfies the relational expression of (Femax-Femin)/(Femax+Femin) ≤ 0.25 wherein when the concentration of Fe is measured at a plurality of places in the target surface, the maximum value of the measured concentration of Fe is Femax, and the minimum value of the measured concentration of Fe is Femin.

Description

W-Ti sputtering target

The present invention relates to a W-Ti sputtering target for forming a W-Ti film as a diffusion preventing layer for preventing diffusion of elements between each other, for example, between a bump used for mounting a semiconductor element and a base electrode.

This case is based on the Japanese Patent Application No. 2014-207343 filed on October 8, 2014 in Japan, and claims priority.

Conventionally, when a semiconductor wafer is mounted on a substrate, for example, Au bumps or solder bumps are formed on the Al electrode or the Cu electrode.

Here, for example, when the Al electrode is in direct contact with the Au bump, Al and Au diffuse into each other, and an intermetallic compound of Al and Au is formed, which may cause an increase in resistance or a decrease in adhesion. also. For example, when the Cu electrode is in direct contact with the solder bump, Cu and the Sn in the solder mutually diffuse, and an intermetallic compound of Cu and Sn is formed, which may cause an increase in resistance or a decrease in adhesion.

Therefore, for example, using the W-Ti sputtering target disclosed in Patent Documents 1 and 2, a W-Ti film is formed as a diffusion preventing layer that prevents diffusion of elements between the base electrode and the bump.

Further, the W-Ti sputtering target systems described in Patent Documents 1 and 2 are each produced by a powder sintering method.

Here, when a W-Ti film is formed as a diffusion preventing layer between the base electrode and the bump, after the W-Ti film is formed on the entire surface of the base electrode, a bump is formed to etch away the region where the bump is not formed. -Ti film. However, this W-Ti film has a problem of poor productivity due to the very slow etching rate.

Therefore, Patent Document 3 discloses that the etching rate can be improved by using a W-Ti sputtering target to which Fe is added in a small amount to form Fe in the formed W-Ti film.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent No. 2606946

[Patent Document 2] Japanese Patent Publication No. 05-295531

[Patent Document 3] Japanese Invention Patent No. 4747368

However, as described above, by slightly adding Fe in the W-Ti film, the etching rate is improved, but in the case where the Fe concentration in the W-Ti film is deviated, the etching rate in the W-Ti film is locally changed, and Uniform etching is not possible.

Therefore, a W-Ti sputtering target is desired which is capable of forming a W-Ti film having a small variation in Fe concentration and a uniform etching rate.

The present invention has been accomplished in view of the foregoing, and aims to provide a A W-Ti sputtering target capable of forming a W-Ti film having a small variation in Fe concentration and a uniform etching rate.

In order to solve the above problems, a W-Ti sputtering target system according to an aspect of the present invention has a composition in which Ti is contained in a range of 5 mass% or more and 20 mass% or less, and is in a range of 25 mass ppm or more and 100 mass ppm or less. Containing Fe, the remainder consists of W and inevitable impurities. It is characterized by measuring Fe concentration in a plurality of places in the target surface. When the measured Fe concentration is the maximum value of Fe _max and Fe concentration When Fe _min is satisfied, the relationship of (Fe _max -Fe _min )/(Fe _max +Fe _min )≦0.25 is satisfied.

In the W-Ti sputtering target of the present invention thus constituted, since Fe is contained in a range of 25 ppm by mass or more and 100 ppm by mass or less, the etching rate of the film-formed W-Ti film can be improved.

Further, the Fe concentration is measured in a plurality of places in the target surface, and since the maximum value (Fe _max ) of the measured Fe concentration and the minimum value (Fe _min ) of the Fe concentration satisfy the above relationship, the Fe in the target surface can be suppressed. The deviation of the concentration. Therefore, a W-Ti film having a small variation in Fe concentration and a uniform etching rate can be formed.

As described above, according to the present invention, it is possible to provide a W-Ti sputtering target which can form a W-Ti film having a small variation in Fe concentration and a uniform etching rate.

Fig. 1 is a flow chart showing a method of manufacturing a W-Ti sputtering target according to an embodiment of the present invention.

Fig. 2 is an explanatory view showing a measurement position of a Fe concentration in a target surface of a W-Ti sputtering target having a circular target surface.

Fig. 3 is an explanatory view showing a measurement position of a Fe concentration in a target surface of a W-Ti sputtering target having a rectangular target surface.

Fig. 4 is an explanatory view showing a place where the etching rate of the W-Ti film formed on the substrate is measured in the embodiment.

[Formation of the Invention]

Hereinafter, a W-Ti sputtering target according to an embodiment of the present invention will be described with reference to the accompanying drawings.

The W-Ti sputtering target of the present embodiment is used, for example, for bonding a liquid crystal driver IC to a COF tape, between the Au bump formed on the liquid crystal driver IC and the Al pad portion (base electrode). The W-Ti film is sputtered as a diffusion preventing layer to form a film.

The W-Ti sputtering target of the present embodiment has a composition containing Ti in a range of 5 mass% or more and 20 mass% or less, Fe in a range of 25 mass ppm or more and 100 mass ppm or less, and the remainder being W and none. It can be avoided by impurities that can be avoided.

Moreover, the Fe concentration is measured at a plurality of places in the target surface, and when the maximum Fe concentration measured is Fe _max and the minimum Fe concentration is Fe _min , (Fe _max -Fe _min )/(Fe _max + is satisfied). Fe _min ) ≦ 0.25 relationship.

Explain the reason for the composition of the components specified above.

<Ti: 5 mass% or more and 20 mass% or less>

When the Ti content in the W-Ti sputtering target is less than 5% by mass, the adhesion between the formed W-Ti film and the base electrode is lowered. On the other hand, when the Ti content in the W-Ti sputtering target exceeds 20% by mass, the electric resistance of the film-formed W-Ti film rises, and the film-formed W-Ti film cannot sufficiently prevent the formation of the bump. The element (in the present embodiment, Au) and the element constituting the base electrode (Al in the present embodiment) are mutually diffused.

Therefore, in the present embodiment, the content of Ti in the W-Ti sputtering target is set to be in the range of 5 mass% or more and 20 mass% or less.

Further, the lower limit of the content of Ti is preferably 7% by mass or more, and more preferably 9% by mass or more. Further, the upper limit of the content of Ti is preferably 15% by mass or less, and more preferably 13% by mass or less.

<Fe: 25 mass ppm or more and 100 mass ppm or less>

When the content of Fe in the W-Ti sputtering target is less than 25 ppm by mass, the etching rate of the W-Ti film to be formed may not be sufficiently improved. another When the content of Fe in the W-Ti sputtering target exceeds 100 ppm by mass, the film-formed W-Ti film cannot sufficiently prevent the elements constituting the bump (in the present embodiment, Au) and the elements constituting the base electrode. (Al in the present embodiment) is mutually diffused.

Therefore, in the present embodiment, the content of Fe in the W-Ti sputtering target is set to be in the range of 25 ppm by mass or more and 100 ppm by mass or less.

Further, the lower limit of the content of Fe is preferably 30 ppm by mass or more, and more preferably 35 ppm by mass or more. Further, the upper limit of the content of Fe is preferably 75 ppm by mass or less, more preferably 50 ppm by mass or less.

(Fe _max -Fe _min )/(Fe _max +Fe _min )≦0.25

When the W-Ti film is formed using the W-Ti sputtering target in the present embodiment, the entire surface of the target surface of the W-Ti sputtering target is formed into a film.

Here, the Fe concentration is measured at a plurality of places in the target surface, and the Fe concentration in the target surface is determined when the maximum value (Fe _max ) of the measured Fe concentration and the minimum value (Fe _min ) of the Fe concentration satisfy the above relationship. The deviation becomes smaller. Therefore, in the W-Ti film formed by using this W-Ti sputtering target, the variation in Fe concentration also becomes small, and the etching rate becomes uniform.

Further, (Fe _max -Fe _min ) / (Fe _max +Fe _min ) is preferably 0.2 or less, more preferably 0.15 or less. Moreover, the lower the (Fe _max -Fe _min ) / (Fe _max +Fe _min ), the better, but the extreme decrease of (Fe _max -Fe _min ) / (Fe _max +Fe _min ) leads to an increase in cost, therefore ( Fe _max -Fe _min )/(Fe _max +Fe _min ) may be 0.005 or more.

Here, in the present embodiment, when the target surface of the W-Ti sputtering target is circular, as shown in FIG. 2, two strips are mutually orthogonal at the center of the circle (1) and the center of the circle. The concentration of Fe was measured at five points of the outer peripheral portions (2), (3), (4), and (5) on the straight line, and the maximum value (Fe _max ) of the above Fe concentration and the minimum value of Fe concentration (Fe _{min) were obtained.} ). The outer peripheral portions (2), (3), (4), and (5) may be, for example, a position from the periphery of the target to a center side of about 10 mm.

Further, when the target surface of the W-Ti sputtering target is rectangular, as shown in FIG. 3, the intersection (1) at the diagonal crossing and the corner portions (2), (3), (on each diagonal line) At 5 points of 4) and (5), the Fe concentration was measured, and the maximum value (Fe _max ) of the above Fe concentration and the minimum value (Fe _min ) of the Fe concentration were obtained. The corner portions (2), (3), (4), and (5) may be, for example, positions from the vertex to the intersection side of about 10 mm.

The number of places where the Fe concentration is measured may be 5 or more and 20 or less. At that time, the measurement local system may be a point where the target center point is about 10 mm from the intersection of the straight line passing through the center and the outer periphery of the target toward the center side.

Next, an embodiment in which the W-Ti sputtering target of the present embodiment is manufactured will be described with reference to a flowchart of Fig. 1.

As shown in Fig. 1, the method for producing a W-Ti sputtering target according to the present embodiment includes a mixing and pulverizing step S01 in which a raw material powder blended with a predetermined blending amount is mixed and pulverized, and a mixed pulverized raw material powder. The sintering step S02 is performed by heating, and the processing step S03 of the sintered body obtained by the processing.

First, Ti powder, W powder, and Fe powder were prepared as raw material powders. Here, as the Ti powder, a purity of 99.999 mass% or more and an average particle diameter of 1 μm or more and 40 μm or less are preferably used. Also, as W powder At the end, it is preferred to use a purity of 99.999 mass% or more and an average particle diameter of 0.5 μm or more and 20 μm or less. Further, as the Fe powder, those having a purity of 99.999 mass% or more and an average particle diameter of 75 μm or more and 150 μm or less are preferably used.

<mixing and pulverizing step S01>

When the raw material powder is weighed, Ti is contained in a range of 5 mass% or more and 20 mass% or less, Fe is contained in a range of 25 mass ppm or more and 100 mass ppm or less, and the remainder is composed of W and inevitable impurities. The composition is simultaneously mixed and pulverized. In the present embodiment, the weighed raw material powder is mixed by a ball mill, and a ball made of a cemented carbide is used, and the mixture is pulverized by a grinding device.

By this mixing pulverization step S01, the Fe powder is pulverized until the average particle diameter becomes 10 μm or less.

<Sintering step S02>

Next, the raw material powder (mixed powder) which has been mixed and pulverized as described above is sintered in a vacuum or an inert gas atmosphere or a reducing atmosphere. In the sintering step S02, the Fe powder which has been pulverized to have an average particle diameter of 10 μm or less is uniformly diffused in W.

Here, the sintering temperature in the sintering step is preferably set in accordance with the melting point Tm of the W-Ti alloy to be produced.

In the sintering step S02, as the sintering method, normal pressure sintering, hot pressing, or hot hydrostatic pressure pressing may be employed.

In the present embodiment, the raw material powder (mixed powder) is filled in a graphite mold, and is sintered by a vacuum hot pressing at a pressure of 10 MPa or more and 60 MPa or less and a temperature of 1000 C or more and 1500 ° C.

<Processing Step S03>

The sintered body obtained in the sintering step S02 is subjected to a cutting process or a grinding process to be processed into a sputtering target of a predetermined shape.

The W-Ti sputtering target of this embodiment was produced by the above steps. This W-Ti sputtering target is bonded to a back sheet made of Cu or SUS (stainless steel) or other metal (for example, Mo) using In as a solder.

According to the W-Ti sputtering target of the present embodiment configured as described above, since Fe is contained in a range of 25 ppm by mass or more and 100 ppm by mass or less, the etching rate of the W-Ti film formed can be improved.

Then, the Fe concentration is measured at a plurality of places in the target surface, and the maximum value (Fe _max ) of the measured Fe concentration and the minimum Fe concentration (Fe _min ) satisfy (Fe _max -Fe _min ) / (Fe _max + Fe _min ) ≦ 0.25 relationship, and suppress the deviation of Fe concentration in the target surface. Therefore, a W-Ti film having a small variation in Fe concentration and a uniform etching rate can be formed.

In addition, in the present embodiment, the Ti powder, the W powder, and the Fe powder are mixed and pulverized, and the Fe powder before sintering has a particle diameter of 10 μm or less, so that Fe particles can be uniformly diffused in the mother phase during sintering. In W, Fe can be uniformly distributed throughout the sintered body. The particle diameter of the Fe powder before sintering is preferably 5 μm or less, more preferably 2 μm or less, but is not affected by this. Limited. Further, the smaller the particle diameter of the Fe powder before sintering, the better, but if the particle diameter of the Fe powder before sintering is extremely lowered, the cost is increased. Therefore, the particle diameter of the Fe powder before sintering can be 0.1 μm or more.

In addition, when a fine Fe powder containing 50% or more of the entire particles of 50 μm or less is used as it is, it is necessary to operate as a dangerous substance. However, in the present embodiment, Fe powder having an average particle diameter of 75 μm or more and 150 μm or less is used. The other raw material powders (Ti powder and W powder) are mixed and pulverized to have a particle diameter of 10 μm or less, and the ratio of the Fe powder is sufficiently low, and the handling becomes easy.

The embodiment of the present invention has been described above, but the present invention is not limited thereto, and can be appropriately modified without departing from the scope of the present invention.

For example, in the present embodiment, the raw material powder may be mixed and pulverized by using a grinding device, but the raw material powder may be mixed and pulverized by another method.

Further, a method of mixing and pulverizing the raw material powder includes a planetary ball mill, a vibration ball mill, and the like.

Examples of the inevitable impurities in the W-Ti sputtering target include Na, K, Ca, Ni, Cr, Mn, and the like. The total of these unavoidable impurities is preferably 0.01% by mass or less, but is not limited thereto.

[Examples]

Hereinafter, the results of an evaluation test evaluated for the effects of the W-Ti sputtering target of the present invention will be described.

<Example of the invention>

As the raw material powder, a Ti powder having a purity of 99.999 mass% and an average particle diameter of 15 μm, a W powder having a purity of 99.999 mass% and an average particle diameter of 1 μm, and an Fe powder having a purity of 99.999 mass% and an average particle diameter of 100 μm were prepared. The Ti powder, the Fe powder, and the W powder were weighed in such a manner as to have the composition shown in Table 1.

Among the Ti powder, Fe powder and W powder weighed, W powder and Fe powder were placed in a grinding device (NIPPON COKE Industrial Co., Ltd. MA1D) together with a super hard alloy ball having a diameter of about 5 mm. The mixture was pulverized in an Ar environment under conditions of 300 ppm for 1 hour. Further, inside the mixing container of the attritor, in order to prevent the incorporation of impurities from the container during the pulverization and mixing, the inner layer of the W foil is applied. Here, the input weight of the superhard alloy ball is about 10 times the input weight of the W powder and the Fe powder.

The mixed powder of the W powder, the Fe powder, and the Ti powder were mixed by a rotary ball mill apparatus to obtain a mixed powder. Here, the mixed powder before sintering was observed by an EPMA apparatus, and the Fe particles were identified by analyzing the image by the characteristic X-ray surface, and the particle diameter was confirmed. The particle size is shown in Table 1. The Fe particle systems tested all had particle sizes of less than 10 μm.

The obtained mixed powder was filled in a graphite mold, and a hot-pressed sintered body was produced by vacuum hot pressing under the conditions of pressure: 15 MPa, temperature: 1200 ° C, and holding for 3 hours, and the obtained hot-pressed sintered body was machined. A W-Ti sputtering target of the present invention having a diameter of 152.4 mm and a thickness of 6 mm was produced.

<Comparative example>

As the raw material powder, a Ti powder having a purity of 99.999 mass% and an average particle diameter of 15 μm, a W powder having a purity of 99.999 mass% and an average particle diameter of 1 μm, and an Fe powder having a purity of 99.999 mass% and an average particle diameter of 100 μm were prepared. The Ti powder, the Fe powder, and the W powder were weighed in such a manner as to have the composition shown in Table 1.

The Ti powder, the Fe powder, and the W powder were weighed by rotating a ball mill apparatus to obtain a mixed powder. That is, in the comparative example, the pulverization of the raw material powder was not performed. Here, the mixed powder before sintering was observed by an EPMA apparatus, and the Fe particles were identified by analyzing the image by the characteristic X-ray surface, and the particle diameter was confirmed. The particle size is shown in Table 1. The Fe particles detected had a particle diameter substantially as shown in Table 1 as the maximum value.

The obtained mixed powder was filled in a graphite mold, and a hot-pressed sintered body was produced by vacuum hot pressing under the conditions of pressure: 15 MPa, temperature: 1200 ° C, and holding for 3 hours, and the obtained hot-pressed sintered body was machined. A W-Ti sputtering target of a comparative example having a diameter of 152.4 mm and a thickness of 6 mm was produced.

<Fe concentration in the target surface>

When the target surface of the obtained W-Ti sputtering target is a circular (circular target), as shown in FIG. 2, the center of the circle (1) and the two straight lines passing through the center and orthogonal to each other At a position of about 10 mm (2), (3), (4), (5), using a bit made of a superhard alloy to collect the composition Samples for analysis.

Further, when the target surface of the obtained W-Ti sputtering target is a rectangular shape (square type target), as shown in FIG. 3, the intersection point (1) from the diagonal intersection and the corner portion from each diagonal line are about 10 mm. At the five points of positions (2), (3), (4), and (5), a sample for composition analysis was collected using a drill made of a cemented carbide.

The Fe concentration of these samples was analyzed by ICP emission spectrometry. The measurement results are shown in Table 2.

<Formation of W-Ti film>

Next, the above-described examples of the invention and the W-Ti sputtering target of the comparative example were welded to a back sheet made of oxygen-free copper, and this was mounted on a sputtering apparatus (SIH-450H manufactured by ULVAC Co., Ltd.) under the following conditions. Sputtering is performed to form a film.

Substrate: Si substrate with a diameter of 100 mm

Reaching vacuum: <5×10 ^-5 Pa

Distance between substrate and target: 70mm

Electricity: DC 600W

Gas pressure: Ar 1.0Pa

Substrate heating

Film thickness: 300nm

<W-Ti film etching rate evaluation>

Among the 100 mm diameter Si substrates thus obtained, from Fig. 4 A sample of 20 mm square was cut out at the position of the three places shown. Further, the sample was cut into two portions of 10 mm × 20 mm, and one of the cut samples was immersed in 31 vol% hydrogen peroxide water at a liquid temperature of 30 ° C for 5 minutes by a water bath. After taking out from hydrogen peroxide, the sample was sufficiently washed with pure water, and the dry air was blown off to blow off the droplets of the adhered pure water, and the sample was dried.

For both the side of the sample which was not immersed in the hydrogen peroxide water and the side which was immersed, the cross section was observed by a field emission type scanning electron microscope (FE-SEM: Hitachi High-Tech Co., Ltd. SU-70). The film thickness of the W-Ti film. The film thickness difference between the side immersed in hydrogen peroxide and the side not immersed was determined, and the film thickness difference was divided by the immersion time (5 minutes), and the etching rate at each position of the substrate having a diameter of 100 mm was calculated. The results are shown in Table 3.

In Comparative Example 1-6, as shown in Table 2, it was confirmed that the variation in the Fe concentration in the target surface became large. When the variation in the Fe concentration in the target surface is large, it is presumed that the raw material powder is not pulverized, and Fe particles having a large particle diameter are used for sintering.

In particular, in Comparative Examples 2 and 5 in which the Fe concentration was low, the Fe concentration was locally small, and the maximum difference in Fe concentration was also increased.

In the W-Ti film of Comparative Example 11-16 formed by using the W-Ti sputtering target of Comparative Example 1-6, it was confirmed that the etching rate was not uniform.

Further, in the W-Ti films of Comparative Examples 12 and 15 formed by using the W-Ti sputtering targets of Comparative Examples 2 and 5 having a low Fe concentration, it was confirmed that the local etching rate was extremely slow.

With respect to this, in the inventive examples 1-6, it was confirmed that the variation in the Fe concentration in the target surface became small. It is estimated that the variation in the Fe concentration in the target surface is small, and the raw material powder is mixed and pulverized, and the Fe particles having a small particle diameter are used for sintering.

Further, in Examples 3 and 6 of the present invention in which the concentrations of Examples 2, 5 or Fe of the present invention having a low Fe concentration were low, the variation in Fe concentration was small and stable.

In the W-Ti film of Inventive Example 11-16 formed by using the W-Ti sputtering target of Inventive Example 1-6, it was confirmed that the etching rate was uniform.

In particular, in the W-Ti film of the inventive examples 12 and 15 formed by using the W-Ti sputtering target of the inventive examples 2 and 5 having a low Fe concentration, Fe is also surely added to the W-Ti film. The etch rate is stable.

Further, in the W-Ti films of the inventive examples 13 and 16 formed by using the W-Ti sputtering targets of the inventive examples 3 and 6 having a high Fe concentration, variations in the etching rate were sufficiently suppressed.

According to the results of the above confirmation experiment, it was confirmed that a W-Ti film having a small variation in Fe concentration and a uniform etching rate can be formed according to the example of the present invention.

[Industry use possibility]

According to the W-Ti sputtering target of the present invention, a W-Ti film having a small variation in Fe concentration and a uniform etching rate can be formed. The W-Ti sputtering target of the present invention is suitable, for example, for forming a W-Ti film as a diffusion preventing layer which prevents diffusion of elements between each other between the bumps used for mounting the semiconductor element and the substrate electrode.

Claims (1)

A W-Ti sputtering target having a composition containing Ti in a range of 5 mass% or more and 20 mass% or less, Fe containing 25 mass ppm or more and 100 mass ppm or less, and the remainder being W and none. Consistent impurities are formed, and the Fe concentration is measured at a plurality of places in the target surface. When the maximum Fe concentration measured is Fe _max and the minimum Fe concentration is Fe _min , the (Fe _max -Fe _min ) is satisfied. / (Fe _max + Fe _min ) ≦ 0.25 relationship.