Method for roughness reduction in manufacturing optical device structures
Embodiments described herein relate to a method of using an apparatus for forming waveguides. The method includes positioning a substrate at a first rotation angle, exposing the substrate to an ion beam, forming first partial trenches defined by adjacent angled device structures with the first device angle, rotating the substrate to a second rotation angle, exposing the substrate to the ion beam, etching the first partial trenches, and repeating the method from about 1 cycle to about 100 cycles to form a plurality of trenches defined by adjacent angled device structures. The first rotation angle is selected to form one or more angled device structures with a first device angle relative to a vector parallel to the substrate. The ion beam is configured to contact the substrate at a beam angle ϑ relative to a surface normal of the substrate.
1 . A method for forming a waveguide, comprising:
positioning a substrate at a first rotation angle relative to a datum line of the substrate, the first rotation angle selected to form one or more angled device structures with a first device angle relative to a vector parallel to the substrate;
exposing the substrate to an ion beam, the ion beam configured to contact the substrate at an beam angle ϑ relative to a surface normal of the substrate;
forming first trenches defined by adjacent angled device structures with the first device angle;
rotating the substrate to a second rotation angle relative to a datum line, wherein the second rotation angle is from about −20° to about 20°;
exposing the substrate to the ion beam;
removing a roughness and a hard mask material from a sidewall of the first trenches using the ion beam; and
repeating the method from about 1 cycle to about 100 cycles to form a plurality of trenches defined by adjacent angled device structures.
2 . The method of claim 1 , wherein the trenches in the plurality of trenches have a first sidewall and a second sidewall, the first sidewall and the second sidewall having a sidewall thickness variation of less than about 20 nm.
3 . The method of claim 1 , wherein the second rotation angle is different from the first rotation angle.
4 . The method of claim 1 , further comprising forming a plurality of second trenches defined by adjacent angled device structures with a second device angle.
5 . The method of claim 4 , wherein the second device angle is different from the first device angle.
6 . The method of claim 1 , wherein a device layer is disposed over the substrate such that the one or more angled device structures are formed in the device layer.
7 . The method of claim 1 , further comprising a patterned resist disposed over the substrate, the patterned resist having a plurality of hard mask structures, wherein adjacent hard mask structures define gaps to expose the substrate.
8 . A method for forming a waveguide, comprising:
positioning a substrate at a first rotation angle relative to a datum line of the substrate, the first rotation angle selected to form one or more angled device structures with a first angle relative to a vector parallel to the substrate;
exposing the substrate to an ion beam, the ion beam configured to contact the substrate at a beam angle ϑ relative to a surface normal of the substrate;
forming a trench defined by adjacent angled device structures, the trench having a first sidewall and a second sidewall;
rotating the substrate to a second rotation angle relative to the datum line, wherein the second rotation angle is from about −20° to about 20°;
exposing the substrate to the ion beam;
removing a roughness and a hard mask material from a sidewall of the trench using the ion beam;
rotating the substrate to a third rotation angle relative to the datum line, wherein the third rotation angle is from about −20° to about 20°;
exposing the substrate to the ion beam;
removing the roughness and the hard mask material from a sidewall of the trench using the ion beam; and
repeating the method from about 1 cycle to about 100 cycles to form a plurality of trenches defined by adjacent angled device structures.
9 . The method of claim 8 , wherein the second rotation angle is different from the third rotation angle.
10 . The method of claim 8 , wherein a sidewall thickness variation of the first sidewall and the second sidewall is less than about 20 nm.
11 . The method of claim 8 , wherein the third rotation angle is from about −10° to about 10°.
12 . The method of claim 8 , wherein a device layer is disposed over the substrate such that the one or more angled device structures are formed in the device layer.
13 . The method of claim 8 , further comprising a patterned resist disposed over the substrate, the patterned resist having a plurality of hard mask structures, wherein adjacent hard mask structures define gaps to expose the substrate.
14 . A method for forming a waveguide, comprising:
positioning a substrate at a first rotation angle relative to a datum line of the substrate, the first rotation angle selected to form one or more angled device structures with a first angle relative to a vector parallel to the substrate, the substrate having a patterned resist disposed thereon, the patterned resist comprising:
a plurality of hard mask structures; and
one or more gaps, each of the gaps defined by adjacent hard mask structures;
exposing the substrate to an ion beam, the ion beam configured to contact the substrate at an beam angle ϑ relative to a surface normal of the substrate;
forming a trench defined by adjacent angled device structures, the trench having a first sidewall and a second sidewall, wherein the trench is formed using the ion beam having a substrate etch chemistry to remove the substrate;
rotating the substrate to a second rotation angle relative to the datum line, wherein the second rotation angle is from about −20° to about 20°;
exposing the substrate to the ion beam;
removing the roughness and the hard mask material from a sidewall of the trench using the ion beam; and
removing the hard mask structures, wherein the hard mask structures are removed by the ion beam generated by a hard mask etch chemistry different than the substrate etch chemistry.
15 . The method of claim 14 , wherein a sidewall thickness variation of the first sidewall and the second sidewall is less than about 20 nm.
16 . The method of claim 14 , wherein the second rotation angle is different from the first rotation angle.
17 . The method of claim 14 , further comprising:
rotating the substrate to a third rotation angle relative to the datum line, wherein the third rotation angle is from about −20° to about 20°;
exposing the substrate to the ion beam; and
removing the roughness and the hard mask material from the sidewall of the trench using the ion beam.
18 . The method of claim 17 , wherein the third rotation angle is different from the first rotation angle and the second rotation angle.
19 . The method of claim 14 , wherein a device layer is disposed over the substrate such that the one or more angled device structures are formed in the device layer.
20 . The method of claim 19 , wherein the angled device structures are formed using the ion beam having a device layer etch chemistry to remove the device layer.