JPH0112832B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for forming a protective film for protecting the active surface of a metal thin film, a semiconductor thin film, etc. from the surrounding environment, and particularly relates to a method for forming a protective film for protecting active surfaces of metal thin films, semiconductor thin films, etc. The present invention relates to a method suitable for protecting the surface of a thin film magnetic recording medium.

BACKGROUND OF THE INVENTION In various fields, there is a demand for stable protective films in the form of thin films to protect the surfaces of various functional elements, recording media, etc. using metal thin films, semiconductor thin films, etc. from the surrounding environment. Metal thin film magnetic recording media are required to keep the distance between the medium and the magnetic head as small as possible in order to take advantage of their characteristic high-density recording, but if the metal thin film itself is exposed to the surrounding environment, it will be exposed to moisture, moisture, etc. Its surface is easily corroded by the action of corrosive gases, and
Since it is easy to cause wear due to sliding with the magnetic head, it is necessary to form a protective film on the surface. 1000Å film layer
The thickness should preferably be several hundred Å or less.

In the past, several proposals have been made to form a protective film on a metal or inorganic compound by bombarding the target material with inert gas ions, and these methods have been proposed for use in metal thin film magnetic recording media using plastic film as a substrate. Although consideration was given to applying them, most of them were found to be inferior in flexibility and would crack when run by a magnetic head, or were not compatible with the magnetic head and could be scraped. It is also known to form a protective film on the surface of a material using a tetrafluoroethylene polymer as a target, and although this was investigated as a surface protective layer for a metal thin film type magnetic recording medium, it was found that the corrosion resistance was poor.

In view of the above points, the present inventors attempted to target an unprecedented polymer, and as a result, they targeted an aromatic hydrocarbon polymer and injected it into a mixed atmosphere of reducing gas and inert gas. It has become clear that the desired protective film can be formed by sputtering.

Here, examples of aromatic hydrocarbon polymers include polystyrene and poly-α-methylstyrene.

This olefin polymer formed into a film or formed as a coating on an aluminum plate is used as a target to reduce hydrogen, hydrocarbons, silane, phosphine, etc. with an inert gas such as argon, krypton, or xenon. The target is evaporated by ion bombardment in a mixed atmosphere of aggressive gases and deposited on the surface of the substrate to be protected.
In other words, it sputters. Note that the reducing gas has a stabilizing effect by reacting with active points in the produced film.

For sputtering methods, regular RF or DC
Known methods such as the sputtering method, magnetron type RF or DC sputtering method, and ion beam sputtering are possible, but the magnetron type RF sputtering method is used for forming a protective film on a metal thin film type magnetic recording medium using a plastic film as a substrate. is optimal.
In the case of this magnetron type RF sputtering method,
Mixed gas pressure: 10 ^-4 to 10 ^-2 Torr, target power
Directly on a ferromagnetic metal thin film made of Fe, Co, Ni, their alloys, or their alloys with other metals under conditions of 0.5 to 5 W/ ^cm2 , or via a nonmagnetic layer such as Al or Cr. When a protective film with a thickness of 50 Å to 1000 Å is formed at a deposition rate of 1 to 50 Å/sec, the corrosion resistance of the metal thin film and the wear resistance against magnetic heads are significantly improved. This will be explained below using a specific example.

Example A Co ferromagnetic thin film with a thickness of 0.2 μm was formed on a long polyester film with a thickness of 15 μm by continuous vacuum oblique evaporation method and cut into tapes, which was designated as Sample A. This sample A was sputtered under the following conditions, and the thickness was
A protective film of 100 Å was formed. This was designated as Sample B (Example 1).

Target: Polystyrene film, thickness 100μm Atmosphere: 4×10 ^-2 Torr, Ar+H ₂ (10%) Target power: 2.5W/cm ² Sputtering time: 30sec Using another sample A, sputtering was performed under the following conditions, and the thickness was A protective film with a thickness of 100 Å was formed. This was designated as Sample C (Example 2).

Target: Poly-α-methylstyrene film thickness 75μm Atmosphere: 4×10 ^-2 Torr, Ar+H ₂ (10%) Target power: 2.5W/cm ² sputtering time: 30sec Using another sample A, the following conditions were applied. A protective film with a thickness of 100 Å was formed by sputtering. This is sample D
(Comparative example) Target: Polystyrene film 100 μm thick Atmosphere: 4×10 ^-2 Torr, Ar Target power: 2.5 W/cm ² Sputtering time: 60 sec These samples were left at 40°C and 90% RH. As a result of a moisture resistance test, the number of days required for rust to be observed on the magnetic surface using an optical microscope was as follows.

Sample A: 12 days (comparative example) B: 55 days C: 60 days D: 30 days (comparative example) In addition, each of the above samples was separately tested to have the same functions as a commercially available home video tape recorder. The still time was measured using a still tester and the results were as follows.

Sample A: 30 minutes (comparative example) B: 75 minutes C: 80 minutes D: 50 minutes (comparative example) As is clear from the above examples, according to the present invention, a sputtered film with a thickness of about 100 Å By forming such a ferromagnetic thin film, the corrosion resistance and abrasion resistance of the ferromagnetic thin film can be greatly improved, and it is very useful industrially.

Claims (1)

[Claims] 1 A method for forming a protective film on a metal thin film magnetic recording medium, which method uses polystyrene or poly-α-
A method for forming a protective film, comprising evaporating a target made of methylstyrene by a sputtering method in a mixed atmosphere of a reducing gas and an inert gas, and depositing the target on the surface of the metal thin film.