JPH04236760A - Formation of titanium nitride film - Google Patents

Abstract

PURPOSE:To enhance the adhesive strength of the titanium nitride film formed by ion mixing treatment to the base material. CONSTITUTION:Titanium (total charge of 2X10<17>-4X10<17> ions/cm<2>) is accelerated and injected into the titanium film (0.1-0.2mum thick) formed on the surface of a base material to form mixing layer of the base material and titanium between the base material and titanium film. At this time, an accelerating voltage (200-400kV) is impressed for almost the average intrusion length of titanium to reach the boundary region between the base material surface and the titanium film. Titanium is further vapor-deposited, and nitrogen ion is implanted to form a titanium nitride film in 3mum thickness. The peel load of the titanium nitride film is increased to 80-100N.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a titanium nitride film with increased adhesion strength.

0002

2. Description of the Related Art In recent years, ion mixing treatment, which combines ion implantation treatment and vacuum film formation treatment, has been developed as a technique for modifying the surface of a base material. In the ion mixing process, ion-implanted gas ions such as nitrogen, oxygen, and hydrogen combine with the deposited metal to form a film with strong adhesion. The reason for the strong adhesion of this film is that a mixing layer is formed in the boundary area between the base material surface and the film, the reaction is accelerated by the energy of high-energy gas ion collisions, and the gas ions are unbalanced. It is speculated that this is because it can be injected from below.

[0003] A method for forming a titanium nitride film using this ion mixing process is disclosed in Japanese Patent Laid-Open No. 1-168856.
As disclosed in the publication, rolling rolls, bearings,
A method of forming a titanium nitride film on the surface of a mold or the like is known. This method found the optimal conditions for forming a titanium nitride film on rolling rolls, etc., and uses nitrogen ions as the gas ions and titanium as the vapor-deposited metal.
The nitrogen ion acceleration voltage is 10 to 40 kV, the nitrogen ion current density is 0.5 to 2.0 mA/cm2, the Ti deposition rate is 5 angstroms/s or more, the total nitrogen ion input is 1018 ions/cm2, and the total Ti deposition amount is 5×10
A titanium nitride film is formed under conditions of 18 ions/cm2.

By the way, the titanium nitride film formed by the above-mentioned ion mixing process is said to have high adhesion strength to the base material because of the mixing layer formed therein as described above. However, in industry, there is a demand for further improvement in the adhesion strength of the titanium nitride film described above.

[0005]

[Problems to be Solved by the Invention] The present invention was developed in view of the above-mentioned circumstances, and its purpose is to accelerate acceleration so that the average penetration depth is approximately at the boundary area between the surface of the base material and the titanium film. An object of the present invention is to provide a method for forming a titanium nitride film in which the adhesion strength of the titanium nitride film is further improved by implanting titanium or base material atoms into the titanium film using a voltage.

[0006]

[Means for Solving the Problems] The inventors of the present invention have conducted further intensive research into a method of manufacturing a titanium nitride film. and,
The inventor laminated a titanium film of the required thickness on the surface of the base material,
It has been found that the adhesion strength of the titanium nitride film can be further improved if titanium or base material atoms are implanted into the titanium film at an accelerating voltage such that the average penetration depth is approximately at the boundary between the surface of the base material and the titanium film. However, based on this knowledge, the method of the present invention was developed.

That is, the method for forming a titanium nitride film of the present invention is a method of forming a titanium nitride film on a metal base material by an ion mixing process, and the titanium film is laminated on the surface of the base material by the film forming process. In the first step, titanium or base material atoms are implanted into the titanium film at an accelerating voltage such that the average penetration depth is approximately at the boundary between the surface of the base material and the titanium film. a second step of forming a mixing layer of titanium and base material atoms in the boundary area of It is characterized by being carried out in sequence.

The base material used in the present invention may be carbon steel, steel such as alloy steel such as stainless steel, cemented carbide such as WC-Co, or in some cases aluminum, silicon, copper, titanium, or magnesium. system can be used. In the case of steel, for example, ferrite, pearlite,
A structure containing at least one of austenite, martensite, and bainite can be used.

In the first step, a titanium film is laminated on the surface of a metal base material by a film forming process. The film forming process is a method of depositing particles on a base material to form a film on the surface of the base material, and typical examples include vacuum evaporation and sputtering, in which titanium is evaporated and deposited in a vacuum. In the first step, the thickness of the titanium film and the film formation rate can be appropriately selected as necessary, but for example, the thickness is 0.03 to 0.8 μm, particularly 0.05 to 0.3 μm.
It can be μm.

In the second step, titanium or base material atoms are implanted into the titanium film at an accelerating voltage such that the average penetration depth is approximately at the boundary between the surface of the base material and the titanium film. A mixing layer of titanium and base material atoms is formed in the boundary region with the film. In ion implantation, the depth distribution of implanted ions usually has a Gaussian distribution or a shape approximating a Gaussian distribution, and the average penetration depth of implanted ions is fundamentally related to the accelerating voltage. Therefore, in the present invention, the accelerating voltage is set so that the average penetration depth is in the boundary area between the surface of the base material and the titanium film. In the second step, when titanium is implanted, the acceleration voltage of titanium can generally be 50 to 400 kV, and the total amount of titanium implanted in the second step is, for example, 5×
It can be set to 1015 to 7×1017 ions/cm2. If the base material is steel, iron, which is a component of the base material, can be injected instead of titanium, but in this case, the acceleration voltage of iron can generally be 50 to 400 kV, and the The total amount of iron injected in the second step is, for example, 5
×1015 to 7×1017 ions/cm2. In the second step, it is preferable to heat the base material to a desired temperature to diffuse the elements, and in this case, the heating temperature is 200 to 600.
°C.

[0011] The third step is an ion mixing process in which an implantation process for injecting nitrogen ions and a vacuum film formation process for forming a titanium film are performed together. Ion mixing processing is also called dynamic mixing processing or ion beam assisted deposition. The above-mentioned implantation process is a means of accelerating ionized nitrogen in a vacuum using an electrostatic field or the like to transform it into high-energy particles and implanting them into the base material under non-equilibrium conditions. Note that the nitrogen ion is in the form of only the atomic ion N+, and the atomic ion N
+ or a form containing molecular ion N2 + . The vacuum film forming process in the third step is a means of depositing titanium particles in a vacuum, and as in the first step, vacuum evaporation and sputtering are typical methods in which titanium is evaporated and deposited by applying an electron beam to the titanium, as in the first step. It is something like that.

In the third step, the ratio N/Ti of titanium and nitrogen ions reaching the base material is substantially 1.
At the beginning or middle stage of the third step, the ratio of titanium to nitrogen ions reaching the base material is N, so that nitrogen ions gradually increase.
/Ti can be set. Here, the arrival ratio means the rate at which constituent atomic ions or constituent atoms for film formation that are introduced per unit time reach the surface of the base material.

In the third step, the total amount of nitrogen ions to be implanted can be selected as appropriate; for example, 1×1017 to 10×1017i.
ons/cm2. The titanium deposition rate in the third step can be, for example, 1 to 30 angstroms/sec. The total titanium input amount can be selected as appropriate, but for example, 1 x 1017 to 10 x 1017 io
It can be set to ns/cm2.

[0014] Here, the total amount of nitrogen ion implantation was calculated using Equation 1. Here, in Equation 1, D1 is the input amount (ions/cm2) of nitrogen ions (atomic ions N+, molecular ions N2+), and I is the current density (A/c
m2), the implantation time is T (sec), (3/2) is the correction coefficient, and N+ is 50% of the nitrogen ions, N
When we estimate that 2 + is 50%, we take into account that in the presence of one N+ and one N2 + , there are two charges but three nitrogen atoms. It is something. Further, the total amount of titanium input was calculated using Equation 2. Here, in Equation 2, D2 is the input amount of titanium (
pieces/cm2), M is the deposition rate (angstroms/s
ec), d is the specific gravity of titanium (4.6 g/cm3)
, the input time is T (sec).

[0015]

[Math. 1] D1=I×(1/1.6×10-19)×(3/2)
×T

[0016]

[Math. 2] D2=M×{d×10-8 (cm)/47.9}×6.
02×1023×T {d×10-8(cm)/47
．． 9} means the number of moles of titanium per 1 angstrom x 1 cm x 1 cm. By the way, it is known that the base material temperature generally affects accelerated diffusion etc. during ion implantation, so in the third step of the present invention, the base material temperature can be set to, for example, 100 to 500°C. . Note that the degree of vacuum during film formation varies depending on the nitrogen flow rate,
Generally 1.0×10-5 to 5×10-6 Tor
It can be r.

[0017]

[Operation] When looking at the cross section of the structure in which the titanium nitride film of the present invention is in close contact, from the inside to the surface layer, the metal surface of the base material,
It changes continuously from a mixing layer consisting of a metal-metal combination of metal atoms of the base material and titanium to a titanium nitride film.

[0018]

[Example] An example of the present invention will be shown below. In this example, an ion mixing device was used. The ion mixing device consists of a vacuum chamber that is a reaction chamber, a bucket-shaped ion source that ionizes gas, a gas supply source that sends gas to the ion source,
It has a sample holder (water-cooled), an electron beam heating evaporation unit that performs titanium deposition, a vacuum exhaust system that exhausts the inside of the vacuum chamber, and a crystal oscillation type film thickness meter. In this device, atomic ions N+ and molecular ions N2 + are generated in approximately 50% each.

[0019] Carbon steel (JIS S4
5C) according to the example. 1~NO. 6 was formed. The composition of this carbon steel is 0.45% carbon, 0.20% silicon, 0.70% manganese, 0.02% phosphorus,
The sulfur content is 0.02%. Further, the structure of this carbon steel is a mixed structure containing ferrite and pearlite. In this example, the surfaces of each test piece were polished with a buff and washed with acetone. The surface roughness of each test piece was 1.0 to 0.
It is 1 μRZ.

After holding the test piece in the sample holder, the inside of the vacuum chamber is initially evacuated and the degree of vacuum is increased to 2.5×.
It was set to 10-6 Torr. In this state, as a pretreatment,
Sputter cleaning was performed by irradiating the surface of the test piece with nitrogen ions. Accelerating voltage for sputter cleaning is 5k.
The experiment was carried out under conditions of V, beam current density of 0.5 mA/cm2, and irradiation time of 30 seconds.

Next, in the first step, 1.0×10-5
Titanium was vacuum-deposited on the surface of the specimen by electron beam heating under a vacuum of Torr to 1.0×10 −6 Torr, and a titanium film of a predetermined thickness was laminated on the surface of the base material of the specimen. Table 1 shows the thickness of the titanium film in each test piece laminated in the first step. Test piece No. 1 and test piece No. 2, 0.1 μm, test piece No. 3 and test piece No. 4 and 0.
15 μm, test piece No. 5 and test piece No. 0.2 at 6
It was set as μm.

Thereafter, in a second step, titanium was accelerated and implanted into the titanium film at a predetermined acceleration voltage such that the average penetration depth was approximately at the boundary between the surface of the base material and the titanium film. At this time, the test piece was heated to 400°C using a heater device to achieve thermal diffusion of the elements. Through this second step, a mixing layer of titanium and base material atoms was formed in the boundary area between the surface of the base material and the titanium film. Table 1 shows the acceleration voltage values in the second step.
Shown below. As shown in Table 1, test piece No. 1 and test piece No. 2 at 200kV, test piece No. 3 and test piece no.
．． 4, 300kV, test piece No. 5 and test piece No. 6
The voltage was set to 400kV. Table 1 also shows the total amount of titanium implanted in the second step. As shown in Table 1, test piece No. 1 in 2x
1017 ions/cm2, test piece No. 2 = 4 x 1
017 ions/cm2, test piece No. 2x10 in 3
17 ions/cm2, test piece No. 4 x 101
7 ions/cm2, test piece No. 5 = 2 x 1017
ions/cm2, test piece No. 4×1017i in 6
ons/cm2.

Next, in the third step, titanium was deposited on the titanium film having the mixing layer and nitrogen ions were implanted at an accelerating voltage of 10 kV, thereby laminating a titanium nitride film. In the third step, the titanium deposition rate was 10 angstroms/sec. The deposition rate of titanium was measured using a crystal oscillation type film thickness meter near the test piece. Note that nitrogen ions were not allowed to hit the film thickness meter. Also, in the third step,
The current density of nitrogen ions starts from 0 and gradually increases until the ratio of titanium and nitrogen ions reaches N/Ti.
is set to substantially equal to 1. That is, in the third step, the final nitrogen ion current density is 0.95 mA/cm2.
0.01mA/cm2・s until this value is reached.
Increased by ec. Then, the nitrogen ion beam current was kept constant at 0.95 mA/cm2, and a titanium nitride film with a thickness of 3 μm was formed on each test piece.

In the third step, the ion beam size of the beam current is 150 mm x 150 mm, the nitrogen gas flow rate is 10 to 20 sccm, and the base material temperature of the test piece is 200 to 200 sccm.
The temperature was 300°C, and the base material temperature was measured with a thermocouple. In this example, the incident angle with respect to the normal to the surface of the base material of the test piece is 0° for nitrogen ions and 45° for Ti. In the test piece according to this example manufactured as described above, a mixing layer of the base material component and the film component, that is, a mixed layer of iron and titanium, was interposed between the base material and the titanium film. There is.

[0025] The adhesion strength of the test piece according to the example was tested using an auto-scratch tester (manufactured by CSEM). The test conditions were a diamond tip diameter of 0.1m.
m, the scratch speed was 0.5 mm/min, and the loading rate was 100 N/min. The test results are shown in Table 1. As shown in Table 1, test piece NO.
1~NO. 6 gave good results. That is, test piece No. 1, the peeling load was 81N, and test piece No. 1 had a peeling load of 81N. 2
In this case, the peeling load was 88N, and furthermore, the peeling load was 88N. 3～
Test piece No. No. 6 did not peel off even under a load of 100N.

[0026]

[Table 1] Next, test piece No. 4, the depth distribution of the chemical composition of the mixing layer was investigated by AES (Auger electron spectroscopy). Specifically, an AES device (manufactured by JEOL Ltd., Augescope JAMP-30) was used, and the measurement room was set at 10-8P.
After evacuation to below a, the electron beam voltage was 10 kV, the beam current was 5 x 10-7 A, and the measurement area was 0.01 mm2.
This was investigated by detecting Auger electrons under these conditions. The concentration of the constituent elements was calculated by correcting the peak intensity at each depth using a sensitivity coefficient and setting the total amount of the measured elements as 100%.

The results are shown in FIG. In FIG. 1, the horizontal axis represents the depth from the surface of the titanium nitride film, and the vertical axis represents the concentration. Figure 1
As shown in Figure 2, nitrogen gradually decreases from around 2 μm in depth, and becomes 100% titanium from P1 to P2.Furthermore, from around 2.2 μm in depth, titanium decreases and iron increases, and then iron gradually decreases. increase, depth 2.4
Iron becomes 100% from around μm. As can be understood from FIG. 1, when looking at the cross section of the structure in which the titanium nitride film according to this example is in close contact, from the inside to the surface layer, the metal surface of the base material, the metal atoms (iron) of the base material and the titanium It changes continuously from a mixing layer consisting of a metal-metal combination, a titanium layer, and a titanium nitride film.

Comparative examples were also tested in the same manner. In the comparative example, the thickness of the titanium film was that of test piece No. 7, 0.1 μm, test piece No. 8 and 0.2 μm, and test piece No. In No. 9, no titanium film was laminated. Then, test piece No. 1 according to the comparative example. 7~NO. For Example No. 9 as well, ion mixing treatment was performed under basically the same conditions as in the third step of the above-described example, and a titanium nitride film was formed.

The adhesion of the comparative example described above was also tested using an auto-scratch tester in the same manner as described above. The test results are shown in Table 1. As shown in Table 1, test piece No. In specimen No. 7, the peeling load was 15 N, and in addition, in specimen No. 7, the peeling load was 15 N. In test piece No. 8, the peeling load was 19 N. In No. 9, the peeling load was 40N. As described above, in the comparative example, the adhesion strength of the titanium nitride film is low.

(Application Example) Since the titanium nitride film according to the present invention has high adhesion strength, it can be applied to members that require wear resistance and seizure resistance. For example, in automotive parts, it can be applied to piston rings, engine valves, pinion shafts, and piston pins.

[0031]

According to the method for forming a titanium nitride film of the present invention, it is possible to obtain a titanium nitride film with even higher adhesion to the base material, as is clear from the above test results.

[Brief explanation of the drawing]

FIG. 1 is a graph showing concentration distribution by AES.

Claims (1)

[Claims] 1. A method for forming a titanium nitride film on a metal base material by ion mixing treatment, the method comprising: a first step of laminating a titanium film on the surface of the base material by film formation treatment;
Titanium or base material atoms are implanted into the titanium film at an accelerating voltage such that the average penetration depth is approximately at the boundary between the surface of the base material and the titanium film, and the interface between the surface of the base material and the titanium film is a second step of forming a mixing layer of titanium and base material atoms in the boundary region, and a third step of depositing titanium and implanting nitrogen ions into the titanium film having the mixing layer to stack a titanium nitride film. 1. A method for forming a titanium nitride film, comprising sequentially carrying out the following steps.