KR930003516B1 - Titanium tungsten target material for sputtering and manufacturing method therefor - Google Patents

Abstract

No content.

Description

Titanium-tungsten target material for sputtering and manufacturing method thereof

1 is a photograph showing the microstructure of an alloy as a sintered material.

2 is a photograph showing the microstructure of an alloy which is a target material according to the present invention obtained by heat treatment for 5 hours.

3 is a photograph showing the microstructure of an alloy, which is a target material according to the present invention, obtained by heat treatment for 24 hours.

4 is a photograph of a microstructure showing the size of fractured surface crystal grains, which is a target material according to the present invention, obtained by heat treatment for 50 hours.

5 is a graph showing the relationship between heat treatment time and titanium area ratio.

6 is a graph showing the relationship between the heat treatment time and the area of titanium-tungsten alloy phases.

7 is a graph showing the relationship between heat treatment time and average diameter of crystal grains.

8 is a graph showing the relationship between the heat treatment time and the number of particles deposited on the wafer surface having a diameter of 6 inches.

9 is a graph showing the relationship between the heat treatment temperature and the titanium area ratio.

10 is a graph showing the relationship between the heat treatment temperature and the area ratio of the titanium-tungsten alloy phase.

11 is a graph showing the relationship between the heat treatment temperature and the average diameter of the crystal grains.

12 is a graph showing the relationship between the heat treatment temperature and the number of particles deposited on the wafer surface having a diameter of 6 inches.

The present invention relates to a titanium-tungsten (Ti-W) target material used to form or fabricate a barrier metal layer for use in semiconductor devices and a method of manufacturing the same.

As the integration of LSI has increased in recent years, the movement of aluminum (Al) by the interdiffusion in the contact portion between the aluminum wiring and the semiconductor substrate silicon has been a problem. As a countermeasure against such a problem, it has been examined to interpose the barrier metal layer in the space between the aluminum wiring and the silicon substrate.

Titanium-tungsten thin films (typically composed of 10 wt% titanium and the balance of tungsten) are often used as barrier metal layers. The method of sputtering a target is used as a method of forming such a titanium-tungsten thin film.

Generally, such titanium-tungsten target materials for thin films are prepared by mixing and hot-pressing tungsten powder and titanium powder.

However, since titanium powder provided as a raw material of a normal titanium-tungsten target has a high oxygen content, only a target having a high oxygen content is obtained.

In such a target material having a high oxygen content, as oxygen is released during sputtering, undesirable problems such as cracking of the target, oxidation of the resulting film, and change in film quality occur.

US 4,838,935 describes a method for reducing the oxygen content of such titanium-tungsten targets. In this document titanium-tungsten target materials with reduced carbon and oxygen content can be obtained with high density and low porosity. Titanium-tungsten target material is obtained by replacing one or more fractions of titanium powder with titanium hydride and by using tungsten powder and hydrogenated powder with a distribution of binodal particle diameters or by using a mixture of titanium hydride powder and titanium powder. Can be obtained.

In addition, Japanese Patent Laid-Open No. 63-303017 describes a method of reducing the oxygen content of a titanium-tungsten target. In this method, tungsten powder and titanium hydride powder are mixed together and hot pressed after dehydrogenation or with dehydrogenation.

Since the use of the titanium hydride powder itself is effective for preventing oxidation and the grinding property is better than the titanium powder, the amount of oxygen pick-up can be reduced when the titanium hydride powder is pulverized.

In this way, a titanium-tungsten target having an oxygen concentration of 900 ppm or less can be obtained.

As mentioned above, in the titanium-tungsten target material, research for reducing oxygen content has been extensively performed.

However, the publication does not describe how the structure of titanium and tungsten constituting the target affects sputtering. That is, the publication does not describe at all what relates to the microstructure, in particular the presence of a titanium phase, to the occurrence of particle phenomena which will be described later during sputtering.

With the high density and thinning of electrode patterns of recent semiconductor products, even when sputtered using the above-described low-oxygen titanium-tungsten target, large particles called "particles" are produced in the thin film as a result of sputtering. This has caused a new problem of disconnecting the electrode wiring.

The generation of such particles could not be solved simply by reducing the oxygen content of the titanium-tungsten target.

To solve this problem, the inventor of the present invention has examined in detail the relationship between the target structure and the generation of particles and found that the giant titanium particles are related to the generation of particles. That is, the inventors have found that when both titanium and tungsten are present, the atomic weight titanium is selectively sputtered, and the tungsten particles adjacent or embedded in the large titanium particles are scattered from the ticket material in the form of large diameter particles. This is one of the reasons for the generation of matrix particles.

It is therefore an object of the present invention to provide a titanium-tungsten target material for the sputtering method, which is an adjusted or controlled structure in which particles of a thin film or deposited film hardly occur, and a method of manufacturing such a target material.

The inventors have found that due to the difference in the sputtering rates of titanium and tungsten, it is effective for producing a titanium-tungsten alloy phase as a target material in which tungsten particles are not deposited on the film.

The present invention provides a titanium-tungsten target material for sputtering, characterized in that the structure essentially comprises a titanium-tungsten alloy phase having an area ratio of 20% or more of the microstructure occupying the tungsten phase, the titanium phase and the titanium-tungsten target material cross section. to provide. The titanium-tungsten target material is composed of dispersed tungsten particles, titanium phase (or particles) dispersed adjacent to the titanium-tungsten particles substantially surrounding the tungsten particles (or phases).

Formation of the titanium-tungsten alloy phase can substantially reduce the amount of titanium phase to prevent the occurrence of crude titanium particles in the target material of the present invention. The difference in the sputtering rate of the tungsten phase and the titanium phase can be reduced by forming a titanium-tungsten alloy phase.

The area ratio of the titanium-tungsten alloy phase is 20% or more, which is a requirement for substantially reducing the deposition of particles in the thin film. The titanium-tungsten alloy phase can hardly be formed when the alloy contains the titanium-tungsten alloy phase to the extent that the alloy is formed in the fraction compressed to bond the tungsten powder and the titanium powder to each other.

In the present invention, the area ratio of the titanium-tungsten alloy phase is limited to 20% or more in order to designate the amount of the titanium-tungsten alloy phase that can reduce the generation of particles.

Certain alloys of titanium and tungsten can be used as titanium-tungsten alloy phases despite their composition. Titanium-tungsten alloy phase containing fine α-titanium precipitated upon cooling is not included in the present invention.

In the present invention, the tungsten and titanium phases do not necessarily include only tungsten and titanium, respectively. For example, when heating the sintered body of tungsten and titanium powder, it is natural that a small amount of titanium diffuses on the tungsten of the obtained structure. Likewise, small amounts of tungsten can diffuse onto titanium.

The average diameter of the crystal grains in the titanium-tungsten target material is preferably 10 μm or less in the present invention and is determined by the following method. Photograph showing the structure of the wavefront of the target material is taken. A number of plain straight lines are drawn on the photo at 20mm intervals. The number of crystal grains divided by the line and the diameter are measured. The total diameter of each crystal grain is divided by the crystal grain index. The share is defined as the average diameter of the crystal grains. As the average diameter of the crystal grains in the titanium-tungsten target material increases, the sputtering method affects the crystal orientation of each crystal grain. As the sputtering rate for each crystal grain changes, irregularities are generated on the target surface. Particles increase in the plate membrane because sputtered particles adhere to or separate from the surface irregularities.

It is desirable for the target to be as small as possible to have a grain size. There is no problem when the crystal grain size is 10 μm or less.

In addition, since the titanium phase can cause the deposition of particles on the substrate, it is preferable that the titanium phase be as small as possible. When the area ratio of the titanium phase occupying the cross section of the target material is 10% or less, the frequency of generation of particles is greatly reduced. Therefore, an area ratio of 10% or less is preferable.

Moreover, in this invention, it is preferable that the area ratio of the titanium-tungsten alloy phase which occupies the cross section of a target material is 60% or more.

It is desirable to further increase the amount of titanium-tungsten alloy to reduce the deposition of particles. By increasing the area ratio of the titanium-tungsten alloy phase preferably at least 60%, more preferably at least 80%, it is possible to obtain a target material in which particles are less deposited on the substrate.

The distribution of each of the particles and the alloy phase is of paramount importance in the target material of the invention. Furthermore, it is preferable that it is 600 ppm or less in order to obtain a thin film with a uniform oxygen content. In the present invention, a target material having a low oxygen content can be obtained. For example, it is produced by simultaneously grinding and mixing in a non-oxidizing atmosphere using hydrogenated high purity titanium powder.

The present invention also relates to a method for producing a titanium-tungsten target material obtained by pressure sintering tungsten powder and titanium powder to obtain a sintered body. The obtained sintered compact is heat-treated to form a titanium-tungsten alloy phase.

More particularly, the present invention relates to a method for producing a titanium-tungsten target material in which a sintered body is obtained by mixing and pulverizing tungsten powder and titanium hydride powder, and then pressing and sintering both powders after dehydrogenation or while dehydrogenating. The sintered body obtained to substantially surround each tungsten particle is heated to form a titanium-tungsten alloy phase.

The purity of tungsten powder is preferably at least 99.99%, more preferably at least 99.999%, while the purity of high purity titanium is preferably at least 99.99%.

Titanium hydride powder is used in the present invention because the oxygen content in the target material can be reduced.

Titanium and tungsten powder can be mixed and then ground. However, in the present invention, it is possible to prevent the shape of the heterogeneous mixture caused by the specific gravity difference of titanium and tungsten. have. This can be accomplished using a device such as a ball mill or attritor, where the powder is mechanically ground and mixed.

Titanium and tungsten powder are preferably pulverized so that the average diameter of the particles is 5 μm or less. This reduction in particle size uniformly disperses titanium and tungsten, thereby preventing the increase of titanium particles when the powder is sintered and promoting the alloying of titanium and tungsten by heat treatment.

In this invention, it is preferable that heat processing temperature range is 1300-1500 degreeC. This is because a titanium-tungsten alloy phase is formed through diffusion treatment while suppressing the growth of crystal grains.

Titanium and tungsten can be mixed together at a specific mixing ratio to form a complete solid solution. It is preferable that heat processing temperature is 1500 degrees C or less. On the other hand, when the heat treatment temperature is less than 1300 ° C., titanium and tungsten are hardly alloyed even after the heat treatment for 50 hours, which is not practically preferable.

It can be used to hot sinter the hot isostatic press (hereinafter referred to as HIP) or the hot press.

Orthogonal particles having a maximum diameter of at least 0.5 μm can be dispersed to be present at about 0.1 or less per cm ² . This particle is present on the surface of the thin film obtained by sputtering the titanium-tungsten target of the present invention. Thus, a semiconductor device with extremely few defects can be obtained.

Example 1

High purity tungsten powder (more than 99.999% purity, average particle diameter of 5 μm or less) and hydrogenated high purity titanium (more than 99.99% purity and average particle diameter of 75 μm or less, hereinafter referred to as titanium hydride), so that the hydrogenated titanium is 10.36 wt% Mix together. The mixture is introduced into a dedicated ball mill using tungsten balls and pots with tungsten liners. The inside of the pot is evacuated and replaced with argon gas to a non-oxidizing atmosphere and mixed together while grinding the mixture for 90 minutes under the above conditions.

Titanium hydride of 20 µm or more was not observed in the obtained mixed powder. The average diameter of the particles of the mixed powder is 4 µm and the oxygen content is 540 ppm.

HIP cans with an internal diameter of 40 mm are filled with mixed powder. The mixed powder is heated at 700 ° C. for 24 hours and dehydrogenated while evacuating the can to 5 × 10 ⁻⁵ Torr. After dehydrogenation is performed, the HIP cans are sealed. HIP treatment is carried out at 1000 atm, 1250 ° C. for 2 hours. 1 is an enlarged photograph 600 times the microstructure of the obtained sintered body. In FIG. 1, the white particles are particles of tungsten phase, while the gray portion present in the tungsten particles is titanium phase. Even if tungsten is dispersed in particulate form in the sintered body, titanium partially coagulates. At this stage, the titanium-tungsten alloy phase cannot be detected.

By changing the heat treatment time and evacuating the can to 10 ^-5 Torr, the sintered body is alloyed at 1380 ° C to obtain a target material.

The oxygen content of the obtained target material is substantially 550 ppm.

2 is a photograph showing a microstructure of one of the target materials obtained after the heat treatment for 5 hours, while FIG. 3 is a photograph showing a microstructure of one of the target materials after the heat treatment for 24 hours.

In Figures 2 and 3, the white portion is the tungsten phase particles and the gray portion substantially surrounded by the tungsten particles is the titanium-tungsten alloy phase. The black part is a titanium-tungsten alloy phase or a titanium phase dispersed adjacent to the tungsten particles.

As in the third diagram, the tungsten particles exist in particulate form as a result of the heat treatment for 24 hours, and most of them are covered with a titanium-tungsten alloy phase. Tungsten particles surrounded by the titanium phase are not detected. It has been found that the titanium phase is composed of an extremely small percentage of the target material.

4 is a photograph showing the microstructure of the target material after heat treatment for 50 hours. It is a 600 times magnification photograph obtained by observing the wavefront of a target material with a scanning electron microscope. As can be seen from FIG. 4, the target material which has been heated for 50 hours is composed of crystal grains, each of which has an average diameter of 10 m or less.

5 shows the area ratio of the titanium phase occupying the cross section of the target material obtained by changing the heat treatment time. Similarly, FIG. 6 shows the area ratio of the titanium-tungsten alloy phase occupying the target material cross section obtained by also varying the heat treatment time.

It was found that the titanium phase decreased with increasing heat treatment time length. When the heat treatment is carried out for 20 hours or more, the area ratio of the titanium phase is reduced to 10% or more, and the plane foot ratio of the titanium-tungsten alloy phase is increased by 80% or more.

As can be seen in FIG. 4, it is a photograph showing the microstructure of the wavefront of the target material obtained at various heat treatment times. Multiple parallel straight lines are drawn on this photo at 20 mm intervals. The average diameter of the crystal grains is calculated by measuring the crystal grain number and diameter divided by the straight line.

7 shows the average diameter of the crystal grains at this stage. As is apparent from FIG. 7, crystal grains grow with increasing heat treatment time. It is also evident that the crystal grains grow slowly at a heat treatment temperature of 1380 ° C. and this heat treatment temperature is preferred.

The obtained target material is processed into a target material having a diameter of 30 mm. This processed target material is used to perform a sputtering method on a 6 inch wafer. 8 shows the number of particles on a wafer having a diameter of 0.5 μm or more when the target material obtained at various heat treatment times is used during sputtering.

Comparing FIGS. 5 and 6 to FIG. 8, it was found that the titanium phase was reduced by alloying the target material, while at the same time the titanium-tungsten alloy phase was increased while the number of particles was greatly reduced. In addition, titanium-tungsten alloying can suppress the generation of particles on the wafer. The area ratio of the titanium phase was found to be preferably 10% or less.

Example 2

The sintered compact obtained by the same method as Example 1 is heat-processed for 24 hours, changing the heat processing time length. The area ratio of the titanium phase and the area ratio of the titanium-tungsten alloy phase are measured.

FIG. 9 shows the measurement of the area ratio of titanium phase, while FIG. 10 shows the measurement of the area ratio of titanium-tungsten alloy.

In FIG. 9, the titanium area ratio decreases considerably at the heat treatment temperature of 1300 DEG C or higher, while in FIG. 10, the area ratio of the titanium-tungsten alloy increases significantly at the same temperature.

11 shows the diameters of the crystal grains obtained in the same manner as in Example 1. FIG. As can be seen from FIG. 11, since the crystal grains grow considerably at a temperature of 1500 DEG C or higher, heat treatment at a temperature of 1500 DEG C or lower is preferable.

Check the number of deposited particles. These particles are produced by using the obtained target material during sputtering in the same manner as in Example 1. 12 shows the results of the investigation.

As is apparent from FIG. 12, the number of particles generated can be reduced by heat treatment at a temperature of 1300 占 폚 or higher.

It is demonstrated above that the heat treatment in the temperature range of 1300 to 1500 ° C. for about 24 hours is particularly preferred and may be a practical heat treatment during the formation of the titanium-tungsten plywood phase.

The method according to the invention can produce a titanium-tungsten target material having a novel structure in which tungsten particles and a titanium phase are dispersed, while the titanium-tungsten alloy phase mainly constitutes the structure. The structure is characterized in that the structure contains little large titanium particles and the diameter of the crystal grains is small. By using the target material according to the present invention it is possible to carry out sputtering which generates very few particles. Therefore, it is possible to provide a target and a thin film which are very effective for improving the quality of a semiconductor device. In addition, the target material of the present invention has an advantage of suppressing cracks in the target, oxidation of the resulting film, and changes in the quality of the sputtered film, in addition to the above-described feature of generating a small number of particles.

Claims (11)

Titanium for sputtering, comprising a titanium-tungsten alloy phase having an area ratio of 20% or more of the microstructure occupying a tungsten phase, a titanium phase and a titanium-tungsten target material cross section. Tungsten target material. A sputtering structure comprising essentially a dispersed tungsten particles, a titanium-tungsten alloy phase substantially surrounding the tungsten particles, and a titanium phase dispersed adjacent to at least one of the titanium-tungsten alloy phase and the tungsten particles. Titanium-tungsten target material. 3. The titanium-tungsten target material for sputtering according to claim 1, wherein the average diameter of the crystal grains is 10 μm or less. The titanium-tungsten target material for sputtering according to any one of claims 1 to 2, wherein the area ratio of the titanium phase occupying the cross section of the target material is 10% or less. The titanium-tungsten target material for sputtering according to any one of claims 1 to 2, wherein the area ratio of the titanium-tungsten alloy phase occupying the cross section of the target material is 60% or more. The titanium-tungsten target material for sputtering according to any one of claims 1 to 2, wherein the oxygen content is 600 ppm or less. Press sintering the tungsten powder and the titanium powder to form a sintered body; And heating the obtained sintered body to form a titanium-tungsten alloy phase, thereby producing a titanium-tungsten target material for sputtering. Mixing and grinding tungsten powder and titanium hydride powder; Pressing-sintering the tungsten powder and the titanium hydride powder after dehydrogenation or while dehydrogenating to form a sintered body; And heating the obtained sintered body to form a titanium-tungsten alloy phase, thereby producing a titanium-tungsten target material for sputtering. The method according to any one of claims 7 to 8, characterized in that the heat treatment is carried out at a temperature range of 1300 to 1500 ° C, to produce a titanium-tungsten target material for sputtering. 9. A method according to claim 8, characterized in that the mixing and grinding are carried out mechanically simultaneously. 9. A method according to any one of claims 7 and 8, characterized in that it is pressure sintered using a hot isostatic press to produce a titanium-tungsten target material for sputtering.