KR960001594B1 - Ti-w sputtering target materials and the method for making - Google Patents

Abstract

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Description

Ti-W target material and its manufacturing method

1 is a metal texture photograph of a target material (target material) of an embodiment of the present invention.

2 and 3 are photographs of metal structures of the target material of the comparative example.

4 is a graph showing the relationship between the W area ratio, the number of particles generated and the alloying heat treatment temperature of the target material of the present invention.

5 is a graph showing the relationship between the average grain size of the target material of the present invention and the alloying heat treatment temperature.

[Industrial use]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a Ti-W target material used for forming a barrier metal layer used for a semiconductor device, and the like and a method of manufacturing the same.

[Prior art]

Barrier metal layers are needed as a countermeasure for migration of Al wiring due to high integration of LSI in recent years.

As the barrier metal layer, many Ti-W thin films (typically having a composition of Ti: 10 wt% and the rest of W) are used, and a method of sputtering a target is adopted as the formation method.

Generally this thin film Ti-W target material is manufactured by mixing W powder and Ti powder, and hot pressing.

However, the Ti powder, which is a raw material of the conventional Ti-W target material, has a high oxygen content, and only a target material having a high oxygen content is obtained due to oxygen pick up when the Ti powder is finely pulverized. there was.

In such a target material with a high oxygen content, the release of oxygen during sputtering causes cracking of the target material, oxidation of the resulting thin film, and change (deterioration) in the thin film quality, which is not suitable.

Recently, as a method of reducing the oxygen content of such Ti-W targets, a method of using hydrogenated Ti powder instead of Ti powder has been described in U.S. Patent Nos. 4,838,935 and JP 63-303017. .

The use of this hydrogenated Ti powder is effective for preventing oxidation on its own and at the same time, since the crushability is better than that of Ti powder, the amount of oxygen pickup at the time of grinding can be reduced.

In this way, by using the hydrogenated Ti powder as Ti powder, the Ti-W target of the oxygen concentration set to 900 ppm or less was obtained.

[Problem to Solve Invention]

However, according to the high density and thinning of the electrode pattern of recent semiconductor products, the electrode wiring is formed by attaching the large particles and the so-called particles to the thin film formed by sputtering using the above-described low oxygen concentration Ti-W target and sputtering. There has been a new problem of disconnecting.

This particle generation cannot be solved only by reducing the oxygen content of the Ti-W target, and was assumed to be related to coarse Ti particles and Ti segregation present in the Ti-W target structure.

The present inventors examined the relationship between target tissue and particle generation in detail and found that coarse Ti phase is related to particle generation. That is, since Ti, which is light in atomic weight, is selectively sputtered in Ti and W, the place where Ti is present is perforated. In this case, it was found that scattering of the W phase surrounded by the coarse Ti phase or the coarse (phase) group or the W phase near the coarse Ti phase was scattered from the target material as a large phase cause of particle generation.

An object of the present invention is to provide a Ti-W target material controlled to a structure with extremely low particle generation and a method for producing the same.

[Means for solving the problem]

The present invention is effective because the Ti phase is diffused as a target material without scattering of the W phase due to the difference in the sputtering rate between Ti and W, and the Ti-W alloy phase is heated by heating to a specific temperature at which the grain size is not coarsened. We found that it was effective to arrange and to eliminate Ti phase.

That is, the present invention is a Ti-W target material comprising a W phase and a Ti-W alloy phase surrounding it.

The target material of the present invention forms a Ti-W alloy phase by heating the material obtained by sintering the Ti powder and the W powder in a specific temperature range, thereby disappearing the Ti phase.

By dissipating the Ti phase in this manner, Ti having a small atomic weight is not selectively sputtered, and generation of particles can be significantly reduced.

Moreover, although this invention reduces by alloying with W phase Ti by the said heat processing, it is good that the area ratio which the W phase occupies for the Ti-W target material cross section is 15% or less.

Although the W phase has a small degree in order to perform a homogeneous sputter | spatter, especially when a ratio which occupies for 10% or less of a target material cross section can obtain a homogeneous thin film.

In addition, in the present invention, when the average crystal grain size is particularly 15 µm or less, the influence of the crystal orientation of each crystal grain is less, and a homogeneous thin film is obtained by sputtering, which is good. In the present invention, the heat treatment of the sintered body is advantageous for the diffusion of Ti as the temperature is high, but a heat treatment temperature of 1550 ° C. or less is suitable for making the crystal grain size 15 μm or less. Moreover, when a small average grain size, for example, 10 micrometers or less is needed, the heat processing temperature is preferably 1500 degrees C or less.

Here, the Ti-W target of the present invention is mixed and pulverized W powder and hydrogenated Ti powder having a particle diameter of 25 μm or less, finely powdered to an average particle diameter of less than 5 μm and a maximum particle diameter of less than 10 μm, and then dehydrogenated. Alternatively, pressure sintering is carried out while dehydrogenating to obtain a sintered body, and the resulting sintered body is heat-treated from 1300 to 1550 ° C. to obtain a substantially W phase and a Ti-W alloy phase structure surrounding it.

The particle size of the hydrogenated Ti powder is 25 µm or less for facilitating fine powdering in the mixed grinding process and for promoting the reaction of Ti to the Ti-W alloy.

The smaller the particle size of the hydrogenated Ti, the smaller the condition that the Ti phase does not oxidize.

In the mixed pulverizing treatment, a device for performing pulverized mixing such as a ball mill or an attritor may be used. In the present invention, the pulverized mixing may be performed separately from the pulverizing and mixing, the pulverizing and mixing may be performed simultaneously, or the Ti powder and the W powder may be in the form of fine powder or may be mixed.

The Ti powder and W powder hydrogenated by the pulverization mixing treatment are finely divided to an average particle diameter of less than 5 µm and a maximum particle diameter of less than 10 µm. Such fine powdering is important for substantially eliminating the Ti phase without growing grains in the case where the reaction system is heated to increase the area of the reaction system.

In particular, when the maximum particle diameter exceeds 10 µm, the Ti phase remains even after long time heat treatment, which is not suitable for practical use.

Moreover, heat processing the obtained sintered compact from 1300 to 1550 degreeC is for producing | generating a Ti-W alloy phase, suppressing growth of a crystal grain by the diffusion reaction by heating. When heated above 1550 ℃, since the raw material is almost pure material of Ti and W, the grain size of the sintered body becomes too large to obtain a homogeneous thin film having a large influence on the crystal orientation, and less than 1300 ℃, it hardly alloys even for more than 50 hours. It is not suitable for practical use.

In the above-mentioned pressure sintering, a hot hydrostatic press (hereinafter referred to as HIP) or a hot press is used.

The impurity concentration of oxygen, radioactive elements, etc. should be as low as possible for the delivery of Ti, hydrogenated Ti, and W as raw materials. The incorporation of oxygen deteriorates the electrical properties of the thin film, and the incorporation of radioactive elements is associated with a malfunction and breakdown of the semiconductor device.

EXAMPLE

Example 1

Hydrogenated high purity Ti (purity 99.99% or more, average particle diameter 75 μm or less: hereinafter referred to as hydrogenated Ti) was classified into a 500 mesh (25 μm) sieve, and a purity W powder (purity 99.999% or more, average particle size 5 μm or less) ) Is mixed to a hydrogenated Ti 10.36wt%, and inserted into a tungsten tension pot and a dedicated ball using a tungsten ball, vacuum evacuated the vessel, and then substituted with argon gas for 90 minutes in a non-oxidizing atmosphere. Mix while grinding.

The obtained mixed powder was 3.1 micrometers in average particle diameter, and was 8 micrometers of maximum inputs.

In addition, the oxygen content of the mixed powder was 820 ppm.

The obtained mixed powder was filled into a HIP tube having an internal diameter of 400 Ø, heated at 700 ° C. for 24 hours while evacuating to 5 × 10 ⁻⁵ torr and subjected to dehydrogenation. After dehydrogenation, the HIP tube was sealed and HIP treatment was performed under conditions of 1250 ° C. × 2 hours at 1000 atm.

600 times the structure | tissue photograph of the obtained sintered compact is shown in FIG. In FIG. 2, the white particles are in the W phase, and the gray portions present in the W phase are in the Ti phase. As shown in FIG. 2, no Ti-W alloy phase is identified at this stage. The average crystal grain size of the sintered compact at this time was 4 micrometers.

Subjected to heat treatment for the alloy under the conditions of 1380 ℃℃ × 24 hours in a vacuum of 10 ^-5 Torr sintered body (torr) to obtain a target material.

The oxygen content of the obtained target material was usually 850 ppm, and the average crystal grain diameter was 6 micrometers.

600 times the tissue photograph of the obtained target material is shown in FIG.

In FIG. 1, the white portion is W phase, and the gray portion substantially enclosing the W phase is a Ti-W alloy phase.

As shown in FIG. 1, the target material which Ti phase was not confirmed was obtained.

This target material was processed into 300 phi to be a target. This target was used to sputter onto a 15.3 cm (6 inch) wafer.

As a result of inspecting the number of particles in the sputtered film, it was confirmed that the number of particles in particles of 0.5 µm or more was very small, and that of particles in particles of 0.3 µm or more was 12.

Comparative Example 1

HIP treatment was carried out under the same conditions as in Example, to obtain a sintered body similar to the structure shown in FIG. This sintered compact was processed into 300 phi as it was, without heat-processing for the alloying performed in Example 1, and it was set as the target.

The target was sputtered onto a 15.3 cm (6 inch) wafer under the same conditions as in Example 1.

As a result of inspecting the number of particles in the sputtered film, 30 particles from 0.5 µm or more particles and 140 particles from 0.3 µm or more became very large as compared with Example 1, which was not suitable.

Comparative Example 2

In this comparative example, the hydrogenated Ti powder used as a raw material uses a large particle size and adjusts the precision of particle generation.

The high purity W powder (purity of 99.999% or more and the average particle diameter of 5 m or less) is made 10.36wt% without classifying hydrogenated high purity Ti (purity 99.99% or more, average particle diameter of 75 µm or less: hereinafter referred to as hydrogenated Ti). The mixture was blended and inserted into a dedicated ball mill using a tungsten tension container and a tungsten ball, and then the inside of the container was evacuated, and then replaced with argon gas and mixed while grinding in a non-oxidizing atmosphere for 90 minutes.

The obtained mixed powder was 4.0 micrometers in average particle diameter, and was 19 micrometers in maximum particle diameter.

The obtained mixed powder was packed into a HIP tube having an internal diameter of 400 Ø in the same manner as in Example 1, and heated at 700 ° C. for 24 hours while evacuating to 5 × 10 ⁻⁵ Torr for dehydrogenation. After dehydrogenation, the HIP tube was sealed and subjected to HIP treatment at 1250 ° C for 2 hours at 1000 atm.

The target material which alloyed the obtained sintered compact similarly to Example 1 was obtained.

The oxygen content of the obtained target material was 550 ppm, and the average crystal grain diameter was 6 micrometers.

In FIG. 3, the structure | tissue photograph of the obtained target material is shown. In FIG. 3, the white portion is in the W phase, the gray portion Ti-w alloy substantially enclosing the W phase, and the black portion in the Ti-w phase is the Ti phase. Thus, when the raw material powder of hydrogenated Ti exceeds 25 micrometers in particle size, it will remain in Ti phase even if heat processing of a sintered compact is performed.

This target material was processed into 300 phi to be a target. This target was used to sputter onto a 15.3 cm (6 inch) wafer.

As a result of inspecting the number of particles in the sputter film, eight particles of 0.5 µm or more were equivalent to Example 1, but 0.3 µm or more had more than 40 particles of Example 1, and the Ti phase was different from the present invention in particle generation. It was confirmed that there was no superior.

Example 2

For the alloying obtained in the same manner as in Example 1, the target material obtained by changing the heat treatment for alloying at a vacuum degree of 10-5 for 24 hours to the heat treatment temperature was subjected to the sintered compact before the heat treatment.

The obtained target material was processed into 300 phi to be a target.

Using this target, sputtering was performed on a 15.3 (6 inch) wafer, and particle generation conditions of 0.3 mm or larger were observed.

The relationship between the W area ratio of this target material, the number of particle generations, and the heat processing temperature for alloying is shown in FIG.

In addition, in the Example which heat-treated 1300 degreeC or more, it confirmed that it was the structure without a Ti phase by the observation of the target structure.

It was found from FIG. 4 that increasing the heat treatment temperature decreases the W area ratio, and consequently decreases the number of particles. In addition, the W area ratio is smaller because the number of particles decreases, but when the W area ratio is 15% or less, it is found that the W area ratio is 15% or less because the particle number hardly depends on the W area ratio.

In addition, the relationship between the average grain size and the alloying heat treatment temperature measured by the observation of the target material fracture surface is shown in FIG.

It was also found from FIG. 5 that when the heat treatment temperature of alloying exceeds 1550 ° C., the average grain size rapidly increases and is not suitable.

[Effects of the Invention]

The present invention is extremely effective for improving the quality of semiconductor devices because sputtering of extremely high quality can be performed by the Ti-W target material which is hard to generate particles. In addition, since the target agent of the present invention has a low oxygen content, it is possible to prevent degradation of electrical characteristics by the cracking of the target material and oxidation of the resulting thin film, and also to have a good effect of suppressing the change (deterioration) of the quality of the thin film.

Claims (5)

A Ti-W target material comprising a W phase and a Ti-W alloy phase surrounding it. Ti-W target material which consists of a W phase and the Ti-W alloy phase which surrounds this, and whose average grain size is 15 micrometers or less. The Ti-W target material according to claim 1, wherein the area ratio of the W phase in the Ti-W target material cross section is 15% or less. The Ti-W target material according to claim 2, wherein the area ratio of the W phase in the Ti-W target material cross section is 15% or less. W powder and hydrogenated Ti powder having a particle diameter of 25 µm or less are mixed and ground, and finely powdered to an average particle diameter of less than 5 µm and a maximum particle diameter of less than 10 µm, followed by pressure sintering after dehydrogenation or pressure sintering while dehydrogenation. To obtain a target composed of a W phase and a Ti-W alloy phase enclosing the obtained sintered body by heating the obtained sintered body from 1300 ° C to 1550 ° C.