JPH087219A - Amorphous carbon thin film and its production - Google Patents

Abstract

PURPOSE:To produce a carbon thin film having high hardness by forming an amorphous carbon thin film in a plasma treatment device so that the film has a specified range of peak area ratio of SP<3>/SP<2> in the absorbance peaks measured by IR absorption spectrum. CONSTITUTION:The plasma treating device is equipped with a vacuum chamber and electrode 1 which can be evacuated to the pressure lower than the atmospheric pressure and can produce plasma by applying high voltage, a ground electrode 3, a disk substrate 2 to be treated, a third electrode 12 on which DC voltage is applied, and a device 4 to apply DC positive voltage. Further, the treating device is equipped with a chalk coil 9, a high frequency power supply 5, a blocking capacitor 10, an evacuating mechanism 7, etc. Plasma is produced by introducing CH4 gas into the device, controlling the flow amt. and the evacuating rate to obtain const. pressure, and applying high voltage. An amorphous carbon thin film having 5 to 11 peak area ratio of SP<3>/SP<2> absorbance peaks in the IR absorption spectrum is formed to make the wear rate minimum.

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 thin film, a manufacturing method and a manufacturing apparatus therefor.

[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 usual plasma CVD process, the substrate to be processed is processed either on the ground side electrode or on the electrode on the side 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, C
From the measurement results of the ion energy analyzer in the plasma CVD process using H ₄ gas, neutral radical particles and main ion components It can be confirmed that the film formation is mainly performed.

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. That is, since the absolute amount of H in the molecule that constitutes the film is large, an increase in double bonds occurs due to dehydrogenation, and it is difficult to form a film containing mainly C single bond with 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. For the film quality of the deposited film, the ratio of the peak area of the absorbance of SP ³ / SP ² determined by IR (infrared absorption spectrum), the ratio of H (the amount of hydrogen was measured by the Hydrogen Forward Scattering method) and the Raman spectrum The purpose of the present invention is to obtain a magnetic recording medium having a high hardness thin film, which can be promoted comprehensively.

[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, the ones that can be confirmed to be negatively ionized and present in the plasma are C to CH and hydrogen atoms attached to each C atom. In plasma CVD without conventional ion selection As shown in 2, when the film forming method using negative ions is used, the absolute amount of hydrogen contained in the film is reduced. This eliminates the need for dehydrogenation in the film using high-energy ions, and suppresses the formation of double bonds accompanying it.

Therefore, the amount of hydrogen per unit volume in the film can be made smaller than in the case of using the conventional positive ions, and a film mainly containing a C single bond can be obtained.

[0011]

According to the present invention, the proportion of H in the carbon thin film formed by selectively using negative ions under a certain condition is 30% or less, and the Raman spectrum component is 1520 cm- ^1.
The characteristics with only one peak are shown below.
This is probably because hydrogen and double bonds were reduced in the film compared to the structure obtained by conventional film formation using positive ions, so that the bond order was low and the structural component close to a single bond was increased. To be The Raman spectrum can also be confirmed from the fact that there is no peak at 1580 cm ^-1 , which corresponds to the stretching vibration of the double bond, and that only one peak is obtained.

The film has a Vickus hardness of 3000 Hv or more.

Further, S of the absorbance peak obtained from IR
It was confirmed that when the P ³ / SP ² peak area ratio is 5 to 11, the wear rate of the film is minimized. It is considered that this is because when the peak area ratio is 5 or less, the ratio of double bonds in the film increases and the film hardness decreases. On the other hand, if the peak area ratio in which the SP ³ component observable by IR (terminated with hydrogen) increases is 11 or more, the island-shaped SP ³ component increases and the bond network is suppressed. become. Therefore, it is considered that the film quality is close to that of the mixed film of hydrocarbon compounds, and the film hardness decreases, so that the wear rate increases.

[0014]

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 evacuating at least to a pressure lower than atmospheric pressure, and also serves as a vacuum chamber electrode 1 for applying a high voltage to generate plasma, a ground side electrode 3 and a disk substrate to be processed. 2, a third electrode 12 for holding the same and applying a DC positive voltage, a DC positive voltage applying device 4 and a choke coil 9 for applying the voltage, a high frequency power source 5 for applying a high frequency power to the electrode 1, and a blocking An insulating material 11 for insulating between the capacitor 10 and the electrodes, a gas introduction mechanism 6 for introducing a gaseous substance into the plasma generation region, and an exhaust mechanism for keeping the inside of the vacuum chamber / electrode 1 below atmospheric pressure. 7 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. After that, a high voltage with a frequency of 13.56 MHz was applied to generate plasma. Effective power is 2k
It was W.

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 has a characteristic with a peak at 1520 cm- ¹ . For reference, the 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 FIG.
It is shown in (b). 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 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.

Further, when a high hard film having an SP ³ / SP ² peak area ratio of IR (infrared absorption spectrum) absorbance peaks of 5 to 11 obtained from the present invention is used as a protective film of a magnetic recording medium, FIG. The wear rate showed the minimum as shown in. Furthermore, the film thickness is 20 for the conventional protective film using positive ions.
In the protective film formed by using the negative ions of the present invention, the sliding resistance and the abrasion resistance obtained in the same range were obtained at a film thickness of 10 nm.

As a second embodiment, an experiment was carried out 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
Of membrane In comparison, since the F content was lower, steric hindrance due to C atoms was likely to occur as shown in FIG. 9, and a stable film having higher hardness was obtained. In addition, in FIG.

FIG. 10 is a block diagram showing the construction of an embodiment of a plasma processing apparatus for disk substrates which can perform simultaneous double-sided processing in the present invention. Here, the plasma generated on both sides of the substrate was adjusted to match with the phase difference signal generator so that interference between plasmas did not occur in the center hole of the disk.

Next, FIG. 11 shows a sectional view of a magnetic recording medium having a high hardness thin film according to the present invention. here,
It is used as the protective film 14.

[0025]

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 the relationship between the SP ³ / SP ² ratio obtained by IR and the wear rate.

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

FIG. 9 is a diagram showing a film structure when negative ions in a reaction gas CF ₄ gas are mainly used.

FIG. 10 is a configuration block diagram of an embodiment of a double-sided simultaneous plasma processing apparatus for a disk substrate.

FIG. 11 is a schematic sectional view of a magnetic disk.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electrode for vacuum chamber, 2 ... Disk substrate to be processed, 3 ... Electrode on ground side, 4 ... Positive 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 ... Third electrode, 13 ... Lubrication film, 14 ... Protective film, 15 ... Magnetic film, 16 ... Cr base film, 17 ... Ni-P plating, 18 ... 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 (11)

[Claims] 1. A vacuum container, an evacuation unit for maintaining the pressure in the vacuum container at a pressure lower than atmospheric pressure, an electrode for generating plasma in the vacuum container, and a gaseous substance supplied to the plasma generation unit. And a peak area ratio of SP ³ / SP ² of the absorbance peak obtained by IR (infrared absorption spectrum), which is formed by using a plasma processing apparatus equipped with
An amorphous carbon thin film characterized by: 2. The proportion of H in the film (Hydrogen Forward
The amorphous carbon thin film according to claim 1, wherein the amount of hydrogen measured by the Scattering method is 30% or less. 3. The amorphous carbon thin film according to claim 1, wherein the Raman spectrum (by argon laser excitation) component has only one peak at 1520 cm ⁻¹ or less. 4. The amorphous carbon thin film according to claim 1, which has a film Vickus hardness of 3000 Hv or more. 5. A method for producing an amorphous carbon thin film, which comprises forming the amorphous carbon thin film according to claim 1 by selectively using negative ion active species in plasma. 6. The method for producing a carbon thin film according to claim 5, wherein a gas containing carbon and fluorine is used as a raw material, and negative ion active species are selectively used. 7. The plasma processing method according to claim 5, wherein a positive DC bias voltage is superimposed on the output of the high frequency power source when the plasma is generated using the high frequency power source. Processing equipment. 8. A plasma processing apparatus, wherein a positive DC bias voltage is applied to a substrate to be processed to perform the plasma processing method according to claim 5. 9. A magnetic disk manufacturing apparatus comprising the plasma processing apparatus according to claim 7. 10. A magnetic disk and a magnetic head, wherein an amorphous carbon thin film according to claim 1, 2, 3 or 4 is formed as a protective film on a recording film made of a thin film magnetic material. 11. A magnetic disk drive comprising the member according to claim 10 with a motor, an arm and the like attached thereto.