KR20020053997A - Manufacturing method of Ta films by magnetron sputtering - Google Patents

Abstract

PURPOSE: A method for forming a Ta coating film by sputtering is provided which easily forms a β-phase having a high activity by controlling substrate temperature and substrate bias voltage using a nonequilibrium magnetron sputtering evaporation source as a sputtering evaporation source. CONSTITUTION: In a method for forming a Ta coating film on the surface of a Ti material using a sputtering evaporation source, the method for forming the Ta coating film by sputtering comprises the process of forming the Ta coating film on the surface of the Ti material by controlling substrate temperature of the Ti material and substrate bias voltage respectively so that a ratio of X ray diffraction peak to a phase of the Ta coating film(β/α) becomes 1 or more using a nonequilibrium magnetron sputtering evaporation source as a sputtering evaporation source(2), wherein a bias voltage is not impressed to the substrate(4), the substrate is floated, and the ratio of X ray diffraction peak(β/α) is represented in a ratio of magnitudes of β peak and α peak.

Description

Manufacturing method of Ta films by magnetron sputtering

The present invention relates to a film forming method used to form a tantalum (Ta) film on the material to improve the properties of the insoluble anode, and more specifically, using a sputtering method using an unbalanced magnetron sputtering evaporation source, but the substrate temperature and the substrate bias voltage It relates to a film forming method for forming a tantalum film having a high activity β- by adjusting the.

Ta metal has excellent refractory properties while having refractory properties, and its application is expanding in various fields. When Ta is manufactured into a film, two phases appear. One is an α phase having a body-centered cubic structure such as Ta metal, and the other is a β phase having a tetragonal tetragonal structure.

The α phase is widely used as a protective coating because of its excellent mechanical and chemical properties, as well as its ductility and processability. On the other hand, the β phase is a hard, brittle, thermodynamically very unstable film and is known to be converted to the α phase between 750 and 1000 ° C.

The Ta film has been widely used for the surface protection film of the diffusion barrier film, the electromagnetic element, the X-ray optics, and the various reaction vessels. The salt coating method (Molten salt), the chemical vapor deposition method, or the sputtering method is used for the formation of a Ta film. However, in the case of the salt bath method or the chemical vapor deposition method, the substrate must be heated to a high temperature of 800 ° C. or more, so that many constraints are involved in selecting the substrate. Therefore, in recent years, the sputtering method is most frequently used, because the sputtering method enables the formation of a film at a low temperature close to room temperature and easy control of the phase according to process variables.

In the case of Ta, the reason why the sputtering is particularly manufactured among various physical vapor deposition methods is that when the sputtering method is used, the coating property is excellent, the process is simple, and the deposition efficiency is higher than that of other physical vapor deposition methods. In the case of manufacturing Ta by vacuum deposition, there is a disadvantage in that the evaporation rate is low due to the high melting point and the film property is poor, and in the case of arc deposition, the coating is difficult because the generation and control of the arc is not easy.

The role of Ta in an insoluble anode can be divided into two categories. One is to increase the adhesion between the Ti substrate and the IrO ₂ (iridium oxide) coating layer as a buffer layer, and the other is to keep the IrO ₂ coating layer stable in a strong acid atmosphere. This is because Ta is highly reactive with Ti as a substrate and IrO ₂ as a coating layer, thereby forming a very chemically strong bond.

In general, there are two types of anodes used in electroplating facilities. One is a soluble anode, and in addition to forming an electric field in an electrolytic solution, it serves to supply plating ions while being dissolved through an electrochemical reaction. One is an insoluble anode that only serves as a carrier of current to the electrolyte and does not supply plating ions.

Of these two types of anodes, insoluble anodes do not require constant exchange of ions, so that the distance between the steel sheet and the anode can be kept very close and at a constant distance, thereby eliminating defects in the plated steel sheet appearing in the soluble anode. High current density operation is possible.

However, unlike soluble anodes, zinc The plating solution shows a strong acid because the supply of ions depends solely on the chemical dissolution reaction. Therefore, the insoluble anode is not dissolved in such a strongly acidic plating solution, and physical properties with excellent electrical conductivity are required to increase plating efficiency. Usually, Pb-based materials are used by alloying Sn in order to increase mechanical strength, but when Pb ions are eluted in the plating solution, there is a disadvantage of causing black spots on the plating layer.

Recently, the coating of iridium oxide (IrO ₂ ) on Ti substrates as a new material for insoluble anodes has been in the spotlight, and these materials do not dissolve in the two requirements mentioned above, namely strong acidity, and have excellent electrical conductivity. It has all the properties to meet. In addition, since the life of the anode is proportional to the thickness of the coating layer, it is necessary to eventually coat the IrO ₂ of the thick film. However, when the thickness of the coating layer is increased, cracks are generated in the coating layer, and when oxygen ions are generated at the anode, the Ti substrate is oxidized and eventually the bath voltage is increased.

The manufacturing method of the IrO ₂ -based insoluble anode is as follows. First, a Ti substrate is prepared and appropriate surface treatment is performed. As a surface processing method, a processing method of applying roughness to a surface has been frequently used as a means for increasing the surface area of a substrate and improving adhesion to the coating layer. However, recently, mirror surface treatment is often performed. This is because a technology has been developed that can secure sufficient adhesion while using mirror surfaces. The buffer layer coating layer is then coated with a thickness of usually 2-3 mm to form by physical vapor deposition, in particular sputtering. At this time, if the thickness is too thin, the role of the buffer layer becomes insignificant, and if it is too thick, the manufacturing cost increases but also adversely affects the service life. Ta is most widely used for the coating material of the buffer layer, and tantalum oxide or Ta-Ir alloy thin films are also used. Although it is known that the buffer layer is not a big problem in use even if it is not coated separately, it is mostly used to improve the adhesion between the IrO ₂ layer and the Ti substrate, to secure the stability of the IrO ₂ layer, and to improve the life and the stable quality of the coated steel sheet. Is the method adopted by the anode manufacturer.

Then, the Ir-containing compound is coated by a coating method (coating a gel solution), followed by drying and finally forming an IrO ₂ coating layer through heat treatment. However, in order to make the thickness of the IrO ₂ film constant, application and heat treatment must be repeated several times. Through this series of processes, IrO ₂ -based insoluble anodes are manufactured.

The technique of such a method is disclosed in Japanese Patent Laid-Open Nos. 46-21884, 63-235493, 6-69695, 6-681198, 7-166350 and 7-258897. It is introduced.

However, as described above, in the case of the Ta film, since the activity varies depending on the phase of the formed film, the lifetime of the insoluble anode is related to how to control the two phases. However, in the above known art, no reference is made to this.

Accordingly, the present invention has been made to solve the problems of the prior art as described above, by using a sputtering method using an unbalanced magnetron sputtering evaporation source, but by adjusting the substrate temperature and the substrate bias voltage, β-phase with high activity It is an object of the present invention to provide a method for forming a tantalum film that can be easily formed.

1 is a schematic view of a film forming apparatus for explaining the present invention,

2 is a graph showing X-ray diffraction (XRD) analysis data for explaining the present invention.

♠ Explanation of symbols on the main parts of the drawing ♠

1: vacuum chamber 2: sputtering evaporation source

3: Ta target 4: substrate

5: Substrate holder 6: Substrate heating device

7, 7 ': shutter 8: substrate rotating device

9: substrate bias power supply 10: thickness meter

11: gas inlet 12: vacuum gauge

According to the present invention for achieving the above object, in the method for forming a Ta film on the surface of the Ti material using a sputtering evaporation source, using a non-equivalent magnetron sputtering evaporation source as the sputtering evaporation source for the phase of the Ta film The Ta film is formed on the surface of the Ti material by adjusting the substrate temperature and the substrate bias voltage of the Ti material so that the ratio (β / α) of the X-ray diffraction peak is 1 or more.

Hereinafter, with reference to the accompanying drawings, a preferred embodiment of the method for forming a tantalum film by sputtering according to the present invention will be described in detail.

In the drawings, FIG. 1 is a schematic diagram of a film forming apparatus for explaining the present invention, and FIG. 2 is a graph showing X-ray diffraction (XRD) analysis data for explaining the present invention.

The present invention is carried out by providing a sputtering evaporation source in a conventional vacuum deposition apparatus. As shown in FIG. 1, a sputtering evaporation source 2, a Ta target 3, and a substrate 4 are provided in the vacuum chamber 1. In addition, inside the vacuum chamber 1, the substrate holder 5, the substrate heating apparatus 6, the shutters 7 and 7 ', the thickness measuring device 10, the gas inlet 11 for injecting gas and the degree of vacuum are measured. The vacuum gauge 12 etc. are provided. The sputtering evaporation source 2 uses a non-equilibrium magnetron method, and an electromagnet (not shown) is used as a method for maintaining the non-equilibrium.

The specimen 4 should be subjected to pretreatment before and after loading in the container. In the present invention, ultrasonic cleaning was used as a pretreatment method before being loaded into the container. The method of pretreatment of the specimens will depend on the nature of the specimen being treated and the contaminants to be removed. As a result of the experiment, ultrasonic cleaning using a cleaning agent or a solvent after light polishing is appropriate, but industrially, sand blasting and chemical cleaning are used. Contaminants typically present in components such as fixtures, tools and bearings include lubricants, cutting oils, oxides and fingerprints.

In the present invention, a plate-like material was used as the substrate, and thus the most convenient ultrasonic cleaning was used as the experimental result. The pretreated specimen (4) is mounted on the substrate holder (5), the Ta target (3) is fixed to the sputtering evaporation source (2), the vessel is closed and evacuated to the desired degree of vacuum using a vacuum pump (not shown).

When the vacuum degree is less than 10 ^-5 Torr, argon gas is injected to clean the specimen 4 and a negative voltage is applied to the specimen 4 to clean the specimen 4. Purging of the specimen 4 includes removing impurities such as organic matter present in the specimen 4 as well as naturally occurring oxide films. At this time, if impurities are not sufficiently removed, the adhesiveness is affected, so sufficient clean work must be performed. The cleaning of the specimen 4 is carried out by inducing a glow discharge (plasma discharge) by applying a negative voltage of 400 to 1000 V to the specimen in an argon gas atmosphere of about 10 ^-2 Torr. In this way, argon ions present in the discharge region collide with the specimen to remove impurities present in the specimen.

After the cleaning of the specimen 4 is finished, the next step is to clean the Ta target (3). The cleaning of the Ta target 3 is to remove impurities existing on the surface of the target 3 and is performed immediately before the sputtering process. Usually, the Ta target 3 is cleaned by sputtering for about 3 minutes after generating a plasma by applying power to the sputtering evaporation source 2. In this manner, when the Ta target 3 is cleaned, the shutter 7 attached to the substrate 4 and the shutter 7 'attached to the sputtering evaporation source 2 are simultaneously opened to form a Ta film in earnest.

In the figure, reference numeral 8 denotes a substrate rotating apparatus, and 9 denotes a substrate bias power supply, respectively.

Hereinafter, the present invention will be described in more detail through experimental examples of the present invention as shown in Table 1. Table 1 is to compare the ratio of the phase (β / α) measured by coating X-ray diffraction (XRD) after coating the invention and comparative examples to explain the effect of the present invention, the ratio of this XRD measured phase (β / α) shows the ratio of the magnitudes of the β (002) and α (110) peaks after obtaining the relative intensity of the peaks of the XRD data in a text file (see FIG. 2).

Inventive Example 1 forms a Ta film on a Ti substrate used for an insoluble anode. The specimen 4 used in Inventive Example 1 was a plate-like material having a length of 5 cm, a length of 5 cm, and a thickness of 1 mm. These specimens 4 are ultrasonically cleaned for 10 minutes using acetone and alcohol before being charged into the vacuum chamber 1. Then, the Ta target 3 is installed, the substrate 4 is mounted, the vacuum chamber 1 is closed and the evacuation is performed using a vacuum pump. When the vacuum degree is 10 ⁻⁵ Torr or less, 1.2 × 10 ⁻² Torr of argon gas is injected through the gas inlet 11 to clean the substrate 4 to perform secondary cleaning of the specimen by glow discharge. At this time, the applied voltage of the board | substrate 4 was 400V, and current is 200-400 mA, and it clean | cleans for 30 minutes. After cleaning the specimen and the vacuum degree is below 10 ^-5 Torr, inject argon gas to 5 x 10 ^-3 Torr, apply 400V power to the sputtering evaporation source (2) to generate plasma, and then target Ta for 3 minutes. (3) to clean. Next, the shutters 7 and 7 'are opened and a Ta film is formed on the substrate 4 for 15 minutes.

In forming the Ta film in Inventive Example 1, the distance between the substrate 4 and the Ta target 3 was 24 cm, the voltage and current applied to the Ta target 3 were 400V, 8A, and the current applied to the electromagnet was 6A. The evaporation rate of Ta was 0.08 µm, the substrate bias voltage was 0 V, and the substrate temperature was at room temperature.

Inventive Example 2 is the same as Inventive Example 1 except that each substrate is floated without applying ground or power and a film is formed with an evaporation rate of 1.0 μm.

Inventive Example 3 is the same as the Inventive Example 1 except that the evaporation rate is 0.05 μm.

Inventive Example 4 is the same as Inventive Example 1 except that the film is formed with a substrate temperature of 100 ° C. and a deposition time of 30 minutes.

Comparative Example 1 is the same as the Inventive Example 1 except that a substrate bias voltage of 50 V is applied.

Comparative Example 2 is the same as that of Inventive Example 1, but the substrate bias voltage is applied to 100V.

Comparative Example 3 is the same as in Inventive Example 1, but the evaporation rate is 0.2㎛.

Comparative Example 4 is the same as that of Inventive Example 1, but the film is formed with a substrate temperature of 200 ℃.

Comparative Example 5 is a case where a film is formed by using a general magnetron evaporation source.

Example No. Evaporation rate (㎛ / min) Substrate Bias Voltage (V) Substrate temperature (℃) β / α Inventive Example 1 0.08 0 Room temperature 4 Inventive Example 2 1.0 No (Floating) Room temperature 5 Inventive Example 3 0.05 0 Room temperature 3 Inventive Example 4 0.08 0 100 2 Comparative Example 1 0.08 50 Room temperature 0.2 Comparative Example 2 0.08 100 Room temperature 0.1 Comparative Example 3 0.2 0 Room temperature 0.1 Comparative Example 4 0.08 0 200 0.2 Comparative Example 5 0.2 100 Room temperature 0.1

As described above, when the film is manufactured by the method of the present invention (Invention Examples 1, 2, 3, 4), the β film having a higher activity than the conventional method can be easily formed and the film phase can be controlled. It can be seen.

As described in detail above, the method for forming a tantalum film by sputtering according to the present invention has the effect of easily forming a β-phase having high activity by controlling a substrate temperature and a substrate bias voltage using a sputtering method using an unbalanced magnetron sputtering evaporation source. There is.

The technical details of the method for forming a tantalum film by sputtering of the present invention have been described above with reference to the accompanying drawings, but this is by way of example and not by way of limitation.

In addition, it is obvious that any person skilled in the art can make various modifications and imitations without departing from the scope of the technical idea of the present invention.

Claims (4)

In the method of forming a Ta film on the surface of the Ti material using a sputtering evaporation source, The non-equivalent magnetron sputtering evaporation source is used as the sputtering evaporation source, and the substrate temperature and the substrate bias voltage of the Ti material are respectively adjusted such that the ratio (β / α) of the X-ray diffraction peak with respect to the Ta film phase is adjusted to 1 or more. A Ta film is formed on the surface of a raw material, The method of forming a tantalum film by sputtering. The method for forming a tantalum film according to claim 1, wherein a bias voltage is not applied to the substrate. The method of forming a tantalum film by sputtering according to claim 1, wherein the substrate is floated. The sputtering according to any one of claims 1 to 3, wherein the ratio (β / α) of the X-ray diffraction peaks is expressed as a ratio of the magnitude of the β (002) peak and the α (110) peak. Method of forming a tantalum film by