Electrochemical etching of magnetic recording layer
View Patent ↗A method of fabricating a perpendicular magnetic recording disk is described. The method may include providing a magnetic recording layer disposed above a substrate with a plurality of intermediate layers disposed there between and electrochemically etching the magnetic recording layer.
1. A method of fabricating a perpendicular magnetic recording disk, the method comprising:
providing a magnetic recording layer disposed above a substrate with a plurality of intermediate layers disposed there between of the perpendicular magnetic recording disk; and
electrochemically etching the magnetic recording layer using a chelating agent to convert the magnetic recording layer into an electrochemically etched magnetic recording layer, the electrochemically etched magnetic recording layer having a first raised area and a first recessed area patterned thereon, the first raised area and the first recessed area being separated by a sidewall, wherein:
a first region of the first recessed area has a first cobalt-to-platinum (Co/Pt) ratio, the first region being located at a center of the first recessed area,
a second region of the first recessed area has a second Co/PT ratio, the second region being located adjacent to the first region,
a third region of the first recessed area has a third Co/Pt ratio, the third region being located between the second region and the first raised region,
a fourth region of the first recessed area has a fourth Co/Pt ratio, the fourth region being located between the third region and the first raised area,
the first Co/Pt ratio is greater than zero and less than 0.5, and
each of the first, second, third, and fourth Co/Pt ratios are different from each other.
2. The method of claim 1 , wherein the electrochemical etching of the magnetic recording layer generates a pattern of recessed areas formed therein, the pattern of recessed areas including the first recessed area.
3. The method of claim 1 , wherein the chelating agent comprises citric acid.
4. The method of claim 1 , wherein electrochemically etching the magnetic recording layer further comprises applying a reversely pulsed voltage waveform to the perpendicular magnetic recording disk while immersed in an electrochemical bath comprising an electrolyte solution.
5. The method of claim 1 , wherein the chelating agent comprises ethylenediaminetetraacetic acid (EDTA).
6. The method of claim 1 , wherein the chelating agent comprises one of a group consisting of phosphonate, malic acid, oxalic acid, polar amino acid, succinic acid, ascorbic acid, dicarboxymethylglutamic acid, gluconate, tartrate, glycine, pyridine and imidazole derivatives.
7. The method of claim 1 , wherein electrochemically etching the magnetic recording layer further comprises applying a reversely pulsed voltage waveform to the perpendicular magnetic recording disk while immersed in an electrochemical bath comprising an electrolyte solution.
8. The method of claim 7 , where the waveform is a square wave.
9. The method of claim 8 , wherein a pulse period of the waveform is in a range of 0.1 milliseconds (ms) to 20 ms.
10. The method of claim 8 , wherein the waveform has an upper positive voltage range from 1.5V to 3.5V and a lower negative voltage range from −1.5V to −3.5V.
11. The method of claim 8 , wherein the square wave has a positive pulse with a duty cycle in a range of 20 to 90 percent.
12. The method of claim 8 , wherein the square wave has a positive pulse with a 70 percent duty cycle and a 5 millisecond period for 15 seconds.
13. The method of claim 1 , wherein electrochemically etching the magnetic recording layer further comprises applying a constant voltage to the perpendicular magnetic recording disk while immersed in an electrochemical bath comprising an electrolyte solution.
14. The method of claim 1 , comprising electrochemically etching the magnetic recording layer using a plurality of different chelating agents.
15. The method of claim 1 , wherein the electrochemically etching is performed at a bath temperature of in a range of 40 to 60 degrees Centigrade with the chelating agent under constant agitation.
16. The method of claim 1 , wherein providing the magnetic recording layer comprises:
depositing the magnetic recording layer above the substrate;
depositing a first protection layer above the magnetic recording layer;
depositing a masking layer above the first protection layer;
imprinting a masking layer; and
ashing the masking layer and the first protection layer to expose areas of the magnetic recording layer to be electrochemically etched.
17. The method of claim 16 , further comprising:
rinsing the electrochemically etched magnetic recording layer;
removing the masking layer and the first protection layer; and
depositing a second protection layer above the magnetic recording layer.