JPH1096076A - Formation of amorphous carbon coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating having high hardness by prescribing the ion acceleration voltage till gas ions generated in a plasma generating chamber arrive at a substrate. SOLUTION: As for the amorphous carbon coating, by using an ECR sputtering method, the one having wear resistance more excellent than that by the other methods can be obtd. That is because ion assist and low gas pressure sputtering is made possible. The fig. shows the ion assist dependency of the wear characteristics of the carbon coating produced by the ECR sputtering method. Thereby, it is found that, in the case the accelerating voltage of the ion assist increases, the wear amt. reduce. It has been confirmed that, particularly, in the case where the accelerating voltage is set to >=60V, a high hardness carbon coating having hardness approximately equal to that of bulk diamond can be obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a protective film used for a magnetic recording medium capable of high-density recording.

[0002]

2. Description of the Related Art In recent years, in a hard disk, which is an external storage device of a computer, the flying height of a magnetic head has been required to be reduced with the increase in recording density. Has reached. In the future, in order to further increase the recording density of the hard disk, it is required to further reduce the flying height of the magnetic head. To this end, the establishment of a contact recording technique for causing a magnetic head and a medium to run in contact with each other is strongly demanded as a breakthrough for higher density in the future. For this purpose, it is particularly important to improve the durability of the protective film formed on the magnetic thin film, and in recent years, research on the protective film has been actively conducted. Conventionally, SiO ₂ and amorphous carbon films have been studied as protective films for hard disks, and various fabrication methods have been studied. In recent years, amorphous carbon has been particularly promising as a protective film.

At present, this amorphous carbon film is roughly classified into two types, namely, a CVD method and a sputtering method.

[0004] First, the CVD method is a method in which a raw material gas such as CH ₄ is decomposed in a plasma and ionized, and an electric field is applied thereto to collide with a substrate to form a thin film. This method includes many elementary processes such as a decomposition process in a plasma of a source gas, a decomposition process when ions collide with a substrate, and an association, decomposition, and reaction process on the substrate. For this reason, this method has a drawback that the controllability of the formed film is poor because the elementary processes at each stage are involved in complicatedly when the film forming conditions are changed.

[0005] On the other hand, the sputtering method is a method in which constituent atoms of a target are knocked out by collision with sputter gas ions. Since the number of elementary processes of film growth is smaller than that of the CVD method, the film has excellent controllability. Known sputtering methods include diode sputtering, ion beam sputtering, and ECR sputtering. In such a sputtering method, various devices have been devised in order to control the diffusion ability, reactivity, adhesion rate, and the like of sputtered atoms on the film growth surface.
For this purpose, diode sputtering uses a DC
Alternatively, a technique has been used in which an RF bias is applied and ions in the plasma collide with the substrate. However, in this method, since the target and the substrate are located at positions facing each other, high-speed particles such as recoil argon that jump out of the target enter the substrate, which has a disadvantage that the controllability of ion irradiation by bias application is restricted. Was. In the ion beam sputtering method, the substrate is irradiated with an ion beam using a plurality of ion guns, so that the diffusing ability of the sputtered atoms can be controlled. However, with an ion gun for ion beam sputtering, it is difficult to reduce the ion acceleration voltage to several tens of volts or less, and it is also difficult to obtain an ion current density of 10 mA or more. For this reason, this method also has a disadvantage that the range in which the state of the substrate surface can be adjusted by ion irradiation is limited.

The amorphous carbon film is made of SP2
It is said that the film is an amorphous film in which bonding and SP3 bonding are mixed. In order to control the hardness of the amorphous carbon film, it is necessary to control the bonding state of carbon atoms. In order to control the bonding state of the carbon atoms, it is necessary to control the energy state of the sputtered carbon atoms when they reach the substrate. For this purpose, a method of controlling the energy state of carbon atoms by ion irradiation is considered to be effective. However, the conventional sputtering method has a disadvantage that this energy control cannot be performed precisely.

[0007]

SUMMARY OF THE INVENTION The present invention has been proposed to remedy the above-mentioned drawbacks, and its object is to precisely control the energy of sputtered carbon atoms on a substrate and to achieve high hardness. An object of the present invention is to provide a formation method for manufacturing an amorphous carbon film having excellent durability.

[0008]

In order to solve the above-mentioned problems, the present invention introduces a plasma generation chamber provided in a magnetic field and introduces a plasma gas and a microwave to the plasma generation chamber by electron cyclotron resonance. Generating a plasma in the plasma generating chamber by the divergent magnetic field, and drawing the plasma into the film forming chamber from the plasma extracting window of the plasma generating chamber, and coaxially arranged to surround the drawn plasma flow. In a method of forming an amorphous carbon film on a substrate installed in the film formation chamber by sputtering a target made of carbon with plasma, the gas ions generated in the plasma generation chamber are accelerated until they reach the substrate. The voltage to be applied is set to 60 V or more. Normally, plasma is generated using electron cyclotron resonance, and using a divergent magnetic field,
A method of extracting plasma and performing sputtering using this plasma is called ECR sputtering. This EC
In applying the R sputtering method to the formation of the amorphous carbon film, in particular, the voltage accelerated until the gas ions generated in the plasma chamber reach the substrate is increased by 60%.
By setting it to V or more, an amorphous carbon film having extremely high hardness can be produced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The feature of the present invention is that the ECR
In a method of forming an amorphous carbon film by using a sputtering method, an acceleration voltage for ion assist is set to 60 V or more.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. Note that the present invention is not limited by the present embodiment.

Embodiment 1 First, a method for forming an amorphous carbon film will be described. Here, ECR sputtering and R
The F sputtering method was used. A silicon substrate was used as the substrate. The amorphous carbon film was produced under the following conditions.

(ECR sputtering method) Argon gas pressure: 5 × 10 ^-5 to 8 × 10 ^-4 Torr, microwave: power 300 to 700 W, target DC voltage: 300 to 700 V, distance between target and substrate: 5
１５15 cm, substrate temperature: room temperature (RF sputtering method) Argon gas pressure: 1 × 10 ^{−2 −1} × 10 ⁻¹ Torr, R
F power: 200 W, distance between substrate and target: 4.
5cm, substrate temperature: room temperature

For the evaluation of the wear resistance of the carbon film produced as described above, a surface scratch test by AFM was used. Diamond having a radius of curvature of 70 nm was used for the probe. The feed pitch was 4 nm, and a scratching experiment was performed with a load of 10 to 100 μN in two cycles in a range of 1 × 1 μm ² .
Thereafter, the wear depth was measured in a 5 × 5 μm ² range under a light load condition of about ² μN.

FIG. 1 shows the load dependence of the average wear depth of the ECR sputtered and RF sputtered amorphous carbon films evaluated by AFM. R in the figure is a region showing the wear characteristics of the amorphous carbon film produced by the RF sputtering method, E
L indicates the wear characteristic of the carbon film produced by weakening ion assist (low ion assist) by ECR sputtering, and Eh represents the wear characteristic of carbon film produced by increasing ion assist (high ion assist) by ECR sputtering. Area. In FIG. 1, low ion assist corresponds to the case where the ion acceleration voltage is 20 V or lower, and high ion assist corresponds to the case where the ion acceleration voltage is 60 V or higher.

As shown in FIG. 1, it can be seen that the wear resistance (R) of the RF sputtered carbon film is inferior to the films (EL and Eh) produced by the ECR sputtering method. Here, the wear characteristics of the RF sputtered and ECR sputtered carbon films strongly depend on the gas pressure at the time of film formation, and as the gas pressure decreases, the wear resistance characteristics improve. In this embodiment, the gas pressure of the RF sputtering method is 1 × 10 ⁻² to 1 × 10 ⁻¹ Torr, and the gas pressure of the ECR sputtering method is 5 × 10 ⁻⁵ to 8 ×.
A carbon film manufactured at 10 ^-4 Torr was used. ECR
It can be seen that the sputtering method is superior in abrasion resistance because a film can be formed by sputtering at a lower gas pressure. It is considered that this is because the number of collisions between sputtered carbon atoms and gas molecules decreases as the gas pressure decreases, and the energy of the carbon atoms when reaching the substrate increases.

As described above, the wear characteristics of the ECR sputtered carbon film are superior to those of the RF sputtered carbon film.
Here, the features of the ECR sputtering method are that 1) ion assist is possible and 2) low gas pressure sputtering is possible. Here, the gas pressure reduction of 2) is also effective,
As in 1), it has the effect of supplying the kinetic energy of ions or neutral atoms to the substrate. These irradiation effects are EC
It has a strong influence on the wear characteristics of the R sputtered carbon film, and the wear resistance is improved by increasing the ion irradiation effect. In particular, in the carbon film (Eh) with enhanced ion irradiation shown in FIG. Shows high wear resistance.

FIG. 2 shows the ion assist dependency of the wear characteristics of the amorphous carbon film produced by the ECR sputtering method.
Here, the amount of wear when the load is fixed at 80 μN is shown. FIG. 2 shows the relationship between the acceleration voltage of ion assist and the wear characteristics.

As shown in FIG. 2, when the acceleration voltage of the ion assist increases, the amount of wear decreases. In the wear experiment shown in FIG. 1 where ion assist was strengthened (E
h) corresponds to the case where the ion acceleration voltage is set to 60 V or higher. As shown in FIG. 2, as the ion assist acceleration voltage is increased, the wear characteristics are improved, and the hardness is almost equal to that of bulk diamond. A high hardness carbon film was obtained.

Example 2 FIG. 3 shows the relationship between the film thickness and the sputtering time when a carbon film is formed by ECR sputtering. The manufacturing conditions for the films of Samples A, B, and C in the figure are as follows. Sample A was a film prepared at an ion assist acceleration voltage of 15 V and a current density of 1 mA, and Sample B was used.
Is ion assisted acceleration voltage of 80 V and current density of 0.1 m
A, a film formed with a target voltage of 700 V, sample C is an ion assisted acceleration voltage of 80 V and a current density of 0.1 m
A, a film formed with a target voltage of 300V.

As shown in FIG. 3, Sample A shows a case where the ion assist is weakened. In this case, it can be seen that the straight line representing the deposition rate passes through the origin. On the other hand, Samples B and C are cases where ion assist is strengthened, and have an acceleration voltage of 80 V and a current density of 0.1 mA. Sample B is C
The voltage applied to the target is 2.3 times (700 times
V / 300 V). In samples B and C, it can be seen that the straight line representing the deposition rate does not pass through the origin. When a silicon substrate was irradiated with only argon ions under the same conditions without applying a voltage to the target, an etching rate of 200 ° / min was obtained. As described above, when the ion assist is strongly applied, etching occurs, and the straight line indicating the deposition rate does not pass through the origin. When the voltage applied to the target is increased, the sputtered carbon atoms increase, so that the etching effect apparently weakens, and the x-intercept of the straight line indicating the deposition rate decreases.

In the ECR sputtering method, when the acceleration voltage of the ion assist is increased, etching occurs, and when this effect is enhanced, the abrasion resistance is improved due to the carbon atoms incorporated in the film. It is considered that the incident ions remove the carbon atoms having a weak bonding state by reverse sputtering.

[0022]

As described above, according to the present invention, in the ECR sputtering method, a high hardness amorphous carbon film almost equivalent to bulk diamond is formed by setting the acceleration voltage of ion assist to 60 V or more. can do.

[Brief description of the drawings]

FIG. 1 is a diagram showing the dependency of wear characteristics on a sputtering method.

FIG. 2 is a diagram showing the ion assist voltage dependence of wear characteristics of an amorphous carbon film produced by a CR sputtering method.

FIG. 3 is a diagram showing a relationship between a film thickness and a sputtering time.

Claims (1)

[Claims] A step of introducing a plasma gas and a microwave into a plasma generation chamber provided in a magnetic field to generate plasma in the plasma generation chamber by electron cyclotron resonance; Extracting the plasma from the plasma extraction window of the plasma generation chamber into the film formation chamber, and sputtering the target formed of coaxial carbon so as to surround the extracted plasma flow with plasma, thereby forming the film. In the method of forming an amorphous thin film for forming a carbon film on a substrate installed in a chamber, a voltage accelerated until the gas ions generated in the plasma generation chamber reach the substrate is 60 V or more. A method for forming an amorphous carbon film.