JPH0773454A - Production of carbon protective film and plasma treating device - Google Patents

Abstract

PURPOSE:To provide a magnetic recording medium having a high-hardness protective film by superposing a positive DC bias voltage on the output of a high-frequency power source at the time of forming plasma by using the high-frequency power source, thereby executing film formation selectively using the negative ion active species in plasma. CONSTITUTION:An electrode 1 commonly used as a vacuum chamber is evacuatable to a pressure below the atm. pressure and generates plasma when a high voltage is impressed thereto. A DC positive voltage impressing device 4 and a choke coil 9 impresses a DC positive voltage to a substrate holder 3 commonly used as a third electrode holding a disk substrate 2 to be treated. The high-frequency power source 5 supplies high-frequency electric power to the electrode 1 commonly used as the vacuum chamber via a blocking capacitor 10. As a result, the film formation selectively using the negative ions of C, CH<-> which are ion active species without contg. many H atoms is executed to obtain the film mainly composed of the C single bond having the small quantity of H, and the magnetic recording medium having the high-hardness protective film of the quality quantitively and collectively evaluated from Raman spectra.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording medium having a highly hard amorphous carbon protective film, and a manufacturing method and manufacturing apparatus for the same.

[0002]

2. Description of the Related Art A thin film forming technique for a substrate to be processed using a plasma processing apparatus is widely used for forming a thin film on a magnetic disk or an optical disk by using a sputtering technique, a CVD technique or the like.

Particularly in high frequency plasma CVD,
As disclosed in Japanese Unexamined Patent Publication No. 62-83471, a method of performing etching with high-energy ions or ion-assisted film formation is known, and reactive ion etching or high-hardness carbon film formation is performed. .

However, the film forming process on the substrate to be processed is often unclear from an academic point of view, and the relationship between the ion active species attacking the substrate to be processed and the film quality to be formed is not clear. In the ordinary plasma CVD process, the substrate to be processed is processed either on the ground side electrode or on the electrode to which a high frequency is applied. In this case, it is formed by neutral radical particles and positive ions accelerated by the sheath. It is believed that a membrane treatment is performed. For example CH
_From the measurement results of the ion energy analyzer in the plasma CVD process using ₄ gases, the spectra of CH ₃ + ions and C ₂ H ₅ + ions were observed as the highest intensity as the neutral radical particles and the main ion component, It can be confirmed that the film is formed mainly with positive ions.

At this time, dehydrogenation from the film surface is carried out in order to promote hardening of the film. As a method of doing this, ions accelerated at a larger potential are implanted into the film surface.
However, as shown in FIG. 1, the rate of generation of double bonds increases with dehydrogenation on the surface of the film, which also causes graphitization of the film quality. In other words, since the absolute amount of H in the molecule constituting the film is large, the number of double bonds increases with dehydrogenation, which makes it difficult to form a C single bond-based film having a small amount of H.

[0006]

As described above, in the conventional plasma CVD technique, the main ionic active species used during film formation are positive ions containing many H atoms,
There was a situation in which it was difficult to form a film containing mainly C single bonds with a small amount of H.

In the present invention, a film mainly containing a C single bond having a small amount of H is formed by performing film formation by selectively using negative ions such as C to and CH to which are ionic active species not containing a large amount of H atoms. And quantitatively and comprehensively promoting it from the Raman spectrum of the formed film quality to obtain a magnetic recording medium having a high hardness protective film.

[0008]

In order to achieve the above object, the present invention is provided with a mechanism for applying a positive DC bias to a substrate holding portion of an ion plasma processing apparatus to attract negative ions to the surface of the substrate. The film was selectively formed using this.

Specifically, when CH ₄ gas is used as the reaction gas, it is C ~ or CH ~ that can be confirmed to be negatively ionized and present in the plasma, and hydrogen atoms attached to each C atom. The number of CH is the main ion component in the conventional plasma CVD without ion selection.
It becomes 1/2 or less as compared with ₃ + ions and C ₂ H ₅ + ions. That is, as shown in FIG. 2, when the film forming method using negative ions is used, the absolute amount of hydrogen contained in the film is reduced.

Therefore, the amount of hydrogen per unit volume in the film can be made smaller than that obtained when the conventional positive ions are used. This suppresses the formation of double bonds, and as a result, it is possible to obtain a film mainly containing C single bonds with a small amount of H.

[0011]

According to the present invention, the Raman spectrum of the carbon protective film formed with only negative ions shows a characteristic having only one peak at 1520 cm to ¹ or less. This is because the hydrogen and double bonds are reduced from the film as compared with the conventional film having an amorphous structure obtained by film formation using positive ions, so that a diamond structure is formed by a C single bond. It is considered that the components increased. The present spectrum can be confirmed because there is no peak in the Raman spectrum components 1580 cm ~ ¹ corresponding to stretching bond vibrations of the double bond. Further, since only one peak is obtained, it can be expected that the clusters are formed of components having the same structure with a small cluster size.

[0012]

EXAMPLES Next, examples of the present invention will be described.

FIG. 3 shows the configuration of an embodiment of the plasma processing apparatus for disk substrates of the present invention.

The plasma processing apparatus according to the present invention is capable of exhausting at least a pressure below atmospheric pressure, and also serves as a vacuum chamber / electrode 1 for generating a plasma by applying a high voltage, a disk substrate 2 to be processed, and this. A third electrode 3 for holding and applying a DC positive voltage, a DC positive voltage applying device 4 for applying the voltage, a choke coil 9, a high frequency power source 5 for applying high frequency power to the electrode 1, and a blocking capacitor 10. An insulating material 11 for insulating between the electrodes, and a gas introduction mechanism 6 for introducing a gaseous substance into the plasma generation region.
And an exhaust mechanism 7 for keeping the inside of the vacuum chamber / electrode 1 at atmospheric pressure or below, and a valve 8 for partitioning the vacuum chamber / electrode 1 and the exhaust mechanism 7.

In the present apparatus, by introducing a CH ₄ gas as the reaction gas, the pressure was adjusted flow rate and the exhaust rate so that 6.7P _a constant. Then frequency 13.56MHz
Was applied to generate a plasma. The effective power was 2 kW.

After that, a positive DC voltage of 400 V was applied to the disk substrate 2 to be processed. As a result of forming the film in this state, data of the formed Raman is shown in FIG. Here, the Raman spectrum characteristic having a peak per 1520 cm ~ ¹ is obtained. For reference, Raman data obtained when the choke coil is removed by setting the DC bias equivalent to the conventional method to 0 V is also shown in (b) of FIG. From this comparison, it can be seen that the peak positions are clearly shifted.

Next, the relationship between the ratio of H in the film (the amount of hydrogen measured by the Hydrogen Forward Scattering method) and the Raman peak position when the DC bias voltage is increased and the energy of the ion active species is increased is shown in FIG. 5 shows. From this figure, increase in energy (increase in DC bias value) regardless of whether positive or negative ions are used
As a result, the proportion of H in the film tended to decrease. on the other hand,
The peak wavelength position of the Raman spectrum tended to shift to the higher wavenumber side as the energy increased. In general, the shift of Raman peak to the higher wave number side means graphitization of the film quality and an increase of carbon clusters having C = C bonds. Therefore, the intersection of both characteristic curves is selected as the best point for keeping the proportion of H in the film low and the double bond C = C low. Therefore, the best points of the characteristic curves when using positive ions and when using negative ions were compared. Here, the amount of hydrogen in the film was about 1/2 or less in absolute value when negative ions were used. Regarding the Raman peak position, it was confirmed that the film formed using negative ions had a peak at a lower wavelength side than when positive ions were used for any ion active species energy.

Next, FIG. 6 also shows the relationship between the film hardness and the energy of the ion active species. Here, as the characteristics of the positive ions and the negative ions, a film hardness characteristic curve having the energy value of the ion as a peak at the intersection of the H characteristic curve and the Raman peak characteristic curve in FIG. 5 was obtained. As for the absolute value of the film hardness, when the negative ions were used, a Vickus hardness of 4500 Hv which was 1500 Hv higher than that obtained when the positive ions were used was obtained.

When the high hardness film of the present invention is used as a protective film for a magnetic recording medium, the conventional protective film using positive ions has the same sliding resistance and abrasion resistance as obtained at a film thickness of 20 nm. The protective film formed by using the negative ions of the invention has a film thickness of 10 n
Similar results were obtained with m.

As a second embodiment, an experiment was conducted by using CF ₄ gas as a reaction gas in the apparatus shown in FIG. C using negative ions mainly composed of F ~ produced by CF ₄ gas
In forming the film, positive ions CF ₃ + ions, CF ₂ +
Compared with the F content in the fluorine-based C film using ions,
Since the F content was lower, steric hindrance due to C atoms was likely to occur as shown in FIG. 8, and a stable film having higher hardness was obtained. Note that FIG. 7 shows a film structure obtained by using positive ions CF ₃ + ions and CF ₂ + ions.

Next, FIG. 9 shows a sectional view of a magnetic recording medium having a high hardness protective film according to the present invention. here,
It is used as the protective film 13.

[0022]

According to the present invention, a carbon film having high hardness can be formed. Therefore, in the magnetic recording medium, the carbon film thickness can be reduced and the read / write characteristics can be improved.
It is possible to form a film corresponding to high recording density.

[Brief description of drawings]

FIG. 1 is a diagram showing a film forming process in the case of mainly positive ions in a reaction gas CH ₄ gas.

FIG. 2 is a diagram showing a film forming process when negative ions in a reaction gas CH ₄ gas are mainly used.

FIG. 3 is a diagram showing a basic configuration of an embodiment of a plasma processing apparatus.

FIG. 4 is a diagram showing Raman spectrum characteristics of a film obtained by the present invention.

FIG. 5 is a diagram showing the relationship between the energy of ion active species, the ratio of H in the film, and the Raman peak wavelength.

FIG. 6 is a diagram showing a relationship between ion active species energy and film hardness.

FIG. 7 is a diagram showing a film structure when positive ions in a reaction gas CF ₄ gas are mainly used.

FIG. 8 is a diagram showing a film structure when negative ions in a reaction gas CF ₄ gas are mainly used.

FIG. 9 is a diagram showing a schematic cross-sectional view of a magnetic disk.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Vacuum tank and electrode, 2 ... Processed disk substrate, 3 ... 3rd electrode and substrate holder, 4 ... DC power supply, 5 ... High frequency power supply, 6 ... Gas introduction mechanism, 7 ... Exhaust mechanism, 8 ... Gate valve, 9 ... Choke coil, 10 ... Blocking capacitor, 11 ... Insulating member, 12 ... Lubrication film, 13 ... Protective film, 14 ... Magnetic film, 15 ... Cr base film, 16 ... Ni-P plating, 17 ... Aluminum substrate.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Naruhiko Fujimaki 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Stock Manufacturing Research Institute, Hitachi, Ltd. (72) Inventor Ryo Kito 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Production Engineering Research Laboratory, Hitachi, Ltd.

Claims (8)

[Claims] 1. A method for producing a carbon protective film, which comprises selectively using negative ion active species in plasma in a plasma CVD method. 2. A method for producing a carbon protective film, characterized in that, in plasma CVD, a gas containing carbon and fluorine is used as a raw material, and negative ion active species are selectively used. 3. A plasma processing apparatus, characterized in that a positive DC bias voltage is applied to a substrate to be processed in order to perform the plasma processing method according to claim 1. 4. The plasma processing apparatus according to claim 3, wherein a positive DC bias voltage is superimposed on the output of the high frequency power source when plasma is generated using the high frequency power source. . 5. Amorphous carbon protection formed by the plasma CVD method according to claim 1 or 2, characterized in that the Raman spectrum (by argon laser excitation) has only one peak at 1520 cm to ¹ or less. film. 6. A magnetic disk manufacturing apparatus comprising the plasma processing apparatus according to claim 3 or 4. 7. The method according to claim 5, wherein the recording film is made of a thin film magnetic material.
A magnetic disk comprising the amorphous carbon protective film described above. 8. A magnetic disk drive comprising the magnetic disk according to claim 7 with a magnetic head, a motor, an arm and the like attached thereto.