Sputtered carbon overcoat in a thin-film medium and sputtering method

• US 5,679,431 A
• Filed: 04/01/1994
• Issued: 10/21/1997
• Est. Priority Date: 10/08/1993
• Status: Expired due to Term

• Current Assignee: WD Media Incorporated (Western Digital Corporation)
• Original Assignee: HMT Technology Corp. (Western Digital Corporation)
• Inventors: Do, Hoa Van, Chen, Ga-Lane
• Primary Examiner(s): KILIMAN, LESZEK B
• Application Number:
  US08/221,875
• Time in Patent Office: 1,299 Days
• Field of Search: 428/695, 428/900, 428/408, 428/556, 428/657, 428/65.3, 428/65.5, 428/694 T, 428/694 TD, 428/694 TC, 204/192.12, 204/298.12, 204/192.2, 204/298.13
• US Class Current: 428/833.5
• CPC Class Codes: C23C 14/0605 Carbon
• CPC Class Codes: G11B 5/727 Inorganic carbon protective coating, e.g. graphite, diamond like carbon or doped carbon
• CPC Class Codes: G11B 5/8408 protecting the magnetic layer
• CPC Class Codes: Y10S 428/90 Magnetic feature
• CPC Class Codes: Y10T 428/26 Web or sheet containing structurally defined element or component, the element or component having a specified physical dimension
• CPC Class Codes: Y10T 428/265 1 mil or less
• CPC Class Codes: Y10T 428/30 Self-sustaining carbon mass or layer with impregnant or other layer

Abstract

A thin-film magnetic recording medium having a carbon overcoat composed of an overcoat sublayer and an overcoat surface layer is described. The overcoat surface layer is a hydrogen- or nitrogen-containing sputtered carbon layer with high wear-resistance. The overcoat sublayer functions to reduce the diffusion of nitrogen or hydrogen from the surface layer to the magnetic recording layer. Also described is a method of sputtering the nitrogen-containing surface layer in which the graphite target is attached to the target electrode by thermally conducting, electrically conducting materials.

Claims

1. In a thin-film medium having a substrate, a magnetic thin-film layer, and a sputtered, nitrogen-containing, wear-resistant overcoat on the layer, an improvement comprising:

(a) a sputtered, non-magnetic, substantially nitrogen-free sublayer disposed between said overcoat and said magnetic layer and having a thickness between 25-100 Å

.

2. The medium of claim 1, wherein said sublayer is composed of a sputtered material selected from the group consisting of carbon, chromium and titanium.

3. The medium of claim 1, wherein said sublayer is between 25-50 Å

in thickness and is composed of carbon.

4. The medium of claim 1, which has a coercivity at least 15% higher than the same medium in the absence of said sublayer.

5. The medium of claim 1, wherein said overcoat is formed by sputtering from a graphite target under an atmosphere consisting essentially of 60-80 atomic percent argon and 20-40 atomic percent nitrogen.

6. In a method of producing a carbon overcoat in a thin-film magnetic recording medium having a magnetic recording layer, where said overcoat is produced by sputtering a nitrogen-containing carbon surface layer from a graphite target under an atmosphere composed of 60-80 atomic percent argon and 20-40 atomic percent nitrogen, an improvement, comprising

sputtering a non-magnetic, substantially nitrogen-free sublayer to a thickness between 25-100 Å

prior to sputtering the carbon surface layer.

7. The method of claim 6, wherein said sublayer sputtering is from a target material selected from the group consisting of carbon, chromium, and titanium.

8. The method of claim 6, wherein said sublayer sputtering is from a graphite target and is effective to deposit a layer between 25-100 Å

in thickness.

9. The method of claim 7, wherein the graphite target is bonded to a stainless steel cathode cap by means of (i) an electrically conductive, thermally conductive coating formed on each of the confronting surfaces of said target and cathode cap, and (ii) a solder effective to bond to said coatings and which has a melting temperature above 150°

C.

10. A method of forming a sputtered hydrogen or nitrogen containing layer on a disc, comprising

placing the disc in the target-deposition region of a graphite target that is bonded to a stainless steel cathode cap by means of (i) an electrically conductive, thermally conductive coating formed on each of the confronting surfaces of said target and cathode cap, and (ii) a solder effective to bond said coatings and which has a melting temperature above 150°

C.; and

sputtering graphite from the target onto the disc under a hydrogen or nitrogen containing atmosphere.

11. The method of claim 10, wherein said coatings are formed of a metal selected from the group consisting of copper, silver and gold.

12. The method of claim 10, wherein said coatings are copper and have a thickness between 0.2-10 μ

m.