Method of making an ultra-sharp tip mode converter for a HAMR head
View Patent ↗A mode converter for use in a Heat-assisted magnetic recording (HAMR) read head to couple or bend light (e.g., from an external laser diode) into a tapered waveguide, and subsequently, to a near field transducer is provided. The mode converter may have an ultra-sharp tip, e.g., less than 200 nm to achieve a desired optical output. Manufacturing such a mode converter involves a two-pattern transform process, where overlay control (using a first edge, such as a right edge, as a reference layer relative to which positioning of a second edge, such as a left edge, is measured) allows for aligning of the right and left edges of a tip portion of the mode converter to ultimately create the ultra-sharp tip.
1. A method of manufacturing a mode converter comprising:
forming a mode converter process film stack comprising a stop layer, a core material, a buffer layer, a first cladding layer, and a hard mask layer;
defining a first edge of the mode converter;
transferring the first edge into the hard mask layer;
defining a second edge of the mode converter, wherein respective ends of the first and second edges define a mode converter tip;
transferring the second edge into the hard mask layer;
forming a temporary mode converter pattern on the hard mask layer;
temporarily transferring the mode converter pattern into the core material to form a final mode converter including the mode converter tip;
removing the hard mask layer and the buffer layer; and
depositing a second cladding layer over the final mode converter including the mode converter tip.
2. The method of claim 1 , wherein the mode converter tip is defined by the first and second edges and has a width less than 200 nm.
3. The method of claim 1 , wherein the mode converter tip is defined by the first and second edge and has a width ranging from approximately 200 nm to approximately 300 nm.
4. The method of claim 1 , wherein the stop layer comprises an Aluminum Oxide (AlOx) reactive ion etch stop layer approximately 2-3 nm thick.
5. The method of claim 1 , wherein the core material comprises Tantalum Pentoxide (Ta 2 O 5 ).
6. The method of claim 1 , wherein the buffer layer comprises Silicon Dioxide (SiO 2 ).
7. The method of claim 1 , wherein the hard mask layer comprises one of Chromium (Cr), Ruthenium, or other metallic material.
8. The method of claim 1 , wherein the hard mask layer is deposited on the buffer layer using a bi-layer lift-off process to produce an open metal seed window.
9. The method of claim 1 , wherein the defining of the first edge comprises defining via a first deep ultraviolet scanner photolithography process.
10. The method of claim 9 , wherein the transferring of the first edge comprises transferring via a first hard mask reactive ion etch process.
11. The method of claim 10 , wherein the defining of the second edge comprises defining via a second deep ultraviolet scanner photolithography process.
12. The method of claim 11 , wherein the transferring of the second edge comprises transferring via a second hard mask reactive ion etch process.
13. The method of claim 11 , further comprising defining positions of the first and second edges to define the mode converter tip by measuring a position of the second edge relative to the first edge, the first edge acting as a reference layer.
14. The method of claim 1 , wherein the second cladding layer comprises SiO 2 .
15. A method of manufacturing a mode converter comprising:
defining first and second edges of the mode converter using a sequential dual photolithography process;
transferring the defined first and second edges into a hard mask layer of a mode converter process film stack to form a mode converter tip pattern;
transferring the mode converter tip pattern onto a core material of the mode converter process film stack to form the mode converter;
removing the hard mask layer; and
depositing a protective layer on the mode converter.